Hydrodynamic wave loading on floating and moored constructions in steep waves (GWI.6433)
Project nummer:
gwi6433
Omschrijving van het onderzoek
Extreme waves, their impact loading on floating structures and the resulting dynamic response of these structures have long been subjects that could only be studied with experimental methods. The complex wave kinematics and highly non-linear fluid-structure interaction could not be predicted with existing numerical methods. However, recent research by the partners of this proposal has shown that new hydrodynamic models based on the Navier–Stokes equations, in combination with a VOF-based method for the description of the free-surface dynamics, are able to predict such effects. Experimental validation has on the other hand also revealed aspects in the numerical model that need further extension and improvement. This relates to the physical and mathematical aspects of:
- Modelling of steep and overtopping waves (to better describe the oncoming waves)
- Air entrapment during the actual wave impact (to better model the physics of wave impact)
- Vessel-wave dynamics (to describe the coupled dynamics of wave and vessel motion).
Zonal modelling (to reduce the computational effort).
The proposal will focus on these vital and complex modeliing issues, and to their computational implementation. Further experimental validation of the method is necessary, and will also form part
of the project. The deliverables of the project will be, next to scientic papers and two PhD theses, a validated simulation method (including documentation) to analyse wave loading on floating or moored (offshore)
platforms.
Utilisation
In heavy storms the wave loads and resulting motions of ships and floating offshore structures are large. These are a serious threat to the safety and operability of these vessels and the well-being of the crew. Various incidents with serious damage have been reported, also in the North Sea. In these heavy storms, wave and vessel motions can become so large that water flows onto the deck of a ship. This problem is known as ’green water loading’. The term "green water" is used to distinguish between the spray (small amounts of water and foam) flying around and the real solid seawater on the deck.
Recent studies have shown an increase of these green water incidents in offshore operations. From 1995 to date 17 green water incidents have been identified on 12 UK FPSOs/FSUs (floating production, storage and offloading units); some installations have experienced more than one incident. For instance, during a winter storm in January 1995 a fire-fighting platform was destroyed on the Emerald FSU (Figure 1). Another major example is severe wave impact damage to the bow of the Schiehallion FPSO in 1998, resulting in an evacuation of the personnel and expensive offshore hull repairs and an upgrade of the complete bow structure of this FPSO. Generic examples of this type of phenomena are:
- Green Water Loading:sudden and extremely violent water motions on the deck
- Wave impact loading on the outside the hull
- Sloshing of the cargo inside the hull
- Wave run up against fixed and floating structures and coastal protection structures, such as dikes.
The industry has recognised the importance of understanding and predicting hydrodynamic wave loading and has co-operated in experimental research on these subjects for a long time already. A large number of these projects have been co-ordinated by MARIN. Utilisation of the delivered methodology and software will therefore take place in close co-operation with MARIN and their extensive industrial contacts in the shipping and offshore industry. In particular, the proposal will be complementary to the ComFLOW-2 joint-industry project (JIP) that is currently being defined by MARIN as a followup of the SAFE-FLOW JIP (with 26 industrial partners). The ComFLOW-2 JIP is focussed on the validation of the developed numerical models for specific wave impact problems in the shipping and offshore industry
Resultaten van het onderzoek
Publications and animations of the ComFLOW research (including the preceeding projects) can be found through the ComFlo website.
Gebruikers
Er zijn vier bedrijven bij dit project betrokken.
Projectleider
| Prof.dr. A.E.P. Veldman |
Rijksuniversiteit Groningen
Wiskunde en Natuurwetenschappen
Wiskunde |
Postbus 800
9700 AV Groningen |
Status van het project
| Gestart |
: 01-07-2004 |
| Einddatum |
: 01-01-2008 |
Trefwoorden
Floating bodies, Hydrodynamic wave loading, Hydrodynamica, Non-linear surface waves, Numerical flow simulation, Numerical modelling, Off-shore technologie, Offshore platforms