Transient rotating flow over a moving surface with a magnetic field

The transient flow and heat transfer on a moving surface in a rotating fluid in the presence of a magnetic field have been investigated. The unsteadiness in the flow field has been introduced by the sudden change in the surface velocity or the fluid angular velocity. The parabolic partial differential equations governing the unsteady flow and heat transfer have been solved by using an implicit finite-difference scheme in combination with the quasilinearization technique. The computations have been carried out from the initial steady state to the final steady state. The effects of the sudden change in the surface velocity on the flow and heat transfer are found to be more significant than those of the impulsive change in the angular velocity of the fluid. When the surface velocity is suddenly reduced, the surface shear stress is found to vanish in a small time interval after the start of the impulsive motion, but it does not imply flow separation. The surface shear stress for the primary flow increases with the magnetic field and the fluid angular velocity, but the surface heat transfer decreases. The surface shear stress for the secondary flow increases with the angular velocity of the fluid, but decreases with increasing magnetic field