横摆角下汽车尾部湍流特征量的PIV试验分析

汽车尾部湍流场是汽车压差阻力的主要来源,在HD-2汽车模型风洞中,首先使用测力天平和测压系统,对横摆角工况下汽车模型的气动六分力和纵对称截面48个测点的表面压力进行了测量,然后利用PIV测量技术对模型在横摆角分别为0°、15°的尾部湍流场进行了测量,获得该模型尾流场的速度场、涡量场和雷诺应力流场信息,通过计算得出尾流场区域空间相关系数和湍流积分尺度。结果表明:在横摆角工况下,汽车模型尾部涡流的结构呈现向上发展的趋势;尾流场拖拽涡的范围和强度的增大导致了模型气动力出现较大的增加;湍流积分尺度的变化表明,尾部涡流区的分离噪声与涡流分离位置有关,在汽车尾部造型设计中,要尽量推迟尾部涡流的分离。

PIV Experimental Analysis of Automobile Wake Field Turbulent Characteristics under the Yaw Angle Condition

Automobile wake turbulent flow field is the main source of vehicle pressure drag. First, aerodynamic six-component and surface pressure distribution (at 48 measuring points) along longitudinal symmetry plane of an automobile model under the yaw angle condition were obtained in a HD-2 automobile model wind tunnel by using force balance and a manometry system. Then, wake turbulent field of model was measured under the yaw angles 0°and 15°, respectively, by using PIV technology. The data of velocity field, turbulent field and Reynolds stress flow field were obtained, based on which, the spatial correlation coefficient of fluctuating velocity area and corresponding turbulent integral scale were calculated. Results show that under the yaw angle condition, the trailing vortex structure of model shows upward trend of development; the increase of vortex scope and intensity leads to larger increase of aerodynamic force. The change of turbulence integral scale indicates that the noise from tail vortex area is related to the vortex separate position, and the tail vortex separation should be postponed.