汽车后视镜流场的试验与数值研究

Experimental and Numerical Investigations of Flow Field of Automotive Rear View Mirror

摘要:

为了解后视镜的流场特性,以风洞试验与数值计算为手段,对后视镜的压力场与速度场进行测量和计算,并将测量结果与数值计算结果进行比较,评估两者的异同.数值计算结果与风洞试验结果的平均静压与速度、脉动速度的标准差以及自功率谱密度的一致性表明,所使用的数值计算方法具有可行性,能够较为真实地反映出后视镜的流场特性,数值计算结果与风洞试验结果能够相互验证.试验段近地面的平均静压变化反映出后视镜尾部的流动状态,能量耗散最为强烈的地方出现在远离后视镜约1.0倍后视镜直径的区域,回流区域影响范围可达3.0倍后视镜直径.后视镜尾部带有强烈的脉动速度,剪切层侧的速度脉动比其他区域大,个别测点脉动速度标准差数值可达来流速度的0.3倍,它们的主要能量集中在中低频区域.

Abstract:

Pressure and velocity fields of flow over an outside rear view mirror are investigated by wind tunnel test and numerical simulations,and their results are compared.The agreement of average static pressure and average velocity,standard deviation and power spectral density of fluctuating velocity between the results from wind tunnel test and the results from numerical simulations indicates that test results and numerical results validate each other,and the numerical simulation approach is feasible and can reflect the flow field characteristics of mirror.The features of the flow field downstream the mirror,as reflected by the average static pressure distribution of test section floor,show that the position where the energy dissipation is the strongest is located at one diameter distance downstream of the mirror,and the recirculation zone can affect the flow field three diameters downstream of the mirror.High intensity fluctuating velocity can be found at the wake of mirror and their energy are foucs on low and middle frequency.The strength of fluctuating velocity at the shear layer region is larger than other regions.At the shear layer region,the σ(u′)/u进 value can reach 0.3 at certain point.