Numerical investigation of stably stratified turbulent channel flow under non-Boussinesq conditions

Abstract

The low Mach number flow between two isothermal infinite parallel horizontal walls at different temperatures under the influence of gravity is studied using Large-Eddy Simulation (LES). As a result of high temperature difference between two walls and strong property variations, the Boussinesq approximation is not valid and is not used. Various test cases with different wall temperature ratios, ranging from 1.01 to 6, and different Richardson numbers, Ri = gL _ref/u ² _ref, ranging from 0 to 60, are considered. In the range of temperature ratio and Richardson number considered, the flow stayed turbulent. The study reports on a systematic investigation of the flow regimes. The mean flow properties, the fluctuating values, as well as the energy budgets are presented. The results are in good agreement with the available data in the literature.

Keywords:

• stably stratified flow
• non-Boussinesq conditions
• variable density flows
• low Mach number approximation
• Large-Eddy Simulation (LES)

Acknowledgments

The authors would like to thank Prof. Miltiadis Papalexandris at Universite Catholique de Louvain (UCL), Belgium, for several helpful discussions during the preparation of this manuscript.