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Source URL: http://www.llnl.gov/casc/asciturb/simulations.shtml

ASCI Turbulence PPM Simulations
Rayleigh-Taylor Simulation

A parallelized compressible PPM code has been used to simulate the Rayleigh-Taylor instability and turbulent mixing. The domain is a unit cube spanned by a grid containing 512 points in each of the three directions. This case was run on the ASCI Blue-Pacific ID System at LLNL using 128 nodes. The initial equilibrium state consists of a gamma = 5/3 gas, in which each of the subvolumes above and below the midplane (z = 0.5) are in hydrostatic equilibrium. The internal energies are piecewise constant, while the density and pressure decrease exponentially with height, but have different scale heights above and below the midplane. The density has a jump from 1 just below, to 2 just above the midplane, corresponding to an Atwood number of 1/3, and the pressure is continuous across the midplane. The sound speed corresponding to the equilibrium state below the midplane is 1.0. Other parameters are Prandtl number is 1.0 and viscosity (normalized to the sound speed and box size) is 0.00004. The boundaries are periodic in the horizontal directions and impenetrable in the vertical direction. Time is in units of sound-wave transit times (below the interface). A random spectrum of low-level velocity perturbations away from the equilibrium state is initially imposed.

The figure above shows the temperature field at time t=4.0 .