Investigation of free convection flow around near horizontal surfaces using particle image velocimetry

In this work, an analysis of free convection fluid flow characteristics around a flat heated surface, slightly inclined to the horizontal, has been carried out with the help of particle image velocimetry technique. Experiments were performed on a plate immersed in water and subjected to a uniform heat flux. The influence of different inclinations of the plate and heat fluxes on the flow characteristics has been analyzed. Based on the flow characteristics, different regimes-attached, transition, and buoyant plume regime-have been identified. It is observed that the onset of transition increases with the inclination angle and decreases with the heat flux. On the other hand, the length of the transition regime increases with an increase in the inclination angle and heat flux. The plume width or plume regime is found to first decrease due to necking and then increase in the vertical direction due to horizontal diffusion. Also, an increase in heat flux and inclination angle causes an increase in plume width at a particular height from the plate. It is observed that the inner velocity boundary layer thickness decreases in the laminar regime and increases in the transition regime along the length of the plate.