Effect of sensor mounting and flow history on measured wall pressure spectra

Abstract

An experimental study of wall pressure fluctuations beneath a turbulent boundary layer was carried out on aplate model with a streamwise varying pressure gradient along the plate length. The wall pressure fluctuationswere measured with flush-mounted Kulite sensors, and mean velocity measurements across the boundary layerwere performed by using a single-wire hot-wire anemometer. A variety of streamwise pressure distributionswere imposed by changing the position and the angle of attack of a NACA 0012 airfoil installed above theplate. The effect of the upstream flow history on the wall pressure spectra in the presence of the streamwisevarying pressure gradient was studied. Spectral attenuation due to the spatial averaging associated with a finitesensor size was corrected via the Corcos correction. The results show that the Corcos correction to themeasured Kulite spectra leads to an overprediction of the spectral intensity at medium frequencies and anunderprediction at high frequencies. Hence, a new correction is proposed based on the measured spectralattenuation. Finally, the measurements also indicate that even slight imperfections in sensor mounting andrelatively weak upstream flow disturbances can have a significant influence on the measured spectra of the wallpressure fluctuations.