To simulate high turbulence, an active turbulence grid can increase turbulence intensities up to 45%. A large diameter fan and specialized acoustic treatment allow the tunnel to operate at low noise levels of 76.4 dB at 20 m s⁻¹. Seamless honeycomb and screens in the airline together with a carefully designed contraction reduce centreline turbulence intensities to less than or equal to 0.030% at all operating speeds. The tunnel is closed-circuit and can produce airspeeds up to 50 m s⁻¹ in a rectangular test section that is 1.0 m wide, 0.82 m tall and 1.73 m long. To study flight in both laminar and turbulent environments, a multi-purpose wind tunnel for studying animal and small vehicle flight was built at Stanford University. Flow can be laminar and quiet at high altitudes but highly turbulent near the ground, and gusts can rapidly change wind speed. However, the atmosphere in which animals fly is even more complex. Existing facilities can simulate laminar flow during straight, ascending and descending flight, as well as at different altitudes. Our understanding of animal flight benefits greatly from specialized wind tunnels designed for flying animals. © 2017, Budapest University of Technology and Economics. The paper outlines a methodology for the evaluation and representation of the beamforming data in the following forms: source strength level based third-octave spectra obtained using background noise subtraction maps presenting the loci of source strength level maxima noise source maps for frequency bands of anticipated vortex shedding noise. The present paper is confined to reporting on experimental results for arbitrarily selected representative incidences, Reynolds numbers, frequency bands, and profiles. The dataset incorporates a wide range of incidence and Reynolds-numbers investigated. The measurement setup enables the correlation of the streamwise evolution of the blade boundary layer with the associated noise characteristics.
The phased array microphone measurements offer spatially resolved information on the generated noise. It aims at documenting the establishment of an acoustic beamforming dataset for the three profiles. The paper presents wind tunnel experiments, supplemented with phased array microphone measurements, on 2D basic models of low-speed axial fan blade sections: a flat plate, a cambered plate, and a RAF6-E airfoil.