Oscillatory MHD flow past an impulsively started porous plate

A two-dimensional time dependent MHD oscillatory flow past an impulsively started infinite porous plate with variable suction in conducting fluid is studied analytically. Present analysis is similar to the work done by Messiha. A reverse type of flow in the mean velocity profile is observed when the plate moves in the direction opposite to that of the flow. The mean velocity increases when the plate moves in the direction of the flow and decreases when it moves in the opposite direction. The mean velocity is enhanced by an applied magnetic field. The fluctuating parts of the velocity were not affected by the motion of the plate for uniform suction at the plate. The real and imaginary parts of the fluctuating velocities increase, respectively with the plate moving opposite and in the same direction of the fluid flow. The transient velocity profile showed similar behaviour as the mean velocity profiles. The amplitude of the skin friction at the plate increases with increase in the magnetic field and frequency. The amplitude of the skin friction is larger when the plate moves against the fluid flow. The phase angle of the skin friction has been found to decrease with increase in the plate velocity when the plate moves against fluid flow and increases with decreasing magnetic field