PhD defense by Amélie Ferrand

Inertial particles dynamics in a turbulent/non-turbulent interface

Images of a turbulent air flow laden with water droplets in wind tunnel experiments
Images of a turbulent air flow laden with water droplets in wind tunnel experiments

On the 18th of December 2023 at 2 pm, Amélie Ferrand wil defend her PhD in room K118 at the LEGI building.


Her work was initiated and supervised by Martin Obligado (LEGI) and Alberto Aliseda (Washington University), and co-supervised by Nathanaël Machicoane (LEGI).

The project was funded by Tec21 and the University of Washington as part of a long term visitor project started in 2020.


Many environental phenomena involve inertial particles advected in an inhomogeneous turbulent flow. Over the last decades, many studies have focused on the simplified case of homogeneous and isotropic turbulence. Nevertheless, most relevant applications feature non-homogeneous turbulence presenting a turbulent/non-turbulent interface. This thesis aims to study the motion of small, heavy inertial particles advected by a turbulent/non-turbulent interface.


The thesis is divided into three main parts. In a first part, we present a method to analyse experimentally single-phase turbulent flows using solely statistics on points where the fluctuating velocity is equal to zero. We demonstrate that voids of zero crossings primarly control the degree of turbulence and the Taylor Reynolds number.


In a second part, we explore the settling velocity modification of inertial particles in homogeneous isotropic turbulence through wind tunnel experiments. Our findings confirm that the settling enhancement decreases significantly with increasing values of the Taylor Reynolds number. Additionally, this study reveals that large-scale structures have a significant impact on the settling rate, even at constant turbulent intensity and Reynolds number.


In the third part, we present wind tunnel experiments on the dynamics of inertial particles advected in a turbulent/non-turbulent interface. Only the high-turbulence side is laden with inertial particles, and we are interested in how their properties change as they travel across the interface, particularly their preferential concentration and settling velocity.


Our observations confirm that particles tend to oversample high-energetic events within the mixing layer. Finally, the interface is also associated with an increase in clustering intensity and a stronger enhancement of the settling velocity.


Keywords: wind tunnel experiments, inertial particles, turbulent/non-turbulent interface

About Amélie Ferrand

Amélie has obtained an engineering diploma from the ENSEEIHT school in Toulouse with a speciality in fluid mechanics and environmental flows. During her studies, she has spend one semester as an Erasmus student at the Arctic University of Norway and obtained a master diploma about ocean, atmospheric and climate science from the University Paul Sabatier (Toulouse).