Experimental Study of Vibration and Acoustic Radiation of a Pipe Induced by Fully-Developed Turbulent Air Flow

Abstract

Experimental results are presented concerning the vibro-acoustic response of a pipe excited by an internal fully-developed turbulent air flow. The internal wall pressure field generated by the flow, the vibration response and the external acoustic field were measured for Reynolds numbers Re = UoD/v ranging from 5.3 × 105 to 12.5 × 105. The measured statistical properties of the wall pressure field include power spectral densities and cross-spectra. Power spectral density is analyzed after cancellation of a contaminating acoustic component of the wall pressure fluctuations. Convection velocity and correlation lengths are calculated from measured cross-spectra to complete a Corcos model for the cross-spectrum of the turbulent wall pressure fluctuations. The ratio of convection velocity to centerline velocity ranges from 0.7 to 0.8. The coefficient α1 of the standard Corcos model is calculated from the longitudinal correlation length and is found to be around 0.18. To have further information about the convection velocity and correlation lengths in a lower frequency range than presented here, the measured cross-spectral data need to be decontaminated from the acoustic component of the wall pressure. The acceleration response of the pipe wall shows the influence of the structural modes of the test section. Only some of them have a significant influence on the external acoustic field.