阶背式MIRA模型气动阻力数值模拟网格无关性研究

对汽车气动阻力数值模拟结果影响较大的网格划分形式和方法进行了对比研究.利用现有充分的计算资源,建立阶背式MIRA模型,通过划分常见的四面体网格和混合网格,分别对两种网格形式在整车周围和车身尾部对网格进行加密,并保证足够多的网格数量,得到了数值稳定的网格无关性的阻力系数结果,总结出了阻力系数随网格加密的变化趋势,并与现有风洞试验值进行对比分析.结果表明：网格一旦加密后阻力系数即有显著下降,随着网格数的不断增加,阻力系数均呈现出明显的下降趋势,且下降幅度逐渐减小,最后都能在3000万网格左右得到网格无关性的结果.最终四种方案的阻力系数值均小于风洞试验值,且与之存在一定的误差.

Grid Independence Research for Numerical Simulation of Aerodynamic Drag on Notchback MIRA Model

Some grid generation methods were discussed comparatively, which have a great influence on the result of numerical simulation of vehicle aerodynamic drag. Based on current adequate computing resource, the notchback MIRA model was built and tetrahedral mesh and hybrid mesh were separately divided for it. Then grid refinement was respectively performed around the model and at the rear of the model. At the same time, suf- ficient grid number was guaranteed. Numerically stable and grid - independent drag coefficients were obtained and variation tendency of drag coefficient with the grid number growth was summarized. In addition, the results of numerical simulation were compared with those of wind tunnel test. The results showed that once grid refinement is implemented, drag coefficient is significantly decreased. The decline curve of drag coefficient gradually levels off with the increasing grid number and grid - independent results can be gained when the grid number increases to about 30 million. Each final drag coefficient is less than the experimental data of wind tunnel test and there is a deviation between them.