Experimental And Numerical Investigation On The Interaction Of Shock Wave With Gas Cylinders

When a perturbed interface separating two different fluids is impulsively acceler-ated,the initial perturbation on the interface gradually grows due to the induction of the baroclinic vorticity deposited on the interface and eventually the turbulent mixing emerges,which is known as Richtmyer-Meshkov instability(RMI).In view of the con-siderable academic value and extensive engineering applications of RMI in the fields of the supersonic combustion ramjet,supernovas explosion as well as inertial confne-ment fusion and so on,many researchers have conducted extensive and in-depth re-search on RMI and achieved fruitful results in the past few decades.Simultaneously,the shock-cylinder interaction(SCI)has been considered as one of the most fundamental configurations for studying the evolution of RMI,because the local angle between the shock and the interface ranges from 0 to 180 degrees during the shock-cylinder interac-tion.In this work,the interaction of a converging/planar shock wave with single/double heavy-gas cylinders is experimentally and numerically investigated,concentrating on the effects of Atwood number,aspect ratio and cylinder coupling on the evolution of the shocked cylinder.Experiments are carried out in a horizontal shock tube and a hor-izontal converging shock tube without the reflected shock,respectively.An idea 2D circular/elliptical gas cylinder can be generated by a soap film technique,simultane-ously,the shock-cylinder interaction can be captured by a high-speed schlieren system.The numerical method 2-Dimensional Vectorized Adaptive Solver(VAS2D)and High-Order and Double-Flux(HOWD)are applied to simulate the shock-cylinder interac-tions,and a digital image processing procedure is also developed to extract more flow field information from experimental images for more in-depth analysis.In this work,the effects of Atwood number and aspect ratio on the interaction between a planar shock and a single circular/elliptical gas cylinder are studied.Results show that Atwood number has a great influence on the wave patterns inside and outside the cylinder,resulting in the emergence of different shock focusing.Subsequently,the downstream interface exhibits different morphologies such as the inward and outward jets due to the extreme high pressure after shock focusing.Simultaneously,the fact can also be demonstrated that the early development of the jets mainly depends on the pressure pulsation during the shock focusing and the later development can be ascribed to the induction of the vorticity deposited on the jet head.Similarly,aspect ratio has a great influence on the wave patterns as well as the subsequent shock focusing.Some special phenomena such as the inward jet and the secondary vortex pair can be observed on the downstream interface,and the interface evolution as well as the material mixing also manifest great differences due to the difference in baroclinic vorticity distribution caused by the aspect ratio.In the double gas cylinders studies,the effects of cylinder coupling on the interac-tion between a planar/converging shock and double circular gas cylinders are studied.Results show that the initial spacing between two gas cylinders plays a decisive role in the later cylinder evolution,which is distinct from the single cylinder case.During the evolution of the double gas cylinders with smaller initial spacing,the gas cylinder cou-pling is more intense,resulting in the generation of the mushroom and twisted jet at the downstream interface.However,the evolution of the double gas cylinders with larger initial spacing is more similar to the independent evolution of two single gas cylinders,the gas cylinder coupling is relatively weak.By comparing the evolution of the dou-ble cylinders accelerated by the planar and converging shock,remarkable distinctions,which may originate from the coupling of the multiple effects(Bell-Plesset(BP)effect,nolinear effect and cylinder coupling)under the converging cases,can be observed.