A comparison of mix models for the Rayleigh–Taylor instability Original Research Article

Four mix models, implemented into an Arbitrary Lagrangian–Eulerian (ALE) multi-physics code, are compared on simulations of the Rayleigh–Taylor instability. The specific models of interest are a mass diffusion model, the image turbulence model, the BHR turbulence model, and a multifluid interpenetration mix model. The bubble growth rates produced by the different models are compared to experimentally determined growth rates. The diffusion model reproduces the characteristic image growth for diffusion processes and therefore does not reproduce instability growth rates, as expected. The image and BHR turbulence models reproduce the nominal instability growth rates at multiple Atwood numbers with a single set of model parameters. The multifluid interpenetration model exhibits diffusion-like behavior and therefore does not reproduce instability growth rates. All four models exhibit Cauchy-like convergence in the mixing layer width with decreasing mesh size, although the multifluid model exhibits both a larger error for a given mesh size and a slower convergence rate than the turbulence models.