Proceedings of the Thirty-second (2022) International Ocean and Polar Engineering ConferenceShanghai, 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

Large Eddy Simulations for Floating Wind Turbine Under Complex Atmospheric Inflow
Shun Xu1, Nina Wang2, Decheng Wan1*, Sergei Strijhak3
1Computational Marine Hydrodynamics Lab (CMHL), School of Naval Architecture, Ocean and Civil Engineering,
Shanghai Jiao Tong University, Shanghai, China
2Key Laboratory of Far-shore Wind Power Technology of Zhejiang Province, Huadong Engineering Corporation Limited, Hangzhou, China
3Ivannikov Institute for System Programming of the Russian Academy of Sciences, Moscow, Russia*Corresponding author

capacity of wind turbine in 2020 reached up to 93GW, resulting 53%
growing compared with the last year. The development trend of windturbine is gradually towards to large-scale and floating type, leading tothe significant impact on the aerodynamic performance and fatigue loadof the wind turbine induced by the complex atmospheric boundary layer(ABL) inflow. Therefore, the numerical simulation for studying theoperation performance of FOWT under the complex ABL inflow is very
necessary.
The complex ABL inflow on the onshore wind turbine has been widely
researched. Churchfield et al. [3] incorporate the large eddy simulations(LES) and actuator line model (ALM) to present a numerical study ofatmospheric and turbine wakes on wind turbine dynamics with two
different atmospheric stability and surface roughness, they point out thatthe turbulence structures generated in the ABL can cause the isolatedloading events as significant as when wind turbine waked by a upstream
turbine. Lee et al. [4] study the effects of atmospheric stability and surface
roughness on wind turbine fatigue load, the results show that the twoparameters have evidently impacts on turbine fatigue load. Lu et al. [5]investigate the characteristics of wind turbine wakes under a stableboundary layer inflow, they argue that a skewed spatial structure iscaused by the Coriolis force and a part of turbulence energy is driven
away from the center of turbine wakes. Ning and Wan [6] investigate thewake meandering and its effects to wind turbulence aerodynamics.
Compared with the onshore wind turbine, the inflow wind conditions aremore simplified on the FOWT. Cheng et al. [7] perform the fully coupled
aero-hydrodynamic responses of a FOWT with the combined uniform
wind inflow and regular incident wave. In order to consider theproperties of ABL inflow, the shear wind inflow is adopted for theFOWT, and the wind turbine blades are modeled by the ALM method [8].
However, the wind turbine aerodynamic performance is significantlyaffected by the complex ABL inflow due to the large-scale developmentof wind turbine blades. Li et al. [9] study the effects of wind fields toFOWT aerodynamic performance, and the thrust force and power
generation become very unstable because of the presence of turbulencewind fields. Johlas et al. [10, 11] examine the turbine wake characteristics
of FOWT in complex ABL inflow and the effects of different platforms
to wake characteristics and platform motions.
In the present study, the numerical simulation of FOWT under complex
ABL inflow is investigated. The LES method incorporated with theALM is adopted to investigate the aerodynamic performance of FOWT,ABSTRACT
The development of wind turbine towards to larger-scale and floatingtype, leading to the significant impact on the aerodynamic performanceand fatigue load of the wind turbine induced by the complex atmosphericinflow. In this study, the numerical investigation of floating wind turbine(FOWT) under complex atmospheric boundary layer (ABL) inflow isperformed. The NREL 5MW reference turbine mounted on the OC4
floating platform is adopted as the research object. Large eddy
simulations (LES) combined with the actuator line model is used for thewind turbine blades numerical simulation, and the platform motions aresolved by the potential theory. The complex ABL inflow is generatedusing a precursor LES method with long-enough time to obtain the quasiequilibrium state turbulence. And the calculation results are comparedwith the uniform wind inflow. The oscillation amplitude of the rotor
power for FOWT under uniform inflow does not exceed 40% with theexcitation of regular incident wave, while the amplitude for ABL inflow
reaches up to 100%. Long-term significant response of rotor power isobserved because of the large-scale high-velocity airflow upstream theturbine rotor plane. The later asymmetric distribution of ABL inflow
velocity is responsible for evidently response of aerodynamic yaw
moment amplitude. For the floating platform motions, the oscillating
amplitude of yaw motion for ABL inflow is over 2°, while the output
value for uniform inflow is steady and does not exceed 0.2°. The
differences of the other five platform motions are not significantly
observed.

KEY WORDS: floating wind turbine; atmospheric boundarylayer; larger eddy simulations; actuator line model; precursor
simulation.
INTRODUCTION
In recent years, the traditional fossil resources are gradually difficult tomeet the significant demand of energy with the greatly development ofsociety. However, wind energy has received increasing attention due tothe properties of non-polluting, renewable and large reserves [1], whichis responsible for the prosper growth of the wind turbine technology.
According to the 2021 Global Wind Energy Report [2], the installed190