Scaling laws and vortex profiles in two-dimensional decaying turbulence - art. no. 065301

We use high resolution numerical simulations over several hundred of turnov er times to study the influence of small scale dissipation onto vortex stat istics in 2D decaying turbulence. A scaling regime is detected when the sca ling laws are expressed in units of mean vorticity and integral scale, like predicted in Carnevale et al., Phys. Rev. Lett. 66, 2735 (1991), and it is observed that viscous effects spoil this scaling regime. The exponent cont rolling the decay of the number of vortices shows some trends toward xi =1, in agreement with a recent theory based on the Kirchhoff model [C. Sire an d P. H. Chavanis, Phys. Rev. E 61, 6644 (2000)]. In terms of scaled variabl es, the vortices have a similar profile with a functional form related to t he Fermi-Dirac distribution.