Investigation of motions of a floating wind turbine foundation with multiple moonpools

In this paper the motions of a barge-type floating foundation installed with four moonpools and a VAWT are investigated through physical model tests and numerical calculations. The characteristics of motion responses and mooring tether tensions under various wave conditions are examined. The gyroscopic effects of turbine rotations are studied by varying the mass and the rotational speed of wind turbine. Linear potential calculations are carried out using WAMIT. It is found that the gyroscopic effect due to turbine rotations can be significant. The first-order motions of the floating system are substantially reduced by the gyroscopic effect, while the second-order motions and tether tensions may be significantly increased. The viscous damping of water motions in moonpools is found not negligible to produce reasonable predictions.