Study Of Unsteady Load And Nonlinear Dynamic Response Of Offshore Wind Turbine

With all kinds of unsteady factors and coupling effects, it is rather difficult to accurately predict the overall dynamic responses of the offshore wind turbine. And it helps a lot to improve the design level and the computing accuracy of the offshore wind turbine with aerodynamic, structural and hydrodynamic coupled.Based on the wind turbine design process, the unsteady loads, the nonlinear dynamic responses and the overall dynamic responses are calculated.A free vortex wake method is presented to compute the unsteady aerodynamic loads on the large scale wind turbine under the unsteady operating conditions of wind shear and dynamic yawing.A geometrical nonlinear finite element method is developed to compute the blade deformation using the Galerkin method and the Hamilton principle. The blade is simplified as a beam model. Its nonlinear stiffness matrix and tangential stiffness matrix are set up, based on which the kinetic equation is formed. The Newmark immediate integration and the modified Newton-Raphson method are used for the time marching. The nonlinear dynamic responses are compared with the linear ones,demonstrating that the nonlinear calculation is more accurate and necessary.The dynamic responses of the onshore and offshore wind turbines are computed and analyzed. The tower of the onshore wind turbine is modeled with the finite element method and the floating platform of the offshore wind turbine is modeled as a rigid body. The wave is simulated with the spectrum function and the wave load is computed with the Morison equations.Finally, the overall dynamic responses of the offshore wind turbine with TLP in different conditions are computed and analyzed, providing meaningful information for the offshore wind turbine design.