Three dimensional MHD stagnation flow due to a stretchable rotating disk

The three dimensional steady MUD laminar stagnation point flow of an electrically conducting fluid on a radially stretchable rotating disk in the presence of a uniform vertical magnetic field is the main concern of the present study. The problem is an extension of the well-known von Karman stagnation problem to the configuration with a stretchable disk with or without rotation. An exact similarity reduction of the Navier-Stokes equations leads to a system of ordinary differential equations describing the stagnation flow. The system is governed by a stretching and a rotation parameters, based on the wall stretching and angular velocity. Employing a highly accurate spectral numerical integration scheme, the effects of these parameters on the flow are examined. The quantities of particular physical interest, such as the torque and the wall shear stresses are calculated and discussed. Contrary to the classical von Karman flow, for small rotational speeds of the disk, magnetic field is found to thicken the boundary layer when small wall stretching is taken into account. (C) 2012 Elsevier Ltd. All rights reserved.