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Numerical Analysis, Field Testing and Experimental Assessment of Offshore Wind...
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Numerical Analysis, Field Testing and Experimental Assessment of Offshore Wind Turbines

A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "A3: Wind, Wave and Tidal Energy".

Deadline for manuscript submissions: closed (31 March 2022) | Viewed by 27876

Special Issue Editors

Dr. Madjid Karimirad

E-Mail Website
Guest Editor
School of Natural and Built Environment, Queen’s University Belfast, Belfast, UK
Interests: marine structures; offshore mechanics; floating wind turbines; offshore renewable energy; stochastic dynamics; experimental and numerical assessment
Special Issues, Collections and Topics in MDPI journals
Dr. Amy Robertson

E-Mail Website
Guest Editor
National Renewable Energy Laboratory, 15013 Denver W Pkwy, Golden, CO 80401, USA
Interests: offshore wind system dynamics; structural dynamics modelling; verification and validation; data analysis
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Although offshore wind turbines (OWTs) have seen rapid growth in the past decade, the further development of these structures to reduce the levelized cost of energy (LCOE) needs proper experimental and numerical analysis and thorough field assessment. Therefore, research-driven developments to explore new concepts/structures, testing methodology, numerical modelling tools and simulation methods are required.

Offshore wind turbines are subject to complicated loads and load effects, which demand the comprehensive numerical modelling representation of physics. Important factors affecting the design, functionality, structural integrity and performance of offshore wind turbines include—but are not limited to—fluid–structure interaction, controller actions, intense dynamic effects, non-linear loadings, extreme and harsh weather conditions, and impact pressure loads. The interdependence between loads, load effects and structural strength requires more advanced numerical tools, nonlinear modelling and innovative testing procedures.

We invite researchers and scientists to contribute original research articles that will stimulate the continuing progress of the OWTs field, with a focus on state-of-the-art numerical modelling and the experimental assessment of offshore wind engineering. We are particularly interested in articles describing new methodologies, analytical and numerical tools, as well as theoretical methods dealing with engineering problems. Potential topics include, but are not limited to:

  • Innovative experimental methods
  • Scaling and scale effects
  • Statistical methods and environmental resource assessment
  • Wind, wave and current interactions
  • Comprehensive handling of engineering problems, in particular, design aspects
  • Numerical methods for structural and fluid dynamics
  • Computational fluid dynamics (CFD)
  • Finite element methods (FEM)
  • Fluid–structure interaction (FSI)
  • Aero-hydro-servo-geo-elastic models for fixed and floating offshore wind turbines
  • Automatic control methods applied for OWTs engineering problems
  • Robust nonlinear models for fast simulation
  • Comprehensive numerical methods for high-fidelity simulation of behaviour and functionality
  • Verification and validation, code-to-code comparison, as well as experiments
  • Insight into the philosophy and power of numerical simulations
  • Nonlinearities in physical systems and numerical models
  • Coupled effects between floater and mooring system
  • Soil–structure interaction
  • Higher order wave loads and responses
  • Field and laboratory testing and experimental procedures

Dr. Madjid Karimirad
Dr. Amy Robertson
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Energies is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • nonlinear modeling
  • numerical simulations
  • offshore wind turbines
  • floating wind turbines
  • experimental assessment
  • field and laboratory testing
  • dynamic analysis

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Related Special Issue

Published Papers (6 papers)

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Research

23 pages, 4133 KiB  
Article
Numerical Assessment of a Tension-Leg Platform Wind Turbine in Intermediate Water Using the Smoothed Particle Hydrodynamics Method
by Bonaventura Tagliafierro, Madjid Karimirad, Iván Martínez-Estévez, José M. Domínguez, Giacomo Viccione and Alejandro J. C. Crespo
Energies 2022, 15(11), 3993; https://doi.org/10.3390/en15113993 - 28 May 2022
Cited by 19 | Viewed by 4250
Abstract
The open-source code DualSPHysics, based on the Smoothed Particle Hydrodynamics method for solving fluid mechanics problems, defines a complete numerical environment for simulating the interaction of floating structures with ocean waves, and includes external libraries to simulate kinematic- and dynamic-type restrictions. In this [...] Read more.
The open-source code DualSPHysics, based on the Smoothed Particle Hydrodynamics method for solving fluid mechanics problems, defines a complete numerical environment for simulating the interaction of floating structures with ocean waves, and includes external libraries to simulate kinematic- and dynamic-type restrictions. In this work, a full validation of the SPH framework using experimental data available for an experimental test campaign on a 1:37-scale floating offshore wind turbine tension-leg platform (TLP) is presented. The first set of validation cases includes a surge decay test, to assess the quality of the fluid–solid interaction, and regular wave tests, which stimulate the mooring system to a large extent. During this phase, tendons (tension legs) that are simulated by MoorDyn+ are validated. Spectral comparison shows that the model is able to capture the surge and pitch dynamic amplification that occurs around the resonant fundamental mode of vibration. This work concludes with a numerical investigation that estimates the response of TLP under extreme events defined using multiple realizations of irregular sea states; the results suggest that the tendon loads are sensitive to the sea-state realization, providing maximum tendon peak forces in a range of ±10% about the mean. Furthermore, it is shown that the load pattern that forms from considering the relative position of the tendons to the incident wave direction leads to higher forces (≈20%). Full article
(This article belongs to the Special Issue Numerical Analysis, Field Testing and Experimental Assessment of Offshore Wind Turbines)
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17 pages, 3760 KiB  
Article
Development of Combined Load Spectra for Offshore Structures Subjected to Wind, Wave, and Ice Loading
by Moritz Braun, Alfons Dörner, Kane F. ter Veer, Tom Willems, Marc Seidel, Hayo Hendrikse, Knut V. Høyland, Claas Fischer and Sören Ehlers
Energies 2022, 15(2), 559; https://doi.org/10.3390/en15020559 - 13 Jan 2022
Cited by 3 | Viewed by 2924
Abstract
Fixed offshore wind turbines continue to be developed for high latitude areas where not only wind and wave loads need to be considered but also moving sea ice. Current rules and regulations for the design of fixed offshore structures in ice-covered waters do [...] Read more.
Fixed offshore wind turbines continue to be developed for high latitude areas where not only wind and wave loads need to be considered but also moving sea ice. Current rules and regulations for the design of fixed offshore structures in ice-covered waters do not adequately consider the effects of ice loading and its stochastic nature on the fatigue life of the structure. Ice crushing on such structures results in ice-induced vibrations, which can be represented by loading the structure using a variable-amplitude loading (VAL) sequence. Typical offshore load spectra are developed for wave and wind loading. Thus, a combined VAL spectrum is developed for wind, wave, and ice action. To this goal, numerical models are used to simulate the dynamic ice-, wind-, and wave-structure interaction. The stress time-history at an exemplarily selected critical point in an offshore wind energy monopile support structure is extracted from the model and translated into a VAL sequence, which can then be used as a loading sequence for the fatigue assessment or fatigue testing of welded joints of offshore wind turbine support structures. This study presents the approach to determine combined load spectra and standardized time series for wind, wave, and ice action. Full article
(This article belongs to the Special Issue Numerical Analysis, Field Testing and Experimental Assessment of Offshore Wind Turbines)
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38 pages, 5910 KiB  
Article
OC6 Phase Ia: CFD Simulations of the Free-Decay Motion of the DeepCwind Semisubmersible
by Lu Wang, Amy Robertson, Jason Jonkman, Jang Kim, Zhi-Rong Shen, Arjen Koop, Adrià Borràs Nadal, Wei Shi, Xinmeng Zeng, Edward Ransley, Scott Brown, Martyn Hann, Pranav Chandramouli, Axelle Viré, Likhitha Ramesh Reddy, Xiang Li, Qing Xiao, Beatriz Méndez López, Guillén Campaña Alonso, Sho Oh, Hamid Sarlak, Stefan Netzband, Hyunchul Jang and Kai Yuadd Show full author list remove Hide full author list
Energies 2022, 15(1), 389; https://doi.org/10.3390/en15010389 - 5 Jan 2022
Cited by 28 | Viewed by 5463
Abstract
Currently, the design of floating offshore wind systems is primarily based on mid-fidelity models with empirical drag forces. The tuning of the model coefficients requires data from either experiments or high-fidelity simulations. As part of the OC6 (Offshore Code Comparison Collaboration, Continued, with [...] Read more.
Currently, the design of floating offshore wind systems is primarily based on mid-fidelity models with empirical drag forces. The tuning of the model coefficients requires data from either experiments or high-fidelity simulations. As part of the OC6 (Offshore Code Comparison Collaboration, Continued, with Correlation, and unCertainty (OC6) is a project under the International Energy Agency Wind Task 30 framework) project, the present investigation explores the latter option. A verification and validation study of computational fluid dynamics (CFD) models of the DeepCwind semisubmersible undergoing free-decay motion is performed. Several institutions provided CFD results for validation against the OC6 experimental campaign. The objective is to evaluate whether the CFD setups of the participants can provide valid estimates of the hydrodynamic damping coefficients needed by mid-fidelity models. The linear and quadratic damping coefficients and the equivalent damping ratio are chosen as metrics for validation. Large numerical uncertainties are estimated for the linear and quadratic damping coefficients; however, the equivalent damping ratios are more consistently predicted with lower uncertainty. Some difference is observed between the experimental and CFD surge-decay motion, which is caused by mechanical damping not considered in the simulations that likely originated from the mooring setup, including a Coulomb-friction-type force. Overall, the simulations and the experiment show reasonable agreement, thus demonstrating the feasibility of using CFD simulations to tune mid-fidelity models. Full article
(This article belongs to the Special Issue Numerical Analysis, Field Testing and Experimental Assessment of Offshore Wind Turbines)
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14 pages, 2322 KiB  
Article
Modeling the TetraSpar Floating Offshore Wind Turbine Foundation as a Flexible Structure in OrcaFlex and OpenFAST
by Jonas Bjerg Thomsen, Roger Bergua, Jason Jonkman, Amy Robertson, Nicole Mendoza, Cameron Brown, Christos Galinos and Henrik Stiesdal
Energies 2021, 14(23), 7866; https://doi.org/10.3390/en14237866 - 24 Nov 2021
Cited by 20 | Viewed by 7724
Abstract
Floating offshore wind turbine technology has seen an increasing and continuous development in recent years. When designing the floating platforms, both experimental and numerical tools are applied, with the latter often using time-domain solvers based on hydro-load estimation from a Morison approach or [...] Read more.
Floating offshore wind turbine technology has seen an increasing and continuous development in recent years. When designing the floating platforms, both experimental and numerical tools are applied, with the latter often using time-domain solvers based on hydro-load estimation from a Morison approach or a boundary element method. Commercial software packages such as OrcaFlex, or open-source software such as OpenFAST, are often used where the floater is modeled as a rigid six degree-of-freedom body with loads applied at the center of gravity. However, for final structural design, it is necessary to have information on the distribution of loads over the entire body and to know local internal loads in each component. This paper uses the TetraSpar floating offshore wind turbine design as a case study to examine new modeling approaches in OrcaFlex and OpenFAST that provide this information. The study proves the possibility of applying the approach and the extraction of internal loads, while also presenting an initial code-to-code verification between OrcaFlex and OpenFAST. As can be expected, comparing the flexible model to a rigid-body model proves how motion and loads are affected by the flexibility of the structure. OrcaFlex and OpenFAST generally agree, but there are some differences in results due to different modeling approaches. Since no experimental data are available in the study, this paper only forms a baseline for future studies but still proves and describes the possibilities of the approach and codes. Full article
(This article belongs to the Special Issue Numerical Analysis, Field Testing and Experimental Assessment of Offshore Wind Turbines)
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26 pages, 8865 KiB  
Article
OC6 Phase Ib: Floating Wind Component Experiment for Difference-Frequency Hydrodynamic Load Validation
by Amy Robertson and Lu Wang
Energies 2021, 14(19), 6417; https://doi.org/10.3390/en14196417 - 8 Oct 2021
Cited by 11 | Viewed by 3307
Abstract
A new validation campaign was conducted at the W2 Harold Alfond Ocean Engineering Laboratory at the University of Maine to investigate the hydrodynamic loading on floating offshore wind substructures, with a focus on the low-frequency contributions that tend to drive extreme and fatigue [...] Read more.
A new validation campaign was conducted at the W2 Harold Alfond Ocean Engineering Laboratory at the University of Maine to investigate the hydrodynamic loading on floating offshore wind substructures, with a focus on the low-frequency contributions that tend to drive extreme and fatigue loading in semisubmersible designs. A component-level approach was taken to examine the hydrodynamic loads on individual parts of the semisubmersible in isolation and then in the presence of other members to assess the change in hydrodynamic loading. A variety of wave conditions were investigated, including bichromatic waves, to provide a direct assessment of difference-frequency wave loading. An assessment of the impact of wave uncertainty on the loading was performed, with the goal of enabling validation with this dataset of numerical models with different levels of fidelity. The dataset is openly available for public use and can be downloaded from the U.S. Department of Energy Data Archive and Portal. Full article
(This article belongs to the Special Issue Numerical Analysis, Field Testing and Experimental Assessment of Offshore Wind Turbines)
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15 pages, 5982 KiB  
Article
The Effect of a Flexible Blade for Load Alleviation in Wind Turbines
by Azael Duran Castillo, Juan C. Jauregui-Correa, Francisco Herbert, Krystel K. Castillo-Villar, Jesus Alejandro Franco, Quetzalcoatl Hernandez-Escobedo, Alberto-Jesus Perea-Moreno and Alfredo Alcayde
Energies 2021, 14(16), 4988; https://doi.org/10.3390/en14164988 - 13 Aug 2021
Cited by 8 | Viewed by 2406
Abstract
This article presents the analysis of the performance of a flexible wind turbine blade. The simulation analysis is based on a 3 m span blade prototype. The blade has a flexible surface and a cam mechanism that modifies the aerodynamic profile and adapts [...] Read more.
This article presents the analysis of the performance of a flexible wind turbine blade. The simulation analysis is based on a 3 m span blade prototype. The blade has a flexible surface and a cam mechanism that modifies the aerodynamic profile and adapts the surface to different configurations. The blade surface was built with a flexible fiberglass composite, and the internal mechanism consists of a flexible structure actuated with an eccentric cam. The cam mechanism deforms five sections of the blade, and the airfoil geometry for each section was measured from zero cam displacement to full cam displacement. The measured data were interpolated to obtain the aerodynamic profiles of the five sections to model the flexible blade in the simulation process. The simulation analysis consisted of determining the different aerodynamic coefficients for different deformed surfaces and a range of wind speeds. The aerodynamic coefficients were calculated with the BEM method (QBlade®); as a result, the data performance of the flexible blade was compared for the different deformation configurations. Finally, a decrease of up to approximately 6% in the mean bending moment suggests that the flexible turbine rotor presented in this article can be used to reduce extreme and fatigue loads on wind turbines. Full article
(This article belongs to the Special Issue Numerical Analysis, Field Testing and Experimental Assessment of Offshore Wind Turbines)
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