Hydrodynamic energy flux in a many-particle system

In this letter, using energy transfers, we demonstrate a route to thermalization in an isolated ensemble of realistic gas particles. We performed a grid-free classical molecular dynamics simulation of two-dimensional Lenard-Jones gas. We start our simulation with a large-scale vortex akin to a hydrodynamic flow and study its non-equilibrium behavior till it attains thermal equilibrium. In the intermediate phases, small wavenumbers ($k$) exhibit $E(k) \propto k^{-3}$ kinetic energy spectrum whereas large wavenumbers exhibit $E(k) \propto k$ spectrum. Asymptotically, $E(k) \propto k$ for the whole range of $k$, thus indicating thermalization. These results are akin to those of Euler turbulence despite complex collisions and interactions among the particles.