Vortex structure for flow over a heaving cylinder with a flexible tail

Hu, Yao-Wei; Pan, Chong; Wang, J. J.

doi:10.1007/s00348-014-1682-z

Cited by 10 publications

(4 citation statements)

References 20 publications

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“…In the experiment of Hu, Pan & Wang (2014), a circular cylinder with a FSP was forced to oscillate by the external sinusoidal excitation in the free stream, and the influence of the excitation frequency and L/D on the wake vortex structure was investigated. With the change of the excitation frequency and L/D , four different vortex shedding modes were observed in the wake, namely the 2S Kármán vortex, 2S reserved Kármán vortex, 2P mode and P + S mode.…”

Section: Introductionmentioning

confidence: 99%

Fluid–structure–sound interaction in noise reduction of a circular cylinder with flexible splitter plate

Fan

Wang

2021

J. Fluid Mech.

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Section: Introductionmentioning

confidence: 99%

Fluid–structure–sound interaction in noise reduction of a circular cylinder with flexible splitter plate

Fan

Wang

2021

J. Fluid Mech.

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“…Present study evaluates the effect of asymmetric oscillations of the cambered flexible wake splitter on the flow over a bluff body which has not been experimentally investigated yet. Moreover, the effective stiffness (П) of the present cambered flexible wake splitter (П =1.71) falls well in the range of chord-wise effective stiffness of few insects like bees and hawkmoths (0.19 ≤ П c ≤ 3.0) [6]. Equation (1) shows the expression for effective stiffness of the cambered flexible wake splitter,…”

Section: Introductionmentioning

confidence: 65%

“…The study also presented the effect of bending stiffness of the flexible splitter plate. In an experimental study it is shown that the flow characteristics of an oscillating circular cylinder significantly change with the increase in the length of the flexible tail particularly in between L/D = 3 & 4 [6]. The vortex shedding pattern changes from 2S_Karman mode at L/D = 2 to 2P mode at L/D = 3 and at L/D = 4 to 2S_reverse Karman vortex mode.…”

Section: Introductionmentioning

confidence: 99%

Flow Over a Square Cylinder With an Attached Cambered Flexible Wake Splitter

Sharma¹,

Dutta²

2019

Topical Problems of Fluid Mechanics 2019

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Particle Image Velocimetry (PIV) study is performed to analyse the effects of flow over a cambered flexible wake splitter attached to the lee side of a square cylinder at an intermediate Reynolds number (Re D = 600, where D is the blocking width of the cylinder). The study shows that the cambered flexible wake splitter (length, L = 8D) undergoes vortex induced, asymmetric low amplitude flapping due to which near wake becomes slightly asymmetric. The flexible film increases the centre line celerity in the wake by transferring momentum to the fluid downstream and reduces the wake width due to less entrainment of free stream fluid. Wake splitters beyond a particular length, interact with the primary vortices and shed secondary vortices on either side of the wake splitter due to Coanda effect. In the present study, shedding of asymmetric secondary vortices is observed which owes to the increased pressure in the lower wake envelope due to asymmetric flapping of the cambered splitter. The study indicates towards the positive lift generation due to asymmetric flapping of the cambered film.

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“…These two small-scale vortices are not the commonly thought trailing-edge vortex that is generated due to the motion of the film's trailing edge. For instance, in the experiment of Hu, Pan & Wang (2014), where a cylinder with a flexible film is forced to heave periodically in the free stream of a water tunnel, a clear trailing-edge vortex with a comparable size to that of the primary vortex is induced by the active downward or upward motion of the film's trailing edge. Besides, for the film of in the present investigation, a trailing edge vortex is formed from the shear layer induced by the motion of the trailing edge towards the negative direction (§ 3.5.1).…”

Section: Resultsmentioning

confidence: 99%

Passive bionic motion of a flexible film in the wake of a circular cylinder: chaos and periodicity, flow–structure interactions and energy evolution

Duan,

Wang

2024

J. Fluid Mech.

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The self-sustained interactions between a flexible film and periodic vortices epitomize the spirit of fish swimming and flag flapping in nature, involving intricate patterns of flow–structure coupling. Here, we comprehensively investigate the multiple coupling states of a film in the cylinder wake mainly with experiments, complemented by theoretical solutions and nonlinear dynamical analyses. Four regimes of film motion states are identified in the parameter space spanned by the reduced velocity and the length ratio. These regimes are (i) keeping stationary, (ii) deflection flutter, (iii) hybrid flutter and (iv) periodic large-amplitude flapping, each governed by a distinct coupling mechanism, involving regular and irregular Kármán vortices, local instability of the elongated shear layers and 2P mode vortex shedding. The film futtering in regimes (ii) and (iii) is substantiated to be chaotic and bears a resemblance to the ‘entraining state’ of fish behind an obstacle in the river. The periodic flapping in regime (iv) manifests itself in an amalgam of standing and travelling waves, and has intrinsic relations to the ‘Kármán gaiting’ of fish in periodic vortices. With the spatiotemporal reconstruction for the periodic flapping, we procure the energy distributions on the film, revealing the energy transfer processes between the film and the large-scale vortices. The findings unequivocally indicate that the flow–structure interaction during the energy-release stage of the film is more intense than that during the energy-extraction stage. Given the similarities, the mathematical and physical methods presented in this work are also applicable to the research on biological undulatory locomotion.

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Vortex structure for flow over a heaving cylinder with a flexible tail

Cited by 10 publications

References 20 publications

Fluid–structure–sound interaction in noise reduction of a circular cylinder with flexible splitter plate

Fluid–structure–sound interaction in noise reduction of a circular cylinder with flexible splitter plate

Flow Over a Square Cylinder With an Attached Cambered Flexible Wake Splitter

Passive bionic motion of a flexible film in the wake of a circular cylinder: chaos and periodicity, flow–structure interactions and energy evolution

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