Swimmer dynamics in externally driven fluid flows: The role of noise
Swimmer dynamics in externally driven fluid flows: The role of noise
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外部驱动流体流动中的游泳者动力学：噪声的作用
DOI：
10.1103/physrevfluids.7.014501
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发表时间：
2021-08
影响因子：
2.7
通讯作者：
S. Berman;K. Mitchell
中科院分区：
文献类型：
--
作者：
S. Berman;K. Mitchell
本文从理论上研究了在外部驱动的流体流动中，流体动力学输运障碍物附近细长微泳者运动的随机涨落效应。聚焦于二维双曲线流，我们考虑平移和旋转扩散以及翻滚的影响，即在游泳者方向的突然跳跃。无论扩散或翻滚是波动的主要来源，我们发现，噪音显着增加的概率，游泳者越过单向障碍的流动，阻止游泳者返回到其初始位置。我们采用渐近方法计算的概率密度的噪声游泳者的轨迹在一个给定的流体流，产生的解决方案，时间依赖的福克-普朗克方程在弱噪声限制。这个过程反映了量子力学中的半经典近似，同样涉及计算从游泳者的福克-普朗克方程导出的哈密顿系统的最小作用路径。使用半经典的技术，我们计算（i）的稳态取向分布的游泳者与旋转扩散和翻滚和（ii）的概率，扩散游泳者越过单向障碍。半经典的结果与蒙特卡罗计算相比毫不逊色。1 ar X iv：2 10 8. 10 48 8v 2 [phys ic s.流量[2 2 N/2 02 1
We theoretically investigate the effect of random fluctuations on the motion of elongated microswimmers near hydrodynamic transport barriers in externally-driven fluid flows. Focusing on the two-dimensional hyperbolic flow, we consider the effects of translational and rotational diffusion as well as tumbling, i.e. sudden jumps in the swimmer orientation. Regardless of whether diffusion or tumbling are the primary source of fluctuations, we find that noise significantly increases the probability that a swimmer crosses one-way barriers in the flow, which block the swimmer from returning to its initial position. We employ an asymptotic method for calculating the probability density of noisy swimmer trajectories in a given fluid flow, which produces solutions to the timedependent Fokker-Planck equation in the weak-noise limit. This procedure mirrors the semiclassical approximation in quantum mechanics and similarly involves calculating the least-action paths of a Hamiltonian system derived from the swimmer’s Fokker-Planck equation. Using the semiclassical technique, we compute (i) the steady-state orientation distribution of swimmers with rotational diffusion and tumbling and (ii) the probability that a diffusive swimmer crosses a one-way barrier. The semiclassical results compare favorably with Monte Carlo calculations. 1 ar X iv :2 10 8. 10 48 8v 2 [ ph ys ic s. fl udy n] 2 2 N ov 2 02 1