Intermittency of bubble deformation in turbulence

TL;DR

This paper investigates how bubbles deform in intense turbulence by analyzing the tip velocity of their deformation, revealing scale-dependent energy transfer and intermittency characteristics that differ from fluid velocity statistics.

Contribution

It introduces a novel analysis of bubble tip velocity in 3D turbulence, linking deformation dynamics to eddy scales and intermittency, with a model explaining extreme deformation events.

Findings

Tip velocity spectrum resembles Lagrangian fluid statistics

Intermittency of tip velocity exceeds that of velocity increments

Model explains extreme deformation by small, energetic eddies

Abstract

The deformation of finite-sized bubbles in intense turbulence exhibits complex geometries beyond simple spheroids as the bubbles exchange energy with the surrounding eddies across a wide range of scales. This study investigates deformation via the velocity of the most stretched tip of the deformed bubble in 3D, as the tip extension results from the compression of the rest of the interface by surrounding eddies. The results show that the power spectrum based on the tip velocity exhibits a scaling akin to that of the Lagrangian statistics of fluid elements, but decays with a distinct timescale and magnitude modulated by the Weber number based on the bubble size. This indicates that the interfacial energy is primarily siphoned from eddies of similar sizes as the bubble. Moreover, the tip velocity appears much more intermittent than the velocity increment, and its distribution near the extreme tails can be explained by the proposed model that accounts for the fact that small eddies with sufficient energy can contribute to extreme deformation. These findings provide a framework for understanding the energy transfer between deformable objects and multiscale eddies in intense turbulence.