Laminar swirling flow in an annulus with porous walls

Flow of an incompressible viscous fluid under constant pressure gradient in a porous annulus is considered, with surface mass transfer, both in the radial and circumferential directions. Expressions for the fully developed velocities are then obtained. With these fully developed velocities on a section of the annulus, on which the origin of co-ordinates lies, the downstream decay of the swirl velocity is analysed, subject to the condition that the velocities on the boundaries are now purely radial. The perturbations in the axial and radial velocities, caused by the decaying swirl, are also determined. It is observed that the decay of the swirl velocity is faster for suction at the inner boundary and injection at the outer andvice versa.