Wind Turbine Aerodynamics and Vorticity-Based Methods by Emmanuel Branlard

Author:Emmanuel Branlard
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

(22.1)

The above factors are applied to the momentum theory induced velocities and . They imply a redistribution of the inductions over the AD without changing their azimuthal averages. The former factor corresponds to the classical BEM yaw-model. The total induced velocities to be used in the velocity triangle are and . The added components are absent in the non-yawed case. To further close the system, the vorticity distributions , and need to be computed, which in turn require the knowledge of , h and . The skew angle may be determined using different methods.1 It is here assumed given. The value is taken as the average integrated value of circulation on the rotor blades. For simplicity, the helical wake pitch is assessed using the distance run by the tip-vortex in one rotor rotation: .

Fig. 22.1Top-view of the wake cross-section laying in the plane , data for . The velocities induced by the tangential vorticity along the fore-aft diameter of the rotor () are shown. Their relative fluctuations around the mean induction, or envelope, has a slope of . The distribution of velocity produces normal forces that can possibly (e.g. below stall) generate a restoring moment

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