Europhys. Lett, 43 (6), pp. 671-676 (1998)
A coalescence model for freely decaying
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.
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 . A mean-field analytical argument yielding the approximation is shown to slightly overestimate the decay exponent whereas Molecular Dynamics simulations give , in agreement with recent laboratory experiments and simulations of Navier-Stokes equation.