Centre for Molecular Simulation, Swinburne University of Technology, Hawthorn, Victoria 3122, Australia.
J Chem Phys. 2010 Jun 28;132(24):244706. doi: 10.1063/1.3450302.
In this work we show how different use of thermostating devices and modeling of walls influence the mechanical and dynamical properties of confined nanofluids. We consider a two dimensional fluid undergoing Couette flow using nonequilibrium molecular dynamics simulations. Because the system is highly inhomogeneous, the density shows strong fluctuations across the channel. We compare the dynamics produced by applying a thermostating device directly to the fluid with that obtained when the wall is thermostated, considering also the effects of using rigid walls. This comparison involves an analysis of the chaoticity of the fluid and evaluation of mechanical properties across the channel. We look at two thermostating devices with either rigid or vibrating atomic walls and compare them with a system only thermostated by conduction through vibrating atomic walls. Sensitive changes are observed in the xy component of the pressure tensor, streaming velocity, and density across the pore and the Lyapunov localization of the fluid. We also find that the fluid slip can be significantly reduced by rigid walls. Our results suggest caution in interpreting the results of systems in which fluid atoms are thermostated and/or wall atoms are constrained to be rigid, such as, for example, water inside carbon nanotubes.
在这项工作中，我们展示了不同的热定设备和壁面建模如何影响受限纳米流体的力学和动力学性质。我们考虑二维流体在非平衡分子动力学模拟中经历库埃特流动。由于系统高度不均匀，密度在通道中表现出强烈的波动。我们比较了直接对流体施加热定设备和对壁面进行热定所产生的动力学，还考虑了使用刚性壁的影响。这种比较涉及对流体混沌性的分析和对通道内机械性能的评估。我们研究了两种具有刚性或振动原子壁的热定设备，并将它们与仅通过振动原子壁传导进行热定的系统进行了比较。在孔中观察到压力张量的 xy 分量、流动速度和密度以及流体的 Lyapunov 定位发生了敏感变化。我们还发现，刚性壁可以显著减少流体的滑移。我们的结果表明，在解释流体原子被热定和/或壁原子被约束为刚性的系统的结果时需要谨慎，例如，碳纳米管内的水。
