Wang Mengying, Ottino Julio M, Umbanhowar Paul B, Lueptow Richard M
Department of Mechanical Engineering, Northwestern University, Evanston, Illinois, United States of America.
Department of Chemical and Biological Engineering, Northwestern University, Evanston, Illinois, United States of America.
PLoS One. 2025 Aug 7;20(8):e0329766. doi: 10.1371/journal.pone.0329766. eCollection 2025.
Removing dispersed material, such as pollutants, from dynamic fluid environments like the ocean or the atmosphere is challenging when the flow is chaotic. Here the capture of passive tracer particles by a mobile collector (MC) is studied in a model two-dimensional chaotic flow with vortices. Four simple capture strategies for determining the MC direction are considered, all of which rely on periodic measurement of the local particle distribution. The ultimate success of a strategy depends on its associated motion and detection parameters as well as the underlying fluid flow. When the flow is fully chaotic or the relative velocity of the MC is large, the four strategies exhibit nearly equal effectiveness. However, when the flow is less chaotic and the relative MC velocity is small, the collector can become trapped in or outside of a vortex. Changing the particle detection parameters can prevent trapping, which improves capture. In the absence of trapping and for both high and low relative velocities of the MC, a scaling analysis explains the dependence of the capture rate on the relevant dimensionless variables based on timescales for the mobile collector and the underlying flow. For a wide range of parameters and all four capture strategies, the capture timescale depends linearly on a combination of the characteristic kinematic timescale related to the relative motion of the collector and the gradient timescale related to the underlying flow field, confirming that the capture process is properly characterized.
在诸如海洋或大气等动态流体环境中，当流体流动呈混沌状态时，去除诸如污染物等分散物质极具挑战性。在此，我们研究了在一个具有涡旋的二维混沌流模型中，移动收集器（MC）对被动示踪粒子的捕获情况。我们考虑了四种用于确定MC方向的简单捕获策略，所有这些策略都依赖于对局部粒子分布的周期性测量。一种策略最终的成功与否取决于其相关的运动和检测参数以及潜在的流体流动。当流动完全混沌或MC的相对速度较大时，这四种策略表现出近乎相同的有效性。然而，当流动的混沌程度较低且MC的相对速度较小时，收集器可能会被困在涡旋内部或外部。改变粒子检测参数可以防止被困，从而提高捕获率。在不存在被困情况且MC相对速度无论高低时，尺度分析基于移动收集器和潜在流动的时间尺度，解释了捕获率对相关无量纲变量的依赖性。对于广泛的参数范围以及所有四种捕获策略，捕获时间尺度线性依赖于与收集器相对运动相关的特征运动学时间尺度和与潜在流场相关的梯度时间尺度的组合，这证实了捕获过程得到了恰当的表征。
