On the influence of cross-sectional deformations on the aerodynamic performance of wind turbine rotor blades

The aerodynamic performance of a wind turbine rotor blade depends on the geometry of the used airfoils. The airfoil shape can be affected by elastic deformations of the blade during operation due to structural loads. This paper provides an initial estimation of the extent to which cross-sectional deformations influence the aerodynamic load distribution along the rotor blade. The IEA 15 MW reference wind turbine model is used for this study. A constant wind field at the rated wind speed is applied as a test case. The resulting loads are calculated by an aero-servo-elastic simulation of the turbine. The loads are applied to a 3D finite element (FE) model of the rotor blade, which serves to calculate the cross-sectional deformations. For the individual cross-sections in the deformed configuration, the new lift and drag coefficients are calculated. These are then included in the aero-servo-elastic simulation and the obtained results are compared with those of the initial simulation that is based on the undeformed cross-sections. The cross-sectional deformations consist of a change in the chord length and the geometry of the trailing edge panels and depend largely on the azimuth position of the blade. The change in the airfoil geometries results in altered aerodynamic characteristics and therefore in a deviation of the blade root bending moments, the maximum change of which is -1.4 % in the in-plane direction and +0.71 % in the out-of-plane direction. Although these values are relatively small, the initial results imply that further investigations should be carried out with more complex wind fields and different rotor blade designs to identify aero-structural couplings that may be critical for the design of rotor blades or other wind turbine components.