Bubbling from nozzles submerged in water: Transitions between bubbling regimes

Abstract

Abstract The bubble formation and coalescence phenomena above submerged nozzles having diameters between 1 and 7 mm were studied visually in a stagnant water column. Air was supplied at the nozzles under constant flow rate conditions and the field of view extended from the nozzle exit up to 14 cm above it. The air Reynolds number based on the nozzle diameter covered a range between 50 and 40000. The study was focused on a unified description of the bubbling phenomena, beginning from the single bubble formation up to the jet formation, and the transitions between the various bubbling regions. It was concluded that for nozzles, as injector devices and for the air/water system investigated, the Reynolds number is the controlling variable for the bubbling phenomena above the nozzles and for the transition between the various bubbling regions.