Plateforme Coriolis

The « Coriolis » rotating platform, 14 m in diameter, is the largest turntable in the world. Its total weight is 150 tons, and 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. <br /><br />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). 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. <br /><br />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. <br /><br />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. <br /><br />A wide variety of local probes is also available, including ultrasonic and laser Doppler velocimeters, salinity and temperature sensors. <br /><br />