Molecular Dynamics Simulation of Nanoscopic Couette Flow and Lubricated Nanoindentation

摘要

Summary form only given. Molecular dynamics simulation is a powerful tool for the investigation of nanoscopic processes that are hard or impossible to investigate by experiment in detail at the molecular level. The present work concerns tribological properties of model systems which are described by the Lennard-Jones truncated-shifted potential. Two related scenarios are studied: 1) Couette flow; 2) lubricated contact of two solid bodies. The influence of the solid-fluid interaction energy on the tribological properties, which is found to be significant, controls the adhesion of the fluid at the solid surface and therefore the wetting properties of the system. In particular, it is shown here that the solid-fluid interaction energy decisively affects the heat balance of stationary non-equilibrium states for the studied systems, regarding both the source and the sink term. Thereby, various phenomena combine in a non-trivial way: Firstly, upon increasing the solid-fluid interaction energy, the friction coefficient increases, so that more heat is dissipated. This leads to an enhanced heating of the surrounding fluid. Simultaneously, the thermal resistance at the solid-fluid interface decreases due to a stronger thermal coupling between the substrate and the adsorbed fluid. Since a greater solid-fluid interaction energy leads to a higher average fluid temperature (at otherwise constant conditions), the thermal conductivity of the fluid increases, which reinforces these effects by enhancing the transfer of the dissipated heat to the fluid.