Because offshore wind farms have significant advantages such as high wind speed, small wind shear, small turbulence and high output power, offshore wind power is playing an increasingly important role in the utilization of renewable energy. Through more than 20 years’ development of offshore wind power, we can understand that the development trend is large-scale, deep-sea floating type, low cost, high reliability and remote controllability. This article focuses on the development trend of offshore wind power and designs a new large-scale deep-sea floating offshore wind turbine using the principle of gyroscopic. To improve the wind resistance of floating offshore wind turbine with a high center of gravity so that it can ensure the safety and normal operation under severe weather conditions.In recent years, 20MW floating offshore wind turbine with blades longer than 100m are under discussion. The pitch and roll degrees of freedom of such a large floating offshore wind turbine will also increase proportionally. In addition to reducing the pitch and roll degree of freedom from the perspective of floating offshore wind turbine's own design, this research focuses on the gyroscopic effect from precession and rotational axis retention effect from rotational inertia, and studies the possibility of restraining the shake movement. However, generally speaking, the gyroscopic effect and the rotational axis retention effect are obtained through the rotation of a rigid body, and the assumption in this article is to obtain the above shaking motion suppression effect through the annular flow of water in the torus welded to the below of the periphery of the underwater buoyancy providing part. The torus section has a double structure with a large external torus and a small internal torus. The large external torus and the small internal torus have the same center of the tube and the same center of the torus. The radius of the tube of the external torus is determined so that it has neutral buoyancy in order to keep the constant draft of the floating offshore wind turbine, and the tube of the internal torus is filled with still water. It is assumed that the water flows at a constant angular velocity to form an annular flow. The principle is the same as the rotation of a rigid body, but at this time the torus itself does not need to make a rotational movement, and the control force to restrain the shaking movement of the floating offshore wind turbine is obtained by changing the flow angular velocity of the annular flow in the tube of the internal torus.As a basic research, this article will numerically discuss how the gyroscopic effect and rotational axis retention effect obtained from the annular flow will affect the shaking motion of the floating offshore wind turbine based on potential theory. The radius from the center of the tube to the center of the torus, the diameter of the tube of the small internal torus and angular velocity of the annular flow will be seen as design variables in this paper.

Possibility of Reducing Spar-Type FOWT Hydrodynamic Response Using a Torus Structure With Annular Flow

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

OMAE 2021

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