An experimental study of gravity waves through segmented floating viscoelastic covers

Abstract With climate changes and global warming, the extent of Marginal Ice Zone (MIZ) in the polar region is widening, and there is now more research attention on the wave interactions with broken ice covers within the zone to gain insights into its future sea conditions. Towards this objective, the dispersion and attenuation of surface waves propagating through segmented floating viscoelastic covers was investigated experimentally in this study. The covers were made of oil-doped Polydimethylsiloxane (PDMS) material, with different curing agent percentages to vary their rheological properties. For stiffer covers, the measurements showed that the effect of segmentation on wavelength modification was significant, and the dispersion relation agreed generally with the existing theoretical predictions for discrete floating elastic segments despite the presence of the additional viscosity for the material. At the same time, the earlier empirical formula based on the concept of “equivalent rigidity” to represent the segmented elastic cover, did not work well for the conditions investigated. With more flexible covers, however, the effect of segmentation became insignificant for thin cover thickness. Given the present experimental conditions, we confirmed that the effect of scattering was negligible, and the wave attenuation should be attributed to the various dissipative mechanisms. An empirical relation for the attenuation was established based on the experimental results, to quantitatively relate the attenuation coefficient to the incident wave characteristics and cover properties. The relation identifies a significant inverse relationship with the viscosity of cover material, and thus confirms the essential role of viscoelastic representation for the attenuation predictions.