带电粘弹性液滴线性和非线性行为研究

The motion of electrically charged liquid droplets is a fundamental problem in many practical applications such as electrospray, inkjet printing, fuel atomization, micro/nanofluidics, and mass spectrometry. In addition, viscoelastic materials are often used for electrically charged liquid droplets in these applications. Therefore, carrying out basic researches on electrically charged viscoelastic liquid droplets helps us understand and control the more complex electrohydrodynamic systems in those practical applications, which is of significance. Building appropriate theoretical models, selecting appropriate numerical methods, and setting up the corresponding experiment platform, this project will perform a systematical study on the linear and nonlinear dynamic behaviors of electrically charged viscoelastic liquid droplets theoretically, numerically and experimentally. It will study the effects of viscoelasticity, surface tension, electrostatic force, electrical conductivity, electrical permittivity and other parameters on the oscillation, deformation and breakup of the droplets, as well as the effects of the surrounding medium on the linear and nonlinear behaviors of the droplets. It will solve the critical charge amount to maintain the droplets linearly and nonlinearly stable as well as those factors influencing the critical charge amount, providing guidance for the practical applications. Moreover, as a fundamental research, it will enrich the contents of electrohydrodynamics and non-Newtonian fluid mechanics.

在诸如电雾化、喷墨打印、燃油雾化、微/纳流控、质谱分析等许多实际应用中，带电液滴的运动是一个根本性问题，另外，在这些应用中，带电液滴经常用到粘弹性材料，因此，对粘弹性流体带电液滴开展基础性研究有助于我们了解并掌控实际应用中更为复杂的电流体力学系统，具有重要的意义。本项目拟通过理论、计算和实验相结合的方法，选取合适的理论模型和数值算法，搭建相应的实验平台，系统地研究粘弹性流体带电液滴的线性和非线性动力学行为，研究粘弹性、表面张力、电场力、电导率、介电常数等参数对液滴振动、变形和破碎的影响规律，研究周围介质对液滴线性和非线性行为的影响，研究液滴保持线性和非线性稳定的临界带电量以及影响临界带电量的因素，为实际应用提供指导性建议。而且，本项目作为基础性研究，也会丰富电流体力学和非牛顿流体力学的内容。

液滴的运动、变形和破碎是流体力学中的一个重要问题。而在很多应用如雾化、乳化、生物流体、芯片实验室、制药中所产生的液滴经常采用高分子聚合物材料。这些高分子聚合物具有黏弹性，属于非牛顿流体的范畴。本项目采用理论、计算和实验的方法，系统深入地研究了带电或不带电黏弹性液滴的线性稳定性和非线性动力学行为，包括对带电黏弹性液滴、悬浮在不相溶黏弹性流体中的黏弹性液滴、同心复合液滴的小振幅振动特性的理论研究，电场、流体导电性、外部流体和受限空间等因素对黏弹性射流非线性动力学行为的影响的一维数值模拟，带电射流上液滴沿径向拉伸变形、非轴对称失稳的实验观测，实现了研究目标，基本完成了原计划中的各项内容，在Journal of Fluid Mechanics、Physics of Fluids、Physical Review Fluids、Journal of Non-Newtonian Fluid Mechanics上发表学术论文8篇。