Experimental investigation on short-term fatigue damage of slack and hybrid mooring for wave energy converters

摘要

Two mooring systems, namely a slack mooring and a hybrid mooring are proposed for the application of wave energy converters' station keeping. The performance of these two mooring systems are assessed by hydrodynamic model tests on a point absorber-mooring system. Totally, four sea states are considered, including two operational and two survival wave conditions. The snap events are found in slack mooring when point absorber operates in survival conditions. Besides, the snap loads are closely related to the significant wave height and wave peak period. The hybrid mooring shows good performance in preventing snap loads. The short term mooring fatigue damage is estimated by the T-N curve method, while the load cycles are counted by the rainflow counting technique based on the measured mooring tension time series. The effects of T-N curve as well as snap loads on mooring fatigue damage are discussed, and the fatigue results of these two mooring systems are compared. In the last part of this study, the uncertainties in mooring fatigue estimations are discussed.