The Lift Force on a Cylinder Vibrating in a Current

Moe, Geir; Wu, Zhanjun

doi:10.1115/1.2919870

Cited by 94 publications

(59 citation statements)

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“…In fact these, and a great many further response plots in Govardhan & Williamson (1999), support the fact that for constant m* , the peak amplitude remains constant, irrespective of the individual A beautiful collapse of these response plots emerges when we normalize velocity by ;*/f *, rather than ;* alone. [;*/f * is equivalent to &&true'' reduced velocity in Hover et al (1998) and Moe and Wu (1990).] This appears to be the "rst demonstration of such a collapse of data from free vibration experiments.…”

Section: Amplitude Response Wake Modes and The Andandgriffin'' Plotmentioning

confidence: 76%

“…As mentioned earlier, it is evident by inspection of equation (5), that f * depends on the &&e!ective added mass'' coe$cent C # , whose signi"cance clearly increases as mass ratio m* becomes smaller. Experimentally, the departure of f * from unity, through the lock-in regime, was shown by Moe & Wu (1990), and more recently is reported in Khalak & Williamson (1997b) and in Gharib et al (1998). We shall return to the question of the departure of f* from unity, later in the present work.…”

Section: Motions and Forces In Vortex-induced Vibrationsmentioning

confidence: 88%

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Motions, Forces and Mode Transitions in Vortex-Induced Vibrations at Low Mass-Damping

Khalak

Williamson

1999

Journal of Fluids and Structures

909

565

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These experiments, involving the transverse oscillations of an elastically mounted rigid cylinder at very low mass and damping, have shown that there exist two distinct types of response in such systems, depending on whether one has a low combined mass-damping parameter (low m* ), or a high mass-damping (high m* ). For our low m* , we "nd three modes of response, which are denoted as an initial amplitude branch, an upper branch and a lower branch. For the classical Feng-type response, at high m* , there exist only two response branches, namely the initial and lower branches. The peak amplitude of these vibrating systems is principally dependent on the mass-damping (m* ), whereas the regime of synchronization (measured by the range of velocity ;*) is dependent primarily on the mass ratio, m*. At low (m* ), the transition between initial and upper response branches involves a hysteresis, which contrasts with the intermittent switching of modes found, using the Hilbert transform, for the transition between upper}lower branches. A 1803 jump in phase angle is found only when the #ow jumps between the upper}lower branches of response. The good collapse of peak-amplitude data, over a wide range of mass ratios (m*"1}20), when plotted against (m*#C ) in the &&Gri$n'' plot, demonstrates that the use of a combined parameter is valid down to at least (m*#C ) &0)006. This is two orders of magnitude below the &&limit'' that had previously been stipulated in the literature, (m*#C ) '0)4. Using the actual oscillating frequency ( f ) rather than the still-water natural frequency ( f , ), to form a normalized velocity (;*/f* ), also called &&true'' reduced velocity in recent studies, we "nd an excellent collapse of data for a set of response amplitude plots, over a wide range of mass ratios m*. Such a collapse of response plots cannot be predicted a priori, and appears to be the "rst time such a collapse of data sets has been made in free vibration. The response branches match very well the Williamson}Roshko (Williamson & Roshko 1988) map of vortex wake patterns from forced vibration studies. Visualization of the modes indicates that the initial branch is associated with the 2S mode of vortex formation, while the Lower branch corresponds with the 2P mode. Simultaneous measurements of lift and drag have been made with the displacement, and show a large ampli"cation of maximum, mean and #uctuating forces on the body, which is not unexpected. It is possible to simply estimate the lift force and phase using the displacement amplitude and frequency. This approach is reasonable only for very low m*.

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Section: Amplitude Response Wake Modes and The Andandgriffin'' Plotmentioning

confidence: 76%

Section: Motions and Forces In Vortex-induced Vibrationsmentioning

confidence: 88%

Motions, Forces and Mode Transitions in Vortex-Induced Vibrations at Low Mass-Damping

Khalak

Williamson

1999

Journal of Fluids and Structures

909

565

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“…Over a decade later, Moe & Wu (1990) carried out an investigation in which the ratio of natural frequencies in streamwise and transverse directions (i.e. f n,X /f n,Y ) was 2.18.…”

Section: (A ) Frequency and Amplitude Responsementioning

confidence: 99%

Two-degree-of-freedom vortex-induced vibration of a pivoted cylinder below critical mass ratio

Leong

Wei

2008

Proc. R. Soc. A.

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In this study, we investigated two-degree-of-freedom (2d.f.) vortex-induced vibrations (VIVs) of a circular cylinder with a pinned attachment at its base; it had identical mass ratios and natural frequencies in both streamwise and transverse directions. The cylinder had a mass ratio, m Ã of 0.45, and a mass damping, (m Ã CC A )z, equal to 0.0841. Laserinduced fluorescence flow visualization and digital particle image velocimetry experiments were conducted over a Reynolds number range, 820%Re%6050 (corresponding to the reduced velocity range, 1.1%U Ã %8.3). Measurements and visualization studies were made in a fixed plane at the cylinder mid-height, providing a two-dimensional picture of a highly three-dimensional system. However, significant insights can be gained from these experiments and form the basis of this paper. A large transverse amplitude response, A Ã Y w2 (or four diameters peak-to-peak), in the upper branch was observed. The streamwise amplitude response exhibits an even higher peak amplitude, A Ã X w2:5, which is approximately 125% of peak A Ã Y . Results show that there is no lower branch for this system and the transverse upper branch exhibits asymptotic behaviour, i.e. a wide regime of resonance. For ReO3000, the Strouhal number for the vortex shedding was 0.16 (G9%). Both the transverse cylinder oscillation and vortex-shedding frequencies, f OS,Y and f VS , respectively, were virtually identical throughout this range. While the streamwise oscillation frequency is typically twice the transverse oscillation frequency for a 2d.f. system, this is not the case at the lowest reduced velocities where oscillations first occur. Under these conditions the streamwise and transverse oscillation frequencies were identical. Finally, we observed that the cylinder wake exhibits both the PCS vortex-shedding mode and a desynchronized vortex pattern, which are uncommon for flow past a cylinder experiment. Very interestingly, the wide U Ã range over which resonance occurs is dominated by a desynchronized vortex pattern. These results clearly demonstrate the differences that arise in 2d.f. VIV occurring below the critical mass ratio.

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“…As the equations of motion governing viscous flow are difficult to solve, experiments have been the most important source of new insight. Examples of typical experiments are free vibration of elastically mounted rigid cylinders (Feng, 1968;Vikestad, 1998;Govardhan and Williamson, 2000;Jauvtis and Williamson, 2004) and cylinders undergoing forced motions (Sarpkaya, 1978;Moe and Wu, 1990;Morse and Williamson, 2009;Aglen and Larsen, 2011;Yin and Larsen, 2012). Experiments with long flexible structures have also been performed, both under controlled laboratory conditions (Chaplin et al, 2005;Trim et al, 2005;HueraHuarte et al, 2014) and in more realistic field environments (Huse et al, 1998;Vandiver et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Time domain simulation of vortex-induced vibrations in stationary and oscillating flows

Thorsen

Sævik

Larsen

2016

Journal of Fluids and Structures

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This paper focuses on the further development of a previously published semi-empirical method for time domain simulation of vortex-induced vibrations (VIV). A new hydrodynamic damping formulation is given, and the necessary coefficients are found from experimental data. It is shown that the new model predicts the observed hydrodynamic damping in still water and for cross-flow oscillations in stationary incoming flow with high accuracy. Next, the excitation force model is optimized by simulating the VIV response of an elastic cylinder in a series of experiments with stationary flow. The optimization is performed by repeating the simulations until the best possible agreement with the experiments is found. The optimized model is then applied to simulate the cross-flow VIV of an elastic cylinder in oscillating flow, without introducing any changes to the hydrodynamic force modeling. By comparison with experiment, it is shown that the model predicts the frequency content, mode and amplitude of vibration with a high level of realism, and the amplitude modulations occurring at high Keulegan-Carpenter numbers are well captured. The model is also utilized to investigate the effect of increasing the maximum reduced velocity and the mass ratio of the elastic cylinder in oscillating flow. Simulations show that complex response patterns with multiple modes and frequencies appear when the maximum reduced velocity is increased. If, however, the mass ratio is increased by a factor of 5, a single mode dominates. This illustrates that, in oscillating flows, the mass ratio is important in determining the mode participation at high maximum reduced velocities.

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The Lift Force on a Cylinder Vibrating in a Current

Cited by 94 publications

References 0 publications

Motions, Forces and Mode Transitions in Vortex-Induced Vibrations at Low Mass-Damping

Motions, Forces and Mode Transitions in Vortex-Induced Vibrations at Low Mass-Damping

Two-degree-of-freedom vortex-induced vibration of a pivoted cylinder below critical mass ratio

Time domain simulation of vortex-induced vibrations in stationary and oscillating flows

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