bluuebunny/crossref_metadata_2025 huggingface dataset:
Exploration of Strategies to Improve Continual Learning From Irregular Sequential Drilling Data
Authors: Pacis Felix James , Wiktorski Tomasz , Ambrus Adrian , Alyaev Sergey
Published: September 2023

Economic and environmental objectives incentivize drilling wells faster, increasing the rate of penetration (ROP). A prerequisite for ROP optimization is an accurate ROP model that provides the expected rate given a set of drilling inputs and in response to downhole parameters in real-time. Relatively seldom and often different drilling operations make it difficult to collect a large dataset for supervised training of universal ROP predictors. Thus, ROP Deep Learning (DL) models often suffer from poor generalization. This work introduces continual learning as a new paradigm for data-driven ROP modelling. We subdivided historical drilling data from the Volve field and Marcellus Shale into smaller sections to imitate actual operations with irregular time-series data coming sequentially. In continual learning, each incoming section serves first as a testing set and is subsequently added to the training set. Using transfer learning, we continuously fine-tune the current DL model with varying amounts of recent data to adapt it to new conditions. Continual learning improved the ROP prediction accuracy for both J-shaped-well and horizontal-well test cases compared to the conventional one-off training paradigm. Furthermore, we documented the model performance for different fine-tuning configurations through a series of sensitivity analyses. We also discussed the challenges and trade-offs when implementing continuous learning for ROP prediction.
Complexities of Capturing Large Plastic Deformations Using Digital Image Correlation: A Test Case on Full-Scale Pipe Specimens
Authors: Johnson Tyler , Langer Doug , Frigon Ethan , Timms Chris , Kobayashi Shunichi , Tsuru Eiji
Published: September 2023

This paper identifies the challenges associated with using digital image correlation (DIC) measurements for full-scale bending tests that result in large deformations, and it describes techniques to address these challenges. Full-scale bend tests experimentally determine the strain capacity of line pipe, which is a critical parameter in strain-based design and assessment. DIC is a preferred measurement technique for these tests as it provides non-contact, full-field measurements of the pipe deformation over time.

The primary challenges identified in using DIC for full-scale, large-deformation pipe testing relate to the speckle pattern, imaging system, and DIC performance measurement. A series of procedure and equipment improvements have been developed to address each of these challenges and to help improve the overall accuracy of the measurement system.

The successful implementation of the DIC technique is illustrated through a recent full-scale pipe bend test of a 4.45-metre-long section of 24-inch diameter, X65 pipe. The pipe was subjected to severe bending (up to a 51° bend angle), resulting in the formation of a self-contact buckle. The test was monitored using four DIC systems (each system consisting of stereo cameras) incorporating the recommended procedure and equipment improvements identified herein. The DIC results were validated against conventional strain gauges.
Research on a General Virtual Visualization System of Finite Element Analysis Result Data of Ship Structure
Authors: Wei Pengyu , Li Chuntong , Wei Naikun , Jiang Ze , Luo Xiaomeng , Wang Deyu
Published: September 2023

The sharing of finite element analysis (FEA) data during the design process is a key requirement for success in collaborative design environments. However, the efficiency of sharing finite element analysis (FEA) data using a standardized neutral format is still relatively low because the format must accommodate a wide range of data types produced from multidisciplinary analysis applications. This paper proposes a strategy for efficient visualization and sharing heterogeneous FEA data in the collaborative design and review of ship structures. Our approach achieves substantial data compression by storing only essential FE information. An object-oriented approach is adopted maximize the efficiency of managing multidisciplinary data, our format also allows the use of multi-level management of FEA visualization data. The FEA model data and results are transformed into a common visual data architecture that is easily interpretable in virtual reality applications. We implemented a system based on our approach, several examples from commercial FEA systems are provided to demonstrate the effectiveness of the format. The virtual visualization of these complex FEA data effectively enhances the efficiency of scientific communication, model evaluation and validation, and interdisciplinary discussion of research findings.
Analytical, Numerical, and Field Data Investigation for Deriving the Condition of Stick-Slip Drill String Vibration
Authors: Kaneko Tatsuya , Inoue Tomoya , Wada Ryota , Katsui Tokihiro , Suzuki Hiroyoshi
Published: September 2023

Several studies have been conducted on the stick-slip type of torsional vibration, which reduces drilling efficiency and sometimes damages drill bits and pipes, using numerical experiments, small-scale model experiments, or field data on the land rig. However, an analytical investigation into stick-slip conditions or a field data investigation of deepwater drilling has not been sufficiently studied. This study derives the conditions for stick-slip occurrence through analytical, numerical, and field data investigations and discusses a method to reduce stick-slip vibration.

First, we derive a simple expression for stick-slip using an analytical solution of a single mass-spring-damper model. Additionally, we numerically experiment using a multi-mass model to consider the mass distribution that cannot be considered in the analytical solution. Furthermore, we analyze the field data from deepwater drilling and experiment with a numerical model to examine the actual phenomena.

As a result, the analytical and numerical investigations have shown that stick-slip can be prevented by appropriately adjusting the rotational speed and the weight on bit. However, the field data investigation showed that the forced torsional vibration due to the vibration of the weight on bit was predominant in deepwater drilling. In this case, suppressing the amount of fluctuation of weight on bit is crucial to reduce the torsional vibration.
Hydrodynamic Modelling of Modularized Floating Photovoltaics Arrays
Authors: Zhang De-Qing , Du Jun-Feng , Yuan Zhi-Ming , Zhang Ming , Zhu Feng-Shen
Published: September 2023

Large arrays of floating photovoltaics (FPV) are emerging to be an attractive solution to renewable energy production and ocean space utilization. FPV arrays are typically buoyed by hundreds of modularized floating bases arranged in ocean surface. The total performance of the FPV arrays is significantly affected by the hydrodynamic interactions between these individual floaters. As the size of the array increases, more time will be required to calculate the entire hydrodynamic properties. From the engineering point of view, it is a challenging task to fully consider the radiation interactions among the modularized FPV floaters. In fact, when the distance between two floating bodies is large enough, their interaction will gradually vanish. The present study developed a cut-off scheme to improve the computational efficiency while providing a reliable prediction of the interaction effects in engineering practice. A cut-off radius is introduced in this scheme to determine the coupling range in which the radiation hydrodynamic interactions should be considered. The cut-off radius is determined by three parameters, including the modular shape, wave frequency and accuracy requirement. Several arrays of rectangular FPV bases were taken as examples to show how to quantify the radiation interactions and find an optimal cut-off radius. The effect of wave direction, gap distance, and connection type were also investigated. The results from the validation case showed that the hydrodynamic interaction can be well predicted using the proposed cut-off scheme, while more than half of the computational time can be saved.
Fault Diagnosis of Rolling Bearing Under Marine Noisy Environments and Varying Working Conditions
Authors: Gao Chao , Guo Yongjin , Han Bing , Liang Xiaofeng , Wang Hongdong , Yi Hong
Published: September 2023

Rolling bearings are the core components of ship rotating mechanism, and accurate fault diagnosis has great significance in preventing serious failures of them and performing effective maintenance strategy during navigation. However, varying working conditions and cabin noisy environment would affect the monitored signals of bearings, resulting in the degradation of diagnosis performance. To address this problem, a new fault diagnosis method combining the Denoising Convolutional Auto-Encoder (DCAE) and the multi-scale Residual Net (MSRNet) is proposed in this paper. The DCAE model is designed for denoising. The fully-connected layers of Denoising Auto-Encoder (DAE) are replaced with one-dimensional convolutional layers. In the MSRNet, multiple-size convolutional kernels are utilized in each residual block for extracting multi-scale features of the signals. Typical bearing failure dataset is used for validation. The experimental results show superior performance on noise resistance and domain adaptation of the proposed method under noisy environments and varying working conditions.
Numerical Simulation of Nonlinear Regular and Irregular Waves Based on HOS-CFD Method
Authors: Liu Wuyang , Yu Jiawei , Dong Guohua , Yao Chaobang , Meng Fanliang
Published: September 2023

In naval architecture and ocean engineering, efficient and accurate generation and propagation of nonlinear waves is an important problem to be solved. Due to the use of pseudo-spectral method and fast Fourier transforms (FFTs), High-Order Spectrum (HOS) is an efficient and stable potential flow theory model for simulating nonlinear waves. However, the HOS method cannot consider the effect of viscosity, which makes it difficult to solve the interaction problem between wave and structure. Meanwhile, the CFD method consumes a lot of computational time and resources to solve a large viscous wave field. Therefore, this paper intends to build a HOS and CFD coupling calculation model: The regular and irregular wave fields generated by the HOS method are reconstructed and interpolated, and then the nonlinear wave field information is transmitted to the computational domain from the boundary velocity inlet of the in-house viscous solver HUST-SHIP. The influence of mesh size on coupling is discussed, and the accuracy of the coupling method is validated by simulating various types of waves. The generation of nonlinear wave field and the coupling with viscous flow solver are obtained, which lays a solid foundation for the subsequent analysis of the interaction between nonlinear waves and ships and marine structures.
A Tensile Test and Finite Element Analysis of DH36 High-Tensile Steel at Cryogenic Temperature
Authors: Nubli Haris , Kim SangJin , Sohn Jung Min , Jung Dongho , Cho Joung Hyung
Published: September 2023

Excessive exposure to LNG weakens and causes a brittle fracture to steels. Therefore, all risks that can lead to LNG spillage must be minimized or mitigated by applying a cryogenic temperature resistance material to the ship’s structure. Higher strength steel that considers low temperature such as DH grade is recommended to be used for ships carrying LNG cargo.

In this study, material fracture idealization of DH36 steel under a tensile load and low temperature is presented. The fracture strain of the steel could be affected by temperature reductions due to the hardening effect, as well as the element size in the Finite Element (FE) model would influence the fracture strain behavior. Thus, the stress-strain curve of DH36 has to be calibrated for the use in FE model. A sensitivity analysis with temperatures and element sizes was presented. The strain rate effect was neglected since the quasi-static mode was performed in the tensile test. The temperature is applied from 25°C (room temperature) to −160°C. The element sizes of 0.5mm to 5.0mm were used in the FE model of the specimen. This investigation found that the ultimate tensile and yield stresses were increased with a slightly increased upon the fracture strain along with the decrease in temperature. Furthermore, the procedure of the tensile test and FE analysis are discussed in this paper.
Progressive Collapse Behavior of Ship Structures Considering Fluid-Structure Interaction Effect
Authors: Zhou Ji , Pei Zhiyong , Wu Weiguo , Ding Jianliang
Published: September 2023

The collapse behavior of ship structures has great significance to structural safety and reliability design. In the present research, a nonlinear finite element method considering the fluid-structure interaction is proposed to analyze the progressive collapse behavior of a typical container ship test model.

The fluid-structure interaction analysis system is constructed adopting STAR-CCM+ and ABAQUS to obtain the moment curvature relationship with time history. The structural collapse response under series wave conditions varying wave length and height is investigated and discussed.

The proposed nonlinear analysis considering the fluid-structure interaction can provide a rational way for evaluating the collapse behavior of ship structures in waves. The obtained results have reference for the progressive collapse behavior of ship structures.
Investigating Damage Initiation in Wind Turbine Blade Coating Under Repeated Raindrop Impacts
Authors: Kuthe Nikesh , Pandey Vibhuti Bhushan , Ahmad Suhail , Mahajan Puneet , Mishnaevsky Leon
Published: September 2023

The Wind Turbine Blade (WTB) coating is a protective layer that sustains repeated raindrop impacts. These impacts cause cyclic stresses, fatigue, and the resulting erosion of the leading edge of the blade coating. The high-intensity rains in India make this problem more critical. The presence of voids (manufacturing defects) in the coating leads to local stress concentration and enhances the intensity of erosion. This erosion causes an increase in the drag coefficient and a reduction in the lift coefficient leading to an underperformance of the turbine. Several studies are reported in the literature to understand the damage estimation of the coating. However, the effects of the voids radii and their locations on the rate of degradation of the coating due to repeated impacts need further investigation. In the present study, it is learnt that voids in the coating cause faster damage propagation. That results in the deterioration of the impact-damping performance, causing an early failure of the material. The study also demonstrates that in the case of coating without voids, the damage starts from the surface and travels downwards. Whereas, in the case of coating with voids, the damage accumulates rapidly in its vicinity. The study is performed in two steps. Firstly, the stresses in the coating are computed using a finite element model employing smoothed particle hydrodynamics (SPH) in ABAQUS/Explicit. Hence, the fluid-solid interaction study is performed. In the second stage, the fatigue damage of coating is predicted by employing the continuum damage mechanics (CDM) approach. The comparison of results in the above two cases demonstrates that the present model with voids is found to be more realistic for estimating nonlinear damage accumulation, micro-cracks initiation and growth. Thus, it is presently adopted to visualise the effect of voids radii and their locations on WT coating subjected to rain-induced fatigue. The results obtained by the present realistic model are validated with the established experimental observations.
Numerical Study on the Evolution of Vortices Influenced by Downstream Undulating Foil With Different Lateral Distances
Authors: Wang Pengfei , Li Ruoxin , Yu Kai
Published: September 2023

In this work, we numerically simulate the hydrodynamic performance of an undulating foil at different lateral distances behind a cylinder, focusing on the evolution of the vortex street at each stage. Computations are conducted using unsteady incompressible Navier-Stokes solver with a moving adaptive mesh for laminar flow. We found that the secondary vortex induced by the Karman vortex street at the leading edge of the foil is the main reason for the thrust increase of the foil. The evolution of vortices corresponding to different lateral distances are different. A small lateral distance between the cylinder and the foil could make the vortex evolution complex. Meanwhile, the secondary vortex could be generated easily, and the foil could gain a large thrust. As the distance increases, the lift force of the foil tends to increase first and then decrease. An optimal distance exists at which lift reaches its maximum value, and this is also related to the distribution and strength of the vortex.
Data-Driven Modeling of Long-Term Riser Response to Irregular Waves Considering Wave Directionality
Authors: Cheng Ankang , Low Ying Min
Published: September 2023

Prediction of riser response to irregular waves has long been of industrial interest. But numerical simulation is often time consuming due to system nonlinearity and excitation stochasticity, especially in the context of reliability assessment where tons of repetitions are targeted. In this regard, data-driven modelling techniques have been proposed and applied by many researchers in the past decades. However, most established surrogate models were constructed in essence for single sea states and require vessel motions or their derivatives for input. These facts preclude them from fully playing the role of numerical models in prediction. In this paper, a data-driven model of long-term riser response considering wave directionality is developed based on nonlinear autoregressive networks with exogenous inputs (NARX) using fluid velocities. The adoption of fluid velocities stems from wave physics. It not only guarantees the good model performance in conjunction with the ensemble technique, but also allows prior knowledge about ocean environment to apply. Through design of experiments, only a limited number of numerical simulations for riser response to random short-term sea states need to be conducted to prepare data for training networks. The resultant model works well in the most critical case where all long-term wave variables including wave direction come into effect. A floating production system is used as an example for demonstration.
A Monte Carlo Approach for VIV Fatigue Damage Estimation of Subsea Pipelines Subjected to Design, Installation and Operational Uncertainties
Authors: Sales Leonardo , Mohammed Mohammed , Gil Cyprian
Published: September 2023

Obtaining a realistic prediction of the fatigue damage of pipelines employed in the subsea industry is vital for safe operations, as they are permanently subjected to wind-sea waves, swell and marine currents. Considering pipeline fatigue damage due to vortex-induced vibration (VIV) over its life cycle is critical in the design phase. Several VIV fatigue damage prediction models have been and are being developed by oil companies and research institutes. Uncertainties in the input data, such as in the effective axial tension, wall thickness, structural damping, water depth, and others, can influence the selection of materials, welding procedures, fulfilment of safety criteria, and other important decisions; therefore, on the total cost of the project. Reliable predictions of VIV fatigue damage are vital to controlling the degradation and ensuring the integrity of the operation at an optimized cost.

This paper aims to evaluate the variability of VIV fatigue damage prediction when uncertain inputs in wall thickness, water depth, structural damping, gap height, effective axial force, and Hi-Lo weld cap are considered. To this, a sensitivity analysis is conducted and an in-house software used for estimating VIV fatigue damage over the pipeline life cycle is employed combined with a Monte Carlo simulation. A case study based on a synthetic Norwegian offshore oil field is used. The information can support oil and gas companies in focusing on the most critical input parameters and uncertainties when carrying out a VIV fatigue damage analysis in new projects, and to help visualize the uncertainties in free span analysis.
Wind Turbine Load Monitoring During Model-Test in a Wave Basin
Authors: Gueydon Sébastien , Bayati Ilmas , Bosman René , van Kampen Wouter , de Ridder Erik-Jan
Published: September 2023

For the testing of floating wind turbines in a wave basin, several methods have been developed to include the wind turbine loads acting on the floating foundation. To simplify, there is one main choice for the modelling of the wind turbine loads at the scale of the basin: using a physical rotor in a wind field, or using hybrid methods where the wind turbine loads are computed and applied by actuators to the model. Each approach aims at reproducing the loads that the wind turbine generates at the Froude scale chosen for the construction of the model. Transferring these loads can therefore be seen as a step that is common to all methods. While these loads are essential for the modelling of the wind turbine and its interaction with the floating foundation, they are not yet systematically measured nor reported in all basin tests of a floating wind turbine. Most surprisingly, the benefit of measuring of the wind turbine loads transferred to the floating foundation are not explicitly mentioned in the main guidelines on how to test floating wind turbines [e.g.: ITTC]. This paper gives some examples of diverse test set-ups where these loads are measured and it explains how the wind turbine thrust is analytically retrieved from these measurements. It also emphasizes why monitoring the loads actually transferred to the floater adds up to the quality of the test results and confidence in the experiments.
A New Integrated Finite Volume–Finite Volume Numerical Model for Wave-Structure Interactions
Authors: Rai Ranjodh S. , Ma Zhihua , Qian Ling , Bai Wei , Lin Zaibin , Khait Anatoliy
Published: September 2023

This paper presents a new integrated (hybrid) hydrodynamic numerical model which couples a finite volume-based fully nonlinear potential flow (FNPF) solver with an incompressible two-phase Navier-Stokes (NS) solver in OpenFOAM. The coupling procedure follows a domain (zonal) decomposition approach in which an overlapping relaxation zone is utilised to implement a weak (one-way) coupling. The method for transferring information is simple, and the coupling accurate. Indeed, given that both solvers have been developed in OpenFOAM and are finite volume-based, only a method to calculate the volume fraction from the free-surface elevation has to be implemented: the velocity and pressure are already calculated as part of the FNPF solution and can be transferred accordingly — simplifying things greatly and avoiding unwanted errors. In addition, existing advanced OpenFOAM functionalities are used for the required interpolation. The relaxation zone then also ensures the coupling process is stable through a smooth transition from the FNPF solution to the N-S solution, as well as by absorbing any reflected waves. The new model is then validated through a number of benchmark test cases involving wave propagation, transformation, and structure interaction. It is shown to produce accurate numerical solutions that agree well with existing theoretical results and experimental data.
Steel Lazy Wave Riser Optimization Using Particle Swarm Optimization Algorithm
Authors: Lal Mayank , Yenduri Anurag , Sebastian Abhilash
Published: September 2023

Steel lazy wave risers have become a preferred riser solution as offshore oil and gas developments are happening in deeper waters and harsher environments. Steel lazy wave risers work well with FPSOs even though FPSO motions are worse compared to other floating platforms such as Spars and Semisubmersibles. FPSOs offer a tremendous advantage compared to other floating platforms as they can be used in regions with inadequate pipeline infrastructure to transport oil and gas to shore. The targeted placement of buoyancy modules on steel lazy wave risers improves the strength and fatigue performance compared to steel catenary risers making them feasible for use with FPSO’s. Also, buoyancy modules on steel lazy wave risers help reduce the top tension compared to steel catenary risers which gains significance in ultra-deepwater developments where top tensions for steel catenary risers make them an infeasible riser solution.

Steel lazy wave riser configuration design is dependent on a few parameters such as hang-off angle, length to start of buoyancy section, length of buoyancy section, type of buoyancy, and buoyancy factor. Theoretically, there are infinite solutions for a steel lazy wave riser configuration. Hence, the design of steel lazy wave riser is an optimization problem in which the parameters that govern the design can be varied to get an optimized configuration. In this paper, the particle swarm algorithm which is a bio-inspired algorithm is used to find an optimal solution for steel lazy wave riser configuration. The solution space is searched for an optimal steel lazy wave riser configuration based on an objective function which is a function of strength response, fatigue response, and cost. Solutions with poor interference response are penalized in the algorithm and rejected as part of the solution space search process. Finding an optimal solution automatically will help reduce the overall cost of risers which is a significant part of any offshore development. Also, it will help in making the riser design efficient from strength and fatigue point of view in addition to making it robust and streamlined.
Is the 100-Year Return Value for Significant Wave Height Increasing in the Tasman Sea?
Authors: Ewans Kevin , Jonathan Philip
Published: September 2023

Climate change is frequently reported to be the cause of an apparent increase in the occurrence and intensity of extreme events around the globe. Recent studies have found that increases can be expected in sea state extremes for some regions of the world’s oceans. We investigate temporal trends in storm peak significant wave height for a central Tasman Sea location, using output from the FIO-ESM v2.0 CMIP6 Earth System Model of [1], [2]. These data include time-series of significant wave height for several Shared Socioeconomic Pathways (SSP) as well as 165-year historical and 700-year pre-industrial realisations. This allows estimates to be made of 100-year return values for significant wave height at the end of the 21st century, for several future atmospheric forcing scenarios, and comparison of these against estimates for present day, based on the historical data base, and estimates for pre-industrial conditions. The estimates are made with a non-stationary extreme value analysis method that allows return values of storm peak significant wave height to be estimated as a function of time and to quantify if changes in return values are statistically significant. Evidence supporting climate-related changes at the Tasman location studied is weak. Estimates of most probable changes in 100-year return value for storm peak significant wave height between 2015 and 2100, for the three SSP scenarios considered, suggest the assumption of a 2m increase in 100-year return value to be reasonable, whilst noting that this value is small compared to the inherent uncertainty (of at least ±5m) present.
Short-Term Sea Surface Elevation Prediction Using Deep Learning Methods
Authors: Pang Tak Yin , Ding Boyin , Liu Lingqiao , Sergiienko Nataliia
Published: September 2023

Many ocean applications such as control optimization of wave energy converters and ship navigation rely on ocean wave prediction to improve the efficiency and safety of offshore operations. The two main types of ocean wave prediction methods are deterministic sea wave prediction (DSWP) and same point prediction. DSWP are based on several upstream wave measurements, which aid in prediction but are expensive due to the amount of measuring equipment necessary. Furthermore, the majority of DSWP are physical models that work on certain sea states such as deep water condition and are based on a knowledge of ocean physics and the assumptions of linear wave theory. On the other side, same-point prediction solely uses past measurements to estimate future sea elevation, which reduces measurement costs but adds extra complexity. For same-point prediction, researchers in the existing literature apply data-driven models such as auto-regressive models or neural networks; nevertheless, neural networks do not perform better.

In this paper, we examine the performance of Temporal Convolutional Networks (TCNs) and traditional Artificial Neural Networks (ANNs) for short-term ocean wave prediction on the same point wave measurement. With dilated causal convolutional layers and residual blocks, TCNs are designed to extract features from complex long-term patterns and capture the nonlinearity of the wave time series data. Wave time series data are simulated using the Pierson-Moskowitz spectrum with different levels of non-linearity for the experiment. The experiment results illustrate the efficacy of two deep learning models as influenced by nonlinearity and noise levels, but TCNs do not outperform ANNs in the same point wave prediction.
On the Distribution of Aerodynamic Load and Stress on Wind Turbine Blade
Authors: Dao My Ha , Le Quang Tuyen , Zhao Xiang
Published: September 2023

Making use of a large database obtained from high-fidelity CFD simulations of a 5MW NREL wind turbine, we perform an analysis of loading distributions on different sections of the turbine blade and their possible shifts with respect to the change in the operating conditions, i.e. inflow wind speed, rotating speed, tilt and pitch angles. In this paper, we will present a computational fluid dynamics model designed for mass generation of aerodynamic loading data, a finite element analysis structural model for simulating the turbine deformation and stress. Finally, verification of the model, data processing and analysis, and the results of loading and stress distributions on different sections of the turbine blade will be presented.
Hydroelastic Responses of a Circular Net Cage Under Wave Action
Authors: Ma Mingyuan , Zhang Hong , Jeng Dong-Sheng , Wang Chien Ming
Published: September 2023

The accurate assessment of hydrodynamic loads acting on a fish-cage is a topic that has received considerable attention in engineering. However, the sheer complexity of such a net-type structure makes it difficult to model with computational fluid dynamics (CFD) techniques. This has resulted in empirical methods being most commonly used in engineering practice. The present study proposes an efficient numerical model for predicting the hydro-elastic behavior of net cages under wave action. The finite element method (FEM) based dynamic solver AquaSim was adopted to simulate the hydro-elastic behavior of the net-type structure with a modified Morrison formula being used to estimate the hydrodynamic loads acting on the net structure. Beam elements and truss elements were employed to model the floating collar and mooring lines respectively, and the net chamber itself was modelled by membrane elements. The simulation results show that the net at the top of the cage undergoes more significant deformation due to the surface wave effect. The parametric study revealed that the cage system has an obvious nonlinear relationship with the incident wave amplitude. These findings provide a reference for the engineering design of marine aquaculture systems.
A Detailed Analysis Framework of Fully Coupled Dynamic Responses for Offshore Wind Turbine Blade
Authors: Wang Baoxuan , Liang Xu , Zhang Jianwei , Rui Shengjie , Zha Xing , Wang Shaoyang , Chen Yue
Published: September 2023

As the critical components of a wind turbine to capture wind energy, blades are complex structures, both in terms of shape and composite layup. The outside shape of blades is designed based on aerodynamic considerations, while the internal architecture mainly depends on the bearing capacity of the structure. In the wind turbine industry, the aerodynamic loads of the blade are calculated by the Blade Element Momentum (BEM) based models and then coupled with the dynamic responses of the whole system. The structure dynamics calculation of this method is usually based on highly simplified beam-elements model, which is an efficient calculation model that only applicable to the preliminary design, the final design and inspection of the blade structure requires more detailed three-dimensional (3D) finite element analysis. In this regard, this work developed a set of automatic algorithms to implement the time-domain ANSYS calculation based on OpenFAST and associate the deformation of 3D blade finite element model with the loads acting on it at each time step so as to carry out multi-scale detailed analysis of dynamic responses such as stress/strain on the global blade and local components including skin, spar, shear web and their constituent materials within the integrated framework. As a practical example, the program was used to analyze one of the blades for a 5MW jacket offshore wind turbine in normal power production state under the combined action of wind, wave and current. The effect of soil-structure interaction and marine growth were also taken into account, so as to reflecting the advantages of the integration. In this example, each module of the developed algorithm and the overall calculation results were checked, and the feasibility of the framework was verified. This methodology can be used to perform the detailed analysis of blade structure and material dynamic responses in the integrated design of wind turbines, providing a good starting point for subsequent studies.
Alternative Rope Materials in Towed Fishing Gear to Reduce Plastic Waste, A Comparative Study of Mechanical Properties and Tolerance Against Wear and Tear
Authors: Moe Føre Heidi , Hatlebrekke Hanne Hjelle , Grimaldo Eduardo
Published: September 2023

This paper presents a comparative study assessing the wear tolerance of rope materials in demersal fisheries, specifically seine ropes and dolly ropes. Fourteen different rope materials were assessed in this study, including conventional and alternative commercially available synthetic polymers, and biodegradable materials including natural fibre ropes and custom-made polyester monofilaments. The sample materials were subjected to controlled wear from a rotating abrasive drum. Tensile testing was performed to determine and compare mechanical properties of the samples before and after exposure to wear. A wear tolerance coefficient has been suggested, i.e. a comparative unit between the different rope material samples and a standard blended polyester/polyethylene rope material as reference.

The tested nylon ropes showed the lowest reduction in breaking strength post wear and thus the highest wear tolerance of all tested materials. Conventional and biodegradable polyester ropes and monofilaments also performed well compared to the standard reference rope.

The performed tests did not only consider the effect of different raw materials, but the combined effect of material and structural properties. A rope’s tolerance to wear may be affected not only by the mechanical properties of the raw material, but also fibre thickness and cross section, and rope thickness, structure and lay of rope.

This study demonstrated the potential of using biodegradable polymers with higher tolerance to wear than conventional non-degradable plastic materials as a circular solution to reduce microplastic pollution caused by demersal fisheries worldwide. Application of alternative commercially available ropes and hard-lay rope structures may increase the tolerance to wear and by that reduce plastic waste.
Ship Performance Evaluation and Green Ship Type Scheme Under Complex Channel Conditions
Authors: Lian Zhengchen , Wang Lizheng
Published: September 2023

At present, the interaction and adaptability between ships and complex channels reflect the efficiency of ship operation. Therefore, it is very important to explore the adaptability of navigable ship types and complex channels. In order to study the ship performance evaluation and carbon emission scheme under complex channel conditions, this paper selects the numerical simulation of four typical working conditions of typical ships in the navigation tunnel environment of the Three Gorges New Channel and the numerical calculation of corresponding ship carbon emission inventory. Through model calculation and verification, the effective power of the real ship under various working conditions can be obtained. By analyzing the curve of power changing with speed, it can be concluded that with the increase of ship speed, the water depth has a greater impact on the power of the real ship than the channel width. Based on the ship power at different tonnage and speed, the emission list of four ship types in the speed range of 1–3m/s is obtained by using the emission coefficient method. To carry out the adaptability analysis of ships in key sections and propose the green ship type scheme with excellent comprehensive performance.
Online Modeling of Ship Maneuvering Motion With Varying Loading Conditions
Authors: Yu Yao-Hui , Wang Zi-Hao , Qu Dong , Song Rui , Peng Yan
Published: September 2023

As influenced by the changes in ship loading conditions, the dynamic characteristics of the ship will change accordingly, leading to inaccuracy of the established ship motion model. Therefore, it is necessary to update the model to consistently provide accurate motion predictions. This paper investigated the adaptability of two online learning modes (i.e., incremental learning and sliding window) when the ship loading conditions change. The incremental learning method updates the model quickly with streaming data, while the sliding window method retrains the model with batch data over a period of time. The ε-Support Vector Regression (ε-SVR) is selected as the identification algorithm due to its good generalization ability and nonlinear mapping ability. The KCS container ship is taken as the study object. By changing its loading conditions, the incremental learning and sliding window methods are tested and verified with different amounts of new data. The results indicate that ε-SVR combined with the sliding window has better performance than combined with the incremental learning. The accuracy of the two methods is compared, and the adaptability is further analyzed.
Numerical Investigation of Comprehensive Behaviors of OMNI-Max Anchors in Sand
Authors: Zhang Chengyang , Liu Haixiao , Xiao Zhong , Zhang Wei
Published: September 2023

OMNI-Max anchors are newly developed gravity installed anchors(GIAs) with great potential due to its keying and diving behaviors when subjected to pullout loading. Although the motion behavior of OMNI-Max anchors in clay has been relatively well studied, the attention to OMNI-Max anchors in sand has been relatively limited. In recent years, the booster attached at the tail of the GIAs can make the anchor to achieve a greater initial embedment depth during the installation process, which provides the feasibility for the application of GIAs in sand. This paper investigates the trajectory of OMNI-Max anchors upon pullout in sand, focusing on whether it can dive. The study employs the coupled Eulerian-Lagrangian (CEL) method with a bounding-surface plasticity model which has the ability to reflect the strain hardening of loose sand and strain softening of dense sand. The results indicate that the anchor can not dive in sand under certain conditions unless the position of the shackle are changed. A parametric study is also carried out to quantify the effects of various factors including embedment depth, soil property, cable parameters and the friction coefficient on the behavior of OMNI-Max anchors.
Hydrodynamic Forces on a Near-Bottom Pipeline Subject to Wave-Induced Boundary Layer
Authors: Yin Guang , Ong Muk Chen , Ye Naiquan
Published: September 2023

Hydrodynamic forces on small diameter subsea pipelines and cables placed near seabed are important for their on-bottom stability design. In offshore environments, these pipelines are usually subjected to extreme wave conditions. The present study investigates hydrodynamic forces acting on a pipeline near a flat seabed subjected to a wave-induced boundary layer flow. The Keulegan-Carpenter numbers (KC) of the wave-induced boundary layer flow are 20, 140 and 200, defined based on the pipeline diameter (D), the maximum velocity of the undisturbed near-bed orbital velocity (Uw) and the period of the incoming oscillatory flow (Tw). Reynolds number is 1 × 104 based on Um and D. A seabed roughness ratio ks/D (ks is the Nikuradse equivalent sand roughness) of up to 0.1 and different gap ratios of G/D = 0.05∼0.5 between the pipeline and the seabed are considered. Numerical simulations have been carried out based on two-dimensional (2D) Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations combined with the k-ω Shear Stress Transport (SST) turbulence model. A preliminary one-dimensional (1D) simulation is carried out to obtain a fully developed wave-induced boundary layer velocity profile, which is used as inlet flow for the 2D simulations. The numerical model is validated against the experimental data reported by Sumer et al. (1991)[1] at KC = 10. Influences of KC, ks/D and G/D on the hydrodynamic forces and the surrounding flows are discussed in detail.
Basic Study on Monitoring Technique for Concretes Prestressed With CFRP by Using Fiber-Optic Sensors
Authors: Zhang Tianjun , Azuma Shungo , Hanaoka Daishin , Tanaka Yasushi , Miyazato Shinichi , Kageyama Kazuro , Murayama Hideaki
Published: September 2023

Carbon fiber reinforced plastic prestressed concrete (CFRPC) is a material that utilizes CFRP strand cables as tendons, exhibiting exceptional performance in terms of specific stiffness, strength, and high corrosion resistance [1]. Particularly when used in offshore structures, it is considered to overcome the drawbacks of steel strand cables [2]. In this study, we propose the use of fiber-optic sensors to assess the structural integrity when considering the application of CFRPC to long-life offshore structures. We perform two experiments. First, we conduct tensile tests on three types of CFRP strand cables and one steel strand cable to measure the strain distributions and understand the differences in mechanical properties between the steel and CFRP strand cables, as well as differences between different types of CFRP coatings. Second, we fabricate a CFRPC beam with the CFRP strand cable and bond fiber-optic sensors to a CFRP strand and outside of the concrete beam to measure the strain distribution and verify the feasibility of structural health monitoring of CFRPC. Through these two experiments, we continuously measure the strain along the length of the CFRP strand and the strain distribution of CFRPC from the introduction of prestress until the crack develops. We also investigate the relationship with the breakage behavior and evaluate the mechanical properties, such as the stiffness of the strand cables during the tensile test.
Study on Self-Propelled Wake Characteristics of Surface Ship
Authors: Xiang Han , Deng Weihua , Zou Yanlin , Wang Xunming , Feng Dakui
Published: September 2023

The complex wake generated by the coupling of the propeller rotating wake, the separated wake and the free surface wave-making has a great influence on the multi-ship parallel, replenishment and recovery. The study of self-propelled near-field wake of surface ships is of great significance to the design of ships close to the mother ship, such as recovery boats. This paper focuses on the near-field turbulent wake, propeller rotating wake and Kelvin wake area behind the hull. The ship model DTMB5415M with the propeller model PROP4058 is selected as the research object. URANS simulation method is used to simulate the wake velocity, flow field pressure. The wave pattern, and the wake velocity are simulated and analyzed. The wave height distribution, velocity distribution of the hull wake field and the flow characteristics are obtained. Grid Sensitivity verification is done and the grid is monotonically convergent. At the same time, the wave crest and trough cross sections are found. Taking into account the smallest possible wave height and speed, as well as the shortest possible distance, the optimal path for the recovery boats can be planned.
Predicting the Rate of Cement Plug Failure
Authors: Charabin Scott , Frigaard Ian A.
Published: September 2023

Plugging is an essential part of decommissioning wells. Often cement plugs are set at various depths to isolate critical zones of interest. These zones can include production zones, aquifers and surfaces, ensuring the wellbore is isolated correctly. The cement plug should hydrate and form an impenetrable barrier between the subsurface and the surface. Since the cement slurry, containing a yield stress, is typically denser than the fluid below, there is a tendency to destabilize mechanically. Proper selection of cement properties, namely the yield stress, is therefore essential to the success of the abandonment process. If the cement does not set correctly, the well integrity is compromised and another cement plug will need to be placed.

This motivates the study of this paper, we study the interface between the cement and lighter Newtonian fluid. Over the initial setting time, the interface can become unstable allowing light fluid to propagate upwards into the denser fluid. Experimental studies conducted with water under a denser yield stress fluid show that the interface usually takes the form of a long finger moving centrally upwards. If this finger can reach a critical height in the cement plug before it sets sufficiently, the plug will lose its integrity and fail. Therefore, being able to predict the velocity of the finger is of critical importance. We scale our experimental setup to give an accurate representation of a typical western Canadian well. We can then derive an analytical expression for the flow rate and mean velocity of both the viscous finger and the dense fluid flowing down. We then explore this finger propagation by varying the critical parameters of the heavier fluid, namely the density and yeild stress. Experiments show that the model accurately predicts the velocity of the finger for a range of rheological properties and densities. The speed of the finger is found to be governed by the yield stress, the density contrast, and the ratio of effective viscosities.
Modeling Oceanic Variables With Graph-Guided Networks for Irregularly Sampled Multivariate Time Series
Authors: Fialho Coelho Jefferson , Rodrigues de Barros Marcel , Fabricio Deberaldini Netto Caio , Marino Moreno Felipe , Palmiro de Freitas Lucas , Sproesser Mathias Marlon , Gagliardi Cozman Fábio , Dottori Marcelo , Satoshi Gomi Edson , Aoun Tannuri Eduardo , Helena Reali Costa Anna
Published: September 2023

Forecasts of ocean dynamic variables are essential to ensure safe operations at sea and in coastal regions. However, one difficulty with such forecasts is the need to handle multiple scales and repetitions in data, as well as noise caused by sensors malfunction. We describe a data-driven approach to predict oceanic variables under those circumstances; we take as a case study the prediction of water current velocity and sea surface height in an estuarine system in the southeastern coast of Brazil. We propose a generic method that can be applied to a variety of practical cases with little to no adaption, using a Graph Neural Network to model the system dynamics. We provide evidence that our method produces robust forecasts. It does so by employing forecast data from the state-of-the-art physics-based model “Santos Operational Forecasting System” (SOFS). The approach has lower computational costs and requires almost no domain-specific knowledge. We compare our model with SOFS and ARIMA-like forecast models in experiments.