Search Results (961)

Offshore wind energy is an attractive renewable energy source due to its advantages. However, the chaotic marine environment makes the analysis of offshore wind energy extremely difficult. Furthermore, studying the behavior of wind turbines under rare and hazardous natural events such as rogue waves is crucial for the safety and operation of wind turbines and the platforms mounted on them. Therefore, this study numerically investigates the aerodynamic, hydrodynamic, and structural properties of the National Renewable Energy Laboratory (NREL) 5 MW wind turbines under the effect of the Draupner wave, the first marine rogue wave ever recorded. To this end, the geometric and structural information of the NREL 5 MW wind turbines mounted on monopile and jacket platforms is explained. The characteristics of the Draupner wave and the variations in its wave height time series are investigated. The recorded wave height time series values are imported into the QBlade program, and the dynamics of NREL 5MW monopile and jacket wind turbines are simulated. Based on the simulation data, the aerodynamic, hydrodynamic, and structural properties of these structures are examined and analyzed. The results demonstrate that Draupner waves have a significant effect on the aerodynamic, hydrodynamic, and structural parameters of the wind turbines. These parameters are observed to reach their highest values, particularly between the 250th and 280th seconds, when the Draupner wave height reaches its peak. Our findings indicate that the jacket structure experienced higher total forces due to its larger wetted surface area and geometric complexity, while the monopile foundation showed higher inertial loading in the X-direction because of its larger added mass. Additionally, we observed that total aerodynamic power generation is significantly affected by the passage of the Draupner rogue wave. We discuss our findings and their limitations. This numerical study is intended to be a milestone for researchers working on the structural health of offshore wind turbines and platforms under the effect of rogue waves. Full article

This study investigates the extreme wave event that caused damage to the main breakwater at Chancay Port, Peru, on 24 August 2025 (the 824 event), through high-resolution nested numerical wave simulations. The research reveals the underlying mechanisms and causation of the damage. Results indicate that the extreme waves originated from a powerful storm in the Southern Pacific’s Roaring Forties around 20 August. The storm generated long-period swell that propagated to Chancay Port, resulting in significant wave heights of 4.2–4.4 m offshore, exceeding the 475-year return period design standard and ranking as the most severe wave event in the past 30 years. Localized modeling further demonstrates that the swells induced nonlinear transformations in front of the breakwater, with wave heights reaching up to 7 m along the structure and generating complex standing waves near the bend. Comprehensive analysis concludes that the damage was caused by the combined effects of this rare extreme remote swell and localized hydrodynamic interactions with the breakwater. Full article

This study examines the hydrodynamic performance and energy conversion mechanisms of a dual-float wave energy converter (WEC) to address the limitations of single-float WECs regarding energy capture efficiency and cost-effectiveness. A three-dimensional numerical wave tank is constructed utilizing computational fluid dynamics (CFDs) technology and STAR-CCM+ to simulate the dynamic response of the dual-float system under specific wave conditions characterized by a height of 0.1 m and a period of 1.5 s. The effects of a front-rear configuration with a quarter-wavelength spacing on the converter’s power output, turbofan rotational characteristics, and heave motion are systematically analyzed. The results indicate that the wave-facing float attains a consistent rotational speed of 4 rad/s, exhibiting significant fluctuations in heave displacement and velocity. Conversely, the downstream float exhibits diminished motion amplitude, a constant rotational velocity of 2.5 rad/s, and curtailed power generation attributable to wave diffraction and energy shielding from the wave-facing float. The mutual hydrodynamic interference between the floats influences the total energy conversion efficiency, as evidenced by the dual-float system’s array impact factor of 0.989. A parametric study covering multiple wave conditions and float spacing is supplemented to reveal the influence law of key parameters on system performance. This paper elucidates the fundamental mechanism of hydrodynamic coupling in dual-float arrays and offers a theoretical foundation and technical guidance for the optimal design and engineering application of arrayed WECs. Full article

Two types of high-frequency water-level oscillations, wind waves and gravity waves in Batemans Bay, New South Wales, Australia, were analyzed by observed water-level and significant wave height data combined with numerical modelling output. The high-frequency wind waves were closely correlated with the tidal-depth change, giving strong evidence of wave–tide coupling and its phase-locked manner. This was supported by modelling the effect of bottom friction induced by a sandbar southeast of the water-level measurement site. The lower-frequency quarter wave, a type of gravity wave, oscillated across the whole bay. Its frequency of approximately 1 h was close to the theoretical value based on the bay dimensions. The topographic and geometric settings of the bay are the principal reasons for the characteristics of these waves. This observation has significant implications for the bay–shelf water exchange and induced hydrodynamics in similar embayments elsewhere in the world. Full article

Landslides occurring on reservoir banks in steep, high-gradient canyon areas pose a significant risk of surge disasters when they slide into the water. This can endanger the lives and property of downstream residents and damage coastal infrastructure. Therefore, researching the formation mechanisms, disaster evolution, and risk assessment of the landslide-surge disaster chain in such areas is essential. This paper takes the Laowuchang landslide in the Shuibuya Reservoir area of the Qingjiang River, China, as its research object. Using GeoStudio 2018 software, it evaluates the landslide’s stability under varying reservoir water levels and rainfall conditions. For potential unstable scenarios identified, a full-chain numerical simulation of the landslide–tsunami disaster was conducted based on the Tsunami Squares method, with a focus on analyzing the wave characteristics during generation, propagation, and run-up processes. Furthermore, the paper assesses the risk of landslide–tsunami disasters in the Laowuchang landslide area. The research findings indicate that: (1) Under the long-term continuous river incision, limestone of the Triassic Daye Formation slides along weak interlayers, inducing large-scale collapses. Subsequently, part of the landslide mass is transported by water, while most accumulates in the near-shore area of the Qingjiang River, ultimately shaping the present morphology of the landslide. (2) The Laowuchang landslide is stable under static water levels of 375 m and 400 m, with corresponding safety factors of 1.137 and 1.167, respectively. Under combined static water level and heavy rainfall conditions, the slope stability decreases significantly, with safety factors of 1.034 and 1.064, respectively. Under reservoir drawdown conditions, the slope tends to be unstable, with a safety factor of 1.047. (3) Numerical simulation results indicate that if the Laowuchang landslide fails into water by the speed of 12 m/s and with a volume of 2 million m³, the maximum initial wave height can reach 15.9 m. The tsunami’s affected range spans 10 km upstream and downstream from the landslide mass, with four houses and one substation within a 2 km up and downstream falling into high-risk areas. If abnormal increases in landslide displacement occur, relocation and risk avoidance measures should be implemented. The findings of this study provide a scientific basis for the prevention and response to landslide–tsunami disasters in similar high and steep canyon terrains. Full article

Background: Atrial arrhythmias represent a frequent long-term complication in patients with atrial septal defects (ASDs). Interatrial block (IAB), reflecting delayed or impaired conduction across Bachmann’s bundle, has been proposed as an electrophysiological substrate predisposing to atrial arrhythmogenesis. However, evidence regarding its prevalence and clinical correlates in pediatric patients with ASD remains limited. The present study aimed to characterize interatrial conduction patterns and assess the occurrence of IAB in children with large secundum ASD undergoing percutaneous closure. Methods: Between January 2020 and March 2024, 37 consecutive pediatric patients (median age 6 years, range 5–11) with large ostium secundum ASD were included in a retrospective analysis of a prospectively maintained institutional database. Standard 12-lead electrocardiograms were recorded before and within 24 h after defect closure. P-wave morphology and duration were systematically analyzed, and IAB was classified according to the Bayés de Luna criteria. Results: The median Qp/Qs ratio was 1.69 (1.32–2.24), with a mean pulmonary artery pressure of 19 mmHg (17–22). IAB was identified in 24.3% of patients before the procedure, predominantly as first-degree IAB. Following device implantation, IAB prevalence (29.7%) and P-wave parameters remained unchanged, with no significant differences compared with baseline. No associations were observed between IAB and defect size, hemodynamic burden, or device characteristics, whereas anthropometric variables, including weight, height, and body surface area, showed a significant correlation with IAB occurrence. During a median follow-up of 199 days, no atrial arrhythmias were documented. Conclusions: In this pediatric cohort with large ASD, IAB was present in approximately one quarter of patients and appeared unrelated to anatomical or procedural factors, supporting the hypothesis of an underlying congenital conduction abnormality. Early recognition of IAB may therefore have implications for long-term arrhythmic risk stratification in this population. Full article

Reanalysis wave datasets are essential for understanding wave conditions along the West African coast, a region with over 350 million people and diverse economic activities. This study evaluates the effectiveness of various datasets, including ERA5, WAVERYS, satellite (HY-2B/HY-2C), and buoy measurements, focusing on significant wave height (Hs). WAVERYS was found to better match in situ conditions compared to ERA5, making it the preferred dataset for climate estimation. This study found that wave heights (Hs) of WAVERYS in the region range from 0.5 m to 3.2 m, with waves primarily coming from the south and southwest, having periods between 3.8 s and 25 s. Swell, originating from the South Atlantic Ocean, dominates the wave climate, while local wind waves contribute only about 5% to the overall sea state energy. Seasonal analysis showed that the highest waves occur between June and September, coinciding with the South Atlantic winter and stronger winds. The validation performed in this study confirms that the WAVERYS reanalysis can reliably be used as a source of wave data in the Gulf of Guinea. This recommendation is based on its consistently better agreement with the available in situ observations and its improved representation of wave dynamics in the region. At locations where buoy measurements exist, in situ data should remain the primary reference for site-specific applications; however, such measurements are spatially sparse and temporally limited across West Africa. Consequently, WAVERYS provides a practical and robust alternative for regional-scale analyses, long-term assessments, and operational applications in areas lacking direct observations, making it particularly valuable for coastal risk assessment, engineering design, and marine operations in the region. Full article

This paper presents the numerical results of a turbulent vortex in wave–current boundary layers, based on Large Eddy Simulations. Rough wall flow problems have always been a research hotspot in the field of fluid mechanics. The turbulent vortex structure within wave–current boundary layers is of great significance for the study of flow characteristics. However, little is known about turbulent vortices in combined wave–current flows. The purpose of this paper is to investigate the differences in the average velocity profile when waves are superimposed on turbulence compared to when waves and turbulence exist independently, and to demonstrate the evolution process of the turbulent vortex structure formed when waves are superimposed on turbulence. The study adopted rough wall simulations and verified the computational results. The findings indicate that under rough wall conditions, stronger secondary flows and turbulent vortex structures are formed within the boundary layer, and an increase in roughness enhances the turbulence intensity within the boundary layer. Additionally, the impact of wall height on the flow structure cannot be overlooked. This paper also presents the evolution process of the turbulent vortex structure within wave–current boundary layers, providing new insights for the study of rough wall flow-related issues. For the interaction of waves and turbulence under rough wall conditions, high-precision numerical discretization schemes are adopted to construct a bottom boundary layer numerical model. This is achieved by summarizing the progress of existing conclusions, understanding the research progress of numerical simulation in the wave–current boundary layer, constructing high-precision numerical discretization schemes, establishing a physical model of the studied problem and abstracting it into a mechanical model, establishing the entire geometric shape and its spatial influence area, performing spatial grid division, adding the initial conditions required for the solution, and selecting the LES algorithm. Full article

The present study aims to provide a comprehensive and integrated analysis of the potential of offshore renewable energy resources in the maritime sector located at the Danube mouth area in the Black Sea, one of the most complex and dynamic hydrological and climatic systems in Eastern Europe. In the current context of climate change, the Danube mouths are of strategic importance due to the specific morphology of the area and the high potential for harnessing multiple renewable sources such as wind, wave, and solar energy. Therefore, this research supports sustainable development and adaptation to climate change. At the same time, predicted climate change may increase the frequency of extreme events, such as storms, sudden changes in water levels, and increased wave heights, which can affect navigational safety, ecosystem integrity, and coastal infrastructure. Thus, this research seeks not only to identify the energy potential of renewable resources but also to assess their risks and vulnerabilities. Using a wide range of data types, three time periods were studied for the main Danube mouth: Sulina and St. George. Both Sulina and St. George present future wind and wave intensification trends, especially in high-emission scenarios, without significant changes in the dominant direction. St. George remains the area with the more intense regime, while Sulina has more moderate episodes, but with a slightly more evident increase in the frequency of 6–12 m/s winds. At the same time, solar radiation shows a slight increase in recent years, especially in the summer season. Harnessing these resources has the potential to, for example, power coastal communities and offshore installations, providing clean and reliable energy while reducing greenhouse gas emissions. Full article

Urban traffic noise poses escalating environmental challenges in rapidly urbanizing regions with high-density buildings, yet systematic investigations into its spatiotemporal characteristics remain relatively scarce. This study addresses this research gap via the synchronized on-site monitoring of traffic noise and traffic flow on a representative arterial road in Guangzhou, China. The analysis reveals that nighttime equivalent continuous A-weighted sound levels (L_Aeq) are 3.0–4.0 dB(A) higher than those during the congested daytime peak, a phenomenon primarily driven by higher vehicle speeds under nighttime free-flow traffic conditions. The spatial analysis uncovers complex three-dimensional noise propagation dynamics specific to urban street canyons. Vertical profiling demonstrates a counterintuitive pattern where noise levels do not attenuate with building height, and upper floors experience marginally higher noise exposure than the ground floor, which is attributed to the canyon effect, where multiple sound wave reflections offset the natural distance attenuation. A validated three-dimensional computational model was further employed to evaluate the efficacy of noise mitigation strategies, showing that an integrated intervention combining porous asphalt pavement and acoustic barriers achieves a maximum noise attenuation of 19.9 dB(A) at ground-level receptors. This significant reduction stems from a synergistic effect: porous asphalt reduces noise at the source on a global scale, while acoustic barriers provide localized shielding for the lower floors of adjacent buildings. This research concludes that effective traffic noise control in high-density urban areas requires three-dimensional, multi-faceted strategies addressing noise source characteristics, transmission pathways, and receptor vulnerabilities. Full article

Under the combined pressures of natural variability and human activities, the area of tidal flats has been gradually decreasing, with most muddy coasts experiencing varying degrees of erosion. The central coast of Jiangsu Province, a world-renowned region for extensive tidal flats, has witnessed intensifying erosion of its muddy coasts in recent years. To mitigate further coastal erosion, an ecological submerged breakwater (ESB) was constructed in the intertidal zone north of the Sheyang River estuary to reduce wave impact on the shoreline. This study evaluates the wave attenuation performance of the ESB based on wave observations conducted at stations deployed on the seaward and landward sides of the structure in May 2025. Results indicate that the breakwater effectively reduces wave height, but its performance exhibits significant dynamic characteristics. During the observation period, the maximum attenuation rate for significant wave height (H₁/₃) reached 76.3%, with an average rate of 33.8%. Wave dissipation efficiency was closely related to sea state: under calm conditions (H₁/₃ < 0.4 m), the average attenuation rate was only 18.4%, whereas under severe sea states (H₁/₃ ≥ 0.4 m), it increased markedly to 57.6%. The wave transmission coefficients (K_t) span a wide range from 0.20 to 0.99, indicating a significant dynamic variability in the wave attenuation performance of the ESB. The performance of the ESB was primarily controlled by two key factors: incident wave height and submergence depth of the structure. Compared to “zonated” natural ecosystems such as oyster reefs, coral reefs, salt marshes, and mangroves, the ESB, as a “linear” engineered structure, achieves comparable wave attenuation within a limited spatial footprint. A promising future strategy involves using the ESB as a frontline defense, integrated with landward ecological restoration measures like salt marsh rehabilitation, to establish a hybrid “grey-green” coastal protection system that synergistically enhances both coastal resilience and ecological function. This study provides a scientific basis for the design and performance evaluation of ecological engineering solutions for protecting eroding muddy coasts. Full article

Artificial reefs (ARs) are eco-friendly coastal protection infrastructures that mitigate wave-induced erosion while maintaining hydrodynamic connectivity and supporting ecological functions. This study evaluates the protective efficacy of a shellfish-algae reef system—a new type of AR—within the Houlong Bay coastal restoration project (Quanzhou, China) using an integrated numerical modeling approach. A coupled model system was established, incorporating MIKE 21 FM for hydrodynamics, MIKE 21 SW for waves, and MIKE ZERO ST for sediment transport, using unstructured triangular grids to resolve complex coastal topography. The model was validated against field data, including tidal currents and wave heights, showing good agreement. Pre-implementation simulations identified key coastal issues: insufficient wave attenuation in the southern fishery port segment, which results in localized erosion. Post-project simulations demonstrate that the novel integrated system—comprising shellfish-algae reefs, broad gentle beaches, and coastal vegetation—effectively reduced nearshore current speeds by approximately 0.15 m/s and attenuated significant wave heights by up to 70% during typhoon events. Short-term (1-year) sediment evolution showed mild deposition (0.1–0.8 m) at the toe of the artificial beach, which is consistent with design expectations. Long-term (10-year) simulations further confirmed coastal stability, with minimal long-term shoreline retreat (maximum 15 m) and low net alongshore sediment transport (annual average: 800 m³). This study provides a validated, data-driven reference for the design and implementation of AR-based restoration strategies in semi-enclosed bays, highlighting their dual role in erosion control and sustainable coastal management. Full article

Docking vessels are used to transport and launch landing crafts, for launching offshore platforms, and in other marine operations. This research develops a new concept for docking vessels, with the aim of optimizing landing operations. Our idea involves separating the functions of transit and landing into two different vessels, where the transporter is the docking vessel of the lander. This generates an efficient concept, as efficient transportation craft and efficient landing craft have different properties to fulfil their functional requirements. The separation enables the design of each vessel with appropriate performance in areas such as cruising speed, range and seakeeping. These functional specifications affect the whole naval architecture of the vessels. This concept is applicable for shores with no harbor facilities, where landing may be necessary for supply or survey. The transporter provides a floating base to the landing craft, with advanced cruising performance, while the lander design has optimal features for shallow water maneuvering and for landing. The docking vessel is of a Semi-SWATH (Small Water-Plane Area Twin Hull) type. A critical aspect of the design concept is the feasibility of launching and docking operations. This research develops this new concept for docking vessels and applies hydrodynamic response analysis to the transporter’s interaction with the lander, for several operational sea states. The method used for the hydrodynamic analysis involves modeling the vessels and solving the wave–body problem for the two interacting vessels, in the frequency domain as well as in the time domain. The time domain analysis enables us to determine the motion of the vessels in real sea spectra, including the representation of the nonlinear response of fenders between the vessels. We apply the AQWA software 2021 developed by ANSYS. The results validate the suitability of this docking application up to a significant wave height of 1.5 m, which present a margin of 0.1 m above the upper limit of sea state 3: 1.4 m. This shows the feasibility of conducting launching and docking operations using this unique design; there is a significant possibility of using this technique to achieve fast and comfortable transportation to a natural shore with no terminal facilities. Full article

The vast potential of deep-sea wind resources has driven substantial research focus on floating offshore wind turbines (FOWTs) in recent years. The wet-towing of the FOWT is critically challenged by the harsh conditions and remote locations of deep-sea sites. This paper proposes an innovative concept of FOWT based on the in-service FOWT “Sanxia Yinling”, establishing a numerical model of wet-towing for the FOWT in AQWA. The experiments of free-decay and wet-towing resistance in still water at the towing tank are carried out to validate reliability of the numerical model-integrated viscous damping and resistance coefficient of wind and current. Then, the method is applied to evaluate the effects of sea states and wet-towing speeds for the dynamic responses of the towing system. The results show that the natural periods of the FOWT in heave, roll and pitch DOFs all exceed 25 s, which is sufficiently longer than the typical wave spectral peak. In addition, the numerical model is verified against experimental data, showing close agreement. For the established towing configuration, safe operation requires sea states to be maintained at or below level 4 (significant wave height ≤ 2.5 m) and the towing speed at or below four knots. It is also found that a slack-taut cycle in towing lines at low speeds, which is attributed to wave excitation. Full article

Currently, most wave observation equipment is used for fixed-point measurements, and there is a relative scarcity of ship-borne real-time wave measurement devices, which limits comprehensive and three-dimensional monitoring of wave characteristics. This paper introduces the Wave Acquisition Stereo System (WASS) and describes the design and construction of a ship-borne stereoscopic vision experimental apparatus. Sea trials were conducted to evaluate the system’s ship-borne wave-measurement performance and to quantify the effect of deployment parameters on accuracy. The results indicate that the device reliably retrieves wave parameters; compared with concurrent buoy observations, the error in significant wave height did not exceed 0.14 m. Research confirms that deployment parameters have a significant impact on measurement outcomes: sampling frequency directly affects the accuracy of wave-parameter estimation; a higher sampling rate (10 Hz) improves the reliability of the calculated results. The baseline-to-height ratio has an optimal range (0.1–0.3), and values outside this interval reduce measurement accuracy. Under a fixed geometric configuration, the observation field exhibits a band-shaped low-error zone aligned with the baseline direction. Full article