| dc.description.abstract | In the recent years, much attention has been given to the design of offshore wind turbines. Today, the largest wind turbine has a rotor diameter of 164m. The harsh environments expose the turbines to large forces from wind and waves. During the service years of a turbine, extreme wind loads must be expected. And the need for tools to accurately analyse the mechanical properties of the turbine blade arise. \\
Isogeometric analysis was introduced in \cite{Hughes2005} in 2005. One of the advantages of isogemetric analysis is that we may use the same mathematical model for geometry and analysis, hence no discretization error occur. \\
With an increased size, the blades of wind turbines become relatively more flexible, and the wind load grows with the size of the blade. Peak wind loads will give large deformations. A nonlinear analysis is required for optimum results \cite{Yuan2009}. \\
In this thesis, we have developed a static non-linear isogeometric finite element solver in Matlab, using bsplines as basisfuction. We started by a study of the basic properties of bsplines. We then derived the linear elasticity equation, and implemented a linear finite element code to solve this. From this, we took the step to nonlinear analysis. We derived the weak form for the Updated Lagrangian Formulation. This resulted in a nonlinear finite element algorithm, which we have implemented in Matlab. \\
For verification, the nonlinear isogeometric solver was compared to the isogeometric NFE program IFEM with a high level of correlation. We applied the nonlinear solver to a twisted bar case, and the wind turbine blade of the
NREL offshore 5-MW baseline wind turbine. | |
