An experimental study of unsteady natural convection in a reservoir model cooled from the water surface

The general characteristics of unsteady natural convection flow in a reservoir model cooled from the water surface are presented in this paper. Flow visualization was carried out using thermo-chromic liquid crystals, and quantitative temperature measurements were conducted using a PIT (particle image thermometry) technique. The experimental photographs clearly show different stages of the flow development including the growth of a thermal boundary layer below the water surface, the onset of convective instabilities, and further flow development. The present results indicate that the convective motions in reservoirs induced by night-time cooling have a significant impact on water quality and transport of nutrients and pollutants.