A5074256363- Fluid Dynamics and Turbulent Flows
- Particle Dynamics in Fluid Flows
- Advanced Thermodynamics and Statistical Mechanics
- Ocean Waves and Remote Sensing
- Geomagnetism and Paleomagnetism Studies
- Solar and Space Plasma Dynamics
- Granular flow and fluidized beds
- stochastic dynamics and bifurcation
- Nonlinear Dynamics and Pattern Formation
- Plant Water Relations and Carbon Dynamics
- Material Dynamics and Properties
- Aeolian processes and effects
- Complex Systems and Time Series Analysis
- Coastal and Marine Dynamics
- Oceanographic and Atmospheric Processes
- Ecosystem dynamics and resilience
- Magnetic and Electromagnetic Effects
- Phase Equilibria and Thermodynamics
- Planetary Science and Exploration
- Experimental and Theoretical Physics Studies
- Combustion and flame dynamics
- Fluid dynamics and aerodynamics studies
- Methane Hydrates and Related Phenomena
- Landslides and related hazards
- Characterization and Applications of Magnetic Nanoparticles
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2015-2024
Service de Physique de l'État Condensé
2014-2024
Université Paris-Saclay
2017-2024
Centre National de la Recherche Scientifique
2015-2024
CEA Paris-Saclay
2015-2024
Institut Rayonnement-Matière de Saclay
2009-2022
École Normale Supérieure de Lyon
2014-2019
Laboratoire de Physique de l'ENS de Lyon
2014-2019
Direction des énergies
2012-2018
Université Claude Bernard Lyon 1
2017
The von Kármán Sodium (VKS) experiment studies dynamo action in the flow generated inside a cylinder filled with liquid sodium by rotation of coaxial impellers (the geometry). We first report observations related to self-generation stationary when forcing is Rπ-symmetric, i.e., rotate opposite directions at equal angular velocities. bifurcation found be supercritical neutral mode whose geometry predominantly axisymmetric. then different dynamical regimes observed not symmetric, including...
The absorption of light or radiation drives turbulent convection inside stars, supernovae, frozen lakes and the Earth's mantle. In these contexts, goal laboratory numerical studies is to determine relation between internal temperature gradients heat flux transported by flow. This constitutive law convection, be input into large-scale models such natural flows. However, in contrast with radiative heating flows, experiments have focused on driven cooling plates: transport then severely...
We report on the transition between two regimes of heat transport in a radiatively driven convection experiment, where fluid gets heated up within tunable heating length $\ell$ vicinity bottom tank. The first regime is similar to one observed standard Rayleigh-B\'enard experiments, Nusselt number $Nu$ being related Rayleigh $Ra$ through power-law $Nu \sim Ra^{1/3}$. second corresponds "ultimate" or mixing-length scaling thermal convection, varies as square-root $Ra$. Evidence for these have...
We report the observation of several dynamical regimes magnetic field generated by a turbulent flow liquid sodium (VKS experiment). Stationary dynamos, transitions to relaxation cycles or intermittent bursts, and random reversals occur in fairly small range parameters. Large scale dynamics result from interactions few modes. The low dimensional nature these is not smeared out very strong fluctuations flow.
We report that the power driving gravity and capillary wave turbulence in a statistically stationary regime displays fluctuations much stronger than its mean value. show probability density function (PDF) has most probable value close to zero involves two asymmetric roughly exponential tails. understand qualitative features of PDF using simple Langevin-type model.
We experimentally study resonant interactions of oblique surface gravity waves in a large basin. Our results strongly extend previous experimental performed mainly for perpendicular or collinear wave trains. generate two crossing at an acute angle, while we control their frequency ratio, steepnesses and directions. These mother mutually interact give birth to whose properties (growth rate, response curve phase locking) are fully characterized. All our found good quantitative agreement with...
A segregation phenomenon in a horizontally vibrated monolayer of granular matter is studied experimentally. In binary mixture small spheres and larger disks, the collapse speed disks increases dramatically with increasing temperature. The scaling behavior can be understood by applying arguments from kinetic gas theory.
We report an experimental study of a dilute "gas" inelastically colliding particles excited by vibrations in low gravity. show that recording the collision frequency together with impulses on wall container gives access to several quantities interest. observe mean does not scale linearly number N container. This is due dissipative nature collisions and also directly related non extensive behaviour kinetic energy (the granular temperature intensive).
An experimental study reveals a new statistical regime for 1D propagation of deep-water gravity waves where coherent structures (solitons, extreme events) coexist with random waves. Such state is predicted theoretically by integrable turbulence but thus far had not been observed in this context.
Significance Turbulent convection is the main process through which nature moves fluids around, be it in deep planetary and stellar interiors or external fluid layers of planets their satellites. Laboratory studies aim at reproducing resulting fully turbulent flows, with goal determining effective transport coefficients to input into coarse geophysical astrophysical models. Crucial these applications rotation, competes convective processes set emergent properties. Building on a recent...
A bifurcating system subject to multiplicative noise can display on-off intermittency. Using a canonical example, we investigate the extreme sensitivity of intermittent behavior nature noise. Through perturbative expansion and numerical studies probability density function unstable mode, show that intermittency is controlled by ratio between departure from onset value spectrum at zero frequency. Reducing frequency shrinks regime drastically. This effect also modifies distribution duration...
We report the first experimental observation of a bistable dynamo regime. A turbulent flow liquid sodium is generated between two disks in von Kármán geometry (VKS experiment). When one disk kept at rest, bistability observed stationary and an oscillatory magnetic field. The branches occur vicinity codimension-two bifurcation that results from coupling modes present study regimes detail region we understand terms dynamical system theory. Despite very nature flow, bifurcations field are...
A new experimental facility has been designed and constructed to study driven granular media in a low-gravity environment. This versatile instrument, fully automatized, with modular design based on several interchangeable cells, allows us investigate research topics ranging from dilute dense regimes of such as gas, segregation, convection, sound propagation, jamming, rheology—all without the disturbance by gravitational stresses active Earth. Here, we present main parameters, protocols,...
In his seminal work on turbulence, Kolmogorov made use of the stationary hypothesis to determine power density spectrum velocity field in turbulent flows. However, our knowledge, constraints that processes impose fluctuations energy flux have never been used context turbulence. Here, we recall spectra injected power, dissipated and converge a common value at vanishing frequency. Hence, show intermittent Gledzer-Ohkitani-Yamada (GOY) shell model fulfills these constraints. We argue they can...
Experimental results are presented on the segregation of a mixture spheres with two different sizes, rolling circularly vibrating table. Beyond critical density particles demixing occurs leading to clustering larger ones. A monodisperse layer shows liquid-solid-like phase transition at slightly lower density. These particle densities both found be independent driving frequency, but decrease increasing vibration amplitude.
We study different types of stationary dynamos observed in the Von Kármán sodium (VKS) experiment when varying electromagnetic boundary conditions on (and in) impellers. The flow is driven with two impellers made soft iron (Monchaux et al 2007 Phys Rev. Lett. 98 044502) or using one soft-iron impeller and stainless steel impeller. magnetic field mapped 40 three-dimensional probes distributed within its surroundings. Symmetry coupling properties are then retrieved from direct probe...
Three-dimensional convection driven by internal heat sources and sinks (CISS) leads to experimental numerical scaling laws compatible with a mixing-length-or 'ultimate'-scaling regime [Formula: see text]. However, asymptotic analytic solutions idealized two-dimensional simulations have shown that laminar flow can transport even more efficiently, The turbulent nature of the thus has profound impact on its properties. In present contribution, we give this statement precise mathematical sense....
We report the first experimental observation of a spatially localized dynamo magnetic field, common feature astrophysical dynamos and convective simulations. When two propellers von Kármán sodium experiment are driven at frequencies that differ by 15%, mean field's energy measured close to slower disk is nearly 10 times larger than one faster one. This strong localization field when symmetry forcing broken in good agreement with prediction based on interaction between dipolar quadrupolar mode.
We report on the observation of surface gravity-wave turbulence at scales larger than forcing ones in a large basin. In addition to downscale transfer usually reported turbulence, an upscale is observed, interpreted as inverse cascade weak theory. A steady state achieved when reaches scale between wavelength and basin size, but far from latter. This saturation, which depends wave steepness, probably due emergence nonlinear dissipative structures such sharp-crested waves.
Abstract
We present recent results on noise-induced transitions in a nonlinear oscillator with randomly modulated frequency. The presence of stochastic perturbations drastically alters the dynamical behaviour oscillator: noise can wash out global attractor but also have constructive role by stabilizing an unstable fixed point. random displays rich phenomenology remains elementary enough to allow for exact calculations: this system is thus useful paradigm study bifurcations and ideal testing ground...
The onset and dynamics of flow in shallow horizontally oscillating granular layers are studied as a function the depth layer imposed acceleration. Measurements velocity made from top side presented frame reference container. As is also found for avalanches inclined layers, thresholds starting stopping slightly different. variation with acceleration Gamma{start} similar to corresponding tangent angle tan(theta{start}) same container at low frequencies, but deviates frequency increased....