Coriolis platform

Diameter of 13 m and height of 8 m. For experimental modelling of oceanic or atmospheric flows, with or without density stratification or topography. Dealine proposals: Dec. 18, 2010

Description of facility:

Technical data

The « Coriolis » rotating platform, 14 m in diameter, is the largest turntable in the world. Its total weight is 150 tons and it supports an extra load of 180 tons. The axis of rotation is vertical with an accuracy ± 3.10^-6 rad. Its rotation period can be set with high stability (dT/T = 10^-4) between 30 and 1000 s and can be modulated by computer control in order to generate permanent or oscillating circular flows, so to simulate tidal effects for instance.

The platform is equipped with a tank of 13 m diameter and 1.2 m height. It can be filled with homogeneous or density stratified water with any vertical profile (e.g. multilayer or linear). The stratification is made by filling the tank through the bottom with increasingly salty water, obtained by computer controlled mixing from two underground tanks with specified salinity and temperature (within 1C). Various fixed or moving obstacles can be installed in the tank (transverse channel 10 m long and 4 m wide, annular shelf, oscillating plates, towed cylinder, cylindrical plunger …). All the instruments, including lasers and computers, stay on the platform, where electricity, water and computer network are available, like in an ordinary laboratory. Researchers can stay on the platform during rotation. Many operations are then easier than in a small rotating tank.

Thanks to the large dimensions, large Reynolds number (inertia/viscous friction) can be reached, and Rossby numbers (inertia/rotation) as low as 10^-3 -10^-2, like in natural geophysical or environmental flows. This is obtained with negligible centrifugal effects, e.g. small curvature of isopycnals.

The facility is equipped with continuous Argon laser ( 8 W) and Yag solid laser, and use highly transparent water for illumination along a large scale laser sheet. Particle Imaging Velocimetry (PIV) systems provide time resolved velocity fields in both horizontal and vertical planes of up to 3 m x 4 m in size, with a relative precision 2%. The laser sheet position is scanned by a computer controlled system, so that image correlation for PIV can be made in a volume. Both vorticity and divergence fields can be computed from the PIV data and directly compared with numerical computations.

Various techniques of flow visualization are available, with dye, hydrogen bubbles or tin oxyde electrolytically released from a wire. Illumination devices and high quality video cameras are available. Tracking of float motion by image processing is available to record lagrangian trajectories in a plane.

A wide variety of local probes is also available, including ultrasonic and laser Doppler velocimeters, salinity and temperature sensors.

1. Capacitive probes of free surface displacement with a precision 0.01 mm.
2. Ultrasonic probes for height displacement of salinity interface, with a precision 0.3 mm.
3. Ultrasonic probes for measuring density profiles at up to fifteen locations simultaneously.
4. Ultrasonic velocimeters (9 channels) with a precision 0.1 mm/s for velocities in the range 0-20 cm/s.
5. Conductivity probes for measuring time series of local density fluctuations and high resolution density profiles.

Probe displacements and data acquisition are controlled by computer. Tools for data processing and analyses are available.

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