Knudsen Henning Arendt, Sandnes Bjørnar, Flekkøy Eirik Grude, Måløy Knut Jørgen
Department of Physics, University of Oslo, Oslo, Norway.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Feb;77(2 Pt 1):021301. doi: 10.1103/PhysRevE.77.021301. Epub 2008 Feb 5.
Pattern forming processes are abundant in nature. Here, we report on a particular pattern forming process. Upon withdrawal of fluid from a particle-fluid dispersion in a Hele-Shaw cell, the particles are shown to be left behind in intriguing mazelike patterns. The particles, initially being uniformly spread out in a disc, are slowly pulled inwards and together by capillary and pressure forces. Invading air forms branching fingers, whereas the particles are compiled into comparably narrow branches. These branches are connected in a treelike structure, taking the form of a maze. The characteristic length scale within the structure is found to decrease with the volume fraction of the particles and increase with the plate separation in the Hele-Shaw cell. We present a simulator designed to simulate this phenomenon, which reproduces qualitatively and quantitatively the experiments, as well as a theory that can predict the observed wavelengths.
图案形成过程在自然界中很常见。在此，我们报告一种特定的图案形成过程。从亥姆霍兹槽中的颗粒 - 流体分散体中抽出流体后，颗粒会留下有趣的迷宫状图案。这些颗粒最初均匀分布在一个圆盘中，通过毛细力和压力缓慢向内聚拢。侵入的空气形成分支状指状物，而颗粒则聚集成相对较窄的分支。这些分支以树状结构相连，形成迷宫的形式。发现该结构内的特征长度尺度随颗粒的体积分数减小，并随亥姆霍兹槽中的平板间距增大。我们展示了一个设计用于模拟此现象的模拟器，它能定性和定量地重现实验结果，还提出了一种可以预测观测波长的理论。
