  I solve the Relativistic Navier Stokes Equations assuming boost invariance
and rotational symmetry. I compare the resulting numerical solutions for two
limiting models of the shear viscosity. In the first model the shear viscosity
is made proportional to the temperature. Thus, $\eta \propto T/\sigma_0$ where
$\sigma_0$ is some fixed cross section (perhaps $\sigma_0 \sim
\Lambda_{QCD}^{-2}$) . This viscosity model is typical of the classical
Boltzmann simulations of Gyulassy and Molnar. In the second model the shear
viscosity is made proportional to $T^3$. This model is typical of high
temperature QCD. When the initial mean free path of the $T^3$ model is four
times larger than the $T/\sigma_0$ model, the two models of viscosity produce
the same radial flow. This result can be understood with simple scaling
arguments. Thus, the large transport opacity needed in classical Boltzmann
simulations is in part an artifact of the fixed scale $\sigma_0$ in these
models.
