Acoustical characteristics of two-phase horizontal intermittent flow through an orifice

Abstract

This study addresses acoustical characteristics, in particular, sound generation of intermittent flow regime in a horizontal pipe through an orifice, based on recorded pressure fluctuations and videos of upstream and downstream flow of the orifice. The flow regimes of interest are plug flow and slug flow, respectively, where sharp-edged and rounded entrance orifice are tested. In principle, the noise generated in the intermittent flow regime through an orifice increases with a higher gas flow rate. The pressure fluctuation spectra show a haystack configuration with a peak at a low frequency associated with a sequence of elongated gas bubbles. It demonstrates that the sound generation is predominately governed by dynamic of elongated gas bubbles in intermittent flow through the orifice. Particularly, in plug flow, an additional small hump is detected close to St = 0.2, i.e., vortex-shedding at the orifice exit contributes the sound generation in addition to the bubble dynamic. Furthermore, non-dimensional power of the downstream intermittent flow decays with St-a. The value of a increases with a higher liquid rate, and the haystack-like shape at the peak frequency widens as the gas rate increases. In plug flow, the rounded entrance orifice generates less noise by resulting in a smaller pressure drop compared to the sharp-edged orifice in general; however, it generates noise in high frequency.