Vortex shedding from a circular cylinder in moderate-Reynolds-number shear flow

Kiya, Masaru; Tamura, Hisataka; Arie, Mikio

doi:10.1017/s0022112080001899

Cited by 108 publications

(84 citation statements)

References 6 publications

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“…Some contradictory results were however reported in comparable Reynolds number ranges, for example an increase of the time-averaged in-line force with the shear parameter , and no clear trend was identified concerning the effect of the shear on the vortex shedding frequency. The suppression of vortex shedding beyond a critical value of the shear parameter, observed by Kiya et al (1980) and Tamura et al (1980), but also by Cheng, Whyte & Lou (2007) in the case of a square cylinder, for Re < 200, was generally not reported in other works. In sheared current, the Reynolds number is defined based on the inflow velocity at the centre of the body.…”

Section: Introductionmentioning

confidence: 68%

Vortex-induced vibrations of a cylinder in planar shear flow

2017

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 18137 The system composed of a circular cylinder, either fixed or elastically mounted, and immersed in a current linearly sheared in the cross-flow direction, is investigated via numerical simulations. The impact of the shear and associated symmetry breaking are explored over wide ranges of values of the shear parameter (non-dimensional inflow velocity gradient, β ∈ [0, 0.4]) and reduced velocity (inverse of the non-dimensional natural frequency of the oscillator, U * ∈ [2, 14]), at Reynolds number Re = 100; β, U * and Re are based on the inflow velocity at the centre of the body and on its diameter. In the absence of large-amplitude vibrations and in the fixed body case, three successive regimes are identified. Two unsteady flow regimes develop for β ∈ [0, 0.2] (regime L) and β ∈ [0.2, 0.3] (regime H). They differ by the relative influence of the shear, which is found to be limited in regime L. In contrast, the shear leads to a major reconfiguration of the wake (e.g. asymmetric pattern, lower vortex shedding frequency, synchronized oscillation of the saddle point) and a substantial alteration of the fluid forcing in regime H. A steady flow regime (S), characterized by a triangular wake pattern, is uncovered for β > 0.3. Free vibrations of large amplitudes arise in a region of the parameter space that encompasses the entire range of β and a range of U * that widens as β increases; therefore vibrations appear beyond the limit of steady flow in the fixed body case (β = 0.3). Three distinct regimes of the flow-structure system are encountered in this region. In all regimes, body motion and flow unsteadiness are synchronized (lock-in condition). For β ∈ [0, 0.2], in regime VL, the system behaviour remains close to that observed in uniform current. The main impact of the shear concerns the amplification of the in-line response and the transition from figure-eight to ellipsoidal orbits. For β ∈ [0.2, 0.4], the system exhibits two well-defined regimes: VH1 and VH2 in the lower and higher ranges of U * , respectively. Even if the wake patterns, close to the asymmetric pattern observed in regime H, are comparable in both regimes, the properties of the vibrations and fluid forces clearly depart. The responses differ by their spectral contents, i.e. sinusoidal versus multi-harmonic, and their amplitudes are much larger in regime VH1, where the in-line responses reach 2 diameters (0.03 diameters in uniform flow) and the cross-flow responses 1.3 diameters. Aperiodic, intermittent oscillations are found to occur in the transition region between regimes VH1 and VH2; it appears that wake-body synchronization persists in this case.

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Section: Introductionmentioning

confidence: 68%

Vortex-induced vibrations of a cylinder in planar shear flow

2017

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“…For the square cylinder case, Ayukawa et al [9] and Hwang and Sue [10] reported positive mean lift coefficient (lift force acting from low velocity side to high velocity side), whereas Cheng et al [13,14] and Lankadasu and Vengadesan [15,16] reported negative mean lift coefficient. For the circular cylinder case, Kiya et al [18] and Kwon et al [19] reported positive mean lift coefficient whereas others reported negative mean lift coefficient. The reason for the above discrepancy among the reported mean lift coefficient is attributed to the number of parameters necessary viz, Reynolds number, blockage ratio, three-dimensionality effect, geometry and magnitude of the shear or combinations of any of these.…”

Section: Introductionmentioning

confidence: 97%

“…Non-uniform flow could be either a linear or nonlinear variation of the longitudinal velocity component magnitude in the transverse direction. As a starting point, linear shear flow past a square cylinder [9][10][11][12][13][14][15][16] as well as a circular cylinder [17][18][19][20][21][22][23] has been studied. Except experimental results of Kiya et al [18] and 1116 A. LANKADASU AND S. VENGADESAN Kwon et al [19], all others reported that Strouhal number either decreases or remains constant and the mean drag coefficient decreases with increasing shear parameter.…”

Section: Introductionmentioning

confidence: 99%

Shear effect on square cylinder wake transition characteristics

Lankadasu

Vengadesan

2010

Numerical Methods in Fluids

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SUMMARYThe transition of square cylinder wake flow from two-dimensional (2-D) to three-dimensional (3-D) when inflow is subjected to linear shear is examined numerically. The value of the non-dimensional shear parameter (K ) considered in this study are 0.0, 0.1, and 0.2. The range of Reynolds number (Re) defined based on the centerline velocity and cylinder width is from Re = 150 to 700. The transition of the wake flow from 2-D laminar to 3-D is marked by streamwise vortical structures. Unlike in uniform flow, in shear flow the transition is characterized by single mode of spanwise wavelength. The critical Reynolds number (Re crit ), at which the transition from 2-D to 3-D occurs, is less in case of shear flow. The magnitude of the mean lift coefficient increases with increasing shear parameter on the positive side. The strength of the Karman vortices on the top side is higher and on the bottom side is lower when compared with the same in the uniform flow.

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“…The mean lift and drag coefficients tended to decrease with increasing the shear parameter. They also observed that the vortex shedding frequency tended to decrease with the increase of the shear parameter, although they highlighted that this observation was opposite to the one obtained by Kiya et al (1980) when studying shear flow past circular cylinders. Lankadasu and Vengadesan (2008) also reported a decrease in the mean lift and drag coefficients with increasing shear, and for a given Reynolds number.…”

Section: Introductionmentioning

confidence: 84%

“…It was shown by previous investigations on circular cylinders, e.g., Jordan and Fromm (1972), Kiya et al (1980), Kwon et al (1992), Mukhopadhyay et al (1999), Xu and Dalton (2001), Sumner and Akosile (2003), that the flow approaching with linear shear greatly alters the vortex dynamics in the wake, when compared to the uniform flow case. They attributed this phenomenon to the constant vorticity embedded in the free-stream.…”

Section: Introductionmentioning

confidence: 92%

A numerical investigation of wake and mixing layer interactions of flow past a square cylinder

Mushyam

Bergadà

2016

Meccanica

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Aquesta és una còpia de la versió author's final draft d'un article publicat a la revista Meccanica.La publicació final està disponible a Springer a través de http://dx.doi.org/10.1007/s11012-016-0400-8 This is a copy of the author 's final draft version of an article published in the journal Meccanica. Abstract:The aim of the present study is to simulate and analyze the interaction of two dimensional flow past a square cylinder in a laminar regime with an upstream mixing layer developed by an axis symmetrical horizontal splitter plate. The mixing layer is generated upstream of the square cylinder by mixing two uniform streams of fluid with different velocities above and below the splitter plate. A range of upstream domain lengths, distances between the splitter plate and the square cylinder, and upstream velocity ratios between the two streams of fluid are analyzed. Unconfined flow over a square cylinder placed in uniform upstream flow is initially analyzed as it plays a crucial role in understanding the properties of the wake. The results are compared with the existing literature to validate the code developed and they are found to be in very good agreement. It is observed from the present study that at smaller velocity ratios, the vortices shed into the wake consist of both clockwise and anticlockwise moment vortices. As velocity ratio is increased only clockwise moment vortices are shed downstream and anticlockwise vortices are shed as Kelvin-Helmholtz instabilities. In all simulations undertaken the same phenomena is observed independent of the upstream Reynolds number, indicating that velocity ratio is a primary parameter influencing the flow. Different instability modes were observed and they were highly dependent on the upstream velocity ratio.

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Vortex shedding from a circular cylinder in moderate-Reynolds-number shear flow

Cited by 108 publications

References 6 publications

Vortex-induced vibrations of a cylinder in planar shear flow

Vortex-induced vibrations of a cylinder in planar shear flow

Shear effect on square cylinder wake transition characteristics

A numerical investigation of wake and mixing layer interactions of flow past a square cylinder

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