Nonlinear Wave-Ice-Interaction

This research project addresses the fundamental question of nonlinear wave-ice interaction under solid ice focusing on nonlinear wave propagation and dispersion of waves. The objective is to verify if nonlinearity takes place under solid ice. Thereby, nonlinear wave-ice interaction as well as the impact of the solid ice characteristics on this interaction will be investigated. The investigations comprise numerical simulations accompanied by experiments. Special nonlinear wave groups and typical swell conditions in the vicinity of ice covers will be investigated. Envelope soliton and Peregrine breather solutions will be applied representing exact solutions of the Nonlinear Schrödinger Equation (NLSE). The application of such nonlinear wave groups are predestined for the objective of this research proposal – verification that nonlinearity takes place under solid ice – as these wave groups’ can only be observed within experiments if nonlinear wave-wave interaction takes place. This denotes that the existence of such wave groups in the ice tank is the direct proof.The goal of the experiments is to verify experimentally for the first time that nonlinearity takes place under solid ice resulting in stable wave groups as well as exaggerated wave amplitudes. With the help of the Peregrine breather it shall be shown that modulation instability will lead to an exaggerated wave height far away from the edge of the solid ice. In addition, and based on numerical simulations, selected swell cases of special interest regarding nonlinear phenomena will be reproduced in the ice tank. Besides focusing on nonlinear wave effects under solid ice, the effect of solid ice on the wave length and wave energy propagation, respectively, will also be investigated, i.e. the change of wave length due to the sudden presence of solid ice will be measured and compared to theoretical findings.The experiments will be conducted in two different ice types. One will be seeded model ice, where properties of waves and ice will be scaled according to the state of the art, i.e. geometrically scaled while maintaining Froude and Cauchy similitude, where damping properties might be exaggerated compared to naturally grown ice. The second ice type will be regular, naturally grown ice in the basin, where the ice strength might be high, but the elastic deformation and related restoring forces as well as the damping of waves is considered to be more similar to sea ice. The objective here is to assess possible differences between the two ice types and to evaluate whether the state of the art model ice does even allow a scaling of the problem following the current state of the art.

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