Comparison of RANS Model and Self-Similarity Predictions Corresponding to Small Atwood Number, Transitional Rayleigh–Taylor Mixing

Profiles of mean and turbulent fields across the mixing layer obtained from direct numerical simulation data [O. Schilling and N. J. Mueschke, Physics of Fluids 22, 105102 (2010)] corresponding to a small Atwood number, transitional Rayleigh–Taylor mixing experiment in a water channel facility are compared to the profiles predicted by three- and four-equation mechanical–scalar Reynolds-averaged Navier–Stokes models and to analytical self-similar profiles [O. Schilling, Physics of Fluids 33, 085129 (2021)] at various times. The models are initialized in several different ways, and both time-dependent and constant model coefficients are used. It is shown that all profiles are in very good agreement. Many self-similar quantities are evaluated as a function of time using the time-dependent model coefficients, and are compared to their values using late-time constant coefficients, and are also compared to the dynamic model predictions and DNS data.