Magnetohydrodynamic effects on the liquid metal film flowing along an inclined plate related with plasma facing components

The liquid metal film Plasma Facing Component (PFC) has been considered as one of the most promising ways to realize a long time working PFC. However, due to the existence of a magnetic field, the magnetohydrodynamic effects appearing in the liquid metal film flow directly influence the reliability of the flowing liquid metal limiter or divertor. In the present study, considering the influence of the flow rate, the transverse magnetic field and the inclination angle, we carry out experiments on the liquid metal film flowing along an inclined conducting stainless steel plate. The Laser Profilometer(LP), as well as the high-speed camera are respectively adopted to obtain the local film thickness quantitatively and free surface structures qualitatively. We observe the magnetohydrodynamic effects of liquid metal film flow, such as the nonmonotonic change of film thickness, the reduction of film flow velocity and the weakening of free surface waves in the direction of magnetic lines. Moreover, the film thickness increases with an increasing flow rate, while decreases with an increasing inclination angle at a constant value of the magnetic field. While plotting the relative film thickening $\delta_{en}$ and the reduction of flow velocity against the Stuart number $N$, we find that there is a critical $N$, $N_{cr}\approx0.1$, at which $\delta_{en}$ starts increasing dramatically. The $\delta_{en}$sin$\beta$, from all of the experimental data, collapses onto one line, which can be scaled as $\delta_{en}$sin$\beta$ $\sim N$. The present experimental data and its scaling law are useful to estimate the magnetohydrodynamic effects on liquid metal film flows while designing the liquid metal film PFC.