Dynamics of Drop Formation in an Electric Field.
Dynamics of Drop Formation in an Electric Field.
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DOI：
10.1006/jcis.1999.6136
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发表时间：
1999-05
影响因子：
9.9
通讯作者：
P. Notz;Osman A. Basaran
中科院分区：
文献类型：
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作者：
P. Notz;Osman A. Basaran
电场对形成一滴无粘性的，完全导电的液体从毛细管从平行板电容器的顶板突出到周围的动态惰性，绝缘气体的效果进行了计算研究。该自由边界问题由描述液滴瞬态形状的表面伯努利方程和描述液滴内部速度势和液滴外部静电势的拉普拉斯方程组成，采用线法结合有限元法进行空间离散。所采用的有限元算法依赖于明智地使用重新网格化和元素添加到两个区域的自适应网格，以适应大的域变形，并允许计算进行，直到颈部的厚度连接一个即将形成的液滴的毛细管中的其余液体小于0.1%的毛细管半径。计算的准确性通过显示在没有电场的情况下用新算法进行的预测与边界积分计算非常一致来证明（Schulkes，R. M. S. M. J. Fluid Mech.278，83（1994））和对水滴的实验测量（Zhang，X.，和巴萨兰、O. A. Phys. Fluids 7（6），1184（1995））。在存在电场的情况下，该算法预测，随着所施加的场的强度增加，液滴形成的模式从简单滴下变为喷射，再变为所谓的微滴下，这与实验观察一致（Cloupeau，M.，和Prunet-Foch，B.《气溶胶科学杂志》25（6），1021（1994）; Zhang，X.，和巴萨兰、O. A. J. Fluid Mech.326，239（1996））。计算预测的初级液滴体积和液滴长度在分手的报告在很宽的范围内的值的比率的电力，重力和惯性力的表面张力。与前面提到的管中的流速和电场强度均为非零的情况相比，还考虑了流速为零并且通过将场强从某个值脉冲地改变为较大值来启动动态的情况。当场强的阶跃变化幅度很小时，新的瞬态计算结果雅阁早期稳定性分析的结果（巴萨兰，O.一、和Scriven，L. E.《胶体界面科学杂志》140（1），10（1990）），从而提供了对新算法的准确性的又一证明。版权所有1999年学术出版社。
The effect of an electric field on the formation of a drop of an inviscid, perfectly conducting liquid from a capillary which protrudes from the top plate of a parallel-plate capacitor into a surrounding dynamically inactive, insulating gas is studied computationally. This free boundary problem which is comprised of the surface Bernoulli equation for the transient drop shape and the Laplace equation for the velocity potential inside the drop and the electrostatic potential outside the drop is solved by a method of lines incorporating the finite element method for spatial discretization. The finite element algorithm employed relies on judicious use of remeshing and element addition to a two-region adaptive mesh to accommodate large domain deformations, and allows the computations to proceed until the thickness of the neck connecting an about to form drop to the rest of the liquid in the capillary is less than 0.1% of the capillary radius. The accuracy of the computations is demonstrated by showing that in the absence of an electric field predictions made with the new algorithm are in excellent agreement with boundary integral calculations (Schulkes, R. M. S. M. J. Fluid Mech. 278, 83 (1994)) and experimental measurements on water drops (Zhang, X., and Basaran, O. A. Phys. Fluids 7(6), 1184 (1995)). In the presence of an electric field, the algorithm predicts that as the strength of the applied field increases, the mode of drop formation changes from simple dripping to jetting to so-called microdripping, in accordance with experimental observations (Cloupeau, M., and Prunet-Foch, B. J. Aerosol Sci. 25(6), 1021 (1994); Zhang, X., and Basaran, O. A. J. Fluid Mech. 326, 239 (1996)). Computational predictions of the primary drop volume and drop length at breakup are reported over a wide range of values of the ratios of electrical, gravitational, and inertial forces to surface tension force. In contrast to previously mentioned cases where both the flow rate in the tube and the electric field strength are nonzero, situations are also considered in which the flow rate is zero and the dynamics are initiated by impulsively changing the field strength from a certain value to a larger value. When the magnitude of the step change in field strength is small, the results of the new transient calculations accord well with those of an earlier stability analysis (Basaran, O. A., and Scriven, L. E. J. Colloid Interface Sci. 140(1), 10 (1990)) and thereby provide yet another testament to the accuracy of the new algorithm. Copyright 1999 Academic Press.