Computational tool for preliminary analysis of eigenvalues of wind turbine blades
With the growing participation of wind energy in the Brazilian and world energy matrix, investments in research are constantly being made by companies for the development of new wind turbines.
During wind turbine operation, the blade is subjected to high-speed winds, which can cause unwanted phenomena if the project is not considering important variables, such as flexion and torsion vibrations caused by the rotation movement during the passage of air through the blades of the turbine blade.
This phenomenon can cause coupling of the natural frequencies of vibration and that, if not taken into account, generate effects of Fluid-Structure Interaction, causing serious damage to the operator and manufacturer, in addition to putting people's lives at risk during operation.
During the first stages of wind turbine design, it is necessary to determine the vibration frequencies, in addition to the modal forms. Therefore, the objective of this master's work is to develop the first version of a computational code for analysis of eigenvalues of wind turbine blades with flexotorsional behavior.
A wind turbine blade is modeled as an Euler-Bernoulli beam with cross-section varying along its length, which when rotating with a given angular velocity suffers flexotortional deformations. Hamilton's principle is used to derive the blade's equation of motion.
In this qualification phase, the blade is seen as a prismatic beam without rotational movement (stationary beam). The eigenvalues problem was solved analytically, based on the work of Dokumaci (1987), and numerically, using two methods, Assumed Modes and Ritz-Galerkin, both presented in the work of L. Meirovitch (2001). Furthermore, a parametric study was carried out in order to determine the parameters with the greatest influence on the natural vibration characteristics of the blade.