A Analyzing the Impact of Multiple Foundation Stiffness Correlation on the Natural Frequency of Offshore wind turbines

Laib Abdelghani; Rachid  Bakhti; benahmed baizid

doi:10.56748/ejse.24605

Authors

Laib Abdelghani university of Bouira https://orcid.org/0009-0005-1541-6943
Rachid Bakhti university of Bouira
benahmed baizid Djelfa university

DOI:

https://doi.org/10.56748/ejse.24605

Keywords:

Finite element analysis, Natural frequency, Wind turbines, tapered tower, beam element, foundation stiffness

Abstract

The analysis of wind turbine behavior should avoid unplanned resonance, as it can increase fatigue damage. It is essential to rigorously evaluate the natural frequency of wind turbines in the initial design stage. This estimation can be done through two steps, the first one is the computing of the fixed base natural frequency of the wind turbine. The second is the estimation of the foundation stiffness effect. This paper examines the error margin of four correlations of foundation stiffness namely Randolph, Davies and Budhu, DNV, and Higgins in the estimation of the natural frequency of wind turbines. The fixed base natural frequency was estimated in this paper using a special-purpose finite element computer program called TurbiSoft through beam and volume elements. A reference 5.0 MW offshore wind turbine and 9 other turbines from different wind farms have been analyzed. For the fixed base natural frequency, obtained results demonstrate the reliability of the finite element program TurbiSoft through an error margin between 1-4% for the reference 5.0 MW offshore wind turbine. For the natural frequency of the whole system, the estimated error marking was between 9-20% which is an important value.
This significant error is attributed to the low accuracy of these four correlation formulas for predicting the foundation flexibility contribution. The results from the four correlation formulas used are quite similar, with a difference in the error margin of less than 1%. However, the largest error margins are observed with the Higgins formula, which has been originally developed for short monopiles, even though the analyzed monopiles can be considered short, with monopile slenderness ratios less than 8.

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References

A. Abdullahi and Y. Wang. 2021. “Digital Twin-like Model Updating of a Laboratory Offshore Wind Turbine with Few-Parameters Soil-Structure Interaction Model.” SHMII 10 Porto, Portugal: Proceedings of the 10th International Conference on Structural Health Monitoring of Intelligent Infrastructure.

Adhikari, S., and S. Bhattacharya. 2012. “Dynamic Analysis of Wind Turbine Towers on Flexible Foundations.” Shock and Vibration, 19 (1): 37–56.

Alkhoury, P., A. Soubra, V. Rey, and M. Aït‐Ahmed. 2021. “A full three‐dimensional model for the estimation of the natural frequencies of an offshore wind turbine in sand.” Wind Energy, 24 (7): 699–719.

Arany, L., S. Bhattacharya, S. Adhikari, S. J. Hogan, and J. H. G. Macdonald. 2015. “An analytical model to predict the natural frequency of offshore wind turbines on three-spring flexible foundations using two different beam models.” Soil Dynamics and Earthquake Engineering, 74: 40–45.

Arany, L., S. Bhattacharya, J. H. G. Macdonald, and S. J. Hogan. 2016. “Closed form solution of Eigen frequency of monopile supported offshore wind turbines in deeper waters incorporating stiffness of substructure and SSI.” Soil Dynamics and Earthquake Engineering, 83: 18–32.

Bakhti, R., B. Benahmed, and A. Laib. 2024. “Finite Element Investigation of Offshore Wind Turbines Natural Frequency with Monopile Foundations System.” J. Vib. Eng. Technol., 12 (2): 2437–2449.

Blevins, R. D. 2001. Formulas for natural frequency and mode shape. Malabar, Florida: Krieger Publishing.

Davies, T. G., and M. Budhu. 1986. “Non-linear analysis of laterally loaded piles in heavily overconsolidated clays.” Géotechnique, 36 (4): 527–538.

Dj. Amar Bouzid, R. Bakhti, and S. Bhattacharya. 2018. “The dynamics of an offshore wind turbine using a FE semi-analytical analysis considering the interaction with three soil profiles.”

DNV-OS-J101. 2014. “Design of offshore wind turbine structures.” Oslo, Norway.

Higgins, W., C. Vasquez, D. Basu, and D. V. Griffiths. 2013. “Elastic Solutions for Laterally Loaded Piles.” J. Geotech. Geoenviron. Eng., 139 (7): 1096–1103.

Huang, H. S. 2022. “Simulations of 10MW wind turbine under seismic loadings.” Composite Structures, 279: 114686.

J.H Vught. 2000. “Considerations on the dynamics of support structures for an offshore wind energy converter.” Ph.D thesis. The Netherlands: Delft University of Technology.

Kaiser, H. F. 1972. “The JK method: a procedure for finding the eigenvectors and eigenvalues of a real symmetric matrix.” The Computer Journal, 15 (3): 271–273.

Ko, Y.-Y. 2020. “A simplified structural model for monopile-supported offshore wind turbines with tapered towers.” Renewable Energy, 156: 777–790.

Owji, R., G. Habibagahi, and M. Veiskarami. 2023. “Effects of Cyclic and Post-cyclic Loading on Lateral Response of Flexible Piles Embedded in Dry Sand.” Int J Civ Eng, 21 (4): 633–645.

Park, G., D. You, K.-Y. Oh, and W. Nam. 2022. “Natural Frequency Degradation Prediction for Offshore Wind Turbine Structures.” Machines, 10 (5): 356.

Randolph, M. F. 1981. “The response of flexible piles to lateral loading.” Géotechnique, 31 (2): 247–259.

Rong, X.-N., R.-Q. Xu, H.-Y. Wang, and S.-Y. Feng. 2017. “Analytical solution for natural frequency of monopile supported wind turbine towers.” Wind and Structures, 25 (5): 459–474.

Seo, Y.-H., M. S. Ryu, and K.-Y. Oh. 2020. “Dynamic Characteristics of an Offshore Wind Turbine with Tripod Suction Buckets via Full-Scale Testing.” Complexity, 2020: 1–16.

Shi, S., E. Zhai, C. Xu, K. Iqbal, Y. Sun, and S. Wang. 2022. “Influence of Pile-Soil Interaction on Dynamic Properties and Response of Offshore Wind Turbine with Monopile Foundation in Sand Site.” Applied Ocean Research, 126: 103279.

Steinacker, H., F. Lemmer, S. Raach, D. Schlipf, and P. W. Cheng. 2022. “Efficient multibody modeling of offshore wind turbines with flexible substructures.” J. Phys.: Conf. Ser., 2265 (4): 042007.

Van Der Tempel, J., and D.-P. Molenaar. 2002. “Wind Turbine Structural Dynamics – A Review of the Principles for Modern Power Generation, Onshore and Offshore.” Wind Engineering, 26 (4): 211–222.

Xu, Y., G. Nikitas, T. Zhang, Q. Han, M. Chryssanthopoulos, S. Bhattacharya, and Y. Wang. 2020. “Support condition monitoring of offshore wind turbines using model updating techniques.” Structural Health Monitoring, 19 (4): 1017–1031.

You, Y.-S., K.-Y. Song, and M.-Y. Sun. 2022. “Variable Natural Frequency Damper for Minimizing Response of Offshore Wind Turbine: Principal Verification through Analysis of Controllable Natural Frequencies.” JMSE, 10 (7): 983.