自由来流湍流与三维壁面局部粗糙诱导平板边界层不稳定T-S波的数值研究

采用直接数值模拟（DNS）方法，研究了在自由来流湍流与三维壁面局部粗糙作用下平板边界层内诱导产生不稳定T-S波的物理问题.数值结果可知，在平板边界层内发现了二维和三维T-S波组成的波包空间序列以及求得了波包向前传播的群速度大小，从而证明了自由来流湍流与三维壁面局部粗糙作用是激励平板边界层内诱导产生不稳定T-S波的一种机制.随后，建立了平板边界层内被激发的二维和三维T S波的初始幅值与自由来流湍流度，三维壁面局部粗糙的流向长度、展向宽度及法向高度之间的关系.这一问题的深入研究，进一步完善了流动稳定性与湍流理论.

Numerical Study of Unstable T-S Waves Excited by Interaction Between Free-Stream Turbulence and 3D Localized Wall Roughness in Flat-Plate Boundary Layer

The direct numerical simulation (DNS) method was adopted to study the physical problem of unstable Tollmien-Schlichting (T-S) waves in the flat-plate boundary layer under the interaction between free-stream turbulence and 3D localized wall roughness.The numerical results show that the spatial arrays of the wave packets composed of 2D and 3D T-S waves form in the flat-plate boundary layer,with the propagation speeds of the wave packets calculated.Then it is proved that the interaction between the free-stream turbulence and the 3D localized wall roughness makes the mechanism for excitation of unstable T-S waves in the flat-plate boundary layer.Subsequently,the relations between the initial 2D & 3D T-S wave amplitudes and the free-stream turbulence intensity,the roughness length,the roughness width and the roughness height,were built.The in-depth research of this problem is conducive to understanding of the hydrodynamic stability theory.