  The temporal evolution of a dilute granular gas, both in a compressible flow
(uniform longitudinal flow) and in an incompressible flow (uniform shear flow),
is investigated by means of the direct simulation Monte Carlo method to solve
the Boltzmann equation. Emphasis is laid on the identification of a first
"kinetic" stage (where the physical properties are strongly dependent on the
initial state) subsequently followed by an unsteady "hydrodynamic" stage (where
the momentum fluxes are well-defined non-Newtonian functions of the rate of
strain). The simulation data are seen to support this two-stage scenario.
Furthermore, the rheological functions obtained from simulation are well
described by an approximate analytical solution of a model kinetic equation.
