Ahmed模型不同后背倾角下的流场及气动噪声研究

Investigation of Flow Characteristics and Aerodynamic Noise for an Ahmed Body with Different Rear Slant Angles

摘要:

应用雷诺时均法Realizable k–ε的湍流模型对Ahmed模型在不同后背倾角下进行了定常流场的分析，并进行流场的大涡模拟(LES) 计算.基于流场的压力脉动和速度脉动分布，获取并分析了模型表面压力脉动级分布及远场气动噪声特性，并对远场噪声与模型气动阻力的关系进行了探讨.结果表明，不同后背倾角模型中气流分离特征差异较大，导致模型尾部压力脉动强度差异明显，从而影响辐射至远场的噪声能量及其分布，且噪声能量与模型的气动阻力具有一定的关系.合理设计后背倾角，对于尾部气动噪声的控制非常重要.

Abstract:

The realizable k –ε method was used for steady simulation of external airflow of Ahmed model with different rear slant angles, and the large eddy simulation (LES) method was employed for transient simulation. Based on the pressure and velocity fluctuation distribution, Ahmed body surface pressure fluctuation level distribution and aerodynamic noise characteristics in the far field were studied. Furthermore, the relationship between wind noise radiated in the far field and aerodynamic drag was studied. The results show that there is a significant difference between model rear pressure and velocity fluctuation distribution of Ahmed model at different rear slant angles due to different flow separation pattern, which influences the noise power radiated to the far field and its distribution. Additionally, there exists a certain relationshape between noise power and aerodynamic drag. Therefore, optimizing rear slant angle is very important for rear wind noise control.