Development of Vortex Filament Method for Aerodynamic Loads on Rotor Blades

Licentiate thesis, 2013

Wind power is currently one of the most reliable new energy sources serving as an alternative to fossil fuel generated electricity and is known as a widely distributed clean and renewable source of energy. It is now the world’s fastest growing energy source and has also become one of the most rapidly expanding industries. The aerodynamics of a wind turbine are governed by the flow around the rotor, where the prediction of air loads on rotor blades in different operational conditions and its relation to rotor structural dynamics is crucial for design purposes. One of the most important challenges in wind turbine aerodynamics is therefore to accurately predict the forces on the blade, where the blade and wake are modeled by different approaches such as the Blade Element Momentum (BEM) theory, the vortex method and Computational Fluid Dynamics (CFD). Here, the application of the vortex filament method for wind turbine aerodynamic performance is used. Different blade models such as the lifting line and the lifting surface with prescribed and free wake models are studied. The main purpose is to find the proper combination of blade and wake models for the aerodynamic loads as well as the computational time in order to develop an accurate and efficient aerodynamic tool. The results of the different approaches are compared with the BEM method and GENUVP code (see the acknowledgments).