Thermal lattice Boltzmann approach-based numerical study of nanofluid magnetohydrodynamic forced convection in a back-facing stepped porous channel

Abstract

Unsteady laminar magnetohydrodynamic forced convection and entropy generation inside a backward-facing step (BFS) porous channel with Cu-H₂O nanofluid under a tilted magnetic field is numerically handled using a thermal lattice Boltzmann method (TLBM) with two distribution functions. The Darcy-Brinkman-Forchheimer (DBF) equations filled up with the energy equation (with local thermal equilibrium assumption) have been drawn up as the governing equations model. Their numerical solutions unveiled streamlines, Nusselt number, pumping power, performance index and entropy generation, and impacts of influential parameters (Hartmann number (Ha = 0; 10; 20; 100, 200), Darcy number (Da = 10⁻³; 10⁻²; 10⁻¹), magnetic tilt angle (γ = 0, π∕4, π∕2), nanoparticles’ volume fraction (φ = 1 − 4%), medium porosity (ε = 0.6, 0.7, 0.8). The irreversibility analysis is also addressed to highlight the flow behavior. Regarding the validation of the modeling approach deemed, a consensus has been achieved with results available in the literature. Computations revealed that the volume fraction provides a fair performance rating with moderate pumping power. Likewise, the average Nusselt number, the average entropy generation, the pumping power and the performance index have a direct relationship with the Hartmann number, the nanoparticles volume fraction and the magnetic field tilt. Moreover, it can be stated the Cu-H₂O nanofluid that seems worthwhile in terms of heat transfer efficiency compared to other examined nanofluids. Entropy generation due to the magnetic field was identified as the main source of irreversibility processes in all cases. Based on the outcomes, it is thought that applying a magnetic field can help minimize entropy generation in practical applications.

Keywords:

• Backward-facing step
• Magnetohydrodynamic flow
• Nanofluid
• Porous medium
• Thermal lattice Boltzmann method

Disclosure statement

No potential conflict of interest was reported by the author(s).

Declaration of non-publication

The authors stated that this manuscript has never been published anywhere else (even partially) nor simultaneously submitted for publication elsewhere.