Acronym: TurbInt²

Keywords: Turbulence, Atomization, Two-phase Flows, CFD

Supervision:

• Christophe Dumouchel

• Jorge César Brändle de Motta

• Fabien Thiesset

Start: Autumn 2025

Application:

By email to jorge.brandle@coria.fr (Subject: "TurbInt² application") with:

• Curriculum Vitæ

• Cover letter

• Recomendation letter

• Transcript of records

Documents can be in English or French.

Profile

The student must hold a Master's degree in science (energy, engineering, fluid mechanics,...). Attention will be paid to the following points:

• Proficiency in fluid mechanics, and if possible, with some knowledge of two-phase flows.

• Experience in numerical simulation (CFD).

• Proficiency in programming, preferably in Python and/or Fortran.

• Strong oral and written communication skills in English.

Abstract

Heterogeneous fluid flows, i.e. non-miscible fluids separated by an interface, are found in many industrial situations (e.g. fuel injection, bubble reactors, emulsion production for the pharmaceutical or food industries, etc.) and natural situations (e.g. ocean-atmosphere exchanges). A persistent obstacle to the prediction and/or optimization of these systems stems from the difficulty of characterizing the breakup of fluid structures (such as jets, waves, drops or bubbles) in the presence of a turbulent flow. Indeed, this breakup is linked to complex, highly multiscale exchanges between the fluid phases, which carry turbulent kinetic energy, and the interface, which carries interfacial surface tension energy. This coupling remains an open question, yet one that is essential for developing effective predictive models and optimization tools.

The project-team formed by the coordinator of this PhD proposal has recently made progress on this issue with the thesis of I. Roa and the ANR JCJC DropBreak (J. C. Brändle de Motta). They focused on the breakup of an isolated drop evolving in isotropic homogeneous turbulence (see figure below). It was observed that turbulence deforms and wrinkles the interface, which initially opposes deformation via the effect of surface tension. Under some peculiar conditions, turbulence is such that a critical state of deformation is reached, the surface tension no longer opposes deformation, but instead precipitates the rupture of the drop, which becomes irremediable. The properties of the turbulence and the interface that lead to this critical state seem unclear, although it is likely to assume that a tipping point occurs in the exchange of momentum and kinetic energy between the carrier phases and the interface.

This thesis follows the line of I. Roa's thesis and the ANR DropBreak project. It aims to explore the exchanges between the turbulent kinetic energy carried by the flow and the surface energy carried by the interface, from the initial deformations to the critical state before breakup. To this end, numerical simulations will be used in together with an analytical framework characterizing the energy balance at the surface separating the two phases. The link between the scale distributions of turbulence and the scale distribution of interface folds, will also be explored.