二维T-S波在壁面局部喷吸边界层流中的演化

Study on evolution of 2D T-S wave in boundary layer with localized ejection and suction

采用壁面设置局部法向速度模拟喷吸条件,数值计算获得稳定的三维边界层基本流的数值解。在此基础上,研究不稳定的二维扰动T-S波在空间演化过程的非线性问题;探讨边界层壁面局部无量纲喷吸速度0.004,0.000 6对二维T-S波非线性演化的影响及其对增长率的贡献。数值计算结果表明,边界层平均流剖面的改变促进了扰动波的快速增长,增强了流体运动的不稳定性,扩大了中性曲线的不稳定区域范围,不稳定的二维T-S波获得了更大的增长率;不稳定的二维扰动T-S波在非线性演化过程中,由于非线性相互作用不断增强,逐渐诱导激发出三维扰动速度及高次谐波,其三维扰动基本波的流向波数和频率与二维扰动波的流向波数和频率相同;正、负相间流向涡及强剪切层已初步形成。

The numerical solution of basic flow in a three-dimensional boundary layer was numerically determined using localized ejection and localized suction. On this basis, the nonlinear spatial evolution processes of a two-dimensional unstable disturbance T- S wave were studied, and the 0.004-and 0.0006-velocity localized ejection and suction effects on tim nonlitrear evolution of the two-dimensional T-S wave and on the growth rate are discussed. Numerical results show that the change in the average flow is a key factor that causes fast growth of the disturbance wave, enhances the instability of flow, enlarges the unstable region of the neutral curve, and adds to the growth rate of the unstable two-dimensional T-S wave. In the process of the evolution, because of the gradual increase of nonlinear interactions, the three-dimensional disturbance velocity and high-frequency harmonics are induced, and the stream wave number and frequency of three-dimensional are the same as those of the two-dimensional disturbance wave. Positive and negative staggering stream vortices and an intense shear layer are formed.