Journal of Waterway, Port, Coastal, and Ocean Engineering

The submerged floating tunnel (SFT) is a newly developed traffic structure for crossing the long waterway. On the basis of the vehicle–tunnel coupled vibration, the vortex-induced effect of the SFT in the water flow field is considered through a wake oscillator model. The tunnel is modeled as an Euler–Bernoulli beam supported by the continuous elastic foundation. The vehicle is regarded as a spring–mass block moving on the tube with a damping term. The finite-difference method is carried out to calculate the fluid–vehicle–tunnel coupled system vibration response evolution. The effects of the buoyancy weight ratio (BWR), the structural span, the vehicle weight, and the distributed flow field on the fluid–vehicle–tunnel coupled vibration are discussed. The results show that the vehicle moving in the SFT will aggravate the fluid–tunnel coupled vibration. The reverse displacement of the vehicle is driven by the coupled vibration. With an increase in the flow velocity, the short-span SFT will vibrate more intensively than the long-span SFT. The heavy-weight vehicle moves more stably during the fluid–vehicle–tunnel coupled vibration. The characteristics of the distributed flow field could be indirectly reflected by the vehicle vibration response.

A submerged oscillating heave plate is utilized as a mechanism in some marine structures for vibration reduction. Quantifying the hydrodynamic properties in axial (heave) oscillations has been extensively archived in published research. However, the rotational hydrodynamic properties of an isolated plate under forced oscillation have not been investigated, which may be of relevance when such structures undergo roll or pitch oscillations. This paper reports on an experimental study that aims to find the trends of the rotational hydrodynamic coefficients versus vibration amplitude for an isolated disk. Furthermore, formulae for nondimensional rotational coefficients based on empirical fits to experimental data will help to generalize these coefficients to full scale. The experimental tests were conducted in two sets. In the first set, disks of different sizes were excited in rotation around their central axis, whereas in the second set the disks were oscillated at a distance from the rotational axis. Generally and in accordance with results for heave oscillations, the results of the hydrodynamic coefficients show an increasing linear trend versus vibration amplitude.

This paper studies the effect of the wave front-current angle on the scour around a circular pile. An experimental study was carried out in the Coastal, Ocean and Sediment Transport (COAST) laboratory at the University of Plymouth (UK) using a single monopile of 0.125 m in diameter and an 8 m long by 1.5 m wide by 0.2 m high sand pit. The results obtained during the test campaign show the influence of the angle between waves and currents on both the maximum scour depth and the time scale of the process. Wave fronts partially aligned with current (65°) produce deeper scour holes than perpendicular forcing conditions (90°). Wave fronts partially against the current (115°) produce less scour than any of the two previous scenarios. The addition of waves reduced the maximum scour depth, compared with the current-only case. The development of the scour hole was found to be more rapid when waves are added to the current, with 50% of the final scour achieved in half the time. The results show that wave direction relative to the current is an important component in scour prediction.

Extreme high still water levels (EHSWLs) are calculated at four tide stations located along North San Francisco Bay for a range of return periods. The observed hourly still water level varying from 7 years to 122 years measurement durations and predicted tide data for the tide stations are used in the study. The conventional annual block maxima (ABM), r-largest order statistics (r-LOS), peak over threshold (POT), and convolution (joint probability) methods are used to calculate the return levels. The return level estimates by the four methods are critically compared, and the merits and limitations of the methods are investigated. Various other research questions such as the effect of the probability distribution and block size on the return level estimates, the accuracy of return level estimates with limited annual maximums, the effect of the data resolution on the return level estimates with the convolution method are investigated. The analyses show that using a limited annual maximum affects the return level estimates most. The error can go up to 0.37 m in the 100-year return level at the San Francisco station. The direct extreme value analysis (EVA) methods produce very similar results, whereas the convolution method results in significantly (0.16 m) higher return levels. The monthly and daily block sizes in the block maxima method estimate very close return levels to annual block size. The differences produced due to the probability distributions alternative to generalized extreme value (GEV) are within or very close to the 95% confidence margin of error (MOE) of ABM-GEV estimates.

Concave front pile-supported breakwaters, namely, Galveston wall-shaped pile-supported breakwater (GS-PSB) and circular cum parabola-shaped pile-supported breakwater (CPS-PSB), have proven to be more effective in dissipating incident wave energy compared with vertical front pile-supported breakwaters. However, the run-up and the dynamic pressures on the concave front are reported to be high. In the present experimental study, an attempt is made to improve the hydrodynamic performance of the GS-PSB and CPS-PSB by mounting tubular wave screens on their seaside as an additional energy dissipator. The tubular wave screen is comprised of horizontally aligned circular tube sections with diameter and spacing leading to a porosity of 25%. The models were subjected to the action of regular and random waves in a wave flume covering intermediate to deepwater conditions. It is found that the impact of tubular wave screen on the hydrodynamic performance of the both the models differs. While, the tubular wave screen marginally affects the transmission, the reduction in reflection is more for GS-PSB due to its steeper slope. The energy dissipation offered by GS-PSB in deepwater conditions is found to significantly improve due to the presence of the wave screen, which is not the case with the CPS-PSB model. The run-up and dynamic pressures over the concave profiles are found to reduce for both models. A qualitative assessment of overtopping for both the models is also reported herein.

Analyses of the equilibrium conditions of an anchor and a cable of a ship at anchoring are presented. Three conditions are considered: (1) a part of the cable lies on the seafloor; (2) no part of the cable lies on the seafloor and rises from the seafloor with a zero gradient of the slope; and (3) a nonzero gradient of the slope. In the third condition, a coefficient is introduced to represent the effects of the vertical component of the cable tension on the holding force of an anchor while considering the decrease in the apparent anchor weight. Formulas of the holding force limit in each condition are presented by analyzing the parameters representing the three cable conditions. Numerical examples demonstrate the effects of extended cable length, water depth, soil properties of the seafloor, and the coefficient of upward cable tension on the holding force limit and parameters characterizing the three cable conditions. Measuring the safety of anchoring in terms of the extended cable length and the current cable conditions associated with the risk allowance for dragging anchors is discussed.

An innovative booster is proposed with the aim of increasing the final penetration depth of the OMNI-Max anchor in the clayey seabed with high strength gradient. The booster is attached to the tail of the OMNI-Max anchor, which is beneficial in improving both gravitational and kinetic energies of the hybrid anchor (i.e., booster + OMNI-Max anchor) during installation and can be retrieved after dynamic installation. The present study carried out two categories of large deformation numerical analyses to simulate the dynamic penetration processes of OMNI-Max anchors and hybrid anchors in normally consolidated and lightly overconsolidated clay. The coupled Eulerian–Lagrangian (CEL) approach was used to investigate the effects of impact velocity, booster weight, and soil strength characteristics (including the strain-rate behavior, the strain-softening behavior, and the undrained shear strength) on the final penetration depth of the anchor. Due to the limitations of the CEL approach in simulating the adhesion friction at the anchor–soil interface, a thin layer region method coupled in the computational fluid dynamics (CFD) approach was used to investigate the effect of the friction coefficient at the anchor–soil interface on the final penetration depth of the anchor. Based on numerical simulation results, a comprehensive prediction model based on the anchor total energy was established to rapidly predict the final penetration depth of the OMNI-Max anchor and the hybrid anchor by considering the strain-rate effect, strain-softening effect, and friction coefficient at the anchor–soil interface.

The direct simulation of inundation in developed urban areas presents a much greater challenge than the more common bare earth simulations that use roughness, which are used in many tsunami studies. This study intercompares the performance of four longwave models for tsunami inundation on a detailed topographical model of Kainan, Wakayama, Japan, with laboratory results. All simulations include buildings, which have a large impact on overland flood propagation. Inter-model comparisons yield several apparent characteristics: (1) variations between models were small in areas that are always wet; (2) wetting, drying, and overland propagation increased inter-model variation in the inundation front arrival time, maximum water surface elevation, and overland flow velocities; (3) inundated areas and maximum water surface elevations show lower inter-model variation (V) than inundation front velocity and maximum current velocities. Sources for V appeared to occur from differences in wetting, drying, and detailed code implementation rather than major differences in model physics. Using published tsunami fragility models, V led to significant differences in the predicted damage. Differences were largest for fragilities that used velocity and lower for fragilities that only used maximum inundation depths. Based on these results, inundated areas and water levels from building-resolving simulations might be assigned relatively higher confidence, and all the predicted velocities should be considered to have a greater error and potentially should be considered only when using ensembles.

Along sandy coastlines, submerged, shore-parallel sandbars play an essential role in shoreline morphology by dissipating wave energy through depth-induced wave breaking. While wave breaking and sediment transport around sandbars are complex three-dimensional (3D) processes, shoreline morphology is typically simulated with depth-averaged models that feature lower computational demand than do 3D models. In this context, this study examines the implications of depth-averaging the flow field and approximating the breaking process in nonhydrostatic models (e.g., XBeach nonhydrostatic) for the hydro- and morphodynamic processes around sandbars. The implications are drawn based on reproducing large-scale experiments of a barred beach profile using the single-layer (XBNH) and the reduced two-layer (XBNH+) modes of XBeach. While hydrodynamic processes were predicted with high accuracy on the sandbar’s seaward side, wave heights were overpredicted on the bar’s landward side. The overestimation was due to the simplified reproduction of the complex breaking process near the sandbar’s peak, particularly in terms of the generated turbulence in the water column. Moreover, the velocity profile with a strong undertow could only be represented in a simplified way even using the two-layer mode XBNH+, thus resulting in inaccurate predictions of sediment loads around the sandbar. A parametric study is performed, and it revealed which model parameters control the simulation of the wave-breaking process. Thus, wave height predictions could be improved by tuning the energy-dissipation parameters. However, flow velocities and morphodynamic predictions could not be improved accordingly. Thus, this study identifies possible hydrodynamic model improvements, such as incorporating a roller dissipation model. Moreover, it improves understanding of key drivers and processes that should be included in nonhydrostatic depth-averaged models to simulate morphological changes around sandbars more efficiently.

Predictions of storm surge and flooding require models with higher resolution of coastal regions, to describe fine-scale bathymetric and topographic variations, natural and artificial channels, flow features, and barriers. However, models for real-time forecasting often use a lower resolution to improve efficiency. There is a need to understand how resolution of inland regions can translate to predictive accuracy, but previous studies have not considered differences between models that both represent conveyance into floodplains and are intended to be used in real time. In this study, the effects of model resolution and coverage are explored using comparisons between forecast-ready and production-grade models that both represent floodplains along the US southeast coast, but with typical resolutions in coastal regions of 400 and 50 m, respectively. For two storms that impacted the US southeast coast, it is shown that, although the overall error statistics are similar between simulations on the two meshes, the production-grade model allowed a greater conveyance into inland regions, which improved the tide and surge signals in small channels and increased the inundation volumes between 40% and 60%. Its extended coverage also removed water level errors of 20–40 cm associated with boundary effects in smaller regional models.

The oscillatory flow within the oscillatory boundary layer at the bottom of propagating surface waves is determined by numerically solving the vorticity–stream function problem when the flow regime is turbulent. Two alternative vorticity equations are considered. The first equation is “exact” and is obtained by applying the curl operator to the Reynolds equation. The second equation is obtained by assuming that a turbulent eddy diffusivity is linearly related to the turbulent eddy viscosity and can be used to model the vorticity dynamics close to the bottom. Even though the second equation requires less computational resources and has been employed previously, it provides inaccurate results, and the use of the full equation is recommended.

This study presents a detailed analysis of the mechanics of scour around a square structure due to an inland-propagating tsunami-like bore using physical modeling. A series of hydraulic bores was simulated using the dam-break method in a flume at the University of Ottawa Hydraulics Laboratory. The dam-break bore was generated by releasing water from an impoundment through a rapidly opening swing gate. A novel video-recording system was used to record the evolution of the scour and vortex structure around the structure; image processing allowed tracking of the time and spatial evolution of the scour around the structure. In addition, different characteristics of a generated bore, final scour topography, and the relationship between scour depth and bore characteristics are assessed. The test program was designed such that propagation over the dry bed, typical of the first tsunami-induced inundation, was investigated. It was found that the high velocity and relatively short duration of a tsunami-like bore can induce rapid scour around the structure. The deeper bore depth over dry bed conditions resulted in faster rates of infiltration and scour. Furthermore, it was found that the longer duration of a turbulent bore induced more scour depth compared to that produced by a height-equivalent solitary or long wave.

A dredging backlog in American harbors has produced inefficiencies, delays, and lost revenues for waterway-based logistics and trade. Policymakers have called for increased spending to address maintenance concerns that underscores the need to improve the allocation of public funds or innovate on alternative financing mechanisms. The cost of dredging in the United States has increased more than 250% since 1990 which calls into question the sustainability of current practices. Given that the objective of dredging is to facilitate waterways transport, this study investigated the tradeoffs between transportation cost savings and maintenance spending in the Great Lakes. We use Monte Carlo simulations to calculate Maritime Transport Efficiencies (MTE) as mass per time for bulk iron ore vessels, the predominant vessels on the Great Lakes waterway. Transportation costs, assessed over a range of uncertain demand and fuel pricing, are predicted from natural variations in water surface elevation. Estimates of MTE applied to predict transportation costs are useful in determining annual demand levels for dredging when considered in aggregate, suggesting an opportunity for market-driven funding models for harbor maintenance. Cost savings are evident under conditions such as high-water levels or reduced demand. Increased transportation costs, predicted using MTE, are compared to dredging expenditure. Considering dredging and operating costs together reveals total cost savings. This study produces a quantitative understanding of demand-driven harbor needs which may lead to market-based funding decisions.

The impact forces of submarine landslides (i.e., non-Newtonian fluids) on oil and gas pipelines, especially the most dangerous drag force, are of great significance in the design of deep-water pipelines. The drag force is composed of two parts: the pressure drag force and the frictional drag force. However, previous studies have not quantified their proportion and magnitude, and thus it is highly difficult to analyze their evolution characteristics and mechanisms in detail. In this paper, a methodology to quantitatively obtain the pressure and frictional drag forces of submarine landslide-ambient water–pipeline interaction using computational fluid dynamics (CFD) is first proposed. Second, under four typical Reynolds number conditions, homogeneous fluidized submarine landslides impacting suspended pipelines applied by two boundary conditions (i.e., free slip and no-slip wall boundary conditions on the pipeline surface) are systematically simulated, respectively. Third, the quantitative relationship between the total, pressure, and frictional drag force coefficients is established, and the variation of their characteristic values with changing Reynolds number is analyzed. Finally, the evolutionary mechanism of the frictional drag force is explained by the change in the tangential stress of the landslide in the boundary layer on the pipeline surface, and the variation mechanism of the pressure drag force with changing Reynolds number is elucidated by the boundary layer separation, streamline evolution, and distributed pressure variation around the pipeline, which provides a theoretical basis for submarine pipeline design.