  Head-on collisions between nuclei of different size at Fermi energies may
give rise to extremely deformed dynamical regimes and patterns. Those latter,
may suddenly turn into a stream of nuclear clusters, resembling collimated
jets. Because the underlying instabilities are inadequately described by usual
modelling approaches based on equilibrium approximations, this mechanism
resulted rather unnoticed, even though it should be frequently registered in
experiments. We employ the Boltzmann-Langevin equation to specifically address
out-of-equilibrium conditions and handle dynamical fluctuations. An interesting
interplay between surface and volume instabilities is discussed for the first
time. Stable and rather regular patterns of streaming clusters arise from these
conditions. Counterintuitively, we find that these clustered structures are not
triggered by cohesive forces and they recall the granular flow of a stream of
dry sand.
