  The piston shock problem is a prototypical example of strongly nonlinear
fluid flow that enables the experimental exploration of fluid dynamics in
extreme regimes. Here we investigate this problem for a nominally
dissipationless, superfluid Bose-Einstein condensate and observe rich dynamics
including the formation of a plateau region, a non-expanding shock front, and
rarefaction waves. Many aspects of the observed dynamics follow predictions of
classical dissipative---rather than superfluid dispersive---shock theory. The
emergence of dissipative-like dynamics is attributed to the decay of large
amplitude excitations at the shock front into turbulent vortex excitations
which allow us to invoke an eddy viscosity hypothesis. Our experimental
observations are accompanied by numerical simulations of the mean field,
Gross-Pitaevskii equation that exhibit quantitative agreement with no fitting
parameters. This work provides an avenue for the investigation of quantum shock
waves and turbulence in channel geometries, which are currently the focus of
intense research efforts.

Quantum Gases