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Hydrodynamics of Schooling: Stabilit...

Costa Ormonde, Pedro,

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Hydrodynamics of Schooling: Stability and Performance of Oscillatory Swimmers at High Reynolds Numbers /

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Hydrodynamics of Schooling: Stability and Performance of Oscillatory Swimmers at High Reynolds Numbers // Pedro Costa Ormonde.
作者:	Costa Ormonde, Pedro,
面頁冊數:	1 electronic resource (126 pages)
附註:	Source: Dissertations Abstracts International, Volume: 85-11, Section: B.
Contained By:	Dissertations Abstracts International85-11B.
標題:	Fluid mechanics. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30990050
ISBN:	9798382337609

Hydrodynamics of Schooling: Stability and Performance of Oscillatory Swimmers at High Reynolds Numbers /
Costa Ormonde, Pedro,

Hydrodynamics of Schooling: Stability and Performance of Oscillatory Swimmers at High Reynolds Numbers /Pedro Costa Ormonde. - 1 electronic resource (126 pages)

Source: Dissertations Abstracts International, Volume: 85-11, Section: B.

This dissertation work examines the hydrodynamic interactions that occur in fish schools. Oscillatory foils and fish-like robots are used as simple models to represent fish in a school with varying degrees of fidelity. Experiments are designed to study the stability and energetics of schooling formations at high Reynolds numbers. This methodology allows for a detailed observation of the flowfields, forces, and energetics and, consequently, a complete hydrodynamic description of the interactions that occur among schooling individuals. A novel robotic platform is developed to study the two-dimensional stability of self-propelled oscillatory swimmers. For the first time for high Reynolds number swimmers, the spontaneous self-organization of two two-dimensionally unconstrained pitching foils into a side-by-side formation is observed and the swimmers further enjoy at 15% increase in their swimming speed. A force map framework, constructed from time-averaged force measurements of constrained swimmers, is shown to successfully predict the stability features of a school of unconstrained swimmers. Three constrained 3D pitching foils (AR= 3) are used to study the mechanisms and energetics of a small school, specifically probing the classic diamond formation, a canonical arrangement largely studied due to its symmetry and hypothesized performance benefits. Significant collective performance gains of the trio are observed of approximately a doubling in thrust and a 60% increase in efficiency over three foils in isolation. Three distinct hydrodynamic mechanisms are also examined: vortex-body interactions, body-body interactions and the drafting mechanism. Compact schooling formations yield the highest measured energetic enhancements, and the drafting mechanism does not provide a hydrodynamic benefit for pitching hydrofoils. When a foil is directly in the jet flow downstream of another individual its performance is affected by the oncoming wake, and the spatial phase is traditionally used to define the synchronization between the wake flow and the foil kinematics. It is shown that: (1) a spatial phase model must use the actual wake wavelength rather than an assumed wake wavelength (freestream velocity times the period of oscillation) to predict performance peaks and troughs, and (2) a spatial phase model can predict the performance of a follower foil with the flowfield information from any upstream leader foils alone, i.e. the optimal placement of a follower downstream of leaders is known from the flows produced by the leaders. Finally, a high-fidelity experiment with 3D biorobots, inspired by the morphological features of the yellow-fin tuna, is performed to examine the streamwise stability of two interacting fish-like swimmers. A side-by-side formation is verified to be one-dimensionally stable in the streamwise direction. The stable formation was observed for both in-phase and out-of-phase tail beat synchronizations, in contrast to previous results for heaving hydrofoils for which the in-phase synchrony is unstable. The findings reported in this dissertation provide novel insights on the self-organization of fish schools and contribute to describe the hydrodynamic mechanisms that determine the energetics of swimming in a group.

English

ISBN: 9798382337609Subjects--Topical Terms:

528155
Fluid mechanics.
Subjects--Index Terms:

Biomimetics

Hydrodynamics of Schooling: Stability and Performance of Oscillatory Swimmers at High Reynolds Numbers /
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520 $a This dissertation work examines the hydrodynamic interactions that occur in fish schools. Oscillatory foils and fish-like robots are used as simple models to represent fish in a school with varying degrees of fidelity. Experiments are designed to study the stability and energetics of schooling formations at high Reynolds numbers. This methodology allows for a detailed observation of the flowfields, forces, and energetics and, consequently, a complete hydrodynamic description of the interactions that occur among schooling individuals. A novel robotic platform is developed to study the two-dimensional stability of self-propelled oscillatory swimmers. For the first time for high Reynolds number swimmers, the spontaneous self-organization of two two-dimensionally unconstrained pitching foils into a side-by-side formation is observed and the swimmers further enjoy at 15% increase in their swimming speed. A force map framework, constructed from time-averaged force measurements of constrained swimmers, is shown to successfully predict the stability features of a school of unconstrained swimmers. Three constrained 3D pitching foils (AR= 3) are used to study the mechanisms and energetics of a small school, specifically probing the classic diamond formation, a canonical arrangement largely studied due to its symmetry and hypothesized performance benefits. Significant collective performance gains of the trio are observed of approximately a doubling in thrust and a 60% increase in efficiency over three foils in isolation. Three distinct hydrodynamic mechanisms are also examined: vortex-body interactions, body-body interactions and the drafting mechanism. Compact schooling formations yield the highest measured energetic enhancements, and the drafting mechanism does not provide a hydrodynamic benefit for pitching hydrofoils. When a foil is directly in the jet flow downstream of another individual its performance is affected by the oncoming wake, and the spatial phase is traditionally used to define the synchronization between the wake flow and the foil kinematics. It is shown that: (1) a spatial phase model must use the actual wake wavelength rather than an assumed wake wavelength (freestream velocity times the period of oscillation) to predict performance peaks and troughs, and (2) a spatial phase model can predict the performance of a follower foil with the flowfield information from any upstream leader foils alone, i.e. the optimal placement of a follower downstream of leaders is known from the flows produced by the leaders. Finally, a high-fidelity experiment with 3D biorobots, inspired by the morphological features of the yellow-fin tuna, is performed to examine the streamwise stability of two interacting fish-like swimmers. A side-by-side formation is verified to be one-dimensionally stable in the streamwise direction. The stable formation was observed for both in-phase and out-of-phase tail beat synchronizations, in contrast to previous results for heaving hydrofoils for which the in-phase synchrony is unstable. The findings reported in this dissertation provide novel insights on the self-organization of fish schools and contribute to describe the hydrodynamic mechanisms that determine the energetics of swimming in a group.
546 $a English
590 $a School code: 0105
650 4 $a Fluid mechanics. $3 528155
650 4 $a Mechanics. $3 525881
650 4 $a Mechanical engineering. $3 649730
653 $a Biomimetics
653 $a Bio propulsion
653 $a Reynolds propulsion
653 $a Hydrodynamics
653 $a Oscillatory foils
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710 2 $a Lehigh University. $b Mechanical Engineering. $e degree granting institution. $3 3770463
720 1 $a Moored, Keith W. $e degree supervisor.
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