This paper investigates the combined effects of magnetohydrodynamics (MHD), double-diffusive convection, radiative heat transfer, and viscous dissipation in a porous wavy cavity. The Darcy–Forchheimer model and Rosseland approximation are employed; the dimensionless governing equations are solved using the Galerkin finite element method with triangular elements. Key quantitative findings include: the Hartmann number suppresses convective transport, reducing average Nusselt and Sherwood numbers by up to 59% at $Ha=50$; the radiation parameter $N_1$ enhances heat transfer by 169% as $N_1$ varies from 0.01 to 10; viscous dissipation paradoxically reduces wall heat flux by 33% despite increasi... More >