Pseudo1ntellectual's video: RT Instability 3D-RT by DSMC 7 Billion Particles

The applications of the Rayleigh-Taylor instability---i.e. the mixing of a heavy fluid on top of a light in a gravitational field ---range from astrophysics (supernova explosions), to geophysics (formation of salt domes), all the way to inertial confinement fusion (collapse of ICF capsules), as well as the general turbulent mixing of fluids. Therefore, its fundamental understanding is of relevance not only to the foundations of hydrodynamics but also to a broad range of subjects, including physics, chemistry, biology, and geology. We show that quantitative theoretical investigations on the atomistic level of the Rayleigh-Taylor instability --- as the classical example of complex turbulent hydrodynamic flows --- compare favorably to recent experiments. Using the latest generation of supercomputers (the LANL Q machine) we solve Newtonian equations of motion for up to 100 million particles for as many as 250,000 integration steps --- an enormous numerical venture. A quantitative comparison of these ``nanohydrodynamic'' flows with continuum descriptions (Navier-Stokes equations) and macroscopic experiments demonstrates that large-scale atomistic simulations can provide insight into complex hydrodynamic phenomena. The movie gives a nice impression of what happens during such instabilities; it shows a quasi 2 dimensional simulation including about 12 million atoms interacting via Lenard-Jones potentials (only the repulsive part for the AB interaction in order to maximize surface tension) Computer power increased dramatically since 2003 and the Rayleigh-Taylor problem is able to be run with over 7 billion particles on BlueGene/L. Also, the Atwood number (A=(rho1-rho2)/(rho1+rho2), rho1/2=mass density of heavy/light fluid) dependence has been investigated in more detail.