凹型粗糙元对边界层稳定性的影响

为了能够利用eN方法对带有凹型粗糙元的平板边界层进行转捩预测.通过数值模拟和流动稳定性的方法研究了马赫数为4.5的超声速边界层中凹型粗糙元对扰动演化的影响.对两种尺度的凹型粗糙元下扰动沿流向的幅值和增长率分布进行了计算.结果表明:凹型粗糙元对基本流的影响只是局限在凹型粗糙元及其附近很小的范围内.凹型粗糙元对扰动幅值的演化有抑制作用,尺度越大抑制作用越明显.在凹型粗糙元的后面,凹型粗糙元对扰动幅值的增长率的影响很小,相对变化量在2%以内.验证了对壁面有凹型粗糙元的情况,可以通过流动稳定性分析加N值修正的方法进行转捩预测. 

Effect of concave groove on the stability of boundary layer

In order to predict the transition position using e^N method for flat boundary layer with concave groove, the effects of concave groove on the evolution of disturbance in supersonic boundary layer with Mach number of 4.5 were studied by numerical simulation and flow stability method. The amplitude and growth rate distribution along the flow direction with two sizes of concave groove was revealed. The results show that the range of effect of concave groove on the basic flow is only limited in the concave groove and near range. Concave groove has a suppressed effect on the evolution of disturbance to some extent, the bigger size means the more obvious inhibitory effect. After concave groove, the effect of concave groove on the growth rate of disturbance amplitude is little, and relative variation is smaller than 2%.At the same time, the position of transition can be predicted more accurately with a smaller concave groove by e^N method combined with stability analysis and a correction factor of N.