Extreme Loading on Floating Offshore Wind Turbines (FOWTs) under Complex Environmental Conditions
Lead Research Organisation:
Lancaster University
Department Name: Engineering
Abstract
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Publications
Ortolani A
(2020)
Computational Fluid Dynamics Analysis of Floating Offshore Wind Turbines in Severe Pitching Conditions
in Journal of Engineering for Gas Turbines and Power
Ortolani A
(2022)
Multi-fidelity Analyses of Rotor Loads of Floating Offshore Wind Turbines with Wind/Wave Misalignment
in Journal of Physics: Conference Series
Ortolani A
(2020)
Cross-comparative analysis of loads and power of pitching floating offshore wind turbine rotors using frequency-domain Navier-Stokes CFD and blade element momentum theory
in Journal of Physics: Conference Series
| Description | One of the key findings of the investigations into unsteady rotor aerodynamics of floating offshore wind turbines (FOWTs) performed by Lancaster University and overseas research partners is the discovery of how low the reliability currently is of low-fidelity engineering codes used for the industrial design and verification of utility-scale FOWTs. This shortcoming is due primarily to the fact that these codes struggle to correctly predict rotor aerodynamics when the direction of the wind is not normal to the rotor plane. This condition occurs very frequently during regular and extreme FOWT operation, due to sea wave induced motion of the whole turbine and misalignment of the directions of mean wind and sea wave propagation. This research has quantified the level of error affecting load predictions - obtained with state-of-the-art codes used in industry - of FOWTs in regular and extreme conditions. These conditions are often characterised by the occurrence of periodic aerodynamic loads caused by excitations of different fundamental frequency (e.g. sea wave frequency and frequency corresponding to the rotor angular speed). For the first time, this research has studied these types of operating conditions by means of high-fidelity Computational Fluid Dynamics (CFD). This has been made possible by the very high computational performance (low runtime) of Lancaster's harmonic balance nonlinear frequency-domain COSA and ARCTIC CFD codes. The use of diverse independent high-fidelity CFD codes (including the COSA and ARCTIC research codes) and state-of-the-art commercial CFD software has enabled achieving new insight into FOWT unsteady aerodynamics, also making available to the R&D community new benchmarks for the development of future high-fidelity simulation-based FOWT design technology. The achieved quantification of the misprediction of FOWT unsteady aerodynamics of low-fidelity FOWT models, particularly in terms of aerodynamics-induced structural loads, provides invaluable data for improving low-fidelity engineering codes for utility-scale FOWT design, which still play a crucial role in industrial FOWT R&D, due to their low computational cost. At the same time, the project has demonstrated for the first time the substantial computational cost reduction of FOWT high-fidelity CFD analysis, achieved by using nonlinear frequency-domain CFD. Combined with machine learning, the relatively low cost of the harmonic balance CFD technology opens the way to using CFD on a routinely base in industrial FOWT design, enabling performance improvements and cost reductions of these large machines. |
| Exploitation Route | The COSA high-fidelity code used to achieve the planned outcomes, namely the COSA harmonic balance code, was made opensource in November 2023 and is now available to all on GitHub at https://github.com/LANCASTER-CFD/COSA. Reference floating offshore wind turbine cases highlighting the quantitative shortcomings of low-fidelity analysis technologies have been published in the two opensource outcomes below. Unrestricted access to these reference use cases has made available to the community key data and information for the development of new efficient high-fidelity design technologies and for developing corrections for the very fast low-fidelity FOWT design technologies used in industry, which will continue to play a key role in the ongoing FOWT growth in the UK and abroad. 1) High-fidelity Time- and Nonlinear Frequency-Domain Analysis of Unsteady Loads of Floating Offshore Wind Turbines in Yawed Wind, 4th Wind Energy Science Conference, Glasgow, United Kingdom, 23-26 May 2023. https://drive.google.com/file/d/1-vURufsSDGgXGVvaVLRIW8byJkiDL55m/view?usp=sharing 2) A. Ortolani, F. Papi, A. Bianchini, G. Persico, J. Drofelnik, M.S. Campobasso, Multi-fidelity Analyses of Rotor Loads of Floating Offshore Wind Turbines with Wind/Wave Misalignment, Journal of Physics: Conference Series, Vol. 2265, no.4, ref. 042010, June 2022. DOI: 10.1088/1742-6596/2265/4/042010. Also presented at TORQUE Conference, 1st - 3rd June 2022, Delft, The Netherlands. |
| Sectors | Aerospace Defence and Marine Energy Environment |
| Description | The novel insight into floating offshore wind turbine (FOWT) aerodynamics achieved in this research by means of unique computationally efficient computational fluid dynamics (CFD) technologies developed at Lancaster University will smooth the way for and increase the success of the further floating wind installations in the UK and abroad in a number of ways. The novel knowledge of FOWT aerodynamics has highlighted important mispredictions of FOWT aerodynamic loads obtained by using the low-fidelity FOWT codes in widespread use in industrial FOWT design. The quantification of these errors will initially allow a recalibration of the safety factors used in industrial design and, ultimately, the improvement of this industrial design methodology, guided by the new quantitative knowledge of FOWT flow physics developed in this project. Moreover, the accurate data obtained with the high-fidelity aerodynamic studies of FOWTs in realistic operating conditions offer the industrial and academic communities unprecedented data for the development of new high-fidelity technologies for direct use in industrial FOWT development. Ultimately these outcomes will play a key role in extending life, increasing operation safety, and boosting renewable energy harvesting, of FOWTs. This will not only contribute to the net zero targets of the UK and many other countries, but will also reduce the levelized cost of energy of floating wind, a critical requirement to consolidate the growth and acceptance of this technology. |
| Sector | Aerospace, Defence and Marine,Energy,Environment |
| Description | ARCHER2 eCSE, eCSE04-1 |
| Amount | £98,717 (GBP) |
| Funding ID | eCSE04-1 |
| Organisation | Daresbury Laboratory |
| Sector | Private |
| Country | United Kingdom |
| Start | 09/2021 |
| End | 09/2022 |
| Title | COSA software. This is a parallel structured multi-block Navier-Stokes code for the analysis of general time- and frequency-domain problems. COSA features the nonlinear harmonic balance solution method, enabling extremely rapid computation of highly nonlinear periodic flow fields. |
| Description | The COSA harmonic balance Navier-Stokes Computational Fluid Dynamic code enables solving highly nonlinear periodic flow fields, such as those of floating offshore wind turbine rotors very rapidly. The computational cost of this harmonic balance CFD code has been shown to be between 20 and 30 times than the conventional time-domain method for wind turbine unsteady aerodynamics. The code has very high parallel efficiency, which enables its use for complex wind turbine problems from small to large0size computers, including the UK ARCHER2 National Supercomputing Service at the University of Edinburgh. |
| Type Of Material | Improvements to research infrastructure |
| Year Produced | 2023 |
| Provided To Others? | Yes |
| Impact | The code has only recently been made publicly available. It played a pivotal role in the wind turbine aerodynamic research of this EPSRC project, and we do expect it to achieve larger impact in the near future, due to its wider availability. |
| URL | https://github.com/LANCASTER-CFD/COSA |
| Description | Multi-fidelity analysis and design of floating offshore wind turbines |
| Organisation | University of Florence |
| Country | Italy |
| Sector | Academic/University |
| PI Contribution | I contributed high-fidelity simulation-based analyses of floating offshore wind turbine (FOWT) rotor aerodynamics, computed with Lancaster's harmonic balance Computational Fluid Dynamics (CFD) code, to complementary investigations at the Department of Industrial Engineering at the University of Florence. The investigations in Italy were performed in the framework of the Horizon Europe project FLOATECH. The Department of Industrial Engineering, a longstanding research partner of Lancaster University, worked at validating and improving new analysis and design software for FOWT applications, and the CFD data provided by Lancaster contributed to these aims. |
| Collaborator Contribution | The University of Florence contributed comprehensive analyses of an agreed FOWT test case obtained with state-of-the-art multi-disciplinary low-fidelity wind turbine code. The cross-comparative analyses performed by University of Florence and Lancaster University resulted in two outputs at two highly ranked International wind energy events, namely: a) High-fidelity Time- and Nonlinear Frequency-Dimain Analysis of Unsteady Loads of Floating Offshore Wind Turbines in Yawed Wind, 4th Wind Energy Science Conference, Glasgow, United Kingdom, 23-26 May 2023, presented by Dr. M. Sergio Campobasso and b) Multi-fidelity Analyses of Rotor Loads of Floating Offshore Wind Turbines with Wind/Wave Misalignment, presented by Dr. M. Sergio Campobasso at the TORQUE Conference, 1st - 3rd June 2022, Delft, The Netherlands. This work asl received scientific contributions from the Department of Energy of Politecnico di Milano. |
| Impact | A. Ortolani, F. Papi, A. Bianchini, G. Persico, J. Drofelnik, M.S. Campobasso, Multi-fidelity Analyses of Rotor Loads of Floating Offshore Wind Turbines with Wind/Wave Misalignment, Journal of Physics: Conference Series, Vol. 2265, no.4, ref. 042010, June 2022. DOI: 10.1088/1742-6596/2265/4/042010 . Also presented at TORQUE Conference, 1st - 3rd June 2022, Delft, The Netherlands. High-fidelity Time- and Nonlinear Frequency-Dimain Analysis of Unsteady Loads of Floating Offshore Wind Turbines in Yawed Wind, 4th Wind Energy Science Conference, Glasgow, United Kingdom, 23-26 May 2023. https://drive.google.com/file/d/1-vURufsSDGgXGVvaVLRIW8byJkiDL55m/view |
| Start Year | 2021 |