Dissertations / Theses: 'CFD experimental'

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Hardie, Staffan. "Drag Estimations on Experimental Aircraft Using CFD." Thesis, Mälardalen University, Department of Mathematics and Physics, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-334.

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The drag approximations done in the initial design phase needed to be verified. A model of the aircraft has been analyzed with CFD and results examined to see how accurate the estimations were. A step by step analysis was made and then a simulation was run. The drag results of the CFD analysis did not meet the goal of the initial design study. Several reasons for this are discussed. The analysis shows that the aircraft design works well aerodynamically but also shows a few areas where the design can be improved.

Det approximerade värdet på luftmotståndet som gjordes I den preliminära designfasen behövde verifieras. En flygplansmodell har analyserats med CFD och resultaten har undersökts för att se hur exakta antagandena var. En analys gjordes steg för steg och slutligen har en simulering utförts. Det uppmätta luftmotståndet motsvarade inte målet i den preliminära designfasen. Flera olika anledningar till detta diskuteras. Analysen visar att denna flygplansdesign fungerar bra aerodynamiskt men identifierar också en del punkter på vilken den kan förbättras.

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li, zhiliang. "EXPERIMENTAL AND CFD INVESTIGATIONS OF LIFTED TRIBRACHIAL FLAMES." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3048.

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Experimental measurements of the lift-off velocity and lift-off height, and numerical simulations were conducted on the liftoff and stabilization phenomena of laminar jet diffusion flames of inert-diluted C3H8 and CH4 fuels. Both non-reacting and reacting jets were investigated, including effects of multi-component diffusivities and heat release (buoyancy and gas expansion). The role of Schmidt number for non-reacting jets was investigated, with no conclusive Schmidt number criterion for liftoff previously known in similarity solutions. The cold-flow simulation for He-diluted CH4 fuel does not predict flame liftoff; however, adding heat release reaction leads to the prediction of liftoff, which is consistent with experimental observations. Including reaction was also found to improve liftoff height prediction for C3H8 flames, with the flame base location differing from that in the similarity solution - the intersection of the stoichiometric and iso-velocity contours is not necessary for flame stabilization (and thus lift-off). Possible mechanisms other than that proposed for similarity solution may better help to explain the stabilization and liftoff phenomena. The stretch rate at a wide range of isotherms near the base of the lifted tribrachial flame were also quantitatively plotted and analyzed.
Ph.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering PhD

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3

Wang, Zhiguo. "Experimental studies and CFD simulations of conical spouted bed hydrodynamics." Thesis, University of British Columbia, 2006. http://hdl.handle.net/2429/61.

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Conical spouted beds have been commonly used for drying suspensions, solutions and pasty materials. They can also be utilized in many other processes, such as catalytic partial oxidation of methane to synthesis gas, coating of tablets, coal gasification and liquefaction, pyrolysis of sawdust or mixtures of wood residues. The main objectives of this work include both the experimental research and mathematical modelling of the conical spouted bed hydrodynamics. For experimental research, pressure transducers and static pressure probes were applied to investigate the evolution of the internal spout and the local static pressure distribution; optical fibre probes were utilized to measure axial particle velocity profiles and voidage profiles; the step tracer injection technique using helium as the tracer and thermal conductivity cells as detectors was used to investigate the gas mixing behaviour inside a conical spouted bed. It was found that many factors might affect calibration of the effective distance of an optical fibre probe. Therefore, a new calibration setup was designed and assembled, and a comprehensive sensitivity analysis was conducted to calibrate the optical probes used in this study. For mathematical modelling, a stream-tube model based on the bed structure inside a conical spouted bed was proposed to simulate partial spouting states. By introducing an adjustable parameter, this model is capable of predicting the total pressure drop under different operating conditions, and estimating axial superficial gas velocity profiles and gauge pressure profiles. A mathematical model based on characteristics of conical spouted beds and the commercial software FLUENT was also developed and validated using measured experimental data. The proposed new CFD model can simulate both stable spouting and partial spouting states, with an adjustable solids-phase source term. At stable spouting states, simulation results agree very well with almost all experimental data, such as static pressure profiles, axial particle velocity profiles, voidage profiles etc. A comprehensive sensitivity analysis was also conducted to investigate the effect of all possible factors on simulation results, including the fluid inlet profile, solid bulk viscosity, frictional viscosity, restitution coefficient, exchange coefficient, and solid phase source term. The proposed new CFD model was also used successfully to simulate gas mixing behaviours inside a conical spouted bed, and simulate cylindrical packed beds as well as cylindrical fluidized beds in one code package.

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Supamusdisukul, Jirapat. "Experimental investigation of wing-fuselage integration geometries including CFD analyses." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8141.

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Thesis (M.S.) -- University of Maryland, College Park, 2008.
Thesis research directed by: Dept. of Aerospace Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

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Prasser, Horst-Michael, Tobias Sühnel, Christophe Vallée, and Thomas Höhne. "Experimental investigation and CFD simulation of slug flow in horizontal channels." Forschungszentrum Dresden, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:d120-qucosa-28061.

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For the investigation of stratified two-phase flow, two horizontal channels with rectangular cross-section were built at Forschungszentrum Dresden-Rossendorf (FZD). The channels allow the investigation of air/water co-current flows, especially the slug behaviour, at atmospheric pressure and room temperature. The test-sections are made of acrylic glass, so that optical techniques, like high-speed video observation or particle image velocimetry (PIV), can be applied for measurements. The rectangular cross-section was chosen to provide better observation possibilities. Moreover, dynamic pressure measurements were performed and synchronised with the high-speed camera system. CFD post-test simulations of stratified flows were performed using the code ANSYS CFX. The Euler-Euler two fluid model with the free surface option was applied on grids of minimum 4∙105 control volumes. The turbulence was modelled separately for each phase using the k-ω based shear stress transport (SST) turbulence model. The results compare well in terms of slug formation, velocity, and breaking. The qualitative agreement between calculation and experiment is encouraging and shows that CFD can be a useful tool in studying horizontal two-phase flow. Furthermore, CFD pre-test calculations were done to show the possibility of slug flow generation in a real geometry and at relevant parameters for nuclear reactor safety. The simulation was performed on a flat model representing the hot-leg of the German Konvoi-reactor, with water and saturated steam at 50 bar and 263.9°C. The results of the CFD-calculation show wave generation in the horizontal part of the hot-leg which grow to slugs in the region of the bend.

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Ebrahimi, Mohammadreza. "CFD-DEM modelling of two-phase pneumatic conveying with experimental validation." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/9693.

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A wide range of industrial processes involve multiphase granular flows. These include catalytic reactions in fluidized beds, the pneumatic conveying of raw materials and gas-particle separators. Due to the complex nature of multiphase flows and the lack of fundamental understanding of the phenomena in a multiphase system, appropriate design and optimized operation of such systems has remained a challenging field of research. Design of these processes is hampered by difficulties in upscaling pilot scale results, the difficulties involved in experimental measurements and in finding reliable numerical modelling methods. Significant work has been carried out on numerical modelling of multiphase systems but challenges remain, notably computational time, appropriate definition of boundary conditions, relative significance of effects such as lift and turbulence and the availability of reliable model validation. The work presented in this thesis encompasses experimental and numerical investigations of horizontal pneumatic conveying. In the experimental work, carefully controlled experiments were carried out in a 6.5 m long, 0.075 m diameter horizontal conveying line with the aid of the laser Doppler anemometry (LDA). Initially, LDA measurements were performed to measure the gas velocity in clear flow. Good agreement was observed between the theory and experimental measurements. For two-phase experiments, spherical and non-spherical particles with different sizes and densities were used to study the effect of particle size and solid loading ratio on the mean axial particle velocity. Three different sizes of spherical glass beads, ranging from 0.9 mm to 2 mm and cylindrical shaped particle of size 1x1.5 mm were employed. It was found that by increasing the particle size and solid loading ratios, the mean axial particle velocity decreased. Turbulence modulation of the carrier phase due to the presence of spherical particles was also investigated by measuring fluctuating gas velocity for clear gas flow and particle laden flow with different particle sizes and solid loading ratios. Results suggested that for the size ranges of particles tested, the level of gas turbulence intensity increased significantly by adding particles, and the higher the solid loading ratio, the higher the turbulence intensity. With the rapid advancement of computer resources and hardware, it is now possible to perform simulations for multiphase flows. For a fundamental understanding of the underlying phenomena in pneumatic conveying, the coupled Reynolds averaged Navier-Stokes and discrete element method (RANS-DEM) was selected. The aim of the modelling section of this study was to evaluate the abilities of coupled RANSDEM to predict the phenomena occurring in a research-sized pneumatic conveying line. Simulations for both one-way and two-way RANS-DEM coupling were performed using the commercial coupled software FLUENT-EDEM in an Eulerian- Lagrangian framework, where the gas is simulated as a continuum medium, while solid phase is treated as a discrete phase. In one-way coupling simulations, a considerable discrepancy in mean axial particle velocity was observed compared to the experimental results, meaning two-way coupling was required. It was further found that the inclusion of Magnus lift force due to particle rotation was essential to reproduce the general behaviour observed in the experiments. Turbulence modulation also was investigated numerically. Experimental and simulation results of gas and particle velocities were compared showing that the RANS-DEM method is a promising method to simulate pneumatic conveying. However, some discrepancy between simulation and experimental results was observed. Most studies in two-phase flow fields have focused on spherical particles. However the majority of particles encountered in industry involve non-spherical granules which show considerably different transportation behaviour compared with spherical particles. Further modelling of cylindrical particles was conducted using a multisphere model to represent cylindrical particles in the DEM code. Drag and lift forces and torque equations were modified in the code to take the effect of particle orientation into account. The framework developed was evaluated for two test cases, indicating a good agreement with the analytical and experimental results. The transportation of isometric (low-aspect-ratio) non-spherical particles in pneumatic conveying was also modelled. The simulation results of mean axial particle velocity agreed well with the experimental measurements with the LDA technique.

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7

Prasser, Horst-Michael, Tobias Sühnel, Christophe Vallée, and Thomas Höhne. "Experimental investigation and CFD simulation of slug flow in horizontal channels." Forschungszentrum Dresden-Rossendorf, 2007. https://hzdr.qucosa.de/id/qucosa%3A21634.

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For the investigation of stratified two-phase flow, two horizontal channels with rectangular cross-section were built at Forschungszentrum Dresden-Rossendorf (FZD). The channels allow the investigation of air/water co-current flows, especially the slug behaviour, at atmospheric pressure and room temperature. The test-sections are made of acrylic glass, so that optical techniques, like high-speed video observation or particle image velocimetry (PIV), can be applied for measurements. The rectangular cross-section was chosen to provide better observation possibilities. Moreover, dynamic pressure measurements were performed and synchronised with the high-speed camera system. CFD post-test simulations of stratified flows were performed using the code ANSYS CFX. The Euler-Euler two fluid model with the free surface option was applied on grids of minimum 4∙105 control volumes. The turbulence was modelled separately for each phase using the k-ω based shear stress transport (SST) turbulence model. The results compare well in terms of slug formation, velocity, and breaking. The qualitative agreement between calculation and experiment is encouraging and shows that CFD can be a useful tool in studying horizontal two-phase flow. Furthermore, CFD pre-test calculations were done to show the possibility of slug flow generation in a real geometry and at relevant parameters for nuclear reactor safety. The simulation was performed on a flat model representing the hot-leg of the German Konvoi-reactor, with water and saturated steam at 50 bar and 263.9°C. The results of the CFD-calculation show wave generation in the horizontal part of the hot-leg which grow to slugs in the region of the bend.

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Semenzin, Clayton S. "Determination of Centrifugal Blood Pump Characteristics using CFD and Experimental Analysis." Thesis, Griffith University, 2021. http://hdl.handle.net/10072/401348.

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Background Cardiovascular diseases are the leading cause of death throughout the developed world, attributed to approximately 17.8 million deaths worldwide in 2017 with increasing prevalence due to the aging population. Cardiovascular diseases generally result in heart failure. While the best treatment option for heart failure patients is heart transplantation, there is a severe deficiency in the availability of donor hearts. Rotary Blood Pumps (RBPs) utilised as Ventricular Assist Devices (VADs) provide an alternative treatment option. These devices are small implantable pumps that support the failing heart by providing power to augment circulation. The development of RBPs generally begins with initial designs obtained using traditional pump design methods (such as that developed by Stepanoff). However, studies have shown that this approach produces RBP prototypes far from optimal in design. Traditional theory relies on design constants derived empirically for large industrial pumps and these do not scale down well when applied to the much smaller RBPs. The initial designs are therefore generally quite poor and require an iterative build-and-test approach to obtain suitable pump prototypes – a process that is expensive and time consuming. Therefore, by improving the methodology for obtaining initial designs to better reflect the final product, development time can be greatly reduced. A popular avenue for analysing the effect of design variations and to further develop early prototypes of RBPs is to employ Computational Fluid Dynamics (CFD) simulations. These numerical simulations provide detailed data regarding the flow fields within these devices. However, a range of simulation options is available, leading to a wide range of potential predictions. In an attempt to provide a benchmark case, the FDA presented a challenge in which a pump design and test conditions were defined, allowing for direct comparison amongst different simulation approaches from a number of labs/RBP developers. The purpose of this thesis was to produce a gross design tool to provide a good starting point in RBP prototyping and a CFD simulation approach for verification that can also be used as a design refinement tool. Methods Formulating a design method for pumps requires the generation of empirical data. A number of pump design variables was identified as having an impact on pump performance, and a large number of experimental tests would have been needed to test the influence of each. Instead, a Design of Experiments (DOE) was utilised to streamline the process. The DOE outputs a relatively small number of tests required to fit a statistical model. Each design specified by the DOE was examined experimentally using a custom-built automated pump test platform to generate a number of performance measures. The obtained results were used to formulate a Response Surface Method (RSM) statistical model that showed acceptable fit to the input data. Coupled with desirability functions, the RSM model allowed for design optimisation. This tool essentially replaces Stepanoff’s traditional design methodology. The RSM model provides a robust tool that allows the user flexibility in design optimisation goals. The FDA pump was investigated in this thesis and a wide variety of simulation approaches was examined to determine which was most accurate. A range of factors were considered which included: mesh density, interface position between the rotating and stationary zones, steady vs. transient simulations, discretisation schemes, time step size and choice of turbulence model. The most appropriate option from each investigative study was selected to determine a recommended simulation approach. Final simulations were performed using these recommendations and were compared to the FDA experimental results to confirm the suitability of the suggested settings. Determination of Centrifugal Blood Pump Characteristics using CFD and Experimental Analysis iii The statistical model developed was used to design two different impellers as validation test cases. The first impeller was designed to optimise the maximum efficiency, P – Q curve slope and efficiency consistency. The second impeller was designed to mimic the approach used in traditional design methods for RBPs in setting a target design point as the primary objective and the aforementioned factors (from the first impeller) as secondary objectives. These two case studies underwent statistical performance predictions, CFD simulations, PIV analysis and experimental hydraulic testing to validate the statistical and CFD models. Results From the initial CFD study, a hybrid SBES turbulence model with full transient simulation on a fine grid with small time steps proved to be the most suitable both in terms of pressure rise generated by the FDA pump and resulting velocity fields when compared to published experimental results. From these findings the CFD modelling strategy was established. CFD results for the two validation pumps showed pressure rises matching the experimental data (8% and 1% difference for each impeller) within an acceptable range (<10% from the mean). The simulated velocity fields also closely replicated the PIV data for the majority of the flow domain. The statistical performance predictions well reflected those measured experimentally with the majority of data points falling within its confidence intervals. The hydraulic results also supported the main goal of this thesis, whereby an impeller generated using the statistical model, operated far closer to the target design point than that of a blood pump designed following Stepanoff’s methodology. Overall, both the statistical model and CFD approach provided accurate predictions and the purpose of the thesis was achieved. Final Remarks The statistical and CFD models developed in this thesis yield an effective design tool and verification methodology and show improvement over the current traditional design methods and accuracy in simulated results. Ultimately, the utilisation of these tools will lead to a reduction in the development time for new RBPs and provide a good understanding of the flow dynamics within these pumps, leading to improved pump designs reaching patients sooner. These tools are readily generalizable and could be adopted as design tools now.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Eng & Built Env
Science, Environment, Engineering and Technology
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Naronikar, Aditya, and Anton Riström. "CFD and Experimental Study of Refuelling and Venting a Fuel System." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-159297.

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In 1999, California Air Resources Board (CARB) implemented a regulation that required all gasoline cars sold in California be fitted with an Onboard Refueling Vapor Recovery System (ORVR). The ORVR system is designed to prevent Volatile Organic Compounds (VOCs) from escaping into the atmosphere during refuelling by storing the gas vapours in a carbon canister. Due to the complex nature of the fuel system, making design changes could have large implications on the ORVR performance of the vehicle. It is therefore desirable to develop a CFD model that can predict the effects of design changes, thereby reducing the need to perform physical tests on each design iteration. This master thesis project was performed at the Fuel Systems department at Volvo Cars in order to help reduce project lead times and product development costs by incorporating CFD as a part of the fuel system development cycle. The CFD results obtained were validated through experimental tests that were also performed as part of this project. In this master thesis project, a CFD model was developed to simulate the refuelling of gasoline for a California specification Volvo XC90 with an OPW-11B pump pistol. The model was set up in STAR-CCM+ using the Eulerian Volume of Fluid model for multiphase flow, the RANS realizable k-epsilon turbulence model and the two layer all y+ wall treatment. The effects of the carbon canister were modelled as a porous baffle interface in the simulations where viscous and inertial resistances of the porous media were adjusted to obtain a desired pressure drop across the canister. This method proved to be a suitable simplification for this study. The effects of evaporation as well as a chemical adsorption model for the carbon canister have been excluded from the project due to time limitations. It was found that the CFD simulations were in good agreement with the experimental results, especially with respect to capturing the overall behaviour of the fuel system during refuelling. It was found that resolving the flow spatially (and temporally) in the filler pipe was a crucial part in ensuring solver stability. A pressure difference between experiment and simulation was also observed as a consequence of excluding evaporation from the CFD model. After the CFD model had been verified and validated, changes to different parts of the fuel system were investigated to observe their effects on ORVR performance. These included changing the recirculation line diameter, changing the carbon canister properties and changing the angle of how the pump pistol was inserted into the capless unit. It was found that the recirculation line diameter is a very sensitive design parameter and increasing the diameter would result in fuel vapour leaking back out into the atmosphere. Similarly, increasing the back pressure by swapping to a different carbon canister would result in the leakage of fuel vapour. On the other hand, insignificant changes in system behaviour were observed when the fuel pistol angle was changed.

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Riström, Anton, and Aditya Naronikar. "CFD and Experimental Study of Refuelling and Venting a Fuel System." Thesis, Luleå tekniska universitet, Rymdteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-75410.

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In 1999, California Air Resources Board (CARB) implemented a regulation that required all gasoline cars sold in California be fitted with an Onboard Refueling Vapor Recovery System (ORVR). The ORVR system is designed to prevent Volatile Organic Compounds (VOCs) from escaping into the atmosphere during refuelling by storing the gas vapours in a carbon canister. Due to the complex nature of the fuel system, making design changes could have large implications on the ORVR performance of the vehicle. It is therefore desirable to develop a CFD model that can predict the effects of design changes, thereby reducing the need to perform physical tests on each design iteration. This master thesis project was performed at the Fuel Systems department at Volvo Cars in order to help reduce project lead times and product development costs by incorporating CFD as a part of the fuel system development cycle. The CFD results obtained were validated through experimental tests that were also performed as part of this project. In this master thesis project, a CFD model was developed to simulate the refuelling of gasoline for a California specification Volvo XC90 with an OPW-11B pump pistol. The model was set up in STAR-CCM+ using the Eulerian Volume of Fluid model for multiphase flow, the RANS realizable k − ε turbulence model and the two layer all y + wall treatment. The effects of the carbon canister were modelled as a porous baffle interface in the simulations where viscous and inertial resistances of the porous media were adjusted to obtain a desired pressure drop across the canister. This method proved to be a suitable simplification for this study. The effects of evaporation as well as a chemical adsorption model for the carbon canister have been excluded from the project due to time limitations. It was found that the CFD simulations were in good agreement with the experimental results, especially with respect to capturing the overall behaviour of the fuel system during refuelling. It was found that resolving the flow spatially (and temporally) in the filler pipe was a crucial part in ensuring solver stability. A pressure difference between experiment and simulation was also observed as a consequence of excluding evaporation from the CFD model. After the CFD model had been verified and validated, changes to different parts of the fuel system were investigated to observe their effects on ORVR performance. These included changing the recirculation line diameter, changing the carbon canister properties and changing the angle of how the pump pistol was inserted into the capless unit. It was found that the recirculation line diameter is a very sensitive design parameter and increasing the diameter would result in fuel vapour leaking back out into the atmosphere. Similarly, increasing the back pressure by swapping to a different carbon canister would result in the leakage of fuel vapour. On the other hand, insignificant changes in system behaviour were observed when the fuel pistol angle was changed.In 1999, California Air Resources Board (CARB) implemented a regulation that required all gasoline cars sold in California be fitted with an Onboard Refueling Vapor Recovery System (ORVR). The ORVR system is designed to prevent Volatile Organic Compounds (VOCs) from escaping into the atmosphere during refuelling by storing the gas vapours in a carbon canister. Due to the complex nature of the fuel system, making design changes could have large implications on the ORVR performance of the vehicle. It is therefore desirable to develop a CFD model that can predict the effects of design changes, thereby reducing the need to perform physical tests on each design iteration. This master thesis project was performed at the Fuel Systems department at Volvo Cars in order to help reduce project lead times and product development costs by incorporating CFD as a part of the fuel system development cycle. The CFD results obtained were validated through experimental tests that were also performed as part of this project. In this master thesis project, a CFD model was developed to simulate the refuelling of gasoline for a California specification Volvo XC90 with an OPW-11B pump pistol. The model was set up in STAR-CCM+ using the Eulerian Volume of Fluid model for multiphase flow, the RANS realizable k − ε turbulence model and the two layer all y + wall treatment. The effects of the carbon canister were modelled as a porous baffle interface in the simulations where viscous and inertial resistances of the porous media were adjusted to obtain a desired pressure drop across the canister. This method proved to be a suitable simplification for this study. The effects of evaporation as well as a chemical adsorption model for the carbon canister have been excluded from the project due to time limitations. It was found that the CFD simulations were in good agreement with the experimental results, especially with respect to capturing the overall behaviour of the fuel system during refuelling. It was found that resolving the flow spatially (and temporally) in the filler pipe was a crucial part in ensuring solver stability. A pressure difference between experiment and simulation was also observed as a consequence of excluding evaporation from the CFD model. After the CFD model had been verified and validated, changes to different parts of the fuel system were investigated to observe their effects on ORVR performance. These included changing the recirculation line diameter, changing the carbon canister properties and changing the angle of how the pump pistol was inserted into the capless unit. It was found that the recirculation line diameter is a very sensitive design parameter and increasing the diameter would result in fuel vapour leaking back out into the atmosphere. Similarly, increasing the back pressure by swapping to a different carbon canister would result in the leakage of fuel vapour. On the other hand, insignificant changes in system behaviour were observed when the fuel pistol angle was changed.

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Camara, Enrique. "Validation of Time Domain Flutter PredictionTool with Experimental Results." Thesis, KTH, Kraft- och värmeteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160541.

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In turbomachinery applications as propulsion and power generation, there is a continuous endeavour to design engines with higher efficiency, driving the compressor and turbine blades towards slimmer and more aerodynamically loaded configurations that frequently operate with fluids at higher temperatures and speeds. This combination of reduced design space and adverse operating environment makes the blades more susceptible to flutter and challenges the designer to predict its occurrence. Nowadays there are different CFD solvers that allow the prediction of flutter in turbomachinery; some of them are more efficient than others and provide considerable computational power savings when compared with traditional CFD methods that sometimes require the simulation of several or all the blades in a given row. The present thesis work is aimed at investigating the strengths and potential limitations of a novel time marching method for Flutter prediction in the Travelling Wave Mode (TWM) domain available in ANSYS CFX 14.5. The results are compared with experimental measurements obtained at the KTH test rig and CFD simulations in the Influence Coefficient Domain (INFC) performed in a previous MSc. Thesis in 2013. An approach in CFX to solve flutter is the Fourier Transformation method that uses only two passages with phase lagged periodic boundary conditions. In the previous thesis only one operating point was calculated using this method. This project focuses on the extension of the calculations to various operating points and expanding the solver validation.

Thesis work done at Siemens Industrial Turbomachinery, Finspang, Sweden.

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Songyu, Cao. "Experimental and CFD Study of Wind-Induced Response for Bridge Cables with Ice accretion." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32985.

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Cable-stayed bridges are massive structures which rely on their structural elements such as deck girder, towers and stay-cables for their stability. The bridge stay-cables can be considered as the most flexible elements of the cable-stayed bridges, and thus their structural stability integrity is verified for several phenomena which might affect them. Wind and wind/rain induced vibrations for bridge stay-cables were comprehensively studied by researchers worldwide; however recent projects have identified a new type of cable vibrations caused by ice accretion formed around the cable circumference. The current research proposed two ice accretion profiles for inclined bridge cables and has experimentally investigated the wind-induced vibrations of the two models for the bridge stay-cables with ice accretion, under different vertical (inclination) and horizontal (yaw) angles, and for different wind speeds. Initially, three models of the bridge cable with 1.0 cm and 2.0 cm ice profile were tested in the wind tunnel of cross-section 61 cm × 90 cm, and a maximum wind speed of 30 m/s. In total 6 cases with 1.0 cm ice thickness and 3 cases with 2.0 cm ice thickness were investigated and the vertical and torsional oscillatory displacements were recorded for wind speeds from 1.5 m/s to 15 m/s at intervals of 1.5 m/s. The wind-induced vibrations were analyzed and were compared with the response reported for cables without ice and with the rain-induced response for stay-cables. Computational Fluid Dynamics (CFD) simulations were performed to observe the drag, lift and pressure coefficients around the surface of the accreted cable models yawed and inclined at α = 0°, β = 0° and α = 60°, β = 15° under the effect of 10 m/s and 15 m/s wind speed applied for both cases. A verification for galloping divergent instability was conducted based on the Den Hartog formulation and the vertical vibrations obtained from the wind tunnel experiment.

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Seemann, Patrick. "Design of 120cc Single Cylinder Experimental Engine for Analysis of Intake Swirl and Multiple Ignition Sites." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_theses/219.

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The intent of this thesis is to design, build, and test a cylinder head with variable swirl and ignition sites. The design aspect used Solid Works Floworks to model airflow within the head and cylinder. Swirl rate and volumetric flow rate were calculated from the results. Many design iterations took place before a suitable design was accomplished. Once the suitable design was reached, it was built using the rapid prototyping method known as 3-D printing (Fused Deposition Modeling). Valve guides and seats were installed in the head. Then valves, springs, and retainers were installed to allow for testing. The inlet was created using stereo-lithography due to its smooth surface finish and thin walls. A pin wheel swirl measuring device was built to measure tangential rotation rate of gasses in the cylinder. The experimental head was tested on the University of Miami flow bench in the Internal Combustion Engines Laboratory. The results of the experimental work and theoretical modeling were compared. The results matched closely. The difference between experimental and theoretical values for high swirl flow rates were less than 3% error and the swirl ratio was less than 10%. For the low swirl scenario, error was less than 30%. The measured flow rate for the high swirl scenario was 28.87 CFM and the swirl ratio was measured as 2.87. SolidWorks Floworks created accurate results for the high swirl scenario and further experimentation should be conducted for different geometries.

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Vivekanandhan, Bagya. "Analysis on experimental and numerical modelling of floating structures using cfd codes." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.

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This research is focused on the study and analysis of dynamics of floating bodies. The research is carried out in two stages, an experimental process followed by a numerical process. At the first stage, Experimental tests were performed in the wave flume of the Laboratory of Hydraulic Engineering at DICAM, University of Bologna. Two prototypes of floating bodies, a cylinder and a barge, were tested for catenary and spring mooring systems under regular and irregular wave conditions. For each tested wave, the wave-structure interaction was measured by means of wave gauges and the dynamic motion of the structure is observed by means of two GOPRO cameras, recording the movement of the object from the top side of the flume and from the lateral side. The second stage is begun with an numerical analysis that is implemented by means of a numerical model which is primarily based on the Computational Fluid Dynamics (CFD). The same wave conditions as used in the experimental tests are modeled using OpenFOAM, an open source platform for CFD practices. The OpenFOAM model includes a mesh of a wave flume within which a dynamic mesh is meshed. The role of this dynamic mesh is to contain the floating body and set boundaries for the motion of the floating body. The movements of the floating body with respect to the dynamic mesh is observed. The refinement of the Meshes plays a significant role in the simulation. BlockMesh refinement plays a vital role in the simulations. The OpenFOAM model is sensitive to the refinement of the meshes, hence, the overset mesh and the primary mesh are made sure to be of the equal refinement in order to obtain an accurate result. At the end of the simulation, the experimental and numerical results from first and the second stage respectively are compared for an advance understanding of the wave-structure behavior under the given boundary conditions.

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Xinzhe, Wang, and Li Xin. "Experimental and CFD Study of Flow Phenomenon in Flowrate-amplified Flotation Element." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-200558.

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Focusing on reducing the air consumption of an air flotation rail system, a flowrate-amplified flotation element was recently developed. This new flotation element ulitises the rotational flow to intake extra air via an intake hole, and thus, effectively improves the flotation height. Compared to a conventional flotation element, the flowrate-amplified flotation element can reduce air consumption by approximately 50% for the same load and flotation height. To gain an understanding of the flow phenomenon in the flowrate-amplified flotation element, experiments and CFD simulations are conducted in this study. Based on the results, we found that the flowrate-amplified flotation element could take a part of the kinetic energy of the rotating air to suck in extra air. The intake hole greatly affects the pressure field and velocity field of the flotation element. Additionally, the effects of the variant gap height and supplied flow rate were also discussed. The results indicate that the pressure distribution decreases as the gap height increases and increases as the supplied flow rate increases.

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Vieira, Neto José Luiz. "Estudo Experimental e de Simulação por CFD de Escoamentos em Seções Anulares." Universidade Federal de Uberlândia, 2011. https://repositorio.ufu.br/handle/123456789/15056.

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The increasing activity of oil and gas extraction in deep water has stimulated several studies to solve problems encountered in drilling wells. During the drilling operation, a fluid (drilling mud) is pumped through the column to the bottom, carrying to the surface the drill cuttings generated, through the annular space formed between the column and the borehole wall. In this type of flow may appear a kind of hydrodynamic instability characterized by the appearance of toroidal vortices. This type of instability (Taylor-Couette) may profoundly alter the pressure drop of the flow, the shear stress at the borehole wall and the ability of carrying the solids. Moreover, during the process of drilling a well it is necessary promotes the well cementing and coating to provide a mechanical support, as well as, to isolate it from different rock formations traversed. For this step to be successful, the drilling mud must be completely removed from the annular space, and this removal may be impaired in wells which have varying eccentricity along the tube. Due to high costs of correction transactions and loss of drilling time, it is crucial to predict the mud flow around the annular. The effects of this variation of the eccentricity have not been much discussed in the literature, and they may have great influence on the displacement of the mud in the annular space. As an initial phase of work, numerical simulations were performed to study the flow and the emergence of Taylor- Couette instabilities in a concentric annular section, in order to compare them with literature data. Numerical simulations were developed in annular periodic sections, concentric and eccentric (E = 0.5) in order to obtain average profiles of axial and tangential velocities using different turbulence models, aiming at a comparison of simulated results with experimental data from literature. Later, it was made an experimental study and simulation to assess the effect of internal axis rotation on the pressure drop in the flow of non-Newtonian fluids (aqueous solutions of xanthan gum and carboxymethyl cellulose with 0.2% by weight) in a section annular concentric and the other with fixed eccentricity (E = 0.75). Finally, it was elaborated an experimental design (3k) with four variables, such as, xanthan gum concentration (0.05%, 0.10% and 0.15% by weight), eccentricity (0.0, 0.23 and 0.46), fluid flow rate (5, 7 and 9 m3/h) and internal rotation axis (0, 100 and 200 rpm). Following this planning, experimental data of pressure drop were collected, as well as, numerical simulations (CFD) in periodic annular sections to get results of axial velocity, in order to evaluate the effect of variable eccentric rotation on the fluid dynamics of non-Newtonian flows in annular spaces.
A crescente atividade de extração de petróleo e gás em águas cada vez mais profundas tem impulsionando diversos estudos para solucionar problemas encontrados na perfuração de poços. Durante a operação de perfuração, um fluido (lama de perfuração) é bombeado através da coluna até o fundo do poço, retornando à superfície carreando os cascalhos gerados pela broca, passando pelo espaço anular formado entre a coluna e a parede do poço. Neste tipo de escoamento pode ocorrer um tipo de instabilidade hidrodinâmica caracterizada pelo aparecimento de vórtices toroidais. Este tipo de instabilidade (Taylor-Couette), pode alterar profundamente a perda de carga do escoamento, a tensão cisalhante na parede do poço e a capacidade de carreamento de cascalho. Além disto, durante o processo de perfuração de um poço é necessário promover o revestimento e a cimentação do poço para fornecer a sua sustentação mecânica, bem como, para isolá-lo das diferentes formações rochosas atravessadas. Para esta etapa ser bem sucedida, a lama de perfuração deve ser completamente removida do anular, sendo que, esta remoção pode ser prejudicada em poços que apresentem excentricidade variando ao longo do tubo. Devido aos altos custos das operações de correção e a perda de tempo de perfuração, é fundamental prever este deslocamento da lama ao redor do anular. Os efeitos desta variação da excentricidade ainda não foram muito abordados na literatura e podem apresentar grande influência no deslocamento da lama no espaço anular. Como etapa inicial do trabalho, foram realizadas simulações numéricas para estudar o escoamento com surgimento de instabilidades do tipo Taylor-Couette em uma seção anular concêntrica, com intuito de compará-las com trabalhos da literatura. Depois foram desenvolvidas simulações numéricas em seções anulares periódicas, concêntrica e excêntrica (E = 0,5), a fim de obter perfis médios de velocidades axial e tangencial usando diferentes modelos de turbulência, visando uma comparação dos resultados simulados com os dados experimentais da literatura. Posteriormente, foi feito um estudo experimental e de simulação para avaliar o efeito da rotação do eixo interno sobre a queda de pressão no escoamento de fluidos não-Newtonianos (soluções aquosas de Goma Xantana e de Carboximetilcelulose a 0,2% em peso) numa seção anular concêntrica e outra com excentricidade fixa (E = 0,75). Finalmente, elaborou-se um planejamento fatorial de experimentos do tipo 3k com quatro variáveis, tais como, concentração de Goma Xantana (0,05%, 0,10% e 0,15%), excentricidade (0,0; 0,23 e 0,46), vazão volumétrica (5, 7 e 9 m3/h) e rotação do eixo interno (0, 100 e 200 rpm). Seguindo este planejamento foram levantados dados experimentais de queda de pressão, bem como, simulações numéricas (CFD) em seções periódicas para obtenção de resultados de velocidade axial, com intuito de avaliar efeito do movimento de rotação excêntrica variável sobre a dinâmica do escoamento de fluidos não-Newtonianos em espaços anulares.
Doutor em Engenharia Química

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Ferreira, Tales Adriano. "Avaliação numérica e experimental de um veículo de competição de milhagem." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/3/3150/tde-20072011-090936/.

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Dentre as competições nas quais estudantes são desafiados a construir protótipos com finalidades específicas, está a de fazer um veículo que transporte uma pessoa e percorrera a maior distância com um litro de combustível. Um dos fatores que contribuem para o consumo é a resistência aerodinâmica, assim prever seus efeitos é essencial para um bom projeto. Nesse contexto o presente trabalho teve por objetivo avaliar de forma numérica e experimental o escoamento ao redor de um veículo de milhagem e calcular os coeficientes aerodinâmicos de arrasto e sustentação dessas duas formas. Também foi estudada a sensibilidade desses coeficientes ao número de Reynolds e, no caso do teste virtual, aos modelos de turbulência. Através dos resultados de simulações verificou-se que a porção frontal do veículo é a maior responsável pelo arrasto e pela sustentação negativa. Os coeficientes de arrasto caíram com o aumento do número de Reynolds tanto nos ensaios virtuais quanto nos experimentais. Na comparação entre os modelos de turbulência, k-E e k-w em suas formas padrão foram os que mais destoaram em relação aos outros apresentando valores de CD maiores. Os resultados experimentais apresentaram a mesma tendência dos numéricos, e ficaram mais próximos do k- padrão, mas acredita-se que um ângulo de ataque negativo do modelo devido à montagem tenha provocado um aumento no CD obtido experimentalmente. Os valores dos coeficientes de sustentação baixaram com o número de Reynolds nos testes numéricos e aumentaram nos ensaios experimentais. Nas simulações observou-se que a alta velocidade entre as rodas dianteiras devido à pequena distância entre o veículo e o piso era responsável por boa parte da sustentação negativa. Por questões de montagem não foi possível repetir esse efeito solo de forma similar nos experimentos. Os resultados numéricos de visualização do escoamento apresentaram boa concordância com os experimentais.
Among the many competitions in which students are challenged to build up prototypes with specific purposes there, is one in which the goal is to design a car to carry one person and make it go as long as it can with one liter of fuel. One of the factors that contribute for fuel consumption is the aerodynamic resistance, so to predict its effects is essential for a good design. In this context, the present work had as goals the numerical and experimental evaluation of flow around a Supermileage vehicle and to calculate its drag and lift coefficients in these both ways. It was also studied the sensitivity of these forces to Reynolds number and, in the virtual case, to turbulence models. Thanks to simulation results it was verified that the front part of the model is responsible for great part of drag and negative lift. The drag coefficients fell with the increase of Reynolds number in both numerical and experimental tests. In a comparison of turbulence models comparison, k-E and k-w in their standard forms presented higher CD values than the other models. Experimental CD results showed the same tendency of numerical ones, and were closer to standard k-, although it was believed that a negative angle of attack due to experimental assembly issues has made for a higher experimental CD. Lift coefficients values fell with the increase of Reynolds number in virtual analysis and grew in experimental tests. In the simulations it was observed that the high velocity between the two front wheels, due to the short distance between the vehicle and the ground, is responsible for a large portion of the negative lift. Owing to assembly issues it was not possible to reproduce this ground effect on experimental tests. Flow visualization results presented good agreement between experimental and numerical testing.

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Nasro-Allah, Youssef. "Experimental and numerical investigation of electrostatic effects in gas-solid fluidized beds." Thesis, Toulouse, INPT, 2019. http://www.theses.fr/2019INPT0136.

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Les lits fluidisés gaz-solides sont largement utilisés dans les procédés industriels pour l'énergie tels que la combustion, la polymérisation, les récepteurs solaires, la gazéification de la biomasse et le raffinage du pétrole. Dans ces procédés, les forces électrostatiques ont été généralement négligées. Cependant, le phénomène présente des problèmes majeurs tels que l'encrassement des murs, la défluidisation, les étincelles, les explosions de poussière et parfois des incendies. A l'échelle moléculaire, le contact entre deux particules génère un transfert d'électrons/ions, induisant une charge sur chaque particule. Par conséquent, le gaz environnant transporte un champ électrique, ce qui produit une force supplémentaire connue sous le nom de force de Lorentz. Le phénomène dépend des propriétés des matériaux et les conditions opératoires. Plusieurs travaux dans la littérature ont étudié l'effet de chaque paramètre. Cependant, il y a un manque d'étude combinant à la fois des mesures expérimentales et la modélisation théorique avec des simulations numériques. La présente étude s'inscrit donc dans ce contexte. Elle fait partie de la Chaire d'attractivité BIREM (BIological, REacting, Multiphase flows) attribuée au Professeur Rodney Fox, soutenue financièrement par l'Université de Toulouse, dans le cadre du programme de recherche IDEX. Le projet est hébergé par la Fédération de recherche FERMaT. Dans ce travail, des expériences ont été réalisées sur différentes distributions granulométriques, différents matériaux et différentes conditions opératoires. Le dispositif expérimental, conçu et réalisé lors de cette thèse, consiste en une colonne en plexiglas de 1 m de hauteur et 0,1 m de diamètre. La technique de mesure utilisée est une coupe de Faraday reliée à un électromètre. Les résultats montrent deux catégories de particules : les "dropped" particules qui tombent immédiatement après l'ouverture de la vanne et les "wall" particules qui collent à la paroi. Les résultats ne montrent aucun effet de l'humidité relative sur la vitesse minimale de fluidization (Umf). L'évolution de la charge nette du lit en fonction du temps de fluidisation a montré une tendance exponentielle qui atteint une valeur d'équilibre pour les deux catégories. Les "wall" ont été chargées de 250 à 450 fois plus que les "dropped". La charge diminue en augmentant l'humidité relative. Les petites particules ont présenté une charge positive alors que toutes les autres distributions étaient chargées négativement. La charge d'équilibre des "dropped" n'a pas été influencée par l'augmentation de la vitesse alors que le temps d'équilibre a été légèrement augmenté. La charge d'équilibre des "wall" a été significativement augmentée. D'autre part, le travail numérique a modélisé la force de Lorentz dans une approche eulérienne. Les simulations ont été réalisées avec NEPTUNE_CFD. Les murs étaient supposés mis à la terre. Le modèle a été validé sur plusieurs cas de test. Par la suite, un modèle de tribélectrification (génération de charge) a été développé dans une approche eulérienne en s'inspirant d'analogie avec des modèles dans la littérature. Les conditions aux limites ont été élaborées en utilisant des hypothèses moins restrictives. Une estimation des temps caractéristiques de génération et de diffusion des charges a été réalisée, montrant que l'échelle de temps est très élevée (plusieurs jours) et ne correspond pas aux résultats expérimentaux (15 à 20 min). Un coefficient correcteur a été proposé pour être en accord aux résultats expérimentaux. De plus, des simulations numériques sur un lit fluidisé ont été réalisées. Le régime permanent a été considéré atteint et la charge d'équilibre a été imposée sur les particules. Les simulations visaient à comparer le cas sans et avec charge. L'effet de la charge sur les propriétés d'écoulement a été mis en évidence. Ces résultats ont mis en évidence l'effet crucial de l'électrostatique sur la suspension fluidisée gaz-particules
Gas-solid fluidized beds are widely used in industrial processes for energy such as chemical looping combustion, catalytic polymerization, solar receiver, biomass gasification and petroleum refinery. In all these processes, electrostatic forces were usually neglected. In polyolefin industry, the phenomena of electrostatic charges presents a major issues including wall fouling. At a molecular scale, the contact between two particles generates a transfer of electrons/ions, inducing a charge on each particle. As a result, the surrounding gas carries an electric field, resulting in an additional force to the momentum equation known as Lorentz force. The phenomenon depend on many parameters, including materials properties and operating conditions. Several works in literature studied the effect of each parameter. However, there is a lack of research projects which combine both experimental study and theoretical modelling with numerical simulation. Thus, this study falls within the context. It is a part of the Attractivity Chair BIREM (BIological, REacting, Multiphase flows) attributed to Professor Rodney Fox, financially supported by the University of Toulouse, in the framework of the IDEX research program. The project is hosted by the research federation FERMaT. The study aims to combine both experimental study in a lab-scale pilot and the numerical modelling in order to represent the electrostatic force in CFD code through the Euler-Euler formalism. In this work, experiments were performed on different particles size distributions, different materials and different operating conditions. The experimental setup, designed and built during the PhD thesis, consisted of a 1 m height and 0.1 m inner diameter plexiglass column. The measuring technique used for charge is a Faraday cup connected to an electrometer. Results shows two categories of particles: dropped particles that falls immediately after opening the valve and wall particles that stick to the wall. Results show no effect of relative humidity on minimum fluidization velocity (Umf). The evolution of the net charge versus fluidization time showed an exponential trend that reached an equilibrium value for both categories. Wall particles were charged 250 to 450 times than dropped ones. The net charge was decreased by increasing relative humidity. Small particles showed a positive charge whereas all other PSDs were negatively charged. The equilibrium charge of dropped particles did not show significant changes when increasing gas velocity whereas the time needed to reach equilibrium was slightly increased. Wall particles equilibrium charge was significantly increased. On the other hand, the numerical work built an electrostatic model for the Lorentz force in an Eulerian approach. Simulations were carried out with a software called NEPTUNE_CFD. The walls were assumed to be grounded. The model was tested with several test cases. After that, a tribocharging model was developed to take into account the charge generation and transfer. The model was inspired from previous works and transposed into an Eulerian approach. The wall boundary conditions were developed in this study by using less restrictive hypothesis. An estimation of the characteristic times of both charge generation and diffusion was performed, showing that the timescale is very high (several days) and does not match with experimental findings (15 to 20 min). A corrective coefficient was proposed to match with experimental results. Moreover, numerical simulations on a fluidized bed with the same dimensions as the experimental pilot were carried out. In these simulations, the permanent regime was considered. The equilibrium charge was prescribed on the particles. Simulations aimed to compare the no-charge case and the charged case. The effect of the charge on the flow properties were highlighted. These results pointed out the crucial effect of the electrostatic on the gas-particle fluidized suspension

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Vazquez, Numez Bernardo. "An experimental and numerical study of forced convection in ventilated chambers." Thesis, King's College London (University of London), 1997. https://kclpure.kcl.ac.uk/portal/en/theses/an-experimental-and-numerical-study-of-forced-convection-in-ventilated-chambers(5525a851-2a87-4a65-9669-d7098efd28ac).html.

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20

Wang, Zhida. "Experimental and CFD Investigations of the Megane Multi-box Bridge Deck Aerodynamic Characteristics." Thesis, Université d'Ottawa / University of Ottawa, 2015. http://hdl.handle.net/10393/32209.

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The shape of bridge deck sections used for long-span suspension bridges has evolved through the years, from the compact box deck girders, to twin box and multi-box decks sections, which proved to have better aerodynamic behaviour, and to bring economic advantages on the construction material usage side. This thesis presents a study of a new type of multi-box bridge deck for the Megane Bridge, consisting of two side decks for traffic lanes, and two middle decks for railway traffic, connected using stabilizing beams. Aerodynamic static force coefficient measurements were performed on a section model with a scale of 1:80, for Reynolds numbers up to 5.1 × 105 under angles of attack from -10° to 10°. Also there-dimensional CFD simulations were performed by employing a Large Eddy Simulation (LES) algorithm with a standard Smagorinsky subgrid-scale model, for Re = 9.3 × 107 and angles of attack 𝛼= -4°, -2°, 0°, 2° and 4°. The experimental and numerical results were compared with respect to accuracy, sensitivity, and practical suitability. Furthermore, the aerodynamic character for each individual decks including static coefficients, wind flow pattern and pressure distribution were studied through CFD simulation. ILS (Iterative Least Squares) method was applied to extract the flutter derivatives of Megane section model based on the results obtained from free vibration tests for evaluating the flutter stability. A comparison of the flutter derivatives was carried out between bridges with different deck configurations and the results are included in this thesis.

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Sousa, Alves Joao. "Experimental and CFD Analysis of a Biplane Wells Turbine for Wave Energy Harnessing." Thesis, KTH, Mekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-124070.

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Several alternative ways of producing energy came up as the world took conscience of the finite availability of fossil fuels and the environmental consequences of its use and processing. Wave and tidal energy are among the so called green energies. Wave energy converters have been under research for the past two decades and yet there hasn’t been one technology that gathered everyone’s acceptance as being the most suitable one. The present work is focused on a self-rectifying turbine for wave energy harnessing. It’s a self-rectifying biplane Wells with an intermediate stator. The main goal is to evaluate the performance of such a turbine. Two different analyses were performed: experimental and computational. The experimental tests were made so that efficiency, velocity profiles and loss coefficients could be calculated. To do so scaled-down prototypes were built from scratch and tested experimentally. The 3D numerical analysis was possible by using a CFD commercial code: Fluent 6.3. Several simulations were performed for different flow coefficients. Three different degrees of mesh refinement were applied and k-ε turbulence model was the one chosen to simulate the viscous behavior of the flow through the turbine. A steady-state analysis is due and two mixing planes were used at the interfaces between the rotors and the stator. In the end comparisons are made between the experimental and numerical results

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Abdulkadir, Mukhtar. "Experimental and computational fluid dynamics (CFD) studies of gas-liquid flow in bends." Thesis, University of Nottingham, 2011. http://eprints.nottingham.ac.uk/12218/.

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Within the oil industry there is a need to measure and predict the form of the multiphase liquid and gas flows that are present within oil production and processing pipelines. Knowledge of the flow regimes present allows the engineer to optimise the configuration of the pipeline and downstream processes to achieve the most, economic and reliable design. The applications of these technologies are collectively known as flow assurance. Within oil production systems, one component which has received little attention is the characterisation of the multiphase flow around bends under various process conditions. To predict the flow regimes in greater details requires the development of instrumentation that can measure and characterise the flow within the pipes. To circumvent this challenge, two experimental investigations were carried out in two rigs available in the Chemical and Environmental Engineering Laboratories at the University of Nottingham. These are: (1) a 67 mm internal diameter pipe joined to a 90o bend, in which air/silicone oil flows were investigated using advanced instrumentation: Electrical Capacitance Tomography (ECT), Wire Mesh Sensor Tomography (WMS), and high-speed video. The first two provide time and cross-sectionally resolved data on void fraction. The ECT probes were mounted 10 diameters upstream of the bend whilst the WMS was positioned either immediately upstream or immediately downstream of the bend. The downstream pipe was maintained horizontal whilst the upstream pipe was mounted either vertically or horizontally. The bend (R/D = 2.3) was made of transparent acrylic resin. The superficial velocities of the air ranged from 0.05 to 4.73 ms-1 and for the silicone oil from 0.05 to 0.38 ms-1. (2) a 127 mm internal diameter riser joined to a vertical 180o bend, in which measurements of film fraction and liquid film thickness distribution for an air-water system were obtained using the electrical conductance technique. The former was measured using the ring conductance probes placed 17 and 21 diameters, respectively upstream and downstream of the bend, 45o, 90o and 135o within the bend. The latter were obtained using pin and parallel wire probes. The pin probes were used for thin films measurement whilst the parallel wire probes for thick films. The bend, made of transparent acrylic resin, has a curvature ratio (R/D = 3). The superficial velocities of the air ranged from 3.5 to 16.1 ms-1 and for the water from 0.02 to 0.2 ms-1. The experimental results for the 90o bend study reveal that bubble/spherical cap bubble, slug, unstable slug and churn flows were observed before the bend for the vertical pipe and plug, slug, stratified wavy and annular flows when the pipe was horizontal. Bubble, stratified wavy, slug, semi-annular and annular flows are seen after the bend for the vertical 90o bend, the flow patterns remained the same as before the horizontal 90o bend. These results were confirmed by the high-speed videos taken around the bend. For the vertical 180o return bend, the average film fraction was identified to be higher in straight pipes than in bends. For low liquid and higher gas flow rates, due to the action of gravity drainage, film breakdown occurs at the 45o bend. A previously proposed criterion, to determine stratification after the 90o bend, based on a modified Froude number have been shown to be valid for a liquid different from that tested in the original paper. Similarly, for the 180o return bend, the condition for which the liquid goes either to the inside or outside of the bend are identified based on published material. Variations between average liquid film thickness and bend angles are reported for the vertical 180o bend. Contrary to the conclusions reached by Hills (1973) and Anderson and Hills (1974), the liquid film thickness becomes annular flow in the 180o bend at low liquid flow rates and stratified flow at higher liquid superficial velocities. In addition, a CFD code has been used to successfully model the hydrodynamics of the slug flow pattern in a riser and vertical 90o bend, using the Volume of Fluid model based on the Eulerian approach, implemented in the commercial CFD package Star-CCM+. The modelling results are validated with the experiments and also provide more detailed information on the flow such as the velocity field.

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Skirpan, Zachary. "Multiphase CFD benchmark of experimental critical heat flux data at PWR operating conditions." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127300.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Nuclear Science and Engineering, May, 2020
Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 85-89).
Critical Heat Flux (CHF) in flow boiling represents the fundamental upper limit for thermal hydraulic performance of PWR fuel. Currently, the nuclear industry relies on expensive, prototypical experiments using electrically heated, full-height rod assemblies to determine the limit of the boiling crisis. The development of next-generation Multiphase Computational Fluid Dynamics (M-CFD) approaches for the prediction of CHF seeks to represent the detailed physics of the boiling process up to its critical condition, rather than estimating it from ad-hoc thresholds. In this work we evaluate the advancement in M-CFD boiling attained by the Consortium for Advanced Simulation of Light water reactors (CASL). The CASL approach builds off an industry-lab-university collaboration with individual validation of interfacial momentum closures and wall boiling models.
The M-CFD simulations were implemented in the commercially available STAR-CCM+ software, and benchmarked against experimental observations of CHF collected at the University of Wisconsin by Duarte. In this work, 15 M-CFD simulations were completed. Boiling curves were generated for each test case. The modelled boiling characteristics were then compared to expected physical parameters to determine model accuracy. Structural spacers are the main driver of vapor accumulations leading to the breakdown of boiling heat transfer at CHF. Interestingly, M-CFD solutions indicate that the Departure from Nucleate Boiling (DNB) first occurs in areas not measured by the experimental thermal couples used to detect CHF, possibly resulting in a late experimental detection. Additionally, sensitivity studies are conducted for relevant model terms to understand their impact on CHF.
Leveraging the results from this sensitivity study, it is suggested that improved predictions could 1) increase the turbulent dispersion at the wall to account for turbulence under-prediction and 2) increase the minimum bubble size limiter to reflect physically observed coalesced bubble sizes after departure. For future work, higher spatial resolution measurements for detecting DNB are suggested for better experimental CHF predictions. A fully mechanistic approach for modeling the heat flux partitioning and subsequent wall boiling in M-CFD is also needed to more effectively simulate the proper heat transfer mechanisms and boiling physics before CHF. It is the hope that through this work and further M-CFD heat transfer investigations that similar methods may be validated for CHF detection and streamline the fuel design process in the nuclear industry.
by Zachary Skirpan.
S.M.
S.M. Massachusetts Institute of Technology, Department of Nuclear Science and Engineering

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Santolini, Enrica <1989&gt. "Study of ventilation strategies, in agricultural buildings through CFD modeling and experimental analysis." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/8852/1/tesi_dottorato_ES.pdf.

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Environmental control in agricultural and agro-industrial buildings is a very important and topical subject which falls within the domain of precision agriculture and smart food processing. There is a growing interest in the study of systems able to combine active and passive environmental control techniques and in the development of methodologies for modeling and simulating the environmental conditions in the agro-industrial sector. These ones need a process of validation and experimental calibration, but they can investigate specific aspects and variations of the thermo-fluidynamic phenomena involved in the control of environmental parameters. The computational fluid dynamic application (CFD) can give these opportunities and it has been used to study animal comfort in farms, distribution of temperature and humidity in greenhouses, to define structural improvement of greenhouses and to investigate effective ventilation strategies. This thesis is focused on the ventilation aspects in agricultural buildings, with the aim of considering improvement actions to optimize and act on airflow conditions in an experimental greenhouse and in a cellar, where climate control is extremely important. The natural ventilation of a glass greenhouse has been investigated with a particular focus on the effects of internal shading screens on the internal fluid-dynamic and on the crop growing conditions. A deep focus on the characterization of this type of screens has been carried out, with the aim of identifying applicable methodologies for this purpose. Finally, a smart system has been created to be placed in a cellar, for the improvement of the air flows around the barrels, which would thus prevent the molds formation and avoid air stagnation areas. Different configurations have been analyzed to identify the optimal design of the system. In conclusion, CFD approach has allowed to reach conclusions on possible decisions or strategies to improve the ventilation for improving the production and food quality conditions.

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25

Marineau, Eric Christian. "Computational and Experimental Investigation of Supersonic Convection over a Laser Heated Target." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/27919.

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This research concerns the development and validation of simulation of the beam-target interaction to determine the target temperature distribution as a function of time for a given target geometry, surface radiation intensity and free stream flow condition. The effect of a turbulent supersonic flow was investigated both numerically and experimentally. Experiments were in the Virginia Tech supersonic wind tunnel with a Mach 4 nozzle, ambient total temperature, total pressure of 160 psi and Reynolds number of 5 × 10⁷/m . The target consisted of a 6.35 mm stainless steel plate painted flat black. The target was irradiated with a 300 Watt continuous beam Ytterbium fiber laser generating a 4 mm Gaussian beam at 1.08 micron 10 cm from the leading edge where a 4 mm turbulent boundary layer prevailed. An absorbed laser power of 65, 81, 101, 120 Watts was used leading to a maximum heat flux between 1035 to 1910 W/cm². The target surface and backside temperature was measured using a mid-wave infrared camera. The backside temperature was also measured using eight type-K thermocouples. Two tests are made, one with the flow-on and the other with the flow-off. For the flow-on case, the laser is turned on after the tunnel starts and the flow reaches a steady state. For the flow-off case, the plate is heated at the same power but without the supersonic flow. The cooling effect is seen by subtracting the flow-off temperature from the flow-on temperature. This temperature subtraction is useful in cancelling the bias errors such that the overall uncertainty is significantly reduced. A new conjugate heat transfer algorithm was implemented in the GASP solver and validated by predicting the temperature distribution inside a cooled nozzle wall. The conjugate heat transfer algorithm was used to simulate the experiments at 81 and 65 Watts. Most computations were performed using the Spalart-Allmaras turbulence model on a 280, 320 cell grid. A grid convergence study was performed. At 65 Watts, good agreement was found in the predicted surface and backside temperature. On the surface, cooling was underpredicted close to the center and better agreement was seen away form the center. On the backside, good agreement was found for the temperature and temperature difference. Compared to the 65 Watt case, the 81 Watt case displays more asymmetry and a region of increased cooling is found upstream. The increased asymmetry was also seen on the backside by both the thermocouple and infrared temperature measurements. The computation underpredicts the surface temperature by 7% for the flow-off case. Again, cooling is underpredicted at the surface near the center. For all power settings, convective cooling significantly increases the time required to reach a given temperature.
Ph. D.

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Silva, Marcela Kotsuka da. "Estudo numérico e experimental de uma coluna de bolhas operando em regime heterogêneo." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266911.

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Orientadores: Milton Mori, Marcos Akira d'Avila
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: Os principais problemas da simulação da fluidodinâmica em sistemas gás-líquido por CFD são as simplificações do comportamento dinâmico das bolhas. Na maioria dos processos industriais com escoamento gás-líquido em colunas de bolhas, as bolhas estão em velocidades altas e a coluna opera em regime heterogêneo. Existe ainda a influência da geometria do sistema e das propriedades físicas dos fluídos envolvidos no processo. Para que a técnica CFD seja aplicada adequadamente, visando aplicações industriais, é necessário considerar os fenômenos de quebra e coalescência. No entanto, existe uma carência de dados experimentais em tal regime de operação para testar a aplicabilidade dos modelos matemáticos empregados nas simulações. Neste trabalho é apresentado um estudo numérico e experimental de duas colunas de bolhas operando em regime heterogêneo. No primeiro caso, foram realizadas análises quanto a influência de diferentes modelos de arraste, além do emprego das forças interfaciais de sustentação e de dispersão turbulenta. Diferentes modelos de turbulência foram também verificados, tomando a fração volumétrica de gás em diferentes posições axiais e velocidade do gás provenientes da literatura. No segundo caso, realizou-se medidas por meio da técnica PIV de velocidades axiais médias da fase líquida e suas flutuações. Análises de intensidade turbulenta, tensores de Reynolds e energia sindética turbulenta foram realizadas, a fim de obter informações acerca da turbulência em três diferentes velocidades superficiais de gás. Para as análises numéricas foi aplicado um modelo matemático tridimensional, turbulento e transiente para a representação do escoamento nas duas colunas utilizadas. Este modelo trata ambas as fases, gás e líquido, a partir de uma abordagem Euleriana. Diferentes distribuições de tamanhos de bolhas foram empregados por meio do balanço populacional considerando os fenômenos de quebra e coalescência. Perfis radiais de fração volumétrica e velocidade de gás, além de perfis de velocidade média de líquido foram confrontados com dados experimentais publicados e medidos respectivamente. O modelo matemático previu um escoamento semelhante aos que foram encontrados nas colunas propostas
Abstract: The main problems encountered in the simulation of gas-liquid systems with the use of CFD are related to the simplifications of the bubble dynamic behavior. In most industrial procedures with gas-liquid flown in bubble columns, bubbles are at high speed and the column operates in the heterogeneous regime. There still is the influence of the system's geometry and fluids physical properties involved in the process. For correctly applying the CFD technique, aiming industrial applications, it is necessary to consider the breakup and coalescence phenomena. Nevertheless, there is a lack of experimental data available in this operational regimen to test the feasible application of the mathematical models used in simulations. In this work it is presented a numeric and experimental study of two bubble columns operating in the heterogeneous regime. In the first case, analyses of different drag models, besides the employ of the interfacial forces of lift and turbulent dispersion were performed. Different turbulence models were also verified, taking the gas holdup in different axial positions and gas velocity from literature. In the second case, measurements of mean axial liquid velocities and their fluctuations were performed with the PIV technique. Turbulence intensity, Reynolds stress tensors and turbulent kinetics energy analyses were performed in order to obtain information about the turbulence for three different gas superficial velocities. For the numerical analyses a tridimensional, turbulent and transient mathematical model to represent the flow in the two columns was applied. This model treats both phases, gas and liquid, with an Eulerian approach. Different bubbles size distributions were used by population balance considering the breakup and coalescence phenomena. Gas holdup, gas velocity and mean axial liquid velocity radial profiles were confronted to the published and acquired experimental data respectively. The mathematical model predicted a developed flow similar to those found in the proposed columns
Doutorado
Desenvolvimento de Processos Químicos
Doutor em Engenharia Química

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27

Sagerman, Denton Gregory. "Hypersonic Experimental Aero-thermal Capability Study Through Multilevel Fidelity Computational Fluid Dynamics." University of Dayton / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1499433256220438.

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28

Afolabi, Eyitayo Amos. "Experimental investigation and CFD simulation of multiphase flow in a three phase pipe separator." Thesis, University of Newcastle Upon Tyne, 2012. http://hdl.handle.net/10443/1756.

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This thesis describes an experimental study and CFD simulation of the hydrodynamic behaviour of multiphase flow in a 30mm pipe separator. Stereoscopic particle image velocimetry (SPIV) technique was used for three-dimensional velocity measurements of water and air water flows in a pipe separator. The instantaneous and time averaged whole field velocities at three dimensional axial positions were recorded and velocity profiles across the diameter of the pipe separator extracted. Three-phase flow experiments were then conducted to determine the separation efficiency of the air-water-oil flow in a pipe separator. Numerical simulation of the single and multiphase flow behaviour within the separator was then performed through the commercially available CFD software ANSYS FLUENT.

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Ochieng, A., MS Onyango, and KH Kiriamiti. "CFD simulation and experimental measurement of nickel solids concentration distribution in a stirred tank." The Journal of The Southern African Institute of Mining and Metallurgy, 2010. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001926.

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Synopsis Solids suspension influences the quality of mixing and energy requirement in a solid-liquid system, both of which determine the efficiency of industrial processes such as nickel precipitation. Nickel solids concentration distribution in a stirred tank was investigated using computational fluid dynamics (CFD) and experimental methods. The concentration distribution of the nickel solids was compared with that of sand and glass. The laser Doppler velocimetry (LDV) method was used to measure the velocity field for the liquid-only system and an optical technique was employed to determine the axial solids concentration distribution. Regions of inhomogeneity in the tank were identified. It was found that, for a given solids loading, the solids concentration distribution depended on both particle size and particle size distribution. High solids loadings were investigated and a difference in the concentration distribution pattern was obtained with nickel, flint glass and sand particles. The CFD simulation results highlighted problems that could be associated with some conventional experimental methods of determining solids concentration distribution in a stirred tank.

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30

Chowdhury, Mohammed Gofran. "Experimental validation of CFD model predicting wind effects on inclined-roof mounted photovoltaic modules." Thesis, KTH, Energiteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-201033.

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I detta arbete, utvecklades flera CFD modeller för att identifiera och karakterisera el produktion från solceller med hänsyn till instrålning nivån och yttemperaturen. De genoförda experimentella arbete tyder på att när PV-modulen utsätts för väder och vind sker signifikanta förändringar av temperaturen på modulens yta. Förhållandet mellan vindströmningsfältet kring modulen i relation till förändringar i luftspalten samt takkonstruktionens utformning har inte studerats i detalj tidigare. I alla relevanta studier ansågs temperaturen på PV-ytorna vara konstanta. Men i självaverket varieras yttemperaturen och värmeöverföringsgraden beroende på vindströmningsförhållandena kring PV-ytan. Ytterligare förändringar i luftströmmen uppstår i samband med olika luftspalter och olika lutningar på takstrukturen.I den här uppsatsen modellerades vindströmmen med hjälp av en CFD på och kring PV-ytan. Experimenten genomfördes i specialbyggda vindtunnlar med lutande takuppsättningar där en fotovoltisk anordning (BAPV) sattes upp för att validera modellen. En tillfredsställande överensstämmelse observerades när data jämfördes med simulerings Datat.Reynolds Averages Navier Stokes med fasta tillståndslösare användes för att simulera en 3D-geometrisk modell av en BAPV-modul med ett stadigt inloppstillstånd. Denna studie undersöker vindströmningsfältet kring och nära modulens ytor. Vindflödeshastigheten (1-5 [m/s] och luftspalten under modulen (3,5;5,5 [cm]) varierades under studien. Dessutom, senare i denna uppsats studeras effekten av olika lutande takkonstruktioner med 3 olika geometrier. Resultatet visar signifikant känslighet i vindströmningsfältet på grund av små förändringar i lutningen av takkonstruktionen.
Different models have been developed to identify and characterize photovoltaic system output with regards to irradiation and temperature. Experimental investigation suggests that when PV module is subjected to wind then the temperature differences on the module surfaces shows significant changes. The relation of wind flow field around the module in respect to the changing air gap and detailed roof structure was never studied in detail. In all of relevant studies, temperature of the PV surfaces was regarded as constant, whereas both the temperature and heat transfer rate on the module surfaces are variable with respect to positions on the module affected by wind flow conditions. Further changes in air flow occur when subjected to different air gap and different inclined roof structure. In this thesis the wind flow modelling was constructed with CFD. Experiments were performed on purpose built wind tunnel with the inclined roof setup of inclined building applied photo voltaic setup (BAPV) to validate the modelling. A satisfactory agreement was observed while comparing with simulation data and experimental results. Reynolds Averaged Navier Stokes with steady state solver was used to simulate a 3D geometric model of a BAPV module with the steady inlet condition. This study investigates wind flow field around and on near surfaces of the module. Wind flow velocity (1-5 [m/s]) and gap underneath the module (3.5,5.5 [cm]) was varied to study. Moreover, later in this thesis the impact of the different inclined roof structure was also studied with 3 different geometries. The result shows significant sensitivities of wind flow field due to small changes of inclined roof structure.

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31

Liu, Ying. "Computational and experimental investigation of turbulent mixing in multiscale reactors for CFD model validation." [Ames, Iowa : Iowa State University], 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3383368.

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32

Rezende, Hugo Cesar. "Estudo teórico e experimental da estratificação térmica : monofásica em tubulações horizontais." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266765.

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Orientadores: Elizabete Jordão, Moysés Alberto Navarro
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: O escoamento monofásico termicamente estratificado ocorre em tubulações horizontais onde duas camadas diferentes de um mesmo líquido escoam separadamente, sem que ocorra mistura significativa entre as camadas, devido às baixas velocidades e à diferença de densidade (e temperatura). As consequências desse fenômeno não foram consideradas no projeto da maioria das centrais nucleares atualmente em operação. Entretanto, em alguns componentes de centrais nucleares, as diferenças de temperatura podem atingir cerca de 200 °C em uma região bastante estreita nas proximidades da interface entre as camadas de água fria e quente. Nesta condição, as fortes tensões geradas pelas diferenças de dilatação podem comprometer a integridade estrutural e a vida útil de tubulações relacionadas aos sistemas de segurança dessas centrais nucleares. Com o objetivo de estudar o fenômeno da estratificação foi projetada e construída a Instalação de Testes de Estratificação Térmica (ITET), tendo sido realizada uma série de experimentos simulando o bocal de injeção do gerador de vapor de uma central nuclear tipo PWR. Foram estudadas a evolução e as configurações de escoamento em regime de estratificação térmica, assim como a influência do número de Froude nos gradientes de temperatura, na posição da interface entre as camadas de água fria e de água quente e no aparecimento de oscilações desta interface. Os experimentos foram realizados com número de Froude variando de 0,02 a 0,4...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digital
Abstract: One phase thermally stratified flows occur when two different layers of the same liquid at different temperatures flow separately in horizontal pipes without appreciable mixing due to the low velocities and difference in density (and temperature). The phenomenon was not considered in the design stage of most of the operating nuclear power plants. However, temperature differences of about 200 °C have been found in a narrow band around the hot and cold water interface in components under stratified flows. Loadings due to this phenomenon affected the integrity of safety related piping systems. The Thermal Stratification Test Facility (ITET), built to allow the experimental simulation of the thermal stratification, is presented so as the results of some experiments simulating one phase thermally stratified flows in geometry and flow condition similar to a nuclear reactor steam generator nozzle. They have the objective of studying the flow configurations and understanding the evolution of the of thermal stratification process. The driving parameter considered to characterize flow under stratified regime due to difference in specific masses is the Froude number. Different Froude numbers, from 0.02 to 0.4, were obtained in different testes by setting injection cold water flow rates and hot water initial temperatures as planned in the test matrix. Results are presented showing the influence of Froude number on the hot and cold water interface position, temperature gradients and striping phenomenon...Note: The complete abstract is available with the full electronic document
Doutorado
Sistemas de Processos Quimicos e Informatica
Doutor em Engenharia Química

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33

Priyadarshi, Harsh. "Experimental and Numerical Study of Calcium Treatment of Steel." Thesis, Ecole centrale de Nantes, 2019. http://www.theses.fr/2019ECDN0017/document.

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Afin de réduire les effets nocifs des inclusions d'alumine et d'améliorer la coulabilité de l'acier en fusion, le traitement au calcium est largement utilisé pour transformer les inclusions solides en inclusions liquides. Cependant, le traitement au calcium donne des résultats très irréguliers, difficilement explicables. Même si de nombreux efforts ont été déployés pour comprendre le comportement du calcium dans l’acier liquide, il n’a pas encore été prédit avec précision. Par conséquent, le mécanisme par lequel le calcium se dissout dans la masse fondue et transforme les inclusions solides doit être compris pour optimiser les conditions de traitement tels que la vitesse d'injection, la profondeur d'injection, le diamètre du fil d'injection, le temps d'agitation, etc. Afin de comprendre le mécanisme par lequel le calcium se dissout dans l'acier liquide, des expériences en laboratoire ont été effectuées dans un petit four à induction d'une capacité de 2,5 kg de métal. L'objectif est de confronter les résultats expérimentaux avec les résultats du modèle numérique développé. La remontée des gouttelettes de calcium ou des bulles dans l’acier liquide est un problème à trois phases (gouttelettes ou bulles de calcium/acier liquide/air au sommet). Par conséquent, une plateforme de calcul scientifique interne (ICI-tech) basée sur des méthodes par éléments finis est adaptée pour permettre la modélisation de telles solutions. Les écoulements triphasiques sont validés à l’aide de références classiques issues de la littérature. Le modèle de dissolution a été mis en oeuvre dans notre logiciel et la validation du modèle de dissolution a été réalisée. Les gouttelettes et les bulles de calcium sont étudiées dans l’acier liquide et leur coefficient de transfert de masse moyen est indiqué. Afin d'étudier le changement de phase calcium liquide/gaz, un modèle de nucléation a été implémenté dans le code ICI-tech. Un test typique est effectué où la croissance d'une bulle (vapeur d'eau) dans une eau uniformément surchauffée et la croissance d'une bulle de calcium dans du calcium liquide uniformément surchauffé sont calculées
In order to diminish the harmful effects of aluminate inclusions and improve the castability of molten steel, calcium treatment is widely used in Aluminum killed steels. However, calcium treatment gives irregular results. Even with many efforts done to understand the behavior of calcium in liquid steel, it is not yet accurately predicted. Therefore, the mechanism by which the calcium dissolves into the liquid steel and transforms the solid inclusions must be understood to optimize the process conditions such as injection speed, injection depth, injection wire diameter, stirring time, etc. In order to understand the mechanism by which the calcium dissolves into the liquid steel, laboratory scale experiments have been performed in a small induction furnace of 2.5 kg metal capacity. The calcium injections are performed at the temperature below and above the boiling point of calcium. Then, the corresponding yields (calcium recovery) are compared. Rise of calcium droplet or bubble in liquid steel is a three-phase problem (calcium droplet or calcium bubble/liquid steel/air at the top). Therefore, an in-house scientific computational platform (ICI-tech) based on finite element methods is adapted to allow the modeling of such three-phase flows, which is validated using the classical benchmark issued from the literature. The dissolution model has been implemented in our software, and their validation has been performed. Thereafter, the rise of Calcium droplets and bubbles are studied in the liquid steel, and their respective average mass transfer coefficient in the liquid steel is reported. In order to study the calcium liquid/gas phase change, the nucleation model has been implemented in the code (ICI-tech). A typical test is performed where the growth of a bubble (water vapor) in uniformly superheated water and growth of a calcium bubble in uniformly superheated Ca liquid is computed

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Atkins, D. W. "The CFD assisted design and experimental testing of a wing-sail with high lift devices." Thesis, University of Salford, 1996. http://usir.salford.ac.uk/14811/.

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A wingsail is a solid symmetrical aerofoil section which creates thrust in the same manner as a conventional sail. Wingsails may either be used as a sole power unit, e. g. for a yacht or catamaran, or as an auxiliary power unit on a larger craft, e. g. fishing vessels, cargo ships or passenger liners. To augment the thrust created by the wingsail, high lift devices are employed to increase both the maximum lift and the stall incidence of the aerofoil. A wingsail must be symmetrical and capable of creating an equal lift force with the flow approaching the leading edge from either side of the wing centreline, i. e. the wingsail surface must act as either the upper, or lower pressure surface. Initial experimental work proved that using a symmetrical slat as a leading edge high lift device both delayed the separation of flow over the wingsail upper surface and increased the effective camber of the aerofoil. To increase the thrust created still further, this leading edge high lift device was combined with a trailing edge high lift device, a symmetrical single slotted flap. Due to the large number of possible model configurations, a commercially available CFD package was introduced to assist with the design. A series of validation tests comparing the CFD with published and experimental results showed a qualitative agreement with these results. However, the CFD predictions were not sufficiently accurate to be used quantitatively. The computationally designed triple element model was tested experimentally. Lift, drag, pitching moment and pressure distribution measurements were taken from the model. The results of this testing showed that the triple element wingsail increased the plain wing Coax by 68% and the stall incidence by between 4* and 6'. The final triple element wingsail design also increased the thrust of a plain wingsail over the whole operating region. Thrust was increased by up to 83% at the wind angles where a wingsail is most efficient. The results also proved that a commercially available CFD package can be used as an effective and time saving tool for wingsail design.

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Benzon, Shaun. "The Turgo impulse turbine : a CFD based approach to the design improvement with experimental validation." Thesis, Lancaster University, 2016. http://eprints.lancs.ac.uk/82918/.

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The use of Computational Fluid Dynamics (CFD) has become a well-established approach in the analysis and optimisation of impulse hydro turbines. Recent studies have shown that modern CFD tools combined with faster computing processors can be used to accurately simulate the operation of impulse turbine runners and injectors in timescales suitable for design optimisation studies and which correlate well with experimental results. This work has however focussed mainly on Pelton turbines and the use of CFD in the analysis and optimisation of Turgo turbines is still in its infancy, with no studies showing a complete simulation of a Turgo runner capturing the torque on the inside and outside blade surfaces and producing a reliable extrapolation of the torque and power at a given operating point. Although there have been some studies carried out in the past where injector geometries (similar for both Pelton and Turgo turbines) have been modified to improve their performance, there has been no thorough investigation of the basic injector design parameters and the influence they have on the injector performance. The aim of this research is to use modern CFD tools to develop models which aid the better understanding of Turgo impulse turbine runners and injectors and facilitate the optimisation of existing designs. CFD is used to model and optimise both the injectors and the runner of a modern commercial Turgo impulse turbine and the accuracy of the models are verified by carrying out experimental tests on the original and optimised designs. The original designs together with experience in the operation of these turbines were provided by the industrial sponsors of this research Gilbert Gilkes and Gordon Ltd. The research described in this thesis can be split into five main parts: 1.Development of a numerical model to analyses the flow through the Turgo runner using modern CFD tools combined with a series of assumptions to reduce the computational time while still retaining the accuracy of the model. Using this model to optimise the design of the Turgo runner provided by Gilkes. 2.Development of a similar numerical model for a simplified 2D injector design to facilitate a study of the impact of the basic design parameters on the performance over a range of operating conditions. Applying these optimisations to the existing Gilkes design and taking the numerical analysis further by including the full injector geometry as well as the branch pipe and guide vanes. 3.Manufacture and experimental testing of the original and optimised Turgo runners. 4.Manufacture and experimental testing of the original and optimised injector designs. 5.Verification of the numerical models developed in 1.) and 2.) by comparison with the experimental results. The numerical model developed in 1.) includes several simplifying assumptions in order to reduce the computational time and produce models which could solve in reasonable timescales allowing many design variations to be analysed. As the runner simulations require a transient analysis of complex multi-phase free surface flow with a rotating frame of reference they are already computationally costly and efforts have to be made to reduce this computational cost if the models are to be effective for optimisation purposes. The runner model simplifications were the exclusion of any casing interactions by not modelling the casing and the use of a 2 blade model analysing only a single blade passage in order to reduce the size of the computational domain. Several modelling assumptions were also introduced and attempts are made to quantify the effects of these assumptions through unit tests. For discretisation of the domain two mesh sizes were used, a coarse mesh which slightly under predicts the efficiency but was suitable for comparing designs and a fine mesh which gave mesh independent results. The fine mesh took over 4 times longer to solve rendering it unfeasible for optimisation purposes and it was therefore used only at key points to verify the design changes made using the coarse mesh. The analysis and optimisation of the injectors carried out in 2.) use similar CFD tools as the runner analysis however the geometry (excluding the branch pipe and guide vanes) could be simplified into a 2D axisymmetric case operating at steady state conditions. This drastically reduces the solve time and allows the use of a mesh independent model and the analysis of hundreds of designs and operating conditions. Once the optimisations had been carried out, the design changes were verified by extending the model to analyse the 3D case with a straight pipe upstream of the injector and a 3D full case including the branch pipe and guide vanes. In 3.), following the optimisation of the runner in 1.), a Finite Element Analysis (FEA) of the runner was carried out to ensure the optimised runner had sufficient strength for operation at the highest heads recommended for a runner of this size. The design was strengthened based on the results of the FEA and CFD was carried out in conjunction with these changes to ensure minimal loss in hydraulic efficiency. The manufacturing process was also researched and Design for Manufacture and Assembly (DFMA) was applied to the strengthened design identifying two optimised designs (LE4 and LE1) which will be tested before and after additional dressing of the leading edges. Both optimised runner designs were manufactured and tested at the Laboratory of Hydraulic Machines, National Technical University of Athens (NTUA). Following the injector analysis and optimisations in 2.), the optimised injectors were manufactured for experimental testing using both the Pelton and the Turgo test rig at NTUA in 4.). As the design changes made were not critical to the strength of the injectors there was no need to carry out a FEA. The CFD model verification in Part 5.) looks initially at the full Turgo system in order to compare the absolute difference between the numerical efficiency and the experimental efficiency of the original Turgo runner at the best efficiency point. The mechanical losses of the test rig are estimated to determine the experimental hydraulic efficiency. The numerical hydraulic efficiency is then determined by calculating the losses upstream of the injector, using standard pipe flow equations and combing these with the losses through the injector, as well as the numerical efficiency of the runner by simulating the runner using the ‘real jet’ profile produced by the full injector simulations. The results showed the numerical model to be over-predicting the efficiency by 1.26%. The numerical difference in the performance of the two injectors is then compared to the experimental difference measured during testing. This is done by importing the ‘real jet’ profiles produced by the full 3D injector simulations into the LE1 runner simulation. This allows the difference in total efficiency between the injectors combined with the runner to be compared to the experimental differences which also includes the impact of the jet on the runner performance. The comparison between the injectors is less accurate as more uncertainties are introduced when combining these models and the differences are smaller however the CFD was able to predict the improvements to within 0.4%. Finally, the numerical differences between the runner designs and the experimental differences are compared showing that the runner model is able to predict differences in hydraulic efficiency to within 0.1%. This accuracy is largely down to that fact that many of the systematic experimental and modelling errors are cancelled out when comparing only the runners.
The CFD model verification has shown that although the absolute performance of the Turgo system can be modelled numerically to within a good degree of accuracy, it requires combining injector and runner models as well as estimating additional losses in the pipework which can prove time consuming. However for design comparison and optimisations the CFD models have been shown to be far more accurate suggesting that this is where these numerical models are most useful.

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Jalili, Vahid. "Application of CFD in designing a drug delivery mixing chamber : an experimental and computational study." Thesis, University of Greenwich, 2004. http://gala.gre.ac.uk/6196/.

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The purpose of this novel research was to understand the flow behaviour and improve the efficiency of the Volumatic™ spacer, using a combination of engineering tools such as CFD, Laser Doppler Anemometry (LDA) and Row visualization techniques. The lack of information on the Volumatic /A/ spacer meant that, initial understanding had to be gained into the flow behaviour within the spacer. This was initially performed by injecting air carrying a tracer concentration to represent t li<^drug portion of the medicine. The efficiency (volume of drug collected at the mouth piece) was found to be about 6.5% which was in the same order as the figure quoted in the literature Chuffart A series of parametric studies were carried out to discover the effects of various parameters on The overall efficiency of the spacer. In the initial part a series of jet profiles were studied at the inlet, these were in the shape of straight, cone shape and spray jet profiles. It was concluded that the jet with a cone angle of 5° increased the efficiency of the spacer from G.5% to 9.4%. The next stage of parametric study involved reducing the length of the spacer from 0.24 m to 0.12 m and varying the inlet velocity from 40 m/s down to 10 m/s. The findings concluded that t in1 efficiency of the spacer could be increased to 23%, using a velocity of 40 m/s at inlet. The length was reduced from 0.12 m to 0.06 m and a similar study as described above was carried out. This time it was concluded that reducing the velocity to 30 m/s increased the efficiency to 30%. The other interesting feature to come out of this study was that the whole of tIk1 spacer volume was used, hence the drug was mixing better than in the original Volumatic /A/ spacer, where about one third of the spacer volume remained completely empty of the drug. The studies carried out so far had shown that the additional increase in drug delivery efficiency in the case of the Volumatic 7 A/ spacer, was not substantial enough to justify the considerable manufacturing costs which have to be met, if the Volumatic 7 A/ spacer was to be remanufactured in its improved design. The way forward seemed to be in the development of a new design. The new design had to be small enough, so that it could be carried around easily by patients, who do not use1 the current spacer due to its size. The new design had to be economical in terms of manufacture, simple to use and easy to clean. The reasons mentioned above and the current trend towards the tube type spacer designs, implied the logical approach would be to base the design on a similar geometry. A tube type spacer was modelled with two holes drilled directly opposite each other, a distance of 10 mm away from the pMDI's nozzle. The holes introduced a pressure difference, hence directing the drug towards the patient's airway system. The new spacer had a length of 0.1 m. The computational results showed that the efficiency had increased to 71% for this particular design. The CFD results obtained from the initial study on the Volumatic 7 M spacer were validated using LDA measurements. The velocities along four different locations were measured. At each location the velocities were measured at increments of 5 mm for a distance of 50 mm inside the spacer. The LDA results showed very good agreements with those obtained from CFD. The volume of data sampled experimentally at each point was 25,000 data points. This large volume of data eliminated any random sources of error, and as the CF D simulations were carried out some six months prior to LDA results, it was safe to assume that the drug had been modelled accurately. The same experimental set up was used to measure velocity values for the tube spacer, but in this instance, velocity measurements were made only along two planes, due to limited time and availability of the drug source. Finally laser light sheeting was used to illuminate the Volumatic T spacer and a high speed KODAK camera capable of capturing 4500 frames per second was used. The visualization study proved that there was a portion of the Volumatie /A/ spacer which at times was free of any drug. The originality of the work has been described in the following paragraph: Prior to this research there was no comprehensive study available combining engineering tools such as Computational Fluid Dynamics (CFD), Laser Doppler Anemoinetry (LDA) and High Speed Photography to study the (low pattern within the current Volumatic /A/ spacer design and hence analysing its efficiency. The studies carried out were of the impaction type. The results of this study have confirmed that there are several parameters contributing to the efficiency of the Volumatic' A/ spacer. This knowledge was not available in the open literature previously. The initial part of this study has provided a scientific approach to analysing the flow patterns, hence obtaining an accurate value for the efficiency of the current device. This part of the study alone is a valuable tool for industry, because it has given industry data which has not been previously available. The results from this study have indicated that, the Aero Chamber Spacer type design has an efficiency of 71% compared to the current 10% efficiency of the Volumatic 7 A/ spacer. The efficiencies discussed are measured in terms of the percentage of the drug delivered to the mouth piece. The benefit to industry would be saving at a conservative estimate in terms of millions of Pounds annually. This can be calculated from industry's own figures that, 1 out of every 5 new born baby suffers from asthma in various degrees. The drug is the most expensive component of the device, hence a more efficient device would use a lesser quantity of the drug. Finally the combination of techniques used, and the number of data samples taken for example in the case of LDA measurements some 25000 data samples were taken and averaged at each point, has ensured a high degree of accuracy and confidence in the results presented.

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Maciel, Liliane Fernandes. "Brise-chaminé-solar: avaliação experimental e por simulação CFD/EnergyPlus de um dispositivo de ventilação." Universidade Federal de Viçosa, 2016. http://www.locus.ufv.br/handle/123456789/8454.

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Eletrobrás
Dentre os múltiplos critérios a serem considerados na concepção do projeto de escolas, destaca-se o conforto ambiental por apresentar relação direta na eficácia do processo educativo. Esta pesquisa trata do desenvolvimento de um elemento arquitetônico e da avaliação de seu potencial de utilização em salas de aula. O objetivo deste trabalho consiste em conceber e avaliar o desempenho de um brise- chaminé-solar. Investigou-se o potencial de utilização de proteções solares sob a forma de chaminés solares para promover a ventilação natural. Soluções projetuais foram avaliadas parametricamente por meio de dois pacotes comerciais de simulação computacional, cujas potencialidades e fragilidades foram discutidas. Os resultados deste estudo constatam que os programas de simulação predial e de CFD (Dinâmica de Fluidos Computacional) apresentaram discrepâncias relevantes, de modo que se torna arriscada a tomada decisões projetuais com base em resultados de simulação não validados. Em seguida, discutiu-se de forma mais aprofundada a simulação CFD, incluindo os métodos de modelagem, medição in loco, e os desafios pertinentes à validação dos resultados obtidos com ferramentas de simulação CFD. Os dados reais indicaram que os resultados da simulação CFD foram válidos. Ressalta-se a importância da realização de testes para calibração. Por fim, avaliou-se o desempenho térmico e luminoso de uma sala de aula com brise-chaminé-solar. Identificou-se que o dispositivo foi capaz de reduzir a temperatura operativa da sala de aula, alterando os percentuais de horas em conforto térmico. Com relação à renovação de ar, o brise-chaminé-solar alcançou as taxas recomendadas para a qualidade do ar interior. O brise-chaminé-solar apresentou, ainda, capacidade de reduzir os níveis de desconforto por excesso de iluminação em salas de aula, especialmente sob condições de céu encoberto.
Among the multiple criteria to be considered during the design of scholar buildings, the environmental comfort can be highlighted because of its straight relation with the efficacy of the learning process. This research considers the development of an architectural element and evaluates its potential to be used in classrooms. This study aims to design and evaluate the performance of a shading- solar-chimney. It was investigated the potential use of shading devices under the shape of a solar chimney to promoting natural ventilation. Design solutions were parametrically evaluated using two commercial simulation software, for whose the strengths and weakness were discussed. The results showed that building simulation and CFD (Computational Fluid Dynamics) presented relevant discrepancies, in a way that the design decision based on non-validated simulation results might be risky. In addition, the CFD simulation was discussed in a deeper way, including the modeling methods, in loco measurements, challenges about the validation of the results achieved by CFD simulation tools. The measured data indicated that the CFD results are valid. It is emphasized the importance of the calibration tests. Finally, the thermal and lighting performance of a classroom with the shading-solar-chimney was evaluated. It was identified that the shading-solar-chimney was able to reduce the classroom operative temperature and it changed the percentage of hours in thermal comfort. About the air changes, the shading-solar-chimney achieved the recommended rates to interior air quality. The shading-solar-chimney was, also, able to reduce the levels of discomfort by glare in classrooms, especially under overcast sky.

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Amiraftabi, Maryamsadat. "Experimental and CFD–PBM investigation of an agitated bioreactor using a dual helical ribbon impeller." Thesis, Edith Cowan University, Research Online, Perth, Western Australia, 2021. https://ro.ecu.edu.au/theses/2424.

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Throughout past decades, the management of solid waste by producing methane gas, as a renewable source of energy, has featured as an important research objective. Anaerobic digesters are widely used in countries with environmental initiatives and green approaches, where biogas produced from a bioreactor is a carbon neutral source of energy. Biogas contains 70% methane, 30% CO2 and some other gases. The by-product of an anaerobic digester is solid sludge that can be used as either fertilizer or compost. Anaerobic digestion biogas plants can benefit industries by adding value to solid organic waste, reducing fossil fuel usage, eliminating solid waste disposal costs, in addition to generating power. Setting up an anaerobic digestion biogas plant is a green investment for industries interested in environmentally friendly biological processes. A variety of organic solid waste including municipal, industrial, livestock, poultry, meat, and food waste can be digested in an anaerobic system. To treat the large volume of waste generated by industries and urban sewerage systems, more efficient digesters and a continuous improvement of digestion processes are required. To accomplish these objectives, crucial factors including the size, design, and shape of a bioreactor, its working temperature, pH and the hydrodynamics of a system need to be studied. A considerable amount of literature has been published regarding the hydrodynamics of anaerobic digesters. Further, several studies have explored the factors thought to influence the hydrodynamics of anaerobic digesters. These studies have identified that the hydrodynamics of a system could be influenced by the rheological characteristics of sludge, as well as mixer type and shape. Inadequate and poor mixing in a digester can cause the failure of a reactor, non-uniform distribution of mass and heat, imbalanced microbial activity, as well as formation of sediment and scum. Although studies have successfully demonstrated that close-clearance mixers (screw, helical, anchor impellers) increase biogas production, the information about hydrodynamic characteristics and flow field generated by these types of agitators is inadequate. Although hydrodynamics and the rheology of sludge have been studied in the past, more research is required to address these gaps. The application of visual and measuring instruments could facilitate further research on sludge behaviour in an agitated anaerobic digester, but this type of study is not possible due to the opaque nature of real sludge. The main objectives of this project are (i) to find a safe, cheap, clear and stable material that can emulate digested sludge rheological characteristics in a laboratory; (ii) to study and optimize the mixing performance of a dual helical ribbon as an efficient impeller to create an ideal mixing pattern (iii) to investigate the flow pattern and hydrodynamics of a shear thinning fluid in a batch gas-liquid reactor using a combination of a computational fluid dynamics (CFD) simulation and a population balance model (PBM). Study 1 has analysed and compared the Zeta potential, pH resistance, flow curve, viscoelasticity, and thixotropy of four popular model fluids reported previously as ideal simulant of primary, activated, and digested sludge. The results of the correlational analysis indicate that xanthan gum is the best simulant to mimic the rheological characteristics of activated sludge that is sheared less than 100 S-1. There are similarities between the viscosity and flow curve of activated sludge and xanthan gum which can be described by its internal network and molecular structure. This study also compares rheological properties of 2% NaCMC solution and digested sludge containing 3.23% solid sheared between 10-300 S-1, concluding that they behave in an essentially identical manner. The findings from this study provide several contributions towards selecting and applying a clear and safe polymer that emulates the rheological behaviour of sludge. Study 2 has evaluated the performance of a dual helical ribbon impeller in agitating shear thinning fluid. The effects of impeller rotational speed, gas flow rate, clearance to the bottom, and viscosity on power uptake and mixing time have been studied. This study suggests that determining optimum operating conditions can minimize power consumption and time required to achieve the maximum volume of uniformity in reactor. Although the study successfully reports a significant positive correlation between the rotational speed of the impeller and the performance of mixing, there is still a threshold limit for rotational speed. Experimental data shows that power consumption would increase with rotational speed however increasing the rotational speed beyond the certain level does not affect the mixing time significantly. This study suggests two practical equations to estimate power consumption and mixing time under specific operating conditions by applying an ANOVA method. To cover some of the limitations related to the experimental study of hydrodynamics of gasliquid systems, a combination of computational fluid dynamics (CFD) simulation and population balance model (PBM) has been used in the third study. The main purpose of this work is to evaluate the impacts of using a dual helical ribbon on the hydrodynamics of a multiphase reactor. The governing equations and turbulent model of agitated bubbly flow have been solved through a standard k-e model and Eulerian-Eulerian (E-E) multiphase approach. Following grid sensitivity analyses, findings through simulation have been verified by PIV measuring tests. Further, the PBM model has been discretized into five bubble size groups. The results show a positive relationship between rotational speed and bubble breakage. The comparative study indicates an increase in the likelihood of bubble channeling when the rotational speed is insufficient to break the gel-like structure of the liquid. By increasing rotational speed, the bubble hits the blades, breaks, and disperses, leading to improved interfacial area between phases. Further, rotating mechanical blades induce shear stress to bulk of liquid, resulting in a significant drop in viscosity and diminishing the stagnant regions.

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Pavani, Marília Gusman Thomazi. "Estudo experimental e simulação da fluidodinâmica de amido de milho em leito fluidizado pulsado." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/74/74133/tde-26092016-163234/.

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A fluidização é uma operação unitária presente nas indústrias química, farmacêutica e alimentícia. Durante a fluidização, o leito de partículas sólidas é suspenso por um fluxo ascendente de gás. A velocidade mínima de fluidização indica a menor velocidade do gás em que as partículas iniciam a agitação, enquanto a velocidade terminal é caracterizada pela elutriação, ou arraste de partículas juntamente com o gás. Portanto, um leito fluidizado deve operar em uma velocidade de gás que esteja entre a velocidade mínima de fluidização e a velocidade terminal de arraste. No entanto, os sólidos particulados coesivos, caracterizadas pelo grupo de Geldart C, são difíceis de serem fluidizados, devido à formação de canais preferenciais, e são facilmente elutriados. Neste trabalho estudou-se a fluidização de partículas de amido de milho pela passagem de ar a 27 °C. O amido de milho obteve diâmetro médio mássico e densidade do sólido iguais a 30,3 µm e 1446,7 kg/m3, e pôde ser caracterizado como um sólido particulado coesivo, em que a velocidade efetiva de fluidização e velocidade terminal foram iguais a (0,66 e 0,68) m/s, respectivamente. A qualidade da fluidização foi aprimorada pelo uso da pulsação do gás, que possibilitou reduzir a velocidade mínima de fluidização e ampliar a faixa de velocidade de fluidização, de forma a minimizar o arraste de sólidos por elutriação. As frequências de pulsação estudadas foram (0, 5, 10 e 15) Hz. Em uma primeira etapa, foram obtidos os perfis de velocidade queda de pressão a partir de ensaios experimentais. Posteriormente, os perfis experimentais foram utilizados para validação dos modelos de escoamento bifásico Euler-Euler, em simulações realizadas pelo software COMSOL. Dentre os principais resultados, destaca-se que os modelos numéricos puderem descrever com boa aproximação os perfis fluidodinâmicos do sistema binário amido e ar. A aproximação numérica somente foi obtida ao estabelecer um diâmetro equivalente com tamanho de 100 µm, que foi superior ao diâmetro médio mássico. Este resultado evidenciou que a fluidização ocorreu na forma de agregados de partículas, que é característico de sistemas coesivos. O uso da pulsação do ar também resultou ruptura de canais preferenciais, e permitiu o início da fluidização em menores velocidades do ar.
Fluidization is a unit operation in the chemical, pharmaceutical and food industries. During the fluidization, the solid particles is suspended by a stream air flow. The minimum fluidization velocity indicates the lowest gas velocity in which the particles begin agitation while the terminal velocity is characterized by elutriation, or drag the particles along with gas. Therefore, a fluidized bed must be operated at a gas velocity which is between the minimum fluidization velocity and the terminal velocity. However, cohesive solid particles, characterized by Geldart Group C, are difficult to be fluidized due to the formation of cracks and channeling and areeasily elutriated from chamber. In this work, the fluidization of cornstarch particles occurred by anair flow at 27 °C. Cornstarch showed a mean diameter and solid density equal to 30.3 µm and 1446.7 kg/m3 and could be characterized as a cohesive particulate solid. The effective fluidization velocity and the terminal velocity were equal to (0.66 and 0.68) m/s respectively. The fluidization quality was improved by the use of pulsation air flow. The minimum fluidization velocity was reduced, increasing the fluidization velocity operational range. The air pulsation frequency were studied at (0, 5, 10 and 15) Hz. In a first step, the experimental tests obtained the fluidynamics profiles of pressure drop versus air velocity. Subsequently, the experimental profiles were used to validate the Euler-Euler model in simulations by COMSOL software. The main results emphasized that the numerical models described the fluid dynamic profiles with good approximation. The numerical approach established an equivalent diameter of 100 µm, which was greater than the mass median diameter. This result showed that the fluidization occurred in the form of aggregates of particles, which is a characteristic of cohesive systems. The use of air pulsation also resulted in the rupture of channeling and allowed the fluidization at lower air velocities.

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Subramaniam, Vignaesh. "Topology Optimization of Conjugated Heat Transfer Devices : Experimental and Numerical investigation." Thesis, Ecole nationale supérieure Mines-Télécom Lille Douai, 2018. http://www.theses.fr/2018MTLD0013/document.

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Concevoir des dispositifs thermiques plus compacts, nécessitant moins de masse de matière, produisant moins de pertes de charge et présentant un rendement thermique accru représente un enjeu clé pour des performances améliorées à un coût moindre. La présente thèse étudie le potentiel et la validité de l’optimisation topologique en tant qu’outil CFD viable permettant de générer des designs thermiques optimaux par rapport aux approches conventionnelles telles que l’optimisation de forme et paramétrique. La première partie de la thèse présente une étude expérimentale de structures bi matériaux arborescentes optimales obtenues par optimisation topologique. Le problème mathématique d’optimisation topologique est formulé et implémenté dans OpenFOAM®. Il est appliqué au problème d’optimisation de la conduction thermique dans une configuration de type volume-vers-point. Des mesures thermiques expérimentales sont effectuées sur les structures optimisées, en utilisant la thermographie infrarouge afin de quantifier leurs performances de transfert de chaleur et ainsi validé les performances des structures optimales déterminées par le code d’optimisation topologique développé. La deuxième partie de la thèse présente une technique bi-objectif innovante d’optimisation topologique des systèmes de transferts de chaleur conjugués (CHT, Conjugate Heat Transfer) en régimes d’écoulement laminaires. Pour cela, le problème est développé mathématiquement et implémenté dans le solveur OpenFOAM® basé sur une méthode directe par volumes finis. La fonction objectif est formulée par la pondération linéaire de deux fonctions objectifs, l’une pour la réduction de la perte de charge et l’autre pour l’augmentation du transfert de chaleur. Ceci représente une cible très difficile du point de vue numérique en raison de la concurrence entre les deux objectifs (minimisation de la perte de charge et maximisation de la puissance thermique récupérable). Des designs non intuitifs, mais optimaux au sens de Pareto, ont été obtenus, analysés, discutés et justifiés à l’aide de diverses méthodes d’analyses numériques globale et locale. De plus, une configuration identique à une optimisation par une méthode Lattice Boltzmann issue de la bibliographie a été optimisée en utilisant le solveur OpenFOAM® développé. L’objectif, en complément de la comparaison des solutions optimales, est également d’initier un cas de référence pour les futures études dans ce domaine de recherche et d’innovation de façon à pouvoir pleinement comparer les solutions optimales obtenues par différences méthodes et différents solveurs. Enfin, les différents points expérimentaux et numériques mis en lumière et illustrés dans cette thèse démontrent l’importance de la méthodologie et potentiel très important de l’optimisation topologique pour la conception de systèmes thermiques industriels plus performants
Designing thermal devices that are more compact with less mass, less frictional losses and increased thermal efficiency is a key requirement for enhanced performances at a lower cost. The present PhD thesis investigates the potential and validity of topology optimization numerical method as a viable CFD tool to generate optimal thermal designs as compared to conventional approaches like shape and parametric optimization. The first part of the thesis presents an experimental investigation of topology optimized tree-like structures made of two materials. The topolgy optimization mathematical problem is formulated and implemented in OpenFOAM®. It is applied to the topolgy optimization problem of volume-to-point heat removal. Experimental thermal measurements are carried out, on the optimal structures, using infrared thermography in order to quantify their heat transfer performances and thus validate the performances of the optimal structures determined by the developed topology optimization code. The second part of the thesis presents an innovative bi-objective optimization technique for topology optimization of Conjugate Heat Transfer (CHT) systems under laminar flow regimes. For that purpose, an inequality constrained bi-objective topology optimization problem is developed mathematically and implemented inside the Finite Volume based OpenFOAM® solver. The objective function is formulated by linear combination of two objective functions for pressure drop reduction and heat transfer enhancement which is numerically a very challenging task due to a competition between the two objectives (minimization of pressure drop and maximization of recoverable thermal power). Non-intuitive Pareto-optimal designs were obtained, analyzed, discussed and justified with the help of various global and local numerical analysis methods. Additionally, a recent Lattice Boltzmann topology optimization problem form the literature was solved using the developed OpenFOAM® solver. The objective, in addition to the comparison of the optimal solutions, is also to initiate a case of reference for future studies in this field of research and innovation so as to be able to fully compare the optimal solutions obtained by different and different methods. solvers. Finally, the various experimental and numerical findings highlighted and illustrated in this PhD thesis, demonstrate the importance of the methodology and immense potential behind topology optimization method for designing efficient industrial thermal systems

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Bastos, Jaci Carlo Schramm Camara. "Analise experimental e numerica de um jato de dispersão gas-solido." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/267143.

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Orientador: Milton Mori
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica
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Resumo: Apresenta-se nesta pesquisa uma análise experimental e numérica do comportamento da fase dispersa em um jato circular bifásico confinado e uma comparação com jato circular bifásico livre. Nas análises experimentais, uma câmara pentagonal em acrílico foi utilizada como sistema de confinamento para a obtenção de perfis axiais e radiais de velocidade média, flutuação de velocidade (RMS) e intensidade de turbulência. Estes dados foram analisados a fim de desenvolver uma análise completa da região desenvolvida do jato. Três diferentes jatos foram utilizados para a alimentação da fase gás no topo da câmara, mas apenas o jato central foi carregado com partículas entre 60 e 90µm de diâmetro. Os outros dois foram utilizados para proporcionar uma maior interação entre as fases no interior da câmara. A técnica óptica Phase Doppler Anemometry (PDA), foi empregada na medição da velocidade instantânea da fase sólida e do diâmetro das partículas nas diferentes posições axiais a partir do bico do jato. Nove casos de estudo distintos são investigados individualmente e, em seguida, comparados entre si. Estes casos fornecem informações importantes sobre o comportamento e o efeito do confinamento dos jatos sobre o transporte macrocóspico e turbulento das partículas entre o centro e as regiões de contorno do jato. As análises numéricas tratam da modelagem matemática tridimensional, turbulenta e transiente do escoamento no jato bifásico confinado. O modelo trata as fases gás e sólida a partir de uma abordagem Euleriana. O fechamento das equações de transporte foi realizado utilizando o modelo de turbulência de duas equações k-e para a fase gás e modelos de turbulência de zero-equação para a fase sólida, e ainda em alguns casos esta última apenas sofreu efeitos turbulentos advindos da fase contínua. A acurácia das previsões do modelo em um jato de partículas confinadas com as características médias no tempo, assim como os coeficientes da correlação de turbulência foram avaliados. Perfis radiais de velocidade média e fração volumétrica das partículas foram capturados em quarenta e dois níveis, subdivididos em nove casos e comparados aos dados experimentais adquiridos. O diâmetro médio das partículas utilizado nas simulações foi de 75µm e as velocidades iniciais utilizadas variam entre 3 e 11m/s no jato central. O modelo matemático previu um escoamento desenvolvido semelhante ao que foi encontrado experimentalmente.
Abstract: It is presented in this research an experimental and numerical analisys of the dispersed phase behavior in a circular confined two-phase jet and a comparison with circular free two-phase jet. In the experimental analysis, a pentagonal plexiglass chamber was used as confined system for the axial and radial profiles investigation of mean velocity, fluctuation velocity known as RMS velocity and turbulence intensity. These data were analyzed in order to develop a complete analysis in the developed region of the jet. Three different nozzles were used to feed the gas phase at the top of the chamber, but just the central nozzle was loaded with particles between 60 and 90µm of diameter. The other two were used to increase the interaction between the phases in the chamber. An optical technique known as Phase Doppler Anemometry was used to measure the instantaneous velocity of the solid phase and particle diameter in different axial positions of the jet nozzle. Nine different cases of study are investigated individually and then compared among each other. These cases provide important information about the jets behavior and the confinement effect on the macrocospic and turbulent transport of particles between the jet center and the jet contour regions. The numerical analysis deals with three-dimensional, turbulent and transient mathematical modeling of a confined two-phase jet flow. The model treats the gas and the solid phases from an Eulerian approach. The closure of the transport equations have been accomplished by using the k-e turbulence model for the gas phase and the zero-equation turbulence model for the solid phase, and in some cases the latter suffered turbulent effects occuring only from the continuos phase. The accuracy of the model predictions in a particle-laden confined jet with the characteristics as well as turbulence correlation coefficients have been evaluated. Radial mean velocity profiles for the solid phase were computed on forty two axial levels, subdivided in nine cases and compared to the obtained experimental data. The mean particle diameter used in the simulations was 75µm and the initial velocities used vary between 3 and 11m/s. The mathematical model predicted a flow development similar to that found experimentally.
Doutorado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química

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Renjie, Ke. "Experimental and CFD investigations of the fluid flow inside a hydrocyclone separator with an air core." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1449145729.

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Morgan, Ashley T. "Comparison of CFD Simulation and Experimental Data for Heating and Cooling Low N Packed Beds of Spherical Particles." Digital WPI, 2014. https://digitalcommons.wpi.edu/etd-theses/1312.

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This study compared experimental and Computational Fluid Dynamics (CFD) results for heating and cooling in a packed bed (N=5.33). The experimental data was compared between heating and cooling, and was also used to validate the CFD model. The validated models were used to compare theoretical heat transfer parameters. For the experiments, it was found that the effective thermal conductivity was comparable for heating and cooling, and the wall Nusselt number for heating was higher. For the CFD results, it was found that both the wall Nusselt number and effective thermal conductivity were comparable for heating and cooling. The wall Nusselt number was slightly higher for cooling, however this difference decreased as the Reynolds number increased.

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Liu, Hong. "Optimization for Fuel Cells/Fuel Cell Stacks Using Combined Methods---CFD Modeling Analysis, and Experiments." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/297027.

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Fuel cells are one of most environmental friendly energy sources; they have many advantages and may be used in many applications from portable electronic devices to automotive components. Proton exchange membrane (PEM) fuel cells are one of most reliable fuel cells and have advantage such as rapid-startup and ease of operation. This dissertation focuses on PEM fuel cell stack optimization based on operation experimental research and numerical modeling study. This dissertation presents three major research activities and the obtained results by the Ph.D candidate. A novel stack architecture design is introduced in order to decrease mal-distribution and non-uniform output performance between individual cells in order to improve the stack performance. Novel stack architecture includes a novel external bifurcation flow distribution delivery system. One major issue of uniform distribution of reactants inside individual fuel cells and between fuel cells in a fuel cell stack is solved by the novel stack architecture design. A novel method for uniform flow distribution was proposed, in which multiple levels of flow channel bifurcations were considered to uniformly distribute a flow into 2ⁿ flow channels at the final stage, after n levels of bifurcation. Some detailed parameters such as the flow channel length and width at each level of bifurcation as well as the curvature of the turning area of flow channels were particularly investigated. Computational fluid dynamics (CFD) based analysis and experimental tests were conducted to study the effect of the flow channel bifurcation structure and dimensions on the flow distribution uniformity. Optimization design and factors influential to the flow distribution uniformity were also delineated through the study. The flow field with the novel flow distribution was then considered to be used in a cooling plate for large fuel cell stacks and a possible method for cooling electronic devices. Details of the heat transfer performance, particularly the temperature distributions, on the heating surface as well as the pressure losses in the operation were obtained. In the second part of the research, experimental testing, analytical modeling, and CFD methods were employed for the study and optimization of flow fields and flow channel geometry in order to improve fuel cell performance. Based on the experimental results, a serpentine flow field is chosen for CFD and modeling analysis. Serpentine flow channel optimization is based on the parametrical study of many combinations of total channel width and rib ratio. Modeling analysis and in-house made computational code was used to optimize the dimensions of flow channels and channel walls. It is recommended that cell channel design should use a small total channel width and rib ratio. Proton exchange membrane fuel cells were fabricated based on the optimization results. Experimental tests were conducted and the results coincided with the numerical analysis; therefore, small total width and rib ratio design could significantly improve the fuel cell performance. Three dimensional (3D) CFD simulations for various PEM fuel cells were conducted to investigate information such as water and reactants distribution. The direct simulation results of current density distribution proclaim how the channel design influences the performance. The final section of research is stack bipolar plate flow field optimization. Optimized channel geometries are applied to the serpentine channel design for the stack. This serpentine channel design evolved to parallel-serpentine channel and symmetric serpentine channel design. Experimental tests of the stacks using the above flow fields are compared to one another and the results recommend use of the novel symmetric serpentine flow channel for stack bipolar design to achieve best performance.

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Shrestha, Kendra. "Partially Premixed Combustion (PPC) for low loadconditions in marine engines using computationaland experimental techniques." Thesis, KTH, Mekanik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-202624.

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Diesel Engine has been the most powerful and relevant source of power in the automobile industryfor decades due to their excellent performance, efficiency and power. On the contrary, there arenumerous environmental issues of the diesel engines hampering the environment. It has been agreat challenge for the researchers and scientists to minimize these issues. In the recent years, severalstrategies have been introduced to eradicate the emissions of the diesel engines. Among them,Partially Premixed Combustion (PPC) is one of the most emerging and reliable strategies. PPC is acompression ignited combustion process in which ignition delay is controlled. PPC is intended toendow with better combustion with low soot and NOx emission.The engine used in the present study is a single-cylinder research engine, installed in Aalto UniversityInternal Combustion Engine Laboratory with the bore diameter of 200 mm. The thesis presentsthe validation of the measurement data with the simulated cases followed by the study of the sprayimpingement and fuel vapor mixing in PPC mode for different injection timing. A detailed study ofthe correlation of early injection with the fuel vapor distribution and wall impingement has beenmade.The simulations are carried out with the commercial CFD software STAR CD. Different injectionparameters have been considered and taken into an account to lower the wall impingement and toproduce better air-fuel mixing with the purpose of good combustion and reduction of the emissions.The result of the penetration length of the spray and the fuel vapor distribution for different earlyinjection cases have been illustrated in the study. Comparisons of different thermodynamic propertiesand spray analysis for different injection timing have been very clearly illustrated to get insightof effect of early injection. The parameters like injection timing, injection period, injection pressure,inclusion angle of the spray have an influence the combustion process in PPC mode. Extensivestudy has been made for each of these parameters to better understand their effects in the combustionprocess. Different split injection profiles have been implemented for the study of better fuelvapor distribution in the combustion chamber.The final part of the thesis includes the study of the combustion and implementation of EGR tocontrol the temperature so as to get more prolonged ignition delay to accompany the PPC strategyfor standard piston top and deep bowl piston top. With the injection optimization and implementationof EGR, NOx has been reduced by around 44%, CO by 60% and Soot by 66% in the standardpiston top. The piston optimization resulted in more promising result with 58% reduction in NOx,55% reduction in CO and 67% reduction in Soot. In both cases the percentage of fuel burnt wasincreased by around 8%.

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Kent, Jason A. "Numerical and Experimental Analysis of a TurboPiston Pump." ScholarWorks@UNO, 2010. http://scholarworks.uno.edu/td/1189.

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The TurboPiston Pump was invented to make use of merits such as, high flow rates often seen in centrifugal pumps and high pressures associated with positive displacement pumps. The objective of this study is to manufacture a plastic model 12â€ TurboPiston Pump to demonstrate the working principle and a metal prototype for performance testing. In addition, this research includes the study of the discharge valve to estimate the valve closing time and fluid mass being recycled back into the cylinder through hand calculations. Furthermore, a transient simulation was performed in CFD using Fluent to provide a better estimate of what will happen in the actual pump while running. Additionally, an experimental rig was designed to investigate the performance of the first generation valve on the TurboPiston Pump known as the flapper valve. Means to improve the hydrodynamic performance of both valves have been identified for future study.

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Sánchez, Morales Valentin. "Experimental and CFD analysis of the flow in the wake of a vertical axis wind turbine." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/454742.

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Aquesta tesi es divideix en dos blocs on s'analitza el flux d'una VAWT. El primer bloc se centra en l'estudi experimental i numèric d'una VAWT amb vuit pales basada en el fenomen de resistència. A la primera part, la velocitat del vent es fixa en 10 m/s per mesurar la corba de potència de la turbina i els resultats es comparen amb els d'altres turbines Savonius en diferents túnels de vent. També s'ha analitzat la reducció del nombre de pales i s'ha comprovat que el rendiment augmenta. A la segona part, la velocitat del vent s'estableix en 4,5 m/s per a realitzar experiments de visualització de fum. La tècnica de visualització del fum ha permès validar qualitativament les simulacions 2D perquè els patrons de flux visualitzats són similars als simulats numèricament. Les simulacions numèriques han demostrat que el rendiment és més gran amb quatre pales. En el segon bloc, es proposa i analitza un nou model per predir l'estela de les VAWTs. El model es basa en el disc actuador i en els mètodes de Doble tub de flux múltiple. El model, anomenat MAB (Multiple Actuator Block), es basa en la definició, dins el domini computacional, de múltiples blocs paral·lelepipèdics distribuïts al llarg de la trajectòria de les pales. Els embornals volumètrics de moment s'imposen en aquests blocs per modelar l'efecte de les pales sobre el flux. Les simulacions amb el model MAB s'han comparat amb una simulació de volum finit complet usant la tècnica de malla lliscant. Aquesta simulació requereix aproximadament deu vegades més temps de CPU que les simulacions usant el model MAB. S'ha trobat que les característiques a gran escala del deixant llunyana poden ser reproduïdes utilitzant el model MAB.
Esta tesis se divide en dos bloques donde se analiza el flujo de una VAWT. El primer bloque se centra en el estudio experimental y numérico de una VAWT con ocho palas basada en el fenómeno de resistencia. En la primera parte, la velocidad del viento se fija en 10 m/s para medir la curva de potencia de la turbina y los resultados se comparan con los de otras turbinas Savonius en diferentes túneles de viento. También se ha analizado la reducción del número de palas y se ha comprobado que el rendimiento aumenta. En la segunda parte, la velocidad del viento se establece en 4,5 m/s para realizar experimentos de visualización de humo. La técnica de visualización del humo ha permitido validar cualitativamente las simulaciones 2D porque los patrones de flujo visualizados son similares a los simulados numéricamente. Las simulaciones numéricas han demostrado que el rendimiento es mayor con cuatro palas. En el segundo bloque, se propone y analiza un nuevo modelo para predecir la estela de las VAWTs. El modelo se basa en el disco actuador y en los métodos de Doble tubo de flujo múltiple. El modelo, denominado MAB (Multiple Actuator Block), se basa en la definición, dentro del dominio computacional, de múltiples bloques paralelepipédicos distribuidos a lo largo de la trayectoria de las palas. Los sumideros volumétricos de momento se imponen en estos bloques para modelar el efecto de las palas sobre el flujo. Las simulaciones con el modelo MAB se han comparado con una simulación de volumen finito completo usando la técnica de malla deslizante. Esta simulación requiere aproximadamente diez veces más tiempo de CPU que las simulaciones usando el modelo MAB. Se ha encontrado que las características a gran escala de la estela lejana pueden ser reproducidas utilizando el modelo MAB.
This thesis is divided in two blocks where the flow around a VAWT is analysed. The first block is focused on the experimental and numerical study of a VAWT with eight blades based in drag phenomenon. The experiments are carried out in two parts. In the first part, the wind velocity is set to 10 m/s to measure the power curve of the turbine and the results are compared with those of Savonius turbines in different wind tunnels. The reduction of the number of blades of the turbine has been also analysed and it has been found that the performance increases. In the second part, the wind velocity is set to 4.5 m/s to perform smoke visualization experiments. The smoke visualization technique has allowed the qualitative validation of the 2D simulations because the flow patterns visualized are similar to those numerically simulated. The numerical simulations have demonstrated that the four blades turbine generates higher torque than the turbine with eight blades. In the second block, a new model to predict the wake of VAWTs is proposed and analysed. The model is based on the actuator disk and the Double Multiple Stream Tube methods. The model, denoted as Multiple Actuator Block (MAB), is based on the definition, inside the computational domain, of multiple parallelepipedic blocks distributed along the path of the blades. Volumetric momentum sinks are imposed in these blocks to model the effect of the blades on the flow. The simulations with the MAB model have been compared with a complete finite volume simulation using the sliding mesh technique. This simulation requires about ten times more CPU time than the simulations using the MAB model. It has been found that the large scale features of the far wake can be reproduced using the MAB model.

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Lance, Blake. "Experimental Validation Data for CFD of Steady and Transient Mixed Convection on a Vertical Flat Plate." DigitalCommons@USU, 2015. http://digitalcommons.usu.edu/etd/4546.

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Simulations are becoming increasingly popular in science and engineering. One type of simulation is Computation Fluid Dynamics (CFD) that is used when closed forms solutions are impractical. The field of Verification & Validation emerged from the need to assess simulation accuracy as they often contain approximations and calibrations. Validation involves the comparison of experimental data with simulation outputs and is the focus of this work. Errors in simulation predictions may be assessed in this way. Validation requires highly-detailed data and description to accompany these data, and uncertainties are very important. The purpose of this work is to provide highly complete validation data to assess the accuracy of CFD simulations. This aim is fundamentally different from the typical discovery experiments common in research. The measurement of these physics was not necessarily original but performed with modern, high fidelity methods. Data were tabulated through an online database for direct use in Reynolds-Averaged Navier Stokes simulations. Detailed instrumentation and documentation were used to make the data more useful for validation. This work fills the validation data gap for steady and transient mixed convection. The physics in this study included mixed convection on a vertical flat plate. Mixed convection is a condition where both forced and natural convection influence fluid momentum and heat transfer phenomena. Flow was forced over a vertical flat plate in a facility built for validation experiments. Thermal and velocity data were acquired for steady and transient flow conditions. The steady case included both buoyancy-aided and buoyancy-opposed mixed convection while the transient case was for buoyancy-opposed flow. The transient was a ramp-down flow transient, and results were ensemble-averaged for improved statistics. Uncertainty quantification was performed on all results with bias and random sources. An independent method of measuring heat flux was devised to assess the accuracy of commercial heat flux sensors used in the heated wall. It measured the convective heat flux by the temperature gradient in air very near the plate surface. Its accuracy was assessed by error estimations and uncertainty quantification.

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Kuoppala, Oskar. "Cavitation analysis on test rig. : An experimental and CFD study executed in collaboration with Epiroc AB." Thesis, Umeå universitet, Institutionen för tillämpad fysik och elektronik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-188337.

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This master thesis project was done in collaboration with Epiroc Group Ab. Epiroc supplies high-quality drills of various types that can be used both above and below ground. A major problem in their percussive rock drills is that that cavitation is formed. Cavitation is a phenomenon that occurs when a fluid is subject to a sudden pressure drop. This pressure drop causes the liquid to vaporize and create gas bubbles. These gas bubbles will cause erosion to the walls when imploded. These cavitation damages lead to drills breaking and parts having to be replaced preserved. An experimental rig was used to create cavitation. From the experimental rig, it was possible to measure the hydraulic transients that are created when the valve was closed. In this study, we examined whether one can visually see these damages occurring inside the pipe on valve parts that are subjected to these cavitation damages. CFD simulations were used to re-create the closing of the valve in the experimental rig. By exporting pressure data from the experiments one could compare the numerical result to the experimental data. It was also investigated if it is possible to see some connection between the gas formation and the damages seen visually from the experimental part. For the simulation the realizable k − ε methods were implemented with enhanced wall treatment. The mixture model was used since we have a multi-phase flow. Some visual damages were recognized during the experiments. However, no distinguished pattern or specific areas was established. From the simulations, it could be determined that they generated gas when the valve was closed. However, the pressure transients could not be replicated in the numerical result.

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Kucukal, Erdem. "EXPERIMENTAL AND CFD INVESTIGATIONS OF THE FLUID FLOW INSIDE A HYDROCYCLONE SEPARATOR WITHOUT AN AIR CORE." Case Western Reserve University School of Graduate Studies / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=case1424174590.

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Dissertations / Theses on the topic 'CFD experimental'

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