基于γ修正的转捩模型汽车后视镜啸叫理论研究与试验验证

Theoretical Study and Test Validation on Vehicle Rearview Mirror Whistling Based on γ Corrected Transition Model

针对汽车后视镜啸叫声,本文中以κ-ωSST转捩输运函数为基础,引入湍流间歇度γ和动量厚度雷诺数Reθ,详细解释了汽车后视镜表面层流边界层流体变化。将经γ修正的转捩模型应用于某一具体车型,并与风洞试验、声学照相机测试相结合进行验证。结果表明,基于γ修正的转捩模型通过剪切力(或者表面摩擦因数Cf)和动量厚度θ云图可准确预测层流边界层的转捩、分离、再附着的流动现象,结合湍动能κ可明确湍流加剧的原因,从而可准确预测后视镜产生啸叫的倾向。该方法为汽车前期开发阶段后视镜啸叫倾向的评估提供了一定的指导依据,有效缩短了开发周期和降低后期实车啸叫声的测试成本。

Aiming at the whistling of rearview mirror,the turbulence intermittenceγand momentum thickness Reynolds number are introduced to explain the changes in the laminar boundary layers on the surface of rearview mirror in detailed,based on theκ-ωSST transfer function.The transition model being corrected byγis applied to a specific vehicle and verified by wind tunnel test and acoustic camera test.The results show that the corrected transition model can accurately predict the flow phenomenon such as the transition,separation and reattachment of laminar boundary layer though the nephograms of shearing force(or surface friction factor)and momentum thickness,and by combining with the kinetic energyκ,the causes of turbulence intensification can be clarified,and hence the tendency of rearview mirror whistling can be accurately predicted.This method provides certain guidance for estimating the tendency of rearview mirror whistling in the early phase of vehicle development,effectively shortening the lead time and reducing the cost of subsequent real vehicle whistling test.