Hydrodynamic propulsion by large amplitude oscillation of an airfoil with chordwise flexibility

Katz, Joseph; Weihs, D.

doi:10.1017/s0022112078002220

Cited by 216 publications

(115 citation statements)

References 12 publications

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“…Flexibility across the chord can increase propulsive efficiency [13,14]. The efficiency of an oscillating, flexible hydrofoil is increased by 20% with a small decrease in thrust, compared to a rigid propulsor executing similar movements [13].…”

Section: Manta Efficiencymentioning

confidence: 99%

“…Bose et al [13] suggested that the phase difference due to this spanwise flexibility would prevent the total loss of thrust at the end of the stroke. On the other hand, chordwise flexibility at the trailing edge of the fins potentially could increase the efficiency with only a moderate decrease in the overall thrust [14,15]. Thus, efficiencies of actively swimming mantas may be higher than predicted by models of rigid lifting surfaces, because the flexible hydrofoils can help to increase propulsive efficiency.…”

Section: Introductionmentioning

confidence: 99%

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Hydrodynamic Performance of Aquatic Flapping: Efficiency of Underwater Flight in the Manta

et al. 2016

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Abstract:The manta is the largest marine organism to swim by dorsoventral oscillation (flapping) of the pectoral fins. The manta has been considered to swim with a high efficiency stroke, but this assertion has not been previously examined. The oscillatory swimming strokes of the manta were examined by detailing the kinematics of the pectoral fin movements swimming over a range of speeds and by analyzing simulations based on computational fluid dynamic potential flow and viscous models. These analyses showed that the fin movements are asymmetrical up-and downstrokes with both spanwise and chordwise waves interposed into the flapping motions. These motions produce complex three-dimensional flow patterns. The net thrust for propulsion was produced from the distal half of the fins. The vortex flow pattern and high propulsive efficiency of 89% were associated with Strouhal numbers within the optimal range (0.2-0.4) for rays swimming at routine and high speeds. Analysis of the swimming pattern of the manta provided a baseline for creation of a bio-inspired underwater vehicle, MantaBot.

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Section: Manta Efficiencymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hydrodynamic Performance of Aquatic Flapping: Efficiency of Underwater Flight in the Manta

et al. 2016

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“…Flexibility across the chord and span can increase thrust and propulsive efficiency (Katz and Weihs, 1978;Yamaguchi and Bose, 1994;Bose, 1995;Liu and Bose, 1997). Cambering by bending of the flukes throughout the stroke cycle could provide increased lift with a concomitant increase in thrust .…”

mentioning

confidence: 99%

Measurement of hydrodynamic force generation by swimming dolphins using bubble DPIV

Fish

Legac

Williams

et al. 2014

Journal of Experimental Biology

109

101

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Attempts to measure the propulsive forces produced by swimming dolphins have been limited. Previous uses of computational hydrodynamic models and gliding experiments have provided estimates of thrust production by dolphins, but these were indirect tests that relied on various assumptions. The thrust produced by two actively swimming bottlenose dolphins (Tursiops truncatus) was directly measured using digital particle image velocimetry (DPIV). For dolphins swimming in a large outdoor pool, the DPIV method used illuminated microbubbles that were generated in a narrow sheet from a finely porous hose and a compressed air source. The movement of the bubbles was tracked with a high-speed video camera. Dolphins swam at speeds of 0.7 to 3.4 m s −1 within the bubble sheet oriented along the midsagittal plane of the animal. The wake of the dolphin was visualized as the microbubbles were displaced because of the action of the propulsive flukes and jet flow. The oscillations of the dolphin flukes were shown to generate strong vortices in the wake. Thrust production was measured from the vortex strength through the Kutta-Joukowski theorem of aerodynamics. The dolphins generated up to 700 N during small amplitude swimming and up to 1468 N during large amplitude starts. The results of this study demonstrated that bubble DPIV can be used effectively to measure the thrust produced by large-bodied dolphins.

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“…A vast body of work concerning the functional role of passive flexibility in flapping wing systems can be found in the literature (see Shyy et al (2010) for a comprehensive review). The effects of passive flexibility on performance enhancement and some physical mechanisms underlying these effects have been addressed in several studies (Katz & Weihs 1978;Prempraneech, Hover & Triantafyllou 2003;Heathcote & Gursul 2007a;Michelin & Smith 2009;Eldredge, Toomey & Medina 2010;Spagnolie et al 2010; Thiria & Godoy-Diana † Email address for correspondence: zhangx@lnm.imech.ac.cn How flexibility affects wake symmetry properties 165 2010; Ramananarivo, Godoy-Diana & Thiria 2011;Kang et al 2011;Shoele & Zhu 2012).…”

mentioning

confidence: 99%

How flexibility affects the wake symmetry properties of a self-propelled plunging foil

Zhu

Zhang

2014

J. Fluid Mech.

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The wake symmetry properties of a flapping-foil system are closely associated with its propulsive performance. In the present work, the effect of the foil flexibility on the wake symmetry properties of a self-propelled plunging foil is studied numerically. We compare the wakes of a flexible foil and a rigid foil at a low flapping Reynolds number of 200. The two foils are of the same dimensions, flapping frequency, leading-edge amplitude and cruising velocity but different bending rigidities. The results indicate that flexibility can either inhibit or trigger the symmetry breaking of the wake. We find that there exists a threshold value of vortex circulation above which symmetry breaking occurs. The modification of vortex circulation is found to be the pivotal factor in the influence of the foil flexibility on the wake symmetry properties. An increase in flexibility can result in a reduction in the vorticity production at the leading edge because of the decrease in the effective angle of attack, but it also enhances vorticity production at the trailing edge because of the increase in the trailing-edge flapping velocity. The competition between these two opposing effects eventually determines the strength of vortex circulation, which, in turn, governs the wake symmetry properties. Further investigation indicates that the former effect is related to the streamlined shape of the deformed foil while the latter effect is associated with structural resonance. The results of this work provide new insights into the functional role of passive flexibility in flapping-based biolocomotion.

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Hydrodynamic propulsion by large amplitude oscillation of an airfoil with chordwise flexibility

Cited by 216 publications

References 12 publications

Hydrodynamic Performance of Aquatic Flapping: Efficiency of Underwater Flight in the Manta

Hydrodynamic Performance of Aquatic Flapping: Efficiency of Underwater Flight in the Manta

Measurement of hydrodynamic force generation by swimming dolphins using bubble DPIV

How flexibility affects the wake symmetry properties of a self-propelled plunging foil

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