Long Wave Run-Up Resonance in a Multi-Reflection System

Wave reflection and wave trapping can lead to long wave run-up resonance. After reviewing the theory of run-up resonance in the framework of the linear shallow water equations, we perform numerical simulations of periodic waves incident on a linearly sloping beach in the framework of the nonlinear shallow water equations. Three different types of boundary conditions are tested: fully reflective boundary, relaxation zone, and influx transparent boundary. The effect of the boundary condition on wave run-up is investigated. For the fully reflective boundary condition, it is found that resonant regimes do exist for certain values of the frequency of the incoming wave, which is consistent with theoretical results. The influx transparent boundary condition does not lead to run-up resonance. Finally, by decomposing the left- and right-going waves into a multi-reflection system, we find that the relaxation zone can lead to run-up resonance depending on the length of the relaxation zone.

Numerical Study of Three Dimensional Effects of Wave Impact on an Oscillating Wave Surge Converter

A CFD model to study the three-dimensional (3D) effects of wave impact on an Oscillating Wave Surge Converter (OWSC) has been demonstrated. Considering the excessive computational cost of CFD models, a relative small computational domain is used here. The velocity at the outside boundary is prescribed based on the classical non-linear wave theory. A relaxation zone is applied to absorb the diffraction/reflection waves by the device to avoid the re-reflection from the outer boundary. This zone is implemented by adding momentum source terms in the N–S equations to blend the near field flow into the far-field wave environment. The simulation of wave interaction with a fixed flap is performed to demonstrate the validity of the relaxation zone. Simulations of wave interaction with an OWSC by various wave conditions (different wave heights and incident angles) are then carried out to understand the 3D effects of the wave impact. The water elevation in the simulation is in agreement with the observations in the experiment. The variation of the pressure distribution indicates that the wave impact is enhanced at the centre of the flap, due to the water re-entry from the sides of the flap into the centre in 3D tests.