Hydromagnetic flow near an oscillating porous limiting surface

Abstract

Unsteady hydromagnetic flow near a harmonically oscillating limiting surface (e.g., of a star) is considered in presence of a transverse magnetic field. Exact solutions, for a periodic boundary layer without a ‘mean steady flow’,are obtained when the magnetic Prandtl number is unity and there is a normal velocity of injection imposed at the wall. The results are also presented for the case when the wall is subjected to a normal velocity of suction instead of injection. It is observed that two distinct boundary (or hydromagnetic boundary) layers exist and tend to coalesce into a single layer when the magnetic field parameter approaches zero. The thicknesses of these boundary layers are significantly affected by the injection/suction velocity and the applied magnetic field.