Numerical characterization of liquid metal MHD flow in electroconductive thick orifices with asymmetric contraction

In this paper, the 3D MHD flow through an orifice with asymmetric contraction is investigated. This hydraulic element is commonly found in fusion reactor liquid blanket designs, e.g. connecting the manifold and breeding zone region. This component is characterized about flow features and pressure losses using the CFD code ANSYS CFX for the case of electroconductive walls in the range c=0.01÷0.1, Re=108, and Ha=0÷300. The sudden variation of cross section in the orifice causes the induction of electric currents in the streamwise direction that contribute to determine the overall MHD pressure drop. A wide recirculation region is observed in the duct center after the flow egress from the orifice, which could be potentially harmful for efficient tritium transport outside of the blanket. Large pressure loss occurs in the orifice due to the enhanced wall conductivity and non-negligible axial length. The 3D pressure drop term is characterized through a local resistance coefficient (k) that is found to be k≈0.205 for well conducting walls (c=0.1) and k≈0.063 for poorly conducting ones (c=0.01).