Hydroelastic response of a flexible spar floating wind turbine: Numerical modelling and validation

Abstract

This study examines the hydroelastic response of a large floating wind turbine (FWT) through coupled numerical analysis. Four numerical models with different levels of complexity in the hydrodynamic and structural modelling were established for a scaled 10 MW elastic spar FWT using the engineering tool SIMA. Two of them model the platform as a flexible body with distributed wave loads based on either Morison’s equation or based on potential flow theory combined with Morison-type drag. The two other models consider the platform as a rigid body. These models were calibrated and validated against experimental results from a series of characterization tests (hammer test and decay test) and tests in waves (regular and irregular). Results for motions, strains, and tower base fore-aft bending moment are compared. All models predict damped natural periods for rigid body motions close to the experimental results from decay tests (within 4%). Overall, the wave-frequency responses (motion, strain on the platform, and tower base bending moment) in all models agree well with the experimental results in regular waves and irregular waves. For the structural internal loads around the 1st bending mode natural frequency, the distributed potential flow model agrees well with the experiments, while a large overestimation is seen in the flexible model with Morison’s equation.