Magnetohydrodynamic Analysis of Unsteady Williamson Nanofluid Flow over a Permeable Inclined Stretching Sheet with Cattaneo-Christov Double-Diffusion Effects

This paper investigates the unsteady magnetohydrodynamic (MHD) flow of a Williamson nanofluid across a permeable stretching inclined sheet. The work is intended to fill the information gap regarding the simultaneous effects of unsteadiness, inclined sheet/magnetic field geometry, cross-diffusion, Joule heating, thermal radiation, chemical reaction, heat source/sink and suction/injection under non-Fourier and non-Fick transport models in a porous medium. The governing PDEs undergo similarity transformations to produce a system of coupled nonlinear ODEs. The resulting boundary value problem is addressed semi-analytically using the optimal homotopy analysis method (OHAM). The skin friction coefficient, Nusselt number, Sherwood number, velocity, temperature and concentration profiles are analyzed numerically and graphically in relation to significant dimensionless parameters. Results show that fluid velocity is significantly suppressed by the magnetic field and unsteadiness parameters because of the resistive Lorentz force. The skin-friction coefficient increases by about 29.6% when the magnetic parameter is increased from 0.3 to 1.0. When it comes to thermal transport, the Nusselt number drops by around 44% as the Brownian motion parameter increases from 0.1 to 0.7, but geometric optimization performs well; the heat transfer rate is increased by about 26% when the sheet's inclination angle is reduced from π/6 to π/12. Additionally, when the thermal radiation parameter is increased from 0.1 to 0.7, the mass transfer rate shows a significant rise of nearly 68%. This study reveals that the Cattaneo-Christov model offers a more realistic representation of transport mechanisms in viscoelastic nanofluids than classical Fourier and Fick laws, providing important insights for improving conductive nanofluid processing and electromagnetic casting.