Molecular dynamics simulation of a droplet sheared by solid walls

Akinori Fukushima , Nicolas Fillot (1) , Takashi Tokumasu , Philippe Vergne (1)

1 TMI - Tribologie et Mécanique des Interfaces

Considering a nanometer-thick droplet shared by two solid walls, shear forces were evaluated by molecular dynamics simulation. Expressly, shear forces around the contact line regions have been focused and evaluated the velocity dependence of forces. As a result, it has been clarified that no difference is observed between the velocity dependence of force around two contact lines. Recently, due to the development in materials science, new functional materials can be used. These materials realize useful mechanical and energy devices that have small structures in nm-order. Important issues to determine the efficiency of these small devices, mass transport properties are greatly different from those in microscopic states. We have studied this phenomenon through a liquid-vapor interface in a water plug by molecular dynamics simulations [1]. In this study, we have focused on the shearing of a nanometer-thick droplet that can be seen between solids that do not have enough lubricants between them. When a channel size is in nm-order scale, a ratio of a liquid-vapor interface domain among a volume of a droplet is much larger than that of a macroscopic droplet. Therefore the momentum transport through a liquid-vapor interface highly affects the total momentum transport, and cannot be ignored. Thus we clarify the effects of the liquid-vapor interface in microscopic droplet. Figure 1 shows a micro channel model of this simulation. This model is composed of two parallel slabs that have a FCC (001) surface. Two solid walls move along y direction and in an opposite manner. The velocity of the upper wall was set at Vw, and the velocity of the lower wall was set at –Vw. Figure 2 shows a velocity dependence of a friction force on each region. At both liquid-vapor interface regions, the slope of the force against the wall velocity can be calculated as 4.4×10-13 N/(m/s). This means that there is no difference between the dynamics along the advancing direction and that along the receding direction in terms of the increasing rate of the force on the liquid-vapor interface. [1]T. Tokumasu, M. Meurisse, N. Fillot and P. Vergne, Tribology International Journal, 59 (2013), 10-16

Mots clés: Liquid bridge; nano confinement; molecular dynamic simulation

Domaines: Autre

Akinori Fukushima, Nicolas Fillot, Takashi Tokumasu, Philippe Vergne. Molecular dynamics simulation of a droplet sheared by solid walls. 42th Leeds-Lyon Symposium on Tribology "Surfaces and Interfaces, Mysteries at Different Scales", B. BouSaïd & P. Vergne, Sep 2015, Vlapré - Ecully, France. ⟨hal-01222502⟩