Computational Fluid Dynamics Study of the Propulsion Characteristics of Tandem Flapping Fins

Ramamurti, Ravi; Geder, Jason; Viswanath, Kamal; Pruessner, Marius

doi:10.2514/6.2018-0039

Cited by 4 publications

(8 citation statements)

References 10 publications

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“…Based on our prior experience [9,28,29] and literature [15,31] we have opted for a bio-inspired trapezoidal fin with an aspect ratio of 3:1 (Figure 1b). This geometry produced greater thrust in a tandem two-fin configuration than an identical size and aspect ratio rectangular fin [29].…”

Section: B Fin Design Control and Kinematicsmentioning

confidence: 99%

“…For a given axial distance between flapping fins, stroke amplitude and frequency, there appears to be an advantage in terms of the thrust output of the rear fin when δ is varied [9,28,29]. Hence, we look at thrust and power measurements at several δ values to probe the same.…”

Section: A Thrust and Powermentioning

confidence: 99%

“…Our group has also performed multi-fin studies with larger heave amplitudes in the past. In 3D computational studies, Ramamurti et al investigated the effects of fin position and stroke phase offset between tandem pectoral fins [28] and between pectoral and caudal fins [29] where Φ = 20-55 • . Geder et al [30] experimentally investigated the effects of tandem pectoral fin parameters on stroke averaged thrust for that same flap amplitude range.…”

Section: Introductionmentioning

confidence: 99%

“…Motivated by the findings from Warkentin et al [27] and our prior efforts to experimentally characterize stroke-averaged forces for tandem fin systems [28,30], we use experimental thrust measurements, 2-D PIV and 3-D CFD simulations to analyze the flow structures generated by two pectoral fins flapping in close proximity at varying fin stroke phase offsets. The objective is to understand the flow mechanisms that control fin performance, based on which design of multi-fin systems with large heave amplitudes can be optimized and their implications on wake characterstics.…”

Section: Introductionmentioning

confidence: 99%

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Hydrodynamics of tandem flapping pectoral fins with varying stroke phase offsets

Sampath,

Geder,

Ramamurti

et al. 2020

Preprint

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We show how phasing between tandem bio-inspired fins flapping at high stroke amplitudes modulates rear fin thrust production and wake characteristics. Load cell thrust measurements show that the rear fin generates 25% more thrust than the front fin when it lags the latter by a quarter cycle, and performs 8% worse when it leads the front fin by the same amount. The flow interactions between the fins responsible for these observations are analyzed using 2-D particle image velocimetry (PIV) measurements and 3-D computational fluid dynamics (CFD) simulations. Distributions of velocity elucidate variations in the effective flow induced on the rear fin for different phase offsets. Vortex structure interactions and particle rakes reveal the contributions of the leading-and trailing-edge vortices shed by the front fin in modulating the suction at the rear fin leading edge. Furthermore, the wake structure far downstream of the fins changes in its coherence, axial and radial extents for the different phase offsets. These findings are relevant for the design and performance optimization of various unmanned underwater vehicles that utilize such tandem systems.

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Section: B Fin Design Control and Kinematicsmentioning

confidence: 99%

Section: A Thrust and Powermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Hydrodynamics of tandem flapping pectoral fins with varying stroke phase offsets

Sampath,

Geder,

Ramamurti

et al. 2020

Preprint

Self Cite

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show abstract

“…To characterize the effects of flow interactions between oscillating propulsive surfaces caused by time-varying wake structures, we have studied a configuration of tandem, identical geometry fins flapping perpendicular to the direction of flow [15], [16], similar to lift-based pectoral fin motions of some fish species [20]. Using the results of these previous studies, the current research seeks to design and evaluate surrogate models of stroke-averaged and time-varying thrust for this multi-fin system.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Surrogate Models for Multi-fin Flapping Propulsion Systems

Viswanath

Sharma

Gabbita

et al. 2019

Oceans 2019 MTS/Ieee Seattle

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The aim of this study is to develop surrogate models for quick, accurate prediction of thrust forces generated through flapping fin propulsion for given operating conditions and fin geometries. Different network architectures and configurations are explored to model the training data separately for the lead fin and rear fin of a tandem fin setup. We progressively improve the data representation of the input parameter space for model predictions. The models are tested on three unseen fin geometries and the predictions validated with computational fluid dynamics (CFD) data. Finally, the orders of magnitude gains in computational performance of these surrogate models, compared to experimental and CFD runs, vs their tradeoff with accuracy is discussed within the context of this tandem fin configuration.

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Fluid-Structure Modeling and the Effects of Passively Deforming Fins in Flapping Propulsion Systems

Geder

Ramamurti

Sampath

et al. 2021

OCEANS 2021: San Diego – Porto

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Computational Fluid Dynamics Study of the Propulsion Characteristics of Tandem Flapping Fins

Cited by 4 publications

References 10 publications

Hydrodynamics of tandem flapping pectoral fins with varying stroke phase offsets

Hydrodynamics of tandem flapping pectoral fins with varying stroke phase offsets

Evaluation of Surrogate Models for Multi-fin Flapping Propulsion Systems

Fluid-Structure Modeling and the Effects of Passively Deforming Fins in Flapping Propulsion Systems

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