Showing papers in "Journal of Waterway Port Coastal and Ocean Engineering-asce in 2016"

Boussinesq Models and Their Application to Coastal Processes across a Wide Range of Scales

Abstract: In this paper, the development of a class of depth-integrated, phase-resolving models for surface wave propagation, known as Boussinesq-type models (BTMs), is reviewed. This review concentrates on the extension of the leading order formulation for weakly dispersive waves to include a range of physical effects and considers model applications at a range of scales ranging from surf zone processes to ocean basin–scale tsunami propagation. A brief overview of the connection of BTMs to nonhydrostatic models, in either depth-integrated or three-dimensional form, is included.

Pipeline–Seabed Interaction

Abstract: A review of the existing research on the interaction between a pipeline and an erodible bed exposed to waves and/or currents is presented. The review covers three topics: scour, liquefaction, and lateral stability of pipelines. The basic mechanism that leads to scour in two-dimensional (2D) and three-dimensional (3D) cases is first described, as deduced from small-scale laboratory experiments. The onset of scour from piping and the developing tunnel erosion are among the processes described. The lateral expansion of the scour hole along the pipe is described, also based primarily on small-scale laboratory experiments. The state of the art of the mathematical/numerical modeling of the scour processes is presented. The associated self-burial of the pipe is described and compared to field observations. In addition to scour, liquefaction may also constitute a risk for pipeline stability. The cause of liquefaction and the resulting consequence for pipeline stability in a natural environment are discuss...

Modeling the Interaction of Water Waves with Porous Coastal Structures

Abstract: The mathematical modeling of the interaction of water waves with porous coastal structures has continuously been among the most relevant challenges in coastal engineering research and practice. Finding a tool to better predict essential processes, relevant to the functionality and stability of breakwaters and jetties, and how they are affected by permeability, has been hampered by computational limitations that are being overcome. Over the last 60 years, the Journal of Waterway, Port, Coast, and Ocean Engineering has witnessed gradual developments leading from linearized solutions based on wave theories and constant friction coefficients to very sophisticated Eulerian or Lagrangian solvers of the Navier-Stokes (NS) equations, including turbulence within porous media. Today, although not without difficulty, the first steps are being made toward addressing the simulation of a fully three-dimensional interaction of complete sea states with porous structures at prototype scale. In this paper, after po...

Development of MOST for Real-Time Tsunami Forecasting

Abstract: The development, testing, and implementation of a real-time tsunami forecast model, the method of splitting tsunami (MOST), is described. MOST is now used as an operational forecast model for the National Oceanic and Atmospheric Administration’s Tsunami Warning System, and as a tsunami hazard assessment tool in the United States and in many countries around the world. Every step in the development of MOST marked new scientific challenges, improvements of technological and computational capabilities, and new demands of the engineering and hazard mitigation communities for applied and benchmark modeling tools for tsunami hazard assessment.

Simulation of Wave-Plus-Current Scour beneath Submarine Pipelines

Abstract: A fully coupled hydrodynamic and morphologic numerical model was utilized for the simulation of wave-plus-current scour beneath submarine pipelines. The model was based on incompressible Reynolds-averaged Navier–Stokes equations, coupled with k-ω turbulence closure, with additional bed and suspended load descriptions forming the basis for seabed morphology. The model was successfully validated against experimental measurements involving scour development and eventual equilibrium in pure-current flows over a range of Shields parameters characteristic of both clear-water and live-bed regimes. This validation complements previously demonstrated accuracy for the same model in simulating pipeline scour processes in pure-wave environments. The model was subsequently utilized to simulate combined wave-plus-current scour over a wide range of combined Keulegan–Carpenter numbers and relative current strengths. The resulting equilibrium scour depths and trends were shown to be in accordance with existing exp...

Tsunami-Induced Forces on Skewed Bridges

Abstract: Research on the influence of tsunamis on bridges has been based almost exclusively on the results of field surveys and of two-dimensional analysis. Although these analyses can provide estimates of forces and moments on the structure, they do not account for three-dimensional (3D) phenomena, such as channelization, or geometric effects, such as bridge skew. Using a 3D computational fluid dynamics approach, this work analyzes the temporal and spatial dynamics of a bore-type tsunami loading on a model bridge and shows how the skew angle of the bridge relative to the incoming wave can affect the loading history. The analyses found that, unlike a bridge without skew, (1) the bore impact forces on the skewed deck do not all occur at the same time; (2) the skewed bridge is subjected to a force perpendicular to its abutments, which could lead to unseating; and (3) the skewed bridge is subjected to pitching and spinning moments. These effects combine to lead to increased horizontal reactions in the substru...

Breaking-Wave Interaction with Tandem Cylinders under Different Impact Scenarios

Abstract: © 2016 American Society of Civil Engineers. This is the authors' accepted and refereed maniscript to the article.

Turbulence Statistics of Wave-Current Flow over a Submerged Cube

Abstract: This paper describes an experimental study carried out in a laboratory flume to investigate the interaction of a surface wave with a unidirectional current over a submerged cubic obstacle. The three-dimensional velocity field was measured using an acoustic Doppler velocimeter (ADV). The results highlight the changes induced in the mean velocity profile, turbulent intensity, and Reynolds shear stress in a plane of symmetry from the superposition of surface waves of different frequencies. Modifications in the mean velocities, turbulence intensities, and Reynolds shear stresses with respect to the flat surface case, in the vicinity of the cube, are explored. This study also investigates the dominant turbulent bursting event that contributes to the Reynolds shear stress in the near-bed flow influenced by the cube. The results show that near the boundary, the contributions to the total shear stress from ejection and sweep are dominant. However, away from the boundary, the outward and inward interaction...

Simulation of Nearshore Tsunami Breaking by Smoothed Particle Hydrodynamics Method

Abstract: This study applies the numerical model GPUSPH, an implementation of the weakly compressible smoothed particle hydrodynamics (SPH) method on graphics processing units, to simulate nearshore tsunami processes. Two sets of laboratory experiments that involve violent wave breaking are simulated by the three-dimensional numerical model. The first set of experiments addresses tsunamilike solitary wave breaking on and overtopping an impermeable seawall. Comparison with free-surface profiles and laboratory images shows that GPUSPH satisfactorily reproduces the complicated wave processes involving wave plunging, collapsing, splash-up, and overtopping. The other set of experiments investigates tsunamilike solitary wave breaking and inundation over shallow water reefs. The performance of GPUSPH is evaluated by comparing its results with (1) experimental data including free-surface measurements and cross-shore velocity profiles, and (2) published numerical results obtained in two mesh-based wave models: the n...

Behavior of Monopile Foundations for Offshore Wind Farms in Sand

Abstract: Most offshore wind-turbine foundations are monopile foundations. Monopile foundations have the advantages of simple structures and are convenient to construct. In recent years, large-diameter monopile foundations, with diameters larger than 4 m, have been used in engineering applications to increase the bearing capacity of wind turbines. Increasing the foundation pile diameter changes the bearing characteristics from those of traditional small-diameter steel-pipe piles. However, research on the bearing characteristics of large-diameter steel-pipe piles is lacking; no mature method exists to estimate the bearing capacity. On the basis of numerical simulations, the differences between the stress and deformation characteristics of the pile body and the soil around it between large-diameter and small-diameter steel-pipe piles subjected to vertical loads and horizontal loads in sand are investigated in this study. A method to calculate the vertical bearing capacity, considering the soil-arching effect...

Coastal Sediment Transport Modeling for Engineering Applications

Abstract: An effort has been made to improve quantitative understanding of beach morphology and stone structural damage progression and to develop a simple and robust model that is suited for engineering applications. The effort for the last 10 years has produced the cross-shore numerical model CSHORE, which is presently limited to the case of alongshore uniformity and uniform cohesionless sediment including sand, gravel, and stone. CSHORE consists of the following components: a combined wave and current model based on time-averaged continuity, cross-shore and longshore momentum, wave energy or action, and roller energy equations; a sediment transport model for suspended load and bed load; a permeable layer model to account for porous flow and energy dissipation; formulas for irregular wave run-up; a probabilistic model for an intermittently wet and dry zone on impermeable and permeable bottoms for the purpose of predicting wave overwash of a dune and armor layer damage progression, respectively; a drag for...

Using an Oscillating Water Column Structure to Reduce Wave Reflection from a Vertical Wall

Abstract: Wave absorbers are usually needed for reducing wave reflection from vertical walls. Different from traditional wave absorbers, which dissipate wave energy into unusable forms, an oscillating water column (OWC) structure can serve as a wave absorber with the potential to generate electricity. In this study, the hydrodynamic performance of a pile-supported OWC structure in front of a vertical wall was investigated experimentally. The surface elevations inside the OWC chamber were measured at two points for a better description of the motion of the OWC. It was demonstrated that the incident wave energy could be effectively attenuated by the OWC structure. Compared with the pile-supported slotted-barrier-type wave absorbers, the OWC-type wave absorbers could function as effectively as the slotted-barrier-type wave absorbers but with a potential to extract wave energy for electricity generation. The effects of the gap between the OWC structure and the vertical wall were examined, and the experimental r...

Upstream-Cylinder and Downstream-Cylinder Influence on the Hydrodynamics of a Four-Cylinder Group

Abstract: © 2016 American Society of Civil Engineers. This is the authors' accepted and refereed manuscript to the article.

Erosion Stability of Wide-Graded Quarry-Stone Material under Unidirectional Current

Abstract: Scour protection around hydraulic structures in fluvial, estuarine, and coastal waters is an essential component of a meaningful and durable design. The continuous optimization of scour protection systems and design approaches leads to faster and more cost-effective construction processes. Although scour protection now often consists of a two-layer design, approaches that incorporate only one layer depict a major step forward. Therefore, this research focuses on the stability of a wide-graded quarry-stone mixture consisting of crushed granodiorite (Jelsa quarry, Norway) with fractions ranging from 0.063 to 200 mm. The material was exposed to an incrementally increased unidirectional current in a closed-circuit flume. The induced flow field and leading parameters were measured at various positions horizontally and vertically, whereas the erosion rates were determined behind the test bed specimen. With increasing flow velocity the development of a static armor layer was observed at the bed surface. ...

Explicit Wave-Overtopping Formula for Mound Breakwaters with Crown Walls Using CLASH Neural Network–Derived Data

Abstract: The authors are grateful for financial support from the Spanish Ministerio de Economia y Competitividad (Grant BIA2012-33967). The first author was funded through the FPU program (Formacion del Profesorado Universitario, Grant AP2010-4366) by the Spanish Ministerio de Educacion, Cultura y Deporte. The authors also thank Debra Westall for revising the manuscript.

Nautical Depth for U.S. Navigable Waterways: A Review

Abstract: The present state of navigation engineering knowledge concerning nautical depth in ports and waterways with fluid mud is summarized to examine the potential for successful application of the nautical depth concept in U.S. navigable waterways. Nautical depth defines a safe and effective channel bottom criterion in areas where fluid mud confounds conventional acoustic (echo sounder) surveying methods. Fluid mud is a high-concentration suspension that typically behaves as a non-Newtonian fluid. It occurs in ports and channels on all U.S. coastlines and accounts for a significant portion of the United States’ $1 billion dredging expense. Nautical depth has been adopted in multiple ports on three continents. Where nautical depth application is appropriate, it often reduces dredging frequency and dredged material volume and can provide water quality benefits. Multiple experiments and field experience have shown that vessels can safely transit areas with fluid mud below the keel. The United States’ adopt...

Effects of Vertical Variation in Vegetation Density on Wave Attenuation

Abstract: A physical model experiment was used to investigate irregular wave attenuation through emergent vegetation with variations in stem heights. The experiment was conducted with six peak periods, six incident wave heights, and two schemes of vegetation. One scheme used uniform vegetation (constant stem height) and the other scheme approximated vegetation with larger biomass near the bottom and decreasing linearly to the surface, consistent with observed biomass patterns in the field. Although distributions were different, the total vertical projected area was kept constant between the two schemes. The cross shore variation of wave heights across the vegetation were measured, and losses due to sidewall and bottom friction effects were measured and removed from the wave attenuation in the vegetated cases to isolate the influence of vegetation. The normalized wave height attenuation for each case was fit to the decay equation to determine the difference of vegetation transmission coefficients Kv and damp...

Modeling Wind Effects on Shallow Water Waves

Abstract: A mechanism for the growth of waves by wind is included in a time-domain Boussinesq-type model. To facilitate direct analysis of the effect of wind on nonlinear wave–wave interactions over a flat bottom, a set of three harmonic evolution equations is derived from the time-domain model. These equations simulate the evolution of the principal components of three-wave (triad) nonlinear interactions, now including the effect of wind. A case of wave recurrence, in which energy is cycled between three harmonics, shows that a following wind can increase energy exchange to higher harmonics owing to nonlinearity, whereas an opposing wind suppresses this interaction. The time-domain model is then used to simulate wave propagation over a planar slope in the presence of wind. It is shown that wave growth is assisted by onshore winds and hindered by offshore winds. In addition, wave skewness and asymmetry, which quantify wave shape, are also similarly affected by wind direction. The results also show that the ...

Hydrodynamic Forces and Coefficients on Flexible Risers Undergoing Vortex-Induced Vibrations in Uniform Flow

Abstract: In this study, the distribution and variation of the hydrodynamic forces and hydrodynamic coefficients in both inline (IL) and cross-flow (CF) directions on flexible risers experiencing vortex-induced vibration (VIV) in a uniform flow were investigated. The hydrodynamic forces in the CF and IL directions were theoretically calculated by the Euler-Bernoulli beam vibration equation. With the least-squares method, the hydrodynamic coefficients in both CF and IL directions were further investigated. The results indicate that the hydrodynamic force and vibration displacement almost simultaneously reach their maximums. The excitation coefficients obtained in this paper do not always agree with those obtained by the forced-oscillation tests: some excitation coefficients are even negative within the usual defined exciting nondimensional frequency regime and are related with not only the nondimensional frequency and amplitude but also phase angles of the CF and IL displacements. The added-mass coefficient ...

High-Order Boussinesq-Type Model for Integrated Nearshore Dynamics

Abstract: A two-dimensional high-order Boussinesq-type model was derived to simulate wave propagation and relevant processes in the nearshore zone. Because of its enhanced nonlinear character, the model can describe more accurately the amplitude dispersion compared to its weakly nonlinear counterpart. Extension to the surf zone was accomplished using the eddy-viscosity concept for simulating breaking waves. Swash-zone dynamics were simulated by applying a modified narrow-slot technique. Bottom friction and subgrid turbulent mixing were also incorporated. The model can estimate the wave-induced current field, including the undertow effect. The numerical model relied on a generalized multistep predictor-corrector scheme, and the waves were generated using the source function method. Both the one-horizontal-dimensional (1DH) and two-horizontal-dimensional (2DH) versions were validated against a variety of experimental tests, including regular and irregular wave propagation and breaking on plane beaches and sub...

Assessment of the Total Factor Productivity Change in the Spanish Ports: Hicks–Moorsteen Productivity Index Approach

Abstract: The assessment of the productivity growth of ports is essential to improve their performance and competitiveness. Although there are several nonparametric methodologies to compute the productivity change, the Hicks–Moorsteen productivity index is the only multiplicatively completed index that can be computed without price data. For the first time, the total factor productivity (TFP) change of a sample of ports is evaluated. The analysis covers the 28 ports comprising the Spanish port system, using data over the period 2005–2012. The drivers of TFP—technical change, technical efficiency, mix efficiency, and residual scale efficiency—are also investigated. The results indicate that from 2005 to 2009, the TFP declined significantly owing to the technical change, whereas from 2009 to 2012, the TFP improved significantly. The TFP decomposition illustrates that 10 out of the 28 ports improved their technical change, and 9 out of the 28 ports increased their efficiency change. From a policy and manageria...

Optimized Generation and Absorption for Three-Dimensional Numerical Wave and Current Facilities

Abstract: This article presents an optimized setup for a numerical wave/current facility that allows for fast and efficient generation and absorption of random directional waves, in the presence of uniform noncollinear ambient currents. In this study, the generation of waves was optimized, in terms of computational effort, by replacing the built-in sine and cosine functions with a Taylor series approximation. The mesh in the absorption zone was also optimized with the use of a mesh grading that resulted in larger cells toward the outflow boundary. Results show that the numerical cost is reduced by 70% for the wave generation and by 90% for wave absorption. Results compare very well for wave generation with and without currents with respect to regular wave/current and random wave theories. Wave reflection was generally less than 1% for linear waves, less than 4% for nonlinear waves, and less than 5% for random waves.

Efficiency of Hanging Silt Curtains in Crossflow

Abstract: When dredging in sensitive environments, efforts have to be made to limit the free dispersal of suspended fine sediment from the dredging spill. Especially the use of hanging silt curtains as an environmental mitigation measure is widespread. Despite frequent application, their ability to reduce turbidity levels through vertical diversion of sediment-laden currents remains subject of debate. This paper addresses a series of laboratory measurements and numerical model simulations in order to determine the efficiency of hanging silt curtains, defining a new efficiency parameter. The model was validated against the laboratory experiments. Model simulations focusing on vertical diversion of the sediment-laden current suggest that hanging silt curtains do not have a favorable influence on the settling of suspended sediment when applied in cross-flow. Diversion of currents underneath the curtain causes flow separation and intense turbulent mixing, which counteracts settling of suspended sediment particles. The results imply that the widespread application of hanging silt curtains should be reconsidered from a physical point of view.

Longshore Transport Estimation on Ofir Beach in Northwest Portugal: Sand-Tracer Experiment

Abstract: This work aims to shed some light on longshore sediment transport (LST) in the highly energetic northwest coast of Portugal. Data achieved through a sand-tracer experiment are compared with data obtained from the original and the new re-evaluated longshore sediment transport formulas (USACE Waterways Experiment Station’s Coastal Engineering and Research Center, Kamphuis, and Bayram bulk formulas) to assess their performance. The field experiment with dyed sand was held at Ofir Beach during one tidal cycle under medium wave-energy conditions. Local hydrodynamic conditions and beach topography were recorded. The tracer was driven southward in response to the local swell and wind- and wave-induced currents (Hsb=0.75m, Tp=11.5s, θb=8−12°). The LST was estimated by using a linear sediment transport flux approach. The obtained value (2.3×10−3m3⋅s−1) approached the estimation provided by the original Bayram formula (2.5×10−3m3⋅s−1). The other formulas overestimated the transport, but the estimations resu...

Shipping-Container Impact Assessment for Tsunamis

Abstract: During tsunami inundation, coastal structures are subject to hydrostatic and hydrodynamic forces from the run-up and rundown and to impact forces from floating debris that is picked up by the flow A new chapter in the upcoming revised US design load standard covers these loads To illustrate the application of this methodology for impact loading, it is applied to the determination of shipping-container impact loads for locations in Hilo, Hawaii The steps include identification of the tsunami design zone, computation of the shipping-container impact hazard region, and computation of the design flow velocity and depth within that region The flow velocity is used to determine the design impact force for the structure, and the depth is used to define up to what height impact must be considered The standard provides a new, relatively simple “energy grade line” method that can be used to obtain estimates of these quantities Because the method has not been widely validated within the archival lite

On Higher-Order Boussinesq-Type Wave Models

Abstract: Three enhanced versions of two existing nonlinear Boussinesq-type models are herein derived. These models, along with two other similar solvers, were investigated with respect to their nonlinear and dispersive characteristics. In particular, this study comprises Fourier analysis at first-order, second-order, and third-order harmonics; an investigation of linear and nonlinear dispersion; linear shoaling analysis; and an estimation of transfer functions for subharmonics and superharmonics. The models are also validated against demanding experimental tests of wave propagation over a submerged bar. Conclusions of both a special and a general nature are drawn and discussed concerning the scope of nonlinear upgrade of Boussinesq-type equations, their numerical implementation, and the limitations of such models.

Simulating Tidal Flushing Response to the Construction of a Low-Crested Weir Connecting Port Canaveral to the Banana River, Florida

Abstract: Indian River Lagoon (IRL) is a restricted estuary along the east coast of Florida. Although Banana River, a 50-km-long subbasin of IRL, has an outlet to the ocean through the Port Canaveral Locks, the locks remain closed when there is no passing vessel, resulting in limited circulation, long flushing time, and poor water quality. The purpose of this study was to determine the extent to which constructing a low-crested weir adjacent to Port Canaveral can improve flushing in this region. A computer program was used to simulate the hydrodynamic properties of the study area and determine the two-dimensional (2D) depth-averaged velocity field. Then, passive particles were placed in the Banana River, and their movement was tracked using the Lagrangian particle-tracking model (LPTM). Transport timescales were then computed. Results indicate an improvement in flushing in both the Banana River and the central IRL. In the portion of the Banana River to the south of the port complex, the flushing time was de...

Development of a Vessel-Performance Forecasting System: Methodological Framework and Case Study

Abstract: Terminals rely on optimization tools to determine merchandise location, quay occupation, or vehicle trajectories to minimize the movements and time dedicated to every task. However, operations are developed in an environment that induces variability to the theoretical model used to schedule and control the operations. Given the complexity of the port operations, artificial intelligence systems can act as a valuable tool to analyze such processes. Neural networks in particular are characterized by their capacity to establish nonlinear relationships (and consequently, nonintuitive ones) among the variables; this interaction generates a specific operational response. In the near future, the monitoring of operational variables has great potential to make a qualitative improvement in the operations management and planning models of terminals that use increasing levels of automation. This paper proposes a method to obtain operational parameter forecasts in container terminals. To this end, a case study ...

New Internal-Wave Model in a Two-Layer Fluid

Abstract: To model internal waves, high-level Green-Naghdi (GN) equations that are strongly nonlinear were developed for a two-layer fluid with a rigid lid over the upper layer. The GN models were applied to two internal-solitary-wave cases: weakly dispersive and strongly dispersive. In the weakly dispersive case, the ratio between the upper and lower layers was 1:4.13. In the strongly dispersive case, the two depth ratios between the upper and lower layers were 1:24 and 10.13:1. For both the weakly and strongly dispersive test cases, the converged GN results for wave speed, wave profile, and velocity distribution agreed well with the experimental data and the solution of Euler equations, even for large-amplitude solitary waves. For the strongly nonlinear and strongly dispersive cases, the converged GN results showed better accuracy than some other strongly nonlinear models.

Probability analysis of wave run-ups and air gap response of a deepwater semisubmersible platform using LH-moments estimation method

Abstract: The air gap response in harsh environments, a critical design issue for offshore platforms, is related to the wave run-ups attributable to wave-platform interactions and has the potential to result in serious wave impacts. Therefore, the reliable prediction of wave run-ups and air gap response in harsh environments is a challenging task and needs further study. In this study, probability analysis of the wave run-up data from an experimental study of a deepwater semisubmersible platform was conducted based on the three-parameter Weibull distribution model using the LH-moments method for parameter estimation. One of the highlights in the present study is that the explicit relationships between the first three LH-moments at arbitrary levels and the parameters of the Weibull distribution were established analytically. The accuracy of LH-kurtosis estimation was proposed to determine the appropriate level for probability analysis. The air gap response was found to be more serious in quartering and beam seas than in head seas. In front of the columns along the incoming-wave direction, especially the aft one, the wave run-ups showed higher probability distributions than did the other platform areas, leading to higher likeliness of suffering from negative air gap and wave impact accidents. At the platform center, the wave run-up was found to be significantly lower than the incident wave. This research shows that the probability distributions based on LH-moments at the appropriate level can well represent large wave run-ups, except for that beyond the still-water air gap, where both measurement methods and probability analyses warrant further research.