Developing Simplified Models for Wind Turbine Blades

Simplified beam models provide a computationally efficient method for modeling the vibration of wind turbine blades. The purpose of this paper is to demonstrate the process of developing a simplified beam model of the CX-100 wind turbine blade, and quantifying its predictive capability. The motivation for this study is rooted in the development of NLBeam, a non-linear beam code developed at Los Alamos National Laboratory to simulate the structural dynamics response of wind turbines using the geometrically exact beam theory in a coupled atmospheric hydrodynamics solver. Verification activities used to assess the credibility of NLBeam are investigated. Two models of the CX-100 blade are compared: (1) a three dimensional shell model and (2) a simplified one- dimensional beam model. Two sets of experimental modal data are utilized, one with the CX-100 blade in a fixed-free condition, and one with the CX-100 blade in a fixed-free condition, with large masses applied. By exploring these different configurations of the wind turbine blade, credibility can be established regarding the ability of the FE model to predict the response to different loading conditions. Through the use of test-analysis correlation, the experimental data can be compared to model output and an assessment is given of the predictive capability of the model.