Analysis of the Aerodynamic Loads on a Wind Turbine in Off-Design Conditions

In this work, the aerodynamic loads acting on a large horizontal axis wind turbine are analysed in off-design conditions by means of computational fluid dynamics (CFD) simulations. The turbulent wind flow is solved using an unsteady RANS approach and choosing the \(k-\epsilon \) model. Appropriate boundary conditions are used in combination with modified wall functions in order to preserve the atmoshperic boundary layer (ABL) profiles throughout the entire domain. An overset technique is used to handle the rotation of the blades throughout the simulated time. Changing both the pitch angle of the blades and the tip-speed ratio (TSR) of the turbine, several operating points are investigated. The performance and the loads are highly affected by the ABL, whose effect is highlighted. The performance of the wind turbine in each simulated operating point is compared to the nominal operating point (NOP). The aerodynamic loads are monitored, analysed and mutually compared throughout the motion of the rotor, in order to identify the most critical conditions for the blade structures.