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Showing papers in "Journal of Waterway Port Coastal and Ocean Engineering-asce in 1996"


Journal ArticleDOI
TL;DR: The U.S. Army Corps of Engineers (CE) model for hurricane surface wind fields has been a very useful tool in ocean response (OR) modeling for more than a decade.
Abstract: Approaches for recreating hurricane surface winds in relation to ocean wave, surge, and current modeling are reviewed. A discrete numerical wind field model, based on original developments at New York University in the early 1970s and used extensively by the U.S. Army Corps of Engineers (CE) and others, is described in detail. Limitations of the model are also discussed. The CE model for hurricane surface wind fields has been a very useful tool in ocean response (OR) modeling for more than a decade. Recently, several aspects of the model were upgraded, including increased spatial resolution and capabilities for simulating a wider variety of radial pressure and wind profile forms. The upgraded features of the model are described, and their impact on hurricane simulations is illustrated with a hypothetical hurricane and with hurricanes Camille (1969) and Gilbert (1988). The upgrades are expected to lead to improvements in the accuracy of OR modeling, particularly for small, intense hurricanes and for well-documented storms with broad and/or multipeaked radial wind profiles.

260 citations


Journal ArticleDOI
TL;DR: In this article, the forces and overturning moments on a vertical wall due to the reflection of solitary waves, undular bores, turbulent bores and surges on a dry bed were determined experimentally.
Abstract: The forces and overturning moments on a vertical wall due to the reflection of solitary waves, undular bores, turbulent bores, and surges on a dry bed were determined experimentally. The incident wave celerity, wave profile, runup, force, overturning moment, and pressures were measured. The wave profiles and runup time histories were obtained with a laser-induced fluorescence system. The transition from undular to turbulent bores exhibits a large increase in the maximum measured wave slope, runup, force, and moment. For all cases, the maximum measured force and overturning moment were always less than that computed from the maximum measured runup using hydrostatic considerations. When properly normalized, the runup and force on a vertical wall due to the impingement of bores on a mildly sloping beach and a horizontal bed are shown to agree quite well. The results of this study may be used to estimate the forces on a vertical wall due to turbulent bores traveling on beaches with slopes no steeper than 1/50.

145 citations


Journal ArticleDOI
TL;DR: In this article, the authors used field observations to characterize seiche energy in three small harbors with similar surface areas (∼1 km²), water depths (5-12 m), and swell wave climates.
Abstract: Extensive field observations are used to characterize seiches (periods 0.5–30 min) in three small harbors with similar surface areas (∼1 km²), water depths (5–12 m), and swell wave climates. On the continental shelf just offshore of each harbor mouth, the energy levels of waves in the infragravity frequency band 0.002–0.03 Hz (periods 0.5–10 min) vary by more than a factor of 200 in response to comparably large variations in swell energy levels. Energy levels in this swell-driven frequency band also vary (less dramatically) in response to changes in the swell frequency and with tidal stage. Motions at longer seiche periods (10–30 min) are primarily driven by meteorological and other processes (a tsunami-generated seiche is described). As has often been observed, the amplification of seiche energy within each harbor basin (relative to energy in the same frequency band outside the harbor) varies as a function of seiche frequency, and is largest at the frequency of the lowest resonant harbor mode (i.e., the Helmholtz or grave mode). At all three harbors, the average amplification of the grave mode decreases (by at least a factor of 2) with increasing seiche energy, a trend consistent with a nonlinear dissipation mechanism such as flow separation in the harbor mouth or sidewall and bottom friction.

61 citations


Journal ArticleDOI
TL;DR: In this paper, the interaction of water waves with a tensioned, unstretchable, vertical flexible membrane extended to the seabed is solved in the context of two-dimensional linear wave theory.
Abstract: The interaction of water waves with a tensioned, unstretchable, vertical flexible membrane extended to the seabed is solved in the context of two-dimensional linear wave theory. First, analytic solutions are obtained based on the eigenfunction expansion of the velocity potential in two fluid domains and a continuous tensioned-string dynamic model. In contrast to the rigid-body hydrodynamics, the velocity potentials and membrane equation of motions are obtained simultaneously, since the membrane boundary condition is not known in advance. Second, a boundary element program based on a discrete membrane dynamic model and simple source distribution method is developed. Two different numerical methods, the iteration and whole matrix methods, are developed and both agree well with analytic solutions. Using those computer programs, the performance of a flexible-membrane wave barrier with varying initial tension, length, and mass density is investigated. It is found that almost complete reflection of incident wav...

54 citations


Journal ArticleDOI
TL;DR: In this article, seven tests consisting of 72 runs were conduced to measure wave reflection, overtopping, and overwash of dunes and compared with the empirical formulas developed for coastal structures.
Abstract: Seven tests consisting of 72 runs were conduced to measure wave reflection, overtopping, and overwash of dunes. The measured reflection coefficients and overtopping rates are compared with the empirical formulas developed for coastal structures. The equivalent uniform slope for reflection is assumed to be the beach slope at the still water shoreline. The equivalent uniform slope for overtopping is assumed to be the overall slope between the dune crest and the point where the water depth equals the significant wave height. The toe depth of the coastal structure is assumed to correspond to the water depth immediately seaward of the breaker zone on the beach. The formulas with these adjustments are then shown to predict the order of magnitude of the measured reflection coefficients and overtopping rates. Furthermore, the average volumetric sand concentration in the overwash flow was measured to be approximately 0.04 for these small-scale tests.

53 citations


Journal ArticleDOI
TL;DR: In this paper, a bottom shear stress boundary condition for an unsteady, tidal flow model is derived through theoretical analysis, where the bottom stress is defined for the velocity distribution adjacent to the boundary using a regular perturbation expansion.
Abstract: A formulation specifying the bottom shear stress boundary condition for an unsteady, tidal flow model is derived through theoretical analysis. The unsteady boundary layer equation is solved for the velocity distribution adjacent to the boundary using a regular perturbation expansion. When applied to the bottom layer of the computation grid of a numerical model, the solution relates the bottom shear stress to the velocity and acceleration computed in that layer. Numerical experiments with a hypothetical homogeneous estuary indicate that the error in calculated bottom stress increases with vertical grid spacing if the logarithmic profile is used to relate bottom stress to velocity. The use of the formulation including the correction terms can significantly reduce this error and adequately specify the boundary condition in a numerical model of estuarine flow with a practical range of vertical grid spacing. The numerical experiments also show that, if the roughness height and bottom stress are estimated by fitting a logarithmic profile to the velocity distribution, they may be off by more than 100%.

49 citations


Journal ArticleDOI
TL;DR: In this paper, the authors describe the theory and application of the empirical simulation technique (EST), a statistical procedure for simulating time series and frequency-of-occurrence relationships for non-deterministic multiparameter systems.
Abstract: This paper describes theory and application of the empirical simulation technique (EST), a statistical procedure for simulating time series and frequency-of-occurrence relationships for nondeterministic multiparameter systems. Procedures described are applied to a storm surge analysis for tropical events along the coast of Delaware. The approach involves the numerical simulation of historical events, the analysis of the parameters associated with each event, the application of the EST to that data, and the generation of frequency-of-occurrence relationships for 40 locations within the study area. The development of the input data set of descriptive storm parameters and their respective responses require the use of planetary boundary layer and very large domain hydrodynamic modeling techniques. Development of this input database is described herein. Implementation of the EST is based on N repetitions of T -year simulations; therefore, mean-value frequency relationships are computed and assigned confidence ...

49 citations


Journal ArticleDOI
TL;DR: In this paper, the use of parabolic approximations of the mild-slope wave equation as open boundary conditions is explored, and the parabolic approximation does not describe wave scattering as rigorously as the traditional method, the new model is tested against analytical and other solutions for cases where scattering is extensive.
Abstract: Traditional elliptic harbor wave models are based on the assumptions that the exterior sea region (i.e. the region outside the computational grid) is of constant depth and that the exterior coastlines are collinear and fully reflecting. This paper demonstrates that for most coastal regions, where these assumptions are generally not true, their effect on model results is substantial. This leads to unreliable simulations. Enlarging the model domain to overcome their effects is cumbersome and often prohibitive. To overcome these difficulties, the use of parabolic approximations of the mild-slope wave equation as open boundary conditions is explored. Suitable parabolic equations are derived and interfaced with an elliptic finite-element model. Since the parabolic approximation does not describe wave scattering as rigorously as the traditional method, the new model is tested against analytical and other solutions for cases where scattering is extensive. Errors resulting from the parabolic approximation are found to be extremely small. Further model tests show that for the generally realistic case where exterior reflection coefficients are less than unity, the new method requires considerably smaller domains than the traditional method, resulting in reduced modeling effort. The model is also applied to Toothacher Bay, Maine, and the use of the parabolic boundary conditions eliminates many spurious features in the simulation.

47 citations


Journal ArticleDOI
TL;DR: In this article, a 1DV grid model was developed for the prediction of sediment transport in combined wave-current flow under sheet flow conditions, and the model used a one-equation turbulence closure scheme to simulate vertical mixing processes, and a time-varying reference concentration as the bottom boundary condition for the suspended sediment layer.
Abstract: A one-dimensional, vertical (1DV) grid model has been developed for the prediction of sediment transport in combined wave-current flow under sheet flow conditions. The model uses a one-equation turbulence closure scheme to simulate vertical mixing processes, and a time-varying reference concentration as the bottom boundary condition for the suspended sediment layer. Comparison with recent experimental data shows that the model gives good predictions (within 30%) of the measured net sediment transport rates under different conditions. The results also demonstrate the importance of the “wave-related” contribution to the suspended transport, due to the unsteadiness in the velocity and sediment concentration fields. At certain elevations above the bed, the suspended flux may be in the direction opposite to that of the mean current as a result of the phase relationship between the horizontal velocity and sediment concentration.

46 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the incidence of major wave events for the Southern California offshore region for the period from 1984 to 1995, and found that the significant influence of the world climate event popularly known as El Nino is seen to be a major influence in the recent decade.
Abstract: The incidence of major wave events is investigated for the Southern California offshore region for the period from 1984 to 1995. The significant influence of the world climate event popularly known as El Nino, which had been shown in an earlier study of the first 83 yr of the century, is seen to be a major influence in the recent decade. Although the overall wave intensity (as measured by the median wave height for all observations during a year) has decreased for the most part in the last 20 yr, the number of large wave events has been very much increased. An averaged sea surface temperature anomaly in the tropics is shown to be well correlated with the increases in large wave events.

43 citations


Journal ArticleDOI
TL;DR: In this article, a harmonic tide level model is used to predict tide levels over a longer time by estimating the amplitudes of the harmonic components of a few-day tide record with the assumption of known angular frequencies.
Abstract: Prediction of tide levels is one of the important problems in determining the schedule making of activities or constructions in coastal and oceanic area. Accurate predictions of tide levels could not be obtained without a long length (about one month or more) of tide measurements by conventional methods. A method of using a short length (a few days) of tide measurements to predict tide levels over a longer time is proposed in the present paper. In the method, a harmonic tide level model is used to predict tide levels. The parameters of the tide level model, that is, the amplitudes of the harmonic components, are estimated by Kalman filtering technique using a few-day tide record with the assumption of known angular frequencies. The proposed model is then applied to the short-term tide level prediction of the Kaohsiung Harbor, Taiwan. As a result, the tide levels predicted by the proposed method are in good agreement with the observed data.

Journal ArticleDOI
TL;DR: In this paper, a numerical simulation of tsunami propagation for the 1993 Southwest Hokkaido earthquake tsunami is presented, which is based on the Boussinesq equation, which includes the effects of frequency dispersion.
Abstract: This paper reports a numerical simulation of tsunami propagation for the 1993 Southwest Hokkaido earthquake tsunami. The model is based on the Boussinesq equation, which includes the effects of frequency dispersion. Energy dissipation due to breaking at the tsunami wave front is modeled. The validity of the model was tested with the existing laboratory data of dispersive wave trains breaking on a slope. The model was then applied to the simulation of the 1993 Southwest Hokkaido earthquake tsunami around the southern part of Okushiri Island. Comparison with the physical model demonstrates that it is the dispersion of the wave front which caused focusing of the wave energy at the narrow region on the lee side of the island, consequently increasing the tsunami height.

Journal ArticleDOI
TL;DR: In this paper, it is shown that pile groins act as a hydraulic roughness on the longshore current and that their effect on waves is negligible, but not blocking, the littoral current, the velocity differential between the velocity seaward and in the pile-groin fields is smaller than with impervious groins.
Abstract: Permeable pile groins have been built on the southern shores of the Baltic Sea in large numbers for a century and a half, yet no explanation has been found in the literature on how these function. It is shown that pile groins act as a hydraulic roughness on the longshore current and that their effect on waves is negligible. By reducing, but not blocking, the littoral current, the velocity differential between the velocity seaward and in the pile-groin fields is smaller than with impervious groins. Hence, the circulation in the groin field due to the fluid drag at the seaward boundary is weaker and is concentrated mainly in the velocity interface in the form of small eddies. The reduced littoral current velocity in the pile-groin fields leads to a reduction of turbulence produced at the bed by the wave-current interaction, to a reduced amount of sediment suspended, and to a thinner layer of suspended sediment. Hence, the amounts of sediment advected by superimposed currents are reduced. The reduction is most effective for erosive-wave conditions and enables trapping or holding of sediment until the continuity of littoral transport is reestablished and the cross-shore transports balance over time.

Journal ArticleDOI
Abstract: The numerical wave model HARBD has been used extensively within and outside the U.S. Army Corps of Engineers for estimating waves in harbors. The model was originally developed for long waves (harbor oscillations). It has been extended for use with short waves (wind waves and swell) and validated by several investigations, most notably Chen's (1986) fundamental investigation of long waves in a rectangular harbor. This study focuses on short-wave validation. The model is tested with several simple domains, in most cases with uniform depth. It is validated with laboratory data for irregular wave diffraction around a semi-infinite breakwater. Both broad and narrow directional spreads are considered. The model is also compared to widely accepted curves for regular and irregular wave diffraction through a breakwater gap. Field validation of the model for Kaumalapau Harbor, Lanai, Hawaii, is discussed. Tests demonstrate the effect of input parameters on model results and provide guidelines about the choice of p...

Journal ArticleDOI
TL;DR: In this paper, a boundary element technique using a two-dimensional Green's function is used to investigate the interaction of surface waves with multiple rectangular submarine pits in water of otherwise uniform depth, and it is shown that appropriate selection of pit dimensions and placement may lead to a significant reduction in wave heights behind these structures.
Abstract: Linearized shallow-water wave theory is used to investigate the interaction of surface waves with multiple rectangular submarine pits in water of otherwise uniform depth. The solution is obtained by a boundary element technique using a two-dimensional Green's function. It is shown that appropriate selection of pit dimensions and placement may lead to a significant reduction in wave heights behind these structures. Numerical results have been presented that illustrate the influence of the various pit characteristics on the diffracted wave field. Two pits can provide a shadow region in which wave heights are reduced to 10–20% of the incident wave height. The shadow region, with wave heights reduced to 30% of the incident wave height, is approximately the width of the pits and five wavelengths long. Guidance is given on how to select pit geometries and placement for optimal breakwater performance. An example is also presented that shows how to select a pit to reduce wave heights in a navigation channel.

Journal ArticleDOI
TL;DR: In this paper, the average net cross-shore transport rate and beach profile evolution under random waves are derived by superimposing the transport from individual waves, which belong to an ensemble that represents the random wave field.
Abstract: A numerical model is developed to calculate the average net cross-shore transport rate and beach profile evolution under random waves. Cross-shore transport formulas for random waves are derived by superimposing the transport from individual waves, which belong to an ensemble that represents the random wave field. The transport relationships for individual waves are based on experiments with monochromatic waves in large wave tanks. The model is validated using beach profile data from the SUPERTANK Laboratory Data Collection Project. Three different types of profile evolution events are studied, namely equilibrium erosion with bar formation, berm flooding, and the impact of breaking waves on an offshore mound. The berm flooding tests include the erosion of a well-developed summer berm and the erosion of an artificially constructed foredune, and the offshore mound tests encompass narrow- and broad-crested mounds. The new model represents an attempt to consistently treat random waves in all components of a beach profile change numerical model. Previous approaches to model the profile evolution under random waves have typically involved using statistical wave measures in equations primarily developed for monochromatic waves.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the mechanism and the characteristic parameters affecting local scour around a vertical pile caused by turbulent circular wall jets and identified four types of equilibrium scour hole profiles.
Abstract: This study investigates the mechanism and the characteristic parameters affecting local scour around a vertical pile caused by turbulent circular wall jets. There are two basic scouring mechanisms; the pile obstruction and the jet diffusion mechanisms. The former is dominated by a horseshoe vortex system while the latter is controlled by the bed shear stress as the jet diffuses into the flow. Four types of equilibrium scour hole profiles were identified. The criteria for each type of profile are classified in terms of the densimetric Froude number \IF\do\N and the relative impingement distance \IX\N\Di\N/d\Do\N. Semiempirical equations were developed to delineate the boundary limits for the different profiles. The results show that the maximum equilibrium scour depth \Id\N\Ds\N\De\N and the scour depth at the pile \Id\N\Dpe\N are highly dependent on \IF\N\Do\N; and generally for large \IF\N\Do\N, \IdN\Dse\N = \Id\N\Dpe\N. The scour depths are insensitive to the relative size of the pile to jet diameter \ID\N/d\D0\N. However, \IX\N/di/d\Do\N does not appear to affect \Id\N\Dse\N/d\Do\N but it has a profound influence on \Id\N\Dpe\N/d/Do\N.

Journal ArticleDOI
TL;DR: The diffraction of small-amplitude surface waves by a horizontally submerged disk of elliptic cross section located at a finite depth beneath the free surface is investigated analytically in this article.
Abstract: The diffraction of small-amplitude surface waves by a horizontally submerged disk of elliptic cross section located at a finite depth beneath the free surface is investigated analytically. The fluid domain is divided into three regions, two internal regions, one above and one beneath the disk, and an external region extending to infinity in the horizontal plane. The theoretical formulation leads to solutions for the fluid velocity potentials in each region in terms of series of Mathieu and modified Mathieu functions of real argument. Numerical results are presented for the wave-induced forces and moments, and the variation of water surface elevation in the vicinity of the disk for a range of wave and structural parameters. In particular, the results for the hydrodynamic loads show significant differences from the corresponding estimates for a circular disk, while the results for the water surface elevation clearly show the effect of wave focusing around the rear of the disk.

Journal ArticleDOI
TL;DR: In this paper, an experimental investigation of the reflection of obliquely incident waves from a model rubble-mound breakwater is described, where a least-squares fit to measurements from three wave probes was used to estimate the reflection coefficient and the phase angle of the reflected wave train.
Abstract: An experimental investigation of the reflection of obliquely incident waves from a model rubble-mound breakwater is described. In regular wave tests, the wave height, wave period, and angle of incidence were varied in order to determine relationships between the reflection characteristics and parameters describing the incident waves. For these tests, a least-squares fit to measurements from three wave probes was used to estimate the reflection coefficient and the phase angle of the reflected wave train. Results show that both the reflection coefficient and the reflected phase lag are noticeably dependent on the angle of incidence and that the variation with angle of incidence further depends on the depth to wavelength ratio. Reflection coefficients estimated from the analysis of irregular wave tests are also presented and are compared to reflection coefficients measured in regular wave tests, showing good agreement. For one test with multi-directional waves, directional spectra of the incident and reflected wave fields were obtained using a maximum likelihood fit to measurements from five wave probes, and these indicate increased directional spreading of the reflected wave field relative of that of the incident wave field.

Journal ArticleDOI
TL;DR: In this article, an analytical solution was developed to investigate the behavior of a submerged or surface-piercing, long tethered breakwater of rectangular cross section, and the equations of motion were solved to provide the surge, heave, and pitch responses of the structure.
Abstract: An analytical solution is developed to investigate the behavior of a submerged or surface-piercing, long tethered breakwater of rectangular cross section. The equations of motion are solved to provide the surge, heave, and pitch responses of the structure. The wave reflection and transmission coefficients are calculated. Numerical results are presented for a range of wave and geometric parameters that illustrate the suitability of this type of structure as a barrier to wave action. Small-scale physical model tests were carried out to verify the theory. Reasonable agreement is found between theoretical and experimental values of the reflection and transmission coefficients. It was observed both in the numerical results and model tests that low wave transmission coefficients occur when the diffracted and radiated waves in the lee of the structure are of similar magnitude, but 180° out of phase. The lowest transmission coefficients occurred near the surge natural frequency of the floating breakwater, where significant energy dissipation was present. Under these circumstances, destructive wave interference and energy dissipation combine to give transmission coefficients on the order of 0.5.

Journal ArticleDOI
TL;DR: In this article, a new formula for the spacing of wave-current-induced sand ripples is derived and the agreement between the measurement and the prediction can be much improved as compared with the previous formula.
Abstract: Laboratory data on sand ripple spacing due to combined wave-current motion are collected to examine the validity of the empirical formula proposed by Tanaka and Shuto in 1984. Data from Gray et al. in 1991 and from Van Rijn et al. in 1993 showed considerable discrepancy from the formula. The discrepancy can partly be attributed to insufficient consideration of the grain size effect in the previous study. Furthermore, incorrect evaluation of the orbital diameter due to wave motion, which was pointed out by Christoffersen and Jonsson in 1985, can be another reason for the discrepancy. A new formula for the spacing of wave-current-induced sand ripples is derived. The agreement between the measurement and the prediction can be much improved as compared with the previous formula. The full-range equation for the wave-current friction coefficient proposed by Tanaka and Thu in 1994 is applied in the formulation of steepness of sand ripples. Empirical equations for pure wave ripples can tentatively be used for estimating the steepness of sand waves.

Journal ArticleDOI
TL;DR: In this article, the authors show how the magnitude of the biases can be calculated from the sample length and the shape of the wave spectrum, and they recommend that new wave measurements be recorded continuously whenever possible, and that hindcast verifications and extreme wave calculations be made with smoothed versions of the measured time series of significant wave height.
Abstract: Estimates of significant wave heights made from finite record lengths have a small but important statistical sampling variability. This variability leads to positive biases in the maximum significant wave height in a storm and in design wave heights estimated from extreme value distributions fitted to the data. Since wave hindcasts are often verified by comparing the maximum hindcast and measured significant wave heights in a storm, the bias due to sampling variability can make a correct hindcast appear to be too low. In this paper we show how the magnitude of the biases can be calculated from the sample length and the shape of the wave spectrum. These theoretical calculations agree very well with results from several sets of measurements in the North Sea. We recommend that new wave measurements be recorded continuously whenever possible, and that hindcast verifications and extreme wave calculations be made with smoothed versions of the measured time series of significant wave height.

Journal ArticleDOI
TL;DR: In this paper, a numerical model that simulates two-dimensional ground water flow in a coastal aquifer under beach drainage, including water table lowering and seepage face reduction, is presented.
Abstract: There has been renewed interest in the use of beach dewatering as a technique to combat beach erosion. Although several test and prototype installations have been undertaken worldwide, no guidelines are available to aid the engineering design of such projects. In this paper, we present a numerical model that simulates two-dimensional ground water flow in a coastal aquifer under beach drainage, including water table lowering and seepage face reduction. The boundary element method is applied to solve the Laplace equation for the velocity potential. An internal boundary is used to simulate drainage. We conducted simulations for two different types of drainage systems, i.e., artificial and gravity drainage. The behavior of the water table from the simulations was found to be consistent with field observations. The results also showed that the location and size of the drain affect the efficiency of the drainage system. The system efficiency slightly increases with the size and vertical elevation of the drain. As the drain is shifted landward, the system becomes considerably less efficient. Although they do not represent design criteria, these results indicate considerations which affect the performance of beach dewatering system.


Journal ArticleDOI
TL;DR: In this article, a simplified approach is presented to use Dean's method for determining dry-beach (subaerial) width after equilibrium for arbitrary sediment size, which can be solved easily using a hand calculator.
Abstract: A simplified approach is presented to use Dean's method for determining dry-beach (subaerial) width after equilibrium for arbitrary sediment size. A simple equation is developed relating a key parameter in Dean's method to sediment diameter. Closure depth is shown to be simply related to nearshore mean annual significant wave height. Dean's equations for dry-beach width are dimensionalized and simplified. The key parameter, closure depth, and the equations for dry-beach width are all presented in simple forms that can be solved easily using a hand calculator. Examples are presented for all cases including fill sediment with a mean diameter the same size, larger, and smaller than the native sediment. When the fill sediment is finer than the native sediment a minimum quality of sediment has to be placed before there is any resulting dry beach, and an equation is provided to determine this minimum quantity. The simplified method presented allows an engineer to easily evaluate a large number of scenarios at t...

Journal ArticleDOI
TL;DR: In this paper, the authors describe a methodology for predicting the fate and stability of dredged material disposal sites over long periods of time, ranging from months to years, based on the generation and use of databases of wave and current time series.
Abstract: This paper describes a systematic methodology for predicting the fate and stability of dredged material disposal sites over long periods of time, ranging from months to years. The approach is based on the generation and use of databases of wave and current time series that describe environmental conditions specific to the site. These boundary conditions are used to drive a coupled hydrodynamic, sediment transport, and a bathymetry change model that provides a prediction of the long-term behavior of a disposal site of arbitrary dimensions. An example of an application of this approach is made for a moderately dispersive disposal mound located offshore of the entrance to Mobile Bay, Ala.


Journal ArticleDOI
TL;DR: In this paper, several heuristic methods for sequencing tows through waterway locks, including locks with two dissimilar chambers, were proposed for obtaining good initial solutions, and the resulting improvements in delays and capacity were evaluated by comparing these algorithms with a first-come-first-served (FCFS) operation.
Abstract: This paper presents several heuristic methods for sequencing tows through waterway locks, including locks with two dissimilar chambers. Two algorithms are proposed for obtaining good initial solutions. Of these, the shortest processing time first (SPF) algorithm gives priority to tows with lower processing time per barge, while maximum saving (SAVE) favors tows with the highest relative advantage at particular chambers. The resulting improvements in delays and capacity are evaluated by comparing these algorithms with a first come first served (FCFS) operation. Delay savings of up to 75.85% with SAVE and up to 79.73% with SPF are projected at congested locks. A pairwise exchange algorithm is used to improve the initial solutions obtained with SPF and SAVE. The improved methods, SPF with exchange (SPFX) and SAVE with exchange (SAVEX), further reduce the average barge delay. While SPFX does not improve much on SPF, SAVEX reduces average barge delay by up to 26.5% compared to SAVE. Among all these methods, SPFX yields the smallest barge delay (up to 79.8% less than FCFS). The delay savings can be even greater when upstream and downstream flows are unequal.

Journal ArticleDOI
TL;DR: In this article, a perturbation approach based on the small amplitude and simple harmonic wave theory is proposed to estimate the wave forces from the pressure differences in front and behind the array of cylinders.
Abstract: Based on Kakuno and Liu's perturbation theory, the formula for wave forces acting on an array of vertical cylinders is derived. The perturbation approach is based on the small amplitude and simple harmonic wave theory. Furthermore, the distance between two adjacent cylinders is assumed to be smaller than the wave length of incident waves so that flow separations and energy dissipation are confined with the neighborhood of cylinders. The wave forces are calculated from the pressure differences in front and behind the array. Laboratory experiments are performed by using square cylinders. Theoretical results agree with the experimental data very well over a range of water depths.

Journal Article
TL;DR: In this paper, the effect of macrocystis kelp forest on the propagation of surface gravity waves was measured over a 67-day period at four locations around a 350m-wide kelp bed off Carlsbad, California.
Abstract: The effect of a Macrocystis kelp forest on shoreward propagating surface gravity waves was measured. Observations were made over a 67-day period at four locations around a 350-m-wide kelp bed off Carlsbad, California. Instruments were located directly offshore and onshore of the kelp bed at depths of 13 m and 8 m, respectively, and at control stations at the same depths, but displaced 750 m alongshore, away from the kelp bed. The bathymetry between the offshore and onshore sites was gently sloping and featureless. The measured spectra, significant wave height, mean wave direction at peak frequency, and total radiation stress differed only slightly between the offshore kelp and control stations and were similar at the onshore sites. The similarity of the wave field at the onshore kelp and control sites shows that this typical southern California kelp bed, with an average density of about 10 plants per 100 m 2 , does not have a significant effect on waves. These measurements can be used to place upper bound...