Abstract
This paper summarizes the coupled hydro-mechanical modelling of a moored floating Oscillating Water Column device suitable for offshore wave energy exploitation. The device which is floating in finite depth waters, and it is exposed to the wave action of regular surface waves, consists of an exterior partially immersed toroidal body supplemented by a coaxial interior truncated cylinder, moored through tensioned tethers as a TLP platform. In the formed annulus area between the two solids, water oscillates pushing the dry air above the surface through an air turbine placed at the top of the device’s chamber. The considered numerical implementation involves the hydrodynamic modelling of the floater through an analytical method that accounts for the mooring- and the air turbine- characteristics. Numerical results are presented in the frequency domain concerning the motion dynamics of the moored floater. Furthermore, since fatigue damage is known to be a significant issue for moored offshore floating structures, the strength in the mooring system based on the tension forces at the top of the tethers under different design environmental conditions, is simulated under deterministic and probabilistic approaches. The objective of the analysis is to investigate which sea states yield the dominating contribution to fatigue damage accumulation in the offshore OWC, based on wave records near Kassos Island, at the Aegean Sea.