Hydrodynamic performance of a T-shaped floating breakwater

It is critical to protect coastal and offshore structures. Most current studies and scientific investigations are centered on how to protect seashore with an efficient and cost-effective system. This study involved the testing of a new floating breakwater configuration (FB). A series of experiments were carried out in the lab of The Higher Institute of Engineering (El-shorouk City) on the new model and the traditional vertical plane FB without a curved face to compare their behaviours and performance in wave attenuation. The incident, reflected, and transmitted wave heights were measured, and the coefficients of reflection, transmission, and energy dissipation were calculated using these measurements. In terms of hydrodynamic performance, the curved-face floating breakwater outperformed the traditional vertical floating breakwater, according to the study's highlights. The curved face model significantly reduced wave transmission values when compared to the traditional vertical configuration. The greater the concavity of the curve, the better the model handles waves, especially when the wave steepness is low.

The efficiency of a pontoon-type fixed floating breakwater (FB) is investigated numerically with the use of the COBRAS model. The RANS equations, combined with a k-ε turbulence model, and the VOF technique for tracking the free surface are used in a 2D vertical plane. The study is focused on the effects of the FB shape on the hydrodynamic characteristics of the structure (wave overtopping, transmission and reflection characteristics and flow velocity and turbulence). The studied FB configurations are a rectangular, and a trapezoid with slope of 45o, under the action of monochromatic waves. Surface elevation, RTD coefficients and detailed velocities and turbulence kinetic energy around the structure are presented. The efficiency of the FB, acting mostly in a reflective manner, is improved considerably when the shape is trapezoid and wave overtopping occurs, due to higher energy dissipation around the structure.

Journal of Hydraulic Research, 2005

In the present study the hydrodynamic interaction of regular and irregular waves with floating breakwaters (FBs) in shallow and intermediate waters is examined experimentally in a large-scale facility. The experiments were conducted in the CIEM flume of the

Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 2024

Floating breakwater is a better alternative than the conventional method. It is an effective coastal engineering unit used to protect coastal regions such as harbours and marinas from erosive waves. It has many other applications such as offshore renewable energy generation, infrastructure preservation, temporary structure, and provides a controlled environment for aquaculture activities. The floating breakwater such as the double cylindrical floating breakwater (DCFB) is claimed to have effective wave attenuation characteristics. A lab scale investigation was done by placing the DCFB in a controlled wave basin in with wave generator to generate wave and wave gauge to quantify the wave transmission coefficient. The wave transmission coefficient represents the effectiveness of the breakwater system in attenuating incoming waves, where an effective breakwater system will result in a low transmission coefficient value. In this study, the DCFB's effectiveness in terms of wave transmission coefficient was investigated with two different configurations where the spacing between the cylinders of the DCFB units are 0.2 m and 0.6 m respectively. Results show that the configuration of DCFB units with 0.5 m cylinder spacing are more effective in absorbing incoming wave height resulting in lower transmission coefficient. Furthermore, some prospective areas had been identified for future enhancement.

Nowadays, the application of floating breakwaters in small or recreational harbors has found more popularity. These types of breakwaters are more flexible in terms of design, configuration and especially installation compared with fixed breakwaters. In the current study, the performance of floating breakwater (FBs) under regular waves was studied using the physical modeling method. For the modeling practice, a wave flume with a flap-type wave generator and progressive wave absorber was designed, constructed and used in order to investigate the performance of FBs. In this regard, a number of geometrical and hydrodynamic parameters were chosen including the degree of freedom, width variation, FB shapes (pontoon, T and types) and draft depth. In each scenario the water level variation was measured in three points along the flume. Based on the measured water levels transmission, reflection and energy dissipation coefficients were obtained. The effect of each parameter on the performance of FBs was investigated and the best configuration was proposed for further studies. According to the collected experimental data, the mathematical descriptions for calculating the transmission coefficient were also proposed.

Mathematical Problems in Engineering, 2021

This paper is presented to develop the hydrodynamic performance of double-row floating breakwater (FBW) by changing cross-sectional geometry in the high wave periods. The ANSYS-AQWA software is employed for the present calculations, which is a potential-based boundary element method (BEM). The rectangular moored pontoons in the single- and double-row types are selected, and the results of the wave transmission coefficient and response amplitude operator (RAO) are presented and compared. The numerical results showed good agreement with experimental data at different wavelengths, wave height, and the distance between double-row FBWs. Then, the performance results of FBWs for five shapes (rectangular, π-shaped, plus-shaped, triangular-shaped, and box-shaped) in the wave transmission coefficient, RAO, and mooring line tension are presented and compared to each other. The results showed that the plus-shaped FBW has a better performance in reducing wave transmission than other shapes. In ...

Geosciences

The purpose of the work presented in this paper is to study the reflection and transmission coefficients resulting from the interactions of regular waves with a rectangular breakwater sited at the bottom of a tank. The present investigation is devoted to the analysis of the reflection and transmission coefficients within the framework of linearized potential flow theory using two methods, a numerical method based on the improved version of the meshless singular boundary method, and the analytical approach within the plane wave model. The numerical method is first validated by studying the accuracy of the numerical computations with respect to the number of boundary nodes and the location of the vertical boundaries of the computational domain, for different immersion ratios (h/d) and different relative lengths (w/d) of the obstacle. To assess the limitations of the analytical approach, a comparison analysis is carried out between the analytical and numerical results. To improve the c...

Journal of Marine Science and Engineering, 2020

The present paper deals with the analytical evaluation of the hydrodynamic characteristics of an array of vertical axisymmetric bodies of arbitrary shape, placed in front of a reflecting vertical breakwater, which can be conceived as floaters for wave power absorption. At the first part of the paper, the hydrodynamic interactions between the floaters and the adjacent breakwater are exactly taken into account using the method of images, whereas, the interaction phenomena between the floaters of the array are estimated using the multiple scattering approach. For the solution of the problem, the flow field around each floater of the array is subdivided into ring-shaped fluid regions, in each of which axisymmetric eigenfunction expansions for the velocity potential are made. In the second part of the paper, extensive theoretical results are presented concerning the exciting wave forces and the hydrodynamic coefficients for various arrays’ arrangements of axisymmetric floaters. The aim o...

مجلة علوم البحار والتقنيات البيئية

This study presents a simplified analytical approach, based on power transmission theory, to estimate the transmission coefficient of a π-shaped floating breakwater (FB) with finite width. In evaluating the transmitted wave power, this approach considers both the incident wave kinetic power and the heave oscillation of the FB. Additional power due to the acceleration of the floating body and the hydrodynamic mass increases the transmitted wave power behind the FB and consequently increases the transmission coefficient. The proposed theoretical approach is validated using laboratory-scale experimental data obtained from the literature for π-shaped FB. The results of the proposed approach are in good to excellent agreement with those of experimental studies. In addition, the reliability of the proposed approach is assessed by comparing its results with those of other theoretical models. The effects of sea depth, relative draft, and incident wave height on the magnitude of the transmis...

Journal of Offshore Mechanics and Arctic Engineering-transactions of The Asme, 2009

Moored floating breakwaters with a leeward boundary, assimilating the port quay walls are described by a large number of coupled variables. This complicates their design and requires a detailed parametrical and motion analysis to assess their hydrodynamic performance. A diffraction-radiation boundary value problem is developed. It arises from the interaction of linear waves on a moored floating breakwater with a leeward boundary described by a partial reflective sidewall. The effects of the sidewall clearance, structural parameters, mooring lines stiffness, and their angle of inclination on the transmission coefficient and the dynamic motion of the floating breakwater are considered. The transmission coefficient is strongly affected by the motion itself and the allowable length change in the mooring lines. to 216.91.96.130. Redistribution subject to ASME license or copyright; see http://www.asme.org/terms/Terms_Use.cfm Fig. 6 Effect of breakwater width on the transmission coefficient "k r = 1, left; k r = 0.3, right… Fig. 7 Effect of the mooring line angle on the transmission coefficient "k r = 1, left; k r = 0.3, right…

Journal of Marine Science and Engineering, 2021

In the present study, the problems of diffraction and radiation of water waves by a cylindrical heaving wave energy converter (WEC) placed in front of a reflecting V-shaped vertical breakwater are formulated. The idea conceived is based on the possible exploitation of amplified scattered and reflected wave potentials originating from the presence of V-shaped breakwater, towards increasing the WEC’s wave power absorption due to the wave reflections. An analytical solution based on the method of images is developed in the context of linear water wave theory, taking into account the hydrodynamic interaction phenomena between the converter and the vertical wall. Numerical results are presented and discussed concerning the hydrodynamic forces on the absorber and its wave power efficiency for various examined parameters, namely, the breakwaters’ forming angle, the distance between the converter and the vertical walls and the wave heading angle. The results show that the amount of the harv...

Ocean Engineering, 2008

This paper studies the interaction of linear water waves with a moored floating breakwater with a leeward boundary composed from a vertical wall. This describes a real modelling for the case of ports in contrary to the problems of unbounded domains. It involves the application of a partial reflection boundary condition for this sidewall. In fact, the partial reflection problem in practical application is of great importance in the design of a harbour or breakwater and mainly for short waves. The reflection coefficient of the harbour boundary (sidewall) plays an important role in modifying the performance of the floating breakwater. Moreover, it reduces the resonant peaks appearing inside the ports due to the energy accumulation in an enclosed domain. The effects of the variation of structural parameters of the breakwater on the transmitted wave height are discussed in details for various values of partial reflection.

Journal of Hydraulic Research, 2006

Wave interactions with a fixed floating breakwater (FB) are investigated both numerically and experimentally. Laboratory experiments of large scale have been performed in the CIEM flume of the Catalonia University of Technology, Barcelona and measurements are compared with numerical results obtained with the use of the COBRAS model. The latter solves the two-dimensional, unsteady Reynolds averaged Navier-Stokes (RANS) equations in the vertical plane (2D-V). The k-ε turbulence model is also used for the computation of the Reynolds stresses as well as the Volume Of Fluid method for "tracking" the variation of the free surface. The effects of relative draught dr/D (dr = structure draught, D = water depth) and the FB configuration (breakwater without and with an attached seaward plate with the same dr/D) on the hydrodynamic characteristics (transmission, velocity, vorticity, turbulence) are investigated. Experimental water surface elevation, velocities at selected locations and pressure distribution around the structure are compared satisfactorily with computed results for dr/D equal to 0.325 and 0.2 and the two FB configurations. Detailed computed velocities, vortices and turbulence kinetic energy in the vicinity of the structure indicate the effects of dr/D and FB configuration on the flow pattern and the turbulence structure at the two sides of the structure.

Applied Ocean Research, 2012

In the present paper, linear hydroelastic analysis is performed for the assessment of the behavior of a Flexible Floating Breakwater (FFB), which represents not only a structure for shore protection but also a device for wave energy production with the utilization of a linear hydraulic Power Take-Off mechanism (PTO). The linear hydroelastic analysis is conducted in frequency domain with a radiation/diffraction 3D hydrodynamic model considering the effect of the flexibility of the FFB as well as the damping associated with the energy extraction by the PTO mechanism. A framework for this analysis is proposed and demonstrated, which includes three components: (a) a 3D structural model for an initial eigenvalue analysis, (b) a 3D hydrodynamic model for the hydroelastic analysis and (c) a numerical analysis for the calculation of the forces associated with the PTO and, also, for the estimation of the generated power. FFB consists of a grid of flexible floating modules connected flexibly in two directions by: (a) connectors with known properties and (b) hydraulic Power Take-Off mechanisms with known linear damping characteristics. The PTO mechanisms can be oriented in any possible direction in space. The investigation of the FFBs' behavior is executed for two grids with different number of modules as well as for different combinations of translational and rotational stiffness of the FFB's connectors and different damping coefficients of PTO. The combined effect of wave energy extraction, behavior and a desired level of protection by the FFB is illustrated.

Port-Said Engineering Research Journal, 2017

Recently, the investigations on the hydrodynamic performance of floating breakwaters have great interest to researchers because of its high advantages in protecting marinas and small craft harbors. For the purpose of improving the hydrodynamic performance of the stepped-slope floating breakwater type, this research had been carried out as an approach to investigate experimentally the resulting hydrodynamic performance of a composite pile supported breakwater consists of a stepped-slope floating body moving only in heave motion overlying a fixed submerged horizontal plate in a constant water depth, d = 30 cm. The transmission, reflection and losses coefficients had been determined individually for each of the stepped-slope floating, fixed submerged horizontal plate and the composite breakwaters. The results showed that the performance of the stepped-slope floating breakwater tested using different relative draft values, Df /d, of the floating body had been significantly improved and achieved extra wave damping by reducing the transmission coefficients by a ratio range between 23 % to 52 %, when using the submerged fixed horizontal plate underneath the floating body, with definite improvement value depends on plate relative submergence depth, dp /d and plate relative thickness, tp /d. For a composite breakwater using two relative submergence depths of the plate, it had been found that a significant higher wave attenuation takes place with a configuration using dp /d = 0.33 than that obtained when using dp /d = 0.50. Furthermore, plate relative thickness achieved wave attenuation improvement for the composite breakwater especially for the configuration using dp /d = 0.33 and tp /d = 4%.