Bubbles generate their own kind of turbulence

As bubbles rise, they impart turbulence to an otherwise quiescent fluid. Boiling water reactors include bubbles, and in metallurgical applications and bioreactors, injecting bubbles can promote better mixing. Natural flows, like the liquid metal at the core of the Earth, also host bubbly turbulence. Understanding this bubble-induced turbulence, and building models that can account for it, are crucial for each of these environments.

Paul et al. simulated bubbly turbulence in comparison to classical turbulence to see if existing classical models can be used to characterize bubbly systems. The team found that bubble generated turbulence differs fundamentally from classical isotropic turbulence, so that bubbly flows require their own class of models.

“We were interested in the liquid phase dynamics, so we wanted to know how much bubble shape and physical processes like breakup and coalescence influence the bubbly turbulence,” said author Immanuvel Paul. “Knowing answers to these questions would be greatly beneficial to many industries that rely on the mathematical modelling of these systems.”

Bubble shape, topology, breakup, and coalescence did not affect the fine-scale characteristics of bubbly turbulence, and so do not need to be accounted for in future models.

By better understanding turbulent bubbly systems, the researchers aim to study their impacts on mixing.

“We are particularly interested in the mixing of liquid metals in metallurgical applications and the mixing of biological components in the biomedical industry, where bubbly turbulence plays a major role,” said Paul.

Source: “The role of breakup and coalescence in fine-scale bubble-induced turbulence: Part I - dynamics,” by Immanuvel Paul, Bruño Fraga, Michael S. Dodd, and Chris Lai, Physics of Fluids (2022). The article can be accessed at https://doi.org/10.1063/5.0094573 .