合成射流激励频率对车辆气动阻力的影响

Influence of Driving Frequency Using Synthetic Jets on Aerodynamic Drag of a Ground Vehicle

摘要:

利用大涡模拟方法，研究了激励频率对三维地面车辆气动阻力的影响规律及其控制机理.流动分析结果表明:合成射流布置在车辆顶部和斜背交界处，在不同激励频率下实现车辆减阻，当频率低于90 Hz时，增大频率，阻力增大；频率高于90 Hz，随着频率的增大，阻力减小；频率达到1 500 Hz时，阻力不再减小.斜背附着距离和雷诺应力分布的差异解释了气动力随不同激励频率变化的原因.不同激励频率下的频谱分析表明：合成射流控制了斜背动态附着现象，导致速度、压力和阻力系数频谱峰值皆对应激励频率.

Abstract:

Based on Largeeddy simulation, influences of driving frequency on aerodynamic drag of a threedimensional ground vehicle and flowcontrol mechanism was studied. The results of flow analysis indicate that when synthetic jet array is located at the junction of the roof and the slant, drag reduction is realized with different frequencies. When driving frequency is lower than 90Hz, the aerodynamic drag increases with the driving frequency raise. When the frequency is more than 90Hz, the aerodynamic drag decreases with the frequency increase. While the aerodynamic drag fail to decrease with the frequency 1500Hz. The difference in the recirculation zone and the distribution of Reynolds stress contributes to the variation trend of the aerodynamic drag with different driving frequency. Frequency spectrum analysis reveals that the dynamic attachment flow on the slant is controlled by synthetic jet array with different driving frequency, so that the peak frequency of power spectral density of velocity, surface pressure and aerodynamic drag is related to driving frequency.