Surface viscometry in a uniform magnetic field

This paper addresses an original numerical coupling between surface mechanics of a gradually oxidizing liquid metal surface, and a supporting annular MHD flow, in the general layout of the classical annular viscometer, originally developed by Mannheimer et al. [J. Colloid Interface Sci. 32 (1970) 195-211]. A purely hydrodynamic interplay between a main azimuthal flow (induced by a rotating floor) and a secondary overturning flow generated by centrifugation is found to be strongly affected by both surface viscous shear and surface viscous dilatation. When centrifugation competes with electromagnetic effects, advection of the main flow by the secondary flow is proved to affect significantly the core MHD flow, leading to original MHD flow patterns. The latter phenomenology reveals to be relevant to characterise the surface viscosities of a gradually oxidising liquid metal surface.