On Wind Turbine structural stiffness influence on wake flow

In this work we test a Fluid–Structure Interaction (FSI) method based on the SOWFA+ OpenFAST framework. The linear structural module of FAST is coupled to SOWFA’s Actuator Line simulations to perform the aeroelastic analysis of a wind tunnel scaled model (1:75) of the DTU 10 MW turbine. The objective is to give a quantitative description of the turbine stiffness influence on the wake flow by varying the model structural properties. The simulations are performed in two different operating conditions: below rated (TSR = 7.5) and above rated (TSR = 5.5). Turbulence is generated by positioning disturbing elements at the inlet, analogously to what was done in the reference wind tunnel tests. Results show that flexibility starts to have a considerable impact on the wake velocity deficit when the tip deflection is somewhere between 4% and 12% of the blade length. Based on these results, an indication is given of when the accuracy obtainable with the CFD-CSD coupling justifies the increased computational cost.