On the prediction of equilibrium states in stably stratified homogeneous sheared turbulence

An assessment of second-order closure models in the prediction of stratified homogeneous shear flows has been conducted. The emphasis is placed on analyzing the effects of three modeled dissipation rate equations on the prediction of equilibrium states. It is found that second-order closure models are unable to reproduce the main features of stratified homogeneous shear flow. In particular, the models considered cannot predict an important experimental observation, namely, the existence of a stationary gradient Richardson number, Rs, below which the turbulent kinetic energy, K, shows exponential growth and, above which, K, decays exponentially. This result is partly due to deficiencies in the modeled dissipation rate equation.It is shown, herein, that the performance of second-order closure models will substantially improve if stationary conditions of the turbulent kinetic energy K and the dissipation rate ε are satisfied.