Variable cross-sectional effect on bi-directional blades–tower–soil–structure dynamic interaction on offshore wind turbine subject to wind–wave loads

• Published in: Beni-Suef University Journal of Basic and Applied Sciences Vol. 12; no. 1; pp. 107 - 15
• Main Authors: El Absawy, Mostafa A., Elnaggar, Zakaria, Ibrahim, Hesham H., Taha, M. H.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.12.2023; Springer; Springer Nature B.V; SpringerOpen
• Subjects: Aerodynamic loads; Aerodynamics; Air-turbines; Alternative energy sources; Blades; Case studies; Comparative analysis; Dynamic response; Energy resources; Environmental conditions; Euler-Lagrange equation; Euler–Lagrange equations; Finite element analysis; Finite element method; Hermite polynomials; Investigations; JONSWAP spectrum; Mathematical analysis; Medicine; Medicine & Public Health; Model accuracy; Morison equation; Numerical model; Numerical models; Offshore; Offshore structures; Optimization techniques; Renewable resources; Robustness (mathematics); Shape functions; Simulation; Simulation methods; Soil structure; Soils; Sustainability; Turbine industry; Turbines; Turbulence models; Variable cross-sectional tower; Vibration; Wind effects; Wind power; Wind turbine; Wind turbines; Dynamic response; Morison equation; JONSWAP spectrum; Numerical model; Euler–Lagrange equations; Blade element moment theory; Von Karman turbulence model; Wind turbine; Variable cross-sectional tower; Flexible foundation
• DOI: 10.1186/s43088-023-00444-y
• ISSN: 2314-8543; 2314-8535

Background This study introduces a numerical model designed to simulate interactions occurring between a wind turbine's tower and the surrounding soil, as well as between the nacelle, blades, and the surrounding environment. This simulation accounts for both fore–aft and side-to-side movements. To describe these interactions, the model leverages the Euler–Lagrange equations. It calculates wave loads utilizing the Morison equation, with wave data generated based on the JONSWAP spectrum. Furthermore, aerodynamic loads are determined using the blade element moment theory, and the wind spectrum is generated using the Von Karman turbulence model. The tower is represented as a variable cross-sectional beam, employing a two-noded Euler beam element with two degrees of freedom: transverse displacement and rotation, and utilizing Hermite polynomial shape functions. Results In a comparative analysis against experimental data, this modified model demonstrates significant enhancements in accurately reproducing the dynamic behavior of wind turbines with variable cross-sectional towers, outperforming models that approximate the tower with a constant cross section. Our findings reveal that the modified model achieves a remarkable improvement of 15% in replicating the tower's dynamic response when compared to the constant cross-sectional models. As a case study, a 5 MW monopile wind turbine with a flexible foundation, specifically the one provided by the National Renewable Energy Laboratory (NREL), is employed to simulate its dynamic response. Conclusions This research presents a robust numerical model for simulating wind turbine behavior in various environmental conditions. The incorporation of variable cross-sectional tower representation significantly improves the model's accuracy, making it a valuable tool for assessing wind turbine dynamics. The study's findings highlight the importance of considering tower flexibility in wind turbine simulations to enhance their real-world applicability.