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arXiv · 2606.18745

Extension of a multi-region free-surface MHD solver beyond the inductionless approximation

Min Ki Jung·Brian Wynne·Francisco Saenz·Yufan Xu·Jabir Al-Salami·Yong-Su Na·Egemen Kolemen
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Abstract

Free-surface liquid metal flows are a leading candidate for the plasma-facing components of future fusion reactors, but existing transient, three-dimensional, free-surface MHD solvers rely on the inductionless approximation, in which the induced magnetic field is neglected. This paper extends the open-source solver FreeMHD [B. Wynne et al., Phys. Plasmas 32, 013907 (2025)] beyond that approximation, resolving the induced field self-consistently with a vector-potential formulation that enforces $\nabla\cdot\boldsymbol{B}=0$ by construction while preserving the original multi-region, two-phase framework. It is verified against the analytical Shercliff and Hunt duct flows, against flows driven by a time-varying applied field, and against the deformation of a free liquid metal jet crossing a non-uniform field, and validated against free-surface height measurements from the LMX-U experiment. The experiment validates the overall free-surface solution rather than finite-$R_m$ effects, which the transient-field cases verify. To our knowledge this is the first open-source, fully three-dimensional free-surface liquid metal solver to resolve the evolution of the induced magnetic field, providing a basis for modeling the finite magnetic Reynolds number conditions expected in large-scale, transient fusion events.

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Min Ki Jung, Brian Wynne, Francisco Saenz, Yufan Xu, Jabir Al-Salami, Yong-Su Na, Egemen Kolemen. 2026-06-17. Extension of a multi-region free-surface MHD solver beyond the inductionless approximation. https://arxiv.org/abs/2606.18745

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