纳米级孔隙中水分子流动机制的分子动力学模拟研究

The Molecular Simulation of Water Molecules Flow Mechanism in Nanoscale Pore

摘要: 近年来，随着页岩气开发与研究的兴起，研究纳米尺度下多孔介质中的渗流问题成为了流体力学界关注的焦点。这是因为在空隙中页岩气的流动规律与页岩的孔隙大小是紧密相关的。在纳米尺度下研究受限空间中水的动力学机制，利用水受限于几何平板这样的模型是十分有必要的。本文利用分子动力学模拟水分子在受限的环境下，构造两块彼此平行的石墨烯平板，改变两平板间的距离，观察水的流量与密度的变化。我们的研究观察到流体的动力学行为与经典微管中的poiseuille流中的是非常不同的。从1 nm到2 nm之间水的密度分布发生了很大的变化；从4 nm到5 nm之间水的速度以及氢键分布都发生了很大的变化。我们认为在受限空间中，几何平板之间距离的大小对水分子动力学行为的影响是比较大的，并且这种变化是非线性的。

Abstract: Recently, the development and research of shale gas attract many researchers’ attention on the study of nanoscale in the field of porpous flow. This is due to the fact that the flow rule of shale gas in the gap and the size of shale pore are closely related. In the nanoscale, it is very necessary to use the model of water confined to the geometric tablet to study the dynamic mechanism of water. In this paper, we use the molecular dynamic simulation to research on the distribution of water molecule in the confining environment. We observe that the distribution of water molecule is changing with the varying H (the vertical distance between the two CNPs). Our study observed that the fluid dynamics behavior and classic microtubules in poiseuille flow have a significant difference. From system H = 1 nm - 2 nm, water density distribution has an obviously difference; from system H = 4 - 5 nm, the velocity and hydrogen bonds distribution has a considerable increase. The changing ordering of water molecule is the essential reason to it, and this change is non-linear. So we can say that the length of H plays a key role to the nanofluid.