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，在宏观尺度上边界条件可能偏离无滑移行为。 对于狭缝状纳米孔中的流体流动，我们证明表面形貌可以有效控制滑移长度，当与孔壁和流体的分子结构匹配时，滑移长度趋近于零。 使用具有泵式驱动机制的边界驱动、能量守恒的NEMD模拟，我们研究了两种类型的孔壁——分别模拟晶体和非晶体材料——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泊肃叶理论一致。 对于这两个孔，我们分别观察到部分滑移和无滑移行为。 水力渗透率证实模拟流动处于达西区。 然而，流体的限制导致其有效粘度低于本体值；宽孔表现出边界和本体类似流动之间的转变。 此外，流动的热隔离导致流体温度沿流动方向线性增加，我们将这一现象与强烈的粘性耗散和热对流联系起来，利用流体力学的守恒定律。 注意到所研究的流体模型不会形成液滴，我们的发现挑战了之前报道的滑移、溶剂排斥性和耗竭区之间相关性的普遍性。 此外，它们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，因为在这些情况下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. For fluid flow in slit-shaped nanopores, we demonstrate that surface morphology provides an efficient control on the slip length, which approaches zero when matching the molecular structures of the pore wall and the fluid. 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 Poiseuille theory for incompressible, Newtonian fluids when adjusted for surface slip. For the two pores, we observe partial slip and no-slip behavior, respectively. The hydrodynamic permeability corroborates that the simulated flows are in the Darcy regime. However, the confinement of the fluid gives rise to an effective viscosity below its bulk value; wide pores exhibit a crossover between boundary and bulk-like flows. 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. Noting that the investigated fluid model does not form droplets, our findings challenge the universality of previously reported correlations between slippage, solvophobicity, and a depletion zone. Furthermore, they 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.