Large eddy simulation of a thermally stratified turbulent channel flow with temperature oscillation on the wall

Thermally stratified turbulent channel flow with temperature oscillation on the bottom wall of the channel is investigated by use of large eddy simulation (LES) approach coupled with dynamic subgrid-scale (SGS) models. The objective of this study is to deal with the influence of the temperature oscillation on characteristics of thermally stratified turbulent flow and to examine the effectiveness of the LES technique on predicting unsteady turbulent flow driven by time-varying buoyancy force. To validate the present calculation, thermally stratified turbulent channel flow is computed and compared with available data obtained by direct numerical simulation (DNS), which confirm that the present approach can be used to study stably and unstably stratified turbulent flow satisfactorily. Further, to elucidate the effect of the temperature oscillation on turbulent flow with different Richardson numbers and oscillation periods, some statistical quantities including the phase-averaged resolved velocities, temperature and their fluctuations, turbulent heat fluxes, and turbulence structures based on instantaneous velocity and temperature fluctuations are analyzed.