三方程在汽车外流场仿真计算中的应用

Application of Three-equation Turbulence Model in Numerical Simulation of Vehicle External Flow Field

汽车外流场仿真计算有多种模型,通过仿真和试验研究找到计算精度和效率高的模型对汽车外流场的仿真计算具有十分重要的意义。在使用三方程模型进行汽车外流场的计算中,由于涡粘系数μt考虑了湍流空间尺度和湍流时间尺度对湍流输运的影响,k-ε-v2湍流模型更多地反映了湍流输运的物理机理,有着比切应力传输、k-ε湍流模型更高的计算精度,是汽车外流场较为理想的数值仿真模型。运用涡粘型k-ε-v2湍流模型、切应力传输(Shear stress transport,SST)模型、k-ε湍流模型对汽车绕流进行数值仿真,将计算的阻力系数和试验数据进行对比,结果证实k-ε-v2湍流模型的优越性。给出汽车纵对称面上的压力系数与试验值的对比曲线,使用湍流k-ε-v2模型所计算的距车尾0.1m处的湍动能分布、速度矢量线及外部流线图。

There are many kinds of turbulence models for automobile external flow field simulation. It is a very important significance to find a kind of turbulence model with high calculation efficiency and precision from the turbulence model s for vehicle external flow field simulation. Three equation k -ε-v^2 turbulent model is used to simulate automobile external flow field, because the effect of turbulence spatial scale and turbulence time scale to turbulence transportation is involved in the calculation of eddy viscidity coefficient μ1 and more physical mechanism of turbulence transportation is described in the model, therefore, k -ε-v^2 turbulent model has higher calculation precision than shear stress transport （SST） and k - ε turbulent model. So, three-equation model is a comparatively ideal numerical simulation model of vehicle external flow field. The presented simulation example of car external flow field with the eddy viscosity type three equation k -ε-v^2, SST model and k -ε turbulent model, through comparison of calculated drag coefficients of car with experimental date, validate the advantages of k - ε-v^2 turbulent model. In additional, the curve of pressure coefficient of car longitudinal symmetry face calculated by three models and wind tunnel pressure coefficient experimental data is compared. Turbulent kinetic energy distribution, velocity vector, exterior streamline graph at the position of 0.1 m away from the car rear simulated by k-ε-v^2 turbulent model, are also shown.