Detailed CFD-BEM analysis about the effects of twist and taper of HAWTs on the rotational augmentation phenomenon

The rotational effects on blade flow in Horizontal Axis Wind Turbines (HAWTs) are essential for accurate rotor design, as they significantly influence blade performance. While advanced Computational Fluid Dynamics (CFD) methods have improved the understanding of centrifugal pumping mechanism, existing 1D design codes often require case-specific calibration due to limited generality of stall delay corrections. This study proposes a novel approach to address these limitations by examining the isolated effects of blade twist and taper on rotational augmentation through an integrated CFD-BEM (Blade Element Momentum) methodology. The analysis is based on the modification of the NREL Phase II rotor, introducing a prescribed taper with constant pitch in one scenario and variable twist with constant chord in another, while holding rotor dimensions and operating conditions constant for direct comparison. CFD models, employing Generalized k-omega (GEKO) tunable coefficients, demonstrated improved model accuracy with reduced computational costs, indicating a potential path for broader GEKO tuning applications in wind turbine simulations. Results indicate that, even under identical conditions, the centrifugal pumping mechanism is more sensitive to blade twist than to taper, underscoring the need to refine the dependency of rotational augmentation on twist distribution in advanced stall delay models.