法向速度扰动对平板壁面流场影响研究

Study On The Effect of Normal Velocity Disturbance In Wall Turbulence

平板壁面流动是一种非常常见的流动现象,由于气流与平板的相互作用,也就是粘性的作用,在平板壁面形成边界层,这种粘性边界层的存在,造成了平板虚假的弯曲,直接影响着机器、设备当中平板壁面的性能。粘性边界层在一定情况下会发生一定程度的改变,例如在原有平板流场当中加入法向扰动改变法向速度就有可能影响原有的粘性边界层。本文采用麦考马克方法计算了法向速度扰动添加前后平板间流场变化情况,采用普朗特混合长度理论计算了脉动速度和雷诺应力变化情况。结果发现,添加法向速度扰动会使得速度分布发生改变,平板接近壁面处速度增加,脉动速度减小,雷诺应力减小30%,也就是说添加法向速度扰动,平板壁面流动的湍流强度有所下降,这会使得平板壁面摩擦阻力减小,壁面振颤减小,可以采用这种方法来改善机器、设备当中平板壁面的性能。

The flat-plate flow is one of the important phenomenon in the equipment.Due to the interaction between flow and the flat-plate,which is the effect of the viscosity,the wall boundary layer is formed.It is seemed that the flat-plate has been bended.it has a direct impact on the performance of the flat-plate in the equipment.Flow field near the flat-plate is an important factor influencing the performances.In this paper,McCormack method is choosed to calculate the velocity distribution near the flat-plate,the prandtl mixing length theory has been used to calculate the fluctuating velocity and Reynolds stress.It is concluded that if the normal velocity disturbance is used,the boundary layer velocity distribution changes slightly,the velocity is higher near the wall.The fluctuating velocity is reduced.The Reynolds stress is reduced about 30%.This suggests that the turbulence intensity and the frictional resistance is reduced.This will reduce the friction resistance and flutter of the flat-plate.This method can be used to optimize the performance of the of the flat-plate in the equipment.