BTGNX: A MEMS microphone array for the acoustic benchmark wind tunnel experiment for tip-gap noise

Abstract

A generic experiment has been carried out to investigate the tip leakage flow between a flat plate and a non- rotating airfoil. The measurements were carried out in the open test section of the acoustic wind tunnel at DLR Braunschweig (AWB) and the experiment is called the "Braunschweig Tip-Gap-Noise Experiment" (BTGNX). The experimental setup consists of a microphone array for the acoustic source localization from the acoustic far field, static pressure measurements to determine the wing lift distribution and the MEMS microphone sensors integrated into the flat casing plate to record the fluctuating surface pressures distribution. The presentation focusses on the experimental setup of the surface microphone array which consists of 265 MEMS microphones. This MEMS array allows the determination of the fluctuation pressure distribution in dependency of the various experimental parameter such as free flow velocity, angle of attack and the gap between flat plate and wing tip. Furthermore, the analysis of the MEMS microphone data gives inside into the surface flow distribution as well as the near field acoustic pressure field to locate and identify the main sound source mechanism.