Esmaeeli A
Southern Illinois University at Carbondale, 62901, Carbondale, IL, USA.
Eur Phys J E Soft Matter. 2018 Nov 20;41(11):135. doi: 10.1140/epje/i2018-11745-1.
The transient behavior of a leaky dielectric liquid drop under a uniform AC electric field of small strength is investigated, using a closed form analytical solution. The drop settles to a quasi-steady state in a relaxation time that is set by the viscosities of the drop and the ambient fluid and the surface tension, and oscillates around a mean deformation with a frequency that is twice the electric field frequency. The mode of instantaneous deformation remains the same (oblate or prolate) or switches between oblate and prolate, depending on the relative importance of the time-periodic component of the deformation compared to that of the time-exponential. The structure of the flow field and its evolution is studied for representative fluid systems at a high and a low electric field frequency. The individual contribution of the net tangential and normal electric stresses, which are the driving forces of the problem, on the flow structure and drop deformation is characterized. On the basis of the mean (time-independent) and time-periodic components of the driving forces, the flow field is represented as the superposition of three different flow patterns. It is shown that the interplay of these flow patterns leads to formation and destruction of toroidal vortices, and that the residence time of these vortices correlates inversely with the field frequency.
利用封闭形式的解析解，研究了在小强度均匀交流电场下泄漏介电液滴的瞬态行为。液滴在由液滴和周围流体的粘度以及表面张力所确定的弛豫时间内达到准稳态，并以电场频率两倍的频率围绕平均变形振荡。瞬时变形模式保持不变（扁球形或长球形），或者在扁球形和长球形之间切换，这取决于变形的时间周期分量与时间指数分量的相对重要性。针对高、低电场频率下的代表性流体系统，研究了流场结构及其演变。表征了作为问题驱动力的净切向和法向电应力对流动结构和液滴变形的各自贡献。基于驱动力的平均（与时间无关）分量和时间周期分量，将流场表示为三种不同流动模式的叠加。结果表明，这些流动模式的相互作用导致了环形涡旋的形成和破坏，并且这些涡旋的停留时间与场频率成反比。
