Boundary‐layer flow on a permeable surface with an exponentially decreasing outer flow

Abstract The boundary‐layer flow when a permeable surface is moving in the same direction or in the opposite direction as the outer flow is investigated. Plate and outer flow are exponentially moving to the left or plate is moving exponentially to the right while outer flow is moving exponentially to the left. Both numerical and asymptotic solutions are presented to discuss not only the existence of the bifurcation to dual solutions as well as the analysis of the flow behavior when approaching the limits of the parameters involved. Multiple solutions are observed when the surface is moving in the opposite direction to the outer flow and the respective critical points are identified. It is also found that, when the surface is moving in the same direction with the outer flow where the surface velocity is large and greater than the outer flow velocity, the solution is independent of the wall mass transfer rate. Solutions for large rates of fluid injection and suction through the surface are obtained.