bluuebunny/crossref_metadata_2025 huggingface dataset:
MECHANICALLY COUPLED BUOYANT FLAPS: THEORY AND EXPERIMENT
Authors: Sollitt Charles K. , Lee Chung-Pan , McDougal William G. , Perry Thomas J.
Published: June 2019

A system composed of two buoyant flaps hinged at the sea floor and coupled with weighted mooring lines is modeled analytically and experimentally. The system behavior is described theoretically utilizing an eigenseries representation of linear wave theory in the vicinity of the breakwater. The structure dynamics are modeled in terms of structure weight, inertia, buoyancy, damping, mooring line tension and the wave pressure field. The mechanically coupled system provides shelter by reflecting incident waves and by attenuating wave energy through structural and viscous damping. The structure can be tuned to minimize wave transmission within a particular frequency range by changing the flap spacing and adjusting the mass and equilibrium position of the mooring line weights. The theory is validated with experimental results for models fabricated from inflatable, parallel-tube membranes. Buoyancy and inertia are changed by filling tubes with air and/or water. Single and double flaps are examined with and without mooring lines. Incident, reflected, and transmitted waves are measured as well as flap motion. Theoretical results are corroborated by the experiments and the importance of including damping in the model is demonstrated.
2 - D CIRCULATION IN THE SARONIC GULF
Authors: Christodoulou George C. , Kouloumbis Arthanassios E. , Aza Alice O.
Published: June 2019

The paper refers to mathematical modeling of the 2-D hydrodynamic circulation in the Saronic Gulf, in Greece. The finite element method is followed to evaluate the flow behaviour. Two grids are employed, a coarse one for initial model adaptation and a finer one for a more detailed study of circulation patterns. Actual tide data are obtained at the boundary of the domain and a typical compound tide is introduced; however residual tidal currents are found to be negligible. Wind-generated flow fields under several prevailing wind directions are determined and their comparison to qualitative field evidence is satisfactory. Furthermore, a possible surface tilt along the open boundary associated with large scale circulation in the Aegean Sea, is studied and shown to produce, significant motion in the Gulf. Based on circulation patterns obtained, preliminary estimates of dispersion from a proposed sea outfall for Athens sewage can be made. Further work proceeds towards quantitative verification of the model in connection with the proper description of forcing mechanisms and their superposition.
TSUNAMI THREAT EVALUATION BY HISTORICAL DOCUMENTS, NUMERICAL MODEL AND STOCHASTIC MODEL
Authors: Nakamura Shigehisa
Published: June 2019

An evaluation of local tsunami threat was studied first refering to the historical documents and the catalogs. Secondly, an example of a numerical model of a finite difference method was discussed in relation to problems for reproducing the past local tsunamis and predicting a forthcoming tsunami. Lastly, a stochastic model was utilized in order to evaluate an exceedance probability of tsunami occurrencein an interested time period at an interesting local area where the concerened information or prediction was in need. The evaluation of a local tsunami threat is useful to get a more effective measure for the tsunami warning system and for protection works.
A GRID MODEL FOR SHALLOW WATER WAVES
Authors: Holthuijsen Leo H. , Booij Nico
Published: June 2019

Waves in coastal regions can be affected by the bottom, by currents and by the local wind. The traditional approach in numerical modelling of these waves is to compute the wave propagation with so-called wave rays for mono-chromatic waves (one constant period and one deep water direction) and to supplement this with computations of bottom dissipation. This approach has two important disadvantages. Firstly, spectral computations, e.g. to determine a varying mean wave period or varying shortcrestedness, would be rather inefficient in this approach. Secondly, interpretation of the results of the refraction computations is usually cumbersome because of crossing wave rays. The model presented here has been designed to correct these shortcomings: the computations are carried out efficiently for a large number of wave components and the effects of currents, bottom friction, local wind and wave breaking are added. This requires the exploitation of the concept of the spectral action balance equation and numerical wave propagation on a grid rather than along wave rays. The model has been in operation for problems varying from locally generated waves over tidal flats to swell penetration into Norwegian fjords. A comparison with extensive measurements is described for young swell under high wind penetrating the Rhine estuary.
AN ADJUSTABLE MARINE FENDER SYSTEM PROGRAMMED WITH THE AID OF NUMERICAL MODELS IN ORDER TO MINIMIZE BERTHING AND MOORING LOADS
Authors: Risselada Tj. J. , Deelen C.
Published: June 2019

An adjustable marine fender system, programmed with the aid of mathematical models, can substantially contribute to safer berthing and mooring of ships with various water displacements, operating at high or at low speed under varying wind, wave and current conditions. This doesn't only imply a reduction of risks to vessel and terminal structures but also in case of exposed sites or of unruly waters, a - possible substantial - reduction of ship's costly down-time.
DETERMINATION OF WIND STRESS (DRAG) COEFFICIENT FOR COASTAL WATERS UNDER VARIABLE METEOROLOGICAL AND OCEANOGRAPHIC CONDITIONS
Authors: Hsu S.A.
Published: June 2019

On the basis of a parametric model of wind stress (drag) coefficient over water surfaces and related experiments, objective procedures to obtain this coefficient under variable wind and wave conditions are outlined and recommended for oceanographic applications and air-sea interaction studies. Methods for both fully and non-fully developed sea conditions are given.
LATERAL MIXING AND WAVE DIRECTION IN THE WAVE-CURRENT INTERACTION REGICN
Authors: Kim Kyoung Ho , Toru Sawaragi , Ichiro Deguchi
Published: June 2019

The lateral mixing coefficient, in which the wave energy dissipation by wave breaking is taken account and the assumption of Richardson's 4/3 power law is involved, is derived for the surf zone and the diffusion of tracers injected in the wave-current interaction region is discussed experimentally to investigate the proposed lateral mixing coefficient. Furthermore measurements of velocity field on the three dimensional sloping beach of plane wave flume have been made by a bidirectional electromagnetic current meter. The results were used to investigate the characteristics of the structure of on-offshore and alongshore mean currents arid the techniques for the determination of wave angle in the surf zone.
CIRCULATION KINEMATICS IN NONLINEAR LABORATORY WAVES
Authors: Kim Tae-in , Hudspeth Robert T. , Sulisz W.
Published: June 2019

A weakly nonlinear solution is presented for the two-dimensional wave kinematics forced by a generic wavemaker of variable-draft. The solution is valid for both piston and hinged wavemakers of variable draft that may be double articulated. The second-order propagating waves generated by a planar wave board are composed of two components; viz., a Stokes second-order wave and a second-harmonic wave forced by the wavemaker which travels at a different speed. A previously neglected time-independent solution that is required to satisfy a kinematic boundary condition on the wavemaker as well as a mixed boundary condition on the free surface is included for the first time. A component of the time-independent solution is found to accurately estimate the mean return current (correct to second-order) in a closed wave flume. This mean return current is usually estimated from kinematic considerations by a conservation of mass principle.
DECOMPOSITION OF NONLINEARLY REFLECTED IRREGULAR WAVES BY THE WAVE BREAKING AND DEFORMATION
Authors: Kimura A.
Published: June 2019

This paper deals with a new method to decompose incident and reflected waves from the measured data of irregular standing waves. The theory by Goda et al. is extended to cope with the reflection from such a coastal structure that has a sloping surface and brings about different reflection coefficient for each incident waves. Irregular standing waves are decomposed into incident and reflected irregular waves by the shortterm wave spectrum analysis method. And the reflection coefficient of the approximated zero-up-cross waves are defined as the ratio between envelopes of these irregular wave profiles. The calculated reflection coefficients can be discussed in terms of the incident zero-up-cross wave parameters such as a wave steepness, Ursell parameter, etc. An effective wave gauge system to measure irregular standing waves which have a wide band spectrum is also discussed and a method to compose the system is proposed.
LARGE-ANGLE PARABOLIC EQUATION METHODS
Authors: Kirby James T.
Published: June 2019

Large-angle parabolic equation methods for the propagation of surface water waves are discussed. The methods described here are limited to forms which are solvable by the Crank-Nicolson method, but are successful in opening the allowed range of propagation directions to ~ 50° with respect to normal incidence.
WAVE GROUPINESS AS A SOURCE OF NEARSHORE LONG WAVES
Authors: List Jeffrey H.
Published: June 2019

Data from a low energy swell-dominated surf zone are examined for indications that observed low frequency motions are simply group-forced bounded long waves. Time series of wave amplitude are compared to filtered long wave records through cross-spectral and cross-correlation analysis. These methods are found to have limited usefulness until long waves are separated into seaward and shoreward components. Then a clear picture of a rapidly shoaling bounded long wave emerges, with a minimum of nearly one fourth of the long wave amplitude being explainable by this type of motion close to shore. Through the zone in which waves were breaking, and incident wave amplitude variability decreased by 50%, the contribution from the bounded long wave continued to increase at a rate much greater than a simple shoaling effect. Also present are clear signs that this amplified bounded long wave is reflected from a position close to the shoreline, and is thus released from wave groups as a free, offshore-progressive wave.
EVALUATION OF A MODIFIED STRETCHED LINEAR WAVE THEORY
Authors: Lo Jen-Men , Dean R.G.
Published: June 2019

Many experimental investigations of the drag and inertia force coefficients have relied on the determination of water particle kinematics from measured wave forms. Since the pioneering work of Airy (1845), Stokes (1847, 1880) and others, a number of wave theories have been developed for predicting water particle kinematics. Clearly, the use of a certain wave theory will lead to corresponding force coefficients. Therefore, a wave theory that provides more accurate water particle kinematics is very important. Reid (1958) developed the simple superposition method for predicting water particle kinematics from a measured sea surface that could be either random or periodic. The method is based upon linear long-crested wave theory. Borgman (1965, 1967, 1969a, 1969b) introduced the linearized spectral density of wave force on a pile due to a random Gaussian sea. The drag force component has been approximated in the simplest form by a linear relation. This method, however, cannot calculate properties of the wave field and wave force above the mean water level. Wheeler (1969) applied simple superposition with a stretching factor in the vertical coordinate position for hurricane-generated wave data during Wave Project II. With this method it was possible to evaluate the wave force above the mean water level.
AN EFFICIENT STATISTICAL METHOD OF ESTIMATION OF EXTREME MARITIME EVENTS USING TWO SETS OF RELATED INFORMATION
Authors: Manoha B. , Bernier J. , Graff M.
Published: June 2019

The construction of marine works necessitates a good knowledge of the extreme events which can affect it, such as the storm waves or the water levels. A statistical method of estimation of these extreme events has been developped at L.N.H. The principle of this method, based on the theory of renewal processes, is presented hereafter, as well as the results that it can provide. Some applications of the method are described in the paper ; in particular the application to a site where the available data are insufficient, and where the method enables to precise the results by using complementary numerous data on a neighbouring site, is presented.
APPROXIMATION DESCRIPTIONS OF THE FOCUSSING OF WATER WAVES
Authors: Peregrine D.H.
Published: June 2019

Underwater shoals and spurs focus water waves that propagate over them. The normal theoretical approach to finding a more accurate solution of the linear equations is to interpret the envelope of crossing rays as a cusp of caustics (see Figure 1) and to use Pearcey's function (Pearcey 1946). In practical cases the ray pattern is rarely sufficiently well defined to enable the cusp parameters to be deduced. An alternative approach is presented in which a length of wave crest heading towards the focussing region is approximated by an arc of a circle or parabola (Figure 2). Corresponding approximate solutions for linear and weakly nonlinear waves are described.
WAVE HEIGHT DECAY MODEL WITHIN A SURF ZONE
Authors: Sakai Shigeki , Hiyamizu Kouetsu , Saeki Hiroshi
Published: June 2019

A model for wave height decay of a spilling breaker is proposed. The energy dissipation of a breaking wave is approximated by that of a propagating bore. In order to explain the gentle decay of spilling breaker at the initial stage, a development of a foam region, which indicates the amount of foam on the wave profile and determines the rate of energy dissipation, is considered. In addition to this formulation, the energy and momentum balance equations are described by a linear wave theory in shallow water and are simultaneously solved. Comparisons with experimental results show that the model gives a good prediction in both inner and outer regions, and that two coefficients in the present model are related to the deep water wave steepness and the slope of beaches.
VORTEX FORMATION IN PLUNGING BREAKER
Authors: Sakai T. , Mizutani T. , Tanaka H. , Tada Y.
Published: June 2019

By a flow visualization of a plunging breaker on 1/20 slope beach in a wave tank, an existence of 2nd and 3rd horizontal vortices(Miller, 1976) and slanting vortex (Nadaoka et al., 1986) is confirmed. A MAC method is applied to simulate a violent motion after an impinging of a jet from a crest of a plunging breaker on the trough surface. The calculated maximum water particle velocity in the jet is found to reach three times the linear long wave celerity. Values of circulation of the first four horizontal vortices are calculated and their changes in time are discussed.
TIDAL COMPUTATIONS FOR THE YELLOW SEA
Authors: Choi Byung Ho
Published: June 2019

A two-dimensional numerical model of the Yellow Sea has been used to compute cotidal and coamplitude charts and harmonic constants of tidal currents for the four major tidal constituents M2, S2, Ki, Oi tides in the region with the mesh resolution of 1/5 degree latitude by 1/4 degree longitude finite difference grid system. An additional model incorporating dynamical grid nesting procedure which employs a one-third grid refinement scheme was also used to reproduce the M2 tidal regime in more detailed resolution for the part of west coast of Korea where extensive coastal development including potential tidal power and land reclamation scheme is concerned. Comparisons between observations and model result have been carried out based on coastal gauges and moored current meter data. Reasonable agreement was found between obsevations and model results, thus supporting the computed distribution of tides in the region. It was also shown that the dynamically linkaged model particularly well within 5% in amplitude and 5 degrees in phase of observed M2 tide in the refined mesh region of the west coast of Korea.
REAL-TIME WAVE FORECASTING WITH ADAPTIVE ARMAX MODELS
Authors: Wensink H. , Schilperoort T.
Published: June 2019

A method is described for improving the accuracy of the wave predictions which are required for the operational guidance of the shipping traffic in approach channels to harbours and to support offshore activities. The method, as being described here, is based on the assimilation of wave physics and real-time hydrometeorological observations into a statistical time series model called ARMAX.
A NEW EQUILIBRIUM ANALYSIS FOR NEARSHORE TIDAL BASINS
Authors: Diechmann R. , Partenscky H.W.
Published: June 2019

A large tidal flat area of about 40 tidal basins with catchment areas of between 10 and 790 km2 exists along the coast of the German Bight. Not all of these tidal basins are morphologically stable. The main parameter necessary for determining the state of equilibrium is the volumetric capacity of the concave portions of the tidal basin. In order to examine the equilibrium state it is necessary to compare the volumetric capacity of the tidal basin determined from hydrographic charts (measured volume) with a theoretical volume given by newly developed stability criteria representing averaged conditions (volume balances). Significant deviations between the theoretical and the measured volumes indicate a state of non-equilibrium. Using stability criteria it is possible to desribe the state of equilibrium of a tidal basin in a stepwise manner either from the bottom of the tidal basin to the datum plane MHW in order to obtain a cross-sectional stability profile, or from the shore to the seaward boundary of the basin in order to obtain a longitudinal stability profile. The applicability of the new method for analyzing the equilibrium of a tidal basin will be demonstrated by the example of the Suderau tidal basin in the north of Germany.
FEDERAL JETTY AND SAND DIKE AT THE ENTRANCE OF FIRE ISLAND INLET, NEW YORK
Authors: Galvin Cyril , Rooney Charles J. , Nersesian Gilbert K.
Published: June 2019

Prior to construction at Fire Island Inlet, Fire Island was moving westward at more than 200 feet per year, the north shore of the inlet was eroding severely, and navigation in the inlet was difficult. The Federal Jetty, completed in 1941, and the sand dike, built in 1959, have halted the westward migration, eliminated the severe erosion, and partially improved navigation, with minimal maintenance or repair to the structures. There has been a large net accretion of sand east of the jetty and west of the dike, an unknown part of which is at the expense of shores to the west of the inlet. At the State Park on the south side of the inlet interior, erosion accelerated, probably because of the dike. The middle and ocean segments of the 4750-foot Federal Jetty are now (1987) in good condition, although the design implies a stability coefficient for the quarrystone jetty head at time of construction that would now be considered risky. Stability has been promoted by a stone blanket under and east of the jetty, a thick stone apron seaward of the jetty, a low (8 feet MLW) crest, and armor stone that has been partially keyed in place. Damage due to scour, common at other single-jetty inlets, is absent here because longshore transport, which easily overtops the low crest, keeps the inlet channel away from the jetty. Although the two seaward segments of the jetty remain in good condition, the inshore segment of the jetty is in poor condition, despite its apparently sheltered location. The cumulative effects of waves, possibly channeled to the site along recurved spits during storms, have damaged 1200 feet, and tidal scour has destroyed about 230 feet. The damaged segment has a design cross section which is onefifth and one-twelfth the cross sections of the jetty trunk and head.
TWO-DIMENSIONAL EMPIRICAL EIGENFUNCTION MODEL FOR THE ANALYSIS AND PREDICTION OF BEACH PROFILE CHANGES
Authors: Hsu T.W. , Liaw S.R. , Wang S.K. , Ou S.H.
Published: June 2019

A two-dimensional empirical eigenfunction model is proposed for the analysis and the prediction of beach profile change due to longshore and cross-shore sediment transports. Beach profile data from Redhill coast, Taiwan, measured every two months at 150 meters interval along the detached breakwaters are analyzed and the relative importance from two directions is investigated. Furthermore, by employing the method of Markov process and linear regression, a prediction model is formulated which takes into account the effect of breaking waves, bottom sediment and radiation stress of waves. This 2-D model is shown to be effective in the analysis and the prediction of beach changes near the coastal structures.
IMPACT OF OFFSHORE DREDGING ON BEACHES ALONG THE GENKAI SEA, JAPAN
Authors: Kojima Haruyuki , Ijima Takeshi , Nakamuta Takaaki
Published: June 2019

Offshore dredging has been taking place in the coast of the Genkai Sea, Japan, since the early 1970's, which totaled more than 20 million cubic meters. In order to evaluate the impact of offshore dredging on shorelines as well as the adjacent sea bed, comprehensive coastal engineering studies were carried out over the last four years. The results obtained are not sufficient to establish a direct cause-andeffect relationship between offshore dredging and beach erosion; however, the correlation is sufficient to serve as a warning of a potentially serious problem. Moreover, the dredged holes above 30 meter depth are found to trap the sand from the neighboring bed, and considerable movement of sediment by wave action was observed above 3 5 meter depth. Thus, offshore mining that would minimize interruption of beach littoral system should be operated below 35 meter depth in the study area.
WAVE RUN-UP ON A NATURAL BEACH
Authors: Takezawa Mitsuo , Mizuguchi Masaru , Hotta Shintaro , Kubota Susumu
Published: June 2019

The swash oscillation, waves and water particle velocity in the surf zone were measured by using 16 mm memo-motion cameras and electromagnetic current meters. It was inferred that incident waves form two-dimensional standing waves with the anti-node in the swash slope. Separation of the incident waves and reflected waves was attempted with good results using small amplitude long wave theory. Reflection coefficient of individual waves ranged between 0.3 and 1.0. The joint distribution of wave heights and periods in the swash oscillation exhibited different distribution from that in and outside the surf zone. This indicates that simple application of wave to wave transformation model fails in the swash zone.
EROSION AROUND A PILE DUE TO CURRENT AND BREAKING WAVES
Authors: Bijker E.W. , De Bruyn C.A.
Published: June 2019

Tests have been performed on a vertical pile subject to current only and to a combination of current with normal waves and current with breaking waves. The scour around the pile produced by current only is decreased by normal short waves superimposed upon that current and increased when breaking waves are superimposed upon the current. After analysis of the velocity profiles in the undisturbed area upstream of the pile and next to the pile, the following explanation is found for this phenomenon. When normal short waves are superimposed upon a current, the bottom shear stress of the combination of current with waves is increased more in the undisturbed area than next to the pile in the scour area. This results in a decrease of the scour around the pile. Due to the large values of the orbital velocity under breaking waves this effect is reversed for the combination of a current with breaking and relatively long waves. This results in an increase of the scour around the pile.
DESIGH OP POCKET BEACHES- THE SPANISH CASE
Authors: Berenger Jose Ma , Enriquez Javier
Published: June 2019

Pocket beach is a usual method to restore an eroded or regressive: coast without natural sand supply. Nowadays, there are more than 40' of these beaGhes on. the Spanish coasts and a lot of them all over the world. This paper deals with the design parameters of pocket beaches, based on the analysis of data collected from 24 existing beaches on the Mediterranean coast of Spain. Fourteen of these beaches have been studied in detail; nine of them located on the Alboran Sea and. the other five on the coast of Cataluna. Data from 10 additional be.aciLes have also been considered-. Different parameters such as structural design, location of breakwaters, beach planform, beach profile, wave conditions at the site and sediment-ary conditions have been analyzed. A mathematical model has been used for the study of the shoreline equilibrium planform. Practical coastal criteria-design considerations have been drawn from the observed behaviour of "the aforementioned beaches.
BED RESPONSE TO FAIRWEATHER AND STORM FLOW OH THE SHOREFACE
Authors: Green Malcolm O. , Boon John D. , List Jeffrey H. , Wright L. Don
Published: June 2019

Bailard's (1981) model of combined-flow, total-load sediment transport was used to calculate sediment flux at 8-m depth on a wave-dominated shoreface during fairweather and during a storm. Waves were skewed onshore during fairweather, however it was the reversing tidal current that controlled predicted transport direction. Transport direction during the early phase of the storm was also controlled by the mean flow, this time a wind-driven jetlike flow with an offshore component. As the storm progressed, waves became more organized and highly skewed, and by the end of the storm, predicted sediment transport was turned onshore by the shoreward-skewed waves against the mean flow. Measurements of changes in relative bed elevation at the 8-m depth site were used to verify the transport predictions. A total of 6 cm of accretion occurred over H.5 days of low-energy flow. It was found that predicted onshore transport was strongly correlated with erosion at the 8-m depth site, and predicted offshore transport was strongly correlated with accretion. Five cm of scour occurred during the initial phase of the storm, followed by 15 cm of rapid accretion. Onset of accretion was coincident with the organization of surface waves into long-period swell, and the maximum accretion rate was coincident with the most highly-skewed waves.
BEACH PROFILE CHANGE UNDER VARYING WAVE CLIMATES
Authors: Kai Yen , Rushu Ren , Liang Wang
Published: June 2019

In the present paper results of experimental study of two-dimensional transformation of sandy beach under varying wave climates are presented. The varying wave climates were composed of different systems of regular waves exerted one after another on the model beach. Through experiments it was found that sandy beach transformation within surf zone could be expressed by the changes of characteristic point A and characteristic slope tan 13, and that although the expression for beach erosion-accretion criteria is dimensionless, similitude scale effects should still be taken into consideration.
REALISTIC ECONOMIC BENEFITS FROM BEACH NOURISHMENT
Authors: Dean Robert G.
Published: June 2019

A method is presented and Illustrated with examples to establish appropriate storm damage reduction and recreational benefits from beach nourishment projects. Unlike previous methods, benefits to project adjacent areas are recognized due to sand transport out of the project area and deposition on adjacent beaches. Assuming homogeniety along the shoreline, the character of storm damage reduction and recreational benefit relationships are such that sand transported from a project area and deposited on adjacent beaches always results in an increase rather than a reduction in benefits. A central element in calculating storm damage reduction benefits is the establishment of a proportional damage curve for upland structures as a function of beach width and storm return period. To illustrate the method, limiting cases are presented in which (A) all sediment remains within the area placed, and (B) all sediment spreads out immediately over a long segment of shoreline. Using Monte Carlo simulation to represent the random character of the storms, the method is applied to 15 realistic cases with varying project lengths, representative wave heights, added beach widths and interest rates. The present worth storm damage reduction and recreational benefits are calculated to demonstrate the effects of the various parameters. It is found that for short project lengths and relatively large wave heights, the benefits from project adjacent areas exceed those in the project area where the sand is placed. Although no littoral control structures, such as jetties are included in the present application, the method could be extended readily to include their effects.
GENERALIZED WAVE THEORY FOR A SLOPING BED
Authors: Swart D.H. , Crowley J.B.
Published: June 2019

This paper discusses the development from first principles of a first-order solution for non-breaking waves on a gently sloping bottom. The theory is derived in a similar fashion as was done by Swart and Loubser (1978) for vocoidal waves on a horizontal bottom. The resulting covocoidal theory was compared to an extensive data set for waves over a sloping bottom (Nelson, 1981) and is tested for analytical validity. It adheres exactly to continuity and the kinematic free surface boundary condition, and shows comparable errors in the dynamic free surface boundary condition to that found for the better, general horizontal bed wave theories.
CARIBBEAN BEACH-FACE SLOPES AND BEACH EQUILIBRIUM PROFILES
Authors: Boon John D. , Green Malcolm O.
Published: June 2019

Field measurements performed on two Caribbean islands revealed that two-dimensional nearshore bottom morphology is well represented by Dean's (1977) model of the beach equilibrium profile, h - A xm, where h is depth below mean water level at a distance x offshore and A is a scale factor. For the curvature, m, we obtained an average value of approximately m - 1/2 through least squares curve fitting of observed profile data, yielding a more concave and therefore steeper profile inshore than m - 2/3, the average previously reported by Dean for quartz sand beaches in the United States. Furthermore, an objective measure of beach steepness was found to be A-*-'1", a quantity which utilizes both of Dean's parameters and which may serve as a surrogate for the beach-face slope, tan /3, on highly concave beaches. Reasonable correlations were found between A?-'m and the environmental parameter, H^ /gDT , where H^ is breaker height, D is sediment grain size, T is wave period and g is gravitational acceleration. Improved prediction of Caribbean beach slopes and beach equilibrium profiles is an important practical result.
SEDIMENT SUSPENSION DUE TO LARGE SCALE EDDIES IN THE SURF ZONE
Authors: Nadaoka Kazuo , Ueno Seizo , Igarashi Tatsuyuki
Published: June 2019

Laboratory experiments using a fiber-optic LDV system and a small pressure transducer have been made to reveal detailed characteristics of the velocity field in the surf zone and its relationship to the sediment suspension with special reference to the three-dimensional large scale eddies referred to as "obliquely descending eddies", the existence of which was recently revealed by Nadaoka (1986). A conditional sampling technique has been used to find that the obliquely descending eddies bring highly intermittent intensive turbulence to the bottom with the large onshoreward momentum at the upper layer of the water and thus essentially characterize the turbulent flow field in the surf zone. Visual observation and concentration measurements, especially a coherence analysis of two data sets of concentration close to the bottom, have shown that the sediment suspension is mostly governed by such large scale eddies in a wide extent of the surf zone; i.e., the eddies hit the bottom and then lift up the sediment into suspension, yielding the spot-like sediment cloud in accordance with the three-dimensional eddy structure.
VALIDATION OF CROSS-SHORE TRANSPORT FORMULATIONS
Authors: Seymour Richard J. , Castel David
Published: June 2019

Seymour and King (1982) evaluated eight models for predicting cross-shore transport using beach profile data from the Torrey Pines experiment of the Nearshore Sediment Transport Study (NSTS). None of the models showed useful skill in predicting the sense, or direction, of transport. Three more data sets were acquired under NSTS and have been used in the present work to re-evaluate the original four models as well as another six not previously tested. The three new data sets include two nominally plane West Coast beaches and a barred beach on the Atlantic coast, each under a variety of wave conditions. Six of the models evaluated claimed a capability to predict the sense of the cross-shore transport, two predicted the beach slope as a result of cross-shore movement, and two gave detail predictions of changes to the beach profile position and shape. The performance of the six models predicting direction of transport ranged from a skill factor of 0.49 (less than chance) to only 0.68. Five of the models required large changes to their calibration factor (usually based upon laboratory data) in order to have approximately the same skill in predicting erosion or accretion. One of the slope models was validated and the other gave no useful results. One of the two generalized models gave interesting results in predicting the time history of profile changes on the plane beaches for which it was developed. The other general model was not evaluated because it exhibited the lowest skill in predicting direction of transport.
VERTICAL VARIABILITY OF COASTAL SEDIMENT TRANSPORT
Authors: Zeidler Ryszard B.
Published: June 2019

The semiempirical theory of turbulent diffusion may be used as a mathematical tool for description of suspended sediment mechanics. The Author's solutions, with their exponential vertical profiles of sediment concentration, are presented in various ranges of time, space, and external factors. The inherent concept of eddy diffusivity K is shown to be ambiguous and incoherent. Therefore it is purposeless to investigate thoroughly the vertical profiles and other details of K. Accordingly, the Author makes use of his own and alien laboratory and field findings to propose such estimates of K under regular waves and currents which are not continuous functions of the vertical coordinate but instead are locally averaged over depth layers. These estimates become more complex in real coastal zones due to the randomness of waves and currents, wave breaking, three-dimensionality and nonstationarity of nearbed turbulence, a variety of interactions, and other sources of sediment dispersion. Hence gross estimates of averaged K seem even more appropriate; some formulae are put forward. The vertical profiles of sediment concentration are presented herein along with examples of sediment transport rates measured in nearshore zones.
BED LOAD TRANSPORT DUE TO NON-LINEAR WAVE MOTION
Authors: Tanaka Hitoshi
Published: June 2019

The bed load transport rate due to wave motion is measured in a wave flume. The modified stream function theory of the author ( Tanaka (1988) ) is applied to the formulation of the sediment transport rate in order to include the non-linearity. The proposed formula predicts well except near the surf zone where the effect of the acceleration plays an important role.
FIELD CALCULATIONS OF WAVE ENERGY DISSIPATION AND RELATED BEACH PROFILE
Authors: Tallent James R. , Yamashita Takao , Tsuchiya Yoshito
Published: June 2019

The process by which wave energy dissipates across the surf zone and its affect on the bed profile is, of course, a topic of immediate concern and debate. Various concepts of the wave energy dissipation process have been modeled, however, additional research is needed before confidence can be placed in a particular calculation scheme. In addition to the problems associated with proper model derivation a method of application and result interpretation of actual surf zone field data must be devised and understood. This is, of course, prerequisite to any realistic use of a wave energy dissipation model in an engineering project. The following study was therefore conducted in order to examine the applicability of surf zone field data to wave energy dissipation models and to investigate the bed profile relationship. Two wave energy dissipation models were selected for comparison in this study, the 'Undertow Model'(UM) which is based on the conservation of wave energy flux across the surf zone (3), and the 'Turbulent Bore Model'(TBM) which is based on hydraulic jump theory (2). Individual waves were identified in the wave record by employing the zero up-crossing method, and wave energy calculations were based on small amplitude wave theory, Svendsen's nonlinearity parameter Bo (4), and the 1/3 Significant Wave classification.
EFFECTS OF ENERGY LOSS NEAR BED SURFACE ON WAVE-INDUCED PORE PRESSURE IN SAND LAYER
Authors: Maeno Yoshi-Hiko
Published: June 2019

The effects of energy loss near the interface between the water and the sand bed on the wave-induced pore pressure are investigated by laboratory experiments. The interface between them includes the complicated factors: (1) roughness of seabed surface such as ripples; (2) boundary layer thickness in the sediment; (3) concentration of suspended sediments. These factors have been studied with respect to dimensionless parameters (e.g. Reynolds number, sediment Reynolds number, the ratio of orbital diameter to sand grain diameter, and Shields number), since many experimental formulas including these parameters have been proposed for predicting the geometry of roughness and the concentration of suspended sediments. The parameters described above are examined in relation to the damping characteristics of the wave-induced pore pressures. The transmissivity of pressure is constant until a critical value of the dimensionless parameters, and then decreases with increasing parameters. The critical values indicate the bed regime boundary of flat bed to ripple bed. Examinations of waveinduced pore pressure make it possible to predict the bed regime boundary.
TOWARDS MODELLING COASTAL SEDIMENT TRANSPORT
Authors: Nielsen Peter
Published: June 2019

Sediment transport data from the field and laboratory tests are used to gain insight into two fundamental questions. Firstly: What is the relative importance of coexisting waves and currents for the resulting sediment transport? Secondly: Is the influence of grain size as strong as traditional models predict, or is it as weak as the empirical CERC-formula indicates? Wave tank data reveal that the oscillatory velocity will in most cases determine the direction as well as the magnitude of the shore normal sediment transport, and wave flume data on shore normal transport as well as field data on littoral drift show weaker grain size dependance than traditional sediment transport models predict. It is suggested that wave dominance as well as weak grain size dependence are manifestations of the fact that the dominant transport mechanisms are often more organised than the diffusion process on which many traditional models are based.
GENTLE SLOPE SEAWALLS COVERED WITH ARMOUR UNITS
Authors: Toyoshima Osamu
Published: June 2019

Since the early 1960's, many seawalls against the beach erosion have been constructed in Japan, most of which were of vertical type. As a result, some of the seawalls even encouraged the beach erosion due to the reflected waves on the steep front of the seawalls. The author then proposed seawalls of new types with gentle front slope(l to 3) covered with armour units in 1981, and over one hundred fieldworks have successfully been carried out. In 1985, the author proposed reforming the existing vertical type seawalls into the gentler front slope (1 to 5 or 6) seawalls. The laboratory test on the gentle slope seawall was made, and some experimental fieldworks were carried out. At this time, these new type gentler slope seawalls are successful.
COHERENT EDDIES INDUCED BY BREAKERS ON A SLOPING FIELD
Authors: Matsunaga Nobuhiro , Takehara Kosei , Awaya Yoichi
Published: June 2019

The separation of boundary layer occurs periodically near a breaking point when incident waves climbing up a sloping bed are about to break. Not the breaker but the separation forms an unsteady coherent eddy, which suspends a large amount of bed material. A row of steady vortices has been found along the water surface of an offshore zone. Its formation is due to the shear instability between shoreward steady flow induced near the bed and offshore steady flow near the water surface. Moving in the offshore direction, the steady vortices repeat amalgamation each other and increase their intervals at the order of mean water depth. They decay after reaching to the region where the shear rate is not enough between the two steady flows. This shear instability may be excited by the periodic separation of boundary 1aye r.
SIMULATION OF WAVE FORCES ON A HORIZONTAL CYLINDER
Authors: Tsuzuki Susumu , Horikawa Kiyoshi , Watanabe Akira
Published: June 2019

The characteristics of wave forces acting on a horizontal circular cylinder were investigated through numerical calculations as well as experimental findings. The laboratory data on wave forces were analyzed by the concept of wave force path and classified into two types. One is the circular type and the other one is the 8 - shaped type. In order to analyze the above phenomena, the discrete vortex method was applied with appropriate assumptions. The comparison between the numerically calculated results and laboratory data shows that the simulation model proposed in this paper seems to be favorable to predict the wave forces acting on a horizontal circular cylinder within a certain range of conditions.
IRREGULAR WAVE LOADING ON A CONICAL STRUCTURE
Authors: Jamieson Wayne W. , Mansard Etienne P.D. , Mogridge Geoffrey R.
Published: June 2019

The horizontal forces, vertical forces and overturning moments exerted by waves on a fixed model of a 45" conical structure are presented. Irregular wave loading tests were conducted for a range of conditions described by base diameter on peak period wave length D/Lp from 0.31 to 1.76, water depth on peak period wave length h/Lp from 0.11 to 0.63, and significant wave height on peak period wave length Hm./Lp up to 0.07. Time series records, spectral densities and transfer functions for the irregular wave loading tests are used to illustrate the nonlinear nature of the measured wave loads. In most cases, similar trends in wave loading were observed for irregular and regular wave tests. For deep-water waves, the irregular and regular force measurements showed spectral peaks at the second harmonic of the wave frequency even though the waves themselves had relatively small second-order components. However, unlike the regular wave loading results, the fundamental spectral peak frequency for the irregular wave forces occurred at a frequency considerably lower than the peak frequency of the waves. Although linear diffraction theory provided a reasonable estimate of the wave forces for waves of low steepness, larger deviations were often present for higher wave steepness results. Comparison of theory and experiment for overturning moments was generally very poor for most wave conditions.
ON 3-DIMENSIONAL STABILITY OF RESHAPING BREAKWATERS
Authors: Burcharth H.F. , Frigaard Peter
Published: June 2019

The paper deals with the 3-dimensional stability of the type of rubble mound breakwaters where reshaping of the mound due to wave action is foreseen in the design. Such breakwaters are commonly named sacrificial types and berm types. The latter is due to the relatively large volume of armour stones placed in a seaward berm. However, as also conventional armoured breakwaters sometimes do contain a berm it is assumed that a better and more ambiguous designation would be "reshaping" mound breakwaters. The principle of reshaping breakwaters is to use relatively fine rock material which will then be eroded to S-shape profiles if sufficient amount of material is provided, Fig. 1. This type of breakwater can be constructed and maintained without the use of expensive specialized equipment. For a detailed discussion see Baird et al., 1984.
WAVE CLIMATE OFF RIO DE JANEIRO
Authors: De Souza Maria Helena Severo , Ribeiro Carlos Eduardo Parente
Published: June 2019

The offshore area northern off Rio de Janeiro State (fig. 1a) is a big oil production region known as Campos basin. In some locations oil is being exploited in water depths of A00 meters, among the largest in the world and new promising fields shall be exploited above 1000 meters. The design and operation of structures and other oceanic systems for such depths is being a big challenge for ocean engineers and the knowledge of environmental conditions is of paramount importance. Wave data is still scarce in the area mainly that concerned with directional spectra.
STRUCTURAL RESPONSE OF DOLOS IN WAVES
Authors: Tedesco Joseph W. , McGill Preston B. , Melby Jeffrey A. , McDougal William G.
Published: June 2019

Several numerical models for estimating wave forces on dolosse are presented. These models are incorporated into a finite element method (FEM) analysis of a 42-ton unit. The results of the analysis permit identification of unit structural failure with respect to wave conditions.
WAVE FORCES ON ARMOR BLOCKS
Authors: Losada M.A. , Medina R. , Alejo M.
Published: June 2019

Experimental measurements of hydrodynamic forces on a cubic block near the bottom under solitary waves were carried out. Horizontal and vertical forces were recorded and instantaneous and averaged values of hydrodynamic coefficients CD, C,, and C,_ for different boundary conditions, gap between block and bottom, e, and two or three-dimensional flow, were obtained. Horizontal and vertical forces were found to depend strongly on e/D, where D is the block side . Instantaneous values of hydrodynamic coefficients vary considerably during the wave passage and differ appreciably from the averaged coefficients.
HYDRAULIC ASPECTS OF WETLAND DESIGN
Authors: Walker James R. , Bertolotti Andrea , Flick Reinhard E. , Feldmeth C. Robert
Published: June 2019

Tidal wetland preservation, restoration and creation have become requisites for coastal development projects in the United States. A basic approach to design of tidal wetlands is presented, stressing cooperation between regulatory agencies, biologists, engineers, and developers. Basic principles of wetland functions are explained and presented as criteria for engineering design. A description of wetlands is given to identify biological features relevant to design. Also, some key features of tides are summarized as they affect wetland design. A numerical model was used to demonstrate how tidal wetlands may be designed to conform with criteria developed by the agencies and biologists. This approach has been used on wetland designs in California, but the approach may be applicable to other areas of the world.
COASTAL GENESIS
Authors: De Vroeg J.H. , Smit E.S.P. , Bakker W.T.
Published: June 2019

In order to investigate the effect of enchanced sea level rising (greenhouse effect), of sand mining in the North sea and the largescale effects of beach nourishment, the Rijkswaterstaat (Governmental Board for Ways, Waterways and Harbours) started the project "Coastal Genesis". This paper deals about research, carried out at the Delft University of Technology in the scope of this project. The behaviour of the Holland coast at three timescales, i.e. 15 years, 1000 years and 6000 years is considered. Use is made of line models. New techniques are developed for finding the coastal constants of these models (the use of Kalman filtering) and for simulating the effect of sea level rise on coastal accretion and erosion. An extensive set of data on coastal topography, the JARKUS dataset is analyzed. It is concluded that the effect of cross-shore transport becomes more and more dominant compared to the longshore transport when the time scale increases. A physical conception is displayed, which explains more or less the accretion of the Dutch coast between 4000 Before Christ and the Roman times, and the erosion later on.