Noise Generation and Propagation Within Corrugated Pipes

Corrugated pipes have the advantage of being flexible but the disadvantage of generating unacceptable levels of noise. The noise generated within these pipes is due to oscillation of vortices formed within the corrugations. The noise can induce vibration and unacceptable fatigue damage. Consequently, it is desirable to have a method for predicting the flow conditions that facilitate noise and the noise levels that are generated. This paper develops a theoretical model for the noise generation by considering the interaction of an acoustic wave with the vortices. The key issue that emerges is the delay or phase angle between vortex production in the corrugations and an acoustic standing wave. For the usual conditions, where there are many corrugations in a wavelength, it is possible to form a differential equation for the build-up and saturation of an acoustic resonance. The relative few parameters within this differential equation provide a good basis for modeling the occurrence and level of noise produced. It is anticipated that some experimental input will always be needed for particular corrugation geometries.