Molecular dynamics study on the slippage of liquid lithium flow in tungsten nanochannels

As the use of liquid lithium (Li) as the plasma facing material in a fusion device becomes widespread, more and more research work has been dedicated to the numerical simulations of Li flow based on the Navier-Stokes equations. However, the slip condition of Li on a solid surface hasn't been fully understood. The most common and simplest boundary condition, which is no-slip, is just one of the allowable conditions ranging from pure slip to multilayer locking. In this work, molecular dynamics simulations of the Couette flow were performed to investigate the slip properties of liquid Li on tungsten (W) surfaces. The atomic structures near the surfaces were inspected. The influence of temperature, lattice orientation and biaxial strain of wall surfaces, as well as the surface roughness, were discussed. It was found that the slip length is always negative suggesting that the wall always retards the movement of liquid Li. Among all the factors, surface roughness has the most significant effects on the slippage. Two sectional linear relationships between the slip length and the height of the roughness elements were discovered. As the height of roughness elements reaches a critical point, micro vortexes begin to form and change the slope of the linear relationship.

Automated summary

As the use of liquid lithium as the plasma facing material in fusion devices becomes more common, research on numerical simulations of lithium flow has increased. However, the slip condition of liquid lithium on a solid surface is still not fully understood. In this study, molecular dynamics simulations were used to investigate the slip properties of liquid lithium on tungsten surfaces. Factors such as temperature, lattice orientation, biaxial strain, and surface roughness were considered, and it was found that surface roughness has the most significant effect on slip. Two sectional linear relationships between slip length and roughness height were discovered, with the formation of micro vortexes changing the slope of the relationship when the roughness height reaches a critical point.