Document Type : Full Length Research Article
Authors
1
Sultan Moulay Slimane University, Polydisciplinary Faculty, Team of research in renewable energies and technological innovation, Laboratory of research in physics and science for engineer, Béni-Mellal, Morocco
2
Faculty of Sciences and Technologies, Laboratory of Industrial Engineering and Surface Engineering, Sultan Moulay Slimane University, B.P. 523, Beni-Mellal 23000, Morocco
3
Sultan Moulay Slimane University, Polydisciplinary Faculty, Team of modern and applied physics, Laboratory of search in physics and science for engineer, Béni-Mellal, Morocco.
4
Sultan Moulay Slimane University, Polydisciplinary Faculty, Team of research in renewable energies and technological innovation, Laboratory of research in physics and science for engineer, Béni-Mellal, Morocco.
Abstract
This study numerically compares three thermo-dependent viscosity models—the Reynolds, Vogel-Tammann-Fulcher (VTF), and Williams-Landel-Ferry (WLF) models—in natural double-diffusive convection within a square cavity filled with a non-Newtonian binary fluid. The influence of the thermo-dependence parameter m and the behavior index n is assessed under fixed thermal and concentration conditions on vertical walls and adiabatic, impermeable horizontal walls. The dimensionless conservation equations for momentum, heat, and mass are solved using the finite volume method with a power-law scheme. Variations in m and n are examined for each viscosity model to quantify their effects on flow structures, Nusselt, and Sherwood numbers. The results demonstrate the importance of accounting for both thermo-dependent viscosity and rheological effects, providing validated guidance on model selection for accurate prediction of coupled heat and mass transfer in thermally sensitive, non-Newtonian systems. An increase in m intensifies flow circulation and enhances heat and mass transfer, while decreasing n (more pseudoplastic behavior) further improves transport performance. The VTF and WLF models produce results in close agreement with the Reynolds model, with only minor deviations for specific parameter combinations. Quantitatively, increasing m from 1 to 3 strengthens convective circulation by 45%, and enhances heat and mass transfer by 50% and 60%, respectively. Likewise, decreasing the behavior index to n = 0.6 produces 65% growth in flow strength, 40% in heat transfer, and 50% in solutal transport, highlighting the strong coupling between rheology and buoyancy dynamics.
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