Search Results (585)

Ecological evidence for epifaunal communities on offshore wind farm structures remains geographically concentrated in temperate Northeast Atlantic systems, whereas comparable studies from the subtropical Northwest Pacific remain limited. We sampled upper, middle, and lower layers of five pile-supported structures in a shallow offshore wind farm in the northern South China Sea during spring and autumn, integrating taxon-specific wet biomass, occurrence data, environmental variables, beta-diversity partitioning, and eight functional traits. Taxon richness, functional trait-combination richness, and total wet biomass were lower in the upper layer than in the middle and lower layers, while wet-biomass-weighted Shannon diversity was lower in the upper than in the lower layer. Season and layer × season effects were not significant. Beta-diversity partitioning showed contributions of both turnover and nestedness-resultant dissimilarity, with relative contributions varying descriptively among seasons and layer contrasts. Measured environmental variables explained limited community variation, and the overall db-RDA was not significant, whereas variation partitioning identified the vertical layer as the only predictor group with a significant independent contribution. Global RLQ and FDR-corrected fourth-corner analyses did not support trait–environment coupling. These results extend evidence of vertical epifaunal differentiation to a geographically underrepresented subtropical Northwest Pacific offshore wind farm and support multi-layer sampling for biofouling assessment. Full article

Pile foundations transmit structural loads to deeper subsoil strata whenever the soil in the vicinity of the ground surface lacks sufficient strength and stiffness to ensure an adequate factor of safety against ultimate failure or warrant settlements to remain below acceptable limits. In many in situ conditions, piles are embedded in layered subsoil medium. In several circumstances, piles are subjected to tensile loading. Large and high-rise civil infrastructure subjected to wind loading, transport infrastructure under horizontal loading due to moving vehicles, offshore structures withstanding wind and wave loading, underground structures subjected to hydrostatic pressure due to buoyancy, etc., are some examples where tension loads are imparted on the supporting piles. The imparted uplift loads in these tension piles are balanced by the negative skin friction induced at the pile–soil interface. In this paper, an analytical model using systematic application of established upper bound shear stress theory to three-layered soil configurations has been developed to formulate the ultimate uplift capacity of tension piles in three-layered soil. The model adopted appropriate correlations for upper bound interface shear stresses in different soils as well as tensile failure of pile material itself. The developed solution was validated by comparing with available experimental results. Thereafter, a case study was performed to study the influence of the variation of pile geometries and relative stiffness on ultimate uplift capacities. Important conclusions were drawn from the entire study. Full article

The rapid upscaling of offshore wind turbines has made local scour around monopile foundations a critical concern for foundation capacity and long-term service safety. This state-of-the-art review examines local scour geometry and its implications for monopile bearing performance. Drawing predominantly on the literature published between 1990 and 2026, the review systematically evaluates the influence of foundation dimensions, wave–current conditions, and seabed properties on scour development, and critically assesses key geometric parameters—including maximum scour depth, width, side slope angle, volume, and three-dimensional morphology—for their representation of soil loss and use in current engineering practice. The applicability and limitations of physical experiments, empirical methods, numerical simulations, and field monitoring are compared. The mechanistic linkage between scour geometry and bearing response is elucidated through stress-path alterations, soil confinement degradation, and geometric interactions, with effects on lateral capacity, cyclic response, and natural frequency analyzed. The findings demonstrate that maximum scour depth alone is insufficient; reliable assessment requires multi-parameter characterization incorporating width, slope, volume, and 3D morphology. Distinct from existing reviews focused on prediction or monitoring, this review contributes a systematic elucidation of the mechanistic pathways—soil removal, stress unloading with confinement degradation, and stiffness migration—through which geometry affects bearing performance, and proposes standardized reporting protocols. Future research priorities include addressing scale effects for large-diameter monopiles, advancing long-term 3D monitoring, and developing coupled hydrodynamic–geotechnical frameworks. This review offers a structured reference for researchers and practitioners in scour assessment and foundation design. Full article

With the rapid global expansion of wind energy and increasing deployment of large offshore turbines, achieving reliable sensorless control of wind energy conversion systems (WECSs) has become increasingly important. This paper presents a comprehensive review of modern sensorless control techniques for the doubly fed induction generator (DFIG), which is a dominant technology in variable-speed WECSs. This review focuses on control strategies and rotor speed and position estimation techniques, covering their theoretical foundations, operational characteristics, and emerging research trends. In addition, sensorless operations of the DFIG beyond power generation, including grid synchronisation and stand-alone operation, are presented, providing a foundation for future research in the field. Full article

Grouted connection segments are key load-transfer components in offshore wind jacket structures, and their axial compressive performance is essential for the safety and reliability of the foundation system. This paper develops a finite element model of a grouted connection segment incorporating steel-fiber-reinforced high-strength grout to investigate its mechanical behavior and parametric effects under axial compression. A 1:7-scale model test is conducted to verify the numerical model through comparisons of the load–displacement response and strain responses at key locations. The steel tubes are simulated using a trilinear hardening elastoplastic model, while the steel-fiber-reinforced high-strength grout is represented using the concrete damaged plasticity model with corresponding tensile and compressive constitutive relationships and damage parameters to characterize its nonlinear response. Based on the validated model, a full-scale numerical model is established to analyze the effects of steel tube thickness, shear key spacing, shear key height, and shear key width using the control variable method. The results indicate that steel tube thickness has the most significant influence on the ultimate bearing capacity and can improve the load-bearing capacity and ductility of the structure. Shear key spacing mainly affects axial stiffness and deformation compatibility, while shear key height and width have limited effects on the ultimate bearing capacity but contribute to local deformation control and stiffness enhancement. The findings provide a validated numerical basis for evaluating the axial compressive behavior of steel-fiber-reinforced grouted connections and offer a useful reference for the design and parameter optimization of grouted connection segments in deep-water offshore wind jacket structures. Full article

This study evaluates the offshore wind resource along the Mauritanian Atlantic coast, focusing on ten offshore zones and hub heights up to 100 m. The primary objective is to characterize the spatial variability of the wind resource and provide a preliminary assessment of offshore energy potential. Wind speed data derived from ERA5 were analyzed using Weibull distribution parameters, wind power density, and turbine-based energy production estimates. To support the preliminary identification of suitable offshore wind sites, the study also considers bathymetric conditions, marine spatial constraints, preliminary geotechnical aspects, and uncertainty analysis. The results reveal a systematic increase in wind speed with height and a pronounced north–south gradient along the coast. Zone 1 (Nouadhibou) exhibits an annual mean wind power density of 740.84 W/m², with a monthly maximum of 1237.27 W/m² observed in June, confirming the exceptional wind conditions in the northern offshore zones. The bathymetric analysis indicates that the northern and central sectors are generally more suitable for fixed-bottom foundations, whereas deeper offshore areas may require floating wind technologies. Although these findings provide a robust preliminary assessment of the offshore wind potential, further geophysical and geotechnical investigations, together with environmental and techno-economic assessments, are required before confirming the suitability of the identified sites. Overall, this work provides a first technical framework for the preliminary identification and comparison of promising offshore wind zones along the Mauritanian Atlantic coast. Full article

Offshore wind power has expanded rapidly in recent decades and is expected to continue growing through the deployment of larger turbines in deeper waters. The safe and stable operation of offshore wind turbines (OWTs) depends critically on foundation performance, which is severely threatened by seabed scour. To better understand these threats, this paper reviews recent studies on the effects of seabed scour on the structural performance and safety of fixed-bottom offshore wind turbine foundations (OWTFs), focusing on four aspects: (1) the changes induced by scour in both the seabed morphology and the soil mechanical state, which form the basis for the subsequent analyses; (2) the effects of scour on the bearing capacity and natural frequency of the foundation, covering both its static and dynamic performance; (3) the behavior of scoured foundations under long-term cyclic loading during normal operation and under transient seismic action during extreme events; and (4) the role of scour protection in enhancing structural safety. Several future research directions are also highlighted. This review offers helpful insights for assessing scour-induced risk and for designing scour protection from a structural safety perspective, thereby supporting the safe operation of OWTs. Full article

Tetrapod piled jacket foundations, widely adopted for large-capacity offshore wind turbines, are frequently affected by scour, which substantially alters their lateral mechanical responses. Nevertheless, existing studies on this subject remain limited and mostly adopt simplified uniform scour assumptions that deviate significantly from actual field conditions. This study conducted lateral-loading model tests on scoured tetrapod piled jacket foundations, with the local scour geometry idealized based on the non-uniform scour-hole morphology reported in field monitoring and flume test studies. The evolution law of the lateral bearing capacity of the foundations with scour development is revealed, and the differences in lateral bearing performance under uniform and non-uniform scour are systematically compared. A three-dimensional finite element model is established and validated against test data to verify its accuracy and reliability. Additionally, comprehensive parametric analyses are performed to supplement the experimental results, exploring the influences of flow angles, corresponding scour-hole morphologies and lateral load directions on the lateral bearing performance of tetrapod piled jacket foundations. The pile bearing mechanism and internal force distribution characteristics are further clarified. The research findings can provide a theoretical basis for the safe service of offshore wind turbines supported by tetrapod piled jacket foundations. Full article

As critical components of offshore wind farms, suspend export cables have attracted increasing attention owing to their complex dynamic responses under combined wave–current loading and cable–soil interaction, leading to structural failure and fatigue damage. A numerical framework is developed in the present study to investigate the dynamic responses of a power cable extending from an offshore wind turbine foundation located in the South China Sea. The model of the cable is described by using the absolute nodal coordinate formulation, considering the hydrodynamic load and cable–seabed interaction via the Morison equation and Randolph–Quiggin model, respectively. After model validation, the response characteristics of the cable under different metocean conditions are analyzed. The effects of waves, currents, and related environmental factors on structural strength, fatigue damage, and wear damage are further evaluated. The dynamic response of the cable exhibits pronounced non-uniformity along the arc length. The wave return period mainly affects the response amplitude, whereas the incident angle has a more significant influence on the dynamic response. Damage assessment further shows that instantaneous strength failure is not critical, as the maximum stresses remain below the allowable stress. Instead, fatigue damage and contact wear are concentrated near the transition region and touchdown point, where oblique wave–current action intensifies cyclic bending and wear growth. The results are expected to provide theoretical support and useful reference for the design, installation, operation and maintenance of cables in offshore wind farms. Full article

In cold and humid environments in high-latitude, high-altitude, and offshore regions, ice accretion sometimes occurs on airfoil blade surfaces, such as those of wind turbines. Therefore, a potential hazard exists for the equipment. For this reason, the aerodynamic characteristics of the airfoil blade degrade and power generation decreases. In the present study, the icing characteristics of airfoils in cold and foggy environments were investigated. A novel icing wind tunnel with a low LWC of 0.3 g/m³ and a small MVD of 10 μm was designed and built. An airfoil sample with the aerodynamic profile of NACA 0018 was selected, and the effects of the airfoil material and the temperature on the icing area, the thickness of ice, and the coverage scope of ice were tested and analyzed. The experimental results showed that the temperature had a more significant effect on the icing characteristics in comparison with the airfoil material. At the medium temperature, −7 °C in the present study, the icing area, the thickness of ice, and coverage scope all reached their maximum value. Specifically, the maximum cross-sectional icing areas (CIAs) on the aluminum airfoil at −4 °C, −7 °C, and −10 °C for 60 min were 35.088 mm², 66.357 mm^2, and 51.538 mm², respectively, and those on the FRP airfoil were 36.204 mm², 70.352 mm², and 47.814 mm², respectively. The FRP airfoil had a larger icing area and thickness of ice. In contrast, the aluminum airfoil had a larger coverage scope of ice, which was −0.10~0.15. In addition, the aerodynamic performance of the iced airfoil, including C_d and C_m, was also obtained through CFD. The research findings provided a foundation for further exploring the atmospheric icing of wind turbines and other structures with airfoil profiles. Full article

Maritime object detection remains challenging because of complex sea-surface backgrounds, adverse illumination conditions, and severe class imbalance, especially when safety-critical targets such as search-and-rescue vessels are sparsely represented. To address these challenges, we propose a cascaded hybrid DINOv2-YOLOv8n detection framework for maritime scenes. Rather than relying only on supervised learning from raw RGB images, the proposed method introduces semantic priors from a frozen DINOv2 encoder and projects them into a compact representation for a YOLOv8n-based detector. To improve robustness under diverse maritime conditions, the framework uses a sea-state-aware online augmentation strategy and is trained with the standard YOLO detection objective. Experiments on the Maritime Target Data Sharing Project (MTDSP) dataset show that the proposed framework achieves strong detection performance. Specifically, it obtains an overall mAP@0.5 of 89.4% and a precision of 100% on the test set. For sparse search-and-rescue vessels and rigid offshore structures, it achieves mAP@0.5 scores of 99.5% and 96.3%, respectively. These results indicate that combining foundation-model semantic priors with a lightweight detector can improve the reliability of maritime object detection under complex sea-surface conditions. Full article

Offshore wind farm (OWF) development raises concerns regarding potential conflicts with local fisheries and marine ecosystems. This study investigated the spatiotemporal dynamics of gillnet and trawl fisheries in the coastal waters off Changhua, Taiwan, across various development phases. (2016–2024). Spatial analysis revealed distinct operational patterns: gillnet fleets operated within and adjacent to wind farms, while trawl activities were concentrated in northern offshore waters, largely avoiding the development zone. The gillnet fishery demonstrated a significant increase in Income Per Unit Effort (IPUE), suggesting that local fishers successfully employed adaptive strategies. The IPUE of the trawl fishery indicated a slightly lower value during this period. These findings indicate that current OWF development has historically coexisted with gillnet fisheries without causing economic loss. The catch composition of gillnet fisheries remained stable, dominated by Silver croaker and Pharaoh cuttlefish. The species diversity indices of both fisheries showed a stable to increasing trend driven by seasonal variability rather than construction impacts. The habitat-driven shift in community structure was observed within the wind farm zone (gillnet fisheries), where the dominance of benthic species (e.g., Flatfish) transitioned toward reef-associated taxa (e.g., Spotted catfish, Black Sea bream). This indicates that the turbine foundations may function as artificial reefs, supporting a more complex assemblage. Nevertheless, the observed habitat alterations highlight the necessity for long-term monitoring to ensure the sustainable symbiosis of renewable energy expansion and marine resource conservation. Full article

Owing to transportation, installation, grid-connection, and maintenance requirements, nearshore offshore wind farms are often located close to busy shipping routes, substantially increasing the risk of ship–offshore wind turbine (OWT) collisions. To enhance the impact resilience of OWT support structures against ship collisions, a novel honeycomb sandwich fender is proposed for tower protection. Nonlinear transient analyses were performed using ANSYS/LS-DYNA to simulate a 5000 t ship traveling at 2 m/s and colliding with a 4 MW OWT supported by a single-column tripod foundation. The effects of rubber and aluminum foam cores on the crashworthiness and protective performance of the fender were compared. The results show that the rubber core stores collision energy through recoverable large deformation and releases most of the stored energy during unloading, resulting in pronounced energy restitution and prolonged structural excitation. By contrast, the aluminum foam core dissipates 7.5 MJ through cell-wall buckling, progressive crushing, and plastic collapse, corresponding to 75% of the initial kinetic energy of the ship. Compared with the rubber-core fender, the higher initial stiffness of the aluminum foam increases the peak contact force by 23.1%, from 13.0 to 16.0 MN. However, its irreversible energy-dissipation mechanism reduces the maximum tower-top displacement by 40.0%, from 1.25 to 0.75 m, and decreases the residual tower stress after three successive collisions by 25.0%, from 200 to 150 MPa. These results demonstrate that, despite transmitting a higher peak contact force, the aluminum foam fender provides more effective overall protection under the collision conditions considered because of its greater irreversible energy-dissipation capacity. Full article

To address the challenge of fatigue life prediction caused by multiple-crack interactions in ship and offshore structures, this study proposes a dynamic Bayesian network (DBN)-based method for predicting the fatigue life of structures with multiple cracks, which is systematically validated through physical experiments. First, a numerical model of a representative structure containing a central hole and multiple initial cracks was established based on the coupled simulation platform of ABAQUS and Franc3D. The nonlinear interaction behavior among multiple cracks under different geometric configurations was systematically investigated. Subsequently, a neural network surrogate model was developed, in which geometric features and crack lengths were employed as inputs and key fracture mechanics parameters were taken as outputs, enabling efficient prediction of complex stress intensity factor (SIF) fields. On this basis, fatigue crack growth experiments were conducted on DH36 high-strength steel specimens containing multiple cracks, and crack evolution data under realistic cyclic loading conditions were obtained. Finally, by coupling the surrogate model with the Paris law as the state transition equation and incorporating sparse experimental observations as dynamic updating information, a dynamic Bayesian network framework based on the particle filtering algorithm was established. This framework enables posterior probability tracking of multiple-crack fatigue states and rolling prediction of the remaining fatigue life. The results demonstrate that the proposed method can effectively mitigate the error accumulation associated with deterministic simulation models during long-term open-loop prediction while relying only on a limited number of discrete observation anchors. Consequently, the prediction accuracy of the fatigue life of multiple-crack systems is significantly improved. Furthermore, under crack co-propagation conditions, the proposed framework exhibits a strong capability to capture the propagation retardation of secondary cracks induced by shielding effects. The proposed method provides a theoretical foundation and technical support for the dynamic assessment of fatigue damage and the development of digital twins for complex structures containing multiple cracks. Full article