In this paper, a dynamics kernel for a multibody system with wave and wind loads was developed and applied to the dynamic response analysis of an offshore wind turbine on a floating platform. The floating offshore wind turbine was modeled as a multibody system consisting of several bodies constrained with mechanical joints. To carry out dynamic response analysis of the multibody system, a dynamics kernel was developed. In this kernel, the inertial reference frame and the body-fixed reference frames were defined, and the kinematic relations between the rigid bodies were imposed by defining various types of joints. The kernel was used to solve the equations of motion of the multibody system, derived by using recursive formulation. For the dynamic response analysis of the offshore wind turbine, an external force calculation module was developed. The developed module calculates the hydrostatic force considering the nonlinear effects and the linearized hydrodynamic force by using the 3D Rankine panel method, and the mooring force for the forces exerted on the floating platform. Additionally the aerodynamic force was calculated based on the blade element momentum theory for the blades.
Due to the limitation of supply and harmfulness of fossil fuel, the interest in renewable resources such as wind power is growing. Land-based wind power has been the world's fastest growing renewable energy source for more than a decade now. On-land turbines, however, are limited in size to about 3 MW due to transportation constraints. Also, it is advantageous for- offshore wind turbines to develop very large multi-megawatt turbines to make it worth the cost because the offshore support structure becomes a large factor in the overall cost equation. These are the reasons why 5-MW wind turbines are installed at locations that are farther away from the coastline.
