Numerical simulations of vortex-induced vibrations on vertical cylindrical structure with different aspect ratios

Rahman, Mohd Nordin Abdul; Leggoe, Jeremy; Thiagarajan, Krish; Mohd, Mohd Hairil; Paik, Jeom Kee

doi:10.1080/17445302.2015.1013783

Cited by 29 publications

(7 citation statements)

References 20 publications

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“…Notably, the modified wake oscillator displayed its ability in modelling free vibration of 3D structure for VIM prediction. The model predictions can probably be enhanced by improving the coupling terms of Equation (21), where the correction factor could be integrated into the aspect ratio parameter with thorough validation and calibration of experimental data. Surprisingly, this study had successfully predicted VIM of floaters by initiating a parameter of the aspect ratio ranging from 0.2 to 2.0 to capture the 3D phenomenon.…”

Section: Resultsmentioning

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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Section: Resultsmentioning

confidence: 99%

“…The outcomes for various L/D were obtained by solving Equations (11), (13), and (21) of the modified WOM. Comparison was made with empirical yields obtained by Fig.…”

Section: Influence Of L/d On M* =436mentioning

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

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“…The vibration of the structures was expected to reduce as the aspect ratio reduced. The combined effect of the aspect ratio, the end conditions and the free surface affects the correlation length of the vortex formation, reducing the vibration of the structure [28]. In experiments simulating infinite length cylinders, the free surface and end conditions are eliminated by means of endplates or wall channels.…”

Section: Resultsmentioning

confidence: 99%

Experiments on Vortex-Induced Vibration of a Vertical Cylindrical Structure: Effect of Low Aspect Ratio

Rahman¹,

Thiagarajan²

2015

Int. J. Automot. Mech. Eng.

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Studies in offshore engineering have shown that vortex-induced vibration (VIV) of a slender offshore riser can be fundamentally different from that of a cylindrical spar structure. Under similar environments, the primary difference between the two structures affecting vortex shedding relates to the aspect ratio (length to diameter ratio, L/D). In the present investigation, careful experiments were carried out on the VIV of an elastically mounted cylinder with a varying aspect ratio. Experiments were conducted by forcing the vertical cylinders in still water. Of particular interest was the measurement of the response amplitude, hydrodynamic forces, Strouhal number (St) and the lock-in region while the aspect ratio of the cylinder varied from L/D = 0.5 to L/D = 13. The experiments were conducted in the subcritical flow region (7.4 × 10 3 < Re < 2 × 10 5 ), corresponding to a range of reduced velocity U r from 2 to 14. Comparisons with experimental results obtained from the literature showed meaningful trends. It was found that the response amplitude of the structure decreased as the aspect ratio was reduced. The decrease in response amplitude was accompanied by a decrease in the correlation length of the vortex shedding and the hydrodynamic forces experienced by the structure. The Strouhal number and lock-in region, too, showed a significant reduction with a lower aspect ratio. It is apparent that the aspect ratio influenced the occurrence of the VIV, which affected the hydrodynamics of the fluidstructure interaction between the fluid and the bluff body.

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“…The outlet is set as a pressure outlet at 0-gauge pressure. The bounding top and bottom of the domain are set to symmetry at free slip condition type in order to reduce computational power and solid blockage effect [29,30].…”

Section: Boundary Conditionsmentioning

confidence: 99%

A Fundamental CFD Investigation of Offshore Structures for Artificial Coral Reef Development

Rahman¹,

Nazri²,

Fitriadhy³

et al. 2020

CFDL

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Rigs-to-Reefs (R2R) is an alternative for oil and gas industry for decommissioning purpose. The program will benefit marine life as an artificial reef for a sustainable solution to promote ecosystem growth. For any oil platform considered for reefing, an extensive study on the suitability and performance of the artificial reef is essential. These studies will evaluate the stability and relevance of the structure as an artificial reef when deployed on the seabed. This paper presents the research on dynamic response and flow characteristics of a conceptual proposed R2R platform. The Computational Fluid Dynamics (CFD) simulation is intended to study the dynamic responses and flow characteristics analysis of a jacket oil platform for optimal settlement and growth of corals. Artificial reef performances were evaluated by calculating the performance indices of the upwelling and back eddy profile. It was found that the upwelling efficiency index is higher at current direction normal to the platform due to the higher frontal area exposed to the incoming flow. Meanwhile, back eddy efficiency index shows a significant low value for all directions. The CFD results presented will be discussed in terms of the possibility of better performance of an artificial reef which considering engineering and biological aspects

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Numerical simulations of vortex-induced vibrations on vertical cylindrical structure with different aspect ratios

Cited by 29 publications

References 20 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

Experiments on Vortex-Induced Vibration of a Vertical Cylindrical Structure: Effect of Low Aspect Ratio

A Fundamental CFD Investigation of Offshore Structures for Artificial Coral Reef Development

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