A coalescence model for freely decaying two-dimensional turbulence

E. Trizac

doi:doi:10.1209/epl/i1998-00415-5

DOI: 10.1209/epl/i1998-00415-5

Europhys. Lett, 43 (6), pp. 671-676 (1998)

A coalescence model for freely decaying
two-dimensional turbulence

E. Trizac

Laboratoire de Physique (URA 1325 du CNRS), Ecole Normale Supérieure de Lyon
69364 Lyon Cedex 07, France

(received 9 March 1998; accepted in final form 13 July 1998)

PACS. 47.27Eq - Turbulence simulation and modeling.
PACS. 05.70Ln - Nonequilibrium thermodynamics, irreversible processes.
PACS. 02.70Ns - Molecular dynamics and particle methods.

Abstract:

We propose a ballistic coalescence model (punctuated-Hamiltonian approach) mimicking the fusion of vortices in freely decaying two-dimensional turbulence. A temporal scaling behaviour is reached where the vortex density evolves like $t^{-\xi}$ . A mean-field analytical argument yielding the approximation $\xi=4/5$ is shown to slightly overestimate the decay exponent $\xi$ whereas Molecular Dynamics simulations give $\xi =0.71\pm 0.01$ , in agreement with recent laboratory experiments and simulations of Navier-Stokes equation.

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