  Polymer melts represent the flow-history-dependent behavior. To clearly show
this behavior, we have investigated flow behavior of an entangled polymer melt
around two cylinders placed in tandem along the flow direction in a two
dimensional periodic system. In this system, the polymer states around a
cylinder in downstream side are different from the ones around another cylinder
in upstream side because the former ones have a memory of a strain experienced
when passing around the cylinder in upstream side but the latter ones do not
have the memory. Therefore, the shear stress distributions around two cylinders
are found to be different from each other. Moreover, we have found that the
averaged flow velocity decreases accordingly with increasing the distance
between two cylinders while the applied external force is constant. While this
behavior is consistent with that of the Newtonian fluid, the
flow-history-dependent behavior enhances the reduction of the flow resistance.
