Missions

Bubble columns are widely used in a range of industrial applications, including biomethanation, hydrogen production, CO₂ sequestration, and separation processes. Despite their broader relevance, the complex flow dynamics in these systems are not fully understood, especially in the heterogeneous regime, where the collective effect plays a significant role. In particular, mesoscale structures emerge, giving rise to buoyancy-driven turbulent convection [Mezui et al., J. Fluid Mech., 2022, 2023; Obligado et al., Chemical Eng. Sci., 2025]. Several fundamental questions remain open: What are the mechanisms that govern the formation and evolution of these mesoscale structures? Does an asymptotic heterogeneous state exist at large gas flow rates? How does the flow develop along the axial direction of the column? Additionally, the presence of surfactants introduces further complexity. When surfactants are added, liquid foam layer forms in the column. Understanding the bubble size distribution and dynamics within the foam layer is essential for optimizing separation processes.
Main missions:
- Investigating the flow dynamics in air-water bubble columns,
- Identifying the mechanism(s) controlling meso-scale structures,
- Determining relevant scaling laws that describe the mean and fluctuation of local gas concentration.
- Characterizing the foam layer when adding surfactants with a focus on bubble size distribution
- Optimizing the separation processes based on insights from foam dynamics

Activities

Main tasks:
- Experimental investigation of air-water bubble columns in the heterogeneous regime (i.e. at large injected gas flow rate);
- Experimental investigation of the foam dynamics when adding surfactants;
- Development of models and/or scaling laws for meso-scale structures characteristics, for gas concentration…
The experimental setups, including a fully operational bubble column, is available on the PEI platform (https://www.pei-grenoble.fr/) part of the Research Federation Fed3G (https://www.fed3g.fr/). Some adaptations will be required to meet specific research objectives. The experimental investigations will be carried out notably using the newly developed Doppler optical probes [Lefebvre et al., Chemical Eng. Sci., 2022]. Signal acquisition and processing, as well as the data post-processing tool will need to be adapted or extended for the current application.
Secondary tasks:
- Supervision of undergraduate or master students.
- Collaboration and discussion of research results with team members,
- Participation to an on-going collaboration with Shizuoka University,
- Communication of research results (seminars, publications…).

Skills

We are looking for a motivated postdoctoral researcher with a strong interest in experimental work and two-phase flow phenomena. The candidate will have a solid background in physics and/or fluid mechanics, as well as the ability to conduct experiments in an independent and rigorous manner.
Expected skills :
- PhD in fluid mechanics, condensed matter pysics, or a related field.
- Excellent academic record, preferably with prior experience in measuring techniques and/or data acquisition and signal processing, in fluid mechanics,
- Ability to design, adapt, and conduct experiments, and to analyze and interpret results independently and creatively,
- Excellent written and oral communication skills in English,
- Ability to present research findings at scientific meetings and conferences,
- Strong teamwork and collaboration skills, with the ability to work I a multidisciplinary research environment,
- Ability to participate in potential scientific exchanges with Japan.

Work Context

The Laboratoire des Ecoulements Géophysiques et Industriels, LEGI - https://www.legi.grenoble-inp.fr/web/ is a Joint Research Unit (UMR 5519) of the Centre National de la Recherche Scientifique (CNRS), the Institut National Polytechnique de Grenoble (Grenoble INP) and the University Grenoble-Alpes (UGA). LEGI carries out a wide range of research activities with a common ground: fluid mechanics and related transport phenomena. The research will take place in the EDT (Two-Phase flows and turbulences) research team that studies fundamental flow mechanisms involving complex dynamics related to non-linearity, instabilities or turbulence, in single- or multi-phase fluids. Close collaborators in the EDT team will be Ms. Zhujun Huang and Alain Cartellier.
In terms of local environment, the LEGI participates in the Research federation Fed3G (https://www.fed3g.fr/) that regroups 8 research laboratories in mechanics and process engineering in Grenoble. All these laboratories are also strongly interacting within the Labex Tec21 (https://www.tec21.fr/).

Constraints and risks

Laser sources are used in the project.