No / The paper presents an incompressible Smoothed Particle Hydrodynamics (SPH) model to investigate the wave overtopping of coastal structures. The SPH method is a grid-less Lagrangian approach which is capable of tracking the large deformations of the free surface with good accuracy. The incompressible algorithm of the model is implemented by enforcing the constant particle density in the pressure projection. The SPH model is employed to reproduce a transient wave overtopping over a fixed horizontal deck and the regular/irregular waves overtopping of a sloping seawall. The computations are validated against the experimental and numerical data and a good agreement is observed. The SPH modelling is shown to provide a promising tool to predict the overtopping characteristics of different waves. The present model is expected to be of practical purpose if further improvement in the spatial resolution and CPU time can be adequately made.

The primary function of seawalls and embankments is to protect against damage and injury caused by flooding. Coastal flooding is caused by combinations of high tides, waves, wind set-up and storm surges driven by low-pressure systems. However with global warming causing sea levels to rise and with increased storminess causing more extreme waves and storm surges, the likelihood of overtopping of seawalls with zero or negative freeboard may well be expected to increase. Researchers using physical and numerical models to develop design formulae have widely investigated wave overtopping of seawalls with positive freeboard. However the design of seawalls with zero or negative freeboard has attracted much less attention, and some variation exists between overtopping discharge calculated with current design formulae. The focus of this thesis is the extreme situation when overtopping caused by storm waves is combined with surge levels above the embankment crest. The local highly accelerative flow over the embankment crest caused by the high surge level will significantly alter the flow at the crest. This is likely to have a highly non-linear effect upon the overtopping waves. In this thesis, the flow is investigated with a 2DV numerical model based on the Reynolds averaged Navier-Stokes (RANS) equations developed by Lin and Liu (1998a). The model describes the flow characteristics of a breaking wave such as the velocities within the wave as well as the turbulence at the seabed boundary layer. As an example of the model’s ability to describe complex hydrodynamic flows, this study investigates its ability to represent the second order mass transport under progressive and standing waves. The model results are compared with available theory and experimental results. This shows that mass transport is successfully predicted, although there is some variation in the magnitude compared to the experimental and theoretical results. To consider the model’s ability to simulate storm surge wave overtopping of embankments, the RANS model has been used to simulate an experimental study conducted by Hughes and Nadal (2009). To examine the success of the model at reproducing the wave generation, transformation and overtopping processes the model results have been compared with the experimental laboratory data. This makes possible a wave-by-wave comparison of overtopping parameters such as discharge, depth and velocity for a storm surge event. Additionally the overtopping discharge predicted by the model is compared with design formulae and the differences in the overtopping discharge calculated with current design formulae are investigated and explained. Finally, the RANS model is used to determine the effect of embankment crest width on the magnitude of the overtopping discharge. Results from RANS model tests are used to provide design guidance in the form of an equation that allows the effect of crest width to be included when evaluating combined discharge at embankments.

Yes / This research paper presents an incompressible smoothed particle hydrodynamics (ISPH) technique to investigate a regular wave overtopping on the coastal structure of different types. The SPH method is a mesh-free particle modeling approach that can efficiently treat the large deformation of free surface. The incompressible SPH approach employs a true hydrodynamic formulation to solve the fluid pressure that has less pressure fluctuations. The generation of flow turbulence during the wave breaking and overtopping is modeled by a subparticle scale (SPS) turbulence model. Here the ISPH model is used to investigate the wave overtopping over a coastal structure with and without the porous material. The computations disclosed the features of flow velocity, turbulence, and pressure distributions for different structure types and indicated that the existence of a layer of porous material can effectively reduce the wave impact pressure and overtopping rate. The proposed numerical model is expected to provide a promising practical tool to investigate the complicated wave-structure interactions. / Nazarbayev University Seed Grant, entitled “Environmental assessment of sediment pollution impact on hydropower plants”. S. Shao also acknowledges the Royal Society Research Grant (2008/R2 RG080561)

There is a good deal of uncertainty and sensitivity in the results for wave impact. In a practical situation, many parameters such as the wave climate will not be known with any accuracy especially the frequency and severity of wave breaking. Even if the wave spectrum is known, this is usually recorded offshore, requiring same sort of (linear) transfer function to estimate the wave climate at the seawall. What is more, the higher spectral moments will generally be unknown. Wave breaking, according to linear wave theory, is known to depend on the wave spectrum, see Srokosz (1986) and Greenhow (1989). Not only is the wave climate unknown, but the aeration of the water will also be subject to uncertainty. This affects rather dramatically the speed of sound in the water/bubble mixture and hence the value of the acoustic pressure that acts as a maximum cutoff for pressure calculated by any incompressible model. The results are also highly sensitive to the angle of alignment of the wave front and seawall. Here we consider the worst case scenario of perfect alignment. Given the above, it seems sensible to exploit the simple pressure impulse model used in this thesis. Thus Cooker (1990) proposed using the pressure impulse P(x, y) that is the time integral of the pressure over the duration of the impact. This results in a simplified, but much more stable, model of wave impact on the coastal structures, and forms the basis of this thesis, as follows: Chapter 1 is an overview about this topic, a brief summary of the work which will follow and a summary of the contribution of this thesis. Chapter 2 gives a literature review of wave impact, theoretically and experimentally. The topics covered include total impulse, moment impulse and overtopping. A summary of the present state of the theory and Cooker’s model is also presented in Chapter 2. In Chapter 3 and Chapter 4, we extend the work of Greenhow (2006). He studied the berm and ditch problems, see Chapter 3, and the missing block problem in Chapter 4, and solved the problems by using a basis function method. I solve these problems in nondimensionlised variables by using a hybrid collocation method in Chapter 3 and by using the same method as Greenhow (2006) in Chapter 4. The works are extended by calculating the total impulse and moment impulse, and the maximum pressure arising from the wave impact for each problem. These quantities will be very helpful from a practical point of view for engineers and designers of seawalls. The mathematical equations governing the fluid motion and its boundary conditions are presented. The deck problem together with the mathematical formulation and boundary conditions for the problem is presented in Chapters 5 and 6 by using a hybrid collocation method. For this case, the basis function method fails due to hyperbolic terms in these formulations growing exponentially. The formulations also include a secular term, not present in Cooker’s formulation. For Chapter 5, the wave hits the wall in a horizontal direction and for Chapter 6, the wave hits beneath the deck in a vertical direction. These problems are important for offshore structures where providing adequate freeboard for decks contributes very significantly to the cost of the structure. Chapter 7 looks at what happens when we have a vertical baffle. The mathematical formulation and the boundary conditions for four cases of baffles which have different positions are presented in this chapter. We use a basis function method to solve the mathematical formulation, and total impulse and moment impulse are investigated for each problem. These problems are not, perhaps, very relevant to coastal structures. However, they are pertinent to wave impacts in sloshing tanks where baffles are used to detune the natural tank frequencies away from environmental driving frequencies (e.g ship roll due to wave action) and to damp the oscillations by shedding vortices. They also provide useful information for the design of oscillating water column wave energy devices. Finally, conclusions from the research and recommendations for future work are presented in Chapter 8.

Coastal flooding from wave overtopping causes considerable damage. Presently, to model wave overtopping one can either make use of physical model tests or empirical tools such as those described in the EurOtop manual. Both these methods have limitations; therefore, a quick and reliable numerical model for wave overtopping would be a very useful tool for a coastal engineer.This research aims to test and develop a numerical model (in one horizontal dimension) for nearshore waves, runup and overtopping. The Shallow Water And Boussinesq (SWAB) model solves the Boussinesq-type equations of Madsen and Sorensen (1992) for non breaking waves and the nonlinear shallow water equations for breaking waves. Through testing against a range of physical model data using regular and random waves, the SWAB model's transfer from non-breaking to breaking waves was optimised. It was found that a wave height to water depth ratio worked consistently well as a breaking criterion.A set of physical model tests were carried out, based on previous field testing of wave overtopping that had previously taken place at Anchorsholme, Blackpool. The SWAB model was used to simulate some of these physical model tests, giving good results for mean overtopping rates. SWAB models the force imposed by steep walls and recurve walls on the incident flow; this force was found to have a significant effect on overtopping rates. A comparison was made between mean overtopping rates from the SWAB model, the physical model tests, empirically-based software (PC-Overtopping) and the field data. The physical model and SWAB results compared well with the field data, though the empirical software gave large overestimates.The SWAB model was applied to the analysis of overtopping at Walcott, Norfolk. It was found that beach levels affected overtopping rates, but not as much as different randomly phased wave trains. A simulation of a recent storm event was performed, with overtopping rates being slightly lower than those reported by local residents. A joint probability analysis showed that the predicted frequency of such an event was in line with these reports.An alternative modelling technique was also tested, where a spectral energy model was coupled with a nonlinear shallow water solver. Results for wave runup parameters were very accurate, when the coupling location is at the seaward edge of the surf zone. Extension of this modelling technique into two horizontal dimensions would be more straightforward than with the SWAB model.

[EN] The influence of the type of armor on wave overtopping on mound breakwaters is usually represented by the roughness factor. However, different values of roughness factor for the same armor unit are given in the literature. Thus, the roughness factor depends not only on the type of armor, number of layers and permeability but also on the formula and database considered. In the present thesis, a new methodology based on bootstrapping techniques is developed and applied to characterize the roughness factors for different armor units. Differences up to 20% appeared when comparing the optimum roughness factors with those given in the literature. Armor porosity greatly affects the roughness factor and the armor stability: higher armor porosities reduce wave overtopping as well as hydraulic stability. Therefore, armor porosity values usually recommended in the literature should be used to avoid damage during lifetime. Formulas with few variables are easy to apply but they allow the roughness factor to absorb the information not explicitly included in the formula. However, the CLASH neural network avoids this problem and gives excellent estimation for wave overtopping on mound breakwaters. In this thesis, a new formula which emulates the behavior of the CLASH neural network is developed. The new formula has 16 parameters, six dimensionless input variables (Rc/Hm0, Ir, Rc/h, Gc/Hm0, Ac/Rc and a toe berm variable based on Rc/h) and two reduction factors (¿f and ¿ß). The new formula is built-up after systematic simulations using the CLASH neural network and provides the lowest prediction error. Wave overtopping on mound breakwaters can be minimized by increasing the crest freeboard, usually with a concrete crown wall. Crown walls must resist wave loads and armor earth pressure to be stable. In the present study, small-scale test results with cube- and Cubipod-armored mound breakwaters are used to develop a new estimator for calculating horizontal and up-lift forces from waves. The new formulas include four dimensionless input variables (¿f Ru0.1%/Rc, (Rc-Ac)/Ch, ¿(L_m/G_c ) and Fc/Ch) and the crown wall geometry. The roughness factor selected for overtopping prediction is used to consider the type of armor. Up-lift forces decreased sharply with increasing foundation levels. The new formulas provide the lowest error when predicting wave forces on crown walls. / [ES] La influencia del tipo de elemento del manto sobre le rebase de diques en talud se caracteriza habitualmente mediante el factor de rugosidad (¿f). Sin embargo, en la literatura existen diferentes valores del factor de rugosidad para el mismo tipo de elemento. El factor de rugosidad no depende solo del tipo de elemento, número de capas y permeabilidad del núcleo sino también de la formulación y de la base de datos empleada. En la presente tesis se desarrolla y aplica una nueva metodología basada en técnicas de bootstrapping para caracterizar estadísticamente el factor de rugosidad de diferentes elementos (entre ellos el Cubípodo) sobre diferentes formulaciones de rebase. Se observan diferencias de hasta el 20% entre los factores de rugosidad óptimos y los que se proporcionan en la literatura. La porosidad del manto afecta notablemente al factor de rugosidad pero también a la estabilidad del manto; mayores porosidades proporcionan menor rebase pero también menor estabilidad hidráulica. Por ello, las porosidades de diseño recomendadas deben emplearse para evitar daños durante la vida útil. Fórmulas con pocas variables de entrada son sencillas de emplear pero absorben a través del factor de rugosidad toda la información que no se incluye explícitamente en las variables de entrada. En cambio, la red neuronal de CLASH evita en gran medida estos inconvenientes y al mismo tiempo proporciona excelentes para estimar el rebase sobre diques en talud convencionales. En la presente tesis se ha desarrollado una fórmula explícita que permite emular el comportamiento de la red neuronal de CLASH. La nueva fórmula posee 16 parámetros, seis variables de entrada (Rc/Hm0, ¿0,-1, Rc/h, Gc/Hm0, Ac/Rc y una variable para representar a la berma de pie basada en Rc/h) y dos factores de reducción (¿f y ¿ß). La nueva fórmula se construye en base a simulaciones controladas empleando la red neuronal de CLASH y proporciona el menor error en la predicción de rebase sobre diques en talud de entre los estimadores estudiados. Una de las maneras más efectivas de disminuir el rebase sobre diques en talud es incrementar la cota de coronación mediante un espaldón de hormigón. Estas estructuras sufren el impacto del oleaje y deben ser diseñadas para resistirlo. En la presente tesis se han empleado ensayos de laboratorio de cubos y Cubípodos para desarrollar una nueva fórmula que permita calcular las fuerzas horizontales y verticales del oleaje sobre el espaldón. Las nuevas fórmulas incluyen la influencia de cuatro variables adimensionales (¿f Ru0.1%/Rc, (Rc-Ac)/Ch, ¿(L_m/G_c ) y Fc/Ch) y de la geometría del espaldón. Incluyen la influencia del tipo de elemento mediante el factor de rugosidad al igual que las fórmulas de rebase. Las fuerzas verticales disminuyen significativamente con el aumento de la cota de cimentación. Las nuevas fórmulas proporcionan el menor error de predicción sobre los registros de laboratorio analizados. / [CAT] La influència del tipus d'element del mantell principal en l'ultrapassament dics en talús és caracteritza habitualment mitjançant el factor de rugositat (¿f). En canvi, en la literatura existeixen diferents valors del factor de rugositat per al mateix tipus d'element. Així doncs, el factor de rugositat no depèn només del tipus d'element, nombre de capes i permeabilitat del nucli però també de la formulació i de la base de dades utilitzada. En la present tesi es desenvolupa i aplica una nova metodologia basada en tècniques de bootstrapping per a caracteritzar estadísticament el factor de rugositat de diferent elements (entre ells el Cubípode) utilitzant diferents formulacions d'ultrapassament. S'observen diferències fins al 20% entre els factors de rugositat òptims i els que apareixen en la literatura. La porositat del mantell afecta notablement el factor de rugositat però també a l'estabilitat del mantell; majors porositats proporcionen menor ultrapassament però també menor estabilitat hidràulica. Per això, les porositats de disseny recomanades deuen emprar-se per a evitar danys durant la vida útil. Formules amb poques variables d'entrada són senzilles d'utilitzar però absorbeixen mitjançant el factor del factor de rugositat tota la informació que no s'inclou de manera explícita en les variables d'entrada. D'altra banda, la xarxa neuronal de CLASH evita en gran mesura aquests inconvenients i al mateix temps proporciona excel·lents resultats per a estimar l'ultrapassament sobre els dics en talús convencionals. En la present tesi s'ha desenvolupat una formulació explícita que permet emular el comportament de la xarxa neuronal de CLASH. La nova formulació té 16 paràmetres, sis variables d'entrada (Rc/Hm0, Ir, Rc/h, Gc/Hm0, Ac/Rc i una variable per a representar la berma de peu basada en Rc/h) i dos factors de reducció (¿f y ¿ß). La nova fórmula es construeix mitjançant simulacions controlades amb la xarxa neuronal de CLASH i proporciona el menor error en la predicció de l'ultrapassament sobre dics en talús de entre els estimadors analitzats. Una de les maneres més efectives de disminuir l'ultrapassament sobre dics en talús és incrementar la cota de coronació mitjançant un espatller de formigó. Aquestes estructures sofreixen l'impacte de les ones i deuen ser dissenyades per a resistir. En la present tesi, s'utilitzen assajos de laboratori de cubs i Cubípodes per a desenvolupar una nova formulació per a calcular les forces horitzontals i verticals causades per l'onatge en l'espatller. Les noves fórmules inclouen la influència de quatre variables adimensionals (¿f Ru0.1%/Rc, (Rc-Ac)/Ch, ¿(L_m/G_c ) y Fc/Ch) i de la geometria de l'espatller. Inclouen la influència del tipus d'element mitjançant el factor de rugositat al igual que les fórmules d'ultrapassament. Les forces verticals disminueixen significativament amb l'augment de la cota de cimentació. Les noves fórmules proporcionen el menor error en la predicció sobre els registres de laboratori analitzats. / Molines Llodra, J. (2016). Wave overtopping and crown wall stability of cube and Cubipod-armored mound breakwaters [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/62178 / TESIS

Thesis (MScEng)--Stellenbosch University, 2014. / ENGLISH ABSTRACT: Sea-level rise due to climate change results in deeper water next to existing coastal structures, which in turn enables higher waves to reach these structures. Wave overtopping occurs when wave action discharges water over the crest of a coastal structure. Therefore, the higher waves reaching existing structures will cause higher wave overtopping rates. One possible solution to address increasing overtopping, is to raise the crest level of existing coastal structures. However, raising the crest level of a seawall at the back of a beach, will possibly obstruct the view to the ocean from inland. Alternatively, recurves can be incorporated into the design of both existing and new seawalls. The recurve wall reduces overtopping by deflecting uprushing water seawards as waves impact with the wall. The main advantage of seawalls with recurves is that their crest height can be lower, but still allow for the same wave overtopping rate as vertical seawalls without recurves. This project investigates the use of recurve seawalls at the back of a beach to reduce overtopping and thereby reducing the required wall height. The objectives of the project are twofold, namely: (1) to compare overtopping rates of a vertical seawall without a recurve and seawalls with recurves; and (2) to determine the influence that the length of the recurve overhang has on the overtopping rates. To achieve these objectives, physical model tests were performed in a glass flume equipped with a piston type wave paddle that is capable of active wave absorption. These tests were performed on three different seawall profiles: the vertical wall and a recurve section with a short and a long seaward overhang, denoted as Recurve 1 and Recurve 2 respectively. Tests were performed with 5 different water-levels, while the wall height, wave height and period, and seabed slope remained constant. Both breaking and non-breaking waves were simulated. A comparison of test results proves that the two recurve seawalls are more effective in reducing overtopping than the vertical seawall. The reduction of overtopping can be as high as 100%, depending on the freeboard and wave conditions. Recurve 2 proves to be the most efficient in reducing overtopping. However, in the case of a high freeboard (low water-level at the toe of the structure), the reduction in overtopping for Recurve 1 and Recurve 2 was almost equally effective. This is because all water from the breaking waves is reflected. Even for the simulated lower relative freeboard cases, the recurve walls offer a significant reduction in overtopping compared with the vertical wall. A graph is presented which shows that the length of the seaward overhang influences the overtopping performance of the seawall. As the seaward overhang length increases, the wave overtopping rate decreases. However, for high freeboard cases the length of the seaward overhang becomes less important. The graph gives designers an indication of how recurves can be designed to reduce seawall height while retaining low overtopping. It is recommended that further model tests be performed for additional overhang lengths. Incorporation of recurves into seawall design represents an adaptation to problems of sea-level rise due to global warming / AFRIKAANSE OPSOMMING: Stygende seevlak as gevolg van klimaatverandering, veroorsaak dat dieper water langs bestaande kusstrukture voorkom. Gevolglik kan hoër golwe hierdie strukture bereik. Golfoorslag vind plaas wanneer water oor die kruin van ‘n kusstruktuur, hoofsaaklik deur golfaksie, spat of vloei. Dus sal hoër golfhoogtes tot verhoogde golfoorslag lei. Een moontlike oplossing vir hierdie verhoogde golfoorslag is om die kruinhoogte van bestaande kusstrukture te verhoog. In die geval van ‘n seemuur aan die agterkant van ‘n strand, kan hoër strukture egter die see-uitsig na die see vanaf die land belemmer. Om hierdie probleem te vermy, kan terugkaatsmure in die ontwerp van bestaande en nuwe seemure ingesluit word. Terugkaatsmure verminder golfoorslag deurdat opspattende water, afkomstig van invallende golwe terug, na die see gekaats word. Die grootste voordeel van ‘n terugkaatsmuur is dat hierdie tipe muur ‘n laer kruinhoogte as die vertikale seemuur sonder ‘n terugkaatsbalk, vir dieselfde golfoorslagtempo kan hê. Hierdie projek ondersoek dus die gebruik van terugkaatsmure aan die agterkant van ‘n strand met die doel om golfoorslag te verminder en sodoende die vereiste muurhoogte te verminder. Die doelwit vir die projek is tweeledig: (1) om die golfoorslagtempo van terugkaatsmure te vergelyk met dié van ‘n vertikale muur sonder ‘n terugkaatsbalk; en (2) om die invloed van die terugkaatsmuur se oorhanglengte op die golfoorslagtempo te bepaal. Om bogenoemde doelwitte te bereik, is fisiese modeltoetse in ‘n golfkanaal, wat met ‘n suiertipe golfopwekker toegerus is en wat aktiewe golfabsorbering toepas, uitgevoer. Hierdie toetse is op drie verskillende seemuurprofiele, naamlik ‘n vertikale muur en ‘n terugkaatsmuur met ‘n kort en lang oorhang, genaamd “Recurve 1” en “Recurve 2” onderskeidelik, uitgevoer. Die muurhoogte, die seebodemhelling asook die golfhoogte en –periode is tydens al die toetse konstant gehou. Vir elke profiel is toetse by 5 verskillende watervlakke vir beide brekende en ongebreekte golwe uitgevoer. Uit die toetsresultate is dit duidelik dat terugkaatsmure meer effektief as vertikale mure is om golfoorslag te beperk. Die vermindering van golfoorslag kan tot 100% wees, afhangende van die vryboord en golftoestande. Daar is bevind dat “Recurve 2” golfoorslag die effektiefste verminder. In die geval van hoë vryboord (lae watervlak by die toon van die struktuur) is daar egter gevind dat “Recurve 1” en “Recurve 2” die golfoorslag feitlik ewe goed beperk. Dit is die geval aangesien alle water van die brekende golwe weerkaats word. In die geval van ‘n lae vryboord, word die voordeel van die terugkaatsmuur teengewerk deurdat daar ‘n kleiner verskil in golfoorslagtempo’s tussen die drie profiele is. ‘n Grafiek is voorgelê wat wys dat die lengte van die terugkaatsmuur se oorhang golfoorslag beperk. ‘n Groter oorhanglengte van die terugslagmuur veroorsaak ‘n groter vermindering in golfoorslag. Vir gevalle met ‘n hoë vryboord, is daar egter gevind dat die oorhanglengte van die terugslagmuur minder belangrik is. Hierdie grafiek gee ontwerpers ‘n aanduiding van hoe terugslagmure ontwerp kan word met ‘n lae hoogte terwyl ‘n lae oorslagtempo behou word. Die gebruik van terugslagmure bied ‘n aanpassing vir die probleme van seevlakstyging, as gevolg van klimaatverandering.

学位授与大学：京都大学 ; 取得学位: 博士(工学) ; 学位授与年月日: 2007-09-25 ; 学位の種類: 新制・課程博士 ; 学位記番号: 工博第2844号 ; 請求記号: 新制/工/1418 ; 整理番号: 25529 / An atmosphere-ocean coupled model was developed based on a preexisting non-hydrostatic mesoscale atmosphere model (MM5) and non-hydrostatic ocean circulation model (MITgcm). This model together with a pre-established wind-wave-currents coupled model was applied to a number of regional environmental issue and disaster events to reproduce the present status and past situations and to help our understanding of the physical processes of such problems in terms of atmosphere-ocean interactions including the sea surface waves in the interface between air and sea. The disaster events and environmental issue studied in this thesis are follows. 1) Storm surge induced by Hurricane Katrina in the Gulf coast of USA in 2005. 2) Extreme high waves at Hara coast, Suruga Bay in Japan caused by the super-Typhoon TIP in 1979. 3) Positive and negative feedbacks in typhoon-ocean interaction in case of Typhoon ETAU in 2003. 4) Thermal water circulation in a dam-made lake (Yachiyo Lake) in Hiroshima, Japan concerning on the hydrodynamics in the lake. 5) Reanalysis of the past 47 storms that caused disasters in West Kyushu, Japan. 6) Wave overtopping simulation over through the submerged offshore breakwater and enhance seawall. The Regional Environment and Disaster Prevention Simulator is proposed and constructed based on the regional atmosphere-ocean coupled model in this thesis of which the objective was improvement of the numerical assessment method to disaster events and environment problems by introducing he coupling effects between different systems. / Kyoto University (京都大学) / 0048 / 新制・課程博士 / 博士(工学) / 甲第13373号 / 工博第2844号 / 新制||工||1418(附属図書館) / 25529 / UT51-2007-Q774 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 関口 秀雄, 教授 間瀬 肇, 教授 中北 英一 / 学位規則第4条第1項該当

This thesis describes experiments that were carried out using focused wave groups in the UK Coastal Research Facility (UKCRF). Considerable effort was put into calibrating the UKCRF to determine the relationship between the input signals sent to the paddles and the waves generated in the facility. Focused wave groups of various sizes and phases, based on NewWave theory were generated, and measurements were made of the resulting surface elevation data, water particle kinematics, wave runup and overtopping volumes. NewWave theory models the profile of extreme waves in a Gaussian (random) sea. The thesis describes the first time this model has been applied in the context of coastal wave transformation. A method for the separation of the underlying harmonic structure of a focused wave group is described and results presented. This technique has been used in relatively deep water but is shown to work successfully in the coastal zone until wave overturning. A method has been devised to provide a theoretical Stokes-like expansion of the free and bound waves to model the surface elevation and water particle kinematics of the focused wave groups. Satisfactory agreement is achieved between the theoretical predictions of UKCRF measurements. Suggestions are made for an improved model. The underlying harmonic structure of the focused wave groups is presented as stacked time histories that give insight into the wave transformation process from deep to shallow water. Particular attention is paid to the low frequency wave generated as the wave group interacts with the beach. This is compared to the low frequency wave that is generated by a solitary wave in the UKCRF. Runup and overtopping measurements are in reasonable agreement with predictions based on certain empirical formulae, but not others. These comparisons are useful in identifying those formulae able to predict runup and overtopping of extreme waves in the coastal zone.