论文标题
外部场中主动磁悬浮液的紧急图案形成
Emergent pattern formation of active magnetic suspensions in an external field
论文作者
论文摘要
我们通过分析我们最近开发的介质连续体模型来研究均匀外部场中弱磁性活性悬浮液的集体自组织。我们的模型基于smoluchowski方程，用于在对齐场中的粒子概率密度函数，该粒子密度函数与活动和对齐扭矩产生的流动的平均场描述相结合。对Smoluchowski方程进行线性稳定性分析以及所得的定向力矩方程与非线性3D模拟相结合，我们全面地描述了不稳定性模式，这是活动和磁场强度的函数。对于足够高的活性和中等磁场强度，活动引起的流动与外部磁性扭矩之间的竞争使极性稳态不稳定。结果，出现了四个不同的集体运动动态模式。推动者的不稳定性模式包括由弯曲扭转不稳定性和动态骨料管理的行进带。对于拉特勒，有限尺寸和系统跨越了柱状浓缩区域，其主要是沿田间方向迁移的splay变形。值得注意的是，在非常强的磁场下，我们观察到极性稳态的重入流体动力稳定性。
We study collective self-organization of weakly magnetic active suspensions in a uniform external field by analyzing a mesoscopic continuum model that we have recently developed. Our model is based on a Smoluchowski equation for a particle probability density function in an alignment field coupled to a mean-field description of the flow arising from the activity and the alignment torque. Performing linear stability analysis of the Smoluchowski equation and the resulting orientational moment equations combined with non-linear 3D simulations, we provide a comprehensive picture of instability patterns as a function of strengths of activity and magnetic field. For sufficiently high activity and moderate magnetic field strengths, the competition between the activity-induced flow and external magnetic torque renders a homogeneous polar steady state unstable. As a result, four distinct dynamical patterns of collective motion emerge. The instability patterns for pushers include traveling bands governed by bend-twist instabilities and dynamical aggregates. For pullers, finite-sized and system spanning pillar-like concentrated regions predominated by splay deformations emerge which migrate in the field direction. Notably, at very strong magnetic fields, we observe a reentrant hydrodynamic stability of the polar steady state.
