Active matter invasion of a viscous fluid: Unstable sheets and a no-flow theorem
Active matter invasion of a viscous fluid: Unstable sheets and a no-flow theorem
复制标题
DOI：
10.1103/physrevlett.122.098002
复制
发表时间：
2019-03-04
影响因子：
8.6
通讯作者：
Spagnolie, Saverio E.
中科院分区：
文献类型：
--
作者：
Miles, Christopher J.;Evans, Arthur A.;Spagnolie, Saverio E.
我们研究了流体动力学相互作用的运动或不运动的产生应力的游泳者或颗粒侵入周围粘性流体时的稀释悬浮液的动力学。对齐的推杆颗粒的殖民地被示出为在颗粒取向的方向上伸长，并经历横向浓度不稳定性的级联，在很小的时间由一个方程，该方程还描述了Saffman-Taylor不稳定性在Hele-Shaw细胞，或瑞利-泰勒不稳定性在通过多孔介质的二维流动。对齐的推粒子的薄片总是不稳定的，而对齐的拉粒子的薄片可以是稳定的（不动的粒子），也可以是不稳定的（能动的粒子），其生长速率在力偶极强度上是非单调的。我们还证明了一个令人惊讶的“无流定理”：一个分布最初各向同性的方向立即失去各向同性，但在这样一种方式，导致没有流体流动的所有地方和所有的时间。
We investigate the dynamics of a dilute suspension of hydrodynamically interacting motile or immotile stress-generating swimmers or particles as they invade a surrounding viscous fluid. Colonies of aligned pusher particles are shown to elongate in the direction of particle orientation and undergo a cascade of transverse concentration instabilities, governed at small times by an equation that also describes the Saffman-Taylor instability in a Hele-Shaw cell, or the Rayleigh-Taylor instability in a two-dimensional flow through a porous medium. Thin sheets of aligned pusher particles are always unstable, while sheets of aligned puller particles can either be stable (immotile particles), or unstable (motile particles) with a growth rate that is nonmonotonic in the force dipole strength. We also prove a surprising "no-flow theorem": a distribution initially isotropic in orientation loses isotropy immediately but in such a way that results in no fluid flow everywhere and for all time.