Abstract
Coastal defence works, such as breakwaters, are structures that aim to support the action of waves and dissipate their energy. Therefore, they provide conditions for stabilizing the coast, protecting ports, beaches and other coastal infrastructures and ecosystems. Semicircular breakwaters have been applied in different locations around the world due to their aesthetic advantages and high structural performance. Marine structures are subject to hydrodynamic actions normally estimated through physical models. However, these models are complex to implement, involving high costs and long experimental procedures. Thus, alternative methodologies for studying the hydrodynamic performance of these structures are of great use. This work presents the results of the application of a computational fluid dynamics (CFD) tool to study the stability of a perforated semicircular breakwater, based on a rubble mound foundation. The model was validated against experimental results of the critical weight necessary to resist sliding, taking into account the effects of water depth and different characteristics of the waves. A comparison is made between the perforated and the non-perforated solution in terms of the breakwater’s performance to dissipate wave energy. Dissipation conditions of this energy, in the exposed face, are also evaluated in detail, in order to assess the potential of this structure as a biological refuge for marine species. Both solutions show similar performance in terms of results obtained for the wave reflectivity coefficient. The turbulence dissipation on the exposed face of the perforated breakwater is limited to a region of restricted extension around it, which is advantageous in terms of the passage of species into the breakwater.
Highlights
Breakwaters are coastal protection structures generally built out into the sea to protect the emerged beach, cliffs, dunes or harbours from the action of waves
As reported by [1] and [2], the semicircular breakwater was developed in the early 90s of the last century in Japan, and a 36 m prototype of this type of breakwater was built at the port of Mayazaki between 1992 and 1993
They are pre-fabricated reinforced concrete structures, with semicircular hollow perforations on the exposed face, and are installed over a rubble mound foundation. They are more economical, stable and efficient than conventional breakwaters, being suitable for installation over coastal stretches of low resistant capacity [3]. Previous studies of this type of coastal structures have concentrated essentially on the evaluation of hydrodynamic parameters, such as pressure, reflection coefficients, runup, rundown and aspects related to the dissipation of energy by the breakwater
Summary
Breakwaters are coastal protection structures generally built out into the sea to protect the emerged beach, cliffs, dunes or harbours from the action of waves. As reported by [1] and [2], the semicircular breakwater was developed in the early 90s of the last century in Japan, and a 36 m prototype of this type of breakwater was built at the port of Mayazaki between 1992 and 1993 As a rule, they are pre-fabricated reinforced concrete structures, with semicircular hollow perforations on the exposed face, and are installed over a rubble mound foundation. The authors in [11,12,13] and [14] presented results of the hydrodynamic performance characteristics of the breakwater, analyzing the influence of water depth, holes and the height of the rubble mound foundation base They concluded that a semicircular breakwater perforated in half a section dissipates more energy, reflects less energy and is subject to lower dynamic pressures. Porosity of breakwaters has an important effect on wave dynamics (eg., [15,16])
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