Study of slow-drift damping on wind tracking performance of a new-type FOWT ‘Optiflow’ with single-point mooring

Abstract

Single-Point Mooring (SPM) is a cost-effective and promising solution that can be utilized to station a Floating Offshore Wind Turbine (FOWT). However, it poses new challenges such as wind tracking performance and slow-drift motion, which are unexplored. In this study, an attempt is made to understand the wind tracking performance of a new-type FOWT ‘Optiflow’ moored by SPM system. Real-Time Hybrid Model (ReaTHM) testing is conducted on a 1/60 scale model and motion about the moored point is observed. It is found from experiments that the model follows the wind in rated, cut-out and storm conditions. Forced yawing test is also carried out on a 1/200 scale model to obtain a database of slow-drift damping (SDD) force coefficient. A time-history simulation code is developed to incorporate the slow-drift motion response following the wind. Two cases of simulation, one with slow-drift damping and another without slow-drift damping are carried out. Comparing the experimental and simulation results, it is revealed that the simulation with slow-drift damping coefficient predicts the wind tracking phenomenon better than the simulation without slow-drift damping coefficient. It is concluded that slow-drift damping is an important factor while simulating the turning motion of ‘Optiflow’ about the moored point.