bluuebunny/crossref_metadata_2025 huggingface dataset:
A 3D NUMERICAL INVESTIGATION OF FINE SEDIMENT TRANSPORT IN AN OSCILLATORY CHANNEL
Authors: Hsu Tian-Jian , Yu Xiao , Ozdemir Celalettin E. , Balachandar S.
Published: December 2012

Recent findings on a diverse range of muddy seabed states revealed by 3D, turbulence-resolving simulations are first reviewed. These transitions have critical implications to offshore delivery of fine sediment in the ocean and wave dissipation. Assuming a small particle Stokes number, the Equilibrium approximation to the Eulerian two-phase flow equations is applied. The resulting simplified equations are solved with a high-accuracy pseudo-spectral scheme in an idealized oscillatory bottom boundary layer (OBBL). For a typical energetic muddy shelf, the Stokes Reynolds number Reï,, is no more than 1000 and all of the scales of flow turbulence and their interaction with sediments are resolved. With increasing sediment availability or settling velocity, the seabed state evolves from well-mixed sediment distribution, to the formation of lutocline and a complete laminarization of the OBBL. More recently, we further include rheological stress in the simulations in order to study the interplay between turbulence and rheology in determining the flow regimes and hydrodynamic dissipation. To include rheological stress, we extend the numerical model with a hybrid spectral and compact finite difference scheme. A sixth-order compact finite difference is implemented in vertical direction to keep the spectral-like accuracy. The model is validated with analytical solutions using simple Newtonian rheology in laminar condition. Preliminary results at Reï¤=600 reveal that when rheology is incorporated, high viscosity can trigger earlier laminarization of OBBL. When OBBL is laminarized, sediments settle and higher concentration is accumulated near the bed that further enhances viscosity and hydrodynamic dissipation. Our preliminary finding that rheology encourages laminarization may explain why large attenuation of surface waves over muddy seabed is ubiquitous and the highest dissipation rate is often observed during the waning stage of a storm.
INVESTIGATIONS ON SCOUR DEVELOPMENT AT TRIPOD FOUNDATIONS FOR OFFSHORE WIND TURBINES: MODELING AND APPLICATION
Authors: Stahlmann Arne , Schlurmann Torsten
Published: December 2012

Regarding offshore constructions, there is still a lack in knowledge of scour progression for complex structures like foundations for offshore wind energy converters at present, which is however necessary for its dimensioning. As an example of such complex structure types, tripod foundations are constructed in German offshore wind farms at present. In order to describe physical processes and influencing factors on scour progression from a scientific point of view, comprehensive investigations on the scouring phenomena for tripod foundations have been carried out and will be partly presented here. The overall investigation method consists of a combination of 1:40 small and 1:12 large scale physical model tests in wave flumes, numerical simulations using CFD methods and in-situ measured scour data. For the numerical modeling part, a sediment transport model formulation has been implemented into OpenFOAM software code. The results show a general variability of scour depending on the load boundary conditions and structural parameters. Scours occur both at the foundation piles and directly under the structure, which in this form could not be predicted using standard approaches, but which has to be taken into account when regarding the soil mechanical stability and the final dimensioning of the foundations.
MANAGEMENT OF AEOLIAN SAND TRANSPORT ON A DIKE, DUNKIRK SEAPORT, FRANCE
Authors: Tresca Antoine , Ruz Marie-Hélène , Raison Stéphane , Grégoire Pascal
Published: December 2012

The shoreline of Dunkirk Seaport partly consists of a macrotidal beach oriented WSW-ENE backed by a 6 km long coated dike called "digue du Braek†. Aeolian sand transport was estimated on asphalt by means of sand traps. Also, time-averaged wind speed profiles were measured using cup anemometers under various wind velocities and directions along a transversal profile on the dike and the upper beach. High rates of sand transport enabled the setup of different kinds of experimental windbreaks on asphalt, in order to test potential dune formation on this kind of substrate. Under oblique onshore winds, it was regularly observed that amounts of sand captured in the traps placed on the dike were more important than those in traps placed on the upper beach. These results were related to sand sources: windblown sand captured on the dike originated from the coastal dunes developed at the dike toe, while sand trapped on the upper beach came from the tidal zone were aeolian transport is limited by complex intertidal bar-trough topography. It also appeared from the topographic surveys carried out on the windbreaks that although their location seemed to play a major role on the amount of sand captured, fences and synthetic fabrics deployed on sandy surfaces were also able to trap windblown sand on the seaport dike.
RIVERBED EVOLUTION OF YANGTZE ESTUARY AND ITS RESPONSE TO THE HYDRODYNAMIC CHANGES AT UPSTREAM
Authors: Chen Yongping , Jiang Ninglin , Zhang Changkuan
Published: December 2012

The riverbed evolution of upper part of Yangtze estuary, Chengtong reach, is analyzed by comparison of 6 sets of bathymetry data during 1977~2011. The significant changes of water depth profiles along 6 representative cross-sections indicate the reach is still in the process of development. In order to get a better understanding of the effect of river discharge at upstream on the riverbed evolution of Chengtong reach, a series of numerical experiments are implemented by specifying different river discharge conditions at the upper boundary. The corresponding discharge ratio at main sub-reaches is compared to reveal the response of the riverbed evolution to the hydrodynamic changes at upstream. The results show that with the increase of river discharge, the discharge ratio in the main channels of Fujiangsha sub-reach and Rugaosha sub-reach increases, but it changes to decrease when the upstream river discharge becomes very large; however, the discharge ratio in the main channel of Tongzhousha sub-reach always decreases with the increase of river discharge at upstream.
FIELD MEASUREMENTS OF BEDFORMS IN A RIP CHANNEL ON A MACRO-TIDAL BEACH
Authors: Thorpe Antony , Miles Jon , Masselink Gerd , Russell Paul , Scott Tim , Austin Martin
Published: December 2012

A Sand Ripple Profiler (SRP) was deployed in a rip channel on a dissipative sandy beach to measure bedform height (âˆ†), length (Î») and migration rate (Mr¬) throughout a macro-tidal cycle with an offshore significant wave height of 0.7 m and peak period of 10 s. At lower tidal elevations in the strong offshore flow of the rip current (maximum = 0.4 m/s) bedforms (âˆ† = 0.15 m, Î» = 3 m) were found to migrate offshore (Mr = 0.21 m/hr). Outside of active rip current conditions (water depth (h) = >~2.5 m) bedforms were found to be of smaller scale (âˆ† = 0.09 - 0.12 m, Î» = 1 - 1.2 m) migrating onshore at a rate of 0.35 m/hr at mid tide (h = 3.3 m) and 0.03 m/hr at high tide (h = 6.3 m). Onshore migration rates were found to increase with increased wave skewness and velocity variance.
DUNE EROSION ABOVE REVETMENTS
Authors: Van Thiel de Vries Jaap
Published: December 2012

In a situation with a narrow dune, the dune base can be protected with a revetment to reduce dune erosion during extreme events. To quantify the effects of a revetment on storm impact, the functionality of the numerical storm impact model XBeach (Roelvink et al., 2009) is extended to account for the complex morphodynamics around revetments. Here the focus is on dune erosion above revetments, which is simulated with a simple avalanching algorithm that is triggered by the combined runup of short waves and long waves. The simulated runup statistics depend on the incident wave groupiness and associated long wave variance.
STUDY OF CLIFF SHORELINE EROSION
Authors: Gómez-Pina Gregorio , Muñoz-Pérez Juan José , Figueres Miguel , Garrido Joaquín M. , Ponce de León Daniel , Pérez Angela , Velasco Marta , Lizondo Susana
Published: December 2012

In this paper the cliff shoreline erosion on the coastline between Punta Montijo and the Chipiona Port (Cadiz, Spain) is studied. The reasons which cause this erosive phenomenon and the future erosive tendency of these cliffs are estimated, obtaining magnitudes of recession and the rate at which it will occur. Analysis of the current situation has been carried out by determining its plan shape, the study of the theoretical erosion profile of the cliffs and the verification of their failure. The future evolution of the cliffs shoreline has been analysed through the simulation of its recession and the study of the profile response to storm wave action. Finally, is presented a model to estimate the recession of the cliff shoreline.
MODELING ALTERNATIVES FOR EROSION CONTROL AT MATAGORDA COUNTY,TEXAS, WITH GENCADE
Authors: Frey Ashley , Rosati, III James , Connell Kenneth J. , Hanson Hans , Larson Magnus
Published: December 2012

Matagorda Peninsula and Sargent Beach, Texas, USA, have experienced some of the highest rates of erosion along the Texas coast. In order to increase protection from tropical events and slow beach habitat erosion, several structural alternatives were studied. These alternatives were modeled with GenCade, a newly developed 1D shoreline change and sand transport model. GenCade was calibrated and validated over the 60 miles of shoreline in Matagorda County. Then separate GenCade grids and simulations were conducted for the structural alternatives at Matagorda Peninsula and Sargent Beach. At Matagorda Peninsula, different groin lengths and spacing between groins were modeled with and without beach fills and mechanical bypassing. The alternatives at Sargent Beach included detached breakwaters, groins, and beach fills. Although the process described in this paper only includes a small part of a more detailed study, these simulations helped lead to a recommendation of the selected alternatives for preliminary engineering design.
MODELLING MULTI-DECADAL SHORELINE VARIABILITY AND EVOLUTION
Authors: Mole Melissa A. , Davidson Mark A. , Turner Ian L. , Splinter Kristen D. , Goodwin Ian D. , Short Andrew D.
Published: December 2012

A robust and practical methodology for predicting future shoreline behaviour along sandy coastlines would be valuable to a broad range of coastal engineering applications. Present approaches for predicting shoreline evolution range from simple linear trend models, which cannot predict observed complex behaviour, to coupled hydrodynamic / sediment transport models, with seasonal to multi-year forecasting generally beyond present model capabilities. In this work a simple empirical shoreline variability model, ShoreFor (Shoreline Forecast), is investigated using a multi-decadal dataset to assess model performance at daily to decadal timescales. Model performance is assessed at five alongshore locations within an embayed study site that experience varying exposure to the offshore wave climate due to prominent adjacent headlands and display alongshore variable behaviour. To determine model sensitivity to input wave conditions, both the measured offshore and transformed (modelled) nearshore wave data are used and results compared. Strengths and limitations of the ShoreFor model are identified and discussed, along with ongoing model development and planned application of this modelling technique for shoreline forecasting using future water level and wave climate scenarios.
TRANSPORT OF RESUSPENDED DREDGED SEDIMENT NEAR CORAL REEFS AT APRA HARBOR, GUAM
Authors: Lackey Tahirih , Gailani Joseph , Kim Sung-Chan , King David , Shafer Deborah
Published: December 2012

Model studies have been conducted to investigate the potential coral reef exposure from proposed dredging associated with development of a new deepwater wharf in outer Apra Harbor, Guam. The Particle Tracking Model (PTM) was applied to quantify the exposure of coral reefs to material suspended by the dredging operations at proposed sites. Key PTM features include the flexible capability of continuous multiple releases of sediment parcels, control of parcel/substrate interaction, and the ability to track vast numbers of parcels efficiently. This flexibility has allowed for model simulation of the combined effects of sediment release from clamshell dredging, of chiseling to fracture limestone blocks, of silt curtains, and of flocculation. Because the rate of material released into the water column by some of the processes is not well understood or a priori known, the modeling protocol was to bracket parameters within reasonable ranges to produce a suite of potential results from multiple model runs. Data analysis results include mapping the time histories and the maximum values of suspended sediment concentration and deposition rate. Following exposure modeling, the next phase of the analysis has been an ecological assessment to translate the PTM exposure level predictions into predicted amounts of coral reef damage. The level of potential coral reef impact will be an important component of the final selection process for the new deepwater berthing site.
INNOVATIVE BREAKWATERS DESIGN FOR WAVE ENERGY CONVERSION
Authors: Vicinanza Diego , Stagonas D. , Muller G. , N¸rgaard J. H. , Andersen T.L.
Published: December 2012

This paper intends contributing to an economically and environmentally sustainable development of coastal infrastructures by investigating the possibility of combining together breakwaters and Wave Energy Converters (WEC). The latter change the wave energy to electricity, which may serve both the rubble mound breakwaters and seawalls related activity and the energy demand of small human communities. Wave loadings and overtopping on a seawall and rubble mound breakwater with front reservoir are discussed on the basis of physical 2-D model tests carried out at University of Southampton (UK) and Aalborg University (DK).
STABILITY OF RUBBLE MOUND BREAKWATERS WITH A BERM
Authors: Van Gent Marcel , Smith Gregory M. , Van der Werf Ivo
Published: December 2012

The stability of rock slopes with a horizontal berm has been studied by means of physical model tests. This paper is focussed on the rock slope stability of the slopes above and below the berm. By applying a berm the rock size can be reduced compared to the required rock size for a straight slope without a berm. This reduction can be significant for the slope above the berm. The influence of the slope angle (1:2 and 1:4), the width of the berm, the level of the berm, and the wave steepness have been investigated. Based on the test results prediction formulae have been derived to quantify the required rock size for rubble mound breakwaters with a berm.
STABILITY OF INTERLOCKING ARMOUR UNITS ON A BREAKWATER CREST
Authors: Van den Bosch Ilse , Ten Oever Erik , Bakker Pieter , Muttray Markus
Published: December 2012

The hydraulic stability of single layer, interlocking armour units on low crested and submerged breakwaters was investigated in 2D hydraulic model tests. Displacements of armour units and rocking were monitored and have been applied as indicators for the armour layer stability on the crest, front and rear slope. The effect of freeboard, packing density and wave steepness on the armour layer stability have been investigated. The stability of interlocking concrete armour units on low crested and submerged structures is qualitatively different from rock armour. About 40% to 50% larger armour units are required on the seaward slope and crest of low crested structures (as compared to conventional high crested breakwaters). About 35% larger armour units are required on the rear slope. Larger armour units are not required on submerged breakwaters if the water depth on the crest exceeds 50% of design wave height.
WAVE OVERTOPPING AT BERM BREAKWATERS IN LINE WITH EUROTOP
Authors: Sigurdarson Sigurdur , Van der Meer Jentsje W.
Published: December 2012

The paper presents the development of a new overtopping formula for berm breakwaters. Overtopping data from hydraulic model tests of berm breakwaters have been gathered and reanalysed in line with the procedure in the EurOtop Manual. The data shows a clear dependency on wave period or wave steepness, which is in contrast to the main conclusion of the CLASH project and the EurOtop Manual for conventional rubble mound breakwaters. The formula is roughly validated on prototype performance.
BREAKWATERS UNDER CONSTRUCTION EXPOSED TO OBLIQUE WAVES
Authors: Mulders Patrick , Verhagen Henk Jan
Published: December 2012

A new series of physical model tests were conducted to analyse the behaviour of a breakwater core when it becomes exposed to wave attack. The emphasis of this research was on the measured influence of a wide stone grading on both the deformation of a breakwater trunk and the occurring longshore transport. This behaviour was investigated for both head-on and oblique waves using two different wave loads. The findings were compared to the currently available formulas and the validity of these formulas for the tested range of parameters was (re)checked. In general a clear distinction was found in the processes between tests with narrow grading and wide grading. It turned out that both the parameters describing the two-dimensional deformation and the longshore transport show an increase for wider grading.
FAILURE MECHANISM OF KAMAISHI BREAKWATERS DUE TO THE GREAT EAST JAPAN EARTHQUAKE TSUNAMI
Authors: Arikawa Taro , Sato Masaharu , Shimosako Kenichiro , Hasegawa Iwao , Yeom Gyeong-Seon , Tomita Takashi
Published: December 2012

Many breakwaters were damaged by the Great East Japan Earthquake of March 11, 2011. The majority of the breakwaters were destroyed or deformed under tsunami overflow; however, the failure mechanism under tsunami overflow is not clear. Therefore, with the main objective of this report being to clarify the stability of breakwaters under tsunami overflow, hydraulic model experiments and numerical simulations were conducted with Kamaishi Bay breakwaters as the subject, and failure mechanisms of the trunk of the breakwaters were examined.
STABILITY OF HARDLY RESHAPING BERM BREAKWATERS
Authors: Lykke Andersen Thomas , Van der Meer Jentsje W. , Burcharth Hans F. , Sigurdarson Sigurdur
Published: December 2012

The present paper deals with stability of berm breakwaters designed to be hardly or sometimes partly reshaping. Burcharth (2008, 2011) showed by comparison to the performance of a prototype berm breakwater that the Van der Meer formulae for stability of conventional rock armour including low crests could predict the deformations of the front slope in terms of the eroded area. The present paper verifies the method by comparison to model test results. It is found that the Van der Meer formula for plunging waves predicts very well the eroded area of the reshaped profile, even if it is applied in the surging wave area. Moreover, a simple method to estimate the erosion area based on recession formulae and the depth of intersection of reshaped and initial profile is presented and is applicable for hardly reshaping to fully reshaping. Even when using the only very simple and inaccurate estimate of the depth of intersection the last method leads to scatter quite similar to the first method when considering hardly and partly reshaping berm breakwaters. The influence of the slope angle is though expected to be more correctly included for hardly reshaping breakwaters using the method for straight non-overtopped slopes when the slope angle is 1:1.5 or flatter.
ADAPTATION OF EXISTING BREAKWATERS TO SEA LEVEL RISE - OVERTOPPING EFFECT
Authors: Nguyen Dang-Trinh , Brossard Jérôme
Published: December 2012

This paper describes the wave overtopping measurements of small scale maritime breakwater in sea level rise scenarios which are supposed in French program GICC (Gestion et Impacts du Changement Climatique - Management and Impacts of Climate Change). Many reinforced solutions have been carried out with the purpose to conserve the overtopping rate; among them, the influence of raising freeboard crest is analyzed. The test results are compared with results from literature and with the empirical models presented by Owen (1980), Van der Meer (1998) and Besley (1999). Since then, a guideline is proposed for a better prediction of wave overtopping with various types of high crown-wall.
OPEN TYPE QUAY STRUCTURES UNDER PROPELLER JETS
Authors: Yuksel Yalcin , Kayhan Selahattin , Celikoglu Yesim , Cihan Kubilay
Published: December 2012

In recent years, dramatically increases in ship dimensions and installed engine power, introduction of new type of special purpose ships and use of roll-on/roll-of, ferries, container ships can cause damage which in many cases threatens to undermine berth structures. Vessel jets of these types of ships can change flow area and cause erosion and scour around foundation of berth structures. Due to the damages in berth structures maintenance and repair cost may increase and also cause management losses. For this reason vessel jet induced the flow area around the berth structures during ships berthing and un-berthing operations are extremely important factor for the port structure design. This study is related with investigation of the flow characteristics at the sea bed around the pile, experimentally. Vessel jets were simulated both as circular wall jet and also propeller jet. The objective of this study is to determine the sea bed shear stress and velocity profiles along the jet axis for open type wharf structures (around a cylindrical piles and also on the slopes). Hot film anemometers were used to measure the magnitude of the bed shear stresses. The results from propeller jet experiments explained the erosion over the slopes. Bed shear and velocity profile measurements were carried out on the rigid bed conditions.
TURBINEâˆ'CHAMBER COUPLING IN AN OWC WAVE ENERGY CONVERTER
Authors: Lopez Ivan , Iglesias Gregorio , Lopez Mario , Castro Francisco , Rodríguez Miguel ngel
Published: December 2012

Oscillating Water Column (OWC) systems are one of the most popular technologies for wave energy conversion. Their main elements are the chamber with the water column and the air turbine. When studying the performance of an OWC system both elements should be considered together, for they are effectively coupled: the damping exerted by the air turbine affects the efficiency of the conversion from wave power to pneumatic power in the OWC chamber, which in turn affects the air flow driving the turbine. The optimum level of damping is that which maximizes the efficiency of the conversion from wave to pneumatic power. In this work the turbine-chamber coupling is studied through a combination of physical and numerical modeling.
AN EVALUATION OF THE PHYSICAL IMPACT AND STRUCTURAL INTEGRITY OF A GEOTEXTILE SURF REEF
Authors: Rendle Emma Jane , Davidson Mark
Published: December 2012

Geotextile artificial surfing reefs (ASR) are being considered by coastal planners due to their multifunctional potential for coastal protection and habitat provision, as well as additional recreational amenity. However, little research exists on the impact of submerged geotextile structures on the physical marine environment. Europe's first ASR was constructed in 2009 on the south coast of England in Boscombe and is the case study for this paper. This research investigates the claims regarding the structural resilience of an ASR, the modifications to the inshore wave climate and the shoreline response induced by the introduction of an ASR to a system. The Boscombe ASR has suffered from damage, two major geotextile sand filled containers have degraded in this shallow marine environment in two years post-construction. Observations and simulations presented indicate ameliorated wave field leeward of the ASR. There is little shoreline response, given the structures distance offshore, and no salient or widening of the beach has occurred.
SIMULATION OF EXTREME WAVE INTERACTION WITH MONOPILE MOUNTS FOR OFFSHORE WIND TURBINES
Authors: Gao Feng , Mingham Clive , Causon Derek
Published: December 2012

Extreme wave run-up and impacts on monopile foundations may cause unexpected damage to offshore wind farm facilities and platforms. To assess the forces due to wave run-up, the distribution of run-up around the pile and the maximum wave run-up height need to be known. This paper describes a numerical model AMAZON-3D study of wave run-up and wave forces on offshore wind turbine monopile foundations, including both regular and irregular waves. Numerical results of wave force for regular waves are in good agreement with experimental measurement and theoretical results, while the maximum run-up height are little higher than predicted by linear theory and some empirical formula. Some results for irregular wave simulation are also presented.
STABILITY PREDICTION ON ARMOR BLOCKS FOR SUBMERGED BREAKWATER BY COMPUTATIONAL FLUID DYNAMICS
Authors: Matsumoto Akira , Mano Akira , Mistui Jun , Hanzawa Minoru
Published: December 2012

An evaluation model of the critical condition on armor block stability for submerged breakwaters was proposed by the author before (2011). However, the effect of the force normal to the block was not included in the model. Moreover, the drag and inertia coefficients were set to 1.0 as tentative values. In this study, the proposed model is improved by the inclusion of the wave force in the normal direction and the use of the fluid force coefficients determined by a 3D numerical computation.
STABILITY OF WAVE-DISSIPATING CONCRETE BLOCKS OF DETACHED BREAKWATERS AGAINST TSUNAMI
Authors: Hanzawa Minoru , Matsumoto Akira , Tanaka Hitoshi
Published: December 2012

In recent years, the risk of occurrence of tsunamis generated by near shore earthquakes, such as, Tokai, Tonankai, Nankai and off-Miyagi is considered to be higher than before, as well as off shore tsunamis traveling long distances, e.g., the 2010 Chilean tsunami. On March, 11th, 2011 the huge, devastating tsunami generated by The 2011 off the Pacific coast of Tohoku Earthquake attacked and damaged the east coast area of Japan. Tsunami forces onto vertical walls, such as seawalls, has already been studied in detail, e.g., Asakura et al.(2002) and Kato et al.(2006). In Japan, detached breakwaters made with wave-dissipating concrete blocks such as Tetrapods have been widely applied. However, the effects of detached breakwater on tsunami disaster mitigation have not been studied. In our study, hydraulic model tests have been systematically and carefully carried out using solitary tsunami waves to evaluate the stability of concrete blocks following the our previous study on the effect of detached breakwaters from the viewpoint of reducing run-up and wave pressure onto seawalls behind the detached breakwaters (Hanzawa et al., 2011).
CIRCULATION PATTERNS AND SHORELINE RESPONSE INDUCED BY SUBMERGED BREAKWATERS
Authors: Villani Mara , Bosboom Judith , Zijlema Marcel , Stive Marcel J.F
Published: December 2012

Submerged shore-parallel breakwaters for coastal defence (henceforth SBWs) are a good compromise between the need to mitigate the effects of waves on the coast and the ambition to ensure the preservation of the landscape and water quality. However, if not properly designed, such structures can force circulation patterns that enhance shoreline erosion rather than shoreline accretion. Numerical models can be used to investigate the structure-induced circulation patterns and the resulting shoreline response. However, being computationally demanding these models are most suitable for advanced stages of the design process. The aim of this paper is to present a simple criterion to qualitatively identify whether an accretive or erosive circulation pattern can be expected in the lee of the structures. The criterion is based on analytical considerations and builds on the model presented by Bellotti (2004, 2007). It is validated against the non-hydrostatic free surface numerical model SWASH (Zijlema et al. 2011) and experiments performed by Haller et al. (2002). The validation indicates that the proposed analytical model is capable of providing a rapid first assessment of the potential shoreline response mode for SBW design.
TIME-DEPENDENT PERFORMANCE-BASED DESIGN OF CAISSON BREAKWATER CONSIDERING CLIMATE CHANGE IMPACTS
Authors: Kim Seung-Woo , Suh Kyung-Duck
Published: December 2012

A time-dependent performance-based analysis was conducted to analyze the influences of sea-level rise and wave-height increase due to climate change on caisson sliding of the breakwaters designed in different water depths. We used the Goda's spectral method to overcome the time-consuming problem in the calculation of the wave height at the breakwater site. In general, severe caisson sliding occurred when considering the climate change impacts. However, the influence of sea-level rise on the stability of caisson sliding is insignificant compared with that of wave-height increase. Especially, since the characteristics of caisson sliding are different depending on water depths, we have to establish countermeasure against these features for the design and maintenance of a caisson breakwater.
EXTERNAL AND INTERNAL WAVE SET-UP AT POROUS PBA REVETMENTS ON A SAND FOUNDATION
Authors: Foyer Gisa , Oumeraci Hocine
Published: December 2012

Wave set-up is generally considered for the stability analysis of beaches, but not or not explicitly for the design of revetments. Based on large-scale model results with regular and irregular waves, it is shown in this paper that this is not justified. For this purpose, the wave set-up on a porous bonded revetment and the related internal set-up in the sand foundation below the revetment are analysed for different breaker types. The results particularly show that (i) considerable set-up values are obtained for almost all breaker types, (ii) a good correlation exists with the deep water wave length for both external and internal set-up and (iii) the internal set-up is significantly affected by the wave set-up on the slope. Empirical formulae for the prediction of the external and internal set-up are also proposed for both regular and irregular waves.
THE EFFECT OF EMBANKMENT CREST WIDTH ON COMBINED OVERFLOW AND WAVE OVERTOPPING
Authors: Jones David , Reeve Dominic , Zou Qingping
Published: December 2012

In this paper a Reynolds-averaged Navier-Stokes based wave model (RANS) has been used to investigate how the discharge caused by combined overflow and wave overtopping of embankments is influenced by embankment crest width. The results demonstrate that embankments with a narrower crest width can expect significantly increased discharge in accordance with that expected for flow over weirs. The experimental results have been used to explain the difference in discharge found with the current design formulae for combined overflow and wave overtopping.
KD AND SAFETY FACTORS OF CONCRETE ARMOR UNITS
Authors: Medina Josep R. , Gómez-Martín M. Esther
Published: December 2012

Recommended design KD are associated to implicit global safety factors to Initiation of Damage (IDa) and Initiation of Destruction (IDe). Zero-damage criterion is valid for double-layer armors of massive CAUs, but single-layer armors require a lower-than-zero damage criterion. A simple methodology is proposed to calculate design KD for Cubipod armors and to obtain reasonable explicit global safety factors to IDe and IDa when compared to benchmark CAUs. The stringent SF(IDe5%) is the lowest for double-layer trunk armors, higher for double-layer roundhead armors and the highest for single-layer trunk armors. Single-layer roundhead armors were not analyzed.
ON MOORING DESIGN OF WAVE ENERGY CONVERTERS: THE SEABREATH APPLICATION
Authors: Martinelli Luca , Ruol Piero , Cortellazzo Giampaolo
Published: December 2012

The design of a mooring system of a Wave Energy Converter is a challenging process that points out several unsolved technical problems, mostly related to the highly non-linear hydrodynamic phenomena occurring when high waves (e.g. 8 m high with 200 m wavelength) propagate in relatively shallow waters (e.g. 20 m). The aim of this note is to point out the relevance of the non-linear response of a WEC anchored in relatively shallow waters (shallow in the "non-linear† sense) in terms of loads applied to the mooring lines. Further, the effects of this cyclic load on the anchors is investigated. Note that to some extent it is like checking the importance of geotechnical and coastal engineers in the design process of the WEC structure and its mooring system (typically carried out by naval architects). The whole mooring design process is first outlined and then it is schematically applied to a specific case, namely a promising Italian device named SeaBreath (www.seabreath.it), in view of a possible deployment in the Adriatic Sea. The main concern of mooring designers is related to resonance effects induced by the second order drift. Therefore specific tests have been carried out in the 36 m long x 1.0 m wide x 1.3 m high wave flume of Padova University. Tests focused on the forces on the mooring lines induced by the sum of two regular waves of similar frequency. The mooring design is still far from complete: the physical model proved the relevance of the aforementioned effects but a numerical investigation (not yet performed) is required to draw final conclusions.
SOLITARY WAVE INTERACTION WITH A SUBMERGED PERMEABLE BREAKWATER: EXPERIMENT AND NUMERICAL MODELING
Authors: Wu Yun-Ta , Hsiao Shih-Chun , Chen Guan-Shiue
Published: December 2012

We study the interactions between a non-breaking solitary wave and a submerged permeable breakwater experimentally and numerically. The particle image velocimetry (PIV) technique was employed to measure instantaneous free surface displacements and velocity fields in the vicinity of the porous media. The porous media, consisted of uniform glass-made spheres, was mounted on the seafloor. Quantitative mean properties were obtained by ensemble averaging 30 repeated instantaneous measurements. In addition, two different numerical considerations are taken to simulate the experiments. One is to model an idealized volume-averaged porous media using a two-dimensional (2D) volume of fluid (VOF)-type model. This model is based on the Volume-Averaged Reynolds-Averaged Navier-Stokes (VARANS) equations coupled with the non-linear k-Îµ turbulence closure solver. The other is to model the real porous breakwater constructed by spheres using a three-dimensional (3D) VOF-type model. This model solves 3D incompressible Navier-Stokes equations with Large-eddy-simulation (LES) model. The comparisons were performed between measurements, 2D and 3D numerical results for the time histories of the free surface elevation, instantaneous free surface displacements and corresponding velocity properties around the permeable object. Fairly good agreements were obtained. The verified 3D numerical results were used to trace the trajectories of fluid particle around the porous media to help understand the possible sediment movements in suspended loads. Also, the 2D numerical model is used to estimate the energy reflection, transmission and dissipation using the energy integral method by varying the aspect ratio and the grain size of the permeable obstacle.
ANALYSIS OF WAVE INTERACTION WITH SUBMERGED ADJACENT PORO-ELASTIC BREAKWATERS
Authors: Lan Yuan-Jyh , Hsu Tai-Wen , Chen Ching-Yu
Published: December 2012

In this study, the problem of wave interaction with two closely submerged adjacent porous elastic breakwaters is investigated theoretically. The porous elastic breakwaters are assumed to be homogeneous, isotropic and elastic. Lan and Lee's (2010) analytical solution is extended to the problem subject to proper boundary conditions. Using general solutions for each region and the matching boundary conditions, a set of simultaneous equations is thus developed and solved numerically. The present analytic solutions compare favorably with simplified cases of the poro-elastic submerged breakwater. Changes of the width of two adjacent breakwaters, the permeable coefficient effect on wave profile, and the effect of materials and configurations of breakwaters on wave variation are the focus of the present paper. The results show that a large amount of energy dissipates when the adjacent structures both have the same soft material and dimension of width with higher permeability. Different materials and shapes of structures could significantly influence the reflection coefficient.
GRANULAR OPEN FILTERS ON A HORIZONTAL BED UNDER WAVE AND CURRENT LOADING
Authors: Wolters Guido , Van Gent Marcel R.A.
Published: December 2012

Rubble mound coastal structures typically contain granular filters in one or more layers. These filters are normally geometrically tight (to prevent material washout), often difficult to realize in the field, and expensive. An alternative is a geometrically open filter (i.e. a large ratio of the size of toplayer material and underlayer material), designed in such a way that it fulfills its filter functions with only minimal base material loss or settlement. Potential applications of open filters include bed protections and toe & slope configurations of coastal structures. Proper guidelines on the design of open filters under wave and current loading could lead to significant cost and material savings, and to a more practical application of filters in the field. The physical model tests conducted in this study focus on granular open filters on a horizontal sand bed under wave and combined wave & current loading.
NUMERICAL ANALYSES AND EXPERIMENTS OF DEFORMABLE RUBBER MEMBRANE PARAPETS
Authors: Chun Insik , Kim Sunsin , Ko Janghee , Park Woosun
Published: December 2012

It has been reported that global warming has invoked an ever increasing typhoon intensity as well as a long-term rise in sea levels which jointly cause severe coastal wave overtopping. A simple measure to cope with this undesirable change is to simply increase the crest height of coastal structures. This measure is certainly effective in the prevention of wave overtopping, but it can also reduce coastal visibility and lead to the degradation of waterfront seascapes. In this paper, Deformable Rubber Membrane Parapets (DRMP), which not only suppress the wave overtopping in storm periods, but also can retain coastal seascapes in milder conditions, are presented. With numerical analyses using a nonlinear finite element program and hydraulic experiments, the air controlled expansion and contraction of the parapets are investigated, together with their structural behaviors and stability against wave overtopping.
UPLIFT FORCES ON WAVE EXPOSED JETTIES: SCALE COMPARISON AND EFFECT OF VENTING
Authors: Gaeta Maria Gabriella , Martinelli Luca , Lamberti Alberto
Published: December 2012

The large-scale experiments described herein were carried out at Forschungs-Zentrum Kuste (FZK), Hannover (Germany) by a research team composed by the Universities of Bologna, Edinburgh, Southampton, Plymouth and the Coast & Harbor Engineering Inc (USA). Wave-induced loads on close-to-prototype jetties were measured. Experimental evidence indicates the presence of force peaks with a short space-time correlation structure, carried by convective processes with a velocity of the order of the wave celerity. After a 100 Hz sampling, forces on the deck bays and front induced by regular and irregular waves are analyzed, focusing the effects on the wave-in-deck loads of (i) wave irregularity, (ii) air venting and (iii) experiment scale in the evaluation of maximum and quasi-static loads. A comparison with the small-scale results is carried out, but differences could not be directly ascribed to scale effects only.
INVESTIGATIONS ON SCOUR DEVELOPMENT AROUND A GRAVITY FOUNDATION FOR OFFSHORE WIND TURBINES
Authors: Wilms Mayumi , Stahlmann Arne , Schlurmann Torsten
Published: December 2012

Due to insufficient insights about the scour development around the STRABAG gravity foundation, the Franzius-Institute conducted small- and large-scale physical model tests in wave flumes on a scale of 1:50 and 1:17 in order to investigate the wave-induced scouring phenomena around the foundation and to design a scour protection system. The tests on scour development without a scour protection system show that the main areas which are vulnerable to scour are the contact areas of the foundation. Furthermore, the experiments show that a scour protection system is necessary for the given and investigated wave boundary conditions; the performance of the selected protection system using geotextile sand containers is verified. Additional numerical simulations indicate an amplification of the resulting flow around the foundation under combined loads (waves and current), but without significant change of the flow pattern
RESILIENCE OF DIKES AFTER INITIAL DAMAGE BY WAVE ATTACK
Authors: Klein Breteler Mark , Bottema Marcel , Kruse G.A.M. , Mourik G.C. , Capel A.
Published: December 2012

The resilience of a dike is quantified in this research as the residual strength, which is the time between initial damage to a dike and dike breach. Unique experiments have been carried out in the Delta Flume of Deltares with a 8.5 m high dike with a clay liner and sand core. Below the still water level the dike was protected with a concrete block revetment and above the water level there was grass on the clay. The tests were carried out with large waves: Hs = 1.6 m. A formula to quantify the erosion of the clay layer as a function of time is derived by combining present and previous experimental results. A formula to quantify the erosion rate of the sand core is derived by combining the present experimental results with existing dune erosion models. The derived formulas make it possible to calculate the probability of failure of the typical Dutch coastal dike with wave attack. This is an important step in the understanding of dike safety.
PLACEMENT GRIDS, POROSITY AND RANDOMNESS OF ARMOR LAYERS
Authors: Pardo Vicente , Herrera Maria Piedad , Molines Jorge , Medina Josep Ramon
Published: December 2012

Armor porosity and armor unit randomness are much easier to control in small-scale models constructed by hand than in prototype. Differences between design and prototype armor porosities and design and armor unit randomness can generate significant model effects. This paper describes realistic 3D placement tests with cube and Cubipod CAUs, using a small-scale crawler crane and pressure clamps. This research aims to estimate workable armor porosities at prototype scale and to determine the prototype placement grids to obtain the armor porosities commonly tested in laboratories. A new methodology based on laser scanning was developed to measure armor unit randomness. This methodology can be applied to both small-scale models and prototypes. Armor Randomness Indexes (ARIs) are proposed to measure the randomness of cube and Cubipod armor units. The ARI values were higher for Cubipods than for cubes.
PERFORMANCE ANALYSIS OF COMPOSITE SEMICIRCULAR BREAKWATERS OF DIFFERENT CONFIGURATIONS AND POROSITIES
Authors: Teh Hee Min , Venugopal Vengatesan , Bruce Tom
Published: December 2012

The perforated free surface semicircular breakwater developed by Teh et al. (2010) was experimentally proven to be an effective anti-reflection structure with high energy dissipation ability. However, the performance characteristics of the breakwater deteriorated with a decrease in the immersion depth and an increase in wavelength. To enhance the performance of the breakwater with limited immersion depth, wave screens of different configurations and porosities were introduced below the free surface semicircular caisson. The hydrodynamic characteristics of these composite breakwaters were investigated in irregular waves using physical modelling. Comparisons of the experimental results showed that the semicircular caisson with a double screen of 25% porosity was a better breakwater configuration compared to that with a single screen. The extension of wave screen was also found to be particularly helpful in attenuating longer waves.
STABILITY FORMULA FOR TETRAPOD INCORPORATING SLOPE EFFECT
Authors: Suh Kyung-Duck , Kang Jin-Sung
Published: December 2012

To develop a stability formula for Tetrapods armoring rubble mound breakwaters, sixty hydraulic model tests have been conducted for various wave conditions and slope angles of breakwaters. The test results are used, along with the data of previous researchers, to develop a new stability formula. The developed formula is proven to be applicable to breakwaters with various slope angles with reasonable accuracy. It is also shown to be applicable to low-crested breakwaters and different packing densities, if the corresponding terms are incorporated in the formula. The uncertainty of the proposed formula is also given.
EFFICIENCY OF TIDAL TURBINE FARMS
Authors: Christian Colin , Vennel Ross
Published: December 2012

The paper investigates the efficiency of tidal turbine farms and looks at the effects of various parameters. Numerical modelling and analytic solutions are used. The two methods are compared and differences highlighted. Some loose guidelines are included.
MECHANISMS OF COASTAL DIKE FAILURE INDUCED BY THE GREAT EAST JAPAN EARTHQUAKE TSUNAMI
Authors: Kato Fuminori , Suwa Yoshio , Watanabe Kunihiro , Hatogai Satoshi
Published: December 2012

Based on the results of field surveys, coastal dike failures caused by the Great East Japan Earthquake were classified into eight patterns. The results of hydraulic model experiments related to major failure patterns reinforced the proposed failure processes. In addition, the aggregated length of each failure pattern showed that failure from scouring at the landward toe is the dominant failure pattern.
STRUCTURAL STABILITY OF CUBE AND ROCK-ARMOURED SUBMERGED BREAKWATERS FOR BEACH PROTECTION
Authors: Sanchez-Gonzalez Jose Francisco , Ortiz Dolores M. , Garrido Joaquin M. , Martin Manuel
Published: December 2012

This paper presents the results from a new set of 3-D physical model tests performed in a 6.5 m wide flume at the Centre for Harbour and Coastal Studies in Madrid. These results will contribute to enhance the existing knowledge obtained in previous studies. Among other variables, they cover concrete-cubes armours and the submergence is increased, with a higher model scale. Damage criterions are discussed and proposed for both types of armour. The latter takes into account the different damage growth observed between rock and cubes-armours. Lower thresholds are proposed for cubes in order to increase the safety, though still allowing some movements before considering the damage is reached.
STATIC AND DYNAMIC LOADS ON THE BOTTOM ROW OF ARMOUR UNITS: A THEORETICAL AND PHYSICAL MODEL STUDY
Authors: Van de Koppel Michael Alexander , Muilwijk Michiel , Verhagen Henk Jan
Published: December 2012

A physical model study on the row averaged static and dynamic load on the bottom row of single layer armour units in order to investigate the influence of various parameters such as the number of rows on the slope of a breakwater and the initial relative packing density.