Lunate-tail swimming propulsion as a problem of curved lifting line in unsteady flow. Part 1. Asymptotic theory

Cheng, H. K.; Murillo, Luis E.

doi:10.1017/s0022112084001373

Cited by 63 publications

(25 citation statements)

References 15 publications

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“…The lunate planform has been shown to be efficient in analytical models of unsteady, low amplitude propulsion (Lighthill, 1970;Cheng and Murillo, 1984;Karpouzian et al, 1990), originally applied to bony fish, sharks, whales and dolphins. The rigidity of the wings may indicate an attempt to maintain this efficient shape in straight and turning flight.…”

Section: Discussionmentioning

confidence: 99%

Vortex wake and flight kinematics of a swift in cruising flight in a wind tunnel

Henningsson

Spedding

Hedenström

2008

Journal of Experimental Biology

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SUMMARY In this paper we describe the flight characteristics of a swift (Apus apus) in cruising flight at three different flight speeds (8.0, 8.4 and 9.2 m s–1) in a low turbulence wind tunnel. The wingbeat kinematics were recorded by high-speed filming and the wake of the bird was visualized by digital particle image velocimetry (DPIV). Certain flight characteristics of the swift differ from those of previously studied species. As the flight speed increases, the angular velocity of the wingbeat remains constant, and so as the wingbeat amplitude increases, the frequency decreases accordingly, as though the flight muscles were contracting at a fixed rate. The wings are also comparatively inflexible and are flexed or retracted rather little during the upstroke. The upstroke is always aerodynamically active and this is reflected in the wake, where shedding of spanwise vorticity occurs throughout the wingbeat. Although the wake superficially resembles those of other birds in cruising flight, with a pair of trailing wingtip vortices connected by spanwise vortices, the continuous shedding of first positive vorticity during the downstroke and then negative vorticity during the upstroke suggests a wing whose circulation is gradually increasing and then decreasing during the wingbeat cycle. The wake (and implied wing aerodynamics)are not well described by discrete vortex loop models, but a new wake-based model, where incremental spanwise and streamwise variations of the wake impulse are integrated over the wingbeat, shows good agreement of the vertical momentum flux with the required weight support. The total drag was also estimated from the wake alone, and the calculated lift:drag ratio of approximately 13 for flapping flight is the highest measured yet for birds.

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Section: Discussionmentioning

confidence: 99%

Vortex wake and flight kinematics of a swift in cruising flight in a wind tunnel

Henningsson

Spedding

Hedenström

2008

Journal of Experimental Biology

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“…In principle, these relations can be extracted from any of the numerous studies published during the last 40 years; the works of Lighthill (1970), Chopra (1974Chopra ( , 1976, Chopra & Kambe (1977) and Cheng & Murillo (1984) are pertinent examples. Nonetheless, we prefer using none of them 'as is'.…”

Section: K1mentioning

confidence: 99%

Speed limits on swimming of fishes and cetaceans

Iosilevskii

Weihs

2007

J. R. Soc. Interface.

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Physical limits on swimming speed of lunate tail propelled aquatic animals are proposed. A hydrodynamic analysis, applying experimental data wherever possible, is used to show that small swimmers (roughly less than a metre long) are limited by the available power, while larger swimmers at a few metres below the water surface are limited by cavitation. Depending on the caudal fin cross-section, 10-15 m s K1 is shown to be the maximum cavitation-free velocity for all swimmers at a shallow depth.

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“…The tails of some of the fastest swimming animals closely resemble high aspect ratio foils. As a result, flapping foils have been studied extensively using theoretical and numerical techniques [72], [137], [138], [74], [13], [51], [83], [114], [115], [94], [95], and experimentally [109], [17], [68], [6], [98].…”

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confidence: 99%

Review of Experimental Work in Biomimetic Foils

Triantafyllou

Techet

Hover

2004

IEEE J. Oceanic Eng.

402

196

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Abstract-Significant progress has been made in understanding some of the basic mechanisms of force production and flow manipulation in oscillating foils for underwater use. Biomimetic observations, however, show that there is a lot more to be learned, since many of the functions and details of fish fins remain unexplored.This review focuses primarily on experimental studies on some of the, at least partially understood, mechanisms, which include 1) the formation of streets of vortices around and behind two-and three-dimensional propulsive oscillating foils; 2) the formation of vortical structures around and behind two-and three-dimensional foils used for maneuvering, hovering, or fast-starting; 3) the formation of leading-edge vortices in flapping foils, under steady flapping or transient conditions; 4) the interaction of foils with oncoming, externally generated vorticity; multiple foils, or foils operating near a body or wall.Index Terms-Biomimetics, fish swimming, flapping foil propulsion. I. OVERVIEW OF LITERATURE BIOMIMETIC studies and observations from fish and cetaceans have provided a wealth of information on the kinematics, i.e., how these animals employ their flapping tails and several fins to produce propulsive and maneuvering forces (see reviews in [123] The fluid mechanics and force mechanics of foils have been investigated with the goal of understanding the principles of this different paradigm of propulsion and maneuvering, so as to apply it to enhance existing technology. The tails of some of the fastest swimming animals closely resemble high aspect ratio foils. As a result, flapping foils have been studied extensively using theoretical and numerical techniques [72] II. BASIC PARAMETERS AND DEFINITIONSIn a foil with maximum chord length and maximum span , moving at steady speed , and at an angle of attack , the parameters of relevance are (a) the geometric shape (rectangular, delta-shaped, etc.); (b) the aspect ratio (AR), defined to be equal to the ratio of an average span over an average chord; (c) the angle of attack ; and (d) the Reynolds number , where is the kinematic viscosity of the fluid.

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Lunate-tail swimming propulsion as a problem of curved lifting line in unsteady flow. Part 1. Asymptotic theory

Cited by 63 publications

References 15 publications

Vortex wake and flight kinematics of a swift in cruising flight in a wind tunnel

Vortex wake and flight kinematics of a swift in cruising flight in a wind tunnel

Speed limits on swimming of fishes and cetaceans

Review of Experimental Work in Biomimetic Foils

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