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Breakwaters are used to reduce incoming wave energy at harbors and shorelines. This paper presents a comparison of novel two-dimensional hybrid intelligent models for the idealization of the effects of waves on the performance of moored rectangular floating breakwaters (FBs). Fluid structure interactions (FSIs) were idealized by airy-type monochromatic regular waves generated in a numerical wave tank. The coupled Volume of Fluid-Fast Fictitious Domain (VOF-FFD) interpolation method was used to evaluate FB motions. Different forms of Least Squares Support Vector Machine Methods (LSSVMs) that utilized 183 data streams were used to model FB performance for different wave height-to-water depth ratios, dimensional aspect ratios, and specific length-to-water depth ratios. Of those, 80% were used to train the model and 20% to test it. Parametric studies have shown that during training a Least Squares Support Vector Machine Method-Bat Algorithm (LSSVM-BA) with R2 = 0.8725, MAE = 0.0276, and RMSE = 0.0488 presents the most appropriate model for the evaluation of FB performance. Notwithstanding this, during testing a Least Squares Support Vector Machine Method-Cuckoo Search (LSSVM-CS) Algorithm with corresponding values of 0.6841, 0.0519, and 0.0708 performs better.

A preliminary experimental study on the hydrodynamic behaviors of double-row floating breakwaters is carried out in a wave flume under regular wave action. The floating breakwater chosen as the experimental subject is a dual rectangular pontoon floating breakwater. The hydrodynamic behaviors of the floating breakwater are validated through the calculation of the wave transmission coefficients, the wave reflection coefficients, the motion responses of the floating breakwaters and the mooring forces for different waves and structural parameters. The dynamic responses of single-row floating breakwater as a control group are also examined in the present experiments. The results indicate that double-row floating breakwaters significantly reduces the transmission coefficients as compared with single-row floating breakwater, especially for short-period wave, which is attributed to dissipation caused by eddies and moon-pool effect. However, the reflection performance is almost identical between two types. It is also found that the motion responses of the single-row and double-row floating breakwaters are similar. Spacing distance between double-row floating breakwaters has a significant influence on the windward mooring tension of the model at the upstream location, which always keeps the largest level in all mooring forces.

This study examines the impact of the spacing parameter on the efficacy of an array of hybrid modules functioning as both floating breakwaters and wave energy converters. The dual functionality is ensured by the ability of the device to autoadjust its submergence. The behavior of multiple 1:40 scaled modules was tested in the wave tank of the University of Campania “Luigi Vanvitelli”. The objective was to assess the hydraulic performance of the array by analyzing transmission, reflection, and dissipation coefficients under different wave conditions. Specifically, the transmission coefficient ranges between 0.85 and 0.51, depending on the relative wavelength and wave steepness, while the reflection and dissipation coefficients vary, respectively, between 0.70–0.20 and 0.55–0.3. In any case, the results underscore the critical importance of the spacing parameter.

The present study investigates the effect of moorings on hybrid floating breakwaters of different configurations based on potential flow theory. The mooring analysis is performed for the regular wave incidence for five different shapes of hybrid floating breakwaters, namely, rectangular, box, H, Π, and trapezoidal, integrated with a single J-shaped oscillating water column (OWC). The mooring lines are considered to be nonlinear catenary sections that are analysed for open mooring and cross mooring configuration. The hydrodynamic analysis is performed using Ansys-AQWA and the effectiveness of the moorings is evaluated in terms of the mooring line tension and the floating structure’s motion response, and comparisons are made for the influence of different mooring configurations and the implications of changing the design of the hybrid floating breakwater. The regular gravity wave frequency range is taken into consideration and the hydrodynamic properties are reported for the entire range of regular wave frequencies. Additionally, for a few chosen wave frequencies the analysis of structural forces and moment is performed for long and short waves. The study suggests that a hydrodynamically stable hybrid floating structure integrated with an oscillating water column can provide good and effective wave energy conversion and wave attenuation. Thus, with the help of the findings of the present study, the researchers will be able to examine the stability of hybrid floating breakwater structures under the action of regular waves with normal incidence.

Floating breakwater layouts require flexible adjustment to accommodate sheltered area bathymetry. However, most studies have focused solely on straight layouts and have neglected the influence of complex nearshore bathymetry and structures. This work investigates streamlined-layout double-row floating breakwaters with wing plates designed for a specific port. Wave attenuation performance, motion responses, mooring tensions, and surface wave pressures under realistic nearshore conditions are systematically evaluated through a water tank experiment. The results demonstrate that the wave attenuation performance improves as incident wave height and period decrease, with the attenuation rate increasing by 6.32~11.05%. However, both the motion responses and the uplift pressures on the head and tail modules change slightly. The maximum prototype-scale changes in the maximum amplitudes of surge, heave, and pitch are +0.0625 m, −0.488 m, and +3.8523°, respectively, and the uplift pressures on the head and tail modules exhibit maximum changes of +2.3 kPa and −5.6 kPa, respectively. Additionally, wave reflection induced by nearshore structures influences both harbor tranquility and breakwater motion response.

An experimental investigation on the hydrodynamic performance of a box-floating breakwater in different terrains is performed in a 2D wave flume under regular wave actions and irregular wave actions, respectively. The wave transmission coefficients, motion responses and mooring forces are focused to validate the hydrodynamic performance of the box-floating breakwater. The performance of the box-floating breakwater in flat terrain is also experimentally investigated for comparison. The influences of the terrain width and quantity on the hydrodynamic behaviors of the box-floating breakwater are discussed and analyzed. The results indicate that the box-floating breakwater in different terrains has a better wave attenuating ability than the box-floating breakwater in flat terrain due to wave energy loss caused by the interaction between the breakwater and terrain. However, the width of terrain has a limited effect on the hydrodynamic performance of the floating breakwater. For double terrains, the wave attenuation performance of the box-type floating breakwater increases with the decrease of the spacing between double terrains, especially for long-period waves. It is also found that terrain has significant influences on the roll and heave motions, while terrain hardly affects the sway motions. In addition, terrain plays an important role in the mooring forces, while the width and quantity of terrain weakly affect the mooring forces of box-floating breakwater. To investigate the hydrodynamic performance of rectangular floating breakwater in different terrains systematically, Smoothed Particle Hydrodynamics (SPH) methods is used. It can be concluded that the results of SPH show a good agreement with the experimental results.

Floating breakwaters are widely applied on the ocean water surface to protect human infrastructure from the destructive power of waves. This study designs and investigates the performance of a novel symmetric-pontoon floating breakwater with a symmetric pair of hydrofoils. Based at the Cranfield Ocean Systems Laboratory, the system was constructed and tested in various wave conditions using different fin configurations. The floating structure was anchored using a symmetric four-point mooring system. The tested waves were regular and symmetric perpendicular to the propagating direction. Key parameters, including the attenuated wave amplitude, motions of the breakwater, and the mooring forces, were measured. The wave parameters utilised for testing covered 1.61–5.42 relative wavelength to structural length, with wave heights of 3 cm and 5 cm. Results showed the 90° fin configuration can reduce wave transmission by up to 74%, with the lowest mooring forces at 3.05 relative wavelength, enhancing the performance of wave energy dissipation and structural seakeeping. At 90° setup, the mooring force was lowest at 2.41 relative wavelength. This research can inform novel designs of breakwaters to improve protection abilities for coastal cities and offshore infrastructures, especially renewable energy systems.

By adding a cylindrical airbag on the leeward side of a cuboid pontoon, a new-type double-row floating breakwater is designed to improve the wave attenuation performance, and its hydrodynamic characteristics are studied through numerical simulations. First, based on the smoothed particle hydrodynamics (SPH) method, a numerical model used to simulate the interaction between waves and moored floating bodies is built. The fluid motion is governed by the Navier–Stokes equations. The motion of the floating body is computed according to Newton’s second law. The modified dynamic boundary condition is employed to treat the solid boundary. The lumped-mass method is adopted to implement the mooring system. Then, two physical model experiments on waves interaction with cuboid and dual cylindrical floating pontoons are reproduced. By comparing the experimental and numerical wave transmission coefficients, wave reflection coefficients, response amplitude operators and mooring force, the reliability of the numerical model is validated. Finally, the validated numerical model is applied to study the influence of separation distance and wave parameters on the hydrodynamic characteristics of the double-row floating breakwater. The results indicate that the optimal separation distance between pontoon and airbag is 0.75 times the wavelength. At such separation distance and within the concerned 1–4 m wave heights and 4–7 s wave periods, the pontoon-airbag system presents better wave attenuation performance than a single pontoon. This improvement weakens as wave height increases while it strengthens as the wave period increases. In addition, the double-row floating breakwater is more effective in a high-wave regime than in a low-wave regime. In the case of short waves, attention should be paid to the stability and mooring reliability of the seaward pontoon, while in the case of long waves, care needs to be taken of the leeward airbag.

A three-dimensional numerical model was established based on ANSYS-AQWA (R19.0) software for the purpose of analyzing the hydrodynamic characteristics of a floating breakwater. This study examines three distinct floating breakwaters with different cross-sectional designs in order to evaluate their respective wave dissipation capabilities. It is suggested that the horizontal multi-cylinder floating breakwater exhibits a superior ability to dissipate waves when compared to both the single-cylinder and square pontoon configurations and can be deemed the most advantageous shielding strategy for potential engineering applications. Subsequently, this study examines the effects of influential parameters, including a large cylinder diameter, a small cylinder diameter, the angular position of the small cylinder, and the height and period of the incident wave, on the wave transmission coefficient. An empirical formula for the wave transmission coefficient was derived based on the numerical results. Additionally, the effects of influential parameters, including wind speed, current velocity, incident wave height and period, and water depth, on the maximum total mooring force were investigated. Furthermore, an empirical formula for the maximum total mooring force is proposed for practical implementation in engineering.

Floating breakwaters have recently been generating increasing interest as a vital means to provide shelter and protect the ever-increasing number of structures deployed at sea. Notwithstanding the novel ideas being put forward, to date, floating breakwater deployment has been limited to inshore and shallow water areas. The scale of such structures has been restricted to the smaller spectrum. Furthermore, whilst some concepts to integrate floating breakwaters with other offshore systems have been proposed to benefit from cost-sharing strategies, studies related to floating breakwaters integrating energy storage are lacking in the open literature. The present research investigates the wave attenuating and dynamic performance of a large-scale floating breakwater in deep seas with a hydro-pneumatic energy storage system also integrated within the structure. This article highlights the arising need for floating breakwaters and sheds light on the present-day technological status of floating wave breakers. It then lays the ground for the proposed, novel floating breakwater concept that aims to address the current knowledge gaps in this field of study. The simulation results generated from numerical modelling via the potential flow solver ANSYS® AQWA™ have been promising, connoting that the addition of hydro-pneumatic energy storage to a floating breakwater will not lead to a degradation in the dynamic performance or wave breaking efficiency of the floating structure.