NUMERICAL STUDY OF THE BOUSSINESQS EQUATI ONS OF THE UNSTEADY LAMINARNATURAL-CONVECTION INSIDE A VERTICAL AXISYMMETRICAL ELLIPSOID FILLED WITH AIR

The authors observed the transition of the system between two states o f equilibrium by solving, with the help of a finite-difference method, the thermal unsteady laminar natural convection equations in an axisy mmetric ellipsoid with vertical great axis filled with air. They showe d that the number of convective cells varies from one to one by passin g through a maximal value that depends on the Grashof number and on th e aspect ratio. Simultaneously, the instantaneous average Nusselt numb er decreases in a monotonous way with time when the flow is unicellula r and increases or decreases abruptly with each appearance or disappea rance of cells.