Coexistence of two elastic surface modes enhanced by viscous losses

Abstract

Spatial profiles of electrically excited surface waves on agarose gels were measured as a function of frequency and concentration of the agarose. Two surface waves were observed in the low-frequency region. One is a Rayleigh wave, which shows the elastic behavior up to a certain frequency and then gradually disappears with the increase in frequency. The other wave is also elastic; however, it has higher value of phase velocity than the Rayleigh wave and approaches the dispersion of the capillary wave in the high-frequency region. The surface response function analysis shows that the semi-infinite viscoelastic media support the propagation of the two elastic surface waves, but not the propagation of the elastic and pure capillary waves as was claimed previously. Moreover, the theoretical analysis reveals that the viscous losses effectively enhance the coexistence of the two elastic surface modes.