Natural Convection Heat Transfer in Vertical Fluid Layers of High Aspect Ratio

A two-dimensional numerical analysis is made on the effect of aspect ratio on flow and heat transfer characteristics of natural convection in a slender fluid layer enclosed between two vertical plates of different temperatures. It is shown that the boundary layer instability induces the hook-shaped flows and that its growth disrupts the large-scale circulatory flow into cellular flows of smaller scales, which in part include the renewed boundary layers. Then it is suggested that there exists a transition region where the average heat transfer coefficient increases with the increase of the height of a vertical fluid layer, as is seen in the transition region from laminar to turbulent natural convection along a single vertical plate. Discussion is also made on the nature of instability to yield cellular flows of smaller scales.