WIND TUNNEL MEASUREMENTS OF PRESSURE FLUCTUATIONS AND STRUCTURAL RESPONSE INDUCED BY THE TURBULENT BOUNDARY LAYER AT HIGH MACH NUMBER, PART 1: VELOCITY AND PRESSURE FIELD CHARACTERIZATION

The results of an experimental campaign performed in a transonic wind tunnel and aimed at measuring wall pressure fluctuations and the velocity field inside the turbulent boundary layer in high Mach number flows are presented. To overcome the limitation related to the thin wind tunnel boundary layer, extremely critical for this kind of study, innovative tripping systems have been designed to generate artificial boundary layers of different thickness. Velocity measurements are performed with a linear array of Pitot tubes mounted on a rake whereas wall pressure fluctuations are measured on a rigid panel with arrays of pressure sensors located in three different directions over a quarter of circle. The results obtained from the comparisons between measured and theoretical velocity profiles demonstrated the possibility to reproduce with this novel setup the characteristics of a turbulent boundary layer excitation for Mach number values ranging between 0.4 and 0.8. Pressure data are used to investigate the dependence of pressure spectra on mean velocity parameters and on the Mach number leading to the determination of theoretical predictive models for the auto and cross-spectral density to be used for the vibroacoustic analysis.