Herrero Cecilia, Omori Takeshi, Yamaguchi Yasutaka, Joly Laurent
Univ Lyon, Univ Claude Bernard Lyon 1, CNRS, Institut Lumière Matière, F-69622 Villeurbanne, France.
Department of Mechanical Engineering, Osaka University, 2-1 Yamadaoka, Suita 565-0871, Japan.
J Chem Phys. 2019 Jul 28;151(4):041103. doi: 10.1063/1.5111966.
Flows in nanofluidic systems are strongly affected by liquid-solid slip, which is quantified by the slip length and by the position where the slip boundary condition applies. Here, we show that the viscosity, slip length, and hydrodynamic wall position (HWP) can be accurately determined from a single molecular dynamics (MD) simulation of a Poiseuille flow, after identifying a relation between the HWP and the wall shear stress in that configuration. From this relation, we deduce that in gravity-driven flows, the HWP identifies with the Gibbs dividing plane of the liquid-vacuum density profile. Simulations of a generic Lennard-Jones liquid confined between parallel frozen walls show that the HWP for a pressure-driven flow is also close to the Gibbs dividing plane (measured at equilibrium), which therefore provides an inexpensive estimate of the HWP, going beyond the common practice of assuming a given position for the hydrodynamic wall. For instance, we show that the HWP depends on the wettability of the surface, an effect usually neglected in MD studies of liquid-solid slip. Overall, the method introduced in this article is simple, fast, and accurate and could be applied to a large variety of systems of interest for nanofluidic applications.
纳米流体系统中的流动受到液固滑移的强烈影响，液固滑移由滑移长度和滑移边界条件适用的位置来量化。在此，我们表明，在确定该构型中流体动力学壁位置（HWP）与壁面剪应力之间的关系后，可通过对泊肃叶流动的单个分子动力学（MD）模拟精确确定粘度、滑移长度和流体动力学壁位置（HWP）。基于此关系，我们推断在重力驱动的流动中，HWP与液体 - 真空密度分布的吉布斯分界面一致。对限制在平行冻结壁之间的通用 Lennard - Jones 液体的模拟表明，压力驱动流动的 HWP 也接近吉布斯分界面（在平衡时测量），因此这提供了一种对 HWP 的低成本估计方法，超越了通常假设流体动力学壁处于给定位置的做法。例如，我们表明 HWP 取决于表面的润湿性，这一效应在液固滑移的 MD 研究中通常被忽略。总体而言，本文介绍的方法简单、快速且准确，可应用于纳米流体应用中大量感兴趣的系统。
