Ying-Tien Lin

Gravity currents, driven by density differences, are widely observed in natural environments and engineering applications. However, their interactions with bed forms such as ripples remain insufficiently understood. In this study, three‐dimensional Large‐Eddy Simulation, validated against lock‐exchange experiments, is employed to explore the kinematic and dynamic evolution of gravity currents over rippled beds. The geometric parameters of ripples (including wave height, wavelength, and lee‐side slope angle) are found to exert significant influences on flow characteristics, mixing efficiency and sediment transport capacity through their coupled effects on flow separation, energy redistribution and bed shear stress. A key result is the identification of a dual‐layer vortex structure: ripple‐induced separation vortices in the lower layer and Kelvin‐Helmholtz (K‐H) instability vortices at the upper density interface. Ripples regulate current motion by mediating potential and kinetic energy conversion and dissipation redistribution, producing stepwise variations in potential energy and accelerating kinetic energy decay by a factor of 2.3. A steep lee‐side slope enhances the bulk entrainment coefficient by 35%–50%, while ripples systematically reduce bed shear stress by 20%–35%, leading to deposition on the lee‐side and erosion on the stoss‐side. The results also indicate that internal density‐driven forces primarily govern entrainment intensity. This study advances the theoretical understanding of coupled gravity current‐ripple interactions and provides insights for practical applications in reservoir sediment management and estuarine regulation.

Tsunami-induced scour around coastal embankments and nearshore structures is a primary cause of structural instability and failure. However, the hydrodynamic mechanisms by which coastal vegetation mitigates this scour remain insufficiently understood. This study employs three-dimensional numerical simulations to investigate the influence of rigid and flexible vegetation on overflow-induced scour downstream of embankments and local scour around structures under tsunami-like inundation. The simulations were conducted using Ansys Fluent 2021R2, utilizing the Volume of Fluid (VOF) method to capture the free surface and the RNG k − ε turbulence model within the Reynolds-averaged Navier–Stokes (RANS) framework. Computational geometries were reconstructed from laboratory experiments, and the model’s reliability was validated against measured water surface profiles. The results demonstrated that vegetation significantly alters flow dynamics, velocity distributions, vortex structures, and both the magnitude and patterns of bed shear stress within scour holes. Specifically, in overflow-induced scour, vegetation suppresses scour intensity by inducing backwater effects, enhancing momentum diffusion, attenuating flow impingement on the bed, and reducing peak bed shear stress. Conversely, for local scour around structures, vegetation increases upstream water depth while intensifying downstream wake vortices, leading to scour hole elongation—particularly under dense and tall vegetation. These findings offer novel insights into the hydrodynamics of vegetation-induced scour mitigation and provide guidelines for optimizing vegetation configurations to enhance the tsunami resilience of coastal infrastructure.

This study employed large eddy simulation coupled with a mixture model to investigate downslope gravity currents (GCs) flowing through a cylindrical pile in the two-layer stratified environment. Sixteen simulation cases were performed, covering a range of ambient stratified strength and pile submergence ratios. Results demonstrate that ambient stratification determines the fate of GCs head upon impinging the pycnocline, leading to underflow-dominated, interflow-dominated, or interflow morphological patterns with increasing ambient stratified strength. The pile disrupts the coherence of GCs head, promoting dilution of the concentration core, and enhancing the vertical redistribution of dense fluid from the underflow into interflow. The vortex-strain structures of GCs inherently transition from lateral bands to longitudinal stripes but are reorganized by the ambient stratification into vortex-stripes intensified, weakened, or suppressed regimes and also adjusted by the pile into a strain-dominated pattern, particularly upstream of the emergent configuration. Acting as a localized energy sink, the pile shortens the dominance period of kinetic energy and enhances the dissipated energy of GCs. The potential-kinetic energy reversal is modulated by internal waves (IWs): locked IWs facilitate bidirectional energy exchange with GCs under weak ambient stratification, whereas launched IWs cause unidirectional energy loss of GCs under moderate and strong ambient stratification. Irreversible mixing quantified by the background potential energy is maximized for the case with a shallow-submerged pile configuration, which optimally balances wake production and wall shear-induced turbulence. The pile reduces the peak friction velocity at GCs head but enhances it downstream via wake effects, with these influences being moderated by ambient stratification. This work provides critical insight into the coupled dynamics of GCs with stratified environments and pile obstacles, offering a valuable foundation for assessing seabed scouring potential and optimizing the design of offshore infrastructures.

Flow dynamics in strongly curved channels with submerged vegetation play a crucial role in riverine ecological processes and morphodynamics, yet the combined effects of sharp curvature and rigid submerged vegetation remain inadequately understood. This study presents a comprehensive experimental investigation into the influence of rigid submerged vegetation on the flow characteristics within a 180° strongly curved channel. Laboratory experiments were conducted in a U-shaped flume with varying vegetation configurations (fully vegetated, convex bank only, and concave bank only) and two vegetation heights (5 cm and 10 cm). The density of vegetation ϕ was 2.235%. All experimental configurations exhibited fully turbulent flow conditions (R_e > 60,000) and subcritical flow regimes (F_r < 1), ensuring gravitational dominance and absence of jet flow phenomena. An acoustic Doppler velocimeter (ADV) was employed to capture high-frequency, three-dimensional velocity data across five characteristic cross-sections (0°, 45°, 90°, 135°, 180°). Detailed analyses were performed on the longitudinal and transverse velocity distributions, cross-stream circulation, turbulent kinetic energy (TKE), power spectral density, turbulent bursting, and Reynolds stresses. The results demonstrate that submerged vegetation fundamentally alters the flow structure by increasing flow resistance, modifying the velocity inflection points, and reshaping turbulence characteristics. Vegetation height was found to delay the manifestation of curvature-induced effects, with taller vegetation shifting the maximum longitudinal velocity to the vegetation canopy top further downstream compared to shorter vegetation. The presence and distribution of vegetation significantly impacted secondary flow patterns, altering the direction of cross-stream circulation in fully vegetated regions. TKE peaked near the vegetation canopy, and its vertical distribution was strongly influenced by the bend, causing the maximum TKE to descend to the mid-canopy level. Spectral analysis revealed an altered energy cascade in vegetated regions and interfaces, with a steeper dissipation rate. Turbulent bursting events showed a more balanced contribution among quadrants with higher vegetation density. Furthermore, Reynolds stress analysis highlighted intensified momentum transport at the vegetation–non-vegetation interface, which was further amplified by the channel curvature, particularly when vegetation was located on the concave bank. These findings provide valuable insights into the complex hydrodynamics of vegetated meandering channels, contributing to improved river management, ecological restoration strategies, and predictive modeling.

This study uses the Contingent Valuation Method (CVM), a quantitative approach, with interval regression and Ordinary Least Squares (OLS) models to assess the non-use values of the Zhongjieshan and Liuheng Marine Ranches. The aim of the study is to quantify the monetary value of non-market benefits, examine socioeconomic influences on stakeholders’ Willingness to Pay (WTP), and provide a basis for ecological compensation mechanisms. Zhongjieshan’s annual non-use value is estimated at 28.99–30.81 million CNY (Chinese Yuan) (median WTP 74.33–78.99 CNY per person), while Liuheng’s value is higher at 108–111 million CNY (median WTP 150.20–153.89 CNY per person), suggesting greater ecological and recreational potential at Liuheng. The results show robust model performance, with minimal WTP differences. WTP for Liuheng is primarily influenced by income and environmental awareness, while Zhongjieshan shows a distance-decay effect. Visitor profiles reveal that Zhongjieshan attracts younger, moderately educated visitors, while Liuheng draws more highly educated, economically diverse groups. These findings suggest that Zhongjieshan should prioritize community-based co-management, while Liuheng should focus on high-quality, technology-driven ecological leisure development. The study also emphasizes the need for targeted awareness campaigns and supports the creation of diversified ecological compensation mechanisms beyond government funding.

The Changjiang estuary–Hangzhou Bay region is a critical zone of land–sea interaction, where Total Suspended Matter (TSM) dynamics significantly influence coastal ecology and engineering. While previous studies have examined individual factors affecting TSM variability, the synergistic effects of “tide–monsoon–current” interactions and the actual pathways of turbid plume transport remain poorly understood. Using GOCI satellite data, in situ buoy measurements, and voyage data from 2020, this study applied Data Interpolating Empirical Orthogonal Functions (DINEOFs) and comprehensive spatio-temporal analysis to reconstruct continuous high-resolution TSM fields and elucidate multi-factor controls on TSM dynamics. Based on this high-resolution dataset of TSM, we found that, during the dry season, elevated TSM concentrations are primarily driven by wind–tide resuspension and transport under the comprehensive forcing of the Jiangsu Alongshore Current (JAC), the Yellow Sea Warm Current (YSWC), and wind–tide-induced flows. Contrary to the conventional understanding, the Jiangsu-origin surface TSM can transport to the outer sea without supplementing the TSM in the Turbidity Maximum Zone (TMZ). The YSWC in autumn can cause either low C_TSM gradients or high gradients nearshore depending on whether it is carrying Korean coastal turbid water or not. During the wet season, stratification induced by the Changjiang freshwater discharge suppresses wind–tide resuspension, reducing TSM concentrations in the TMZ and the Qidong water. However, the Changjiang freshwater combined with the Taiwan Warm Current (TWC) dilutes surface TSM in Hangzhou Bay, where the two water masses meet on the 10 m isobath. These insights into factor interactions and TSM plume pathways provide a scientific basis for improved environmental monitoring and coastal management.

Coral reefs face severe threats from bleaching and degradation driven by natural and anthropogenic factors, such as global warming and ocean acidification. Internal solitary waves (ISWs) breaking in reef-lagoon systems play a critical role in modulating coral reef ecosystems by inducing upwelling currents that deliver cold, nutrient-rich deep water to reefs, potentially mitigating thermal stress and coral bleaching. However, the hydrodynamic processes governing ISW-driven upwelling and their ecological implications remain underexplored. This study advances prior research by using synchronized particle image velocimetry and planar laser-induced fluorescence in laboratory experiments to measure high-resolution velocity and density fields over realistic reef-lagoon topographies. These measurements enable precise quantification of upwelling dynamics, including maximum run-up height, upwelling velocity, and cold-water intrusion extent and duration. We also analyze bottom Reynolds stress and turbulent burst events via quadrant analysis to elucidate mechanisms of turbulent transport, sediment resuspension, and material exchange under varying coral roughness conditions. Our findings reveal that higher ISW amplitudes enhance upwelling intensity, promoting cold-water propagation across the reef flat, while rough coral surfaces play a dual role: they impede upwelling spread but enhance near-bed turbulence and material exchange. By linking hydrodynamic metrics, such as run-up speed and upwelling flux to ecological proxies like nutrient delivery, sediment deposition, and thermal stress relief, this study provides novel insight into physical–ecological coupling in reef systems. These results deepen our mechanistic understanding of ISW-driven processes and offer a scientific foundation for developing targeted coral reef conservation and restoration strategies.

The digital economy has emerged as a transformative force, creating new opportunities for sustainable development, especially within the marine fisheries sector. This study examines the impact of the digital economy on the green total factor productivity (GTFP) of fisheries in China’s coastal regions from 2011 to 2022. Using panel data from 11 coastal provinces, we employ the Slack-Based Measure (SBM) model and the Global Malmquist–Luenberger (GML) index to assess GTFP and analyze the effects of digital economic development. Our findings indicate the following: (1) the digital economy significantly enhances fishery GTFP, improving both resource efficiency and environmental sustainability; (2) the impact varies across regions, reflecting notable regional heterogeneity in digital infrastructure and adoption; and (3) a threshold effect exists, whereby the influence of the digital economy on GTFP varies depending on the level of digital economic development. This research underscores the dual role of digital technologies in boosting fisheries’ economic productivity while promoting greener, more sustainable practices. This study provides valuable insights for policymakers aiming to integrate digital transformation into the sustainable development of marine fisheries.

In recent decades, Offshore Wind Turbines (OWTs) have become crucial to the clean energy transition, yet they face significant safety challenges due to harsh marine conditions. Key issues include blade damage, material corrosion, and structural degradation, necessitating advanced materials and real-time monitoring systems for enhanced reliability. Carbon fiber has emerged as a preferred material for turbine blades due to its strength-to-weight ratio, although its high cost remains a barrier. Structural Health Monitoring Systems (SHMS) play a vital role in detecting potential faults through real-time data on structural responses and environmental conditions. Effective monitoring approaches include vibration analysis and acoustic emission detection, which facilitate early identification of anomalies. Additionally, robust data transmission technologies are essential for SHMS effectiveness. This paper reviews material design strategies, data acquisition methods, and safety assessment techniques for OWTs, addressing current challenges and future directions in the field.