Low-wavenumber turbulent boundary layer wall-pressure measurements from vibration data over smooth and rough surfaces in pipe flow

The vibration response of a thin cylindrical shell excited by fully developed turbulent pipe flow is measured and used to extract the fluctuating pressure levels generated by the boundary layer. Parameters used to extract the turbulent fluctuating pressure levels are determined via experimental modal analyses of the water-filled pipe and measured vibration levels from flow through the pipe at 5.8 m/s. Measurements are reported for hydraulically smooth and fully rough surface conditions. Smooth wall-pressure levels are compared to the turbulent boundary layer pressure model of Chase [The character of the turbulent wall pressure at subconvective wavenumbers and a suggested comprehensive model. Journal of Sound and Vibration112 (1) (1987) 125–147] and the measurements of Bonness et al. [Low-wavenumber turbulent boundary layer wall-pressure measurements from vibration data on a cylinder in pipe flow. Journal of Sound and Vibration329 (2010) 4166–4180]. Results for the smooth pipe match the predicted smooth wall-pressure spectrum and correspond to a normalized low wavenumber-white level which is −41 dB below the maximum level at the convective peak. Pressure levels from the fully rough condition display a low-wavenumber-white level which is 28 dB below the convective peak level. This suggests an increase of 13 dB in low-wavenumber wall pressure for the uniformly distributed roughness elements in this study over a hydraulically smooth surface.