Concept, design and characterization of a small aeroacoustic wind tunnel facility with application to airfoil measurements

Abstract

Experimental investigation of flow-induced sound and sources of soundnecessitates an adequate environment of low interfering noise and suppression of unwanted sources of sound. In order to investigate the sound from fluidstructure interactions, a low-noise wind tunnel has been designed and implemented. This paper gives an overview of the design criteria and specifications, along with an aeroacoustic and aerodynamic characterization of the facility. The suitability to airfoil self-noise studies is explored and first measurements with a model airfoil are presented. The paper concludes with an outlook on future applications. © 2009 Institute of Noise Control Engineering.

Design of a low-noise aeroacoustic wind tunnel facility at Brunel University

“…Similarly, low background noise is reported and many airfoil self noise studies have been carried out using this facility 14,15 . There are also other university-based aeroacoustic wind tunnels, for example in refs [16][17][18] , which have been built for different purposes.…”

Experimental study on the self-noise of a turbulent round jet investing a cambered aerofoil

“…The authors used two microphone types for the far-field and the nearfield measurements. They obtained the measured time series from positioned probes, to give an acceptable trade-off between signal-to-noise ratio and directivity according to Winkler et al [25] and Bianchi et al [26].…”

“…The only limitation in this case is that this measurement technique neglects the blade aerodynamic interaction with other blades. Winkler et al (2007) first proposed this approach for the trailing edge noise study of a highly cambered NACA five digit aerofoil at zero degrees angle of attack, with and without a boundary layer tripping (Roger and Moreau [11]). …”

“…The far-field measurements were taken in the fully anechoic chamber with the medium at rest. The authors based this approach for the far-field measurements, following Winkler et al [25], on the linear aerodynamic and acoustic theory of isolated aerofoil and extended it to a finite span blade's interaction with a fully turbulent jet. Concerning the correlation technique, the authors adopted the approach standard in the turbomachinery practices which Mongeau and co-authors [24] first introduced, and extensively used in successive works on subsonic jets and subsonic speed axial fans.…”

Reduction of airfoil trailing edge noise by trailing edge blowing

“…Two external silencers attenuate extraneous noise emanating from the pressurized air supply system. The wind tunnel (for details see Winkler and Carolus [20]) exhausts in a semi-anechoic chamber (4.5 m x 3.23 m x 2.9 m) which allows acoustic measurements according to ISO 3745 [21] Since the surface pressure fluctuations in the TE region are acoustically relevant, one rapidprototyping TE was instrumented with nine flush mounted miniature pressure transducers (Knowles Acoustics, FG-3329-P07), figure 3 (right). This arrangement of sensors allowed the synchronous determination of the stream-and spanwise unsteady pressure distribution in the TE region.…”