Analysis of flows driven by a torsionally–oscillatory lid in a fluid-saturated porous enclosure with thermal stable stratification

Abstract

The convection flow caused by a torsionally–oscillatory lid with thermal stable stratification in an enclosure filled with porous medium is studied in this paper. The governing continuity, momentum and energy transport equations are solved by a semi-implicit projection finite element method. The Grashof number and Reynolds number for ranges 10 4⩽Gr⩽10 6, 10 2⩽Re⩽10 3 are involved in this research for Darcy number 10 −2, 10 −4, 10 −6 and porosity 0.4, 0.6. The results present that the permeability of porous medium deeply dominates the flow field and diminishes the flow strength as the permeability is decreased. The increase in the value of Gr/(Re 2·Da) retards the stable stratification from the top surface to extend into the interior domain. The influence of oscillatory frequency is so serious in heat flux variation at some particular frequency corresponding to the resonant frequency. There is an evident resonant frequency at Da=10 −2 condition; however, this phenomenon is not clear for Da⩽10 −4 at different oscillatory frequencies.