A blade element momentum method with lateral entrainment correction

The accuracy of the blade element momentum (BEM) method is influenced by various factors, including tip/hub flows and three-dimensional stall effects. While these aspects have been extensively investigated, the lateral entrainment effect has received comparatively little attention. Conventional BEM relies on a closed flow tube control volume, which neglects mass exchange across the boundaries during rotor operation. To overcome this limitation, an entrainment correction model is derived in this study. Comparisons with existing correction models and experimental data indicate that the proposed method enhances prediction accuracy under medium to high wind speeds, particularly in the blade root region. The proposed entrainment-corrected BEM model is further incorporated into the Wilson blade design method, and its effectiveness within a BEM-based blade design framework is investigated through actuator line model simulations. Simulation results show that the turbine designed using the entrainment corrected BEM–Wilson method achieves a 5.4% increase in power coefficient at the rated tip speed ratio, while also inducing higher turbulence intensity and promoting faster wake recovery downstream.