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The knowledge of the acoustic behavior of a multiperforated plate is important to design a combustion chamber. It is characterized by the acoustic impedance or the Rayleigh conductivity. Experiments have been performed in the ONERA flow duct to study the acoustic response of a multiperforated plate, without and with bias flow. The geometry of the perforated plate is representative of industrial applications, as well as the bias flowMach number (around 0.3) and the Strouhal number (around5.10−3). An inverse method isused to educe the impedance of the plate from Laser Doppler Anemometry measurements of the acoustic velocity above the plate. The issue of the accuracy of the educed value is specifically adressed. It is shown that the perforated plate is highly reflective with bias flow,as predicted by the models available in the literature. This is due to the combination of the very low Strouhal number and high bias flow Mach number. Consequently, on contrary to the case without flow, in the configuration with bias flow the eduction process shows one’s limits and cannot give a very precise impedance value.

Impedance eduction of perforated plates at low Stouhal numbers and high bias flow Mach number