冲击射流的彩虹纹影实验研究

超声速冲击射流在短距、垂直起降飞行器（S/VTOL）以及火箭发射等方面应用广泛，但是伴随着流场与噪声等诸多方面的问题。要研究这一类问题，必先研究这一类超声速流动的波系结构。文章利用彩虹纹影测量系统，对不同距离不同压比的冲击射流进行实验研究，得到了清晰的彩虹纹影实验结果，细致地呈现了冲击射流的波系结构。基于实验结果，对三种不同结构的冲击射流的波系结构进行了详细分析。发现喷嘴与挡板距离较大时，形成的射流结构与自由射流相似，壁面附近的射流区域不明显。随着距离减小，冲击射流出现壁面冲击区附近射流比较剧烈的现象。距离进一步减小时，出现滞止泡等结构，滞止泡的形状与压比相关。此外，实验表明冲击射流形成的马赫盘大小、形状与来流压比相关。

Experimental research on supersonic impinging jet by rainbow schlieren

Impinging jets widely exist in many engineering fields,such as a short takeoff vertical landing （S/VTOL）,as well as rocket lunching.It’s important to know the shock wave structure of impinging jets.In a simple rainbow schlieren system,the knife edge in the cut-off plane is replaced by a tricolor filter with a background color center and two colors separated by central band.The direction of the filter can usually be adjusted so that the density gradients in different direction can be examined.The rainbow schlieren apparatus requires no laser source, the optical alignment is simple,and it is tolerant to minor mechanical imperfections and/or vibrations.In this paper,the rainbow schlieren method is used in impinging jets experiments at different range and pressure ratio.Some perfect experimental results are gotten.Three kinds of impinging j ets are discussed and found that the size and shape of mach disk are depended on the pressure ratio.The result shows that when the distance between nozzle and ground plate is relatively large,the structure of impinging jet is similar to free jet,and the jet district near the ground plate is weakly.As the distance become closer,the jet region near the ground plate becomes stronger and a big stagnation bubble appears in the recirculation flow region at a particular pressure ratio.