Showing papers in "Journal of the Waterways, Harbors and Coastal Engineering Division in 1972"

Maximum breaker height

Abstract: Based on a re-evaluation of available experimental data on breaking waves, a relationship between the breaker height-breaking depth ratio, the incident wave steepness and the beach slope is found. This relationship, when combined with experimental observations of breaker travel, permits an estimate of the maximum breaking wave height a coastal structure might experience given a design wave period and design depth at the structure site. Breaker-type classification according to inshore and offshore parameters as presently defined cannot be reconciled to observations of the relationship between breaker-height index, wave steepness and beach slope. Revised criteria for breaker classification are presented.

Spectral resolution of breakwater reflected waves

Abstract: A means of resolving incident and reflected wave heights for a partial standing wave through the use of two fixed wave sensors is demonstrated. Field studies were conducted in which the waves incident to the permeable rubblemound breakwater located in Monterey Harbor, CA, are spectrally resolved into incident, reflected and transmitted wave components. Power-spectra and cross-spectra are calculated for various characteristic sea states. Amplitude and phase are determined for the spectral wave components compromising the partial standing wave phenomena and reflection and transmission coefficients determined. The reflection coefficients vary between 0.3 and 0.7 and the transmission coefficients between 0.1 and 0.2. The transmission and reflection coefficients are shown to be dependent on the frequency and amplitude of the incident waves and the tidal stage.

Equilibrium Beach Profile Scale-Model Relationship

Abstract: A model law for two-dimensional, laboratory beach profiles assumed to be at equilibrium is considered herein. An experimental program has been performed and the extensive laboratory beach profile data indicate a relationship or model law between the four basic scale ratios; the horizontal scale, vertical scale, sediment size ratio, and the relative specific weight ratio. Graphical forms of the experimentally derived model law are presented for efficient use. Recommendations are presented to optimize the practical application of scale model technology to coastal movable beds.

Wave Forces on Submerged Bodies

Abstract: In the design of submerged oil storage vessels where the structure generally has limited net negative buoyancy, the wave forces are of considerable importance in the design. This paper deals with the interaction of a train of regular surface waves with a large submerged oil storage tank resting on the ocean floor, in water of finite depth. Linear wave theory is used to describe the incident wave and viscous effects are neglected on the basis that the size of the submerged object is large compared to the height of the incident wave. The problem is formulated in the form of a potential flow problem and to solve this problem, point wave sources are distributed over the immersed surface. The strengths of these sources are then adjusted to satisfy the no-flow condition at the surface of the object. Results from a computer program based on these theoretical concepts are compared with experimental results from wave channel testing.

Oscillations in harbors with connected basins

Abstract: A theory is presented to analyze the response to periodic incident waves of an abritrary-shape harbor containing several inter-connected basins. The domain of interest is divided into an open-sea region and several inner basins depending on the harbor geometry. The solution in each region is formulated in terms of the unknown normal velocity at the entrance, or at the common boundary between basins, or both; the velocity is then determined by matching solutions for various regions. It has been found that the theoretical results agree well with experiments both for an irregular shape harbor and a harbor composed of two connected circular basins. Various aspects of the response of harbors composed of connected circular basins as well as circular harbors with rectangular entrance channels and side channel resonators are discussed. To a first approximation it appears that the response curve of a harbor composed of coupled basins can be synthesized from the response curves of the individual basins.

Statistical Properties of Missouri River Bed Forms

Abstract: A logarithmic resistance relationship for flow near rough boundaries was formulated which relates bed form dimensions to flow resistance in large alluvial channels with dune beds. Bed profile data, obtained from a reach of the Missouri River at Omaha, NE, were analyzed statistically to obtain characteristic bed form dimensions. Different statistical techniques were explored and the zero-crossing distances and amplitudes analysis is shown to be the one best suited for this investigation. Estimates of bed form dimensions obtained form the preceding analyses together with frequency distributions of bed elevations, wave lengths, amplitudes and heights of the dune bed forms are presented. A plot of the bed form friction factor versus a modified relative roughness parameter incorporating statistical estimates of bed form dimensions is presented and is shown to be roughly consistent with the Karman-Prandtl logarithmic law.

Environmental aspects of dredging in estuaries

Abstract: Salt marsh estuarine environments along the Intracoastal Waterway of the southeastern Atlantic coast were studied to determine the environmental effects of dredging in these areas. The study dealt with the chemical response of salt marsh seidments to the deposition of dredge materials and with the water quality response to dredging and deposition of sediments in a salt marsh estuarine environment. After the initial destruction of the salt marsh plants due to spoil deposition, the rate of reequilibration of the marsh sediments to their original state (suitable for revegetation) is greatly dependent on the depth of the dredge spoil deposit. In natural and relatively unpolluted areas, dredging has no significant effects on water quality when either diked or undiked confinement techniques are used. In polluted areas in marine environments, water quality impairment caused by dredging activites do not necessarily bear any simple relation to the composition of the sediemtns to be dredged.

Waves generated by horizontal motion of a wall

Abstract: An experimental investigation of the characteristics of surface waves generated by the time dependent horizontal motion of a vertical wall in water has been made, and the results compared with the numerical solutions obtained by Noda (1969) using linear theory. The experiments were made in two test flumes using various water depths, wall displacements and velocities of wall motion to determine the range of validity of the linearizaed solutions. The comparison of linear theory with the experimental data show the theory can be useful to the design engineer even for nonlinear waves at small distances from the wall.

Wave Transmission by Overtopping

Abstract: This report presents a semi-empirical theory for ocean wave transmission past breakwaters by overtopping, based on an evaluation of the energy content of the overtopping water. While several coefficients are subject to further investigation, the data show that the general form of the equations developed is correct. Comparison with large-scale model tests reinforces this belief, and comparison of an intermediate theoretical result predicting the volume of overtopping water with published data again shows reasonable agreement. An envelope curve for the transmission coefficient, based on all available data, gives a simple tool for preliminary design estimates of the transmission coefficient.

Mathematical Model of River Hooghly

Abstract: Finite difference solutions to the one-dimensional equations of motion for shallow water waves have been applied to the tidal region of the River Hooghly. Reproduction of flow conditions was achieved by optimization of the friction parameters and refinements or adjustments to the available data. The mathematical model formulated is capable of satisfactory reproduction of tidal levels and velocities throughout the section of the river considered. The neglect of the tidal bore as a discontinuity did not adversely affect the overall reproduction of tidal elevations in the river. If a more detailed reproduction of the propagation of the bore is required recourse should be made to the method of characteristics. Comparison of the two finite difference schemes suggests that improvement in the overall accuracy of the model is unlikely to result from increased accuracy in the numerical solution of the equations of motion.

Analysis of Floating Plate under Ocean Waves

Abstract: The interactions between a large elastic floating plate and ocean waves are investigated. The plate is moored to the ocean bottom and the type of waves considered are either wind-induced random waves or Tsunami-runup-like tidal waves. The analysis is based on a boundary-value problem formulation; i.e., the plate and ocean together are considered as an integral system and related through the continuity conditions at the fluid-solid interface. The wind-induced random waves are simulated through a digital computer according to the spectrum of ocean surface elevation and the response analyses are performed in the time domain using a technique consisting of modal expansion and numerical integration. The results show that a large floating plate with or without anchors can be excited by waves with wave length comparable to the width of the plate producing very large bending moments.

Wave Diffraction by Detached Breakwater

Abstract: A thin barrier of finite length in water of finite depth and infinite extent is considered. An incident gravity wave, attacking the obstacle from infinity, is diffracted and scattered by the thin b...

Effects of Irregular Wave Trains on Rubble-Mound Breakwaters

Abstract: Results of model tests on a typical cross section of a rubble-mound breakwater are presented. The structure was protected against wave attack by a cover layer consisting of a double layer of dolos armor units of 43 g. These units were intended to represent 0.19 ton prototype units to a scale of 1/16. All tests were carried out on a slope of 1:1.5. The armor units were first submitted to attack by nonbreaking waves of the regular type and then by nonbreaking waves of the irregular type. Two kinds of irregular waves simulating a narrow-band spectrum and a wide-band spectrum were used. Wave heights and periods were measured with the help of resistance type wave gages. Two types of damage were identified: the stable and the unstable damage. The test results are presented showing the significant wave height and the damage coefficient versus the stable and unstable damage.

Physical and dynamical scales for generation of wind waves

Abstract: An analysis is given of relevant physical scales on which coupling takes place between long and short waves, and dynamic scales for coupling of wind and waves, in the generation of wind waves. Based on these scales and on a separation criterion, it is argued that the airflow separates from dominant waves in the laboratory and from ripples superimposed on dominant waves in the field. This difference may account for the discrepancy between the laboratory-determined growth rate and that observed in the field. Finally, some consideration is given to observational evidence and critical scales relating to the nonlinear mechanism for wave generation.

Oil booms in tidal currents

Abstract: The oil capacity of a boom deployed in U-shape in a current depends primarily on the densimetric Froude number, with a critical Froude number above which the boom holds no oil, and an increasing capacity below this value. In low currents, the oil capacity is limited by the oil running out of the mouth, or to the top of the U. The forces on such a boom without oil are similar to those on any flat plate, and fix the shape of the U. With a boom full of oil, the forces are nearly independent of current velocity. The change in depth of the resultant force, as the boom fills with oil, requires adequate stability.

Mechanical excitation of offshore tower model

Abstract: A large scale model of a bottom-pivoted, surface-piercing, cylindrical oil-drilling platform was built to obtain experimental data on hydrodynamic coefficients applicable to the structure. The wave force on the structure was simulated by a mechanical device in still water. Thus, the number of variables to calculate the drag and added mass coefficients associated with the structure for use in conjunction with the Morison Equation was reduced. For instance, water particle velocity and acceleration were eliminated from the equation. Test runs were made at different simulated sea conditions. Consistent drag and added mass coefficients were obtained using various data reduction techniques.

Reducing ice formation at navigation dams

Abstract: Increasing the turbulence at the movable gates of the Mississippi River Navigation Dams in the St. Paul District by discharging over bulkheads during the winter rather than under the gates has prevented severe icing at the dam. This study has shown that movement of the gates has been facilitated substantially, but maintenance costs on the bulkheads have increased. Providing aeration facilities culverts through the earth dams and slots through emergency spillways, have increased dissolved oxygen in downstream slackwaters and have benefited fish life by reducing stagnation. Additional aeration is possible by improving facilitations.

Capacity-Feedback Relationship for Port of Bangkok

Abstract: Specific objectives of this research were: (1) To ascertain whether or not berth service times at the port of Bangkok are state-dependent; (2) to determine the effect of this feedback phenomenon on berth capacity; and (3) to suggest the means of making the unloading operation more responsive to the number of ships in the system. Both the macroscopic and microscopic approaches were employed to fulfill these objectives. The macroscopic study of arrivals and departures of 2,273 ships for two 1 yr. periods revealed that although berth operations were influenced by the number of ships queued, this feedback had not been a planned instrument of the Port Authority. The microsopic analysis of a large number of repetitions of the unloading cycle for ships carrying various types of cargo gave the possible or ideal capacity, while the microscopic tracer study of making a continuous record of the cargo-handling operation of a single ship throughout its entire stay at a berth suggested a practical capacity for the 10-berth facility.

Mardyck Lock Acts as Salt-Water Barrier

Abstract: The Mardyck lock provides access for inland waterway traffic from the Dunkerque docks to a navigation canal. But at Dunkerque the canal is below sea level and intrusion of sea water into the freshwater canal must be prevented. This lock is the first to be constructed to a new design principle and assures complete exchange of water contained in the lock and takes advantage of specific gravity differences between freshwater and salt water.

Cyclic Sedimentation in Agua Hedionda Lagoon, Sourthern California

Abstract: Agua Hedionda Lagoon is near Carlsbad, CA, and is near the middle of the Oceanside littoral sedimentation cell. Since its initial dredging in 1954, the lagoon has become a coastal sediment trap that must be dredged almost yearly. The purpose herein is to show the rate of sediment deposition in the lagoon from 1955 to 1961.

Resonant Response of Offshore Structures

Abstract: A nonlinear deterministic mathematic model is used to investigate the resonant response of a tall offshore structure under the action of periodic deep water waves. The added mass which is attributed to the acceleration of a body in the fluid is taken into consideration. The fundamental period of vibration of a structure is lengthened due to the effect of the added mass. An incremental numerical technique is employed to obtain the solution. The results show that even when damping due to drag is considered, the response of the structure at resonance is greatly amplified.

Coastal currents of pacific northwest

Abstract: To plan and design ocean outfall for sewage, cooling water or other wastes it is necessary to have a knowledge of the nearshore current velocities and directions. An overview is presented of available nearshore current measurement of the Pacific Northwest Coast along with some theoretical methods for calculating velocities. Current contributions are considered from tides, winds, waves and upwelling. Available current data indicate that in nearshore areas effects due to bottom and shore configurations overshadow geostrophic and Ekman layer effects. Generally, theoretical methods for calculation of current velocities in coastal waters (within 5 nautical miles of the coastline) can give approximate values. However, for specific information it is usually necessary to perform local measurements.

Development of Bottom Panels in River Training

Abstract: Two new specific projects show the development of the panels as permanent river training structures. New information and references concerning 6 yr. of progress in theory, scale models and experiments in situ are presented herein. The works on the Loire River in France are linked with the cooling system of a nuclear power plant; on the Chao Phya River, the project deals with the improvement of navigation over a 100-km long reach. After 14 yrs. of experiments on large and wide waterways in Africa and Asia, followed by training works on medium wide reaches in France and Thailand, the scope of bottom panels on alluvial river with a gentle slope has been broadly investigated. This comparatively inexpensive method has been quite well controlled, however, the feasibility of panels must always be studied very carefully under new hydraulic and economic conditions.

Containerization--a system still evolving

Abstract: It has been only 6 yr. since the container revolution altered general cargo shipping on the ocean trade routes. Sea-Land, by announcing its intention of serving the North Atlantic trade route, spurred intensive readjustment by ports and shipping interests and thrust into the forefront--the containership. The rapid evolution of the containership as a unique carrier is traced. The demands for specialized port facilities to keep pace with the realities of service are explored in some depth. It is demonstrated that the container system of today is not an end in itself, it is a way-point in the evolution of a means of cargo handling.