bluuebunny/crossref_metadata_2025 huggingface dataset:
GEOMORPHOLOGY OF THE SOUTHERN COAST OF ALASKA
Authors: Hayes Miles O. , Ruby Christopher H. , Stephen Michael F. , Wilson Stephen J.
Published: June 2019

The shoreline of southern Alaska is a narrow coastal plain dominated by large glaciers, periodic earthquake activity, and strong extratropical cyclones. Studies on the coastal geomorphology and sediments carried out in 1969-71 and in the summer of 1975 were directed at defining geological hazards with respect to developing shore facilities for OCS oil exploration activities. Most of the shoreline was found to undergo rapid changes and experience a variety of serious environmental hazards. The safest potential port areas are located inside Icy Bay and Yakutat Bay. The coastal areas in the vicinity of the Malaspina Glacier and the Copper River delta are examples of the two principal shoreline types (glacial outwash plain and deltaic). The coastal area surrounding the Malaspina Glacier, the largest piedmont glacier in the world, was classified into 5 categories on the basis of its geomorphology, sediments, and local glacial history: 1. Regional retreating coast: This area, which is located at the mouth of Icy Bay, is eroding rapidly (approximately 1.5 km since 1900) as a result of retreat of a glacier (up the bay) a distance of over 40 km since 1900. Consequently, it should not be developed. 2. Prograding spits: Sandy spits that have built into either side of Icy Bay since the retreat of the glacier are also unstable because of the general recession of the shoreline as a result of erosion at the mouth of the bay. 3. Abandoned glacial coasts: These areas, located on the inner eastern shores of Icy Bay and Yakutat Bay, are coastlines of relatively low wave energy composed of. abandoned glacial tills, kame terraces, and outwash sediments. These are the most stable and least hazardous areas on the southern Alaska coast. 4. Actively eroding glacial margins: This area, located at Sitkagi Bluffs on the southernmost terminus of the Malaspina Glacier, is an eroding scarp of glacial till jutting into the Gulf of Alaska. 5. Glacial outwash coasts: These shorelines are highly variable and are usually dominated by prograding spits composed of sand and gravel.
SAND MOVEMENT INVESTIGATIONS BY MEANS OF RADIOACTIVE TRACERS IN A HYDRAULIC MODEL AND IN THE FIELD
Authors: Rohde Hans
Published: June 2019

The Lower and the Outer Elbe constitute the sea-going navigation channel which has the heaviest shipping traffic in the Federal Republic of Germany. In order to obtain and maintain the fairway depth necessary for shipping, river construction works and dredging are applied to an equal extent (5). In order to investigate the practicability of these measures in detail, large hydraulic models of the River Elbe Estuary are available at the Coastal Department of the Federal Institute for Hydraulic Engineering (AuBenstelle Kiiste der Bundesanstalt fur Wasserbau) at Hamburg. The problems which result from the displacement of the sands and the fairways, as well as those of sediment transportation, are especially investigated in a model with a moveable bed consisting of granulated polystyrol (5)» Details concerning the construction, instrumentation, and questions concerning the scale ratios of this model were given by VOLLMERS during the 13th International Conference on Coastal Engineering 1972 in Vancouver (7). Fig. 1 shows the River Elbe Estuary and the outer boundaries of the model, the length scale of which is 1 : 8oo and the depth scale 1 : loo. Fig. 2 shows a view of the model in the direction of the ebb current.
IOWA SEDIMENT CONCENTRATION MEASURING SYSTEM
Authors: Nakato Tatsuaki , Locher Frederick A. , Glover John R. , Kennedy John F.
Published: June 2019

The Iowa Sediment Concentration Measuring System (ISCMS) is an electro-optical instrument developed in 1969 (Glover, Bhattacharya, and Kennedy 1969) for measurement of suspended solid concentrations in unsteady solid-liquid flows. It has been used extensively in laboratory investigations to determine spatial and temporal variations of sediment concentration in a variety of steady, unsteady, uniform, and nonuniform flows (Bhattacharya 1971; Danushkodi 1974). Concurrent measurements of concentration and velocity fluctuations have been used together to obtain estimates of mass transfers in unsteady sediment-laden flows, with the goal of improving the understanding of the underlying mechanisms responsible for sediment entrainment and suspension (Nakato 1974). Interpretation of the data gathered in these experiments pointed out the need for a more thorough understanding of how the optical and electronic components of the ISCMS respond to the passage of individual sediment particles through the optical field of the transducer (Locher et at. 1974). An investigation was undertaken to determine the sensitivity of the ISCMS output to the position of a particle in the transducer field; the role of particle velocity in determining the ISCMS output; the effects of particle translucency and size on the output of the system; and the dependency of mean concentration estimates on integration time.
SEDIMENT TRANSPORTATION AND DEPOSITION MODELS FOR MOBILE BAY, ALABAMA
Authors: April Gary C. , Ng Samuel , Brett C. Everett
Published: June 2019

The objective of this study is the application of hydrodynamic and material transport mathematical models for Mobile Bay in predicting sediment transport and deposition profiles within the bay system. Of particular importance are the seasonal variations of sediment distribution which are critically influenced by current patterns within the estuary. Both point and non-point sources of sediment will be included in the analysis. Results will be presented in two ways. The first or long term variations in sediment distribution will be assessed by correlation with tidal cycle average velocities at various locations within the bay. Calculated distribution patterns will be compared with observed bathemetic data over the past century. The net effect of the construction of the Mobile ship channel on deposition patterns within the bay will also be evaluated. Secondly, short term variations in sediment transport and deposition resulting from man-made and natural disturbances will be analysed using a sediment transport model. This model will include deposition, bulk fluid transport and resuspenslon characteristics and will be capable of predicting localized, short term sediment patterns from maintenance dredging operations within the bay. Model trend results will be compared with field data collected during recent dredging activities and high altitude photographic data obtained for the bay area.
WAVE-FORMED RIPPLES IN NEARSHORE SANDS
Authors: Dingler John R. , Inman Douglas L.
Published: June 2019

Ripples are generated and modified by wind-generated waves and their profiles are controlled by the nature of the near-bottom wave motion and by the size of the bed material. Wave-formed ripples develop under a definable set of conditions called the ripple regime. The ripple regime is bounded by those conditions that initiate grain motion, low-wave intensity, and by those that cause the disappearance of ripples, onset of sheet flow. Sheet flow occurs when intense wave motion causes several grain layers to be in motion. Three distinct ripple types occur in nearshbre areas of fine sand - relict ripples, vortex ripples, and transition ripples. Vortex and transition ripples lie within the active ripple regime, whereas relict ripples do not. Ripples in fine sand were studied in the field at La Jolla, California, where profiles were obtained using a newly developed high-resolution sonar capable of vertical resolution of the order of one millimeter. Simultaneous profile and wave-pressure measurements permit correlation of the ripple profiles with individual waves and with the wave spectrum. The sonar, with its rapid scan capability (^ one meter per second), gives instantaneous measurement of the actively changing bed features in nearshore waters. The combination of bottom scans and wavepressure measurements extends previous wave-ripple studies to include all of the nearshore ripple regime. The relation between the wave and ripple data from this study is best shown by plotting ripple steepness n/A against the wave form of the Shields relative stress criterion 0. Vortex ripples (n /\ ^_ 0.15) occur for 0 values less than 40 but greater than the minimum value which is determined by the onset of grain motion.
ORIGIN OF SUBMARINE DUNES
Authors: Yalin M.S.
Published: June 2019

The turbulent bursting process is outlined and attention is drawn to the fact that the "coherence distance" of the regenerating macroturbulent eddies is of a magnitude that is much the same as the length of dunes. Consequently it is postulated that the length of dunes is merely the "imprint" of the coherence distance on the deformable surface of a movable bed and the origin of dunes is explained accordingly. It is shown that the frequently observed similarity between tidal and unidirectional dunes is due to the similarity of the tidal transport and the transport corresponding to an intermittent unidirectional flow. The explanations presented herein are expected to be valid for dunes caused by both unidirectional flows and tidal currents.
TRANSPORT MECHANISM IN TIDAL DUNES
Authors: Nasner Horst
Published: June 2019

An interesting question arising within the scope of the further development of the German tidal rivers Elbe and Weser, is whether tidal dunes or sand waves will be formed after the navigation channel deepenings and that the success of the development measures will thus be partially or fully undone. In order to be able to better assess the formation and regeneration of these large patterns after dredging, heightened knowledge of the sand transport in a tidal dune field is necessary. A possibility of investigating the sand transport in a tidal river with pronounced tidal dunes in the field, can be realized by measurings with luminaries or tracers. The advantage of investigations in the field is, that all laboratory required scale effects are eliminated. The more difficult measuring comprehension of the course of the test in prototype must be solved through purposefully planned investigation programs. Subsequent to observations of many years standing, on behavior of four tidal dune areas in the navigation channel of the Weser River estuary (6), investigations were carried out with luminaries above reach 1 (Fig. 1) from September till November 1974. The aim was, to obtain information on the transport mechanism for tidal dunes and heightened knowledge on the causes of regeneration after dredging.
WAVE ACTION ON LARGE OFF-SHORE STRUCTURES
Authors: Apelt C.J. , Macknight A.
Published: June 2019

The paper describes investigations carried out in order to design for the wave action, both wave force and scour, on large off-shore berthing structures sited approximately 1.3 miles (2.1 km) off-shore near Hay Point, North Queensland, in 56 feet (17 m) of water at low tide, the tidal range being 20 feet (6 m). The region is a cyclone area and the structures must be capable of withstanding attack from maximum predicted waves with period of 8.25 seconds and amplitude of 24 feet (7.3 m). The main units in the berthing structures are concrete caissons sunk on to the ocean bed and the largest of these have plan dimensions of approximately 150 feet (46.7 m) by 135 feet (41.4 m) with four columns approximately 40 feet (12.2 m) square projecting through the water surface. No theoretical method available at the time of the investigation was capable of accurate calculation of wave forces on these structures. A scale model was tested to obtain wave forces and the paper compares results from the model with those of numerical methods and discusses the application of the results to the design functions. Scour effects were also modelled and the results used as the basis for design of scour protection.
CYLINDRICAL CAISSON BREAKWATER: STRAIN MODEL TESTS
Authors: Gravesen Helge , Brodersen Finn P. , Larsen Jorn S. , Lundgren H.
Published: June 2019

The distribution of shook pressures on a vertical face breakwater is so random from one shock to the next that the determination of the internal forces in a thin-balled reinforced-concrete structure is difficult even when a large number of pressure cells is used in a model test. Therefore a technique has been developed that allows the direct determination of the internal stresses by means of strain gauges. The new technique has been applied to a breakwater consisting of a series of cylindrical caissons. The results show that a strain gauge model is more advantageous than a pressure cell model because of its simpler data analysis and better determination of the quantities required for design.
WAVE FORCES ON SUBMERGED OBJECTS
Authors: Vongvisessomjai Suphat , Silvester Richard
Published: June 2019

Limitations of the Morison equation for computing wave forces on small submerged structures have encouraged the use of dimensionless relationships containing only height, period and water depth. However in dividing the force by the theoretical drag force or inertia force a relationship can be found with the Keulegan parameter (U. T/D) over a wide range of conditions and different types of wave. The U. value can be determined from empirical and theoretical data for all depths and wave steepnesses. The relating coefficients for various dimensions and shapes of submerged object are predictable from potential theory or modified slightly because of viscous and such other forces induced by bottom and free surface boundaries. For computing wave forces on a submerged object which is large compared to the wave length, the Morison equation is replaced by the Diffraction theory. Criteria for selecting the latter theory are presented.
NEW DESIGN PRINCIPLES FOR RUBBLE MOUND STRUCTURES
Authors: Bruun Per , Gunbak Ali Riza
Published: June 2019

This paper describes the effect of wave period on the stability of rubble mound breakwaters. Introductorily wave run-up and run-down on smooth slopes and on rubble mounds were measured, and breaker types were observed and recorded for different incoming wave and slope characteristics. The surf similarity parameter, 5 = , 9° = /-~ - ~^r ' T was found practical for /H/L0 / 2TT /H description of breaker type, run-up and run-down on both smooth and permeable slopes. Pressure measurements along the smooth slopes and in the core of a rubble mound were undertaken with two different core materials. It was shown that the most dangerous condition for the stability of rubble mounds occurs at the so-called "resonance condition". Resonance refers to the situation that occurs when run-down is in a low position and collapsing- plunging wave breaking takes place simultaneously and repeatedly at or close to that location. This corresponds to a range of E, values in between 2 and 3. Photographic instrumentation was introduced and tested to quantify the initial damage on a rubble mound. This paper is a 1/3 abstact of a thesis for the Dr. Eng. degree by Ali Riza Giinbak.
DESIGN AND CONSTRUCTION OF HUMBOLDT JETTIES, 1880 to 1975
Authors: Magoon Orville T. , Sloan Robert L. , Shimizu Nobuyuki
Published: June 2019

In the Chief of Engineers annual report of 1877, it was concluded that "The only way...in which a safe entrance could be obtained into this harbor would be by the construction of two parallel jetties, of very heavy stone, about 500 yards apart, from the north and south spits at the entrance." In 1882, a special Board of Engineers concluded that the "occupation of the south breaker spit by a structure...carried to low water and running from the south head (spit) in a north-westerly direction..." be built. Construction of the south jetty began in 1889 and of the north jetty, subsequently authorized, in 1891. Due to the severe wave action, a number of rubble-mound construction techniques including stone, concrete cubes, tetrahedrons, and finally dolos armor units have been used. A description will be given of the construction and associated results. Experience with the reinforced and unreinforced concrete dolosse units will also be discussed.
EXPERIMENTAL STUDIES OF STRESSES WITHIN THE BREAKWATER ARMOR PIECE "DOLOS"
Authors: Lillevang Omar J. , Nickola Wayne E.
Published: June 2019

Stresses induced within the breakwater armor piece "Dolos", when it is subjected to loads, are not reliably inferred from the two dimensional techniques of analysis used in conventional design of structures. Other methods that take the solid geometry of the dolos into consideration are available, and comprehensive application of one of them, three-dimensional photoelastic stress analysis, is reported here.
EFFECT OF BROKEN DOLOSSE ON BREAKWATER' STABILITY
Authors: Davidson D. Donald , Markle Dennis G.
Published: June 2019

Although the use of rubble-mound structures for protection of coastal areas is common throughout the world and considerable hydraulic design data have been developed to aid the designer, very little data are provided on the structural integrity of individual armor units and the effect of broken units on the stability of such structures. The forces to which such structures are subjected are complicated and vary with type and geometry of the structure, depth of water, bottom configuration seaward of the structure, water level relative to the crown of the structure, and wave dimensions. Since all of these parameters are involved, accurate determination of wave forces cannot be calculated; and although it is not impossible to model the structural strength of armor units or measure forces on individual armor units, there are physical limitations which make the tasks extremely difficult. There is one way, however, that a breakwater stability model, as it exists today, can provide useful information on this subject and that is to purposely break given numbers of armor units and observe the effect on the overall stability of the structure. Such tests have been conducted at the U. S. Army Engineer Waterways Experiment Station for the Atlantic Generating Station (AGS) Breakwater in which specific answers were desired; thus, the data are limited to the dolos armor unit. The data do provide, however, significant indications regarding the type and extent of breakage (cluster or random) that is most detrimental to the overall stability of the structure; whether costly reinforcing steel is warranted to assure reduced armor breakage; and where necessary, data from this type study can be used as a basis for setting maintenance criteria that will prevent deterioration of the breakwater due to armor unit breakage.
LABORATORY STUDY ON PERVIOUS CORE BREAKWATERS
Authors: Kondo Hideo , Toma Satoshi , Yano Kenji
Published: June 2019

Effects of permeable core layer installed in trapezoidal and rectangular breakwaters have been studied experimentally and analytically. As the materials for armour and core use of the lattice composed of circular cylinders was made in addition to rocks. Perforated plates were also applied as a kind of very thin core. Expermental results show that the reflected wave heights from breakwater could be reduced considerably by locating the core layer shoreward within it while core thickness controls the transmitted wave heights in the protected water area. Harmonic analysis about the water surface in lattice armour reveals that the second harmonic waves take a pattern of standing wave distribution having a node at the seaward face of breakwater. Thin perforated plates work success-- fully for reducing the transmitted wave heights when they are installed at the rear face of breakwater. An analytical approach to predict the transmission and the reflection coefficients is applied for the present experimental data and shown to be useful.
WAVE TRANSMISSION THROUGH. TRAPEZOIDAL BREAKWATERS
Authors: Madsen Ole Secher , White Stanley M.
Published: June 2019

Previous publications resulting from this study dealt with, certain aspects of the interaction of normally incident waves with a porous structure. Madsen and White (1976a), hereafter referred to as (I), developed a semi-empirical procedure for the prediction of reflection coefficients of rough impermeable slopes. Madsen (1974) with, discussion by Kondo (1975) and Closure by Madsen (1976), collectively referred to as(ll)hereafter, developed an explicit solution for the transmission and reflection coefficients of homogeneous rectangular crib-style breakwaters. When viewing the interaction of incident waves with, a trapezoidal, multilayered breakwater as a problem of energy dissipation, the problem treated in (II) may he regarded as an idealized analysis accounting for the internal dissipation of energy within the structure, whereas (I) may be regarded as an idealized analysis of the energy dissipation on the seaward face of the breakwater, i.e., the external energy dissipation. The present paper presents a synthesis of the results obtained in (I) and (II) into an approximate procedure for the prediction of wave reflection from and transmission through trapezoidal, multilayered breakwaters. The present paper presents only the major points of the approximate procedure. Thus, extensive references to (I) and (II) are made and only the determination of the hydraulically equivalent breakwater is presented in some detail. For a presentation of the entire development of this model for the reflection and transmission characteristics of trapezoidal, multilayered breakwaters the reader is referred to Madsen and White (1975) or Madsen and White (1976b) where detailed numerical examples of the use of the procedure may also be found.
Slit-type Breakwater; Box-type Wave Absorber
Authors: Nagai Shoshichiro , Kakuno Shohachi
Published: June 2019

A box-type wave absorber, which is composed of a perforated vertical front-wall and a perforated, horizontal bottom-wall, has been proved by a number of experiments to show lower coefficients of reflection and more distinguished reduction of wave pressures than the perforated vertical- wall breakwater. A breakwater of composite-type, which is 1500 m long and to be built at a water depth of 10 to 11 m below the Datum Line in the Port of Osaka, is being designed to set this new type of wave absorber in the concrete caissons of the vertical-walls which is named "a slit-type breakwater". The typical cross-section of the breakwater and the advantages of the slit-type breakwater are presented herein.
METHOD OF ANALYSES FOR TWO-DIMENSIONAL WATER WAVE PROBLEMS
Authors: Ijima Takeshi , Chou Chung Ren , Yoshida Akinori
Published: June 2019

One of the most powerful tools to analyze the boundary-value problems in water wave motion is the Green's function. However, to derive the Green's function which satisfies the imposed boundary conditions is sometimes difficult or impossible, especially in variable water depth. In this paper, a simple method of numerical analyses for two-dimensional boundary-value problems of small amplitude waves is proposed, and the wave transformation by fixed horizontal cylinders as an example of fixed boundaries, the wave transformation by and the motion of a cylinder floating on water surface as example of oscillating boundaries and the wave transformation by permeable seawall and breakwater as example of permeable boundaries are calculated and compared with experimental results.
DESIGN, ANALYSIS AND FIELD TEST OF A DYNAMIC FLOATING BREAKWATER
Authors: Agerton D.J. , Savage G.H. , Stotz K.C.
Published: June 2019

Interest in floating breakwaters has been generated in recent years because the concept offers the potential of providing a less expensive alternative to traditional, solid wall type barriers for providing permanent wave protection to the thousands of new recreational boat harbors and marinas that have been built in the past 20 years. Also, they may be able to provide temporary, mobile wave protection during construction and installation of offshore facilities for oil transfer and production operations, defense facilities and other offshore structures in deeper water (depths exceeding 50 to 100 feet). The engineering director of one of the largest and most active offshore oil producing companies recently stated that they would be willing to pay up to $6 million for a mobile, floating breakwater that had the proven capability to significantly reduce risks due to wave action during offshore erection in the North Sea or elsewhere. Considering the investment in just one deep water oil production platform already exceeds $100,000,000, the worth of such a reusable, wave protection system during the critical erection period of a platform should be large.
OCEAN WAVE RECORD ANALYSIS BY TUCKER'S METHOD - AN EVALUATION
Authors: Dattatri J. , Nayak I.V.
Published: June 2019

The planning and design of any Coastal Engineering structure requires adequate knowledge of the wave characteristics. It is desirable that this knowledge of waves is based on instrumentally recorded data over a number of years, so that reliable values could be used for the computation of the design wave. Analysis of instrumentally recorded data to yield the relevant wave characteristics like the significant wave height, though not complicated is too time consuming. A simple method of analysis has been proposed by Tucker (9, 10), wherein the relevant information is obtained with only a few measurements of the larger waves. This method is also recommended by Draper (6) in his plea for uniformity of the analysis and presentation of wave data. This paper deals with the application of the Tucker's method to analysis of waves recorded off the Mangalore Harbour on the West Coast of India.
PROTECTION OF MARITIME STRUCTURES AGAINST SHIP COLLISIONS
Authors: Oda Kazuki , Nagai Shoshichiro
Published: June 2019

This paper deals with the analytical and experimental studies on a new device to prevent the accidents of ship collisions with maritime structures. The practical protection device was designed on the basis of this study and it has been in use for the prevention of ship collisions of a class of 1,000 G/T with a boring tower for the geological survey of the sea beds of a narrow straits in which quite a many ships navigate.
LOW-COST SHORE PROTECTION ON THE GREAT LAKES: A DEMONSTRATION/RESEARCH PROGRAM
Authors: Armstrong John M.
Published: June 2019

Shore erosion is currently causing millions of dollars of damage to shoreline property along the Great Lakes (1,2). Erosion is caused by the energy of waves and currents which are produced by large wind storms. The erosion process on the Great Lakes is most severe when lake levels are near the top of their 6-foot (1.8 meter) range'for several years as is currently being experienced. The severe erosion process continues even after lake levels fall, as the bluffs have become unstable and waves from intense storms can still attack them. In order to alleviate the erosion damages to beaches and bluffs, shoreline owners must rely on shore protection methods. Effective methods of shore protection are designed to slow or stop the erosion process by dissipating wave energy and/or preventing bluff attack. However, the most effective methods are very expensive, costing over $200 per foot ($656 per meter) of shoreline. (Costs are calculated, for the purposes of this study, as the length of shoreline which is expected to be protected by the shore protection methods. For sites utilizing revetments, artificial nourishment, and seawalls, the length is the stretch of shoreline actually covered by the method. For locations utilizing groin systems and breakwaters, the system was designed to protect the entire length of the sites; the costs have been calculated on that basis. Whether these systems actually protect that length of shoreline is to be determined by this study.) Shoreline homeowners are usually not able to meet such expenses, and often resort to less efficient and costly alternatives. Private shoreline owners need accurate, reliable information about effective low-cost shore protective methods in order to reduce or alleviate the severe erosion damages to their shoreline.
NEGATIVELY BUOYANT SLOT JETS
Authors: Shahrabani D.M. , Ditmars J.D.
Published: June 2019

The behavior of negatively buoyant slot jets discharged from near the bottom of stagnant and flowing receiving-water environments of uniform density was studied in laboratory experiments. In particular, the locations of the maximum height of rise and maximum horizontal displacement were determined as well as the centerline dilutions at those points. Experiments in stagnant environments were conducted for discharges at angles of 30°, 45°, 60°, and 90° from the horizontal and with discharge densimetric Froude numbers of 10, 20, 30, 40 and 50. For flowing environments, discharges at angles of 45° and 90° for the same range of densimetric Froude numbers were directed into uniform currents with discharge to ambient velocity ratios of 15 and 25. The reattachment eddy formed between the jet and bottom boundary was found to have significant effects on the slot jet trajectories and dilutions. Dilutions at the maximum height of rise and maximum horizontal displacement were less than those predicted for slot jets far removed from the influence of the bottom boundary. The strictly two-dimensional discharges studied provide lower bounds on the dilutions to be expected for the cases of slots of finite length or merged multiport diffuser discharges in which the reattachment eddy is not as well developed.
SIX-PARAMETER WAVE SPECTRA
Authors: Ochi Michel K. , Hubble E. Nadine
Published: June 2019

In an attempt to develop a systematic series of wave spectra covering a variety of spectral shapes observed in the ocean, this paper presents a newly developed series of wave spectra which involves six parameters. In the development of the six-parameter wave spectra, the spectra are decomposed into two parts. Each part is expressed by a mathematical formula with three parameters, and the total spectrum is expressed by the combination of two sets of three-parameter spectra. Results of analysis have shown that the six-parameter wave spectra thus derived appear to represent almost all stages of development of a sea during a storm. Then, from the statistical analysis of 800 spectra observed at the North Atlantic Ocean, the values of the six-parameters are expressed in terms of significant wave height so that a family of spectra for a desired sea severity can be generated.
GUIDELINES FOR THE DESIGN OF AIR BUBBLE SYSTEMS
Authors: Ismail Nabil
Published: June 2019

Based on a literature review of theoretical and experimental work on air-bubble systems, guidelines for the ideal design of submerged distributors discharging air into water are presented. A comprehensive study of gas-liquid dispersions was carried out to find out the effect of physical properties, distributor arrangement, and the air flow rate, on the flow pattern within the jet. This review revealed that the distributor arrangement largely influences the characteristics of the dispersion within the zone of flow establishment. Also, upon analyzing the experimental results of air-water systems, it was found that the zone of flow establishment extends to greater distances of the water depth than that in the case of one-phase turbulent plumes. Furthermore, the experimental results showed that the efficiency of air bubble plumes can be increased by the proper design of the distributor. Recommendations for the distributor design are given, which include, diameter of orifices and their spacings, pressure drop across orifices, number of manifolds, and the maximum air flow rate.
FIELD STUDIES OF SUBMERGED-DIFFUSER THERMAL PLUMES WITH COMPARISONS TO PREDICTIVE MODEL RESULTS
Authors: Frigo A.A. , Paddock R.A. , Ditmars J.D.
Published: June 2019

Thermal plumes from submerged discharges of cooling water from two power plants on Lake Michigan were studied. The system for the acquisition of water temperatures and ambient conditions permitted the three dimensional structure of the plumes to be determined. The Zion Nuclear Power Station has two submerged discharges structures separated by only 94 m. Under conditions of flow from both structures, interaction between the two plumes resulted in larger thermal fields than would be predicted by the superposition of single non-interacting plumes. Maximum temperatures in the near-field region of the plume compared favorably with mathematical model predictions. A comparison of physical-model predictions for the plume at the D. C. Cook Nuclear Plant with prototype measurements indicated good agreement in the near-field region, but differences in the far-field occurred as similitude was not preserved there.
THERMAL DISCHARGES: PROTOTYPE vs. HYDRAULIC MODEL
Authors: Parker Gary C. , Fang C.S. , Kuo Albert Y.
Published: June 2019

Data on physical parameters in the James River around the condenser cooling water discharge of the Surry Nuclear Power Plant, taken prior to and during plant operation, were analyzed to determine the physical effects of the thermal discharge on the area and to compare the prototype distribution of excess temperature to predictions based on hydraulic model experiments. The results of this investigation indicated that the increase in water temperatures due to the thermal discharge did not represent a significant alteration of the physical environment outside the mixing zone. The thermal discharge experienced turbulent mixing and entrainment near the outfall and temperatures decreased rapidly in this region. Field data on temperature distributions around the discharge, when compared to predictions based on hydraulic model experiments, indicate that the model predictions were conservative.
ADAPTABILITY OF PREDICTION METHOD OF HYDRAULIC MODEL EXPERIMENT FOR THERMAL DIFFUSION
Authors: Kato Masanobu , Wang Akira
Published: June 2019

In formation processes of the region of water temperature rise caused by the cooling water discharge from thermal and nuclear power stations located on the site facing the ocean, flow of discharged cooling water itself, current and turbulence existing in the sea region play an important role. Their motions are predominant in the horizontal direction in the sea region. The horizontal scale of thermal extent is, therefore, extremely larger than the vertical scale of thermal extent. Therefore, whenever the diffusion experiments of discharged warm water in the far field are conducted by hydraulic model method, the model which has a difference in the geometrical reduced rate between the horizontal and vertical directions, what is called, the distorted model must be used, so that the effects of the viscosity and the surface tension on the experimental model can be avoided. In such a model, the horizontal scale is determined by the relation between the size of the experimental water basin and the surface area of the sea region to be reproduced. But, there is no clear method of choosing the vertical scale, though there are some suggestions about it. For example, the similarity of the 4/3 power law of the diffusion coefficient gives a relation between the vertical scale and the horizontal scale of the hydraulic model. On the other hand, the similarity of the surface heat exchange coefficient gives another relation between the vertical scale and the horizontal scale of hydraulic model if the surface heat exchange coefficients of hydraulic model and prototype are not same. Therefore, it is better to give some allowance in the determination of the vertical scale of the hydraulic model within the range where the reproducibility of the diffusion phenomena can be conserved.
DYNAMICS OF A LONGITUDINALLY STRATIFIED ESTUARY
Authors: Imberger Jorg
Published: June 2019

Introduction. A partially stratified estuary is defined as one which possesses a quite definite longitudinal salinity gradient from the mouth to the head of the estuary, but only a very weak vertical or transverse salinity structure. For an estuary to exhibit such characteristics it must possess a source of fresh water near the head of the estuary, sufficient vertical mixing to overcome the potential energy associated with such a fresh water inflow and be very much longer than its width to reduce transverse variations. If the estuary is very shallow (a few meters) then wind generated turbulence is often sufficient to eliminate most or all the vertical structure. Deeper, or very sheltered, estuaries require additional strong tidal shears to break up the vertical density gradients. However, in both cases the mixing is usually not sufficient to completely homogenize the estuary longitudinally and it is found that these estuaries display a near linear salinity gradient along the principle axis of the estuary throughout most of the spring and summer months. Such a density gradient drives a gravitational circulation within the estuary which leads to a net transport of salt from the sea mouth to the head of the estuary. Two dimensional theories (see for instance Rat tray and Mitsuda (1974)) have been established, but In general these greatly underestimate the longitudinal transport found in such estuaries and three dimensional circulation effects must be considered. Fischer (1972) was the first to recognise this fact and he carried out a first order analysis which pointed to a greatly increased longitudinal dispersion. However, Fischer (1972) carried out his analysis only to first order, not explaining how the transverse pressure field, set up by the first order velocity field convecting the longitudinal density gradient, is balanced. It is the purpose of this paper to give a rigorous foundation to Fischer's (1972) hypothesis that it is the transverse variations in velocity which yield the greatest contribution to any longitudinal transport of the density or any passive pollutant. Furthermore, the presented theory is applied to a local Western Australian estuary which is ideally suited for such a comparison complying strictly to the assumptions of the theory.
INTERFACIAL INSTABILITY IN STRATIFIED FLOW
Authors: French Richard H.
Published: June 2019

When heated water from a thermal power plant is discharged onto the free surface of an estuary or river, a density stratified flow consisting of superposed layers of hot and cold water is established. Such a flow is characterized by an initially stable interface at which there is zero velocity difference and a decaying density difference. Since it is known that after the density difference has decayed sufficiently the interface will be destroyed by turbulent eddies generated at the bottom boundary, it is pertinent to inquire if the point of interfacial stability can be easily located. It is the purpose of this paper to examine the question of interfacial stability in the presence of boundary generated turbulence and in the absence of interfacial shear. Although the problem of interfacial stability has been previously investigated, scant attention has been given to the case of a two layer flow without shear in the presence of boundary generated turbulence. Keulegan (1949) investigated a turbulent current of fresh water moving over a quiescent pool of saline water. He concluded that the stability of the interface could be adequately described by a single dimensionless parameter, the "Keulegan" number.
NUMERICAL MODELING OF DISPERSION IN STRATIFIED WATERS
Authors: Christodoulou George C. , Connor Jerome J.
Published: June 2019

A numerical model is developed for the quantitative description of the dispersion process in a two-layer system which represents an approximation for a natural coastal water body during the summer season when a distinct thermocline usually exists. The formulation is based on the convection-diffusion equation, vertically integrated between the layer boundaries. Layer velocities and thicknesses are assumed to be obtained from a separate hydrodynamic model. The quantification of the physical processes of entrainment and mixing through the density interface as well as the horizontal dispersion mechanisms is discussed. The finite element method is chosen for numerical implementation because of its flexibility in grid layout and easier handling of spatial and temporal variability. Triangular elements with linear interpolation functions are used for the spatial discretization, while a simple implicit iterative scheme based on the trapezoidal rule is employed for time integration. The method is shown to be unconditionally stable, for an arbitrary grid and both one- and two-layer problems, when there is no iteration and the parameters are constant. General convergence criteria required by the iteration procedure are developed and expressed in terms of the basic parameters of the problem and are subsequently confirmed by numerical experiments. Verification of the model is performed by comparison with analytical solutions derived for counterflow conditions. Finally the model is applied to a particle dispersion experiment carried out recently in the Massachusetts Bay and comparisons with field data are presented.
DETERMINATION OF THE INTERFACIAL EDDY DIFFUSION COEFFICIENT OF A HIGHLY STRATIFIED ESTUARY
Authors: Wang Yu-Hwa
Published: June 2019

Estuaries may be sequentially classified into highly stratified, moderately mixed and vertically homogeneous. An important difference between moderately stratified or vertically homogeneous estuaries, and highly stratified estuaries (salt wedges) is that, in the former, tidal currents are sufficient to cause turbulent mixing of fresh water and sea water over the full depth of the estuary. In the latter, a distinct interface or interfacial layer exists which separates the two nearly homogeneous layers. The vertical advectlon of salt in this two-layer flow is the dominant process in maintaining the salt balance. This paper presents an analytical model describing this process. Experiments have been conducted in the laboratory to compare with the developed theory. A large number of publications concerning estuarine dynamics are available for moderately mixed and vertically homogeneous estuaries. Relatively little information, however, is available for highly stratified estuaries. In an earlier work Keulegan (1949) defined the critical velocity of the upper layer at which the entrainment of the salt water layer starts. A summary of Keulegan's work may be found in Chappter 11 of the book, "Estuary and Coastline Hydrodynamics" edited by Ippen (1966). Recently Partheniades et. al. (1975) reviewed Schijf-Schonfeld's analytical work and Keulegan's experimental data with regard to the length, shape and shear stresses of a saline wedge. Wang (1975) compared his laboratory measurements of interfacial stresses with Lock's Theory.
FRICTION AT THE INTERFACE OF TWO-LAYERED FLOWS
Authors: Tamai Nobuyuki
Published: June 2019

Viscous perturbed velocity field induced by interfacial waves is solved to the first order in terms of wave amplitude for sharply stratified flows described in a curvilinear coordinate system assuming that the external velocity is uniform and constant along the interface. A new type of formula for the interfacial friction coefficient is proposed based on the theoretical result on viscous dissipation in the boundary layer along the interface. The interfacial friction coefficient is supposed to be inversely proportional to the square root of the product of the Reynolds number of a moving layer and the densimetric Froude number to the fifth. The new formula agrees with observed data better than the best empirical law does especially in the range of large Reynolds number. It is found out, however, that the proportional constant may be affected by stability of the two-layered flow system concerned.
NUMERICAL MODELLING - AN AID TO ASSESSING FIELD DATA
Authors: Riedel H.P. , Wilkinson F.L.
Published: June 2019

After the completion of 5 years of field measurements, complemented by extensive numerical modelling in 1974, the hydraulics of Cockburn Sound, Western Australia, are now understood in enough detail to allow the rate of exchange of water between the Sound and the ocean to be determined. Flow patterns in Cockburn Sound tend to be complicated by the superimposition of many driving influences, the most important being wind, but by using the output of a numerical model most of these patterns are predictable. Current magnitudes within Cockburn Sound have not reduced so that the rate of dispersion of effluents released by the industrial complex on the eastern side of the Sound has not changed. However, flow rates through the southern entrance to Cockburn Sound have been reduced to between 30 to 45$ of the rates which occurred prior to the causeway construction. This means that the mean discharge rate is now 570 m3/sec through the causeway bridges compared to a rate of about 1500 m3/sec before the causeway construction.
PREDICTION OF POLLUTANT DISTRIBUTION IN ESTUARIES
Authors: Kuo A.Y. , Jacobson J.P.
Published: June 2019

A method was developed for predicting the distribution of sewage constituents which would result from a proposed sewage outfall in estuaries or coastal seas. The method is based on the mathematical relationship between the solutions of the mass-balance equations with and without a decay term and on the assumption that both the dispersion and decaying processes are linear, acting independently. The application of the method requires dye dispersion experiments and a numerical model employing the results of the experiments. This approach makes it possible to predict the concentration field of sewage constituents with differing decay rates by using tracer release experiment employing a conservative tracer. The method has been applied to assess the environmental impact of a proposed sewage outfall in Hampton Roads, Virginia. Two dye dispersion experiments were performed, one a continuous release over a flood tide cycle and the other over an ebb tide cycle. Horizontal distributions of dye were measured at subsequent slack waters before flood and ebb. The results were used to predict the concentration fields of total nitrogen, total phosphorus, coliform bacteria, biochemical oxygen demand, dissolved oxygen deficit and chlorine residuals, which would result from the proposed sewage outfall.
WAVE DIRECTION COMPUTATIONS WITH THREE GAGE ARRAYS
Authors: Esteva D.
Published: June 2019

Wave direction is an important parameter in the solution of many coastal engineering problems such as the estimation of sediment transport and the response of coastal structures. Wave-gage arrays are among the most widely proposed systems for measuring wave direction. In late March 1970, the U.S. Army Coastal Engineering Research Center (CERC) installed an array of five pressure sensors off the California coast. Figure 1 gives the location of the array, its geometry and dimensions. The water depth at the site was approximately 9.14 meters (30 feet) and the gages were positioned .76 meters (2.5 feet) from the bottom. One use for the array data would be to compare redundant values of wave direction and estimate the level of accuracy of the computations. Redundant values of direction were obtained from the ten three-gage arrays possible with five gages. Three-gage arrays offer some advantages over arrays involving a larger number of gages and have been proposed by many investigators. An obvious advantage involves economics. Non-linear arrays offer the advantage over linear arrays that straight forward mathematical expressions can be derived for the unambigous computation of direction. These expressions involve the phase differences between gage pairs for the waves present, no recourse to two-dimensional spectral analysis is necessary. However, it is necessary to assume long and relatively straight crested waves, traveling in well determined directions, and geometrically stationary over the array. The first two assumptions are supported by high altitude aerial photographs, Figure 2 and, by radar scans of the wave field, Figure 3. Fujinawa (1975) conjectures that narrow directional spread is responsible for the incomplete recovery of the true directional spectrum from field records in his computations using high directional resolution.