Two-degree-of-freedom vortex-induced vibration of circular cylinders with very low aspect ratio and small mass ratio

Gonçalves, Rodolfo T.; Rosetti, Guilherme F.; Franzini, Guilherme Rosa; Meneghini, Júlio Romano; Fujarra, André Luís Condino

doi:10.1016/j.jfluidstructs.2013.02.004

Cited by 45 publications

(13 citation statements)

References 49 publications

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“…Typically, A=12 and ε=0.3 (Facchinetti et al 2004). The overdots (•) of Equations (8) and (9) are derivatives with respect to dimensionless time, t.…”

Section: Coupling Of Wake and Structural Oscillatorsmentioning

confidence: 99%

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Modified wake oscillator model for vortex-induced motion prediction of low aspect ratio structures

Rahman

Hussin

Mohd

et al. 2019

Ships and Offshore Structures

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Modified wake oscillator model for vortex-induced motion prediction of low aspect ratio structures Floating structures, such as Spar platform, are likely to experience significant motions while operation due to Vortex-induced Motion (VIM). The main features of VIM include aspect ratio and mass ratio of the structure. This paper focuses on further development of a previously published semi-empirical method called wake oscillator model (WOM) for VIM, which aims to derive a mathematical correlation in modelling all features of the phenomenon. Analytical solution is proposed to coupled WOM and structure oscillator model based on the Van der Pol equation by integrating mass ratio, m* = 4.36, and various low aspect ratios between 0.3 and 2.0. Additionally, a new approach was initiated to embed several empirical parameters linked to the aspect ratio in the existing WOM. It was found the aspect ratio parameter in the modified WOM significantly affected the performance of the model for estimation of VIM on floating structures.

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“…Typically, A=12 and ε=0.3 (Facchinetti et al 2004). The overdots (•) of Equations (8) and (9) are derivatives with respect to dimensionless time, t.…”

Section: Coupling Of Wake and Structural Oscillatorsmentioning

confidence: 99%

“…Gonçalves et al (2013), who investigated the influence of L/D upon low aspect ratio circular cylinders.Fig. 6illustrates the transverse amplitudes for the mass ratio of * = 4.36 for the following aspect ratios of / = 0.30, 0.40, 0.50, 0.75, 1.00,1.50, and 2.00.…”

mentioning

confidence: 99%

Modified wake oscillator model for vortex-induced motion prediction of low aspect ratio structures

Rahman

Hussin

Mohd

et al. 2019

Ships and Offshore Structures

View full text Add to dashboard Cite

show abstract

“…That is because a large safety factor is applied during the design stage due to lack of knowledge and understanding on VIV prediction. Extensive study about VIV was done for a few decades, such as [2] [3][4][5][6][7][8][9][10][11][12][13], and thus attempts to reduce the VIV of structures have been done. It is important to know that many object shapes may lead to VIV.…”

Section: Introductionmentioning

confidence: 99%

Analytical modelling prediction by using wake oscillator model for vortex-induced vibrations

Hussin¹,

Harun²,

Mohd³

et al. 2017

J. MECH. ENG. SCI.

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Explorations by oil and gas companies have moved from shallow to deep water to satisfy consumers' changing needs. A circular-shaped cylinder structure placed in deep water is also known spar platform, is normally floated and subjected to severe conditions which cause unpleasant motions and fatigue damage to the structure. Wake oscillator model is considered a semi-empirical model that is most suitable for the evaluation of Vortexinduced Vibrations (VIV) structure features during the design stage. This work focuses on validation of wake oscillator model for VIV with previously semi-empirical method. Wake oscillator and structure oscillator models are coupled based on the Van der Pol Equation. The coupled models were evaluated and analytically validated. The results showed a qualitative and quantitative agreement with previous analytical, at the same maximum peak amplitude response, 0 = 0.22, with 1.2% percentage error . Meanwhile, experimental results from literature only showed a qualitative agreement but not in quantitative agreement. Analytical modelling may offer potential means for investigating VIV features and provide a fundamental analysis by using a cost saving but reliable method. Further works should be done to characterise the VIV and Vortex-induced Motions phenomenon for spar platform.

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“…In the free-surface region, it is known that vortex shedding is suspended and small size vortex is shed [3]. Goncalves et al [4] found that the free surface and the end cell strengthen the 3-dimensionality of the flow around a floating body.…”

Section: Introductionmentioning

confidence: 99%

The effects of free surface and end cell on flow around a finite circular cylinder with low aspect ratio

2015

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Vortex-induced motion is an oscillatory phenomenon which occurs to a floating body with low aspect ratio. The basic phenomenological study about the effects of free surface and end cell on flow around a finite fixed circular cylinder was investigated in this study using particle image velocimetry and hydrodynamic force measurement. It was found from the former experiment that the wake of the cylinder is influenced by the both end cell and free surface. Blowup and back flow are generated from the end cell, and their effects are suspended by free surface. The result of hydrodynamic force measurement showed the effect of Reynolds number, Froude number, and the aspect ratio of the floating body on the hydrodynamic force. Fluctuating components of hydrodynamic coefficients decrease for increasing Reynolds number, Froude number, and the aspect ratio. On the other hand, the mean drag coefficient increases as Froude number increases and decreases as the aspect ratio increases. The interpretation to these results was discussed in comparison with flow structures observed in the experiment. In addition, it was found that the effect of Reynolds number on the mean drag coefficient changes at different aspect ratios. A possible interpretation to this phenomenon was proposed.

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Two-degree-of-freedom vortex-induced vibration of circular cylinders with very low aspect ratio and small mass ratio

Cited by 45 publications

References 49 publications

Modified wake oscillator model for vortex-induced motion prediction of low aspect ratio structures

Modified wake oscillator model for vortex-induced motion prediction of low aspect ratio structures

Analytical modelling prediction by using wake oscillator model for vortex-induced vibrations

The effects of free surface and end cell on flow around a finite circular cylinder with low aspect ratio

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