The Impact of Extreme Wave Events on a Fixed Multicolumn Offshore Platform
- Nagi Abdussamie (University of Tasmania) | Roberto Ojeda (University of Tasmania) | Yuriy Drobyshevski (University of Tasmania) | Giles Thomas (University College London) | Walid Amin (University of Tasmania)
- Document ID
- International Society of Offshore and Polar Engineers
- International Journal of Offshore and Polar Engineering
- Publication Date
- September 2017
- Document Type
- Journal Paper
- 293 - 300
- 2017. The International Society of Offshore and Polar Engineers
- Offshore platforms, slamming pressure, wave-in-deck loads
- 1 in the last 30 days
- 42 since 2007
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The pdf file includes a Discussion by Abbas Khayyer of Kyoto University, and the Authors’ Reply.
This paper presents an experimental and numerical investigation into the magnitude and distribution of the hydrodynamic loads affecting a fixed multicolumn offshore platform (rigidly mounted tension leg platform) when subjected to extreme wave events. All wave load components, including wave-in-deck slamming pressures, were predicted using a commercial computational fluid dynamics (CFD) code STAR-CCMC and compared against experimental measurements. Slamming pressures were calculated using both data obtained locally at discrete points and globally averaged over the whole exposed area of the deck. In all simulated cases, the deck area exposed to a wave-slamming event was found to be in contact with a water–air mixture with a significant proportion of air phase. It was concluded that the slamming pressure data for the exposed area provided better insights into the pressure changes due to air compressibility and its content.
When a large wave (extreme wave event) impacts the deck of an offshore structure, significant wave-in-deck and slamming loads occur. These slamming events could generate major global and local loads, which can cause structural damage to the deck, generating large forces in the tendons and risers and adversely affecting the motions of floating structure such as tension leg platforms (TLPs) and semisubmersibles. The problem of wave-in- deck impact on a floating platform can be quite complicated because of the contributions of many parameters such as the platform offset, set-down, and tendon dynamics (API, 2010).
The simplest way to investigate wave-in-deck impact problems is a simplified rigid model of the deck structure idealized as a flat plate or as a box shape (Baarholm, 2009; Bhat, 1994; Scharnke and Hennig, 2015). Current design practices (API, 2007; DNV, 2010; ISO, 2007) recommend a number of theoretical approaches such as the global/silhouette approach “simplified loading model” (API, 2007) and a detailed component approach, e.g., the momentum method (Kaplan et al., 1995) to evaluate the wave-in-deck loads of fixed platforms. Since such engineering approaches rely on the potential flow theory to calculate the change of fluid momentum during the wave impact, when using wave kinematics of a nondisturbed wave field the effects of diffraction and entrapped air are neglected.
|File Size||3 MB||Number of Pages||10|