bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation of Hull Vane on a Medium Froude Number Displacement Hull
Authors: Gopinath Sathiyamoorthy , Ashok Kumar , Rajagopalan Vijayakumar 
Published: September 2023

Abstract
As a result of the rise in atmospheric emissions and an effort to move toward green shipping through de-carbonization, the International Maritime Organization (IMO) decided to enact some regulations and guidelines in the form of the Energy Efficiency Design Index (EEDI) and the Energy Efficiency Existing Ship (EEXI) on newly built and existing vessels respectively. Researchers emphasized reducing frictional and wave-making resistance components acting on the ship to explore solutions that will advance the idea of green shipping. Wave-making resistance components are predominant for a displacement vessel operating at higher speeds. Until now, Energy saving devices (ESD), In particular, Hull Vane (HV) has been extensively used as a promising methodology for minimizing wave-making resistance. Several experimental and numerical research works have been carried out on high-speed ships using HV to establish favorable trim and reduce wave-making resistance. However, the benefit of an HV for a medium-speed Froude number vessel is yet to be explored where nearly fifty percent of the total resistance is due to the wave-making component. This study includes the numerical analysis of a candidate medium-speed displacement hull to estimate the hydrodynamic characteristics, by using the VOF method and RANS solver. The numerical results are discussed on reduction in the pressure resistance, wave height, sinkage, and trim of the vessel with and without HV. The experimental work on the resistance of the candidate hull was used to validate the numerical results. The comprehensive numerical study was performed at medium speeds to analyze the effect of the hull vane to understand the improved hydrodynamic behavior of the hull.
Wellhead and Well Casing Integrity During an Event of Drift-Off: A Study Case of an Integrated Riser Analysis Solution Using On-Site Conditions
Authors: Sarnáglia do Amaral Acácio , Araujo das Virgens Edmo , Venero Germain , Mussel Dias Soares da Silva Thiago , Bohan Paul 
Published: September 2023

Abstract
The modern oil rig uses the dynamic position system (or DP System) to maintain position and provide ways for the rig to accomplish its mission. Although the DP System has improved its reliability over the years, it can eventually fail and produce a critical incident called a drift-off. In this situation, the riser, wellhead and well casing will be subject to a fairly large amount of stress that must be properly evaluated.
It is well established in the offshore industry to perform this assessment by performing a time domain coupled analysis simulating the behavior of a riser, wellhead and well casing in the event of drift-off. This is commonly called drift-off analysis.
Over the past few years, significant improvements have been achieved in the mathematical models of these analyses, but even today we add many conservative factors to cover forthcoming operation uncertainties. Major factor are environmental conditions used on the analysis. Seeking to cover all scenarios, extreme colinear values are used as analysis input, resulting in narrow unfeasible operational watch circles for shallow waters or sensitive wells.
In this article we present the practical methodology and the results of our experience using commercial software Optima™ that performs drift-off analysis using on-site conditions. By using actual and short forecasted conditions, on-site analysis results provided valid feasible watch circles, allowing operations to take place in safely manner.
Verification of Swarm Intelligent Underwater Robot System for Marine Environment Observation With Vehicle Loss Compensation and Functionality Maintenance
Authors: Kobatake Kanako , Arima Masakazu 
Published: September 2023

Abstract
There are many problems facing the oceans. These problems are mainly caused by the changing marine environment. In order to understand and solve these problems, it is necessary to obtain detailed and long-term marine environment data.
In this study, we have attempted to construct a detailed and long-term marine observation method that covers a wide area. It is necessary to adopt observation equipment that can be operated for extended periods and move decisively on its own. The authors have focused on an Autonomous Underwater Glider (AUG) which is a vehicle with low energy consumption and a long operating time. However, in underwater operations, there is always the possibility of vehicle failure. We thus propose an advanced pathfinding system that is unaffected by the loss of some vehicles since each vehicle can independently decide its behavior in accordance with surrounding information from its latest observations.
Finally, the effectiveness of the proposed method is verified by operational simulations monitoring Japan’s Exclusive Economic Zone for a year and by factoring in the loss of some vehicles. In these simulations, we have evaluated the influence to an observation system when some randomly selected vehicles stop operating.
Lifecycle Assessment of Fuel Saving in Bulk Carrier With a Flettner Rotor
Authors: Sogihara Naoto , Kume Kenichi 
Published: September 2023

Abstract
Reduction of greenhouse gas (GHG) from shipping sector is urgent issue. International Maritime Organization (IMO) adopted the initial strategy on the reduction of GHG emissions from ships. This has accelerated researches and developments on the technologies for energy savings in design and operation stage. A lot of attentions are paid to an application of natural energy to propelling a ship and especially wind propulsion is expected as an effective system for achieving energy saving in operation.
This study focuses to a rotor ship as a ship with wind propulsion and addressed a bulk carrier having a rotor onboard. A rotor ship can obtain the thrust force from encountering winds based on Magnus effect and consequently can achieve fuel saving in operation. For spreading the use of a rotor widely, it is necessary to evaluate the fuel saving since the cost for building a rotor ship is larger than that for ordinary ship.
For evaluating the fuel saving in a rotor ship with accuracy, the external force such as added resistance in winds and waves should be predicted. For predicting the added resistance, this study applies the methods described in ITTC-RP. The lift and drag force of a rotor is estimated based on the computational studies on a rotating cylinder in uniform flow. Solving the equilibrium equations on the forces acting on a rotor ship navigating with constant speed provides the power-curves in actual seas on which the calculation of fuel oil consumption is based.
Furthermore, based on the power-curves and the calculated fuel oil consumption, the lifecycle assessment of fuel saving in a rotor ship, which is considering the effects of aging and fouling for hull and propeller, is conducted. Fuel saving throughout ship’s life based on the lifecycle assessment is reported in this paper.
Predictions of Wind Loads on FPSO With POD-Based Discrete Empirical Interpolation Methods
Authors: Xing Xiuqing , Dao My Ha , Zhang Baili , Lou Jing , Tan Wei Siang , Cui Yongdong , Khoo Boo Cheong 
Published: September 2023

Abstract
As the Proper Orthogonal Decomposition (POD) based Discrete Empirical Interpolation Method (DEIM) constructs specially selected interpolation indices that define an interpolation-based projection without carrying out the orthogonal projection as the POD-based Reduced Order Method (ROM) does, we apply the DEIM method to reconstruct and predict the wind load on an FPSO in this study. High-fidelity CFD simulation is adopted to collect snapshots for the reduced-order model. Effects of the number of DEIM selected interpolation points are tested. Testing results indicate that DEIM can predict the wind load on the FPSO with high accuracy even with only 5 interpolation points. Considering the limited installation locations over the scaled models in wind tunnels, DEIM’s feature of interpolation indices selection for an optimal subspace approximation could be helpful to determine the optimal sensor positions, and consequently to offer guidance for sensor positioning for wind tunnel tests and improve the prediction accuracy of the ROM-based data assimilation models.
Design Considerations on Semi-Submersible Columns and Pontoons for Floating Wind
Authors: Ivanov Glib , Hsu I Jen , Ma Kai-Tung 
Published: September 2023

Abstract
Floating Offshore Wind Turbine (FOWT) is an innovative technology with little industry guidance for its hull design. Various FOWT floaters with different hull shapes claim to support the same turbines. Structural integrity and material expense analyses of different pontoon shapes were conducted, and it was found that some configurations, such as those with every two columns connected by one pontoon, have advantages over others. However, it is important to note that the choice of pontoon shape should be based on the wave loading conditions the floater will be exposed to. While a T-shaped pontoon provides a cost-effective solution under certain wave loading scenarios, it may not be the best option for all conditions. Specifically, ring pontoon designs with full bracing were found to be necessary for withstanding certain wave loads. Therefore, it is important to consider different Dominant Load Parameters (DLP) and ensure that a FOWT floater can withstand all applicable DLPs. An uneven hexahedral column shape, which combines the best attributes of square and round shapes, is proposed as a better alternative. It offers ease of manufacture and relatively good hydrodynamics, while bracing is found to be necessary for withstanding the wind turbine’s incurred moment and forces. The conclusion is that column design should prioritize manufacturing costs over hydrodynamic performance.
A Statistical Approach for Estimating Sea Ice Thickness
Authors: Veber Joshua , Brown Jeffrey , Wang Jungyong , Browne Thomas , Veitch Brian , Molyneux David 
Published: September 2023

Abstract
Sea ice reporting and ice charts are a necessary simplification of highly variable sea ice conditions over large areas. Ice conditions are typically shown using egg codes. These codes can be used to determine an equivalent ice thickness as a method for calculating a ship’s ice resistance. This approach does not acknowledge the variability within the chosen region, such as the presence of ridges, ice pressure and snow cover. A new statistical method is proposed to use live capture data including the speed and resistance from a medium ice breaker to estimate the changing ice thickness. The thickness is calculated using the ship’s regression model for the ship’s performance based on model scale tests. Measured thrust data from the ship is used in conjunction with the thrust deduction factor and open water resistance to derive the ice resistance and subsequent thickness. The statistical ice thickness is compared against the equivalent ice thickness derived from the ice egg codes to determine the accuracy of current ice reporting and identify the variance within a defined region. This statistical approach may also assist in identifying features such as ridges, including the frequency of encountering these events. This analysis has high potential for sources of error, such as the changes in force required to bend and break ice sheets. Therefore, the data must be adequately analyzed to eliminate such noise while preserving the ability to identify changes to ice thickness. The potential implications of this research are an improved awareness of the variability in sea ice, and improvements to the methods for reporting and characterizing sea ice conditions.
A 4 Degree of Freedom Velocity / Power Prediction Program for Wind (Assisted) Vessels
Authors: Oettle Johannes , Krüger Stefan 
Published: September 2023

Abstract
This paper presents a velocity prediction program (VPP) respectively a power prediction program (PPP) for ships driven or assisted by wind propulsion systems named “E4-SAIL”. The program balances the forces acting on the ship in the four degrees of freedom (4DOF) surge, sway, roll and yaw. Therefore, environmental forces caused by wind, current and seastate can be considered. The VPP/PPP is embedded within the design environment “E4”, so the pediction can be refined directly within the design process whenever more information on the ship is known. Thanks to the integration into the design environment, the calculation of the transversal forces acting on the hull and the forces due to the seastate takes into account the shape of the hull instead of using only an amount of ship parameters. Because the VPP/PPP is intended for use in the early design stage, the calculations have to run very fast, so that the effect of several changes in hullform and floating position can easily be checked during the design process. The individual force components are presented and an exemplary calculation for a tall ship is shown.
A Combination of Surrogate Model and Subset Simulation Method for Long-Term Extreme Response Analysis of Marine Risers
Authors: Miao Qingqing , Cheng Ankang , Low Ying Min 
Published: September 2023

Abstract
Evaluating the long-term extreme response of marine risers generally involves numerous time-consuming simulations of offshore structures in the time domain. Traditionally, the most rigorous reliability analysis method — Monte Carlo Simulation (MCS) is employed to account for both varying long-term environmental loads and short-term wave dynamics through extensive sampling. The number of simulations required by MCS is impractical when targeting long return periods to meet the industry standard. Subset Simulation (SS) as a variance reduction method has been widely applied to solve low failure probability problems. It significantly improves the efficiency of MCS while preserving accuracy. However, the computational time demanded by SS is still intolerable when simulating complex numerical models of offshore structures. Many recent studies have proposed the use of surrogate models, especially artificial neural networks (ANN) to predict the dynamic response of offshore structures for more efficient reliability analysis. This paper presents a method that combines artificial neural networks and subset simulation for long-term extreme response prediction. The ANN is well-constructed using designed training data sets of varying environmental conditions for accurate prediction. The efficiency and accuracy of the proposed method are verified through a case study to predict the extreme top riser stress of a floating production system. The structure is exposed to sea states characterized by a joint-probabilistic description of significant wave height (Hs), spectral period (Tp), and wave direction (θw). The proposed method has been shown to accurately estimate the long-term extremes with a remarkable reduction in computational time.
Wake Effects on the Drag Force Estimation of Downstream Fish Cages
Authors: Cheng Hui , Aydemir Onur , Ong Muk Chen 
Published: September 2023

Abstract
A typical fish farm in Norway usually consists of 6 to 12 fish cages, and these fish cages are moored together in a grid shape. Due to wake effects, individual fish cages may experience different flow velocities depending on their positions in the fish farm. Hereby, the drag forces on individual fish cages can be different. Without knowing the exact flow velocity, the drag forces on the downstream fish cages are difficult to estimate. This will cause difficulties in the mooring system design, as these drag forces are important input variables. In this paper, the computational fluid dynamic (CFD) method combined with a porous media model is employed to study the flow field through and around fish cages. The drag forces on the downstream fish cages are investigated and the wake effects on fish farm design will be discussed.
Potential Root Causes for Failures in Floating PV Systems
Authors: Zhao Shengnan , Low Ying Min , Rodríguez-Gallegos Carlos David , Reindl Thomas 
Published: September 2023

Abstract
To mitigate climate change and reduce the dependency on fossil fuels, the adoption of renewable energy has grown significantly in the last decade. Solar energy as one of the major renewable resources is taking up more and more share of green energy in the world. However, one problem of deploying large-scale photovoltaic (PV) system is the required land usage, especially for the countries with land scarcity and high population density. To overcome this issue, floating PV (FPV) systems have emerged as an interesting option. It has been more than 15 years since the first FPV system was installed in Aichi, Japan. Since then, different FPV technologies have been developed. Despite their potential advantages, many issues arise due to the harsher environmental conditions and the more complex configuration of FPV system compared to conventional ground-mounted installations. This paper aims to conduct an analysis of potential root causes for failures in FPV systems during the operation and maintenance, which is based on FPV systems monitored by the Solar Energy Research Institute of Singapore (SERIS) and other literature sources. Besides, an introduction of the development of FPV system and a review of current float technologies are also presented. Finally, a summary of the challenges and an outlook of the opportunities for the deployment of FPV systems is provided.
Motion-Based Wave Inference With Neural Networks: Transfer Learning From Numerical Simulation To Experimental Data
Authors: Alencar Bisinotto Gustavo , Cardozo de Mello Pedro , Gagliardi Cozman Fabio , Aoun Tannuri Eduardo 
Published: September 2023

Abstract
The directional wave spectrum, which describes the distribution of wave energy along frequencies and directions, can be estimated from the measured motions of a vessel subjected to a particular sea condition by resorting to the wave-buoy analogy. Several methods have been proposed to address the inverse estimation problem; recently, machine learning techniques have been assessed as further alternatives. However, it may be difficult to gather large datasets of in-service motion responses and the associated sea states to train effective data-driven models.
In this work, an encoder-decoder neural network is trained with the synthetic responses of a station-keeping platform supply vessel (PSV) to estimate the directional wave spectrum. This estimation model is directly applied to perform wave inference from motion data of wave basin tests with a small-scale model of the same vessel. Furthermore, fine-tuning is also used to incorporate experimental data into the neural network model.
Results show a satisfactory match between estimated and measured values, both with respect to the energy distribution and the integral spectrum parameters, indicating that the proposed approach can be employed to obtain data-driven wave inference models when there is little or no availability of measured motion records and the corresponding sea conditions.
Unbonded Flexible Pipeline Upheaval Buckling Design and Sensitivity Analysis
Authors: Eriksen Morten , Larsen Anders Astrup , Pedersen Tommy , Ollgaard Larsen Henrik , Shanks Andrew , Gavouyere Thierry , Kristian Boe Johan , Caracol Rui , Liu Jian , Clements Richard , Pires Roberta , Zhu Linfa , Tan Zhimin 
Published: September 2023

Abstract
Flexible pipelines are often subjected to cover requirements on the seabed due to protection or stability issues. These requirements may be satisfied using a range of techniques, e.g. covering the pipe with rocks or soil. Due to pressure and thermal expansion in operation the pipe may be susceptible to lateral or upheaval buckling (UHB) out of the cover which may violate the cover requirements and could ultimately be detrimental to the flexible pipe.
The present paper is concerned with the design of reliable and cost-efficient cover solutions for unbonded flexible pipes. A new DNV guideline will introduce “Allowing Irreversible Displacement” design approach which allow for the pipe to move within the cover provided that the end-of-life limit states for pipe and cover are satisfied.
The paper includes a description of how a model following that approach may be defined, including considerations on load case matrix and a discussion on relevant sensitivity cases to ensure conservatism in the cover design. A case study is included to show how the principles of the guideline may be applied in UHB design.
Monitoring the Rotational Performance of a Weathervaning Mooring System
Authors: Minnebo Joerik , Chen Jiaxing , Gu Haoyuan 
Published: September 2023

Abstract
Within this paper, an approach to monitoring the rotational performance of weathervaning systems is proposed, by mainly looking at the so-called release events: the maximum rotation (or break-out angle) of the geostationary side of the turret, where the mooring yaw stiffness overcomes the static friction moment internal to the rotational interfaces of the floating facility. The physics of the stick-slip and release behavior are reiterated, the multiple dependencies are identified, and various performance characteristics are defined which will support long term operational monitoring of the turret’s weathervaning capacity.
Practical methods and examples are presented to individually monitor the governing dependencies. In the end, an unsupervised machine learning algorithm is proposed to identify any unwarranted increases in break-out angle: an anomaly detection method based on isolating the contribution of each of the dependencies on the release event dynamics.
Research on Deformation Characteristics of Cruise Superstructure Based on Digital Twin
Authors: Liu Siyuan , Pei Zhiyong , Yang Bin , Wu Weiguo 
Published: September 2023

Abstract
In order to master the structural response characteristics, a digital twin model of the cruise structural experiment model is constructed to grasp the deformation and interaction mechanism between the main hull and plump superstructure under each loading condition.
The structural matrix of the experiment model is constructed to establish the reduced order model. Furthermore, the real-time response of the cruise structural experiment model can be predicted by the kriging agent model. Subsequently, the experiment model of a cruise ship is taken as the object. Three typical cross-section measuring points are arranged in the midship area to monitor structural response. Ten groups of different working conditions are designed to compare the response characteristics. It is found that the structural response error between the results of the digital twin model and the experiment remains small under each loading condition.
The digital twin model can represent the character of the experiment model effectively. The interaction mechanism between the main hull and superstructure can be investigated using the proposed digital twin model to improve the safety and reliability of the cruise ship structure.