Simulation of flexible filaments in a uniform flow by the immersed boundary method

Huang, Wei‐Xi; Shin, Soo Jai; Sung, Hyung Jin

doi:10.1016/j.jcp.2007.07.002

Cited by 371 publications

(303 citation statements)

References 32 publications

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“…Concerning the numerical implementation, following [6]'s formulation we discretise the Eq. 4 together with the in-extensibility condition with second order centered finite differences on a staggered, uniform one dimensional grid where the tension is collocated in the centre of each interval.…”

Section: Elastic Flaps and Filaments Modelmentioning

confidence: 99%

The PELskin project: part IV—control of bluff body wakes using hairy filaments

et al. 2016

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The passive control of bluff body wakes using a sparse layer of elastic hairy filaments has been investigated via a series of numerical simulations and compared to selected experiments under well-controlled boundary conditions. It has been found that a distribution of filaments spaced half of the dominant three dimensional instability and resonating with the main shedding frequency can drastically delay the three dimensional transition of the wake behind a circular cylinder. It will also be shown that when using a pair of rows of filaments symmetrically spaced by an azimuthal angle, the wake topology can be deeply affected as well as the value of the integral force coefficients of the cylinder. In the most favourable case, a coupled three dimensional transition delay and strongly reduced values of the drag and of the lift fluctuation can be simultaneously achieved. These results hold also for higher Reynolds-number flows as shown in experiments on a cylinder with hairy flaps attached to the aft part. The lock-in effect of structural vibration of the flaps with the vortex shedding is assumed to be the reason for a sudden change in the shedding cycle as soon as the motion amplitude is high enough to modify the wake. In line with this hypothesis, it has been demonstrated that a long elastic filament pinned on the centerline of a forced spatially developing mixing layer can interact with the vortex dynamics delaying the pairing process-leading to a reduced thickness of the layer. These findings show that a properly designed fluid structure interaction can indeed lead to technological benefits in terms of wake control: drag reduction, vibration control and possibly palliation of aeroacoustic emissions.

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Section: Elastic Flaps and Filaments Modelmentioning

confidence: 99%

The PELskin project: part IV—control of bluff body wakes using hairy filaments

et al. 2016

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“…The inextensibility condition of the filament is enforced by solving a Poisson equation for ζ [11][12][13]. Extensive validations of the immersed boundary solver can be found in Ref.…”

Section: Numerical Methods For Fsi Simulationmentioning

confidence: 99%

“…The motions of the fluid and the filament are governed by the Navier-Stokes equations coupled with a geometrically nonlinear structural equation [11][12][13] …”

Section: Governing Equationsmentioning

confidence: 99%

Underlying principle of efficient propulsion in flexible plunging foils

Zhu

Zhang

2014

Acta Mech Sin

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Passive flexibility was found to enhance propulsive efficiency in swimming animals. In this study, we numerically investigate the roles of structural resonance and hydrodynamic wake resonance in optimizing efficiency of a flexible plunging foil. The results indicates that (1) optimal efficiency is not necessarily achieved when the driving frequency matches the structural eigenfrequency; (2) optimal efficiency always occurs when the driving frequency matches the wake resonant frequency of the time averaged velocity profile. Thus, the underlying principle of efficient propulsion in flexible plunging foil is the hydrodynamic wake resonance, rather than the structural resonance. In addition, we also found that whether the efficiency can be optimized at the structural resonant point depends on the strength of the leading edge vortex relative to that of the trailing edge vortex. The result of this work provides new insights into the role of passive flexibility in flapping-based propulsion.

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“…Eq. (3) is equivalent to those used by Zhu and Peskin [37], Connell and Yue [38] and Huang et al [39] for flexible structures. Eq.…”

Section: Model Problem and Governing Equationsmentioning

confidence: 99%

“…(3) and (6)). We largely follow the discretization and solution procedure proposed by Huang et al [39], but make some modifications to the boundary conditions to allow free movement of the self-propelled foil in the horizontal direction.…”

Section: Structural Solvermentioning

confidence: 99%