Slamming Wave Impact of a Composite Buoy for Wave Energy Applications: Design and Large-Scale Testing

In the European FP6 project SEEWEC, the design of a wave energy converter has been studied. The floating point absorbers that extract the wave energy were a crucial structure for the efficient functioning of this device and were manufactured from filament wound composite. Their mechanical design was to a large extent dominated by the survivability requirement in extreme storm conditions. During such storms, the structure is hit by very large waves. The associated mechanical loading by the waves is called slamming, which is characterized by very high local water pressures (several tens of bar) with short duration (ms) that act on the structure. This study discusses the mechanical design of the filament wound composite floating point absorbers, with the focus on the storm survivability conditions. The finite element calculations have been supported by small-scale and large-scale experimental tests, where the large-scale tests simulate the repeated wave impacts under yearly storm conditions and the survival under extreme storm conditions. It has been proved that a design that takes into account the deformability of the structure can withstand the slamming loads, although it does not comply with the international design codes which assume rigid behavior of the impacted structure. Further, the experimentally measured slamming peak pressures strongly depend on the rigidity of the composite structure. Given the broad context of the covered research work and the imposed page limitations, this study does not pretend to give all the details of all the individual steps in the design and testing processes, but rather gives a comprehensive overview of the complete chain of design decisions and validations between finite element simulations and experiments. POLYM. COMPOS., 32:700-713, 2011. (c) 2011 Society of Plastics Engineers