Description
- Abstract:
- Bubbles may seem ephemeral or even trivial, but they play surprisingly important roles in both nature and industry. From driving circulation in the upper ocean to mixing chemicals in industrial reactors, bubbly flows influence transport, mixing, and energy transfer across a wide range of systems. Yet, much of what we know about bubble behavior comes from studies in simple Newtonian fluids, such as water. The real world, however, is rarely that straightforward. This dissertation explores the more complex and fascinating world of bubbly flows in non-Newtonian and viscous Newtonian fluids. We focus on swarms of bubbles rising in a quiescent viscoelastic fluid—fluids that exhibit both viscous (liquid-like) and elastic (solid-like) properties—where bubble dynamics are often non-intuitive. Through a combination of experiments and basic theoretical analysis, we investigate how the interplay of viscous and elastic forces alters the way bubbles rise, interact, and stir the surrounding fluid—a phenomenon known as elastic pseudoturbulence. We also examine whether this elastic, bubble-driven agitation can mimic turbulence, even in the absence of inertia, at low Reynolds numbers. To establish a baseline for comparison, we first analyze bubbly flows in Newtonian fluids at low Reynolds numbers, where inertia is negligible and viscous effects dominate. Building on this foundation, we then investigate how elasticity and viscosity influence the dynamics of bubble-induced turbulence in viscoelastic fluids. Specifically, we focus on the wakes generated by swarms of rising bubbles and quantify the resulting mixing and flow behavior using statistical tools such as energy spectra, spatial correlations, and other turbulence diagnostics.
- Notes:
- Thesis (Ph. D.)--Brown University, 2025
Citation
Ravisankar, Mithun,
"Bubbly flows in non-Newtonian and viscous Newtonian fluids"
(2025).
Engineering Theses and Dissertations.
Brown Digital Repository. Brown University Library.
https://repository.library.brown.edu/studio/item/bdr:dc75ehka/
