展向振荡对激波/湍流边界层干扰的影响

周期振荡作为一种有效的壁面流动控制手段受到广泛关注，而其对激波/湍流边界层干扰的影响目前鲜有研究。本文采用高精度直接数值模拟（DNS）方法对马赫数2.9、12°激波入射角、强振荡下的激波/湍流边界层干扰进行了系统研究。通过与无振荡工况的定量比较，揭示了展向强振荡对干扰区内复杂流动结构的影响规律及作用机制，如分离泡尺度、物面压力脉动非定常特性、物面剪切的非定常特性及统计特征等。研究发现：在展向强振荡作用下，分离点位置提前，间歇区长度增大；同时由于分离泡内强黏性耗散的影响，展向振荡的穿透高度约为分离泡高度的4%，因而对流动结构不会产生实质影响。但展向强振荡会对壁面附近流动造成显著影响，如强振荡诱导的壁面展向速度远大于流向速度，造成流向剪切与展向剪切之间夹角的概率密度函数峰值从0°偏移到80°~90°之间。物面压力及剪切本征正交分解分析表明，展向振荡会导致模态能量从低阶模态向高阶模态转移，降低低频运动的能量占比，增强再附后Görtler涡等壁面附近旋涡结构的强度。

Effect of spanwise oscillation on interaction of shock wave and turbulent boundary layer

Spanwise oscillation has been studied extensively as an effective drag reducing tool. However, research on its impact on the shock wave/boundary layer interaction is still rare. In this paper, we perform a Direct Numerical Simulation (DNS) of oblique shock wave/boundary layer interaction at Ma=2.9 with 12° incident angle. Through a quantitative comparison with the case without oscillation, the impact of the oscillation on complex structures in size of separation bubbles, fluctuations of wall pressure and statistical characteristics of wall shear stresses is revealed. With strong spanwise oscillation, the separation position moves upstream and the intermittency length increases. The penetrating depth of the spanwise oscillation is about 4% of the separation bubble height due to the viscous dissipation of the boundary layer. Therefore, the general structures of the interaction will not be affected. Since the spanwise velocity is much larger than the streamwise velocity in the near wall region, the peak of probability density functions of the angle between wall shear stress components shifts from 0° to 80°-90°. The proper orthogonal decompositions of wall pressure and wall shear stresses indicate that the model energy will be transferred from the lower-order modes to higher-order ones, and the proportion of energy in low-frequency motion is reduced, while the structures after reattachment such as Görtler vortices will be strengthened.