Analysis of Engineering Models by CFD-based aeroelastic Simulations of Wind Turbine Blades

Nowadays, wind energy significantly contributes to the share of renewable energy. Accordingly, the size of the turbines is increasing with large and slender rotor blades. Increasing the rotor diameter increases its outboard flexibility. Therefore, it becomes increasingly important to accurately model and understands the aeroelasticity of such slender blades in more detail. The state-of-the-art simulation tools for wind turbines' aeroelasticity utilize engineering models to find the aeroelastic response of the wind turbine. These tools use simplified methods such as BEM to find the unsteady aerodynamic loads and 1D structural models to determine the surface deformations. The present work is dedicated to assess the accuracy level of the engineering models by means of CFD-based aeroelastic simulations of large slender bladed Horizontal Axis Wind Turbine (HAWT). For this purpose, an implementation of a medium-fidelity and a high-fidelity aeroelastic simulation tool are presented. In both models, a CFD model is used to find the unsteady aerodynamic loads including the 3D effects which is one of the engineering models' (such as BEM) limitations. In the medium-fidelity model, the CFD is coupled to a 1D FE beam model while in the high-fidelity, the CFD is coupled to a full 3D FE shell model. An explicit Fluid-Structure Interaction (FSI) coupling approach is used to conduct the coupling between the stand-alone solvers. An increase in the power resulting from the CFD-based simulations was predicted due to the large edgewise deformation as the blade radial force was contributing to the power by the offset due to the large edgewise deformation. In contrary, the radial forces were completely excluded in the BEM calculations and only the normal and tangential forces were used to determine the turbine performance.