Oblique wave scattering by a bottom-mounted perforated semicircular breakwater under ice cover

Abstract

Submerged, seabed-mounted perforated semicircular breakwaters (SBWs) can serve as effective structures for reducing wave energy beneath ice-covered waters, where incident waves often fracture and destabilise sea ice. To investigate this, a linear potential flow model based on the multipole expansion method is developed to study oblique wave scattering by such a breakwater beneath a floating ice cover, modelled as a thin elastic plate. The model is validated against established results for the free surface case and shows excellent agreement. Unlike the free surface model, the presence of the ice cover introduces flexural rigidity, which significantly modifies the hydrodynamic response by altering the reflection and transmission characteristics. In particular, ice rigidity governs the partitioning of wave energy, with stiffer ice enhancing reflection and suppressing transmission, while more flexible ice promotes wave propagation beneath the cover. Additionally, higher porosity increases transmission, whereas larger incidence angles (\(\beta = 75^\circ \)) lead to stronger reflection. These findings highlight the important role of ice cover in governing wave–structure interaction and the potential of such structures to limit wave-induced ice breakup in polar and subpolar regions.