阶背车尾流结构的数值模拟分析

Numerical Analysis of Wake Structure for Hatchback Car

尾流结构对高速行驶车辆的经济性、操纵稳定性和安全性存在直接影响。建立典型阶背车仿真模型,在计算区域内进行网格划分,为提高分析精度对模型尾部进行网格加密。采用计算精度和稳定性较高k-ε标准双方程模型,对流项采用三阶迎风格式离散,压力速度耦合采用SIMPLE方法。对相同尺寸的实体缩尺模型进行风洞试验研究,结果表明:经过模型上表面气流在后视窗前缘发生分离,部分气流在后视窗与行李厢盖板之间的区域内形成回流,部分气流在行李厢盖上再附着并分离脱落;在压差作用下分离流与来自模型两侧的气流共同形成旋向相反的尾部涡流,随着距离的增加旋度逐渐减小,并在距模型尾部三倍车身长度附近涡流基本消失。

Wake structure of an automobile has direct effect on its economy, steering stability and safety while its speed is high. The simulation model for a hatchback car was set up, and its computational zone was meshed. Local meshes behind the hatchback car were refined in order to improve simulation precision. Flow field around the model was analyzed by using k -~ double-equation model whose precision and stability were fine, and convective item was discrete by third-order upwind style, and pressure and velocity was coupled using SIMPLE method. The same-size body model was tested in the wind tunnel. Results show that airflow through top surface of the model separates at foreside of rearview window, and some airflow comes into being circumfluence in the zone between rearview window and baggage cover, and some airflow reattaches at baggage cover and separates. Airflow mentioned above and airflow from both sides of the model form rear eddy current whose rotation direction is opposite at action of pressure difference, and its curl decreases gradually and vanishes while distance reaches triple model length.