179 research outputs found
Resonant and antiresonant bouncing droplets
When placed onto a vibrating liquid bath, a droplet may adopt a permanent
bouncing behavior, depending on both the forcing frequency and the forcing
amplitude. The relationship between the droplet deformations and the bouncing
mechanism is studied experimentally and theoretically through an asymmetric and
dissipative bouncing spring model. Antiresonance effects are evidenced.
Experiments and theoretical predictions show that both resonance at specific
frequencies and antiresonance at Rayleigh frequencies play crucial roles in the
bouncing mechanism. In particular, we show that they can be exploited for
droplet size selection.Comment: 4 pages, 4 figures and 1 vide
Diffusive foam wetting process in microgravity
We report the experimental study of aqueous foam wetting in microgravity. The
liquid fraction along the bubble edges is measured and is found to be a
relevant dynamical parameter during the capillary process. The penetration of
the liquid in the foam, the foam inflation, and the rigidity loss are shown all
to obey strict diffusion processes.Comment: 4 pages, 6 figures, submitted to Phys. Rev. Let
A fountain of droplets
A vessel is plunged upside down into a pool of 50 cSt silicone oil. An air
bell is then created. This bell is vertically shaken at 60 Hz that leads to the
oscillation of the air/oil interface. The edges of the immersed vessel generate
surface waves that propagate towards the center of the bell. When the amplitude
of the oscillation increases, wave amplitude increases. We study the influence
of the angle between successive sides on the wave patterns. Two kinds of vessel
have been studied: a triangular and a square prism. The shape of the air/oil
meniscus depends on the angle between the sides of the considered prism. As the
amplitude of the oscillation is increased, the triple line, which is the
contact line between the solid and the air/oil interface, moves up and down.
Above a given acceleration that depends on the immersion depth and on the shape
vessel, wave goes under the corner edge of the bell. During the oscillation,
the wave generates at the edges presents a singularity that leads eventually to
a jet and a drop ejection. A drop is ejected at each oscillation. More
complicated ejection can be produced with further increase of the amplitude.
This is a sample arXiv article illustrating the use of fluid dynamics videos.Comment: 3 pages, 2 figures, 2 movies (high-res and low-res
Rolling/Slipping Motion of Euler's Disk
We present an experimental study of the motion of a circular disk spun onto a
table. With the help of a high speed video system, the temporal evolutions of
(i) the inclination angle , (ii) the angular velocity and
(iii) the precession rate are studied. The influence of the mass of
the disk and the friction between the disk and the supporting surface are
considered. %The motions of disks with different masses and over different
surfaces are studied. The inclination angle and the angular velocity
are observed to decrease according to a power law. We also show that the
precession rate diverges as the disk stops. Exponents are measured
very near the collapse as well as on long range times. Collapsing times have
been also measured. The results are compared with previous theoretical and
experimental works. The major source of energy dissipation is found to be the
slipping of the disk on the plane.Comment: Submitted for publication (2003) - 6page
Granular size segregation in underwater sand ripples
We report an experimental study of a binary sand bed under an oscillating
water flow. The formation and evolution of ripples is observed. The appearance
of a granular segregation is shown to strongly depend on the sand bed
preparation. The initial wavelength of the mixture is measured. In the final
steady state, a segregation in volume is observed instead of a segregation at
the surface as reported before. The correlation between this phenomenon and the
fluid flow is emphasised. Finally, different ``exotic'' patterns and their
geophysical implications are presented.Comment: 8 page
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