  The synchronized molecular dynamics simulation via macroscopic heat and
momentum transfer is proposed for the non-isothermal flow behaviors of complex
fluids. In this method, the molecular dynamics simulations are assigned to
small fluid elements to calculate the local stresses and temperatures and are
synchronized at certain time intervals to satisfy the macroscopic heat- and
momentum- transport equations. This method is applied to the lubrication of a
polymeric liquid composed of short chains with ten beads between parallel
plates. The rheological properties and conformation of polymer chains coupled
with the local viscous heating are investigated with a non-dimensional
parameter, i.e., the Nahme-Griffith number, which is defined by the ratio of
the viscous heating to the thermal conduction at the characteristic temperature
required to sufficiently change the viscosity. The present simulation
demonstrates that strong shear thinning and transitional behavior of the
conformation of the polymer chains occur with a rapid temperature rise when the
Nahme-Griffith number exceeds unity. The results also clarify that the
reentrant transition of the linear stress-optical relation occurs for large
shear stresses due to the coupling of the conformation of polymer chains and
heat generation under shear flows.
