A Posteriori Analysis of Closures in RANS Models of a Small Atwood Number, Transitional Rayleigh–Taylor Mixing Experiment*

Profiles of closure models and of mean and turbulent transport equation budgets 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 performed in a water channel facility are compared to the profiles predicted by three- and four-equation mechanical–scalar Reynolds-averaged Navier–Stokes models at early-, intermediate-, and late-times. The models are initialized in several different ways, and both time-dependent and constant model coefficients are used. It is shown that the models provide very good predictions of the closure models used, as well as of the equation budgets. Comparisons to profiles obtained from analytical self-similar solutions valid in the Boussinesq limit are also presented.