MHD Casson Nanofluid Flow over a Stretching Rotating Disk with Heat Source and Spatially Varying Magnetic Field

This paper investigates the steady magnetohydrodynamic (MHD) flow and heat transfer of a Casson nanofluid over a stretching, rotating disk in the presence of a spatially varying magnetic field and internal heat source. The model incorporates the Buongiorno nanofluid framework, which accounts for nanoparticle motion due to Brownian diffusion and thermophoresis, and includes velocity, thermal, and concentration slip conditions at the disk surface. Unlike traditional studies assuming a uniform magnetic field, the present work considers a magnetic field that decays exponentially away from the disk surface, providing a more realistic representation of applied magnetic fields in practical systems such as electromagnetic processing and rotating machinery. Additionally, the influence of an internal heat generation term is included in the energy equation to simulate thermal sources within the fluid. By applying similarity transformations, the governing nonlinear partial differential equations are reduced to a system of coupled ordinary differential equations. These equations are solved numerically using the bvp4c function in the Matlab computer language. The effects of various physical parameters such as magnetic field strength and gradient, slip coefficients, Casson fluid index, and heat source intensity are systematically explored. The results reveal that increasing the magnetic field strength or the heat source significantly enhances the thermal boundary layer, while velocity profiles are suppressed near the disk due to magnetic damping. The presence of multiple slips and the Casson fluid model further alter the flow and thermal behavior, making the system tunable for thermal management applications.