Dynamic Barriers to Swimming Agents in Complex Fluid Flows

复杂流体流动中游动剂的动态势垒

• 批准号: 1825379
• 负责人: Kevin Mitchell
• 金额: $ 39万
• 依托单位: University of California - Merced
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-08-15 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1825379&HistoricalAwards=false
• 关键词: Dynamic; Barriers; Swimming; Agents; Complex

The motion, orientation, and control of self-propelled bodies in aqueous environments is an active field of scientific research. This field clearly has important engineering applications to, for example, swarms of autonomous underwater vehicles, collections of aerial drones, or swimming microrobots. This field is also important for understanding the fundamental physics of swimming organisms, such as bacteria, larvae, or even artificial colloidal particles. Many past studies focused on the interactions between bodies (agents) within a stationary ambient fluid; these interactions can lead to collective behavior like schooling, flocking, and group alignment. However, few studies have explored the motion of swimming agents in complicated flows that are caused by external disturbances. The current research will explore how isolated, self-propelled swimming agents are transported within such a flow. This is important for understanding swimming in the "real world", where swimmers often encounter nonnegligible, even turbulent, background flows. This work seeks to identify regions that are inaccessible to a swimmer, or accessible only after a long time. In many cases, these regions are delineated by geometric barriers that are not imposed by physical walls, but rather arise from subtle interactions between the dynamics of the swimmer and that of the flow. This work will develop techniques to predict where such barriers exist. These studies will be conducted in collaboration with a Bucknell University investigator, who is conducting experiments on bacteria in microfluidic flows.For several decades it has been understood that invariant manifolds are the critical structures controlling the transport of passive tracers in fluids exhibiting chaotic advection. More recently, Lagrangian coherent structures have provided an analogous framework for passive advection in unsteady, aperiodic flows. The objective of this research is to extend these theories to agents that are both advected in the fluid and propelled under their own power. The passive invariant manifolds, and Lagrangian coherent structures, are no longer the most relevant objects. Rather, new objects called swimming invariant manifolds (SwIMs), which depend explicitly on the swimming speed, appear to be the key structures. This research will develop the theoretical framework for SwIMs, assess their importance to the transport of swimmers, and apply this framework to various scenarios, including: (i) swimmers of differing aspect ratios; (ii) steady, periodic, and aperiodic fluid flows; (iii) flows in 2D and 3D; (iv) hyperbolic versus elliptic flows; (v) the influence of stochastic effects in the swimmer's direction, and (vi) interactions between swimmers.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

水环境中自走体的运动、定向和控制是一个活跃的科学研究领域。这一领域显然具有重要的工程应用，例如，自主水下航行器群、空中无人机集合或游泳微型机器人。这个领域对于理解游泳生物的基本物理学也很重要，比如细菌、幼虫，甚至人工胶体粒子。过去的许多研究集中在固定环境流体中物体（介质）之间的相互作用；这些相互作用会导致集体行为，如学校教育、群体聚集和群体结盟。然而，很少有研究探讨在外界干扰下复杂水流中游动因子的运动。目前的研究将探索孤立的、自我推进的游泳体是如何在这样的流中运输的。这对于理解“真实世界”中的游泳是很重要的，因为游泳者经常会遇到不可忽略的，甚至是湍流的背景流。这项工作旨在确定游泳者无法进入的区域，或者只有在很长一段时间后才能进入的区域。在许多情况下，这些区域是由几何屏障划定的，而不是由物理墙壁施加的，而是由游泳者和水流之间的动态微妙的相互作用产生的。这项工作将开发预测这些障碍存在的技术。这些研究将与巴克内尔大学的一名研究人员合作进行，他正在对微流体中的细菌进行实验。几十年来，人们已经认识到不变流形是控制无源示踪剂在混沌平流流体中输运的关键结构。最近，拉格朗日相干结构为非定常非周期流动中的被动平流提供了一个类似的框架。本研究的目的是将这些理论扩展到在流体中平流并在自身动力下推进的介质中。被动不变流形和拉格朗日相干结构不再是最相关的对象。相反，被称为游泳不变量流形（SwIMs）的新对象似乎是关键结构，它明确地依赖于游泳速度。本研究将开发游泳的理论框架，评估其对游泳者运输的重要性，并将该框架应用于各种场景，包括：(i)不同宽高比的游泳者；（ii）稳定的、周期性的和非周期性的流体流动；（iii）二维和三维流动；（iv）双曲流与椭圆流；(v)游泳者方向上随机效应的影响，以及（vi）游泳者之间的相互作用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

Noise-Induced Aggregation of Swimmers in the Kolmogorov Flow

科尔莫哥洛夫流中噪声引起的游泳者聚集

• DOI: 10.3389/fphy.2021.816663
• 发表时间: 2022
• 期刊: Frontiers in Physics
• 影响因子: 3.1
• 作者: Berman, Simon A.;Ferguson, Kyle S.;Bizzak, Nathaniel;Solomon, Thomas H.;Mitchell, Kevin A.
• 通讯作者: Mitchell, Kevin A.

Swimmer dynamics in externally driven fluid flows: The role of noise

• DOI: 10.1103/physrevfluids.7.014501
• 发表时间: 2021-08
• 期刊: Physical Review Fluids
• 影响因子: 2.7
• 作者: S. Berman;K. Mitchell

Transport barriers to self-propelled particles in fluid flows

• DOI: 10.1103/physrevfluids.6.l012501
• 发表时间: 2021-01-14
• 期刊: PHYSICAL REVIEW FLUIDS
• 影响因子: 2.7
• 作者: Berman, Simon A.;Buggeln, John;Solomon, Thomas H.
• 通讯作者: Solomon, Thomas H.

Trapping of swimmers in a vortex lattice

将游泳者困在涡格中

• DOI: 10.1063/5.0005542
• 发表时间: 2020
• 期刊: Chaos: An Interdisciplinary Journal of Nonlinear Science
• 作者: Berman, Simon A.;Mitchell, Kevin A.
• 通讯作者: Mitchell, Kevin A.

Barriers Impeding Active Mixing of Swimming Microbes in a Hyperbolic Flow

阻碍双曲线流中游动微生物主动混合的障碍

• DOI: 10.3389/fphy.2022.861616
• 发表时间: 2022
• 期刊: Frontiers in Physics
• 影响因子: 3.1
• 作者: Yoest, Helena;Buggeln, John;Doan, Minh;Johnson, Payton;Berman, Simon A.;Mitchell, Kevin A.;Solomon, Thomas H.
• 通讯作者: Solomon, Thomas H.