Flexible Coupled Multi-Body Dynamic Research of Floating Offshore Wind Turbines

As offshore wind turbines are built further offshore and in deeper waters, it becomes increasingly economically viable to mount the wind turbine on a floating structure that is tethered to the sea floor rather than conventional methods of using a concrete anchor or driven monopoles. Mounting a wind turbine on a floating structure allows for it to be located in much deeper water which comes with the benefits of higher and more consistent wind loads as well as greater public acceptance due to lower visual and environmental impacts that otherwise accompany offshore wind turbines. But they are not without their issues, mounting a tower and a turbine on a floating structure vastly increases the complexity of the system, as it must not only remain buoyant but also limit responses in pitch, roll and heave as well as maintaining position in a large variety of conditions. Excessive responses lead to higher structural stresses and as such would incur higher costs to make the system structurally sound compared to a system with reduced responses, the efficiency of the turbine is also reduced by large rotational responses in pitch and roll which would also add additional wearing onto the turbine components increasing the need for repair and maintenance. As such being able to predict the responses of a floating offshore wind turbine (FOWT) system due to the multiple loads it is put under and reduce them would be required for cost-effective, efficient, and safe designs.
The aim of this project is to improve the accuracy of dynamic response prediction of FOWTs and to develop a numerical programme to solve the aero-hydro-elastic-mooring-servo coupled equations of a FOWT. This project is undertaken in partnership between Newcastle University, the ReNU Centre for Doctoral Training, and the Offshore Renewable Energy Catapult.
This aero-hydro-elastic-mooring-servo numerical programme will consider the loads from aerodynamics, hydrodynamics, and mooring lines acting on the FOWT in various conditions, this will be coupled with structural and multi-body dynamics in order to predict the response of the FOWT in various sea states. Furthermore, control theory will be applied in order to discern methods of damping and reducing the responses of the FOWT using control systems. It will allow designers to consider different floating body concepts and which concept of floating body would be suitable for the area of operation that the FOWT will be placed in. The programme will be applied for code-to-code comparison with other codes as well as with published basin experimental data or full-scale measured data. It will also be applied in industry practice with a 7MW FOWT with the support of the Offshore Renewable Energy Catapult.
This project is funded by the EPSRC Centre for Doctoral Training in Renewable Energy Northeast Universities (ReNU) for funding though grant EP/SO23836/1.