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Wave-induced forces on an armour layer unit are key parameters for assessing the stability of rubble mound coastal revetment, but how to predict them accurately and efficiently remains an open question. This study explores the feasibility of using the Morison-type equation to convert numerically simulated porous media flow in an armour layer into the forces on a single armour unit. Wave flume tests are conducted, in which the forces on a cuboid placed in the armour layer of a sloped revetment were measured. In conjunction, numerical simulations were performed using an OpenFOAM solver, which treats the revetment as a porous media. The validated flow simulation was synchronized with the force measurement to illustrate the correlations between the predicted porous media flow and the impact force. Based on these correlations, a Morison-type predictor, which consists of inertial force, drag force, pressure gradient force and lift force, is proposed. The calibrated model can reasonably approximate the temporal variation of wave-induced force. However, it is found that the inertial coefficients vary significantly with the dynamic stability number and the initial submergence of the armour unit. Additional research is required to give a sufficiently large dataset for calibrating empirical formulae.

Dune recovery interventions that integrate natural, sustainable, and soft solutions have become increasingly popular in coastal communities. In the present study, the reliability of an innovative non-toxic colloidal silica-based solution for coastal sand dunes has been verified for the first time by means of laboratory experiments. An extensive experimental campaign aimed at studying the effectiveness of the use of nanosilica has been conducted in the 2D wave flume of the EUMER laboratory at the University of Salento (Italy). The study was first based on a horizontal seabed and then a cross-shore beach-dune profile was drawn similar to those generally observed in nature. Detailed measurements of wave characteristics and observed bed and cross-shore beach-dune profiles were analyzed for a wide range of wave conditions. In both cases, two sets of experiments were carried out. After the first set of experiments performed resembling the native conditions of the models composed with natural sand, the effects of the injection of the mineral colloidal silica-based grout were investigated. The observations show that mineral colloidal silica increases the mechanical strength of non-cohesive sediments reducing the volume of dune erosion, thus improving the resistance and longevity of the beach-dune system.

Sea wave reflection from coastal protection structures is one of the main issues in the coastal design process. Several empirical formulas have been proposed so far to predict reflection coefficient from rubble mound breakwaters and smooth slopes. The aim of this study is to investigate wave reflection from a rubble mound structure placed in front of a vertical concrete seawall. Several experimental tests were performed on a two-dimensional wave flume by reproducing on a rubble mound structure with a steep single primary layer armored with a novel artificial unit. A new approach for the prediction of the reflection coefficient based on dimensional analysis is also proposed, and a new empirical equation is derived. The performance of the proposed equation was compared with widespread existing formulas, and a good accuracy was found.

Air turbines are commonly used in Oscillating Water Column (OWC) devices for wave energy conversion. The purpose of this paper is to simulate the performance of an OWC turbine through the implementation of an Actuator Disk Model (ADM) in Fluent®. A set of different regular wave tests are developed in a 2D numerical wave flume. The model is tested using the information analysed from experimental tests on a Wells type turbine, carried out in wind tunnel. Linear response is achieved in terms of pressure drop and air flow in all cases, proving effectively the actuator disk model applicability to OWC devices.

This paper presents a two-dimensional numerical model of nearshore random wave transformation with a focus on model calibration and verification with both laboratory and field data. The model is based on the energy balance equation including diffraction and dissipation terms (Mase, 2001). The energy dissipation is determined based on the formulation by Dally et al. (1985), with new expressions for the stable wave height and decay coefficients. These coefficients are estimated based on the local beach slope and offshore wave conditions. The model is calibrated with several data sets from the Large-scale Sediment Transport Facility (LSTF) at the Coastal and Hydraulics Laboratory in USA. Then, the model is verified against a large number of data sets, including LSTF data for cases with structures, laboratory data from the Great Wave Flume in Hanover, the field data from Egmond in the Netherlands, Duck in USA, and Cancun in Mexico. The validation showed that the model could reproduce the observations well. The relative root-mean-square error varies from 5% to 7.6% for laboratory data, and from 10.3% to 18.6% for field data. The coefficient of determination varies from 0.81 to 0.97, demonstrating good agreement between the model and the measurements.

Oscillating water column (OWC) devices for wave power extraction are appealing, but are still in need of research. In this study, a series of wave-flume experiments was conducted to examine the hydrodynamic performance of a rectangular OWC device fixed in regular waves. Two types of orifices, slot orifices and circular orifices, were used to simulate the nonlinear power take-off (PTO) mechanism, and the effects of orifice geometry were examined. A two-point measurement method was proposed to reconstruct the instantaneous spatial profile of the water surface inside the OWC chamber for reducing bias in the measured wave power extraction efficiency. The flow characteristics of PTO were described by a quadratic loss coefficient, and our experimental results showed that the quadratic loss coefficient of the slot orifices varied with wave period and slot geometry. Empirical formulas were proposed for the quadratic loss coefficients of the two types of orifices. The ability to determine the quadratic loss coefficient of an orifice will allow us to design orifices for small-scale tests and calculate the power extraction using only pressure measurement. Our results also suggested that the pressure coefficient should be more reliable than the amplification coefficient as an indicator of the power extraction performance of an OWC device.

Liang, B.; Ma, S.; Pan, X., and Lee, D.Y., 2017. Numerical modelling of wave run-up with interaction between wave and dolosse breakwater. In: Lee, J.L.; Griffiths, T.; Lotan, A.; Suh, K.-S., and Lee, J. (eds.), The 2nd International Water Safety Symposium. Journal of Coastal Research, Special Issue No. 79, pp. 294–298. Coconut Creek (Florida), ISSN 0749-0208. Breakwaters play an important role in coastal disaster prevention and mitigation. In this study, a numerical modelling of the wave run-up on dolosse breakwater is set up by integrating the CAD software SolidWorks and the CFD software FLOW-3D. The breakwater is built with the lower porous media and the upper armour blocks (dolosse), which is different from the current approach that treats the whole rubble mound breakwater as porous media. The numerical wave flume has been validated by analytic solutions of Stokes wave theory. The computational results are in good agreement with the empirical formulas under different wave conditions. The model...

Numerical studies of performance of a 3-bladed Savonius type horizontal-axis wave energy converter are presented. Numerical simulations based on a volume of fluid (VOF) method coupled with a finite volume method (FVM) approach are performed in a numerical wave flume (NWF) for specified values of flow physics and turbine blade geometry conditions. Once validated against experimental data, the numerical simulations are extended to investigate the overall performance of the turbine over a very large range of wave height, wave frequency, and the submergence level for the same water depth in the context of optimization of a design of a small scale Savonius rotor. From the numerical results obtained and validated against the experimental data it can be concluded that the flow characteristics are strongly dependent upon differing wave propagation conditions and energy conversion rate can be increased with a proper combination of selected wave height and frequency for the investigated parametric value range.

Tremendous economic loss and environmental damages are caused by oil-spilling accidents in sea. Accurate prediction of the underwater spreading and surface drifting of oil spills is important for the emergency response. In the present study, numerical investigation on the underwater spread and surface drift of oil spilled from a submarine pipeline under the combined action of wave and current was carried out to examine the effects of physical ocean environment, leaking flux and spilled oil density and viscosity. Reynolds-Averaged-Navier-Stokes (RANS) equations, realizable k - e turbulence model and volume of fluid (VOF) model are employed to describe the multiphase flow, and velocity-boundary wave-making technique combined with the sponge layer damping absorber technique realizes the numerical wave flume. Oil spill experiments were conducted to validate the numerical model. The calculation results indicate that compared with the environmental conditions of still water, only current and only wave, a larger scope of underwater spreading and relatively slower rising rate and relatively faster drifting rate of oil droplets are observed under the combined action of wave and current. The leaking flux affects the floating time and dispersion concentration, while the ocean environment affects the horizontal migration and surface drifting. Under the specific conditions of present work, oil density has obvious effect on the underwater spread but limited effect on the surface drifting, while oil viscosity has little effect on both the two processes.

Freak waves are large and unexpected surface waves with huge wave heights that can lead to severe slamming to ships and marine structures. However, there are only few researches conducted to investigate the wave impact on the deck-house caused by freak waves. In order to understand the phenomena and be able to calculate the structural response of the deck-house structures, a 2-D numerical wave flume is built in which freak waves are generated. A simplified method is proposed to approximate the deck-house wall as an Euler beam with intermediate elastic bearings. By applying an implicit iterative algorithm, the fluid-structure interaction (FSI) is considered. Three simulations are performed, including a regular wave impact against a rigid wall, a laboratory-scale freak wave impact against an elastic wall, and the deck-house impact caused by a full-scale freak wave. Visual snapshots are taken to show the entire wave slamming phenomena. Fluid pressures adjacent to the wall are reported to indicate the influence of hydroelasticity. The displacements of the vertical wall and the deck-house wall from a semi-submersible barge are analyzed with the fast Fourier transformation (FFT) and wavelet transformation method.

Understanding the hydrodynamic interactions between ocean waves and the oscillating water column (OWC) wave energy converter is crucial for improving the device performance. Most previous relevant studies have focused on testing onshore and offshore OWCs using 2D models and wave flumes. Conversely, this paper provides experimental results for a 3D offshore stationary OWC device subjected to regular waves of different heights and periods under a constant power take–off (PTO) damping simulated by an orifice plate of fixed diameter. In addition, a 3D computational fluid dynamics (CFD) model based on the RANS equations and volume of fluid (VOF) surface capturing scheme was developed and validated against the experimental data. Following the validation stage, an extensive campaign of computational tests was performed to (1) discover the impact of testing such an offshore OWC in a 2D domain or a wave flume on device efficiency and (2) investigate the correlation between the incoming wave height and the OWC front wall draught for a maximum efficiency via testing several front lip draughts for two different rear lip draughts under two wave heights and a constant PTO damping. It is found that the 2D and wave flume modelling of an offshore OWC significantly overestimate the overall power extraction efficiency, especially for wave frequencies higher than the chamber resonant frequency. Furthermore, a front lip submergence equal to the wave amplitude affords maximum efficiency whilst preventing air leakage, hence it is recommended that the front lip draught is minimized.

Freak waves are huge and unexpected surface waves in the ocean which usually lead to severe destructions to ships and offshore structures. Green water is one of the most commonly observed phenomena when ships and marine structures encounter with freak waves. As a result, freak waves will likely to create significant wave impact on the deck structures. However, the existing researches on the interaction between freak waves and marine structures are still inadequate. In order to investigate the green water phenomenon caused by freak waves and the structural response of the deck, a 2-D numerical wave flume is built in which a nonlinear freak wave based on the Peregrine breather solution is generated. By setting an elastic bare deck horizontally in the flume, the fluid-structure interaction (FSI) is considered during the green water event. To approximate the complicated real decks, a deck model containing intermediate elastic supports are used. The simulation results include the snapshots of the entire green water process, the pressures of the fluid on the deck and the displacements of the elastic decks analyzed with the fast Fourier transformation (FFT) and the wavelet transformation method. By comparing the results of the rigid deck, the elastic bare deck and the elastic deck with intermediate elastic supports, advisable conclusions are drawn.

This work presents an experimental investigation of the dynamic responses of a freestanding bridge tower model under coupled wave and wind actions. A test model with a geometric scaling of 1:100 was manufactured, and the test was performed in a wind tunnel and wave flume. The dynamic responses of the test model were measured under three cases of wind, wave and wind-wave coupled actions. The displacement, acceleration and bending moment were analyzed for the model with different wind speeds and wave exposures. The test results indicated that the coupled wind-wave effects are clear for lower wind speed with regular waves when the wave period is in the resonant region of the structures. When the wave period is far from the resonant frequency of the structure or the wind speed is much higher, the coupled wind-wave action does not significantly affect the dynamic responses of the bridge tower.

To date there were few research on the effect of non-linearity properties of the ocean waves on the performance of wave energy converter (WEC), which uses a series of unidirectional gear. One such parameter is the variation of wave period. The influence of wave period variations on the performance of physical model of the wave energy converters have been investigated at the Hydraulics Laboratory, Department of Civil Engineering, Hasanuddin University Indonesia. This WEC physical model was fabricated and assembled at Politeknik ATI Makassar Indonesia. The investigation steps consists of physical model development, physical model investigation at wave flume prior to the wave period variation, measuring input output parameters of the physical model under test and empirical model formulation based on observed data analysis. Physical model test carried out on the wave flume at the Hydraulics Laboratory of the Department of Civil Hasanuddin University, at a water depth of 25 cm, wave height between 5-9 cm and wave period between 1.2 - 2.2 seconds. Investigation result based on flywheel radial speed (RPM) and torque (Nm) indicated that calculated harvested power was inversely proportional with the wave period. The longer the period of the waves, the energy produced is getting smaller. The derived empirical formula was y = -85.598x + 208.53 and R² = 0.8881. Y is energy produced (Watt) and X is the wave period (Second). Formulations generated from this study could be used as a reference for future research in dealing with wave period variations on a design one way gear wave energy converter as a source of renewable energy.

Tsunami wave force acting on a spherical storage tank located in coastal areas is measured and discussed for future tsunamis in this study. The horizontal and vertical components of tsunami wave force are measured in a series of hydraulic experiments. In the experiments, bore waves like tsunamis are generated in a two-dimensional wave flume by opening a gate at a reservoir. The horizontal tsunami wave force has several crests which correspond to the crests of the inundation depth. The horizontal tsunami wave force is approximately estimated by drag force. The time series of the vertical tsunami wave force show downward force in several moments as well as upward force. The measured vertical tsunami wave force is much smaller than the buoyancy acting on the spherical storage tank because of the flow between the bottom of the spherical storage tank and the surface of the storage site.

We studied pore water pressure responses in silty seabed under random wave action through a series of experiments in a wide wave flume. Unlike previous experiments involving regular waves, we focus on random waves including wind-induced short waves and long waves so as to gain further insights into seabed responses and liquefaction risks posed by random waves. In particular, the study investigated how the secondary long waves that were induced by incident short wave groups affected the seabed responses. The test results revealed that these long waves could cause much larger seabed responses than the short waves (eight times larger in our flume tests). Although they had smaller wave heights than the short waves, the long waves were found to contribute much more significantly to the cumulative pore pressure than previously recognized. The likely reason is that the long waves are disproportionally effective in generating cumulative excess pore pressure, confirming qualitatively some of the earlier theoretical predictions. One of the implications from these research findings is that the existing design methods when applied to random waves could grossly underestimate liquefaction potential in silty sediment bed if either spectrum-based mean wave parameters or significant wave parameters were used.

Physical model tests were performed in a wave flume at Deltares with rock armoured slopes. A shallow foreshore was present. At deep water, the same wave conditions were used, but by applying different water levels, the wave loading on the rock armoured slopes increased considerably with increasing water levels. This allowed an assessment of the effects of sea level rise. Damage was measured by using digital stereo photography (DSP), which provides information on each individual stone that is displaced. Two test series were performed five times. This allowed for a statistical analysis of the damage to rock armoured slopes, which is uncommon due to the absence of statistical information based on a systematic repetition of test series. The statistical analysis demonstrates the need for taking the mean damage into account in the design of rock armoured slopes. This is important in addition to characterising the damage itself by erosion areas and erosion depths. The relation between damage parameters, such as the erosion area and erosion depth, was obtained from the tests. Besides tests with a straight slope, tests with a berm in the seaward slopes were also performed. A new method to take the so-called length effect into account is proposed to extrapolate results from physical model tests to real structures. This length effect is important, but is normally overlooked in the design of rubble mound structures. Standard deviations based on the presented model tests were used.

Shoreline erosion takes place due to the movement of sand by tides, wave actions, and wave-induced currents. The conventional techniques used for coastal protection such as artificial armor units and rubble mound are costly, and transportation is difficult in remote areas. Moreover, they may not be suitable for poor soil conditions. In this paper, the detailed physical experimental studies were carried out for a geo-tube saline embankment with ten geo-tubes in a four-layer configuration in a wave flume. This soft engineering solution may be particularly viable since the location is remote with poor soil strata. The studies include a scaled model (1:10) of geo-tube embankment with and without gabion boxes to check its possible utilization for coastal protection. The model is tested in the deep wave flume equipped with a piston type wave maker. The embankment is studied for two different water depths of 0.4 m and 0.5 m. The chosen 0.4-m water depth characterizes the high tide condition, while the 0.5-m water depth reproduces the combined high tide and storm surge conditions. The regular wave heights are varied in the range of 2 to 16 cm with a corresponding wave period of 1.5 to 2.2 s. Three probe methods are used to obtain the hydrodynamic parameters, based on which a geo-tube embankment protected with gabion box as armor is designed and constructed along the coast of Pentha (Odisha, India).

Experimental tests on the interaction between waves and a submerged rubble-mound breakwater (SBW) were performed in the wave flume at the Institute of Hydroengineering PAS in Gdansk (Poland). A model of a submerged breakwater was prepared based on the constructions built in 2006 in the Polish zone of the Baltic coast, in Gdansk Bay, in the region of Gdynia Orlowo (Orlowo Cliff). The tests were carried out for regular waves (varying parameters: height, period, length, and steepness) whose parameters were determined on the basis of the actual wind field occurring in Gdansk Bay. The experiment was conducted for two water levels corresponding to the actual long-term mean sea level (msl) of 500 cm as well as a storm surge of 550 cm. The research has focused on the analysis of the amount of wave energy transmitted into the lee region and the determination of parameters that affect the transmission size. Types of wave-breaking were described based on the extensive video and photographic documentation prepared during the measurements. Based on the results obtained from the experiment and the previous research on the functioning of submerged breakwaters in the coastal zone, including both numerical modelling as well as field research and field observations, the efficiency of the structure was assessed.

Given the rapid progress made in understanding the dynamics of an offshore floating body in an ocean environment, the present study aimed to simulate ocean waves in a small-sized wave flume and to observe the motion of a cylindrical floating body placed in an offshore environment. To generate regular ocean waves in a wave flume, we combined a wave generator and a wave absorber. In addition, to precisely visualise the oscillation of the body, a set of light-emitting diode illuminators and a high-speed charge-coupled device camera were installed in the flume. This study also focuses on the spectral analysis of the movement of the floating body. The wave generator and absorbers worked well to simulate stable regular waves. In addition, the simulated waves agreed well with the plane waves predicted by shallow-water theory. As the period of the oncoming waves changed, the movement of the floating body was substantially different when tethered to a tension-leg mooring cable. In particular, when connected to the tension-leg mooring cable, the natural frequency of the floating body appeared suddenly at 0.391 Hz as the wave period increased. Copyright (C) 2016 Society of Naval Architects of Korea.

This paper concerns on the propagation of transient wave groups, focusing at one point in time and space to generate large waves. A numerical wave tank is developed based on the commercial software package FLUENT. Velocity inlet method is applied to reproduce the focused waves in this model, and the results are compared with linear and second-order theoretical results. The continuous wavelet transform is employed to analyse the time–frequency characteristics of the focused waves. Forces due to focused waves acting on a semi-submerged horizontal cylinder is investigated and compared with the regular wave sharing with identical wave crest height and trough-to-trough period. Secondary load cycle is observed which may cause “ringing”. This developed model is expected to serve as a basis for strongly nonlinear waves, such as freak waves.

In this paper, a novel approach for simulating Oscillating Water Column (OWC) using lattice Boltzmann method (LBM) is presented. A direct comparison between a real wave flume and a 3D-Large Eddy Simulation (LES) numerical lattice Boltzmann (LB) wave flume is developed through the analysis of an OWC energy converter in order to validate the LBM approach for simulating OWCs. The numerical model uses a Volume-of-Fluid (VOF) approach and handles the water–air coupling into the OWC air chamber. The experimental and numerical setup are described. Comparisons for water level during free oscillation test, water level and air pressure under regular wave attacks are given and show that the LB model is accurate. We also discuss the efficiency of the simulated OWC. The 3D numerical model offers a powerful tool in order to study the 3D phenomena occurring into OWCs.

This article presents numerical simulations of tsunami waves that are generated using different experimental techniques in laboratory tests. Comparisons of the numerical predictions of the tsunami wave shapes with different experimental measurements of the wave shapes have been carried out, and a good agreement was obtained. Four different laboratory techniques to create tsunami waves were examined: a sudden release of a water column, a horizontal or vertical motion of a piston, and a rotation of a rigid plate. Comparison of waves of the same height that are formed by these four different methods shows that the horizontal piston motion produces the shortest wave, and the vertical piston motion produces the longest wave. The wave produced by a plate rotation is similar to the wave caused by the “water column release,” but it is slightly longer. It was found that different techniques produce different wave characteristics; therefore, selection of the proper laboratory technique requires some considerations including a comparison with the required real tsunami wave that should be simulated. It should be emphasized that this research aims at simulating the tsunami waves that are produced by different common laboratory techniques; however, it refrains from assessing the adequacy of any of this techniques to properly represent a real specific tsunami wave. Further to developing the computational procedures for tsunami wave simulations, this article extends the numerical study to examine the interaction of a tsunami wave with a rigid wall and investigate the dynamic pressure distribution on the wall surface. It was found that the peak pressure of a tsunami wave acting on a rigid wall that is produced by the horizontal piston has the lowest magnitude (among the waves of the same height, caused by these four techniques), while the pressure due to a rotational plate has the highest magnitude.

The power generation of regular water waves from a horizontal-axis single Savonius rotor is experimentally investigated in an experimental wave flume in the context of the performance assessment of the rotor in intermediate-to-shallow water depths for different parametric conditions. A number of prototypes with multiple blades of 3–5 with the same diameter and blade curvature angle are fabricated in-house and tested to measure both the long-term average torque and power generated at different submergence levels, wave heights and wave periods. The experiments are performed in the wave-current flume equipped with a piston-type wave maker with an active wave absorption capability. The energy performance of the rotor is comparatively assessed for each experimental test case based on quantitative comparison of obtained wave-to-mechanical energy conversion efficiency (ECE) to suggest a possible optimum blade number, positioning and wave physical conditions for the investigated range of wave flow characteristics. It is found that higher ECE values can be achieved at higher wave heights and blade numbers for the lower wave periods when the rotor is placed at the water surface and/or just below the surface. This study provides a proper guideline for performance analysis of such device(s) for further studies.

In this study, a numerical method for predicting solitary wave forces on a typical coastal bridge deck with girders is utilised in order to obtain an alternative way to assess solitary wave forces on coastal bridge decks with sufficient accuracy. Firstly, a wave model based on the solitary wave theory representing the incident wave of tsunamis is applied through a computational fluid dynamics computer program, where the shear stress transport k-ω model is adopted as the turbulent closure for the Reynolds Averaged Navier–Stokes model equations. Then, the numerical wave profiles and the predicted wave forces are compared with the analytical solutions and the reported laboratory measurements, respectively. These verifications assure the results in the following parametric study reliable. Finally, comparisons between the numerical results and those acquired through the empirical methods are conducted in order to examine the appropriateness of these empirical procedures regarding this specific case. Fu...

Offshore substructures have been developed to support structures against complex offshore environments. The load at offshore substructures is dominated by waves, and deformation of waves caused by interactions with the current is an important phenomena. Wave load simulation of fixed offshore substructures in waves with the presence of uniform current was carried out by numerical wave tank technique using the commercial software, FLUENT. The continuity and Navier-Stokes equations were applied as the governing equations for incompressible fluid motion, and numerical wavemaker was employed to reproduce offshore wave environment. Convergence test against grids number was carried out to investigate grid dependency and optimized conditions for numerical wave generation were derived including investigation of the damping effect against length of the damping domain. Numerical simulation of wave and current interactions with fixed offshore substructure was carried out by computational fluid dynamics, and comparison with other experiments and simulations results was conducted. Copyright (C) 2016 Society of Naval Architects of Korea. Production and hosting by Elsevier B.V.

The present experimental study investigates the generation and propagation of regular water waves and their interactions with an in-house fabricated horizontal-axis 3-bladed Savonius rotor in an experimental wave flume (EWF) equipped with a piston-type wave maker with active absorption capability to assess the rotor performance for different parametric conditions namely, wave height, wave period and submergence level in intermediate-to-shallow water depths. The motion of the wave particles around the Savonius rotor is observed during the experiments as well as measuring the power and torque performance of the rotor to make a reliable assessment of the water movement with the rotor positioning for different inflow wave boundary conditions. The wave-to-mechanical energy conversion efficiency (ECE) of the present device is determined for each case to suggest a possible optimum positioning accompanied with optimum wave heights and frequencies for the manufactured small scale prototype. The present results suggest that experimental solutions within the wave flume can provide a proper guideline for performance analysis of such devices in intermediate-to-shallow water depths for further studies of optimization of design of Savonius rotor type sea and/or ocean wave energy conversion devices for different operating conditions provided that optimum physical flow conditions are satisfied.

This paper describes an investigation of the generation of desired sea states in a numerical wave model. Bimodal sea states containing energetic swell components can be coastal hazards along coastlines exposed to large oceanic fetches. Investigating the effects of long-period bimodal seas requires large computational domains and increased running time to ensure the development of the desired sea state. Long computational runs can cause mass stability issues due to the Stokes drift and wave reflection, which in turn affect results through the variation of the water level. A numerical wave flume, NEWRANS, was used to investigate two wave generation methods: the wave paddle method, allowing for a smaller domain; and the internal mass source function method, providing an open boundary allowing reflected waves to leave the domain. The two wave generation methods were validated against experimental data by comparing the wave generation accuracy and the variance of mass in the model during simulations. Results show that the wave paddle method not only accurately generates the desired sea state but also provides a more stable simulation, in which mass fluctuation has less of an effect on the water depth during the long-duration simulations. As a result, it is suggested that the wave paddle method with active wave absorption is preferable to the internal wave maker option when investigating intermediate-depth long-period bimodal seas for long-duration simulations.

Floating structures are commonly seen in coastal and offshore engineering. They are often subjected to extreme waves and, therefore, their nonlinear dynamic behaviors are of great concern. In this paper, an in-house CFD code is developed to investigate the accurate prediction of nonlinear dynamic behaviors of a two-dimensional (2-D) box-shaped floating structure in focused waves. Computations are performed by an enhanced Constrained Interpolation Profile (CIP)-based Cartesian grid model, in which a more accurate VOF (Volume of Fluid) method, the THINC/SW scheme (THINC: tangent of hyperbola for interface capturing; SW: Slope Weighting), is used for interface capturing. A focusing wave theory is used for the focused wave generation. The wave component of constant steepness is chosen. Comparisons between predictions and physical measurements show good agreement including body motions and free surface profiles. Although the overall agreement is good, some discrepancies are observed for impact pressure on the superstructure due to water on deck. The effect of grid resolution on the results is checked. With a fine grid, no obvious improvement is seen in the global body motions and impact pressures due to water on deck. It is concluded that highly nonlinear phenomena, such as distorted free surface, large-amplitude body motions, and violent impact flow, have been predicted successfully.

Closely-spaced piles are the most essential components for the structural safety of some types of coastal and offshore structures. Wave-induced loading of such piles is among the most uncertain issues in the design of pile group-supported marine structures. Therefore, the correct estimation of the wave loading of a pile within a pile-group in different arrangements is crucial for both safety and costs. Unlike the case of single isolated piles, less attention have been paid to pile groups where wave–pile group interaction is more obvious due to interference effects that affect the wave-induced flow around the piles. In this study, the pile group effect on the wave loading of a slender pile due to non-breaking and focused breaking waves is investigated by means of small scale experiments performed in the 2 m-wide wave flume of Leichtweiss-Institute for Hydraulic Engineering and Water Resources (LWI) in Braunschweig, Germany. Different pile arrangements including single, side by side, tandem, 2×2 and staggered with relative spacing of SG/D=0.5–5 were tested. Based on the results of this study an improved understanding of the processes associated with the interaction of waves and pile groups has been achieved.

Over the past decade, the use of imaging devices to perform quantitative measurements has seen wide-scale adoption and has become integral to the emerging fields of research, such as computer vision and artificial intelligence. Recent studies, published across a wide variety of fields, have demonstrated a vast number of ways through which image-based measurement systems can be used in their respective fields. A growing number of studies have demonstrated applications in coastal and ocean research. Edge detection methods have been used to measure water surface and bedform elevation from recorded video taken during wave flume experiments. The turbulent mixing of air and water, induced by the breaking waves and the runup processes, poses a particular problem for the edge-detection methods, since they rely on a sharp contrast between air and water. In this paper, an alternative method for tracking water surface, based on color segmentation, is presented. A set of experiments were conducted whereby the proposed method was used to detect water surface profiles for various types of breaking waves interacting with a rubble mound breakwater. The results were further processed to compute the surface velocity during runup. The time-history of surface velocity is shown to closely parallel the point measurements taken nearby the instrumented armor unit. These velocities can potentially serve as boundary conditions for determining the dynamic loads exerted on the armour units. Further, the image processing results are used to remove the time-varying buoyant force from the measured force acting on an individual armour unit, providing additional insight into how the forces develop over time.

A combined Curtain and Pile Foundation's breakwater called the Single Curtain Pile Foundation Breakwater (SCPFB), was designed to dissipate wave energy in an intermediate water depth instead of constructing a rubble mound-type breakwater. ( CT ). The physical modeling of the SCPFB is was conducted at the Ocean Wave Research Laboratory in Institut Teknologi Bandung in a 2D wave flume to measure the breakwater’s transmission coefficient in the intermediate water depth condition The waves generated in the wave flume were monochromatic. The scaling applied the principle of Froude similarity, where the Froude number of the model equaled to the Froude number of the prototype. Wave heights and wave periods data were observed by both visual observation and wave probes. The incoming wave heights and transmitted wave heights before and after the SCPFB, respectively, were measured and processed to obtain the CT . The relationships between CT and non-dimensional variables such as the relative incident wave steepness, water depth, and curtain draft were obtained. Comparisons with similar research are shown.

Ports are one of the most vulnerable coastal utilities in case of marine natural hazards such as tsunamis and need to be protected against their devastating effects. Thus, studying the effects of tsunamis on protective structures such as breakwaters is critical. The Sea of Marmara is a part of an active earthquake zone that has generated tsunamis in the history. In terms of population density, coastal utilization, and economic potential, Marmara coastline seems most vulnerable to marine hazards. The availability of natural stones allows for wide use of rubble mound breakwaters as coastal protective structures in Turkey. The stability of these types of structures under the attack of storm waves has already been studied. However, their stability and performance under the effect of long waves and tsunami attacks have not yet been studied experimentally. The present study is a case study focusing on Haydarpasa Port, located at the southern entrance of Istanbul Bosphorus Strait (North coast of the Sea of Marmara). It aims to investigate the performance level of the port in case of tsunami attack. Physical model experiments were conducted in the 105-m long wave flume in the Port and Airport Research Institute (PARI), Japan, with a Froude-type length scale of 1/30. The experiments conducted to test the stability of rubble mound breakwater were twofold: (i) solitary wave experiments and (ii) tsunami overflow experiments. The heights of incoming tsunami waves were selected from results of simulations were conducted in the same region (Oyo Int. Co., 2007; Ayca, 2012; Yalciner et al., 2014; Guler et al., 2014; Aytore, 2015). First, the incoming solitary wave heights were selected as 5, 7.5, and 10 cm. Using the overflow heights obtained from solitary wave experiments, i.e., wave height at the top of crown wall when the solitary waves are overtopping the crown wall, tsunami overflow experiments were conducted ranging from an overflow height of 1.1 cm to 4.6 cm. Results of these experiments showed that Haydarpasa Breakwater, especially the crown wall of the breakwater, is not stable under a moderate tsunami attack. Therefore, an improved cross section was also tested under the same conditions, and the improvement proved successful. (C) 2015 Elsevier B.V. All rights reserved.

This study experimentally investigated the effect of nearby buildings, termed macroroughness on the tsunami loading. The hydraulic experiment was conducted in a 1 m x 1 m with 40 m long wave flume at a scale of 1:100. Nominal wave height of 40 mm was simulated in this study. Both the building model and the macroroughness elements consisted of 66 mm high solid blocks. Wave pressures exerted on frontal and back faces of the building model were discussed in detail in this paper. Experimental results showed that the macroroughness elements had a significant impact on tsunami loading in the inundation zone. Sheltering effect was exhibited by the seaward macroroughness elements, showing significant reduction in the front face pressures. With the presence of the landward macroroughness elements, the wave pressures at the back face of the building model increased significantly at the initial impact.

Although great efforts have been devoted to revealing the formation mechanisms of rogue waves, the study of wave–structure interaction such as the green water phenomenon is still not sufficient. Since the traditional Ritter׳s solution of dam-breaking model gives improper estimations on the rogue wave overtopping, a combined wave-dam-breaking (CWDB) model is proposed. The CWDB model is deduced from the Ritter׳s solution, by including the influence of the rogue wave propagation as well as the delayed effect of the dam-breaking problem. Various rogue waves, which are based on the Peregrine breather solution of nonlinear Schrodinger (NLS) equation, are generated in a numerical wave flume. The rogue waves impinge onto a horizontal deck placed at the center part of the tank, creating green water on the deck surface. The CWDB model is validated by making comparisons with both numerical results and existing experimental measurements. Great improvement can be revealed by contrasting the results of the CWDB model with those of the Ritter׳s solution.

In this study, the green water phenomena on rectangular shaped structure is numerically simulated by STAR-CCM+ to investigate the flow pattern including the velocity profiles in bubbly water flow. 5 phases of the formation of green water in front of and over the rectangular shaped structure is simulated at the design condition which is scaled down by 1:125 from FPSO operating in GOM. All numerical results are compared with the experimental results performed in a two dimensional wave flume. The water deformation due to the green water are obtained by the high speed CCD camera with employing the shadow graphy technique, which is allowed to take the bubbly water flow into images. A series of image taken by shadow graphy technique is analyzed with MQD method to calculate the velocity in bubbly water flow.

In this study, we proposed a new type of dual-buoy wave energy converter (WEC) exploiting multi-resonance and analyzed the experimental results from a model test in a 2-D wave flume. A dual-buoy WEC using multi-resonance has two advantages: high efficiency at the resonant frequencies and the potential to extend the frequency range available to extract wave power from the WEC. The suggested WEC was composed of an outer buoy and an inner buoy sliding vertically inside the outer buoy. As the power take-off device, a linear electric generator (LEG) consisting of permanent magnets and coils fixed at each buoy was adopted. Electricity was produced by the relative heave motion between the two buoys. To search for the optimal shape of a dual-buoy WEC, we conducted experiments on the heave motion of a two-body system in regular waves without an LEG installed. Model tests with six combinations of experimental models were conducted in order to find the motion characteristics of a dual-buoy WEC. It was found that model 2, which included a ring-shaped appendage to move the resonant frequency of the outer buoy toward a high value, showed a higher relative heave response amplitude operator (RAO) curve than model 1. In addition, the double-peak shape of the heave RAO curve shown for model 2 indicated the extension of the frequency range for extracting wave power in irregular waves.

The perforated caisson is widely applied to practical engineering because of its great advantages in effectively wave energy consumption and cost reduction. The attentions of many scientists were paid to the fluid-structure interaction between wave and perforated caisson studies, but until now, most concerns have been put on theoretical analysis and experimental model set up. In this paper, interaction between the wave and the partial perforated caisson in a 2D numerical wave flume is investigated by means of the renewed SPH algorithm, and the mathematical equations are in the form of SPH numerical approximation based on Navier-Stokes equations. The validity of the SPH mathematical method is examined and the simulated results are compared with the results of theoretical models, meanwhile the complex hydrodynamic characteristics when the water particles flow in or out of a wave absorbing chamber are analyzed and the wave pressure distribution of the perforated caisson is also addressed here. The relationship between the ratio of total horizontal force acting on caisson under regular waves and its influence factors is examined. The data show that the numerical calculation of the ratio of total horizontal force meets the empirical regression equation very well. The simulations of SPH about the wave nonlinearity and breaking are briefly depicted in the paper, suggesting that the advantages and great potentiality of the SPH method is significant compared with traditional methods.

In this study, a structural identification method is proposed to assess the integrity of gravity-type caisson structures by analyzing vibration features. To achieve the objective, the following approaches are implemented. Firstly, a simplified structural model with a few degrees-of-freedom (DOFs) is formulated to represent the gravity-type caisson structure that corresponds to the sensors\' DOFs. Secondly, a structural identification algorithm based on the use of vibration characteristics of the limited DOFs is formulated to fine-tune stiffness and damping parameters of the structural model. Finally, experimental evaluation is performed on a lab-scaled gravity-type caisson structure in a 2-D wave flume. For three structural states including an undamaged reference, a water-level change case, and a foundation-damage case, their corresponding structural integrities are assessed by identifying structural parameters of the three states by fine-tuning frequency response functions, natural frequencies and damping factors.

Submerged plates are widely used as breakwater device and wave energy convertor in costal and ocean engineering. It is of practical importance to account for the effects of plate on wave transformation and nonlinear wave loads on the plate. In this paper, a 2D fully nonlinear numerical wave flume is developed to investigate the nonlinear interactions between a regular wave and a submerged horizontal plate by use of a higher-order boundary element method (HOBEM) based on potential theory. An acceleration potential method is adopted to calculate the transient wave loads on the plate. The proposed model is verified against the published experimental and numerical data for nonlinear wave scattering by a submerged plate. Then numerical tests are performed to investigate the high free harmonics induced by the submerged plate and nonlinear wave loads on it. The second-order analysis shows a resonant behavior which is related to the ratio of the plate length to the second beat length. The wave-load analysis shows that the pressure on the upper surface oscillates more frequently than that on the lower surface.

Submerged breakwaters are gaining more popularity as a potential coastal protection structure resulting in moderate wave transmission with significant wave energy dissipation. Submerged breakwaters are mainly adopted to prevent erosion and to dissipate the incident wave energy. In addition, the premature wave breaking facilitates the wave surfing activities by proper designing of submerged breakwater. In the present study, the experiments are conducted on submerged breakwaters in a two dimensional wave flume to investigate the influence of stepped and smooth front slope of the submerged breakwater, its height and width in reducing wave energy. A total number of eighteen sets of experiments has been conducted for three different breakwater heights (31 cm, 28 cm and 26 cm) and three different breakwater widths (10 cm, 20 cm and 30 cm) with stepped and smooth front slope of breakwater. The submerged breakwater models are subjected to regular waves of four different wave heights and five different wave periods in a constant water depth of 31 cm, to determine wave transmissions characteristics. The influence of relative breakwater width, relative depth of submergence of the breakwater and roughness of breakwater front slope on wave transmission are analyzed and discussed in this paper.

Coastal structures are subjected to marine environmental forces due to waves, wind and currents. The wave forces are the dominant forces and are decisive in the design of coastal structures. Structural stability as well as functional performance of a coastal structure depends on design wave conditions. Design of these flexible rubblemound structures is complex due to complexity in wave-structure interaction. As such, the design of rubblemound structures is mainly finalised by hydraulic model studies. A major aspect in the design of rubblemound structures is the minimum weight of the armour units required to withstand the design wave condition. A number of empirical formulae are available for the design. The stability of armour unit is related to the wave height in these formulae. The formulae raise a question about a design wave height to be chosen to represent the random sea wave conditions. The design wave height to be used in stability formulae and in the regular wave tests in the laboratory for rubblemound breakwaters is often defined in terms of statistical height related to the ocean waves such as significant wave height (Hs) i.e. average of the highest one third waves in a wave train. It has been commonly assumed that the destructive effect of random waves is equivalent to that of regular waves having a height equal to Hs, and the armour unit's weight is often determined with this assumption, using stability formulae. However, the results of stability tests in a wave flume under random waves and regular waves indicated that the equivalent regular wave height characterizing the random wave spectra may vary between (H1/10) to (H1/5). The design procedures for the coastal rubblemound structures, selection of design wave height and equivalence of the monochromatic and random waves are described in the paper.

Coastal Hazards are physical phenomena that expose a coastal area to risk of property damage, loss of life and environmental degradation. Rapid-onset hazards last over periods of minutes to several days and examples include major cyclones accompanied by high waves and surges or tsunamis created by submarine earthquakes and landslides. Slow-onset hazards develop incrementally over longer time periods and examples include erosion and gradual inundation. A physical process such as wave run-up is very important with regard to the design of sloping coastal structures. To assess the influence of surface roughness elements on a beach for reducing the wave run-up, energy dissipation and extreme wave events. This helps in reducing the inundation by wave flooding during storms and tsunamis. Results of the monochromatic waves on energy dissipation blocks of different configurations show a considerable energy dissipation and corresponding reduction of wave run-up on the beach. Three different of dissipation blocks i.e. Rectangular, Semi Circular and trapezoidal shapes were used in the present experimental study. These dissipation blocks may be submerged or emerged during a tidal cycle. Keeping the dissipation block height constant, water depth was varied to achieve three different relative block heights to simulate the tidal fluctuations in the coastal environment. The experiments are carried out in the wave flume of 45m long, 1.2 m wide and 1.2m deep in the Department of Civil Engineering, Andhra University College of Engineering (A), Visakhapatnam, India. The dissipation blocks with three different spacings of 0.05m, 0.1m and 0.15m was fixed on a sloping flume bed of 1: 35. The water depth can be varied from 0.25 m to 0.80 m.

In this study, in order to investigate wave force and wave-induced overturning moment according to the support structure types and sea levels, wave force tests were carried out for the three offshore support structures of Monopile, GBS, and Hybrid under three sea levels of HSWL, MSL, and LSWL. As the results of this study, it was found that, as the wave height increased at the shallow water (LSWL), wave force increased significantly because of the wave nonlinearity, named wave shoaling. Also, as the structural member size became larger, wave nonlinearity effects on wave force at the shallow water (LSWL) were reduced because of the wave diffraction effect of the large-sized member. Accordingly, variations of wave force and wave-induced overturning moment according to the wave heights and sea levels were larger in the slender member and smaller in the large-sized member. Therefore, it was concluded that wave force and wave-induced overturning moment of the large-sized support structure were little sensitive to the wave height and sea level than the slender support structure. Maximum overturning moments occurred at the HSWL in the Monopile, at the MSL in the GBS, and at the LSWL in the Hybrid, respectively.

Analogue models or scale experiments of estuaries and short tidal basins are notoriously difficult to create in the laboratory because of the difficulty to obtain currents strong enough to transport sand. Since Osborne Reynolds' experiments over a century ago, experimental tidal flow has been driven by periodic sealevel fluctuations. Recently we discovered a novel method to drive periodic tidal currents: periodically tilting the entire flume. This leads to sediment transport in both the ebb and flood phase which in tidal systems with dynamic channel and shoal patterns. Here we compare the tidal currents driven by sealevel fluctuations with those driven by tilting. We use a bespoke flume of 20 m by 3 m with rough bed: the Metronome. Experiments were run in a straight flume with different tilting periods and with either one or both boundaries open at constant head with free inflow and outflow. Also experiments were run with flow driven by periodic sealevel fluctuations. We recorded surface flow velocity along the flume with Particle Imaging Velocimetry and water levels along the flume. Furthermore we compared the results to a one-dimensional model with shallow flow equations for a rough bed. We found that Reynolds’ method results in negligible flows along the flume except for the first few meters, whereas flume tilting results in nearly uniform, reversing flow velocities along the entire flume that are strong enough to move sand. A periodically tilting flume therefore has the potential to simulate estuaries as observed in a pilot experiment and opens up the possibility of systematic biomorphological experimentation with self-formed estuaries.

The present paper deals with a study of the damping induced by a turbine in the power take off of an small scale Oscillating Water Column Wave Energy Converter. In order to study the turbine-induced damping, an experimental setup was built. The experimental setup consists of a wave flume 2000 mm long, 190 mm high and 96 mm wide with an impermeable beach as a dissipative system at the end to avoid wave reflections. The system is all built in Plexiglas to allow optical real-time observation. An Oscillating Water Column chamber model was placed in the measurement area between the wave-maker and the dissipative beach. The chamber was 37 mm long, 200 mm high and 96 mm wide also built in Plexiglas. In order to study the effect of turbine-induced damping on the system, a calibrated and variable hole was used to simulate the turbine presence, while outflow and inflow air velocity were measured by means of Particle Image Velocimetry (PIV) method. Pressures and velocities of air and water as well as the free water surfaces evolution were measured at different wave frequencies and heights.

The Overtopping BReakwater for Energy Conversion (OBREC) is an overtopping type wave energy converter, totally embedded into traditional rubble mound breakwaters. The device consists of a reinforced concrete front reservoir designed with the aim of capturing the wave overtopping in order to produce electricity. The energy is extracted through low head turbines, using the difference between the water levels in the reservoir and the sea water level. This paper investigates the nature and magnitude of wave loadings exerting on various parts of the structure. The results improve the overall knowledge on the device behavior, completing the highlights from the complementary test campaign carried out in the same wave flume in 2012 (Vicinanza et al., 2014). The formulas provided have been used to design the first OBREC prototype breakwater in operation since January 2016 at Naples Harbour (Italy).

This paper presents the results of a 2D experimental model application of an alternative environment-friendly coastal structure, an inclined thin plate (ITP). The primary objectives of this study were to understand (a) wave energy dissipation mechanism of ITP, (b) wave attenuation performance of ITP, and (c) the influence of ITP on water particle (orbital) velocity characteristics. In order to achieve these objectives, flume experiments were conducted for different inclination angles of ITP (i.e. 0, 5, 10, and 15°). During the experiments, water surface elevations were measured and instantaneous velocity profiles were recorded by a new generation acoustic Doppler velocimeter (ADV-Vectrino II). The experimental data revealed the fundamental physical facts regarding the dissipation mechanism and performance of ITP, which may be a base for the effective design of such coastal protection structures in the future. A tentative method based on multi-parameter regression of experimental data is proposed to determine the wave transmission performance of ITP. Finally, the practical application of an ITP structure is discussed in the light of the achieved results.

The placement of flushing culverts in breakwaters is a simple way to counteract a decline in water quality in harbour basins. A series of 63 experiments, which were conducted in a physical model of a breakwater in a 2D wave flume, are used to investigate the effect of the wave properties as well as the geometrical characteristics of the flushing culvert placed on breakwaters, in the temporal water surface profiles, the harmonic generation and the transmission coefficient. It is shown (i) that the harmonic generation downwave of the structure is more intense when wave nonlinearity increases; (ii) the harmonic generation and the transmission coefficient is mostly affected by the culvert's dimensions, especially the culvert's width as it is associated with the energy transmitted to the lee side of the structure and with diffraction. A 2D coupled-mode system (CMS) model is applied for the numerical simulation of waves propagating through flushing culverts at seawater level that are never perfectly filled with water. Good comparisons with the experimental results for linear and weakly non-linear waves and wider culverts are shown; proving the usefulness of the CMS model in calculating the effectiveness of a flushing culvert in an every-day basis of harbour function.