Vortex-induced vibrations
TL;DR: In this paper, a review summarizes fundamental results and discoveries concerning vortex-induced vibration (VIV) that have been made over the last two decades, many of which are related to the push to explore very low mass and damping, and to new computational and experimental techniques that were hitherto not available.
Abstract: This review summarizes fundamental results and discoveries concerning vortex-induced vibration (VIV), that have been made over the last two decades, many of which are related to the push to explore very low mass and damping, and to new computational and experimental techniques that were hitherto not available. We bring together new concepts and phenomena generic to VIV systems, and pay special attention to the vortex dynamics and energy transfer that give rise to modes of vibration, the importance of mass and damping, the concept of a critical mass, the relationship between force and vorticity, and the concept of "effective elasticity," among other points. We present new vortex wake modes, generally in the framework of a map of vortex modes compiled from forced vibration studies, some of which cause free vibration. Some discussion focuses on topics of current debate, such as the decomposition of force, the relevance of the paradigm flow of an elastically mounted cylinder to more complex systems, and the relationship between forced and free vibration.
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TL;DR: In this paper, the authors present control methods for flow over a bluff body such as a circular cylinder, a 2D bluff body with a blunt trailing edge, and a sphere.
Abstract: In this review, we present control methods for flow over a bluff body such as a circular cylinder, a 2D bluff body with a blunt trailing edge, and a sphere. We introduce recent major achievements in bluff-body flow controls such as 3D forcing, active feedback control, control based on local and global instability, and control with a synthetic jet. We then classify the controls as boundary-layer controls and direct-wake modifications and discuss important features associated with these controls. Finally, we discuss some other issues such as Reynolds-number dependence, the lowest possible drag by control, and control efficiency.
827 citations
TL;DR: Although there are a great many papers dedicated to the problem of a cylinder vibrating transverse to a fluid flow, the authors observes a rather dramatic departure from previous results, which would suggest a possible modification to offshore design codes.
Abstract: Although there are a great many papers dedicated to the problem of a cylinder vibrating transverse to a fluid flow (, that one observes a rather dramatic departure from previous results, which would suggest a possible modification to offshore design codes.
588 citations
Cites background from "Vortex-induced vibrations"
...Vortex-induced vibration of cylinders free to respond transverse to the fluid flow has been well studied, and several reviews discuss this problem (see for example Sarpkaya 1979; Bearman 1984; Williamson & Govardhan 2004)....
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TL;DR: In this paper, a selective review of recent research on vortex-induced vibrations of isolated circular cylinders and the flow and vibration of circular cylinders in a tandem arrangement is presented, a common thread being that the topics raised are of particular interest to the author.
568 citations
TL;DR: A non-boundary-conforming formulation for simulating complex turbulent flows with dynamically moving boundaries on fixed Cartesian grids is proposed and the concept of field-extension is also introduced to treat the points emerging from a moving solid body to the fluid.
537 citations
Cites background from "Vortex-induced vibrations"
...Vortex-induced vibration of a circular cylinder is a problem that has been extensively studied both experimentally and numerically (see [67] for a recent review), and will be used in the present study to evaluate the accuracy and efficiency of the proposed methodology....
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TL;DR: In this paper, the authors summarize fundamental results and discoveries concerning vortex-induced vibration, that have been made over the last two decades, many of which are related to the push to very low mass and damping, and to new computational and experimental techniques that were hitherto not available.
533 citations
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TL;DR: In this paper, the authors present a comprehensive review of vortex shedding in two-dimensional bluff-body wakes and present irrespective of whether the separating boundary layers are laminar or turbulent, and if the body is flexible this can cause oscillations.
Abstract: When placed ih a fluid stream, some bodies generate separated flow over a substantial proportion of their surface and hence can be classified as bluff. On sharp-edged bluff bodies, separation is fixed at the salient edges, whereas on bluff bodies with continuous surface curvature the location of separation depends both on the shape of the body and the state of the boundary layer. At low Reynolds numbers, when separation first occurs, the flow around a bluff body remains stable, but as the Reynolds number is increased a critical value is reached beyond which instabilities develop. These instabilities can lead to organized unsteady wake motion, dis organized motion, or a combination of both. Regular vortex shedding, the subject of this article, is a dominant feature of two-dimensional bluff-body wakes and is present irrespective of whether the separating boundary layers are laminar or turbulent. It has been the subject of research for more than a century, and many hundreds of papers have been written. In recent years vortex shedding has been the topic of Euromech meetings reported on by Mair & Maull (1971) and Bearman & Graham (1980), and a comprehensive review has been undertaken by Berger & Wille (1972). Vortex shedding and general wake turbulence induce fluctuating pres sures on the surface of the generating bluff body, and if the body is flexible this can cause oscillations. Oscillations excited by vortex shedding are usually in a direction normal to that of the free stream, and amplitudes as large as 1.5 to 2 body diameters may be recorded. In addition to the generating body, any other bodies in its wake may be forced into oscillation. Broad-band force fluctuations, induced by turbulence produced in the flow around a bluff body, rarely lead to oscillations as severe as those caused by vortex shedding. Some form of aerodynamic instability, such that move-
1,251 citations
TL;DR: In this paper, the authors showed that there exist two distinct types of response in a very low mass and damping regime, depending on whether one has a low combined mass-damping parameter (low m*ζ), or a high mass-ding parameter (highm*δ).
944 citations
TL;DR: In this article, the transverse vortex-induced vibrations of an elastically mounted rigid cylinder in a fluid flow were studied for the first time in free vibrations, and the existence of more than one mode transition for low (m*ζ) and high (m *δ) combined mass-damping parameters was analyzed.
Abstract: In this paper, we study the transverse vortex-induced vibrations of an elastically mounted rigid cylinder in a fluid flow. We use simultaneous force, displacement and vorticity measurements (using DPIV) for the first time in free vibrations. There exist two distinct types of response in such systems, depending on whether one has a high or low combined mass–damping parameter (m*ζ). In the classical high-(m*ζ) case, an ‘initial’ and ‘lower’ amplitude branch are separated by a discontinuous mode transition, whereas in the case of low (m*ζ), a further higher-amplitude ‘upper’ branch of response appears, and there exist two mode transitions.To understand the existence of more than one mode transition for low (m*ζ), we employ two distinct formulations of the equation of motion, one of which uses the ‘total force’, while the other uses the ‘vortex force’, which is related only to the dynamics of vorticity. The first mode transition involves a jump in ‘vortex phase’ (between vortex force and displacement), ϕvortex, at which point the frequency of oscillation (f) passes through the natural frequency of the system in the fluid, f ∼ fNwater. This transition is associated with a jump between 2S [harr ] 2P vortex wake modes, and a corresponding switch in vortex shedding timing. Across the second mode transition, there is a jump in ‘total phase’, phis;total , at which point f ∼ fNvacuum. In this case, there is no jump in ϕvortex, since both branches are associated with the 2P mode, and there is therefore no switch in timing of shedding, contrary to previous assumptions. Interestingly, for the high-(m*ζ) case, the vibration frequency jumps across both fNwater and fNvacuum, corresponding to the simultaneous jumps in ϕvortex and ϕtotal. This causes a switch in the timing of shedding, coincident with the ‘total phase’ jump, in agreement with previous assumptions.For large mass ratios, m* = O(100), the vibration frequency for synchronization lies close to the natural frequency (f* = f/fN ≈ 1.0), but as mass is reduced to m* = O(1), f* can reach remarkably large values. We deduce an expression for the frequency of the lower-branch vibration, as follows:formula herewhich agrees very well with a wide set of experimental data. This frequency equation uncovers the existence of a critical mass ratio, where the frequency f* becomes large: m*crit = 0.54. When m* < m*crit, the lower branch can never be reached and it ceases to exist. The upper-branch large-amplitude vibrations persist for all velocities, no matter how high, and the frequency increases indefinitely with flow velocity. Experiments at m* < m*crit show that the upper-branch vibrations continue to the limits (in flow speed) of our facility.
775 citations
605 citations
"Vortex-induced vibrations" refers background in this paper
...The practical significance of VIV has led to a large number of fundamental studies, many of which are discussed in the comprehensive reviews of Sarpkaya (1979), Griffin & Ramberg (1982), Bearman (1984), Parkinson (1989); in a book chapter by Anagnostopoulos (2002); and in books by Blevins (1990),…...
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...Perceived problems regarding the validity of this widely used plot were pointed out clearly in a number of papers by Sarpkaya (1978, 1979, 1993, 1995)....
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DOI•
01 Jan 1968535 citations
"Vortex-induced vibrations" refers background or methods in this paper
...On the other hand, in Figure 2, for high mass-damping, it is well known that Feng (1968) found a hysteresis between the initial and lower branches....
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...Consider the switch in the timing of vortex shedding described by Zdravkovich (1982) when the amplitude jumps from the initial to lower branch in high massdamping cases such as Feng (1968)....
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...Feng (1968) contributed some important classic measurements of response and pressure for an elastically mounted cylinder....
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...In (a), we compare the classical response amplitudes of Feng (1968) (triangle symbols), with Brika & Laneville (1993) (open symbols), both at the same (m∗ζ ) in air....
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...Open symbols in (a) show the contrasting high-m∗ζ response data of Feng (1968)....
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