In this work,the laminar-to-turbulent transition phenomenon around the two-and three-dimensional ellipsoid at different Reynolds numbers is numerically investigated.In the present paper,Reynolds Averaged Navier Stokes...In this work,the laminar-to-turbulent transition phenomenon around the two-and three-dimensional ellipsoid at different Reynolds numbers is numerically investigated.In the present paper,Reynolds Averaged Navier Stokes(RANS)equations with the Spalart-Allmaras,SST k-ω,and SST-Trans models are used for numerical simulations.The possibility of laminar-toturbulent boundary layer transition is summarized in phase diagrams in terms of skin friction coefficient and Reynolds number.The numerical results show that SST-Trans method can detect different aspects of flow such as adverse pressure gradient and laminar-to-turbulent transition onset.Our numerical results indicate that the laminar-to-turbulent transition location on the 6:1 prolate spheroid is in a good agreement with the experimental data at high Reynolds numbers.展开更多
Reynolds-Averaged Navier-Stokes(RANS) Computational Fluid Dynamics(CFD) has been widely used in compressor design and analysis. However, reasonable prediction of compressor flow and its impact on compressor performanc...Reynolds-Averaged Navier-Stokes(RANS) Computational Fluid Dynamics(CFD) has been widely used in compressor design and analysis. However, reasonable prediction of compressor flow and its impact on compressor performance remains challenging. In this study, Menter’s Shear Stress Transport(SST) model and its variants, as well as the ω-based Reynolds stress model(Stress-BSL) are assessed. For a single rotor(Rotor 67), under the peak efficiency operating condition, all studied turbulence models predict its performance with reasonable accuracy;under the off-design conditions, SST with Helicity correction(SST-Helicity) shows superiority in predicting the effect of flow on the spanwise distribution of aerodynamic parameters. For Darmstadt’s 1.5-stage transonic axial compressor, SST-Helicity outperforms SST, SST with the Quadratic Constitutive Relation(SST-QCR) and Stress-BSL in predicting the performance as well as the spanwise distribution of aerodynamic parameters. At the design rotating speed, the stall margin given by SST-Helicity(20.90%) is the closest to the experimental measurement(24.81%), which is more than twice that by SST(8.71%) and 1.5 times that by SST-QCR(14.14%). This paper demonstrates that SSTHelicity model, together with a good quality and sufficiently refined grid, can capture the compressor flow features with reasonable accuracy, which results in a credible prediction of compressor performance and stage matching.展开更多
The heat transfer of supercritical fluids is a vastly growing field, specifically to find suitable <span style="font-family:Verdana;">alternative to replace conventional R134a, which can be beneficial ...The heat transfer of supercritical fluids is a vastly growing field, specifically to find suitable <span style="font-family:Verdana;">alternative to replace conventional R134a, which can be beneficial for climate change. A </span><span style="font-family:Verdana;">considerable suggestion is R515A which possesses considerably lower global warming potential. The present simulations are designed to study supercritical fluid R515A under cooling conditions in horizontal position. The effect of pressure, mass flux, heat flux and tube diameter were considered for horizontal tube in the vicinity of pseudo critical temperature. Numeri</span><span style="font-family:Verdana;">cal investigations on heat transfer characteristics of supercritical fluid R515A were per</span><span style="font-family:Verdana;">formed using widely used shear-stress transport (SST) model. Moreover, heat transfer correlations </span><span style="font-family:Verdana;">were developed and suggested to accurately predict Nusselt number within 10% accuracy. </span><span style="font-family:Verdana;">The simulation results showed about 3.98% average absolute deviation.</span>展开更多
A three-equation transition model based on the transition V-model is proposed for subsonic flows in this study. Considering the mechanical approximation of the generation process of the pre-transitional vorticities, t...A three-equation transition model based on the transition V-model is proposed for subsonic flows in this study. Considering the mechanical approximation of the generation process of the pre-transitional vorticities, the value of laminar Reynolds shear stress related to the mean shear deformation was calculated in the original transition V-model. Then a new transition model, named V-SA model, was proposed, which considered the phenomenological process of transition and presented great results for flows with and without pressure gradient. It is well-known that the baseline Shear Stress Transport(SST) turbulence model shows excellent performance of accuracy and robustness in plentiful flow cases, but it is important to predict boundary layer transition. The current model(V-SST) successfully couples the V-model to the SST turbulence model by introducing the effective turbulent viscosity and additional correction terms into the transport equations. A thorough evaluation of its ability to predict transition features is performed versus the well-documented flat plate of ERCOFTAC, including T3A and T3B without pressure gradient, T3L2 and T3L3 with semi-circular leading edge, the three-dimensional 6:1 prolate-spheroid under two angles of attack, and the NLR-7301 airfoil under different Mach numbers. Numerical results show that the current model has an attractive and superior performance in the simulation of boundary layer transition processes.展开更多
基金Erfan Kadivar acknowledges the support of Shiraz University of Technology Research Council.
文摘In this work,the laminar-to-turbulent transition phenomenon around the two-and three-dimensional ellipsoid at different Reynolds numbers is numerically investigated.In the present paper,Reynolds Averaged Navier Stokes(RANS)equations with the Spalart-Allmaras,SST k-ω,and SST-Trans models are used for numerical simulations.The possibility of laminar-toturbulent boundary layer transition is summarized in phase diagrams in terms of skin friction coefficient and Reynolds number.The numerical results show that SST-Trans method can detect different aspects of flow such as adverse pressure gradient and laminar-to-turbulent transition onset.Our numerical results indicate that the laminar-to-turbulent transition location on the 6:1 prolate spheroid is in a good agreement with the experimental data at high Reynolds numbers.
文摘Reynolds-Averaged Navier-Stokes(RANS) Computational Fluid Dynamics(CFD) has been widely used in compressor design and analysis. However, reasonable prediction of compressor flow and its impact on compressor performance remains challenging. In this study, Menter’s Shear Stress Transport(SST) model and its variants, as well as the ω-based Reynolds stress model(Stress-BSL) are assessed. For a single rotor(Rotor 67), under the peak efficiency operating condition, all studied turbulence models predict its performance with reasonable accuracy;under the off-design conditions, SST with Helicity correction(SST-Helicity) shows superiority in predicting the effect of flow on the spanwise distribution of aerodynamic parameters. For Darmstadt’s 1.5-stage transonic axial compressor, SST-Helicity outperforms SST, SST with the Quadratic Constitutive Relation(SST-QCR) and Stress-BSL in predicting the performance as well as the spanwise distribution of aerodynamic parameters. At the design rotating speed, the stall margin given by SST-Helicity(20.90%) is the closest to the experimental measurement(24.81%), which is more than twice that by SST(8.71%) and 1.5 times that by SST-QCR(14.14%). This paper demonstrates that SSTHelicity model, together with a good quality and sufficiently refined grid, can capture the compressor flow features with reasonable accuracy, which results in a credible prediction of compressor performance and stage matching.
文摘The heat transfer of supercritical fluids is a vastly growing field, specifically to find suitable <span style="font-family:Verdana;">alternative to replace conventional R134a, which can be beneficial for climate change. A </span><span style="font-family:Verdana;">considerable suggestion is R515A which possesses considerably lower global warming potential. The present simulations are designed to study supercritical fluid R515A under cooling conditions in horizontal position. The effect of pressure, mass flux, heat flux and tube diameter were considered for horizontal tube in the vicinity of pseudo critical temperature. Numeri</span><span style="font-family:Verdana;">cal investigations on heat transfer characteristics of supercritical fluid R515A were per</span><span style="font-family:Verdana;">formed using widely used shear-stress transport (SST) model. Moreover, heat transfer correlations </span><span style="font-family:Verdana;">were developed and suggested to accurately predict Nusselt number within 10% accuracy. </span><span style="font-family:Verdana;">The simulation results showed about 3.98% average absolute deviation.</span>
基金supported by the National Natural Science Foundation of China(No.11721202)。
文摘A three-equation transition model based on the transition V-model is proposed for subsonic flows in this study. Considering the mechanical approximation of the generation process of the pre-transitional vorticities, the value of laminar Reynolds shear stress related to the mean shear deformation was calculated in the original transition V-model. Then a new transition model, named V-SA model, was proposed, which considered the phenomenological process of transition and presented great results for flows with and without pressure gradient. It is well-known that the baseline Shear Stress Transport(SST) turbulence model shows excellent performance of accuracy and robustness in plentiful flow cases, but it is important to predict boundary layer transition. The current model(V-SST) successfully couples the V-model to the SST turbulence model by introducing the effective turbulent viscosity and additional correction terms into the transport equations. A thorough evaluation of its ability to predict transition features is performed versus the well-documented flat plate of ERCOFTAC, including T3A and T3B without pressure gradient, T3L2 and T3L3 with semi-circular leading edge, the three-dimensional 6:1 prolate-spheroid under two angles of attack, and the NLR-7301 airfoil under different Mach numbers. Numerical results show that the current model has an attractive and superior performance in the simulation of boundary layer transition processes.
基金supported by the Department of Science and Technology of Jilin Province(Grant No.YDZJ202201-ZYTS568)the National Natural Science Foundation of China(Grant No.82172593)the Doctoral Program Foundation of Jilin Medical University(Grant No.JYBS2021025LK).
