https://orcid.org/0000-0002-7287-4693
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ABSTRACT
The reflection of surface gravity waves by a vertical wall breakwater connected with a thick surface porous layer is analysed under the framework of potential flow theory. The thick surface porous layer is placed within the confined space available between the vertical permeable wall and the impermeable seawall. The analytical investigation is progressed by creating the hidden water chamber beneath the surface porous layer. The Matched Eigenfunction Expansion Method (MEEM) is used based on the continuity of velocity and pressure along with orthogonal mode-coupling relation. The hidden water chamber will be helpful to enhance the trapping of incident wave energy and also to reduce the quantity of construction material. The present study results are well agreed with the results available in the literature when a hidden water chamber is absent. The effect of permeable wall porosity, thick surface layer porosity, angle of wave contact, depth of the surface porous layer, thickness of the permeable wall, and hidden chamber spacing on wave reflection against incident wave properties and breakwater physical properties are studied. A comparative study is performed between three different types of porous breakwaters to investigate the integrity of the proposed breakwater. The minor value of wave reflection and gradual reduction of fluid force experienced by the rigid wall is achieved due to the presence of a surface layer, which maximises the incident wave damping, as most of the wave energy propagates near the free surface.
Acknowledgement
ED acknowledges Jawaharlal Nehru Technological University Anantapur, for providing the facilities to conduct this research. ESR thank the Civil Engineering Department, G. Pulla Reddy Engineering College, Kurnool, Andhra Pradesh for providing the facilities to conduct the research work.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Nomenclature
| aj | = | positions of the breakwaters |
| b | = | The thickness of the vertical porous wall |
| dj | = | Depth of the porous structure |
| fj | = | linearized friction factor in each of the porous layer |
| fjn | = | vertical eigenfunction in each region |
| g | = | acceleration due to gravity |
| h | = | Water depth |
| i | = | imaginary number |
| KR | = | reflection coefficient |
| kjn | = | wave number in the x-direction |
| l | = | wave number in the z-direction |
| M | = | truncated number |
| R10 | = | the complex amplitude of the reflected wave |
| S | = | Spacing of hidden trapping chamber |
| sj | = | inertial force in each of the porous layer |
| T30 | = | the complex amplitude of the transmitted wave |
| t | = | time |
| ζj | = | free surface wave elevation |
| ω | = | wave frequency |
| λ | = | wavelength |
| ϕ | = | velocity potential |
| δmn | = | Kronecker delta |
| θ | = | angle of contact |
| γjn | = | wave number in the y-direction |
| ϵj | = | porosity in each of the porous layer |
| ρ | = | fluid density. |