基于尺度自适应模拟的汽车天窗风振噪声特性分析

采用尺度自适应湍流模型对一个简易天窗进行数值模拟,通过与试验结果对比,验证数值计算方法的准确性。针对某轿车天窗风振噪声问题,进行不同来流速度条件下的数值模拟,模拟结果表明,轿车天窗风振噪声是声反馈和亥姆霍兹共振两种机制共同作用的结果。在发生亥姆霍兹共振时,通过对一个周期内天窗开口处涡运动对乘员耳旁处压力的影响分析,揭示天窗产生风振的压力特性。深入地研究剪切层失稳特性,对于最强的风振噪声,流向上和横向上速度的方均根值最大,表明亥姆霍兹共振加剧了剪切层里的扰动,产生的风振能量最高。在乘员舱发生亥姆霍兹共振的风速条件下,随着乘员人数的增加,风振噪声的峰值声压级有所降低,与之相关的频率变化很小。

Analysis of Car Sunroof Buffeting Noise Based on Scale-adaptive Simulation

Scale adaptive simulation (SAS) turbulence model is employed to simulate a simplified sunroof noise. Compared with the experimental data, the accuracy of the numerical computational method based on the SAS turbulence model is validated. Aiming at the problem of vehicle sunroof buffeting noise, the numerical simulations of different inflow velocity are conducted. The results indicate that vehicle sunroof buffeting noise is mainly caused by aeroacoustic feedback and Helmholtz resonance. When Helmholtz resonance occurs, the characteristics of sunroof buffeting are revealed through the analysis of the monitor’s pressure caused by vortex shedding from the leading edge in one period. An intensive study on shear layer instability is conduct, for the case of the strongest sunroof buffeting noise, the root mean square of the velocity fluctuations in the streamwise and transverse directions are all the biggest, respectively, which indicate that the disturbance of shear layer is amplified by Helmholtz resonance and thus generates the strongest buffeting energy. As different number of passengers in cabin increases under the wind condition of Helmholtz resonance, the peak sound pressure levels of the buffeting somewhat decrease, and the associated frequencies have little change.