Richtmyer-Meshkov instability induced by the interaction of a shock wave with a rectangular block of SF6

In this article the interaction of a shock wave with a rectangular block of sulphur hexafluoride (SF6), occupying part of the test section of a shock tube, is studied by experimental and numerical means. The difference between the ratios of the specific heats of the two gases (air and SF6) gives rise to numerical problems (generation of spurious waves at their interface). This necessitated the development of a multifluid algorithm (augmented Navier-Stokes formulation). The governing equations are based on a thermodynamically consistent and fully conservative formulation. A Riemann-problem-based scheme (the weighted average flux method) is used to integrate the hyperbolic part of the system. To this end, a new approximate Riemann problem solver has been formulated to account for the variable ratio of specific heats. The resulting algorithm was implemented in an adaptive mesh refinement code, which allowed high-resolution simulations to be performed on desktop computers. The evolution of the flow is well captured by the two-dimensional numerical solution, up to the point at which dimensionality effects become significant. The experimental evidence and numerical solutions complement each other to allow the time-evolving features present to be accurately identified and tracked, and the resulting flow physics to be discussed. Where possible, quantitative geometric comparison is made between both sets of results and good agreement demonstrated. (c) 2007 American Institute of Physics.