Measurements of Sound Radiated from Local Wall Pressure Events in Turbulent Wall-bounded Flow

초록

The wall pressure fluctuations beneath a turbulent boundary layer over a flat plate have been investigated in an anechoic wind tunnel facility. This anechoic wind tunnel consists of acoustically-lined duct, muffler, and splitter-type silencer for noise suppression and vanes for reducing head losses involved. To improve spectra characteristics in high frequency range, a 1/8" pressure-type microphone sensor, which has a pin-holed cap of various diameters, was employed in this experiment. It is shown that the transducer with a dimensionless diameter d+ of 7.9 resolves the high frequency pressure fluctuations most effectively among ones with various diameters. The pressure events high amplitude could be also detected, which have the shapes of pulse and contributed to far-field sound significantly with a delay of traveling time.