Wake topology and hydrodynamic performance of low-aspect-ratio flapping foils

Dong, Haibo; Mittal, Rajat; Najjar, Fady

doi:10.1017/s002211200600190x

Cited by 367 publications

(307 citation statements)

References 60 publications

(75 reference statements)

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“…It is worth pointing out that the evolution of braided vortices does not clearly exhibit the phenomena of "spanwise narrowing". This is different from the result of a flapping ellipsoidal foil in the work of Dong et al [22], but in agreement with that of Ellenrieder et al [23]. The appearance of the spanwise narrowing seems to be dependent on the morphology and the kinematics of the flapping foil.…”

Section: Wake Structuressupporting

confidence: 63%

“…These vortices braid together and are located within a narrow strip region along the horizontal axis of the fish body. The topology of the flow structures is also very similar to that of a flapping ellipsoidal foil in the work of Dong et al [22]. It is worth pointing out that the evolution of braided vortices does not clearly exhibit the phenomena of "spanwise narrowing".…”

Section: Wake Structuressupporting

confidence: 52%

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Numerical Simulation of a Three-Dimensional Fish-like Body Swimming with Finlets

Wang

Zhang

2012

Commun. comput. phys.

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Abstract. The swimming of a 3D fish-like body with finlets is numerically investigated at Re = 1000 (the Reynolds number is based on the uniform upstream flow and the length of the fish-like body). The finlets are simply modeled as thin rigid rectangular plates that undulate with the body. The wake structures and the flow around the caudal peduncle are studied. The finlets redirect the local flow across the caudal peduncle but the vortical structures in the wake are almost not affected by the finlets. Improvement of hydrodynamic performance has not been found in the simulation based on this simple model. The present numerical result is in agreement with that of the work of Nauen and Lauder

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Section: Wake Structuressupporting

confidence: 63%

Section: Wake Structuressupporting

confidence: 52%

Numerical Simulation of a Three-Dimensional Fish-like Body Swimming with Finlets

Wang

Zhang

2012

Commun. comput. phys.

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“…The 3D incompressible Navier-Stokes equations were discretized using a cell-centered, collocated arrangement of the primitive variables, and was solved using a finite difference-based Cartesian grid immersed boundary method [29]. The immersed-boundary treatment is the same as that in Dong et al [30]. The equations were integrated in time using the fractional step method, which consists of three-steps.…”

Section: Viscous Modelmentioning

confidence: 99%

“…This method was successfully applied in many simulations of flapping propulsion [31][32][33]. More details about this method can be found in [29,30]. Validations about this solver can be found in our previous works [32,34].…”

Section: Viscous Modelmentioning

confidence: 99%

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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“…Borazjani and Sotiropoulos carried out fluid-structure interaction simulations to investigate the hydrodynamic mechanism in carangiform swimming [24][25]. Dong et al simulated the motion flapping ellipsoidal foil and analyzed the wake structures [26]. Some other studies focused on the caudal fin propulsion, but the shapes of the caudal fins were usually simplified as plates or ellipsoidal foils.…”

Section: The Geometric Model Of a Caudal Finmentioning

confidence: 99%

Numerical Study on Hydrodynamic Performance of Bionic Caudal Fin

2016

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Abstract:In this work, numerical simulations are conducted to reveal the hydrodynamic mechanism of caudal fin propulsion. In the modeling of a bionic caudal fin, a universal kinematics model with three degrees of freedom is adopted and the flexible deformation in the spanwise direction is considered. Navier-Stokes equations are used to solve the unsteady fluid flow and dynamic mesh method is applied to track the locomotion. The force coefficients, torque coefficient, and flow field characteristics are extracted and analyzed. Then the thrust efficiency is calculated. In order to verify validity and feasibility of the algorithm, hydrodynamic performance of flapping foil is analyzed. The present results of flapping foil compare well with those in experimental researches. After that, the influences of amplitude of angle of attack, amplitude of heave motion, Strouhal number, and spanwise flexibility are analyzed. The results show that, the performance can be improved by adjusting the motion and flexibility parameters. The spanwise flexibility of caudal fin can increase thrust force with high propulsive efficiency.

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Wake topology and hydrodynamic performance of low-aspect-ratio flapping foils

Cited by 367 publications

References 60 publications

Numerical Simulation of a Three-Dimensional Fish-like Body Swimming with Finlets

Numerical Simulation of a Three-Dimensional Fish-like Body Swimming with Finlets

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

Numerical Study on Hydrodynamic Performance of Bionic Caudal Fin

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