带控制的超声速二维后台阶流动显示

在Mach数3.4的来流条件下，对二维后台阶流动精细结构开展了实验研究.实验分为后台阶上游无控制加粗糙带扰动及微涡流发生器（micro-vortex generator，MVG）扰动3种状态，采用基于纳米示踪的平面激光散射（nano-tracer based planar laser scattering，NPLS）方法获得了流向和展向切面内的高时空分辨率流动显示图像，并测量了模型表面静压分布.对大量NPLS图像取平均，研究了流场结构的时间平均规律，对比不同时刻的瞬态流场精细结构图像，发现不同状态下的湍流大尺度结构的特征时间.有粗糙带状态相对无粗糙带台阶下游回流区压力更低，而下游压力较高，台阶上游区别不大；受MVG控制后台阶下游附近区域压力突增；MVG对流动的控制改变能力较强，粗糙带能调整台阶上下游附近流动平稳过渡，流场壁面压力没有突变. 

Visualization on Supersonic Flow over 2D Backward Facing Step with Control

The fine flow structures over a backward facing step (BFS) under Mach 3.4 were studied experimentally. The experiments were carried out as three states:without control, with roughness and with micro-vortex generator (MVG) control to the upstream flow of BFS. The streamwise and spanwise flow images with high spatial-temporal resolution were captured via nano-tracer based planar laser scattering (NPLS) technique and the surface static pressures were measured using micro-electric pressure scanning valve. Based on the large number of instantaneous flow images, the time-averaged flow was investigated. From contrasts among the flow structures at different times, the characteristic time of the large scale turbulent structures was claimed out. With roughness control, the pressure in the recirculation flow region is lower than that without control, while the pressure downstream is larger. With MVG control, the pressure around the step increases in a very short distance. MVG will change the flow state strongly than other types and the roughness can adjust the flow around the step to be transited with few differences.