  Motivated by a recent experiment [Phys. Rev. Lett. 106, 150401 (2011)] we
simulate the collision between two clouds of cold Fermi gas at unitarity
conditions by using an extended Thomas-Fermi density functional. At variance
with the current interpretation of the experiments, where the role of viscosity
is emphasized, we find that a quantitative agreement with the experimental
observation of the dynamics of the cloud collisions is obtained within our
superfluid effective hydrodynamics approach, where density variations during
the collision are controlled by a purely dispersive quantum gradient term. We
also suggest different initial conditions where dispersive density ripples can
be detected with the available experimental spatial resolution.
