Wind-Turbine Trailing-Edge Noise Reduction by Means of Boundary-Layer Suction

Abstract

Distributed boundary-layer suction has numerically and experimentally shown great potential to reduce flow-induced trailing-edge noise. The paper aims at the transfer of this potential to an industrial full-size wind turbine by means of a dedicated suction system design and, hence, is meant to point out whether the predicted, airfoil-related improvements carry over to wind turbines represented by the N117, not hitherto in liaison with active flow control. Guidance is given through the different design steps involving the suction-followed blowing of the fluid and being continually dictated by industrial constraints and requirements. Because the processes of trailing-edge noise reduction and effective power alteration are intimately bound together, great emphasis is put on an accurate prediction of pump power requirement, with the latter being based on a detailed suction hardware system implying pressure losses across each component. Exploiting the limited installation space, a total trailing-edge noise reduction of 3.6 dB is coupled with a net enhancement of total rotor power of 4.75%. As of a cross-over noise reduction level of 5 dB, the enhancement of aerodynamic power no longer compensates for the pump power requirement and, hence, aeroacoustic demands are implemented to the detriment of aerodynamic performance.