Interparticle arrival time analysis of bubble distributions in a dropshaft and hydraulic jump

Abstract

The analysis of bubble clustering in air–water flows may provide some measures of the bubble–turbulence interactions. A cluster of bubbles is as a group of two or more bubbles, with a distinct separation from other bubbles. This paper compares the results of a clustering study in a dropshaft and in a hydraulic jump to point out differences/similarities between those complex turbulent flows. The clustering process was studied through the analysis of the interparticle arrival time (IAT) of the bubbles. The results highlighted the presence of clustering in both bubbly flows due mostly to turbulent break-up. The range of bubbles sizes mainly affected by clustering was identified. The results showed that the bubbly flow in the dropshaft had a density of bubbles per unit flux larger than that in the hydraulic jump. Overall, the results demonstrated the relevance of the IATs analysis in the study of bubbly flows.

Keywords:

• Air bubble entrainment
• bubble clustering process dropshaft
• hydraulic jump
• interparticle arrival time analysis
• laboratory experiments
• Poisson distribution

Acknowledgements

The first author acknowledges the financial support from the Exchange Program for Professors and Researchers of the University of Napoli Federico II for the year 2003 and 2006 and the preliminary work carried out by his former student O. Casoria.