  High velocity clumps joined to the outflow source by emission with a "Hubble
law" ramp of linearly increasing radial velocity vs. distance are observed in
some planetary nebulae and in some outflows in star formation regions. We
propose a simple model in which a "clump" is ejected from a source over a
period $\tau_0$, with a strong axis to edge velocity stratification. This
non-top hat cross section results in the production of a highly curved working
surface (initially being pushed by the ejected material, and later coasting
along due to its inertia). From both analytic models and numerical simulations
we find that this working surface has a linear velocity vs. position ramp, and
therefore reproduces in a qualitative way the "Hubble law clumps" in planetary
nebulae and outflows from young stars.
