Thermal Relaxation and Induced Magnetic Field Influence on Power-Law Fluid Motion over Rotating Porous Surface: An entropy approach

This numerical study addresses the flow and heat transfer characteristics of a power-law non-Newtonian fluid across a rotating disk with the presence of porous media, induced magnetic fields, non-linear thermal radiation and Cattaneo–Christov heat flux model. The coupled non-linear governing equations are solved numerically using the fourth order Runge-Kutta shooting method. The effect of significant parameters on the radial, azimuthal and axial velocities, temperature profiles, induced magnetic field components, entropy production, Bejan number, skin friction and Nusselt number is studied. The results reveal that the non-Newtonian fluid index has a considerable effect on the velocity distribution. The effective viscosity of shear-thinning fluids is less, and hence the axial velocity is higher. The magnetic damping and porous resistance decrease the radial and azimuthal velocities. Increasing the disk rotation increases the azimuthal motion and magnetic induction; on the other hand, larger magnetic fields suppress the fluid flow by Lorentz forces. The Eckert number, thermal radiation and thermal relaxation parameter play a significant role in thermal behavior changing temperature profiles and entropy formation in the boundary layer. The combined impacts of rotation, porosity, magnetic field and viscous dissipation considerably affect the surface transport parameters such as skin friction and heat transmission. Induced magnetic field components decrease with a high reciprocal magnetic Prandtl number, and the Bejan number falls with a high Brinkman number but increases with heat radiation. These results provide a full understanding of the interaction of rheological, magnetic and thermal components in rotating disk systems, yielding insights that may help to build and improve thermal-fluid and magnetohydrodynamic devices.