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DOE OSTI · 2585268

Evaluation of probability density function descriptions for three-component Rayleigh–Taylor mixing

Ferguson, Kevin [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000166537482)·Morgan, Brandon E. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000301701856)
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Abstract

Results from simulations of a three-component Rayleigh–Taylor (RT) mixing problem are presented. These simulations are conducted in heavy–light–heavy and heavy–intermediate–light configurations, and each of these configurations are further considered in high- and low-Reynolds-number regimes. This results in RT-unstable flow with one or both interfaces initially unstable, permitting the influence of problem configuration on the statistical description of three-component RT-driven mixing to be considered. Mass fraction covariances are observed to undergo a sign change through the mixing layer in all four configurations considered. This appears to be unique to the multi-component case and represents another way in which multi-component RT mixing differs from the two-component case. Qualitative and quantitative comparisons of joint and marginal probability density function (PDF) descriptions of species concentration are made. Three-, five-, and six-parameter model PDFs are compared against simulation data to assess how accurately they describe the mixing, and it is found that three-component mixing requires at least a five-parameter model PDF to accurately describe the mixing. Notably, the marginal distributions of three-component mixing do not appear to conform to a beta distribution, representing a departure from the classical two-component RT case. In conclusion, statistical neutrality also appears to influence the optimal choice of model PDF, which is found to be a function of problem configuration.

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Ferguson, Kevin [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000166537482), Morgan, Brandon E. [Lawrence Livermore National Laboratory (LLNL), Livermore, CA (United States)] (ORCID:0000000301701856). 2025-05-21. Evaluation of probability density function descriptions for three-component Rayleigh–Taylor mixing. https://doi.org/10.1016/j.physd.2025.134717

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