Vortex spectrum in superfluid turbulence: Interpretation of a recent experimentP.-E. Roche1 and C. F. Barenghi2
1 Institut NÉEL, CNRS/UJF - BP166, F-38042 Grenoble Cedex 9, France
2 School of Mathematics, University of Newcastle - Newcastle upon Tyne, NE1 7RU, UK
received 4 September 2007; accepted in final form 30 November 2007; published February 2008
published online 3 January 2008
We discuss a recent experiment in which the spectrum of the vortex line density fluctuations has been measured in superfluid turbulence. The observed frequency dependence of the spectrum, f -5/3, disagrees with classical vorticity spectra if, following the literature, the vortex line density is interpreted as a measure of the vorticity or enstrophy. We argue that the disagrement is solved if the vortex line density field is decomposed into a polarised field (which carries most of the energy) and an isotropic field (which is responsible for the spectrum).
67.40.Vs - Vortices and turbulence.
47.37.+q - Hydrodynamic aspects of superfluidity: quantum fluids.
67.57.De - Quantum fluids and solids; liquid and solid helium: Superflow and hydrodynamics.
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