Design and characterization of a small aeroacoustic wind tunnel

Experimental investigation of sources of sound is required to fundamentally understand the noise generation mechanisms. In order to investigate the sound from fluid-structure interactions, a low-noise wind tunnel has been designed and implemented. Speeds up to a test section velocity of 81 m/s are possible based on a square nozzle of dimension 180×180mm², thus the maximum Reynolds number is near 1×10⁶. The wind tunnel is driven by a separate, low noise level centrifugal fan controlled by a variable frequency drive. Design and construction considerations for the major tunnel sections, i.e. inlet, anechoic chamber, diffuser, muffler, are described. Aerodynamic and acoustic calibration of the tunnel is discussed in relation to design criteria. Initial testing demonstrated that a sufficiently low background noise level has been obtained. Moreover, the suitability to flow induced cavity noise is explored with a cavity mode. The paper concludes with suggestions for improvements and provides an outlook on future applications.