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

Experimental Study of Dynamic Characteristics of an Ultra-Large Jacket Offshore Wind Turbine Under
Wind Loads Using Joint Aero-Hydro-Elastic Similarities
Ying Li1, Dongzhe Lu2,3, Wenhua Wang2,3, Xin Li2,3
1Chinese-German Institute of Engineering, Zhejiang University of Science and Technology, Hangzhou, China
2Institute of Earthquake Engineering, Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian, China
3

State Key Laboratory of Coastal and Offshore Engineering, Faculty of Infrastructure Engineering,Dalian University of Technology, Dalian, China

substructure is the preferred for the offshore wind farms in the depth of30 - 50 m, because of its advantages, such as relative smallhydrodynamic loads and deformations.
The dynamic characteristics of typical bottom-fixed offshore windturbines (OWTs) are studied by Chen et al. (2011) and He et al (2012).
In the study, the finite element (FE) model of the OWT support
structure is established, and the rotor nacelle assembly (RNA) issimulated by a concentrated mass and shell - beam elements
respectively. Besides the above simplified FE model, the coupledanalysis model of OWT which can simulate the flexibilities of RNA
and support system is proposed by researchers (Popko et al., 2012). To
investigate the influence of the jacket structural parameters and pilesoil interactions on the dynamic responses of OWT, Shi et al. (2013)
and Plodpradit et al. (2019) established the coupled analysis model of ajacket OWT, and the coupling effects between the RNA and support
system are proved. The comparisons between the simplified FE andcoupled model are carried out by Chen et al. (2017), and the remarkableinfluence of RNA on the tower motions are observed. Using the aero,hydro and elastic analysis theories, Zhao et al. (2021) established thefully coupled analysis model of an ultra-large semi-submersible
floating OWT, the influence of mechanical control strategies on theplatform motions are discussed.
According to the related studies, the scaled model design of RNA is akey issue for the dynamic model tests of OWTs. The recommended
design methods can be categorized as: (1) The equivalent scaled
circular disk model, such as the study of Ren et al. (2016), Wan et al.
(2015) and Ahn and Shin (2019). (2) The geometry scaled RNA model,
the principle feature of such model is that the airfoils of the prototype
rotor system are applied in the scaled RNA model (Martin, 2009). (3)The performance scaled RNA model, the airfoils of the blade model are
redesigned based on the aerodynamic similarities, such as the study ofDu et al. (2016). (4) The real time hybrid test model, the prototype
RNA numerical model is reserved instead of the scaled physical model(Sauder et al., 2016; Urban et al., 2019), in order to satisfy theaerodynamic similarities. By comparing with the first two methods, theperformance scaled RNA model can improve the aerodynamic loads

ABSTRACT
In order to investigate the coupling mechanisms of bottom fixedoffshore wind turbines (OWTs) under environmental loads, the scaled
physical model of DTU 10-MW wind turbine with jacket substructureis designed. The geometry scale ratio is selected as 1/75 in the study,
and the joint Froude number and elastic similarity is applied to design
the scaled model of the support system. Meanwhile, the airfoil ofSD7032 is applied and the sectional geometries are updated in thedesign of blade model, in order to ensure the similarity of aerodynamicloads. Meanwhile, the drivetrain and mechanical control systemdeveloped accordingly. Then the performance scaled RNA model isdeveloped. The simulation accuracy of the RNA model is primarilyvalidated. Sequentially, the dynamic tests of the scaled OWT model
under different wind speeds are conducted. The coupling mechanisms
are obtained from the experimental data, such as the coupling effects
between the rotor and support system. It can be seen the remarkableinfluence of the rotational frequencies on the structural responses of an
operation OWT, besides the OWT fundamental frequency. The
fundamental and blade collective flap modes dominate the responses ofOWT in the parked state. Therefore, it proved the necessity of applying
coupled numerical model in the analysis of OWTs.

KEY WORDS: offshore wind turbine; dynamic model test; couplingmechanisms; Froude similarity; aerodynamic similarity.

INTRODUCTION
According to the Global Wind Energy Council (GWEC), more than
235GW of new offshore wind capacity would be installed worldwide inthe next decade. At the end of 2021, China became the world's largest
offshore wind power market. The offshore regions with a depth of 2550 m is one of the most potential areas for the development of China's
offshore wind power, with a wind energy development potential of400GW. Compared with the other fixed substructures, the jacket-type308