Evolution Of Shock-accelerated Double-layer/double-component Gas Cylinder

The development of a corrugated interface separating two different fluids subjected to a shock wave is referred to as the Richtmyer-Meshkov(RM)instability.After the shock passage,the interface deforms continuously accompanied by a perturbation growth due to the baroclinic and pressure perturbation mechanisms.Then,secondary instabilities become pronounced and massive small-scale vortices are generated,which subsequently induce the turbulent mixing.RM instability is important in both practical engineering and natural phenomena such as inertial confinement fusion,supersonic combustion and supernova explosion.The interaction of a shock wave with a gas cylinder has always been a hot topic in the study of RM instability.Extensive work has been done on the interaction between shock wave and single-layer gas cylinder,and abundant results have been obtained.However,the studies of double-layer or double-component gas cylinder are rare.In this work,developments of the shock-accelerated double-layer gas cylinder have been experimentally and numerically investigated.Then the developments of the shock-accelerated double-component gas cyliner have been considered numerically.In the study of double-layer gas cyliner,we focus on the difference between evolution of double-layer and single-layer gas cyliner.It is found that the inner and outer gas cyliners develop independently at the early stage.Then the presence of inner gas cyliner changes the behaviors of the shock movements,and a vortex pair rather than an outward jet is created at the downstream interface of the outer cylinder.The leftmost interface of the double-layer gas cylinder is accelerated by the impact of the rarefaction waves that are generated from the upstream interface of the inner cylinder,and the linear stage of the leftmost interface movement is prolonged or shortened.Besides,the shock waves and the rarefaction waves reverberate between interfaces,accelerating and decelerating the interface movement continuously.Consequently,the continuous waves’effect results in the failure of the nonlinear model in predicting the leftmost interface.By changing the initial conditions,the effects of the inner and outer radius ratios,the eccentricity of inner gas cylinder and the Mach number of incident shock wave on the evolution of double-layer gas cylinder are investigated.Results show that the inner and outer gas cylinder couple with each other at the late stage,and the larger the radius ratio,the stronger the coupling strength.The development of the width and height of the inner and outer gas cylinder will be affected by the position of the inner one and the mixing between gases will be promoted when the inner gas cylinder is positioned upstream or the Mach number of incident shock wave is increased.Finally,the existing circulation models are used to calculate the circulation of the inner and outer gas cylinder respectively,and the total circulation is obtained by the linear superposition of them.The results show that the reliability of the models is ralated to the incident shock Mach number.In the study of double-component gas cylinder,two double-component gas cylinders are obtained by changing the arrangement order of two components in the gas cylinder.It is found that the arrangement order of gases has obvious effects on the wave patterns and interface evolution.When the shock wave impacts the SF6-helium gas cylinder,the wave pattern inside gas cylinder is relatively simple,and SF6 and helium gas cylinders separate from each other and develop independently at the late stage.When the shock wave impacts the helium-SF6 gas cylinder,the free precursor refraction and free precursor von Neumann refraction are formed because of the complex interaction betweem shock waves inside gas cylinder.Helium is quickly mixed with SF6 and air after helium gas cylinder is divided into two parts.In addition,the pressure distribution in two cases is also significantly different.In the SF6-helium gas cylinder,the pressure peak is formed at the center point of SF6/helium interface when the first transmitted shock wave passes through the SF6/helium interface.In the helium-SF6 gas cylinder,the pressure peak appears outside the downstream interface when the third transmitted shock wave reaches its convergent center.Finally,the analysis of material mixing shows that helium is more likely to be mixed with air or SF6 and the mixing efficiency is greatly affected by the arrangement order of gases.