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This research work evaluates the wave trapping efficiency of the periodic array of two-layer pile-rock breakwaters (TPRBs) placed far away from vertical rigid wall. The analytical model is developed to study the effect of TPRBs on the variation of wave reflection and reduction of fluid force experienced by wall based on the classical potential flow and porous media flow theory. The effect of the uneven seabed on wave trapping by TPRBs is added to show its significance, and the porous structure consists of a pair of layers with individual porosities. The seaside and leeside protection walls are introduced to secure the two-layer rock from vertical and horizontal failures. Thus, the continuity of velocity and pressure is applied in the vertical and horizontal directions. The eigenfunction expansion method based on orthogonal mode-coupling relation is used to solve the unknown coefficients. The effect of incident wave properties and TPRBs physical properties on wave trapping is reported as a function of breakwater width, gap region, and trapping chamber length. The correctness of the present study results is verified with the available results. The study strongly suggests that the variation of wave reflection by TPRBs is a trivariate function, which would depend upon the width, spacing, and porosity of the TPRBs. Around 30–40% reduction of wave reflection is obtained after introducing the TPRBs. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The comprehensive usage of an array of natural or artificial semi-circular breakwaters (SCBs) as supporting structures to secure the floating/fixed structures are received increasingly more consideration in recent years. The performance characteristics of bottom-fixed SCB in the presence of a floating dock are investigated under the framework of linear wave theory. The edge conditions such as continuity of velocity and pressure along the SCB and zero-flow condition near rigid surfaces are adopted. The multi-domain boundary element method (MBEM) is used to examine the wave attenuation performance of the whole breakwater system in two dimensions. The correctness of the present study's numerical results is confirmed by performing the comparative study with the readily available experimental and analytical results reported by various researchers. The reflection, transmission, energy loss coefficients, and fluid force experienced by floating dock are examined as a function of incident wave properties and breakwater physical properties. The Bragg resonant reflection and performance comparison with other shapes are also studied. The study results strongly suggest that the damage of floating structures and leeward locales due to incident wave stroke is minimized with the introduction of porosity for SCB located on the seabed by dissipating the wave energy. A pair of bottom-fixed SCBs having 10-20% breakwater porosity placed far away from the dock is identified as the optimal choice to reduce the fluid force experienced by the dock and wave transmission coefficient. [ABSTRACT FROM AUTHOR]

The propagation of surface gravity waves in the presence of finite floating elastic plate over varying sea bottom profile is investigated using the Timoshenko-Mindlin plate theory. The continuity of velocity and pressure at the interfaces along with the continuity of deflection, slope, bending moment and shear force is employed with the support conditions at the plate edges. The numerical computation is performed to obtain the hydroelastic behaviour of the floating elastic plate due to abrupt change in bottom topography. The validation of the present analytical model is performed with the known results available in the literatures. Further, a detailed comparison of the numerical results is presented for different step bottom topography on the hydroelastic characteristics of a floating elastic platform. The present study will provide an insight into the effect of the ocean bottom profile on wave propagation due to the presence of a large floating elastic plate. [ABSTRACT FROM AUTHOR]

The two-layer pile-rock porous breakwater consisting of the upper porous layer, middle porous layer placed over the bottom rigid layer (elevated bottom) is proposed as an active wave absorber for significant wave damping and wave trapping. The two-layer rock core is placed between the two thin porous barriers (piles), and the thin barriers/ piles are useful to reduce the wave force experienced by active two-layered breakwater. The eigenfunction expansion method is used to analyse the physical problem on considering the continuity in fluid velocity and pressure along with mode-coupling relation based on classical linearised potential flow theory. The developed analytical model is validated with the available results and then various hydrodynamic characteristics such as wave reflection, transmission, damping, wave forces on seaward, leeward barriers and wave force experienced by the vertical cliff are presented. The porosity of surface layer shows an effective role in reducing the harmonic oscillatory pattern in the hydrodynamic quantities, and the study suggests the higher surface layer porosity ε s = 0.8 as compared with bottom layer porosity for optimal wave damping. [ABSTRACT FROM AUTHOR]

The attenuation of the incident wave interacting with a very large floating structure (VLFS) in the presence of vertical barriers is analysed considering small amplitude wave theory. The VLFS is considered to be articulated and is modelled based on Timoshenko-Mindlin plate theory. The eigenfunction expansion method along with the orthogonal mode-coupling relation is employed for the case of finite water depth. The numerical study is performed to analyse the wave reflection, transmission and dissipation characteristics due to the articulated floating plate for the case of bottom standing and surface piercing vertical porous barriers. The hydroelastic behaviour in terms of deflection and strain for an articulated floating thick elastic plate in the presence of porous barriers is analysed. The study reveals that the magnitude of wave attenuation is enhanced due to the presence of vertical porous barriers and also provides an understanding in mitigating the structural response. [ABSTRACT FROM AUTHOR]

Gravity wave interaction with porous structures is investigated under the assumption of linearized wave theory. Multiple porous blocks of finite thickness with finite spacing are investigated under the action of oblique ocean waves considering leeward unbounded region and confined region. The eigenfunction expansion method is employed to analyse the effect of multiple-confined regions in the trapping of oblique waves. The study outcomes are validated with numerical and experimental results available in the literature. The friction factor and the inertia effect of the porous medium are considered and different porosity conditions are adopted to determine the wave reflection coefficient, transmission coefficient, wave dissipation and wave force impact on the leeward wall. The functional efficiency of multiple fully extended porous structures is studied for different values of porosity, water chamber length, angle of incidence, friction factor and spacing between the porous blocks. The seabed is assumed to be uniform impermeable bottom and uneven bottom (step approximation is adopted). The study demonstrates that the better wave blocking is achieved with the increase in the series of porous structures and the confined regions can be used effectively for the trapping of oblique waves. The present study will be helpful in the design of porous structures for security of coastal facilities and coastal structures in offshore environment. [ABSTRACT FROM AUTHOR]