dc.description.sponsorship | Two-dimensional flow of an incompressible viscous fluid past an infinite, porous plate in a porous medium is considered for the unsteady flow with the following conditions: 1) the suction velocity normal to the plate is constant, 2) the free stream velocity ascillates in time about a constant mean. (3) the temperature of the plate is kept constant, (4) the difference between the temperature of the plate and the free stream is considerably large causing convection currents.Approximate solutions for the coupled non-linear equations are obtained for velocity and temperature. Expression for the mean velocity, mean temperature and the mean skin friction are derived. The effects of the Grashof number G, the Prandil number P, the Eckert number E, and the Darcy number d, on the mean motion of air and water are studied. It is found that the mean velocity, for air, increases due to more cooling (G>0) of the plate by the free convention currents, for any value of d, when E is constant. In the presence of heated (g<0) plate, the mean velocity is negative for d=o near the boundary layer and as a d increases the mean velocity gradually decreases in magnitude and becomes positive with further increase in d. heating and cooling have separate effects on the mean velocity for fluids for any value ofd with large Pradil number. In the case of heating the plate, the mean velocity increases whereas in the case of cooling of the plate, the mean velocity decreases with increasing Pradil number. | en_US |