Journal articles on the topic 'A validated 3-D CFD technique'
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Zhiyang, Zhang, Ma Yong, Jiang Jin, Liu Weixing, and Ma Qingwei. "3-D Simulation of Vertical-Axial Tidal Current Turbine." Polish Maritime Research 23, no. 4 (December 1, 2016): 73–83. http://dx.doi.org/10.1515/pomr-2016-0072.
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Abstract Vertical-axial tidal current turbine is the key for the energy converter, which has the advantages of simple structure, adaptability to flow and uncomplex convection device. It has become the hot point for research and application recently. At present, the study on the hydrodynamic performance of vertical-axial tidal current turbine is almost on 2-D numerical simulation, without the consideration of 3-D effect. CFD (Computational Fluid Dynamics) method and blade optimal control technique are used to improve accuracy in the prediction of tidal current turbine hydrodynamic performance. Numerical simulation of vertical-axial tidal current turbine is validated. Fixed and variable deflection angle turbine are comparatively studied to analysis the influence of 3-D effect and the character of fluid field and pressure field. The method, put the plate on the end of blade, of reduce the energy loss caused by 3-D effect is proposed. The 3-D CFD numerical model of vertical-axial tidal current turbine hydrodynamic performance in this study may provide theoretical, methodical and technical reference for the optimal design of turbine.
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Garg, Nitin, Gaetan K. W. Kenway, Zhoujie Lyu, Joaquim R. R. A. Martins, and Yin L. Young. "High-Fidelity Hydrodynamic Shape Optimization of a 3-D Hydrofoil." Journal of Ship Research 59, no. 04 (December 1, 2015): 209–26. http://dx.doi.org/10.5957/jsr.2015.59.4.209.
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With recent advances in high-performance computing, computational fluid dynamics (CFD) modeling has become an integral part in the engineering analysis and even in the design process of marine vessels and propulsors. In aircraft wing design, CFD has been integrated with numerical optimization and adjoint methods to enable high fidelity aerodynamic shape optimization with respect to large numbers of design variables. There is a potential to use some of these techniques for maritime applications, but there are new challenges that need to be addressed to realize that potential. This work presents a solution to some of those challenges by developing a CFD-based hydrodynamic shape optimization tool that considers cavitation and a wide range of operating conditions. A previously developed three-dimensional compressible Reynold saveraged Navier-Stokes (RANS) solver is extended to solve for nearly incompressible flows, using a low-speed preconditioner. An efficient gradient-based optimizer and the adjoint method are used to carry out the optimization. The modified CFD solver is validated and verified for a tapered NACA 0009 hydrofoil. The need for a large number of design variables is demonstrated by comparing the optimized solution obtained using different number of shape design variables. The results showed that at least 200 design variables are needed to get a converged optimal solution for the hydrofoil considered. The need for a high-fidelity hydrodynamic optimization tool is also demonstrated by comparing RANS-based optimization with Euler-based optimization. The results show that at high lift coefficient (CL) values, the Euler-based optimization leads to a geometry that cannot meet the required lift at the same angle of attack as the original foil due to inability of the Euler solver to predict viscous effects. Single-point optimization studies are conducted for various target CL values and compared with the geometry and performance of the original NACA 0009 hydrofoil, as well as with the results from a multipoint optimization study. A total of 210 design variables are used in the optimization studies. The optimized foil is found to have a much lower negative suction peak, and hence delayed cavitation inception, in addition to higher efficiency, compared to the original foil at the design CL value. The results show significantly different optimal geometry for each CL, which means an active morphing capability was needed to achieve the best possible performance for all conditions. For the single-point optimization, using the highest CL as the design point, the optimized foil yielded the best performance at the design point, but the performance degraded at the off-design CL points compared to the multipoint design. In particular, the foil optimized for the highest CL showed inferior performance even compared to the original foil at the lowest CL condition. On the other hand, the multipoint optimized hydrofoil was found to perform better than the original NACA 0009 hydrofoil over the entire operation profile, where the overall efficiency weighted by the probability of operation at each CL, is improved by 14.4%. For the multipoint optimized foil, the geometry remains fixed throughout the operation profile and the overall efficiency was only 1.5% lower than the hypothetical actively morphed foil with the optimal geometry at each CL. The new methodology presented herein has the potential to improve the design of hydrodynamic lifting surfaces such as propulsors, hydrofoils, and hulls.
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Taco-Vasquez, Sebastian, César A. Ron, Herman A. Murillo, Andrés Chico, and Paul G. Arauz. "Thermochemical Analysis of a Packed-Bed Reactor Using Finite Elements with FlexPDE and COMSOL Multiphysics." Processes 10, no. 6 (June 7, 2022): 1144. http://dx.doi.org/10.3390/pr10061144.
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This work presents the thermochemical analysis of a packed-bed reactor via multi-dimensional CFD modeling using FlexPDE and COMSOL Multiphysics. The temperature, concentration, and reaction rate profiles for methane production following the Fischer–Tropsch (F-T) synthesis were studied. To this end, stationary and dynamic differential equations for mass and heat transfer were solved via the finite element technique. The transport equations for 1-D and 2-D models using FlexPDE consider dispersion models, where the fluid and the catalyst can be treated as either homogeneous or heterogenous systems depending on the gradient extents. On the other hand, the 3-D model obtained in COMSOL deems the transport equations incorporated in the Porous Media module. The aim was to compare the FlexPDE and COMSOL models, and to validate them with experimental data from literature. As a result, all models were in good agreement with experimental data, especially for the 2-D and 3-D dynamic models. In terms of kinetics, the predicted reaction rate profiles from the COMSOL model and the 2-D dynamic model followed the temperature trend, thus reflecting the temperature dependence of the reaction. Based on these findings, it was demonstrated that applying different approaches for the CFD modeling of F-T processes conducts reliable results.
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Amorim, Felipe Grossi L., Marcio E. Guzzo, Leonardo Mayer Reis, R. O. Coelho, and Ramon Molina Valle. "Numerical Validation of the Ethanol Spray Produced by a Direct Injection Injector for Different Pressure Conditions." Applied Mechanics and Materials 798 (October 2015): 213–18. http://dx.doi.org/10.4028/www.scientific.net/amm.798.213.
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This study presents a methodology to validate CFD simulations of the spray fuel injection using an experimental bench and optical measurement tools along with the Shadowgraph Technique. The parameter used for validating the experiments is the penetration rate, under situations of 6 bar and 100 bar injection pressures. The results show a penetration rate difference lower than 3% between the numerical model and the physical test. The visual plots, considering the shape and angles of the spray, also matched. Once validated, the numerical model could be applied to dynamic models of internal combustion engines and used to elaborate injection strategies for future projects.
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Li, Qing, Can Kang, Shuang Teng, and Mingyi Li. "Optimization of Tank Bottom Shape for Improving the Anti-Deposition Performance of a Prefabricated Pumping Station." Water 11, no. 3 (March 22, 2019): 602. http://dx.doi.org/10.3390/w11030602.
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High flexibility of prefabricated pumping stations in collecting and transporting storm water has been recognized. Nevertheless, flows inside such a complex system have rarely been reported. The present study aims to reveal water-sand flow characteristics in a prefabricated pumping station and to optimize geometric parameters of the tank to mitigate sand particle deposition. Five tank schemes, varying in the ratio of the diameter to the height of the tank bottom (D/L), were investigated. Flows in the pumping station were simulated using the computational fluid dynamics (CFD) technique. Test data were used to validate the numerical scheme. Three-dimensional water-sand flows in the pumping station were described. Underlying mechanisms of sand particle deposition were explained. The results indicate that the risk of deposition is high at the tank bottom side, close to the tank inlet. Both the tank bottom geometry and the inlet suction of the pump contribute to sand particle deposition. The averaged sand volume fraction at the pump inlet reaches its minimum at D/L = 3. Sand particle velocity at the pump inlet varies inversely with D/L. The highest intensity of the vortex at the pump inlet arises at D/L = 3. The best anti-deposition performance of the pumping station is attained at D/L = 3.
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Song, Eui-Hyeok, Kye-Bock Lee, and Seok-Ho Rhi. "Thermal and Flow Simulation of Concentric Annular Heat Pipe with Symmetric or Asymmetric Condenser." Energies 14, no. 11 (June 6, 2021): 3333. http://dx.doi.org/10.3390/en14113333.
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The current research work describes the flow and thermal analysis inside the circular flow region of an annular heat pipe with a working fluid, using computational fluid dynamics (CFD) simulation. A two-phase flow involving simultaneous evaporation and condensation phenomena in a concentric annular heat pipe (CAHP) is modeled. To simulate the interaction between these phases, the volume of fluid (VOF) technique is used. The temperature profile predicted using computational fluid dynamics (CFD) in the CAHP was compared with previously obtained experimental results. Two-dimensional and three-dimensional simulations were carried out, in order to verify the usefulness of 3D modeling. Our goal was to compute the flow characteristics, temperature distribution, and velocity field inside the CAHP. Depending on the shape of the annular heat pipe, the thermal performance can be improved through the optimal design of components, such as the inner width of the annular heat pipe, the location of the condensation part, and the amount of working fluid. To evaluate the thermal performance of a CAHP, a numerical simulation of a 50 mm long stainless steel CAHP (1.1 and 1.3 in diameter ratio and fixed inner tube diameter (78 mm)) was done, which was identical to the experimental system. In the simulated analysis results, similar results to the experiment were obtained, and it was confirmed that the heat dissipation was higher than that of the existing conventional heat pipe, where the heat transfer performance was improved when the asymmetric area was cooled. Moreover, the simulation results were validated using the experimental results. The 3-D simulation shows good agreement with the experimental results to a reasonable degree.
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Ruggles, Arthur E., Bi Yao Zhang, and Spero M. Peters. "Positron Emission Tomography (PET) for Flow Measurement." Advanced Materials Research 301-303 (July 2011): 1316–21. http://dx.doi.org/10.4028/www.scientific.net/amr.301-303.1316.
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Positron Emission Tomography (PET) produces a three dimensional spatial distribution of positron-electron annihilations within an image volume. Various positron emitters are available for use in aqueous, organic and liquid metal flows. Preliminary experiments at the University of Tennessee at Knoxville (UTK) injected small flows of PET tracer into a bulk water flow in a four rod bundle. The trajectory and diffusion of the tracer in the bulk flow were then mapped using a PET scanner. A spatial resolution of 1.4 mm is achieved with current preclinical Micro-PET imaging equipment resulting in 200 MB 3D activity fields. A time resolved 3-D spatial activity profile was also measured. The PET imaging method is especially well suited to complex geometries where traditional optical methods such as LDV and PIV are difficult to apply. PET methods are uniquely useful for imaging in opaque fluids, opaque pressure boundaries, and multiphase studies. Several commercial and shareware Computational Fluid Dynamics (CFD) codes are currently used for science and engineering analysis and design. These codes produce detailed three dimensional flow predictions. The models produced by these codes are often difficult to validate. The development of this experimental technique offers a modality for the comparison of CFD outcomes with experimental data. Developed data sets from PET can be used in verification and validation exercises of simulation outcomes.
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de Rochefort, Ludovic, Laurence Vial, Redouane Fodil, Xavier Maître, Bruno Louis, Daniel Isabey, Georges Caillibotte, et al. "In vitro validation of computational fluid dynamic simulation in human proximal airways with hyperpolarized 3He magnetic resonance phase-contrast velocimetry." Journal of Applied Physiology 102, no. 5 (May 2007): 2012–23. http://dx.doi.org/10.1152/japplphysiol.01610.2005.
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Computational fluid dynamics (CFD) and magnetic resonance (MR) gas velocimetry were concurrently performed to study airflow in the same model of human proximal airways. Realistic in vivo-based human airway geometry was segmented from thoracic computed tomography. The three-dimensional numerical description of the airways was used for both generation of a physical airway model using rapid prototyping and mesh generation for CFD simulations. Steady laminar inspiratory experiments (Reynolds number Re = 770) were performed and velocity maps down to the fourth airway generation were extracted from a new velocity mapping technique based on MR velocimetry using hyperpolarized 3He gas. Full two-dimensional maps of the velocity vector were measured within a few seconds. Numerical simulations were carried out with the experimental flow conditions, and the two sets of data were compared between the two modalities. Flow distributions agreed within 3%. Main and secondary flow velocity intensities were similar, as were velocity convective patterns. This work demonstrates that experimental and numerical gas velocity data can be obtained and compared in the same complex airway geometry. Experiments validated the simulation platform that integrates patient-specific airway reconstruction process from in vivo thoracic scans and velocity field calculation with CFD, hence allowing the results of this numerical tool to be used with confidence in potential clinical applications for lung characterization. Finally, this combined numerical and experimental approach of flow assessment in realistic in vivo-based human airway geometries confirmed the strong dependence of airway flow patterns on local and global geometrical factors, which could contribute to gas mixing.
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Karuppa Raj, R. Thundil, and M. P. Dhyan Shankar. "Effect of Convergent Angle on Flow Characteristics of Y-Shaped Diffusers Using CFD." Applied Mechanics and Materials 592-594 (July 2014): 1909–13. http://dx.doi.org/10.4028/www.scientific.net/amm.592-594.1909.
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Diffusing ducts are used in fluid flow systems, mainly in aeroplane engine inlets to decelerate the flow and to correspondingly increase the static pressure. The main problem in achieving a high pressure recovery is the flow separation which results in non-uniform distribution and excessive losses. The present work is aimed to study the flow characteristics in Y-shaped diffusing ducts. The Y-shaped diffuser has rectangular inlets and the outlet is circular with a certain settling length for the flow to be stabilized. The diffuser is modeled in CATIA V5 and further discretized using ICEMCFD12.1. Hexahedral mesh is generated for all diffuser cases, which have been used to capture the hydrodynamic boundary layers. ANSYS CFX 12.1 based on finite volume technique, using k-ε turbulence model is adopted for predicting the flow. The flow field through the 3-dimensional domain is captured by solving the appropriate governing equations namely, the continuity equation and the momentum equation. The convergence criterion is set to 10E-06 for mass and momentum. The whole investigation is done in two phases: in the first phase a commercial CFD code is validated for the results obtained for an S-shaped diffuser and in the second phase the same idea is then extended for the analysis of Y-shaped diffuser. The coefficient of static pressure, cross flow and axial flow velocity distributions are calculated based on the mass averaged quantities for the Y-shaped diffusers (30o and 40o).
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Nasraoui, Haythem, Zied Driss, Ahmed Ayadi, Abdallah Bouabidi, and Hedi Kchaou. "Numerical and experimental study of the impact of conical chimney angle on the thermodynamic characteristics of a solar chimney power plant." Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering 233, no. 5 (June 27, 2019): 1185–99. http://dx.doi.org/10.1177/0954408919859160.
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The goal of this paper is to study and optimize the conical chimney angle (α) of a divergent solar chimney power plant (DSCPP) by using CFD technique. The local airflow characteristics were analyzed in four configurations with different conical angles α = 0°, α = 3°, α = 6° and α = 9°. The first design is validated experimentally by using a pilot prototype build at the National School of Engineers of Sfax, Tunisia. In addition, some experimental results of the temperature, the velocity and the power output were presented during a typical day. A novel mathematical correlation was developed to prove the effect of the conical angle and the DSCPP scale on the power output. In fact, the relationship between the optimum conical angle and the system scale was performed based on both quadratic and cubic regressions. The computational results ensure that the conical chimney angle presents a parabolic tendency with the turbulence airflow characteristics and the power output. The performance of the DSCCP was degraded since the conical angle is greater than α = 3°. Furthermore, the optimum angle decreases with an increasing system scale. A commercial solar chimney with a conical angle around α = 1° presents an efficient system.
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Oyeneyin, Babs Mufutau, Said Mufarji, and Donald Igwegbu. "Innovative Solutions to Fines Management in High Permeability Sands." Advanced Materials Research 18-19 (June 2007): 287–92. http://dx.doi.org/10.4028/www.scientific.net/amr.18-19.287.
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Formation impairment due to fines migration during drilling and production continues to cause injectivity or inflow reduction. In high permeability sandstone formations or sandpacks, fines migration pose major concerns in the oil industry as it leads to reduction in oil/gas production. The problem is further enhanced in mature reservoirs where increased water ingress and multiphase production aggravate the fines mobilisation and migration. Proper fines management can optimise productivity, safeguard facilities and reduce well maintenance cost. Today’s core flood tests as part of risk assessment limit tests to single phase or at best two-phase oil/water flow. This paper presents the unique technique adopted to analyse fines migration mechanisms in a true multiphase environment. The technique integrates CFD and 3-D reservoir simulation concepts to define and quantify the effects of different operating conditions on discretised reservoir blocks. From the results obtained detailed mapping of prevailing pore blocking mechanisms and corresponding impairment profiles are presented as functions of operating conditions and completion strategies. The paper introduces a parallel experimental programme being initiated at The Robert Gordon University(RGU) to validate the simulation predictions. The paper is concluded with suggestions (supported by flow efficiency case studies) on contemporary innovations in fines management ranging from a radical use of expandable screens (ESSTM) or expandable slotted liners (ESLTM) or the intelligent VSSTM Screen to specialist application of glass or ceramic beads for pore diameter control and near wellbore reinforcement to initiate secondary filtration
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Spyropoulos, Nikos, Dimitris Vlastos, George Papadakis, John M. Prospathopoulos, and Vasilis A. Riziotis. "A strongly coupled Eulerian Lagrangian method applied in unsteady 3D external flows around Wind Turbine rotors." Journal of Physics: Conference Series 2265, no. 3 (May 1, 2022): 032008. http://dx.doi.org/10.1088/1742-6596/2265/3/032008.
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Abstract This paper presents a hybrid CFD solver that couples a standard Eulerian approach that solves the compressible Navier-Stokes equations under a cell-centered finite volume discretization, with a Lagrangian one, based on particles representation which carry mass, pressure, dilatation and vorticity. The velocity field is calculated using the Helmholtz’s decomposition theorem. Computational performance is enhanced by employing the Particle Mesh (PM) technique in order to solve the Poisson equations for the scalar potential ϕ and the stream function ψ. Even though validated for 2D flows over airfoils, this specific solver is used for the first time in order reproduce the flow around a wind turbine rotor. The validation simulations concern axial flow over the wind turbine model rotor used in the New MEXICO experimental campaign. Results of the hybrid solver, presented as blade pressure distribution and axial flow velocities are compared against the ones produced by its pure Eulerian counterpart and experimental measurements. PM grids of up to 5 points per chord of the blade section at 75% radius have been used. Comparison with the standard Eulerian solver suggest that the produced blade loads are over-predicted by approximately 7% near the tip and 14% near the root. However, the calculated velocity field is much closer to the experimental measurements as compared to the one produced by the Eulerian approach, which is attributed to the reduced numerical diffusion of the Lagrangian-vorticity formulation.
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Beabpimai, Wiroj, and Tawit Chitsomboon. "Numerical Study of Effect of Blade Twist Modifications on the Aerodynamic Performance of Wind Turbine." International Journal of Renewable Energy Development 8, no. 3 (August 19, 2019): 285–92. http://dx.doi.org/10.14710/ijred.8.3.285-292.
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This paper aims to investigate aerodynamic performance of a wind turbine blade with twist modifications using computational fluid dynamics (CFD). The phenomenon of 3D stall-delay effect in relation to blade twist is the key feature to be investigated in order to improve efficiency of a wind turbine. The NREL (National Renewable Energy Laboratory) Phase VI wind turbine rotor was used for validation and as the baseline rotor. The baseline blade geometry was modified by increasing/decreasing the twist angles in the inboard, mid-board and outboard regions of the blade in the form of a symmetrical curve with maximum twist angle of 3°. The steady incompressible Reynolds-averaged Navier-Stokes (RANS) equations with the k-ω Shear Stress Transport (SST) turbulence closure model were used for the calculations at wind speeds ranging from 5-20 m/s. The computational results for the baseline Phase VI rotor were validated against experimental data and a good agreement was found. The computational results for the modified blades were compared against those of the baseline blade. It was found that increase of annual energy production of up to 5.1% could be achieved by this modification technique. ©2019. CBIORE-IJRED. All rights reserved
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VIDYA, C., J. SHEEJA, and M. SEKAR. "TOWARDS REDUCING COMPUTATIONAL EFFORT IN VORTEX INDUCED VIBRATION PREDICTIONS OF A CYLINDRICAL RISER." Periódico Tchê Química 16, no. 33 (March 20, 2019): 841–53. http://dx.doi.org/10.52571/ptq.v16.n33.2019.856_periodico33_pgs_841_853.pdf.
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Vibrations induced by flow, generally referred to as vortex induced vibrations, are of great importance in the design of marine risers. These flexible cylindrical risers undergo vibrations of very high amplitude when the vortex shedding frequency matches the natural frequency of the riser. Such vibrations are capable of putting the safety of crew working on offshore platforms in question. Hence the prediction of response of such structures is considered very important. Although a lot of numerical work has been done in this field treating the problem as a two-way fluid structure interaction, the fact that these works demand very high computational efforts has not made it pertinent where high end computing resources are not readily available. A quick prediction of the structural response of such slender structures needs to be handy to the engineers at times of need. This paper addresses a solution technique for such a problem through an economical method for quick and reliable prediction of riser response under vortex induced vibration utilizing minimum computational effort for moderate Reynolds number (Re = 3 x 105). Two dimensional flow simulations are carried out using RANSE based CFD followed by the uniform mapping of hydrodynamic forces on to the three dimensional riser. The grid used for the numerical simulation has been well validated against wind-tunnel experimental results for Re= 5.3 x 104. Hydrodynamic forces corresponding to the first three harmonics of natural frequency of the riser have been used as input in the structural solver to analyse the response using finite element method. Trajectories of the cylinder in the first three modes of vibration have been obtained, a typical eight figure pattern which is characteristic for lock-in vibration. It is found that the method is quite effective in the quick computation of flow induced vibration problems for low and moderate Reynolds numbers.
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Kouichi, Hamza, Pierre Ngae, Pramod Kumar, Amir-Ali Feiz, and Nadir Bekka. "An optimization for reducing the size of an existing urban-like monitoring network for retrieving an unknown point source emission." Geoscientific Model Development 12, no. 8 (August 22, 2019): 3687–705. http://dx.doi.org/10.5194/gmd-12-3687-2019.
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Abstract. This study presents an optimization methodology for reducing the size of an existing monitoring network of the sensors measuring polluting substances in an urban-like environment in order to estimate an unknown emission source. The methodology is presented by coupling the simulated annealing (SA) algorithm with the renormalization inversion technique and the computational fluid dynamics (CFD) modeling approach. This study presents an application of the renormalization data-assimilation theory for optimally reducing the size of an existing monitoring network in an urban-like environment. The performance of the obtained reduced optimal sensor networks is analyzed by reconstructing the unknown continuous point emission using the concentration measurements from the sensors in that optimized network. This approach is successfully applied and validated with 20 trials of the Mock Urban Setting Test (MUST) tracer field experiment in an urban-like environment. The main results consist of reducing the size of a fixed network of 40 sensors deployed in the MUST experiment. The optimal networks in the MUST urban region are determined, which makes it possible to reduce the size of the original network (40 sensors) to ∼1/3 (13 sensors) and 1∕4 (10 sensors). Using measurements from the reduced optimal networks of 10 and 13 sensors, the averaged location errors are obtained as 19.20 and 17.42 m, respectively, which are comparable to the 14.62 m obtained from the original 40-sensor network. In 80 % of the trials with networks of 10 and 13 sensors, the emission rates are estimated within a factor of 2 of the actual release rates. These are also comparable to the performance of the original network, whereby in 75 % of the trials the releases were estimated within a factor of 2 of the actual emission rates.
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Smolka, Jacek, Andrzej J. Nowak, and Dawid Rybarz. "Improved 3-D temperature uniformity in a laboratory drying oven based on experimentally validated CFD computations." Journal of Food Engineering 97, no. 3 (April 2010): 373–83. http://dx.doi.org/10.1016/j.jfoodeng.2009.10.032.
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Talpallikar, M. V., C. E. Smith, M. C. Lai, and J. D. Holdeman. "CFD Analysis of Jet Mixing in Low NOx Flametube Combustors." Journal of Engineering for Gas Turbines and Power 114, no. 2 (April 1, 1992): 416–24. http://dx.doi.org/10.1115/1.2906607.
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The Rich-burn/Quick-mix/Lean-burn (RQL) combustor has been identified as a potential gas turbine combustor concept to reduce NOx emissions in High Speed Civil Transport (HSCT) aircraft. To demonstrate reduced NOx levels, cylindrical flametube versions of RQL combustors are being tested at NASA Lewis Research Center. A critical technology needed for the RQL combustor is a method of quickly mixing bypass combustion air with rich-burn gases. In this study, jet mixing in a cylindrical quick-mix section was numerically analyzed. The quick-mix configuration was five inches in diameter and employed 12 radial-inflow slots. The numerical analyses were performed with an advanced, validated 3-D Computational Fluid Dynamics (CFD) code named REFLEQS. Parametric varation of jet-to-mainstream momentum flux ratio (J) and slot aspect ratio was investigated. Both nonreacting and reacting analyses were performed. Results showed mixing and NOx emissions to be highly sensitive to J and slot aspect ratio. Lowest NOx emissions occurred when the dilution jet penetrated to approximately midradius. The viability of using 3-D CFD analyses for optimizing jet mixing was demonstrated.
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Al-Hattab, Mohammad, and Nuha Hamada. "Prediction of nodes mobility in 3-D space." International Journal of Electrical and Computer Engineering (IJECE) 11, no. 4 (August 1, 2021): 3229. http://dx.doi.org/10.11591/ijece.v11i4.pp3229-3240.
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<span>Recently, mobility prediction researches attracted increasing interests, especially for mobile networks where nodes are free to move in the three-dimensional space. Accurate mobility prediction leads to an efficient data delivery for real time applications and enables the network to plan for future tasks such as route planning and data transmission in an adequate time and a suitable space. In this paper, we proposed, tested and validated an algorithm that predicts the future mobility of mobile networks in three-dimensional space. The prediction technique uses polynomial regression to model the spatial relation of a set of points along the mobile node’s path and then provides a time-space mapping for each of the three components of the node’s location coordinates along the trajectory of the node. The proposed algorithm was tested and validated in MATLAB simulation platform using real and computer generated location data. The algorithm achieved an accurate mobility prediction with minimal error and provides promising results for many applications.</span>
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Shang, Yidan, Kiao Inthavong, Dasheng Qiu, Narinder Singh, Fajiang He, and Jiyuan Tu. "Prediction of nasal spray drug absorption influenced by mucociliary clearance." PLOS ONE 16, no. 1 (January 28, 2021): e0246007. http://dx.doi.org/10.1371/journal.pone.0246007.
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Evaluation of nasal spray drug absorption has been challenging because deposited particles are consistently transported away by mucociliary clearance during diffusing through the mucus layer. This study developed a novel approach combining Computational Fluid Dynamics (CFD) techniques with a 1-D mucus diffusion model to better predict nasal spray drug absorption. This integrated CFD-diffusion approach comprised a preliminary simulation of nasal airflow, spray particle injection, followed by analysis of mucociliary clearance and drug solute diffusion through the mucus layer. The spray particle deposition distribution was validated experimentally and numerically, and the mucus velocity field was validated by comparing with previous studies. Total and regional drug absorption for solute radius in the range of 1 − 110nm were investigated. The total drug absorption contributed by the spray particle deposition was calculated. The absorption contribution from particles that deposited on the anterior region was found to increase significantly as the solute radius became larger (diffusion became slower). This was because the particles were consistently moved out of the anterior region, and the delayed absorption ensured more solute to be absorbed by the posterior regions covered with respiratory epithelium. Future improvements in the spray drug absorption model were discussed. The results of this study are aimed at working towards a CFD-based integrated model for evaluating nasal spray bioequivalence.
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Budnikov, A. V., E. I. Shmelev, D. A. Kulikov, A. V. Loginov, S. M. Dmitriev, N. A. Pribaturin, P. D. Lobanov, A. S. Suvorov, and A. V. Stulenkov. "Measurements of the Hydrodynamic and Vibrational Characteristics to Validate Numerical Calculations of the Structure Excitation by Fluid Flow." Devices and Methods of Measurements 10, no. 3 (September 9, 2019): 223–32. http://dx.doi.org/10.21122/2220-9506-2019-10-3-223-232.
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Structure vibration under the influence of unsteady hydrodynamic forces caused by the flow around their surfaces can adversely affect durability and rupture life. Reducing the adverse effects of hydrodynamic forces is currently possible with the help of linked CFD and vibration calculations. However, for an adequate description of the associated processes one should use calculation models and approaches specific to the hydro-vibration problem. To justify and validate such approaches, an experimental model was developed and a series of structure excitation tests in water flow was carried out.The model comprises two cylinders installed sequentially in water crossflow. Vibration levels, pressure and velocity fluctuations were measured in the tests as a functions of the flow velocity. The application of different non-intrusive measurement techniques was possible due to relatively simple test model construction which may be used for cross-validation and experimental uncertainty quantification.Flow-structure interaction, caused by synchronization effect of the flow separation frequency (or it’s spectral components) and eigenfrequency of cylinder, was analyzed based on simultaneously measured data. The tests performed gave the information about dynamical characteristics of the flow and vibration parameters of cantilevered cylinders. The experimental results are used for identification of required accuracy of hydrodynamic forces calculation by CFD and validation of oneand two-way linked methods for flow excitation frequency calculation.
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Saka, M., D. Hirota, H. Abe´, and I. Komura. "NDE of a 3-D Surface Crack Using Closely Coupled Probes for DCPD Technique." Journal of Pressure Vessel Technology 120, no. 4 (November 1, 1998): 374–78. http://dx.doi.org/10.1115/1.2842346.
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A procedure of applying the d-c potential drop technique using the closely coupled probes to NDE of a 3-D surface crack is newly developed. The calibration equation for three sensors which differ in the distance between the probes is derived. Experiments validated the use of the calibration equation for the NDE of cracks. The method to use the three sensors properly based on the measuring sensitivity is shown.
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Zhu, D. D., and Z. L. Ji. "Transmission loss prediction of reactive silencers using 3-D time-domain CFD approach and plane wave decomposition technique." Applied Acoustics 112 (November 2016): 25–31. http://dx.doi.org/10.1016/j.apacoust.2016.05.004.
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Zeng, Yang, Masafumi Katsuta, and Tomohiro Anamizu. "Numerical Simulation of Heat Flow in a Vehicle Cabin Using the Personal Air Conditioning System." Advanced Materials Research 694-697 (May 2013): 755–61. http://dx.doi.org/10.4028/www.scientific.net/amr.694-697.755.
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The personal air conditioning system is used in the battery electric vehicle instead of the traditional one and the experiment validated that this system can make passengers feel comfort after four minutes. All the system can only consume electric power 338.8 W, which is less than the traditional air conditioning of cabin. A simplified 3-D N box vehicle cabin model was created to simulate the thermal distribution under this system by using the CFD analysis and the results of calculation have good agreement with the experiment recording.
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Smolka, Jacek. "Genetic algorithm shape optimisation of a natural air circulation heating oven based on an experimentally validated 3-D CFD model." International Journal of Thermal Sciences 71 (September 2013): 128–39. http://dx.doi.org/10.1016/j.ijthermalsci.2013.04.014.
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Yacob, Filmon, Daniel Semere, and Nabil Anwer. "Variation propagation modeling in multistage machining processes considering form errors and N-2-1 fixture layouts." International Journal of Advanced Manufacturing Technology 116, no. 1-2 (June 21, 2021): 507–22. http://dx.doi.org/10.1007/s00170-021-07195-z.
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AbstractVariation propagation modeling of multistage machining processes enables variation reduction by making an accurate prediction on the quality of a part. Part quality prediction through variation propagation models, such as stream of variation and Jacobian-Torsor models, often focus on a 3-2-1 fixture layout and do not consider form errors. This paper derives a mathematical model based on dual quaternion for part quality prediction given parts with form errors and fixtures with N-2-1 (N>3) layout. The method uses techniques of Skin Model Shapes and dual quaternions for a virtual assembling of a part on a fixture, as well as conducting machining and measurement. To validate the method, a part with form errors produced in a two-stationed machining process with a 12-2-1 fixture layout was considered. The prediction made following the proposed method was within 0.4% of the prediction made using a CAD/CAM simulation when form errors were not considered. These results validate the method when form errors are neglected and partially validated when considered.
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Oyegbile, Benjamin, Guven Akdogan, and Mohsen Karimi. "Experimental and CFD Studies of the Hydrodynamics in Wet Agglomeration Process." ChemEngineering 2, no. 3 (July 19, 2018): 32. http://dx.doi.org/10.3390/chemengineering2030032.
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In this study, an experimentally validated computational model was developed to investigate the hydrodynamics in a rotor-stator vortex agglomeration reactor RVR having a rotating disc at the centre with two shrouded outer plates. A numerical simulation was performed using a simplified form of the reactor geometry to compute the 3-D flow field in batch mode operations. Thereafter, the model was validated using data from a 2-D Particle Image Velocimetry (PIV) flow analysis performed during the design of the reactor. Using different operating speeds, namely 70, 90, 110, and 130 rpm, the flow fields were computed numerically, followed by a comprehensive data analysis. The simulation results showed separated boundary layers on the rotating disc and the stator. The flow field within the reactor was characterized by a rotational plane circular forced vortex flow, in which the streamlines are concentric circles with a rotational vortex. Overall, the results of the numerical simulation demonstrated a fairly good agreement between the Computational Fluid Dynamics (CFD) model and the experimental data, as well as the available theoretical predictions. The swirl ratio β was found to be approximately 0.4044, 0.4038, 0.4044, and 0.4043 for the operating speeds of N = 70, 90, 110, and 130 rpm, respectively. In terms of the spatial distribution, the turbulence intensity and kinetic energy were concentrated on the outer region of the reactor, while the circumferential velocity showed a decreasing intensity towards the shroud. However, a comparison of the CFD and experimental predictions of the tangential velocity and the vorticity amplitude profiles showed that these parameters were under-predicted by the experimental analysis, which could be attributed to some of the experimental limitations rather than the robustness of the CFD model or numerical code.
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Lai, L. S., G. S. Djambazov, C. H. Lai, and K. A. Pericleous. "Comparison of Higher-Order Numerical Schemes and Several Filtering Methods Applied to Navier-Stokes Equations with Applications to Computational Aeroacoustics." Journal of Algorithms & Computational Technology 3, no. 3 (September 2009): 443–59. http://dx.doi.org/10.1260/174830108788251746.
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In computational acoustics, fluid-acoustic coupling methods for the computation of sound have been widely used by researchers for the last five decades. In the first part of the coupling procedure, the fully unsteady incompressible or compressible flow equations for the near-field of the unsteady flow are solved by using a Computational Fluid Dynamics (CFD) technique, such as Direct Numerical Simulation (DNS), Large Eddy Simulation (LES) or unsteady Reynolds averaged Navier-Stokes equations (RANS) the CFD predictions are then used to calculate sound sources using the acoustic analogy or solving a set of acoustic perturbation equations (APE) leading to the solution of the acoustic field. It is possible to use a 2-D reduced problem to provide a preliminary understanding of many acoustic problems. Unfortunately 2-D CFD simulations using a fine-mesh-small-time-step-LES-alike numerical method cannot be considered as LES, which applies to 3-D simulations only. Therefore it is necessary to understand the similarities and the effect between filters applied to unsteady compressible Navier-Stokes equations and the combined effect of high-order schemes and mesh size. The aim of this study is to provide suitable LES-alike methods for 2-D simulations. An efficient software implementation of high-order schemes is also proposed. Numerical examples are provided to illustrate these statistical similarities.
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KHAN, Md Akhtar, and Chinmaya PADHY. "Aerodynamic and Experimental Analysis of Bio-mimic corrugated dragonfly aerofoil." INCAS BULLETIN 12, no. 2 (June 5, 2020): 73–85. http://dx.doi.org/10.13111/2066-8201.2020.12.2.7.
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In this work, experimental and computational approach is used to understand the corrugation attitude of a bio-inspired dragonfly mimicked corrugated airfoil at low Reynolds number varying from 15000 to 75000 to understand the advantages of pleated corrugated airfoil. The CFD analysis is carried out on the 2-dimensional bio-mimetic corrugated ‘Pantala flavescens’ dragonfly forewing to predict the aerodynamic characteristics of the corrugated dragonfly aerofoil with varying angle of attack from 0° to 8°. The computational analysis of the wing profile is done using the ANSYS-19 ICEM CFD and FLUENT software. For the experimental test, the model is printed in 3-D printer machine and tested in subsonic Wind Tunnel at different speeds and different angle of attacks using a wind tunnel 6-component balance. The computational simulation reveals the exemplary results of the pleated airfoil (corrugated aerofoil) with new design constraints. Finally, the computational result is validated with experimental results.
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Allio, Andrea, Rosa Difonzo, Alberto Leggieri, François Legrand, Rodolphe Marchesin, and Laura Savoldi. "Test and Modeling of the Hydraulic Performance of High-Efficiency Cooling Configurations for Gyrotron Resonance Cavities." Energies 13, no. 5 (March 4, 2020): 1163. http://dx.doi.org/10.3390/en13051163.
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The design and manufacturing of different full-size mock-ups of the resonance cavity of gyrotrons, relevant for fusion applications, were performed according to two different cooling strategies. The first one relies on mini-channels, which are very promising in the direction of increasing the heat transfer in the heavily loaded cavity, but which could face an excessively large pressure drop, while the second one adopts the solution of Raschig rings, already successfully used in European operating gyrotrons. The mock-ups, manufactured with conventional techniques, were hydraulically characterized at the Thales premises, using water at room temperature. The measured pressure drop data were used to validate the corresponding numerical computational fluid dynamics (CFD) models, developed with the commercial software STAR-CCM+ (Siemens PLM Software, Plano TX, U.S.A.) and resulting in excellent agreement with the test results. When the validated models were used to compare the two optimized cooling configurations, it resulted that, for the same water flow, the mini-channel strategy gave a pressure drop was two-fold greater than that of the Raschig rings strategy, allowing a maximum flow rate of 1 × 10−3 m3/s to meet a maximum allowable pressure drop of 0.5 MPa.
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Moon, Jiyoung, Dela Quarme Gbadago, and Sungwon Hwang. "3-D Multi-Tubular Reactor Model Development for the Oxidative Dehydrogenation of Butene to 1,3-Butadiene." ChemEngineering 4, no. 3 (July 21, 2020): 46. http://dx.doi.org/10.3390/chemengineering4030046.
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The oxidative dehydrogenation (ODH) of butene has been recently developed as a viable alternative for the synthesis of 1,3-butadiene due to its advantages over other conventional methods. Various catalytic reactors for this process have been previously studied, albeit with a focus on lab-scale design. In this study, a multi-tubular reactor model for the butadiene synthesis via ODH of butene was developed using computational fluid dynamics (CFD). For this, the 3D multi-tubular model, which combines complex reaction kinetics with a shell-side coolant fluid over a series of individual reactor tubes, was generated using OpenFOAM®. Then, the developed model was validated and analyzed with the experimental results, which gave a maximum error of 7.5%. Finally, parametric studies were conducted to evaluate the effect of thermodynamic conditions (isothermal, non-isothermal and adiabatic), feed temperature, and gas velocity on reactor performance. The results showed the formation of a hotspot at the reactor exit, which necessitates an efficient temperature control at that section of the reactor. It was also found that as the temperature increased, the conversion and yield increased whilst the selectivity decreased. The converse was found for increasing velocities.
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TODA, Yasuyuki, Yun-Sok LEE, and Hiroyuki SADAKANE. "Hydrodynamic Forces Acting on a Ship Hull under Lateral Low Speed Motion-III : Basic Consideration Using 3-D CFD Technique." Journal of Japan Institute of Navigation 106 (2002): 87–95. http://dx.doi.org/10.9749/jin.106.87.
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Ducrozet, G., F. Bonnefoy, D. Le Touzé, and P. Ferrant. "3-D HOS simulations of extreme waves in open seas." Natural Hazards and Earth System Sciences 7, no. 1 (January 25, 2007): 109–22. http://dx.doi.org/10.5194/nhess-7-109-2007.
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Abstract. In the present paper we propose a method for studying extreme-wave appearance based on the Higher-Order Spectral (HOS) technique proposed by West et al. (1987) and Dommermuth and Yue (1987). The enhanced HOS model we use is presented and validated on test cases. Investigations of freak-wave events appearing within long-time evolutions of 2-D and 3-D wavefields in open seas are then realized, and the results are discussed. Such events are obtained in our periodic-domain HOS model by using different kinds of configurations: either i) we impose an initial 3-D directional spectrum with the phases adjusted so as to form a focused forced event after a while, or ii) we let 2-D and 3-D wavefields defined by a directional wave spectrum evolve up to the natural appearance of freak waves. Finally, we investigate the influence of directionality on extreme wave events with an original study of the 3-D shape of the detected freak waves.
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Yu, Dayu, Liyu Tang, and Chongcheng Chen. "Three-dimensional numerical simulation of mud flow from a tailing dam failure across complex terrain." Natural Hazards and Earth System Sciences 20, no. 3 (March 16, 2020): 727–41. http://dx.doi.org/10.5194/nhess-20-727-2020.
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Abstract. A tailing dam accident can cause serious ecological disaster and property loss. Simulation of a tailing dam accident in advance is useful for understanding the tailing flow characteristics and assessing the possible extension of the impact area. In this paper, a three-dimensional (3-D) computational fluid dynamics (CFD) approach was proposed for reasonably and quickly predicting the flow routing and impact area of mud flow from a dam failure across 3-D terrain. The Navier–Stokes equations and the Bingham–Papanastasiou rheology model were employed as the governing equations and the constitutive model, respectively, and solved numerically in the finite volume method (FVM) scheme. The volume-of-fluid (VOF) method was used to track the interface between the tailings and air. The accuracy of the CFD model and the chosen numerical algorithm were validated using an analytical solution of the channel flow problem and a laboratory experiment on the dam-break problem reported in the literature. In each issue, the obtained results were very close to the analytical solutions or experimental values. The proposed approach was then applied to simulate two scenarios of tailing dam failures, one of which was the Feijão tailing dam that failed on 25 January 2019, and the simulated routing coincided well with the in situ investigation. Therefore, the proposed approach does well in simulating the flow phenomenon of tailings after a dam break, and the numerical results can be used for early warning of disasters and emergency response.
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Wilson, Robert V., Fred Stern, Hugh W. Coleman, and Eric G. Paterson. "Comprehensive Approach to Verification and Validation of CFD Simulations—Part 2: Application for Rans Simulation of a Cargo/Container Ship." Journal of Fluids Engineering 123, no. 4 (July 10, 2001): 803–10. http://dx.doi.org/10.1115/1.1412236.
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Part 2 of this two-part paper provides an example case study following the recently developed comprehensive verification and validation approach presented in Part 1. The case study is for a RANS simulation of an established benchmark for ship hydrodynamics using a ship hydrodynamics CFD code. Verification of the resistance (integral variable) and wave profile (point variable) indicates iterative uncertainties much less than grid uncertainties and simulation numerical uncertainties of about 2%S1(S1 is the simulation value for the finest grid). Validation of the resistance and wave profile shows modeling errors of about 8%D (D is the measured resistance) and 6%ζmax(ζmax is the maximum wave elevation), which should be addressed for possible validation at the 3%D and 4%ζmax levels. Reducing the level of validation primarily requires reduction in experimental uncertainties. The reduction of both modeling errors and experimental uncertainties will produce verified and validated solutions at low levels for this application using the present CFD code. Although there are many issues for practical applications, the methodology and procedures are shown to be successful for assessing levels of verification and validation and identifying modeling errors in some cases. For practical applications, solutions are far from the asymptotic range; therefore, analysis and interpretation of the results are shown to be important in assessing variability for order of accuracy, levels of verification, and strategies for reducing numerical and modeling errors and uncertainties.
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Atifatul Ismah Ismail. "Effect of Cavities in Suddenly Expanded Flow at Supersonic Mach Number." CFD Letters 13, no. 9 (September 30, 2021): 57–71. http://dx.doi.org/10.37934/cfdl.13.9.5771.
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The contribution from the base drag due to the sub-atmospheric pressure is significant. It can be more than two-thirds of the net drag. There is a need to increase the base pressure and hence decrease the base drag. This research examines the effect of Mach Number on base pressure. To accomplish this objective, it controls the efficacy in an enlarged duct computed by the numerical approach using Computational Fluid Dynamics (CFD) Analysis. This experiment was carried out by considering the expansion level and the aspect cavity ratio. The computational fluid dynamics method is used to model supersonic motion with the sudden expansion, and a convergent-divergent nozzle is used. The Mach number is 1.74 for the present study, and the area ratio is 2.56. The L/D ratio varied from 2, 4, 6, 8, and 10, and the simulated nozzle pressure ratio ranged from 3 to 11. The two-dimensional planar design used commercial software from ANSYS. The airflow from a Mach 1.74 convergent-divergent axi-symmetric nozzle expanded suddenly into circular ducts of diameters 17 and 24.5 mm with and without annular rectangular cavities. The diameter of the duct is taken D=17mm and D=24.5mm. The C-D nozzle was developed and modeled in the present study: K-ε standard wall function turbulence model was used with the commercial computational fluid dynamics (CFD) and validated. The result indicates that the base pressure is impacted by the expansion level, the enlarged duct size, and the passage’s area ratio.
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Shahzad, M., and X. X. Zhu. "Reconstructing 2-D/3-D Building Shapes from Spaceborne Tomographic Synthetic Aperture Radar Data." ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XL-3 (August 11, 2014): 313–20. http://dx.doi.org/10.5194/isprsarchives-xl-3-313-2014.
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In this paper, we present an approach that allows automatic (parametric) reconstruction of building shapes in 2-D/3-D using TomoSAR point clouds. These point clouds are generated by processing radar image stacks via advanced interferometric technique, called SAR tomography. The proposed approach reconstructs the building outline by exploiting both the available roof and façade information. Roof points are extracted out by employing a surface normals based region growing procedure via selected seed points while the extraction of façade points is based on thresholding the point scatterer density <i>SD</i> estimated by robust M-estimator. Spatial clustering is then applied to the extracted roof points in a way such that each roof cluster represents an individual building. Extracted façade points are reconstructed and afterwards incorporated to the segmented roof cluster to reconstruct the complete building shape. Initial building footprints are derived by employing alpha shapes method that are later regularized. Finally, rectilinear constraints are added to yield better geometrically looking building shapes. The proposed approach is illustrated and validated by examples using TomoSAR point clouds generated from a stack of TerraSAR-X high-resolution spotlight images from ascending orbit only covering two different test areas with one containing relatively smaller buildings in densely populated regions and the other containing moderate sized buildings in the city of Las Vegas.
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Musa, Amir A. B., Xiong Wei Zeng, Qing Yan Fang, and Huai Chun Zhou. "Numerical Simulation on Improving NOx Reduction Efficiency of SNCR by Regulating the 3-D Temperature Field in a Furnace." Advanced Materials Research 807-809 (September 2013): 1505–13. http://dx.doi.org/10.4028/www.scientific.net/amr.807-809.1505.
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The optimum temperature within the reagent injection zone is between 900 and 1150°C for the NOX reduction by SNCR (selective non-catalytic reduction) in coal-fired utility boiler furnaces. As the load and the fuel property changes, the temperature within the reagent injection zone will bias from the optimum range, which will reduces significantly the de-NOX efficiency, and consequently the applicability of SNCR technology. An idea to improve the NOX reduction efficiency of SNCR by regulating the 3-D temperature field in a furnace is proposed in this paper. In order to study the new method, Computational fluid dynamics (CFD) model of a 200 MW multi-fuel tangentially fired boiler have been developed using Fluent 6.3.26 to investigate the three-fuel combustion system of coal, blast furnace gas (BFG), and coke oven gas (COG) with an eddy-dissipation model for simulating the gas-phase combustion, and to examine the NOX reduction by SNCR using urea-water solution. The current CFD models have been validated by the experimental data obtained from the boiler for case study. The results show that, with the improved coal and air feed method, average residence time of coal particles increases 0.3s, burnout degree of pulverized coal increases 2%, the average temperature at the furnace nose decreases 61K from 1496K to 1435K, the NO emission at the exit (without SNCR) decreases 58 ppm from 528 to 470 ppm, the SNCR NO removal efficiency increases 10% from 36.1 to 46.1%. The numerical simulation results show that this combustion adjustment method based on 3-D temperature field reconstruction measuring system in a 200 MW multi-fuel tangentially fired utility boiler co-firing pulverized coal with BFG and COG is timely and effective to maintain the temperature of reagent injection zone at optimum temperature range and high NOX removal efficiency of SNCR.
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Piriyakulkit, Piriyakorn, and Siripon Anantawaraskul. "Deconvolution of Microstructural Distributions of Ethylene/1- Butene Copolymer Blends using Artifi cial Neural Network." Chiang Mai Journal of Science 49, no. 1 (January 31, 2022): 217–22. http://dx.doi.org/10.12982/cmjs.2022.019.
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Polymer blending is a useful approach to tailor-make microstructural distributions (e.g., molecular weight distribution (MWD), chemical composition distribution (CCD)) and product properties. A technique to help identify polymer components and their weight fractions in the unknown blends is desirable for the product development. In this work, artifi cial neural network (ANN) models were developed to help identify this information from microstructural distributions and validated with simulated datasets of various binary blends of polyolefi n with different characteristics. The proposed models are multilayer perceptron network with 2 hidden layers; the backpropagation algorithm is used for the network training. Three types of input data were compared: (1) MWD, (2) CCD, and (3) MWD+CCD. Optimum topologies for each types of input data were also determined.
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Hirsch, E., E. Agassi, and I. Koren. "A novel technique for extracting clouds base height using ground based imaging." Atmospheric Measurement Techniques Discussions 3, no. 5 (October 4, 2010): 4231–60. http://dx.doi.org/10.5194/amtd-3-4231-2010.
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Abstract. The height of a cloud in the atmospheric column is a key parameter in its characterization. Several remote sensing techniques (passive and active, either ground-based or on space-borne platforms) and in-situ measurements are routinely used in order to estimate top and base heights of clouds. In this article we present a novel method that combines thermal imaging from the ground and sounded wind profile in order to derive the cloud base height. This method is independent of cloud types, making it efficient for both low boundary layer and high clouds. In addition, using thermal imaging ensures extraction of clouds' features during daytime as well as at nighttime. The proposed technique was validated by comparison to active sounding by ceilometers (which is a standard ground based method), to lifted condensation level (LCL) calculations, and to MODIS products obtained from space. As all passive remote sensing techniques, the proposed method extracts only the height of the lowest cloud layer, thus upper cloud layers are not detected. Nevertheless, the information derived from this method can be complementary to space-borne cloud top measurements when deep-convective clouds are present. Unlike techniques such as LCL, this method is not limited to boundary layer clouds, and can extract the cloud base height at any level, as long as sufficient thermal contrast exists between the radiative temperatures of the cloud and its surrounding air parcel. Another advantage of the proposed method is its simplicity and modest power needs, making it particularly suitable for field measurements and deployment at remote locations. Our method can be further simplified for use with visible CCD or CMOS camera (although nighttime clouds will not be observed).
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Jiang, Hanjun, Yan Yan, Xiyang Zhu, and Chun Zhang. "A 3-D Surface Reconstruction with Shadow Processing for Optical Tactile Sensors." Sensors 18, no. 9 (August 24, 2018): 2785. http://dx.doi.org/10.3390/s18092785.
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An optical tactile sensor technique with 3-dimension (3-D) surface reconstruction is proposed for robotic fingers. The hardware of the tactile sensor consists of a surface deformation sensing layer, an image sensor and four individually controlled flashing light emitting diodes (LEDs). The image sensor records the deformation images when the robotic finger touches an object. For each object, four deformation images are taken with the LEDs providing different illumination directions. Before the 3-D reconstruction, the look-up tables are built to map the intensity distribution to the image gradient data. The possible image shadow will be detected and amended. Then the 3-D depth distribution of the object surface can be reconstructed from the 2-D gradient obtained using the look-up tables. The architecture of the tactile sensor and the proposed signal processing flow have been presented in details. A prototype tactile sensor has been built. Both the simulation and experimental results have validated the effectiveness of the proposed 3-D surface reconstruction method for the optical tactile sensors. The proposed 3-D surface reconstruction method has the unique feature of image shadow detection and compensation, which differentiates itself from those in the literature.
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Vuyyuru, Nagi Reddy, A. Malleswara Reddy, B. Ramadevi, Y. Ravindra Kumar, and B. Janaki Durga Prasad. "A Simple, Specific, Mass Compatible and Validated Gas Chromatographic Method for the Estimation of Piperidine-3-amine Content in Linagliptin Finished and Stability Samples without Derivatization." Asian Journal of Chemistry 32, no. 10 (2020): 2567–72. http://dx.doi.org/10.14233/ajchem.2020.22817.
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A new simple, selective, highly sensitive, specific (stability indicating), robust, rugged and mass compatible gas chromatographic method and sample with direct injection-mode was developed for the quantitative determination of amino-3-piperidine (3-aminopiperidine, 3-AMP) in linagliptin. As the CAD-LC method did not proved for specificity and pre-derivitizations are challenging task for quality control (QC), a simple GC method has been developed. Compared to LC-CAD method, which is not proved for specificity and pre-column derivitization methods having the limitations to analyze the reaction monitoring in-process samples and degradation samples, the present method is selective, simple, cost effective, QC friendly, widely available GC technique with direct injection and high in sensitivity. Also this method is mass compatible, specificity proved by forced degradation, method was validated as per ICH guidelines. Mass balance was proved by analyzing the stressed samples for net degradation by HPLC and assay by HPLC methods. This GC method also provides an advantage to analyze the in-process samples to monitor the progress of the synthetic process, where the reaction monitoring samples are unpurified or non-isolated samples and contains many process related impurities (reference) and solvents, which will have interference with 3-AMP in LC-CAD and pre-column derivitization methods. This method involves simple sample preparation process and direct injection with GC-FID technique. Hence, this method can be used to analyze the finished product samples, degradation samples, stability samples and reaction monitoring samples. The method was developed with widely available GC column (diphenyl dimethyl polysiloxane as stationary phase, 30 m length, 0.53 mm internal diameter & 5.0 μm thickness), helium as carries gas, FID detector set at 240 ºC, column oven starts at 200 ºC and starts increases after 2 min with 20 ºC/min and holds up to 11 min, which will ensure the column bake. The solvents used for the process were well separated from 3-AMP peak. Mass balance was reported > 99%. The limit of quantification and limit of detection values for 3-AMP were 0.002% (0.4 μg/mL) and 0.007% (1.4 μg/mL) of targeted concentration (20 mg/mL), respectively. The method was precise at LOQ and at specification level with %RSD values 2.8 and 4.7, respectively. Linearity was established in the range of 0.0014 mg/mL (LOQ) to 0.045 mg/mL for 3-AMP with correlation coefficient (r2 > 0.9995). The percentage recoveries were obtained between 99.9% and 104.4%. The range of the method was established from LOQ (0.0014 mg/mL) to 150% (0.045 mg/mL) of the specification targeted limit of 0.15% (0.03 mg/mL). The standard and spiked sample solutions were studied up to 2 days and are stable at room temperature. The forced degradation studies were performed by using HCl, NaOH, H2O2 thermal, UV radiation and water. A mild degradation bout 0.25% was observed in base degradation condition, which was confirmed with mass number by GC-MS analysis. Validation parameters were evaluated according to the International Conference on Harmonization (ICH) Q2 guidelines.
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Yousif, Aadil, Rashid Mir, Jamsheed Javid, Jameel Barnawi, Mohammed M. Jalal, Malik A. Altayar, Salem Owaid Albalawi, and Faisel M. Abuduhier. "Clinical Utility of Amplification Refractory Mutation System-Based PCR and Mutation-Specific PCR for Precise and Rapid Genotyping of Angiotensin-Converting Enzyme 1 (ACE1-rs4646996 D>I) and Angiotensin-Converting Enzyme 2 (ACE2-rs4240157T>C) Gene Variations in Coronary Artery Disease and Their Strong Association with Its Disease Susceptibility and Progression." Diagnostics 12, no. 6 (May 26, 2022): 1321. http://dx.doi.org/10.3390/diagnostics12061321.
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Background: Experimental clinical and research studies demonstrated that the renin–angiotensin system (RAS) affects the pathogenesis of atherosclerosis and the prognosis of coronary heart disease (CHD). The results show that ACE2 (angiotensin I-converting enzyme 2) might act as a protective protein for cardiovascular diseases; however, only a few studies in human populations have been carried out. The aim of this study was to develop, optimize, and validate a direct T-ARMS-based PCR assay for the precise and rapid genotyping of ACE1-rs4646996 D>I and ACE2-rs4240157T>C and study their association with coronary artery disease susceptibility and progression. Methodology: This study included 149 consecutive coronary artery disease patients and 150 healthy controls. We utilized T-ARMS for the precise and rapid genotyping of ACE2-rs4240157; rs4646994. Results: Our results indicated that the ACE1-rs4646996 D>I genotypes observed between CAD cases and controls were statistically significant (p < 0.008) and, similarly, the ACE2-rs4240157T>C genotypes observed were significant (p < 0.0001). Moreover, the frequency of the D allele (ACE1-D>I) and C allele (ACE2-rs4240157T>C) was found to be higher among CAD patients than the HC. Our results indicated that in the codominant model, the ACE2-ID genotype was strongly associated with increased CAD susceptibility in a codominant model with an OR of 2.37, (95%) CI = (1.023–5.504), and p < 0.04. Similarly, the ACE2-DD genotype was strongly associated with an increased CAD susceptibility with an OR of 3.48, (95%) CI = (1.49 to 8.117), and p < 0.003. Similarly, in allelic comparison, the D allele was strongly associated with CAD susceptibility with an OR of 1.59, (95%) CI = (1.12–2.24), and p < 0.003. Our results revealed that there was a significant correlation between ACE2-I/D genotypes and hypertension, T2D, and obesity (p < 0.05). The results of ACE2 rs4240157 genotyping indicated a strong association in the codominant model with an increased CAD susceptibility with an OR of 3.62, (95%) CI = (2.027 to 6.481), and p < 0.0001. Similarly, in a dominant inheritance model, a strong association is observed between the ACE2 rs4240157 (CT+CC) genotype with an OR of 6.34, (95%) CI = (3.741 to 10.749), and p < 0.0001. In allelic comparison, the T allele was strongly associated with CAD susceptibility with an OR of 5.56, (95% CI = (3.56 to 7.17), and p < 0.0001. Similarly, our results revealed that there was a significant association of the ACE2-rs4240157T>C genotypes with Triglycerides (mg/dL), HDL-C (mg/dL), total Cholesterol (mg/dL), and C-reactive protein (mg/L) in CAD. Conclusion: It was indicated that the ARMS technique and MS-PCR assay proved to be fast, accurate, and reliable for ACE2-rs4240157T>C and ACE1-rs4646996 D>I, respectively, and can be used as a potential molecular tool in the diagnosis of genetic diseases in undeveloped and developing countries—where there might be a shortage of medical resources and supplies. ACE1-I>D genotypes were strongly associated with T2D, hypertension, and obesity (p < 0.002). Besides the ACE2-rs4240157 CT heterozygosity genotype, the T allele was strongly associated with CAD susceptibility. Future longitudinal studies in different ethnic populations with larger sample sizes are recommended to validate these findings
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Basha, Omar M., Li Weng, Zhuowu Men, and Badie I. Morsi. "CFD Modeling with Experimental Validation of the Internal Hydrodynamics in a Pilot-Scale Slurry Bubble Column Reactor." International Journal of Chemical Reactor Engineering 14, no. 2 (April 1, 2016): 599–619. http://dx.doi.org/10.1515/ijcre-2015-0165.
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Abstract A multiphase-Eulerian, three-dimensional (3-D), computational fluid dynamics (CFD) model was built to investigate the local hydrodynamics of a pilot-scale (0.29 m ID, 3 m height) Slurry Bubble Column Reactor (SBCR). The model was first validated against the gas holdup radial profiles in an air-water-glass beads system obtained in a 0.254 m ID and 2.5 m height column under ambient conditions at various superficial gas velocities by Yu and Kim (Bubble characteristics in the radial direction of three-phase fluidized beds. AIChE Journal 34, 2069–2072, 1988). The model was next validated against the gas holdup radial profile data for N2-Drakeol-glass beads system obtained in a 0.44 m ID and 2.44 m height reactor, including internals, operating under ambient conditions at various superficial gas velocities by Chen et al. (Fluid dynamic parameters in bubble columns with internals. Chemical Engineering Science 54, 2187–2197, 1999). The model was also validated against experimental data obtained in our lab for N2-Fischer Tropsch (F-T) reactor wax-Fe catalyst system obtained in a pilot-scale, Slurry Bubble column Reactor, SBCR (0.29 m ID, 3 m height) under pressures and temperatures up to 25.9 bar and 490 K, respectively. These three validations led to the selection of the turbulence and interphase drag coefficient models, and the optimization of the solution method, mesh size and structure and the step size. Moreover, the inclusion of RNG k-ε turbulence model coupled with the Wen-Yu (Mechanics of Fluidization. Chemical Engineering Progress Symposium Series 62, 100–111, 1966) / Schiller-Naumann (A drag coefficient correlation. Zeitung Ver. Deutsch. Ing 77, 318–320, 1935) drag correlations, and the mass transfer coefficients were found to provide the most accurate predictions of the experimental data. The CFD model was then used to investigate local gas holdup, liquid recirculation, local turbulence intensities, bubble diameters, and solids distribution throughout our pilot-scale SBCR, operating under typical F-T process conditions. The model predictions showed strong liquid recirculation and backmixing near the walls of the reactor, and the solid-phase velocity vectors closely followed those of the liquid-phase. A relatively high liquid turbulence intensities were observed in the vicinity of the sparger upon startup, however, after reaching a steady state, the liquid turbulence intensities became more evenly distributed throughout the reactor. The liquid turbulence intensities were slightly higher near the center of the reactor, and closely resembled the velocity vectors. Also, the Sauter mean bubble diameters increased, whereas the solids distribution decreased with reactor height above the gas distributor.
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LEE, MYUNGSUNG, and NAHMKEON HUR. "A DETAILED CFD SIMULATION OF THE 2003 DAEGU METRO STATION FIRE." International Journal of Air-Conditioning and Refrigeration 20, no. 03 (September 2012): 1250014. http://dx.doi.org/10.1142/s2010132512500149.
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The Daegu metro station fire on 18 February 2003 was a tragic accident that claimed 192 lives in South Korea. The fire was set by an arsonist in a stopped train at the Daegu metro station, and spread to another train arriving at the station on the opposite track. The present numerical study aims to reproduce the Daegu metro station fire using a transient 3-D CFD simulation with detailed geometry of the station and tunnels in order to understand the behavior of the smoke and heat responsible for human losses in such accidents. The actual motion of the arriving train was also considered by using a moving mesh technique, and the fire development and CO gas generation were modeled with the enthalpy and scalar source terms. The evolutions of the temperature and CO gas distributions in the station were obtained in detail from the present simulation. The heat and CO concentrations at some critical locations (such as staircases) were shown and discussed in detail. The results of the present numerical study could provide useful data for future emergency plans of metro stations in case of fire.
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Obando Vega, Felipe Andrés, Ana Paola Montoya Ríos, Jairo Alexander Osorio Saraz, Rafaella Resende Andrade, Flávio Alves Damasceno, and Matteo Barbari. "CFD Study of a Tunnel-Ventilated Compost-Bedded Pack Barn Integrating an Evaporative Pad Cooling System." Animals 12, no. 14 (July 11, 2022): 1776. http://dx.doi.org/10.3390/ani12141776.
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Evaporative cooling is one of the most efficient techniques to reduce heat stress in cows in agricultural facilities. Additionally, compost-bedded pack barn has been shown to improve the welfare and production of cows. Two techniques were combined and analysed by developing a computational fluid dynamics (CFD) model of a tunnel-ventilated compost-bedded packed barn that integrated the heat and airflow dynamics of an evaporative pad cooling system. This allowed us to study the distribution of dry-bulb temperature, relative humidity and airflow velocity inside the barn based on the external environmental conditions, thickness of the pad, water temperature and specific manufacturer characteristics of the pad, providing optimal cooling pad location, size and operating conditions in the barn. Employing experimental data the CFD model was validated showing good agreement. The Equivalent Temperature Index for dairy Cattle (ETIC) was used to determine the level of stress of the cows considering the airflow velocity. It was found a moderate stress due to high relative humidity and low airflow velocity. From the predicted results, it was recommended to increase the airflow velocity above 3 m s−1 when simultaneously the external dry-bulb temperature and relative humidity exceed 30 °C and 55%, respectively, simultaneously. Additionally, installation of baffles at the pad outlet to drive the airflow to the floor was suggested to improve the drying of the compost-bedded closed to the pads, where a low airflow velocity region was established.
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Merah, A., and A. Noureddine. "Reactive Pollutants Dispersion Modeling in a Street Canyon." International Journal of Applied Mechanics and Engineering 24, no. 1 (February 1, 2019): 91–103. http://dx.doi.org/10.2478/ijame-2019-0006.
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Abstract Reactive pollutant dispersion in a 3-D urban street canyon is numerically investigated using a computational fluid dynamics (CFD) code (Ansys-CFX), with the k–ε turbulence model and includes transport equations for NO, NO2, and O3 with simple photochemistry. An area emission source of NO and NO2 was considered in the presence of background O3 with an ambient wind perpendicular to the along-canyon direction. The results showed that the magnitude of NOx (NO+NO2) concentrations on the leeward side of the upstream buildings was much larger than the windward side of the downstream building, due to the entrainment and dispersion of traffic emissions by the primary vortex. The reverse is the case for ozone with higher concentrations on the windward side compared to the leeward side. The model has been validated against no-reactive pollutant experimental data of the wind tunnel experiments of Hoydysh and Dabberdt [1].
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Khan, Ambareen, Abdul Aabid, and S. A. Khan. "CFD analysis of convergent-divergent nozzle flow and base pressure control using micro-JETS." International Journal of Engineering & Technology 7, no. 3.29 (August 24, 2018): 232. http://dx.doi.org/10.14419/ijet.v7i3.29.18802.
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This paper presents numerical study was undertaken to identify the use of the micro-jets to regulate the pressure in the region from two-dimensional convergent-divergent (CD) Nozzle. At the exit of the divergent nozzle in the base region 1 mm of two micro-jets orifice diameter has been arranged at ninety degrees at pcd 13 mm to control base pressure. The inertia level at the inlet to suddenly expanded duct was 1.87. The micro-jets are suddenly expanded into a two-dimensional planar area ratio of 3.24. The L/D of the duct was 1, 2, 4, 5, 6, 8 and 10. The total wall pressure distribution from inlet to the outlet too was recorded. The results indicate that the micro-jets can oblige as the effective regulators of the pressure in the base area. The duct wall pressure field is not negatively affected by the dynamic control. Nozzles were operated with the NPR in the range from 3 to 11. The results show that we can fix the flow parameter which will result in the maximum gain in the base pressure, velocity and temperature. The convergent-divergent nozzle geometry has been modeled and simulated employing turbulence models: K-ε standard wall function turbulence model from the code was validated with the commercial computational fluid dynamics.
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Sohail, Amir, Asma Al Menhali, Soleiman Hisaindee, and Iltaf Shah. "An LC-MS/MS Method for Analysis of Vitamin D Metabolites and C3 Epimers in Mice Serum: Oral Supplementation Compared to UV Irradiation." Molecules 26, no. 17 (August 26, 2021): 5182. http://dx.doi.org/10.3390/molecules26175182.
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Introduction: The most common forms of vitamin D in human and mouse serum are vitamin D3 and vitamin D2 and their metabolites. The aim of this study is to determine whether diet and sunlight directly affect the circulating concentrations of vitamin D metabolites in a mouse model. We investigated the serum concentrations of eight vitamin D metabolites—vitamin D (vitamin D3 + vitamin D2), 25OHD (25OHD3 + 25OHD2), 1α25(OH)2D (1α25(OH)2D2, and 1α25(OH)2D3)—including their epimer, 3-epi-25OHD (3-epi-25OHD3 and 3-epi-25OHD2), and a bile acid precursor 7alpha-hydroxy-4-cholesten-3-one (7αC4), which is known to cause interference in liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. Method: The LC-MS/MS method was validated according to FDA-US guidelines. The validated method was used for the analysis of mouse serum samples. Forty blood samples from mice were collected and divided into three groups. The first group, the DDD mice, were fed a vitamin D-deficient diet (25 IU VD3/kg of diet) and kept in the dark; the second group, the SDD mice, were maintained on a standard-vitamin D diet (1000 IU VD3) and kept in the dark; and the third group, SDL, were fed a standard-vitamin D diet (1000 IU VD3) but kept on a normal light/dark cycle. LC-MS/MS was used for the efficient separation and quantitation of all the analytes. Results: The validated method showed good linearity and specificity. The intraday and interday precision were both <16%, and the accuracy across the assay range was within 100 ± 15%. The recoveries ranged between 75 and 95%. The stability results showed that vitamin D metabolites are not very stable when exposed to continuous freeze–thaw cycles; the variations in concentrations of vitamin D metabolites ranged between 15 and 60%. The overlapping peaks of vitamin D, its epimers, and its isobar (7αC4) were resolved using chromatographic separation. There were significant differences in the concentrations of all metabolites of vitamin D between the DDD and SDL mice. Between the groups SDD (control) and SDL, a significant difference in the concentrations of 3-epi-25OHD was noted, where C3 epimer was about 30% higher in SDL group while no significant differences were noted in the concentrations of vitamin D, 25OHD, 1α25(OH)2D, and 7αC4 between SDD and SDL group. Conclusions: A validated method, combined with a simple extraction technique, for the sensitive LC-MS/MS determination of vitamin D metabolites is described here. The method can eliminate the interferences in LC-MS/MS analysis caused by the overlapping epimer and isobar due to them having the same molecular weights as 25OHD. The validated method was applied to mouse serum samples. It was concluded that a standard-vitamin D diet causes an increase in the proportion of all the vitamin D metabolites and C3 epimers and isobar, while UV light has no pronounced effect on the concentrations of the majority of the vitamin D metabolites except 3-epi-25OHD. Further studies are required to confirm this observation in humans and to investigate the biochemical pathways related to vitamin D’s metabolites and their epimers.
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Zhu, Junhong, Tim Frerich, and Axel S. Herrmann. "CFD modeling and validation of heat transfer inside an autoclave based on a mesh independency study." Journal of Composite Materials 55, no. 18 (January 31, 2021): 2469–87. http://dx.doi.org/10.1177/0021998320979043.
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Autoclave processing is the main technology used in the manufacturing of structural aerospace composite parts. To optimize the autoclave process, the thermal behavior of the part and mold can be investigated through simulations. Computational fluid dynamics (CFD) provide a significant contribution to studies on heat transfer and airflow patterns, which are key points in an optimization applied to achieve a homogeneous temperature distribution inside composite parts. The solution is produced by solving the 3 D unsteady Navier–Stokes equations. This paper describes a systematic numerical study using the CFD approach to significantly improve the modeling efficiency of the heat transfer coefficient (HTC) inside an autoclave and maintain a high level of accuracy. Considering the modeling cost, calculation time, and accuracy of the results, a reasonable hybrid mesh is used based on a mesh independency study. The level of grid independence is examined using the general Richardson extrapolation method. In addition, a more robust autoclave model is presented, which is unaffected by the inlet turbulence. Further, the inlet fluid velocity and turbulence models have been identified as sensitive influencing factors. In this study, the Spalart–Allmaras turbulence model shows the best performance compared with the standard [Formula: see text] and [Formula: see text] SST models. Finally, the results are validated with the experimental data. The mean error of the simulated temperatures in the calorimeter for the front, middle and rear positions are [Formula: see text]C, [Formula: see text]C, and [Formula: see text]C, indicating a good agreement with the experiments. This paper provides guidelines on the use of a CFD simulation to predict the heat transfer during the autoclave curing process with high accuracy and reduced numerical effort.
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Puppi, Dario, Gianni Pecorini, and Gianluca Parrini. "Additive Manufacturing of Anatomical Poly(d,l-lactide) Scaffolds." Polymers 14, no. 19 (September 27, 2022): 4057. http://dx.doi.org/10.3390/polym14194057.
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Poly(lactide) (PLA) is one of the most investigated semicrystalline polymers for material extrusion (MEX) additive manufacturing (AM) techniques based on polymer melt processing. Research on its application for the development of customized devices tailored to specific anatomical parts of the human body can provide new personalized medicine strategies. This research activity was aimed at testing a new multifunctional AM system for the design and fabrication by MEX of anatomical and dog-bone-shaped PLA samples with different infill densities and deposition angles. In particular, a commercial PLA filament was employed to validate the computer-aided design (CAD) and manufacturing (CAM) process for the development of scaffold prototypes modeled on a human bone defect. Physical-chemical characterization of the obtained samples by 1H-NMR spectroscopy, size exclusion chromatography (SEC), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC) demonstrated a small reduction of polymer molecular weight (~5%) due to thermal processing, as well as that the commercial polymer employed was a semicrystalline poly(d,l-lactide). Mechanical characterization highlighted the possibility of tuning elastic modulus and strength, as well as the elongation at break up to a 60% value by varying infill parameters.