  Strongly nonlinear phononic crystals were assembled from stainless steel
spheres. Single solitary waves and splitting of an initial pulse into a train
of solitary waves were investigated in different viscous media using motor oil
and non-aqueous glycerol to introduce a controlled viscous dissipation.
Experimental results indicate that the presence of a viscous fluid dramatically
altered the splitting of the initial pulse into a train of solitary waves.
Numerical simulations qualitatively describe the observed phenomena only when a
dissipative term based on the relative velocity between particles is
introduced.
