  The collective flow of nucleons and that of fragments in the 12C + 12C
reaction below 150 MeV/nucleon are calculated with the antisymmetrized version
of molecular dynamics combined with the statistical decay calculation. Density
dependent Gogny force is used as the effective interaction. The calculated
balance energy is about 100 MeV/nucleon, which is close to the observed value.
Below the balance energy, the absolute value of the fragment flow is larger
than that of nucleon flow, which is also in accordance with data. The
dependence of the flow on the stochastic collision cross section and its origin
are discussed. All the results are naturally understood by introducing the
concept of two components of flow: the flow of dynamically emitted nucleons and
the flow of the nuclear matter which contributes to both the flow of fragments
and the flow of nucleons due to the statistical decay.
