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微通道内流动因表面积/体积比值极大,造成许多微尺度效应,进而使微通道内出现完全不同于宏观流动的流体密度分布特性.本文以纳米通道内液态Poiseuille流为对象,采用非平衡分子动力学模拟方法研究了流体原子间相互作用强度εLL,流体原子间平衡距离σLL以及壁面原子与流体原子间平衡距离σLS对通道内流体密度分布的影响规律.数值模拟中,统计系综取微正则系综,势能函数选用LJ/126模型,壁面设为Rigid-atom壁面,温度校正使用速度定标法,牛顿运动方程的求解则采用Verlet算法.模拟结果表明,随εLL的减弱,近壁面区密度分布的振荡幅度则逐渐增大;而σLL则同时影响流体原子的存在形态和密度分布,较大的σLL会造成流体原子在整个通道内呈现面心立方结构的类似固体排列,较小的σLL会使得流体原子呈现不断变化的“团簇”结构;随σLS的变大,近壁面区流体密度振荡幅度增大,且流体密度分布起点离壁面越远.另外,本文还从近壁面区流体原子的“俘获-逃逸”行为角度,初步解释了原子间相互作用强度对密度分布的影响规律.
Due to the large surface area / volume ratio in microchannels, many microscale effects are caused in the microchannels, resulting in a fluid density distribution completely different from the macroscopical flow in the microchannels.In this paper, the liquid Poiseuille flow in the nanochannels is used as the object, The dynamics simulation method is used to study the influence of the interaction strength εLL between fluids, the equilibrium distance between fluid atoms σLL and the equilibrium distance between wall atoms and fluid atoms σLS on the distribution of fluid density in a channel. In numerical simulation, For the ensemble and potential energy function, the LJ / 126 model was chosen, the wall was set as Rigid-atom wall, the velocity calibration was used for temperature correction, and Verlet algorithm was used to solve the Newton equation of motion.The simulation results show that with the decrease of εLL, While the oscillation amplitude of σLL gradually increases. However, σLL also affects the existence and density distribution of the fluid atoms. Larger σLL will result in a fluid-like solid-like arrangement of face-centered cubic structures throughout the channel. The smaller σLL Making the fluid atoms showing a continuously changing “cluster ” structure; as σLS becomes larger, near the wall area fluid density oscillation amplitude And the starting point of the distribution of fluid density is further away from the wall.In addition, the influence of the interaction intensity between atoms on the density distribution is also preliminarily explained from the “trap-escape” behavior of the fluid atoms in the near-wall region.