On the wall pressure field in turbulent pipe flow

Piezoelectric transducer and condenser microphone spectral measurements of wall pressure fluctuations in turbulent pipe flow were compared. A one decade range of Reynolds number was involved. Results show that large discrepancies between values of the ratio of rms pressure to dynamic pressure in turbulent boundary layers and turbulent pipe flows are attributable to effects of differences in Reynolds number which necessarily occur when sensors of different diameters have equal values of transducer size parameter. Nondimensional spectra, plotted in forms appropriate to various convection mechanisms, are similar, either in the intermediate frequency range or in the high frequency range, depending on the form of nondimensionalization. A two component spectral model of the pressure field, one consistent with convection of large scale turbulence at outer region velocities, the other with convection of wall region turbulence of wall region velocities, was derived. It exhibits all the salient features of the experimentally observed behavior.