Semicircular Breakwater Research Articles

Hydrodynamic Characteristics of Seaside Perforated Semicircular Breakwaters due to Random Waves

The semicircular breakwater (SBW) is a composite breakwater consisting of a semicircular caisson resting on a rubble mound. The SBW function as a barrier dissipates the incident wave energy and creates tranquility on its leeside. The dynamic pressures due to random waves exerted on seaside perforated SBWs with 7, 11, and 17% of its exposed surface area with perforations were measured. The measured pressures are compared with experimental results of SBW without perforations. In addition, the forces exerted on the caisson alone are measured. The reflection coefficient, runup characteristics, measured total forces, and dynamic pressures in a dimensionless form are presented as a function of relative water depth. The tests were conducted for surface piercing conditions. The effect of the water depth, perforations, and rubble mound height on the above stated variables are brought out, the details of which are reported in this technical note.

Oblique Irregular Waves Load on Semicircular Breakwater

Based on oblique irregular wave physical model tests, the hydraulic characteristics of the semicircular breakwater are studied in this paper. The variations of wave forces on unit length of semicircular breakwater with the main effective factors including wave steepness Hs/Ls , relative wave height Hs/d, d′/Hs and the angle of incidence θ0 are studied. In addition, the longitudinal distribution of wave forces, and the longitudinal load reduction are analyzed. Some empirical formulae of the longitudinal distribution coefficient and the longitudinal load reduction factor are presented for practical use. Particularly, the conditions for trough values of the total horizontal wave forces are larger than crest values are discussed.

Modeling the interaction of solitary waves and semi-circular breakwaters by using unsteady reynolds equations

A vertical 2-D numerical wave model was developed based on unsteady Reynolds equations. In this model, the k-epsilon models were used to close the Reynolds equations, and volume of fluid (VOF) method was used to reconstruct the free surface. The model was verified by experimental data. Then the model was used to simulate solitary wave interaction with submerged, alternative submerged and emerged semi-circular breakwaters. The process of velocity field, pressure field and the wave surface near the breakwaters was obtained. It is found that when the semi-circular breakwater is submerged, a large vortex will be generated at the bottom of the lee side wall of the breakwater; when the still water depth is equal to the radius of the semi-circular breakwater, a pair of large vortices will be generated near the shoreward wall of the semi-circular breakwater due to wave impacting, but the velocity near the bottom of the lee side wall of the breakwater is always relatively small. When the semi-circular breakwater is emerged, and solitary wave cannot overtop it, the solitary wave surface will run up and down secondarily during reflecting from the breakwater. It can be further used to estate the diffusing and transportation of the contamination and transportation of suspended sediment.

Wave forces on submerged, alternately submerged, and emerged semicircular breakwaters

The wave forces acting on semicircular breakwaters are studied by using a numerical model based on a hybrid method of boundary element method (BEM) and finite difference method (FDM) in this paper. Three typical hydrodynamic statuses of submerged, alternately submerged, and emerged conditions of the semicircular breakwater are taken into account. A dissipative term is introduced to simulate the energy loss when a wave breaks near the breakwater. Wavemaker technology and the nonreflected open boundary are adopted in the paper. Five sets of laboratory experimental data that consist of semicircular breakwaters with different diameters and shapes have been used to calibrate and verify the numerical model, and good agreements are obtained between the numerical results and the experimental data. For the convenient use in practical projects, a simplified formula for calculating the total wave forces on the breakwaters has been derived from the numerical results.

Dynamic pressures and forces exerted on impermeable and seaside perforated semicircular breakwaters due to regular waves

The semicircular breakwater (SBW) is a composite breakwater consisting of a semicircular caisson resting on a rubble mound. The SBW function as a barrier dissipates the incident wave energy and creates tranquillity on its leeside. The dynamic pressures due to regular waves exerted on seaside perforated SBWs with 7 and 11% of exposed surface area with perforations were measured. The measured pressures are compared with those exerted on impermeable SBWs. In addition, the forces exerted on the caisson alone are measured. The reflection coefficient, measured total forces on the caisson of the models, and the pressures are presented as functions of relative water depth. The effect of the water depth and the percentage of perforations on the above stated variables are examined, details of which are reported in this paper.

Dynamic pressures and run-up on semicircular breakwaters due to random waves

The dynamic pressures due to random waves of predefined spectral characteristics exerted on a semicircular breakwater model at five different elevations along the depth are measured. In addition, the wave run-up on the model and its reflection characteristics are measured. The results on the variation of the frequency pressure spectra along the depth and the run-up spectra are reported in this paper. The average spectral characteristics as well as statistical properties of the above two parameters are presented. The average reflection coefficient is reported as a function of the wave steepness, described as the ratio of the significant wave height to the square of the peak period.

Field Demonstration test on a Semi-Circular Caisson Breakwater

The first semi-circular breakwaters have been erected at Miyazaki Port in Japan. This type of breakwater, having a hollow structure with a semi-circular cross section, is expected to exhibit superb characteristics in terms of sliding stability and low reflectively under a severe natural environment that includes high waves and poor soil conditions. In addition, its unique design provides excellent scenery enhancement. Field demonstration tests by erecting test breakwaters have been conducted since 1991 at Miyazaki port in an effort to verify stability, member safety and construction ease of the semi-circular breakwater in an actual sea area, as well as to establish practical design and construction methods.

Waves in a Harbor with Protruding Breakwaters

Wave induced oscillation is studied for a model harbor with a circular basin and a straight coast. Half of the basin is indented from the main coastline but the other half is bounded by a semicircular breakwater with a small opening.