标题： 狭缝状纳米孔内的流体流动：分子尺度表面形貌的作用 显示英文标题

标题： Fluid flow inside slit-shaped nanopores: the role of surface morphology at the molecular scale

摘要： 非平衡分子动力学(NEMD)模拟流体流动突显了纳米尺度流动与经典流体力学的特殊性。 特别是，由于各种因素，在宏观尺度上边界条件可能偏离无滑移行为。 在此背景下，我们研究了狭缝状纳米孔中表面形貌对流体流动的影响。 我们证明表面形貌能有效控制滑移长度，当孔壁和流体的分子结构匹配时，滑移长度接近于零。 通过使用泵-like驱动机制的边界驱动、能量守恒NEMD模拟，我们检查了两种类型的孔壁——分别模仿晶体和非晶体材料——它们对流动表现出显著不同的表面阻力。 调整表面滑移后，所得的流速分布与不可压缩牛顿流体的Hagen-Poiseuille理论一致。 对于两个孔，我们分别观察到部分滑移和无滑移行为，这与靠近表面的流体层和耗竭有关。 然而，流体的限制导致有效粘度随孔宽变化显著。 对水力渗透率的分析表明，模拟流动处于达西区。 此外，流动的热隔离导致流体温度沿流动方向线性增加，我们利用流体力学的守恒定律将其与强烈的粘性耗散和热对流联系起来。 我们的发现强调了在分子尺度上进行建模的必要性，以准确捕捉边界附近和纳米多孔材料中的流体动力学，因为在这些地方宏观模型可能不适用。 显示英文摘要

摘要： Non-equilibrium molecular dynamics (NEMD) simulations of fluid flow have highlighted the peculiarities of nanoscale flows compared to classical fluid mechanics. In particular, boundary conditions can deviate from the no-slip behavior at macroscopic scales due to various factors. In this context, we investigate the influence of surface morphology in slit-shaped nanopores on the fluid flow. We demonstrate that the surface morphology effectively controls the slip length, which approaches zero when the molecular structures of the pore wall and the fluid are matched. Using boundary-driven, energy-conserving NEMD simulations with a pump-like driving mechanism, we examine two types of pore walls--mimicking a crystalline and an amorphous material--that exhibit markedly different surface resistances to flow. The resulting flow velocity profiles are consistent with Hagen-Poiseuille theory for incompressible, Newtonian fluids when adjusted for surface slip. For the two pores, we observe partial slip and no-slip behavior, respectively, which correlate with fluid layering and depletion near the surfaces. However, the confinement of the fluid gives rise to an effective viscosity that varies substantially with the pore width. Analysis of the hydrodynamic permeability shows that the simulated flows are in the Darcy regime. Additionally, the thermal isolation of the flow causes a linear increase in fluid temperature along the flow, which we relate to strong viscous dissipation and heat convection, utilizing conservation laws of fluid mechanics. Our findings underscore the need for molecular-scale modeling to accurately capture the fluid dynamics near boundaries and in nanoporous materials, where macroscopic models may not be applicable.