bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental and Numerical Investigation on the Dynamic Response of Platform for a Spar-Type Floating Wind Turbine Under Aerodynamic and Hydrodynamic Forces
Authors: Wang Baoxuan , Liang Xu , Jiang Xue 
Published: October 2022

Abstract
Developing floating offshore wind turbines (FOWTs) operating in the deep sea is crucial for reducing carbon emissions and exploiting marine renewable energy. Compared with a fixed-bottom wind turbine, the FOWT with a moving floating platform faces more complex external environment and challenging operating conditions. Its 6-DOF motions with long periods and significant amplitudes will, in turn, affect the dynamic response and performance of FOWT. Therefore, it is necessary to take a deep insight into the dynamic response of floating platforms for FOWTs under aerodynamic and hydrodynamic forces. In this regard, the present study carried out a series of tank tests based on a scaled spar-type FOWT, employing AI-based software-in-the-loop hybrid testing method. Tests were performed in wave-only cases, wind-only cases and combined wind-wave cases to investigate the effect of wave frequency and wind speed on platform motions. Corresponding simulations were also conducted to compare with the test results. In this study, attention was focused on the law reflected by test results and evaluating the applicability and validity of the employed hybrid testing approach. Results show that the natural frequency of yaw can be affected by constant thrust force generated by fan. Wind speed rather than regular wave frequencies have a significant impact on the mean value of platform motions. The amplitude and standard deviation of motions are simultaneously controlled by wind speed and wave frequency. The spectral peak frequencies of surge, sway and yaw are wind-speed dependent in wind-only cases. With the increase of wave frequency, the spectral peak frequencies of 6-DOF motions gradually change from wave frequency into their own natural frequencies. Moreover, numerical calculations generally coincide with the testing results. This work attempts to provide reference and guide for understanding the dynamic response of FOWTs and develop a more reliable hybrid scaled testing method.
Short-Term Forecasting of Surface Wave Elevation Based On an Autoregressive Model
Authors: Chen Jialun , Zhao Wenhua , Milne Ian , Draper Scott 
Published: October 2022

Abstract
Predicting ocean wave elevations on a wave-by-wave basis has been gaining increased attention recently. It has the potential to improve the efficiency and safety of a wide range of offshore operations, such as crane lifts and control of wave energy converters. This study investigates the use of a data-driven technique, specifically the autoregressive model, to predict surface wave elevation in the ocean based only on past measurements at a specific location. The confidence interval of the prediction is provided to quantify uncertainty. The influence of bandwidth on prediction and the cut-off frequency, which is a compromise between improvement in the prediction accuracy and the quantity of discarded wave components is also explored. In this study, the data are digitally filtered into low- and high-pass components. The prediction demonstrates significant improvement in accuracy and prediction horizon compared to the original unfiltered prediction results.
On Design Parameters for Accidental Ice Loading on Ship Hulls
Authors: Leira Bernt J. , Chai Wei , Radhakrishnan Gowtham 
Published: October 2022

Abstract
Ice ridges and icebergs generally pose a major threat to both ships and offshore facilities that operate in Polar regions. In many cases these features will govern the structural design loads. It is not practical or feasible to design a ship to withstand any possible ice impact load without damage, so following the principles of risk-based design, the tolerable consequences of an impact should be determined also considering the associated probability of occurrence. The following limit state design criteria are usually applied in structural design: (i) Serviceability Limit States (ii) Ultimate Limit States (ULS) (iii)Fatigue Limit States (FLS) (iv)Abnormal/Accidental Limit States (ALS). The ALS corresponds to impact events with a very low probability to occur, and its intention is to ensure that a ship hull structure does not suffer from a complete loss of integrity.
It is natural to consider methods that can serve to reduce the number of relevant load cases to be analysed, and to identify the most likely combinations of the relevant design parameters. Accordingly, the so-called environmental contour method becomes of significant interest. Utilization of this approach is illustrated in connection with the ULS and ALS in the present paper.
Propulsive Performance of Morphing and Heaving Foil
Authors: Dev Singh Pragalbh , Neogi Ishan , Niral Shah Vardhan , Joshi Vaibhav 
Published: October 2022

Abstract
Biological locomotion, observed in the flexible wings of birds and insects, bodies and fins of aquatic mammals and fishes, consists of their ability to morph the wings/fins. The morphing capability holds significance in the ability of fishes to swim upstream without spending too much energy and that of birds to glide for extended periods of time. Simplifying the wing or fins to a foil, morphing refers to the ability of the foil to change its camber smoothly, without sharp bends on the foil surface. This allows precise control over flow separation and vortex shedding. Compared to conventional trailing-edge extensions or flaps, used in rudders and elevators in submarines and ships, morphing foils provide better control of thrust and lift characteristics. This study aims at understanding the importance of the morphing of foil combined with a sinusoidal heaving motion on thrust generation. A two-dimensional variational stabilized Petrov-Galerkin moving mesh framework is utilized for modelling the incompressible low Reynolds number flow across the flapping foil. The morphing motion is characterized by the extent of morphing, measured as an angle of deviation from the initial camber, and the point of initiation of morphing on the foil as a percentage of its chord length. The effect of the foil morphing and the heaving motion on the propulsive performance are investigated. The extent of morphing is varied from −30° and 30°, and the point of initiation ranges from 15% to 50% of the chord. The Reynolds and Strouhal numbers for the study are 1100 and 0.2, respectively. The results from the current work can pave the way for enhanced engineering designs in bio-mimetics and give insights on design conditions for optimal thrust performance.
Sensor Data for Maintenance Planning of Topside Piping
Authors: Horn Agnes Marie , Wiggen Frode , Gustafsson Sandra 
Published: October 2022

Abstract
The wish to better know the condition of equipment and thus be able to plan and perform maintenance before a critical failure occurs has existed for many years. Early leak detection of liquid and gas from topside process piping is a critical task for economical and safety reasons. For an operator, there is a need to accurately detect, and localize leaks to timely recover them cost-effectively, or the most viable solution to be able to prevent leaks to happen. The latter named prognostic maintenance, condition-based maintenance or predictive maintenance represents a well-known method where the goal is to ensure preventive measures are taken in due time where leak may happen in a piping system.
There is a rapid development in sensor technologies, algorithm development, data storage systems, data transfer, data processing and computing power. The robustness and reliability of electronic components is constantly improving while the cost is decreasing. To ‘unhide’ hidden failures through condition knowledge and thus reduce inspection and unnecessary repairs and testing efforts on critical (e.g. safety) equipment is a compelling need for the Energy sector today. Digitalization is currently boosting this technology both within model-based prognostics, data-driven prognostics, and hybrid solutions. To make use of this development, classical understanding of fatigue, corrosion and moisture penetration on piping systems must be combined with several IT-related disciplines. The paper will discuss the latest state-of-the art related to sensor monitoring systems with the aim to provide sound recommendations related to fatigue, corrosion and moisture penetration on piping system for topside process piping.
On the Quality of Laboratory Water Waves Generated Mechanically by Flap Wavemakers
Authors: Fouques Sébastien , Akselsen Andreas , Harris Trevor , Brett Kent 
Published: October 2022

Abstract
In laboratories such as ocean basins, surface waves are generated mechanically by imposing an oscillatory motion on one or several vertical boundaries. The shape and characteristics of the wavemaker have a direct impact on the wave heights and periods that can be generated, but also on the quality of the waves obtained in the basin. Here, quality is defined in terms of spurious waves generation, meaning it is directly related to the predictability of the wave field in the basin. Additional factors affecting wave quality can be either mechanical, like the precision of the imposed flap motion, or hydrodynamic, like the amplitude of the flap angle.
In this paper, we investigate the quality of waves generated mechanically by several types of flap-wavemakers, including double-hinged and single-hinged ones, with various hinge depths. The amplitude of second-order spurious waves is evaluated analytically and compared to laboratory experiments carried out in SINTEF’s ocean basin. Third-order effects that results from using a second-order correction of the flap motion are also addressed. Then, the ability of deep-hinged wavemakers to generate short waves, either steep or with small amplitudes, is assessed based on measurements performed at NRC’s towing tank facility. Finally, recommendations on choosing a wavemaker design are proposed.
General Review and Analysis of Research in CEARCTIC and CEPOLAR Projects
Authors: Lu Liangliang , Kuikka Sakari , Kujala Pentti 
Published: October 2022

Abstract
With the climate change and the decreasing of Arctic sea ice, Arctic shipping receives increasing attentions from both the industries and academia due to a large amount of uncertainties involved. CEARCTIC (Centre of Excellence for Arctic Shipping and Operations) and CEPOLAR (Centre of Excellence for Scenario-based Risk Management in Polar Waters) projects are therefore established and worked continuously from year 2013 to 2022, focusing on various fields regarding safe Arctic shipping. Extensive research work has been carried out in CEARCTIC and CEPOLAR framework during the multi-year projects towards safe Arctic shipping. The outcomes are mainly published in scientific journal and conference papers, where various subjects, research directions and methods have been focused and applied. Therefore, it is vital to review the research to better understand the status and overall research of Arctic shipping. This paper aims to review and analyze the research papers published in the framework of the projects, from the viewpoint of research topics, research methods, practical purposes, and risk governance so that a general picture of research on the Arctic shipping can be seen from these perspectives. Based on review and analysis, potential gaps and clues for future research directions towards the Arctic shipping can also be identified.
Towards a Market and Industrially Driven Green Transition of the Norwegian Oil and Gas Industry
Authors: Skorpa Ragnhild , Sørum Lars , Ytrehus Jan David 
Published: October 2022

Abstract
On a world basis, the Norwegian oil and gas industry accounted for 2.5% of the global production in 2020, and even though the CO2 equivalent per unit barrel produced is among the lowest in the world, over 25% of the domestic emissions (scope 1 emissions) in Norway are related to offshore oil and gas production. The oil and gas industry are now undergoing a green transition with high emission reduction ambitions. The aims are a 50% emission reduction by 2030, and towards zero for 2050. With this they are transitioning from exclusive traditional oil and gas to energy supply with a broader portfolio. This includes integrating renewables such as wind, solar and electrification, both research- and operational wise, and optimize production of oil and gas.
Important aspects for acceleration of the green shift in general, will be the ability to develop, adopt and implement new and sustainable technology fast. Specifically, the emission reductions in oil and gas production will be achieved through integrating renewables, system integration, enhanced energy efficiency, novel technologies and general improvements through competence optimalization, digitalization etc. These initiatives are strengthened through earmarking of funding from remedies, to accelerate transition to a sustainable oil and gas industry.
This paper describes and discusses how Norwegian R&D support and efforts represents important parts of the ongoing green transition of the oil and gas industry in Norway.
Input-Unknown Estimation for Arrays of Wave Energy Conversion Systems via LTI Synthesis
Authors: Papini Guglielmo , Pasta Edoardo , Paduano Bruno , Faedo Nicolás , Mattiazzo Giuliana 
Published: October 2022

Abstract
The incoming menace of global overheating and depletion of fossil fuels, highlight the need for alternative, renewable, energy sources. In this context, ocean wave energy has a massive potential to contribute towards global decarbonisation. In optimising wave energy converters (WEC) productivity, state-of-the-art, model-based optimal control techniques are fundamental to enhance energy absorption efficiency. However, the vast majority of these optimal approaches inherently require wave excitation force estimators. In particular, in array configurations, the interaction between WEC devices has to be taken into account to achieve a consistent excitation force estimation. In this paper, a linear time-invariant (LTI) estimation approach for a WEC farm is proposed. The technique proposed is based upon the so-called ‘simple and effective estimator’, recently presented in the WEC literature, which reformulates the wave excitation force estimation problem as a traditional tracking loop. The results show that the proposed approach provides accurate estimates of the exciting force for every device in the array, with almost no design effort, and mild computational requirements.
An Impact Load Identification Method Based on Green’s Kernel Function
Authors: Zhou Xueqian , Xu Yishi , Yang Yu , Lu Gang , Ren Huilong 
Published: October 2022

Abstract
Ships and offshore platform structures experience complex dynamic loads during their lifetime. Impact loads is one of the types of dynamics loads where the duration of action is very short. The relative velocity between impacting body and the structure being impacted is usually high, and which may have a significant influence on the safety of ship structures. The load, as an input of structure calculation, plays an important role during the calculation progress and directly influences the accuracy of the result. Identification of the loads acting on the structures are important for structure design, analysis of strength, estimation of fatigue life and also data driven models of structures, however, most of these types of loads are difficult to identify. A possible approach is to measure the response of the ship structure, and then identify the location of action and the time histories with load identification techniques. In this study, a Green’s kernel function based time-domain inverse method for estimating the impact load is studied. The Tikhonov regularization method and TSVD method are used to deal with the ill-conditioned problem in the inversion, and the ill-conditionness of the matrix is reduced to a certain extent so as to improve the identification accuracy. An Improved Maxwell-Betti method is used to identify the location of impact load at an unknown position. The proposed method is validated through numerical simulation and experiment for a typical structure used in naval architecture and ocean engineering.
A Study on the Error Characteristics and Compensation Algorithm for Strain Gauge in Ship Structure Monitoring Systems
Authors: Zhou Xueqian , Yang Yu , Xu Yishi , Li Chenfeng , Ren Huilong 
Published: October 2022

Abstract
The ship structural stress monitoring system is one of the main technical approaches to realize intelligent ship hull structure, and it has been applied to high-performance ships and large-scale merchant cargo ships in recent years. The structure monitoring system can not only serve as the input of data-driven digital twin models of ships structures, but is also the basis for the derived decision support system. For this reason, it is crucially important to obtain accurate stress in the structure, and the error characteristics of strain gauges under possible combinations of load and temperature that a ship may undergo must be investigated. For a ship structure, the error characteristics of the strain gauges can be investigated by comparing the measures from the strain gauges installed on the ship and the stress obtained from numerical simulation. A neural network to compensate the errors of the strain gauges can be trained through measures from strain gauges and the numerical results for the stress at the same location. In this study, the analysis of the performance and the error characteristics of the strain gauges on a beam test piece are conducted. An experimental investigation of the response of two types of fiber Bragg grating strain gauge at different temperatures and different loads are conducted in the same approach. The performance and error characteristics of the strain gauges under different loads and temperatures are analyzed. Based on the analysis of error characteristics, various BP neural networks are constructed to compensate the errors of the strain gauges. Comparison of compensation results and experimental results of two types of fiber Bragg grating strain gauge shows that the proposed method can effectively reduce the influence of the error on the accuracy of the gauge. Application of this method requires the training samples of measures and numerical results for the stresses under known static loading conditions like berthed in a harbor or moving in calm water. Thus it is feasible to update the neural networks for the compensation of errors during the operation of ships.
Wave Impact on Semi-Submersible Units: A Review of Design Standards
Authors: Gopalakrishnakurup Renjeev 
Published: October 2022

Abstract
On 15 February 1982, the damage sustained by the portholes on the ballast control room onboard the drilling rig Ocean Ranger during a storm kick started a chain of events that resulted in the loss of 84 lives and the rig. The event led to an update of MODU Code that govern the design of Mobile Offshore Drilling Units. Semi-submersible mobile offshore units have evolved in their design and utility since 1982. Most recently, on 30 December 2015, a fatality occurred onboard COSL Innovator when a storm hit the unit. The incident led to changes in the assessment of airgap and structural adequacy of existing designs operating in harsh environment such as North Sea. A comprehensive assessment of the consequences of wave impact on the deck structure of a semi-submersible is still required to understand the safety and reliability of such units subjected to similar incidents. This review paper is an attempt to list important design aspects of Semi-submersible mobile offshore units affected by wave impact on the deck and the current design requirements. Some of the important aspects that require consideration are stability, watertight integrity, local and global structural strength, stationkeeping, impact on safety critical equipment and control systems and safety of persons in living area subjected to wave impact.
Analysis of Chain Fatigue Test Data for New and Used Mooring Chains
Authors: Hørte Torfinn , Yang Limin , Okkenhaug Siril 
Published: October 2022

Abstract
DNV is currently running a Joint Industry Project, “NorMoor JIP”, which is now approaching the end of phase 3. In this phase the fatigue limit state of mooring lines with studless chains for permanent units has got the main attention, where a new design method and safety factors for fatigue has been calibrated using structural reliability analyses. Phases 1 and 2 was covering the ultimate and accidental limit states respectively. The JIP has participants from energy companies, engineering companies, rig-owners, manufacturers and marine authorities. It is a global study covering Gulf of Mexico, Northern Europe and Brazil waters.
The focus in the present paper is on the chain fatigue strength. NorMoor JIP has obtained access to a large number of tension-tension fatigue test data for studless chain of various sizes, both new and used. The tests are carried out at different mean load levels and load ranges and provide a unique opportunity to study how the fatigue strength is influenced by mean load and degree of corrosion. Considerations have also been made to obtain consistency in the test results for tests with different number of links in the test sample.
The main result from analyzing the test data is an S-N based fatigue strength formulation, where the nominal stress range versus number of cycles to failure is given as a function of nominal mean stress and corrosion category. The data support keeping the slope of the S-N curve at m = 3, hence, logA is fitted to the data as a function of mean stress and corrosion category. The overall fit to all data has been checked for sub-groups of data such as new chain, used chain of different corrosion category, different chain diameter and different mean load. Prior to performing the fit, the test data were adjusted to represent number of cycles to failure for the weakest out of 6 links. This adjustment was implemented for tests with number of links different from 6 and is based on extreme value statistics. For corrosion, seven corrosion categories are used, based on guidance provided by the LifeMoor project at Sintef/NTNU. More work is needed to more precisely specify the categories. The formulation proposed uses nominal stress based on the reference diameter for new chain.
A series of 3 papers is published at the OMAE2022 documenting the work done in the NorMoor Phase 3 on the fatigue limit state of mooring lines. Additional to the strength formulation from the present paper, the importance sampling method, developed in NorMoor and presented in OMAE2022-81441, is used in the structural reliability analysis and code calibration presented in OMAE2022-81463.