汽车外后视镜流致振特性及其流动机理

Fluid-induced vibration and flow mechanism of automotive external rearview mirror

采用双向流固耦合的方法对汽车外后视镜扰流进行仿真分析,对主要的振动形式进行阐述,探究其振动的机理。首先,研究了刚性后视镜模型,得到后视镜的阻力系数Cd和升力系数Cl,为流致振动的研究提供一个比较的基础,同时验证了仿真方案的可行性。再对流致振后视镜绕流进行数值模拟,研究流致振后视镜在不同来流速度下的振动特性,得到阻力和升力系数、振动的振幅、涡脱频率等参数随速度的变化趋势。结果表明:当涡脱频率与后视镜结构的固有频率接近时,可以引起后视镜强烈的振动,而且对振动强度的影响程度远远大于对风场强度的影响。

Based on fluid-solid interaction method, simulation analysis of the flow around the external rearview mirror was carried out to investigate the mechanism of fluid-induced vibration, and the main vibration forms were described. First, the rigid external rearview mirror model was investigated to get the drag coefficient Cd, and lift coefficient CI, which provide a comparison basis for the study of fluid- induced vibration and verify the feasibility of the simulation program. Then, the flow around the external rearview mirror was simulated by numerical method to investigate the vibration characteristics of the mirror under different velocities. The changes of the drag and lift coefficients, vibration amplitude, frequency of vortex shedding and other parameters with the velocity were obtained. Results show that strong vibration of the mirror occurs when the vertex shedding frequency is approach to the structural natural frequency of the external rearview mirror, and the vibration strength is far greater than the impact strength of the wind.