Numerical investigation of arc plasma–electrode interaction and the resulting molten pool dynamics in a single-spark discharge

A unified model is developed to investigate the coupled interaction between arc plasma and the electrode surface, focusing on molten pool dynamics and heat transfer behavior. The model solves unified governing equations in the whole computational domain, coupling magnetohydrodynamics, heat transfer, and phase change. The gas–liquid interface is captured using a level-set method, with material properties smoothly transitioned across the interface. The interaction between plasma flow, current conduction, and molten pool deformation is quantitatively analyzed. The results reveal that the formation of the crater-like structure is governed by the competition between recoil pressure and surface tension, where recoil pressure induces the central depression while surface tension acts to restore the molten surface. The arc-induced drag force and Lorentz force contribute to molten metal redistribution, while gravity is negligible. The deformation of the molten pool further modifies the current density and heat flux distributions, leading to deviations from conventional Gaussian assumptions at later stages. Experimental measurements of surface morphology are used to validate the model, showing good agreement in both depth and width.