Cascade-like and cyclic heat transfer characteristics affected by enclosure aspect ratios for low Prandtl numbers

For low Prandtl-number fluids, heat-transfer characteristics under the influence of the aspect ratio for buoyancy-driven recirculating flows in rectangular enclosures (with left hot, right cold, top/bottom insulated walls) behave differently from those for high-Pr fluids. At Ra=106 and Pr=0.025, as the enclosure widens, time-averaged and hot-wall-spatially-averaged heat transfer first decreases, then cascades downward. Locally, heat transfer peaks at a few locations, and these peaks travel cyclically as time elapses. For completeness, the present study serves as a sequel of a previous high-Pr investigation.