bluuebunny/crossref_metadata_2025_split huggingface dataset:
Marine Ducted Thruster Underwater Radiated Noise Control Through Leading-Edge Tubercle Blade Modifications - a Numerical Hybrid Approach
Authors: Stark Callum , Shi Weichao , Xu Yunxin , Troll Moritz 
Published: October 2022

Abstract
Anthropogenic-related underwater radiated noise (URN) has a detrimental impact on marine creatures who utilise the acoustic environment to perform basic living functions. Ambient ocean noise levels are increasing due to the growth of global shipping activity, where the propeller under cavitating conditions typically dominates the URN signature of marine vessels. Therefore, reducing cavitation severity and the subsequent URN is critical for future marine craft. This paper aims to assess the noise mitigation capability of LE tubercles on a benchmark Kaplan-type ducted propeller blade in cavitating conditions using computational fluid dynamics (CFD), detached eddy simulations (DES) are implemented to solve the hydrodynamic flow-field and the Schnerr-Sauer model is used to describe the cavitation behaviour. Both near and far-field noise is predicted within the hydroacoustic analysis. The Ffowcs-Williams Hawkings (FW-H) acoustic analogy was utilised to propagate the generated noise into the far-field. In summary, it was found that the LE tubercle modified ducted propeller blades could produce a noise reduction in the far-field at most test conditions considered to a maximum of 6dB overall average sound pressure level (OASPL). This is believed to be predominantly due to the introduction of the counter-rotating vortex pairs and subsequent alteration of the local pressure field over the blade suction side, which ultimately reduces the sheet cavitation severity over the blade surface by funnelling the cavitation behind the tubercle trough region.
Motion Performance of Miniaturized Spar-Buoy With Ring-Fin Motion Stabilizer for Wind Observations by Doppler Lidar and Development of Stabilized Platform to Mount the Doppler Lidar
Authors: Yamamoto Yusuke , Kinugasa Mizuki , Morita Mayo , Katayama Toru 
Published: October 2022

Abstract
In this paper, motion performance of a miniaturized spar-buoy with a ring-fin motion stabilizer comparing with the previous studied the same type spar-buoy is experimentally investigated and compared with the performance of the previous studied large size spar-buoy[2], and they are confirmed that its pitch amplitude increases at the same wave period or the same wave height, and its maximum pitch amplitude may not change much, moreover, the tendency is not related to the mooring system or water depth.
Moreover, it is investigated to reduce its pitch amplitude further. By placing the Doppler Lidar on a rigid body swing as a motion stabilized platform and constructing an active control that keeps the Doppler Lidar upright using a reinforcement learning, the motion of the sensor itself is reduced and the accuracy of measurement is improved.
Numerical simulations are conducted using the motion data of the spar-buoy in regular and irregular waves measured by scale model tests, and it is confirmed that it is possible to reduce the motion of the Doppler Lidar itself by adjusting the control gain of the motion stabilized platform by using a constant damping coefficient or the variable damping coefficients decided by the skyhook damper theory In order to reduce the motion further, an external force cancellation control using the motion of the spar-buoy in irregular waves simulated by the supervised machine learning is also applied.
Analysis of Life Extension Performance Metrics for Offshore Wind Assets
Authors: Yeter Baran , Garbatov Yordan , Guedes Soares Carlos 
Published: October 2022

Abstract
The objective of the present study is to investigate systematically the key metrics to evaluate the life extension performance of offshore wind farm operations. Finding the appropriate performance metric for an operation is essential for a durable, reliable, and profitable offshore wind farm operation. The analyzed key performance metrics are gross profit margin, return on asset, compounded annual rate of return of initial investment and levelized cost of energy. The mean value and standard deviation of each performance metric are calculated within a probabilistic techno-economic assessment framework for a single offshore wind asset, which is later extended to evaluate the whole offshore wind farm by a multi-asset portfolio optimization. The Markowitz modern portfolio theory is applied to estimate the maximum risk-adjusted ratio and Sharpe ratio, for the key performance metrics. Subsequently, the key performance metrics are compared to identify the most suitable metrics at different stages of the life extension. Moreover, the present study investigates the effect of different uncertainty levels associated with the stochastic variables in the techno-economic assessment. Finally, the suitability of performance metrics is analyzed and discussed for different offshore wind farm sizes and related recommendations are given.
Inspection and Maintenance Planning for Offshore Wind Support Structures: Modelling Reliability and Inspection Costs at the System Level
Authors: Giro Felipe , Mishael Jose , Morato Pablo G. , Rigo Philippe 
Published: October 2022

Abstract
In the context of achieving a decarbonized economy, wind farms installed farther offshore provide the opportunity of harnessing more stable wind energy. Exposed to the combined cyclic loading of wind and waves, offshore wind substructures withstand, however, harsh fatigue and corrosion deterioration mechanisms throughout their operational life. In this scenario, Inspection and Maintenance (I&M) planning methods enable efficient control of structural failure risks by timely allocating inspection and maintenance interventions. In this work, we discuss the benefits of approaching I&M planning at the system level, thus determining strategies that are influenced by system risk metrics. To support the discussion, I&M policies are identified for an offshore wind support structure composed of 12 fatigue hotspots located at three weld connections and exposed to varying corrosion-fatigue deterioration intensities. Within the numerical experiments, the heuristics-based policy search is conducted both at component and system levels, exploring various structural redundancy settings. The results demonstrate that a systematic treatment of structural reliability can only be achieved by modelling the entire structural system, assigning and considering global failure risk metrics during the policy search. Independently of the investigated structural reliability model, system-based I&M policies outperform component-based strategies.
Dynamic Property of a Floating Multi-Body System for Dual Barge Float-Over Operation With a Mechanical TLS (Topside Lifting System)
Authors: Zhao Shujie , Gao Zhen , Li Dejiang , Meng Xun 
Published: October 2022

Abstract
TLS (Topsides Lifting System) utilization is a modern fast lifting technology developed for offshore platform installation. The positive prospects have seen from its sound and efficient performance at the offshore operation. To improve the feasibility of dual barge float-over operations, two new individual barges are designed in application with TLS. The targeting TLS system is equipped with motion compensation system that consists of several sets of lifting beams. Because the flexible mechanical couplings and the hydrodynamic interactions between bodies, the dynamic characteristics of system will be more complex. Some of the eigen modes might be excited by wave loads and could potentially lead to large responses. To demonstrate the dynamic properties of the new operation mode, a mechanical and hydrodynamic coupled multi-body model is established. Each lifting beam is modeled as a rigid body with X and Y degree of freedom relative to the barge. The motion compensation system is considered with a passive mode, and a spring-damper model is used to simulate its property. The coupled hydrodynamic forces of two barges are analyzed first. The eigen value analysis is conducted to identify the natural periods and eigen modes of the coupled multi-body system. A strong coupling of roll and sway motions of barge, and the heave motion of topside is observed. The sensitivity study about the parameters of lifting beams for system natural periods are carried out. The motions of barges and topside and the global dynamic loads acting on topside in regular waves are also presented. The results indicate that the heave motions decrease but the roll and pitch motions increase at their natural frequency compared with motions of the rigid connected system. The global dynamic loads acting on topside are decreased. The analyzed dynamic properties provide an initial cognition reference of the new operation system and help with the system design especially for TLS.
Mitigating Spurious Low-Frequency Waves in a Model Basin With a Ramped Floor
Authors: Düz Bülent , Scharnke Jule , de Wilde Jaap 
Published: October 2022

Abstract
Low-frequency (LF) content of the waves present in a finite model basin may have multiple sources and associated consequences. Typically the horizontal natural periods of the moored structures are long and in the same range as the LF range. As such, the response of the moored structures in shallow water might be significantly affected by the spurious LF waves. The first goal here was to investigate whether the available numerical simulation tools can capture the underlying physics regarding the spurious LF waves in a basin with a ramped floor. It was seen that even though the heights of the short waves were underestimated when reflected waves from the beach reached the area of interest, the heights and phases of the LF waves were captured with an acceptable accuracy. The second goal was to investigate the approach of generating a correction signal (otherwise known as “anti-wave”) in order to mitigate the spurious LF wave content in the basin. The results of the CFD simulations showed that it was possible to reduce the amount of spurious LF waves. Following this outcome, the approach was tested in a model basin at MARIN with a ramped floor (the Offshore Basin - OB). The experiments were carried out with and without an LNG tanker in the OB using an irregular wave at one water depth. The measurements showed that the spurious LF content was mitigated with the correction signal. As a result, a reasonable reduction in the low-frequency surge motion of the ship was observed.
Multiple Hinged Floaters – An Experimental Study on Hydrodynamic Responses in Waves
Authors: Assbrock Gerrit , Lucas Jorge , Ley Jens 
Published: October 2022

Abstract
Exploiting space at sea is a conceivable solution in case of land scarcity in coastal areas. A modular floating platform can meet this growing need. The modularity allows platform expansions by linking multiple floaters with dedicated connectors. A durable structural design of connectors requires a reliable prediction of loads in waves. Multi-body hydrodynamics and effects of wave shielding are decisive factors that need to be considered. This experimental study comprised the measurement of motions and loads in long-crested waves with different configurations of floaters. Three component force gauges captured the loads acting on the connectors. An optical tracking system measured the motions of the connected floaters in regular waves and irregular sea states of different steepness’. The experimental results revealed higher order structural responses, relative motions, and impact loads subject to the wave’s steepness. Tensioning and compressing loads showed to be asymmetric and occurred at different return periods.
Estimation of Vertical, Horizontal and Torsional Rigid Body Loads of an Ultra-Large Container Ship (ULCS) in Regular Waves
Authors: P. P. Vijith , Rajendran Suresh 
Published: October 2022

Abstract
Predicting hull responses and structural loads is essential for the robust design of ships. The Ultra Large Container Ships (ULCS) are subjected to non-linear wave loads due to the low block coefficient and pronounced bow flare. They are highly susceptible to torsional loads because of the large open cross-section which is subjected to unsymmetrical hydrodynamic loading. A time domain method based on strip theory is developed for estimating the coupled rigid body motions and wave-induced loads acting on an Ultra large containership. A 2D-Panel method is followed to calculate the added mass and damping coefficients. A body-nonlinear approach is followed to capture the major source of non-linearity in the structural load estimation due to Froude-Krylov and restoring forces. Case studies are conducted for an Ultra-large container ship in small amplitude regular waves. Motions and structural load (vertical, horizontal, and torsional load) RAOs are being investigated for various wave headings, and the results are compared with the published experimental results. The proposed method is computationally efficient to capture coupled rigid body responses and sectional loads, including torsion.
Performance of the Observation-Based Source Terms in a High-Resolution Wave Hindcast for the North Sea
Authors: Rapizo Henrique , Liu Qingxiang , Babanin Alexander V. 
Published: October 2022

Abstract
A 30-year wave hindcast for the North Sea covering the period of 1990–2020 is described. The simulations are performed by nesting a 5 km SWAN wave model to a global WAVEWATCH III implementation. For the coastal nest several options of the ST6 physics are tested, including choices for the coefficients of whitecapping dissipation, wind drag formulation and scaling of wind speed U10 to friction velocity u*. The results are shown for the two most widely used wind reanalyses: the CFSR and ERA5. The model dataset is validated and calibrated against satellite and several buoy measurements, allowing for the assessment of model performance in the different areas of the North Sea. The ERA5 reanalysis outperforms the CFSR winds in all validation metrics except for a negative bias in wind speed, which is more noticeable for the upper quantiles. Similar results are observed for significant wave height when comparing model results forced by the two reanalysis winds. The ST6 source term performs considerably better than the source terms of van der Westhuysen et al. However, the results are sensitive to the choice of the ST6 tuning parameters, which are in turn also dependent on the forcing winds. Further tests are performed by correcting the wind stress to account for the observed wind speed bias, which is a part of the ST6 implementation. Finally, the long-term statistics of wave height are briefly presented, with emphasis on the wave height extremes.
A Basic Study on the Effect of Deep Learning to Determine the Control Force to Maximize the Power Generation of PA-WEC in Irregular Waves
Authors: Murai Motohiko , Sakamoto Sho 
Published: October 2022

Abstract
As an alternative energy source to fossil fuels, marine renewable energy is expected to have a huge potential. Wave energy is one of the marine renewable energy sources. The feature of a PA-WEC, which is one of the Wave Energy Converter (WEC), can generate electricity directly from the change of magnetic field caused by the relative motion of the coil and the moving part of the floating body with permanent magnet. It is also possible to control the stiffness relation by applying a force to the moving part of the floating body by changing the current in the coil. By taking advantage of this characteristic, it is possible to generate electricity efficiently in a wide periodicity band. As for this efficient power generation, the authors have shown the analytical optimum solutions for the regular and irregular wave problems, including arrayed PA-WEC problems, for maximizing the power generation considering the copper loss in the generator. On the other hand, it is not easy to decompose the unknown irregular wave components into multiple regular wave components with high accuracy from time to time in the actual ocean. Therefore, the authors have been investigating the possibility of estimating the optimal control force at each moment in an unknown irregular wave by using an AI model. Then we showed that the AI model trained on regular waves can estimate the control force close to the theoretical solution for irregular waves.
In this study, the AI model is incorporated into the equations of motion, and the time series response of the power generation is obtained in an unknown irregular wave. From the comparison with the analytical optimal solution of the power generation, the possibility of applying the AI model was investigated. As a result, it was shown that, depending on the combination of the training model and input conditions, it is possible to obtain about 70% of the power generation compared to the theoretical solution.
Development of a Permeability Reduction Model Using Deep Learning for CO2 Hydrate Storage
Authors: Yamaguchi Alan Junji , Sato Toru , Tobase Takaomi , Wei Xinran , Huang Lin , Zhang Jia , Bian Jiang , Liu Tie-Yan 
Published: October 2022

Abstract
Global warming is an important environmental issue, and carbon capture and storage (CCS) is a major technology to reduce the emission of greenhouse gases. Captured carbon dioxide (CO2) can be stored in aquifers onshore or offshore seabed regions. Nevertheless, a small risk exists in which CO2 may leak due to natural phenomena opening cracks in the caprock. The natural formation of CO2 hydrates may create a new impermeable layer managing to block a possible leakage. It is of utmost necessity to understand and evaluate the permeability change due to the hydrate formation. Numerical simulation on different spatial scales has been essential for this purpose. The main objective of this study is to create a new framework for permeability reduction due to CO2 hydrate formation. Using machine learning, a multiscale approach links a large reservoir scale hydrate formation model with a microscale model. Detailed information from the hydrate shape can be obtained from the microscopic range to predict the new permeability reduction coefficient. Initial results have shown that this approach can obtain the permeability change due to CO2 hydrate formation with reasonable accuracy.
Numerical Study on Weld Magnification Method for a Semi-Circular Surface Crack Under an Arbitrary Stress Distribution
Authors: Kyaw Phyo Myat , Osawa Naoki , Tanaka Satoyuki , Gadallah Ramy 
Published: October 2022

Abstract
Marine structures are mainly constructed using welded components, and cyclic loadings trigger the fatigue cracks, mostly at the joints. Precise assessment of fatigue crack propagation (FCP) depends on the accuracy of stress intensity factors (SIFs) solutions. Magnification factors (Mk) have been proposed and widely employed in the calculation of SIFs for welded joints as a proven method to obtain SIFs accurately and efficiently. However, no previous study has reported the Mk equations for SIF solutions under arbitrary stress distributions. It is needed to derive such Mk equations so that arbitrary stress distributions can be considered in the estimation of SIFs and complications of analysis procedures can be reduced to some extent. In this report, MkIFM equations for T-butt joints with semi-circular surface cracks under arbitrary stress distributions are developed. The MkIFM and numerical results are achieved by employing the Influence Function Method (IFM) and the equations are developed using the Regression Analysis. The proposed MkIFM equations are validated for SIF evaluations under membrane loading and also for welding residual stress distributions. The validity of the proposed MkIFM equations is demonstrated against numerical solutions.
A Comprehensive Evaluation of Rheological Models for Non-Aqueous Drilling Fluids
Authors: Gucuyener Ismail Hakki , Gurcay Onur Kazim , Yanik Samed 
Published: October 2022

Abstract
This article presents a comparison of Power’s law, Bingham plastic, Casson, Herschel-Bulkley, Unified Herschel-Bulkley, Robertson-Stiff, Gucuyener, Sisko and modified Sisko models using a rheological database of extensive real field and laboratory datasets. In this study, 778 field and laboratory shear rate/shear stress datasets collected from four different sources for oil-based (OBM) and synthetic-based (SBM) muds were evaluated. Rheological measurements were made using Couette coaxial cylinder rotational viscometer such as Fann-35 type viscometers, in the shear rate range of 5.11 to 1022 s−1.
This study presents a simplified algorithm, called direct method, to determine the parameters of three-parameter nonlinear models. The direct method enables parameterization of three-parameter nonlinear models using the linear least squares method and significantly improves their performance. In addition, a MATLAB code based on the Gauss-Newton method was created to parameterize the nonlinear models. The nonlinear regression provided the best fit in many cases by calculating negative model parameters making the models physically senseless.
The goodness of fit of the models considered here was determined by comparing the resulting mean relative error and residual mean square values. The results of this study showed that the three-parameter models predicted better rheological fit than the two-parameter models for non-aqueous drilling fluids. The fit accuracy of the three-parameter models parameterized using the direct method is very close to that obtained by nonlinear regression. The modified Sisko, Gucuyener and Sisko models gave an excellent match to most of the shear rate-shear stress data sets evaluated in this study.
Designing Subsea Processing Systems Using a Hybrid Genetic Algorithm
Authors: Sales Leonardo , Jäschke Johannes , Stanko Milan 
Published: October 2022

Abstract
Designing a subsea production system is a task that takes several months to complete by an experienced and multidisciplinary team of engineers. In this work, a computerized hybrid method to find optimal designs and support subsea production system design using a genetic algorithm combined with a gradient search method is proposed.
The genetic algorithm is formulated to optimize the structure of the production system, while the gradient method solves the continuous non-linear variables related to flow rates, reservoir deliverability, equipment capacities, and others. The study case is based on the Goliat field. This hybrid approach is compared with an exact method.
The hybrid method successfully finds subsea configurations that maximize the net present value in shorter running times when compared to an exact method. The methodology presented provides an advancement toward modelling and automated decision-making in subsea production system design.