Large-Amplitude Intermittent Swimming in Viscous and Inviscid Flows

Akoz, Emre; Pan, Han; Li, Geng; Dong, Haibo; Moored, Keith W.

doi:10.2514/1.j056637

Cited by 13 publications

(18 citation statements)

References 20 publications

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“…Further details of the method and extensive validations of the solver can be found in [32]. Further validations and applications of the solver can be found in [21,23,33,37,48].…”

Section: Methodsmentioning

confidence: 99%

Three-dimensional scaling laws of cetacean propulsion characterize the hydrodynamic interplay of flukes' shape and kinematics

Ayancik

Fish

Moored

2020

J. R. Soc. Interface.

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Cetaceans convert dorsoventral body oscillations into forward velocity with a complex interplay between their morphological and kinematic features and the fluid environment. However, it is unknown to what extent morpho-kinematic features of cetaceans are intertwined to maximize their efficiency. By interchanging the shape and kinematic variables of five cetacean species, the interplay of their flukes morpho-kinematic features is examined by characterizing their thrust, power and propulsive efficiency. It is determined that the shape and kinematics of the flukes have considerable influence on force production and power consumption. Three-dimensional heaving and pitching scaling laws are developed by considering both added mass and circulatory-based forces, which are shown to closely model the numerical data. Using the scaling relations as a guide, it is determined that the added mass forces are important in predicting the trend between the efficiency and aspect ratio, however, the thrust and power are driven predominately by the circulatory forces. The scaling laws also reveal that there is an optimal dimensionless heave-to-pitch ratio h* that maximizes the efficiency. Moreover, the optimal h* varies with the aspect ratio, the amplitude-to-chord ratio and the Lighthill number. This indicates that the shape and kinematics of propulsors are intertwined, that is, there are specific kinematics that are tailored to the shape of a propulsor in order to maximize its propulsive efficiency.

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“…Further details of the method and extensive validations of the solver can be found in [32]. Further validations and applications of the solver can be found in [21,23,33,37,48].…”

Section: Methodsmentioning

confidence: 99%

Three-dimensional scaling laws of cetacean propulsion characterize the hydrodynamic interplay of flukes' shape and kinematics

Ayancik

Fish

Moored

2020

J. R. Soc. Interface.

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“…Importantly, they surmised that if metabolic energy losses were considered, continuous swimming may be preferable to burst-and-coast motion. Akoz et al [16] also investigated pitching airfoils using both viscous and inviscid two-dimensional numerical simulations. Chung [17] performed two-dimensional numerical simulations showing energy savings associated with burstand-coast swimming, and attributed this to differences in the wake structure between burst-coast and continuous swimming.…”

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confidence: 99%

Burst-and-coast swimming is not always energetically beneficial in fish (Hemigrammus bleheri)

2020

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Burst-and-coast swimming is an intermittent mode of locomotion used by various fish species. The intermittent gait has been associated with certain advantages such as stabilizing the visual field, improved sensing ability, and reduced energy expenditure. We investigate burst-coast swimming in rummy nose tetra fish (Hemigrammus bleheri) using a combination of experimental data and numerical simulations. The experiments were performed in a shallow water channel where the tetra fish swam against an imposed inflow. High speed video recordings of the fish were digitized to extract the undulatory kinematics at various swimming speeds. The kinematics data were then used in Navier–Stokes simulations to prescribe the undulatory motion for three-dimensional geometrical models of the fish. The resulting steady-state speeds of the simulated self-propelled swimmers agree well with the speeds observed experimentally. We examine the power requirements for various realistic swimming modes, which indicate that it is possible to use continuous swimming gaits that require considerably less mechanical energy than intermittent burst-coast modes at comparable speeds. The higher energetic cost of burst-coast swimming suggests that the primary purpose of intermittent swimming may not be to conserve energy, but it may instead be related to a combination of other functional aspects such as improved sensing and the likely existence of a minimum tail-beat frequency. Importantly, using sinusoidal traveling waves to generate intermittent and continuous kinematics, instead of using experiment-based kinematics, results in comparable power requirements for the two swimming modes.

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“…A clear evidence of the classical U-shaped form for the COT curves 35 , 36 is obtained and a minimum value appears in a quite small range about . The presence of a virtual body allows also for the calculation of the propulsor efficiency since the thrust, balancing the known drag at cruising speed, is now available 37 , 38 . Interestingly, the range where we find the maximum efficiency of the propulsor, reported in Fig.…”

Section: Resultsmentioning

confidence: 99%

The performance of a flapping foil for a self-propelled fishlike body

Paniccia

Padovani

Graziani

et al. 2021

Sci Rep

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Several fish species propel by oscillating the tail, while the remaining part of the body essentially contributes to the overall drag. Since in this case thrust and drag are in a way separable, most attention was focused on the study of propulsive efficiency for flapping foils under a prescribed stream. We claim here that the swimming performance should be evaluated, as for undulating fish whose drag and thrust are severely entangled, by turning to self-propelled locomotion to find the proper speed and the cost of transport for a given fishlike body. As a major finding, the minimum value of this quantity corresponds to a locomotion speed in a range markedly different from the one associated with the optimal efficiency of the propulsor. A large value of the feathering parameter characterizes the minimum cost of transport while the optimal efficiency is related to a large effective angle of attack. We adopt here a simple two-dimensional model for both inviscid and viscous flows to proof the above statements in the case of self-propelled axial swimming. We believe that such an easy approach gives a way for a direct extension to fully free swimming and to real-life configurations.

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Large-Amplitude Intermittent Swimming in Viscous and Inviscid Flows

Cited by 13 publications

References 20 publications

Three-dimensional scaling laws of cetacean propulsion characterize the hydrodynamic interplay of flukes' shape and kinematics

Three-dimensional scaling laws of cetacean propulsion characterize the hydrodynamic interplay of flukes' shape and kinematics

Burst-and-coast swimming is not always energetically beneficial in fish (Hemigrammus bleheri)

The performance of a flapping foil for a self-propelled fishlike body

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