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- R Monchaux, M Berhanu, +13 authors F Ravelet
- Physical review letters
- 2007

We report the observation of dynamo action in the von Kármán sodium experiment, i.e., the generation of a magnetic field by a strongly turbulent swirling flow of liquid sodium. Both mean and fluctuating parts of the field are studied. The dynamo threshold corresponds to a magnetic Reynolds number R(m) approximately 30. A mean magnetic field of the order of… (More)

- Panagiotis Kallinikos, Michael Berhanu, Clare O'Donnell, Andrew J M Boulton, Nathan Efron, Rayaz A Malik
- Investigative ophthalmology & visual science
- 2004

PURPOSE
Corneal confocal microscopy is a reiterative, rapid, noninvasive in vivo clinical examination technique capable of imaging corneal nerve fibers. Nerve fiber tortuosity may indicate a degenerative and attempted regenerative response of nerve fibers to diabetes. The purpose of this study was to define alterations in the tortuosity of corneal nerve… (More)

- M. Berhanu, G. Verhille, +14 authors C. Pirat
- 2010

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)

- Michael Berhanu, Arshad Kudrolli
- Physical review letters
- 2010

We investigate the spatial structure of cohesive granular matter with spheres floating at an air-liquid interface that form disordered close packings with pores in between. The interface is slowly lowered in a conical container to uniformly compress and study the system as a function of area fraction ϕ. We find that the free area distributions associated… (More)

- M. Berhanu
- 2006

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)

- F Ravelet, M Berhanu, +12 authors F Pétrélis
- Physical review letters
- 2008

We report the observation of several dynamical regimes of the magnetic field generated by a turbulent flow of liquid sodium (VKS experiment). Stationary dynamos, transitions to relaxation cycles or to intermittent bursts, and random field reversals occur in a fairly small range of parameters. Large scale dynamics of the magnetic field result from the… (More)

- Marie-Julie Dalbe, Darija Cosic, Michael Berhanu, Arshad Kudrolli
- Physical review. E, Statistical, nonlinear, and…
- 2011

Capillary attraction between identical millimeter-sized spheres floating at a liquid-air interface and the resulting aggregation are investigated at low Reynolds number. We show that the measured capillary forces between two spheres as a function of distance can be described by expressions obtained using the Nicolson approximation at low Bond numbers for… (More)

- R Volk, F Ravelet, +8 authors F Pétrélis
- Physical review letters
- 2006

We study the effect of a turbulent flow of liquid sodium generated in the von Kármán geometry, on the localized field of a magnet placed close to the frontier of the flow. We observe that the field can be transported by the flow on distances larger than its integral length scale. In the most turbulent configurations, the mean value of the field advected at… (More)

- M. BERHANU, F. DAVIAUD, B. DUBRULLE
- 2009

We report the first experimental observation of a bistable dynamo regime. A turbulent flow of liquid sodium is generated between two disks in the von K ´ armán geometry (VKS experiment). When one disk is kept at rest, bistability is observed between a stationary and an oscillatory magnetic field. The stationary and oscillatory branches occur in the vicinity… (More)

- Luc Deike, Daniel Fuster, Michael Berhanu, Eric Falcon
- Physical review letters
- 2014

This work presents direct numerical simulations of capillary wave turbulence solving the full three-dimensional Navier-Stokes equations of a two-phase flow. When the interface is locally forced at large scales, a statistical stationary state appears after few forcing periods. Smaller wave scales are generated by nonlinear interactions, and the wave height… (More)