ISSN Online: 2377-424X
ISBN Print: 0-89116-559-2
International Heat Transfer Conference 8
TRANSITION TO UNSTEADY NATURAL CONVECTION OF AIR IN VERTICAL DIFFERENTIALLY HEATED CAVITIES: INFLUENCE OF THERMAL BOUNDARY CONDITIONS ON THE HORIZONTAL MALLS
Resumo
We investigate the influence of thermal boundary conditions imposed on the horizontal walls of a differentially heated cavity on the triggering of unsteady solutions to the 2-D Boussinesq equations. We determine the critical values of the Rayleigh number at which unsteady convection appears in a cavity with perfectly conducting horizontal boundaries of aspect ratio in the range 1 to 10 and compare with those previously obtained in the case of adiabatic horizontal walls. It is shown that for small aspect ratio cavities the new boundary condition can have a dramatic effect on the value of the critical Rayleigh number since the basic mechanism leading to unsteady motion is then associated to a thermal instability of the flow. We furthermore show that this bifurcation possesses all the characteristic features of a Hopf bifurcation and this can be used to determine with accuracy the critical Rayleigh number.