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

1.为了抑制管道中伪激波的振荡，将被动边界层控制技术应用于矩形管道中的伪激波。激波-边界层干扰的被动控制由位于激波边界层干扰区域的多孔表面和下面的空腔或增压室组成。在这项研究中，伪激波上游的马赫数保持不变，多孔表面的孔隙率和空腔体积是变化的。研究了这些参数对伪激波静态和动态特性的影响.伪激波基本上受被动边界层控制和所谓的无激波状态之类的流型的影响，L.鳄鱼，已观察到的纹影光学方法和压力测量。而伪激波的长度和伪激波两侧的压比不受边界层被动控制的影响.当对伪激波采用被动边界层控制技术，使分叉头激波的根部位于多孔表面的上游边缘时，伪激波的振荡基本上得到抑制。特别地，通过被动控制，振荡的高频分量几乎消失。这可能是由于与激波相互作用而与壁面分离的附面层会重新附着并变得稳定。从这一点可以得出结论，该方法是有效的抑制伪激波的振荡。

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.