粗糙元诱导的高超声速边界层转捩

基于有限体积方法，直接数值模拟了高超声速边界层内不同形状粗糙元导致的强制转捩现象；为了能够深入探究强制转捩机理，解析小尺度运动，同时又能够较好地捕捉激波，采用高阶色散最小耗散可调（MDCD）格式对Navier-Stokes方程组对流项进行重构。计算结果表明，数值结果与对应的实验值吻合较好；该方法能解析小尺度的流动结构以及规则结构的破碎与失稳过程，可揭示粗糙元引起的强制转捩机理，即此类强制转捩主要由粗糙元顶部的三维剪切层失稳导致。对多种粗糙元的转捩效果进行了定量研究，影响因素包括粗糙元形状、几何参数等。

Roughness element induced hypersonic boundary layer transition

Hypersonic boundary layer transition from laminar to turbulent induced by different isolated roughness elements is investigated using direct numerical simulation based on finite volume formulation. To explore the transition mechanism through resolving the small flow structure, and capture shock wave in hypersonic flow, the high order minimized dispersion and controllable dissipation (MDCD) scheme is used to reconstruct the convection terms of Navier-Stokes equations. The numerical results agree well with experimental data. The numerical method adopted in this article is able to resolve small flow structures and their break-up and instability procedure. And it shows that the transition is dominated by the instability of the three-dimensional shear layer on top of the roughness elements. The effect of roughness element shape and geometrical parameters on transition mechanisms, and the transition results of multiple roughness elements are quantitatively studied.