MHD flow over a moving flat plate with a step change in the magnetic field

Boundary layer behavior over a moving continuous surface is an important type of flow occurring in several engineering processes. For example, many metallurgical processes involve the cooling of continuous strips or filaments by drawing them through a quiescent fluid. However, by drawing such strips in an electrically conducting fluid subject to a magnetic field, the rate of cooling can be controlled and a final product of desired characteristics can be achieved. Another interesting application of hydromagnetics to metallurgy lies in the purification of molten metals from non-metallic inclusions by the application of a magnetic field. Kumar i et al. [1], Andersson [2], Vajravelu [3], and Watanabe and Pop [4] have recently studied the laminar boundary layer flow over a flat plate which issues from a slot at x = 0 and moves with a constant velocity in an electrically conducting fluid in the presence of a transverse magnetic field which acts over the whole flow region x > 0. However, an important practical situation is that of an external magnetic field of the form (see Chiam [5])