可压缩性对激波冲击V形空气/氦气界面演化的影响

Compressibility effect on shock-induced air/helium chevron interface evolution

通过实验在激波管中研究了平面激波冲击下V形空气/氦气界面的演化过程,重点关注了可压缩性和初始振幅对扰动增长的影响.结果表明:对于小振幅情况,马赫数基本不影响线性模型的有效性;但对于大振幅情况,由于大振幅效应降低了线性增长率,这使得线性模型在低马赫数时就失效,而且随着马赫数的提高,线性模型与实验增长率之间的差异会越来越大.在考虑大振幅效应和高马赫数效应后,强激波冲击下大振幅界面的扰动增长率可以被很好地预测.入射激波引起的可压缩性可以通过物质压缩和几何压缩两项来反映,且几何压缩被证实起主导作用.针对单模界面的一些非线性模型被用来预测V形界面的振幅增长,但它们只在初期是有效的,到中后期就偏离了实验结果.

Shock tube experiments of a periodic air-helium chevron interface impacted by a planar shock wave are conducted.Effects of the compressibility and the initial amplitude on the perturbation growth are highlighted.For small initial amplitudes,the shock Mach number has limited effects on the reliability of the linear model.For high initial amplitudes,however,the linear model is generally invalid because the high amplitude effect will reduce the linear growth rate.Under the high initial amplitude condition,the increase of the shock Mach number further aggravates the discrepancy of the experimental result with the theoretical prediction.By considering the high amplitude effect and the high Mach number effect,the linear growth rate of the interface with high initial amplitude impacted by a strong shock wave can be well predicted.The compressibility effect induced by the incident shock wave can be illustrated by the material compression and the geometric compression of the interface,and the latter is found to be dominant.In the nonlinear regime,some nonlinear models proposed for single-mode interfaces are verified to be valid only at very early stages.