Prediction of the characteristics of turbulent flows with strong streamline curvature, such as flows in turbomachines, curved channel flows, flows around airfoils and buildings, is of great importance in engineering a...Prediction of the characteristics of turbulent flows with strong streamline curvature, such as flows in turbomachines, curved channel flows, flows around airfoils and buildings, is of great importance in engineering applications and poses a very practical challenge for turbulence modeling. In this paper, we analyze qualitatively the curvature effects on the structure of turbulence and conduct numerical simulations of a turbulent Uduct flow with a number of turbulence models in order to assess their overall performance. The models evaluated in this work are some typical linear eddy viscosity turbulence models, nonlinear eddy viscosity turbulence models （NLEVM） （quadratic and cubic）, a quadratic explicit algebraic stress model （EASM） and a Reynolds stress model （RSM） developed based on the second-moment closure. Our numerical results show that a cubic NLEVM that performs considerably well in other benchmark turbulent flows, such as the Craft, Launder and Suga model and the Huang and Ma model, is able to capture the major features of the highly curved turbulent U-duct flow, including the damping of turbulence near the convex wall, the enhancement of turbulence near the concave wall, and the subsequent turbulent flow separation. The predictions of the cubic models are quite close to that of the RSM, in relatively good agreement with the experimental data, which suggests that these models may be employed to simulate the turbulent curved flows in engineering applications.展开更多
Simulations of tip vortex wetted flows and cavitating flows are carried out by using a RANS model. Two types of turbule- nce models, with and without the Boussinesq turbulent-viscosity hypothesis, are adopted in compa...Simulations of tip vortex wetted flows and cavitating flows are carried out by using a RANS model. Two types of turbule- nce models, with and without the Boussinesq turbulent-viscosity hypothesis, are adopted in comparing with experimental results regarding the vorticity, the strain rate and the Reynolds shear stress distributions in the vortex region. The numerical results imply that the spatial phase shift between the mean strain rate and the Reynolds stresses can be accurately modeled by the nonlinear κ-ε turbulence model, the tip vortex cavitation region can only be predicted using the nonlinear κ-ε turbulence model. The mecha- nism of the over-dissipation due to the turbulence model is analyzed in terms of the turbulence production, which is one of the dominant source terms in the transport equations of energy.展开更多
文摘Prediction of the characteristics of turbulent flows with strong streamline curvature, such as flows in turbomachines, curved channel flows, flows around airfoils and buildings, is of great importance in engineering applications and poses a very practical challenge for turbulence modeling. In this paper, we analyze qualitatively the curvature effects on the structure of turbulence and conduct numerical simulations of a turbulent Uduct flow with a number of turbulence models in order to assess their overall performance. The models evaluated in this work are some typical linear eddy viscosity turbulence models, nonlinear eddy viscosity turbulence models （NLEVM） （quadratic and cubic）, a quadratic explicit algebraic stress model （EASM） and a Reynolds stress model （RSM） developed based on the second-moment closure. Our numerical results show that a cubic NLEVM that performs considerably well in other benchmark turbulent flows, such as the Craft, Launder and Suga model and the Huang and Ma model, is able to capture the major features of the highly curved turbulent U-duct flow, including the damping of turbulence near the convex wall, the enhancement of turbulence near the concave wall, and the subsequent turbulent flow separation. The predictions of the cubic models are quite close to that of the RSM, in relatively good agreement with the experimental data, which suggests that these models may be employed to simulate the turbulent curved flows in engineering applications.
基金supported by the National Natural Science Foundation of China(Grant No.11332009)the Key Doctoral Program Foundation of Shanghai Municipality(Grant No.B206)
文摘Simulations of tip vortex wetted flows and cavitating flows are carried out by using a RANS model. Two types of turbule- nce models, with and without the Boussinesq turbulent-viscosity hypothesis, are adopted in comparing with experimental results regarding the vorticity, the strain rate and the Reynolds shear stress distributions in the vortex region. The numerical results imply that the spatial phase shift between the mean strain rate and the Reynolds stresses can be accurately modeled by the nonlinear κ-ε turbulence model, the tip vortex cavitation region can only be predicted using the nonlinear κ-ε turbulence model. The mecha- nism of the over-dissipation due to the turbulence model is analyzed in terms of the turbulence production, which is one of the dominant source terms in the transport equations of energy.
