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

•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. 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.