Breakup of an electrified viscous thread with charged surfactants
Breakup of an electrified viscous thread with charged surfactants
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DOI：
10.1063/1.3548841
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发表时间：
2011-02-01
影响因子：
4.6
通讯作者：
Papageorgiou, D. T.
中科院分区：
文献类型：
--
作者：
Conroy, D. T.;Matar, O. K.;Papageorgiou, D. T.
从理论上研究了界面存在离子表面活性剂时带电粘性射流的动力学和破碎。考虑轴对称配置，射流被同心放置的圆柱形电极包围，该电极保持恒定电压。射流和电极之间的环形区域被视为流体动力学被动介电介质，在那里建立电场并驱动流动，以及包括毛细管不稳定性和粘性效应在内的其他物理机制。射流流体被视为对称电解质，并通过考虑 Nernst-Planck 方程对阳离子和阴离子物质进行适当的建模，以便找到影响射流中电场的体积电荷密度。带正电的不溶性表面活性剂存在于界面处，其演变以及局部表面张力系数的所得值与界面处的电势耦合。通过执行非线性细长射流近似，导出了所得到的耦合非线性系统并取得了分析进展。简化模型由许多流体动力学、电气和电动参数描述，并进行了广泛的计算研究来阐明动力学以及相关的线性特性。已经确定，只要外电极足够远，射流就会在有限时间内破裂，并且给出了许多例子，其中无量纲参数可用于控制在拓扑转变之外形成的卫星液滴的尺寸以及破裂的时间。研究还表明，在接近破碎时间时，箍缩解遵循清洁粘性射流的自相似动力学。最后，针对大型德拜层开发了进一步的渐近理论，以产生包含表面电荷扩散效应的附加模型。数值解表明，静电和动电效应的存在增加了卫星的尺寸，但对破裂时间的影响相当微弱。 (C) 2011 年美国物理研究所。 [号码：10.1063/1.3548841]
The dynamics and breakup of electrified viscous jets in the presence of ionic surfactants at the interface are investigated theoretically. Axisymmetric configurations are considered and the jet is surrounded by a concentrically placed cylindrical electrode, which is held at a constant voltage potential. The annular region between the jet and the electrode is taken to be a hydrodynamically passive dielectric medium and an electric field is set up there and drives the flow, along with other physical mechanisms including capillary instability and viscous effects. The jet fluid is taken to be a symmetric electrolyte and proper modeling of the cationic and anionic species is used by considering the Nernst-Planck equations in order to find the volume charge density that influences the electric field in the jet. A positively charged insoluble surfactant is present at the interface, and its evolution, as well as the resulting value of the local surface tension coefficient, is coupled with the voltage potential at the interface. The resulting coupled nonlinear systems are derived and analytical progress is made by carrying out a nonlinear slender jet approximation. The reduced model is described by a number of hydrodynamic, electrical, and electrokinetic parameters, and an extensive computational study is undertaken to elucidate the dynamics along with allied linear properties. It is established that the jet ruptures in finite time provided the outer electrode is sufficiently far away, and numerous examples are given where the dimensionless parameters can be used to control the size of the satellite drops that form beyond the topological transition, as well as the time to break up. It is also shown that pinching solutions follow the self-similar dynamics of clean viscous jets at times close to the breakup time. Finally, a further asymptotic theory is developed for large Debye layers to produce an additional model that incorporates the effects of surface charge diffusion. Numerical solutions establish that the presence of electrostatic and electrokinetic effects increases the sizes of satellites but have a rather weak influence on the time to rupture. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3548841]