Three-Dimensional MHD Casson Fluid Flow with Hall Current and Thermal Radiation: Coupled Heat and Mass Transfer over a Vertically Stretched Surface in a Chemically Reactive Medium

This work examines a three-dimensional magnetohydrodynamic (MHD) Casson fluid flow over a linearly stretched vertical surface under the combined effects of Hall current, thermal radiation, chemical reaction, buoyancy, and Ohmic dissipation. The governing boundary layer equations are reduced to a system of nonlinear ordinary differential equations using similarity transformations and solved numerically with the aid of the Runge–Kutta–Fehlberg method in Maple. Particular emphasis is placed on Hall current–induced cross-flow, which generates a secondary velocity component and alters shear stress characteristics. The results indicate that increasing the magnetic and Hall parameters enhances both streamwise and cross-flow skin-friction coefficients, while reducing heat and mass transfer rates. Radiation thickens the thermal boundary layer and suppresses heat transfer, whereas Casson parameter increases the fluid resistance and weakens the thermal and solutal transport. Chemical reaction significantly enhances the mass transfer due to steeper concentration gradients, with negligible impact on heat transfer. The study provides a unified three-dimensional analysis that captures the coupled influence of Hall-induced cross-flow, radiation, and chemical reaction on momentum, heat, and mass transport. The findings offer greater physical insights into multi-physics interactions relevant to engineering systems such as polymer processing, metallurgical cooling, and biomedical flows.