湍流模型和离散格式在汽车外流场计算中的对比

Comparison of Turbulent Models and Discretization Schemes Based on OpenFOAM for the Numerical Simulation of the Flow Around an Automotive Standard Model

摘要:

以35° Ahmed汽车标准模型为对象，基于OpenFOAM软件研究Realizable k-ε （RKE）， Spalart-Allmaras （SA）和Shear Stress Transport k-ω （SST）3种湍流模型以及Linear Upwind （LU）， Linear UpwindV （LUV）， Localblend， Total Variation Diminishing （TVD）4种速度对流离散格式在Ahmed模型外流场计算中的表现。同时，对比了OpenFOAM、 FLUENT和STARCCM+这3个软件平台的差异。结果表明：OpenFOAM中RKE和SST湍流模型预测的阻力系数较SA模型更接近实验结果；LUV和Localblend等更稳定的格式可以一定程度上减弱计算不稳定性带来的尾迹振荡问题，但只有TVD格式能够完全的抑制这种震荡行为。3种软件平台计算的阻力系数均与实验吻合较好，其中OpenFOAM采用TVD格式的计算误差最小，仅为0.7%。此外， OpenFOAM和STARCCM+可以得到较为合理和相近的三维尾迹流场结构，而FLUENT则会高估流向C柱涡的强度。

关键词:汽车空气动力学;OpenFOAM软件;湍流模型;对流格式;定常计算

Abstract:

The flow around the 35° Ahmed model is numerically explored by using three different turbulence models （the realizable k-ε （RKE）， the Spalart-Allmaras （SA）， and the shear stress transport k-ω （SST）） and four different velocity convection schemes （the linear upwind （LU）， the linear upwindV （LUV）， the localblend， and the total variation diminishing （TVD）） based on OpenFOAM. Then， two other software platforms （FLUENT and STARCCM+） are also used as references. It shows that the numerical results of RKE and SST are more reasonable than those of SA. The stable LUDSV and localblend convective scheme both partly weaken the wake oscillation caused by numerical instability， but only the TVD scheme entirely suppresses this oscillation behavior. The drag coefficients predicted by the three software platforms are all in good agreement with those of the experiment， and the error of OpenFOAM using TVD is the smallest， only 0.7%. In addition， OpenFOAM and STARCCM+ can obtain a more reasonable and similar three-dimensional wake flow structure， while FLUENT overestimates the strength of the streamwise C-pillar vortex.

Key words:vehicle aerodynamics;OpenFOAM;turbulence model;convection scheme;steady simulation