Experiments

| Our
experimental set-up in Rennes is a 3 meter
long rectangular flume, in which a bed of glass beads is eroded by a
water flow coming from a heightened water tank. The flume is covered by
a lid so that the flow does not present any free surface. Starting from
a plane sand surface, we obtain 3D ripples after a few minutes. The
elevation profile of the bed is measured by a laser
telemeter mounted on a motorized rail. The evolution of localized
structures can also be characterized by the deformation of a laser
sheet.   |
We perform P.I.V. (Particle
Imaging Velocimetry)
measurements
to characterize
the water flow properties and to relate them to the bedforms. This
method
consists in seeding the flow with 10 µm shiny particles, and
lightening them
with a powerful laser sheet. The velocity field is then calculated from
the
correlation of two successive images taken by a fast camera.