LES of Stably Stratified Flow with Varying Thermophysical Properties

Abstract

Large eddy simulations of stably stratified, turbulent channel flow subjected to a large temperature gradient have been performed by considering a broad spectrum of stratification. Due to a large thermal gradient across the channel, temperature-dependent fluid properties like viscosity (µ), density (ρ), and thermal conductivity (κ) are considered as variables. With increased stratification, a cluster of laminar patches appears in the near-wall region, and turbulent momentum and buoyancy fluxes are suppressed drastically in the core of the channel due to the formation of internal gravity waves. Variable viscosity results in flow relaminarization on the hot side of the channel (where viscosity is higher). Density tends to stablize the flow by blocking the upward movement of thermal plumes, while thermal conductivity pays the toll for viscosity at high Reynolds number. A mechanistic model for wall heat transfer is developed for buoyancy-effected flows. We have observed qualitatively and quantitatively the pronounced modifications in turbulent structure and flow statistics.