  We consider dissipative phenomena due to the relaxation of an initial
anisotropic local pressure in the fireball created in relativistic heavy-ion
collisions, both for the Bjorken boost-invariant case and for the azimuthally
symmetric radial expansion with boost-invariance. The resulting increase of the
entropy can be counterbalanced by a suitable retuning of the initial
temperature. An increase of the transverse collective flow is observed. The
influence of the shear viscosity on the longitudinal expansion is also studied.
Viscosity reduces the cooling rate from the longitudinal work and counteracts
the pressure gradients that accelerate the longitudinal flow.
