Rotating grid turbulence experiments have been carried out instably stratified fluid at large Reynolds number (10000), using the ″Coriolis″ turntable in Grenoble. Under effects of rotation and stratification the flow degenerates into quasi horizontal motions. This regime is investigated using ascanning imaging velocimetriy which provides time resolved velocity in a volume.
The most obvious effect of rotation is the inhibition of the kinetic energydecay which is in agreement with the quasi geostrophic model whichpredicts an absence of direct energy cascade, like in twodimensional turbulence. In the regime of small Froude and Rossbynumbers, the results show that the dynamics are non-dissipativeand associated with a $k_h^{-3}$ energy spectra and highly intermittent vertical vorticity field, involving intense vortices of both signs.
For higher Rossby number, the results show fundamental differenceswith the quasi geostrophic model. A significant decay of kineticenergy which does not depend on stratification is indeed observed.Moreover, although both cyclones and anticyclones are initiallyproduced, cyclones tend to dominate the flow. |
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