Résumé:
The present study focused on the two-dimensional numerical study of the effect of
dimensionless parameters on the transition from mixed convection (laminar and turbulent) within a cavity with an aspect ratio A. The right vertical wall is fixed and maintained a hot temperature TC, the left vertical wall is movable, it is directed upwards with a velocity U0 and kept at a cold temperature. The two horizontal walls are assumed to be adiabatic. The objective set through this is the determination of the modified Richardson number (critical Ri) to determine the limits of passage between the regimes: forced-mixed and mixed-natural. The governing equations were discretized by the finite volume method on an offset mesh and the SIMPLE algorithm was used for the processing of the velocity-pressure coupling. A Fortran computational code was used to solve the partial differential equations describing the flows of mixed laminar and turbulent convection. Indeed, this work is made up of two parts: for the first part, we started with the study of the influence of the variation of the Prandtl number (Pr = 0.015, 0.71, 2, 7.1, 50 and 100) in the case of a square cavity (aspect ratio equal to 1). Then a study of the effect of geometry was carried out for different aspect numbers: A= 0.5, 1 and 1.25. In the second part, a parametric study of turbulent mixed convection was performed in a square cavity with air as a fluid and a constant Pr number. The standard k-ε turbulence model was chosen to model the Reynolds stresses. The critical parameters, λ (modified Richardson) and n necessary for the transition
between the different types of convection and which are related to each other by the equation
