Large-facility rotating tank experiments

We have made use of two large-scale rotating tank facilities in recent years. Access to both was gained through the Transnational Access programme of the EU Hydralab III Integrated Infrastructure Initiative.

Geostrophic turbulence on a topographic β-plane

(CORIOLIS facility, Grenoble. Lead: Peter Read)

Photograph of the 13m CORIOLIS tankTypical flow pattern: image is approx 5m by 2m.

The 13m diameter rotating CORIOLIS platform in Grenoble was used to reproduce geostrophic and zonostrophic turbulence forced by small-scale convective motion. In our two experiments so far, convection was driven first by a steady flux of dense salty water onto the top surface, and second by direct heating of the lower boundary. The whole tank rotates at constant angular velocity and dynamical effects equivalent to the spherical curvature of a planetary atmosphere are emulated by use of a radially-sloping bottom. The results demonstrate the formation of multiple, undulating, parallel, barotropic zonal jets, in which fluxes maintain the jets against viscous dissipation. These experiments attempt to reproduce the mechanisms thought to be responsible for jet formation in gas giant planet atmospheres and, more controversially, the terrestrial oceans.

Barotropic instability of planetary polar vortices

(CORIOLIS facilities, Trondheim and Grenoble. Lead: Luca Montabone)

Barotropic instabilities arise at the edge of polar vortices in many planetary atmospheres. We studied these phenomena using the 5m diameter CORIOLIS rotating basin[/url] of the Norwegian University of Science and Technology in Trondheim and the 13m diameter rotating CORIOLIS platform in Grenoble.

Schematic of the Grenoble experimentFlow field from the Grenoble experiments: vertical component of relative vorticity showing an unstable tripole structure.

The experiments were conceived to reproduce the evolution of coherent structures at the edge of an atmospheric polar vortex in the laboratory, which are thought to be produced by barotropic instability.

A source-sink technique was used to create a central vortex in homogeneous water with fixed depth. Water was pumped into the system through a source ring at a fixed rate, and was sucked out of the system through a central, circular sink region.

A central 'polar' vortex formed by conservation of angular momentum associated with poleward flux in a rotating frame. Barotropic instabilities were observed and led to the formation of coherent satellite vortices organised in dipole, tripole, quadrupole, and hexagon configurations.