The dynamics of bubbles in anisotropic turbulence
Abstract
Approved for Public ReleaseThe fragmentation of bubbles in turbulent ship wakes is a phenomenon of significant interest. Classical Kolmogorov-Hinze (KH) theories, which describe the breakup of bubbles in turbulence, are based on idealized isotropic conditions. However, the wake of a ship introduces strong shear flows and complex turbulence that likely modify the breakup dynamics. These theories also overlook the directionality of forces and the timescales over which stresses act on bubbles, potentially masking critical interactions between shear flows and turbulence. Additionally, the presence of shear introduces a new timescale, complicating the prediction of bubble breakup in these environments. The challenge of studying bubbly flows in turbulent ship wakes is further compoundedby the sharp gradients in shear and turbulence properties and the limited residence time of bubbles within different sublayers of the wake. These constraints highlight the need for improved experimental methods and refined models that can account for the anisotropic and transient nature of ship wake turbulence.This research aims to elucidate the complex interactions between shear and turbulence in the deformation and breakup of bubbles within ship wakes. To overcome the challenge of limited residence time, a new high-shear-rate experimental facility is being developed. This facility will allow bubbles to be exposed to homogeneous shear turbulence under controlled conditions for extended periods. By independently varying the mean shear and turbulence intensity, the study will systematically explore the relative contributions of shear forces and turbulent eddies to bubble fragmentation. Advanced optical diagnostics will capture detailed statistics on breakup times, resulting bubble sizes, and transient deformations as a function of local flow conditions. The research will test hypotheses regarding the competing effects of shear directionality, stress timescales, and their interactions with small-scale turbulence, ultimately leading to a more comprehensive understanding of bubble dynamics in ship wakes.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 13, 2025
- Source ID
- N000142512097
Entities
People
- Rui Ni
Organizations
- Johns Hopkins University
- Office of Naval Research
- United States Navy