Unsteady MHD Laminar Boundary Layer Flow due to an Impulsively Stretching Surface

The unsteady, incompressible boundary layer flow caused by an impulsively stretching surface under the influence of a transverse magnetic field is investigated. The partial differential equations governing the laminar flow, under boundary-layer approximations, are non-dimensionalised using similarity transformations and then solved numerically using an efficient, implicit finite-difference scheme known as Keller-box method. The numerical solutions are obtained for all dimensionless time from initial unsteady state flow to final steady-state, uniformly valid in the whole spatial region. The numerical results for the surface shear stress are compared with those of the analytical approach results, and they are found to be in good agreement. It is observed that there is a smooth transition from the small time solution to the large time solution. The magnetic field significantly affects the flow field and skin friction coefficient. Indeed, skin friction coefficient found to decrease rapidly, initially, in small time interval before attaining a steadystate for large time.