Parametric study of liquid metal flows in conducting circular ducts in a strong nonuniform magnetic field

Parametric study of main flow characteristics in magnetohydrodynamic flow in the exit duct from a liquid metal blanket has been performed. The flow in such a duct occurs in a nonuniform, decreasing magnetic field. The duct wall is electrically conducting. The wall conductance ratio, $c$, and the gradient of the field, $\gamma$, have been varied in a wide range, $0.01\le c\le 0.5$ and $0.3\le \gamma \le 0.8$ covering most of the cases relevant to fusion. The studies have been performed with asymptotic methods for high values of the Hartmann number and interaction parameter, as well as with FLUENT. Pressure drop correlation has been developed, which is important for blanket design. The results show a significant increase in three-dimensional effects with decreasing wall conductance ratio. For small values of $c$, a stagnant zone is present in the nonuniform field region for all the values of the field gradient, which may create difficulties for tritium removal. If the exit duct is very long, the three-dimensional pressure drop is relatively low, but the effect of the nonuniform magnetic field on the velocity profiles is significant.