Flight test measurement of exterior turbulent boundary layer pressure fluctuations on Boeing model 737 airplane
The exterior pressure fluctuation measurements were carried out on Boeing model 737 airplane in two separate flight tests. A seven-microphone array was used at two different locations along the fuselage. The measurements were carried out for Mach numbers of 0·78, 0·6 and 0·45 for the forward location, and for Mach numbers of 0·78 and 0·45 for the aft location. The pressure power spectral densities (PSD) and root mean square pressure fluctuations were calculated at all five flight conditions. PSD measurements and the subsequent analysis indicated that exterior turbulent boundary layer pressure fluctuation measurements are contaminated by the jet engine noise at Mach 0·45 forward location, and Mach 0·78 and 0·45 aft location. Therefore, other statistical properties, i.e. wideband convection velocity, wide-band spatial correlation, narrow-band convection velocity and the amplitude of cross PSD, are presented only for Mach 0·78 and 0·6 forward location. The measurements at these two flight conditions are compared with the laboratory measurements of the turbulent boundary layer pressure fluctuations on a flat plate. A physical description of the turbulent boundary layer pressure fluctuations is presented.