基于35°Ahmed模型的外流场仿真精确性与被动控制减阻研究

Research on Simulation Accuracy of Exterior Flow Field and on Passive Flow Control to Reduce Aerodynamic Drag Based on 35°Ahmed Model

基于商用CFD计算软件STAR-CCM+,对常见的类车体35°Ahmed模型进行外流场仿真精确度研究,主要从网格类型、湍流模型、网格尺寸3个方面,通过对模型总压差阻力系数、局部的压差阻力系数、模型尾部斜面上方流场选定点的流速3个层级的分析,研究汽车外流场的仿真精确性,寻找到一种可以接受并能应用于工程的仿真方法,即主体网格是四面体网格、k-w湍流模型、网格尺寸控制在较小量级的高质量仿真策略。在此基础上,通过在35°Ahmed模型尾部斜面添加凸起结构,进行35°Ahmed模型被动控制减阻技术研究,表明35°Ahmed模型的阻力主要来源于模型尾部,在模型尾部添加凸起结构,当附加板与斜面角度为30°时,有最优减阻效果。

This paper studies the sinmlation aeeuraeyof automobile exterior flow field with35°Ahmed model with the eomnlereial CFDsoflware STAR -CCM ＋. The research is conducted from aspects such as mesh type, turbunlanee mod- el and mesh size. We analyzedthe three levels data including the tatal pressure drageoeffieient, the local pressure drags coefficient andthe flow velocity at the selected point above the slope of the model. The evaluation of the sinmlation accu- racy is performed step by step and stricter as it goes on. We finally worked out an acceptable and industrially applicable sinmlation method, which features a high - quality- strategy- with the main grids mostly used tetrahedral mesh, k - w tur- bulanee model and meshsize linfited to some order of magnitude. Then,we studiedy the technique of passive control drag reduction by adding the raised structure at the tail of the 35°Ahmed model. The results show that the resistance is mainly derived from the tail of the 35°Ahmed model. Adding a convex structure at the tail of the model will botainopti- mal drag reduction effect when the angle between the additional plate and the inclined surface is 30°.