THREE-DIMENSIONAL MAGNETOHYDRODYNAMIC FLOWS IN SUDDEN EXPANSIONS

Introduction. The three-dimensional, inductionless flow of electrically conducting incompressible fluids in symmetric sudden expansions with rectangular cross-section and walls of finite conductivity, exposed to a uniform magnetic field, is investigated numerically using the fluid dynamic code CFX. The geometry considered is closely related to applications in fusion reactor blankets in which a liquid metal is used as breeder material. The fluid is circulated for removing tritium flowing through manifolds, expansions and contractions. The present study deals with rectangular channels which expand along the magnetic field lines since this condition creates the strongest MHD interaction (see [1] for flows expanding in the direction perpendicular to the magnetic field). The problem of MHD flows in sudden expansions has been studied experimentally by [2] for small interaction parameters (N < 2) and large Reynolds numbers considering ducts with insulating walls. A numerical solution for three-dimensional inertial MHD flow in sudden non conducting expansions under a magnetic field of arbitrary orientation has been described by [3]. The three-dimensional inertial MHD flow in ducts with walls of finite conductivity is still an open problem. The aim of the present work is to investigate the magnetic influence on the size and the occurrence of the separation regions which form behind sharp edges. Results for a fixed Reynolds number, Re = 100, are shown as a reference case. Starting from the flow pattern for hydrodynamic flow, the Hartmann number, Ha, is gradually increased.