Bubble dynamics in Magnetohydrodynamics conditions: Numerical simulation and flow characterization for high density ratio mixture

Many Breeding Blanket (BB) concepts envision the use of a liquid metal (LM) alloy containing lithium to fulfill the functions of tritium production through the tritium breeding reaction, which produces helium as a by-product. This, under appropriate conditions, can nucleate, aggregate into bubbles that can be transported within the main fluid flow. The study of the bubbles transport within the magnetohydrodynamic (MHD) LM flow is mandatory to assess the impact on the BB performance and safety, due to their potential accumulation in some part of the system. In this study, the dynamics of bubbles in MHD conditions is examined using a custom OpenFOAM solver called mhdInterFoam (mIF). This code is capable of modeling a two-phase MHD flow of incompressible, immiscible, and isothermal fluids using the Volume of Fluid (VoF) method. The code has been validated against experimental data, producing results in good agreement with the reference for several bubble diameters (Eötvös number, Eo ≈ 1.5 - 8.5) and magnetic fields up to 1.5 T (Hartmann number, Ha ≈ 0 - 220). Specifically, the magnetic field effects on the bubbles regime of motion are analyzed and the characteristics of the LM flow around the bubbles are presented. The study is performed considering the distribution of fundamental physical quantities, which are challenging to investigate through experimental studies alone.