Both of these projects sought to verify the accuracy more » of offshore wind turbine dynamics simulation tools (or codes) through code-to-code comparison of simulated responses of various offshore structures.
This work was then extended under the Offshore Code Comparison Collaboration, Continuation (OC4) project under IEA Wind Task 30. The Offshore Code Comparison Collaboration (OC3), which operated under the International Energy Agency (IEA) Wind Task 23, was established to verify the accuracy of these simulation tools. Offshore wind turbines are designed and analyzed using comprehensive simulation tools that account for the coupled dynamics of the wind inflow, aerodynamics, elasticity, and controls of the turbine, along with the incident waves, sea current, hydrodynamics, and foundation dynamics of the support structure. This paper investigates the accuracy and stability of the FAST/OrcaFlex coupling operation. In this application, FAST is responsible for capturing the aerodynamic loads and flexure of the wind turbine and its tower, and OrcaFlex models the mooring line and hydrodynamic effectsbelow the water surface.
This can be achieved through the FASTlink coupling module, which couples FAST with OrcaFlex, a commercial simulation tool used for modeling mooring line dynamics. Higher modeling fidelity can be gainedthrough the use of finite element mooring theory. In the case of a floating turbine, continuous cable theory more » is used to emulate mooring line dynamics.
FAST (Fatigue, Aerodynamics, Structures and Turbulence) is a comprehensive simulation tool used for modeling land-based and offshore wind turbines. From an engineering perspective, systembehavior and line loads must be studied well to ensure the overall design is fit for the intended purpose. Mooring and anchor design can appreciably affect the dynamic response of offshore wind platforms that are subject to environmental loads. To enable offshore floating wind turbine design, the following are required: accurate modeling of the wind turbine structural dynamics, aerodynamics, platform hydrodynamics, a mooring system, and control algorithms. The integration of all of these models into comprehensive simulation tools, capable of modeling the fully coupled aeroelastic and hydrodynamic responses of floating offshore wind turbines, is presented.
Hydrodynamic loading includes contributions from hydrostatics, wave radiation, and wave scattering, including free surface memory effects. For offshore wind turbines, additional models of the hydrodynamic loading in regular and irregular seas, the dynamic coupling between the support platform motions and wind turbine motions, and the dynamic characterization of mooring more » systems for compliant floating platforms are also important.
These tools employ sophisticated models of wind-inflow aerodynamic, gravitational, and inertial loading of the rotor, nacelle, and tower elastic effects within and between components and mechanical actuation and electrical responses of the generator and of control and protection systems.
Aeroelastic simulation tools are routinely used to design and analyze onshore wind turbines, in order to obtain cost effective machines that achieve favorable performance while maintaining structural integrity.