A non-planar or a bilateral mixing-layer is studied by means of a series of direct numerical simulations (DNSs). This mixing-layer forms at the interface of two co-current plane Couette flows of different Reynolds numbers. The current DNS study determined the conditions for the onset of shear-layer instability at the interface. The influence of different Reynolds number (of the co-current plane Couette flows) and their Reynolds number ratio on the mixing-layer is studied. A critical Reynolds number of about 500 (or more particularly one of the co-current plane Couette flows must be turbulent) and a Reynolds number ratio greater than 2 is required for the genesis of this bilateral shear-layer instability. Independent of the Reynolds number and the Reynolds number ratio, the temporal evolution of the shear-layer instability followed the same pattern. In addition, the oscillation frequency of the instability was found to increase with increasing Reynolds number and increasing Reynolds number ratio. Further, influence of instability on the local skin friction and the two-point correlation is elaborated on.

通过一系列直接数值模拟（DNS）研究非平面或双边混合层。该混合层在两个雷诺数不同的并流平面库埃特流的界面处形成。当前的DNS研究确定了界面处剪切层不稳定性开始的条件。研究了不同的雷诺数（并流平面库埃特流）和它们的雷诺数比对混合层的影响。大约500的临界雷诺数（或更特别地，并流平面Couette流之一必须是湍流的），并且这种双边剪切层不稳定性的产生需要大于2的雷诺数比。独立于雷诺数和雷诺数比，剪切层不稳定性的时间演化遵循相同的模式。另外，发现不稳定性的振荡频率随着雷诺数增加和雷诺数比增加而增加。进一步，阐述了不稳定性对局部皮肤摩擦和两点相关性的影响。