Bulletin of the American Physical Society
77th Annual Meeting of the Division of Fluid Dynamics
Sunday–Tuesday, November 24–26, 2024; Salt Lake City, Utah
Session A05: Collective Behavior and Active Matter I: Fish schooling |
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Chair: Chengyu Li, Case Western Reserve University Room: Ballroom E |
Sunday, November 24, 2024 8:00AM - 8:13AM |
A05.00001: Learning to school through local sensory information Victor Bueno Garcia, Matthew Uffenheimer, On Shun Pak, Sina Heydari Fish schooling is a widely observed phenomenon in nature, providing benefits to individual fish through collective behavior. Recent studies have shown that stable formations can emerge through passive hydrodynamic interactions in schools of flapping swimmers, without the need for active control. These passive interactions, however, only lead to stable formations when the swimmers are highly coordinated and similar. Differences in their flapping motion and/or size can destabilize these formations and increase the cost of transport for the school. Here, we use a deep reinforcement learning algorithm to control the fapping motion of uncoordinated swimming agents to achieve cohesive schooling formations in a reduced-order model. The swimmers objective is to minimize the cost of transport for the whole group while only sensing the local flow field. We then test the robustness of our controller to perturbations in the swimmers motion and the flow field. Our results contribute to a deeper understating of fish schooling in nature and have potential applications in the design of autonomous underwater vehicle systems. |
Sunday, November 24, 2024 8:13AM - 8:26AM |
A05.00002: In the Wake of Turbulence: Just Keep Swimming…as a Group Michael A Calicchia, Rui Ni Schooling has been shown to be a mechanism utilized by fish to reduce their energy expenditure, particularly when navigating through harsh, turbulent environments. However, the way they interact with each other and the surrounding turbulence to achieve such efficient swimming remains elusive. To uncover the principles utilized by schooling fish when navigating through turbulence, experiments were performed with a school of Giant Danios (Devario Aequipinnatus). By leveraging a unique jet array system, the school was exposed to flow fields with controlled turbulence intensities and energy dissipation rates, while the mean flow and integral length scale were kept constant. Statistics regarding the school size, shape, and kinematics will be presented to quantify how the schooling behavior changes with increasing turbulent kinetic energy. Furthermore, turbulence characteristics of the wake behind the school will be reported to demonstrate how the school modulates the oncoming turbulence. |
Sunday, November 24, 2024 8:26AM - 8:39AM |
A05.00003: Startle Response Triggers Collective Phase Transitions in Schooling Fish Alyssa Chan, Eva Kanso Schooling fish often self-organize into collective patterns such as swarming, milling, or polarized schooling. A group of fish can transition between distinct states due to changes in behavioral rules, environmental factors, or stochastic events. A common stochastic event in fish schools is the startle response to perceived risk; startle is a socially contagious behavior that can propagate through the group, regardless of the presence of an external stimulus. Here, using known self-propelled particle models, we explore how individual-level startle responses influence the switch between distinct group motions in fish schools. This work contributes to understanding the mechanisms behind dynamic transitions and the propagation of responses to risk in collective animal behavior. |
Sunday, November 24, 2024 8:39AM - 8:52AM |
A05.00004: Schooling Fish in Challenging Geometries Hao Cheng, Chenchen Huang, Haotian Hang, Alex Barnett, Eva Kanso Fish often congregate into cohesive groups to navigate environments efficiently and safely, exhibiting various forms of collective motion such as milling, polarized schooling, and turning. Many computational models have been proposed to uncover the mechanisms behind these fascinating phenomena, though most focus on fish schools in unbounded domains. However, to understand how fish navigate and discover complex undersea structures like caves and tunnels, it is essential to formulate models of fish schools in confined domains. Here, we use high-order boundary integral equations to achieve non-penetration boundary conditions for 2D potential flow. We investigate how fish schools behave under confinement, with a narrow channel connecting two semicircular chambers. We examine the effects of this complex geometry on collective behavior, including the splitting and transition between the two chambers. We find surprising interplay between school size and school escape dynamics. Our models and results pave the way towards understanding survival strategies and collective behavior in challenging environments. |
Sunday, November 24, 2024 8:52AM - 9:05AM |
A05.00005: Coarse-grained analysis of extreme-scale fish school Haotian Hang, Chenchen Huang, Alex Barnett, Eva Kanso Collective behavior is ubiquitous in animal groups. In fish schools, global patterns emerge from individual-level behavioral rules and flow interactions. Here, we employed a model of schooling fish based on data-inferred behavioral rules and all-to-all far field inviscid hydrodynamic interaction with 2D dipole model. With the aid of high-performance parallel computing, we studied the emergent collective patterns in large schools of the order of 104 individuals. We found that the structures which emerge globally at lower number of fish (10-100), like milling, schooling, or turning, breakdown with increasing school size. Instead, the school dynamically scatters and reassembles into local structures with rich dynamics and polarization properties. Our preliminary efforts to analyze these dynamics indicate surprising interplay between fish density and local order. These findings pave the way towards creating a novel data-driven framework for describing extreme active matter with free boundaries. |
Sunday, November 24, 2024 9:05AM - 9:18AM |
A05.00006: Collective Swimming Dynamics in Robotic Fish Arrays Muhammad Usman, Hassan Masoud Group travel in animals, such as fish, often serves essential purposes like protection, survival, and endurance. Fish, in particular, face the challenge of hydrodynamic loads, prompting questions about the role of multi-body fluid-mediated interactions in collective swimming. We investigate these interactions using a rotational array of robotic fish with prescribed tail flapping motions, where the swimming speed of each robotic fish is determined by the resulting hydrodynamic effects. We examine how the collective speed of the robotic fish array is influenced by various parameters: the frequency and amplitude of tail flapping, the phase difference between the tail motions of neighboring robots, and the spacing between the fish. Additionally, we assess the cost of transport by measuring the power required to drive the flapping tails. By exploring a wide range of parameters, we identify conditions under which multi-body hydrodynamic interactions either enhance or hinder the swimming performance of the robotic fish array compared to a solo swimmer. Our findings provide valuable insights into the dynamics of collective swimming and the potential applications of robotic fish in understanding and replicating biological group behaviors. |
Sunday, November 24, 2024 9:18AM - 9:31AM |
A05.00007: Free-Swimming Performance and Stability of Schooling Non-Uniformly Flexible Hydrofoils Seyedali Seyedmirzaei Sarraf, Keith W Moored Recent tethered experiments have shown that non-uniform flexible hydrofoils not only have performance and energetic advantages over rigid and uniformly flexible ones, but a pair can also achieve high efficiency via schooling interactions. We present new experiments on a pair of freely-swimming non-uniformly flexible hydrofoils. We developed two wirelessly controllable air-bearing platforms equipped with a motion controller, a servomotor generating sinusoidal pitching motions of the foils, and a data acquisition system measuring energetics, swimming speed, and trajectories. Through video analysis the bending deformations of the foils are also acquired. We examine whether non-uniformly flexible foils can self-organize into stable formations, and their associated schooling benefits. We probe the fluid-structural coupling of the foils that can alter the self-organizational principles previously determined for rigid foils. |
Sunday, November 24, 2024 9:31AM - 9:44AM |
A05.00008: A study on the interaction of fish and marine hydrokinetic turbine wakes: Insights gained via laboratory tests and large-eddy simulations Hossein Seyedzadeh, Guglielmo Sonnino Sorisio, Catherine Wilson, Ali Khosronejad The study of fish behavior in the wake of marine hydrokinetic (MHK) turbines is vital to address the environmental sustainability of renewable energy technology. To gain insight into the connection between the fish behavior and fine-scale turbulent structures, we link the results from our high-resolution large eddy simulations (LES) to experimentally measured fish trajectories in the wake of vertical axis turbines (VAT). The LES results exhibit significant alignment with experimental data on fish behavior, providing a turbulence map to elucidate fish movement within the flow. In addition, the combined effects of rotational direction and lateral distance between twin vertical axis turbines on system efficiency is investigated. Comparative studies conducted in narrow and wide experimental flumes highlight critical factors affecting turbine performance and environmental compatibility. |
Sunday, November 24, 2024 9:44AM - 9:57AM |
A05.00009: Breaking the Mold: A New Way to School Elizabeth A Westfall, Yuanhang Zhu, Quinn Early, Daniel B Quinn A fish can improve its efficiency by swimming near other fish. Studying how neighbor-proximity affects performance leads to a better understanding of fish schools and robot swarms. Due to experimental limitations, vertical offsets between fish neighbors (i.e. offsets along the dorsoventral axis) have received less attention. If the vertically-separated foils are actuated in-phase, they can be placed on the same driveshaft, but out-of-phase actuations are more challenging to reproduce. We present here a new setup that uses horizontal airfoils to enable multi-hydrofoil, vertically separated, out-of-phase motions. We present preliminary force data, optimization tests, and particle image velocimetry (PIV) obtained with our new setup. We compare our results with vertically-separated, in-phase foils actuated with a single driveshaft (Re = 10k – 30k). |
Sunday, November 24, 2024 9:57AM - 10:10AM |
A05.00010: Effect of Schooling on Flow-Generated Noise in Fish: The Role of Fin Flapping Phase and Spatial Arrangement Ji Zhou, Jung-Hee Seo, Rajat Mittal High-fidelity simulations are utilized to investigate how schooling affects the noise generated by fish swimming with their caudal fins. The simulations capture both the flow and the far-field hydrodynamic sound produced by the fluctuating pressure on these carangiform swimmers. We explore the influence of the number of swimmers, the phase relationships of their fin movements, and their spatial configuration. Results indicate that the phase synchronization of fin movements is a crucial factor in the total sound emitted by a group of swimmers. In smaller schools, choosing an optimal phase relationship among the swimmers can greatly reduce the total sound radiated to the far-field. Additionally, the spatial arrangement of the swimmers impacts the overall noise production. In larger schools, even with highly uncoordinated fin movements, there is a significant reduction in far-field sound intensity. These findings have important implications for understanding fish behavior and the development of bioinspired aquatic vehicles. |
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