Jiang Chuntao, Li Wuming, Liu Qingsheng
School of Mathematics and Statistics, Xinyang Normal University, Xinyang, 464000, China.
School of Mathematics and Information Science, Henan Polytechnic University, Jiaozuo, 454000, China.
Sci Rep. 2022 Jun 30;12(1):11072. doi: 10.1038/s41598-022-15323-2.
Understanding the impact of complex boundary on the hydrodynamic properties of methane nanofluidic is significant for production optimization and design of energy-saving emission reduction devices. In the molecule scale, however, the microscopic mechanisms of the influence of the complex boundary on the hydrodynamic characteristics are still not well understood. In this study, a mixture boundary Poiseuille flow model is proposed to study the hydrodynamic properties and explore the molecular mechanisms of confined methane nanofluidic using the Non-equilibrium multiscale molecular dynamics simulation (NEMSMD). In order to investigate the influences of nonslip and rough boundary on hydrodynamic behavior of nanofluidic by the present model in one simulation, the coordinate transformation methods regarding the local symmetry is showed. Simulation results show that the atom number density, velocity and temperature profiles present significant differences near the nonslip boundary and rough wall surface. Moreover, the slip length of methane nanofluidic near the rough boundary decreases with the increasing of the temperature. Furthermore, the viscosity values are calculated by parabolic fit of the local velocity data based on the present model, which demonstrates that the impact of the nonslip boundary on the shear viscosity compared with the experiment result is less than one obtained using the rough boundary. In addition, the local contours of rotational and translational energy are plotted, which show that the rotational and translational energies of nonslip boundary are obvious higher than those of rough boundary. These numerical results are very significant in understanding the impact of complex boundary conditions on hydrodynamic properties in nanofluidic theory and the design of nano-devices.
了解复杂边界对甲烷纳米流体动力学性质的影响对于生产优化和节能减排装置的设计具有重要意义。然而，在分子尺度上，复杂边界对流体动力学特性影响的微观机制仍未得到充分理解。在本研究中，提出了一种混合边界泊肃叶流动模型，采用非平衡多尺度分子动力学模拟（NEMSMD）来研究受限甲烷纳米流体的动力学性质并探索其分子机制。为了在一次模拟中通过本模型研究无滑移边界和粗糙边界对纳米流体动力学行为的影响，展示了关于局部对称性的坐标变换方法。模拟结果表明，在无滑移边界和粗糙壁面附近，原子数密度、速度和温度分布存在显著差异。此外，粗糙边界附近甲烷纳米流体的滑移长度随温度升高而减小。此外，基于本模型通过对局部速度数据进行抛物线拟合来计算粘度值，结果表明与实验结果相比，无滑移边界对剪切粘度的影响小于粗糙边界的情况。另外，绘制了转动能和平动能的局部等值线，结果表明无滑移边界的转动能和平动能明显高于粗糙边界。这些数值结果对于理解纳米流体理论中复杂边界条件对流体动力学性质的影响以及纳米器件的设计具有重要意义。
