Structural dynamics modelling of floating wind turbines: a preliminary study on the role of large rotation

This paper presents a preliminary study to asses the importance of modeling finite rotations in the structural dy- namic analysis of offshore wind turbines. The dynamic problem is formulated with a dependent coordinate ap- proach and the equations of motion are solved by using a suitable Lie-group time-integrator. This approach is aimed at handling with higher accuracy systems undergoing large displacements (rotations) as for the floating wind turbine. In the reality the problem is characterized by a rather complex hydro-aero-elastic interaction, but in this study it is strongly simplified with the intent to preliminary evaluate the benefits that a finite-rotations-based dynamic model can provide in comparison with more traditional time-integrator schemes. The examples presented show that when the system observes large displacements a finite rotation approach is much more accurate and it is strongly recommended.