Convegni ATI - Accesso riservato soci CTI

Autore: D.R. Rousse

Collana: CA - 49 - Perugia 1994

Note:
This paper involves a study of natural convection in a vertical porous medium. The porous layer has an adiabatic outer boundary and its inner boundary is subjected to a thermally stratified inner boundary. For conditions investigated here, no symmetry can be expected for the flow and temperature fields with respect to the vertical diameter, and the whole circular region must be considered. The governing equations were solved by perturbation and numerical approaches. Results indicate that the circulating flow around the annulus reaches its maximum strength when the stratification is nearly horizontal. The flow field for specific orientations of the thermal stratification is characterized by the presence of two convective cells near the inner and outer boundaries, giving rise to flow reversal on these surfaces. When the maximum temperature on the inner boundary is at the bottom of the cavity, the convective motion becomes potentially unstable; for a Rayleigh number below 12, there exists a steadystate solution symmetrical with respect to both vertical and horizontal axes; for a Rayleigh number between 12 and 150, there exists centrosymmetry only, and the net circulation around the cavity is no longer zero; for a Rayleigh number above 150, an unsteady periodic situation develops with the circulating flow alterning its direction around the annulus.