The Influence of Boundary Layer Velocity Gradients and Bed Proximity on Vortex Shedding From Free Spanning Pipelines

Grass, Anthony J.; Raven, P. W. J.; Stuart, R. J.; Bray, J. A.

doi:10.1115/1.3231028

Cited by 114 publications

(59 citation statements)

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“…They also measured velocity fluctuations in the near wake of the cylinder to study the effect of h / d on the Strouhal number of the vortex shedding, St, and reported that the critical gap ratio ͑h / d͒ c , at which the spectral peak of the local velocity fluctuations disappeared, was 0.2-0.3 ͑it should be noted, however, that the disappearance of the spectral peak of the local velocity fluctuations does not necessarily ensure the global cessation of the vortex shedding 5 ͒. Similar measurements of local velocity fluctuations and thereby of ͑h / d͒ c were also carried out at higher and lower Reynolds numbers, [6][7][8] whereas more details of the global cessation of the Kármán vortex shedding were later visualized but only at lower Reynolds numbers, 5,9,10 as summarized in Table I.…”

Section: Introductionmentioning

confidence: 79%

“…It might still be possible to argue that the very thin boundary layer locally developed on the moving ground generates vorticity of opposite sign and thus to interfere with the separated shear layer from the bottom side of the cylinder, just like the cases with a thick boundary layer formed on a fixed ground. 8,24 Judging from the mean spanwise vorticity contours ͓cf. Figs.…”

Section: -7mentioning

confidence: 99%

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Vortex shedding from a circular cylinder near a moving ground

2007

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The flow and force characteristics have been experimentally investigated of a circular cylinder with an aspect ratio of 8.33, with and without end-plates, placed near and parallel to a moving ground, on which substantially no boundary layer developed to interfere with the cylinder. Mean drag and lift measurements, surface oil flow visualization, and particle image velocimetry ͑PIV͒ measurements were carried out at two upper-subcritical Reynolds numbers of 0.4 and 1.0ϫ 10 5 ͑based on the cylinder diameter d͒ to investigate the mechanisms of the ground effect, i.e., the effect of the gap-to-diameter ratio h / d, where h is the gap between the cylinder and the ground. For the cylinder with end-plates, on which the oil flow patterns were observed to be essentially two-dimensional, the drag rapidly decreased as h / d decreased to less than 0.5 but became constant for h / d of less than 0.35, unlike that usually observed near a fixed ground. This critical drag behavior was found to be directly related to a global change in the near wake structure of the cylinder; as h / d decreased the Kármán-type vortex shedding became intermittent at h / d = 0.4, and then totally ceased and instead two nearly parallel shear layers were formed behind the cylinder at h / d = 0.3 and below. For the cylinder without end-plates, however, no such critical change in drag was observed as the Kármán-type vortices were not generated in the near wake region at all h / d investigated. Based on the experimental results obtained, further discussions are also given to the essential cause of the cessation of the Kármán vortex shedding in the ground effect.

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Section: Introductionmentioning

confidence: 79%

Section: -7mentioning

confidence: 99%

Vortex shedding from a circular cylinder near a moving ground

2007

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“…The fundamental effects of gap ratio have been observed by Taneda (1965), Roshko et al (1975), Bearman and Zdravkovich (1978), Burest and Lanciotti (1979), Angrilli et al (1982), Grass et al (1984), Zdravkovich (1985a), Price et al (2002) and Lin et al (2005).…”

Section: Introductionmentioning

confidence: 83%

Simulation of viscous flow around a circular cylinder near a moving ground

Bimbato¹,

Pereira²,

Hirata³

2009

J. Braz. Soc. Mech. Sci. & Eng.

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“…There are a number of publications on experiments aimed at studying the effect of a boundary on the fluidstructure interaction forces for the case of stationary cylinders [13][14][15][16][17][18]. Important conclusions of these studies are that vortex shedding is suppressed for gaps smaller than one third of the cylinder's diameter, and that there is a mean cross-flow force that pushes the cylinder away from the boundary.…”

Section: Introductionmentioning

confidence: 99%

Vortex-induced vibrations of a freely vibrating cylinder near a plane boundary: Experimental investigation and theoretical modelling

Barbosa

Metrikine

et al. 2017

Journal of Fluids and Structures

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This work reports on experiments that were performed with a freely vibrating cylinder exposed to currents and placed near a plane boundary parallel to the cylinder axis. It is observed that the proximity of the boundary affects the vertical response of the cylinder in two ways: (i) for gaps between 0.75 and 2 diameters (D), the amplitude of oscillation is reduced; (ii) for gaps smaller than 0.75D, the cylinder impacts the boundary, resulting in an increase of amplitudes and frequencies of oscillations as the flow is accelerated. The in-line force acting on the cylinder is also examined, and the dependency of its harmonic components on the flow velocity and distance to the boundary is evaluated. Besides the typical amplification of the mean component inside the lock-in region, it is also observed that as the cylinder is placed closer to the boundary, the harmonic component with the frequency of the vertical oscillations increases, while the component with twice that frequency decreases in similar amount.Based on the experimental observations, an existing wake-oscillator model for vortex-induced vibrations is enhanced in order to account for the effect of the boundary. The proposed model introduces an effective damper that is activated when the cylinder reaches a certain distance from the boundary, and a damper/spring set representing the rigidity of the boundary and the dissipation of energy due to impact.

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The Influence of Boundary Layer Velocity Gradients and Bed Proximity on Vortex Shedding From Free Spanning Pipelines

Cited by 114 publications

References 0 publications

Vortex shedding from a circular cylinder near a moving ground

Vortex shedding from a circular cylinder near a moving ground

Simulation of viscous flow around a circular cylinder near a moving ground

Vortex-induced vibrations of a freely vibrating cylinder near a plane boundary: Experimental investigation and theoretical modelling

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