Assessment of the effects of BEM correction models on aerodynamic loads and power under yawed inflow

The classic blade element momentum theory (BEM) assumes an inflow normal to the rotor surface, whereas in practice the inflow effectively hits the rotor skewed. To take this fact into account, the BEM is expanded with appropriate algorithms that correct the BEM results that represent the effects of the skewed inflow. This work compares four yaw correction models, Glauert, Øye, IFPEN, and Branlard, using MoWiT simulations. The effects of each correction model on one-revolution averaged sectional aerodynamic loads and power output are assessed for different yaw angles and wind speeds. For selected skew inflow angles, predictions are compared with CFD is also carried out. The results show that no model outperforms the others for all load quantities, and power prediction becomes less accurate with increasing yaw misalignment. IFPEN provides the closest agreement with power at the available yawed CFD comparison point. This study demonstrates the need to assess load and power prediction separately and stresses the need for variable yaw-loss exponent models across operating conditions.