2025-05-05 ピッツバーグ大学
＜関連情報＞
- https://news.engineering.pitt.edu/pitt-researchers-reveal-how-tiny-swimmers-disrupt-ocean-flow-aps-recognizes-top-fluid-dynamics-paper-of-2024/
- https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.9.033101
- https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.7.094501
群がる活性物質と流れの相互作用： ラグランジュ型コヒーレント構造への影響 Interaction between swarming active matter and flow: The impact on Lagrangian coherent structures
Xinyu Si and Lei Fang
Physical Review Fluids Published: 8 March, 2024
DOI: https://doi.org/10.1103/PhysRevFluids.9.033101
Abstract
We conducted experiments using a typical centimeter swimmer, A. salina, and an electromagnetically driven quasi-two-dimensional flow to study the interaction between active matter and flow. The flow spanned from time-independent cellular flow to weakly time-dependent regimes. We focused on the impact of swarming active matter on hyperbolic Lagrangian coherent structures (LCSs) that mark the most straining regions in the flow. There is one decade of scale separation between active matter agents and the length scale of LCSs. We illustrated that the impact of active matter on LCSs was much more significant compared to localized random noise with similar energy input. In addition, we revealed that the perturbation generated by active matter could couple with the background flow and further deform the LCSs. In addition to the impact on the most straining hyperbolic regions of flow, we also revealed that the rotational elliptical region of the flow was much more susceptible to active matter perturbation in a Lagrangian perspective. We further described how the influence of active matter changed with their number densities and background flow intensities. We revealed that the LCSs could be decently altered even at a small number density of active matter. Through this work, we aim to provide valuable insights and draw attention to the problem regarding the interaction between active matter and external flow structures.
不均質な2次元乱流における遊泳体の優先輸送 Preferential transport of swimmers in heterogeneous two-dimensional turbulent flow
Xinyu Si and Lei Fang
Physical Review Fluids Published: 27 September, 2022
DOI: https://doi.org/10.1103/PhysRevFluids.7.094501
Abstract
We investigate the performance of active swimmers in a strongly heterogeneous two-dimensional weakly turbulent flow. The flow is heterogeneous in Reynolds number along one direction. Using a hybrid experimental-numerical model, we demonstrate that there are three regimes of preferential transport for rodlike swimmers as the swimmers’ intrinsic speed increases. Using Lagrangian statistics along swimmers’ trajectories, we reveal that the three regimes are due to the relative strengths of three different effects: the intrinsic speed of the swimmers, the reorientation ability of the shear layer at the interface of two flow regions, and the attracting Lagrangian coherent structures of the flow field. Our results elucidate the mechanism of preferential transport for swimmers in heterogeneous flow. We hope to raise researchers’ attention to the dynamics of swimmers in strongly heterogeneous flow environments.
