Effects of a premixed layer on the Richtmyer-Meshkov instability

The effects of a premixed layer on the Richmyer - Meshkov instability (RMI) are studied by setting a density gradient for the first shocked fluid in the RMI problems. The RMI with initial density gradients are simulated by using a high resolution arbitrary Lagrangian - Eulerian method. The effects of density gradient and gradient width are analyzed on the basis of the simulation results for the shock from a light fluid to a heavy fluid and for the shock from a heavy fluid to a light fluid. Overall, the premixed layer can suppress the perturbation growth, and the detailed effects are different depending on the detailed premixed configuration. The width of the premixed layer has a very light influence on the perturbation, while the density gradient has quite a significant effect on two kinds of RMIs.