Numerical Study of Natural Solutal Convection in an Isoscele Trapezoidal Cavity

A numerical study of the natural heat and mass transfer in a cavity with a straight isoscele cross-section containing air is made in this paper. The two inclined side walls are kept in natural convection with the surrounding environment. The upper horizontal wall is subjected to a heat flux of constant density, while the lower one is adiabatic. Under the Boussinesq assumption, the thermodynamic conditions are numerically studied using the unsteady convection equations formulated as a secondary variable of vorticity and a stream function, energy and moisture. The system of equations discretised by the implicit finite difference method is solved by the Thomas algorithm. The results show a flow structure, isotherms and isohumidities dependent on the study parameters. Thus, on one hand, an increase in the inclination angle of the walls is accompanied by an increase in the velocity of the fluid. On the other hand, an increase in the aspect ratio or Lewis number leads to a decrease in the fluid’s velocity. The average Nusselt number, which is independent of the Rayleigh number, increases slightly as the inclination angle of the walls decreases. The increase of the Lewis number results in the decrease of the flow velocity components values. It is observed that the maxima values of velocity components were reached for Rayleigh number equal to 7.103.