CREEPING FLOW OF A CONDUCTING FLUID PAST AXISYMMETRICAL BODIES IN THE PRESENCE OF AN ALIGNED MAGNETIC-FIELD

The use of strong magnetic fields for the control of particle settling in metallic systems is investigated in the limit of small inertial and magnetic Reynolds numbers. Finite element calculations of flow around axisymmetric bodies show that the drag increases proportional to the intensity of the magnetic field B or the Hartmann number Ha. The flow field forms boundary layers, which thin with increasing Ha, along surfaces parallel to the flow. For axisymmetric bodies, the boundary layer separates as the poles of the surface are approached and encloses regions of almost stagnant fluid. These regions spread upstream and downstream along the body with increasing Ha, thereby trapping the particle in a column of stagnant fluid. The pressure difference between the leading and trailing fluid columns is responsible for the increased particle drag. Asymptotic analysis with Ha>l confirms the scalings from the computations and clarifies the flow structure near the body. © 1990 American Institute of Physics.