To exploit renewable marine energy resources, floating offshore wind turbines (FOWTs) have attracted extensive attentions over the past few decades. Various concepts of FOWT foundations have been proposed, among which the barge type has many advantages, for example, the simplicity in design and construction. Recently, a concept of ‘damping pool’ was proposed, which can be used to reduce the motion responses and the construction costs. To understand the damping effect of ‘damping pool’, it is therefore important to understand the characteristics of water motions inside the moonpool(s). Moreover, it has been shown by the sea test video that the wave run-up could be significant in reality. Hence, it is necessary to study the wave field due to its practical significance for the safety of on-site maintenance workers and associated facilities.&nbsp;This paper presents a hydrodynamic analysis of a barge-type floating wind turbine platform with four rectangular moonpools. Since it has been shown by our previous experimental data that the second order effects could be of importance in the motion responses, in this study, a second-order time-domain potential flow model was used to perform numerical calculations. The second-order sum or difference frequency exciting forces are calculated based on the QTF (Quadratic Transfer Function) in the frequency domain. The time-domain simulation is realized with a memory effect function.&nbsp;First, our in-house program code was validated against our previous experimental results. Then, the effects of wave direction on the wave field and wave run-up were studied. Particularly, the phase difference between the motions of the floater and the trapped water columns in moonpools were investigated through time-domain simulations to understand the ‘damping effects’ of the moonpools. Finally, the characteristics of the six-degree-of-freedom motions of the floater and associated wave loads were studied through second-order potential flow simulations.

Mean Wave Drift Force on a Barge-Type Floating Wind Turbine With Moonpools

Paper Proceedings: https://asmedigitalcollection.asme.org/OMAE/OMAE2021/volume/85116

OMAE 2021

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