  We consider the flow-driven translocation of single polymer chains through
nanochannels. Using analytical calculations based on the de Gennes blob model
and mesoscopic numerical simulations, we estimate the threshold flux for the
translocation of chains of different number of monomers. The translocation of
the chains is controlled by the competition between entropic and hydrodynamic
effects, which set a critical penetration length for the chain before it can
translocate through the channel. We demonstrate that the polymers show two
different translocation regimes depending on how their length under confinement
compares to the critical penetration length. For polymer chains longer than the
threshold, the translocation process is insensitive to the number of monomers
in the chain as predicted in Sakaue {\it et al.}, {\it Euro. Phys. Lett.}, {\bf
72} 83 (2005). However, for chains shorter than the critical length we show
that the translocation process is strongly dependent on the length of the
chain. We discuss the possible relevance of our results to biological
transport.
