bluuebunny/crossref_metadata_2025 huggingface dataset:
INCIPIENT MOTION RESPONSE DETECTION OF ARTICULATED COASTAL REVETMENT UNDER WAVE LOADING
Authors: Russo Edmond J , Willson Clinton S , Smith Heather
Published: October 2012

Articulated coastal revetments (ACRs) are armoring options for abating earthen levee wave erosion. Stability criteria for ACR design typically allow initial, minor damage during design wave loading conditions (USACE, 2006). Minor wave damages may worsen progressively if not repaired before another design wave loading event. If minor ACR damages evolve under wave action to the point of unraveling, the underlying levee will become exposed to wave forces that could result in breaching (Pilarczyk, 1998). Vulnerability exists in this scenario for catastrophic flood risk management system failure. Current ACR stability limits for maintaining structural integrity under wave attack exist between the thresholds of structure incipient motion and that of initial damage criteria. Using an ACR stability limit that maintains structural integrity would greatly reduce the potential of repeat damage resulting in armor failure. A design challenge exists due to a knowledge gap in detecting and analyzing ACR performance between the thresholds of incipient motion and initial damage (Herbich, 1999). In this research, the threshold of incipient motion for ACRs is explored through small-scale experimentation. Data analysis, including correlations between hydrodynamic forcings and structure responses, extended our understanding of ACR system behavior in specific structural configurations and wave loading conditions.
VOLUME-OF-FLUID MODEL COMFLOW SIMULATIONS OF WAVE IMPACTS ON A DIKE
Authors: Wenneker Ivo , Wellens Peter , Gervelas Reynald
Published: October 2012

ComFLOW is a 3D Volume-of-Fluid (VOF) model to solve the incompressible Navier-Stokes equations including free surface, or to solve the Navier-Stokes equations for two-phase flow problems (two-phase flow: both an incompressible viscous fluid (e.g., water) and a compressible viscous fluid (e.g., air) are present). The problem statement of the present study reads: 'Is ComFLOW capable of accurate prediction of wave impacts on (impermeable) coastal structures such as dikes? And, if so, what are the preferred model settings and associated computing times?'. In this paper, ComFLOW is validated for this purpose by comparison against pressure data as measured in the Delta flume by pressure sensors at dikes. We have selected three different experiments, with typical dike geometries (slope 1:3.5, with and without berm) at which more than 20 pressure sensors were installed. The results can be summarized as follows. The pressure measurements are reproduced well in the simulations. A grid with about 170 grid cells per wave length in the horizontal, and between 4 and 6 grid cells per wave height in the vertical, proves to be sufficiently fine. At such a grid resolution and with about 450 by 35 grid cells in the computational domain, a typical CPU time is 35 minutes for simulations with a model time of 10 wave periods. For the present application, it is preferable to use the one-phase flow model rather than the two-phase flow model, since the former gives better results in the lower located pressure sensors and consumes less CPU time.
WAVE LOADS ON EXPOSED JETTIES: DESCRIPTION OF LARGE SCALE EXPERIMENTS AND PRELIMINARY RESULTS
Authors: Martinelli Luca , Lamberti Alberto , Gaeta Maria Gabriella , Tirindelli Matteo , Alderson John , Schimmels Stefan
Published: October 2012

The large scale experiments described in this paper were carried out at the Large Wave Flume (GWK, Große Wellenkanal) in Hanover (Germany). The research team included Universities of Bologna (IT), Edinburgh (UK), Southampton (UK), Plymouth (UK), HR Wallingford (UK) and Coast & Harbor Engineering Inc (USA). Wave-induced loads on close-to-prototype scale jetties were measured, with particular attention to scale effects due to air content in water. The aim of the paper is to present the tests, describe the impact process and give preliminary results concerning uplift loads.
WAVE OVERTOPPING SIMULATOR TESTS IN VIET NAM
Authors: Le Hai Trung , Van der Meer Jentsje , Jan Schiereck Gerrit , Minh Cat Vu , Van der Meer Gerben
Published: October 2012

Sea dikes in Viet Nam have been built up during a long history. Every year, about 4 to 6 storms attack the coast and cause severe damages of the sea dikes. Till now, little is known about strength and stability of the inner slope covered with grass under impacts of wave overtopping during storm surges. Destructive tests have been performed with the Wave Overtopping Simulator in Viet Nam revealing that grass slopes are able to withstand a certain amount of wave overtopping. In Hai Phong, a slope section covered by Vetiver grass could suffer a maximum wave overtopping discharge of up to 120 l/s per m. In Nam Dinh, three tested locations within a short dike section of 50 m show a large variation in erosion resistance of the Bermuda grass slope with maximum discharge of 20, 40 and 70 l/s per m.
HYDRODYNAMIC PERFORMANCE OF A FREE SURFACE SEMICIRCULAR PERFORATED BREAKWATER
Authors: Teh Hee Min , Venugopal Vengatesan , Bruce Tom
Published: October 2012

The increasing importance of the sustainability challenge in coastal engineering has led to the development of free surface breakwaters of various configurations. In this study, the hydrodynamic characteristics of a perforated semicircular free surface breakwater (SCB) are investigated for irregular wave conditions. The hydrodynamic performance of the breakwater is evaluated in the form of transmission, reflection and energy dissipation coefficients, which are then presented as a function of the relative submergence depth (D/d) and the relative breakwater width (B/Lp), where D = the depth of immersion, d = the water depth, B = the breakwater width and Lp = the wavelength corresponding to the peak wave period. It is found that the wave attenuation ability of the SCB model improves with the increase of D/d and B/Lp. The SCB performs better as an energy dissipater than as a wave reflector. Based on the analysis of measured data, some empirical equations are proposed to predict the performance of the breakwater under varying submergence depths. The behaviour of wave transformation around and within the breakwater's chamber is discussed. Also, the measured horizontal wave forces acting on the SCB are reported.
NUMERICAL MODEL FOR FLAP-GATE RESPONSE TO TSUNAMI AND ITS VERIFICATION BY HYDRAULIC EXPERIMENTS
Authors: Kimura Yuichiro , Niizato Hideyuki , Nakayasu Kyouichi , Yasuda Tomohiro , Mori Nobuhito , Mase Hajime
Published: October 2012

A flap-gate breakwater is a new type structure for coastal disaster reduction against tsunamis and storm surges. The breakwater usually lies down on the seabed and rises up as a seawall with its buoyancy when tsunami or storm surge occurs. In our previous experimental studies, wave blocking capabilities of the flap-gate against tsunamis were confirmed, and the characteristics of the gate motion and wave pressure have been clarified changing wave condition. Present study develops a numerical model considering fluid-body interactions for the flap-gate and validation of the numerical model is conducted. The numerical model consists of combining the overset grid method and level set method for solving both flap-gate motions and free surface water motions accurately. It is shown that the developed numerical model gives accurate predictions of flap-gate motions against hydraulic model experiments.
EXPERIMENTAL STUDY ON THE LOADING AND SCOUR OF THE JACKET TYPE OFFSHORE WIND TURBINE FOUNDATION
Authors: Yang Ray-Yeng , Chen Hsin-Hung , Hwung Hwung-Hweng , Jiang Wen-Pin , Wu Nian-Tzu
Published: October 2012

A 1:36 scale model tests were carried out in the Medium Wave Flume (MWF) and Near-shore Wave Basin (NSWB) at the Tainan Hydraulics Laboratory (THL) with the jacket type offshore wind turbine foundation located in the test area. The loading of typhoon wave with current on the jacket type offshore wind turbine foundation was investigated in the MWF with fixed bed experiment. Meanwhile, the scour around the jacket type offshore wind turbine foundation exposed to wave and current was conducted in the NSWB with the moveable bed experiment. Two locations (water depth 12m and 16m) of the foundations are separately simulated in this study. Based on the analysis from the former NSWB experimental results, the suitable scour protection of a four-layer work around the foundation is also proposed to the impact of scour. Finally, a four-layer scour protection is tested and found to be effective in preventing scour around jacket type foundation of offshore wind turbines at water depth 12m and 16m.
EXPERIMENTAL RESULTS OF BREAKING WAVE IMPACT ON A VERTICAL WALL WITH AN OVERHANGING HORIZONTAL CANTILEVER SLAB
Authors: Kisacik Dogan , Troch Peter , Van Bogaert Philippe
Published: October 2012

Physical experiments (at a scale of 1/20) are carried out using a vertical wall with horizontal cantilevering slab. Tests are conducted for a range of values of water depth, wave period and wave height. A parametric analysis of measured forces (Fh and Fv) both on the vertical and horizontal part of the scaled model respectively is conducted. The highest impact pressure and forces are measured in the case of breaking waves with a small air trap. Maximum pressures are measured around SWL and at the corner of the scaled model. The horizontal part of the scaled model is more exposed to impact waves than the vertical part. Fh and Fv are very sensitive for the variation of water depth (hs) and wave height (H) while variation of wave period (T) has a rather limited effect.
STUDY OF REFLECTION OF NEW LOW-REFLECTIVITY QUAY WALL CAISSON
Authors: Garrido Joaquín María , Ponce de León Daniel , Berruguete Antonio , Martínez Silvia , Manuel José , Fort Lisardo , Yague Diego , González-Escrivá Jose Alberto , Medina Josep R.
Published: October 2012

This paper presents a new low-reflectivity quay wall caisson based on the formation of cell circuits. The cell circuit lengths can be adapted to the specific wave climate conditions at the construction site to obtain the best performance. Results from physical model tests of conventional and cell circuit caissons are described, as well as the construction process and steel reinforcement, which turns out to be quite similar to highly reflective conventional caissons. Neural Network (NN) models are used to describe the nonlinear relationship observed between experimental coefficients of reflection (CR) and the structural and wave conditions for the new low reflectivity quay wall caisson.
3D SIMULATION OF WAVE INTERACTION WITH PERMEABLE STRUCTURES
Authors: Wellens Peter , Borsboom M.J.A. , Van Gent M.R.A.
Published: October 2012

COMFLOW is a general 3D free-surface flow solver. The main objective in this paper is to extend the solver with a
permeable flow model to simulate wave interaction with rubble-mound breakwaters. The extended Navier-Stokes
equations for permeable flow are presented and we show the discretization of these equations as they are implemented in
COMFLOW. An analytical solution for the reflection coefficient of a permeable structure is derived and the numerical
model is compared to the solution. In addition, a validation study has been performed, in which we compare the numerical
results with an experiment. In the experiment, pressures and surface elevations are measured inside a permeable structure.
The measurements are represented well by the simulation results. At the end, a 3D application of the model is shown.
COMPARISONS OF WAVE OVERTOPPING DISCHARGES AND DAMAGES OF THE NTOU VERTICAL SEAWALL DUE TO TWO SIMILAR SUPER TYPHOONS ON KEELUNG COAST OF TAIWAN
Authors: Chen Da-Wei , Tzang Shiaw-Yih , Ou Shan-Hwei
Published: October 2012

In this study, SWAN model was first applied to obtain wave conditions during Typhoon Herb (1996) and Krosa (2007). Then the results were used for estimating the wave overtopping discharge with existing empirical formulae selected from EurOtop manual. In the EurOtop formulae, calculations of overtopping discharges can be improved by adapting average wave period (Tm-1,0) for swell conditions. The results show that the peak overtopping discharges during Typhoon Herb (1996) are larger than those during Typhoon Krosa (2007) at the two selected sites. In addition, the water depth at toe of eastern NTOU seawalls (NTOU 2) are shallower than that at northern NTOU seawall (NTOU 1) so that the discharges at NTOU 1 are larger than those at NTOU 2. The calculations show that the peak wave overtopping discharges during both typhoons are greater than the criteria for damages on back slope of seawalls, which agrees with the NTOU seawall failure event during Typhoon Herb. The predicted failure does not again happen to NTOU seawall during Typhoon Krosa implying the effective reduction in overtopping discharges by lifting up 1m of the crest after rebuilding the previously damaged seawall.
STABILITY OF BREAKWATER ROUNDHEADS DURING CONSTRUCTION
Authors: Van Gent Marcel R.A. , Van der Werf Ivo
Published: October 2012

The presented study focussed on issues related to the hydraulic stability during the construction of rubble mound breakwaters. During construction the temporary roundheads differ from the roundheads in the final stage. Often a submerged uncompleted part of the breakwater is present in front of the section that reached its final crest elevation. This can occur because often the breakwater is being constructed with maritime-based equipment up to a certain elevation while the upper part of the breakwater is being constructed with land-based equipment. Three-dimensional physical model tests were performed to analyse the influence of the submerged part on the stability of the emerged part. The locations incurring the most damage clearly differ. Furthermore, for some combinations of water level, wave direction and structure geometry more damage was found for structures with a submerged part, although most combinations showed that the amount of displaced stones is generally lower for the structures with a submerged part.
OPTIMIZING BREAKWATER DESIGN CONSIDERING THE SYSTEM OF FAILURE MODES
Authors: Campos Alvaro , Castillo Carmen , Molina Rafael
Published: October 2012

Optimization techniques have been applied to breakwater design in order to automate the design process (Castillo et al. 2004, 2006). Since safety of structures is the fundamental criterion for design, a complete knowledge of the potential failure modes, as well as the possible interaction between them, is essential to provide a consistent design. Failure modes are correlated in two ways: through common parameters like HS or by physical interaction. The latter has not yet been precisely identified nor quantified. The aim of the present paper is to advance on the analysis of both types of correlations and to check how the combination of failure modes modifies the failure probability of the whole structure either increasing or decreasing it. An application to a special type of composite breakwater is proposed: the fuse parapet case, where part of the parapet fails under certain circumstances in order to ensure the whole stability of the caisson, despite increasing overtopping events.
MATHEMATICAL MODELLING OF WAVE OVERTOPPING AT COMPLEX STRUCTURES: VALIDATION AND COMPARISON
Authors: Berkenbrink Cordula , Kaiser Ralf , Niemeyer Hanz Dieter
Published: October 2012

A validation study for a mathematical model called OTT-1d from HR-Wallingford modified by the Coastal research Station is presented in this paper. The model is based on the one-dimensional nonlinear shallow water equations (NLSWE) on a sloping bed describing the horizontal mass and momentum balance. Demonstrating for several wave flume test data OTT-1d can be verified as a reliable tool for predicting the mean overtopping discharge at simple an complex geometries. Furthermore a comparison of the modelling results to actual used calculation methods is done to show the limits of each calculation methods relating to the complexity of the structure.
INFLUENCE OF ARMOR UNIT PLACEMENT ON ARMOR POROSITY AND HYDRAULIC STABILITY
Authors: Medina Josep R. , Gómez-Martín M. Esther , Corredor Antonio
Published: October 2012

The handling procedure and placement grid of concrete armor units (CAUs) are the key construction factors of armor layers. This paper analyzes conventional cube and Cubipod CAUs which are handled by pressure clamps and placed randomly. Two methodologies for small-scale blind construction of armor layers in laboratories are compared using a Cartesian system and crawler cranes. Model construction by hand in laboratories is usually done in excellent conditions contrary to actual construction at prototype scale which is blind underwater and is influenced by wind, waves and equipment constraints. For randomly placed CAUs, the layer coefficient is an unnecessary and subjective concept which should be disregarded to prevent misunderstandings when considering armor porosity. For a given CAU, the placement grid affects armor porosity which is directly related to armor hydraulic stability. Crawler cranes can only place CAUs in a narrow armor porosity band; therefore, porosity of small scale armor models constructed by hand must be selected within that viable porosity band to avoid uncontrolled model effects. Armor layers of conventional cubes placed randomly by hand are not realistic if porosity is p%
IMPACT FORCE ANALYSIS ON WAVE DISSIPATING CONCRETE BLOCKS DURING ROCKING MOTION
Authors: Mitsui Jun , Yamamoto Masato , Noboru Satoshi , Nishiwaki Ichiro
Published: October 2012

Breakage of wave dissipating concrete blocks occasionally occurs due to collision with other blocks during rocking motion under wave action. Therefore, an understanding of the impact forces induced by rocking blocks is important to solve this problem. The authors formulated impact forces using impact velocity, properties of materials, and dimensionless parameters depending on the shape of blocks to propose a theory to predict the magnitude of impact force. Fundamental drop tests using tetrapods were also conducted to confirm the proposed formula. Various sizes of blocks were used in the drop tests to reveal the scale effects. It is shown that predicted impact forces agree well with measured ones and that no scale effects concerning impact force seem to exist in the range of this study.
WAVE RUN-UP AND REFLECTION AT RUBBLE MOUND BREAKWATERS WITH ECOPODE ARMOR LAYER
Authors: Calabrese Mario , Buccino Mariano , Ciardulli Francesco , Di Pace Pasquale , Tomasicchio Roberto , Vicinanza Diego
Published: October 2012

In 2008 the authors verified the hydraulic stability of a coastal defense project to be built along the NW coast of Sicily (Italy, Tomasicchio et al., 2009). The intervention consisted of shore parallel barriers armored with a relatively new eco-friendly system: ECOPODETM. In that context the idea arose of conducting an exhaustive experimental campaign on the " hydraulic response " of these units, including wave run-up , wave overtopping, wave transmission and wave reflection observations. The latter has been performed in 2010 at the LInC Laboratory of University of Naples "Federico II†. In this paper results on wave run-up and reflection are presented and discussed.
VALIDITY OF SIMPLIFIED ANALYSIS OF STABILITY OF CAISSON BREAKWATERS ON RUBBLE FOUNDATION EXPOSED TO IMPULSIVE LOADS
Authors: Andersen Lars , Burcharth Hans Falk , Lykke Andersen Thomas
Published: October 2012

Wave slamming on vertical breakwaters cause a sudden, impulsive load that may cause a caisson to slide on its foundation. Alternatively, geotechnical failure may occur in the subsoil. This paper investigates whether simple analytical solutions, accounting only for the sliding along the caisson-foundation interface, can be utilized to properly determine the deformations of the breakwater. Comparisons are made with results obtained by numerical models that include the material response of the soil. Firstly, a computational model is suggested that assumes a fully drained behavior of the subsoil. Secondly, a fully coupled dynamic pore-water-flow model is introduced. The computational examples clearly demonstrate that the deformations of the soil as well as the pore pressures must be
accounted for in order to get a reliable prediction of caisson deformations during wave impact.
OPTIMIZATION OF CAISSON BREAKWATER SUPERSTRUCTURE GEOMETRY USING A 2DV RANS-VOF NUMERICAL MODEL
Authors: Misra Shubhra , Narayanaswamy Muthukumar , Bayram Atilla , Shi Fengyan
Published: October 2012

This paper demonstrates that numerical modeling tools such as a RANS-VOF model can be applied confidently to reduce the level of uncertainty from empirical guidance and provide for a deterministic quantification of the hydraulic response associated with any arbitrary Caisson breakwater superstructure geometry. The RANS-VOF model used for this paper is first satisfactorily validated against laboratory measurements (surface elevation, overtopping and pressure) of a caisson breakwater on a rubble-mound foundation and then applied to several prototype caisson breakwater superstructure geometries. Numerical simulations presented in this paper for prototype geometries demonstrate that curved/inclined parapets, when compared with vertical face caisson breakwaters with the same crest elevation, can lead to large increases in overtopping as well as downward forces. Expectedly, the landward forces are reduced by the implementation of a curved or recessed and inclined parapet when compared to a caisson with a completely vertical face. During large overtopping events, the model results show that much larger short-duration seaward loads can be generated for curved and inclined superstructures when compared to vertical face geometries. This is in general agreement with previous laboratory experiments as well as field observations of seaward caisson sliding and failure resulting from large overtopping events. Further, numerical experiments indicate that the overtopping response of a superstructure can vary noticeably due to small changes in the recessed length of an inclined or curved parapet. The numerical model also easily provides for the quantification of the variation of instantaneous and peak overtopping discharges along the crest of the caisson superstructure, and which can provide for useful guidance in the design of various crest infrastructure components, such as drainage systems, flow deflectors, wave power devices etc.
SLIDING STABILITY OF LANDWARD SLOPE CLAY COVER LAYERS OF SEA DIKES SUBJECT TO WAVE OVERTOPPING
Authors: Van Hoven Andre , Hardeman Bianca , Van der Meer Jentsje W. , Steendam Gosse Jan
Published: October 2012

Sea dikes with landward slopes covered by grass and clay cover layers, subject to wave overtopping, can become unstable and slide. Sliding stability of the cover layer is caused by a decrease in shear strength due to an increase in pore pressure in and underneath the clay cover layer. This holds for both clay dikes and sand dikes with a clay cover layer. A method is presented to determine the potential pore pressure build up due to a storm event with wave overtopping. The method combines of the shelf knowledge and is supported by laboratory measurements and field measurements during prototype scale wave overtopping tests and sliding test on Dutch sea dikes. The method contains three steps: 1) determine the infiltration time, depending on the storm duration and the sea state; 2) determine the infiltration capacity of the dike slope, either by choosing a safe value or field measurement and 3) determine the potential pore pressure build up, determined by step 1) and 2) and the dike structure and geometry. The potential pore pressure build up can be used in the standard stability analyses tools published in Dutch guidelines on dike design and dike safety assessment.
DEVELOPMENT ON OFFSHORE STRUCTURE
Authors: Kouichirou Anno , Nishihata Takeshi
Published: October 2012

Authors have developed the offshore structure for control of sea environment named S-VHS construction

method, which is composed of the sloping top slit-type caisson and steel pipe piles. The sloping top form enables to

realize the remarkable reduction of wave force exerted on the dike body compared with the conventional one.

In this paper, hydraulic feature with wave dissipation ability and wave force reduction effect are verified

through some hydraulic experiments. After the preliminary study for the valid structure form, reflection and

transmission ability for the selected structure models were tested with the hydraulic experiment relevant to the ratio of

caisson width and wave length. Finally, wave force experiment was executed and it revealed the performance of wave

force reduction. Based on the results, we proposed specific design wave force formula for S-VHS construction method.
JETTIES AT BODEGA HARBOR
Authors: Magoon Orville T. , Treadwell Donald D. , Atwood Paul S.
Published: October 2012

To create and maintain a navigable entrance for small craft between the Pacific Ocean and the natural lagoon now referred to as Bodega Harbor, the construction of two rubble-mound jetties and the associated dredging of interior channels were authorized by the United States Congress in the late 1930s. The jetties were built by the United States Army Corps of Engineers in the early 1940s. Elements of the planning, design, construction, monitoring, and maintenance of the jetties are discussed herein.
PRACTICAL APPLICATION OF A JACKET-TYPE BREAKWATER
Authors: Nakamura Takayuki , Kouno Tohru
Published: October 2012

In this study, a new jacket-type breakwater was proposed for the economical construction of breakwaters in deep-sea ports. This breakwater consists of water chambers with two inclined walls and a submerged horizontal plate. In order to reinforce the breakwater structure, the inclined support piles were adopted instead of vertical piles. Accordingly, the inclined walls were used as front and rear curtain walls. Piston mode wave resonance can be employed in the water chamber to effectively dissipate incoming waves by the generation of separated flows and the resultant vortex flows around the front curtain wall. The performance of the proposed breakwater was examined from the theoretical and experimental viewpoints. Considering the experimental results, we decided to construct an economical water-chamber-type breakwater on the adopted site.
REDUCTION ON WAVE OVERTOPPING ON A SMOOTH DIKE BY MEANS OF A PARAPET
Authors: Van Doorslaer Koen , De Rouck Julien
Published: October 2012

A return wall or parapet is a very efficient construction built to reduce wave overtopping over sea structures. One of its main advantages is that this relative small construction can be built in a dike without increasing the crest height yet creating a major reduction in wave overtopping. In this paper only non-breaking waves attacking smooth dikes are investigated. A normal smooth dike, a smooth dike with vertical wall and a smooth dike with parapet have been tested. The results lead to reduction factors for a vertical wall or a parapet that can be introduced in the van der Meer formulas for wave overtopping over smooth dikes. The optimal geometry of the parapet has been subject of the research as well.
PHYSICAL AND NUMERICAL MODELING OF THE WAVECAT© WAVE ENERGY CONVERTER
Authors: Fernandez Hernan , Iglesias Gregorio , Carballo Rodrigo , Castro Alberte , Bartolomé Pedro
Published: October 2012

Wave energy presents a great potential in many coastal regions. This paper deals with WaveCat©, a new Wave Energy Converter (WEC) recently patented by the University of Santiago de Compostela. First, the WaveCat© concept and its main design elements. It is a floating WEC intended for intermediate water depths (50-75 m), whose principle of energy capture is wave overtopping. WaveCat© consists of two hulls, like a catamaran (hence its name); however, unlike a catamaran, the hulls are convergent so as to leave a wedge between them. Waves propagate into this wedge and, eventually, overtop the inner hull sides. Overtopping water is collected in onboard tanks and, subsequently, drained back to sea, propelling ultra-low head turbines in the process. The wave flume tests carried out on a 3D, fixed model at a 1:67 scale are presented. Development work is ongoing, including a numerical model-which is currently being validated based on the results from the physical model-and a 3D, floating physical model at a larger scale (1:30).
LOADS ON WIND TURBINES ACCESS PLATFORMS WITH GRATINGS
Authors: Lykke Andersen Thomas , Frigaard Peter , Rasmussen Michael R , Martinelli Luca
Published: October 2012

The present paper deals with loads on wind turbine access platforms. The many planned new wind turbine parks together with the observed damages on platforms in several existing parks make the topic very important. The paper gives an overview of recently developed design formulae for different types of entrance platforms. Moreover, the paper present new results on loads on grates based on both drag coefficient measurements and preliminary results on
slamming from large scale tests. As expected both investigations show that platforms with grates give a significant reduction in the loads compared to closed plate platforms. The grate multiplication factor, defined as the peak load on the grate platform relative to the peak load on a closed plate platform was found approximately equal to the solidity of the grate.
WAVE LOADS AND STABILITY OF NEW FOUNDATION STRUCTURE FOR OFFSHORE WIND TURBINES MADE OF OCEAN BRICK SYSTEM (OBS)
Authors: Pfoertner Saskia , Oumeraci Hocine , Kudella Matthias , Kortenhaus Andreas
Published: October 2012

The Ocean Brick System (OBS) is a modular system consisting of hollow concrete precast blocs (10m x 10m x 10m) piled up like cubes and interconnected to create a stiff, light and strong structure which can be used for artificial islands, artificial reefs, elevation of vulnerable low lands, deep water ports, breakwaters and foundation of offshore wind turbines. The paper focuses on the experimental results on the wave loading and the stability of the OBS used as
a foundation of the support structure of offshore wind turbines. Diagrams for the prediction of total horizontal forces, vertical forces and overturning moments induced by irregular waves on the OB-structure are derived and verified through additional stability tests and stability analysis.
2-D NUMERICAL WAVE FLUME WITH SOLID-GAS-LIQUID INTERACTION AND ITS APPLICATION
Authors: Kawasaki Koji , Takasu Yoshitaka , Ut Han Dinh
Published: October 2012

A 2-D numerical wave flume based on a multiphase flow model with solid-gas-liquid interaction is presented in this paper. The governing equations are divided into an advection step and a non-advection step by making use of a time splitting method. A CIP method is used to calculate the hyperbolic equations for velocity and pressure at the advection step, while equations at the non-advection step are solved with an extended SMAC method. Conservation equation of mass is directly solved by using a CIP-CSL2 method. A non-reflective wave generator employing a source/sink method for wave generation and an energy dissipation zone are utilized to realize the numerical wave flume. Besides, the constitutive laws of the non-Newtonian fluid are taken into account to make the model capable of simulating the behavior of Bingham fluid. The validity and utility of the numerical wave flume are demonstrated by applying it to wave breaking and post-breaking wave deformation on the slope, the dynamic motion of a floating body under wave action and the collapse of the Bingham fluid column with multiple rigid bodies.
NUMERICAL SIMULATIONS OF SPILLING BREAKING WAVES
Authors: Lubin Pierre , Glockner Stéphane , Kimmoun Olivier , Branger Hubert
Published: October 2012

Numerical simulation of spilling breaking waves is still a very challenging aim to achieve since small interface
deformations, air entrainment and vorticity generation are involved during the early stage of the breaking of the wave.
High mesh grid resolutions and appropriate numerical methods are required to capture accurately the length scales of
the complex mechanisms responsible for the start of the breaking (small plunging jet, white foam, etc.). Numerical
works usually showed better agreements when simulating plunging breaking waves than the spilling case compared
with available experimental data. Kimmoun and Branger (2007) recently experimented surf-zone breaking waves.
Detailed pictures showed a short spilling event occurred at the crest of the waves, before degenerating into strong
plunging breaker. This work is devoted to the qualitative comparison of our numerical results with the experimental
observations, as we will focus on capturing and describing the spilling phase experimented.
SERRE GREEN-NAGHDI MODELLING OF WAVE TRANSFORMATION BREAKING AND RUN-UP USING A HIGH-ORDER FINITE-VOLUME FINITE-DIFFERENCE SCHEME
Authors: Tissier Marion , Bonneton Philippe , Marche Fabien , Chazel Florent , Lannes David
Published: October 2012

In this paper, a fully nonlinear Boussinesq model is presented and applied to the description of breaking waves and shoreline motions. It is based on Serre Green-Naghdi equations, solved using a time-splitting approach separating hyperbolic and dispersive parts of the equations. The hyperbolic part of the equations is solved using Finite-Volume schemes, whereas dispersive terms are solved using a Finite-Difference method. The idea is to switch locally in space and time to NSWE by skipping the dispersive step when the wave is ready to break, so as the energy dissipation due to wave breaking is predicted by the shock theory. This approach allows wave breaking to be handled naturally, without any ad-hoc parameterization for the energy dissipation. Extensive validations of the method are presented using laboratory data.
BOUSSINESQ MODELLING OF SOLITARY WAVE PROPAGATION, BREAKING, RUNUP AND OVERTOPPING
Authors: Orszaghova Jana , Borthwick Alistair G. L. , Taylor Paul H.
Published: October 2012

A one-dimensional hybrid numerical model is presented of a shallow-water flume with an incorporated piston paddle. The hybrid model is based on the improved Boussinesq equations by Madsen and Sorensen (1992) and the nonlinear shallow water equations. It is suitable for breaking and non-breaking waves and requires only two adjustable parameters: a friction coefficient and a wave breaking parameter. The applicability of the model is demonstrated by simulating laboratory experiments of solitary waves involving runup at a plane beach and overtopping of a laboratory seawall. The predicted free surface profiles, maximum runup and overtopping volumes agree very well with the measured values.
PARAMETRIC WAVE-BREAKING ON STEEP REEFS
Authors: Su Shih-Feng , Sheremet Alex , Smith Jane McKee
Published: October 2012

A numerical model based on a nonlinear mild-slope equation, and modified to account for wave dissipation due to breaking is applied to investigate the transformation of the wave spectrum over a fringing reef. The three parameters (Î³, B, F) of the breaking model are calibrated for the best fit between the spectral shapes observed and modeled using an inverse modeling approach. The relationship between optimal values for Î³ and B derived from numerical simulations and other parameters characterizing wave and slope conditions (e.g., deep-water wave steepness, wave dispersivity, nonlinearity parameter) are investigated with the goal of formulating guidelines for the selection of adequate values. The results of this study disagree significantly with previously-proposed empirical relations between Î³ and the deep-water wave steepness, but show good agreement with empirical relations relating Î³ to other parameters. The breaking intensity parameter B shows a largely linear dependency on the nonlinearity parameter.
EXPERIMENTAL AND NUMERICAL STUDIES ON WAVE TRANSFORMATION OVER ARTIFICIAL REEFS
Authors: Ou Shan-Hwei , Hsu Tai-Wen , Lin Jian-Feng , Lai Jian-Wu , Lin Shih-Hsiang , Chang Chen-Chen , Lan Yuan-Jyh
Published: October 2012

A laboratory measurement on the flow field, turbulence and wave energy of spilling breakers over artificial reefs is presented. Instantaneous velocity fields of propagating breaking waves on artificial reefs were measured using Particle Image Velocimeter (PIV) and Bubble Image Velocimeter (BIV). Variations of water surface elevation were observed by using Charge Coupled Device (CCD) cameras with horizontal posture. The experimental results showed that the initial bubble velocity in the aerated region is faster than phase speed with a factor of 1.26. The velocity profiles are identical to the shallow water theory. It is found that a low flow velocity exists due to an opposite but equal onshore and offshore velocity. Significant turbulent kinetic energy and turbulent Reynolds stress are produced by breaking waves in the front of aerated region, then move offshore and decay. The calculated total energy dissipation rate was compared to that based on a bore approximation.
MEASUREMENTS OF PARTICLE VELOCITIES AND TRAJECTORIES IN A WAVE-CURRENT MOTION USING PARTICLE IMAGE VELOCIMETRY
Authors: Umeyama Motohiko , Shintani Tetsuya , Watanabe Shinya
Published: October 2012

This article deals with some physical aspects of a water particle under surface waves, which propagate with or without a current in a constant water depth, using an imaging technique. The use of particle image velocimetry (PIV) made it possible to investigate the velocity and trajectory of each individual water particle. The velocity vector fields and its vertical distributions were estimated at several phases in one wave cycle. The theory of progressive waves based on finite-amplitude approximation was adapted to express the velocity potential, surface displacement and angular frequency. The PIV result showed suitable agreement with a solution solved to the third order by a perturbation method. In addition, the distributions of horizontal and vertical velocity components by the PIV measurement were compared with those by an EC meter. These attempts proved the ability of the PIV technique to accurately measure both temporal and spatial variations of the velocity. This technique was applied to the prediction of particle trajectory in a Eulerian scheme. In the method, the surrounding grid velocities were used to identify a Lagrangian velocity. The measured particle path was compared with the positions found theoretically by integrating the Eulerian velocity to the second order of a Taylor series expansion.
SHORT WAVE BREAKING EFFECTS ON LOW FREQUENCY WAVES
Authors: Daly Christopher , Roelvink Dano , Van Dongeren Ap , Van Thiel de Vries Jaap , McCall Robert
Published: October 2012

The effect of short wave breaking on low frequency waves is investigated using two breaker formulations implemented in a time-dependent numerical model (XBeach): (1) an advective-deterministic approach (ADA) and (2) the probabilistic breaker formulation of Roelvink (1993). Previous research has shown that the ADA breaker model gives different results for the cross-shore pattern of the fraction of breaking waves, which is now shown to affect not only the short wave height but also the short wave groupiness. While RMS short wave heights are comparable to measurements using both breaker models, the ADA breaker model allows higher levels of short wave groupiness into the surf zone. It is shown that this acts as an additional forcing mechanism for low frequency waves in the shoaling and nearshore zone, which, in addition to greater levels of breaking, leads to higher values of wave set-up. These findings are dependent on the complexity of the local bathymetry. For a plane slope, the differences in the low frequency wave heights and set-up predicted by both breaker models are negligible. Where arbitrary breakpoints are present in the field of wave propagation, such as nearshore bars or reefs, the ADA model predicts higher localized set-up, indicative of greater flow over such features. Differences are even more pronounced when the incident wave regime is highly energetic.
LOCAL CONCENTRATION OF SLOWLY VARYING WAVE AND CURRENT FIELDS AROUND THE ABRUPTLY CHANGING BOTTOM SLOPES ALONG THE SHORE
Authors: Tajima Yoshimitsu , Sato Shinji
Published: October 2012

This study aims to investigate physical mechanisms of locally concentrated nearshore hydrodynamic forces under interactive fields of waves and currents on abruptly changing coastal bathymetry. Laboratory experiments were first performed to represent such phenomena and a newly developed monitoring system based on image processing techniques successfully captured the local concentrations of wave fields as quantitative high-resolution data sets. Numerical experiments were then performed to investigate the physical mechanisms of the observed features. It was found that, among the other various possible factors, slowly varying wave-induced nearshore currents have one of the most significant impacts on local concentrations of waves around the abruptly changing bathymetry.
USING THE RASINTERFOAM CFD MODEL FOR WAVE TRANSFORMATION AND COASTAL MODELLING
Authors: Morgan Gerald Charles John , Zang Jun , Greaves Deborah , Heath Andrew , Whitlow Chris , Young John
Published: October 2012

The CFD model, rasInterFoam, part of the OpenFOAM library for continuum mechanics, is used to reproduce experimental results for the propagation of monochromatic waves over a submerged bar. The model is shown to reproduce the experimental results very well on the front face and top of the bar, and give adequate results on the back face, even on extremely coarse meshes. Sensitivity analyses are presented for the model results, investigating the dependence on mesh density and discretisation scheme of the model. The modeling of the wave transformations in the model is shown to be broadly insensitive to these parameters within the ranges tested.
NUMERICAL ANALYSES ON PROPAGATION OF NONLINEAR INTERNAL WAVES
Authors: Yamashita Kei , Kakinuma Taro , Nakayama Keisuke
Published: October 2012

A set of nonlinear surface/internal-wave equations, which have been derived on the basis of the variational principle without any assumptions concerning wave nonlinearity and dispersion, is applied to compare numerical results with experimental data of surface/internal waves propagating through a shallow- or a deep-water region in a tank. Internal waves propagating over a submerged breakwater or a uniformly sloping beach are also simulated. The internal progressive wave shows remarkable shoaling when the interface reaches the critical level, after which physical variables including wave celerity become unstable near the wave-breaking point. In the case of the internal-wave trough reflecting at the vertical wall, the vertical velocities of water particles in the vicinity of the interface are different from that of the moving interface at the wall near the wave breaking, which means that the kinematic boundary condition on the interface of trough has been unsatisfied.
RAPID CALCULATION OF NONLINEAR WAVE-WAVE INTERACTIONS
Authors: Lin Lihwa , Demirbilek Zeki , Zheng Jinhai , Mase Hajime
Published: October 2012

This paper presents an efficient numerical algorithm for the nonlinear wave-wave interactions that can be important in the evolution of coastal waves. Indeed, ocean waves truly interact with each others. However, because ocean waves can also interact with the atmosphere such as under variable wind and pressure fields, and waves will deform from deep to shallow water, it is generally difficult to differentiate the actual amount of the nonlinear energy transfer among spectral waves mixed with the atmospheric input and wave breaking. The classical derivation of the nonlinear wave energy transfer has involved tedious numerical calculation that appears impractical to the engineering application. The present study proposed a theoretically based formulation to efficiently calculate nonlinear wave-wave interactions in the spectral wave transformation equation. It is approved to perform well in both idealized and real application examples. This rapid calculation algorithm indicates the nonlinear energy transfer is more significant in the intermediate depth than in deep and shallow water conditions.
DEVELOPMENT OF A HIGH-RESOLUTION NEARSHORE WAVE FORECASTING/HINDCASTING SYSTEM FOR THE ITALIAN COASTS
Authors: Catini Francesca , Montagna Francesca , Franco Leopoldo , Bellotti Giorgio , Corsini Stefano , Inghilesi Roberto , Orasi Arianna
Published: October 2012

This paper describes a research aimed at developing a high-resolution nearshore wave forecasting/hindcasting system for the Italian coasts. Data recorded by buoys located in shallow water are compared with hindcasted data. The model uses the results of the well-tested large scale meteorological forecasting system named 'Idro-meteo-mare' (SIMM) managed by ISPRA, the Italian Agency for the Environmental Protection and Research, as wind input for WAM and SWAN models. Two different approaches are used for the Adriatic and the Tyrrhenian/Ligurian Sea. In the first eastern basin two/three SWAN nested grids have been used, while in the second western basins two WAM nested grids and a finer SWAN grid have been used. Both methodologies have shown a good accuracy and and a reasonable level of efficiency.
A PROBABILISTIC MODEL FOR THE DETERMINATION OF HYDRAULIC BOUNDARY CONDITIONS IN A DYNAMIC COASTAL SYSTEM
Authors: Groeneweg Jacco , Beckers Joost , Gautier Caroline
Published: October 2012

In 2011 new Hydraulic Boundary Conditions must be established for the statutory assessment of flood protection in the Wadden Sea area, which is a complex tidal system in the northern part of the Netherlands. The aim is to base these normative wave conditions on the wave simulation model SWAN and the probabilistic method Hydra-K, to be consistent with other systems as the Holland Coast and the Zeeland Delta. Assumptions made for the latter water systems, like steady state wind forcing, uniform water levels and neglect of currents, are not valid in the tidal basin of the Wadden Sea. A schematic temporal variation of both wind direction and wind speed is applied to define wind fields that drive the hydrodynamic computations. Both wind fields and resulting water level and current fields form the input of SWAN computations for a large number of combinations of basic wind speed and wind direction, offshore surge level and phase difference between tide and maximum wind speed. The result is a large database of SWAN results that is used as a look-up table in Hydra-K to transform the offshore statistics to the load on the primary sea defenses. In general the more advanced method leads to wave heights that are up to 10% lower and wave periods that are 10-20% smaller than those obtained with the method that is presently applied for the Holland Coast and the Zeeland Delta. These differences can be ascribed to the inclusion of currents and positive shoreward tilt in water level. The inclusion of relevant physics in the hydrodynamic computations increases the accuracy of the resulting HBC. Therefore, the more advanced method will be applied to determine the HBC for 2011.