Dynamic Response Characteristics of a Floating Support Structure of Low Rigidity FOWT with Guywire Supported Tower and Single-Point Mooring

Abstract

　Dynamic response characteristics of a floating support structure of a Floating Offshore Wind Turbines (FOWT) with low rigidity characterized by guywire supported tower and single-point mooring was investigated through wave tank experiments and numerical simulation using analysis code UTWind. The results of the wave tank experiments showed that the motion has a nonlinearity to wave height mostly at resonance condition due to the viscous effect and a waveless response was observed at a specific wave period. Meanwhile, the elastic deformation increases in two wave periods, the peak at longer wave period is caused by the inertial force of motion of RNA and tower, and the peak at shorter wave period is caused by sagging-hogging elastic response of the floater. The comparison of the results from the tank experiment and UTWind simulation confirmed that the calculation is accurate except for the resonance period, as the viscous effect has a significant effect on the response where careful selection of drag coefficient is required. Additionally, the numerical method revealed that upwind guywire is affected by Pitch and Heave, while the downwind guywire is affected by Pitch and Roll. The comparison of results with slightly different incident wave angles revealed that the amplitude of the bending moment significantly changes due to small variations in wave period and incident wave angle at short wave period. Moreover, the study found that Heave motion varies depending on whether the wave comes from front or back of the floater. These findings are crucial for the design of FOWT.