Unsteady Hydromagnetic Natural Convection Flow Past a Vertical Plate with Time-Dependent Free Stream through a Porous Medium in the Presence of Hall Current, Rotation, and Heat Absorption

摘要

An investigation of the unsteady hydromagnetic natural convection flow of a viscous, incompressible, electrically conducting, and heat-absorbing fluid past an infinite vertical plate through a fluid-saturated porous medium with a time-dependent free stream in a rotating system with Hall effects is carried out. An exact solution of the governing equations is obtained using the Laplace transform technique. Two cases of interest are discussed, viz, (1) the impulsive movement of the free stream and (2) the accelerated movement of the free stream. Expressions for the shear stresses at the plate as a result of the primary and secondary flows and the rate of heat transfer at the plate are derived. Asymptotic behavior of the solution is analyzed for both small and large values of time t to highlight the transient approach to the steady-state flow and to gain some physical insight into the flow pattern. A reverse flow exists in the secondary flow direction because of the presence of the thermal buoyancy force and the time-dependent movement of the free stream, which has not yet been reported in the literature. (C) 2016 American Society of Civil Engineers.