Search Results (795)

The detection of bolt preload force is of vital importance for ensuring the structural reliability of equipment under extreme operating conditions. Traditional ultrasonic transducers based on bulk piezoelectric materials suffer from poor long-term coupling stability and high brittleness of the material, which limits their practical applications. In this work, AlN piezoelectric thin films were fabricated by RF magnetron sputtering, and the effects of RF power and target-to-substrate distance on film morphology, crystal structure, and ultrasonic response were investigated. The results show that increasing RF power increased the film thickness and deposition rate, reduced the detected O content on the film surface, and changed the XRD response. The film deposited at 900 W generated ultrasonic longitudinal wave echoes with a relatively high signal amplitude among the tested RF powers. Among the tested target-to-substrate distances, the film deposited at 60 mm showed a relatively higher deposition rate and generated an ultrasonic longitudinal wave echo with a relatively higher amplitude. The measured d₃₃ value of this film was approximately 4.8 pC/N. The AlN thin-film ultrasonic transducers prepared under the selected deposition conditions were directly deposited on bolts, and the effects of temperature and axial load were calibrated using the ultrasonic TOF measurement method. There was a linear correlation between the TOF and the temperature (R² > 99.99%), as well as between the TOF and the axial load. These results indicate that the deposited AlN thin-film transducer has potential for bolt preload measurement in wind turbine bolts. Full article

The deployment of offshore wind farms (OWFs) has increased impressively over the last decade. While a group of frontrunner countries has led early deployment, the offshore wind sector is expanding to new regions; the Thracian Sea represents a promising area for OWFs deployment due to its favorable wind and wave climate. The successful implementation of OWFs projects depends on a comprehensive understanding of local environmental conditions, with particular emphasis on complex wind–wave interactions quantification, as well as on robust and representative power performance evaluation. In the present paper, hourly environmental data spanning 29 years (1993–2021), including wind and wave parameters, are utilized to quantify joint probability distributions at selected four locations in the Thracian Sea. Corresponding environmental contours are derived and presented using a probabilistic model for given return period. The joint probability distributions of wind and wave conditions are estimated and the environmental contour surfaces for 50- and 100-year return periods are calculated and presented for generic use. Furthermore, the power production of an OWF comprising nine IEA 15 MW turbine units arranged in an orthogonal grid layout is assessed through a numerical model developed in an open access computational tool. The model accounts for key physical processes influencing OWF capacity performance, including wake interactions, atmospheric conditions, turbine control strategies, and layout effects. The results indicate a substantial value of annual energy production and capacity factor for different zones within Thracian Sea achieving a value of 526 GWh and 44%, respectively. The presented results provide practical guidance for OWFs development in the Thracian Sea and contributes to reducing uncertainty in early-stage project planning and future engineering studies. Full article

Ultra-high-speed rarefied gas wind tunnels (RGWTs) are critical for estimating the aerodynamic forces acting on spacecraft in very low Earth orbit (VLEO). These tunnels utilize nozzles with large expansion ratios to generate extreme freestream conditions ($Ma>20$, $Kn>1$). However, the large expansion ratio induces a multiscale flow within the nozzle that simultaneously spans the continuum and transitional regimes, making the investigation of such flows extremely challenging. The present work applies a multiscale particle method to investigate the RGWT nozzle flow in a unified manner. Simulations reveal that the nozzle flow is underexpanded and characterized by rarefaction effects, and can be categorized into a central core and a surrounding region comprising the shock wave and boundary layer. This surrounding region occupies a significant portion of the nozzle exit, notably degrading flow quality. The wall suction technique increases the uniform flow radius by 11% at a total pressure of 500 kPa, while its effectiveness is limited at 50 kPa due to heightened rarefaction. Finally, a wall smoothing technique is proposed to improve the quality of nozzle flow by recognizing that strongly rarefied flows are governed by gas-surface interactions. Full article

Offshore renewable energy is widely recognised as a critical pathway for decarbonising electricity systems, but the integration of floating offshore wind turbines with wave energy converters remains technically challenging. This paper presents a structured literature review of hybrid wave–wind offshore energy platforms, drawing on 114 reviewed sources published between 2000 and 2026. The review classifies hybrid concepts using a three-axis framework based on floating platform type, wave energy converter (WEC) integration approach, and energy-dominance category. It then compares representative configurations, including point absorbers, oscillating water columns, flap-type devices, and heaving torus concepts, with emphasis on hydrodynamic response, energy contribution, structural complexity, mooring implications, validation status, and optimization suitability. The findings show that no single hybrid configuration can be ranked as universally superior because reported performance depends strongly on platform geometry, WEC scale, site wave climate, modelling assumptions, and validation maturity. Point absorber systems offer modularity and lower integration complexity, oscillating water column (OWC)-based systems provide protected power take-off (PTO) integration and moderate hydrodynamic interaction, flap-type systems can provide stronger motion-control potential but impose higher structural and mooring demands, and spar–torus concepts remain geometrically compatible with spar platforms but are generally wind-dominated. The review further shows that optimization method selection should depend on problem class: gradient-based methods are most suitable for local PTO tuning, evolutionary methods for non-convex multi-objective layout problems, surrogate-based methods for high-cost coupled simulations, and data-driven methods for adaptive control. The paper concludes that future progress requires standardized benchmark models, transparent evidence-level reporting, multi-physics co-optimization, techno-economic assessment, and systematic experimental or field validation before definitive concept ranking or commercial-readiness claims can be made. For decision-makers, industry stakeholders, and policymakers, the framework supports early-stage concept screening, identification of technology-specific risk factors, prioritisation of validation and investment pathways, and alignment of hybrid-platform development with site conditions, infrastructure constraints, and policy objectives. Full article

In the Anthropocene, the environmental crisis necessitates a radical repositioning of the human-nature relationship. This paper examines the sijo poetry in Musan Cho Oh-hyun’s For Nirvana through an interdisciplinary framework bridging Zen philosophy with material ecocriticism. The study elucidates how Musan deconstructs anthropocentric exceptionalism by restoring agency to the non-human world. Textual analysis reveals three arguments. First, elemental forces like wind and waves are subjectified as primordial teachers through mujō-seppō (non-sentient beings preaching the Dharma), dismantling sovereign human scriptural authority. Second, visceral encounters with animals and insects critique logocentric domination, proposing “epistemological silence” and “radical humility” as alternative eco-politics. Finally, bodily decay and trans-corporeal porosity are reframed as generative pathways toward a radical “ecological Nirvana”—a physical matrix of cyclical renewal. By synthesizing Jane Bennett’s vital materialism with Dōgen’s Zen vision of “walking mountains”, this study deploys a Zen materialism lens that enriches Western theory with the Buddhist soteriology of compassion (karuna). Ultimately, Musan reconfigures Nirvana not as an escapist transcendence, but as a profound somatic descent into the material mesh, where ultimate spiritual realization lies in the ego’s total dissolution into the “walking, talking minerals” of a sacred, suffering ecosystem. Full article

Monopile offshore wind turbines are vulnerable to excessive vibration under coupled wind, wave, and seismic loading because of their slender and flexible structural characteristics. This study investigates a single-sided vibro-impact nonlinear energy sink (SSVI NES) installed inside the nacelle of a 5 MW monopile offshore wind turbine. A reduced-order ten-degree-of-freedom dynamic model is established using the Euler-Lagrange formulation, and turbulent wind, irregular wave, and seismic inputs are generated using TurbSim, the Kaimal and JONSWAP spectra, the Morison equation, and 15 PEER ground-motion records. The proposed SSVI NES is compared with an optimized tuned mass damper (TMD) under nominal and frequency-detuned conditions. Under the nominal design condition, the optimized TMD and the representative SSVI NES reduce the RMS nacelle fore-aft displacement by approximately 55% and 50%, respectively, indicating that the SSVI NES provides near-benchmark vibration mitigation. Meanwhile, the maximum absorber stroke of the SSVI NES is reduced by approximately 40% compared with that of the optimized TMD, which is beneficial for nacelle-integrated implementation. Under frequency detuning, the response-reduction effectiveness of the TMD decreases from approximately 55% to 20%, whereas the SSVI NES retains approximately 80% of its nominal RMS-based control effectiveness. These quantified results show that the SSVI NES offers a balanced combination of competitive nominal response reduction, reduced absorber motion demand, and improved robustness against structural-frequency variations. The proposed device therefore provides a promising passive-control strategy for enhancing the serviceability and multi-hazard resilience of monopile offshore wind turbines. Full article

Marine renewable energy systems, including offshore wind, tidal, and wave technologies, are central to global decarbonisation strategies but remain constrained by reliability-driven costs and uncertainty in long-term structural performance. Existing qualification approaches are largely based on empirical methodologies and deterministic safety factors that inadequately capture coupled degradation mechanisms operating in harsh offshore environments. This review presents a mechanism-based perspective on structural integrity in marine renewable energy systems by linking microstructure-sensitive deformation and damage processes with engineering-scale reliability assessment. Key degradation mechanisms, including corrosion–fatigue, hydrogen embrittlement, wear, and manufacturing-induced variability, are critically examined together with their interactions across multiple length scales. The review synthesises recent advances in multiscale modelling frameworks spanning crystal plasticity, damage mechanics, fracture mechanics, probabilistic reliability methods, and digital twin technologies. Particular emphasis is placed on the role of manufacturing variability, inspection-informed updating, and hybrid physics–data approaches in improving predictive capability and reducing uncertainty. The review identifies major limitations in current offshore qualification practice, including uncoupled degradation assumptions, insufficient representation of manufacturing effects, and limited integration of monitoring data within lifecycle assessment. Building on these findings, an integrated framework is proposed that combines multiscale modelling, manufacturing-aware qualification, adaptive inspection, and digital twin-enabled updating to support predictive and reliability-informed structural integrity assessment for next-generation marine renewable energy systems. Full article

Large language models (LLMs) offer new possibilities for natural-language interaction with geospatial analysis systems, but their use in remote sensing instrument data analysis remains limited by weak execution control, poor reproducibility, and limited integration with domain-specific computation. The paper presents an agent for Incoherent Doppler wind LiDAR (ICDL) data analysis, named ICDL-Agent, a tool-augmented LLM framework for remote sensing instrument workflows. The system maps conversational user requests to executable analysis pipelines for wind retrieval, uncertainty estimation, visualization, and higher-level diagnostics through structured planning over a registry of domain-specific tools. To improve execution reliability, the system combines schema-constrained workflow generation, shared-state reuse of intermediate scientific products, and validation with bounded repair. In addition to supporting routine LiDAR processing, the framework can generate new tools when required and adapt to related analytical tasks through domain-aware guidance and procedural documentation. We evaluate the system on multiple atmospheric wind-observation datasets in China and show that it faithfully reproduces the refined Doppler wind-retrieval pipeline, achieving representative R²/MAE values of 0.52/3.73 m/s against ERA5 and 0.80/2.31 m/s against radiosonde observations, while supporting downstream analyses such as profile comparison, climatological interpretation, and gravity-wave diagnostics. More broadly, this study demonstrates how constrained LLM orchestration can support LiDAR researchers, remote-sensing instrument teams, and geospatial analysts seeking transparent, reproducible, and automated scientific data-processing workflows. Full article

Urban street canyons exert a critical influence on local microclimates; however, the dynamics of mixed convective airflow under unsteady wind and thermal forcing remain poorly quantified. This study systematically investigates the spatiotemporal characteristics of airflow within symmetric and asymmetric street canyons through integrated long-term field measurements and complementary CFD simulations. Field data collected over 120 monitoring days at the Weishui Campus of Chang’an University were analyzed using the Levenberg–Marquardt nonlinear curve-fitting algorithm. The analysis demonstrates that sine functions accurately represent diurnal surface temperature variations during consecutive clear sky periods, whereas polynomial functions of varying orders are required to characterize meteorologically complex episodes, including cold-wave cooling and seasonal transitions. Ambient wind patterns outside the canyon were further classified into two characteristic variation modes: stepwise and gradual. Complementary unsteady RANS simulations, with wall boundary conditions derived directly from the fitted field data, reveal that canyon geometry and meteorological forcing jointly govern the evolution of airflow structures and thermal distributions across seasons. In the symmetric canyon, the flow transitions from complex multi-vortex activity in spring and summer to a more stable regime in autumn, with two well-defined counter-rotating vortices emerging during winter cold-wave events. In the asymmetric canyon, strong summer solar heating sustains a dominant leeward vortex with a strengthening secondary structure, whereas winter cold wave intrusion generates a hierarchically nested vortex system in which secondary and tertiary vortices progressively develop and detach. By coupling empirical surface temperature functions with CFD boundary conditions, this study advances the precision of predictive microclimate models and provides an evidence-based framework for optimizing street canyon geometry to enhance ventilation performance, energy efficiency, and outdoor thermal comfort. Full article

In the boreal winter of the Northern Hemisphere, a weakening of the surface Indonesian throughflow (ITF) is commonly observed. The intraseasonal mechanism of the weakening, namely, the impact of the atmospheric Madden–Julian Oscillation (MJO), is well-known and has been extensively studied. However, a significantly low volume transport of ITF (<100 m in depth) was also observed in the Makassar Strait during the traverse of tropical cyclones (TCs). The observed transport decrease is 0.31 Sv (1 Sv = 10⁶ m³/s) on average, which is ~70% of the estimated influence of the MJO. The time scale of the incurred variation is up to 30 days, comparable to the time of 20–90 days caused by the MJO. The winds in the TC circulation have a major impact on the Makassar Strait’s ITF transport reduction. Numerical experiments reveal that the reduction is due to the along-strait sea level anomaly (SLA) variability that is forced by the winds from the upstream region. The mechanism involves the propagation of coastal Kelvin waves along the Sulawesi Sea generated by the TCs and is confirmed by theoretical analysis. Based on the numerical experiments, this mechanism contributes ~40% to the total ITF transport reduction, while the large-scale guiding circulation surrounding the TCs may contribute to the remaining ITF transport reduction. These results support that TCs are also important forcing components in the intraseasonal variation in surface ITF. Full article

Offshore wind and wave energy have emerged as promising alternatives due to their abundant availability and substantial energy potential. This research explores a V-shaped semi-submersible platform designed to support both wind turbines and wave energy converters (WECs). The V-shaped configuration is selected for its ability to enhance hydrodynamic performance by reducing wave-induced loads and improving motion characteristics, while also providing increased structural stability through a wider effective footprint. In addition, the geometry creates a favourable layout for integrating WECs between the pontoons, enabling efficient wave energy capture without significantly interfering with the aerodynamic performance of the wind turbine. The study assesses the performance of different V-shaped platform configurations, ensuring their motion responses meet the operational limits required for wind turbines. It also examines whether interactions between the platform and coexisting WECs can lead to an improvement in wave energy absorption efficiency. Numerical hydrodynamic diffraction was conducted using the boundary element method in ANSYS AQWA, based on 3D potential flow theory and considering viscous damping effects, to calculate platform motion and the wave power output of WECs with a linear power take-off system. Preliminary analyses revealed that optimising the placement of WECs on a V-shaped semi-submersible can significantly improve energy generation while maintaining acceptable platform motion. This research demonstrates the additional potential of integrated wind-wave energy systems in delivering efficient and sustainable offshore energy solutions. The study also highlights the advantages of a turret mooring system for passive alignment with environmental forces, prolonging platform structure longevity and enhancing energy efficiency. Full article

The primary aim of this research is to assess the wave energy potential along the coast of Oman especially coasts facing Arabian Sea and Indian ocean by analyzing the wave energy distribution and time series of wave heights, obtained through numerical modeling over a three-years period. The study focuses on evaluating the spatial, seasonal, monthly, and directional variability of wave power and energy at multiple coastal locations. The spatial analysis reveals a clear trend of increasing wave power in the southeastern coast, toward the open Indian Ocean, where stronger wind conditions prevail. The monthly analysis indicates that mean wave power peaks during the summer months (June to August), coinciding with the southwest Indian monsoon season, which significantly enhances wave activity along the southern coastline. To simulate and analyze wave characteristics, wave data were obtained from the Global Ocean Waves Analysis and Forecast product provided by Copernicus Marine, which is based on the MFWAM (a third-generation wave model) developed by Météo-France. This dataset enabled the generation of high-resolution data on wave height, period, and direction, providing a comprehensive understanding of wave energy dynamics across the study area. Results indicate that the majority of the annual wave energy is contributed by significant wave heights ranging from 1 to 4 m, suggesting that waves in this range contribute most of the annual wave energy resource in the study area. These findings provide a characterization of the wave energy resource along the coast of Oman and identify the locations and seasons with relatively higher wave energy potential. The results can support future device-specific feasibility studies and technology selection for wave energy development in the region. Full article

The stability and functionality of offshore wind energy systems depend critically on how offshore platforms interact with the geotechnical features of the seabed. This review describes developments in five areas: (i) offshore geotechnical site investigation and strength assessment; (ii) seabed geohazard causes and deep-water mooring challenges; (iii) frameworks for seabed modeling; (iv) sediment behavior influencing anchor and mooring performance; and (v) selection of anchors based on their interactions with various soils. The review emphasizes developments in seabed assessment and modeling using field, lab, and numerical methods. It discusses how the new advances in analytical and simulation frameworks have enhanced our knowledge of anchor–mooring responses, cyclic loading behaviors, and soil–structure interactions under changing seabed conditions. The key findings reveal that: (1) cyclic loadings considerably change anchor holding capacity and evolution of seabed trenching, yet most existing design methods still use quasi-static loads; (2) site-specific data from integrated geophysical–geotechnical surveys are vital to reduce uncertainty in anchor penetration and the frictional resistance of chains; (3) geohazards, such as shallow gas, marine landslides, and seabed erosion, pose under-recognized risks to long-term anchor reliability. The lack of knowledge on the coupled, long-term evolution of the seabed–anchor–mooring line system is identified as another gap in the literature. Major gaps exist in validating the life cycle of anchor performance under real-scale storm–wave sequences for offshore geotechnical risk management in layered soils. At the end of the discussion, the current study also highlights the need for flexible, data-driven frameworks that integrate geotechnical, hydrodynamic, and structural analyses in a coupled framework to improve reliability in next-generation offshore wind energy systems. Full article

A wave-resource characterization along the coast of Vietnam was performed based on the 12-year period from 2007 to 2018, using the structured-grid Simulating WAves Nearshore (SWAN) model with a ~2.3 km spatial resolution. Extensive model validations were performed using an observed nearshore dataset and ERA5 offshore datasets. The wave parameters, significant wave height, wave period, total wave energy and omnidirectional wave power varied both spatially and temporally, with a strong seasonal pattern influenced by the northeast and southwest monsoons, with the impact of the northeast monsoon being stronger. Wave energy resources were highest in winter and lowest in summer, making the southcentral coast of Vietnam a prime location for wave energy harvesting. However, further feasibility and design studies are needed before wave farms can be established. The Gulf of Tonkin and the Gulf of Thailand had lower wave energy due to wind distribution, shadowing effects and changes in water depth. This study also noted the impact of ENSO phases on wave conditions. Year-round, El Niño generally weakened winds, leading to smaller waves and reduced wave energy, while La Niña had the opposite effect. Additionally, tropical cyclones can further amplify significant wave height, especially during both ENSO phases in July, thereby increasing wave energy. Full article

The Gulf of Mexico and the Caribbean Sea are key regions of the western Atlantic, where sea-state conditions are critical for coastal safety and offshore operations. This study analyzes wave climate trends (1981–2022) using WAVEWATCH III simulations validated against buoy observations. The Mann–Kendall test and Theil–Sen estimator were employed to quantify trends in significant wave height (Hs), energy period (Te), and wave power (P), while correlation analysis was performed to explore teleconnections with the Oceanic Niño Index (ONI), Atlantic Multidecadal Oscillation (AMO), and North Atlantic Oscillation (NAO). The results reveal basin-wide increases in mean Hs and P, characterized by pronounced spatial and seasonal heterogeneity. The most robust positive trends occur during winter and spring; in summer and fall, the weaker or negative tendencies, particularly in Te, suggest an intensification of seasonal contrasts rather than uniform change. Teleconnection analysis demonstrates that, among the climate indices considered in this study, ENSO is the primary driver of interannual wave variability in the Caribbean, particularly modulating wave power through remotely generated swell. While the NAO exerts regionally dependent control associated with storm-track modulation, the AMO plays a secondary role, affecting swell-dominated sectors. In contrast, the Gulf of Mexico shows limited sensitivity to large-scale climate modes, with wave variability largely governed by local wind–sea processes. These findings highlight the contrasting wave dynamics between these two basins, providing critical insights for coastal hazard assessments, maritime traffic along major shipping routes, oil spill management, and regional wave energy planning. Full article