bluuebunny/crossref_metadata_2025 huggingface dataset:
Lung Chest X-Ray Image Segmentation for Detection of Pneumonia using Convolutional Neural Network
Authors: Arjuna Nur Amyza , Abdul Wahab Asnida , Gan Hong Seng  , Mohamad Salim Maheza Irna , Ramlee Muhammad Hanif
Published: October 2022

Pneumonia has been identified as the top cause of mortality in children under the age of five, as well as in elderly with comorbidities. According to the World Health Organization, pneumonia reported 14% fatalities in children under the age of five nationwide in 2019. Chest x-ray (CXR) has been commonly used for detection of pneumonia. However, factor such as noise with low levels of intensity and low contrast between the images and the boundary representation can modify CXR images and it also requires highly skilled medical practitioners to accurately interpret the CXR images. Therefore, the goal of this study is to develop an automatic segmentation model to segment the region of interest (ROI) of pneumonia lung CXR images using U-Net architecture. Image enhancement using Contrast Limited Adaptive Histogram Equalisation (CLAHE) and gamma-correction based enhancement technique were applied to increase the quality of CXR images. Statistical analysis on features extracted from the segmented lung CXR images was performed to analyze the performance of the model was developed. The U-Net segmentation model achieves 95.58%, 95.82% and 95.48% accuracy for normal CXR while the model achieves 86.76%, 87.98% and 86.21% accuracy for pneumonia CXR which indicate that the U-Net segmentation for CLAHE x-ray images has better performance in segmenting the ROI of the lungs. As a conclusion, the segmentation model proposed shown to be able to overcome the disadvantages of manual segmentation where the model can be used to perform segmentation automatically on many CXRs at a time.
Study of Locking Compression Plate Through Biodegradable Implant
Authors: Sulong Muhammad Syawal Aiman , Syahrom Ardiyanshah , Zakaria Zulfadzli
Published: October 2022

Orthopaedic implant biomechanics research is booming, especially in bone fixation. Fixation involves securing a plate to a broken bone. The femur fractured mostly. Long bone fractures can be difficult to cure despite technological and medical breakthroughs. This study analyses the performance and optimal screw arrangement for biodegradable locking compression plate. This study compares biodegradable bone plate materials to identify the best (Iron, Zinc and Magnesium). SolidWorks models fracture repair plates and fixes them in a normal walking condition to a mid-ship fracture. Further, finite element analysis was performed on models with homogeneous and isotropic bone and plate. Simulation was done using COMSOL programme and screws. Idealized poroelastic 3D FE femoral model with 5 mm fracture gap and plate-screw design. We saw stress and displacement. The minimal von Mises stress and deformation for 6 screws. Under pure zinc and magnesium load, the highest von Mises stress was 7.94 MPa and the maximum deformation was 0.08 mm, proving that iron was the best material. Based on finite element analysis, the LCP can offer mechanical stability for comminuted fractures, fixing the bone block and promoting bone healing.
An Evaluation of Decision Support Technology in Simulated Offshore Ice Management
Authors: Soper Jonathan , Smith Jennifer , Power Jonathan , Veitch Brian
Published: October 2022

In this research, an experimental method was used to evaluate the effects of a novel digital Decision Support System (DSS) for maritime ice management operations. This was done using a marine bridge simulator to determine whether the use of this technology can improve ice management performance. The experiment used the DSS to assist seafaring cadets in simulated emergency ice management operations. The operation scenarios saw the cadets use a supply vessel under their control to clear sea ice from the lifeboat launch zone of an offshore installation. The DSS allowed participants to request assistance, which was provided through text-based instructions and visual replay of a previous approach from a past study. The cadets usually adopted the strategy recommended by the DSS, but did not demonstrate statistically significant performance improvements, which we attribute to their lack of ship handling experience. This research provides insight into the efficacy of decision support technology in presenting advice for ice management activities. It also describes an effective method for evaluating this technology.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Design and Evaluation of Wellbore Strengthening Materials for Fractured Reservoirs
Authors: Gargılı Uğur , Gücüyener İ. Hakkı , Durgut İsmail , Ay Ahmet , Doğan H. Ali
Published: October 2022

Fractured formations are commonly encountered while drilling carbonate reservoirs. Drilling of fractured formations usually results in lost circulation. In some cases, target zones cannot be reached due severe to lost circulation incidents.

Fractures encountered before reaching target zones can be sealed off by using wellbore strengthening materials (WSM). WSM are drilling fluid additives which are specially sized and designed particulates. They are generally used to strengthen the wellbore and to prevent the occurrence of losses by propping and sealing the fractures while drilling. In this study, experiments were carried out to determine optimum concentration and particle size distribution (PSD) of WSM to seal off fractures with certain sizes.

A non-damaging water-based polymer drill-in fluid with acid soluble marble particles having different concentrations and PSD were used in this study. Plugging efficiency of different blends were tested using modified Permeability Plugging Apparatus by pushing WSM-imbedded drill-in fluid through fracture widths of 400, 800 and 1200 μm manufactured on metal disks. Different WSM blends were compared with each other with regards to sealing time required to reach target pressure of 2000 psi and volume lost until the seal is achieved.

During the study, tests were run to investigate the effect of different PSD, concentration, and fracture width on sealing efficiency. Results were interpreted to determine optimum WSM formulations for different fracture sizes by taking into account continuous particle addition strategy while drilling together with downhole tools limitations. Optimum WSM blends were determined to seal off the mentioned fracture widths successfully.
Bottom Lateral Pressure Effect on the Ultimate Bending Moment of the Scaled Hull Girders
Authors: Ma Hongyang , Wan Qi , Wang Deyu
Published: October 2022

Scaled models are designed as alternatives to true ship structures in ultimate strength experiments. In this paper, a series of true ship hull girders of a 10,000TEU container ship under different scale combinations of geometric length and plate thickness are modeled. At the same time, the scale ratio of bottom water pressure is designed based on the scale ratio of geometric length. The relevant scaling characteristics of hull girders’ ultimate strength and collapse behaviors are investigated based on the nonlinear finite element analysis. Most of all, the effect of bottom water pressure on the ultimate bending moment is explored in detail. Aiming at presenting the mechanism of the bottom water pressure on the scale models. Results show that the bottom water pressure has a significant effect on the ultimate bending moment when the scaling factor of geometric length is close to one. By contrast, the effect of bottom water pressure on the ultimate bending moment is weak when the scaling factor of geometric length is relatively small. The effect of the bottom lateral pressure is to reduce the ultimate bending moment carrying capacity by changing the bending rigidity of the hull girder. The presence of lateral pressure makes the hull girder be more prone to buckle.
Digital Twin of a Maneuvering Ship: Real-Time Estimation of Drift And Resistance Coefficients Based on Ship Motion and Rudder and Propeller Commands
Authors: Uehara Sasaki Humberto A. , Cardozo de Mello Pedro , Aoun Tannuri Eduardo
Published: October 2022

The present work tackles the modeling problem concerning the initial steps of a Digital Twin (DT) application in a maneuvering ship. To envision a real implementation, further problems need to be solved, such as architecture design, communication network, digitalization purpose, etc., subjects which will not be aborded here. Instead, we concentrated on developing a well-rounded general system model that will enable the future employment of DT technology. Some examples can include performance analysis due to degradation of the hull, rudder, or thruster; decision support for maintenance scheduling; or even distance monitoring.

The paper focuses on real-time estimation of the main vessel hydrodynamic coefficients — namely the drift and resistance coefficients — through ship motion measurements (obtained from GNSS and Gyrocompass) and the input commands to the propeller and rudder.

Compared to the previous (OMAE2021-62899), we included proper propeller and rudder models; replaced the Extended Kalman Filter (EKF) with the Unscented Kalman Filter (UKF) and estimated the coefficients directly instead of its linear approximation.

Some maneuvers were tested within a simulated environment called pyDyna — a ship maneuvering simulator implemented on python based on the mathematical model adopted in the TPN-USP Ship Maneuvering Simulation Center. Data from motion sensors were mimicked by inducing a Gaussian white noise in the data retrieved from the simulator in real-time intending to better represent a real-world scenario.

Preliminary results show good adherence and low computational, possibly presenting as a convenient preliminary parameter assessment until more precise and time-consuming methods such as CFD are evoked.
CFD Modelling of Flexible Concrete Mattress Hydrodynamic Forces
Authors: Griffiths Terry , Griggs Randall , Khiadani Mehdi
Published: October 2022

While flexible concrete mattresses have been used extensively in the offshore industry for many decades, relatively little peer-reviewed published data exists to define the hydrodynamic forces and failure modes of these structures.

This paper presents a series of 3D CFD models which provide the predicted hydrodynamic force coefficients for a typical subsea bidirectionally-flexible concrete mattress. In addition, the CFD models also provide insight into the flow dynamics between and within the concrete blocks, allowing an understanding of the relative hydrodynamic forces on each block. The model results provide useful insight when interpreted in conjunction with physical model tests and field data to provide the potential for new design guidance to be developed.
Application of Recurrent Neural Network Long Short-Term Memory Model on Early Kick Detection
Authors: Wang Junzhe , Ozbayoglu Evren M.
Published: October 2022

Long-short term memory [1] (LSTM) is an artificial Recurrent Neural Network (RNN) architecture capable of performing deep learning tasks. With the special feedback feature, the LSTM network is suitable for processing a sequence of data and making a sequence of predictions. It has been successfully applied to many disciplines such as speech recognition, language translation, time series forecasting, and anomaly detection. In this paper, the RNN-LSTM network is applied to real-time drilling data to study the complex dependencies between multiple drilling parameters and common kick indicators. A well-trained model will use the concept of the sliding window to continuously predict the unforeseen value of sensitive kick indicators. With proper analysis, the predicted result is helpful to detect kicks ahead of time. This paper also proposed a general workflow to easily visualize the prediction results. Compared with other time series prediction methods, the LSTM network has the advantages of more accurate multi-step prediction, more physical, and more flexible. The proposed LSTM network uses accelerated GPU computing, the fast computational speed makes both online and offline learning possible. It is concluded that this approach is capable of accurately predicting kick indicators under certain circumstances. It may provide innovative guidance for the application of the LSTM network in early kick detection and future study.
Numerical Investigations on Plastic Responses of Strain-Rate Sensitive Panels Under the Lateral Impact
Authors: Zhou Hongyu , Wang Deyu
Published: October 2022

In the present study, the influence of the stiffening effect and the scale effect of material strain rate sensitivity on the lateral impacted panels is investigated. Rigid-plastic analysis for the collision scenario which fully clamped panels made of strain rate sensitive material struck by the blunt impact mass are conducted. A relationship is suggested to characterize the material strain rate sensitivity through the dynamic flow stress, defined by introducing a related factor n1 based on the theoretical analysis. Numerical simulations of low-velocity impact tests examining dynamic responses of clamped panels struck transversely by an impact block with a hemispherical indenter are presented. The dynamic behaviors obtained by numerical simulations are compared to reveal the influence of dynamic material characteristics on the impact behavior of steel panels. The great consistency between simulation results and predictions of the rigid-plastic analysis illustrates that the proposed rigid-plastic methods are effective to deal with the collision problem taking strain rate sensitivity into account. Moreover, the scale effect of the material strain rate effect on dynamic behaviors included the maximum permanent displacement and the peak impact force of panels is described quantitatively. The quantitative summarizations for the effect of the strain rate sensitivity are given. The maximum permanent displacement and the peak impact force are confirmed to be a power function of the related factor n1.
Fatigue Strength of Fixed Offshore Structures Under Variable Amplitude Loading Due to Wind, Wave, and Ice Action
Authors: Braun Moritz , Dörner Alfons , Willems Tom , Seidel Marc , Hendrikse Hayo , Høyland Knut V. , Fischer Claas , Ehlers Sören
Published: October 2022

Fixed offshore wind turbines are increasingly developed for high latitude areas where not only wind and wave loads need to be considered, but also moving sea ice. Current structural design rules do not adequately consider the effect of ice loading on fatigue life, due to missing studies on fatigue strength of welded joints under combined wind, wave, and ice action. Thus, a methodology to determine combined variable-amplitude loading (VAL) spectra was developed in a previous study. The stress state time-history at an exemplarily selected point in the support structure of an offshore wind energy monopile was translated into a VAL sequence. This sequence is used as an input for fatigue tests of butt-welded joints in the current study. The current study presents the VAL spectrum and the corresponding VAL time series, the results of the fatigue tests and compares them to typical fatigue damage sums for other stress spectra.
Verification of Inverse Propeller Moment Estimation Using a Scale Laboratory Rig
Authors: Nickerson Brendon M. , Laas Jaco , Bekker Anriëtte
Published: October 2022

There has been increasing interest in the loads caused during interaction between ship propellers and ice. Recent research into propeller ice interaction has produced inverse models that can be used to estimate the propeller moment induced by ice impacts. These models rely on the measurement of the output response of the propulsion shaft, which is inverted to obtain the input propeller load. Though these models have been validated numerically and used with full-scale response data, they have not been validated using simultaneous input and output measurements. Reliable full-scale simultaneous measurements can be difficult to obtain due to the harsh conditions experienced during propeller-ice interactions, and the cost involved with direct measurement of propeller loads. Thus, the use of a laboratory rig to verify the inverse method is investigated. An inverse model based on the use of modal superposition to represent the propulsion shaft as a continuous system has been implemented alongside a laboratory scale rig. The input loads and output responses are measured simultaneously during experiments with the scale model. These output responses are provided to the inverse model, and its estimation of the input load are compared to the measured loads. The comparison provides information about the accuracy of the estimations provided by the inverse model. It is found that improvements should be made to the rig in order to conduct more accurate comparisons.
Operational Planning and Power Management System for Offshore Platform With Wind Energy Supply – Impacts on CO2 Reduction and Power Quality
Authors: Svendsen Harald G. , Holdyk Andrzej , Vrana Til Kristian , Mosgren Idun Runde , Wiik Jan
Published: October 2022

This paper considers the operation of offshore oil and gas platform energy systems with energy supply from wind turbines to reduce CO2 emissions. The study is conducted through simulations of a case that reflects a “typical” oil and gas platform on the Norwegian Continental Shelf, with energy demand for gas lift and gas export compressors, separator train, oil export pump, water injection pumps, accommodation and utilities.

The study case with wind energy is compared to a base case with only gas turbines, and both cases have been implemented and analysed in multiple simulation tools. Results have been compared and used to assess the impact of wind integration on CO2 emissions, gas turbine fuel usage and wear and tear, power system frequency stability and other key indicators.

The results are consistent between the modelling tools, and indicate a potential for CO2 emission reduction of 20–25 % for this case with a wind energy share of 26 %. There is some variation depending on the amount of reserve power required and the rules for when to start up and shut down gas turbine generators.
Hydrodynamic Performance Evaluation of a Semi-Submersible Floater Using Open-Source Tools
Authors: Hassani Milad , Li Lin , Kalofotias Filippos , Jiang Zhiyu
Published: October 2022

Floating structures are viable alternatives for supporting wind turbines in deep water. Design of floating support structures is a challenging task, and a design evaluation requires considerations of costs and system performance.

An approach for evaluation of semi-submersible floaters has been developed in this paper. A braceless semi-submersible floater is selected and this floater is designed to support a 5-MW wind turbine in the North Sea. The evaluation framework consists of automatic modeling and numerical simulations in open-source tools. A Python-SALOME-NEMOH interface is used to obtain the hydrodynamic properties for geometries defined by various variables. The geometries are subjected to three performance constraints related to the static platform pitch, metacentric height, nacelle acceleration and wind loads in operating and parked conditions. Finally, the geometries are evaluated using two combined objective functions related to material cost and nacelle acceleration, and the Pareto Fronts are discussed. This work contributes to developing efficient design optimization methods for floating structures.
Water-Depth Identification From Free-Surface Data Using the KdV-Based Nonlinear Fourier Transform
Authors: de Koster Pascal , Brühl Markus , Wahls Sander
Published: October 2022

We propose a novel method to determine the average water depth from shallow, weakly nonlinear water waves that are approximated by the Korteweg-de Vries equation. Our identification method only requires free-surface measurements from two wave gauges aligned in the direction of wave propagation. The method we propose is based on comparing solitonic components in wave packets, which are computed using the nonlinear Fourier transform (NFT) (typical time-series data often contains at least some solitonic components, even when these components are not directly visible). When the correct water depth is used for the normalisation of the wave, the solitonic components found by the NFT remain constant as the wave packet propagates, whereas any other water depth will result in solitonic components that do not remain constant. The basic idea is thus to iteratively determine the water depth that leads to a best fit between the solitonic components of time series measurements at two different gauge positions. We present a proof-of-concept on experimental bore data generated in a wave flume, where the identified water depth is within 5% of the measured value.
Motion Response Prediction of Marine Vessels Based on Hydrodynamic Models Updated Through On-Site Measurements
Authors: Radhakrishnan Gowtham , Leira Bernt J. , Gao Zhen , Sævik Svein , Gomola Alojz
Published: October 2022

Decision support systems in offshore vessels utilize wave parameters in combination with physics-based vessel models to predict the vessel behavior prior to the initiation and execution of a marine operation. These predictions are, usually, accompanied by significant uncertainties inherent in the estimation of wave statistical parameters, idealized parametric spectra, and system variables. Consequently, the predictions may deviate considerably from the real behavior of the vessel. Therefore, this study uses numerical wave spectra corresponding to a site in the North Sea in conjunction with a hydrodynamic model adapted to measurements to make more accurate intermediate-term response predictions. Considering a weather-restricted marine operation, the intermediate-term predictions involve simulating the responses for any time window within the upcoming 72 hours. The vessel model’s uncertainty is minimized by calibrating the influential parameters utilizing the full-scale response measurements within an optimization framework. The subsequent Roll predictions based on calibrated parameters exhibit better alignment with the measured Roll motions. The application of recursive optimization showed a significant reduction in prediction errors in an actual marine operation.
Influence of Aerodynamic Loads on a Dual-Spar Floating Offshore Wind Farm With a Shared Line in Parked Conditions
Authors: Liang Guodong , Jiang Zhiyu , Merz Karl
Published: October 2022

The concept of a shared mooring system, in which adjacent wind turbines are coupled by sharing mooring lines, has been proposed to reduce the mooring costs of floating offshore wind farms. This work investigates the influence of aerodynamic loads on a floating offshore wind farm of two spar wind turbines connected with a shared line in extreme environmental conditions. A case study is performed for the floating offshore wind farm under parked conditions using a numerical simulation tool. The environmental conditions are determined from environmental contours with a return period of 50 years. Turbulent wind and irregular waves are simulated in dynamic analyses. Wind and waves are aligned and two loading directions are considered. Floater motions and structural response are analyzed. The influence of aerodynamic loads is studied by comparing the simulation results under both wind and waves with those under wave-only. It is concluded that the aerodynamic loads affect the horizontal motions of floating offshore wind turbines, the mooring response and the tower-base bending moment significantly in extreme environmental conditions, especially when the loading direction is 90 deg. The findings from this study improve understanding of the design loads of shared mooring systems.
A Numerical Scheme to Investigate Ice Fracture in Level Ice-Ship Interaction
Authors: Xu Ying , Wu Jiameng , Wang Zeping
Published: October 2022

Ice load is a major threat to the structural safety of polar ships. Accurate prediction of ice loads is inseparable from the good presentation of sea ice fractures by using numerical methods. However, sea ice fracture is a typical discontinuity problem and has been a thorny issue.

This paper uses extended finite element method to study the fracture mechanism of level ice when interacts with a rigid plate, which is a simplified structure of ships, to help gain better understanding of the ice load. The numerical simulations are performed based on ABAQUS. The transversely isotropic material model and failure criterion are adopted for the numerical simulation of the level ice. The deformation and stress distribution of the level ice, as well as the location of initial crack and the path of the crack propagating are discussed.

The results of the study show that the level ice fracture is closely related to the local tensile failure. The ice failure mode and ice load are closely related to the impact velocity and inclination. As the cracking process of level ice can be well simulated and the stress state can be well presented, extended finite element method is proved to be an effective method to investigate the ice fracture mechanism.