Abstract
In liquid metal (LM) magnetohydrodynamic (MHD) flows in the access ducts of a breeding blanket of a fusion power reactor, the spatially varying fringing magnetic field can be responsible for high MHD pressure drop, which is one of the blanket feasibility issues. In this study, the velocity field and the pressure drop of the LM MHD flow in a square non-conducting duct have been characterized via numerical computations with COMSOL Multiphysics for the case of a non-uniform magnetic field that decreases in the flow direction. In the computations, four configurations of the fringing magnetic field varying in magnetic field gradient and a wide range of Hartmann (1000<Ha<10,000) and Reynolds (1000<Re<10,000) numbers have been employed. A total of 80 cases were computed providing a database for construction of a pressure drop correlation. The obtained correlation relates the pressure drop coefficient k to Ha, Re and the magnetic field gradient with a high accuracy with the coefficient of determination R-squared of 0.9967. Detailed analysis has been performed on the effect of the flow parameters and the magnetic field gradient on the recirculation flow bubble, which was found to form in the flow in most of the computed cases due to strong 3D MHD effects caused by the magnetic field gradient. Strong inertia effects have been found at higher Re and lower Ha numbers by comparing computed results between full and inertialess flow models.
