带喷流的超声速光学头罩流动显示

在马赫数3.8的超声速风洞中,以高时空分辨率的基于纳米示踪的平面激光散射(NPLS,Nano-tracer based Planar Laser Scattering)技术为实验手段,研究了有无喷流的超声速光学头罩流场的精细结构,清晰地再现了流场中的激波、膨胀波、剪切层和湍流边界层等复杂结构.通过分析时间相关的流场NPLS图像,可以发现流场结构随时间的演化特性.结果表明:无喷流情况下光学窗口上方的大部分流场处于层流状态;有喷流情况下剪切层的层流区域较短,在很短的距离内转捩至湍流状态;喷流出口压力高于外界压力情况下剪切层的转捩位置比压力匹配情况下较为靠前,光学窗口上方的涡结构也较为复杂.比较而言,后者对气动光学性能的影响更大.

Flow visualization of supersonic optical dome with jet

In the Mach 3.8 wind tunnel, fine structures in the flow field of optical dome with or without jet were studied by nano-tracer based planar laser scattering(NPLS), which has high spatiotemporal resolution. Lots of complex structures in the flow field were clearly visible, such as shock wave, expansion wave, shear layer and turbulent boundary layer. The analysis of time-correlated NPLS images revealed the temporal evolution characteristic of flow structures. The results show that most of flow above the optical window without jet cooling is laminar. The laminar zone with jet cooling is much shorter and transits to turbulence in a short distance. The transition point of the shear layer with higher pressure is closer to the injector exit, and the vortices are more complex. Compared to the former, the latter case will induce aero-optical effects even more.