A study on the suppression of oscillation of pseudo-shock waves by means of passive boundary layer control

1.为了抑制管道中拟激波的振荡，将被动边界层控制技术应用于矩形管道中的拟激波。激波-边界层相互作用的被动控制由一个多孔表面和位于激波边界层相互作用区的空穴或真空室组成。在本研究中，拟激波上游的马赫数保持不变，而多孔面的孔隙率和空穴体积是不同的。明确了这些参数对拟冲击静、动态特性的影响。拟激波主要受被动边界层控制的影响，并用纹影光学方法和压力测量观察到了一种所谓的无激波状态，这是L.Crocco提出的拟激波区域耗散现象的极限状态。但是，边界层的被动控制并不影响拟激波的长度和跨拟激波的压力比。当将被动边界层控制技术应用于拟激波，使分叉头部激波位于多孔面上游边缘时，拟激波的振荡基本上得到抑制。尤其是在被动控制的情况下，振荡的高频分量几乎消失。这可能是因为与激波相互作用而与壁面分离的边界层会重新附着并变得稳定。从这一点上可以得出结论，这种方法对抑制拟激波的振荡是有效的。

1. In order to suppress the oscillation of pseudo-shock waves in ducts, the technique of passive boundary layer control has been applied to the pseudo-shock waves in a rectangular duct. The passive control of shock-boundary layer interactions consists of a porous surface and a cavity or plenum underneath located in the region of shock boundary layer interaction. In this study, the Mach number upstream of the pseudo-shock was kept constant, and the porosity of the porous surface and the cavity volume were varied. The effects of these parameters on the static and dynamic characteristics of pseudo-shocks were made clear.2. The pseudo-shock is affected substantially by the passive boundary layer control and a flow pattern like, so called, a shockless state, which is suggested as a limiting state of the dissipative phenomenon in the pseudo-shock region by L. Crocco, has been observed by a schlieren optical method and by pressure measurements. However, the length of the pseudo- shock and the pressure ratio across the pseudo-shock are not affected by the passive control of the boundary layer.3. When the technique of passive boundary layer control is applied to the pseudo-shock so that the foot the bifurcated head shock is located at the upstream edge of the porous surface, the oscillation of the pseudo-shock is substantially suppressed. In particular, the components of high frequencies of the oscillation almost vanish by the passive control. This may be due to the fact that the boundary layer which is separated from the wall by the interaction with the shock would reattach and become stable. From this point, it may be concluded that this method is effective to suppress the oscillation of pseudo-shock waves.