One of the large scale facilities in LEGI is the 36m-long wave
flume (see picture on the right and video below). The flume has
2m-long glass windows on the sides so that one can see the waves
from the side. We use a set of eight video cameras setup by the
company R&D Vision
so that to be able to reconstruct the evolution of the water
surface over 16 meters and resolved in time (see the
case study - PDF
in French). In this way one can get movies of the water
elevation over long durations.
Example of images recorded by
the cameras and a snapshot of the surface reconstruction
Solitons are generated when the depth of water is shallow. In many
cases, Ivan studied the gas with a depth equal to 12 cm.
Example of a realization of a
soliton gas
Solitons have the property to display elastic collisions. They do
not exchange energy. The only effect of the interactions between
the solitons is a jump forward or backward as compared to the
trajectory of a isolated solitons. See below examples of
collisions measured in the flume.
Examples of collisions of a
pair of solitons
A way to inject a large number of solitons in the wave flume is to
take advantage of the phenomenon of fission of a sine wave into a
train of solitons. In this way we can generate several solitons
with a simple motion of the wavemaker.
Example of a time space
reconstruction of the fission of a sine wave into a train of
solitons
We also take advantage of a reflecting wall the end of the flume
opposite to the wavemaker to that to keep the solitons for a
maximum time inside the flume. The organized forgin gets
randomized by the interactions of the solitons and we finally
obtain a random soliton gaz. The scientific goal is then to
characterize the statistical properties of such a gas.
Example of time-space
reconstruction of a soliton gas measured in the wave flume.
Each greenish line is a soliton.
3D image of a time space
reconstruction of a soliton gas
This research has been published
in Physical Review Letters with a "Editor's suggestion" and
a highlight article in Physics
online magazine (PDF).
Ivan being fascinated by the
hypnotic motion of the soliton gas
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