Coastal Engineering最新文献

The interaction between wind and waves largely determines exchanges of mass, momentum, energy, and substances which take place at the air–sea interface. Usually, the parameterization of such interaction considers only the case of progressive waves. However, reflection is practically ubiquitous in the field, especially in coastal areas, and in the lab. Recent experimental studies have extensively treated this subject, showing that even a small amount of wave reflection can significantly modify the free surface elevation and the velocity field on the water side. Nonetheless, a theoretical framework for an exhaustive description of the wave reflection role is still lacking. In this work, an analytical model is developed to emphasize the role of reflection in terms of incident-reflected waves interaction in the 2D momentum equations. A non-null interaction between the incident and the reflected waves is predicted for partially-reflected monochromatic waves, and it is represented by a reflection-induced stress tensor. A phase shift is found among the total wave height, the velocity and the shear stress, with implications on the partition of the wave velocity and stresses. Then, the incident, reflected, and total components of the velocity and of the stresses along the regular wave phase are compared with a set of laboratory experiments, where monochromatic waves in condition of partial reflection are ruffled by an opposing wind. The overlap between experiments and theory is remarkably good, thus validating the entire procedure and assumptions. From the experiments, the fluctuating shear stress and kinetic energy are also extracted for different reflection conditions of the mechanical wave, showing a peak of both quantities near the wave trough (close to the surface). Overall, the experimental analysis gives insights into the velocity, momentum and energy fluxes along the wave phase, based on velocity measurements at one fetch length.

In extreme sea states, steep or breaking waves can produce destructive wave impact loads on surface-piercing structures, such as semi-submersible platforms primarily composed of decks, columns, and pontoons. To reveal the characteristics of breaking wave loads and gain a deeper insight into the wave impacts induced by different breakers, a series of physical tests on a truncated square column with an overhanging deck were conducted in a wave flume. Focused waves were generated to reproduce breaking waves, and a total of 60 test runs were performed. Based on high-speed video recordings of wave motion, four types of wave breaking in the presence of the column structure were identified, including the upward deflected breaker without entrapped air, spilling breaker with air cavity, plunging breaker with small air cushion, and well-developed plunging breaker with large air cushion. Identification parameters and classification criteria for breaker types were proposed. The wave motion features of each breaker type were analyzed in detail, and the spatio-temporal distribution of the resulting local impact pressure and total impact force were discussed. Furthermore, the spatial variation of the pressure impulse and the durations of breaking wave impacts were investigated. The results showed that the wave impact loads caused by different breakers have distinctive spatio-temporal characteristics, and the near-breaking waves usually produce greater impact loads. The location of the maximum local impact load is related to the breaker type, and the spilling breaker is found to cause the most severe wave impact on the column structure. Due to the air entrainment of a larger volume, the local impacts produced by the well-developed plunging breaker should also be attached importance. The research demonstrates that the breaker type could be identified from wave impact loads without using any records of the wave motion. The breaker type must be taken into account for the prediction of breaking wave impact loads on surface-piercing structures in the future.

In this paper, the hydrodynamic performance of a bottom-seated type oscillating water column (OWC) device is investigated by numerical and experimental methods. A coupled SPH (Smoothed Particle Hydrodynamics) - FDM (Finite Difference Method) is proposed to simulate the interaction between waves and the OWC device. The current SPH-FDM model improves grid encryption method, and expand the single-phase SPH-FDM to multiphase SPH-FDM. The results from SPH-FDM align closely with those from the published experimental measurements. Following the successful validations, SPH-FDM and experiment are employed for a series of simulations to investigate the performance of the OWC device. Compared to experimental method, SPH-FDM can obtain global flow field information and avoid the influence of free surface identification and capillarity on vortex determination. In addition, SPH-FDM can naturally captures free surfaces, so it supports further studies on the non-uniformity of water surface in the chamber of OWC which cannot be studied by PIV or pneumatic model.

National weather forecasting agencies routinely issue a range of hazard warnings. But to our knowledge, along sandy coastlines where storm waves and storm surge can result in widespread but location-specific beach erosion and beachfront flooding, no national-scale early warning service for these hazards is presently operational. This paper outlines the scientific basis and implementation of a new framework for large area coastal storm hazards forecasting, currently being tested along the southwest (Indian Ocean) and southeast (Pacific Ocean) coasts of Australia. The system provides 7-day rolling predictions of localized beach erosion and/or coastal flooding linked to forecasted extreme weather events. Coastal setting influences the nature and occurrence of these hazards, with sandy beaches along wave-dominated coasts more prone to erosion and at surge-dominated coasts to flooding. An existing nearshore water-level forecasting system and a new inshore wave modeling capability are used to forecast beach erosion and coastal flooding at every 100 m along the shore. At the regional scale O(100–1 000 km of coastline), a threshold-based decision tree model categorises the predicted extent, location, and severity of erosion and flooding. At a more local scale O(100–1 000 m), physics-based modeling using XBeach focuses on vulnerable or high-value locations, providing specific storm hazard indicators tailored to local needs. This two-tier approach is feasible for national implementation due to the reduced computational effort, limiting intensive modeling to pre-identified critical locations. Delft-FEWS manages the data and modeling workflow, ensuring scalability and compatibility with existing forecast infrastructure. Initial evaluations of the system are promising, with a detailed 2-year evaluation in progress. Future enhancements could include the use of satellite imagery for real-time beach width and dune topography assimilation and exploring alternative modeling approaches to further improve forecast accuracy.

Strong nonlinear effects, such as wave slamming, suction effects, and wave overtopping, may be induced during wave-bridge interaction. However, an accurate understanding of these nonlinear effects is still insufficient. This study comprehensively investigates the wave slamming and suction effects on pier-pile group foundations of sea-crossing bridges in a 1:50 scale laboratory experiment. Random and regular waves with different strengths are generated based on wave conditions at the bridge site. Five water depths with a 2 cm spacing are designed to simulate varying pile cap clearances. Various pile arrangements are also set up to explore the influence of piles. Results show that wave slamming is low-aeration and is triggered mainly on the cap bottom wall, whereas the wave action on the vertical wall of the pile cap is quasi-static. The suction effect is generally recorded in the quasi-static phase of pressures and depends on the water exit process and the wave crest height. Moreover, the pressure oscillation after the impact phase results from the flow separation and rotation at structure corners. The wave slamming enhances with the increasing wave frequency when the impact area is constant, otherwise, it depends on the impact area. On the cap bottom wall, the wave slamming on inter-pile areas is enhanced, but the suction effect is less affected by pile arrangements. The increase in pile cap clearances reduces vertical forces but has less effect on horizontal forces. Additionally, a sustained increase in the wave crest height may reduce the slamming force. An empirical method for predicting wave forces is finally proposed based on the water entry theory and experimental findings. This work enhances the physical understanding of nonlinear effects during wave-bridge interaction and aims to support the design of substructures for sea-crossing bridges.

Following Antuono (2010), a frictional shock wave model with an improved seaward boundary condition (ISBC) was developed to simulate the bore-driven swash hydrodynamics in this study. It is found that bottom friction has a negligible effect when the shock wave propagates towards the original shoreline, whereas it plays important roles in the area near the swash tip and during the backwash. The ISBC increases the swash water depth and the onshore flow velocity, whereas it decreases the flow velocity during the backwash stage, thus the bottom friction effect. A comparison between the present shock wave model and the dam-break model was conducted, which indicates that these two models present similar swash hydrodynamics if the traditional seaward boundary condition is applied, whereas modifications of the water depth and flow velocity under different ISBCs are less significant for the present shock wave model compared to the dam-break model. Swash excursion increases with the ISBC in the shock wave model, which however keeps uniform in the dam-break model. Subsequently, model validation was conducted with respect to the experimental data of Kikkert et al. (2012). Comparing with the dam-break model result, swash hydrodynamics (water depth and flow velocity) in the uprush and early backwash stages could be better reproduced by the present shock wave model.

The paper by Wang et al. (2024) targets an interesting topic in the context of particle methods, namely, volume conservation. This important feature is studied by focusing on the time variation of mean water level under three different scenarios corresponding to hydrostatics, standing wave and dam break, and through consideration of a few variants of the Weakly Compressible Smoothed Particle Hydrodynamics (WCSPH) fluid model. In this discussion, the discussers briefly discuss some issues that could have been further considered in the paper by Wang et al. (2024) to ensure rigorousness and comprehensiveness of the conducted comparative analysis.

Tsunamis can cause extensive damages and loss of lives in coastal communities. Early warning for tsunami can help save lives and mitigate damages from tsunamis. This study aimed to develop an early warning for tsunamis using an artificial neural network (ANN) that can predict maximum tsunami heights and arrival time. Imwon Port, located on the eastern coast of Korea was selected as the target area. A weighted logic tree approach that assigns weights to fault parameters of earthquake based on their importance was proposed to establish tsunami scenarios and generate tsunami big data. Nine offshore observations in the East Sea were used as standard observations for predicting maximum tsunami height and arrival time at Imwon Port. ANN was developed to predict maximum tsunami heights and arrival time. The Kriging method was adopted to investigate the spatial distribution of the maximum tsunami height in the port, and the root mean square error, and coefficient of determination were used to evaluate the model’s performance. The estimates of maximum tsunami heights and arrival times generated by the proposed model agreed with the results of the numerical model. Furthermore, the ANN can generate these estimation quickly, enhancing the effectiveness of early tsunami warnings.

Measuring and modeling ocean waves is a routine task for oceanographers and marine engineers. Accounting for current effects on waves is less common; however, such effects can be non-trivial, particularly for strong currents. Recent research has also found that currents are increasing with global temperatures. Thus, accounting for currents is of potential importance to a growing subset of real-world environments. One significant impact of currents is their modification of dispersion. It is known that, in contrast to dispersion without current, wave–current dispersion is multivalued and anisotropic, meaning it varies with direction and can yield multiple solutions for the same frequency. Strictly speaking, a complete analysis ought to account for all dispersion solutions. This study presents a general wave field solution for linear steady-state two-dimensional surface gravity waves on current. In contrast to existing formulations, it accounts for the complete set of dispersion solutions. The multiple solutions correspond to linearly independent (same frequency) spatial modes with no analogy in models without current. To fully determine the complete temporal and spatial features of a wave field, one must determine the amplitudes of all spatial modes. This can be achieved through the solution of an inverse problem, provided one has sufficient initial conditions. The significance of accounting for all spatial modes is demonstrated through examples. It is shown that a single time-series measurement is insufficient for determining the spatial features of a monochromatic (single frequency) wave. Rather, additional spatial information must be introduced to render the problem well-posed. The theory and methodology presented can be used to improve wave models and measurements.

Ports serve as essential nodes for coastal and maritime transportation and are key sources of income and economic activity in coastal zones. This significance, combined with their location in coastal areas, which are prone to climate-driven impacts, makes them highly susceptible to climate change effects. In this work, a climate change risk assessment methodology for port infrastructures that is focused on compound events analysis is presented. This approach is based on a spatial high-resolution probabilistic framework that enables the evaluation of port performance evolution under the effects of climate change. This assessment draws from a multimodel characterization of the evolution of several climate drivers for different emission scenarios and time horizons. It accounts for multiple port infrastructure risks and considers the compound effects of climate drivers and the interdependencies of infrastructures as complex systems. Performance indicators are developed for the physical assets and services at port locations on a highly granular scale, thus allowing port managers and planners to allocate reserves and develop adaptation plans that reduce climate change risks in the operations of maritime transportation nodes based on port performance forecasts. The methodology is implemented in two case studies set in the northern coast of Spain, demonstrating its applicability and replicability among several locations and scales.