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arXiv 1708.08802cond-mat.softphysics.bio-phphysics.flu-dyn
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弹性胶囊在DC电场中的大变形电流体力学

Large deformation electrohydrodynamics of an elastic capsule in DC electric field

Sudip Das, Rochish M. Thaokar

摘要:

研究了在均匀直流电场作用下,一个含有牛顿流体的球形弹性胶囊在一个弹性膜和另一个牛顿流体中的动力学行为。诸如内部和外部流体介质的电导率以及膜的电容和电导率的电特性的不连续性导致净界面麦克斯韦应力,其可以引起这种弹性胶囊的变形。我们调查这个问题,考虑良好的膜法律薄的弹性膜,充分解决流体力学的斯托克斯流量限制和描述的静电使用的电容器模型。在小变形的极限下,解析理论对动力学的预测相当令人满意。然而,在高毛细管数下的大变形需要数值方法(在本例中为边界元法)来解决这个高度非线性的问题。类似于囊泡,在中间时间,高度非线性的双凹形状以及正方形和六边形的形状时,观察到外部介质更导电。该研究确定的重要性,如高膜电容,低膜电导,低流体动力学时间尺度和高毛细管数观察这些形状转变的参数。过渡是由于大的压缩麦克斯韦应力在两极在中间时间。因此,这种形状转变可以在允许电容的球形小球中看到,可能与界面回复力的性质无关。

英文摘要:

The dynamics of a spherical elastic capsule, containing a Newtonian fluid bounded by an elastic membrane and immersed in another Newtonian fluid, in a uniform DC electric field is investigated. Discontinuity of electrical properties such as conductivities of the internal and external fluid media as well as capacitance and conductance of the membrane lead to a net interfacial Maxwell stress which can cause the deformation of such an elastic capsule. We investigate this problem considering well established membrane laws for a thin elastic membrane, with fully resolved hydrodynamics in the Stokes flow limit and describe the electrostatics using the capacitor model. In the limit of small deformation, the analytical theory predicts the dynamics fairly satisfactorily. Large deformations at high capillary number though necessitate a numerical approach (Boundary element method in the present case) to solve this highly non-linear problem. Akin to vesicles, at intermediate times, highly nonlinear biconcave shapes along with squaring and hexagon like shapes are observed when the outer medium is more conducting. The study identifies the essentiality of parameters such as high membrane capacitance, low membrane conductance, low hydrodynamic time scales and high capillary number for observation of these shape transitions. The transition is due to large compressive Maxwell stress at the poles at intermediate times. Thus such shape transition can be seen in spherical globules admitting electrical capacitance, possibly, irrespective of the nature of the interfacial restoring force.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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