Impact of surface viscosity upon an annular magnetohydrodynamic flow

J. Delacroix - L. Davoust

Grenoble Institute of Technology (Grenoble-INP), University of Grenoble Alpes, CNRS. Materials and Processes Science and Engineering (SIMaP) Laboratory, Electromagnetic Processing of Materials (EPM) Group, 38402 St-Martin d'Hères, France

Abstract
Using a matched asymptotic expansion based on the small parameter 1/Ha , this paper addresses an original analytical coupling between surface rheology of, e.g., a gradually oxidizing liquid metal surface, and a supporting annular MHD flow. It is shown that the level of surface viscosity drives the electrical activation of the Hartmann layers, heavily modifying the MHD flow topology and leading to the emergence of a Lorentz force, for which the interaction with the flow is not classical. These analytical results are compared to a 2D numerical study, highlighting a fair agreement as soon as Ha ≥ 10. Figs 5, Refs 17.