arXiv subjects

Philippe Odier

Publications and source records attributed to Philippe Odier.

21 records · Page 2Linked to original sources

arXiv2009

Induction in a von Karman flow driven by ferromagnetic impellers

We study magnetohydrodynamics in a von Kármán flow driven by the rotation of impellers made of material with varying electrical conductivity and magnetic permeability. Gallium is the working fluid and magnetic Reynolds numbers of order unity are achieved. We find that specific induction effects arise when the impeller's electric and magnetic characteristics differ from that of the fluid. Implications in regards to the VKS dynamo are discussed.

physics.flu-dyn↗

arXiv2009

Mixing in stratified gravity currents: Prandtl mixing length

Shear-induced vertical mixing in a stratified flow is a key ingredient of thermohaline circulation. We experimentally determine the vertical flux of momentum and density of a forced gravity current using high-resolution velocity and density measurements. A constant eddy viscosity model provides a poor description of the physics of mixing, but a Prandtl mixing length model relating momentum and density fluxes to mean velocity and density gradients works well. For $ \approx 0.08$ and $Re_λ\approx 100$, the mixing lengths are fairly constant, about the same magnitude, comparable to the turbulent shear length.

physics.flu-dyn↗

arXiv2005

Fluctuation of magnetic induction in von Kármán swirling flows

Studies of magnetic induction in von Kármán swirling flows have so far linked the time-averaged induced magnetic field to the structure of the mean flow. They have evidenced the Omega and Parker mechanism generated respectively by the flow differential rotation and helicity, which underly the Duddley and James \cite{DuddleyJames} dynamos. Using an array of Hall probes we study here the dynamical regime. In the experimental flow, turbulence is fully developed and large fluctuations are observed in the magnetic induction processes. We find that the large scale turbulent fluctuations have different characteristics when induction results from the differential rotation or from the dynamics of the stagnation point in the mid plane of the von Kármán flow. Symmetry considerations indicate that the dynamical flow spends half of its time away from the time-averaged structure. The consequences of these observations for dynamo experiments are discussed.

physics.flu-dyn↗