THE SPIN-UP OF LIQUID-METAL DRIVEN BY A ROTATING MAGNETIC-FIELD

The paper considers the flow field during spin-up from rest of liquid metal in a cylindrical statio:nary cavity due to a rotating transverse uniform low-frequency magnetic field. It is assumed that the Ekman an d the magnetic Reynolds numbers are small. An approximate model, based on matching of Bodewadt-type layers with an inviscid core, with possi ble influence from the sidewall, for laminar flow is developed. It is shown that the angular velocity in the core is a function of time only . Analytical solutions for the angular velocity and the meridional flo w in the core are presented, and supplemented by finite-difference res ults to show the sidewall effects. The spin-down following the switch- off of the magnetic forcing, the influence of the axial variations of the magnetic field, and the relevance to turbulent flows are discussed .