DOI: 10.1615/TSFP4
OPEN CHANNEL FLOW STRATIFIED BY A SURFACE HEAT FLUX
RESUMO
Large Eddy Simulation (LES) has been used to study flow driven by a constant pressure gradient in an open channel with stable stratification imposed by a constant heat flux at the free surface and an adiabatic bottom wall. Under these conditions a turbulent mixed layer develops underneath a strongly stratified pycnocline. Turbulent properties in the pycnocline and at the free surface are examined as a function of the imposed stratification. It is found that increasing the friction Richardson number, a measure of the relative importance of stratification with respect to boundary layer turbulence, leads to a stronger, thicker pycnocline which eventually limits the impact of wall-generated turbulence on the free surface. Increasing stratification also leads to an increase in the pressure-driven mean streamwise velocity near the free surface and a corresponding increase in mean shear, a decrease in the turbulent Reynolds stress, and a substantial decrease in the eddy viscosity. PDF's and visualizations are employed to understand how stratification affects the interaction of bottom turbulence with the free surface.