TRANSIENT NATURAL-CONVECTION IN A CAVITY WITH WALLS OF FINITE THICKNESS

Numerical studies are made of transient natural convection in a square cavity. The top and bottom end walls are thermally insulated The vert ical solid side walls are affinite thickness and affinite thermal cond uctivity. Flow is driven, from the motionless isothermal initial state , by impulsively increasing (decreasing) the temperature at the outer surface of one (the other) vertical side wad. Numerical solutions are sought to the time-dependent Navier-Stokes equations for the fluid and the solid regions. The ratios of thermophysical properties between so lid and fluid are the significant parameters. As the thermal capacity ratio increases, the development of flow in the fluid region is retard ed. The conductive and convective timescales are estimated. The effect s of the thermal conductivity ratio and of the thickness of the side w ad are delineated. The effect of the system Rayleigh number on transie nt heat transport is analyzed. The applicability of the approximate on e-dimensional thermal conductance model to the transient features is s crutinized.