Structural model to study the dynamics of wind turbine blades

Abstract

The structure of a wind turbine blade is geometrically very complex due to its aerodynamic shape. Generally, the blades are composed by an external shell and internal reinforcements. The whole system provides stiffness to the blade, in a coupled way. Even if the structure changes along distinct cross sections, the blade can be globally-represented by an equivalent beam, with variable stiffness and mass along length. One of the objectives of the present project is to develop a methodology to obtain equivalent properties to a wind turbine blade cross section. It will be used as input to a finite element beam model, representing the blade, keeping its original stiffness and mass. Additionally, we aim to develop a load-model to quantify the aerodynamic forces acting on beam elements. These are non-conservative, depending on the velocity between the blade and the air. To quantify the aerodynamic coefficients, the model will consider existing aerodynamic coefficient curves in literature. The loading will depend on the beam deformed shape, which represents a geometric nonlinearity. It will be implemented in and existing finite element code, developed by the lead researcher.By the end of the project, we expect to be able to simulate the global behavior of wind turbine blades, in operational/extreme scenarios. The model will help to predict loading transmitted from the blades to the remaining wind turbine structure. Furthermore, it would predict internal loads along the blade length. The results are contributions to analysis and design of wind turbine structures. (AU)