来流速度对汽车天窗风振特性的影响

Influence of Stream Velocity on the Buffeting Characteristic of Vehicle Sunroof

针对汽车天窗风振问题,通过理论计算求得某款轿车室内空气共振频率和发生共振的来流速度范围,然后采用大涡模拟方法对其天窗风振特性进行数值仿真,结果表明:当来流速度为15m/s时,该车产生赫姆霍兹共振,共振频率为23.4Hz,最大声压级为131dB,而来流速度对第1、第2阶模态影响较大;采用最小二乘方法拟合开口处剪切层内流向速度分布,服从双曲正切分布规律;根据Rayleigh拐点定理发现天窗开口处存在不稳定模态;速度相关分析的结果表明,靠近开口前缘的两点之间的速度互相关系数小于靠近后缘的两点之间的速度互相关系数;且来流速度越大,两点间的速度互相关系数越大;而汽车天窗后缘和底板附近等部位的风振噪声最大。

Aiming at the problem of vehicle sunroof buffeting, the air resonance frequency and correspond- ing stream velocity range of a car compartment is figured out by theoretical calculation, and a numerical simulation is then conducted on sunroof buffeting characteristics with large eddy simulation technique. The results indicate that a Helmhohz resonance occurs at a steam velocity of 15m/s with a resonance frequency of 23.4Hz and a maximum sound pressure level of 131dB, and the stream velocity has much effects on the first and second modes. The distribution pattern of streamwise velocity in shear layer fitted by least square method follows the hyperbolic tangent law. It is found according to Rayleigh inflection point theorem that there exist unstable modes at the opening region of sunroof. The velocity correlation analysis also reveals that the velocity cross correlation coefficient between two points close to the front edge of sunroof opening is smaller than that between two points close to the rear edge of o- pening, the higher the stream velocity, the greater the velocity cross correlation coefficient between two points, and the rear edge of sunroof opening and the vicinity of floor panel have the highest buffeting noise.