Aeroelastic Simulations Based on High-Fidelity CFD and CSD Models

Abstract

This chapter focuses on the challenges rising when modeling the aeroelasticity of modern wind turbines utilizing high-fidelity methods. A comprehensive review of the state of the art is presented at the beginning, including engineering models. Since the aeroelastic models consist of a flow and a structural solver, a detailed description of the modeling and simulation techniques is provided, including the basic requirement for coupling a computational fluid dynamics (CFD)-based solver with a computational structural dynamics (CSD)-based solver. The challenges related to the simulation of large rotating bodies, as well as moving grids, are described. In the numerical analysis of the aeroelasticity, the blades could be structurally modeled by mainly three different elements. These are beam, shell, and solid elements, by which the accuracy level of the results could be improved. Therefore, different fidelity levels of structural discretization of the wind turbine are discussed in terms of using these elements. To model the blade using beam elements, a cross-sectional analysis tool is needed to extract the beam structure properties out of the full three-dimensional (3D) geometry of the blade. Coupling CFD to CSD needs great attention at the coupling interface between both solvers. Since they have different grid resolution, a mapping grid technique is needed to translate the data at the interface between the nonmatching grids. Moreover, the coupling scheme should be carefully chosen based on the required accuracy level. The chapter ends by presenting high-fidelity results of a state-of-the-art wind turbine model. The effect of the geometrical nonlinearity of the wind turbine blades is discussed. Comparisons between the different structural elements are described based on these results. The effect of the aerodynamic model fidelity is introduced.