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arXiv 1004.5002physics.flu-dyncond-mat.soft
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流体动力学相互作用抑制Poillille流中悬浮液滴的变形

Hydrodynamic interactions suppress deformation of suspension drops in Poiseuille flow

Krzysztof Sadlej, Eligiusz Wajnryb, Maria L. Ekiel-Jeżewska

摘要:

本文对低雷诺数下Poillille流夹带悬浮液滴的演化过程进行了数值研究。悬浮液滴由许多非接触颗粒的云模拟,这些颗粒最初随机分布在粘性流体的球形体积内,该粘性流体与液滴外部的主体流体相同。粒子的位置和速度的演变是由精确的多极润滑校正方法,在{ \sc hydromulipole}数值代码中实现的。液滴的变形被证明是较小的体积分数较大。在高浓度下,紧密颗粒之间的流体动力学相互作用与纯流体液滴的相应伸长相比显著降低了悬浮液液滴沿流动的伸长。由于流体动力学的相互作用,稠密悬浮液滴内的颗粒倾向于在液滴的中心部分停留很长时间;后来,小的团簇偶尔从液滴中分离出来,并通过组成非接触颗粒的准周期轨道稳定下来。这两种效应都显著减少了液滴沿流动的扩散。在大体积分数下,悬浮液滴通过破碎而不稳定,并且在低体积分数下,通过分散成单个颗粒而不稳定。

英文摘要:

Evolution of a suspension drop entrained by Poiseuille flow is studied numerically at a low Reynolds number. A suspension drop is modelled by a cloud of many non-touching particles, initially randomly distributed inside a spherical volume of a viscous fluid which is identical to the host fluid outside the drop. Evolution of particle positions and velocities is evaluated by the accurate multipole method corrected for lubrication, implemented in the {\sc hydromultipole} numerical code. Deformation of the drop is shown to be smaller for a larger volume fraction. At high concentrations, hydrodynamic interactions between close particles significantly decrease elongation of the suspension drop along the flow in comparison to the corresponding elongation of the pure-fluid drop. Owing to hydrodynamic interactions, the particles inside a dense-suspension drop tend to stay for a long time together in the central part of the drop; later on, small clusters occasionally separate out from the drop, and are stabilized by quasi-periodic orbits of the constituent non-touching particles. Both effects significantly reduces the drop spreading along the flow. At large volume fractions, suspension drops destabilize by fragmentation, and at low volume fractions, by dispersing into single particles.

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