NUMERICAL PREDICTION OF 3D THERMOSOLUTAL NATURAL CONVECTION AND ENTROPY GENERATION PHENOMENA WITHIN A TILTED PARALLELEPIPEDIC CAVITY WITH VARIOUS ASPECT RATIOS

摘要

Three-dimensional (3D) thermosolutal natural convection and entropy generation within an inclined enclosure is investigated in the current study. A numerical method based on the finite volume method and a full multigrid technique is implemented to solve the governing equations. Effects of various parameters, namely, the aspect ratio (A_z), buoyancy ratio (N) and inclination angle (γ) on the flow patterns and entropy generation are predicted and discussed. The numerical outcome of the present study shows that, the thermal and solutal isosurfaces exhibit a central stratification that significantly strengthens as the aspect ratio is augmented. It is also found that decreasing the aspect ratio value A_z leads to weakening the total entropy generation and reducing the 3D effects exhibited within the cavity. Moreover, the distribution of total entropy generation is found to decrease by further enhancing the buoyancy ratio value for all A_z investigated. Especial attention is attributed to analyze the periodic flow pattern that appears for Ra = 10~4, A_z = 2, and the inclination angle γ = 75 deg. In terms of irreversibility criterion at the oscillatory regime, total entropy generation (S_(tot)) and Bejan number (Be) are seen to oscillate with the same frequency but in opposing phases and with different amplitudes. Furthermore, the heat and mass transfer rates at the equilibrium state present a maximum and a minimum at the specific inclination values γ = 30 deg and γ = 75 deg. A comparison of 2D and 3D models at normal situation γ = 0 deg is conducted when N varied in the transition range -2 ≤ N ≤ -0.6 demonstrating that the 2D assumption can be adopted for the 3D flows when -0.5 ≤ N ≤ 0.