Investigation of nanofluid through converging-diverging stretching Riga surface

Abstract

This study investigates the magnetohydrodynamic (MHD) flow, heat, and mass transfer of a water-based ferro-nanofluid (Fe₃O₄) through a channel bounded by converging-diverging stretching Riga plates. The Riga plate configuration generates a wall-parallel Lorentz force, offering a unique mechanism for active flow control with reduced energy dissipation compared to traditional MHD systems. The Buongiorno model is employed to incorporate the effects of thermophoresis and Brownian motion, alongside viscous dissipation and thermal radiation. The governing partial differential equations are transformed into a system of nonlinear ordinary differential equations using similarity transformations and solved numerically via the Keller-Box method. The analysis reveals how key dimensionless parameters such as the wall slope (m), modified Hartmann number (Q), Reynolds number (Re), Eckert number (Ec), Brownian motion (Nb), and thermophoresis (Nt) parameters govern the velocity, temperature, and nanoparticle concentration profiles. The study highlights significant implications for enhancing thermal performance and particle distribution control in advanced engineering systems. Key engineering quantities like the skin friction coefficient, Nusselt number, and Sherwood number are also analyzed. Results indicate that the electromagnetic forcing from the Riga plate can enhance flow velocity contrary to traditional MHD damping. Temperature rises with increasing Ec, Nb, and Nt but decreases with stronger radiation (Rd). The concentration boundary layer thins with higher Nb and Nt. The novelty of this work lies in the comprehensive analysis of a ferro-nanofluid within an electromagnetically actuated convergent-divergent geometry, a configuration scarcely addressed in prior literature. Key applications include the design of efficient electronic cooling systems, targeted drug delivery platforms, microfluidic pumps, and advanced materials processing equipment where precise thermal and species management is critical.