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Floating breakwaters (FBs) play an important role in protecting coastlines, marine structures, and ports due to their simple construction, convenient movement, cost-effectiveness, and environmental friendliness. However, the traditional box-type FBs are flawed due to their requiring large sizes for wave attenuation and their overly high level of wave reflection. In this paper, a novel partial T special-type FB with wave attenuation on the surface and flow blocking below the water has been presented. First, the User-Defined Function (UDF) feature in ANSYS Fluent was employed to compile the six degrees of freedom (6-DOF) motion model. A two-dimensional viscous numerical wave flume was developed using the velocity boundary wave-generation method and damping dissipation wave-absorption method, with fully coupled models of the FBs developed. A VOF multiphase flow model and a RANS turbulence model were employed to capture the free flow of gas–liquid two-phase flow. Then, the performance of wave attenuation of the new FB was compared with that of the traditional box-type FB of the same specifications. The simulation results showed that the transmission coefficient of the new FB is significantly lower than that of the box-type FB, and the dissipation coefficient is notably higher, demonstrating excellent performance of wave attenuation, particularly for long-period waves. As wave height increases, the novel FB benefits from its wave attenuation mechanism, with a lower reflection coefficient compared to the box-type FB. Finally, through parametric analysis, some design recommendations of the novel FB suitable for practical engineering applications in deep-sea aquaculture are presented. [ABSTRACT FROM AUTHOR]

Floating breakwaters (FBs) play an important role in protecting coastlines, marine structures, and ports due to their simple construction, convenient movement, cost-effectiveness, and environmental friendliness. However, the traditional box-type FBs are flawed due to their requiring large sizes for wave attenuation and their overly high level of wave reflection. In this paper, a novel partial T special-type FB with wave attenuation on the surface and flow blocking below the water has been presented. First, the User-Defined Function (UDF) feature in ANSYS Fluent was employed to compile the six degrees of freedom (6-DOF) motion model. A two-dimensional viscous numerical wave flume was developed using the velocity boundary wave-generation method and damping dissipation wave-absorption method, with fully coupled models of the FBs developed. A VOF multiphase flow model and a RANS turbulence model were employed to capture the free flow of gas–liquid two-phase flow. Then, the performance of wave attenuation of the new FB was compared with that of the traditional box-type FB of the same specifications. The simulation results showed that the transmission coefficient of the new FB is significantly lower than that of the box-type FB, and the dissipation coefficient is notably higher, demonstrating excellent performance of wave attenuation, particularly for long-period waves. As wave height increases, the novel FB benefits from its wave attenuation mechanism, with a lower reflection coefficient compared to the box-type FB. Finally, through parametric analysis, some design recommendations of the novel FB suitable for practical engineering applications in deep-sea aquaculture are presented.

Assessing the interaction of waves and porous offshore structures such as rubble mound breakwaters plays a critical role in designing such structures optimally. This study focused on the effect of the geometric parameters of a sloped rubble mound breakwater, including the shape of the armour, method of its arrangement, and the breakwater slope. Thus, three main design criteria, including the wave reflection coefficient (Kr), transmission coefficient (Kt), and depreciation wave energy coefficient (Kd), are discussed. Based on the results, a decrease in wavelength reduced the Kr and increased the Kt and Kd. The rubble mound breakwater with the Coreloc armour layer could exhibit the lowest Kr compared to other armour geometries. In addition, a decrease in the breakwater slope reduced the Kr and Kd by 3.4 and 1.25%, respectively. In addition, a decrease in the breakwater slope from 33 to 25° increased the wave breaking height by 6.1% on average. Further, a decrease in the breakwater slope reduced the intensity of turbulence depreciation. Finally, the armour geometry and arrangement of armour layers on the breakwater with its different slopes affect the wave behaviour and interaction between the wave and breakwater. Thus, layering on the breakwater and the correct use of the geometric shapes of the armour should be considered when designing such structures. [ABSTRACT FROM AUTHOR]

The physical limitations of experimental facilities, such as the walls and downstream gate of wave-current flumes, can cause excessive wave reflection. Wave reflection in wave or wave-current flumes is a key phenomenon that often leads to deviations between physical model results and prototype results. If a flume is not equipped with wave absorption systems, either active or passive, in addition to the model’s inaccurate representation of reality, there will be a tendency for the wave paddles to reach the maximum stroke, leading to the abrupt stoppage of the wave generation during the experiments. This research a novel and simple passive wave absorption system in the context of physical modelling studies of scour in the environment of offshore renewable energy technologies. The tests were conducted in the wave-current flume of the Hydraulics Laboratory of FEUP. The results show that the new system reduced the wave reflection coefficient to values within the recommended references for physical modelling studies in offshore engineering. Design hydrodynamic conditions showed reflection coefficients between 11 and 14.5%, and tests without currents revealed reflection coefficients between 7.5 and 10%. This study also highlights how the novel system can easily be adapted to other wave-current flumes and hydrodynamic conditions found in other hydraulics laboratories.

The physical limitations of experimental facilities, such as the walls and downstream gate of wave-current flumes, can cause excessive wave reflection. Wave reflection in wave or wave-current flumes is a key phenomenon that often leads to deviations between physical model results and prototype results. If a flume is not equipped with wave absorption systems, either active or passive, in addition to the model's inaccurate representation of reality, there will be a tendency for the wave paddles to reach the maximum stroke, leading to the abrupt stoppage of the wave generation during the experiments. This research a novel and simple passive wave absorption system in the context of physical modelling studies of scour in the environment of offshore renewable energy technologies. The tests were conducted in the wave-current flume of the Hydraulics Laboratory of FEUP. The results show that the new system reduced the wave reflection coefficient to values within the recommended references for physical modelling studies in offshore engineering. Design hydrodynamic conditions showed reflection coefficients between 11 and 14.5%, and tests without currents revealed reflection coefficients between 7.5 and 10%. This study also highlights how the novel system can easily be adapted to other wave-current flumes and hydrodynamic conditions found in other hydraulics laboratories. [ABSTRACT FROM AUTHOR]

Mooring system is a significant part of very large offshore floating structures (VLFS). In this paper, a single module pontoon type VLFS model considering four mooring types is studied through physical model tests to determine the effects of mooring conditions on the hydroelastic response, mooring force, incident coefficient, reflection coefficient and energy dissipation coefficient. Eight mooring cables are symmetrically arranged on both sides of the model. The floating body model satisfies the similarity of stiffness and gravity, while the cable satisfies the similarity of elasticity and gravity. The results show that the effect of mooring type on mooring force is greater than that on hydroelastic response. Increasing the initial tension of the mooring cable will reduce the amplitude of the leeward of the VLFS model. The mooring angle of the mooring cable will affect the maximum mooring force and the initial tension of the mooring line will affect the wave period in which the maximum mooring force occurs. The transmission coefficient and wave energy dissipation coefficient will change regularly with different mooring types. These results may provide a reference to facilitate the mooring design of VLFS. [ABSTRACT FROM AUTHOR]

Traditional breakwater takes the advantage of high protection performance and has been widely used. However, it contributes to high wave reflection in the seaside direction and poor water exchange capacity between open seawater and an inside harbor. Consequently, a partially permeable stepped breakwater (PPSB) is proposed to ensure safety and good water exchange capacity for an inside harbor, and a 3-D computational fluid dynamics (CFD) mathematical model was used to investigate the hydrodynamic coefficients using Reynolds-Averaged Navier-Stokes equations, Re-Normalization Group (RNG) k-ε equations, and the VOF technique. A series of experiments are conducted to measure the wave heights for validating the mathematical model, and a series of dimensionless parameters considering wave and PPSB effects were presented to assess their relationships with hydrodynamic coefficients, respectively. With the increase in the reciprocal value of PPSB slope, incident wave steepness and permeable ratio below still water level (SWL), the wave reflection coefficient decreases. The wave transmission coefficient decreases with an increase in the reciprocal value of the PPSB slope and incident wave steepness; however, it increases with the increase in the permeable ratio below SWL. With increases in the reciprocal value of the PPSB slope, permeable ratio below SWL and incident wave steepness for relatively high wave period scenarios, the wave energy dissipation coefficient increases; however, it decreases slightly with increases in the incident wave steepness for the smallest wave period scenarios. Furthermore, simple prediction formulas are conducted for predicting the hydrodynamic coefficients and they are well validated with the related data. [ABSTRACT FROM AUTHOR]

Experimental studies of the propagation of wind waves on a complex configuration of berthing facilities of the Taman seaport are presented. The results of experimental studies carried out on the basis of physical simulation are presented. [ABSTRACT FROM AUTHOR]

Yin, Z.; Jin, L.; Liang, B., and Wang, Y., 2017. Numerical investigation of wave reflection from a stepped breakwater. On the basis of a combination of the Reynolds-averaged Navier-Stokes equations, standard k- ℇ equations, and volume-of-fluid technique, a two-dimensional mathematical model was used to investigate the wave reflection performance of a stepped breakwater. A series of experiments was conducted to measure the wave heights and validate the mathematical model, and they exhibited good agreement. The aforementioned mathematical model was used to compute composite wave heights for different still-water depths, incident wave heights, wave periods, single step widths, and stepped breakwater slope scenarios. The two-probes method was used to determine the incident and reflected waves from the records of composite waves. The results showed that the stepped breakwater slope (especially for the gentle scenarios) plays a dominant role in wave reflection, and the wave reflection coefficient increases with increasing slope. However, it decreases with the increase of relative width of a single step and incident wave steepness respectively. Using the Iribarren number and the relative width of a single step, a simple formula for wave reflection coefficient was developed on the basis of the dimensional analysis method. It was validated using the corresponding data. [ABSTRACT FROM AUTHOR]

The objective of the present study is to investigate the performance of a cylindrical floating breakwater system based on 3D experimental tests. The experiments were carried out in the wave basin (36 m* 60 m* 1.5 m )of the Ocean University of China. The cylindrical floating breakwater system consists of 10cylindrical floating breakwater units and 10mesh cages with balls in them, connected by 18 connectors and moored by a taut mooring system. The wave transmission coefficients, reflection coefficients, dissipation coefficients and motion responses of the floating breakwater are measured in both oblique and beam sea conditions. It is found that with the increase of the wavelength, both of the wave transmission coefficients and motion response amplitude of the FB system suffers an increase before it reaches its peak value, followed by a decrease trend. It can be concluded from the experiments that the proposed FB system has a satisfactory performance and it can be used to a wide range of sea conditions. [ABSTRACT FROM AUTHOR]

Abstract: Our understanding of information carried by waves propagating in cardiovascular systems has rapidly advanced in recent years due to usage of modeling and simulations. The present research aims at developing a high-resolution numerical scheme that can be applied to solve mutually interactive one-dimensional (1-D) flows that prevail in tree-like arterial networks. A scheme using finite-volume, Roe-splitting flux-difference method in conjunction with a time-accurate Runge–Kutta marching method was developed. The theory of characteristics was adopted for the treatment of boundary conditions, resulting in a unified formulism using a newly defined reflection coefficient as a measure to quantify the wave reflection occurring at the interior and terminal nodes of the tree-like vascular structure. The derived boundary condition formulas are convenient for dealing with various types of boundary specification requirements that may arise in vascular hemodynamics. There are two computational models, an isolated tubular conduit and a tree-like structure model, that were employed for the present scheme validation and wave simulation demonstration. The objective was to assess the accuracy of the present scheme in capturing long-duration, complex, and tiny wave reflections and re-reflections. The superiority of the present scheme on capturing discontinuous jumps was first demonstrated in the isolated conduit simulation by comparing the results against exact solutions as well as those obtained by Lax–Wendroff method. To evaluate and validate the time-accuracy of the present scheme in treating multiple wave reflections and re-reflections in tree-like structures, a linear wave-tracking algorithm was employed. Compared to the Lax–Wendroff finite-difference method, the present flux-difference Roe-splitting scheme was shown to be more robust and accurate, which offers high-resolution with minimal dissipation and dispersion errors in simulating long-duration, mutually interacting wave reflections and re-reflections that commonly occur in the tree-like arterial network. [Copyright &y& Elsevier]

Porous breakwaters using a caisson-pile group can increase the resistance of the vertical coastal structures in harbors to external heavy impacts, and also help facilitate the exchange of water. This article presents experimental results for the hydraulic performance of independent caisson-pile type breakwaters having three rows of vertical piles, both evenly and unevenly spaced between rows. Compared with even spacing, uneven, sparser spacing tends to have lower wave reflections and higher energy loss coefficients. Wave transmission, by contrast, appears not to be considerably influenced by spacing pattern. The transmission coefficient increases with wave steepness (So,s) and decreases with the ratio of the (total) width of the three pile rows to the wavelength (W/Lo,s). [ABSTRACT FROM AUTHOR]