Wind-induced instability of structures

Parkinson, G. V.

doi:10.1098/rsta.1971.0040

Cited by 65 publications

(14 citation statements)

References 6 publications

(8 reference statements)

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“…Following an analysis presented by Parkinson (1971) and others, the displacement of a cylinder under VIV may be expressed by the harmonic response…”

Section: Analytical Modelling and Preliminary Resultsmentioning

confidence: 99%

On the wake-induced vibration of tandem circular cylinders: the vortex interaction excitation mechanism

2010

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The mechanism of wake-induced vibrations (WIV) of a pair of cylinders in a tandem arrangement is investigated by experiments. A typical WIV response is characterized by a build-up of amplitude persisting to high reduced velocities; this is different from a typical vortex-induced vibration (VIV) response, which occurs in a limited resonance range. We suggest that WIV of the downstream cylinder is excited by the unsteady vortex-structure interactions between the body and the upstream wake. Coherent vortices interfering with the downstream cylinder induce fluctuations in the fluid force that are not synchronized with the motion. A favourable phase lag between the displacement and the fluid force guarantees that a positive energy transfer from the flow to the structure sustains the oscillations. If the unsteady vortices are removed from the wake of the upstream body then WIV will not be excited. An experiment performed in a steady shear flow turned out to be central to the understanding of the origin of the fluid forces acting on the downstream cylinder.Key words: flow-structure interactions, vortex flows, wakes/jets IntroductionGreat strides have been made in understanding the mechanisms involved in vortexinduced vibration (VIV) of an isolated circular cylinder free to vibrate transverse and/or in-line to a fluid flow. Progress has been reviewed by Sarpkaya (1979Sarpkaya ( , 2004, Bearman (1984), Parkinson (1989), Blevins (1990) and Williamson & Govardhan (2004). With the development of offshore oil fields and the deployment of riser pipes, much of the research related to cylinder response focused on conditions with low mass ratio m * and damping ζ . Here, m * is the ratio of mass per unit length of the structure, m, to fluid displaced, ρπD 2 /4, where ρ is fluid density, D is cylinder diameter and ζ is structural damping expressed as a fraction of critical damping. This research revealed a number of extremely interesting phenomena associated with VIV of isolated cylinders.However, there are many flow-induced vibration (FIV) problems that involve two or more cylinders in configurations where the flow field of one cylinder influences

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“…Following an analysis presented by Parkinson (1971) and others, the displacement of a cylinder under VIV may be expressed by the harmonic response…”

Section: Analytical Modelling and Preliminary Resultsmentioning

confidence: 99%

On the wake-induced vibration of tandem circular cylinders: the vortex interaction excitation mechanism

2010

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“…Among the various bluff sections, circular, square and rectangular bodies have received more research attention due to their wide application possibilities. Compared to a circular cylinder, prismatic bodies (non-circular) such as square and rectangular sections could pose additional aerodynamic challenges such as the galloping phenomenon [1,2]). Also, these sections (square and rectangular) are successfully employed in a variety of practical situations such as in bridges, buildings and also in marine applications.…”

Section: Introductionmentioning

confidence: 99%

Influence of corner radius on the near wake structure of a transversely oscillating square cylinder

Kumar

Sohn

Gowda³

2009

J Mech Sci Technol

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The near wake flow field features of transversely oscillating square section cylinders with different corner radii were studied in an attempt to assess the influence of corner radius. The investigation was performed by using particle image velocimetry (PIV) technique in a water channel with a turbulence intensity of 6.5%. Five models were studied with r/B=0, 0.1, 0.2, 0.3 and 0.5 (r is the corner radius and B is the characteristic dimension of the body), and the body oscillation was limited to lock-in condition (at fe/fo=1.0; fe is the excitation frequency and fo is the vortex shedding frequency from a stationary cylinder at the same Re). The corner radius was found to significantly influence the flow features around the bodies. Except for r/B=0.5, for all the other cases of r/B ratios, cycle-to cycle variation in the mode of vortex shedding was observed in the case of oscillating cylinders inducing highly non-linear wake characteristics. Apart from variation in the shedding mode, changes in shedding cycle timing were also observed for sharp and rounded square cylinders. The hgher the r/B ratio, shedding in the near wake was found to be more uniform (lesser variation in shedding cycle timings). Another admissible shedding mechanism is newly identified to operate in the near wake of oscillating cylinders now being called as the 'passive shedding' mechanism. Results indicate that increasing the corner radius suppresses the possible instabilities of the cylinder.

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“…Possibly because of this reason, almost all of the studies reported were attempting to disclose various features of these two kinds of oscillation. Parkinson [1] describes different forms of wind-induced instability of structures with bluff sections (including square), including vortex-excitation and galloping. He specifically brought to light the aspect of variation in the configuration of shear layers and the corresponding pressure distribution on the side surfaces.…”

Section: Introductionmentioning

confidence: 99%

Interference excitation of a square section cylinder

2008

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Wind tunnel experiments were conducted to study the interference excitation of a square section cylinder (test cylinder) and the results are reported in this paper. The study was carried out at some specific relative positions identified between the test cylinder (side dimension B) and the interfering cylinder (side dimension b) so that the latter is never upstream of the former. Experiments were carried out for the b/B ratios of 0.5, 1.0, 1.5 & 2.0. In this paper, emphasis is laid on bringing out the influence of b/B ratio on the vibratory response of the test cylinder, considering a few interference positions. The results show that at a particular relative position, the magnitude of vibrations and the response trend of the test cylinder are markedly influenced by the b/B ratio. Under certain combinations of b/B ratio, relative position and reduced velocity, test cylinder vibrations are considerably magnified and in certain other combinations they are suppressed. Flow visualization results are provided in an attempt to bring out the influence of b/B ratio and also to explain the observed vibratory features of the test cylinder.

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Wind-induced instability of structures

Cited by 65 publications

References 6 publications

On the wake-induced vibration of tandem circular cylinders: the vortex interaction excitation mechanism

On the wake-induced vibration of tandem circular cylinders: the vortex interaction excitation mechanism

Influence of corner radius on the near wake structure of a transversely oscillating square cylinder

Interference excitation of a square section cylinder

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