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

Numerical Investigation on a Fully Coupled Higher-order aero-hydrodynamic Analysis Modelfor Offshore Wind Turbine
Sijia Deng, Dezhi Ning
State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology,Dalian, China;
Yingyi Liu
Research Institute for Applied Mechanics, Kyushu University,Fukuoka, Japan;
Lin Lin, Zhenhua Gu
Shanghai Investigation, Design and Research Institute of China Three Gorges Corporation,Shanghai, China.
hand, with the continuous development of the wind power technology,
onshore wind power in the future will not be able to meet the needs ofrenewable energy developments. On the other hand, the global deep-sea
resources are abundant, the future development of offshore wind power
will be gradually expanded from shallow to deep sea. In deep-sea (over60m water depth), the traditional fixed foundations are not practicallyfeasible due to the high cost and the unguaranteed stability. Therefore,
the development of floating offshore wind turbines (FOWTs) has been a
research focus of both industrial and academic institutions (Butterfieldet al., 2007).

ABSTRACT
A floating offshore wind turbine (FOWT) is always subjected to thecombined action of nonlinear waves and winds in the realistic operatingconditions. It is important to explore the high-order hydrodynamic loads
and the motion responses of the offshore floating wind turbine. Based on
the nonlinear potential flow theory and the perturbative expansion technique, the time-domain higher-order boundary element method(HOBEM) is used to model the hydrodynamics of an offshore floating
wind turbine in the present study. In addition, the Blade Element Momentum Theory (BEMT) is applied to the aerodynamics. The presentmethodology is verified by comparing with the FAST code. It is foundthat the nonlinear effect is significant. This study can provide a reference
for the design of an offshore wind turbine system.

Numerical simulations are widely adopted in the design of engineeringwith the advantages of high speed and low cost. The fully coupled aerohydrodynamic model is the key to a reliable numerical prediction of a
FOWT's dynamic response. Numerical simulations are recommended tobe carried out in the time domain due to the strong nonlinear and coupling effects on FOWT.

KEY WORDS: Floating offshore wind turbine (FOWT); Semisubmersible floating platform; Mooring system; Numerical simulation;
Higher-order boundary element method (HOBEM).

FAST is a widely used aero-hydro-elastic coupling program for simulating the horizontal axis wind turbine turbines. FAST is mainly composedof, an aerodynamic module (AeroDyn), a wind module (Inflow Wind),an control module (ServoDyn), a hydrodynamics module (Hydrodyn)
and other sub-modules (Jonkman and Buhl, 2005; Zandt, 2007). The
AeroDyn module is based on the Blade Element Momentum Theory(BEMT) and generalized wake model (GDW) for predicting aerodynamic loads.The HydroDyn module allows multiple approaches for calculating the hydrodynamic loads on a structure including the potentialflow theory solution, the strip-theory solution, or the hybrid combinationof both (Jonkman et al., 2014). ‘Bladed’ is one of the most well-known
commercial software for the design of wind turbines (European Wind
Energy Association, 2015). The impeller aerodynamic model provided
by Bladed is also based on the combination of the well-known BEMT.
In addition, two main extensions of this theory are built into the software
code as options to deal with non-stationary air aerodynamic properties.

INTRODUCTION
The offshore wind turbine is widely applied to the utilization of wind
power in the ocean engineering. Compared to land-based wind turbines,
floating wind turbines are located in deep-sea, bringing more challenges
in the cost management. However, the economic advantage of offshore
wind turbines are apparent, in terms of a more stable year-round windspeed, a higher proportion of high-quality wind energy, greater turbine
power, less wind farm development space limitations, and less visualpollution, etc. (Barthelmie et al., 2010; Breton and Moe, 2009).
Offshore wind turbine foundation is mainly divided into two forms: fixed
foundation and floating foundation. The fixed foundations are typicallyapplied in the shallow water regions (Musial et al., 2006). On the one

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