Time-dependent MHD Couette flow in a porous annulus

This study presents the solution for the MHD transient Couette flow in an annulus formed by two concentric porous cylinders of infinite length. The fluid flow is induced by either the impulsive or the accelerated movements of the outer cylinder. A uniform magnetic field is assumed to be applied perpendicular to the direction of flow. General solution of the governing equations is obtained using a combination of Laplace transform and the Riemann-sum approximation method of Laplace inversion. The expressions for the skin friction at the two walls are obtained in both cases. The variations of the velocity and the skin friction with respect to the Hartmann number and suction/injection parameter have been discussed. It is found out that suction accelerates the flow whereas injection retards the flow.