Development of a simulation method for evaluating Marangoni convection with free surface for tungsten divertor

Highlights: • Simulation code for evaluating Marangoni convection in molten tungsten. • Simulations of molten tungsten with free surface were conducted. • Developmental processes of Marangoni convection was evaluated. • Vortices due to Marangoni convection were generated. • Surface deformation of molten tungsten by inner flow was observed. - Abstract: A tungsten (W) divertor has been developed for tokamak-type nuclear fusion reactors, such as ITER. Because the divertor will be repetitively subjected to high heat flux when plasma disruption or edge localized mode occurs, W at the surface of the divertor will be melted and solidified during reactor operation. The surface shape of the W divertor after or during such a heat load strongly influences its lifetime. Thus, evaluating the behavior of W in such conditions is important. An important driving force in molten metal is Marangoni convection due to a difference in surface tension resulting from a temperature gradient at the surface. To clarify the mechanism of Marangoni convection in molten W, a simulation method that can simultaneously treat surface deformation and convection in molten W, including Marangoni convection, is required. We have been developing such a simulation code based on the constrained interpolation profile combined unified procedure method. In this paper, we simulated molten W under a given temperature gradient or heat load and validated the model by simulating the flow in a molten W pool with a temperature gradient. The development process of Marangoni convection in molten W with a free surface was evaluated.