Jacques Magnaudet
Présentation
I am a senior researcher at CNRS (the French National Center for Scientific Research), working at the Fluid Mechanics Institute of Toulouse (IMFT). My research focuses on several fundamental aspects of hydrodynamics and turbulence in two-phase flows and inhomogeneous fluids, mostly studied by means of computational and theoretical approaches. I also closely collaborate with experimentalists and occasionally directly supervise simple experiments myself. I am especially involved in two main areas: • the dynamics of particles, drops and bubbles, most notably: • the structure, mixing properties and near-surface interactions of non-standard inhomogeneous turbulence, especially: Other topics I am or have been involved in include: To study these problems and phenomena, I use and sometimes develop a variety of techniques and methodologies. Some of them are analytical, including perturbation approaches, reciprocal theorems and vector field decomposition. Most others are computational. In particular, I developed, first by myself, then with successive generations of students and colleagues, the in-house code JADIM that solves the Navier-Stokes equations, possibly coupled with the transport of passive or active scalars such as temperature, density or surfactant concentration. This code includes boundary-fitted and fixed-grid approaches thanks to which interfacial phenomena may be accurately captured. It allows fully-resolved simulations of two- and three-phase incompressible flows, possibly with moving rigid bodies and interfacial topological changes, from viscous-dominated to fully turbulent regimes. Together with my students and colleagues, I employ these various and complementary tools to dissect and model the physical mechanisms at play in the above types of flow. This frequently yields predictions in the form of generic laws that are then used to understand, predict and sometimes optimize the properties of complex flows of engineering or geophysical relevance. More specifically, through various collaborations with industrial and institutional partners, I have been directly involved in a variety of problems related to nuclear safety (cooling circuits, accident scenarios), steelmaking, chemical engineering (gas separation, fluidization, microfluidics), oil recovery (mixing in wellbores), transportation (interfacial phenomena in aircraft and launcher tanks, bubble-induced drag reduction), defense (bubbly wakes, container emptying, inertial confinement), air-sea interactions (wind-induced waves and near-surface turbulence, CO2 transfer and sequestration), marine pollution (microplastics, oil spills) and volcanology (viscous mixing in magmatic chimneys). A list of my publications in peer-reviewed journals may be found at: • https://www-webofscience-com.insis.bib.cnrs.fr/wos/woscc/citation-report/f43ba4d9-03a0-43ca-86fd-b78f0bfb6fa2-016e0ff02e Records of some talks I gave over the last few years are available through the links below: • Falling styles of gravity/buoyancy-driven disks, ICTS Distinguished lecture (Bengaluru, 2019): • Interplay of a pair of rising bubbles released in line, Multiphase Flows - Advances and Future Directions (online, 2021): • Particles and bubbles getting through interfaces and stratified layers, IJMF Spotlight seminar (online, 2023): • Maxworthy's 1970 experiment on a computer, Perspectives in Hydrodynamics (IIT Bombay, 2024): • In the skin and folds of a pulsating drop, Waves and Instabilities on Fluid Interfaces (IIT Bombay, 2024): • From Leonardo to Stabfem: The long story of path instability of rising bubbles made short, Sectional lecture, 26th ICTAM (Daegu, 2024): Short videos illustrating some of the physical problems I investigated are also available here: • Buoyancy-driven turbulent mixing of two immiscible fluids in an inclined pipe (paper here https://hal.science/hal-01102240/document) • Falling styles of gravity-driven disks (paper here https://hal.science/hal-00908124/file/auguste_10246.pdf) • Les gouttes qui pulsent, a short outreach video (in French) produced by CNRS https://images.cnrs.fr/video/6499, based on this paper: • Fragmentation of the tail past a steel marble crossing an interface separating two immiscible liquids • Air bubbles crossing an interface separating two immiscible viscous liquids
My abridged CV may be found here https://smallpdf.com/fr/file#s=dca9f9fa-d995-477a-b534-55ce82175939
A more complete version can be downloaded at https://smallpdf.com/fr/file#s=d07cedc5-f1ba-4dd1-9207-5c0ec1eaa330
• https://scholar.google.fr/citations?user=bVYTlS4AAAAJ&hl=fr&oi=ao
https://www.youtube.com/watch?v=UUZzh740_Ls
https://www.youtube.com/watch?v=A4J6AqcESy0
https://www.youtube.com/watch?v=wlsu8H9lbgQ
https://www.youtube.com/watch?v=i2kPQqBZVMA
https://www.youtube.com/watch?v=kXOjPCH3DAs
https://app.videas.fr/6b0ce61c-3f1b-4648-93ca-a38860f74061/
Two fluids with slightly different densities, identical viscosities and no interfacial tension are unstably superimposed in a long circular pipe inclined by 15 degrees to the vertical. The fluids are slightly viscous, so that the flow that sets in quickly becomes turbulent. The first of these DNS-based videos provides an overview of the flow dynamics throughout the pipe; colors correspond to isopycnal surfaces, from C=0.9 (blue) to C=0.1 (red), with C=1 referring to the heavy fluid. The second video provides a closer view at the dynamics of the ascending fluid by visualizing the evolution of the C=0.1 iso-surface. The latter is colored by the "swirling strength" intensity, a criterion that helps identify three-dimensional vortical structures:
https://app.videas.fr/1ff8f78d-3acf-491b-8dac-bec6e094303b/
https://app.videas.fr/9444fdfc-379b-4625-b776-230d54858b4c/
An infinitely thin rigid disk is released from rest broadside on in a slightly viscous fluid. The type of path followed by the disk depends on the ratio of the inertial and viscous forces it experiences and on the disk-to-fluid inertia ratio. The first of these DNS-based videos displays the fall of a thin disk performing large-amplitude planar zigzags. In the second video, the disk has more inertia with respect to the fluid and performs complete tumbles; colors reveal the wake structure, based on the lambda2 criterion:
https://app.videas.fr/6c38932f-296b-4117-bea5-fc73005e59a5/
https://app.videas.fr/ed05d78e-6954-46e1-bd47-c65ba0df5c30/
https://www.nature.com/articles/s41467-018-03201-3
A more complete video showing the full experimental sequence analyzed in the paper is available at https://app.videas.fr/893529ac-a0a2-40dd-bc6d-52660c4d8cb5/
A millimeter-sized dichloromethane drop is released on an aqueous bath in the presence of a surfactant, CTAB. The drop spreads over the bath surface. Evaporation-driven Marangoni stresses develop and induce a rim at the edge of the dichloromethane film. The Rayleigh-Plateau instability produces successive circular droplet crowns, while an evaporative instability induces radial wrinkles in late stages. Time variations of interfacial tensions resulting from droplet ejections and specific properties of CTAB make the system able to perform successive large-amplitude pulsations.
(paper here https://hal.science/hal-01660835/file/pierson_19284.pdf)
Steel marbles settle in a silicone oil layer before they cross the interface separating this layer from a water bath. Because of their large density, they easily cross the interface and settle within the water bath with a significant speed, towing a long column (tail) of silicone oil. Provided the oil viscosity is not too large, the Kelvin-Helmholtz instability that develops soon at the tail surface yields a massive fragmentation phenomenon by which the tail breaks up into a myriad of droplets. The silicone oil if 50 times more viscous than water in the first experimental sequence, and is only 5 times more viscous in the second one:
https://app.videas.fr/57b39efd-0a2f-4581-bf8f-7a7aa9728263/
https://app.videas.fr/cec4763e-1b05-43bd-8a70-b2ac9192eacb/
(paper here https://hal.science/hal-00908876/file/Bonhomme_10245.pdf)
These three videos illustrate the complex influence of the viscosity jump encountered by a bubble crossing an interface separating two liquids, and that of the bubble size which dictates its equilibrium shape in the lower fluid. In the first video, an air bubble with a diameter d≈7mm rises first through a very viscous water-glycerin mixture, then through a silicone oil 50 times less viscous. The bubble is slightly larger (d≈11mm) and the two fluids have nearly equal viscosities in the second video. The third video shows a d≈20mm bubble rising first in water, then through a silicone oil 10 times more viscous. As the three videos make clear, increasing the bubble size yields strikingly different shapes (spheroidal, then spherical cap and finally toroidal), while varying the viscosity ratio has a deep impact on the breakthrough dynamics as well as on the geometry and volume of the tail of lower fluid entrained by the bubble.
https://app.videas.fr/e0a6cc53-6082-4cd0-9ade-e7a6dded4502/
https://app.videas.fr/d721e1c7-5753-4534-9f7d-5dc248ec2a6b/
https://app.videas.fr/46490fae-8c9b-48a9-a247-16f07434ea8a/
Domaines de recherche
Publications
Publications
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Experimental characterization of the gas phase during bottle emptying10th International Conference on Multiphase Flow, May 2019, Rio de Janeiro, Brazil |
Simulating the emptying of a water bottle with a multi-scale two-fluid approach2nd International Workshop of Non-Invasive Experimental Tools and Numerical Methods for the Investigation of Non-Reactive and Reactive Gas-Liquid Flows, Jun 2018, Hambourg (Germany), Germany |
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Simulating the emptying of a water bottle with a multi-scale two-fluid approach5th Joint US-European Fluids Engineering Division Summer Meeting, ASME, Jul 2018, Montreal (Canada), Canada. ⟨10.1115/FEDSM2018-83196⟩ |
Simulating the emptying of a water bottle with a multi-scale two-fluid approach1st NEPTUNE_CFD user meeting, Apr 2018, Saclay (92), France |
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Assessment of multi-scale two-fluid approach by simulating the emptying of a bottleDispersed Two-Phase Flows, SHF, Sep 2018, Toulouse, France |
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Chute d'une sphère au travers de l'interface séparant deux fluides visqueuxCFM 2015 - 22ème Congrès Français de Mécanique, Aug 2015, Lyon, France |
Path instabilities of heavy bodies in free fall in a viscous fluid: wake dynamics vs. aerodynamic effects66th APS DFD Annual Meeting, Nov 2013, Pittsburg, Etats-Unis, United States |
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Weakly nonlinear analysis of the flutter motion of thin cylindersErcoftac International Symposium on Unsteady separation in Fluid-Structure Interaction, Jun 2013, Mykonos, Greece |
The rich life of light rising spheres66th APS DFD Annual Meeting, Nov 2013, Pittsburg, Etats-Unis, United States |
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The hard life of air bubbles crossing a fluid/fluid interfaceComplex Fluids & Flows in industry & nature II, Jul 2013, Vancouver (Canada), Canada |
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Linear stability of disks falling or rising freely in a viscous fluid9th Euromech Fluid Mechanics Conference, Sep 2012, Rome, Italy |
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Dynamics of air bubbles crossing a horizontal interface9th Euromech Fluid Mechanics Conference, Sep 2012, Rome, Italy |
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A generalized reciprocal theorem for predicting the force and torque on bodies moving in an unhomogeneous flow at arbitrary reynolds number23rd International Conference on Theoretical and Applied Mechanics, Aug 2012, Beijing, China |
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Dynamique de bulles traversant l'interface séparant deux liquidesCFM 2011 - 20ème Congrès Français de Mécanique, Aug 2011, Besançon, France |
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Simulation de la déformation des neutrophiles : influence de la rhéologie et du type d'écoulementCFM 2011 - 20ème Congrès Français de Mécanique, Aug 2011, Besançon, France |
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Développement d'une méthode de simulation d'écoulements diphasiques turbulentsCFM 2009 - 19ème Congrès Français de Mécanique, Aug 2009, Marseille, France |
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Simulation aux grandes échelles d'écoulements turbulents à phases séparées par une méthode lagrangienneCFM 2009 - 19ème Congrès Français de Mécanique, Aug 2009, Marseille, France |
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Mélange de fluides miscibles sous l'effet de la gravité dans un tube incliné.CFM 2007 - 18ème Congrès Français de Mécanique, Aug 2007, Grenoble, France |
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Le sillage de bulles des naviresCFM 2007 - 18ème Congrès Français de Mécanique, Aug 2007, Grenoble, France |
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Sur la transition entre calottes sphériques et bulles toriquesCFM 2007 - 18ème Congrès Français de Mécanique, Aug 2007, Grenoble, France |
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Ecoulement d'un fluide visqueux autour d'un disque en incidence frontaleCFM 2007 - 18ème Congrès Français de Mécanique, Aug 2007, Grenoble, France |
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Forces et couple sur une bulle ellipsoïdale plongée dans un écoulement cisailléCFM 2007 - 18ème Congrès Français de Mécanique, Aug 2007, Grenoble, France |
Large eddy simulations of Rayleigh-Taylor turbulence5th International Symposium on Turbulence, Heat and Mass Transfer, Sep 2006, Dubrovnik, Croatia. pp.117 |
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A sharp and conservative method for modeling interfacial flows with insoluble surfactants in the framework of a geometric volume-of-fluid approach2025 |
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Wake instability past a sphere settling in a strongly stratified flow2025 |
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Deformation and stability of a gas bubble in a biaxial straining flow2025 |