Approche numérique de la convection naturelle thermo-solutale dans une cavité rectangulaire poreuse saturée de fluide et à orientation variable.

Abstract

In this thesis, heat and mass transfers by natural convection in porous media have been studied numerically. The horizontal walls are subjected to constant temperatures and impermeable to solute transport in the first case and at constant temperatures and concentrations in the second case, while the vertical walls are thermally insulated and are subjected to constant concentrations in the first case, and are considered adiabatic in the second case. The phenomenon of thermo-solutal convection is governed by the conservation equations of mass, momentum, energy and concentration. The porous media are modeled according to the general model of Darcy and Darcy-Brinkman-Forchheimer respectively. The convective flow is governed by different control parameters, namely the angle of inclination (α ), the Rayleigh number (Ra), the ratio of the forces of volume (N), the number of Prandtl (Pr),the number of Lewis (Le), the Darcy number (Da) the form factor (A) and the porosity ε of the porous matrix. The finite volume method was used to solve the basic equations in porous media. Regarding the validation of the calculation code, the agreement obtained between our results and those available in the literature proved to be excellent. The influence of physical and geometrical parameters is examined. In the first case, five solutions characterized by multicellular and single-cell clockwise / counterclockwise, natural / antinatural flows were obtained in the case of the intermediate regime with the variation of the inclination, the structure of the flow intensifies and the transfers of Heat and average mass increase as │N│ increases. In the second case, two solutions characterized by multicellular (-90° ≤α≤0°) and single-cell trigonometric (0°<α≤90°) flows were obtained, the intensity of the flow decreases with increasing of α in both directions, while there was an increase in heat transfer and mass up to inclination 45° and 60° respectively. The structure of the flow intensifies and the average heat and mass transfers increase with the increase of N, Ra and A while the contrary has been found with Le except the mass transfer which keeps its increase.