Mathematics, Faculty of Engineering and Industrial Sciences and Centre for Molecular Simulation, Swinburne University of Technology, Melbourne, Victoria 3122, Australia.
J Chem Phys. 2011 Oct 14;135(14):144701. doi: 10.1063/1.3648049.
We investigate the hydrodynamic boundary condition for simple nanofluidic systems such as argon and methane flowing in graphene nanochannels using equilibrium molecular dynamics simulations (EMD) in conjunction with our recently proposed method [J. S. Hansen, B. D. Todd, and P. J. Daivis, Phys. Rev. E 84, 016313 (2011)]. We first calculate the fluid-graphene interfacial friction coefficient, from which we can predict the slip length and the average velocity of the first fluid layer close to the wall (referred to as the slip velocity). Using direct nonequilibrium molecular dynamics simulations (NEMD) we then calculate the slip length and slip velocity from the streaming velocity profiles in Poiseuille and Couette flows. The slip lengths and slip velocities from the NEMD simulations are found to be in excellent agreement with our EMD predictions. Our EMD method therefore enables one to directly calculate this intrinsic friction coefficient between fluid and solid and the slip length for a given fluid and solid, which is otherwise tedious to calculate using direct NEMD simulations at low pressure gradients or shear rates. The advantages of the EMD method over the NEMD method to calculate the slip lengths/flow rates for nanofluidic systems are discussed, and we finally examine the dynamic behaviour of slip due to an externally applied field and shear rate.
我们使用平衡分子动力学模拟（EMD）结合我们最近提出的方法[J. S. Hansen、B. D. Todd 和 P. J. Daivis，Phys. Rev. E 84, 016313（2011）]研究了简单纳米流体系统（如氩气和甲烷在石墨烯纳米通道中的流动）的流体动力学边界条件。我们首先计算了流体-石墨烯界面摩擦系数，由此可以预测壁面附近第一层流体的滑移长度和平均速度（称为滑移速度）。然后，我们使用直接非平衡分子动力学模拟（NEMD）从泊肃叶流和库埃特流中的流动速度分布计算滑移长度和滑移速度。从 NEMD 模拟得到的滑移长度和滑移速度与我们的 EMD 预测非常吻合。因此，我们的 EMD 方法可以直接计算给定流体和固体之间的这种固有摩擦系数和滑移长度，否则在低压力梯度或剪切率下使用直接 NEMD 模拟计算会很繁琐。讨论了 EMD 方法相对于 NEMD 方法计算纳米流体系统滑移长度/流速的优势，最后研究了由于外部施加的场和剪切率引起的滑移的动态行为。
