Natural convection of a high Prandtl number fluid in a cavity

Transient natural convection in a square cavity heated with a time-dependent heat flux on one vertical wall and cooled by maintaining the opposite wall at a constant temperature was studied experimentally and numerically. The working fluid was silicon oil (Dow Corning fluid 20–200) with a Prandtl number of 230. All experiments were carried out in a cubic cavity of 0.13 m in each side. The heating rate used was 460 W/m2, which corresponds to a Rayleigh number of 4×109. Experimental data included temperature records at particular points and velocity measurements obtained from video images of tracers. The dynamics of the transition to the steady state is characterized by a vortex structure that forms near the heated wall. This structure is generated by shear at the heated wall boundary layer. The results were compared with a numerical simulation and qualitative agreement was obtained.