Effect Of Shock Strength On The Polygonal Interface Evolution Accelerated By Shock Wave

When a shock wave interacts with an initially perturbed interface which separates two different fluids,the vorticity will be generated due to the misalignment of the pressure and the density gradients.The accumulated vorticity leads to the increase of the perturbation amplitude,and the turbulent mixing finally appears.This flow instability phenomenon is often referred to as the Richtmyer-Meshkov instability(RMI).The RMI plays a key role in many engineering applications such as the inertial confinement fusion and the scramjet engine.Besides,the RMI is very important to the academic problems such as the instability problem,the compressible flow and the turbulent flow.Since proposed,studies on the RMI have caught much attention due to its importance.However,most previous work focused on the RMI induced by weak shock waves,and the shapes of the interface consist mainly of cylinder,spherical bubble and single-mode.Nevertheless,the shock waves involved in the engineering applications may be stronger,which will bring different compressible effects to the flow fields,and the shapes of the interface are also complicated.In this thesis,more attention will be paid to the RMI of a square interface accelerated by planar shock waves with different strengths,and of a square/hexagon interface accelerated by a cylindrically converging shock wave,for illustrating the compressible effect.The first work numerically focuses on the evolution of a square interface subjected to a planar shock wave with a different shock intensity based on the procedure VAS2D.The interface considered includes an SF6 cylinder surrounded by air and a helium cylinder surrounded by air.The wave patterns and the evolution of the interface are illustrated,and the compressible effects on the flow field are analyzed qualitatively and quantitatively through the investigation of axial and spanwise distortion of the interface.By analyzing the movement of the upstream vortex pair,the variations of the axial vortex and the vortex spacing in the spanwise direction are obtained.In addition,the circulation in the flow field is numerically studied and compared with the classical models,from which the matching conditions and error analysis are carried out.The second work of this paper is to study the interaction of the converging shock with the square and hexagon Air-SF6 interface based on our semi-annular converging shock tube.The developments of the wave patterns,the interface displacement and the amplitude with time are analyzed.The results show that the experimental results are in good agreement with the numerical results before the shock focusing at the geometry center.