| The flow properties of liquid in microchannel have been paid more attention for their wide applications in different fields. Up to now, little work has been focused on the flow behaviors of liquid metals. Recently, liquid lithium (Li) has been considered as one of the candidate plasma-facing materials (PFMs) because of its excellent properties in fusion reactor applications. Considering an accident condition, liquid Li may contact with Cu components and erode them, which may cause a serious disaster. The study of the flow properites of liquid Li in metal microchannel is crucially for the safe application of liquid Li working as a PFM. With the method of non-equilibrium molecular dynamics simulations, this paper has investigated the flow behavior of liquid Li flowing in metal (Cu and Fe) microchannels. The density and velocity distributions of Li atoms have been obtained. The impact of the dimensions of metal microchannels on the flowing behavior of liquid Li has been studied. Comparative analysis has been performed in these different fluid-solid interfaces, i.e., Li-Cu(100), Li-Cu(110), Li-Cu(111), Fe(100) and Fe(110) respectively. Results show that the density distributions of liquid Li near the interface present an orderly stratified structure. Affected by a larger surface density, a more obviously stratification is found when Li atoms are near the fluid-solid interfaces of Li-Cu(100) and Li-Cu(111) and a wider vacuum gap appeared between Li atoms and Cu(111) interface. When Li atoms are near the Li-Cu(110) interface, a lower stratification can be found and an alloy layer appeared at Li-Cu(110) interface. Because of its lower surface density, Li atoms spread into the bulk Cu more easily. However, the density distributions have little difference when Li atoms are close to the same fluid-solid interface but with different flow directions. Comparative analysis also has been operated between fluid-solid of Li-Fe (110) and Li-Fe(100). The results are similar to the situation of Li-Cu interfaces but the peak value of density profile is larger when the interface is Fe. A wider vacuum gap exists between liquid Li and Fe(110). The velocity of Li atoms in microchannel has a parabolic distribution. Because there exists a wider vacuum gap and stratified structure, the Li atoms closed to the Li-Cu (111) interface has the largest velocity. Closed to the Li-Cu (110) interface, Li atoms have the smallest velocity because of the alloy layer and the lower stratified structure. Due to the diversity of the atomic configurations of Cu (110) face, the liquid Li atoms flow with diverse velocities in different directions on the Li-Cu (110) interface. Similar results can be found in the situation of solid wall of Fe. When Fe as the solid-liquid interface, larger velocity and an obvious velocity slip appeared at the solid-liquid interface of Fe(110).It's also found that the flowing velocity of liquid Li is proportional to the square of microchannel dimensions and increases with it. When liquid Li is flowing on the Li-Cu(100) interface, the simulation result has revealed that the relationship between microchannel dimension and the largest velocity of Li atoms is in good agreement with Navier-Stokes theory result. It is noteweathy that the present result is smaller than the theory result when a "negative slip" occurs at the Li-Cu(110) interface. In contrast, the result is greater than the theory result in the presence of a "positive slip" at Li-Cu(111) interface. Strain rate, stress, heat flux of the flowing liquid Li are discussed as well in this paper. It is found that the stress is independent on the flowing direction but is affected by the channel face. While both the strain rate and heat flux are affected by the two factors. |
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