Acoustic wall treatments for wind tunnel aeroacoustic measurements

Sound absorbing porous materials are used to line a wind tunnel wall, in order to reduce reflections. However, the lining can have a detrimental effect on the acoustic measurements due to an increase in the noise radiated from the walls. In addition, the aerodynamic fidelity of the tunnel can be affected. In the present study, the influence...

Comparison of cavity geometries for a microphone array in an open-jet wind-tunnel experiment

This paper analyses the influence of microphone cavity geometry on beamforming measurements with a turbulent boundary layer present on the microphone array. A 16- microphone array was tested in the anechoic open-jet wind tunnel of the Delft University of Technology. The array was placed on a flat plate mounted flush with the exit nozzle of the...

Deterministic Model of AcousticWave Propagation in a Cavity

A mathematical model is proposed that evaluates acoustic propagation of turbulent boundary layer waves on top of a cavity enclosing a microphone. The goal is to optimize these cavity geometries to improve the signal-to-noise ratio of acoustic measurements. This model predicts the attenuation of the turbulent boundary layer fluctuations...

Comparison between analog and digital microphone phased arrays for aeroacoustic measurements

Microphone arrays are useful measurement devices for estimating the location and strength of sound sources. Numerous comparative studies have been conducted regarding the performance of acoustic imaging methods in the past, but literature lacks of a systematic investigation on the role of the hardware on the measurements. This research...

Effect of trailing edge serration-flow misalignment on airfoil noise emissions

The broadband noise generated by the scattering of turbulent flow at the trailing edge of a NACA 0018 airfoil with trailing edge serrations is investigated, varying both the airfoil angle of attack and serration flap angle. Acoustic emissions from the trailing edge are measured using a microphone array. The noise level is observed to be...