Simulating Vortex Wakes of Flapping Plates

Sheng, Jianxiong; Ysasi, A.; Kolomenskiy, Dmitry; Kanso, Eva; Nitsche, Monika; Schneider, Kai

doi:10.1007/978-1-4614-3997-4_21

Cited by 16 publications

(14 citation statements)

References 26 publications

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“…A vortex-sheet model is efficient for slightly viscous flow because it can present the flow using vortex sheet, which is only one-dimensional in a 2D flow. It allows flow separations at prescribed locations (usually sharp edges), but it agrees quantitatively with Navier-Stokes models in predicting the strength of shed circulation, and the location of the primary vortices in the wake of an oscillated plate 31 . Previous work also shows a good agreement of the vortex-sheet model in predicting the stability boundary of a flapping flag 16 .…”

Section: Introductionmentioning

confidence: 71%

Stability and scalability of piezoelectric flags

Wang

Alben

et al. 2016

Physics of Fluids

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1We investigate the effect of piezoelectric (PZT) material on the flutter speed, vibration mode and frequency, and energy harvesting power and efficiency of a flexible flag in various fluids. We develop a fully coupled fluid-solid-electric model by combining the inviscid vortex sheet model with a linear electro-mechanical coupling model. A resistance only circuit and a resonant resistance-inductance (RL) circuit are considered. For a purely resistive circuit, an increased electro-mechanical coupling factor results in an increased flutter speed, vibration frequency, averaged electric power and efficiency. A consistent optimal resistance is found that maximizes the flutter speed and the energy harvesting power. For a resonant RL circuit, by tuning the inductance to match the circuit frequency to the flag's vibration frequency, the flutter speed can be greatly decreased, and a larger averaged power and efficiency are obtained. We also consider a model scale set-up with several commonly used commercial materials for operating in air and water. Typical ranges of dimensionless parameters are obtained for four types of material that span a wide range of solid density and rigidity values. We find that the resistance only circuit is more effective when the flag is placed in a lighter fluid (e.g. air), while the RL circuit is able to reduce the flutter speed when the flag is placed in a heavier fluid (e.g. water).

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Section: Introductionmentioning

confidence: 71%

Stability and scalability of piezoelectric flags

Wang

Alben

et al. 2016

Physics of Fluids

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“…In this model, vortex sheets approximate the thin viscous boundary layers along the body, which are advected from its trailing edge into the flow downstream. This can be regarded as the inviscid limit of the viscous flow, and gives a good representation of the large-scale features of the flow and the vortex wake dynamics at Reynolds numbers of O(10 2 -10 5 ) [31,39,40]. These flows are challenging to simulate directly due to the need to resolve sharp layers of vorticity in the vicinity of an unsteady, possibly deforming solid boundary.…”

Section: Introductionmentioning

confidence: 99%

Large-amplitude membrane flutter in inviscid flow

Mavroyiakoumou

Alben

2020

J. Fluid Mech.

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We study the large-amplitude flutter of membranes (of zero bending rigidity) with vortex-sheet wakes in 2D inviscid fluid flows. We apply small initial deflections and track their exponential decay or growth and subsequent large-amplitude dynamics in the space of three dimensionless parameters: membrane pretension, mass density, and stretching modulus. With both ends fixed, all the membranes converge to steady deflected shapes with single humps that are nearly fore-aft symmetric, except when the deformations are unrealistically large. With leading edges fixed and trailing edges free, the membranes flutter with very small amplitudes and high spatial and temporal frequencies at small mass density. As mass density increases, the membranes transition to periodic and then increasingly aperiodic motions, and the amplitudes increase and spatial and temporal frequencies decrease. With both edges free, the membranes flutter similarly to the fixedfree case but also translate vertically with steady, periodic, or aperiodic trajectories, and with nonzero slopes that lead to small angles of attack with respect to the oncoming

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“…The comprehension of this intermediate range of Reynolds numbers requires the correct modelling of the vortex dynamics detaching from the swimmer, and considerable efforts in this sense have been widely documented in the literature (see e.g. Michelin et al 2008;Alben 2009;Sheng et al 2012, and references therein). Lighthill (1960) and Wu (1961) established the theoretical foundation to understand reactive force production in a perfect fluid in, respectively, the slender-body limit and the two-dimensional limit.…”

Section: Introductionmentioning

confidence: 99%

Modelling of an actuated elastic swimmer

2017

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We study the force production dynamics of undulating elastic plates as a model for fish-like inertial swimmers. Using a beam model coupled with Lighthill's large-amplitude elongated-body theory, we explore different localised actuations at one extremity of the plate (heaving, pitching, and a combination of both) in order to quantify the reactive and resistive contributions to the thrust. The latter has the form of a quadratic drag in large Reynolds number swimmers and has recently been pointed out as a crucial element in the thrust force balance. We validate the output of a weakly nonlinear solution to the fluid--structure model using thrust force measurements from an experiment with flexible plates subjected to the three different actuation types. The model is subsequently used in a self-propelled configuration ---with a skin friction model that balances thrust to produce a constant cruising speed--- to map the reactive versus resistive thrust production in a parameter space defined by the aspect ratio and the actuation frequency. We show that this balance is modified as the frequency of excitation changes and the response of the elastic plate shifts between different resonant modes, the pure heaving case being the most sensitive to the modal response with drastic changes in the reactive/resistive contribution ratio along the frequency axis. We analyse also the role of the phase lag between the heaving and pitching components in the case of combined actuation, showing in particular a non-trivial effect on the propulsive efficiency.Comment: 20 pages, 11 figure

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Simulating Vortex Wakes of Flapping Plates

Cited by 16 publications

References 26 publications

Stability and scalability of piezoelectric flags

Stability and scalability of piezoelectric flags

Large-amplitude membrane flutter in inviscid flow

Modelling of an actuated elastic swimmer

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