Journal of Waterway, Port, Coastal, and Ocean Engineering

This paper analyzes the problem of oblique water-wave scattering by two thick submerged-horizontal plates in a two-layer fluid. The analysis is based on the small-amplitude water-wave theory in water of finite depth. The solution of the associated boundary value problem was derived through the matched eigenfunction expansion method. Numerical results for the reflection energies of surface and internal waves were computed and analyzed in various configurations. The effects of the geometrical parameters—the submergence, thickness, and length of the submerged plates, and the distance between them—on the reflection energies in surface and internal modes (SM and IM, respectively) are discussed in detail. The study shows that, when the interface lies between the two plates, the largest reflection energies are found in both modes. The numerical results were compared with those available in the literature, and were found to be in good agreement. The energy relation was also derived, and the numerical results were found to satisfy this relation accurately.

Plane waves scattered by a coastal feature exhibit resonance with partially standing waves forming on the windward side and wave dissipation on the leeward side. In this research, the complicated interactions of waves occurring in collections of partially reflecting vertical cylinders were studied using a novel adaptation of the analytic element method. This method organizes the separation-of-variables solution of Hankel and trigonometric functions on an element basis to separate each cylinder’s unknown coefficients from all others. A partially reflective boundary condition is adapted for each element using least squares, and its system of equations is formulated as matrix multiplications of Fourier series terms. A comprehensive solution is then obtained by iteration across all elements. The residual errors achieved demonstrate that the Robin boundary conditions are satisfied with nearly exact precision. Results illustrate the resonance and dissipation occurring within collections of regularly and randomly placed natural and engineered coastal features. This work contributes toward predicting the formation of regions with heavy seas and tranquil zones formed across variations in the wavelength, size of elements, and reflection coefficient, with related applications in acoustics, electromagnetism, and optics.

This article explores the use of the ensemble Kalman filter technique to improve the accuracy of North Sea wave field analyses. A nonhydrostatic convective-permitting mesoscale model was used to provide high-resolution forcing winds. These were adjusted by assimilating measurements of offshore wave heights directly into the wave model state. The ensemble Kalman filter data assimilation was shown to be very efficient, leading (compared to the results without data assimilation) to large reductions (up to 60%) in the root-mean-square error of the offshore wave heights and other model state variables, also (up to 40%) at locations other than those of the observations used.

Tsunamis, impulse waves, and dam failures are disasters that challenge humanity, often leading to massive casualties and extreme economic losses. The highly unsteady flow conditions generated by such events are often in the form of turbulent bores. The purpose of this study was to investigate and validate a new generation system for bores propagating over dry and wet bed conditions. There are multiple techniques to generate such waves experimentally, and the study focused on the generation of tsunami-like inundation conditions through the vertical release of a water volume. A detailed methodology to characterize the generated waves hydraulically, in terms of their wave heights and flow velocities, is presented, and good agreement with the classical dam-break case for both dry bed surges and wet bed bores was demonstrated. Because of the importance of estimating the impact forces induced by such waves, particular attention was given to the wavefront celerity and the velocity profiles measured behind the wavefront; these were found in agreement with Prandtl’s power law for open channel flows, and in-depth measurements allowed for the definition of an expression to estimate flow deceleration behind the wavefront. Along with considerations of the Froude number and momentum, this paper provides relevant information to assist engineers in designing safer infrastructures in areas prone to such extreme loading.

The motion response predictions of side-by-side moored floating liquefied natural gas (FLNG) and liquefied natural gas carrier (LNGC) under oblique waves is critically important to validate operational security. This article studies the hydrodynamic interactions of side-by-side moored FLNG + LNGC under oblique waves by both numerical simulation and model testing. The artificial damping method, calibrated through gap wave elevations measured in model tests, is adopted to simulate the viscous effect in the gap region using the state-of-the-art software HydroStar. The hydrodynamic performances of the side-by-side system under oblique waves are investigated. Relative motions under different wave directions are also investigated, and the resonant phenomena are analyzed through phase shift. The investigations indicate that motion responses of FLNG are less affected by wave directions, whereas the motions of LNGC at the lee side are suppressed due to the shielding effect of FLNG. Relative motions between FLNG and LNGC tend to be amplified with the out-of-phase mode when two vessels oscillate in the opposed directions, induced by gap water resonances at high frequencies, whereas the mode of relative motions induced by roll resonance depends on wave directions and resonance frequencies.

The OmniMax anchor is an efficient anchoring foundation due to its dynamic installation and diving property. When subjected to pullout loading, the anchor is keyed to a new orientation and position to provide holding capacity. However, the trajectory and capacity mobilization of the OmniMax anchor during its keying are still unclear, especially for anchors with shallow embedment depth. The present study investigated the keying process of the OmniMax anchor by using a plasticity model. The anchor yield envelope was established based on a shallowly embedded OmniMax anchor with a tip embedment depth of 1.5 times the anchor length. A series of parametric studies were subsequently carried out to investigate the effects of the soil strength gradient, the padeye offset and padeye eccentricity, the pullout angle at the mudline, and the chain parameters on anchor trajectory and capacity mobilization. The anchor ultimate embedment depth and, hence, the ultimate capacity in the final keying stage were discussed. To keep efficient diving property and high capacity simultaneously, it is recommended that the padeye offset angle should range from 15° to 25°, and the pullout angle at the mudline should be no more than 30°.

The economic significance of the U.S. Marine Transportation System (MTS) generates a need to understand the resilience of the MTS. Resilience is defined herein as a system’s ability maintain a given critical function through preparing, resisting, recovering, and adapting to a disturbance. Past studies quantifying MTS resilience provided conceptual frameworks for measurement; however, detailed and accurate field data throughout each phase of a resilience challenge are extremely difficult to obtain. In addition, port-system resilience analysis techniques must be widely applicable and reproducible. This case study examined the impact of Hurricane Matthew (October 2016) on three ports in the southeastern United States: Charleston, Savannah, and Jacksonville. The study used automatic identification system vessel-position data to calculate two port performance metrics: cumulative dwell time (CDT) and net vessel count (NVC). These metrics were analyzed to quantify system behavior during five stages of the storm: prestorm, prepare, resist, recover, and poststorm. Bayesian changepoint analysis was used to identify the abrupt variations in system performance over time, most notably the transition from recovery to poststorm stages.

A diaphragm quay wall anchored using barrette piles was constructed to increase retained soil elevation and reduce quay wall deflection. This article presents the long-term field-test results of the first practical application of the new structure. The performance of the structure is discussed in terms of the settlement, lateral deflection, bending moment, tensile force, and lateral earth pressure. The maximum lateral displacement was found to be approximately 0.23% of the wall height. The barrette piles exhibited the highest bending moment among the different structures, indicating that they can effectively bear lateral loads. The load-transfer mechanism of the barrette piles can be summarized as a combination of the blocking effect in carrying the horizontal earth pressure and the anchoring effect in carrying the loads from the quay wall through tie-rods. The increase in the spacing between the quay wall and the barrette piles leads to a reduction in the horizontal earth pressure at higher elevations of the structures. Compared to the measurement results, Coulomb’s earth pressure theory significantly overestimates the earth pressure acting on the quay wall. Moreover, the lateral deflection increment as a result of dredging activities is greater than that resulting from superstructure construction.

The dynamic rheological properties of natural cohesive sediments are essential to understanding cohesive sediment transport under waves. In this study, dynamic rheological measurements of natural mud collected from Yueqing Bay, Zhejiang province, China, were conducted under oscillatory shear loadings in a laboratory. The mud samples exhibited nonlinear viscoelastic behavior when the strain amplitude was larger than 0.0005. Mud fluidization began at a large strain amplitude because of the significant decrease in complex viscosity. Strain amplitude was found to play an important role in mud fluidization, whereas frequency had limited influence under small-amplitude oscillatory shear. Time-dependent nonlinear stress waveforms were analyzed to further quantify the nonlinear viscoelastic response of natural mud. The nonlinearity of the samples increased with strain amplitude; however, it decreased at extremely large strain amplitudes.

Using the Israeli Mediterranean as an example, we address the impact of resource variability and device survivability on the design of floating-body wave-energy converters (WECs). Employing a simplified heaving cylinder as a prototypical WEC, several device sizes, corresponding to the most frequently encountered and most energetic sea states in the Israeli Mediterranean, are investigated. The mean annual energy production is calculated based on the scatter-diagram/power-matrix approach. Subsequently, a measure for significant device motions under irregular sea-states akin to the spectral significant wave-height is developed, and cutoffs to regular operation are explored from the perspective of these significant displacements. The impact of this WEC downtime is captured in a refinement of mean annual energy production, which consists of supplementing the scatter-diagram/power-matrix calculations by a Boolean displacement matrix. In the Israeli Mediterranean, where most of the annual incident wave power comes in infrequent winter storms, larger WECs outperform smaller WECs by a greater margin when downtime is taken into account. Analogous displacement cutoffs for refining calculations of mean annual energy production may inform WEC design for other sites.

Ports use soft dredged material for land reclamation to address land scarcity and environmental constraints. Land reclaimed with soft dredged material has the properties of high compressibility and slow consolidation that need to be improved. This laboratory study investigated the effect of a fly ash-based geopolymer binder on the consolidation behavior of soft dredged mud derived from the Port of Townsville, Queensland, Australia. For geopolymer synthesization, an alkali activator solution to aluminosilicate source material mix designs that is used in the geopolymer concrete industry was adopted. The dredged mud sediments were reconstituted at 400% water content dredged mud slurries of nontreated and geopolymer stabilized at 6, 12, and 18% by weight. A series of standard one-dimensional consolidation tests was conducted to study the consolidation and compressibility characteristics of the dredged mud sediments. Taylor’s square root of time curve-fitting method was used to estimate the coefficient of consolidation. The study found that the fly ash-based geopolymer stabilization improved the compressibility, permeability, and consolidation characteristics of the dredged mud sediments. The findings indicate the feasibility of stabilizing dredged mud while still in its slurry form.

During the earthquake that occurred on February 6, 2012, between the Negros and Cebu islands (Philippines), a scuba diver who was about 12 km from the epicenter zone, in about 10 m water depth, was taking audio and video recordings using a GoPro camera. The recorded audio reveals a specific spectral signature few seconds after the earthquake occurrence that appears to be related to hydroacoustic waves. Numerical reproduction of the phenomenon produced waves exhibit a frequency spectrum similar to that recorded. Several previous researches, based on theoretical and/or numerical approaches, indicate that hydroacoustic waves are tsunami precursors and can significantly improve the Tsunami Early Warning System. Currently, such pressure waves generated by submarine earthquakes are seldom measured. Therefore, the records presented in this paper can enhance the research on the in situ data analysis.