  We conduct three-dimensional hydrodynamical simulations of two opposite jets
launched from a binary stellar system into a previously ejected shell and show
that the interaction can form barrel-like and H-like shapes in the descendant
nebula. Such features are observed in planetary nebulae and supernova remnants.
Under our assumption the dense shell is formed by a short instability phase of
the giant star as it interacts with a stellar companion, and the jets are then
launched by the companion as it accretes mass through an accretion disk from
the giant star. We find that the H-shaped and barrel-shaped morphological
features that the jets form evolve with time, and that there are complicated
flow patterns, such as vortices, instabilities, and caps moving ahead along the
symmetry axis. We compare our numerical results with images of 12 planetary
nebulae, and show that jet-shell interaction that we simulate can account for
the barrel-like or H-like morphologies that are observed in these PNe.
