Fragmentation in Turbulence Revisited - Toward a universal theory for turbulent emulsification

Introduction

Droplets and bubbles are omnipresent in many environmental and industrial applications that involve atomization and emulsification processes. The ability to control the size of these dispersed elements in turbulent multiphase flows is essential for design and optimization purposes.

Importance of Fragmentation

Despite the importance of the fragmentation of one fluid in another by turbulent eddies, a universal theory applicable to a majority of the scenarios is still missing. Following the seminal work of Hinze on characterizing the size of the largest stable droplets in turbulence, known as Kolmogorov-Hinze theory, I aim to revisit this concept with a novel deterministic approach through theoretical investigation, experimental characterization, and numerical simulation.

Recent Contributions

In my recent contribution, I have presented a novel description for the Hinze scale based on the concept of enstrophy transport across the scales in turbulence. This could serve as the basis for my deterministic approach to studying turbulent emulsification.

Theoretical Basis

By providing the theoretical basis for sustained homogeneous isotropic turbulent flows, I will measure the spectral rate of enstrophy transport rates by:

1. Vortex stretching
2. Surface tension
3. Other relevant mechanisms

This will be conducted in a drop-laden turbulent flow in the lab using tomographic PIV and shape reconstruction.

Numerical Simulations

Furthermore, by performing direct numerical simulation (DNS), I will explore situations where experimentation may be limited, such as:

1. Highly-dense emulsifications
2. Surfactant-laden environments

The simulations will provide a large dataset based on which we could generate a universal theory for emulsification in turbulent drop-laden and bubbly flows.

Project Goals

The FragTuRe project revisits the fundamental understanding of turbulent fragmentation by a concept that has not been employed before. It aims at generating a novel case-independent universal correlation for the Hinze scale that is essential in many engineering applications.