Onset of Flow Induced Tonal Noise in Corrugated Pipe Segments

Abstract

Corrugated pipes combine smallscale rigidity and largescale flexibility, which make them very useful in industrial applications. The flow through such a pipe can induce strong undesirable tonal noise (whistling) and even drive integrity threatening structural vibrations. Placing a corrugated segment along a smooth pipe reduces the whistling, while this composite pipe still retains some global flexibility. The whistling is reduced by thermoviscous damping in the smooth pipe segment. For a given corrugated segment and flow velocity, one would like to predict the smooth pipe length just sufficient to avoid tonal noise: the onset of whistling. A linear model based on empirical data is proposed that predicts the conditions at the onset of whistling for a composite pipe at moderately high Reynolds numbers, Re: 3000<Re<100,000. Experimental results for corrugated pipes of eight different corrugation geometries are presented revealing fair agreement with the theory. Based on these results, a universal qualitative prediction tool is obtained valid for corrugated pipe segments long compared to the acoustic wavelength.