Abstract
The aim of coastal structures for the defense from erosion is to modify the hydrodynamic fields that would naturally occur with the wave motion, to produce zones of sedimentation of solid material, and to combat the recession of the coastline. T-head groin-shaped structures are among the most adopted in coastal engineering. The assessment of the effectiveness of such structures requires hydrodynamic study of the interaction between wave motion and the structure. Hydrodynamic phenomena induced by the interaction between wave motion and T-head groin structures have three-dimensionality features. The aim of the paper is to propose a new three-dimensional numerical model for the simulation of the hydrodynamic fields induced by the interaction between wave fields and coastal structures. The proposed model is designed to represent complex morphologies as well as coastal structures inside the domain. The numerical scheme solves the three-dimensional Navier–Stokes equations in a contravariant formulation, on a time-dependent coordinate system, in which the vertical coordinate varies over time to follow the free-surface elevation. The main innovative element of the paper consists in the proposal of a new numerical scheme that makes it possible to simulate flows around structures with sharp-cornered geometries. The proposed numerical model is validated against a well-known experimental test-case consisting in a wave train approaching a beach (non-parallel with the wave front), with the presence of a T-head groin structure. A detailed comparison between numerical and experimental results is shown.
Highlights
Coastal defense structures are aimed at modifying the free-surface elevation and velocity fields produced during wave events, in a way to damp the wave energy and to prevent the nearshore wave-induced currents transporting the suspended solid material offshore
The aim of coastal structures for the defense from erosion is to modify the hydrodynamic fields that would naturally occur with the wave motion, to produce zones of sedimentation of solid material, and to combat the recession of the coastline
The aim of the paper is to propose a new three-dimensional numerical model for the simulation of the hydrodynamic fields induced by the interaction between wave fields and coastal structures
Summary
Coastal defense structures are aimed at modifying the free-surface elevation and velocity fields produced during wave events, in a way to damp the wave energy and to prevent the nearshore wave-induced currents transporting the suspended solid material offshore. Several numerical models available in the literature employ the VOF technique, as it is a robust and stable one; OpenFOAM® [18] and IHFOAM® [21] (a model derived from OpenFOAM® designed for coastal and ocean hydrodynamics) are among the most popular numerical models in which the VOF technique is implemented With this technique, a correct assignment of pressure and kinematic boundary conditions at the free surface is difficult, because the vertical fluxes can arbitrarily cross the computational cell. All the above-described numerical models fall under the general class of models in which the free-surface elevation is represented by means of a function of horizontal coordinates and time, so that at a given position in the horizontal plane and in time, a single value of the free-surface elevation is allowed This approach does not make it possible to directly simulate a wave front that curls over, forming a tube. The paper is structured as follows: In Section 2, we describe the model equations; in Section 3, we present the numerical model; in Section 4, the numerical results obtained by the proposed model are compared with the experimental measurements by [33]; and in Section 5, we present the conclusion of the study
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