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

1. 为了抑制管道内伪激波的振荡，将被动边界层控制技术应用于矩形管道内的伪激波。激波-边界层相互作用的被动控制包括一个多孔表面和一个位于激波边界层相互作用区域的空腔或静压室。在本研究中，保持伪激波上游马赫数不变，改变多孔表面孔隙率和空腔体积。明确了这些参数对伪冲击静、动特性的影响。伪激波在很大程度上受被动边界层控制的影响，并且通过纹影光学方法和压力测量观察到一种流型，即所谓的无激波状态，这是L. Crocco提出的伪激波区域耗散现象的极限状态。然而，伪激波的长度和跨伪激波的压力比不受边界层被动控制的影响。将被动边界层控制技术应用于伪激波中，使分岔头脚激波位于多孔表面的上游边缘，可以有效地抑制伪激波的振荡。特别是，在无源控制下，振荡的高频分量几乎消失。这可能是由于由于与激波的相互作用而与壁面分离的边界层会重新附着并变得稳定。由此可以得出结论，该方法对抑制伪激波振荡是有效的。

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.