As a critical regulating component in subsea Christmas tree systems, the cage-type choke valve governs the overall production efficiency and operational reliability of offshore oil and gas exploitation owing to its unique internal flow field characteristics. In accordance with the in situ operating conditions of the target oilfield, this paper performs a numerical simulation and systematic analysis on the flow field behaviors...

In suspended mussel farms, culture-layer food supply can be limited, whereas the 4–8 m subsurface layer is rich in particulate organic matter and seston. Using a representative aquaculture block off Gouqi Island, China, this study examined the hydrodynamic and transport effects of non-uniform hanging-depth layouts. The 0° uniform-depth layout was the reference. Five configurations were modeled: V-shaped, inverted V-shaped, uni...

The gravity navigation reference map is a foundational element of gravity matching-aided navigation systems, as it directly determines positioning accuracy and overall navigation performance. To improve fused gravity anomalies and reduce reliance on manually selected parameters, this study proposes an adaptive multi-scale frequency-domain reconstruction (AMFR) algorithm. Specifically, the target ocean covered by multi-source s...

Deep-sea transportation is faced with complex navigation environments, long voyages, limited emergency response resources, and interacting safety risks. Existing studies have mainly focused on individual risk factors, while the correlations and coupling effects among different factors have received insufficient attention. To identify the key risk factors affecting deep-sea transportation safety, this paper proposes a novel key...

Wave height is a critical parameter for marine hazard warning systems and the structural safety of offshore engineering. The Bohai Sea and its surrounding region is an important economic hub in northern China and serves as the maritime route for the coastal provinces of North, Northwest, and Northeast China. Therefore, the sea state in the Circum-Bohai Sea has a significant impact on the Bohai economic circle. This study analy...

LNG storage tanks are essential facilities for large-scale storage and transportation of cryogenic energy. Because of the flammable, explosive, and ultra-low-temperature characteristics of liquefied natural gas, failures in such systems may result in serious consequences for operational safety and the surrounding environment. Effective identification and prioritization of potential failure modes are therefore crucial for safe...

The suction caisson foundation has been extensively adopted for offshore wind turbine infrastructure owing to its adaptability to deep-water environments, cost-effectiveness, and convenient construction. However, such foundations suffer from relatively low horizontal and vertical bearing capacities when embedded in soft clay deposits. To address this limitation, this study proposes a novel mobile jet-reinforcement technique an...

Four new species of Chromadorea (Nematoda) from marine benthic habitats in Chinese sea areas are described and illustrated. Halichoanolaimus parvulus sp. nov. is characterized by a comparatively smaller body; amphideal fovea comprising 4.5–5 turns; spicules arched, middle portion broad, progressively attenuating distally; gubernaculum slender, comprising two detached lateral elements becoming narrower toward the distal end; a...

Cylindrical floating production storage and offloading (FPSO) units are advancing into deeper waters. Overcoming the severe challenges posed by complex deepwater environments requires the design of mooring systems that balance economic efficiency and mooring performance. This paper proposes an innovative optimization method for cylindrical FPSO mooring systems, combining the Kolmogorov–Arnold Network (KAN) with the Non-dominat...

Offshore wind power currently shows the trend of a larger wind turbine capacity and deep-sea wind farm sites. Traditional wind farms with single-type wind turbines can hardly accommodate the dual requirements of high-efficiency power generation and wake effect mitigation of wind farms. Moreover, the wind shear of fixed wind turbines and the platform motion of floating wind turbines result in insufficient adaptability to a hybr...

Short-sea Roll-on/Roll-off passenger (Ro-Pax) corridors rely on tightly interconnected port pairs. These corridors face significant challenges in recovering efficiently after major disruptions, as recovery operations are often managed separately by each port, prioritizing the clearance of local backlogs. This can lead to system-wide inefficiencies due to the operational dependencies between ports and strict navigational rules....

Submarine pipelines serve as the primary transportation infrastructure for offshore energy resources and are becoming increasingly important in modern industrial and domestic applications. A series of laboratory experiments on the dynamic seabed response of three-dimensional pipeline-seabed systems under random wave and current conditions was conducted. The results demonstrate as follows: (1) Under the combined action of rando...

Human-driven soil erosion is a signal of the widely debated “Anthropocene”. There is widespread controversy regarding the time consistency and time transgression of human-driven soil erosion in the Late Holocene. In this study, three well-dated cores, B10, B14 and W20 from west to east, spanning the past 4–6 ka from the Pearl River Estuary (PRE) shelf, southern China, were selected for elemental tests. Principal component anal...

The coupling of physical transport and phase-transfer processes represents a fundamental mechanism governing metal cycling in estuarine systems under tidal oscillations. Taking Quanzhou Bay as a model system, we conducted continuous observations and sample collection at the river channel (Q1), the turbidity maximum zone (Q2), and the outer bay channel (Q3). The metals (Al, Ti, Ba, Cu, Mn, and Zn) were measured by ICP-MS to sys...

This study investigates the combustion and emission characteristics of a marine low-speed two-stroke engine using diesel-ignited ammonia dual direct injection. Using a validated 3D CFD model, the impact of ammonia blending ratios (Ra) was systematically explored. Results indicate that the strategy of shifting energy from early diesel injection to late ammonia injection physically repositions the combustion phasing. Rather than...

To address the urgent need for high-fidelity motion data for validating navigation algorithms for Unmanned Underwater Vehicles (UUVs), this paper proposes a data generation method based on a parametric motion model. First, based on the principles of rigid body dynamics and fluid mechanics, a decoupled six-degrees-of-freedom (6-DOF) Linear and Angular Acceleration Vector (LAAV) model is constructed, establishing a dynamic mappi...

This study presents a systematic airfoil optimization framework to enhance the hydrodynamic performance of vertical-axis tidal turbines (VATTs) under low-flow conditions. The integrated methodology combines parameterized design, response surface methodology (RSM) optimization, and high-fidelity computational fluid dynamics (CFD) validation to investigate the effects of maximum thickness (Factor A), maximum thickness position (...

The phenomenon of seawater flow-freezing exists during ballast water injection and drainage in polar vessels, but the heat transfer and ice evolution behaviors under low-temperature flow conditions remain unclear. This study developed a computational model for ballast tank freezing using the volume of fluid (VOF) and enthalpy–porosity method, and constructed a scaled experimental platform for the simulation model validation. B...

Offshore pipelines are commonly used for the transportation of oil and gas from offshore to near-shore facilities in the oil and gas industry. In ocean environments, the wave- and current- induced pore-water pressure within the seabed, and the associated seabed liquefaction and local scour around pipelines, are widely recognised as among the key factors in the design of offshore pipelines. In this paper, a series of wave flume...

Amplified Arctic warming has led to a pervasive decline in sea ice cover over recent decades; yet, the pattern and governing mechanisms of sea ice concentration (SIC) state transitions remain unclear. This study reveals pronounced regional contrasts in mean-state SIC during the transition from 1979–2006 to 2007–2024, concurrent with a reduction in the sea ice extent over the same period. The September-mean sea ice in the 70° N...

As a zero-carbon energy carrier, hydrogen is playing an increasingly vital role in the decarbonization of maritime transportation. The hydrogen pressure reducing valve (PRV) is a core component of ship-borne hydrogen storage systems, directly influencing the safety, efficiency, and reliability of hydrogen-powered vessels. However, the marine environment—characterized by persistent vibrations, salt spray corrosion, and temperat...

Rigid wingsails are increasingly adopted for wind-assisted ship propulsion, with Symmetrically Cambered (SC) profiles identified as highly efficient for thrust generation. This study investigates installation layouts for multiple SC wingsails, focusing on aerodynamic interference that limits their performance. A fast 2D potential-flow panel method is employed and benchmarked against wind tunnel and 3D IDDES data. Two represent...

To address the trade-off between acoustic stealth and hydrodynamic efficiency in underwater glider design, this study proposes a coupled multi-physics parametric design framework for acoustic matching structures. Using the “Dolphin” glider as a case, geometric effects on acoustic scattering were analyzed by comparing spherical, capsule, and ellipsoidal structures under acoustic incidence. The ellipsoid configuration showed a s...

The Leizhou Peninsula, located in the northern South China Sea, features coastal waters with dual functions as both marine ranch demonstration zones and ecological protection areas. Remote sensing monitoring of Chlorophyll-a (Chl-a) concentration in this region holds strategic significance for assessing primary productivity, red tide risk, and the sustainability of the blue food economy. This study integrates in situ survey da...

The LICOM Forecast System (LFS), a global eddy-resolving ocean forecasting system, provides 1–15-day forecasts of ocean mesoscale eddies (OMEs). This study conducts a comparative analysis of the forecast results against observational data, thereby evaluating the performance of the LFS. Results show that LFS underestimates the number of eddies by ~10% and their amplitude by ~30%, while overestimating eddy radius by ~5% and velo...