Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering Conference
Shanghai, China, June 5–10, 2022
Copyright © 2022 by the International Society of Offshore and Polar Engineers (ISOPE)
ISBN 978-1-880653-81-4; ISSN 1098-6189

www.isope.org

Fully Coupled Dynamic Analysis of the OO-STAR Floating Wind Turbine in Different Water Depths
Mingsheng Chena,b, Hao Zhoua,b, Chun Bao Lia,b,*
a Key Laboratory of High Performance Ship Technology, Wuhan University of Technology), Ministry of Education,Wuhan, China;b School of Naval Architecture, Ocean and Energy Power Engineering, Wuhan University of Technology,Wuhan, China

same time, the Kincardine offshore wind farm under construction marks
the exploration of the 10MW level of floating wind turbines. The largescale FOWT has deepened its deployment depth. However, The South
China Sea has a vast sea area as the depth of 50 meters (Hsiao et al.,2016). The bottom-fixed substructure can no longer be used at deeper
water depths(＞50m) due to the high cost (Han et al., 2017), Therefore,
it is of great significance to study the mooring and platform dynamic
characteristics of ultra-large floating wind turbines in different water
depths.
The OC4-OC6 research of IEA WIND TASK30 of NREL in theUnited States is a typical study in the field of FOWT. Jonkman et al.
(2007) developed the Hydrodyn module on the basis of the aero-servoelastic coupling onshore wind turbines analysis program-FAST. They
conducted a comprehensive analysis of various types of FOWT andcompare them with the experimental results. Based on the above work,
they obtained a convincing system response data result. Hassan et al.
(2003) used the multi-body dynamics and MBS similar to FAST toestablish the dynamic analysis program Bladed. In terms of analyzing theimpact of water depth on the response of FOWT. Wayman et al. (2006)
analyzed the Shallow Drafted Barge (SDB) and Tension Leg Platform(TLP) concept designed by NREL for a water depth of 10-200m, theresponse of wave excitation, the natural frequency of the system and thestatistical value of the system's movement in various wind and wave
environments were evaluated in certain frequency ranges. Their research
preliminarily verified the feasibility of floating foundation in medium
water (Li et al., 2018). Zhao et al. (2019) studied the motion response
characteristics of the DTU10MW, and compared the difference in themotion response spectrum of DTU10MW and NREL5MW. windturbines under rated operating conditions. The conclusion shows thatwind and waves have a more obvious incentive effect on DTU10MW
wind turbines. Ma et al. (2021) proposed a new mooring scheme tosuppress the pitching motion of the floating wind turbine. The Still water
recovery moment of the mooring scheme is analyzed and discussed. Theconclusion shows that the new mooring scheme has a better restrainingeffect on the pitching motion. Karimirad et al. Error! Reference source notfound.(2012) used the linear finite element (FEM) and MBS to establish astructure dynamics model HAWC2 and explored the feasibility of SPAR
in medium water depths, they designed a "ShortSpar" concept which
suitable for medium water depths, and gave the structure's mooring
schemes and its motion response in medium water depths. The results
show that the standard deviations of the motion response of “ShortSpar”
and classic Spar schemes are close, but the tower surge motion andbending moment of the “ShortSpar” increase. Zhang et al. (2020) studied

ABSTRACT
Floating wind turbine technology has become mature in recent
years, it tends to be large-scale and deep-water deployment. Nowadays
floating wind turbines are mainly semi-submersible platforms that aresensitive to the change of water depth and are mostly designed in deep
water over 100 meters. However, the water depth in the South China Sea
tends to be shallower than the North-sea in Europe, which should resultin different mooring and platform dynamic response characteristics. So,
the adaptability of a large floating wind turbine to the middle and shallow
waters of the South China Sea has attracted much attention in China. In
this paper, the DTU10MW wind turbine designed by the Technical
University of Denmark and the OO-STAR platform proposed by theUniversity of Stuttgart are taken as the research objects. The
hydrodynamic model is established by AQWA. Based on the potential
flow theory, the hydrodynamic coefficients of the OO-STAR platform inthree different water depths are compared and further imported intoOPENFAST for fully coupled time-domain simulation. Firstly, mooring
schemes of different water depths are designed based on the bottom
anchor uplift. Then various natural periods of OO-STAR are evaluated(mainly including platform motion and pitch vibration of the tower),
Finally, based on the power spectral density method, the tower-base foreaft bending moments, platform motion, and mooring response
characteristics are analyzed under the low-frequency excitation load of
turbulence wind and different water depth, and the excitation action of
the 1P effect to the structural response is also considered. It provides areference for the design of super large floating wind turbines in a medium
and shallow seas in China.

KEY WORDS: FOWT; OpenFast; Fully coupled analysis; Different
depth; PSD

1.

INTRODUCTION

Over decades of development in renewable industry, offshore windenergy has become renewable energy indispensably. The total global
installed base of the floating offshore wind turbines (FOWT) is 35.3GW
until 2020 (GWEC 2021). China ranks second in the world with 9.88GW
offshore installed. Without a doubt that FOWT will flourish in China.
The world has entered the operational stage of 5MW FOWT with thecompletion of the world's first floating wind farm (H. R. 2015). At the218