On the development of a computational method for modelling turbulent mixing in sharply stratified flows

A method is presented for computationally modelling turbulent mixing across a sharp stable interface. The turbulence is modelled using a second-moment stress/flux closure because of the anisotropy due to stratification, and the additional anisotropy due to the presence of the sharp interface. The numerical method utilizes an adaptive, moving-grid formulation of the governing transport equations, and solves for the movement of the interface implicitly with the solution of the transport equations. The implicit prediction of the interfacial movement is based on a special solution of the discrete scalar equation for the upper-most control-volume, which is assumed to reside partly in the non-active layer above the interface. Results are presented for the case of mixing due to oscillating-grid turbulence and compared to experimental data. The present predictions demonstrate the viability of the computational method, and the validity of the second-moment closure in sharply stratified flows. (C) 1999 Elsevier Science Inc. All rights reserved.