Heat transfer mechanism in a thermally stratified turbulent flow

An investigation was carried out on the momentum and heat transfer mechanisms of the turbulent structures in an open channel flow, and to characterize the effect of buoyancy on the turbulent structures and the momentum and heat transfers in a thermally stratified flow in stable conditions. Data were taken with laser Doppler anemometry. Time-averaged velocity and temperature profiles were calculated, as were distributions of the Reynolds stresses, turbulent heat fluxes, and the intensities of the streamwise and vertical velocity fluctuations. The Reynolds stresses were determined similar to those in pipe flows. Buoyancy introduced an increasingly negative contribution to the total turbulent momentum flux from the inward interaction motion, although the ejection motion was the most influential parameter in both stable and near-isothermal flows. Good correlations were found for the turbulent momentum and heat fluxes, the intensities of the streamwise and vertical velocity fluctuations, and the temperature fluctuations with the local Richardson number.