Showing papers in "Journal of the Waterway, Port, Coastal and Ocean Division in 1978"
TL;DR: In this article, an experimental and analytical investigation of the forced oscillations of a circular cylinder in uniform flow is presented, where the transverse force has been decomposed into two components and the appropriate force-transfer coefficients have been determined experimentally through the use of a Fourier averaging techinique.
Abstract: The paper presents the results of an experimental and analytical investigation of the forced oscillations of a circular cylinder in uniform flow. The transverse force has been decomposed into two components and the appropriate force-transfer coefficients have been determined experimentally through the use of a Fourier averaging techinique. The results were then incorporated into the equation of motion to predict the dynamic responsee of elastically-mounted cylinders. The numerical predictions were found to be in good agreement with those obtained experimentally.
199 citations
TL;DR: In this article, the quantities of sediment moving as bed load in oscillatory flow over a flat bed were measured with an oscillating tray in still water but some were carried out in a wave flume.
Abstract: Measurements have been made of the quantities of sediment moving as bed load in oscillatory flow over a flat bed. Most of the measurements were made with an oscillating tray in still water but some were carried out in a wave flume. There is good agreement between the two sets of results. For sand and gravel the mean sediment transport rate is observed to vary during the course of the cycle like the fourth power of the velocity of oscillation but with a slight phase lead. For nylon pellets, however, the transport curve is not quite symmetrical about its maximum. Measurements were also made of the random fluctuations in transport rate and these are compared with Abou-Seida's theoretical model. An empirical relationship is derived for the sediment transport rate.
91 citations
TL;DR: In this article, the pore-water pressure field at a pipeline buried in a permeable seabed has been determined from potential theory and the pressure at the pipe integrated to give a net seepage force, of constant magnitude, rotates as the waves pass, thereby tending to force the pipe against the surrounding soil in a cyclic manner.
Abstract: The wave-induced seepage force on buried pipelines has been evaluated theoretically. The seepage force is shown to be large enough to warrant inclusion in future engineering design calculations for pipeline stablity. The pore-water pressure field at a pipeline buried in a permeable seabed has been determined from potential theory and the pressure at the pipe integrated to give a net seepage force. This force, of constant magnitude, rotates as the waves pass, thereby tending to force the pipe against the surrounding soil in a cyclic manner. As each wave trough passes over the pipeline the seepage force acts vertically upwards and when combined with the total bouyant force it increases the likelihood of pipeline flotation.
60 citations
TL;DR: In this article, the interscattering of the waves from various cylinders is taken into consideration in the analysis and a direct solution is obtained through a matrix inversion, which may be applied to design large multilegged offshore platforms where drag effects are negligible.
Abstract: Interaction of waves with a group of vertical cylinders is investigated. The inter-scattering of the waves from various cylinders is taken into consideration in the analysis. A direct solution is obtained through a matrix inversion. The forces on a cylinder due to linear waves in the presence of other cylinders are evaluated. This method may be applied to design large multilegged offshore platforms where drag effects are negligible. The theory has received some experimental verification. Numerical results are also presented for various platform configurations to show the effect of the presence of the neighborhood cylinders on the wave forces on a vertical cylinder. The results are compared with the single cylinder solution.
43 citations
TL;DR: In this article, the wave interaction with large vertical cylinders of arbitrary section extending from the seabed or deep water and piercing the free surface is considered, and a method is developed for the efficient computation of the wave loads on such cylinders.
Abstract: The wave interaction with large vertical cylinders of arbitrary section extending from the seabed or deep water and piercing the free surface is considered. A method is developed for the efficient computation of the wave loads on such cylinders. There is a considerable economy of effort when the present approach is applicable and is used in place of a more general one used to continue for bodies of arbitrary geometry. Good agreement has been obtained with previous analytical, numerical, and experimental results. As examples of the program’s application, results have been presented for the forces on an isolated circular cylinder, neighboring circular cylinders, and a square caisson at arbitrary orientation to the incident wave direction.
37 citations
TL;DR: In this paper, the wave runup around a large circular cylinder is considered and predictions based on both sinusoidal and cnoidal wave diffraction theories are summarized and compared with experimental data obtained under conditions close to the shallow water range.
Abstract: The wave runup around a large circular cylinder is considered. Predictions based on both sinusoidal and cnoidal wave diffraction theories are summarized and compared with experimental data obtained under conditions close to the shallow water range. The cnoidal theory is found to predict the measured runup profiles more closely than does the linear theory, although the measured maximum runups are still significantly greater than either prediction.
30 citations
TL;DR: In this paper, a finite element model for predicting time-dependent flow in shallow coastal areas is presented, based upon the vertically integrated equations of motion combined with the hydrostatic assumption and is applicable to water bodies without vertical stratification.
Abstract: A finite element model for prediction of time-dependent flow in shallow coastal areas is presented herein. The model is based upon the vertically integrated equations of motion combined with the hydrostatic assumption and is applicable to water bodies without vertical stratification. The time integration scheme evolves on a grid with variables staggered in time and is conditionally stable. Consistent treatment of boundaries is facilitated by the flexible grid layout, and the finite element method allows straightforward treatment of convective terms throughout the domain. All variables are defined at the same points in space. The model is applied to predict tidal flow and the flow induced by a hypothetical cooling water circulation system.
28 citations
TL;DR: In this paper, an experimental study to determine the effect of unsteady flow on the hydraulic conductivity of coarse granular porous media is outlined, where the acceleration effect was expressed in terms of two variables, i.e., acceleration coefficient, which is function of the well-known inertia coefficient, and the instantaneous flow acceleration.
Abstract: An experimental study to determine the effect of unsteady flow on the hydraulic conductivity of coarse granular porous media is outlined. The acceleration effect was expressed in terms of two variables, i.e., acceleration coefficient, which is function of the well-known inertia coefficient, and the instantaneous flow acceleration. The inertia coefficient was found by comparing the resistance of both steady and unsteady flows through the same porous matrix. The results are given in two forms to show the effect of the unsteady flow on the hydraulic resistance, and to show the variation of the inertia coefficient with Reynolds number. The experimental results show that virtual mass effect does exist in coarse granular porous media, which is the usual construction material for rubble-mound breakwaters. Also, it was found that the acceleration effect becomes more important for large grain porous media, e.g., for particle sizes equal or larger than 40 mm.
20 citations
14 citations
TL;DR: In this paper, the surface profile, the wave celerity, and the near-bottom fluid particle velocity under the waves are compared to those given by the approximate solutions of Boussinesq, McCowan, and Laitone.
Abstract: Solitary waves are generated in a wave tank by a piston-type wave generator. The measured surface profile, the wave celerity, and the near-bottom fluid particle velocity under the waves are compared to those given by the approximate solutions of Boussinesq, McCowan, and Laitone. It is found that, although Boussinesq's and McCowan's theories are of lower order of approximation than Laitone's theory, they better present the surface profile and the fluid particle velocity of the wave. The wave celerity, on the other hand, is not presented well by McCowan's theory. It is also found that the differences between the theories increase with increasing wave height to water depth ratio. Calculations of the fluid particle velocity near the bottom show that the three theories differ significantly when used to describe the fluid particle velocity square. It is recommended to generally use Boussinesq's theory as it represents the overall solitary wave better than the other two.
13 citations
TL;DR: In this paper, it was shown that there may be characteristic wavelengths for which the potential theory formulation breaks down, and the solution of the boundary value problem cannot be represented by a wave source integral formula.
Abstract: Over the past few years increasing attention has been given to the development of diffraction theories of water wave scattering. These theories take into account the scattering of waves by large submerged or semi submerged objects, as well as effects of both free surface and bottom. The purpose of the present paper is to show that there may be characteristic wavelengths for which the potential theory formulation breaks down, and the solution of the boundary value problem cannot be represented by a wave source integral formula.
TL;DR: In this paper, the runup of irregular waves on smooth slopes of 1:3, 1:2, 1 1:1½ N, and 1: 1 was investigated, where wave height distributions were related to wave height distribution with special emphasis on average runup and 2% runup.
Abstract: Runup of irregular waves on smooth slopes of 1:3, 1:2, 1:1½\N, and 1:1 was investigated. The waves were generated by superposition of component waves and simulated the spectra defined by Bretschneider and Scott. A few narrow frequency band spectra were also generated. Since the waves were nonbreaking for the most part, the reflection process affected the results and thus was investigated in detail. Subsequently runup distributions were related to wave height distributions with special emphasis on average runup and 2% runup. A number of secondary observations with respect to superelevation of mean water level, spectrum bandwidth, runup period and position of the leading edge of the runup were also made.
TL;DR: In this article, the wave-induced setup in the surf zone and on the beach, defined as the height difference between the mean water level and the still water level (SWL) and the influence of typical offshore parameters on this phenomenon, was investigated.
Abstract: During the winter of 1975-76 measurements were made by the Leichtweiss-Institut of the Technical University of Braunschweig at the west coast of the island of Sylt in the North Sea. The purpose of the field investigations was to determine the wave-induced setup in the surf zone and on the beach, defined as the height difference between the mean water level (MWL) and the still water level (SWL) and the influence of typical offshore parameters on this phenomenon. A new scheme was defined to determine the MWL as the mean value of the water surface variations measured at incremental time intervals over a certain time span. The maximum setup on the beach can reach values up to 30% of the incident significant wave height. The field investigations have shown that the rise of the mean water level due to wave setup is significant and should be taken in account in determining the design water level for coastal structures.
TL;DR: In this paper, a finite element model is developed to compute the nearshore currents induced by breaking waves in the surf zone, and the normal incident wave system is employed so as to study the effects of beach topography on the current circulation patterns.
Abstract: A finite element model is developed to compute the nearshore currents induced by breaking waves in the surf zone. The normal incident wave system is employed so as to study the effects of beach topography on the current circulation patterns. The beach topography considered here is of linear plane beach shape with minor undulations in the longshore direction. Ignoring the lateral turbulent diffusion, the finite element representation of the governing equations of mean currents is obtained by the method of weighted residuals. It is shown that, due to the flexible grid discretization, this model can be used to study problems containing more complex beach topography within a large area of interest. Two types of alongshore beach undulations are investigated: rhythmic topography and localized irregular topography. The locations of rip currents depend on the surf zone width and the on-offshore variation of beach profile.
TL;DR: In this paper, the mass-transport velocity near the seabed has been calculated to first and second approximations for both Stokes and cnoidal waves, and a set of curves based on these predictions is presented in a convenient form and permits a ready estimate of the bottom mass transport for any given conditions.
Abstract: The mass-transport velocity near the seabed has previously been calculated to first and second approximations for both Stokes and cnoidal waves. A set of curves based on these predictions is presented in a convenient form and permits a ready estimate of the bottom mass transport for any given conditions. Experiments conducted to test the predictions are described. These, as well as previous experiments, indicate reasonable agreement with the theoretical predictions. Although the onset of turbulence limits the range of validity of the curves, they may still be used but with less reliability. The condition for transition to a turbulent boundary layer adopted by some authors is found to be questionable.
TL;DR: In this article, the hydrodynamic drag on a rectangular group of 50 flat plates, with steady incident flow normal to the front of the group, is shown to be a function of five factors: (1) the acceleration of flow between the plates of a row; (2) the shielding of plates in line with the incident flow; (3) the diversion of flow around the front group; (4) the rejection of flow through the sides of a group; and (5) the formation within the group of an oscillating wake for the whole group.
Abstract: The hydrodynamic drag on a rectangular group of 50 flat plates, with steady incident flow normal to the front of the group, is shown to be a function of five factors: (1)The acceleration of flow between the plates of a row; (2)the shielding of plates in line with the incident flow; (3)the diversion of flow around the front of the group; (4)the rejection of flow through the sides of the group; and (5)the formation within the group of an oscillating wake for the whole group. The drag force on each element of the group was measured for longitudinal and lateral spacings covering the range occurring in existing pier head pile groups that the flat plates simulated.
TL;DR: In this paper, the attenuation of waves propagating along a straight channel bounded by a pair of parallel rubblemound breakwaters is investigated, and a simplified analysis is presented, and on the basis of this, the experimental results are reduced to provide a simple design procedure for the situation under consideration.
Abstract: Laboratory experiments have been performed to investigate the attenuation of waves propagating along a straight channel bounded by a pair of parallel rubblemound breakwaters. As a reasonable approximation, the spatial gradient of wave height is found to vary with the square of the height. Experimental data of the corresponding attenuation coefficient as a function of relative depth are presented for breakwater slopes of 1/1.5, 1/2, and 1/3. A simplified analysis is presented, and on the basis of this, the experimental results are reduced in order to provide a simple design procedure for the situation under consideration.
TL;DR: In this paper, the problem of wave propagation past a vertical wedge has been examined with the intent of generalizing previous solutions and finding useful asymptotic results, and the solutions obtained can be readily incorporated into present computer refraction programs so as to describe the propagation of waves past a wedge more generally than is presently possible.
Abstract: The problem of wave propagation past a vertical wedge has been examined with the intent of generalizing previous solutions and finding useful asymptotic results. Reflection, diffraction, and the subsequent refraction of the incident, reflected, and diffracted waves have been included in the analysis and convenient asymptotic solutions were obtained. Significant effects due to reflection and diffraction were demonstrated and shown to be strongly dependent on wedge angle. The solutions obtained can be readily incorporated into present computer refraction programs so as to describe the propagation of waves past a wedge more generally than is presently possible. The geometrical theory of diffraction used here can also be applied to bodies of any shape so as to describe combined diffraction-refraction effects.
TL;DR: In this article, a 28.8-in diameter sphere was used for a test site in 37 ft of water offshore from Honolulu, where the maximum particle-velocity Reynolds numbers involved are in the range of 5 x 10\u5 to 11 x 10/u5.
Abstract: Wave force coefficients have been obtained for a 28.8-in diam sphere. The work was done at a test site in 37 ft of water offshore from Honolulu. The peak flow velocities encountered during the tests were usually in the 2-fps to 3-fps range. The highest measured flow speed was 4.6 fps. Thus, the maximum-particle-velocity Reynolds numbers involved are in the range of 5 x 10\u5 to 11 x 10\u5. These values, coupled with high turbulence levels in the flow because of the cycling of the sphere.s wake, assure that the data obtained are for transcritical situations. Tight statistical distributions of drag and inertia coefficients were found. However, it was felt most useful to consider a maximum total force coefficient, and this had the variation shown later in this note.
TL;DR: The first jetties at Belle Pass were constructed in 1940 and the average annual recession rate of the coastline in the Belle Pass area between 1885 and 1932 was 79 ft/yr (24m/yr) as mentioned in this paper.
Abstract: Channel enlargement and modifications to the jetties at Belle Pass, the mouth of Bayou Lafourche on the Gulf coast of Louisiana, had become necessary due to increased marine traffic by offshore oil and mining production and the fishing industry, along with the proposed development of nearby Port Fourchon. Permission for construction, required by the Corps of Engineers, was granted after map and aerial photo studies, field observations, and hydraulic model experiments showed that beach erosion, and especially littoral bypassing, would be insignificantly affected by extension to the existing single jetty and construction of a new twin jetty. The average annual recession rate of the coastline in the Belle Pass area between 1885 and 1932 was 79 ft/yr (24m/yr). After construction of the first jetties in 1940, this rate gradually decreased to 25 ft/yr (8 m/yr) by 1974. Most littoral material bypasses the jetties due to inefficient orientation to the present shore line. Field tracking of subsurface floats provided data to calibrate a small, distorted-scale model.
TL;DR: In this article, the peak water line around a vertical circular pile in periodic wave action is measured, showing a nonlinear dependence on incident wave height when the pile radius is very small compared to the wavelength.
Abstract: The measured pattern of peak water line around a vertical circular pile in periodic wave action can disagree with wave-scattering theory, showing a nonlinear dependence on incident wave height when the pile radius is very small compared to the wavelength. The peak water line was measured around piles of several diameters in relatively shallow water with various incident laboratory waves. Features of the patterns indicate that a disturbance like a ship's bow wave forms during peak crest flow when a certain Froude number, incident crest velocity head divided by pile radius, becomes large, on the order of 0.1 - 1.0. The laboratory tests shoudl reproduce basic flow effects in situations of coastal and ocean engineering interest, because field and lab situations have the same Froude number, implying geometric flow similarity.
TL;DR: In this article, the authors investigated the sensitivity of ocean cable structure behavior to variation in physical parameters of the system using the finite element method and two configurations were analyzed, a single point moor relaxation and an anchor deployment simulation.
Abstract: Sensitivity of ocean cable structure behavior to variation in physical parameters of the system was investigated using the finite element method. Two configurations were analyzed, a single point moor relaxation and an anchor deployment simulation. Relaxation behavior for shorter systems is sensitive to changes in buoy coefficient of drag; cable coefficient of drag is significant in longer systems. Changes in cable modulus of elasticity affected travel time by 5% of less for any of the 6-ft, 30-ft, or 60-ft (1.8-m, 9.2-m, or 18.3-m) systems that were analyzed. The dynamic tension magnitude in the deployment of cable structures is in part determined by weight of the system and the initial surface position of the anchor before release. Changes in dynamic tension response were substantially affected by variation of initial surface position. This anchor deployment simulation involved a 6-ft (1.8-m) cable with one end of the cable fixed.
TL;DR: In this article, equations for Stokes fifth-order wave theory are summarized to calculate water particle kinematics, it is necessary to evaluate three parameters by solving simultaneously three nonlinear equations.
Abstract: Stokes fifth-order wave theory is widely used in engineering practice to calculate water particle kinematics for the purpose of determining hydrodynamic forces on ocean structures. As shown by Dean, Stokes fifth-order wave theory is appropriate for engineering use primarily in deep water where depth exceeds half the wavelength.In this note, equations for Stokes fifth-order wave theory, as given by Chappelear, are summarized to calculate water particle kinematics, it is necessary to evaluate three parameters by solving simultaneously three nonlinear equations.
TL;DR: In this paper, the modular assembly methods and use of available connecting materials for an 18-tire module are examined for low cost shore and harbor protection, and the design parameters, material cost, and field tests for both floating tire breakwaters and tire revetments are summarized.
Abstract: Experiment testing has indicated the potential value of using discarded tires as a construction material for low cost shore and harbor protection. The modular assembly methods and use of available connecting materials are examined for an 18-tire module. Engineering design parameters, material cost, and field tests for both floating tire breakwaters and tire revetments are summarized. Floating tire breakwaters are described and have provided wave attenuation in marinas and small harbors in both salt and freshwater. Descriptions of two tire revetment test sites on the Great Lakes are presented. Limited monitoring efforts have shown that the concept of tire revetment mats seem to hold promise as a low cost approach to certain shore erosion problems.