Abstract:
If natural convection in a side heated cavity is initiated by the impulsive heating of one of the side walls, a thermal plume rises up the heated wall and forms a thermal intrusion flowing across the top of the cavity. Experimental data has revealed longitudinal structures in the intrusion. These are thought to be Rayleigh- Benard convection rolls aligned with the direction of the intrusion flow, formed by the unstable stratification of the intrusion flow. A three-dimensional CFD simulation of the flow has revealed similar structures to those in the experiment, but with shorter rolls that do not span the full width of the cavity. However, by modelling the lid of the cavity as a conducting solid, the instability of the intrusion is increased and the simulated roll structures occupy the length of the cavity. The roll formation process is therefore shown to be dependent on the thermal boundary condition at the top wall.