Version francaise

"CORIOLIS" ROTATING PLATFORM

Features:
 

Diameter	14 m
available height	8 m
weight of the rotating part (empty turntable)	150 T
admissible charge	180 T
rotation speed    (constant speed or computer controled speed variations)	0 à 3 turns/min   dw/w10-4
Verticality of the rotation axis	3 10-6 rad

Equipment

Built in 1960, the rotating platform was first used to assess the impact of the projected tidal power plant of Iles Chausey, near Mt St Michel, from a model of the English Channel at scale 1/50000. Renovated in 1987, the platform presently supports a cylindrical basin 13 meters in diameter and 1.2 meter deep. Accessory storage tanks allow to procuce continuous or multi-layer density stratification, by mixing brine and pure water with computer controled filling pumps. The measurement devices include ultrasonic Doppler velocimeters, profilers for salinity and temperature, captors for free surface and density interfaces displacement, video visualization, image processing and Particle Imaging Velocimetry (PIV).

A smaller rotating tank, 2 meter in diameter, is also available.

A major renovation of the big platform has been achived at the beginning of 2003, with the set-up of a large instrumentation support, see sketch and photos of the installation. This provides access to the whole area of the tank, including the central axis (previously used for support). This allows furthermore to increase the field of view and to move cameras with computer controlled motion, to improve the quality of the instrumentation by a good ptrotect against electromagnetic interferences, and it will allow to support a curtain for protection against the wind from rotation.

Why using a rotating platform nowadays?
T he"Coriolis" rotating platform at Grenoble, thanks to its large size, provides access to a range of Rossby and Reynolds numbers for density stratified flows with no equivalent worldwhile. In other words, dynamical regimes with low viscosity and high Coriolis effects can be reached, while the centrifugal force remains negligible. Such regimes are directly relevant for oceanic currents at meso-scale (1-100 km horizontal scale).

While numerical models are reliable for most 2D flows, this is not yet true for 3D flows, especially in the presence of small scale turbulence. A fullly resolved numerical computation of a typical experiment would require a millimeter scale grid mesh, resulting in several billions grid points, still beyond the state of the art in supercomputing. The availability of a 3D scanning PIV system allows to strengthen the complementarity between physical and numerical models.

Furthermore, the rotating platform of Grenoble promotes a fruitfull international collaboration. It is accessible to research teams from European countries and associated states in the frame of the research infrastructure action of the FP6 programme: 'Structuring the European Research Area', see detail information. The plateform allows researchers and students to study and visualize geophysical fluid dynamics with realistic dynamical similarity, helping them to grasp a good physical intuition in these complex phenomena.