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1
Gao, Guo Hua, Jing Zhao, Fei Ma, and Wei Dong Luo. "Hybrid RANS–LES Modeling for Unsteady Cavitating Flow Simulation." Applied Mechanics and Materials 152-154 (January 2012): 1187–90. http://dx.doi.org/10.4028/www.scientific.net/amm.152-154.1187.
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A typical hybrid RANS-LES approach, DES (Detached Eddy Simulation), was introduced into cavitating flow simulation in this paper. The applicability of two DES models, including one equation DES model and SST k-ω DES model, and standard k-ε model was analyzed through experimental data of a water tunnel experiment. Validation results illustrate that the precision of DES method depends on the RANS model used and the length scale used to distinguish LES zone and RANS zone. The SST k-ω DES method can well predict cavitating flow. The averaged results gained through this model are better than those of standard k-ε or one equation DES model. By comparison, the one equation DES model shows little advantage than standard k-ε model to simulate cavitating flow.
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Zhang, Xia Wan, Jie Mao та Liang Yu. "A New k-ω Model for Magnetohydrodynamic Turbulent Duct Flow". Applied Mechanics and Materials 865 (червень 2017): 253–56. http://dx.doi.org/10.4028/www.scientific.net/amm.865.253.
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A solver for MHD turbulent flow and a new RANS model based on k-ω model in the open source toolbox OpenFOAM are developed to investigate magnetohydrodynamic (MHD) turbulent flow. Two electro-magnetic terms in the k and ω transport equations are added to include magnetohydrodynamic (MHD) effects. The modified k-ω is validated by simulating MHD turbulent duct flow. Time-averaged velocity and turbulent kinetic energy profiles simulated by standard k-ω and the modified k-ω in the fully developed section are both reported. The results compare fairly with those obtained from DNS data. A difference of 8.4% in is found between the modified k-ω and DNS, but the RANS model only uses 0.4% of the DNS computation time.
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Kim, Byeong-Cheon, and Kyoungsik Chang. "Assessment of Hybrid RANS/LES Models in Heat and Fluid Flows around Staggered Pin-Fin Arrays." Energies 13, no. 14 (2020): 3752. http://dx.doi.org/10.3390/en13143752.
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In the present work, the three-dimensional heat and fluid flows around staggered pin-fin arrays are predicted using two hybrid RANS/LES models (an improved delayed detached eddy simulation (IDDES) model and a stress-blended eddy simulation (SBES) model), and one transitional unsteady Reynolds averaged Navier-Stokes (URANS) model, called k-ω SSTLM. The periodic segment geometry with a total of nine pins is considered with a channel height of 2D and a distance of 2.5D between each pin. The corresponding Reynolds number based on the pin diameter and the maximum velocity between pins is 10,000. The two hybrid RANS/LES results show the superior prediction of the mean velocity profiles around the pins, pressure distributions on the pin wall, and Nusselt number distributions. However, the transitional model, k-ω SSTLM, shows large discrepancies except in front of the pins where the flow is not fully developed. The vortical structures are well resolved by the two hybrid RANS/LES models. The SBES model is particularly adept at capturing the 3-D vortex structures after the pins. The effects of the blending function switching between RANS and LES mode of the two hybrid RANS/LES models are also investigated.
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Yang, Xiao Long, Kai Yao Hu, Tie Ping Lin, and Jia Yang. "Effect of Turbulence Model on Simulation of Trailing Vortex around Ahmed Body." Applied Mechanics and Materials 52-54 (March 2011): 1905–10. http://dx.doi.org/10.4028/www.scientific.net/amm.52-54.1905.
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The Realizable k-ε Reynolds averaged Navior-Stokes (RANS) turbulence models and SST k-w detached eddy simulation (DES) models are investigated for simulation of external flow and trailing vortex around Ahmed body. The 3-D N-S equations are solved with central finite volume scheme and half-implicit SIMPLE method. The time average parameters of the DES results, such as the pressure, velocity field and drag coefficient Cd, are verified by comparing with RANS and experiment data. The vortex structures of vertical, horizontal plane and cross-section, along with the turbulent kinetic energy of tail vortex are studied in details. The results show that for time averaged parameters both models can get reasonable results, while for capturing the instant flow structure, DES shows advantage over RANS model.
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Lasher, William C., and Peter J. Richards. "Validation of Reynolds-Averaged Navier-Stokes Simulations for International America’s Cup Class Spinnaker Force Coefficients in an Atmospheric Boundary Layer." Journal of Ship Research 51, no. 01 (2007): 22–38. http://dx.doi.org/10.5957/jsr.2007.51.1.22.
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Three semirigid models for International America's Cup Class spinnakers were tested in a wind tunnel with a simulated atmospheric boundary layer. These experiments were also simulated using a commercial Reynolds-averaged Navier-Stokes (RANS) solver with three different turbulence models. A comparison between the experimental and numerical force coefficients shows very good agreement. The experimentally measured differences in the driving force coefficients among the three sails were predicted well by all three turbulence models. The realizable k-e model produced the best results, and the standard k-e model produced the worst. The Reynolds stress model did not perform significantly better than the standard k-e model. The results suggest that RANS can be used as a design tool for optimizing spinnaker shape.
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Chýlek, Radomír, Ladislav Šnajdárek, and Jiří Pospíšil. "Vortex Tube: A Comparison of Experimental and CFD Analysis Featuring Different RANS Models." MATEC Web of Conferences 168 (2018): 02012. http://dx.doi.org/10.1051/matecconf/201816802012.
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The Ranque–Hilsch vortex tube represents a device for both cooling and heating applications. It uses compressed gas as drive medium. The temperature separation is affected by fluid flow behaviour inside the tube. It has not been sufficiently examined in detail yet and has the potential for further investigation. The aim of this paper is to compare results of numerical simulations of the vortex tube with obtained experimental data. The numerical study was using computational fluid dynamics (CFD), namely computational code STAR-CCM+. For the numerical study, a three-dimensional geometry model, and various turbulence physics models were used. For the validation of carried out calculations, an experimental device of the vortex tube of identical geometrical and operating conditions was created and tested. The numerical simulation results have been obtained for five different turbulence models, namely Standard k-ε, Realizable k-ε, Standard k-ω, SST k-ω and Reynolds stress model (RSM), were compared with experimental results. The most important evaluation factor was the temperature field in the vortex tube. All named models of turbulence were able to predict the general flow behaviour in the vortex tube with satisfactory precision. Standard k-ε turbulence model predicted temperature distribution in the best accordance with the obtained experimental data.
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Beg, Md Nazmul Azim, Rita F. Carvalho, Simon Tait, et al. "A comparative study of manhole hydraulics using stereoscopic PIV and different RANS models." Water Science and Technology 2017, no. 1 (2018): 87–98. http://dx.doi.org/10.2166/wst.2018.089.
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Abstract Flows in manholes are complex and may include swirling and recirculation flow with significant turbulence and vorticity. However, how these complex 3D flow patterns could generate different energy losses and so affect flow quantity in the wider sewer network is unknown. In this work, 2D3C stereo Particle Image Velocimetry measurements are made in a surcharged scaled circular manhole. A computational fluid dynamics (CFD) model in OpenFOAM® with four different Reynolds Averaged Navier Stokes (RANS) turbulence model is constructed using a volume of fluid model, to represent flows in this manhole. Velocity profiles and pressure distributions from the models are compared with the experimental data in view of finding the best modelling approach. It was found among four different RANS models that the re-normalization group (RNG) k-ɛ and k-ω shear stress transport (SST) gave a better approximation for velocity and pressure.
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Azorakos, Georgios, Bjarke Eltard Larsen, and David R. Fuhrman. "NEW METHODS FOR STABILIZING RANS TURBULENCE MODELS WITH APPLICATION TO LARGE SCALE BREAKING WAVES." Coastal Engineering Proceedings, no. 36v (December 28, 2020): 19. http://dx.doi.org/10.9753/icce.v36v.waves.19.
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Recently, Larsen and Fuhrman (2018) have shown that seemingly all commonly used (both k-omega and k-epsilon variants) two-equation RANS turbulence closure models are unconditionally unstable in the potential flow beneath surface waves, helping to explain the wide-spread over-production of turbulent kinetic energy in CFD simulations, relative to measurements. They devised and tested a new formally stabilized formulation of the widely used k-omega turbulence model, making use of a modified eddy viscosity. In the present work, three new formally-stable k-omega turbulence model formulations are derived and tested in CFD simulations involving the flow and dynamics beneath large-scale plunging breaking waves.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/T2fFRgq3I8E
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Wu, Cheng, Yi Ping Wang, and Xue Yang. "Evaluation of Various Turbulence Models in Predicting Airflow and Turbulence around a Generic Vehicle Model." Advanced Materials Research 989-994 (July 2014): 3468–72. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.3468.
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For vehicle external aerodynamic computation, the selection of the turbulence model is very important. In current research, ten RANS turbulence models were introduced to compute the time-averaged flow field around the Ahmed model with 25° backlight angle. In order to evaluate the feasibility of the turbulence model, the results were compared with the related published experimental data. The results showed that the two equations RANS turbulence models were more favorable to compute the vehicle external flow field, but parts of the two equations turbulence model just could predict the aerodynamic drag coefficient or lift coefficient effectively. However, the results further revealed that the realizable k-ε could obtain the more accurate drag coefficient and lift coefficient simultaneously, and simulate the complex separation flow in the wake.
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Zhang, Yuxin, Xiao-ping Wu, Ming-yan Lai, Guo-ping Zhou, and Jie Zhang. "Feasibility Study of Rans in Predicting Propeller Cavitation in Behind-Hull Conditions." Polish Maritime Research 27, no. 4 (2020): 26–35. http://dx.doi.org/10.2478/pomr-2020-0063.
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Abstract The propeller cavitation not only affects the propulsive efficiency of a ship but also can cause vibration and noise. Accurate predictions of propeller cavitation are crucial at the design stage. This paper investigates the feasibility of the Reynolds-averaged Navier–Stokes (RANS) method in predicting propeller cavitation in behind-hull conditions, focusing on four aspects: (i) grid sensitivity; (ii) the time step effect; (iii) the turbulence model effect; and (iv) ability to rank two slightly different propellers. The Schnerr-Sauer model is adopted as the cavitation model. A model test is conducted to validate the numerical results. Good agreement on the cavitation pattern is obtained between the model test and computational fluid dynamics. Two propellers are computed, which have similar geometry but slightly different pitch ratios. The results show that RANS is capable of correctly differentiating the cavitation patterns between the two propellers in terms of the occurrence of face cavitation and the extent of sheet cavitation; moreover, time step size is found to slightly affect sheet cavitation and has a significant impact on the survival of the tip vortex cavitation. It is also observed that grid refinement is crucial for capturing tip vortex cavitation and the two-equation turbulence models used – realizable k-ε and shear stress transport (SST) k-ω – yield similar cavitation results.
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Yuan, A. Hui, Zhen Zhe Li, Tai Hong Cheng, and Yun De Shen. "Effect of Turbulence Model to Simulation Accuracy of Wind Turbine Blade." Applied Mechanics and Materials 397-400 (September 2013): 248–51. http://dx.doi.org/10.4028/www.scientific.net/amm.397-400.248.
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With the heightened concern for renewable energy because of significant energy problems, the interest on wind energy has been greatly increased. In this study, 4 kinds of RANS turbulence models were compared and discussed based on developed analysis model. At first, a numerical model for 1kW wind turbine blade was constructed. In the following step, Spalart-Allmaras, standard k-ε, RNG k-ε and Reynolds Stress turbulence models were candidated for comparison. The analysis results show that standard k-ε or RNG k-ε model is relatively good selection under the condition of considering accuracy and computational effort simultaneously. The developed analysis model and simulation results have made a theoretical basis for improving the simulation accuracy of wind turbine blade with minimum computational effort.
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Sakthivel, R., S. Vengadesan, and S. K. Bhattacharyya. "Application of non-linear k-e turbulence model in flow simulation over underwater axisymmetric hull at higher angle of attack." Journal of Naval Architecture and Marine Engineering 8, no. 2 (2011): 149–63. http://dx.doi.org/10.3329/jname.v8i2.6984.
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This paper addresses the Computational Fluid Dynamics Approach (CFD) to simulate the flow over underwater axisymmetric bodies at higher angle of attacks. Three Dimensional (3D) flow simulation is carried out over MAYA Autonomous Underwater Vehicle (AUV) at a Reynolds number (Re) of 2.09×106. These 3D flows are complex due to cross flow interaction with hull which produces nonlinearity in the flow. Cross flow interaction between pressure side and suction side is studied in the presence of angle of attack. For the present study standard k-ε model, non-linear k-ε model models of turbulence are used for solving the Reynolds Averaged Navier-Stokes Equation (RANS). The non-linear k-ε turbulence model is validated against DARPA Suboff axisymmetric hull and its applicability for flow simulation over underwater axisymmetric hull is examined. The non-linear k-ε model performs well in 3D complex turbulent flows with flow separation and flow reattachment. The effect of angle of attack over flow structure, force coefficients and wall related flow variables are discussed in detail. Keywords: Computational Fluid Dynamics (CFD); Autonomous Underwater Vehicle (AUV); Reynolds averaged Navier-Stokes Equation (RANS); non-linear k-ε turbulence modeldoi: http://dx.doi.org/10.3329/jname.v8i2.6984 Journal of Naval Architecture and Marine Engineering 8(2011) 149-163
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Sun, Zixiang, Klas Lindblad, John W. Chew, and Colin Young. "LES and RANS Investigations Into Buoyancy-Affected Convection in a Rotating Cavity With a Central Axial Throughflow." Journal of Engineering for Gas Turbines and Power 129, no. 2 (2006): 318–25. http://dx.doi.org/10.1115/1.2364192.
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The buoyancy-affected flow in rotating disk cavities, such as occurs in compressor disk stacks, is known to be complex and difficult to predict. In the present work, large eddy simulation (LES) and unsteady Reynolds-averaged Navier-Stokes (RANS) solutions are compared to other workers’ measurements from an engine representative test rig. The Smagorinsky-Lilly model was employed in the LES simulations, and the RNG k-ε turbulence model was used in the RANS modeling. Three test cases were investigated in a range of Grashof number Gr=1.87 to 7.41×108 and buoyancy number Bo=1.65 to 11.5. Consistent with experimental observation, strong unsteadiness was clearly observed in the results of both models; however, the LES results exhibited a finer flow structure than the RANS solution. The LES model also achieved significantly better agreement with velocity and heat transfer measurements than the RANS model. Also, temperature contours obtained from the LES results have a finer structure than the tangential velocity contours. Based on the results obtained in this work, further application of LES to flows of industrial complexity is recommended.
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Werner, Sofia, Alessio Pistidda, Lars Larsson, and Björn Regnstrom. "Computational Fluid Dynamics Validation for a Fin/Bulb/Winglet Keel Configuration." Journal of Ship Research 51, no. 04 (2007): 343–56. http://dx.doi.org/10.5957/jsr.2007.51.4.343.
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A wind tunnel test of an America's Cup keel model is used for validation of one Reynolds-averaged Navier Stokes (RANS) code and one potential flow/boundary layer code. The effects of grid size, stagnation point anomaly, and turbulence model on the RANS results are discussed. Various setups of the potential code are compared. The ability of both methods to predict forces and trends are shown. The errors of the RANS code are slightly larger than the experimental error, whereas the potential flow/boundary layer results are within the experimental uncertainty, provided that a correct panelization is used. A comparison of the experimental wake flow pattern to the one computed with RANS is presented. The k-w turbulence model is shown to give the best predictions of the wake.
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Hafid, Mohamed. "Numerical Study of a Turbulent Burner by Means of RANS and Detailed Chemistry." International Journal of Energetica 3, no. 2 (2019): 34. http://dx.doi.org/10.47238/ijeca.v3i2.76.
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The present paper shows a numerical study of the Co-flow turbulent flame configuration using the Reynolds Averaged Navier-Stokes (RANS) modelling with detailed chemistry. The presumed Probability Density Function (PDF) model combined with the k-Ɛ turbulence model is adopted. The GRI Mech-3.0 mechanism that involves 53 species and 325 reactions is used. The effect of the turbulent Schmidt number Sct and the C1ε constant in the turbulent dissipation transport equation is highlighted. Despite the simplicity of RANS approach compared to other complex models such as LES and DNS, the results show that this approach is still able to simulate the turbulent flame.
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Zhao, Minsheng, Decheng Wan, and Yangyang Gao. "Comparative Study of Different Turbulence Models for Cavitational Flows around NACA0012 Hydrofoil." Journal of Marine Science and Engineering 9, no. 7 (2021): 742. http://dx.doi.org/10.3390/jmse9070742.
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The present work focuses on the comparison of the numerical simulation of sheet/cloud cavitation with the Reynolds Average Navier-Stokes and Large Eddy Simulation(RANS and LES) methods around NACA0012 hydrofoil in water flow. Three kinds of turbulence models—SST k-ω, modified SST k-ω, and Smagorinsky’s model—were used in this paper. The unstable sheet cavity and periodic shedding of the sheet/cloud cavitation were predicted, and the simulation results, namelycavitation shape, shedding frequency, and the lift and the drag coefficients of those three turbulence models, were analyzed and compared with each other. The numerical results above were basically in accordance with experimental ones. It was found that the modified SST k-ω and Smagorinsky turbulence models performed better in the aspects of cavitation shape, shedding frequency, and capturing the unsteady cavitation vortex cluster in the developing and shedding period of the cavitation at the cavitation number σ = 0.8. At a small angle of attack, the modified SST k-ω model was more accurate and practical than the other two models. However, at a large angle of attack, the Smagorinsky model of the LES method was able to give specific information in the cavitation flow field, which RANS method could not give. Further study showed that the vortex structure of the wing is the main cause of cavitation shedding.
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Mejia, Omar, Jhon Quiñones, and Santiago Laín. "RANS and Hybrid RANS-LES Simulations of an H-Type Darrieus Vertical Axis Water Turbine." Energies 11, no. 9 (2018): 2348. http://dx.doi.org/10.3390/en11092348.
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Nowadays, the global energy crisis has encouraged the use of alternative sources like the energy available in the water currents of seas and rivers. The vertical axis water turbine (VAWT) is an interesting option to harness this energy due to its advantages of facile installation, maintenance and operation. However, it is known that its efficiency is lower than that of other types of turbines due to the unsteady effects present in its flow physics. This work aims to analyse through Computational Fluid Dynamics (CFD) the turbulent flow dynamics around a small scale VAWT confined in a hydrodynamic tunnel. The simulations were developed using the Unsteady Reynolds Averaged Navier Stokes (URANS), Detached Eddy Simulation (DES) and Delayed Detached Eddy Simulation (DDES) turbulence models, all of them based on k-ω Shear Stress Transport (SST). The results and analysis of the simulations are presented, illustrating the influence of the tip speed ratio. The numerical results of the URANS model show a similar behaviour with respect to the experimental power curve of the turbine using a lower number of elements than those used in the DES and DDES models. Finally, with the help of both the Q-criterion and field contours it is observed that the refinements made in the mesh adaptation process for the DES and DDES models improve the identification of the scales of the vorticity structures and the flow phenomena present on the near and far wake of the turbine.
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Gregorc, Jurij, Ajda Kunavar, and Božidar Šarler. "RANS versus Scale Resolved Approach for Modeling Turbulent Flow in Continuous Casting of Steel." Metals 11, no. 7 (2021): 1140. http://dx.doi.org/10.3390/met11071140.
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Numerical modeling is the approach used most often for studying and optimizing the molten steel flow in a continuous casting mold. The selection of the physical model might very much influence such studies. Hence, it is paramount to choose a proper model. In this work, the numerical results of four turbulence models are compared to the experimental results of the water model of continuous casting of steel billets using a single SEN port in a downward vertical orientation. Experimental results were obtained with a 2D PIV (Particle Image Velocimetry) system with measurements taken at various cut planes. Only hydrodynamic effects without solidification are considered. The turbulence is modeled using the RANS (Realizable k-ε, SST k-ω), hybrid RANS/Scale Resolved (SAS), and Scale Resolved approach (LES). The models are numerically solved by the finite volume method, with volume of fluid treatment at the free interface. The geometry, boundary conditions, and material properties were entirely consistent with those of the water model experimental study. Thus, the study allowed a detailed comparison and validation of the turbulence models used. The numerical predictions are compared to experimental data using contours of velocity and velocity plots. The agreement is assessed by comparing the lateral dispersion of the liquid jet in a streamwise direction for the core flow and the secondary flow behavior where recirculation zones form. The comparison of the simulations shows that while all four models capture general flow features (e.g., mean velocities in the temporal and spatial domain), only the LES model predicts finer turbulent structures and captures temporal flow fluctuations to the extent observed in the experiment, while SAS bridges the gap between RANS and LES.
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Amsha, K. Abo, T. J. Craft, and H. Iacovides. "Computational modelling of the flow and heat transfer in dimpled channels." Aeronautical Journal 121, no. 1242 (2017): 1066–86. http://dx.doi.org/10.1017/aer.2017.68.
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ABSTRACTThe flow and heat transfer characteristics over a single dimple and an array of staggered dimples have been investigated using the Reynolds Averaged Navier-Stokes (RANS) approach. The objective is to determine how reliably RANS models can predict this type of complex cooling flows. Three classes of low-Reynolds number RANS models have been employed to represent the turbulence. These included a linear Eddy Viscosity Model (EVM), a Non-Linear Model (NLEVM) and a Reynolds Stress transport Model (RSM). Variants of the k-ε model have been used to represent the first two categories. Steady and time-dependent simulations have been carried out at a bulk Reynolds number of around 5,000 with dimple print diameter to channel height ratios of D/H = 1.0, 2.0 and ratios of dimple depth to channel height of δ/H = 0.2, 0.4. The linear EVM and the RSM tested both produce symmetric circulations in the dimples, while the NLEVM produces an asymmetric pattern. The mean velocity profiles predicted numerically are generally in good agreement with the data. The main flow characteristics are reproduced by the RANS models, but some predictive deviations from available data point to the need for further investigations. All models report an overall enhancement in heat transfer levels when using dimples in comparison to those of a plane channel.
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Kološ, Ivan, Lenka Lausová, and Vladimíra Michalcová. "RANS and SRS simulations of the flow around a smooth cylinder." MATEC Web of Conferences 310 (2020): 00031. http://dx.doi.org/10.1051/matecconf/202031000031.
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The paper focuses on the numerical simulation of the flow around circular cylinder with Reynolds number 2∙104. The 2D and 3D mesh is used for the computational domain. RANS turbulence model SST k-ω is used for the 2D task. The 3D task is solved using Scale-Resolving Simulation models LES, SAS, DES. Drag coefficient, lift coefficient, pressure coefficient and velocity field in the wake are evaluated.
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Kaewbumrung, Mongkol, and Chalermpol Plengsa-ard. "Relaminarization of a hot air impingement on a flat plate." E3S Web of Conferences 128 (2019): 10004. http://dx.doi.org/10.1051/e3sconf/201912810004.
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The research mainly focuses on a numerical analysis for heat transfer in the transition flow regimes. The simulation is presented by using ANSYS-FLUENT and Reynolds Averaged Navier Stokes (RANS) technique is employed in order to simulate the complex flow fields. The turbulent jet which impinges on the flat plate with a constant surface heat fluxes is tested. The average Nusselt number predictions are also calculate and compared with existing measurement results. The jet Reynolds number is set to 23,000 which based on jet nozzle diameter, while a jet-toplate spacing of H/D is fixed at 2.0. The turbulence models evaluated in the present study are one equation Spalart Allmaras (SA) model, k-ɛ, shear stress transport (SST) k-ω and SST with transition model. It can be summarized that the SA, k-ɛ, and SST k-ω models fail to calculate the global trend of the instantaneous simulated Nusselt number profiles. Only the simulated results from the SST with transition model provides agree fairly well with experimental results. Moreover, the first highest point of predicted Nusselt number are close to the stagnation point and decrease monotonically in the radial direction within the wall jet region. The second peak of Nusselt number prediction is also observed, and the RANS simulations can capture the relaminarization mechanisms within the boundary layer near walls.
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Borello, D., G. Delibra, K. Hanjalić, and F. Rispoli. "Large-eddy simulations of tip leakage and secondary flows in an axial compressor cascade using a near-wall turbulence model." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 223, no. 6 (2009): 645–55. http://dx.doi.org/10.1243/09576509jpe825.
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This paper reports on the application of unsteady Reynolds averaged Navier—Stokes (U-RANS) and hybrid large-eddy simulation (LES)/Reynolds averaged Navier—Stokes (RANS) methods to predict flows in compressor cascades using an affordable computational mesh. Both approaches use the ζ— f elliptic relaxation eddy-viscosity model, which for U-RANS prevails throughout the flow, whereas for the hybrid the U-RANS is active only in the near-wall region, coupled with the dynamic LES in the rest of the flow. In this ‘seamless’ coupling the dissipation rate in the k-equation is multiplied by a grid-detection function in terms of the ratio of the RANS and LES length scales. The potential of both approaches was tested in several benchmark flows showing satisfactory agreement with the available experimental results. The flow pattern through the tip clearance in a low-speed linear cascade shows close similarity with experimental evidence, indicating that both approaches can reproduce qualitatively the tip leakage and tip separation vortices with a relatively coarse computational mesh. The hybrid method, however, showed to be superior in capturing the evolution of vortical structures and related unsteadiness in the hub and wake regions.
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Tachos, N. S., A. E. Filios, and D. P. Margaris. "A comparative numerical study of four turbulence models for the prediction of horizontal axis wind turbine flow." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 224, no. 9 (2010): 1973–79. http://dx.doi.org/10.1243/09544062jmes1901.
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The analysis of the near and far flow fields of an experimental National Renewable Energy Laboratory (NREL) rotor, which has been used as the reference rotor for the Viscous and Aeroelastic Effects on Wind Turbine Blades (VISCEL) research program of the European Union, is described. The horizontal axis wind turbine (HAWT) flow is obtained by solving the steady-state Reynolds-averaged Navier—Stokes (RANS) equations, which are combined with one of four turbulence models (Spalart—Allmaras, k—∊, k—∊ renormalization group, and k—ω shear stress transport (SST)) aiming at validation of these models through a comparison of the predictions and the free field experimental measurements for the selected rotor. The computational domain is composed of 4.2×106 cells merged in a structured way, taking care of refinement of the grid near the rotor blade in order to enclose the boundary layer approach. The constant wind condition 7.2 m/s, which is the velocity of the selected experimental data, is considered in all calculations, and only the turbulence model is altered. It is confirmed that it is possible to analyse a HAWT rotor flow field with the RANS equations and that there is good agreement with experimental results, especially when they are combined with the k—ω SST turbulence model.
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Česenek, Jan. "Space-time discontinuous Galerkin method for the numerical simulation of viscous compressible gas flow with the k-omega turbulence model." EPJ Web of Conferences 180 (2018): 02016. http://dx.doi.org/10.1051/epjconf/201818002016.
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In this article we deal with the numerical simulation of the non-stationary compressible turbulent flow described by the Reynolds-Averaged Navier-Stokes (RANS) equations. This RANS system is equipped with two-equation k-omega turbulence model. The discretization of these two systems is carried out separately by the space-time discontinuous Galerkin method. This method is based on the piecewise polynomial discontinuous approximation of the sought solution in space and in time. We use the numerical experiments to demonstrate the applicability of the shown approach. All presented results were computed with the own-developed code.
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Benim, Ali Cemal, and Björn Pfeiffelmann. "Comparison of Combustion Models for Lifted Hydrogen Flames within RANS Framework." Energies 13, no. 1 (2019): 152. http://dx.doi.org/10.3390/en13010152.
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Within the framework of a Reynolds averaged numerical simulation (RANS) methodology for modeling turbulence, a comparative numerical study of turbulent lifted H2/N2 flames is presented. Three different turbulent combustion models, namely, the eddy dissipation model (EDM), the eddy dissipation concept (EDC), and the composition probability density function (PDF) transport model, are considered in the analysis. A wide range of global and detailed combustion reaction mechanisms are investigated. As turbulence model, the Standard k-ε model is used, which delivered a comparatively good accuracy within an initial validation study, performed for a non-reacting H2/N2 jet. The predictions for the lifted H2/N2 flame are compared with the published measurements of other authors, and the relative performance of the turbulent combustion models and combustion reaction mechanisms are assessed. The flame lift-off height is taken as the measure of prediction quality. The results show that the latter depends remarkably on the reaction mechanism and the turbulent combustion model applied. It is observed that a substantially better prediction quality for the whole range of experimentally observed lift-off heights is provided by the PDF model, when applied in combination with a detailed reaction mechanism dedicated for hydrogen combustion.
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Song, Fang Xi, Lian Hong Zhang, Zhi Liang Wu, and Le Ping Wang. "On Resistance Calculation for Autonomous Underwater Vehicles." Advanced Materials Research 189-193 (February 2011): 1745–48. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.1745.
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Investigation on the turbulence model for resistance calculation for autonomous underwater vehicles (AUV) with the typical Myring shape is presented in this paper using computational fluid dynamics (CFD) method. Resistance calculations of the 3D viscous flow over an AUV model are made by solving RANS equations with different viscous models. Comparison with experiments indicates that the SST k-ω two-equation viscous model is the most appropriate model for the resistance prediction.
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dos Santos, Elizaldo Domingues, Marco Paulsen Rodrigues, Thiago Smith V. C. de Andrade, Liércio André Isoldi, Francis Henrique Ramos França, and Luiz Alberto Oliveira Rocha. "Numerical Study of Different Closure Approaches for Prediction of Forced Convective Turbulent Cylindrical Cavity Flows." Defect and Diffusion Forum 366 (April 2016): 166–81. http://dx.doi.org/10.4028/www.scientific.net/ddf.366.166.
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The present work exhibits a numerical study comparing the fluid dynamic and thermal fields of turbulent, three-dimensional forced convective cylindrical cavity flows obtained with Large Eddy Simulation (LES) and Reynolds-Averaged Navier Stokes (RANS). In the latter approach, three different closure models are employed: Reynolds Stress Model (RSM), standard k – ε and standard k - ω. It is considered a three-dimensional, incompressible, turbulent fluid flow at the steady state with ReD = 22,000 and Pr = 0.71. The main purpose is to investigate whether discrepancies are noticed in time-averaged and statistics of turbulent flows between LES and RANS predictions. Differences in time-averaged and statistical fields can be important for evaluation of convective fluxes in turbulent flows and combined convective and radiative transfer in participant media, i.e., for study of Turbulence-Radiation Interactions (TRI). The spatially-filtered and time-averaged conservation equations of mass, momentum and energy are solved with the Finite Volume Method (FVM). Results showed that time-averaged and RMS thermal fields obtained with LES and RANS presented reasonable discrepancies in regions near the cavity surfaces, which affects the convective fluxes in this region. For the highest temperature region of the cavity (near its inlet) the predictions obtained with LES and RANS are similar, which can led to similar predictions in heat exchange when thermal radiation is taken into account in optically thin participant media. For optically thick media, where local differences increase their importance, the employment of RANS is not recommended.
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Huang, Junji, Jorge-Valentino Bretzke, and Lian Duan. "Assessment of Turbulence Models in a Hypersonic Cold-Wall Turbulent Boundary Layer." Fluids 4, no. 1 (2019): 37. http://dx.doi.org/10.3390/fluids4010037.
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In this study, the ability of standard one- or two-equation turbulence models to predict mean and turbulence profiles, the Reynolds stress, and the turbulent heat flux in hypersonic cold-wall boundary-layer applications is investigated. The turbulence models under investigation include the one-equation model of Spalart–Allmaras, the baseline k - ω model by Menter, as well as the shear-stress transport k - ω model by Menter. Reynolds-Averaged Navier-Stokes (RANS) simulations with the different turbulence models are conducted for a flat-plate, zero-pressure-gradient turbulent boundary layer with a nominal free-stream Mach number of 8 and wall-to-recovery temperature ratio of 0.48 , and the RANS results are compared with those of direct numerical simulations (DNS) under similar conditions. The study shows that the selected eddy-viscosity turbulence models, in combination with a constant Prandtl number model for turbulent heat flux, give good predictions of the skin friction, wall heat flux, and boundary-layer mean profiles. The Boussinesq assumption leads to essentially correct predictions of the Reynolds shear stress, but gives wrong predictions of the Reynolds normal stresses. The constant Prandtl number model gives an adequate prediction of the normal turbulent heat flux, while it fails to predict transverse turbulent heat fluxes. The discrepancy in model predictions among the three eddy-viscosity models under investigation is small.
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Zhong, Wenzhou, Tong Zhang, and Tetsuro Tamura. "CFD Simulation of Convective Heat Transfer on Vernacular Sustainable Architecture: Validation and Application of Methodology." Sustainability 11, no. 15 (2019): 4231. http://dx.doi.org/10.3390/su11154231.
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The global background of energy shortages and climate deterioration demands bioclimatic sustainable buildings. Vernacular architecture can provide a useful resource of passive strategies and techniques for creating inner comfort conditions with minimum heating, ventilation, and air conditioning (HVAC) assistance. The identification and verification of such knowledge are essential for climate responsive or energy passive building design. Among the methods, computational fluid dynamics (CFD) is a useful tool for simulating convective heat transfer of vernacular architecture and predicting the convective heat transfer coefficient (CHTC) and flow field. Geometric complexity and diversity of building samples are crucial in the development of an effective simulation methodology in terms of computational cost and accuracy. Therefore, this paper presents high-resolution 3D steady Reynolds-averaged Navier–Stokes (RANS) CFD simulations of convective heat transfer on Japanese vernacular architecture, namely, “machiya.” A CFD validation study on the CHTC is performed based on wind-tunnel experiments on a cube heated by constant heat flux and placed in a turbulent channel flow with a Reynolds number of 3.3 × 104. Three steady RANS models and two boundary layer modeling approaches are compared and discussed. Results show that the SST k-ω model applied with low Reynolds number modeling approach is suitable for CHTC simulations on a simplified building model. The RNG k-ε model applied with wall functions is an appropriate choice for simulating flow field of a complicated building model. Overall, this study develops a methodology involving RANS model selection, boundary layer modeling, and target model fitting to predict the convective heat transfer on vernacular architecture.
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Güemes, Alejandro, Pablo Fajardo, and Marco Raiola. "Experimental Assessment of RANS Models for Wind Load Estimation over Solar-Panel Arrays." Applied Sciences 11, no. 6 (2021): 2496. http://dx.doi.org/10.3390/app11062496.
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This paper reports a comparison between wind-tunnel measurements and numerical simulations to assess the capabilities of Reynolds-Averaged Navier-Stokes models to estimate the wind load over solar-panel arrays. The free airstream impinging on solar-panel arrays creates a complex separated flow at large Reynolds number, which is severely challenging for the current Reynolds-Averaged Navier-Stokes models. The Reynolds-Averaged Navier-Stokes models compared in this article are k-ϵ, Shear-Stress Transport k-ω, transition and Reynolds Shear Model. Particle Image Velocimetry measurements are performed to investigate the mean flow-velocity and turbulent-kinetic-energy fields. Pressure taps are located in the surface of the solar panel model in order to obtain static pressure measurements. All the Reynolds-Averaged Navier-Stokes models predict accurate average velocity fields when compared with the experimental ones. One of the challenging factor is to predict correctly the thickness of the turbulent wake. In this aspect, Reynolds Shear provides the best results, reproducing the wake shrink observed on the 3rd panel in the experiment. On the other hand, some other features, most notably the blockage encountered by the flow below the panels, are not correctly reproduced by any of the models. The pressure distributions over the 1st panel obtained from the different Reynolds-Averaged Navier-Stokes models show good agreement with the pressure measurements. However, for the rest of the panels Reynolds-Averaged Navier-Stokes fidelity is severely challenged. Overall, the Reynolds Shear model provides the best pressure estimation in terms of pressure difference between the front and back sides of the panels.
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Parente, A., C. Gorlé, J. van Beeck та C. Benocci. "Improved k–ε model and wall function formulation for the RANS simulation of ABL flows". Journal of Wind Engineering and Industrial Aerodynamics 99, № 4 (2011): 267–78. http://dx.doi.org/10.1016/j.jweia.2010.12.017.
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Colli, Matteo, Luca G. Lanza, Roy Rasmussen, and Julie M. Thériault. "The Collection Efficiency of Shielded and Unshielded Precipitation Gauges. Part I: CFD Airflow Modeling." Journal of Hydrometeorology 17, no. 1 (2015): 231–43. http://dx.doi.org/10.1175/jhm-d-15-0010.1.
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Abstract The aerodynamic response of snow gauges when exposed to the wind is responsible for a significant reduction of their collection performance. The modifications induced by the gauge and the windshield onto the space–time patterns of the undisturbed airflow deviate the snowflake trajectories. In Part I, the disturbed air velocity field in the vicinity of shielded and unshielded gauge configurations is investigated. In Part II, the airflow is the basis for a particle tracking model of snowflake trajectories to estimate the collection efficiency. A Geonor T-200B gauge inside a single Alter shield is simulated for wind speeds varying from 1 to 8 m s−1. Both time-averaged and time-dependent computational fluid dynamics simulations are performed, based on Reynolds-averaged Navier–Stokes (RANS) and large-eddy simulation (LES) models, respectively. A shear stress tensor k–Ω model (where k is the turbulent kinetic energy and Ω is the turbulent specific dissipation rate) is used for the RANS formulation and solved within a finite-volume method. The LES is implemented with a Smagorinsky subgrid-scale method that models the subgrid stresses as a gradient-diffusion process. The RANS simulations confirm the attenuation of the airflow velocity above the gauge when using a single Alter shield, but the generated turbulence above the orifice rim is underestimated. The intensity and spatial extension of the LES-resolved turbulent region show a dependency on the wind speed that was not detected by the RANS. The time-dependent analysis showed the propagation of turbulent structures and the impact on the turbulent kinetic energy above the gauge collecting section.
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Meana-Fernández, Andrés, Jesús Fernández Oro, Katia Argüelles Díaz, and Sandra Velarde-Suárez. "Turbulence-Model Comparison for Aerodynamic-Performance Prediction of a Typical Vertical-Axis Wind-Turbine Airfoil." Energies 12, no. 3 (2019): 488. http://dx.doi.org/10.3390/en12030488.
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In this work, different turbulence models were applied to predict the performance of a DU-06-W-200 airfoil, a typical choice for vertical-axis wind turbines (VAWT). A compromise between simulation time and results was sought, focusing on the prediction of aerodynamic forces and the developed flow field. Reynolds-averaged Navier–Stokes equation (U-RANS) models and Scale-Resolving Simulations (SRS), such as Scale-Adaptive Simulation (SAS) and Detached Eddy Simulation (DES), were tested, with k − ω -based turbulence models providing the most accurate predictions of aerodynamic forces. A deeper study of three representative angles of attack (5 ° , 15 ° , and 25 ° ) showed that U-RANS models accurately predict aerodynamic forces with low computational costs. SRS modeling generates more realistic flow patterns: roll-up vortices, vortex packets, and stall cells have been identified, providing a richer unsteady flow-field description. The power spectrum density of velocity at 15 ° has confirmed a broadband spectrum in DES simulations, with a small peak at a Strouhal number of 0.486. Finally, indications regarding the selection of the turbulence model depending on the desired outcome (aerodynamic forces, airfoil flow field, or VAWT simulation) are provided, tending toward U-RANS models for the prediction of aerodynamic forces, and SRS models for flow-field study.
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Roy, Christopher J., Jeffrey Payne, and Mary McWherter-Payne. "RANS Simulations of a Simplified Tractor/Trailer Geometry." Journal of Fluids Engineering 128, no. 5 (2006): 1083–89. http://dx.doi.org/10.1115/1.2236133.
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Steady-state Reynolds-averaged Navier-Stokes (RANS) simulations are presented for the three-dimensional flow over a simplified tractor/trailer geometry at zero degrees yaw angle. The simulations are conducted using a multi-block, structured computational fluid dynamics (CFD) code. The turbulence closure model employed is the two-equation Menter k-ω model. The discretization error is estimated by employing two grid levels: a fine mesh of 20 million cells and a coarser mesh of 2.5 million cells. Simulation results are compared to experimental data obtained at the NASA-Ames 7×10ft wind tunnel. Quantities compared include vehicle drag, surface pressures, and time-averaged velocities in the trailer near wake. The results indicate that the RANS approach is able to accurately predict the surface pressure on the vehicle, with the exception of the base region. The pressure predictions in the base region are poor due to the inability of the RANS model to accurately capture the near-wake vortical structure. However, the gross pressure levels in the base region are in reasonable agreement with experiment, and thus the overall vehicle drag is well predicted.
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Li, Tian, Hassan Hemida, and Jiye Zhang. "Evaluation of SA-DES and SST-DES models using OpenFOAM for calculating the flow around a train subjected to crosswinds." Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 234, no. 10 (2019): 1346–57. http://dx.doi.org/10.1177/0954409719895652.
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Detached eddy simulation (DES) has been widely applied in crosswind stability simulations of trains in recent years. As DES is a hybrid Reynolds Averaged Navier–Stokes (RANS)/large eddy simulation approach, the choice of the RANS model associated with DES is a key factor for an accurate numerical simulation. However, the influence of the RANS model on the flow around trains was not fully investigated in previous researches. In this study, DES with the Spalart–Allmaras (SA) model (SA-DES) and shear stress transport (SST) k−ω model (SST-DES) have been investigated owing to their ability to predict the surface pressure, aerodynamic forces, and the flow field around a 1/25th scale Class 390 train subjected to crosswinds. Numerical simulation results were validated with experimental data. Results show that both SA-DES and SST-DES predict similar trends of the mean flow field around the train. However, there were considerable differences observed in the position of separation points and consequently the separation and attachment lines on the roof and bottom of the train body. The SST-DES results correlated more closely to the experimental data than SA-DES for pressure coefficient on the roof and leeward surface at almost all loops. A slight difference in the side force and roll moment coefficients and a considerable difference in the lift force coefficient were observed for SA-DES and SST-DES. The side force coefficients calculated using SST-DES remain within the experimental uncertainty, whereas the lift force coefficients deviated greatly due to the omission of some underbody geometrical features. Compared to the experimental data, the SST-DES performs better than SA-DES. Therefore, the SST k−ω model is recommended for the RANS model associated with DES.
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Allen, Richard, Fred Mendonça, and David Kirkham. "RANS and DES Turbulence Model Predictions of Noise on the M219 Cavity at M=0.85." International Journal of Aeroacoustics 4, no. 1-2 (2005): 135–51. http://dx.doi.org/10.1260/1475472053730039.
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Two rectangular cavity configurations, with and without bay doors, at Mach 0.85 are investigated with the objective of assessing the ability of 3D CFD with advanced turbulence modelling to predict narrowband and broadband flow noise. A non-linear, two-equation, eddy-viscosity model run in unsteady mode (URANS) is compared with Detached Eddy Simulation (DES) on a cavity with a L/D ratio of 5. In a thorough evaluation, comparisons are made between DES variants published in the literature, namely Spalart-Allmaras, k-ε and k-ω-SST. We also assess the effect on the noise spectra of using different CFD prediction time-samples of approximately 100 flow passes compared with 250 flow passes. Detailed experimental data for both cavity configurations provide a valuable opportunity to compare the predicted spectra at many points along the cavity ceiling and band-limited amplitude along the cavity length. We conclude that for such cavity flows, all DES models perform similarly well and are superior to unsteady RANS due to their inherent ability to resolve broadband structures.
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Kusano, Kazuya, Masato Furukawa, Kenichi Sakoda, and Tomoya Fukui. "Aeroacoustic simulation of a cross-flow fan using lattice Boltzmann method with a RANS model." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 6 (2021): 598–609. http://dx.doi.org/10.3397/in-2021-1578.
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The present study developed an unsteady RANS approach based on the lattice Boltzmann method (LBM), which can perform direct aeroacoustic simulations of low-speed fans at lower computational cost compared with the conventional LBM-LES approach. In this method, the k-ω turbulence model is incorporated into the LBM flow solver, where the transport equations of k and ω are also computed by the lattice Boltzmann method, similar to the Navier-Stokes equations. In addition, moving boundaries such as fan rotors are considered by a direct-forcing immersed boundary method. This numerical method was validated in a two-dimensional simulation of a cross-flow fan. As a result, the simulation was able to capture an eccentric vortex structure in the rotor, and the pressure rise by the work of the rotor can be reproduced. Also, the peak sound of the blade passing frequency can be successfully predicted by the present method. Furthermore, the simulation results showed that the peak sound is generated by the interaction between the rotor blade and the flow around the tongue part of the casing.
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Schmelzer, Martin, Richard P. Dwight, and Paola Cinnella. "Discovery of Algebraic Reynolds-Stress Models Using Sparse Symbolic Regression." Flow, Turbulence and Combustion 104, no. 2-3 (2019): 579–603. http://dx.doi.org/10.1007/s10494-019-00089-x.
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AbstractA novel deterministic symbolic regression method SpaRTA (Sparse Regression of Turbulent Stress Anisotropy) is introduced to infer algebraic stress models for the closure of RANS equations directly from high-fidelity LES or DNS data. The models are written as tensor polynomials and are built from a library of candidate functions. The machine-learning method is based on elastic net regularisation which promotes sparsity of the inferred models. By being data-driven the method relaxes assumptions commonly made in the process of model development. Model-discovery and cross-validation is performed for three cases of separating flows, i.e. periodic hills (Re=10595), converging-diverging channel (Re=12600) and curved backward-facing step (Re=13700). The predictions of the discovered models are significantly improved over the k-ω SST also for a true prediction of the flow over periodic hills at Re=37000. This study shows a systematic assessment of SpaRTA for rapid machine-learning of robust corrections for standard RANS turbulence models.
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Chamanara, Mehdi, Hassan Ghassemi, Manouchehr Fadavie, and Mohammad Aref Ghassemi. "Effects of the Duct Angle and Propeller Location on the Hydrodynamic Characteristics of the Ducted Propeller." Ciencia y tecnología de buques 11, no. 22 (2018): 41. http://dx.doi.org/10.25043/19098642.162.
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In the present study, the effect of the duct angle and propeller location on the hydrodynamic characteristics of the ducted propeller using Reynolds-Averaged Navier Stokes (RANS) method is reported. A Kaplan type propeller is selected with a 19A duct. The ducted propeller is analyzed by three turbulence models including the k-ε standard, k-ω SST and Reynolds stress model (RSM). The numerical results are compared with experimental data. The effects of the duct angle and the location of the propeller inside the propeller are presented and discussed.
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Bassi, F., A. Ghidoni, A. Perbellini та ін. "A high-order Discontinuous Galerkin solver for the incompressible RANS and k–ω turbulence model equations". Computers & Fluids 98 (липень 2014): 54–68. http://dx.doi.org/10.1016/j.compfluid.2014.02.028.
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Khosronejad, Ali, and C. D. Rennie. "Three-dimensional numerical modeling of unconfined and confined wall-jet flow with two different turbulence models." Canadian Journal of Civil Engineering 37, no. 4 (2010): 576–87. http://dx.doi.org/10.1139/l09-172.
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Wall-jet flow is an important flow field in hydraulic engineering, and its applications include flow from the bottom outlet of dams and sluice gates. An in-house three-dimensional (3-D) finite-volume Reynolds-averaged-Navier-Stokes (RANS) numerical model predicts the hydrodynamic characteristics of wall jets with square and rectangular source geometry. Either the low-turbulence Reynolds number k–ω or the standard k–ε turbulence closure models are applied. The calculated results for velocity profile and bed shear stress in both longitudinal and vertical directions compare favourably with both the published experimental results and the FLUENT® finite volume model. The two closure models are compared with the k–ω model, displaying 4% greater average accuracy than the k–ε model. Finally, the influence of lateral confinement of the receiving channel on wall-jet hydrodynamics is investigated, with decreased longitudinal deceleration and decreased bed shear stress observed in a confined jet. This has important implications for sediment transport in the receiving channels downstream of sluice gates.
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Česenek, Jan. "Space-time discontinuous Galerkin method for the numerical simulation of the compressible turbulent gas flow through the porous media." EPJ Web of Conferences 213 (2019): 02011. http://dx.doi.org/10.1051/epjconf/201921302011.
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The article is concerned with the numerical simulation of the compressible turbulent gas flow through the porous media using space-time discontinuous Galerkin method.The mathematical model of flow is represented by the system of non-stationary Reynolds-Averaged Navier-Stokes (RANS) equations. The flow through the porous media is characterized by the loss of momentum. This RANS system is equipped with two-equation k-omega turbulence model. The discretization of these two systems is carried out separately by the space-time discontinuous Galerkin method. This method is based on the piecewise polynomial discontinuous approximation of the sought solution in space and in time. We present some numerical experiments to demonstrate the applicability of the method using own-developed code.
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Sun, M. B., J. H. Liang, and Z. G. Wang. "A modified blending function for zonal hybrid Reynolds-averaged Navier—Stokes/large-eddy simulation methodology." Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering 223, no. 8 (2009): 1067–81. http://dx.doi.org/10.1243/09544100jaero575.
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A modified blending function for zonal hybrid Reynolds averaged Navier—Stokes/large eddy simulation (RANS/LES) methodology was developed using an empirical analogy from Menter k—ω shear stress transport (SST) turbulent model (Menter, 1994) to predict complex turbulent flows. Tests of slot jet in supersonic flow and supersonic flow over compression—expansion ramp was conducted and prediction of separations was well improved when certain model constant was forced on the traditional blending function (Baurle et al., 2003). Analysis based on calculations of flat plate boundary layer demonstrated that an efficient empirical constant could be used in blending function and boundary layer could be well calculated without heavy contamination of RANS on wake region. Validation of the modified zonal hybrid RANS/LES approach for slot jet in supersonic flow, supersonic flow over compression—expansion ramp, supersonic flow over backward facing step, and supersonic cavity flow was conducted. The simulated results showed that the modified blending function performs well on complex turbulent flows. Deficiencies of traditional hybrid zonal RANS/LES method in over-prediction of separations associated with adverse pressure gradient flows were favourably improved.
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Arfaoui, Ahlem, Catalin Viorel Popa, Redha Taïar, Guillaume Polidori, and Stéphane Fohanno. "Numerical Streamline Patterns at Swimmer’s Surface Using RANS Equations." Journal of Applied Biomechanics 28, no. 3 (2012): 279–83. http://dx.doi.org/10.1123/jab.28.3.279.
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The objective of this article is to perform a numerical modeling on the flow dynamics around a competitive female swimmer during the underwater swimming phase for a velocity of 2.2 m/s corresponding to national swimming levels. Flow around the swimmer is assumed turbulent and simulated with a computational fluid dynamics method based on a volume control approach. The 3D numerical simulations have been carried out with the code ANSYS FLUENT and are presented using the standard k-ω turbulence model for a Reynolds number of 6.4 × 106. To validate the streamline patterns produced by the simulation, experiments were performed in the swimming pools of the National Institute of Sports and Physical Education in Paris (INSEP) by using the tufts method.
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Zhang, Ai She, Cui Lan Gao, and De Qian Zheng. "Analysis of Interference Effects of Adjacent Buildings on Wind Pressures." Advanced Materials Research 639-640 (January 2013): 489–92. http://dx.doi.org/10.4028/www.scientific.net/amr.639-640.489.
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This paper presents numerical and experimental investigations of wind-induced interference effects on the pressure distributions on an adjacent building. The relative locations of the interfered building model and the interfering model are sited in staggered arrangement. The wind tunnel tests were carried out in a low-speed boundary layer wind tunnel. The numerical predictions for pressure distribution on the principal building are performed by solving the Reynolds-averaged Navier–Stokes (RANS) equations using the renormalization group (RNG) k–e turbulence model and then compared with the measurements. The RANS equations are solved by the pressure correction procedure of the SIMPLEC method. The simulated pressure, base force and base moment coefficients in different wind directions are generally in good agreement with the corresponding wind tunnel data. It is also found that the wind pressures, base forces and moments on the testing building are affected to some extent by the interference from adjacent buildings. The numerical simulation applying the SIMPLEC method using the QUICK upwind scheme and the RNG k–e turbulence model seems to be a useful tool for the predictions of wind pressures, and especially the wind forces acting on a building with an adjacent building.
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Hartmann, Ralf, Joachim Held та Tobias Leicht. "Adjoint-based error estimation and adaptive mesh refinement for the RANS and k–ω turbulence model equations". Journal of Computational Physics 230, № 11 (2011): 4268–84. http://dx.doi.org/10.1016/j.jcp.2010.10.026.
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Kubacki, S., J. Rokicki та E. Dick. "Simulation of the Flow in a Ribbed Rotating Duct with a Hybrid k-ω RANS/LES Model". Flow, Turbulence and Combustion 97, № 1 (2015): 45–78. http://dx.doi.org/10.1007/s10494-015-9682-5.
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Pant, Chandra Shekhar, Yann Delorme, and Steven Frankel. "Accuracy Assessment of RANS Predictions of Active Flow Control for Hydrofoil Cavitation." Processes 8, no. 6 (2020): 677. http://dx.doi.org/10.3390/pr8060677.
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In this work, we numerically investigate the cavitating flow on the scaled-down 2D model of guided vanes. Furthermore, the effects of wall injection on both the cavitation and on the hydrodynamic performance of the guided vane are studied. The numerical simulations are performed using OpenFOAM v1906. We used a 2D k- ω SST model for modeling the turbulence in the present set of simulations. We studied the flow for two angles of attack, viz. 3 ∘ and 9 ∘ . For the 3 ∘ angle of attack, the present numerical work is in good agreement with the previous experimental work, but for the larger angle of attack, because of flow separation, the present simulations do not capture the flow correctly.
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Dang, Tien Phuc, Zhengqi Gu, and Zhen Chen. "Numerical simulation of flow field around the race car in case." International Journal of Numerical Methods for Heat & Fluid Flow 25, no. 8 (2015): 1896–911. http://dx.doi.org/10.1108/hff-04-2014-0107.
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Purpose – The purpose of this paper is to gain a better understanding of the flow field structure around the race car in two cases: stationary wheel and rotating wheel. In addition, this paper also illustrates and clarifies the influence of wheel rotation on the aerodynamic characteristics around the race car. Design/methodology/approach – The author uses steady Reynolds-Averaged Navier-Stokes (RANS) equations with the Realizable k-ε model to study model open-wheel race car. Two cases are considered, a rotating wheel and stationary wheel. Findings – The results obtained from the study are presented graphically, pressure, velocity distribution, the flow field structure, lift coefficient (Cl) and drag coefficient (Cd) for two cases and the significant influence of rotating case on flow field structure around wheel and aerodynamic characteristics of race car. The decreases in Cd and Cl values in the rotating case for the race car are 16.83 and 13.25 per cent, respectively, when compared to the stationary case. Originality/value – Understanding the flow field structures and aerodynamic characteristics around the race car in two cases by the steady RANS equations with the Realizable k-ε turbulence model.
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Afailal, Al Hassan, Jérémy Galpin, Anthony Velghe, and Rémi Manceau. "Development and validation of a hybrid temporal LES model in the perspective of applications to internal combustion engines." Oil & Gas Science and Technology – Revue d’IFP Energies nouvelles 74 (2019): 56. http://dx.doi.org/10.2516/ogst/2019031.
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CFD simulation tools are increasingly used nowadays to design more fuel-efficient and clean Internal Combustion Engines (ICE). Within this framework, there is a need to benefit from a turbulence model which offers the best compromise between prediction capabilities and computational cost. The Hybrid Temporal LES (HTLES) approach is here retained within the perspective of an application to ICE configurations. HTLES is a hybrid Reynolds-Averaged Navier Stokes/Large Eddy Simulation (RANS/LES) model based on a solid theoretical framework using temporal filtering. The concept is to model the near-wall region in RANS and to solve the turbulent structures in the core region if the temporal and spatial resolutions are fine enough. In this study, a dedicated sub-model called Elliptic Shielding (ES) is added to HTLES in order to ensure RANS in the near-wall region, regardless of the mesh resolution. A modification of the computation of the total kinetic energy and the dissipation rate was introduced as first adaptions of HTLES towards non-stationary ICE configurations. HTLES is a recent approach, which has not been validated in a wide range of applications. The present study intends to further validate HTLES implemented in CONVERGE code by examining three stationary test cases. The first validation consists of the periodic hill case, which is a standard benchmark case to assess hybrid turbulence models. Then, in order to come closer to real ICE simulations, i.e., with larger Reynolds numbers and coarser near-wall resolutions, the method is validated in the case of a channel flow using wall functions and in the steady flow rig case consisting in an open valve at a fixed lift. HTLES results are compared to RANS k-ω SST and wall-modeled LES σ simulations performed with the same grid and the same temporal resolution. Unlike RANS, satisfactory reproduction of the flow recirculation has been observed with HTLES in the case of periodic hills. The channel flow configuration has underlined the capability of HTLES to predict the wall friction properly. The steady flow rig shows that HTLES combines advantages of RANS and LES in one simulation. On the one hand, HTLES yields mean and rms velocities as accurate as LES since the scale-resolving simulation is triggered in the core region. On the other hand, hybrid RANS/LES at the wall provides accurate pressure drop in contrast with LES performed on the same mesh. Future work will be dedicated to the extension of HTLES to non-stationary flows with moving walls in order to be able to tackle realistic ICE flow configurations.