  Explicit equations are given for describing the space-time evolution of
non-ideal (viscous) relativistic fluids undergoing boost-invariant longitudinal
and arbitrary transverse expansion. The equations are derived from the
second-order Israel-Stewart approach which ensures causal evolution. Both
azimuthally symmetric (1+1)-dimensional and non-symmetric (2+1)-dimensional
transverse expansion are discussed. The latter provides the formal basis for
the hydrodynamic computation of elliptic flow in relativistic heavy-ion
collisions including dissipative effects.
