FLOW AND HEAT TRANSFER DYNAMICS IN A CUBICAL ENCLOSURE WITH HOT AND COLD SECTORS ON THE SAME VERTICAL WALL
Transient natural convection in an air filled cubical enclosure with hot and cold sectors of equal width placed side by side on a vertical wall and all other walls insulated is numerically studied. After imposing the temperature difference, convection starts at the thermal boundary layers at times which scale as in the differentially heated cavity (DHC). The mid-plane Nusselt number, Numid, increases very rapidly. At Ra > 5×105 oscillations appear just after the initial growth in Numid. The Nusselt number evolution in time is closely similar to that observed in the DHC, and suggests an internal wave mechanism. For high Rayleigh numbers, the oscillations are of higher amplitude and frequency as Ra grows. At all Rayleigh numbers the amplitude of oscillations decreases in time, giving way to a steady regime. Details of the flow and temperature field are used to explain this behavior. The hot wall Nusselt number in steady state scales with Ra with a 0.245 exponent.