Investigation of higher-harmonic wave loads and low-frequency resonance response of floating offshore wind turbine under extreme wave groups

Zeng，Xinmeng1; Shi，Wei2; Feng，Xingya3; Shao，Yanlin4; Li，Xin2

2023-05-01

10.1016/j.marstruc.2023.103401

MARINE STRUCTURES   Impact Factor & Quartile

0951-8339

1873-4170

When floating offshore wind turbines (FOWT) encounter extreme waves in operation, it is a highly nonlinear system involving floater motion and extreme wave–structure interactions. The behavior is crucial for floating offshore wind turbine safety. With the aid of a high-fidelity CFD solver, a harmonic separation method through a ‘Stokes-like’ formulation was adopted to obtain the parameters for each harmonic response. The present study focuses on analyzing higher harmonic load, dynamic motion response, and tension load of the mooring line the DeepCwind semi-submersible FOWT. The results show that the higher-harmonic wave load cannot be ignored in the extreme marine environment, the second harmonic can be over 16% of the linear wave load, and the third harmonic can be over 10% of the linear wave load with large wave steepness. The duration of a focused wave crest interaction with the platform is a short process of only 1.4 s in model scale, corresponding to about 10 s for the prototype. The wave runup at the upstream column is larger than the other columns, and the flow velocity is double that of the wave without the floater in presence. The dynamic response of the floater contains two phases, ’forced oscillations’ is identified to be drag-driven from odd harmonics, and ’free decay’ mainly comes from second-order difference-frequency influence from even harmonics. The properly normalized wave forces of surge and heave motion are not influenced by steepness kA. For surge motion, the total motion mainly comes from the nonlinear low frequency component. For pitch motion, the linear response is dominant in small kA. When the steepness kA increases gradually, the second-order low-frequency response of pitch motion will increase rapidly and dominate the total response.

Floating offshore wind turbine Focused wave group Harmonic separation method Higher harmonics Low-frequency resonance response

SCI

English

Others

National Natural Science Foundation of China["52071058","51939002"] ; Fundamental Research Funds for the Central Universities, China[82233001]

Engineering

Engineering, Marine ; Engineering, Civil

WOS:000950005900001

ELSEVIER SCI LTD

ENGINEERING

2-s2.0-85149059155

Scopus

1.College of Engineering,Ocean University of China,Qingdao,China
2.State Key Laboratory of Coastal and Offshore Engineering,Dalian University of Technology,Dalian,China
3.Department of Ocean Science and Engineering,Southern University of Science and Technology,Shenzhen,China
4.Department of Mechanical Engineering,Technical University of Denmark,Copenhagen,Denmark

Zeng，Xinmeng,Shi，Wei,Feng，Xingya,et al. Investigation of higher-harmonic wave loads and low-frequency resonance response of floating offshore wind turbine under extreme wave groups[J]. MARINE STRUCTURES,2023,89.

Zeng，Xinmeng,Shi，Wei,Feng，Xingya,Shao，Yanlin,&Li，Xin.(2023).Investigation of higher-harmonic wave loads and low-frequency resonance response of floating offshore wind turbine under extreme wave groups.MARINE STRUCTURES,89.

Zeng，Xinmeng,et al."Investigation of higher-harmonic wave loads and low-frequency resonance response of floating offshore wind turbine under extreme wave groups".MARINE STRUCTURES 89(2023).