Experimental study of wave transmission and drift velocity using freely floating synthetic ice floes

Abstract

Wave–ice interactions were investigated experimentally to understand the waves transmitted by the freely floating model ice floes and mean drift velocity of them in a three-dimensional wave basin. The experiments were conducted using square synthetic ice floes made of low-density polyethylene under regular incident waves having different periods and steepnesses. To determine the transmission coefficient (Tc), the wave measurement system was used to observe regular incident wave profiles without model ice floes and wave profiles transmitted by model ice floes varying with three ice-covered lengths and three ice concentrations. A digital camera was used to record the displacement of the model ice floes at the same ice-covered lengths and ice concentrations, and its images were used to calculate the ice concentration and the mean drift velocity of the model ice floes. Also, the effects of the height of waves on the transmission coefficient and on the mean velocity of the ice drift were investigated for some test conditions. The results showed that Tc increased as the wave period increased and that it decreased as the ice concentration and ice-covered length increased. The transmitted wave energy proportion for model ice floes decreased as the wave steepness increased. The mean ice drift velocity normalized by wave celerity (uice/U) was shown to increase as wave steepness increased, and the effect of the ice concentration on uice/U was very small. The value of uice/U was compared with the theoretical Stokes drift velocity normalized by wave celerity, and the difference between them decreased as the wave height increased. uice/U showed good agreement with the mean drift velocity of a single ice floe at lower wave steepness.