Numerical Investigation Of Planar Shock Wave Impacting On The Spherical Gas Density Interface

The study of the interfacial instability has always been one of the hotspots in the research.In particular,the Richtmyer-Meshkov?RM?instability caused by the shock wave impingement is widely found in the natural and industrial practices,which involves many complex physical and chemical processes.Therefore,the related research has vital application value and scientific significance.A detailed numerical study of the interaction of the planar incident and its reflected shock waves with a spherical gas density interface?inert or reactive interface?was carried out respectively.The main research contents and results are listed as follows:?1?In the present study,a high accuracy resolution was adopted to study the process of the shock wave impacting on the SF₆ heavy bubble.The jet formation mechanism of the heavy bubble is analyzed in detail from the qualitative and quantitative perspectives,and the influence of Mach numbers on the bubble deformation was also investigated.The results show that the SF₆ heavy bubble has a strong cumulative energy effect,and the shock focusing process can be divided into two phases.The incident shock wave converges along the streamwise direction inside the gas bubble,and forms a pair of longitudinally symmetrical high pressure regions at first,and then the two high pressure regions collide at the central symmetrical axis to complete the focusing process.At the same time,the initial development stage of the jet is mainly affected by the shock wave focusing,and the late development of the jet is mainly influenced by the effect of vortices on the flow field.With the decrease of the Atwood number,the compression effect of the incident shock wave on the bubble is more obvious,the focusing time is delayed,and the focus position is closer to the downstream interface,however,the peak values of density and pressure of the focus point are reduced.In addition,during the initial stage of jet generation,the increase rates of the different bubble jet lengths increase with the decreases of Atwood number and then maintain a similar growth rate,but the development time of the SF₆jet is longer than the other two gases significantly.?2?The process of the reflected shock wave impacting on the SF₆ bubble was studied numerically by changing the distance from the bubble center to the right wall.The generation mechanism of the jet on the left side of the bubble was analyzed,and the influences of the incident shock Mach numbers were analyzed using the defined integral values.The results show that different end wall distances would affect the deformation degree of the SF₆ bubble before the interaction of the reflected shock wave.When L=79mm,no jet is generated on the left interface of the bubble;While L=27mm,three jets may form on the left interface.The focusing and impingement of the reflected wave are the main causes of the formation of the left-side jet.Moreover,the shock wave variation and bubble deformation processes differ with the different shock intensities.The compression,the mixing rate and the vortices generation speed of the bubble are all enhanced with the increasing Mach numbers.?3?The incident and reflected shock waves impacting on the spherical flame are studied numerically by changing the reflection wall distance and the incident shock Mach number to analyze the combustion characteristics and the structures of the flow filed.The results show that the flame is compressed by the incident shock firstly and then expands quickly.Before the reflected shock wave impinges on the distorted flame,the physical process dominates the evolution of the flame,while the chemical process plays a major role behind the reflected shock.Different reflection wall distances result in different flame shapes,and the effect of viscosity is getting stronger with the distance increases,which inhibit the generation of flame interface folds.In addition,the compression of the flame is significantly enhanced with the increase of the shock intensities.The higher temperature and pressure conditions behind the reflected wave can promote the formation of detonation,which can change the combustion characteristics and the structures of flow filed.