Dipole Oscillations of a Bose-Einstein Condensate in Presence of Defects   and Disorder
  We consider dipole oscillations of a trapped dilute Bose-Einstein condensate in the presence of a scattering potential consisting either in a localized defect or in an extended disordered potential. In both cases the breaking of superfluidity and the damping of the oscillations are shown to be related to the appearance of a nonlinear dissipative flow. At supersonic velocities the flow becomes asymptotically dissipationless. 
M. Albert, T. Paul, N. Pavloff, P. Leboeuf