Mickaël Bourgoin

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Mixing and transport in turbulent flows-which have strong local concentration fluctuations-are essential in many natural and industrial systems including reactions in chemical mixers, combustion in engines and burners, droplet formation in warm clouds, and biological odor detection and chemotaxis. Local concentration fluctuations, in turn, are intimately(More)
The dynamics of particles in turbulence when the particle-size is larger than the dissipa-tive scale of the carrier flow is studied. Recent experiments have highlighted signatures of particles finiteness on their statistical properties, namely a decrease of their acceleration variance, an increase of correlation times-at increasing the particles size-and an(More)
The Von Kármán Sodium experiment yields a variety of dynamo regimes, when asymmetry is imparted to the flow by rotating impellers at different speed F1 and F2. We show that as the intensity of forcing, measured as F1 + F2, is increased, the transition to a self-sustained magnetic field is always observed via a supercritical bifurcation to a stationary(More)
– We report the first experimental observation of reversals of a dynamo field generated in a laboratory experiment based on a turbulent flow of liquid sodium. The magnetic field randomly switches between two symmetric solutions B and −B. We observe a hierarchy of time scales similar to the Earth's magnetic field: the duration of the steady phases is widely(More)
Turbulent transport of material inclusions plays an important role in many natural and industrial situations. Being able to accurately model and predict the dynamics of dispersed particles transported by a turbulent carrier flow, remains a challenge. One critical and difficult point is to develop models which correctly describe the dynamics of particles(More)
We report measurements of the Lagrangian velocity structure functions of orders 1 through 10 in a high Reynolds number (Taylor microscale Reynolds numbers of up to R(lambda) = 815 ) turbulence experiment. Passive tracer particles are tracked optically in three dimensions and in time, and velocities are calculated from the particle tracks. The structure(More)
We present an apparatus that generates statistically homogeneous and isotropic turbulence with a mean flow that is less than 10% of the fluctuating velocity in a volume of the size of the integral length scale. The apparatus is shaped as an icosahedron where at each of the 12 vertices the flow is driven by independently controlled propellers. By adjusting(More)
We study the flow response to an externally imposed homogeneous magnetic field in a turbulent swirling flow of liquid sodium – the VKS2 experiment in which magnetic Reynolds numbers Rm up to 50 are reached. Induction effects are larger than in the former VKS1 experiment (1; 2). At Rm larger than about 25, the local amplitude of induced field components(More)
Acknowledgements First of all I thank God, the Almighty, for blessing me with courage, patience, perseverance, and all one needs to accomplish a doctoral dissertation. At this moment in time, when I look back, I see a long list of people who helped me achieve this important milestone in my life and to those I feel obliged to express my gratitude. The first(More)
We report the first experimental observation of reversals of a dynamo field generated in a laboratory experiment based on a turbulent flow of liquid sodium. The magnetic field randomly switches between two symmetric solutions B and −B. We observe a hierarchy of time scales similar to the Earth's magnetic field: the duration of the steady phases is widely(More)