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During my PhD and the following years, I worked on a new scenario to explain to explain the formation of solar system, based on hydrodynamical turbulence. Using data from laboratory flows, and chemical observations from space missions, I showed that the turbulence generated by nonlinear shear instabilities could produce giant vortices favouring grains condensation and planetesimal growth. This hypothesis is now the basis of many solar system scenarios.
In 1994, I started to work on explanation of turbulence intermittency. I explored scenarii based on log-Poisson statistics, finite size scale invariance, and non-locality of interactions.
In 2001, I joined the VKS team, to work on theoretical and experimental explanation of cosmic magnetic fields through turbulent dynamos. I participated in data campaigns and analysis of the Sodium experiment, and devised a Galerkin method to obtain 3D reconstruction of the magnetic field from sparse measurements. I supervised several post-doc and students to explore the influence of noise on the dynamo instability and show that it has an impeding influence. I also proposed to explain why dynamo in VKS has only been observed with ferro-magnetic disks via enhancement of the alpha effect mechanism by magnetic field collimation of shedding vortices.
In 2005, I started to work on modelling of the large-scale structures of geophysical and astrophysical flows. I adapted the statistical framework of Robert and Sommeria, built for 2D flows to cases with axisymmetry (2D1/2). My theory successfully reproduces features of the mean flow and its bifurcations observed in the von Karman experiment in Saclay. I further supervised 2 PhDs to interpret the turbulent bifurcation in terms of phase transition, analog to the ferro-paramagnetic transition. Since 2009, I applied these concepts in climate modelling, and work on the application and explanation of a min-max entropy production principle for prediction of temperature distribution at the Earth surface.
In 2009, I started collaborating with experimentalists in Grenoble and Lyon to study quantum turbulence. I proposed to build a von Karman experiment filled with Helium4 below and above the lambda point to study turbulence and dissipation processes in classical and quantum flow. The experiment was built in 2011 (SHREK experiment). I have participated to several experimental campaigns, and in data analysis. I have supervised several PhDs and post-docs in Saclay to conduct experiments in water on a scale 1:4 version of SHREK, for calibration and interpretation of the data.
Since 2015, I launched a new area of research, attempting to detect Holder singularities of Navier-Stokes equation in a laboratory turbulent flow by following in scale the extreme events inertial dissipation. We found that they correspond to non-trivial velocity topologies associated with possible footprints of singularities. A striking result of our exploration is the existence of localized significant non-viscous energy transfers even at the Kolmogorov scale. These transfers are taken into account neither by classical Direct Numerical Simulations (DNS) (usually cut above or at the Kolmogorov scale), nor by traditional turbulence models (following K41 phenomenology). Understanding these sub-Kolmogorov transfers and building a new turbulent model compatible is now my main objective. I have written an invited review paper entitled Beyond Kolmogorov cascades (JFM Perspectives, 2019) on this subject.
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ATMOSPHEREno. 11 (2023): 1690-1690
arxiv(2023)
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JOURNAL OF FLUID MECHANICS (2023)
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Physical review. Eno. 6 (2023): 065106
crossref(2023)
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arXiv (Cornell University) (2023)
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