Abstract

A unified model for the analysis of two-dimensional Brinkman-Benard/Rayleigh-Benard/ Darcy-Benard convection in cylindrical and rectangular enclosures (CE/RE) saturated by a Newtonian liquid is presented by adopting the local thermal non-equilibrium (LTNE) model for the heat transfer between fluid and solid phases. The actual thermophysical properties of water and porous media are used. The range of permissible values for all the parameters is calculated and used in the analysis. The result of the local thermal equilibrium (LTE) model is obtained as a particular case of the LTNE model through the use of asymptotic analyses. The critical value of the Rayleigh number at which the entropy generates in the system is reported in the study. The analytical expression for the number of Benard cells formed in the system at the onset of convection as a function of the aspect ratio, So, and parameters appearing in the problem is obtained. For a given value of So it was found that in comparison with the case of LTE, more number of cells manifest in the case of LTNE. Likewise, smaller cells form in the DBC problem when compared with the corresponding problem of BBC. In the case of RBC, fewer cells form when compared to that in the case of BBC and DBC. The above findings are true in both CE and RE. In other words, the presence of a porous medium results in the production of less entropy in the system, or a more significant number of cells represents the case of less entropy production in the system. For small and finite So, the appearance of the first cell differs in the CE and RE problems.