Foil locomotion through non-sinusoidal pitching motion

Das, Anil; Shukla, Ratnesh K.; Govardhan, Raghuraman N.

doi:10.1016/j.jfluidstructs.2019.01.020

Cited by 15 publications

(13 citation statements)

References 54 publications

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“…It is important to note that our observations are consistent with others in the literature who have studied changing motion profiles in particular, and found that performance metrics can be optimized by manipulating the waveform of an airfoil undergoing pitch and/or heave [6,37]. More recent studies by Das et al [39] and Van Buren et al [38] have shown that thrust is maximized with a square-like waveform while efficiency is maximized with a sinusoidal [38] or triangular [39] waveform. In the work presented here, we present a more detailed look at the flow field evolution due to particular features of the body motion, and how that may be contributing to the changes in performance.…”

Section: Discussionsupporting

confidence: 90%

“…In addition to geometry and simple sinusoidal motion, several works have investigated the effects of nonsinusoidal motion [4,6,[37][38][39][40]. Koochesfahani performed some of the earliest work in this area and found that deviating from a sinusoidal motion has significant effect on the wake structure [4].…”

Section: Introductionmentioning

confidence: 99%

“…Das et al, furthered this work using numerical simulations of a self-propelled airfoil. They found that maximum speed was attained with a square-like wave while the energetic efficiency was maximized with a triangle-like wave [39]. Qi et al, found that for small amplitude oscillations, altering the waveform from sinusoidal motion toward a square-like waveform improves performance [40].…”

Section: Introductionmentioning

confidence: 99%

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Experimental Study of Body-Fin Interaction and Vortex Dynamics Generated by a Two Degree-Of-Freedom Fish Model

Brooks

Green

2019

Biomimetics

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Oscillatory modes of swimming are used by a majority of aquatic swimmers to generate thrust. This work seeks to understand the phenomenological relationship between the body and caudal fin for fast and efficient thunniform swimming. Phase-averaged velocity data was collected and analyzed in order to understand the effects of body-fin kinematics on the wake behind a two degree-of-freedom fish model. The model is based on the yellowfin tuna (Thunnus albacares) which is known to be both fast and efficient. Velocity data was obtained along the side of the tail and caudal fin region as well as in the wake downstream of the caudal fin. Body-generated vortices were found to be small and have an insignificant effect on the caudal fin wake. The evolution of leading edge vortices formed on the caudal fin varied depending on the body-fin kinematics. The circulation produced at the trailing edge during each half-cycle was found to be relatively insensitive to the freestream velocity, but also varied with body-fin kinematics. Overall, the generation of vorticity in the wake was found to dependent on the trailing edge motion profile and velocity. Even relatively minor deviations from the commonly used model of sinusoidal motion is shown to change the strength and organization of coherent structures in the wake, which have been shown in the literature to be related to performance metrics such as thrust and efficiency.

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Section: Discussionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Experimental Study of Body-Fin Interaction and Vortex Dynamics Generated by a Two Degree-Of-Freedom Fish Model

Brooks

Green

2019

Biomimetics

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“…To this end, we rely on a high fidelity Lagrangian viscous vortex particle method (Cottet & Koumoutsakos 2000; Eldredge 2007), the details and validation tests can be found in our previous works (Das et al. 2016, 2019).…”

Section: Free and Restrained Self-propelled Foil Configurationsmentioning

confidence: 99%

“…2012; Zhu, He & Zhang 2014; Deng & Caulfield 2016; Verma et al. 2017; Das, Shukla & Govardhan 2019; Lin, Wu & Zhang 2021). This tendency emerges as the thrust produced from a sufficiently intense prescribed harmonic excitation surmounts the hydrodynamic resistance to the foil's motion.…”

Section: Introductionmentioning

confidence: 99%

Contrasting thrust generation mechanics and energetics of flapping foil locomotory states characterized by a unified - scaling

2021

Self Cite

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Self-propelled flapping foils with distinct locomotion-enabling kinematic restraints exhibit a remarkably similar Strouhal number ( $St$ )-Reynolds number ( $Re$ ) dependence. This similarity has been hypothesized to pervade diverse forms of oscillatory self-propulsion and undulatory biolocomotion; however, its genesis and implications on the energetic cost of locomotion remain elusive. Here, using high-resolution simulations of translationally free and restrained foils that self-propel as they are pitched, we demonstrate that a generality in the $St$ - $Re$ relationship can emerge despite significant disparities in thrust generation mechanics and locomotory performance. Specifically, owing to a recoil reaction induced passive heave, the fluid's inertial response to the prescribed rotational pitch, the principal source of thrust in unidirectionally free and towed configurations, ceases to produce thrust in a bidirectionally free configuration. Rather, the thrust generated from the leading edge suction mechanics self-propels a bidirectionally free pitching foil. Owing to the foregoing distinction in the thrust generation mechanics, the $St$ - $Re$ relationships for the bidirectionally and unidirectionally free/towed foils are dissimilar and pitching amplitude dependent, but specifically for large reduced frequencies, converge to a previously reported unified power law. Importantly, to propel at a given mean forward speed, the bidirectionally free foil must counteract the out-of-phase passive heave through a more intense rotational pitch, resulting in an appreciably higher power consumption over the range $10 \leq Re \leq 10^3$ . We highlight the critical role of thrust in introducing an offset in the $St$ - $Re$ relation, and through its amplification, being ultimately responsible for the considerable disparity in the locomotory performance of differentially constrained foils.

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Long-distance sinusoidal actuation in self-propelling apparatus: a novel spiral spring-based crank rocker mechanism

Joshi,

Arakeri

2024

Sādhanā

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Foil locomotion through non-sinusoidal pitching motion

Cited by 15 publications

References 54 publications

Experimental Study of Body-Fin Interaction and Vortex Dynamics Generated by a Two Degree-Of-Freedom Fish Model

Experimental Study of Body-Fin Interaction and Vortex Dynamics Generated by a Two Degree-Of-Freedom Fish Model

Contrasting thrust generation mechanics and energetics of flapping foil locomotory states characterized by a unified - scaling

Long-distance sinusoidal actuation in self-propelling apparatus: a novel spiral spring-based crank rocker mechanism

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