Unsteady separated stagnation-point flow over a moving porous plate in the presence of a variable magnetic field

This paper deals with the numerical study of unsteady separated stagnation point (USSP) flow of an incompressible, viscous, electrically conducting fluid over a porous flat plate which moves in its own plane with a velocity u0(t). A variable magnetic field is applied normal to the plate. The numerical results pertaining to the present study indicate that there exist two solutions for the USSP flow: one is the attached flow solution (AFS) and the other is reverse flow solution (RFS). It results in from the stability analysis that the AFS is stable and physically realizable, while the RFS is not stable and, therefore, not physically realizable. For a stationary plate, the USSP flow is separated for all values of the magnetic parameter (M) and suction/blowing parameter (d) in both AFS and RFS cases. It is found that velocity at a point decreases with the increase in M for RFS but the opposite trend is observed for AFS. The results of the analysis reveal that the number of stagnation points in presence of suction is two while the number of stagnation points in presence of blowing is only one for the RFS. A novel result of the analysis is that for RFS, there is only one stagnation point in absence of magnetic field whereas for a suitable magnetic field, two stagnation points appear.