Search Results (179)

It is crucial for reef revetments to respond dynamically to rigorous wave actions for structural stability and safety. A comprehensive analysis of the interaction between the wave force and wave overtopping in a reef revetment project was conducted based on wave flume experiments. This study explored how wave conditions, the water depth along the reef flat, and the proximity of the reef edge to the revetment project influenced wave overtopping and wave force patterns. The results indicate that as the incident wave height, period, and water depth along the reef flat increased, the average wave overtopping within the revetment project also increased. Additionally, higher levels of average wave overtopping occurred with the decrease in the distance between the revetment project and the reef edge. The peak wave force on the seawall of the revetment project was studied in response to various factors, including wave period, wave height, water depth along the reef flat, and distance to the reef edge. The changes in the maximum wave force reflected those of the average wave overtopping, with a strong linear correlation. The quantitative relationship between these variables was determined, and the wave forces on the seawall could be indirectly estimated using the average wave overtopping volume. This study provides an efficient methodology for assessing the dynamic attributes of revetment projects and the disaster risk of these structures. Full article

A thorough literature review was conducted on the effects of free surface oscillation in open channels, highlighting the risks of the occurrence of positive and negative surge waves that can lead to overtopping. Experimental analyses were developed to focus on the instability of the flow due to constrictions, gate blockages, and the start-up and shutdown of hydropower plants. A forebay at the downstream end of a tunnel or canal provides the right conditions for the penstock inlet and regulates the temporary demand of the turbines. In tests with a flow of 60 to 100 m³/h, the effects of a gradually and rapidly varying flow in the free surface profile were analyzed. The specific energy and total momentum are used in the mathematical characterization of the boundaries along the free surface water profile. A sudden turbine stoppage or a sudden gate or valve closure can lead to hydraulic drilling and overtopping of the infrastructure wall. At the same time, a PID controller, if programmed appropriately, can reduce flooding by 20–40%. Flooding is limited to 0.8 m from an initial amplitude of 2 m, with a dissipation wave time of between 25 and 5 s, depending on the flow conditions and the parameters of the PID characteristics. Full article

This paper presents a novel mathematical framework for assessing and predicting the resilience of critical coastal infrastructures against wave overtopping hazards and extreme climatic events. A probabilistic sensitivity analysis model is developed to evaluate the relative influence of hydrodynamic, geomorphological, and structural factors contributing to wave overtopping dynamics. Additionally, a stochastic Gaussian process (GP) model is introduced to predict the mean overtopping discharge from coastal defences. Both the sensitivity analysis and the predictive models are validated using a large homogeneous dataset comprising 163 laboratory and field-scale tests. Statistical evaluations demonstrate the superior performance of the GPs in identifying key parameters driving wave overtopping and predicting mean discharge rates, outperforming existing regression-based formulae. The proposed model offers a robust predictive tool for assessing the performance of critical coastal protection infrastructures under various climate scenarios. Full article

This study aims to assess the adaptability of coastal areas in the Republic of Korea to future climate change-induced flooding. Coastal areas can be susceptible to complex external factors, including rainfall, tide levels, storm surge wave overtopping, etc. The study employs an integrated approach to address this, connecting hydrological and marine engineering technologies. The models utilized in this study encompass XP-SWMM, ADCIRC, SWAN, and FLOW-3D. This study analyzed floods in 2050 and 2100, considering expected rainfall patterns, sea level rising, and an increase in typhoon intensity based on climate change scenarios for six coastal areas in the Republic of Korea. We reviewed the adaptability of flooding to climate change in each region. Full article

In order to develop green energy, reduce carbon emissions, and alleviate global warming and the green energy crisis, many researchers focus on wave energy, using a device to convert wave energy into electricity. The three main types of wave energy converters are the overtopping type, the oscillating water column type, and the oscillating body type, and for most of them, the power generation efficiency is low. The research team in this paper proposed a wave energy converter for a wave-induced oscillation heave plate. The plate vibrates up and down under the action of waves, and the captured energy of the vibrating plate transfers the energy to the generator, so as to generate electricity. There is electricity only when there is vibration; therefore, the vibration characteristic of the converter is crucial to power generation. So, the vibration characteristics of the energy capture structure of the converter were studied experimentally. The test results show that the energy harvesting device can vibrate, and the vibration effect is good, which further indicates that the device can generate electricity. The effects of different wave conditions and system stiffnesses on amplitude and corresponding amplitude were studied, and the amplitude increases with the increase in wave height and period and decreases with the increase in system stiffness. The amplitude response decreases with the increase in wave height and system stiffness. Under the test conditions, the maximum amplitude of the system is 6.23 cm (when the wave period is 1.40 s, the wave height is 0.25 m, and the system stiffness is 1735.62 N/m), and the maximum amplitude ratio is 0.34 (when the wave period is 1.1 s, the wave height is 0.10 m, and the system stiffness is 1735.62 N/m). Full article

Slopes suffer damage from waves in coastal environments. Precast blocks with well-designed geometrical characteristics can benefit the construction of revetments by mitigating the issue of wave overtopping and dissipating wave energy. In this study, we numerically studied the effect of the geometrical characteristics of precast blocks on wave overtopping by carrying out a numerical simulation of wave overtopping on a slope covered with precast blocks. A total of three different types of blocks were considered in this study to determine the optimal geometric shape using a validated numerical model. Our numerical investigation demonstrated that the roughness of the precast block plays an important role in lessening the height of the wave run-up. Concave and embedded regular hexagons could reduce the wave run-up height by 44.6% compared with smooth slopes within a 2 s wave period. Herein, we evaluate and discuss the influence of the geometrical characteristics of a given precast block, such as thickness, aperture, and wave dissipation notch, on wave run-up. We also present an empirical formula for predicting wave run-up on a slope covered by a concave and embedded regular hexagon-type prefabricated block. This study provides valuable insights into the design of prefabricated revetment blocks. Full article

Over the past three decades, the development and testing of various overtopping wave energy converters (OWECs) have highlighted the importance of accurate wave run-up and overtopping predictions on those devices. This study systematically reviews the empirical formulas traditionally used for predicting overtopping across different types of breakwaters by assessing their strengths, limitations, and applicability to OWECs. This provides a foundation for future research and development in OWECs. Key findings reveal that empirical formulas for conventional breakwaters can be categorized as mild or steep slopes and vertical structures based on the angle of the slope. For the same relative crest freeboards, the dimensionless average overtopping discharge of mild slopes is larger than that of vertical structures. However, the formula features predictions within a similar range for small relative crest freeboards. The empirical formulas for predicting overtopping in fixed and floating OWECs are modified from the predictors developed for conventional breakwaters with smooth, impermeable and linear slopes. Different correction coefficients are introduced to account for the effects of limited draft, inclination angle, and low relative freeboard. The empirical models for floating OWECs, particularly the Wave Dragon model, have been refined through prototype testing to account for the unique 3D structural reflector’s influence and dynamic wave interactions. Full article

In response to the incident of tourists falling into the sea due to waves on the seawall berm at Macau Road, Qingdao, during the passage of Typhoon “Songda” in 2022, a combination of numerical simulations and physical model experiments was performed to investigate the mechanics of the event, with emphasis on the wave flow characteristics and the flow evolution process on the seawall berm as well as the force exerted on a human body-equivalent cylinder model. The study found that the thickness of the return flow was significantly greater than that of the overtopping flow on the landward part of the berm. The recoil forces applied to the model on the berm were larger than the impact forces, and the ratio tended towards 1 as the wave height increased. In addition, the stability of pedestrians on the seawall berm was analyzed. The instability conditions for pedestrians in cross-wave flows differed slightly from those in floods. Full article

Wave overtopping occurring in offshore wind renewable energy structures such as tension leg platforms (TLPs) or semi-submersible platforms is a phenomenon that is worth studying and preventing in order to extend the remaining useful life of the corresponding facilities. The behaviour of this phenomenon has been extensively reported for linear coastal defences like seawalls. However, no referenced study has treated the case of cylindrical structures typical of these applications to a similar extent. The aim of the present study is to define an empirical expression that portrays the relative overtopping rate over a vertical cylinder including a variety of bull-nose type mitigation structures to reduce the overtopping rate in the same fashion as for the linear structures characteristic of shoreline defences. Hydrodynamic interaction was studied by means of an experimentally validated numerical model applied to a non-impulsive regular wave regime and the results were compared with the case of a plain cylinder to evaluate the expected improvement in the overtopping performance. Four different types of parapets were added to the crest of the base cylinder, with different parapet height and horizontal extension, to see the influence of the geometry on the mitigation efficiency. Computational results confirmed the effectivity of the proposed solution in the overtopping reduction, though the singularity of each parapet geometry did not lead to an outstanding difference between the analysed options. Consequently, the resulting overtopping decrease in all the proposed geometries could be modelled by a unique specific Weibull-type function of the relative freeboard, which governed the phenomenon, showing a net reduction in comparison with the cylinder without the geometric modifications. In addition, the relationship between the reduced relative overtopping rate and the mean flow thickness over the vertical cylinder crest was studied as an alternative methodology to assess the potential damage caused by overtopping in real structures without complex volumetric measurements. The collection of computational results was fitted to a useful function, allowing for the definition of the overtopping discharge once the mean flow thickness was known. Full article

One risk posed by hurricanes and typhoons is local inundation as ocean swell and storm surge bring a tremendous amount of energy and water flux to the shore. Numerical wave tanks are developed to understand the dynamics computationally. The three-dimensional equations of motion are solved by the software ‘Open Field Operation And Manipulation’ v2206. The ‘Large Eddy Simulation’ scheme is adopted as the turbulence model. A fifth-order Stokes wave is taken as the inlet condition. Breaking, ‘run-up’, and overtopping waves are studied for concave, convex, and straight-line seafloors for a fixed ocean depth. For small angles of inclination (<10°), a convex seafloor displays wave breaking sooner than a straight-line one and thus actually delivers a smaller volume flux to the shore. Physically, a convex floor exhibits a greater rate of depth reduction (on first encounter with the sloping seafloor) than a straight-line one. Long waves with a speed proportional to the square root of the depth thus experience a larger deceleration. Nonlinear (or ‘piling up’) effects occur earlier than in the straight-line case. All these scenarios and reasoning are reversed for a concave seafloor. For large angles of inclination (>30°), impingement, reflection, and deflection are the relevant processes. Empirical dependence for the setup and swash values for a convex seafloor is established. The reflection coefficient for waves reflected from the seafloor is explored through Fourier analysis, and a set of empirical formulas is developed for various seafloor topographies. Understanding these dynamical factors will help facilitate the more efficient designing and construction of coastal defense mechanisms against severe weather. Full article

The purpose of this research is to develop a new method for automatically optimizing the seawall cross-section with composite slopes and a berm, considering both overtopping discharge and construction cost. Minimizing these competing multi-objectives is highly challenging due to the intricate geometry of seawalls. In this study, the surrogate model optimization algorithm DYCORS (Dynamic COordinate search using Response Surface models) is employed to search for the optimal seawall geometry, coupled with the ANN (Artificial Neural Network) model for determining the overtopping discharge. A total of 20 trials have been run to evaluate the performance of our methodology. Even the worst-performing Trial 7 among these 20 trials shows a satisfactory performance, with a reduction of 17.67% in overtopping discharge and a 12.1% decrease in cost compared to the original solution. Furthermore, compared to other optimization schemes using GAs (Genetic Algorithms) with the same decision vectors, constraints, and multi-objective functions, the methodology has been proven to be more effective and robust. Additionally, when facing different combinations of wave conditions and water levels, there was a 27.8% reduction in objective function value compared to the original solution. The optimal results indicate that this method can still be effectively applied for optimizing the seawall cross-section as it is a general method. Full article

This research examines the overtopping volumes associated with focused wave groups on smooth dikes with an emerged toe. Focused wave groups are employed to represent the highest waves of random sea states in a compact form, obviating the need to model the entire irregular wave train. This study investigates how overtopping volumes are affected by focus location and phase. A total of 418 experimental tests were gathered and analyzed. Data with overtopping volumes below 600 L per meter (prototype conditions) were excluded in order to focus on extreme overtopping events, resulting in 324 relevant test cases. The experiments used first-order wave generation theory to analyze structural response. Subsequent studies will address the errors induced by this approximation and compare it with second-order wave generation. The experiments simulated extreme wave impacts on an idealized coastal layout, comprising a 1:6.3 foreshore slope and three different dike slopes, including vertical structures, with the initial still water level set below the dike toe. This study employed the NewWave theory to generate focused wave groups, with the objective of extending recent research on wave overtopping under varied conditions. The results, analyzed in both dimensional and non-dimensional forms, indicate that overtopping volumes are significantly influenced by the focus phase. Critical focus locations were identified at a distance of one-third of the deep-water wavelength from the toe. Full article

The design of coastal and hydraulic structures must account for extreme conditions, such as wave overtopping, and consider variables that may not be relevant under normal circumstances to ensure safety. This research investigates the characteristics of air cavity pressure and cavity water depth beside an overflowed vertical caisson breakwater, focusing on the influence of flow conditions and hydraulic parameters for a slowly varying, surging-type tsunami. A physical model was used to conduct controlled experiments, enabling the study to explore various scenarios, including subcritical and supercritical downstream flows with varying downstream flume outlet heights and different upstream water depths. Dimensionless equations for air cavity pressure and cavity water depth were derived through multivariate regression analysis, providing a systematic approach to analyze their behaviors under different flow conditions. The results show that air cavity pressure is significantly influenced by the presence of air in the cavity, with a transition from fully ventilated to partially or non-ventilated conditions as the upstream water depth increases. Cavity water depth is observed to be deeper in the non-ventilated case, aligning with previous studies. The derived dimensionless equations demonstrate strong correlations, offering valuable tools for predicting air cavity pressure and cavity water depth under various scenarios, contributing to the design and analysis of hydraulic structures. This study provides insights into wave-structure interactions, extreme wave loads, and the dynamic responses of coastal infrastructures under wave-induced conditions. Overall, this research advances our understanding of air cavity pressure and cavity water depth behaviors, providing essential data for optimizing the design, performance, and safety of hydraulic and marine structures in response to complex ocean wave loads. Full article

A submarine landslide on the edge of the Norwegian shelf that occurred around 8150 ± 30 cal. years BP triggered a major ocean-wide tsunami, the deposits of which are recorded around the North Atlantic, including Scotland. Ground-penetrating radar (GPR) was used here to investigate tsunami sediments within estuaries on the coast of northeastern Scotland where the tsunami waves were funnelled inland. Around the Dornoch Firth, the tsunami deposits are up to 1.6 m thickness, which is exceptionally thick for tsunami deposits and about twice the thickness of the 2004 IOT or 2011 Tohoku-oki tsunami deposits. The exceptional thickness is attributed to a high sediment supply within the Dornoch Firth. At Ardmore, the tsunami appears to have overtopped a beach ridge with a thick sand layer deposited inland at Dounie and partly infilled a valley. Later, fluvial activity eroded the tsunami sediments locally, removing the sand layer. At Creich, on the north side of the Dornoch Firth, the sand layer varies in thickness; mapping of the sand layer with GPR shows lateral thickness changes of over 1 m attributed to a combination of infilling an underlying topography, differential compaction, and later reworking by tidal inlets. Interpretation of the GPR profiles at Wick suggests that there has been a miscorrelation of Holocene stratigraphy based on boreholes. Changes in the stratigraphy of spits at Ardmore are attributed to the balance between sediment supply and sea-level change with washovers dominating a spit formed during the early Holocene transgression, while spits formed during the subsequent mid-Holocene high-stand are dominated by progradation. Full article

With the acceleration of the global warming process, the clean energy crisis is becoming serious; conventional energy is unlikely to solve the current crisis, so people pay attention to new energy. As wave energy is widely distributed, renewable, and clean, hundreds of wave energy converters emerge. In order to understand the research progress of wave energy converters better, this paper divides wave energy converters into overtopping type, oscillating water column type, and oscillating body type according to the working principle and divides the oscillating body type into oscillating float type and oscillating pendulum type by different ways of energy capture. Based on the classification, various types of engineering cases, physical tests and digital simulation, and other academic research results are summarized, especially the generation power and energy conversion efficiency of various devices, and some shortcomings and suggestions are put forward, hoping to provide help for readers to study wave energy generation converters. Full article