Influence of Controlled Viscous Dissipation on the Propagation of   Strongly Nonlinear Waves in Stainless Steel Based Phononic Crystals
  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. 
E.B. Herbold, V.F. Nesterenko, C. Daraio