TRANSIENT MAGNETOHYDRODYNAMIC FILM FLOW, HEAT TRANSFER AND ENTROPY GENERATION FROM A SPINNING DISK SYSTEM: DTM-PADÉ SEMI-NUMERICAL SIMULATION

In the present study, heat transfer and entropy generation for transient magnetohydrodynamic (MHD) film flow from a rotating infinite disk have been studied. Using similarity transformations, the unsteady Navier-Stokes equations and energy equation are reduced to a system of coupled, multi-degree, nonlinear ordinary differential equations, which are then solved using a combination of the differential transform method with Padé approximants (DTM-Páde simulation). Excellent correlation is also achieved with numerical quadrature. Furthermore the equations of entropy generation are also presented and solved using DTM-Páde simulation. The influence of magnetic parameter (M), Prandtl number (Pr), unsteadiness parameter (), film thickness parameter () on radial and tangential velocity components, and also temperature, pressure, entropy generation number and Bejan number are studied graphically. Furthermore 2-dimensional streamline and vector plots are presented at selected time steps. Bejan number is observed to be reduced close to the disk surface with the opposite effect at further distance from the disk, with an increase in magnetic parameter. The contrary behaviour is computed for entropy generation number with increasing magnetic parameter. Pressure is found to be significantly reduced with magnetic parameter whereas temperature is considerably enhanced, the latter due to the conversion of supplementary work (expended in dragging the fluid against the magnetic field) into thermal energy. Radial velocity and skin friction component are strongly decreased with increasing magnetic parameter. The present study has important applications in thermodynamic optimization of magnetohydrodynamic rotating disk generators, magnetic materials processing and fabrication of liquid metals.

Transient; MHD; DTM-Páde; Rotating disk; Entropy generation; Bejan number; Von Karman swirl; pressure; Electro-magnetic materials processing.