Tesi sul tema "Computational fluid dynamics (CFD)"
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1
Dodds, David Scott. "Computational fluid dynamics (CFD) modelling of dilute particulate flows". Swinburne Research Bank, 2008. http://hdl.handle.net/1959.3/44947.
Testo completoAbstract (sommario):
Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, 2008.A thesis submitted for the degree of Doctor of Philosophy, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2008. Typescript. Bibliography: p. 129-142. Includes bibliographical references (p. 259-274)
2
Charmchi, Isar. "Computational Fluid Dynamics (CFD) Modeling of a Continuous Crystallizer". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Cerca il testo completoAbstract (sommario):
Crystallization is one of the most important separation and purification processes in chemical and especially in pharmaceutical industries. Currently most crystallization processes in the industry are based on batch crystallization; however, due to the variation of product quality per batch, efforts
are made to move to continuous processes instead. In this
respect, micro and meso scale reactors represents a promising technology due to enhanced heat and mass transfer rates, which, translated to particle generation,
provide control of size, morphology, and composition. In this
study, a meso-scale continuous crystallizer has been characterized and optimized.
A stirred tubular continuous-crystallizer has been characterized and optimized
in which the crystallization of active pharmaceutical ingredients (APIs) can
be performed under controlled conditions. The crystallizer is formed by two tubes,
one for nucleation and the other one for growth, in order to separate different phenomena
to control better the process and hence the crystal size distribution. The
optimized nucleation tube has a length of 35 cm and a diameter of 3 cm with a
long axial blade across the tube with the length of 30 cm and 2.5 cm of diameter.
The phenomena of mixing helps to achieve homogeneous supersaturation along the
tube to prevent growth during the nucleation and enables narrow residence time
distribution of the crystals in the tube with the help of gravity to achieve narrower
crystal size distribution.
Computational
fluid dynamics (CFD) is used to optimize the process. CFD is the
application of numerical methods to solve systems of partial differential equations
related to
fluid dynamics. The continuity and the momentum equations are the
most commonly applied equations within CFD, and together they can be used to
calculate the velocity and pressure distributions in a
fluid.
3
Kaggerud, Torbjørn Herder. "Modeling an EDC Cracker using Computational Fluid Dynamics (CFD)". Thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9536.
Testo completoAbstract (sommario):
The process used by the Norwegian company Hydro for making Vinyl Chloride Monomer (VCM) from natural gas and sodium chloride has been studied. A three dimensional CFD model representing the firebox of the EDC cracker has been developed using the commercial CFD tool Fluent. Heat to the cracker is delivered by means of combustion of a fuel gas consisting of methane and hydrogen. In the developed CFD model used in this work, the combustion reaction itself is omitted, and heat is delivered by hot flue gas. With the combustion reaction left out, the only means of tuning the CFD model is through the flue gas inlet temperature. With the flue gas inlet temperature near the adiabatic flame temperature, the general temperature level of the EDC cracker was reported to be too high. The outer surface temperature of the coil was reported to be 3-400 K higher than what was expected. By increasing the mass flow of flue gas and decreasing the temperature, the net delivered heat to the firebox was maintained at the same level as the first case, but the temperature on the coil was reduced by 100-150 K. Further reductions in the flue gas inlet temperature and modifications in the mass flow of flue gas at the different burner rows, eventually gave temperature distributions along the reaction coil, and flue gas and refractory temperatures, that resemble those in the actual cracker. The one-dimensional reactor model for the cracking reaction represents the actual cracker in a satsifactorily manner. The cracking reaction was simulated using a simple, global reaction mechanism, thus only the main components of the process fluid, EDC, VCM and HCl, can be studied. The model is written in a way suitable for implementation of more detailed chemical reaction mechanisms. The largest deviation in temperature between measured and simulated data are about 5%. At the outlet the temperature of the process fluid is equal to the measured data. The conversion of EDC out of the firebox is assumed to be 50 wt-%, this value is met exactly by the model.
4
Al-Far, Salam H. "Indirect fired oven simulation using computational fluid dynamics (CFD)". Thesis, London South Bank University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618655.
Testo completo
5
Demir, H. Ozgur. "Computational Fluid Dynamics Analysis Of Store Separation". Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605294/index.pdf.
Testo completoAbstract (sommario):
In this thesis, store separation from two different configurations are solved using computational methods. Two different commercially available CFD codesCFD-FASTRAN, an implicit Euler solver, and an unsteady panel method solver USAERO, coupled with integral boundary layer solution procedure are used for the present computations. The computational trajectory results are validated against the available experimental data of a generic wing-pylon-store configuration at Mach 0.95. Major trends of the separation are captured. Same configuration is used for the comparison of unsteady panel method with Euler solution at Mach 0.3 and 0.6. Major trends are similar to each other while some differences in lateral and longitudinal displacements are observed. Trajectories of a fueltank separated from an F-16 fighter aircraft wing and full aircraft configurations are found at Mach 0.3 using only the unsteady panel code. The results indicate that the effect of fuselage is to decrease the drag and to increase the side forces acting on the separating fueltank from the aircraft. It is also observed that the yawing and rolling directions of the separating fueltank are reversed when it is separated from the full aircraft configuration when compared to the separation from the wing alone configuration.
6
Kleemann, Andreas Peter. "CFD simulation of advanced diesel engines". Thesis, Imperial College London, 2001. http://hdl.handle.net/10044/1/62159.
Testo completoAbstract (sommario):
This study uses CFD methodology to simulate an advanced Diesel engine operated at higher than conventional peak cylinder pressures. The existing mathematical models for Diesel combustion, pollutant formation and wall heat transfer are improved and validated for this operating range. The fluid flow is described via the gas-phase Favre-averaged transport equations, governing the conservation of mass, chemical species, momentum and energy, based on the Eulerian continuum framework. These equations are closed by means of the k — e turbulence model. The liquid phase uses the Lagrangian approach, in which parcels, representing a class of droplets, are described by differential equations for the conservation of mass, momentum and energy. The numerical solution of the gas phase is obtained by the finite volume method applied to unstructured meshes with moving boundaries. Diesel ignition is modeled via a reduced kinetics mechanism, coupled with a characteristic timescale combustion model. Additionally, NOx and soot emissions are simulated. For the elevated cylinder temperatures and pressures, the behaviour of the thermophysical properties of the gases and liquids involved is critically examined. A near-wall treatment is applied accounting for the large gradients of thermophysical properties in the vicinity of the wall. Furthermore an alternative combined combustion and emissions modelling approach, RIF, based on the laminar flamelet concept is tested. The methodology is validated by reference to experimental data from a research engine, a constant volume pressure chamber and a high-pressure DI Diesel engine at various operating conditions. The modified near-wall treatment gives better agreement with the heat transfer measurements. The methodology predicts Diesel combustion evolution reasonably well for the elevated pressures. Best agreement was achieved using the LATCT combustion model combined with a NOx and soot model. The predictions of emissions show encouraging trends especially regarding the soot/NOx tradeoff, but require tuning of model coefficients.
7
Chambers, Steven B. "Investigation of combustive flows and dynamic meshing in computational fluid dynamics". Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/1324.
Testo completoAbstract (sommario):
Computational Fluid Dynamics (CFD) is a field that is constantly advancing. Its advances in terms of capabilities are a result of new theories, faster computers, and new numerical methods. In this thesis, advances in the computational fluid dynamic modeling of moving bodies and combustive flows are investigated. Thus, the basic theory behind CFD is being extended to solve a new class of problems that are generally more complex. The first chapter that investigates some of the results, chapter IV, discusses a technique developed to model unsteady aerodynamics with moving boundaries such as flapping winged flight. This will include mesh deformation and fluid dynamics theory needed to solve such a complex system. Chapter V will examine the numerical modeling of a combustive flow. A three dimensional single vane burner combustion chamber is numerically modeled. Species balance equations along with rates of reactions are introduced when modeling combustive flows and these expressions are discussed. A reaction mechanism is validated for use with in situ reheat simulations. Chapter VI compares numerical results with a laminar methane flame experiment to further investigate the capabilities of CFD to simulate a combustive flow. A new method of examining a combustive flow is introduced by looking at the solutions ability to satisfy the second law of thermodynamics. All laminar flame simulations are found to be in violation of the entropy inequality.
8
Chou, Ching Ju. "The Application of Computational Fluid Dynamics to Comfort Modelling". Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/16686.
Testo completoAbstract (sommario):
This thesis studies thermal comfort in heating, ventilation and air-conditioning (HVAC) scenarios with computational fluid dynamics (CFD) models at domain and occupant levels. Domain level comfort modelling, where the details of the occupant are not modelled, is investigated utilising Fanger’s Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) comfort models. Occupant level comfort modelling, where the occupant geometry and skin temperature are required, is explored using two different models. The first model termed the thermal manikin model couples the University of California Berkeley (UCB) psychological model to a new physiological model which neglects the thermal regulation of the human body, and consists of a central core at constant temperature surrounded by a layer with thickness and corresponding thermal properties to allow the skin temperature to vary over the modelled human body. The second model based on Gagge’s two-node model, which includes thermal regulation, yet assumes the skin temperature of the occupant to be spatially uniform. The models are validated with the experimental results from the Technical University of Denmark, which provides the data of the air flow, and the Indoor Environmental Quality (IEQ) laboratory at the University of Sydney, which offered the actual votes of human subjects for a range of environmental conditions. To conclude, the prediction of the skin temperature and its spatial variation is the most important parameter to predict occupant comfort correctly. The occupant level comfort modelling approach employing the thermal manikin is found to be the superior method to evaluate thermal comfort as it can still be accurate when the environment is complex. However, the computational cost and model setup time is high. Further work employing multi-node thermal manikin models would be a fruitful area of research if the accuracy of occupant comfort prediction in complex thermal environments is of interest.
9
Murad, Nurul Muiz. "Computational fluid dynamics (CFD) of vehicle aerodynamics and associated acoustics". Swinburne Research Bank, 2009. http://hdl.handle.net/1959.3/47824.
Testo completoAbstract (sommario):
Thesis (PhD) - Swinburne University of Technology, School of Engineering and Science, 2009.A thesis submitted in accordance with the regulations for the degree of Doctor of Philosophy, School of Engineering and Science, Swinburne University of Technology, 2009. Typescript. Includes bibliographical references (p. 315-330)
10
Chiu, Ya-Tien. "Computational Fluid Dynamics Simulations of Hydraulic Energy Absorber". Thesis, Virginia Tech, 1999. http://hdl.handle.net/10919/34775.
Testo completoAbstract (sommario):
Hydraulic energy absorbers may be described as high-loss centrifugal turbomachines arranged to operate as stalled torque converters. The device absorbs the kinetic energy of a vehicle in motion and dissipates the energy into water. A steady, single-phase, Computational Fluid Dynamics (CFD) simulation has been performed to investigate the flow field in a hydraulic energy absorber. It was determined that to better predict the performance of the energy absorber, more sophisticated modeling approaches may be needed.
In this research, a steady, two-phase calculation with basic turbulence modeling was used as a first assessment. The two-phase model was used to investigate cavitation effects. Unsteady and advanced turbulence modeling techniques were then incorporated into single-phase calculations. The Multiple Reference Frame (MRF) Technique was used to model the interaction between the rotor and the stator. The calculations provided clearer details of the flow field without dramatically increasing the computational cost.
It was found that unsteady modeling was necessary to correctly capture the close coupling between the rotor and the stator. The predicted torque in the unsteady calculations was 70% of the experimental value and twice of the result in the steady-state calculations. It was found that the inaccuracy of torque prediction was due to (1) high pressures in the regions with complicated geometrical boundaries and, (2) dynamic interactions between the rotor and the stator were not captured fully. It was also determined that the unrealistically low pressure values were not caused by the physical cavitation, but by the lack of proper boundary conditions for the model. Further integration of the modeling techniques studied would improve the CFD results for use in the design of the energy absorber.Master of Science
11
Hari, Sridhar. "Computational Fluid Dynamics (CFD) simulations of dilute fluid-particle flows in aerosol concentrators". Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/1619.
Testo completoAbstract (sommario):
In this study, commercially available Computational Fluid Dynamics (CFD) software, CFX-4.4 has been used for the simulations of aerosol transport through various aerosol-sampling devices. Aerosol transport was modeled as a classical dilute and dispersed two-phase flow problem. Eulerian-Lagrangian framework was adopted wherein the fluid was treated as the continuous phase and aerosol as the dispersed phase, with a one-way coupling between the phases. Initially, performance of the particle transport algorithm implemented in the code was validated against available experimental and numerical data in the literature. Code predictions were found to be in good agreement against experimental data and previous numerical predictions. As a next step, the code was used as a tool to optimize the performance of a virtual impactor prototype. Suggestions on critical geometrical details available in the literature, for a virtual impactor, were numerically investigated on the prototype and the optimum set of parameters was determined. Performance curves were generated for the optimized design at various operating conditions. A computational model of the Linear Slot Virtual Impactor (LSVI) fabricated based on the optimization study, was constructed using the worst-case values of the measured geometrical parameters, with offsets in the horizontal and vertical planes. Simulations were performed on this model for the LSVI operating conditions. Behavior of various sized particles inside the impactor was illustrated with the corresponding particle tracks. Fair agreement was obtained between code predictions and experimental results. Important information on the virtual impactor performance, not known earlier, or, not reported in the literature in the past, obtained from this study, is presented. In the final part of this study, simulations on aerosol deposition in turbulent pipe flow were performed. Code predictions were found to be completely uncorrelated to experimental data. The discrepancy was traced to the performance of the code's turbulent dispersion model. A detailed literature survey revealed the inherent technical deficiencies in the model, even for particle dispersion. Based on the results of this study, it was determined that while the code can be used for simulating aerosol transport under laminar flow conditions, it is not capable of simulating aerosol transport under turbulent flow conditions.
12
Wang, Le. "Study of gas turbine ingress using computational fluid dynamics". Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.604894.
Testo completoAbstract (sommario):
The ingestion of hot mainstream gas into the wheel-space between the rotor and staler discs is one of the most important internal cooling problems for gas turbine designers. To solve this problem, engineers design a rim seal at the periphery of wheel-space and direct a sealing flow from the internal cooling system to prevent ingress. The main aim of this thesis is to build a simple computational model to predict the scaling effectiveness of externally-induced ingress for engine designers. The axisymmetric model represents a gas turbine wheel-space and provides useful information related to the fluid dynamics and heat transfer in the wheel-space. At the same time, this model saves much computation time and cost for engine designers who currently use complex and time-consuming 3D models. The- computational model in this -thesis is called the prescribed ingestion model. Steady simulations are carried out using the commercial CFD code, ANSYS CFX with meshes built using ICEM CFD. Boundary conditions are applied at the ingress inlet of the model using experimental measurements and a mass-based averaging procedure. Computational parameters such as rotational Reynolds number, non-dimensional sealing flow rate and thermal conditions on the rotor are selected to investigate the fluid dynamics and heat transfer at typical experimental rig operating conditions. Different rim seal geometries arc investigated and results are compared with experimental data. In addition to the prescribed ingestion model, two typical axisymmetric rotor-stator system models without ingress arc established. The aim of these rotor-stator models is to investigate the fluid dynamics and heat transfer of the wheel-space in the situation without ingress. The effects of geometry and turbulence model also arc studied in these simulations. Most results from these simulations are in good agreement with experimental data from the literature, which enhances confidence in the prescribed Ingestion model.
13
Postnikov, Andrey. "Wake oscillator and CFD in modelling of VIVs". Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=229013.
Testo completoAbstract (sommario):
With many decades of research devoted to the intriguing nature of vortex-induced vibrations, the offshore industry is constantly looking for new effective solutions in predicting VIV of slender marine structures such as riser pipes. These structures are very sensitive to excitations induced by vortex shedding, which results in vibrations that in certain combinations of waves and current develop into a structural resonance phenomenon known as lock-in. This kind of vibrations can be destructive to some structures and lead to collapse. Many of VIV aspects are far from being understood and advanced modelling is required to investigate the impact of the phenomenon, which significantly affects the service life of marine structures. The main objective of this research is to contribute to the family of semi-empirical models used for prediction of vortex-induced vibrations, with emphasis on low mass ratio elastically supported cylinders capable of moving in cross-flow and in-line directions. In this work a new two degree-of-freedom wake oscillator model has been developed, where vortex-induced lift and drag forces were modelled with two nonlinear self-excited oscillators of van der Pol type. Phenomena exclusive for two degreeof- freedom motion at low mass ratios were examined in detail. Computational fuid dynamics was applied to the problem in order to tune the model parameters. Twodimensional flow past an elastically supported cylinder was considered, and CFD simulation results were used to calibrate the wake oscillator model predictions of the complex fluid-structure interaction.
14
Shaw, Michael James. "An assessment of CFD for transonic fan stability studies". Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709038.
Testo completo
15
Lai, Ho-yin Albert. "Artificial intelligence based thermal comfort control with CFD modelling /". Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21929555.
Testo completo
16
Shelley, Jonathan Knighton. "Incorporating Computational Fluid Dynamics Into The Preliminary Design Cycle". Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd979.pdf.
Testo completo
17
Chang, Bong Jun. "Application of CFD to marine propellers and propeller-hull interactions". Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286067.
Testo completo
18
Johnson, Benjamin Michael Carver. "Computational Fluid Dynamics (CFD) modelling of renewable energy turbine wake interactions". Thesis, University of Central Lancashire, 2015. http://clok.uclan.ac.uk/12120/.
Testo completoAbstract (sommario):
This thesis presents Computational Fluid Dynamics (CFD) simulations of renewable turbines akin to those used for wind, hydro, and tidal applications. The models developed took the form of actuator discs with the solution of incompressible Reynolds-Averaged Navier-Stokes equations with the k-ω SST turbulence models. Simulations were initially conducted of a single turbine in water and air and then two axially aligned turbines to study the flow field interactions. These models were compared with previous theoretical, experimental and numerical data evident in the literature. Generally, good agreement was found between these models and other analogous data sources in terms of velocity profiles in the far wake. The actuator disc method was underpinned using the transient actuator line method, which showed good agreement from a quantitative and qualitative viewpoint. However, it required significant additional computational time when compared to the actuator disc method. Each of the models were developed and solved using complimentary commercially available CFD codes, ANSYS-CFX and ANSYS-Fluent. For this type of study, a critical evaluation of these codes was in all probability performed for the first time, where it is shown that for the studies investigated in this thesis ANSYS-CFX performed better than ANSYS-Fluent with respect to the computational effort (i.e. time and lines of code).
19
Wong, Lak Kin. "Computational Fluid Dynamics Analysis on the Liquid Piston Gas Compression". Digital WPI, 2011. https://digitalcommons.wpi.edu/etd-theses/1104.
Testo completoAbstract (sommario):
"Liquid piston gas compression utilizes a liquid to directly compress gas. The benefit of this approach is that liquid can conform to irregular compression chamber volume. The compression chamber is divided into many small little bores in order to increases the surface area to volume ratio. The heat transfer rate increases with increasing surface area to volume ratio. However, as the bore diameter becomes smaller, the viscous force increases. In order to maximize the heat transfer rate and to minimize the viscous force, computational fluid dynamics is used. ANSYS Fluent is used to simulate the liquid piston gas compression cycle. Having created the model in Fluent, different factors, including diameter, length, liquid temperature, and the acceleration are varied in order to understand how each factor affects the heat transfer and viscous energy loss. The results show that both viscous force and heat transfer rate increase as the diameter decreases. The viscous force increases and the heat transfer decreases as the length increases. Both the viscous force and heat transfer increase as the acceleration increases. The viscous force decreases as the liquid temperature increases. Results show that the highest compression efficiency of 86.4% is found with a 3mm bore radius and a short cylinder. The piston acceleration is advised to be below 0.5g in order to avoid surface instability problem."
20
Limache, Alejandro Cesar. "Aerodynamic Modeling Using Computational Fluid Dynamics and Sensitivity Equations". Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/27033.
Testo completoAbstract (sommario):
A mathematical model for the determination of the aerodynamic forces acting on an aircraft is presented. The mathematical model is based on the generalization of the idea of aerodynamically steady motions. One important use of these results is the determination of steady (time-invariant) aerodynamic forces and moments. Such aerodynamic forces can be determined using computer simulation by determining numerically the associated steady flows around the aircraft when it is moving along such generalized steady trajectories. The method required the extension of standard (inertial) CFD formulations to general non-inertial reference frames. Generalized Navier-Stokes and Euler equations have been derived. The formulation is valid for all ranges of Mach numbers including transonic flow. The method was implemented numerically for the planar case using the generalized Euler equations. The developed computer codes can be used to obtain numerical flow solutions for airfoils moving in general steady motions (i.e. circular motions). From these numerical solutions it is possible to determine the variation of the lift, drag and pitching moment with respect to the pitch rate at different Mach numbers and angles of attack. One of the advantages of the mathematical model developed here is that the aerodynamic forces become well-defined functions of the motion variables (including angular rates). In particular, the stability derivatives are associated with partial derivatives of these functions. These stability derivatives can be computed using finite differences or the sensitivity equation method.Ph. D.
21
Del, Toro Adam. "Computational Fluid Dynamics Analysis of Butterfly Valve Performance Factors". DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1456.
Testo completoAbstract (sommario):
Butterfly valves are commonly used in industrial applications to control the internal flow of both compressible and incompressible fluids. A butterfly valve typically consists of a metal disc formed around a central shaft, which acts as its axis of rotation. As the valve's opening angle is increased from 0 degrees (fully closed) to 90 degrees (fully open), fluid is able to more readily flow past the valve. Characterizing a valve's performance factors, such as pressure drop, hydrodynamic torque, flow coefficient, loss coefficient, and torque coefficient, is necessary for fluid system designers to account for system requirements to properly operate the valve and prevent permanent damage from occurring. This comparison study of a 48-inch butterfly valve's experimental performance factors using Computational Fluid Dynamics (CFD) in an incompressible fluid at Reynolds numbers ranging approximately between 105 to 106 found that for mid-open positions (30-60 degrees), CFD was able to appropriately predict common performance factors for butterfly valves. For lower valve angle cases (10-20 degrees), CFD simulations failed to predict those same values, while higher valve angles (70-90 degrees) gave mixed results. (152 pages)
22
Tanamal, Tan Kong Hong Ryan. "Modelling of fluid flow in multiple axial groove water lubricated bearings using computational fluid dynamics". Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16531/1/Tan_Tanamal_Thesis.pdf.
Testo completoAbstract (sommario):
Extensive research has been conducted in the area of journal bearings over many years for various operating conditions and geometry, effects of different types of lubricants (oil and water), different numbers (zero, one and three) and positions of grooves and the flow of lubricant between the shaft and bearing. One area of research has been developing methods to minimize the experimental time and cost of predicting the performance of journal bearings operating over a wide variety of conditions. This has led to numerical methods being developed and utilised for this purpose. Numerical methods are an important foundation for the development of Computational Fluid Dynamics (CFD). CFD method has proved to be a very useful tool in this research field.
This project uses a CFD (specifically FLUENT) approach to simulate the fluid flow in a water lubricated journal bearing with equal spaced axial grooves. Water is fed into the bearing from one end. The lubricant is subjected to a velocity induced flow, as the shaft rotates and a pressure induced flow, as the water is pumped from one end of the bearing to the other. CFD software is used to simulate the fluid flow phenomenon that occurs during the process. Different parameters such as eccentricity ratio, number of grooves and groove orientation to the load line were examined. Lubricant pressure and velocity profiles were obtained and compared with available theoretical and experimental results.
Two dimensional studies showed that the predicted maximum pressure and load carrying capacity from CFD were similar to the results from theoretical calculations. A small percentage difference (1.78% - 3.76%) between experimental and theoretical results was found. The pressure distribution in the lubricant shows that grooves decrease the pressure and load carrying capacity of the bearing. Swirl or turbulence does occur in the groove is affected by the viscosity of the lubricant.
Three dimensional studies show that the pressure drops linearly from one end of the bearing to the other for no groove, concentric and three grooves cases. As the eccentricity increases, for one groove cases, the shape of the pressure profile changes to parabolic shape at positive region while the other pressure profiles drop linearly. The magnitude of the velocity it the bearing gap increased from 0.8 m/s to about 2.9 m/s when the shaft speed increased from zero to 5.5 m/s for a concentric and no groove case, similar changes were noted for all other cases.
An interesting observation occurs when implementing the pressure profiles along the bearing. At cases such as zero and one groove condition and e = 0.4 and 0.6, lubricant flow back is observed at both inlet and outlet i.e. at certain area of the inlet, lubricant flowed out of the bearing against the supply pressure, a similar situation occurred at the exit of the bearing.
23
Tanamal, Tan Kong Hong Ryan. "Modelling of fluid flow in multiple axial groove water lubricated bearings using computational fluid dynamics". Queensland University of Technology, 2007. http://eprints.qut.edu.au/16531/.
Testo completoAbstract (sommario):
Extensive research has been conducted in the area of journal bearings over many years for various operating conditions and geometry, effects of different types of lubricants (oil and water), different numbers (zero, one and three) and positions of grooves and the flow of lubricant between the shaft and bearing. One area of research has been developing methods to minimize the experimental time and cost of predicting the performance of journal bearings operating over a wide variety of conditions. This has led to numerical methods being developed and utilised for this purpose. Numerical methods are an important foundation for the development of Computational Fluid Dynamics (CFD). CFD method has proved to be a very useful tool in this research field. This project uses a CFD (specifically FLUENT) approach to simulate the fluid flow in a water lubricated journal bearing with equal spaced axial grooves. Water is fed into the bearing from one end. The lubricant is subjected to a velocity induced flow, as the shaft rotates and a pressure induced flow, as the water is pumped from one end of the bearing to the other. CFD software is used to simulate the fluid flow phenomenon that occurs during the process. Different parameters such as eccentricity ratio, number of grooves and groove orientation to the load line were examined. Lubricant pressure and velocity profiles were obtained and compared with available theoretical and experimental results. Two dimensional studies showed that the predicted maximum pressure and load carrying capacity from CFD were similar to the results from theoretical calculations. A small percentage difference (1.78% - 3.76%) between experimental and theoretical results was found. The pressure distribution in the lubricant shows that grooves decrease the pressure and load carrying capacity of the bearing. Swirl or turbulence does occur in the groove is affected by the viscosity of the lubricant. Three dimensional studies show that the pressure drops linearly from one end of the bearing to the other for no groove, concentric and three grooves cases. As the eccentricity increases, for one groove cases, the shape of the pressure profile changes to parabolic shape at positive region while the other pressure profiles drop linearly. The magnitude of the velocity it the bearing gap increased from 0.8 m/s to about 2.9 m/s when the shaft speed increased from zero to 5.5 m/s for a concentric and no groove case, similar changes were noted for all other cases. An interesting observation occurs when implementing the pressure profiles along the bearing. At cases such as zero and one groove condition and e = 0.4 and 0.6, lubricant flow back is observed at both inlet and outlet i.e. at certain area of the inlet, lubricant flowed out of the bearing against the supply pressure, a similar situation occurred at the exit of the bearing.
24
Gilmore, Jordan David. "Computational Fluid Dynamics Analysis of Jet Engine Test Facilities". Thesis, University of Canterbury. Mechanical Engineering, 2012. http://hdl.handle.net/10092/7238.
Testo completoAbstract (sommario):
This thesis investigates the application of CFD techniques to the aerodynamic analysis of a U-shaped JETC. Investigations were carried out to determine the flow patterns present at a number of locations within the structure of a full U-shaped JETC. The CFD solutions produced in these investigations used recommendations from the literature in the set-up of the CFD solver, and provided the computational component towards problem-specific validation of the CFD techniques used.
A structured series of CFD-aided investigation and design processes were then performed. These processes were based around a series of analyses that evaluated the influence of a number of cell parameters in terms of cell airflow efficiency and velocity distortion. Four cell components; the inlet and exhaust stack baffle arrangements, the turning-vanes, the rear of the working section and augmenter entrance, and the lower exhaust stack, including the BB, were investigated in individual analyses. Throughout the investigations the value of CFD as a design tool was constantly assessed.
Overall, the findings suggest that aerodynamic optimisation of the baffle arrangements would provide the greatest gains to cell airflow efficiency. As some cells contain as many as three baffle arrangements, the potential increases made to cell airflow capacity are sizable. Through implementing the findings of the baffle arrangement investigations, static pressure loss across the five-row baseline arrangement was reduced by 79%.
For low levels of velocity distortion in the upstream region of the working section, the need to design the inlet stack baffles in the turning-vane arrangement was highlighted. Mid-baffle vane alignment, consistent flow channels, and sufficiently low chord to gap ratios should be incorporated into a turning-vane design to maximise flow uniformity. The need for the baffle and vane components to combine with the geometry of the cell to limit adverse pressure gradients was found as a requirement to minimise inner corner separation, and the downstream threat it creates to a safe testing environment.
CFD proved to be a valuable analysis tool throughout the investigations performed in this thesis. The number of design iterations analysed, and the detail of data that could be extracted, significantly exceeded what could have been achieved through an isolated experimental testing programme.
25
Coe, Ryan Geoffrey. "Improved Underwater Vehicle Control and Maneuvering Analysis with Computational Fluid Dynamics Simulations". Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23777.
Testo completoAbstract (sommario):
The quasi-steady state-space models generally used to simulate the dynamics of underwater vehicles perform well in most steady flow scenarios, and are therefore acceptable for modeling today\'s fleet of endurance-focused autonomous underwater vehicles (AUVs). However, with their usage of numerous assumptions and simplifications, these models are not well suited to certain unsteady flow situations and for use in the development of AUVs capable of performing more extreme maneuvers. In the interest of better serving efforts to design a new generation of more maneuverable AUVs, a tool for simulating vehicle maneuvering within computational fluid dynamics (CFD) based environments has been developed. Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations are used in conjunction with a 6-degree-of-freedom (6-DoF) rigid-body kinematic model to provide a numerical test basin for vehicle maneuvering simulations. The accuracy of this approach is characterized through comparison with experimental measurements and quasi-steady state-space models. Three state-space models are considered: one model obtained from semi-empirical database regression (this is the method most commonly used in application) and two models populated with coefficients determined from the results of prescribed motion CFD simulations. CFD analyses focused on supporting the design of a general purpose AUV are also presented.Ph. D.
26
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.
Testo completoAbstract (sommario):
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.
27
Kumar, Suman. "Computational fluid dynamics (CFD) and physical modelling of a metal refining process". Thesis, University of Greenwich, 2003. http://gala.gre.ac.uk/6213/.
Testo completoAbstract (sommario):
Impeller-stirred mixing is one of the most important processes employed throughout the chemical, metallurgical and allied industries. The research reported in this thesis is focused on impeller stirred mixing associated with the refining of lead bullion. The aim of this process is to sequentially remove contained impurities such as copper, antimony, silver and bismuth. This occurs in hemispherical vessels, called kettles, where reagents are initially added to the lead bath to form surface dross that contains both the required impurity and a large amount of lead oxide. This dross is then continuously mixed back into the bath to remove the lead oxide and capture more of the required impurity. A key requirement for this process is to obtain and remove dross that contains a high concentration of the impurity. Although this process has been in operation for many years, there is very little known on how the fluid dynamics associated with the mixing process affects final dross content. The aim of this research is to fully investigate the lead refining process using scientific analysis methods that help understand the mixing process and provide design tools which can be used to optimise process conditions. The three methods of analysis used are: (1) Direct readings from a real kettle, (2) Physical modelling (using water), and finally (3) Computational Fluid Dynamics (CFD). The use of physical modelling, exploiting the techniques of similitude, to predict vortex was also validated. An Acoustic Doppler Velocimeter (ADV) probe was used for the velocity measurement at various locations inside the water model and this gave valuable insight about the flow phenomena occurring inside the refining kettle. A particular important finding was that when fluid is stirred above certain rotational speed the vortex depth becomes independent of the Reynolds number of the operation. With regards CFD technology, the Volume of Fluid (VOF) method was used to capture the free surface and the Lagrangian Particle Tracking (LPT) and Algebraic Slip Model (ASM) to simulate the dross phase. Appropriate methods were also used to represent the moving impeller region. Validation of simulation results against experimental data was very encouraging. Computed vortex depth showed the similar trend as observed during the experiments on the physical model. A design strategy was developed that integrates results from both physical and computational modelling to allow optimal process conditions to be predicted at the kettle design stage. The use of this integrated physical and computational modelling methodology successfully helped eliminate surface swirl by introducing baffles to the kettle. The design and introduction of these flow controllers was also validated to ensure that it optimised the dross mixing process and final impurity content in the dross.
28
Reddy, D. N. "Prediction of slam loads on ships using computational fluid dynamics (CFD) techniques". Thesis, University of Strathclyde, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.248950.
Testo completo
29
Roberge, Jennifer Anne. "Use of Computational Fluid Dynamics (CFD) to Model Flow at Pump Intakes". Digital WPI, 1999. https://digitalcommons.wpi.edu/etd-theses/1046.
Testo completoAbstract (sommario):
"This thesis presents a series of physical experiments and numerical simulations intended to determine whether the use of commercially available computational fluid dynamics (CFD) software may provide a viable alternative to the use of physical models for predicting the occurrence of vortices and swirl in pump intakes. The physical experiments were set up at Alden Research Laboratories, Inc. (ARL) of Holden, Massachusetts, using a simple pump intake model donated by ARL for use in this study. Swirl and velocity measurements and dye injections were used to characterize the flow in the physical model. Three flow conditions were chosen for the physical experiments because they demonstrated swirl and vortices developing at the pump intake. Once the physical experiments were performed, FIDAP, a general-purpose finite-element CFD package, was used to simulate the circulation patterns in the vicinity of a pump intake. The model configuration and scale were selected to simulate experimental conditions in the physical pump intake model. Some similarities were also identified in the locations of the models predicted vortex characteristics and the vortex characteristics that were observed in the experimental facility. However, the characteristics of swirl within the pump intake differed from experimental observations. Therefore, additional simulations were conducted to analyze the sensitivity of simulations to model assumptions. These additional simulations showed that the assumptions related to these model parameters have minor affects on the general nature of the predicted vortices, but do affect the predicted vortex strength. This thesis represents a first step in addressing the discrepancies between numerical and experimental results. Additional investigations are recommended to clarify the applicability of CFD to address pump intake problems."
30
El-Achwah, Ahmad Mr. "OPTIMIZING NASAL CANNULAS FOR INFANTS USING COMPUTATIONAL FLUID DYNAMICS". VCU Scholars Compass, 2019. https://scholarscompass.vcu.edu/etd/6096.
Testo completoAbstract (sommario):
Aerosolized medications can potentially be delivered to the lungs of infants through a nasal cannula interface. However, nose-to-lung delivery technologies currently allow for ~1% of the loaded dose to reach an infant’s lungs. Conventional dry powder inhalers (DPI) are superior to other types of inhalers in many ways. However, passive DPIs that operate based on user inhalation and require large volumes of airflow are not applicable to infants. To overcome this challenge, positive pressure DPIs have been developed that enable aerosol delivery to infants. Unless an adequate nasal interface is used with these devices, a significant amount of drug will still be lost. Computational fluid dynamics (CFD) provide a method to assess the performance of a nasal cannula interface and optimize its performance. In this study, a CFD model was first experimentally validated using the low-Reynolds number k-ω turbulence model, then used to assess and optimize several conical diffuser cannula designs for infants. The performance of a cannula depends primarily on two requirements: the amount deposited particles and the cannula’s volume. It was found that 90 and 100 mm long simple diffusers achieved the necessary deposition and volume requirements when operated at 3 and 5 liters per minute, respectively. Additionally, including clean sheath co-flow air with the 70 mm long diffuser achieved the targeted performance requirements. Inclusion of recent advancements in the field with the recommended cannula designs is likely to improve pharmaceutical aerosol delivery to infants using the nose-to-lung approach.
31
Hu, Shishan. "Application of computational fluid dynamics to aerosol sampling and concentration". [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1345.
Testo completo
32
Rogers, Charles. "Computational Fluid Dynamics Analysis of an Ideal Anguilliform Swimming Motion". ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1940.
Testo completoAbstract (sommario):
There is an ongoing interest in analyzing the flow characteristics of swimming fish. Biology has resulted in some very efficient motions and formulating these motions is of interest to engineers. One such theory was written by Dr. William Vorus and Dr. Brandon Taravella involving ideal efficiency. It is therefore interesting to test the calculations to see if it is possible to design a motion that can create thrust without necessarily creating vorticity. The computational fluid dynamics software of ANSYS Fluent was used to calculate the resulting flow field of the eel motion to compare with the theoretical values.
33
Hannon, Justin Wayne. "Image based computational fluid dynamics modeling to simulate fluid flow around a moving fish". Thesis, University of Iowa, 2011. https://ir.uiowa.edu/etd/1142.
Testo completoAbstract (sommario):
Understanding why fish move the way in which they do has applications far outside of biology. Biological propulsion has undergone millions of years of refinement, far outpacing the capabilities of anything created by man. Research in the areas of unsteady/biological propulsion has been increasing in the last several decades with advances in technology. Researchers are currently conducting experiments using pitching and heaving airfoils, mechanized fish, and numerical fish. However, the surrogate propulsors that are being used in experiments are driven analytically, whereas in this study, a method has been developed to exactly follow the motion of swimming fish.
The research described in this thesis couples the image analysis of swimming fish with computational fluid dynamics to accurately simulate a virtual fish. Videos of two separate fish swimming modes were analyzed. The two swimming modes are termed `free-stream swimming' and the `Kármán gait'. Free-stream swimming is how fish swim in a section of water that is free of disturbances, while Kármán gait swimming is how fish swim in the presence of a vortex street. Each swimming mode was paired with two simulation configurations, one that is free of obstructions, and one that contains a vortex street generating D-section cylinder. Data about the efficiency of swimming, power output, and thrust production were calculated during the simulations.
The results showed that the most efficient mode of swimming was the Kármán gait in the presence of a Kármán vortex street. Evidence corroborating this has been found in the literature. The second most efficient means of swimming was found to be free-stream swimming in the absence of obstructions. The other two configurations, which are not observed in experiments, performed very poorly in regard to swimming efficiency.
34
Sharpe, Jacob Andrew. "3D CFD Investigation of Low Pressure Turbine Aerodynamics". Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright1495872867696744.
Testo completo
35
Phillips, Tyrone. "Residual-based Discretization Error Estimation for Computational Fluid Dynamics". Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/50647.
Testo completoAbstract (sommario):
The largest and most difficult numerical approximation error to estimate is discretization error. Residual-based discretization error estimation methods are a category of error estimators that use an estimate of the source of discretization error and information about the specific application to estimate the discretization error using only one grid level. The higher-order terms are truncated from the discretized equations and are the local source of discretization error. The accuracy of the resulting discretization error estimate depends solely on the accuracy of the estimated truncation error. Residual-based methods require only one grid level compared to the more commonly used Richardson extrapolation which requires at least two. Reducing the required number of grid levels reduces computational expense and, since only one grid level is required, can be applied to unstructured grids where multiple quality grid levels are difficult to produce. The two residual-based discretization error estimators of interest are defect correction and error transport equations. The focus of this work is the development, improvement, and evaluation of various truncation error estimation methods considering the accuracy of the truncation error estimate and the resulting discretization error estimates. The minimum requirements for accurate truncation error estimation is specified along with proper treatment for several boundary conditions. The methods are evaluated using various Euler and Navier-Stokes applications. The discretization error estimates are compared to Richardson extrapolation. The most accurate truncation error estimation method was found to be the k-exact method where the fine grid with a correction factor was considerably reliable. The single grid methods including the k-exact require that the continuous operator be modified at the boundary to be consistent with the implemented boundary conditions. Defect correction showed to be more accurate for areas of larger discretization error; however, the cost was substantial (although cheaper than the primal problem) compared to the cost of solving the ETEs which was essential free due to the linearization. Both methods showed significantly more accurate estimates compared to Richardson extrapolation especially for smooth problems. Reduced accuracy was apparent with the presence of stronger shocks and some possible modifications to adapt to singularies are proposed for future work.Ph. D.
36
Ivchenko, Alexander. "Incorporation of OpenFOAM software into Computational Fluid Dynamics process in Volvo Technology". Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-16356.
Testo completoAbstract (sommario):
In this thesis work the feasibility of using open source OpenFOAM software as a solver part for Computation Fluid Dynamics in Volvo Technology is studied. Since the structure of the case in OpenFOAM is rather complex, one of the main purposes of this thesis work was also to make the process of using OpenFOAM as user-friendly as possible. The general conclusion that can be drawn from this work is that a very streamlined workflow can be, and has been, designed and created.
37
Linton, Daniel. "A Hybrid Computational Fluid Dynamics Method for Unsteady Simulation of the Ship-Helicopter Dynamic Interface". Thesis, University of Sydney, 2020. https://hdl.handle.net/2123/22894.
Testo completoAbstract (sommario):
Helicopters operating from ships are exposed to turbulent airwakes which can determine ship-helicopter operating limits. During concurrent operations rotor-rotor interactions add to the complexity of the aerodynamics. Computational fluid dynamics solvers are able to predict these aerodynamics from first principles with the aid of turbulence-resolving approaches such as detached eddy simulation. Although it is possible to create body-fitted grids to resolve the rotor blades and move them, the fuselage, and the ship relative to one another, this is a computationally expensive and labour intensive method. To avoid this expense and while accurately predicting unsteady loading, a time accurate rotor model has been coupled to a Navier-Stokes solver by introducing momentum source terms to the governing equations. A novel coupling algorithm that accounts for the effects of unsteady aerodynamics as well as the induced velocity of the wake has been developed and validated. The coupled rotor model predicts performance, thrust and torque distributions, and unsteady aerodynamic loading of isolated and interacting rotors. A time accurate wake can also be generated by the model. The method requires far fewer grid points to resolve the rotor than a body-fitted grid and grids can be generated automatically. Navier-Stokes simulation of the ship airwake is a complex task and many of the parameters of importance for such simulations have been identified in the literature. A study of grid convergence of velocity spectra and analysis of finite sample error have been performed to add to this knowledge. A method for objectively assessing the finite sample error and determining the minimum sample time required to reach a certain error has been applied to ship airwake simulations for the first time and a minimum level of grid refinement for resolved velocity spectra suggested. The ship airwake and rotor model have been combined for ship-helicopter dynamic interface simulations of single helicopter operations and concurrent helicopter operations involving five rotors. These simulations demonstrate the ability of the method to predict the aerodynamic factors that influence ship-helicopter operating limits and, to the best of our knowledge, contain more vehicles than any previously published dynamic interface simulations.
38
Soria, Guerrero Manel. "Parallel multigrid algorithms for computational fluid dynamics and heat transfer". Doctoral thesis, Universitat Politècnica de Catalunya, 2000. http://hdl.handle.net/10803/6678.
Testo completoAbstract (sommario):
The main purpose of the dissertation is to contribute to the development of numerical techniques for computational heat transfer and fluid flow, suitable for low cost (loosely coupled) parallel computers. It is focused on implicit integration schemes, using finite control volumes with multigrid (MG) algorithms.Natural convection in closed cavities is used as a problem model to introduce different aspects related with the integration of the incompressible Navier-Stokes equations, such as the solution of the pressure correction (or similar) equations that is the bottleneck of the algorithms for parallel computers. The main goal of the dissertation has been to develop new algorithms to advance in the solution of this problem rather than to implement a complete parallel CFD code.
An overview of different sequential multigrid algorithms is presented, pointing out the difference between geometric and algebraic multigrid. A detailed description of segregated ACM is given. The direct simulation of a turbulent natural convection flow is presented as an application example. A short description of the coupled ACM variant is given.
Background information of parallel computing technology is provided and the the key aspects for its efficient use in CFD are discussed. The limitations of low cost, loosely coupled cost parallel computers (high latency and low bandwidth) are introduced. An overview of different control-volume based PCFD and linear equation solvers is done. As an example, a code to solve reactive flows using Schwartz Alternating Method that runs particularly well on Beowulf clusters is given.
Different alternatives for latency-tolerant parallel multigrid are examined, mainly the DDV cycle proposed by Brandt and Diskin in a theoretical paper. One of its main features is that, supressing pre-smoothing, it allows to reduce the each-to-neighbours communications to one per MG iteration. In the dissertation, the cycle is extended to two-dimensional domain decompositions. The effect of each of its features is separately analyzed, concluding that the use of a direct solver for the coarsest level and the overlapping areas are important aspects. The conclusion is not so clear respect to the suppression of the pre-smoothing iterations.
A very efficient direct method to solve the coarser MG level is needed for efficient parallel MG. In this work, variant of the Schur complement algorithm, specific for relatively small, constant matrices has been developed. It is based on the implicit solution of the interfaces of the processors subdomains. In the implementation proposed in this work, a parallel evaluation and storage of the inverse of the interface matrix is used. The inner nodes of each domain are also solved with a direct algorithm. The resulting algorithm, after a pre-processing stage, allows a very efficient solution of pressure correction equations of incompressible flows in loosely coupled parallel computers.
Finally, all the elements presented in the work are combined in the DDACM algorithm, an algebraic MG equivalent to the DDV cycle, that is as a combination of a parallel ACM algorithm with BILU smoothing and a specific version of the Schur complement direct solver. It can be treated as a black-box linear solver and tailored to different parallel architectures.
The parallel algorithms analysed (different variants of V cycle and DDV) and developed in the work (a specific version of the Schur complement algorithm and the DDACM multigrid algorithm) are benchmarked using a cluster of 16 PCs with a switched 100 Mbits/s network.
The general conclusion is that the algorithms developed are suitable options to solve the pressure correction equation, that is the main bottleneck for the solution of implicit flows on loosely coupled parallel computers.
39
Fabritius, Björn. "Application of genetic algorithms to problems in computational fluid dynamics". Thesis, University of Exeter, 2014. http://hdl.handle.net/10871/15236.
Testo completoAbstract (sommario):
In this thesis a methodology is presented to optimise non–linear mathematical models in numerical engineering applications. The method is based on biological evolution and uses known concepts of genetic algorithms and evolutionary compu- tation. The working principle is explained in detail, the implementation is outlined and alternative approaches are mentioned. The optimisation is then tested on a series of benchmark cases to prove its validity. It is then applied to two different types of problems in computational engineering. The first application is the mathematical modeling of turbulence. An overview of existing turbulence models is followed by a series of tests of different models applied to various types of flows. In this thesis the optimisation method is used to find improved coefficient values for the k–ε, the k–ω-SST and the Spalart–Allmaras models. In a second application optimisation is used to improve the quality of a computational mesh automatically generated by a third party software tool. This generation can be controlled by a set of parameters, which are subject to the optimisation. The results obtained in this work show an improvement when compared to non–optimised results. While computationally expensive, the genetic optimisation method can still be used in engineering applications to tune predefined settings with the aim to produce results of higher quality. The implementation is modular and allows for further extensions and modifications for future applications.
40
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.
Testo completo
41
Villamizar, Urbano Montañez 1983. "Estudo da fluidodinâmica em um Erlenmeyer com uso de CFD". [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266101.
Testo completoAbstract (sommario):
Orientador: José Roberto NunhezDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2018-08-25T09:46:44Z (GMT). No. of bitstreams: 1 Villamizar_UrbanoMontanez_M.pdf: 2761421 bytes, checksum: b36bf4d1123da6ad78402c7d206517a3 (MD5) Previous issue date: 2013
Resumo: Os Erlenmeyers agitados têm sido utilizados como uma ferramenta em pesquisa na área biotecnológica e laboratórios industriais, especialmente em estágios iniciais, onde graças a sua praticidade, muitos experimentos podem ser realizados simultaneamente com um baixo custo e virtualmente sem supervisão. No entanto, esses dispositivos só fornecem informação limitada dos processos fenomenológicos que acontecem dentro do Erlenmeyer, tais como a velocidade rotacional, que dá uma ideia dos requerimentos de mistura, etc. Esta limitação pode dificultar a transição de um novo processo da bancada experimental para a escala piloto ou industrial. Alguns estudos de pesquisa têm sido realizados para determinar importantes variáveis de processo, tais como consumo de potência volumétrico, capacidade de transferência de oxigênio, estresse hidrodinâmico, etc. A fluidodinâmica computacional (CFD) tem ganhado importância recentemente no estudo dos fenômenos de transporte, graças aos avanços no desenvolvimento de software especializado, e poder computacional. O objetivo desse trabalho é simular o processo de agitação desenvolvido em um Erlenmeyer agitado em máquinas orbitais, utilizando o pacote computacional CFX versão 14. Os resultados CFD são comparados com os dados experimentais disponíveis para validar o modelo com o objetivo de estudar a fluidodinâmica desenvolvida nestes dispositivos
Abstract: Erlenmeyers have been used as a tool in many biotechnology research and industrial laboratories, especially in its early stages when many experiments can be performed simultaneously at low cost and nearly without supervision. However, these devices offer only limited information on the phenomenological processes occurring within these shake flasks, as the rotational speed which gives an idea of the mixing requirements, etc. This limitation could be a difficulty when trying to scale up new processes developed in laboratories to a pilot plant scale or an industrial processes. Some experimental research has been carried out to determine important process variables in Erlenmeyer agitation such as volumetric power consumption, oxygen transfer capacity, hydrodynamic stress, etc. Computational fluid dynamics (CFD) has recently gained importance in the study of transport phenomena, thanks to advances in the development of specialized software, and computational power. The objective of this work is to simulate the mixing process in an Erlenmeyer flask. The software used is CFX version 14. The CFD results is compared with the experimental data available to validate this computational model in order to study the fluid dynamics that develops in these devices
Mestrado
Desenvolvimento de Processos Químicos
Mestre em Engenharia Química
42
Ahlawat, Paramvir. "CFD Modeling of Hydrodynamics of Fluidized Bed". Thesis, 2009. http://ethesis.nitrkl.ac.in/261/1/PROJECT1.pdf.
Testo completoAbstract (sommario):
The objective of this project is to simulate a gas-solid fluidized by applying CFD techniques in order to investigate hydrodynamics and heat transfer phenomena. Reactor model predictions will be compared with the corresponding experimental data reported in the literature to validate the model . To simulate a gas-solid fluidized bed we need to use the multiphase flow approach . First we have to write the equations for the different flow regimes and then different CFD techniques are applied for discretization of those equations. After that a code is written for calculating the values of volume fraction , velocity and temperature .
43
AD, Thirumuruga, e Paramita Das. "CFD Modelling of a flat plate". Thesis, 2010. http://ethesis.nitrkl.ac.in/1901/1/thiru_proj.pdf.
Testo completoAbstract (sommario):
Performance of an aircraft wing depends on the smoothness of the air flow over it. Any accumulation of frost, snow or ice on the wings or other horizontal surfaces will substantially alter the lifting characteristics of the airfoil and also changes the values of aerodynamic forces exerted on the airfoil. So any small change in flow parameters could affect its performance in a larger scale. This can sometimes be disastrous too. The wings of the airplane are also susceptible to corrosion also due to the excess humidity level. When it comes to large airfoils like aircraft wings, these parameters have to be maintained perfect so that the probability of failure is minimized. The basic test surface for investigating the effects of various parameters to the underlying boundary layer is the universal flat plate. Therefore a flat plate is used for this study.
The present paper concentrates on analyzing various flow parameters of cold air while it flows over a flat plate. Modeling and analysis of the flow were performed using FLUENT, version 6.3. The results obtained are purely the simulation software based calculations.
44
Priyadarshini, Varsa. "Study of Drag Coefficient Using CFD Tools". Thesis, 2012. http://ethesis.nitrkl.ac.in/3476/1/B._Tech_Thesis_108CH045.pdf.
Testo completoAbstract (sommario):
Flow over cylinder is frequently encountered in practice. The objective of this project is modelling and simulation of the flow over a cylinder by using CFD techniques in order to study the values of drag coefficient at different Reynolds number ranging from 1 to 100 at a given Length to Diameter ratio (L/D). Different length to diameter ratio (L/D) of cylinder is considered, ranging from 0.005 to 1 is taken. Study of the variation of drag coefficient at different L/D ratios of the cylinder at a constant Reynolds has been done graphically. Comparison of the values of drag coefficient at L/D equal to one with that of the sphere has been done graphically and discussed. Analysis and discussion of the flow over the cylinder at varying Reynolds number and different L/D ratios using velocity contours, pressure contours, streamlines and vorticity plots.
45
Bhoi, Stutee. "Study of microchannel reactor using cfd analysis". Thesis, 2012. http://ethesis.nitrkl.ac.in/3891/1/THESIS-_STUTEE_BHOI.pdf.
Testo completoAbstract (sommario):
Microchannel reactors involve reaction chamber whose dimensions are typically in the range of micrometers (µm) with volumetric capacity in the range of micro liters (µL). The high surface to volume ratio, efficient heat and mass transfer characteristics and vastly improved fluid mixing allow precision control of reaction with improved conversions,selectivities and yields of desired products. Reverse-flow action is used to utilize the thermal energy inside a reactor.Energy from the reaction and exit gasses are captured and utilized within the reactor by the reversing flow action.The captured thermal energy can be used to preheat the feed or can be extracted from the reactor. The present work is aimed to study the behavior of combustion reaction of methane and propane inside a icrochannel reactor. The advantages of reverse flow reactor have been found out by studying the phenomenon inside a reverse flow reactor. Both steady state and transient imulations has been carried out. Steady state solution was used as the basis for transient solution. The transient solution shows the presence of cyclic steady state temperature profile inside the reactor. The result reveals that the temperature of the gas increases with axial length, reaches maximum and then decreases.With increase in inlet temperature,maximum temperature of the fluid increases.Besides,the temperature peak decreases with increase in mass diffusivity of the mixture and wall heat transfer coefficient. It is also observed that the reaction starts near the wall and then proceed towards the center.
46
Patra, Chinmayee. "Cfd simulations of fluidized bed Biomass gasification". Thesis, 2014. http://ethesis.nitrkl.ac.in/6563/1/M.Tech(R)_Thesis_(611ch304).pdf.
Testo completoAbstract (sommario):
CFD simulation of fluidized bed biomass gasification process has been carried out in the present work. The gas-solid interaction, thermal-flow behavior and gasification process inside a fluidized-bed biomass gasifier are studied using the commercial CFD solver ANSYS/FLUENT13.0. Velocity profile, bed expansion, solid movement, temperature profile, species mass fractions have been focused in the present work. Three phases are used to model the reactor (sand, solid phase for the fuel, and gas phase). All phases are described using an Eulerian approach to model the exchange of mass, energy and momentum. In the present work rice husk is considered as feed material and sand is taken as the inert bed material. The influences of particle properties viz. particle size (530μm, 856μm) and other operating parameters namely, gas velocity (0.05-2 m/s) and temperature (600-1000K) of the gasifier have been investigated comprehensively. It is found that superficial gas velocity has a strong influence on the axial solids velocity and subsequently on the down flow of solids. Gas temperature and species distributions indicate that reactions in the instantaneous gasification model occur very fast and finish very quickly. Temperature of 1000K, superficial velocity of air of 0.7m/s is found to be most favourable for gasification of rice husk with an indication of 100% carbon conversion. On the other hand the reactions in the finite-rate model involve gas-solid reactions which occur slowly with unburnt chars at the exit. The mass fractions of product gas are also validated with the experimental data. Thus the developed simulation model will be a powerful theoretical basis for accurate design of FBG.
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Meher, Bijaya Kumar. "CFD Analysis of a Pulse Tube Cryocooler". Thesis, 2015. http://ethesis.nitrkl.ac.in/7568/1/181.pdf.
Testo completoAbstract (sommario):
Pulse tube refrigerators are latest technical instrument in the field of refrigeration engineering. So they are preferred over other types of cryocooler like Stirling and Gifford-McMahon coolers because of no moving parts in the cooler making the cooler widely useful for various purposes. Other ordinary refrigerators use vapor compression cycle but pulse tube utilizes oscillatory expansion and compression of gas present inside it. Pulse tube cryocooler has long life compared to other refrigerators, high reliability and low vibration because of no solid piston moving. These coolers have vast applications like semiconductor manufacture and its endless use in military for the cooling of the infrared sensors. They are also used for the cooling of astronomical detectors. They are also used for pre coolers of dilution refrigerators. They are used in space application also. In this work study of Stirling type OPT cryocooler is considered for CFD analysis using fluent present in ANSYS15 workbench. 2D axis-symmetric geometry is created and used for CFD analysis. The simulations represent a fully-coupled system operating in steady periodic mode, with a trapezoidal pressure profile. Nothing is assumed rather than ideal gas and no gravity effect. The boundary conditions applied on this model are a oscillating pressure of trapezoid profile created using user defined function (UDF), thermal boundary conditions like adiabatic and known heat flux at the cold end heat exchanger. The purpose is to study the Orifice Pulse tube cryocooler(OPTR) using CFD fluent analysis. Where dimensions of components of OPTR are taken from YP Banjare thesis[1] for values of optimum result. In order to observe refrigeration pressure wave of same specification like frequency and amplitude are applied for both cases as described. For each condition two separate analyses are done. One analysis assumes no load or adiabatic cold-end heat exchanger (CHX); other assumes isothermal or known cooling heat load. Each analysis was started with initial conditions, and carried on until steady periodic conditions are attained. The unsteady CFD model successfully predicts OPTR performance through solving an ideal gas equation and heat transfer. The result is discussed in Result and Discussion section.
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Gopaliya, Manoj Kumar. "CFD modelling of slurry flows through horizontal pipelines". Thesis, 2018. http://localhost:8080/iit/handle/2074/7628.
Testo completo
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Bhola, Deepak Ranjan. "CFD analysis of flow through venturi of carburetor". Thesis, 2011. http://ethesis.nitrkl.ac.in/2296/1/final_report.pdf.
Testo completoAbstract (sommario):
Modern passenger vehicles with gasoline engines are provided with different compensating devices for fuel air mixture supply. Even then there is a high fuel consumption because of many factors. One of the important factors that affect the fuel consumption is that design of carburetor. The venturi of the carburetor is important that provides a necessary pressure drop in the carburetor device. Since different SI engine alternative fuels such as LPG, CNG are used in the present day vehicles to reduce the pollution and fuel consumption. Still for a better economy and uniform fuel air supply there is a need to design the carburetor with an effective analytical tool or software. In this work three parameters namely pressure drop and fuel discharge nozzle angle of the carburetor will be analyzed using computational fluid dynamics. For this analysis CFD will be done using 2 softwares namely GAMBIT and FLUENT. The results obtained from the softwares will be analyzed for optimum design of a carburetor.
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Sain, Suresh. "CFD analysis of flow pattern in electrochemical machining". Thesis, 2011. http://ethesis.nitrkl.ac.in/2452/1/Thesis.pdf.
Testo completoAbstract (sommario):
Electrochemical machining is the advanced machining method and it has been applied to many highly specialize field like aerospace and medical industries. But, in this technology still we have many problems to overcome such as electrolytic processing and disposal of metal hydroxide sludge etc.. Many of machine tools used in this machining method works in a pulsating mode. So besides these vibrations we can’t get accuracy in the results. So to obtain the accurate results we have to overcome these problems, and CFD is considered to be the most powerful tool for that. But there is no such numerical method which can satisfactorily predict the flow. It is necessary to take into account that the unsteady character of electrolyte flow in the inter-electrode space. For this purpose orthogonal coordinate system it to introduce on the anode surface.
For the description of the electrolyte flow the system of the equation of preservation for mass of liquid and we have to find the solutions of different parameters used in this technology and also compare these quantities with the standard values. For these entire CFD analysis purpose one can use Gambit-Fluent software which can provide an overview about the machining parameters like, how they affect the process, which flow velocity is suitable for a particular value of current density.