Contribution
Measurements of hydrodynamic and acoustic wall pressure fluctuations using ultra-thin-precision surface microphone
* Presenting author
Abstract:
Wall pressure fluctuations can be measured with flush- and pinhole-mounted sensors. Typically, to install the sensors, the surface of test objectives needs to be drilled. However, this manner of installation is undesirable or impossible for many industrial applications. Therefore, a surface sensor that can be easily mounted on the surface could be very helpful in measuring wall pressure fluctuations. This paper presents wall pressure spectra measured with GRAS ultra-thin-precision (UTP) microphones. Three mounting configurations were used in the measurements: flush- and pinhole-mounted in a recess on the surface and mounted with a flow-optimized fairing taped on the surface, which can significantly simplify the mounting. The flush-mounting sensor-size-induced high-frequency spectral attenuation and the pinhole-mounting-induced Helmholtz resonance are corrected with published methods. The obtained wall pressure spectra are compared to the spectra measured with pinhole-mounted Kulite sensors. The effect of the mounting with farings on the measured spectra due to the disturbance on TBLs is quantified by comparing to the results measured with the surface-mounted microphone in the recess. Furthermore, the disturbance on the acoustic field due to the faring is also quantified by using a laser-based impulsive sound source.