Collective Performance Benefits and Flow-Mediated Equilibrium for Schooling Swimmers by Melike Kurt (Southampton)

Duration: 37 mins 30 secs

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Collective Performance Benefits and Flow-Mediated Equilibrium for Schooling Swimmers by Melike Kurt (Southampton)'s image

Description:	Talk given by Dr Melike Kurt (University of Southampton) at Aerodynamics and Flight Mechanics group, University of Southampton on 2 February 2021, as part of the Southampton/AFM seminar series.


Created:	2021-02-16 10:36
Collection:	UKFN_Southampton_AFM
Publisher:	University of Cambridge
Copyright:	Dr Melike Kurt
Language:	eng (English)


Abstract:	Schooling fish are one of nature’s most fascinating examples with a myriad of hypotheses related to their functions. One potential function is that fish can experience performance improvements in terms of increased swimming speed or efficiency through the synchronization of body movements and hydrodynamic features. Additionally, freely swimming fish or fish-like swimmers experience forces, pushing and pulling them in multiple directions, that can directly affect the schooling order purely through hydrodynamic interactions. Here, we will examine these two aspects through the experiments using two pitching hydrofoils about their leading edges, as a simple representation of a fish school. First, force and flow measurements are conducted for hydrofoils in in-line and side-by-side arrangements, considering two- and/or three-dimensional flow conditions. These experiments reveal that, although performance improvements can be obtained in both flow conditions, alterations in the flow features can lead to significant differences in peak collective efficiency trends between the two- and three-dimensional interactions. Second, the effect of flow-mediated forces on schooling order has been examined. Experiments for a foil in ground effect (interacting with the ground) prove that there is indeed an equilibrium altitude where the foil experiences zero lift. Similarly, when the forces produced by two hydrofoils in the interaction plane are examined at an out-of-phase synchrony, the foils are found to be attracted into a stable equilibrium position in a side-by-side arrangement where the relative force experienced by individual foils is zero. In addition, the schooling swimmers experience a collective thrust and efficiency increase up to 100% and 40%, respectively, around this equilibrium position, whereas staggered arrangements yield thrust and efficiency gains up to 94% and 87%, respectively, compared to two hydrofoils in isolation. These newfound schooling performance and stability characteristics suggest that three-dimensionality considerations and fluid-mediated equilibria may play a role in the control strategies of schooling fish and fish-inspired robots.

Abstract:

Schooling fish are one of nature’s most fascinating examples with a myriad of hypotheses related to their functions. One potential function is that fish can experience performance improvements in terms of increased swimming speed or efficiency through the synchronization of body movements and hydrodynamic features. Additionally, freely swimming fish or fish-like swimmers experience forces, pushing and pulling them in multiple directions, that can directly affect the schooling order purely through hydrodynamic interactions. Here, we will examine these two aspects through the experiments using two pitching hydrofoils about their leading edges, as a simple representation of a fish school. First, force and flow measurements are conducted for hydrofoils in in-line and side-by-side arrangements, considering two- and/or three-dimensional flow conditions. These experiments reveal that, although performance improvements can be obtained in both flow conditions, alterations in the flow features can lead to significant differences in peak collective efficiency trends between the two- and three-dimensional interactions. Second, the effect of flow-mediated forces on schooling order has been examined. Experiments for a foil in ground effect (interacting with the ground) prove that there is indeed an equilibrium altitude where the foil experiences zero lift. Similarly, when the forces produced by two hydrofoils in the interaction plane are examined at an out-of-phase synchrony, the foils are found to be attracted into a stable equilibrium position in a side-by-side arrangement where the relative force experienced by individual foils is zero. In addition, the schooling swimmers experience a collective thrust and efficiency increase up to 100% and 40%, respectively, around this equilibrium position, whereas staggered arrangements yield thrust and efficiency gains up to 94% and 87%, respectively, compared to two hydrofoils in isolation. These newfound schooling performance and stability characteristics suggest that three-dimensionality considerations and fluid-mediated equilibria may play a role in the control strategies of schooling fish and fish-inspired robots.

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