Journal of Waterway, Port, Coastal, and Ocean Engineering

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’ adoption of the nautical depth concept for select ports and waterways can be expected to reduce dredging frequency and volumes. It offers potential economic and environmental benefits but will require a consensus among federal, state, and local organizations with responsibilities for constructing, operating, maintaining, marking, and using navigable waterways.

Current bubble oil booms (BOBs) create bubble curtains to protect fixed installations in calm waters such as harbors, but fail in more energetic environments. Field and lab studies reveal that area bubble plumes enable BOB applications in such environments. Area bubble plumes exhibit dynamics distinct from point- or line-source plumes, including thicker and more robust outwelling flows and relatively smaller turbulence scales. Area bubble plume studies broaden our understanding of natural systems, where currents and waves are ubiquitous, leading to a variety of marine applications. Laboratory studies in a large flume have investigated the fluid dynamics of shallow line and area bubble plumes. These studies focused on area-plume application to oil spill response, which, based on preliminary tests, featured improved outflows with a downstream barrier. A range of ambient currents, current–plume angles, and airflows were tested. Key to understanding current–plume interactions was the upstream rotor or near-surface recirculation vortex. The strongest outwelling was for a $0.25{\text{ms}}^{-1}$ current and 5-sparger plume (∼unity width-to-depth aspect ratio, $\epsilon$). Owing to acceleration by the rotor, however, the rotor collapsed into this plume at a current of $0.40{\text{ms}}^{-1}$, destroying plume coherency. The fastest surface outwelling was slightly outside the bubble plume edge, and horizontal profiles were well described by two piecewise exponentials. A 10-sparger plume with $\epsilon \sim 2$ was slower but more robust (thicker), allowing its rotor to survive in stronger currents. Vertical profiles of the outwelling flow were well described by an offset Gaussian (subsurface peak) with significantly lower velocity fluctuations than for line-source plumes. Streamline convergence from the rotor was important in reducing turbulence fluctuations. Oblique angle currents led to greater rotor acceleration with the surface outwelling flow largely perpendicular. However, velocities deeper than the main outwelling flow were deflected downstream, showing a highly nonlinear, helical flow in the rotor. These results highlight the importance of better understanding the complex flow fields of area bubble plumes in natural systems and marine engineering applications. Better characterization of the rotor is needed for a range of ambient conditions to enable BOB design optimization.

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 is presented, in which forecasts of vessel performance are obtained. By doing so, the management strategies are supported by an expert system, grounded in the historical data series of quay operation and the climatic conditions observed, as well as the ordinary and extraordinary events that have happened in the past, from which the system is able to learn. This research was based entirely on data gathered from a semiautomated container terminal from Spain.

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 ($H_{sb}=0.75\text{m}$, $T_p=11.5\text{s}$, ${\theta }_b=8-12°$). The LST was estimated by using a linear sediment transport flux approach. The obtained value ($2.3\times {10}^{-3}{\text{m}}^3\cdot {\text{s}}^{-1}$) approached the estimation provided by the original Bayram formula ($2.5\times {10}^{-3}{\text{m}}^3\cdot {\text{s}}^{-1}$). The other formulas overestimated the transport, but the estimations resulting from the new re-evaluated formulas also yield approximate results. Therefore, the results of this work indicated that the Bayram formula may give satisfactory results for predicting the longshore sediment transport on Ofir Beach.

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.

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 K_v and damping factor α. The drag coefficients C_D were estimated under the assumption of uniform, rigid vegetation and linear wave theory. This paper shows that in deeper water, the damping coefficient for the uniform vegetation is higher than that of the nonuniform vegetation because the wave-induced velocity decays exponentially with depth and is less affected by the biomass near the bottom. In shallower water, the ratio of the damping coefficients tends toward unity for the two schemes because the wave-induced velocity is nearly uniform and the vertical projected area was the same between the two schemes. In addition, this study highlights that the effect of vertical biomass distributions can result in changes in C_D ranging from 140% to 170% between the two schemes and that the assumption of a uniform distribution of vegetation biomass is likely more critical than the assumption of rigid vegetation to model wave attenuation due to vegetation.

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 results show that the existence of the gap reduced the energy-extraction efficiency and did not benefit the total energy dissipation. It is suggested that an OWC-type wave absorber should be constructed such that its rear wall is part of the vertical wall.

A vessel-mounted acoustic Doppler current profiler study focusing on channel-scale flow patterns in Galveston Bay near the Houston Shipping Channel and the artificial (dredge spoil) Mid-Bay Island is described. Winds of 5–7 m/s at 215–230° from $N$ were present during data collection, which was conducted both in the deep channel (15 m) and along the shallow (3 m) open water near the channel. For both peak ebb and flood conditions, the tidal circulation forces flow in a direction opposing the wind, which appears to be due to a large-scale flow divergence forced by Mid-Bay Island. The strongest wind-opposing currents were measured closest to the island. During peak flood flow, the shape of the along-channel velocity profile for the open water upwind of the channel at Mid-Bay Island indicated uniform flow, and the salinity profile indicated a well-mixed water column. The near-island along-channel velocity profile showed a near-linear trend and the salinity profile indicated a stratified water column, suggesting that stratification affects the velocity despite the shallowness of the open water adjacent to the ship channel. During peak ebb flow, the near-island along-channel velocities were highly variable, and salinity profiles collected in both the open water and near-island showed stratification. During flood flows, Mid-Bay Island is the first of a chain of dredge-spoil islands encountered by the flow, whereas during the ebb the island is the last of the chain, suggesting that the observed flows are similar to leading and trailing edge effects in a developing horizontal boundary layer around the islands.