EFFECT OF STABLE DENSITY STRATIFICATION SECONDARY FLOW IN COMPOUND CHANNEL

Abstract

Flow measurements were undertaken in a compound channel to investigate the effect of stratification on secondary flow in two-layer density-stratified flow. Secondary flow and salinity were measured using a laser induced fluorescence technique together with a laser Doppler anemometer system. Flow visualisation was also carried out using a digital video camera to demonstrate the effect of stratification on flow. The measured data shows that the size of typical twin vortices in the compound channel reduces as the degree of stratification increases. Two generation mechanisms of secondary flow were recognized on the floodplain, namely non-isotropic turbulence driven secondary flow and density driven secondary flow. The production of turbulent kinetic energy due to buoyancy was found to be not significant in most region but is significant in the water surface region