ferro.gif

_____________________________________________________________________

Non Linear Physics Group - Eric Falcon

_____________________________________________________________________


Instabilities   (papers by our group)


In granular layers:

We report free-surface instabilities in a deep bed of fine granular material of irregular shape under vertical vibrations. At low frequency of vibration, the conical heap due to convective flow becomes unstable above a critical amplitude of vibration and acquires an azimuthal dependence which makes the heap surface corrugated. At even higher amplitude, the heap is no longer stable and splits into small heaps on a hexagonal lattice. At high frequency, we observe standing waves (stripes) at the same frequency as the driving one. The main mechanism of these instabilities can be traced back to the presence of the surrounding gas, since they vanish under vacuum conditions.

hexagons2
hexagons1
Hexagon formation of a powder under vertical vibrations.
Right (left) photo vizualised with a direct (strob) light.
(see Paper)
corrugation
Heap Corrugation of
a powder under
 vertical vibrations.
(see Paper)


The shape of the convective cell within the granular heap has been also studied (see paper)

In ferrofluids:

Rosensweig

We report an experimental study of the inhibition of the instability generated by a magnetic field applied perpendicularly to the surface of a magnetic fluid (the Rosensweig instability), by vertical vibrations of the fluid container. Our measurements are in quantitative agreement with a simple analytical model using the theory of Mathieu functions. Paper






Solid-solid friction:


An apparatus has been built to measure the shear response of a multicontact interface between flat-ended solid bodies, rough at the micron scale. The device makes use of inertia to apply a steady sinusoidal shear force to a slider without direct mechanical drive. Both elastic compliance and damping losses are deduced from the in-phase and out-of-phase components of the submicronic shear displacement. The resolution of the microslip detection is 1 nm. Apparatus design and operation are described, and the application and limitation of the method are illustrated by experimental results with a polymer glass. Paper


PUBLICATIONS on the INSTABILITIES

10. C. Laroche, J.-C. Bacri, M. Devaud, T. Jamin & E. Falcon 2019  Editor's
                        Suggestion
     Physical Review Letters 123, 094502 (2019)
    Observation of the resonance frequencies of a stable torus of fluid

9. E. Falcon, J.-C. Bacri & C. Laroche, 2017
    Physical Review Fluids 2, 102601(R) (2017) - Rapid Communication
    Dissipated power within a turbulent flow forced homogeneously by magnetic particles

In ferrofluid:
8.  T. Jamin, Y. Djama, J.-C. Bacri & E. Falcon 2016
      
Physical Review Fluids 1, 021901(R) (2016)
- Rapid Communication
      
Tuning the resonant frequencies of a drop by a magnetic field

      
7. T. Jamin, C. Py & E. Falcon 2011
       Instability of the origami of a ferrofluid drop in a magnetic field
       Phys. Rev. Lett. 107, 204503 (2011)


6. F. Pétrélis, E. Falcon & S. Fauve  2000
Parametric stabilization of the Rosensweig instability.
          European Physical Journal B, 15, 3 - 6 (2000)

In granular layers:
5. Falcon, E., Castaing, B. & Creyssels, M.  2005:
        Propriétés électriques de la matière granulaire: Bruit et intermittence 
          Bulletin de la Société Française de Physique, 149, 6 - 9 (2005) (in french)
4. Falcon, E., Castaing, B. & Laroche, C. 2004
''Turbulent'' electrical transport in Copper powders
Europhysics Letters 65, 186-192 (2004)
3. Kumar, K., Falcon, E., Bajaj, K. M. S., & Fauve, S. 1999
Shape of convective cell in Faraday experiment with fine granular materials
Physica A , 270, 97-104 (1999).

2. Falcon, E., Kumar, K., Bajaj, K. M. S. & Bhattacharjee, J. K. 1999
Heap corrugation and hexagon formation of powder under vertical vibrations.
Physical Review E, 59, 5, 5716-5720 (1999).

Solid-solid friction:
1. Baumberger,T. , Bureau, L., Busson, M., Falcon, E. & Perrin, B. 1998
An inertial tribometer for measuring micro-slip dissipation at a solid-solid multicontact interface.
Review of Scientific Instruments 69 , 6, 2416-2420 (1998).

home page 


web analytics