Declustering in a granular gas as a finite-size effect.

The existence of dense clusters has been shown to be a transient phenomenon for realistic models of granular collisions, where the coefficient of restitution depends on the impact velocity. We report direct numerical simulations that elucidate the conditions for the disappearance of structures. We find that upon cluster formation the granular temperature and the convective kinetic energy couple and both follow Haff's law. Furthermore, we show that clusters will eventually dissolve in all finite-size systems. We find the strong power law t′∝L12 for the dependency of the declustering time on system size. Our results imply that only in systems close to the initial critical system size both clustering and declustering transitions are observable