SINOPSIS

An exact solution to the unsteady free convection flow of viscous incompressible fluid, in the presence of foreign mass, through porous medium past an impulsively started infinite vertical isothermal plate in a rotating fluid has been derived by the Laplace transform technique. Axial and transverse velocity profiles are shown on graphs and numerical values of skin friction are listed in a table. It is observed that the resistance of the porous medium λ increases as the axial velocity profiles decreases. When air or water is flowing as an infinite medium, the decrease in resistance is greater when λ is large or when the porous medium is more dense. The nondimensional rotational parameter Rc increases when there is a decrease in the axial velocity profiles for all Prandtl numbers, because the Coriolis forces oppose the fluid flow, and hence the motion slows down. When Rc < 1, the Coriolis forces are dominated by inertia forces, hence the product of the nondimensional Rossby number and Reynolds number is large. As Rc < 10⁻³, the flow field becomes unstable and flow is converted to the turbulent flow for all Prandtl numbers (i.e., Pr = 0.71 for air when Ma « 1 and Pr = 7 for water). The flow of water may become unstable at large values of time t. An increase in the Schmidt number Sc leads to a decrease in axial velocity of both air and water. An increase in the diffusion parameter N leads to a rise in axial velocity because the buoyancy flow forces assist the flow and the transverse skin friction increases for both air and water, while the axial skin friction decreases for air and increases for water. As the permeability parameter λ increases, the axial skin friction increases for both air and water. This happens because more resistance is offered to the flow by porous medium than by a medium that is more dense.