  We study the hydrodynamic behavior in two-dimensional, interacting electronic
systems with merging Dirac points at charge neutrality. The dispersion along
one crystallographic direction is Dirac-like, while it is Newtonian-like in the
orthogonal direction. As a result, the electrical conductivity is metallic in
one and insulating in the other direction. One element of the shear viscosity
tensor violates the famous lower bound for the shear viscosity to entropy
density ratio,an effect that can be probed via anisotropic thermal Hagen-
Poiseuille flow.
