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Keywords:

  • MHD flow;
  • rotating disk;
  • Hall current;
  • suction and injection;
  • limiting behavior.

Abstract

An electrically conducting fluid is driven by a rotating disk, in the presence of a magnetic field that is strong enough to produce significant Hall currents. The disk is porous, allowing mass transfer through suction or injection. The limiting behavior of the flow is studied, as the magnetic field strength grows indefinitely. The flow variables are properly scaled, and uniformly valid asymptotic expansions of the velocity components are obtained through parameter straining. The leading order approximations show sinusoidal behavior that is decaying exponentially, as we move away from the disk surface. The two-term expansions of the radial and azimuthal surface shear stress components, as well as the far field inflow speed, compare well with the corresponding finite difference solutions; even at moderate magnetic fields.