力学学报 ›› 2017, Vol. 49 ›› Issue (4): 811-817.doi: 10.6052/0459-1879-16-368

• 流体力学 • 上一篇    下一篇

疏液壁面上亲液杂质对滑移特性的影响

鲍路瑶1, 罗凯1, 文俊1, 胡海豹1,2   

  1. 1. 西北工业大学航海学院, 西安 710072;
    2. 西北工业大学深圳研究院, 广东深圳 518057
  • 收稿日期:2016-12-07 出版日期:2017-07-15 发布日期:2017-08-01
  • 通讯作者: 胡海豹,副教授,主要研究方向:表界面力学行为及其应用.E-mail:huhaibao@nwpu.edu.cn E-mail:huhaibao@nwpu.edu.cn
  • 基金资助:

    国家自然科学基金(51679203)、深圳市基础研究项目(JCYJ20160510140747996)资助

INFLUENCE OF SMALL AMOUNT OF WETTING IMPURITY ON THE SLIP OF LIQUID FLOW OVER NON-WETTING SURFACE

Bao Luyao1, Luo Kai1, Wen Jun1, Hu Haibao1,2   

  1. 1. School of Marine Science and Technology, Northwestern Polytechnical University, Xi'an 710072, China;
    2. Research & Development Institute in Shenzhen, Northwestern Polytechnical University, Shenzhen 518057, Guangdong, China
  • Received:2016-12-07 Online:2017-07-15 Published:2017-08-01
  • Contact: O647 E-mail:huhaibao@nwpu.edu.cn

摘要:

纳米流动系统具有高效、经济等优势,在众多领域具有广泛的应用前景.因该类系统具有极高的表面积体积比,致使界面滑移效应对流动具有显著影响.论文采用非平衡分子动力学模拟方法,研究了疏液壁面表层混入少量亲液原子时纳米通道内液体的滑移特性,并基于分子动理论解释了其影响机制.研究发现,亲液杂质(均布或集中)对液体法向密度振荡程度影响较弱,但会显著改变壁面附近类固体层的分布和液体滑移规律;随亲液杂质占比增加,液体类固体现象更趋明显,壁面处液体接触密度也线性增大,但通道内液体平均速度逐渐降低,滑移长度也迅速减小;相比于集中的亲液杂质,均匀分布亲液杂质对滑移的弱化效应更强.如当亲液杂质占比为28%时,其滑移长度比单纯疏液表面的降低率从50%扩大至56%.基于分子动理论的分析发现,亲液杂质会导致杂质原子附近第一液体层内的原子发生跃迁的能垒加大,即弱化了液体原子的流向跃迁行为,从而降低了滑移量;相比于集中杂质,均匀分布的杂质还会降低固液间的非公度性,致使滑移特性破坏更严重.

关键词:

疏液表面|亲液杂质|滑移|分子动力学

Abstract:

The nanofluidic systems has great promise applications in many areas because of high efficiency and economic performance. During to the very large rate of surface and volume, the interface slip effect will significantly influence the flow properties in nanofluidic systems. The non-equilibrium molecular dynamics simulation was used to investigate the slip properties as liquid flows past non-wetting solid wall which contains small amount of wetting impurity. The underlying mechanism was also discussed based on the molecular kinetic theory. The simulation results indicate that the wetting impurity (uniformly or concentrated distributed) show insignificant influence on density profile of liquid but significantly alters the solid-like structure and slip property of liquid. As the percent of wetting impurity increasing, the solid-like phenomenon of liquid near walls becomes more significant and the contact density increases linearly. At the same time, the average velocity of liquid decreasing and the slip length decreases fast in a linearly way. The uniformly distributed wetting impurity reduces the magnitude of slip more significantly than concentrated distributed at the same percent of wetting impurity. For example, as the percent of wetting impurity is 28%, the slip length decreases 50% (concentrated distributed) and 56% (uniformly distributed) relative to the homogeneous non-wetting wall. The analysis based on the molecular kinetic theory indicates that the existence of wetting impurity enlarges the energy barrier as liquid atoms hopping from one sites to another in the first liquid layer. Thus, the probability of liquid atoms hoping along the flow direction was decreased, i.e. smaller the slip length. In the case of uniformly distributed wetting impurity, the smaller slip arbitrated to the decreasing incommensurability between fluid and wall.

Key words:

non-wetting surface|wetting impurity|slip|molecular dynamics

中图分类号: 

  • O647