Low-wavenumber turbulent boundary layer wall-pressure measurements from vibration data on a cylinder in pipe flow

The response of a structure to turbulent boundary layer (TBL) excitation has been an area of research for roughly 50 years, although uncertainties persist surrounding the low-wavenumber levels of the TBL surface pressure spectrum. In this experimental investigation, a cylindrical shell with a smooth internal surface is subjected to TBL excitation from water in fully developed pipe flow. The cylinder's vibration response to this excitation is used to determine Iow-wavenumber TBL surface pressure levels at lower streamwise wavenumbers than previously reported (k/₁/k_c<0.01). An experimental modal analysis is also conducted on the water-filled cylindrical shell to determine structural parameters which are used to extract TBL pressures. The measured Iow-wavenumber pressure data falls midway between TBL models by Smol'yakov [Acoustical Physics 52(3) (2006) 331-337] and Chase \Journal of Sound and Vibration 112(1) (1987) 125-147] and is roughly 23 dB lower than an early TBL model by Coreos [Journal of the Acoustical Society of America 35(2) (1963) 192-198]. The current data is a few decibels below the lower bound of related measurements in air by Farabee and Geib [ICIASF 75 Record, 1975, pp. 311-319] and Martin and Leehey [Journal of Sound and Vibration 52(1) (1977) 95-120]. A simple wavenumber white form for the TBL surface pressure spectrum at Iow-wavenumber is suggested.