Numerical investigation of 3D MHD pressure drop in a prototypical fusion blanket manifold using OpenFOAM

Reliable prediction of magnetohydrodynamic (MHD) pressure losses in liquid-metal breeding blankets is essential for DEMO reactor design. In the European Dual Coolant Lead–Lithium (EU-DCLL) concept, manifold expansions and contractions are expected to dominate the total pressure drop. This work investigates the three-dimensional (3D) MHD pressure drop associated with a sudden expansion representative of the EU-DCLL bottom manifold, using a customized OpenFOAM solver. The solver is validated against analytical solutions and benchmark numerical codes, demonstrating superior stability and mesh efficiency. A set of 45 simulations is conducted for expansion ratios 4–8, Hartmann numbers 1000–5000, and Reynolds numbers 50–2000, spanning the viscous–electromagnetic (VE), inertial–electromagnetic (IE), and intermediate (IVE) regimes. The results reveal complex 3D current loops and flow reversals at high Hartmann numbers. Building on the Rhodes et al. (2018) formulation, we propose a modified correlation with a finite asymptotic term, applicable across VE, IVE, and IE regimes. The new model captures the numerical database with excellent accuracy (R^2 = 0.9914, RMSE = 0.0021) and predicts a 3D MHD pressure drop of ¿P3D = 1.50 kPa under EU-DCLL operating conditions. These findings improve the theoretical consistency of MHD pressure-loss modeling and support manifold optimization for future DEMO blanket designs.