超浸润材料表面液滴撞击过程的模拟研究

论文总字数：25341字

摘 要

打印技术在推动科学文化进步与发展的同时也在其中汲取营养促使自身得到进步与发展，喷墨打印技术作为打印技术中较为方便的一种打印形式在我们的日常生活与生产中有许多应用。通过改变打印基底的表面润湿特性可以使得给定大小的墨滴在基底上呈现出不同大小的墨斑，从而提高喷墨打印的分辨率。但由于墨滴的尺度较小，目前没有系统的关于微尺度下液滴撞击复杂润湿表面的实验结果。所以我们小组决定建立一个液滴碰撞复杂润湿表面的模型来解决这一研究方面的困难。

我们的主要工作是基于COMSOL Multiphysics 5.2仿真软件的建模与仿真。我们选用两相流水平集法对模型进行简化，为方便计算我们规定液滴正下方为半径为定值亲水界面，亲水界面之外为超疏水界面。为了接近实际情况模型选择二维轴对称形式，我们还规定实验温度为室温且在常规重力场中进行仿真，为提高仿真的精度我们还虚拟了一个相对压力点。由于所学知识有限我们并没有添加液滴蒸发速率和系统内部阻力这两个影响因素。

我们建立的基于COMSOL Multiphysics 5.2的液滴碰撞复杂润湿表面的模型可以改变液滴的初速度，液滴的尺寸，液滴的材料，亲水区域的大小和底面的材料。这样一来就可以使用控制变量法来仿真分析在实际喷墨打印中所需研究的液滴初速度变化、亲水区域大小变化、液滴材料变化对铺展过程的影响的问题，为之后的事物实验提供了理论的参考依据与技术支持。

关键词：液滴碰撞 润湿性 复杂表面 仿真

SIMULATION STUDY OF DROPLET IMPINGEMENT ON THE SURFACE OF SUPER WETTING MATERIALS

Abstract

Printing technology in promoting the progress and development of science and culture in which derive nutrition to promote its progress and development, the inkjet printing technology as a technology to print more convenient a printed form in our daily life and production has many applications. By changing the surface wetting characteristics of the printing substrate, the ink droplets of a given size can be presented with different sizes of ink spots on the substrate, thereby increasing the resolution of the ink jet printing. However, due to the small size of the droplet, there is no systematic experimental results on the droplet impingement on the micro scale at present. So our team decided to build a droplet collision model to solve the complex wetting surface of the difficulties of this research.

Our main work is based on the modeling and Simulation of Multiphysics COMSOL 5.2 simulation software. We choose the two phase flow level set method to simplify the model, in order to facilitate the calculation of the radius of the liquid drop just below for the radius of the hydrophilic interface, beyond the hydrophilic interface for the super hydrophobic interface. To close to the actual situation of the model choice of two-dimensional axial symmetry, we also provide experimental temperature to room temperature and in conventional gravity field in the simulation, to improve the simulation accuracy of our imaginary a relative pressure points. Because of the limited knowledge, we have not added the two influencing factors, such as the evaporation rate of the droplets and the internal resistance of the system.

Based on the Multiphysics COMSOL 5.2, we establish the model of droplet impact complex wetting surface can change the initial velocity of droplets, droplet size, droplet material, the size of the hydrophilic region and the bottom surface of the material. In this way can using control variable method in actual ink-jet printing of the liquid drop initial velocity variation, variation in size of a hydrophilic region, droplet material changes on the spreading process of simulation analysis, after things experiment provides theoretical basis and technical support.

KEY WARDS: Droplet collision ,Wetting property, Complex surface,simulation

目录

摘要 …………………………………………………………………………………… 1

Abstract …………………………………………………………………………… 2

1. 绪论 ……………………………………………………………………… 4
   1. 选题的依据与意义 …………………………………………………… 4
   2. 本文所做工作和创新点 ……………………………………………… 4
2. 理论基础 …………………………………………………………………… 4
   1. 表面润湿特性 ………………………………………………………… 4
      1. 表面润湿特性的经典模型 ………………………………5
      2. 经典模型的修正 …………………………………………6
   2. 格子Boltzmann方法 ……………………………………………………7
      1. 演化方程 …………………………………………………7
      2. 格子结构和粒子离散速度集合 …………………………8
      3. 收缩方程 …………………………………………………9
   3. 固气表面张力的计算 ……………………………………………………11
3. 数学建模 ……………………………………………………………………12
   1. 建模总思路 …………………………………………………………… 13
   2. 模型的选择 …………………………………………………………… 14
      1. 软件的选择 …………………………………………… 14
      2. 模块的选择 …………………………………………… 14
   3. 模型的控制方程及边界条件 ………………………………………… 15
      1. 控制方程 ……………………………………………… 15
      2. 边界条件 ……………………………………………… 16
      3. 初始条件 ……………………………………………… 16
   4. COMSOL建模过程 …………………………………………………… 16
4. 仿真结果分析 ………………………………………………………………17
   1. 初速度速度对液滴撞击过程的影响 ………………………………… 19
   2. 亲水区域大小对液滴撞击过程的影响 ……………………………… 25
   3. 液滴材料对液滴撞击过程的影响 …………………………………… 30
5. 结论与展望
   1. 结论 ……………………………………………………………………43
   2. 展望 ……………………………………………………………………43

参考文献（References） …………………………………………………………… 45

致谢 ………………………………………………………………………………… 46

1. 绪 论

1.1 选题的依据与意义

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