Bubbly flows occur naturally, for example, from wave breaking, gas venting at the sea bed or hydrothermal plumes. In engineering systems or industrial applications, gas bubbles can be exploited to enhance mixing, drive interfacial mass transfer, separate fluid streams or to break-up stratification in large water bodies such as lakes.

Turbulence induced by bubble plumes, for example, can enhance mixing sufficiently to break thermal stratification in deep lakes or to prevent ice formation. In environmental engineering air diffusers and bubble plumes are extensively used in aerobic processes such as Activated Sludge.
In this DCU led research project, the plume acts as a source of oxygen needed to sustain the microbial activity responsible for the digestion of organic matter in sewage water.

A method to correct for bubble recirculation has been proposed and allows for good agreement between measured and simulated volumetric transfer rates. The simulation has shown the important role that the interplay between bubble sizes takes in determining the oxygen transfer efficiency.