Yoshinaga Natsuhiko, Liverpool Tanniemola B
WPI - Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan.
MathAM-OIL, AIST, Sendai 980-8577, Japan.
Phys Rev E. 2017 Aug;96(2-1):020603. doi: 10.1103/PhysRevE.96.020603. Epub 2017 Aug 29.
We study the role of hydrodynamic interactions in the collective behavior of collections of microscopic active particles suspended in a fluid. We introduce a calculational framework that allows us to separate the different contributions to their collective dynamics from hydrodynamic interactions on different length scales. Hence we are able to systematically show that lubrication forces when the particles are very close to each other play as important a role as long-range hydrodynamic interactions in determining their many-body behavior. We find that motility-induced phase separation is suppressed by near-field interactions, leading to open gel-like clusters rather than dense clusters. Interestingly, we find a globally polar ordered phase appears for neutral swimmers with no force dipole that is enhanced by near-field lubrication forces in which the collision process rather than long-range interaction dominates the alignment mechanism.
我们研究了流体动力学相互作用在悬浮于流体中的微观活性粒子集合体集体行为中的作用。我们引入了一个计算框架，使我们能够将不同长度尺度上流体动力学相互作用对其集体动力学的不同贡献区分开来。因此，我们能够系统地表明，当粒子彼此非常接近时，润滑力在决定其多体行为方面与长程流体动力学相互作用起着同样重要的作用。我们发现，近场相互作用抑制了运动诱导的相分离，导致形成开放的凝胶状聚集体而非致密聚集体。有趣的是，我们发现对于没有力偶极的中性游动者会出现全局极性有序相，该相由近场润滑力增强，其中碰撞过程而非长程相互作用主导排列机制。
