Comparisons of a Reynolds-Averaged Navier--Stokes Model with Self-Similar Solutions for Large Atwood Number Rayleigh--Taylor Mixing*

A new high-order, multicomponent, weighted essentially nonoscillatory (WENO) implementation of a three- and four- equation Reynolds-averaged Navier-Stokes (RANS) model incorporating both mechanical and scalar turbulence is used to simulate intermediate-to-large Atwood number Rayleigh-Taylor turbulent mixing. The predicted RANS mixing layer evolution is compared with the analytical self-similar solutions of the transport equations. The terms in the transport equation budgets are compared in detail to their self-similar profiles across the mixing layer. Additionally, the sensitivity of the RANS solutions to variations in the initial conditions and in the model coefficients is explored. The implications of these results for advanced modeling of Rayleigh-Taylor turbulent mixing are discussed.