Abstract-
Rayleigh-Taylor instability (RTI) is the baroclinic generation of vorticity at a perturbed interface subject to acceleration in a direction opposite the mean density gradient. The resulting interpenetration and mixing of materials has far-reaching consequences in many natural and man-made flows, ranging from supernovae to Inertial Confinement Fusion (ICF). In supernovae, the rate of growth of the mixing region is thought to be a controlling factor in the rate of formation of heavy elements. In ICF, accurate prediction of the depth of interpenetration of fluids is crucial in designing capsules to maintain shell integrity. Because of the widespread importance of RTI, much attention over the past half century has been focused on predicting its late-time growth rate. A large-eddy simulation has been conducted of Rayleigh-Taylor instability at a resolution of 1152x1152x1152 grid points. A mixing transition is observed in the flow, during which an inertial range forms in the energy spectrum and the rate of growth of the mixing zone is temporarily reduced. By measuring growth of the layer in units of dominant initial wavelength, criteria are established for reaching the hypothetical self-similar state of the mixing region. A relation is obtained between the rate of growth of the mixing layer and the net mass flux through the plane associated with the initial location of the interface. A mix-dependent Atwood number is defined, which correlates well with the entrainment rate, suggesting that internal mixing reduces the layer's growth rate.
Acknowledgement:
This work was performed under the auspices of the U.S. Department of Energy by the University of California Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.
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