Sandoval Munoz, Claudio Alejandro; (2025) Study of wave run-up and overtopping with Large Eddy Simulations for overtopping wave energy converters. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

This research studied the wave-structure interaction of monochromatic waves and slope structures. A three-dimensional numerical wave tank (Hydro3D-WT) based on the large eddy simulation (LES) method is employed to evaluate the water surface morphology, particle kinematics, turbulent structures, flow energy and dynamic pressures. Hydro3D-NWT’s performance is validated for each case studied with experimental data, analytical solutions, and well- nown empirical formulas used in coastal engineering. First, the interaction of monochromatic waves over a trapezoidal submerged structure is studied. The structure comprises a front slope, a horizontal berm, and a rear slope. Four front slope geometries are implemented. The results show that the front’s geometry slope modifies the evolution of the waves over the structure, affecting the wave profile, the generation of different turbulent structures and the stability of the structure. A sloped structure that represents an overtopping wave energy converter’s runup ramp (OWEC) is next studied. In this section, Hydro3D-NWT is validated for the first time to simulate wave breaking, run-up, overtopping and run-down. The analysis reveals that the run-down flow plays an important role in the energy dissipation over the ramp. Reducing the run-down flow moves the wave-breaking type towards collapsing and surging, less turbulent than plunging waves. This change in the breaking condition reduces the wave’s curl, decreasing turbulence and speeding up the run-up flow. An improvement up to 20 % on the remaining energy in the run-up is recorded when a transition from plunging to collapsing breaking type is achieved. Two geometries that include a gap on the slope to deflect the run-down flow are simulated. The results show that the run-down flow is deflected with the geometries assessed; however, the overtopping is reduced, and therefore, the power available at the crest of the structure is also reduced. Based on the results, four conceptual designs of the OWEC’s run-up ramp are proposed. This study contributes to understanding the hydrodynamics of wave structure interaction. It gives insight into the process that occurs over the run-up ramp of an OWEC and proposes new alternatives to improve its efficiency. The performance of a numerical tool has been tested with complex fluid mechanics scenarios, and its ability to produce detailed data of high interest to coastal engineering has been corroborated.

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