bluuebunny/crossref_metadata_2025 huggingface dataset:
A Power Estimation Method for Hybrid Contra-Rotating Propeller Propulsion System
Authors: Wakabayashi Tomoki , Katsui Tokihiro
Published: August 2024

Due to the recent high level of environmental regulations, there has been increasing of the attention to Energy Saving technics. One of the developing energy saving technics is the Hybrid Contra-Rotating Propeller (HCRP) propulsion system. To date HCRP propulsion system has been applied to limited numbers of ships which has special order like domestic liners in Japan [1][2]. However, HCRP is promising system to be built in major ships like bulk carriers, tankers or container ship which are operated around the world in the future because of its high propulsion efficiency. One practical subject of HCRP is a power estimation method for this complex propulsion system. In these decades, several research projects treated HCRP. TRIPOD project [3][4] treated wide range of topics, which included tank test method, numerical analysis and concept validation adopting HCRP to an existing cargo ship. The mainstream of a power estimation method for HCRP is the way how a total force of two propeller acting as a CRP are treated as pseudo one propeller [5][6]. The feature of HCRP is that two propellers can act independently. It means there exists infinity numbers of rotational speed rate of two propellers and a propulsion performance and a maneuvering performance depends on it [5]. If we use a propeller open water characteristics of a CRP as pseudo one propeller, we can estimate only very limited conditions which are tested in a towing tank. This paper shows the newly developed powering method which use characteristics of individual two propellers and a mutual interaction of propellers acting as a CRP. This method can estimate every condition of revolution rate which made with a feature of HCRP propulsion system. The scope of this research is constructing a tank test method and a powering method and reviewing them with surveying of an actual ship performance.
Research on the Application of Gyrostabilizer in the Motion Control of Floating Offshore Wind Turbine
Authors: Zhang Yu , Yang Xiaolong , Deng Shi , Yang Liang , Zhang Fafu
Published: August 2024

Usually, the floating offshore wind turbine (FOWTs) are linked to the seabed by catenary mooring system, and its motion amplitude is significant under the action of wind and wave. If the pitch angle of FOWTs is too large, the efficiency of power generation will be reduced. Thus, it is necessary to study how to decrease the motion response amplitude of FOWTs. In this paper, a time domain coupled numerical simulation program for FOWTs is developed using the vector form intrinsic finite element (VFIFE) method. The program is composed of the aerodynamics module, hydrodynamics module, dynamic mooring module and core solver module (central difference scheme). In program framework, the partitioned bidirectional weak coupled strategy is used to exchange data between each module, and finally the unified coupled calculation in time domain is realized. Based on the established FOWT model, a gyrostabilizer is proposed to control the motion of the FOWT. Firstly, the coupled governing equation of motion of the FOWT and the gyrostabilizer is derived theoretically, then the control performance of the gyrostabilizer on the motion response of the FOWT is evaluated. The simulation results show that the gyrostabilizer to reduce the motion amplitude of the platform is significantly, but has little effect on reducing the mooring tension.
Offshore Infrastructure Disaster Ontology Construction Based on Feature Engineering
Authors: Li Yi-Lin , Loh Ching Wah , Li Sunwei , Hu Zhen-Zhong
Published: August 2024

In recent years, the South China Sea has faced a surge in marine meteorological disasters, causing substantial financial impacts across Asia and threatening the livelihoods of coastal communities. Despite earnest disaster prevention and mitigation efforts, formidable challenges persist in offshore engineering.

This study conducts a comprehensive analysis of potential transformations, structural failures, and collapses in offshore infrastructure under specific marine and meteorological conditions. It aims to deepen the understanding of the complex and dynamic mechanisms underlying marine disasters. To achieve this, a bottom-up multidimensional feature extraction approach is employed from historical data, considering temporal, spatial, and textual dimensions. Parameters such as spatial-temporal data, physical characteristics, geographical locations, meteorological conditions, and marine environmental factors are meticulously considered. The identified multidimensional features are then analyzed and integrated into an ontology representation, describing the intricate relationship between properties and marine infrastructure disasters. This comprehensive disaster ontology is structured using ontological and feature engineering, encompassing both ontology and epistemological data layers.

In conclusion, this study contributes to improving disaster preparedness and response strategies in the South China Sea and similar regions. By addressing offshore engineering intricacies during marine disasters, it offers valuable insights for more effective risk management and mitigation measures in the future.
Numerical Validation of Second-Order Wave Drift Forces Calculation for Floating Structures
Authors: Ramachandran Krishnavelu , Somayajula Abhilash
Published: August 2024

Accurate estimation of second-order wave drift forces is imperative for predicting the responses of offshore structures, mooring systems, and vessel motions in ocean waves, especially in adverse wave conditions. These wave drift forces are derived from non-linear wave potential effects. Precise estimation of wave drift forces is vital for the design and analysis of offshore platforms, moored structures, and ships operating in challenging wave conditions to ensure safety, stability, fatigue resistance, and long-term structural integrity. This study presents a comprehensive derivation and implementation of second-order wave drift forces for an in-house numerical tool, Hydrodynamic Response Analysis (HydRA). The HydRA program has been developed using a Green function-based 3-D potential flow theory-based panel method code. The numerical investigation focuses on the Benchmark KRISO Container ship (KCS) for this study. The HydRA tool accurately calculates wave drift forces at zero speed case. This numerical simulation tool is capable of accurately assessing rigid body motions and loads in all six degrees of freedom. Validation of the second-order drift forces at zero speed will be conducted against the MDLHydroD and WAMIT programs. This research contributes to the advancement of understanding and predicting second-order wave drift forces, offering valuable insights into the field of fluid-structure interaction and hydrodynamics analysis.
Simplified Fatigue Load Cases Assessment in Tension Leg Platform Floating Offshore Wind Structural Analysis
Authors: Meng Xun , Wang Zhaoyue , Lu Qing , Rawlinson-Smith Robert , Greaves Deborah , Wang Wenping , Fu Qiang
Published: August 2024

Floating offshore wind turbines (FOWTs) are considered a promising solution for wind energy harvesting in deep water, and optimized designs will bring the costs of FOWTs down and increase profitability. However, verifying the fatigue lifetime for the FOWT optimization model requires a large number of loading situations with computationally expensive response analyses. Fatigue damage calculated for six sets of simplified fatigue load cases (FLCs), with different combinations of turbine loads and wave loads, were compared using time-domain simulations in combination with Miner’s Rule, which allows for the identification of optimal parameters in a lifetime perspective, and fair comparisons between the different contribution from loading of the wind turbine and environmental waves. The chosen FLC for fatigue damage verification of the floater scantling model in the present work is applicable for the preliminary design of Tension Leg Platform (TLP) FOWTs, where they can provide a starting design for the detailed design phases. The methodologies can be further extended to account for different FOWT concepts, additional design parameters, and other load combination cases.
Simulating Waves at the Beaches of the Ericeira World Surfing Reserve
Authors: Gomes Tiago , Bihs Hans , Wang Widar , Vaz Guilherme
Published: August 2024

In an attempt to develop a forecast model for surfing waves, the fully nonlinear potential flow code REEF3D::FNPF is applied in the Ericeira World Surfing Reserve. Open-source bathymetry datasets, available in EMODNet, are used to define the domain. After a grid refinement study, simulations with irregular waves are performed, with varying heading directions. These waves are defined through the means of a JONSWAP spectrum, to model the effect of incoming swell. The wave spectrum and several significant wave height definitions are used to assess the impact that swell direction has on the waves of each beach. Moreover, the breaking wave detection algorithm incorporated in REEF3D::FNPF is combined with the Iribarren number to classify the type of breaking wave. This way, the model is able to predict the spatial location of plunging waves, one of the most appropriate types for surfing. Overall, North-South swell conditions produce the least amount of breaking waves, yet some of the beaches in the reserve still present potential for surf given the selected wave conditions.
Experimental Study on Hydrodynamic Damping of an Oscillating Cylinder Under Small Keulegan-Carpenter Numbers
Authors: Dong Guanning , Cheng Liang , Ren Chengjiao , Tong Feifei
Published: August 2024

This paper presents an experimental study on the hydrodynamic drag and inertia coefficients, which were decomposed from the total measured force through Morison equation, of an oscillating cylinder in quiescent water under small Keulegan-Carpenter number (K) conditions. The objective of this study is to address a discrepancy demonstrated by Ren et al. (J. Fluid Mech., vol. 913, 2021, A36) where drag coefficients determined in experiments under small K conditions deviated significantly from those of the analytical solution and direct numerical simulations (DNS). Two experimental inaccuracies responsible for this deviation are identified. The first one is associated with the additional inertia force induced by the oscillating load cell, leading to an overestimation of the inertia coefficient. The second is related to the non-synchronized measurements of signals by multiple sensors. A tiny phase difference between the force (recorded by the load cells) and motion (recorded by the accelerometer) signals is demonstrated to cause significant change in the drag coefficient. Finally, a post-processing strategy is proposed in this study to reduce these inaccuracies. After implementing this strategy, the calculated force coefficients agree well with those obtained from the analytical solutions and DNS.
Application of Irregular Frequency Removal Feature in Capytaine for Anode Cage Installation Over a Monopile Wind Turbine
Authors: Herdayanditya Ivandito , Baert Benjamin , Stempinski Florian , Rauwoens Pieter , Lataire Evert
Published: August 2024

Marine operations in offshore wind farms require hydrodynamic information to perform the operability analysis. An anode cage installation over a monopile wind turbine, an example of marine operations, needs the vessel hydrodynamic parameters and the flow field information around the monopile to perform time domain analysis to estimate the sling tensions during the installation. Capytaine, an open-source Linearized Potential Flow (LPF) solver, is utilized to compute the hydrodynamic parameters and the flow field around the monopile. However, the original version of Capytaine suffers from the irregular frequency problem. An existing method of applying a lid on the free surface is applied to remove this problem. The lid also appears to remove the oscillation of the hydrodynamic solutions in the high frequency. The results are validated by a well-established LPF solver, ANSYS AQWA. Afterward, two numerical model configurations of only the vessel and the vessel with the monopile are investigated where it is seen that the flow field around the monopile is sensitive to the multibody modeling. Therefore, the anode cage installation stages that do not require flow information (e.g. lifting in the air) can be done in single-body simulation, while multibody is inevitable if the flow field starts to play a significant role (e.g. lifting in the splash zone).
Probabilistic Approach of Lateral Buckling Analyses for HPHT Pipelines With Buckle Mitigators
Authors: Bai Qiang , Moura Endryws , Primieri Rodrigo , Brunner Mark , Wang Lijuan
Published: August 2024

This paper presents a probabilistic approach for lateral buckling analysis based on a global FE model via a case study of a 5km long subsea flowline with sleeper mitigators on an undulating seabed. In the case study, axial/lateral pipe-soil interaction (PSI), pipe/sleeper friction factors, and horizontal out-of-straightness (OOS) of flowline at seabed and sleepers are defined as stochastic parameters, while other parameters, including flowline as-laid vertical OOS, pipe section and operating parameters, are defined as deterministic variables. First, the response surfaces for lateral buckling of the full-length flowline due to the stochastic parameters are created through FE analyses based on a load case matrix selected by the Design of Experiments approach. Then, Monte Carlo simulations based on the response surfaces are performed to obtain the distributions of lateral buckling responses, including parameters such as the limit-states for post-buckle, buckle amplitudes, walking speed or end pile loads, rogue and engineered buckle locations. Lastly, the probability distributions of the limit-state unity checks are compared with the target failure probabilities.

This probabilistic approach will require more simulation time compared to the deterministic approach but can provide more detailed probability ranges for the lateral buckling responses and save the project on total cost. This approach can be used to assess the reliability of lateral buckling responses during the detailed design phase of subsea pipelines susceptible to lateral buckling.
Effects of Varying Breadth Ratios on Fluid Resonance in a Narrow Gap Formed Between Two Boxes in Close Proximity
Authors: Gong Shukai , Gao Junliang , Song Zhiwei
Published: August 2024

Fluid resonance within a narrow gap between two boxes in close proximity is investigated based on the open-source CFD package, OpenFOAM. The upstream box keeps fixed but with varying breadths, the downstream box heaves freely under wave actions and has a constant breadth. For comparison, a two-stationary box system is also considered. The aims of this work are to study the effects of the breadth ratio of the two boxes, i.e., the ratio of the breadth of the upstream box to that of the downstream box, on the hydrodynamics of the resonant fluid inside the gap and the motion of the downstream box. It has been found that the amplification of resonant wave height in the gap decreases significantly with the increase of the breadth ratio and the incident wave height, while the fluid resonant frequency seems insensitive to the breadth ratio. Compared with the two-stationary case, the fluid resonant frequency for the two-box system with the downstream box heaving freely shifts towards higher values. Furthermore, for the cases with a smaller incident wave height or a larger breadth ratio, there usually exists a local peak in the curve of the heave displacement versus the incident wave frequency. A larger breadth ratio leads to a smaller heave motion of the downstream box.
Short-Term Extreme Value Prediction for the Dynamical Responses of a Semi-Submersible Platform in Harsh Environment
Authors: He Lin , Chai Wei , Gu Jian , Sinsabvarodom Chana , Chen Junfeng , Shi Wei
Published: August 2024

Deep-sea platforms play a crucial role in the exploration of oil and gas resources. Ensuring the safety of semi-submersible platforms in challenging marine environments is of paramount importance. Consequently, this research is dedicated to the estimation of extreme values for motion responses and the mooring loads of a deep-water semisubmersible platform in the South China Sea. Specifically, numerical simulations are carried out by using commercial software, and the accuracy of the numerical results is verified with experimental data. To assess the safety of mooring systems with multipoint configurations under extreme sea conditions, the environmental contour method (ECM) is applied to select the most severe sea state. For a given sea state, short-term extreme value analysis is performed by using the average conditional exceedance rate (ACER) method. Finally, an analysis of the extreme value predictions is performed in compliance with relevant regulations to evaluate the safety of the mooring system.
On the Applicability of Risk-Based Methods to Optimize Inspection Costs With Focus on a Hydrogen-Fueled Fishing Vessel
Authors: Giannini Leonardo , Salzano Ernesto , Ustolin Federico , Paltrinieri Nicola
Published: August 2024

In an era marked by a growing effort towards environmental sustainability, the development of the hydrogen value chain is crucial for the transformation of the energy landscape. From road transport to aviation and maritime applications, numerous investments and ongoing projects aim at implementing clean hydrogen solutions to reshape entire industries. The spread of hydrogen technologies, however, comes with a rising demand for specific and standardized inspection plans and maintenance activities that are suitable for equipment operating in hydrogen environments. For this reason, a number of critical challenges do emerge. Some main issues of such innovative and environmentally compatible alternatives (i.e., hydrogen-fed fuel cells and hydrogen combustion engines) involve in fact the lack of operational experience and the inexistence of tailored standards and guidelines specifically conceived for hydrogen systems. This may result in a tendency to implement over conservative risk-reducing measures, thus leading to continuous inspection activities and unsustainable associated costs. In fact, an over-conservative risk threshold may imply economic burdens and a competitiveness loss for hydrogen technologies, potentially resulting in the inhibition of their market penetration potential. The current work delves into this problem by addressing the main steps of a cost-benefit analysis based on risk-informed inspection strategies [1] and using a hydrogen-fueled fishing vessel as a practical example, highlighting hazardous scenarios involving the storage system, the costs associated with a hydrogen unwanted release and the measures — inspection and preventive maintenance — that aim at minimizing its likelihood. Through this lens, this paper outlines potential strategies to achieve an optimization of costs and minimization of risk by optimally scheduling inspection procedures, with the idea of supporting the shift towards sustainable energy solutions.
Investigation on Semi-Analytical Solution of Diffracted Wave Field Caused by a Bottom-Mounted Block
Authors: Wang Zerun , Feng Aichun
Published: August 2024

A number of marine structures can be represented by bottom-mounted blocks when analyzing the diffracted wave field. In this paper, the method of domain decomposition and separation of variables are used to derive the velocity potential of diffracted wave field by a bottom-mounted block in a semi-infinite tank. The semi-analytical solutions are compared with the free surface elevation RAO of a block in open waters obtained by commercial software WAMIT, and good agreement is reached. The present solution can be applied as benchmark to verify the results obtained by other numerical methods.
Employing an Asymmetrical Anchoring Solution for Rigid Flowline Riser System Adopting Single Torpedo Piles
Authors: Grevet Simon , Bianco Bruno , Maior Steve , Volpi Eduardo , Genzani Rachel , Solano Rafael F. , Pavone Diego
Published: August 2024

This paper introduces the technical pipeline anchoring solution deployed for rigid flowlines of the Buzios field.

Based on the usual combination of an anchoring pile, a chain and an In-Line Anchor mounted as part of a rigid flowline, this solution stands out on two accounts: the use of torpedo piles, and an asymmetrical configuration with a single fixed point.

This paper addresses the technical challenges associated to it in terms of flowline design in order to guarantee the robustness of the system.

Chain slack management stood as the most critical challenge, due to the inherent extra chain length needed to connect the torpedo pile to the ILA, with the relative angle between the chain and the flowline coming second.

Although one might surmise the design to be governed by the extreme values of these parameters, the analyses carried out demonstrated specific limit states to be occasionally maximized at intermediate values instead, thus requiring more scrutiny and precision in the load cases matrices.

This paper also discusses the importance of properly implementing and modelling the ILA in global flowline models.

Lastly, the benefits of this new solution are discussed, in terms of how it improved installation requirements and overall project readiness.
Numerical Investigation of Vortex-Induced Motions (VIM) on a Semi-Submersible Floating Offshore Wind Turbine
Authors: Yin Decao , Passano Elizabeth , Berthelsen Petter Andreas
Published: August 2024

Vortex-induced motions (VIM) adversely affects the structural integrity and performance of floating offshore wind turbines (FOWT). These motions can impart extreme loads and fatigue stresses on the mooring lines, cables, and other vital substructures, including the nacelle. While semi-submersible platforms with multiple columns are susceptible to VIM, the comprehensive understanding of this phenomenon remains elusive. Historically, model testing has been the primary approach, primarily focused on oil and gas platforms, thereby introducing inherent scaling effects, including Reynolds number effects.

This paper introduces a novel numerical investigation into the VIM behavior of a semi-submersible floater named ‘INO WINDMOOR’. Employing semi-empirical time-domain vortex shedding loads on the platform’s columns, we rigorously explored the VIM responses across a spectrum of current speeds and incident angles.

Our study conclusively demonstrates the presence of VIM in the operational environment of FOWT and underscores the paramount importance of integrating VIM considerations into the design process. This research contributes significantly to advancing our comprehension of VIM effects on semi-submersible FOWT systems, ultimately informing safer and more efficient offshore wind energy solutions.
Utilization of Micro-Annuli Characterization Techniques on Wellbore Samples; Visualization and Permeability Test
Authors: Opedal Nils , Feneuil Blandine , Larsen Idar , Taghipour Ali , Wiggen Even , Skorpa Ragnhild
Published: August 2024

Cement is placed in the annulus between the casing(s) and the surrounding formation rock to ensure no migration of fluids form through the barrier. However, during the operational lifetime of a well changes of pressure and / or temperature lead to extra stresses inside the casing. These stresses can lead to expansions and / or contraction of the casing, with subsequent extra stresses on the surrounding cement sheath. These stresses can result in debonding between the materials or the formation of fractures along the material interfaces or through the material itself. Assessment of the cement is crucial in order to sufficiently manage the integrity of the well. The ideal assessment should consist of 1) a proper visualization of both the sample and fracture geometry, 2) comparison with logging and 3) permeability measurements of the sample/specimen.

This paper describes a study where we have used a unique downscale wellbore cell to mimic the behavior of casing-cement-rock specimens. The specimen was exposed to inner casing pressure cyclic changes and the effect of these cyclic changes are measured using pulse-echo and pitch-catch ultrasonic tool to assess the cement-casing debonding. Furthermore, the specimens are visualized using X-ray CT, and finally the changes in permeability are tested.
An Analysis Method for Fatigue Dynamic Reliability of Ship Structure
Authors: Zhen Chunbo , Zhou Qingwan , Zhang Runze , Xing Shizhu
Published: August 2024

In this paper, the dynamic fatigue reliability analysis method is used to evaluate the fatigue damage of ship structure. Firstly, the limit state equation is established according to the stress strength interference method of fatigue dynamic reliability. Then, according to the characteristics of external load on ship structure, the concept of equivalent stress range and its calculation method for the whole service life of ship structure are given. The time-varying degradation model of fatigue strength is determined according to the characteristics of structural materials, and then a dynamic fatigue reliability analysis method of ship structure is proposed. Finally, taking a bulk carrier as an example, the equivalent stress range of typical hot spots is determined by the direct calculation method of spectral analysis, the structural dynamic reliability and failure probability are calculated, and the fatigue reliability characteristics of hot spots are given. The example results show that, the parts with large fatigue damage have high fatigue failure probability in the early stage of ship service.
Flow-Induced Vibrations of a Square Cylinder With Rigid Upstream Splitter Plate
Authors: Bhatt Dhyey , Nandipeta Vijay Krishna , Joshi Vaibhav
Published: August 2024

Flow across geometries of non-circular cross-section is encountered in many applications such as buildings and offshore semi-submersible columns. In particular, columns of semi-submersibles with square cross-section are subjected to complex ocean currents which could lead to flow-induced vibrations. The possibilities of resonance-type response (vortex-induced vibrations) along with motion-induced instability-type response (galloping) has been observed for such cases, which could be detrimental to the structural integrity. Therefore, it is imperative to control these unwanted oscillations. One possibility is the introduction of a rigid splitter plate on the upstream side of the structure, which has been found to suppress vibrations in case of a circular cross-section. The current study aims to explore this effect by considering a splitter plate of length equal to the side of a square cylinder. A two-dimensional stabilized Petrov-Galerkin variational formulation is utilized to solve the Navier-Stokes equations on an arbitrary Lagrangian-Eulerian moving mesh framework. The rigid cylinder is elastically mounted on a spring and is free to oscillate in the cross-flow direction. The gap between the cylinder and the trailing edge of the splitter plate is varied in the range of 0 to 3D, with D being the side of the cylinder. The study is conducted at Reynolds number of 200 and a mass ratio of 10 in which the galloping-type of instabilities are expected. The results may pave the way for possible passive suppression of flow-induced vibrations for marine structures with square cross-section.
Invasive Marine Species and the Decommissioning of Offshore Oil and Gas Installations: Challenges and Sustainable Management
Authors: de Lima Fasca Hanna , Salomon Paulo Sergio , Costa José Lino , Carneiro Paulo Roberto F. , Couto Thiago Correia , Cordeiro Marcelle Cândido , de Souza Marcelo Igor Lourenço
Published: August 2024

Oil and natural gas (O&G) industries are significant players in the global economy. The lifecycle of O&G installations has reached an age at which many must be decommissioned. Biological invasion is the process by which a species is introduced into a new geographic region caused by the interference of human activities. Scientists and policymakers have identified invasive species as a significant threat to marine ecosystems affecting biodiversity. Today, O&G habitats and invasive species represent only 9% of biodiversity studies relative this field. We provide an overview of invasive species linked to decommissioning operations worldwide and emphasize the Brazilian context to support the sustainable management of decommissioning operations. O&G facilities have contributed to the spread of invasive species, such as the bryozoan Watersipora subatra in Santa Barbara Channel (California) and the sun coral species Tubastraea coccínea and T. tagusensis in the Gulf of Mexico and the Brazilian coast. The Brazilian case highlighted in this study shows several platforms to be decommissioning, and the presence of sun coral along the coast which poses biodiversity in risk. Measures must be taken to control the sun coral dissemination and some recommendations were made in this study to support futures studies.
Investigation of Water Surface Fluctuation and Flow Velocity Inside a Floating Closed Flexible Membrane Fish Cage Under Forced Oscillation Experiment
Authors: Dong Shuchuang , Zhou Jinxin , Han Yunzhou , Bai Shenyi , Kitazawa Daisuke
Published: August 2024

A floating closed fish cage is required for environmental issues such as SDGs (Sustainable Development Goals). The flexible membrane fish cage generally exhibits a reduced motion response. However, the sloshing-induced fluctuations in the internal water remain unclear, despite their critical importance for fish welfare and waste and bait removal in closed fish cages. In the present study, we investigated the water flow velocity, water surface level changes, and fish school behavior in a closed flexible fish cage by forced oscillation experiments. The target fish cage is circular, representing a real fish cage with dimensions of 25 m in diameter, a sheet height of 12.5 m, and a free board of 2.5 m. A 1/50 scale model was designed and attached to a forced oscillation device. To analyze the internal water movement in waves, we reproduced pitch motion using the forced oscillation device. We measured pitching moment, and flow velocity at a depth of 6 cm and 12 cm below water surface, and water level fluctuations on both sides and in the center of the fish cage. 23 zebrafish Danio rerio were placed inside the fish cage, and their behavioral characteristics were observed.

As a result, the pitching moment exhibited an increasing trend with increasing pitch oscillation amplitude, peaking at a pitch oscillation period of 1.05 s. Simultaneously, the internal water surface exhibited pronounced and highly nonlinear fluctuations at the period of 1.05 s. The internal water level at the sides followed a similar trend in both magnitude and change tendency, showing symmetry. The water level measured at the center was significantly lower than that on the sides. Within the measurement range, the flow velocity increased as the oscillation amplitude increased, reaching a maximum of 10.8 cm/s. Despite the complexity of zebrafish fish school behavior under forced oscillation conditions, the fish tended to aggregate in the deeper parts of the net cage. Furthermore, the presence of fish had minimal impact on the pitching moment results. Overall, these findings are expected to provide references for the design and operation of the closed fish cage system.
Study on Wear and Breakage Estimations for Single Point Mooring Chain of Offshore Floating Platform
Authors: Katayama Toru , Hasunuma Ryoya , Yamamoto Yusuke , Taniguchi Tomoki , Fukute Yusuke , Goto Masahiro
Published: August 2024

In this study, a practical estimation method for wear and breakage of mooring chain is investigated. In the method, mooring tension and sliding angle between mooring links are estimated from measured buoy’s motion. At the towing tank of Osaka Metropolitan University, by using motion of a small scale model of buoy with single point slack moored for 75m sea depth, its mooring tension and its motion of the mooring chain are measured in irregular waves. From the results, it is found that the mooring tension at the mooring point is correlated with the vertical acceleration on the buoy regardless of significant wave height and period. Furthermore, it is also found that the sliding velocity at the mooring point is proportion to the pitching angular velocity of the buoy. These results indicate that the wear condition and the breakage possibility at mooring point can be estimated by measuring buoy’s motion. In addition, the feasibility of the wear and breakage possibility estimation for whole mooring chain by using an numerical simulation assimilated to the measured data is investigated.
Development of Calibrated Deterministic Design Approach for Design and Assessment of Offshore Structures Exposed to Environmental Loading
Authors: Tychsen Jesper , Zeeberg Allan , Nielsen Jørgen S. , Cholley Jean-Marc
Published: August 2024

The integrity of offshore structures is commonly demonstrated by proving the structure has sufficient strength to pass code-based strength checks (limit states). Hence, the reliability of any structure exposed to environmental loading from waves, wind, etc. is inherently linked to the requirements of codes and standards.

Design requirements in European codes and standards for onshore structures are commonly calibrated to link code compliance to acceptance criteria expressed in terms of target annual probability of collapse. However, this is not generally the case for codes and standards used in the offshore industry to verify structural integrity and so designers, asset owners etc. of offshore installations will usually not know the failure probability of their code compliant structures. In [4] the common design criteria for the most important offshore code, ISO19902 [5] has been (re-)assessed, and a huge variability across a range of different failure mechanisms is found. In other words, the reliability of code compliant structures is far from uniform: it depends upon the structural configuration, the environment at the installation site, and the location (within the structure) of the weakest failure mechanisms. The result is that structures either have a too low or too high failure probability and cost-benefit is not optimized as a few weak links may control integrity, while major parts of the structure are relatively too strong.

To mitigate the above, we have used a newly developed SRA model [3] that accounts for non-breaking, spilling-breaking and plunging-breaking 3D waves, to calibrate a deterministic engineering approach to align with user defined target failure probability. The work is described in the present paper.
Data-Driven Prediction Method for Remaining Useful Life of Rolling Bearings
Authors: Xu Shiyi , Li Tianyun , Zhang Yao
Published: August 2024

As a critical component of maritime vessels, bearings face various extreme environments and challenges, making them susceptible to high loads and adverse working conditions. Predictive analysis of bearing life allows maritime maintenance teams to take proactive measures, such as actively replacing or repairing damaged bearings, thereby preventing sudden failures and ensuring the reliability and stability of the vessel. To achieve accurate prediction of the remaining life of rolling bearings, this study proposes a novel two-stage strategy for life prediction. In the first stage, time-domain and frequency-domain features are extracted from the original vibration signals of rolling bearings. Subsequently, an adaptive feature selection method autonomously determines the dimensions of the feature subset, identifying the optimal feature subset. In the second stage, the optimal feature subset is input into the proposed ResNet-BiLSTM-ATT model for predicting the remaining useful life of bearings. The proposed prediction strategy has been validated on two public datasets. The results indicate that the proposed data-driven prediction method can accurately predict the remaining life of rolling bearings. This study holds significant practicality in ensuring navigation safety, optimizing maintenance management, and reducing energy wastage.
Assessment of Power Generation Systems With and Without Carbon Capture on Offshore Hydrocarbon Processing Facilities
Authors: Tan Jaime HuiChoo , Lee Chong Jin , Mantry Ravi Kumar
Published: August 2024

There are very few offshore hydrocarbon processing facilities in operation that have implemented combined-cycle power generation systems, and this power scheme deserves more serious consideration and adoption due to its positive effect on carbon reduction. In this study, assessment is made of power generation schemes based on gas-driven power generation system, steam-driven power generation system and combined-cycle power generation system for an example floating production, storage and offloading (FPSO) platform design, to compare the engineering design, fuel gas consumption, equipment weights, and carbon dioxide (CO2) emissions associated to each power generation system. It is found that the combined-cycle power generation system improves energy efficiency, reduces fuel gas consumption and in turn reduces CO2 emissions. Further, potential implementation of an offshore carbon capture system for separating CO2 from the gas turbine flue gases using a proprietary amine absorption technology, is presented. This paper recommends integrating combined-cycle power generation scheme and post-combustion carbon capture on the gas turbine exhausts for reducing the carbon footprint of the power generation system on the facility. Carbon capture of the process waste gas incinerator exhausts can further achieve the overall facility net-zero carbon emissions target, however this aspect is not in the scope of this paper.
A Global Shape Function Method for Dynamic Analysis of Mooring Systems
Authors: Liu Fushun , You Shiji
Published: August 2024

A new global shape function (GSF) based dynamic analysis method for mooring systems of floating structures is proposed, aiming at securing a robust solution to the existing trade-off issue between accuracy and efficiency. Distinguished from the widely used methods, the GSF method is initially derived from Hamilton’s principle, and then the global stiffness matrices are directly constructed under the consideration of global nonlinear strain with the capability of high-computational efficiency, owing to the unemployment of transformation matrices. Each mooring line is discretized into elements using Lagrangian shape functions, which deliberately consider both the Morison forces and the time-varying global stiffness matrices in a set of control equations. The accuracy of the proposed GSF method is firstly verified by experimental results published. Results show that the GFS method has the ability to achieve more accurate results than the solutions of the rod theory applicable to dynamic analysis of the mooring system. Furthermore, an OC4 floating wind turbine is employed to demonstrate at least 35% efficiency improvement than the results by the rod theory, while maintaining the same accuracy. This study sheds light on potential applications in marine engineering.
Spectral Graph-Based Networks for Mooring Line Failure Detection on FPSO
Authors: De Melo Costa José Lucas , Kurike Matsumoto Fernando , Netto Caio F. Deberaldini , de Barros Marcel R. , do Nascimento Queiroz Filho Asdrubal , Gomi Edson S. , Tannuri Eduardo A. , Reali Costa Anna Helena
Published: August 2024

Robust monitoring is vital in offshore oil and gas exploration, especially for Floating Production, Storage, and Offloading (FPSO) platforms pivotal in subsea hydrocarbon extraction. Motivated by the glaring absence of failure detection systems in mooring lines on FPSOs, this work tackles the broader issue of inadequate monitoring and warning systems in the sector despite their pivotal role in safety. Existing approaches often overlook inter-series correlations in multivariate scenarios. The authors introduce Graph Neural Networks (GNNs), particularly Spectral-Temporal GNN (StemGNN), leveraging recent time series processing advancements to fill this gap. Operating in the spectral domain, StemGNN captures intra-series and inter-series correlations, enhancing accuracy. The innovative approach improves classifying multivariate time series, particularly the motion time series of offshore platforms for mooring line rupture detection, considering platform oscillation. This work develops, implements, and tests an alert system for potential cable breaks on offshore platforms. Beyond operational value, it contributes to technological innovation through machine learning, overcoming conventional monitoring limitations. Results show comparable performance to state-of-the-art models, highlighting the proposed model’s suitability for real-world scenarios with noisy or missing data. Its complexity addresses challenges without sacrificing performance, advancing mooring line failure detection in offshore oil and gas, guiding future research.
Adaptive iterative transfer learning for effective snapping shrimp sound detection
Authors: Lee Dawoon , Byun Gihoon , Chung Wookeen
Published: August 2024

This study aims to detect the bioacoustics signal in the underwater soundscape, specifically those produced by snapping shrimp, using adaptive iterative transfer learning. The proposed network is initially trained with pre-classified snapping shrimp sounds and Gaussian noise, then applied to classify and remove snapping-free noise from field data. This separated ambient noise is subsequently used for transfer learning. This process was iterated to distinguish more effectively between ambient noise and snapping shrimp sounds characteristics, resulting in improved classification. Through iterative transfer learning, significant improvements in precision and recall were observed. The application to field data confirmed that the trained network could detect signals that were difficult to identify using existing threshold classification methods. Furthermore, it was found that the rate of false detection decreased, and detection probability improved with each stage. This research demonstrates that incorporating the noise characteristics of field data into the trained network via iterative transfer learning can generate more realistic training data. The proposed network can successfully detect signals that are challenging to identify using existing threshold classification methods.
Spatial transcriptomic characterization of pathologic niches in IPF
Authors: Mayr Christoph H. , Santacruz Diana , Jarosch Sebastian , Bleck Marina , Dalton John , McNabola Angela , Lempp Charlotte , Neubert Lavinia , Rath Berenice , Kamp Jan C. , Jonigk Danny , Kühnel Mark , Schlüter Holger , Klimowicz Alexander , Doerr Jonas , Dick Alec , Ramirez Fidel , Thomas Matthew J.
Published: August 2024

Despite advancements in antifibrotic therapy, idiopathic pulmonary fibrosis (IPF) remains a medical condition with unmet needs. Single-cell RNA sequencing (scRNA-seq) has enhanced our understanding of IPF but lacks the cellular tissue context and gene expression localization that spatial transcriptomics provides. To bridge this gap, we profiled IPF and control patient lung tissue using spatial transcriptomics, integrating the data with an IPF scRNA-seq atlas. We identified three disease-associated niches with unique cellular compositions and localizations. These include a fibrotic niche, consisting of myofibroblasts and aberrant basaloid cells, located around airways and adjacent to an airway macrophage niche in the lumen, containing SPP1
+
macrophages. In addition, we identified an immune niche, characterized by distinct lymphoid cell foci in fibrotic tissue, surrounded by remodeled endothelial vessels. This spatial characterization of IPF niches will facilitate the identification of drug targets that disrupt disease-driving niches and aid in the development of disease relevant in vitro models.
The human CD47 checkpoint is targeted by an immunosuppressive
Aedes aegypti
salivary factor to enhance arboviral skin infectivity
Authors: Marin-Lopez Alejandro , Huck John D. , Esterly Allen T. , Azcutia Veronica , Rosen Connor , Garcia-Milian Rolando , Sefik Esen , Vidal-Pedrola Gemma , Raduwan Hamidah , Chen Tse-Yu , Arora Gunjan , Halene Stephanie , Shaw Albert C. , Palm Noah W. , Flavell Richard A. , Parkos Charles A. , Thangamani Saravanan , Ring Aaron M. , Fikrig Erol
Published: August 2024

The
Aedes aegypti
mosquito is a vector of many infectious agents, including flaviviruses such as Zika virus. Components of mosquito saliva have pleomorphic effects on the vertebrate host to enhance blood feeding, and these changes also create a favorable niche for pathogen replication and dissemination. Here, we demonstrate that human CD47, which is known to be involved in various immune processes, interacts with a 34-kilodalton mosquito salivary protein named Nest1. Nest1 is up-regulated in blood-fed female
A. aegypti
and facilitates Zika virus dissemination in human skin explants. Nest1 has a stronger affinity for CD47 than its natural ligand, signal regulatory protein α, competing for binding at the same interface. The interaction between Nest1 with CD47 suppresses phagocytosis by human macrophages and inhibits proinflammatory responses by white blood cells, thereby suppressing antiviral responses in the skin. This interaction elucidates how an arthropod protein alters the human response to promote arbovirus infectivity.
The plasmid-encoded members of paralogous gene family 52 are dispensable to the enzootic cycle of
Borrelia burgdorferi
Authors: Groshong Ashley M. , Gibbons Nora E. , Moore Brendan P. , Bellamy William T. , Blevins Jon S.
Published: August 2024

Lyme disease, the leading vector-borne disease in the United States and Europe, develops after infection with
Borrelia burgdorferi sensu lato
bacteria. Transmission of the spirochete from the tick vector to a vertebrate host requires global changes in gene expression that are controlled, in part, by the Rrp2/RpoN/RpoS alternative sigma factor cascade. Transcriptional studies defining the
B. burgdorferi
RpoS regulon have suggested that RpoS activates the transcription of paralogous family 52 (PFam52) genes. In strain B31, PFam52 genes (
bbi42
,
bbk53
, and
bbq03
) encode a set of conserved hypothetical proteins with >89% amino acid identity that are predicted to be surface-localized. Extensive homology among members of paralogous families complicates studies of protein contributions to pathogenicity as the potential for functional redundancy will obfuscate findings. Using a sequential mutagenesis approach, we generated clones expressing a single PFam52 paralog, as well as a strain deficient in all three. The single paralog expressing strains were used to confirm BBI42, BBK53, and BBQ03 surface localization and RpoS regulation. Surprisingly, the PFam52-deficient strain was able to infect mice and complete the enzootic cycle similar to the wild-type parental strain. Indeed, the presence of numerous pseudogenes that contain frameshifts or internal stop codons among the PFam52 genes suggests that they may be subjected to gene loss in
B. burgdorferi
’s reduced genome. Alternatively, the lack of phenotype might reflect the limitations of the experimental mouse infection model.
Draft genome sequence of cellulose-degrading
Bacillus stercoris
BHUJPV-SS7 isolated from soil mixed with wood powder
Authors: Singh Saurabh , Pereira Arthur Prudêncio de Araujo , Pellegrinetti Thierry A. , Verma Jay Prakash
Published: August 2024

We report a complete genome of
Bacillus stercoris
BHUJPV-SS7 isolated from soil which contains 4,299 predicted genes and 4,012 predicted protein-coding genes within its chromosome (4,115,399 bp), and has 43.51% G + C content and a predicted beta-1,4-glucanase (EC 3.2.1.4) gene.