Transient Electro-Magneto Hydrodynamic (EMHD) Control of Hybrid Nanofluid Flow over 2D Riga Plate: Entropy Generation and Stability Analysis

Abstract

This study investigates the transient Electro-Magneto Hydrodynamic (EMHD) control of hybrid nanofluid flow over a two-dimensional Riga plate, focusing on entropy generation minimization and hydrodynamic stability analysis. The Riga plate, composed of alternating electrodes and permanent magnets, generates an exponentially decaying Lorentz force, which enhances boundary layer flow control. While previous research has primarily examined steady-state EMHD flows, this work addresses the transient behavior critical for real-world dynamic systems. The governing equations for momentum, energy, and nanoparticle concentration are derived and solved analytically using perturbation methods for steady-state conditions and Laplace transforms for transient solutions. A finite difference numerical scheme is employed to validate the results numerically, ensuring accuracy through convergence criteria. Key dimensionless parameters, including the modified Hartmann number (Z), Richardson number (λ), and suction parameter (s), are analyzed to assess their impact on flow, heat transfer, and stability. Results demonstrate that EMHD effects significantly enhance velocity profiles, while Prandtl number (Pr) variations influence thermal boundary layers. Entropy generation analysis reveals that thermal irreversibility dominates near the plate, whereas viscous and Joule heating effects prevail farther away. Stability studies confirm that strong suction (s) stabilizes the flow, suppressing perturbations. Additionally, Nusselt and Sherwood numbers increase with higher Z and s, indicating improved heat and mass transfer efficiency. This study provides critical insights into optimizing EMHD-based thermal systems by minimizing entropy generation and ensuring hydrodynamic stability. The findings have significant implications for microfluidics, nuclear cooling, and aerospace propulsion, where precise thermal management is essential.