中文摘要：

采用风洞实验和数值模拟方法研究平板表面圆柱形粗糙单元引起的M=3超声速边界层转捩问题。实验采用纳米粒子示踪平面激光散射技术（NPLS）对流动结构进行测量。共考察了1mm、2mm和4mm三个不同的粗糙度条件。采用五阶精度加权紧致非线性格式（WCNS—E-5）对风洞实验进行数值模拟和对比。实验及计算表明：粗糙元对边界层干扰后诱导了尾迹流向涡的形成，流向涡通过抬升机制产生剪切层和流向速度条带等不稳定结构；实验流动图像显示，剪切层不稳定在边界层转捩过程中起重要作用；随着粗糙元高度增加，流动分离范围和转捩区域明显扩大，转捩位置有提前的趋势。

英文摘要：

The transition of a supersonic flat-plate boundary layer induced by isolated roughness element is investigated numerically and experimentally at Mach 3. A nanometer particle tracing-based planar laser scattering （NPLS） flow visualization technique is adopted in the wind tunnel experiment for measuring fine structures of a supersonic flow field. Three different roughness heights of lmm, 2mm and 4mm are considered respectively. Calculations are done under wind tunnel conditions by using fifth-order weighted compact nonlinear scheme （WCNS-E-5） for comparison. Good agreements between experimental data and high-order solutions are achieved. It is observed that the shear layer instability appears to be the leading mechanism for transition to turbulence in the wake of roughness element. With increasing height of roughness, the shear layer breaks up earlier and the transition position tends to move forward.