Effects of Hull Flexibility on the Structural Dynamics of a TLP Floating Wind Turbine

Abstract

Structural analysis of floating wind turbines is normally carried out with the hull considered as a rigid body. This paper explores the consequences of modeling the pontoons of a tension leg platform (TLP) wind turbine as flexible structures. The analysis is based on numerical simulations of free decays, structural response to wave excitation and short-term fatigue damage accumulation at chosen points of the platform. In addition, the importance of considering hydroelasticity effects is evaluated. It is observed that pontoon flexibility can change the platform natural periods significantly, as well as the intensity and peak frequencies of internal structural loads. The adoption of a fully rigid-body is shown to be non-conservative for the fatigue damage analysis. Loads due to hydroelasticity have order of magnitude comparable to those related to rigid-body motions, but still lower enough to be considered of secondary importance.