  Periodic boundary conditions for planar mixed flows are implemented in the
context of a multi-chain Brownian dynamics simulation algorithm. The effect of
shear rate $\dot{\gamma}$, and extension rate $\dot{\epsilon}$, on the size of
polymer chains, $\left<R_e^2\right>$, and on the polymer contribution to
viscosity, $\eta$, is examined for solutions of FENE dumbbells at finite
concentrations, with excluded volume interactions between the beads taken into
account. The influence of the mixedness parameter, $\chi$, and flow strength,
$\dot{\Gamma}$, on $\left<R_e^2\right>$ and $\eta$, is also examined, where
$\chi \rightarrow 0$ corresponds to pure shear flow, and $\chi \rightarrow 1$
corresponds to pure extensional flow. It is shown that there exists a critical
value, $\chi_\text{c}$, such that the flow is shear dominated for $\chi <
\chi_\text{c}$, and extension dominated for $\chi > \chi_\text{c}$.
