Shear flow over a rotating porous plate subjected to suction or blowing

An analysis is made of the steady shear flow of an incompressible viscous fluid past a uniformly rotating infinite porous flat plate subjected to uniform suction or blowing. Inside the boundary layer, the pressure gradient dominates the momentum transfer of the outer shear flow. Therefore, the shear-induced component of the free-stream shear flow inside the boundary layer is less than its inviscid value. This results in flow reversal in the absence of suction. It is observed that the zone of reverse flow becomes smaller and smaller with an increase in suction, and when the suction parameter exceeds a certain critical value, no reverse flow occurs at all. The axial velocity toward the plate increases with an increase in suction but decreases with an increase in blowing. It turns out that a torque is exerted in a direction opposite to the direction of rotation of the plate, and the magnitude of the torque is an increasing function of suction. Further, this torque is not influenced by the shear in the external flow. The drag on the plate in the direction of free stream shear flow is always positive when the suction at the plate exceeds a certain critical value. However, in the case of blowing at the plate, this drag may be opposite to the direction of external flow for sufficiently high shear. (c) 2007 American Institute of Physics.