Significant benefits with a cylindrical hull for FPSO, drilling, LNG, and offshore power plant applications

Major, Fredrik; Syvertsen, K.; Aarsnes, J

doi:10.1071/aj07054

Cited by 5 publications

(3 citation statements)

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“…The vortices shed from the edge of the cylinder and diminished instantaneously. In terms of practical application, the circular FPSO is more stable and known to be exhibited higher stability compared to any conventional FPSO (Major and Eggan 2009). However, many other factors need to be considered to conduct a thorough analysis on the structure such as the size, shapes, wave and current profile, buoyancy, mooring types, and also VIV mitigations.…”

Section: Resultsmentioning

confidence: 98%

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

Rahman

Leggoe

Thiagarajan

et al. 2015

Ships and Offshore Structures

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This paper presents a computational fluid dynamics (CFD) study of vortex-induced vibration (VIV) for different aspect ratio (L/D) cylinder. Of particular interest was to measure hydrodynamic forces and numerically investigate the wake behaviour of VIV while varying the aspect ratio. The simulation models represented the actual experimental conditions with idealised free-surface boundary condition to capture the responses from fluid-structure interaction phenomenon. The simulations were performed 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. The results of the cases studied were discussed and compared with the experimental data to verify the accuracy and validity of the present simulation. The comparisons have shown a similar curved-shape drag coefficient plot, and however underestimated the value of the drag coefficients over the reduced velocity. Additionally, the simulations seemed to capture a higher lift force response compared with the experimental data for a low aspect ratio. The correlation length was observed to be longer for larger aspect ratio and proportionally decreases as the aspect ratio decreases.

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Section: Resultsmentioning

confidence: 98%

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

Rahman

Leggoe

Thiagarajan

et al. 2015

Ships and Offshore Structures

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“…Cylindrical drilling platform is the most advanced mobile oil platform. Due to its stability and reliability, it can deal with well harsh ocean environments [5]. The towing process is the necessary preparation step for the deployment of the platform, where the process faces a great variety of risks from a complex nautical environment, the dynamics in towing and maneuvering, to unexpected events during the operation.…”

Section: Introductionmentioning

confidence: 99%

Path following control for towing system of cylindrical drilling platform in presence of disturbances and uncertainties

Jin

Dehmer

et al. 2019

ISA Transactions

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Towing is a critical process to deploy a cylindrical drilling platform. However, the towing process faces a great variety of risks from a complex nautical environment, the dynamics in towing and maneuvering, to unexpected events. Therefore, safely navigating the towing system following a planned route to a target sea area is essential. To tackle the time-varying disturbances induced by wind, current and system parametric uncertainties, a path following control method for a towing system of cylindrical drilling platform is designed based on linear active disturbance rejection control. By utilizing Maneuvering Modeling Group model as well as a catenary model, we develop a three degree-of-freedom dynamic mathematical model of the towing system under external environmental disturbances and internal uncertainties. Furthermore, we design a linear active disturbance rejection control path following controller for real-time tracking error correction based on a guidance method combining cross-track error and parallax. Finally, the path following performance of the towing system is evaluated in a simulation environment under various disturbances and internal uncertainties, where the corresponding tracking error is analyzed. The results show that the linear active disturbance rejection control performs well under both the external disturbance and inherent uncertainties, and better satisfy the tracking performance criteria than a traditional proportional integral derivative controller.

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“…In a circular FPSO, as illustrated in Figure 1, the overall length of the platform is 66 m with a hull diameter of approximately 60 m. This circular FPSO is the world's first cylinder-shaped FPSO and yields L/D ≈ 1.1. Its unique design and technology provide improved motion, higher stability reserves, and a higher deck load capacity than a conventional FPSO [13]. The influence of L/D on VIV response around a circular cylinder was investigated by Nishioka and Sato [14], West and Apelt [15], Lee and Budwig [16], Baban and So [17], Szepessy and Bearman [18], Albarede and Monkewitz [19], Norberg [20], and Nakamura et al [21].…”

Section: Introductionmentioning

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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Significant benefits with a cylindrical hull for FPSO, drilling, LNG, and offshore power plant applications

Cited by 5 publications

References 0 publications

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

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

Path following control for towing system of cylindrical drilling platform in presence of disturbances and uncertainties

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

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