Effects of Hall Current and Rotation on Unsteady MHD Natural Convection Flow Past a Vertical Flat Plate with Ramped Wall Temperature and Heat Absorption

摘要

In the present study, the effects of Hall current and rotation on an unsteady Magneto-Hydrodynamic (MHD) free convection heat and mass transfer of an electrically conducting, viscous, incompressible and heat absorbing fluid flow past a vertical infinite flat plate embedded in non-Darcy porous medium is investigated. The flow is induced by a general time-dependent movement of the vertical plate, and the cases of ramped temperature and isothermal plates are studied. Exact solution of the governing time-dependent boundary layer equations for the momentum, energy and concentration were obtained in closed form by using Laplace Transform technique. Expressions for skin friction due to primary and secondary flows and Nusselt number are derived for both ramped temperature and isothermal plates. Expression for Sherwood number is also derived. Some applications of practical interest for different types of plate motions viz. plate moving with uniform velocity, plate moving with uniform acceleration and plate moving with periodic acceleration are discussed. The numerical values of fluid velocity, fluid temperature and species concentration are displayed graphically whereas the numerical values of skin friction, the Nusselt number and the Sherwood number are presented in tabular form for various values of pertinent flow parameters for both ramped temperature and isothermal plates. It is found that the primary fluid velocity decreases with increasing values of Hall current parameter whereas it has reverse effect on secondary fluid velocity, in all types of motion of plate discussed. The Primary fluid velocity decreases with the increasing value of rotation parameter whereas it has reverse effect on secondary fluid velocity. Hall current tends to reduce the primary skin friction for both ramped temperature and isothermal plate whereas it has reverse effect on secondary skin friction.