Numerical Simulation Of The Effects Of Flow Field Density Non-uniformity And Initial Conditions On Interface Instability

In order to better control the materials mixing process in the engineering applications,interface instability research have received lots of attention.Based on the numerical simulation method,we focus on the influence of initial conditions including the density of flow field,the diffusion of the interface,and the shape of shock wave on RM instability.Based on the Euler method,subgrid scale model and turbulence model,the Multi-Viscosity Fluid and Turbulence(MVFT)code has been utilized to simulate.Firstly,we study the density nonuniformity effects on RM instability by simulating the process of incident shock impacting on different multi-mode cosine interfaces in initially nonuniform flows whose density is Gaussian function.The numerical results show that the evolution of the interface with a large initial amplitude in low density nonuniform area grows fastest,conversely,while that with a small initial amplitude in high density nonuniform area grows slowly.The main reason is that the interface with a large initial amplitude in low density zone possesses a larger density gradient which results in a larger amount of vorticity and circulation,and turbulent energy leading to the fast-changing evolution of the interface.Next,the research about RM instability of diffusive interface shows that,the mechanism of diffusive interface instability is different from the normal interface instability.Due to the inner tangential velocity discontinuity on the interface,there is an obvious phenomena of interface crimp on the edge of the interface,and the spike shape is not so obvious,and bubbles seem to be flatter.Then,the process of sine shock wave loading on interface is simulated,studying the effect of Mach number of sine shock wave and the shape of sine shock wave on the interface instability evolution.The density contours depict the following main features:1.there are jets on the interface,attributed to the sudden climb of pressure of the shock wave troughs caused by the convergence effect.2.The interface instability evolution of nonuniform shock loading interface is different from the normal RM instability.After the sine shock wave impacts on the interface,the interface develops into the similar shape of a "spike".Moreover,the quantitative parameters(circulation and amplitude)are less than the quantity of the plane shock wave loading cases.In this paper,what we researched about the important influence of the flow field and interface,shock wave on the development of the RM instability can be enlightening for the interface instability research.