STEADY AND TIME DEPENDENT CONVECTION IN A RECTANGULAR BOX.

Steady and time dependent free convection in a vertically bounded horizontal fluid layer heated from below and cooled from above has been investigated. The onset of steadY convection was calculated using linear Boussinesq equations and a Galerkin method. The experiments were done with a vacuum insolated rectangular convection box. A special differential interferometer served to visualize the flow configurations. The density profiles were measured by means of a laser-differential interferometer. The influence of steady linear heat conduction profiles as well as that of time dependent nonlinear ones were studied at different heating rates. The test fluids were silicone oil and gases for demonstrating the influence of the Pr number on the onset of convection as well as on the transition to instationary convection. The measured steady and time dependent heat conduction and convection density profiles have been evaluated and compared with previously published results.