Reduction of airfoil trailing edge noise by trailing edge blowing

The Science of Making Torque from Wind 2014

Gerhard, T.^1 ; Erbslöh, S.^2 ; Carolus, T.^1

Institute for Fluid- and Thermodynamics, University of Siegen, 57068 Siegen, Germany^1

Team Leader Aerodynamics, Senvion SE, 24783 Osterrrönfeld, Germany^2

关键词: Acoustic sources;    Microphone arrays;    Small wind turbine;    Surface pressure fluctuations;    Trailing edge blowing;    Trailing edge noise;    Turbulence intensity;    Turbulent boundary layers;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/524/1/012123/pdf
DOI  :  10.1088/1742-6596/524/1/012123

来源: IOP

【 摘 要 】

The paper deals with airfoil trailing edge noise and its reduction by trailing edge blowing. A Somers S834 airfoil section which originally was designed for small wind turbines is investigated. To mimic realistic Reynolds numbers the boundary layer is tripped on pressure and suction side. The chordwise position of the blowing slot is varied. The acoustic sources, i.e. the unsteady flow quantities in the turbulent boundary layer in the vicinity of the trailing edge, are quantified for the airfoil without and with trailing edge blowing by means of a large eddy simulation and complementary measurements. Eventually the far field airfoil noise is measured by a two-microphone filtering and correlation and a 40 microphone array technique. Both, LES-prediction and measurements showed that a suitable blowing jet on the airfoil suction side is able to reduce significantly the turbulence intensity and the induced surface pressure fluctuations in the trailing edge region. As a consequence, trailing edge noise associated with a spectral hump around 500 Hz could be reduced by 3 dB. For that a jet velocity of 50% of the free field velocity was sufficient. The most favourable slot position was at 90% chord length.