Chaos and turbulence in bubbly flows

TL;DR

This paper investigates the chaotic and turbulent behaviors in bubbly flows at different gas volume fractions using simulations and experiments, revealing distinct spectral characteristics and implications for nuclear reactor safety.

Contribution

It demonstrates the transition from deterministic chaos to distributed chaos in bubbly flows and analyzes bubble interactions in turbulent environments, with applications to nuclear reactors.

Findings

High gas volume fraction flows exhibit exponential energy spectra indicating chaos.

Moderate and small gas volume fraction flows show stretched exponential spectra indicating turbulence.

Bubble interactions with turbulent flows are characterized and discussed in the context of reactor safety.

Abstract

Results of direct numerical simulations and laboratory experiments have been used in order to show that the buoyancy driven bubbly flows at high gas volume fraction are mixed by deterministic chaos with typical exponential spectrum of the liquid kinetic energy, whereas at moderate and small gas volume fraction it is a distributed chaos (turbulence or pseudo-turbulence) dominated by the third and second moments of helicity distribution with the stretched exponential spectra of the kinetic energy. Interaction of the bubbles with isotropic (behind an active grid) and near-wall turbulent flows has been also discussed from this point of view with an application to the pressurized water nuclear reactors.