  Using two-dimensional hydrodynamical simulations, we investigate the
interaction of a collimated fast wind (CFW) interacting with a spherical
asymptotic giant branch (AGB) wind as the mechanism for shaping proto-planetary
nebulae and young planetary nebulae. In particular, we compare our simulations
to the observations of an evolved PPN with multiple, highly collimated lobes,
CRL 618.
