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The wave-induced liquefaction of seabed is responsible for causing damage to marine structures. Particle composition and consolidation degree are the key factors affecting the pore water pressure response and liquefaction behavior of the seabed under wave action. The present study conducted wave flume experiments on silt and silty fine sand beds with varying particle compositions. Furthermore, a comprehensive analysis of the differences and underlying reasons for liquefaction behavior in two different types of soil was conducted from both macroscopic and microscopic perspectives. The experimental results indicate that the silt bed necessitates a lower wave load intensity to attain the liquefaction state in comparison to the silty fine sand bed. Additionally, the duration and development depth of liquefaction are greater in the silt bed. The dissimilarity in liquefaction behavior between the two types of soil can be attributed to the variation in their permeability and plastic deformation capacity. The permeability coefficient and compression modulus of silt are lower than those of silty fine sand. Consequently, silt is more prone to the accumulation of pore pressure and subsequent liquefaction under external loading. Prior research has demonstrated that silt beds with varying consolidation degrees exhibit distinct initial failure modes. Specifically, a dense bed undergoes shear failure, whereas a loose bed experiences initial liquefaction failure. This study utilized discrete element simulation to examine the microscopic mechanisms that underlie this phenomenon. [ABSTRACT FROM AUTHOR]

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Copyright of Tropical Geography is the property of Tropical Geography Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lee, B.W.; Baek, D.; Ha, T.; Lee, K.J., and Yoon, J.-S., 2023. Experimental study on hydrodynamic performance of partially perforated-wall caisson breakwaters designed for the southeast coast of Korea. Journal of Coastal Research, 39(1), 167–174. Charlotte (North Carolina), ISSN 0749-0208. If a perforated wall is installed on the front and rear surfaces of the caisson, then it is possible to reduce the wave reflection and the discharge of wave overtopping caused by energy dissipation. Consequently, the energy dissipation helps reduce the transmitted wave and improve the stability of the breakwater. This paper discusses the hydraulic performance (i.e. the wave reflection, wave transmission, discharge of wave overtopping, and stability of breakwater) of four perforated breakwaters as measured by physical experiments in a wave flume. The irregular wave was generated by the wave condition of the target site. Three breakwaters were designed: a perforated wall with a single chamber for a 50-year return period and two perforated walls with double chambers for a 100-year return period. Based on experimental results, the breakwater with a double chamber showed the best performance of 0.612, 0.102, and 0.076 m3/(m · s) for the reflection, transmission coefficient, and overtopping discharge, respectively. In particular, in the stability experiment of the armor units and perforated caissons, the breakwater with double chamber has not experienced any failure in any of the test cases. [ABSTRACT FROM AUTHOR]

This paper experimentally explored the influence of the wave spectrum shape variation on breakwater design. The energy spectrum function generally considered for the design of coastal structures is the JONSWAP spectrum. The laboratory results were therefore used to assess the impact of changing the spectrum shape parameter (PEF). We analysed armour stability and wave overtopping in a wave flume with a geometric similarity ratio of 1:30. The experimental results showed that the PEF has maximum influence on overtopping and wave pressures on the crown wall. For a PEF value of 3.3, overtopping was much higher (30% to 100% higher) than with a PEF of 1. Pressure on the crown wall was 20% higher with a PEF of 3.3 in comparison with that for a PEF equal to 1. The stability of the breakwater's block armour is less sensitive to the PEF variation. [ABSTRACT FROM AUTHOR]

A novel concept of a surge wave energy converter for nearshore applications is investigated experimentally. The centimetre-sized prototype developed in this work represents a proof of concept of a submerged system, which entails a hybrid transduction solution for the electrical conversion of wave energy, that uses piezoelectric elements (PZEs) and dielectric elastomer generators (DEG). The idea is to exploit the horizontal pressure gradient and horizontal water velocity underneath the waves to compress the PZE and inflate each half wave period a soft variable capacitance, which composes the DEG. The electrical charges created by the PZE are used to polarize the DEG, which is able to multiply the input energy. This hybridization is conceived to allow the system to generate electrical energy from waves without conventional high voltage supplies, thus reducing production costs and allowing standalone clean electrical generation. The article provides the preliminary fluid-mechanical measurements performed in a wave flume with a first version of the prototype and supported by a model comprising the fluid/structure interaction, the materials response, and the electrical operations. An estimation of the output energy of a small-sized prototype in constant charge mode is computed, and perspectives for optimizing the system are presented. [ABSTRACT FROM AUTHOR]

Multiple reflections of the waves between structure and wavemaker in hydraulic flumes could change the frequency content of the desired incident wave or result in resonance. A prominent approach to avoid multiple reflections is active control of the wavemaker. This paper proposes a simple and practical active control algorithm for piston-type wavemaker. The block diagram of the control system is presented in real time domain. It is shown that there is no need to use any transfer function or filter in the feedback and feed forward loops and the use of constant gains can yield acceptable results. In the operating frequency range (0.25–2 Hz), it is revealed that the proposed system is very effective at suppressing the excitation of resonant sloshing for regular wave. In the case of irregular waves, it is depicted that the experimental waves agree quite well with the desired wave elevation in frequency domain. In addition, comparison of the results obtained both with and without absorption discloses the good characteristics in time domain. [ABSTRACT FROM AUTHOR]

This article presents a method for obtaining the spatial free surface elevation and velocity field for the water surface in a wave flume over a relatively large measurement area for this type of application (approximately 1.5 m × 1.5 m). The technique employs proprietary videogrammetry software to post-process stereo images captured by multiple synchronised machine vision cameras. Dimensional resolution and other limitations are similar to that experienced for particle imaging velocimetry systems (x, y resolution of 2 mm). Imaging of the free surface was enabled by the use of millions of bespoke slightly positively buoyant fluorescent flakes. Ultraviolet light was used as the primary light source to excite the fluorescent flakes. Reflected ultraviolet light was attenuated by a high-pass filter fitted to the cameras so that only the emitted light from the fluorescent flakes was visible. The software was validated using a simple linear translation experiment. An application is demonstrated for the radiated wave field generated from a submerged sinusoidal heaving sphere for two cases: one single and five consecutive oscillations. Results agree with linear wave theory which indicates that the floating flakes had minimal impact on the water surface particle motion at the scale tested. It is, therefore, concluded that spatial measurement of the free surface elevation and velocity using the method presented has good resolution over a large measurement field. The flakes were found to follow the free surface well, but the measurement area is constrained to where the pattern of flakes exists in the image. Hence, application of floating markers is not suitable for experiments with significant outflow/upwelling which would wash away the floating markers from the intended measurement area. [ABSTRACT FROM AUTHOR]

A comprehensive experimental study was carried out on the regular wave attenuation with a trapezoidal pontoontype floating breakwater (FB) in deep water. The functionalities of two simple FB geometries consist of a rectangle and a trapezoid with the slope of 60° were investigated under the wave attack. A two-dimensional wave flume was used in the experiment; the incident, transmitted waves, mooring line forces and motion responses of the floating breakwaters were measured. Also the influence of the sea state conditions (incident wave height and wave period) and structural parameters (draught of the structure) were investigated using the trapezoidal FB. Our experimental results indicated that the trapezoidal FB significantly reduced the wave transmission and mooring line force when compared with rectangular FBs. A new formula was developed in order to predict the value of the transmission coefficient in trapezoidal FBs with the slope of 60°. Experimental data showed to be consistent with the results of the formula. [ABSTRACT FROM AUTHOR]

Experimental investigations were carried out to assess the wave reflection characteristics of slotted vertical barriers with an impermeable rear wall. This study was carried out to investigate whether these barriers can be used instead of sloped rubble mounds, which occupy a significant area in ports/harbors/marinas, for wave energy dissipation. Thirty-seven different wave barriers (1 vertical wall, 6 different sloped breakwaters, and 30 slotted vertical barriers with porosity in the range of 10-50% and 1-6 slotted barriers) were tested in random wave fields of the JONSWAP spectra in different combinations of significant wave heights and peak periods. For relatively long waves (water depth/wavelength ratio of d/Lp>0.2), the performances of many combinations of slotted vertical barriers were much better than those of the conventional sloped rubble-mound breakwaters. The results of this study show that by increasing the number of porous walls from one to six, it is possible to reduce the value of the reflection coefficient from 0.9 to 0.3, especially for a d/Lp greater than 0.2. Also, the results show that for a d/Lp less than 0.2, increasing the number of porous walls did not significantly reduce wave reflection. Overall, these results suggest that slotted barriers can be a good alternative to sloped rubble breakwaters for ports, harbors, and marinas, especially in places where good-quality stones are expensive. In addition, this solution helps increase the effective use of space inside the harbor better than do sloped rubble-mound structures. [ABSTRACT FROM AUTHOR]

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 Gdańsk (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 Gdańsk Bay, in the region of Gdynia Orłowo (Orłowo 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 Gdańsk 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. [ABSTRACT FROM AUTHOR]

An original method is proposed to extract drift velocity induced by waves propagating in a wave flume. The particle image velocimetry technique is employed to measure velocity fields under regular gravity waves propagating at a constant depth. Based on the measurements, the Eulerian mean current velocity is determined. The instantaneous velocity fields are integrated to calculate particle trajectories and the Lagrangian time-averaged vertical distribution of mass-transport velocity. The Stokes drift velocity is determined by subtracting the Eulerian mean current from the Lagrangian mass-transport velocity. The results are in good agreement with theoretical second-order irrotational solution and confirm applicability of the weakly nonlinear solution for calculating transport processes associated with propagating ocean waves. [ABSTRACT FROM AUTHOR]

The physical simulation method of wave groups in a wave flume is proposed and verified by the experiments. The experimental results demonstrate that random waves with desired wave groupiness, which simultaneously includes the wave group height and length, can be generated satisfactorily at the specified position in a wave flume using the proposed method. Furthermore, the transformation properties of the wave groupiness along the flat-bottomed wave flume are investigated based on the physically simulated waves. Associated proposals with the physical simulation of wave groups are given. [ABSTRACT FROM AUTHOR]

Khoury, A., Jarno-Druaux, A., and Marin, F., 2013. Experimental simulation of sandy beaches under waves and tides: hydro-morphodynamic analysis Proceedings 12th International Coastal Symposium (Plymouth, England), Journal of Coastal Research, Special Issue No. 65, pp. 1791-1796, ISSN 0749-0208.--> Numerous studies have been carried out on sandy beach morphology; however, the physical processes which govern beach morphodynamic are still not well understood, despite the significance of this subject in view of the direct applications for coastal erosion. The present work brings a contribution to the study of these processes from well controlled tests carried out in a 10-m-long and 0.49-m-wide wave flume with macro - and mega-tidal regime simulations. The tests were carried out with very fine or fine sand of relative density s=2.65. The incident waves and the free surface in the shoaling zone were measured with resistive probes. The wave breaking height and the free surface in the swash zone were recorded with an optical method. The temporal evolution of bottom profiles was obtained using an acoustic method. Intertidal bars were generated; such bars were previously not observed in physical modeling to the authors' knowledge. Present experimental results are compared with field observations. Formation processes of intertidal bars are analyzed; we show in particular the significant effect of the relative tide range, of waves asymmetry, and of subtidal bars on these processes. Small local variations of the beach profile in the surf zone exhibit significant outcomes on the runup. [ABSTRACT FROM AUTHOR]

The seawater desalination process is a strong bet for developing regions like the Spanish Mediterranean, to satisfy the increasing fresh water demand, or the Canary Islands, being the desalination the most important artificial water resource. The main characteristic of the waste brine disposal resulting from the desalination process is its high salinity, and consequently, its higher density in comparison with that of the environment. Therefore, the discharge of the concentrated effluent into the sea may cause a negative impact in the sea water quality and its ecosystems, specially regarding the sea grass meadows that cover the Mediterranean coast. In order to make the development of the desalination plants sustainable, the Spanish Ministry of the Environment and Rural and Marine Affairs agreed to invest in Experimental Development Projects within its National Plan for Scientific Research, Development and Technological Innovation. The project entitled "Development and implementation of a methodology to reduce the environmental impact of brine discharges from desalination" has been approved and supported as a part of the Plan. This project is being carried out by the University of Cantabria in collaboration with the Spanish Centre for Experimentation on Public Works (CEDEX). The aim of this study is to find which discharge devices produce the biggest brine dilution, to make the environmental impact on the biocenosis as low as possible. Under this perspective, the behaviour of different jets and discharge devices were investigated in physical models. To this purpose, different instrumentation has been using to measure the conductivity and velocity in the near and far field of the effluent, including a micro scale conductivity and temperature instrument or a doppler velocity profiler. Part of the experiments have been performing in a wave flume of 30 m long, 1m wide and 2 m high, simulating a 3D superficial discharge from a beach with a fixed slope. In this flume different simulations, changing the wave variable (height and period, in an irregular JONSWAP train wave), have been testing. The results obtained with the performed physical model will be presented in this communication. [ABSTRACT FROM AUTHOR]

• Background and Aims Hydraulic pulling forces arising from wave action are likely to limit the presence of freshwater macrophytes in shallow lakes, particularly those with soft sediments. The aim of this study was to develop and test experimentally simple models, based on linear wave theory for deep water, to predict such forces on individual shoots.• Methods Models were derived theoretically from the action of the vertical component of the orbital velocity of the waves on shoot size. Alternative shoot‐size descriptors (plan‐form area or dry mass) and alternative distributions of the shoot material along its length (cylinder or inverted cone) were examined. Models were tested experimentally in a flume that generated sinusoidal waves which lasted 1 s and were up to 0·2 m high. Hydraulic pulling forces were measured on plastic replicas of Elodea sp. and on six species of real plants with varying morphology (Ceratophyllum demersum, Chara intermedia, Elodea canadensis, Myriophyllum spicatum, Potamogeton natans and Potamogeton obtusifolius).• Key Results Measurements on the plastic replicas confirmed predicted relationships between force and wave phase, wave height and plant submergence depth. Predicted and measured forces were linearly related over all combinations of wave height and submergence depth. Measured forces on real plants were linearly related to theoretically derived predictors of the hydraulic forces (integrals of the products of the vertical orbital velocity raised to the power 1·5 and shoot size).• Conclusions The general applicability of the simplified wave equations used was confirmed. Overall, dry mass and plan‐form area performed similarly well as shoot‐size descriptors, as did the conical or cylindrical models of shoot distribution. The utility of the modelling approach in predicting hydraulic pulling forces from relatively simple plant and environmental measurements was validated over a wide range of forces, plant sizes and species. [ABSTRACT FROM AUTHOR]

Green water events may present different features in the initial stage of interaction with the deck of a structure. It is therefore important to investigate the evolution of different types of green water, since not all the events interact with the deck at the same time. In this paper, the evolution of three types of green water events (dam-break, plunging-dam-break, and hammer-fist) are studied. The water surface elevations and volumes over the deck in consecutive green water events, generated by incident [wave trains in a wave flume, were analyzed using image-based methods. The results show multiple-valued water surface elevations in the early stage of plunging-dam-break and hammer-fist type events. Detailed experimental measurements of this stage are shown for the first time. The effect of wave steepness on the duration of the events, maximum freeboard exceedance, and volumes were also investigated. Although the hammer-fist type showed high freeboard exceedances, the plunging-dam-break type presented the largest volumes over the deck. Some challenges for further assessments of green water propagation are reported. [ABSTRACT FROM AUTHOR]

The wave overtopping discharge at coastal defense structures is directly linked to the freeboard height. By means of physical modelling, experiments on wave overtopping volumes at sloped coastal structures are customarily determined for constant water levels and static wave steepness conditions (e.g., specific wave spectrum). These experiments are the basis for the formulation of empirically derived and widely acknowledged wave overtopping estimations for practical design purposes. By analysis and laboratory reproduction of typical features from exemplarily regarded real storm surge time series in German coastal waters, the role of non-stationary water level and wave steepness were analyzed and adjusted in experiments. The robustness of wave overtopping estimation formulae (i.e., the capabilities and limitations of such a static projection of dynamic boundary conditions) are outlined. Therefore, the classic static approach is contrasted with data stemming from tests in which both water level and wave steepness were dynamically altered in representative arrangements. The analysis reveals that mean overtopping discharges for simple sloping structures in an almost deep water environment could be robustly estimated for dynamic water level changes by means of the present design formulae. In contrast, the role of dynamic changes of the wave steepness led to a substantial discrepancy of overtopping volumes by a factor of two. This finding opens new discussion on methodology and criteria design of coastal protection infrastructure under dynamic exposure to storm surges and in lieu of alterations stemming from projected sea level rise. [ABSTRACT FROM AUTHOR]

This paper investigates on a Wave Energy Converter (WEC) named Energy & Protection, 4th generation (EP4). The WEC couples the energy harvesting function with the purpose of protecting the coast from erosion. It is formed by a flap rolling with a single degree of freedom around a lower hinge. Small-scale tests were carried out in the wave flume of the maritime group of Padua University, aiming at the evaluation of the device efficiency. The test peculiarity is represented by the system used to simulate the Power Take Off (PTO). Such dummy PTO permits a free rotation of two degrees before engaging the shaft, allowing the flap to gain some inertia, and then applying a constant resistive moment. The EP4 was observed to reach a 35% efficiency, under short regular waves. The effects, in terms of coastal protection, are small but not negligible, at least for the shortest waves. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Sierra, J. P., Gironella, X., Sánchez-Arcilla, A., Sospedra, J. and Alsina, J. M., 2007.Hybrid modelling of scouring – deposition in front of a coastal structure. Journal of Coastal Research, SI 50 (Proceedings of the 9th International Coastal Symposium), 364 – 368. Gold Coast, Australia, ISSN 0749.0208 Wave-structure interactions in the presence of a sand bottom constitute a complex problem, which is not yet satisfactorily solved. The process of erosion/deposition at the front toe of the structure, in particular, is only crudely defined up to the point that its quantitative dependence on wave conditions, structural permeability or sediment characteristics is poorly known. This paper analyses the scouring/deposition at the toe of detached breakwaters using large scale data from the CIEM wave flume in Barcelona and the simulations from a numerical wave-current-sediment transport model. The LIMORPH code has been developed and tested in a number of European Union research projects. The large scale wave flume data come from past (SCARCOST) and present (HYDRALAB III) European Union research projects. The paper discusses the relative merits of numerical/physical models and the gain in understanding for the underlying hydro/morphodynamic processes when a combination of both types of models is used. This is illustrated by the influence of wave characteristics and freeboard in erosion/deposition patterns. [ABSTRACT FROM AUTHOR]