边界层壁面振动诱导T-S波的直接数值模拟

采用空间模式的平板边界层Blasius解为基本流，利用直接数值模拟方法求解二维不可压扰动方程．研究了边界层对二维壁面局部持续微振动的感受性。计算结果表明，当地扰动速度随时间变化显示弦振动特性，振动周期与壁面加载周期完全一致；扰动速度在空间上具有波动解的特性，流向波数与O一S方程解接近；数值计算获得的扰动幅值增长率稍大于预测值，二者运行趋势基本吻合，且对所计算的雷诺数条件，周期为30的扰动幅值逐渐增长，而周期为20的扰动帽值先增加后衰减；周期为30的扰动的二次谐波明显大于周期为20的扰动；流向扰动速度及法向扰动速度的剖面模值函数在壁面局部振动下游附近与O-S方程解不完全重合，而在壁面局部振动下游较远处则与其重合良好；边界层壁面局部微振动获得的二维扰动解具有T—S波的形式。

DIRECT NUMERICAL SIMULATION OF VIBRATION-INDUCED T-S WAVE ON BOUNDARY LAYER WALL

The spatial growth of the disturbance in the boundary layer is directly numerically simulated, and the receptivity of the Blasius basic flow to the local two-dimensional (2-D) sustainable micro-vibration is investigat-ed.Results show that the disturbance velocity presents the sine vibration features with the change of time, and the vibration period is identical to the vibration of the local wall.The disturbance velocity presents the fluctuation feature downstream, and the streamwise wave length approximates to the results from the Orr-Sommerfeld equa-tion (OSE).The growth rate from direct numerical simulation(DNS) is a little greater than that from OSE, and their trends are almost consistent.Under the condition of Re=2 800, the disturbance amplitude gradually grows in the given computational region with the period T=30.However, it firstly increases and then decreases with the period T= 20.The disturbance harmonic of the former is obviously larger than that of the latter.The maxi-mum streamwise and vertical disturbance velocities from DNS do not fully coincide with those from OSE at the vicinity of the local vibration wall, hut coincide well with the former when they travel downstream.The 2-D dis-turbance induced by the local micro-vibration represents the form of Tollmien-Schlichting (T-S) wave on the boundary layer.