Advances in direct numerical simulation for MHD modeling of free surface flows

The utilization of FLiBe (LiF-BeF₂) free-surface flow as a chamber protection scheme is considered in advanced nuclear fusion reactor. At the design of the nuclear fusion reactor from the viewpoint of thermofluid research, it would be very important to understand the influence of a magnetic field in turbulent free surface flow. On the other hand, turbulent free surface flow (called open channel flow) by direct numerical simulation (DNS) with non-deformable surface was first succeeded by imposing free-slip and non-slip conditions as velocity boundary conditions at the upper and lower, respectively. After that, the research by DNS has been advanced more, it has been clarified that turbulent structures generated from the lower wall travels to the free surface and affected the mechanism of heat and mass transfer at the free surface. The behavior of the structures is affected by the strong magnetic field in the nuclear fusion reactor. Therefore, a DNS of liquid film cooling in the nuclear fusion reactor is performed by authors, and the relations between a magnetic orientation and turbulent flow statistics are clearly observed. In this paper, the DNS result is introduced, and the trial turbulence modeling for MHD free-surface flow by using the DNS database is also discussed.