bluuebunny/crossref_metadata_2025 huggingface dataset:
HYDRAULICS OF GREAT LAKES INLET - HARBORS SYSTEMS
Authors: Sorenson Robert M. , Seelig William N.
Published: June 2019

Reversing currents in inlets on the Great Lakes are generated primarily by long wave seiching modes of the lakes rather than by the tide. In order to investigate the nature of long wave excitation and the generating mechanism for significant inlet velocities, to establish techniques for predicting inlet-harbor system response, and to develop base data for future planning and design studies, field measurements were conducted in 1974-75 at several harbors on the Great Lakes. Data collected includes continuous harbor water level measurements at all sites, inlet velocity measurements at the primary site (Pentwater, Michigan), and channel hydrographic surveys at the sites where more recent data were needed. Historic water level and velocity data for some of the harbor sites was also available. Amplification of harbor oscillations and generation of the highest inlet velocities are caused by the Helmholtz resonance mode which has a period of 1 to 3 hours for the inlet-harbor systems studied. A recently developed simple lumped-parameter numerical model is shown to be quite effective in predicting inlet-harbor response over the range of excitation periods encountered. Selected data from Pentwater are presented to demonstrate the hydraulic response of the inlet harbor system and the applicability of the lumped-parameter numerical model.
CHARACTERISTICS OF TIDAL INLETS ON THE PACIFIC COAST OF JAPAN
Authors: Shigemura Toshiyuki
Published: June 2019

Tidal inlets on the Pacific coast of Japan were studied with respect to three characteristic variables of the throat section:(1) Throat area, A;(2) Throat width, B; and (3) Direction of throat section,0-t-s. For each of these three variables, multiple regression analysis was performed stepwise by introducing external variables such as tidal prism, mean flow rate of tidal flow, wind energy, wave energy and so on into a linear regression model. Exposure condition of throat section to open sea was also introduced into the analysis. First step analysis derived quite reliable result on the direction of throat section: n ,, , ,. n ,, ,,,, . ,, , ,, ,,,,, ' 0ts(degree) = -60.0 + 0.88 Gp^(degree) , r=0.964 where OpWv i-s the direction of wave energy which penetrates into a backed bay through tidal inlet and r the correlation coefficient between 0ts and Spwy However, results on both throat area and throat width were not satisfactory enough even after the performance of more than eighth step analysis on them. Similar analysis was further performed on both throat area and throat width of the classified data due to the magnitude of geometrical parameters ras and rhxb respectively, where ras is the ratio of throat area to mean surface area of backed bay and rhxjj the ratio of the maximum depth at the throat section to throat width. As a result, the former regressions on both throat area and throat width were improved remarkably. Multiple correlation of the regressions were all greater than 0.930.
TIDAL INLET FLOW DYNAMICS AND SEDIMENT MOVEMENT
Authors: Machemehl J.L. , Bird N.E. , Chambers A.N.
Published: June 2019

A numerical simulation model for the computation of tidal and -j fresh water flow exchange through a coastal inlet developed by Amein ) was modified and calibrated with field data (current, water surface elevation and bottom topography) for Lockwoods Folly Inlet, North Carolina. The calibrated model was then used to predict the changes in the flow regimes brought about by natural and manmade changes such as storms and dredging, respectively, and to predict the changes in flow regimes caused by the Lockwoods Folly River. A generalized hypothesis of the patterns of sediment through and bypassing the inlet were formulated from an evaluation of the flow data and from an analysis of the orientation and structure of the bedforms observed in the inlet and on the offshore bar. The bedforms were analysed in the field and from an uncontrolled mosaic made from multispectral aerial photographs. Confirmation and refinement of the transport rates and movement patterns during ebb tide were made by introducing 454 kilograms (1000 lbs.) of fluorescent tracer sand in two colors into the inlet channels. The sediment movement through the inlet was established and correlated with the numerical simulation model. Confirmation and refinement of the transport rates and movement patterns during flood tide were made by introducing 680 kilograms (1,500 lbs.) of fluorescent tracer sand in three colors into the surf zone on the updrift beach and on the offshore bar. The sediment movement indicated the existence of bar bypassing (which was the dominant bypassing mechanism) and tidal flow bypassing. The bypassing mechanism of the inlet was found to agree with other atlantic coast inlets. When used in conjuction with an analysis of bedform and tracer sand data the numerical simulation model was found to be a valid method for monitoring the high energy inlet environment.
MEASUREMENT OF BED FRICTION IN TIDAL INLETS
Authors: Mehta A.J. , Byrne R.J. , DeAlteris J.T.
Published: June 2019

The flow characteristics and the stability of a tidal inlet are governed, among other factors, by the channel bed friction. In order to determine the bed shear stress regime and the frictional characteristics, near-bed velocity profiles were obtained at the throat sections of two inlets, John's Pass and Blind Pass, on the Gulf Coast of Florida. A specially designed steel cage with five current meters in a vertical array was used to obtain the profiles in the bottom one meter of the flow. The profiles were found to be logarithmic but it is noted that, especially near the times of slack water, the effect of inertia becomes significant. However, during the major part of the flood or ebb flow period, frictional effects are dominant. In the fully rough regime of flow, the bed-shear stress - velocity relationship is found to follow the square law, with a constant, characteristic friction factor and Manning's n for each inlet. This friction factor is used in hydraulic formulas, based on uniform, steady open channel flow relationships, to obtain the tidal prism - throat cross-sectional area ratio, which is then compared with that obtained from flow discharge measurements. Agreements and discrepancies in the comparison are discussed. The relationship between the bed shear stress at incipient motion and the grain size at the bed is reviewed, and it is noted that the observed relationship at the two inlets does not agree with the well-known correlation of Shields for uniform sandy beds.
MORPHODYNAMICS OF A WAVE-DOMINATED RIVER MOUTH
Authors: Wright L.D.
Published: June 2019

The mouth of the Shoalhaven River on the southeast coast of Australia is subject to direct attack by high energy waves and offers a general model of wave-dominated river-mouth deposition. During river floods seawater is completely flushed from the lower reaches of the channel and significant quantities of sandy bed load and suspended silts are debouched into the Tasman Sea. However, breaking waves cause intense mixing between the effluent and ambient waters while wave-induced mass transport and setup oppose and partially impound outflow. Unusually rapid deceleration and lateral effluent expansion result. Sediments accumulate in the form of a broad creseentic river-mouth bar with its crest situated about 2 channel widths seaward of the outlet and as broad shallow subaqueous levees capped by swash bars. Post-depositional shoreward return of sands by shoaling waves produces a constricted outlet. During low river stage wave setup enhances flood tidal currents and partially inhibits ebb tide outflow. This leads to a gradual shoreward migration of the river-mouth bar, a narrowing of the constricted outlet and to upstream migration of river-mouth sands into the lower reaches of the channel.
Complete Proceedings - Single PDF Download
Authors: ASCE ASCE
Published: June 2019

Proceedings of the Fifteenth Coastal Engineering Conference, Honolulu, HI, July 11-17, 1976

Sponsored by the State of Hawaii, University of Hawaii, ASCE through its Coastal Engineering Research Council, and American Shore and Beach Preservation Association.
A WORLD WAVE DATA CENTRE
Authors: Draper Laurence
Published: June 2019

There is a growing need for instrumentally-measured wave data, but it is not easy to discover what measurements, if any, may have been made in any particular area« To try to alleviate the situation the Institute of Oceanographic Sciences is establishing an international reference centre which will create and maintain an inventory of such data,, It is appealing for volunteers world-wide to help in identifing locations where waves have been measured. It will be operated through the U0K,, Marine Information and Advisory Service at the Wormley Laboratory of the Institute.
SHINGLE TRACING BY A NEW TECHNIQUE
Authors: Wright Peter , Cross J.S. , Webber N.B.
Published: June 2019

A major drawback of all existing tracer techniques for monitoring shingle movement, except that of labelling with radioactive isotopes, is that tracer recovery rates are invariably low, (commonly less than 15% of the total injected) because recovery is limited to the beach surface. Investigations were made into the possibilities of developing a new tracer that might overcome this problem. The paper describes the results of, and the conclusions drawn from two trial field experiments carried out using metal tracer pebbles. These had specific gravities, size and shape similar to the indigenous beach pebbles, and were recovered both on and beneath the beach surface using metal detectors. By assessing the relative merits and drawbacks of the technique it was concluded that the use of metal pebbles as tracers for shingle beaches is more practical than other methods for most tracing purposes. At present the technique is best suited to investigations ranging in length from a few days to a few months and requiring small to medium-scale injections of 5000 tracer pebbles or less. The considerable scope for the further development and application of the technique is discussed.
A NUMERICAL MODEL FOR SEDIMENT TRANSPORT
Authors: Lepetit J.P. , Hauguel A.
Published: June 2019

We introduce here a numerical two dimensional model for sediment transport which permits to compute the impact of a coastal structure on the bottom evolution. The introduction of current disturbance and some assumptions using difference of time scale between current and bottom evolutions permits to obtain a propagation equation driving the bottom evolution. The model has been calibrated in the case of the local scour around a jetty. At last, it has been applied to the bottom evolution in the vicinity of the new port of Dunkerque.
ON THE GEOMETRY OF RIPPLES DUE TO WAVES
Authors: Yalin M.S. , Karahan E.
Published: June 2019

The present paper is an attempt to determine a single curve for the prediction of the length of ripples forming due to wind waves in shallow waters. The curve is revealed by normalising the field and laboratory data supplied by various authors. The concept of the unified plot embodied by the single curve mentioned is developed by using dimensional methods and by considering the fact that the specific weight and the density of the cohesionless bed material do not affect the length of ripples in a detectable manner. It is shown that the present formulation of the length of ripples due to waves satisfies the requirement of transition into the corresponding formulation of the unidirectional flow ripples when the period and the amplitude of the oscillatory motion increase indefinitely, while their ratio (implying "the velocity") remains finite.
THE INFLUENCE OF DUNE AND FLOW PARAMETERS ON THE FRICTION FACTOR
Authors: Sundermann J. , Vollmers H. , Puls W.
Published: June 2019

Taking for example the flow over a ripple, some results of a hydrodynamic numerical model are presented and compared with experimental results. Special importance is attached to the pressure. On the basis of the used equations the physical reason for the horizontal pressure gradient is investigated. The influence of some dune and flow parameters on the friction is examined.
TIME-LAG OF DUNES FOR UNSTEADY FLOW CONDITIONS
Authors: Nasner Horst
Published: June 2019

Many publications based on theoretical considerations or model tests, give utterance to the demand that there should be unequivocal relations between hydraulic conditions and bed form characteristics which should be generally applicable. These relationships determined for steady conditions and limited water depths should be handled with care when being applied to natural rivers. The bed configurations do not immediately fit themselves to the varying flow conditions. The bed forms need a certain reconstruction time in case of a changing discharge. The time-lag of dunes was observed on numerous rivers, in the past. A general review of investigations made in this field is given by ALLEN (1976 b). In the following contribution, an attempt is made to describe the magnitude of the time lag of bed forms for unsteady flow conditions.
ESTIMATION USING A MOVABLE BED MODEL OF SHORELINE CHANGE CAUSED BY A RECLAMATION PROJECTED INTO THE SEA
Authors: Sato Shoji , Ozasa Hiroaki
Published: June 2019

Recently, many local airports in Japan are considering to extend their runways, so accommodating passenger traffic. But most airports are obliged to extend their runways into the sea on account of the shortage of land and complaints from their neighbors about jet-plane noise. Tokushima Airport is one of such local airports, which is situated on the coast along the Kie-Suido Channel as shown Figure 1. The length of the runway of Tokushima Airport is 1500 m at percent, so a plan to extend the runway by 600 m into the sea has been proposed by the local government. However, Matsushige beach, where the airport is located, is now so seriously eroded that offshore breakwaters are being constructed in the south and the northern part is used for sea-bathing. Therefore, it is necessary to estimate the change of beach profiles, especially of the shoreline, caused by the extension of the runway, and to find countermeasures against unfavorable change. A movable bed model was constructed to estimate such changes, because no numerical simulation using a computer has been developed to estimate changes of a complicated beach topography. Of course, the universal dynamic similarity does not hold for model studies on sand transport problems. Therefore, the characteristics of sand transport at the site are first clarified through analysis of the field observation data, and then the model scale, bed material, and test waves are determined in such a manner that the topographic variation in the model sea bed will become similar to that in the prototype. But, in general, it is difficult to make all of the variations of the sea bed in the model similar to that in the prototype. In this model experiment, the long term changes of the shoreline has been taken as the most important phenomena to be reproduced in the model.
DIFFRACTION CALCULATION OF SHORELINE PLANFORMS
Authors: Dean Robert G.
Published: June 2019

A method is presented, and illustrated with examples, for calculating planforms for a class of "pocket" beaches. This type of pocket beach is formed of mobile sediment due to waves diffracting through an opening in erosion resistant material, for example behind a break in a revetment or behind closely spaced offshore breakwaters. The opening is considered as a series of sources with circular wavelets radiating landward from each element. The height and phasing of each wavelet is varied depending on whether the depth at the element limits the wave height and on the wave direction relative to the opening, respectively. Based on reasonable, but not complete, considerations of sediment transport, the equilibrium bathymetry is considered to exist when the wave front is everywhere tangent to the local bottom contours. A differential equation is developed for the local orientation of the contours; this equation is solved numerically starting from a reference transect and extending the contour until it intersects the line defining the opening. Examples are presented illustrating the method for the following cases: (1) normally incident waves diffracting through a single relatively narrow opening, (2) obliquely incident waves diffracting through a single relatively narrow opening and (3) spiral bays which are contained by two relatively widely spaced headlands. In addition, a procedure is suggested for applying the results to the case of normally and obliquely incident waves diffracting through the openings formed by a series of offshore breakwaters.
CONCENTRATION OF SUSPENDED CLAY IN PERIODIC FLOW
Authors: Watanabe A. , Thimakorn P. , Gupta A. Das
Published: June 2019

A diffusion model of clay-water flow is formulated to determine the time dependent concentration distribution of suspended clay in a two dimensional periodic flow. Taking into account the entrainment rate of the clay particle from the bed, the integrated diffusion equation to yield a solution of the time-variation of the clay concentration in the vicinity of the channel bed is derived. In addition the original diffusion equation is solved by means of the finite element method. An experiment was conducted in a recirculating two dimensional channel where sinusoidal current variation was generated upon the clay-water mixture. Results obtained from the experiment are compared with those derived from the model.
TWO-DIMENSIONAL STABILITY ANALYSIS OF TIDAL BASINS AND TIDAL FLATS OF LARGER EXTENT
Authors: Renger Eberhard
Published: June 2019

Stability studies of natural tidal basin system demand a regime-oriented analysis and a characteristic quantification of the morphological values. Hence it was necessary to create relative form parameterization dependent on the location by means of a two-dimensional system of natural coordinates (z =elevation, s = gully length coordinate). The underlying logic for the determination of the equilibrium of the tidal basins and tidal flats is as follows: When the continuity equation for non-steady flow at any cross-section (s; , Zj.) of a tidal basin, within the mean tidal range is applied, a dimensionless relationship between horizontal and vertical cross-sections (A and P) and tide-generated mean velocities of current (±u) and tidal rise and fall (+ v) can be derived with an accuracy of more than 90 %.
ANOMALOUS DISPERSION OF FOURIER COMPONENTS OF SURFACE GRAVITY WAVES IN THE NEAR SHORE AREA
Authors: Busching Fritz
Published: June 2019

Water level deflections ri (t) have been measured synchronously at some positions in a beach profile on the isle of SYLT / North Sea during severe storm surge conditions as well as at attenuating wave action. A steadily increasing wave period T in the upbeach direction, turning out from strip chart evaluations, is in accordance with the result of FOURIER syntheses. Near shore wave deformation is explained by ANOMALOUS dispersion of the frequency components.
USING FENCES TO CREATE AND STABILISE SAND DUNES
Authors: Willetts Brian B. , Phillips Christopher J.
Published: June 2019

Coastal sand dunes act as a barrier to wind and sea, as a reservoir of sand available to supply areas of eroding coast, and as a trap for mobile sand which would otherwise be blown inland and become a nuisance. Breaches of the dune system and areas bare of vegetation should be avoided or repaired in order to protect the stability of the dunes and so enable these useful functions to be sustained. The agents of initial damage to the dunes are water, which undermines them, and animals (including man) which damage the protective vegetation by grazing or trampling. Of these, man has recently assumed predominant local importance because of the popularity of sea-side holidays and of the land-falls of certain marine engineering works such as oil and gas pipelines and sewage outfalls. The need is therefore increasing for active dune management programmes to ensure that under these accentuated pressures, the coast retain an equilibrium comparable with that delicately balanced equilibrium which obtains naturally at a particular location. Such management programmes are already established in many countries. They tend, however, to be empirical and based on local experience (often of a very small number of people) because the difficulties of generalisation render transfer of information and technique meagre. Accounts of management techniques can be found in the literature (e.g. ref 1) but in most of such papers great emphasis is placed on vegetative restoration. Whilst this is the best way of re-introducing a lasting stability, it is often not a practical way of beginning the restoration of a deteriorating situation. The sand movement or the season may be such that planting alone is unlikely to be successful. It is the authors' opinion that, of the techniques at present available, the placement of porous fences provides the most effective means in relation to cost of creating and stabilising sand dunes (and should normally be supplemented by plantings). The object of this paper is to present a simple numerical model of dune formation at a fence. The model is based on what is known of the physics of air and grain movements near the fence, and the purpose of approaching the problem at such a basic level is to seek sufficient understanding to enable information and prediction methods to be transferred from person to person and applied at different sites. This requires that the processes which take place at the fence be better understood than at present.
BEACH GROUND-WATER OSCILLATIONS
Authors: Lewandowski Andrzej , Zeidler Ryszard B.
Published: June 2019

Oscillations of ground-water table were measured in perforated piezometers distributed across the Baltic beach at the coastal research station of Lubiatowo, Prom spectral and correlation analysis it appears that the most pronounced wind-wave oscillations having a period of about 6 seconds have not been detected in the beach, while longwave oscillations, dominant in the beach spectrum, correlate well with nearshore long waves. Among the longwave oscillations, it is only those having periods about or slightly longer than 100 seconds that obey the Boussinesq law. However, some longer waves may also be generated by the interaction of shorter waves. Oscillations with periods from 50 to 100 s are very coherent throughout the beach. In the absence of stochastic noise and variety of inputs, low values of coherence for other periods indicate presence of nonlinear effects. More light should be shed on the origin of this nonlinearity and theoretical tools should be tried to complement the Boussinesq model.
COASTAL STRUCTURES' EFFECTS ON SHORELINES
Authors: Noble Ronald M.
Published: June 2019

Coastal structures have caused significant impacts to adjacent shorelines, especially when these shorelines are composed of sand. Many times, these shoreline impacts have not been expected due to improper planning prior to the design and construction of these structures. Consequently, excessive erosion and/or deposition of sediment as a result of these structures has necessitated costly, and in some cases, continuous maintenance operations. This paper reviews the expected shoreline effects for an offshore pier-trestle and breakwater system for an LNG marine terminal. Coastal structures originally proposed for the LNG marine terminal consisted of a 4,600-foot-long pile supported "T" head pier/trestle system and a 1,000- foot-long detached rubble-mound breakwater. This investigation involved field and historical aerial photographic examination of 30 structures in the Southern California Bight and a literature review of similar structures in other environments. Also, a review of theoretical and physical model studies applicable to structures within the coastal marine environment was conducted. The results of this investigation of existing structures, in conjunction with theory and model studies, indicate that within the study region, pile-supported piers have no appreciable impact of £he adjacent shoreline. This investigation also indicates that detached breakwaters produce only minimal impact when the offshore distance of the structure is greater than six times the breakwater length. Of course, consideration was also given to the structure's position relative to the littoral zone, to the depth of water at the shoreward face of the structure, and to the wave climate approaching the structure. This study included a review of such factors as the local topography, nearshore bathymetry, beach processes, shoreline configuration, beach materials, range of water levels, and local wave climate. The controlling parameters identified in this study are discussed, and the final recommendations presented. This paper illustrates the importance of proper advance shoreline planning before the final design and construction of shoreline facilities.
COASTAL STUDY OF ESPlRITO SANTO/BRAZIL
Authors: Vivacqua Paulo Augusto , De Araujo Goes Filho Hildebrando , De Sampaio Ferraz Jardim Sayao Otavio
Published: June 2019

The elimination of land transportation costs for raw materials and/or industrialized products has encouraged integration of industrial and port activities and, at many ports, facilities are being built for the installation of industrial complexes adjacent to the port areas. This general trend has been clearly observed along the coast of the State of Espirito Santo, Brazil, north of Rio de Janeiro. Several new port terminals, associated with industrial plants, are under construction or were designed recently. In fact, the State's port development began with its Commercial Port in Vitoria, located at the mouth of the Santa Maria river. The following terminals connected with industries were built at a later date: a) Tubarao Maritime Terminal, which was brought into operation in 1966, sited at the outer end of Espirito Santo Bay, 9 Km away from Vitoria, for iron ore exports. This terminal belongs to the stateowned Companhia Vale do Rio Doce - CVRD. Iron ore exports reached more than 50 milion ton per year during the last three years. b) Ubu Maritime Terminal, inaugurated in 1977 and sited in the south of the State, was designed for exporting pelletized iron ore produced by a plant sited in the port area. This plant receives its raw material (ore fines) through a pipeline approximately 400 Km long. These facilities belong to privately-owned SAMARCO Mineracao S.A., and will have a total export capacity of 7 million tons of pellets per year when it reaches it final expansion phase. c) Barra do Riacho Port, which should start operation in 1978, built by PORTOCEL (owned jointly by PORTOBRAS, Aracruz Celulose and CVRD) is intended to export wood chips and pulp produced at industrial facilities adjacent to the port. In addition to these terminals, there are plans to built other ports which will handle goods to be produced by industries now moving into Espirito Santo.
INFRAGRAVITY WAVES IN STORM CONDITIONS
Authors: Holman R.A. , Huntley D.A. , Bowen A.J.
Published: June 2019

Nearshore sediment is actively reworked during major storms, often significantly altering the nearshore morphology. It has been suggested that infragravity waves with wave periods 30-300 seconds are very important in the formation of major nearshore features. A field study to further understand the nature of infragravity waves was carried out in Martinique Beach, Nova Scotia. Velocity measurements were taken using three electromagnetic flowmeters. Incident conditions varied from calm to swell and wind waves generated by hurricane Belle. Spectral analysis of the low tides revealed a sharp increase in the infragravity band energy associated with the storm. Throughout the storm the spectra of all three instruments were dominated by a strong 100 second peak which remained constant in frequency despite significant changes in the incident wave field. This peak is found to satisfy edge wave theory. A frequency selection mechanism
SCRAP TYRE BREAKWATERS IN COASTAL ENGINEERING
Authors: McGregor Robert Charles , Miller Neil Sinclair
Published: June 2019

The problem of the protection of shorelines and coastal structures from wave action is one of long standing. More recently it has become necessary to examine the feasibility of providing the same sort of wave attenuation for locations further offshore. Where the need for protection is in shallow water, close to the shoreline, bed-based breakwaters are possible and floating breakwaters may only be desirable on the basis of one or more of the following grounds: a) cost, b) requirement for protection being of short duration, c) reduced interference with currents, d) adaptability to changing performance criteria, e) poor foundations. As the water depth becomes larger, the costs of a fixed structure become prohibitive whereas only the anchoring fraction escalates for a floating breakwater. There is an extensive literature extending from 1842 on the floating breakwater concept. Most of the references, however, are postwar following the wartime stimulation of interest in aid of assault landings. Recent sources of state-of-art information are Kowalski (1974) and Adee (1976). The use of scrap automobile tires has been discussed by Candle (1974), Kowalski (1974, 1976) , Noble (1976) and Harms (1978). Candle was proposing what may be called near rigid mats of tires where neighbouring tyres move relatively little with respect to one another, whereas the Noble, Harms and Kowalski designs use the breakwater flexibility. In the Kowalski breakwater**, the tires are formed into groups which are known as modules which allow the breakwater to "breathe" and so dissipate more energy by internal movement as well as making construction easier. Several breakwaters of a fairly simple form have been built using this concept. These have been operational in the U.S.A. for several years and have successfully protected at least one marina through hurricane conditions.
A MODEL LAW FOR WAVE IMPACTS ON COASTAL STRUCTURES
Authors: Ramkema C.
Published: June 2019

For the design of the storm surge barrier in the Eastern Scheldt, a study has been carried out on wave impacts against coastal and marine structures. First a review was made of relevant literature, including both wave impacts on coastal structures and slamming of sea-going vessels. From this, the so-called Bagnolds piston model emerged as most appropriate to describe the wave impacts caused by standing waves against protruding elements. This model was then further elaborated to include both adiabatic and isothermal compression of the air cushion and to allow for the compression of the water. Moreover, a model was developed to determine the spatial pressure distribution. Finally, experiments were performed, the results of which were in satisfactory agreement with the mathematical models. Based upon the results of these studies, a scaling law is presented here, from which the pressure magnitude and the time history of the impact in nature may be determined.
EXTREMAL PREDICTION OF SIGNIFICANT WAVE HEIGHT
Authors: Copeiro Enrique
Published: June 2019

The most generally used procedure for estimating the extremal distribution of ge_o physical variates consists in obtaining a sample of extreme values (for instance a number of annual maxima) and fitting to them a distribution function. One of the main problems - involved in this procedure is the choice of the type of distribution adequate in each case. No general agreement exists, to date, for any geophysical variate. This means a serio us trouble because of the wide range of extrapolations which can usually be obtained by - using different functions. Some of the authors who have tackled this problem have adopted a strictly empirical point of view, going as far in it as to advise to make a choice for each particular case, according to the goodness-of-fit obtained when several types of dis tribution functions are fitted to the sample. Others have instead tried to base the choices on some theoretical foundation, placing less emphasis in the goodness of the fits and generally suggesting the use of one or other of the three well known Asymptotic Extremal Distributions.
LOAD ANALYSIS FROM WAVE GROUPS
Authors: Kuznetsov A.I. , Khaskhatchikh G.D.
Published: June 2019

At the present time sea wave is described by means of two theoretical models, the first is based on regular waves, components of which do not change in time and space, and the second model is based on irregular waves, components of which are randomly changed. The latter coincides to the greater extent with the rolling sea, but even this model does not characterize it to the full» Taking sea wave for a random process, the model of irregular waves does not take into account the sequence of their alternation. Prom the point of view of probability, on which the model of irregular waves is based, the maximum wave may be followed by the minimum wave, and the greater period may be followed by the smallest one. The real sea wave, especially in shore zone, where the main engineering constructions are placed, is characterized by clearly expressed group structure, which includes alternation of a number of great and small waves and the maximum wave is always followed by the wave having almost the same parameters.
DYNAMIC BEHAVIOR OF VERTICAL CYLINDER DUE TO WAVE FORCE
Authors: Sawaragi Toru , Nakamura Takayuki
Published: June 2019

This paper describes the dynamic behavior of a fixed cylindrical pile due to both the in-line or longitudinal force and lift or transverse force in regular waves. Resonant response of the pile due to the lift force in the direction normal to the wave propagation direction is discovered at the period ratios of Tw/Tn=2,3,4,5 and 6 (Tw : the wave period, Tn : the natural period of the pile). Furthermore, the resonant responses in the wave propagation direction due to the in-line force also appear at the same period ratios, in addition to the well known resonance point of Tw/Tn=l. Moreover, dynamic displacements of the pile in the direction normal to the wave propagation direction are longer than those in the wave propagation direction when the period ratio is longer than 1.6 and Keulegan-Carpenter number is larger than 6. Next, for the purpose of the ocean structural design, the methods of estimating the dynamic displacements in both directions and of estimating the dynamic displacements considering both are derived by using Morison's equation and lift force equation formulated by the authors. The displacements calculated are compared exactly with the experimental results to investigate the validity of the proposed method.
WAVE LOADS ON HORIZONTAL CYLINDERS
Authors: Holmes P. , Chaplin J.R.
Published: June 2019

The problem of predicting wave induced loads on cylinders is an enormously complex one. It is clear from the scatter present in most experimental determinations of force coefficients that there are many individual factors which influence the mechanisms of flow induced loading. Among these are some, for instance Reynolds number, separation and periodic vortex shedding, which are inter-related and whose influences cannot be studied in isolation. Others, such as shear flow, irregular waves and free surface effects, can at least be eliminated in the laboratory, in order to approach an understanding of the more fundamental characteristics of the flow. A vertical cylinder in uniform waves experiences an incident flow field which can be described in terms of rotating velocity and acceleration vectors, always in the same vertical plane, containing also the cylinder axis, whose magnitudes are functions of time and of position along the length of the cylinder. Some of the essential features of this flow can be studied under two-dimensional oscillatory conditions, in which either the cylinder or the fluid is oscillated relative to the other along a straight line (planar oscillatory flow). The incident velocity and acceleration vectors are then always concurrent, normal to the cylinder axis, and oscillating in magnitude with time.
DEEPWATER DIRECTION FROM AN INTENSITY ARRAY
Authors: Higgins Alan L. , Seymour Richard J.
Published: June 2019

Knowledge of the distribution of wave intensity along a shoreline can be used to infer deepwater directional information for non-locally generated waves. Measurement of this energy distribution may be accomplished using a network of widely spaced nearshore wave gages known as an intensity array. Analysis for intensity array data uses the principle that deepwater swell of a given frequency produces varying patterns of nearshore wave intensity, which depend on the unrefracted directional energy distribution for that frequency. Assuming linear wave propagation to the measurement sites, this dependence may be inverted and applies at all frequencies. Energy spectra measured at the intensity array may be used in this manner to estimate the deepwater directional spectrum. In Part II, details of the relationship between deepwater directional spectrum and nearshore energy spectra are discussed. In Part III, intensity array data are applied to detection of waves incident within a narrow directional interval. Part IV describes the application of an intensity array to detection of long period southern swell in San Diego, California. Comments regarding the relative merits of the method follow in Part V.
PERIODIC THEORY VELOCITY PREDICTION IN RANDOM WAVE
Authors: Nath John H. , Kobune Koji
Published: June 2019

Large waves in a series of random ocean waves are considered in the design of ocean structures. When random structural vibrations can be ignored, periodic wave theories are used to predict the water particle kinematics for a design wave even though the real wave is irregular. This paper presents the authors' first attempt to quantify the validity of using periodic wave theory for random waves. Measurements of maximum horizontal and vertical velocities were made in laboratory generated periodic and random waves. They compared favorably with predictions from periodic wave theories (even with Airy theory) particularly for the large waves in a series. Since the design wave concept is applied to the largest waves, the conclusion is that periodic wave theory may be adequate, providing an appropriate factor of safety is used to account for the differences between the actual maximum wave kinematics in nature and those in the predictive theory.
HIGHER ORDER WAVE SPECTRA
Authors: Liu Paul C. , Green Albert W.
Published: June 2019

As part of an effort aimed at examining the empirical aspects of nonlinear processes of wind-generated waves, this paper presents calculations and examples of bispectra and trispectra and indicates applications of these results to the study of wave growth processes. Recent publications on wave studies have indicated that the growth process of wind waves is primarily associated with the nonlinear energy flux due to wave-wave interactions. While most of these studies are conjectures from theoretical considerations, it is of interest to explore the nonlinear studies empirically. From available wave data largely recorded at a single station, a first step is to perform bispectral and trispectral analyses of the data. Since the unispectrum provides information on the energy content of the frequency components, the bispectrum and trispectrum generally provide information on the interactive relations between two and three frequency components, respectively. These higher order interactive relations can thus be considered as estimates or characterizations of nonlinear interactions. Hasselmann, Munk, and McDonald (1962), perhaps the first to use bispectral analysis, demonstrated that calculations of observed bispectra of ocean waves correlate reasonably well with theoretically derived bispectra. Other ocean wave bispectra were presented by Garrett (1970) and Houmb (1974). Trispectral analysis has not yet been attempted in practical problems.
COMPUTATIONS OF SHORT WAVES IN SHALLOW WATER
Authors: Abbott M.B. , Petersen H.M. , Skovgaard O.
Published: June 2019

The simulation of short wave propagation, including refraction, diffraction, partial reflection and all other such features, is made possible by a new version of the System 21, Jupiter. The System generated models can describe any bathymetry and topography with any time-varying mean flow, correctly accounting for wave and current interactions, wave-thrusts or radiation stresses, longshore currents and other "second order" effects. The models work with irregular waves just as well as with regular waves. Radiation boundary modules are also provided so that models can be cut-out in any desired region and new features introduced without invalidating the field-study-determined boundary data. As models are system-generated, they can be constructed and run in a few hours, starting from charts, a lay-out of the proposed engineering works and the available boundary data. The development and testing of the System is briefly described, followed by an account of its applications in coastal engineering practice.
WAVE CHARACTERISTICS IN THE SURF ZONE
Authors: Svendsen I.A. , Madsen P.A. , Hansen J. Buhr
Published: June 2019

The equations describing conservation of mass, momentum and energy in a turbulent free surface flow are derived for a controle volume extending over the whole depth. The effect of the turbulent surface oscillations are discussed but neglected in the following analysis, where the equations are applied to the energy balance in a surf zone wave motion. This leads to results for the wave height variation and the velocity of propagation. The results cannot be reconciled completely with measurements and the concluding discussion is aimed at revealing how the model can be improved.
WIND WAVE FREQUENCIES IN A TROPICAL CYCLONE REGION
Authors: Sobay Rodney J.
Published: June 2019

Australia's Coral Sea coast from Bundaberg north to Cape York has a wind wave climate that is almost unique. The coastline is afforded unparalleled protection from the 1900 km Great Barrier Reef, yet it lies in a tropical cyclone region and must expect recurrent intense wind and wave conditions. The Great Barrier Reef is a continuous chain of quite separate coral reef clusters located near the edge of the continental shelf. The separate reefs are often exposed at low tide, the inner fringe of the clusters ranges from 10 km offshore north of Cairns to 200 km offshore south of Rockhampton and the outer fringe is typically some 50 km further offshore, beyond which the ocean bed drops rapidly away. Incident wave energy from the Coral Sea is invariably dissipated on the outer edge of the Reef and wave conditions on the continental shelf can reasonably be considered due to local wind conditions. The Reef imposes an effective fetch limitations on wave generation over the continental shelf and there is, as a consequence, a moderately rapid response of wave conditions to changes in local wind conditions. A pronounced diurnal variation in the wind climate is reflected also in the wave climate and the stability of the region's tropical climate leads to frequent calm to slight sea conditions. This stability however is occasionally exploded by the generation and passage of a tropical cyclone in mid to late summer. Large waves can be generated by the intense winds of the tropical cyclone (hurricane or typhoon), often an order of magnitude greater than those in response to non-cyclonic events. The rational design of coastal structures and the rational pursuit of coastal zone management requires appropriate estimates of the frequency of occurrence of waves of various heights. Ideally such information is obtained from an extreme value analysis of long term wave records at the particular site in question. Permanent wave recording programs unfortunately have only become common practice in the present decade and wave records, if they exist at all for a particular site, are rarely long enough to allow a satisfactory extreme value analysis. It is clear, in the Australian context at least, that historical wave data alone is not yet sufficient to derive satisfactory estimates of long term wave frequencies. The alternative is system modelling. Wind is a major meteorological variable and its long term recording has been a standard meteorological practice now for over half a century.
THE ENERGY SPECTRA OF SURF WAVES ON A CORAL REEF
Authors: Lee Theodore T. , Black Kerry P.
Published: June 2019

The transformation of waves crossing a coral reef in Hawaii including the probability density function of the wave heights and periods and the shape of the spectrum is discussed. The energy attenuation and the change of height and period statistics is examined using spectral analysis and the zero up-crossing procedure. Measurements of waves at seven points along a 1650 ft transect in depths from 1 to 3.5 ft on the reef and 35 ft offshore were made. The heights were tested for Rayleigh, truncated Rayleigh and Wei bull distributions. A symmetrical distribution presented by Longuet-Higgins (1975) and the Weibull distribution were compared to the wave period density function. In both cases the Weibull probability density function fitted with a high degree of correlation. Simple procedures to obtain Weibull coefficients are given. Fourier spectra were generated and contours of cumulative energy against each position on the reef show the shifting of energy from the peak as the waves move into shallow water. A design spectrum, with the shape of the Weibull distribution, is presented with procedures given to obtain the coefficients which govern the distribution peakedness. Normalized non-dimensional frequency and period spectra were recommended for engineering applications for both reef and offshore locations. A zero up-crossing spectrum (ZUS) constructed from the zero upcrossing heights and periods is defined and compared with the Fourier spectrum. Also discussed are the benefits and disadvantages of the ZUS, particularly for non-linear wave environments in shallow water. Both the ZUS and Fourier spectra are used to test the adequacy of formulae which estimate individual wave parameters. Cross spectra analysis was made to obtain gain function and squared coherency for time series between two adjacent positions. It was found that the squared coherency is close to unity near the peak frequency. This means that the output time series can be predicted from the input by applying the gain function. However, the squared coherency was extremely small for other frequencies above 0.25 H2.
DIFFRACTION DIAGRAMS FOR DIRECTIONAL RANDOM WAVES
Authors: Goda Yoshimi , Takayama Tomotsuka , Suzuki Tasumasa
Published: June 2019

Conventional wave diffraction diagrams often yield erroneous estimation of wave heights behind breakwaters in the sea, because they are prepared for monochromatic waves while actual waves in the sea are random with directional spectral characteristics. A proposal is made for the standard form of directional wave spectrum on the basis of Mitsuyasu's formula for directional spreading function. A new set of diffraction diagrams have been constructed for random waves with the proposed directional spectrum. Problems of multi-diffraction and multi-reflection within a harbour can also be solved with serial applications of random wave diffraction.