Julien Aubert

Observations of zonal flow created by potential vorticity mixing in a rotating fluid

Received 3 May 2002; revised 17 July 2002; accepted 18 July 2002; published 24 September 2002. [1] We present an experimental and numerical study of a rotating fluid with a zonal flow produced from small-scale eddies, a common feature of many planetary systems. The apparatus consists of a water-filled annular tank with a sloped bottom. Flow is forced mechanically at small, nonaxisymmetric scales. Potential vorticity is materially conserved and well-mixed. This implies the existence of nonzero axisymmetric vorticity and therefore of zonal flow, which has three zones in this case. The strength of zonal flow has an upper bound imposed by complete depletion of the beta-plane potential vorticity reservoir. INDEX TERMS: 5707 Planetology: Fluid Planets: Atmospheres—structure and dynamics; 5734 Planetology: Fluid Planets: Magnetic fields and magnetism; 5744 Planetology: Fluid Planets: Orbital and rotational dynamics. Citation: Aubert, J., S. Jung, and H. L. Swinney, Observations of zonal flow created by potential vorticity mixing in a rotating fluid, Geophys. Res. Lett., 29(18), 1876, doi:10.1029/ 2002GL015422, 2002.

Non-Extensive Model for Turbulent Flow in a Rapidly Rotating Annulus

We have conducted experiments on turbulence in a rapidly rotating annular tank. The flow is driven by pumping fluid into the tank through a semi-circle of holes; the fluid flows out through a semi-circle of holes on the opposite side of the annulus. We model the system using statistical mechanics with a non-extensive entropy. Assuming conservation of potential enstrophy and energy, we deduce a mean vorticity profile that agrees with the observations. Further, we find that the probability distribution for the vorticity is better fit by nonextensive than extensive theory.

Nonextensivity in Turbulence in a Rapidly Rotating Fluid

We study turbulence experiments on a rotating fluid with a zonal flow produced from small‐scale eddies, a common feature of many planetary systems. Using enstrophyenergy conservation in the Tsallis nonextensive statistical mechanics, we deduce a potential vorticity profile in accord with the observations. A nonextensive formalism is appropriate because long‐range forces between small‐scale vorticies give rise to coherent structures in the turbulence. We find that the nonextensive Tsallis statistics leads to predictions that are in good agreement with the observations at large scales.