Fluid-structure interaction simulation of the breaking wave slamming on an absorber for a wave-energy converter

Wave-energy converters that consist of several egg-shaped structures, the so-called absorbers, which move relative to a large floating platform are currently under development. The maximal stress in the wall of an absorber due to the impact of waves (horizontal or breaking wave slamming) is an important design parameter. This breaking wave slamming is here modelled as the impact of a deformable circular cylinder on a flat water surface. The fluid-structure interaction during this impact is simulated in a partitioned way which means that the flow equations and the structural equations are solved with separate codes. A finite volume flow solver with a Volume of Fluid model for the free surface is coupled with a finite element structural solver which is capable of simulating multi-layer composite materials. Coupling iterations between both solvers are performed using the IQN-ILS algorithm. Initially, the thin-walled circular cylinder made of 5 layers of a composite material has a downward velocity of 5m/s. The damage to the composite material due to the impact is assessed with the Tsai-Wu failure criterion in plane stress condition. Its maximal value is 0.25 so well below the limit of 1. In conclusion, the current design of a composite absorber for a wave-energy converter is not damaged by breaking wave slamming according to the fluid-structure interaction simulations.

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