bluuebunny/crossref_metadata_2025_split huggingface dataset:
Benchmarking Measured Eigenfrequencies: A Case Study of a North Sea Offshore Wind Farm
Authors: Sastre Jurado Carlos , Weijtjens Wout , Stuyts Bruno , Winkler Kristof , Fallais Dominik , Devriendt Christof 
Published: August 2024

Abstract
Offshore wind turbines are dynamic structures that require an accurate estimate of the main eigenfrequencies to avoid resonance and, as a result, increased fatigue damage. This contribution focuses on the first and second mode eigenfrequencies measured over an entire offshore wind farm in the Belgian North Sea. The comparison between the field measurements during parked conditions and design estimations yields the same conclusions as previous studies reported in the literature; eigenfrequencies are systematically underestimated. A comprehensive step-by-step fleet-wide numerical benchmark is thus presented to improve the model predictions and understand the causes of the mismatch. Finite-element analyses, based on the current state-of-the-art soil-monopile interaction models, were considered since the foundation stiffness is identified as a key source of the discrepancy between in situ observations and design models. The importance of environmental parameters in the second mode is studied. The consideration of the contribution of scour protection for a realistic representation of foundation stiffness is discussed as well. The final results show that simulations agree considerably better with the measurements, although a significant bias is still observed for the second mode.
Effects of Strain Hardening and the Lode Dependence of the Fracture Strain Locus on Slant Fracture in Charpy V-Notch Impact Testing
Authors: Wong Wei Jun , Walters Carey 
Published: August 2024

Abstract
Ductile fracture in steels relevant to the offshore and maritime industry is often characterized by the occurrence of slant fracture, which is the development of fracture surfaces that are slanted relative to the original surface of the material. The modeling of this phenomenon is important for describing ductility and fracture toughness accurately in ductile fracture simulations. This work uses a consistency model for viscoplasticity with damage softening within a strain-based framework to investigate the effect of variations in strain hardening and Lode dependence on the slant fracture area and impact energy in Charpy tests. The model is first calibrated to uniaxial tensile, single-edge-notched-bending fracture toughness and instrumented Charpy tests performed on an S690QL steel, and then a parametric study varying the strain hardening and the Lode-dependence is performed. It is seen that an increase in the yield-to-tensile-strength ratio (equivalent to a decrease in the strain hardening exponent) leads to a decrease in the impact energy and negligible difference in the percentage slant fracture area when the damage and rate parameters are kept constant. It is found that the Charpy impact energy is not sensitive to the maximum strains in the fracture strain locus and is mainly affected by the minimum strains in the locus. Finally, the rate-dependent consistency plasticity model with a strain-based damage-softening formulation is capable of simulating slant fracture behavior even in cases where the fracture initiation strain is stress-state-independent and constant.
Dynamic Response Analysis for the Monopile Driving Process of Offshore Wind Turbines
Authors: Wang Kang , Hu Haibin , Feng Xiaoxing , Ni Zhonghua , Yan Yan 
Published: August 2024

Abstract
Monopile is used as supporting part of offshore wind turbines (OWTs) and determines its service time. After the construction, dynamic response of monopiles has been extensively studied under external loads, such as seawater corrosion, offshore wind and pile-soil interaction. However, in the monopile driving of large-capacity OWTs, the hammering force and stress peaks increased several times over. Therefore, in this work, two finite element models were established for the monopile driving process, including the bottom-fixed model and spring-friction model. These models were verified by the construction data from engineering. From the comparison, the data in spring-friction model was more consistent with the engineering condition. It overcame the shortcomings of bottom-fixed model. The inclusion of pile-soil interaction allowed for the determination of pile penetration and lateral friction resistance. The simulation results were more accurate and had less error with engineering data. The numerical simulation was expected to provide reference data for studying the fatigue life analysis of the driving monopile.
Multi Modal Mapping of Sea Ice Fields From Remote Shipborne Instrumentation
Authors: Veggeland Oskar G. , Kim Ekaterina , Skjetne Roger 
Published: August 2024

Abstract
We present a standalone instrumentation system designed to create digital multi-modal maps of the sea ice surrounding ships operating in the Arctic. The system contains a 3D LiDAR scanner and an optical camera for remote sensing. Spatial calibration of the sensors enables us to project point clouds onto the optical images, providing RGB values to the 3D map. The presented system can continuously monitor sea ice and build large-scale maps by running a navigation filter to estimate the system trajectory. This is made possible by internal navigational payloads, making the system independent of the vessel on which it is mounted. The ice field maps are validated by reconstructing images and comparing them to synchronized inputs from the optical camera. Qualitative comparisons between the reconstructed and optical images show that the most prominent features of the sea ice are conserved. We also propose a method to track sea ice roughness over large temporal and spatial scales and show how this can automatically detect areas with a high amount of deformed ice.
Analytical and Numerical Study on Drill-String Torsional Vibration Under Weight-On-Bit Fluctuation
Authors: Kaneko Tatsuya , Inoue Tomoya , Wada Ryota , Katsui Tokihiro , Suzuki Hiroyoshi 
Published: August 2024

Abstract
Understanding drill-string dynamics is essential to improving offshore drilling efficiency and preventing accidents. Previous studies have mainly focused on self-excited oscillations due to stick-slip and bit-bounce. However, in deepwater drilling, large weight-on-bit fluctuations due to ship heaving are a major concern that can affect the dynamics in the torsional direction. This paper reports analytical and numerical investigations on the torsional vibration of a drill string under weight-on-bit fluctuation.
First, the analytical solution of a single-mass model showed that forced oscillations are caused by WOB fluctuations, which have not been examined extensively in previous studies. In addition, for the same amplitude of WOB variation, vibration at the heave frequency has a greater effect on torsional vibration than at the axial self-excited frequency. Furthermore, large WOB fluctuations increase the risk of stick-slip and reverse rotation of the drill bit.
Second, numerical experiments with the multi-mass model yielded results similar to those of the analytical study. These results show the importance of capturing torsional vibrations caused by fluctuations in the WOB and reducing WOB fluctuations.
Dynamic Responses of a Gravity-Type Fish Cage During Lifting Operations in Waves and Current
Authors: Wen Xueliang , Ong Muk Chen , Cheng Hui 
Published: August 2024

Abstract
Aquaculture has experienced remarkable growth over the past four decades. The utilization of fish cage systems at sea has played a pivotal role in promoting the growth of seafood production. As technology advances, the gravity-type fish cages become more and more popular because of the low capital cost for the industrial-scaled fish farming. The lifting operation of gravity-type fish cages is an important procedure for the harvest and de-lice of the fish. In the present study, the static and dynamic responses of the fish cage before and during the lifting operation are investigated numerically. A Morison model is adopted to calculate the hydrodynamic forces acting on the net ropes of the aquaculture nets and a screen model is used to calculate the hydrodynamic forces acting on the net twines of the aquaculture net. The irregular waves are generated using the JONSWAP wave spectrum. The structure of the aquaculture nets is modelled using an extended position-based dynamics (XPBD) method, which was first used in the cloth dynamics simulations in games. The proposed method is effectively validated against the published experiment data to ensure its accuracy and reliability. The static response of the gravity-type fish cage at various current speeds, and the dynamic responses of the fish cage in irregular waves before and during the lifting operation are analyzed. Results show that in a smooth sea state, the drag force of the fish cage is slightly higher than that in a uniform flow with the same current speed and the fish cage volume sightly decreases, while the deformation of the fish cage is similar. During the lifting operation, the lifting force mainly results from the weight of the sinkers at the bottom of the side net. The maximum tension of the net is located at the net ropes connected to the centre point of the bottom net. Therefore, the structure of the bottom net should be enhanced for safety lifting operations.
Combination of Potential Theory and Morison-Like Viscous Drag Terms in the Hydrodynamic Model of a 12 MW Semi-Submersible Floating Wind Turbine
Authors: Souza Carlos Eduardo Silva de , Fonseca Nuno , Berthelsen Petter Andreas 
Published: August 2024

Abstract
Semi-submersible platforms are widely adopted as support structures for floating wind turbines (FWT). Morison-like, quadratic drag terms are typically used for modelling viscous loads on the platform columns and pontoons, with drag coefficients obtained from model tests. One of the challenges when adopting this modelling approach is to achieve a simultaneous representation of damping effects and viscous excitation. In this paper, a systematic procedure is presented to calibrate the drag coefficients of a semi-submersible platform supporting a 12 MW FWT, based on model test results. First, the pontoon coefficients are calibrated based on the heave and pitch motions. Then, it is assumed that viscous excitation in surge is mainly associated with the upper part of the columns, which are subjected to more significant action of the waves. Thus, the coefficients at this portion of the columns are tuned to retrieve the low-frequency motion components not captured by potential theory alone, while the coefficients at the bottom of the columns are adjusted for achieving the necessary level of damping. The final coefficients are chosen based on comparison between the model test results and multiple combinations of the drag coefficients associated with different components of the platform.
Characteristics of Solid-Liquid Two-Phase Flow in Deep Sea Mining Pipelines
Authors: Li Jianing , Chen Nian-Zhong 
Published: August 2024

Abstract
The technical feasibility of the pipeline hydraulic lifting system has been confirmed through multiple offshore trials and it has been currently the most promising deep-sea mining system. When transporting minerals collected from the deep-sea seabed to the sea surface along with seawater, complex multiphase flow upwelling issues are generated. In this paper, in terms of the open-source Computational Fluid Dynamics (CFD) software OpenFOAM®, a Lagrangian solver coupled the Eulerian and Lagrangian phases is established to simulate the flow of solid-liquid two-phase within a vertical riser. In this model, the discrete phase is solved by using the Discrete Element Method (DEM), and the continuous phase is achieved by solving the Navier-Stokes (RNAS) equations, taking into account the complex particle interaction. The movement of solid particles in turbulent flow is calculated and the distribution of solid particles under different conditions is obtained. The flow characteristics of solid-liquid two-phase flow are obtained from the perspectives of internal flow field distribution. The results demonstrate that the established numerical model for solid-liquid two-phase flow is relatively reliable, and the transported flow velocity has a certain impact on the lifting performance of the riser. This research offers a theoretical basis and practical reference for the future design of pipeline lifting systems.
Formulation of Idealized Structural Unit Method to Perform Progressive Collapse Analyses of Welded Box Girders in Bending
Authors: Lindemann Thomas , Kaeding Patrick 
Published: August 2024

Abstract
The Idealized Structural Unit Method (ISUM) is a simplified but very efficient approach to perform progressive collapse analyses of ship structures. Larger structural units are defined as ISUM-plate elements with idealized material and geometrical nonlinearities, that progressive collapse analyses are performed with reduced numerical efforts compared to nonlinear finite element analyses (FEA). A summary of different generations of the ISUM-plate element formulation is proposed. The newest generation of ISUM is described in detail with respect to its applicability to determine the ultimate strength of welded steel structures. The developed concept to apply welding residual stresses to plates and stiffened plate panels is explained. A combined ISUM-plate/beam-column element model to determine the progressive collapse behavior of welded box girders in four-point bending is proposed. The numerical results are compared to experimental data. For further comparison nonlinear finite element analyses are performed. Details about the FE model and the application of welding related imperfections are given. The ISUM model is used to determine the progressive collapse behavior of a box girder specimen for different load cases of biaxial bending. The influence of lateral pressure acting on the bottom structure on the ultimate strength of the box girder specimen is investigated with ISUM.
A Comprehensive Review of CO2 Corrosion in Oil Well Cement: Mechanisms, Determinants, and Mitigation Strategies
Authors: Zhao Feng , Wang Chengwen , Li Dingye , Chen Zehua 
Published: August 2024

Abstract
Carbon capture, utilization and storage (CCUS) is the main technique for carbon neutrality. This emerging technology has been developed to capture CO2 and store it in underground formations, such as aquifers or depleted gas or oil reservoirs. The corrosion of oil well cement by CO2 is a significant challenge which this technology faces. CO2 dissolves in the formation liquid phase to form an acidic fluid that interacts with various components in oil well G cement. As the corrosion progresses, the cement’s mechanical integrity diminishes, permeability escalates, and overall properties degrade. Factors like temperature, pressure, and the inherent properties of the cement significantly influence this reaction process. Over recent years, numerous investigations have delved into the CO2-cement interaction, leading to the innovation of myriad techniques aimed at mitigating this concern. Employing oil well cement, distinguished by its diminished porosity, decreased permeability, and attenuated alkalinity, represents a globally recognized strategy for augmenting CO2 corrosion resistance. Pozzolanic substances and film-forming barrier materials are extensively documented in literature as CO2-resistance potent agents. This paper offers a review of previous research works, encompassing the corrosion mechanism of oil well cement by CO2, various factors affecting CO2 corrosion, and CO2-resistant cement techniques.
Enhancing the Resolution of Large-Scale Sea-Ice Models Through Synthesising Satellite Imagery and Discrete-Element Modelling
Authors: Tsarau Andrei , Lu Wenjun , Lubbad Raed 
Published: August 2024

Abstract
Deformation is a fundamental aspect of sea-ice behaviour, playing a crucial role in the overall dynamics of polar regions. Sea ice deforms as it moves and changes shape in response to external forces and internal stresses. This may lead to the formation of specific narrow deformation structures, including cracks, elongated openings (leads), pressure ridges and shear zones, all of which are important for safety and navigation in polar regions. Cracks and leads also influence the exchange of heat and gases between the ocean and the atmosphere, affecting climate patterns and ecosystems.
Satellite sensors may provide data on local sea-ice conditions, including leads and other deformation features, at high spatial resolution. However, the temporal resolution of these data is often insufficient as it is limited by the satellite’s revisit time and may also be affected by weather conditions. Sea-ice models may be used with various spatial and temporal resolutions. Nevertheless, modelling the dynamics of sea ice, including floes of various sizes and narrow deformation features, using traditional (continuum) models is challenging because of their coarse grids, especially near coastlines and islands. Models based on the Discrete-Element Method (DEM), on the other hand, can resolve the dynamics of individual floes of any sizes and, therefore, are well-suited for modelling the behaviour of sea ice at small scales.
Using high-resolution satellite imagery along with oceanographic reanalysis data and large-scale ice drift predictions to initialise and force a DEM model, we have shown that this model can reproduce short-term ice drift and deformation patterns within a 100-by-100 km2 area near Arctic islands. However, further development of the DEM towards explicit ice fracture, accompanied by upgrades to ocean-current models, may be necessary, especially for long-term simulations (over 24 hours). The present model resolves elements of sea ice on scales of 50 m to 100 kilometres, including floes and leads, and, therefore, can be useful, e.g., in ice navigation and climate studies. To demonstrate a possible application example, we explored the possibility of using this DEM model for assessing routes for ship navigation through ice-covered waters.
Digital Twin-Driven Optimal Design of Connector Stiffness for Floating Multi-Modular Structures - An Application for Floating Solar Energy Harvest
Authors: Nguyen Dong Trong , Sølvberg Stian Hansen , Aas-Hansen Trine 
Published: August 2024

Abstract
This paper proposes an optimization framework for connector stiffness design for multi-modular floating structures, designed for offshore floating solar in open seas. The framework integrates an optimization scheme with a digital twin. An early-phase digital twin was developed to assess the structure’s response to waves as a basis for evaluating a connector stiffness parameter that mitigates environmental effects. An objective function considers module motions and internal connector loads, offering flexibility in tuning based on priorities. Bayesian optimization was adopted to find the global optimal connector stiffness, utilizing Gaussian Process regression. This method is suitable for optimizing objective functions that are expensive to evaluate, e.g. resource-intensive simulations of the response of the large multi-modular structure. The optimization process was validated and verified through model-scaled experiments and simulations in regular waves with different wave periods. In conclusion, the proposed framework demonstrates the capability to find optimal stiffnesses for different sea states, mitigating environmental effects on multi-modular structures. Future work will concentrate on improving the digital twin fidelity, reducing simulation time and developing an optimal control algorithm to enhance overall multi-modular structure performance in real-time.
The Influence of Slot Design and Biofouling on the Hydrodynamics and Dissolved Oxygen Exchange Through a Finfish Open Ocean Aquaculture Structure
Authors: Nguyen Duc , Wakes Sarah , Vennell Ross , Paing Si Thu , Rhone Scott , Kregting Louise , Black Suzy , Janssen Gerard 
Published: August 2024

Abstract
The current study examines the influence of a new design of open ocean aquaculture (OOA) finfish structure and environmental and physical factors on the hydrodynamics and dissolved oxygen (DO) exchange using Computational Fluid Dynamics (CFD). The structure is a 1,500 m3 square cross-section cylinder with mesh placed at the front and back of the body. There are slots on the body of the structure with densities varying between 0% (i.e. no slots) and 12%. Both parallel and perpendicular to the flow direction slots are examined. Biofouling is simulated using a flow reduction ratio through the mesh that varies between 5% and 50%. Fish density is 15 kg.m−3 and water temperature is 15°C with current speed scenarios of 0.1, 0.05 and 0.01 ms−1. We found that increasing the flow reduction ratio through the mesh to simulate biofouling effects results in a decrease of DO inside the structure. For example, flow reduction through the mesh increases from 15% to 50% resulting in the healthy volume fraction inside the structure (i.e. DO &gt; 70% saturated DO) decreases from 0.22 to 0.15, when current speed is 0.01 ms−1. Increasing slot density facilitates flow ventilation through the structure and increases DO inside the structure. Increase of current speed results in an increase of DO inside the structure. For example, the healthy volume fraction increases from 0.19 to 1.0 when the current speed increases from 0.01 to 0.1 ms−1. Overall, we found that CFD modeling is a useful tool to explore the complex relationship between novel OOA structure designs (e.g. various slot densities on the body of structure) and environmental and physical factors (e.g. blockage mesh effects, current speed) on the hydrodynamics and DO exchange.
Hydrodynamic Characteristics of Heave Plates in Shallow Water Using Forced Oscillation
Authors: Li Haoran , Zheng Jinhai , Zhang Jisheng , Xue Mi-An , Yang Chen 
Published: August 2024

Abstract
Heave plates which are widely attached at the base of columns of offshore floating wind turbines (OFWTs) can effectively reduce the resonance oscillations and improve the stability of OFWTs by providing additional added mass and damping. These hydrodynamic forces are strongly affected by the proximity of boundaries in shallow water. In the present work, the variations of added mass and damping coefficients as the heave plate moves a flat and stepped terrain are investigated. A column with a single solid circular heave plate is simulated in a numerical wave tank using forced oscillation tests. The added mass and damping coefficients are determined by fitting time series of the calculated force to Morison’s equation with a least squares procedure. The damping coefficients of heave plate increase with the decreasing water depth in the flat terrain (up to 60% compared to the coefficient in deep water). Similar conclusions are found when the length of stepped terrain is not less than the diameter of heave plate. However, the damping coefficients of heave plate significantly increase in the condition that the length of stepped terrain is smaller than the diameter of heave plate (up to 80% compared to the coefficient in the flat terrain).