绕射激波和反射激波冲击下的Richtmyer-Meshkov不稳定性

利用高速纹影和平面片光测试技术,实验研究低马赫数入射激波绕圆柱体后冲击N2/SF6平面界面,以及来自固壁的反射激波再冲击过程的R-M不稳定性特征.在竖直激波管采用重气体尾部充入,轻气体上部充入,狭缝流出的方式,在实验段狭缝处生成准静止稳定的N2/SF6平面界面.激波与圆柱作用后的流场是复杂的,包括初始的入射波、弯曲反射波、马赫波、由马赫反射产生的滑移线.研究这些复杂流场对界面的作用,对认识界面扰动的生成具有较大帮助.与平面激波作用不同的是,在柱体绕射后的激波冲击下,界面会生成局部扰动.实验结果显示,入射激波作用下界面宽度增长缓慢,而反射激波再冲击后,局部扰动会产生大的"尖钉"和"气泡"结构;反射激波与边界层相互作用产生壁面涡,会加剧湍流混合区的增长;来自尾部固壁的反射稀疏波会再次加剧湍流混合区的增长.

The Richtmyer-Meshkov instability by diffracted incident shock waves and reshock

The developments of Richtmyer-Meshkov instability at gas interface subjected to a diffracted incident shock wave of low Mach number and reshock wave have been experimentally studied using the high-speed schlieren photography and laser sheet technique. The motionless and stable interface is formed in a vertical shock tube by using a downward flow of nitrogen（light gas N2） and an upward flow of heavy gas SF6, which meet at the desired interface location and exit from the lateral slots in the test section walls. The interaction yields of shock waves with rigid cylinder is complex, including the primary incident shock, reflected bow shock, Mach shock, slip lines originated from the triple Mach shock. The understanding of interaction of this with interface, will contribute to the knowledge of the perturbation originated from the complex flow. The planar shock wave diffracted over a cylindrical column produces local perturbation at the gas interface. It has been demonstrated that the thickness of the interface grows slowly under the incident shock wave, while spike and bubble are clearly observed upon reshock. Moreover, the interaction between the reshock wave and the boundary layer generates wall vortices, which enhances the development of Turbulence Mixing Zone（TMZ）. The reflected rarefaction wave from wall-end also accelerates the development of TMZ.