HEAT-FLUX AT SECONDARY BIFURCATION IN RAYLEIGH-BENARD CONVECTION WITH AIR IN A RECTANGULAR CONTAINER

The one-dimensional Ginzburg-Landau equation is applied to describe the initial growth rate of heat flux in Rayleigh-Benard convection with air in rectangular containers of moderate size. The basic features of low Rayleigh number behavior are discussed, including the relevant hydrodynamic instability mechanisms. We show here that the discrete changes in the wavenumber of convection rolls, observed and reported previously for convection in moderate size containers, are accompanied by discrete changes in the slope of the heat transfer curve, and that this behavior at secondary bifurcation is a consequence of the horizontal extent of the container.