An Assessment of Approximate Modeling of Aerodynamic Loads on the UAE Rotor Available to Purchase

This assessment of approximate modeling of aerodynamic loads on the UAE rotor indicates that it can be reasonably accurate when it is based on reliable 2D wind tunnel data, and when flow about the rotor blades is unstalled. This includes loads which figure importantly in the yawing of smaller wind turbines out of higher winds to minimize overshoots in power and loads. A welcome but by no means obvious finding is that the assumption of locally two dimensional flow about substantially yawed rotor blades appears to be reasonably valid even in the presence of the complex induction field due to the skewed wake effects. Dynamic stall, expanding skewed wake effects, and effects due to vortices shed inboard into the wake where the onset of deep stalled flow occurs must be accounted for to better predict side force and center of thrust location on the rotor. Rotational effects on rotor thrust, torque, and blade out-of-plane moments must be accounted for in deep stalled flow as it spreads outboard on the blades at higher wind speeds. These effects appear to be more severe at smaller rotor yaw angles, and lower tip speed ratios. Approximate modeling of these effects at zero yaw appears to be improved with the approach to and onset of fully deep stalled flow about the blades when blade aspect ratio and shape effects on non rotating section aerodynamic characteristics are included in the modeling. This matter requires substantial further study.