Harada S, Mitsui T, Sato K
Division of Sustainable Resources Engineering, Faculty of Engineering, Hokkaido University, N13-W8, 060-8628, Sapporo, Hokkaido, Japan.
Eur Phys J E Soft Matter. 2012 Jan;35(1):1. doi: 10.1140/epje/i2012-12001-6. Epub 2012 Jan 9.
The gravitational settling of inhomogeneously suspended particles in a fluid has been investigated. Of particular interest is whether collective or individual motion of particles is dominant during their settlings, i.e., whether the particles settle as a continuous suspension or they settle individually relative to the surrounding fluid. We observed the settling of a stratified suspension which has the lower and upper concentration interfaces in a quasi-two-dimensional vessel. In some cases, the suspension behaves perfectly as a continuous fluid and the motion of the constituent particle is subject to bulk flow caused by the interfacial instability. In other cases, the particle behaves individually relative to the surrounding fluid. The existence of a concentration interface plays a significant role in these extreme behaviors of suspension. The transition from the collective to individual behaviors can be predicted quantitatively by a parameter which expresses the border resolution of the concentration interface.
研究了流体中不均匀悬浮颗粒的重力沉降。特别令人感兴趣的是，在颗粒沉降过程中，颗粒的集体运动还是个体运动占主导，即颗粒是作为连续悬浮体沉降，还是相对于周围流体单独沉降。我们观察了在准二维容器中具有上下浓度界面的分层悬浮体的沉降。在某些情况下，悬浮体表现得完全像一种连续流体，组成颗粒的运动受界面不稳定性引起的整体流动支配。在其他情况下，颗粒相对于周围流体单独运动。浓度界面的存在在悬浮体的这些极端行为中起着重要作用。从集体行为到个体行为的转变可以通过一个表示浓度界面边界分辨率的参数进行定量预测。
