Análise modal de um modelo simplificado de torre de turbina eólica em escala reduzida

Abstract

The growing demand for renewable energy sources, such as wind energy, has driven research on wind turbines, which are essential for the sustainable generation of clean energy. In this context, studies conducted in the wind tunnel acquired through Furnas' research and development (R&D) program have highlighted the importance of evaluating reduced-scale models of the NREL 5 MW wind turbine tower, considering different structural configurations, including cantilevered beams, beams with concentrated mass at the free end, and the inclusion of Tuned Mass Dampers (TMDs). The use of reduced-scale models enables the simulation and analysis of the dynamic behavior of wind turbine towers under controlled wind tunnel conditions. This study focuses on evaluating the dynamic behavior of beams with concentrated mass subjected to low-velocity flows. The comparison is performed through (a) analytical modeling using Euler-Bernoulli beam theory, (b) numerical modeling using the finite element method (FEM), and experimental validation via (c) experimental modal analysis (EMA) and (d) operational modal analysis (OMA). The experimental results obtained in this study show high agreement with the theoretical predictions of Euler-Bernoulli beam theory and FEM, validating the accuracy of the employed methodologies. The comparison between Euler-Bernoulli and FEM demonstrated that FEM provides a strong correlation between modal shapes, allowing the results obtained for cantilevered beams with mass at the free end and beams with TMDs to be referenced using FEM. The Modal Assurance Criterion (MAC) revealed a correlation above 90% between the modes identified by EMA and OMA in the cantilevered beam model, reinforcing the reliability of the results. Despite some discrepancies observed in the comparison of accelerometer positions along the beam, particularly in the intermediate section, these were attributed to the sensitivity of the methodologies to experimental conditions. FEM enabled a more detailed analysis of the dynamic behavior of the three beam models, confirming the tuning effectiveness for vibration mitigation in wind turbines through TMD implementation