Experimental observations of bubbling regimes at in-line multi-orifice bubblers.

Abstract

Bubble formation and bubbling regimes are well-characterized for the cases of single-orifice bubblers and industrial perforated plates. However, bubbling regimes from bubblers with multiple in-line orifices remain poorly described. Here, we investigate the dynamics of bubble formation at both single-orifice and multi-orifice bubblers, with one, three, five and nine in-line orifices in an 80-cm-long bubbler. We use high-speed videography and image processing to identify the effects of bubbler volume, and the number, spacing, and diameter of orifices, on bubbling regimes, bubble period, and bubble formation time. We identify five main bubbling regimes based on synchronization among orifices, and discuss the parameters affecting the bubbling dynamics. Decreasing bubbler volume leads to a decrease in bubble volume and bubble period, and enhances synchronization. Increasing orifice diameter leads to an increase in bubble volume and enhances synchronization. Spacing between orifices doesn't play an important role in determining the bubbling regime. Based on the experimental observations, we develop new bubbling regime maps constructed using the dimensionless Capacitance number and Weber number.