  It is well known that energy dissipation and finite size can deeply affect
the dynamics of granular matter, often making usual hydrodynamic approaches
problematic. Here we report on the experi-mental investigation of a small model
system, made of ten beads constrained into a 1-d geometry by a narrow vertical
pipe and shaken at the base by a piston excited by a periodic wave. Recording
the beads motion with high frame rate camera allows to investigate in detail
the microscopic dynamics and test hydrodynamic and kinetic models. Varying the
energy we explore different regimes from fully fluidized to the edge of
condensation, observing good hydrodynamic behavior down to the edge of
fluidization, despite the small system size. Density and temperature fields for
different system energies can be collapsed by suitable space and time
rescaling, and the expected constitutive equation holds very well when the
particle diameter is considered. At the same time the balance between
dissipated and fed energy is not well described by commonly adopted dependence,
due to the up-down symmetry breaking. Our observations, supported by the
measured particle velocity distributions, show a different phenomenological
temperature dependence, which yields equation solutions in agreement with
experimental results.
