Possibility of Non-Fickian Mixing at Concentration Interface between Stratied Suspensions
Possibility of Non-Fickian Mixing at Concentration Interface between Stratied Suspensions
复制标题
层状悬浮液之间浓度界面处非菲克混合的可能性
DOI：
10.1016/j.jcis.2020.03.019
复制
发表时间：
2020
影响因子：
9.9
通讯作者：
Y.
中科院分区：
文献类型：
--
作者：
Mori;M.;Tai;T.;Nishimura;K.;Harada;S. and Yamamoto;Y.
假设悬浮在液体中的微米级颗粒的相对运动受流体动力学效应的影响，而纳米级颗粒的相对运动受热效应的影响较大。结果表明，微米级颗粒的分层悬浮液的混合行为与纳米级颗粒遵循Fick扩散定律的分层悬浮液完全不同。这种“非Fickian”混合的微米尺寸的颗粒不仅是由浓度差，但也悬浮液的物理性质。ExperimentsWe进行了实验研究的重力沉降的分层悬浮液的微米尺寸的颗粒浓度梯度反对重力。我们还进行了点力型的数值模拟在相同的条件下，在实验中。特别是，我们专注于浓度界面附近的颗粒的相对运动，这是一个明显的界面之间的上部和下部的悬浮液具有不同concentration.FindingsThe实验和数值结果表明，如果悬浮液中的颗粒的数密度是足够的，浓度界面似乎表现出不可比拟的和界面防止颗粒混合。然而，少数颗粒不能维持浓度界面的密封，然后表现出混溶行为。浓度界面处悬浮颗粒的混合机理与界面的互溶和不互溶特性密切相关。
HypothesisRelative motion of micro-sized particles suspended in liquid is governed by hydrodynamic effect, in contrast to nano-sized particle suspension in which thermal effect is significant. As a result, the mixing behavior of stratified suspensions with micro-sized particles is totally different from those obeying Fick's diffusion law for nano-sized particles. Such a “non-Fickian” mixing of micro-sized particles is determined not only by the concentration difference but also the physical properties of suspensions.ExperimentsWe conducted an experimental study of gravitational settling of stratified suspensions of micro-sized particles with concentration gradients opposed to gravity. We also performed point-force-type numerical simulations under the same conditions as those in the experiment. Particularly, we focused on the relative motion of particles near the concentration interface, which is an apparent interface between the upper and the lower suspensions having different concentrations.FindingsThe experimental and numerical results indicate that, if the number density of particles in suspension is sufficient, the concentration interface seemingly behaves immiscibly and the interface prevents particle mixing. However, a small number of particles cannot maintain the seal of the concentration interface then demonstrates miscible behavior. The mixing mechanism of the suspended particles at the concentration interface is strongly related to the miscible and immiscible characteristics of the interface.