Start Date

2018 1:30 PM

Creative Commons License

Creative Commons License
This work is licensed under a Creative Commons Attribution 4.0 License.

Abstract

In the present study, the flow induced by waves around a physical model of a detached low crested rubble mound breakwater is investigated experimentally. The model was designed with a scale factor of 1/30, parallel to the shoreline, in a coast of constant slope 1/15, assuming Froude similarity. For the design of the rock armor layer, the van der Meer's hydraulic stability formula was applied. Two wave conditions were examined: one with an offshore wave height of 2 m (Case A) and one with the maximum annual characteristic offshore wave height (Case B), calculated in prototype scale. Measurements include surface elevation time series, as well as three-dimensional velocity time series of the flow around the model. Results include flow patterns on the seaward and leeward side of the breakwater for both wave conditions, as well as transmission and reflection coefficients. Along the leeward side, the current profiles have an offshore direction close to the bottom and a shoreward direction close to the free surface where the reduction of the water depth induced an acceleration of the flow, influenced by the overtopping. Transmission and reflection coefficients data were compared with literature equations. The comparison revealed that literature equations tended to underestimate the transmission coefficient due to the critical condition represented by a zero free-board breakwater. About the reflection coefficient, it was found that the literature equations tend to overestimate its value, possibly due to the fact that these formulas were obtained by experiments performed with emerged breakwaters.

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May 17th, 1:30 PM

Experimental Analysis on a Low Crested Rubble Mound Breakwater

In the present study, the flow induced by waves around a physical model of a detached low crested rubble mound breakwater is investigated experimentally. The model was designed with a scale factor of 1/30, parallel to the shoreline, in a coast of constant slope 1/15, assuming Froude similarity. For the design of the rock armor layer, the van der Meer's hydraulic stability formula was applied. Two wave conditions were examined: one with an offshore wave height of 2 m (Case A) and one with the maximum annual characteristic offshore wave height (Case B), calculated in prototype scale. Measurements include surface elevation time series, as well as three-dimensional velocity time series of the flow around the model. Results include flow patterns on the seaward and leeward side of the breakwater for both wave conditions, as well as transmission and reflection coefficients. Along the leeward side, the current profiles have an offshore direction close to the bottom and a shoreward direction close to the free surface where the reduction of the water depth induced an acceleration of the flow, influenced by the overtopping. Transmission and reflection coefficients data were compared with literature equations. The comparison revealed that literature equations tended to underestimate the transmission coefficient due to the critical condition represented by a zero free-board breakwater. About the reflection coefficient, it was found that the literature equations tend to overestimate its value, possibly due to the fact that these formulas were obtained by experiments performed with emerged breakwaters.