Mixing in Rayleigh-Taylor Instabilities

Fluid instabilities and subsequent mixing can play a fundamental role in many astrophysical processes, including the shock of a core-collapse supernova propagating through the outer layers of a massive star and the propagation of a burning front through a white dwarf in a thermonuclear runaway supernova. We present direct numerical simulations of mixing at Rayleigh-Taylor unstable interfaces performed with the Flash code, developed at the ASCI/Alliances Center for Astrophysical Thermonuclear Flashes at the University of Chicago. We present results of both single- and multi-mode studies in 2- and 3-dimensions. Our results indicate that 3-d perturbations grow significantly faster than 2-d perturbations and that grid resolution can have a significant effect on instability growth rates. We also find that unphysical diffusive mixing occurs at the fluid interface, particularly in poorly resolved simulations, making it difficult to maintain the purity of our fluids. This work was supported by the U.S Department of Energy under grant No. B341495.