bluuebunny/crossref_metadata_2025_split huggingface dataset:
Symmetry Breaking of a Rigid-Flexible Coupling System at Low Reynolds Numbers
Authors: Zhang Huanyu , Tian Xinliang , Zhao Yakun , Li Xin , Lu Wenyue 
Published: September 2023

Abstract
Flow past a rigid-flexible coupling system consisting of a rigid plate and a trailing closed flexible filament was simulated numerically. An immersed boundary method was developed based on OpenFOAM to solve this fluid-structure interaction (FSI) problem. Three simulations including flow past a rigid circular cylinder, a rigid plate, and two flexible loops were conducted to validate our code. The motion modes transition and dynamic performance of the coupling system were investigated at low Reynolds numbers (Re ≤ 80), where the tension coefficient and bending coefficient of the filament were fixed. According to the symmetry of the filament motion, six motion modes have been identified for different filament lengths and Reynolds numbers, i.e. symmetric and stationary (SS) mode, asymmetric and stationary (AS) mode, regular and unilateral flap (RUF) mode, transition motion (TM) mode, symmetric and bilateral flap (SBF) mode, and asymmetric and bilateral flap (ABF) mode. Moreover, symmetry breaking was discovered in the AS, RUF, and ABF modes. The positions of the filament at different times were drawn to describe its movement and distinguish motion modes. Meanwhile, the drag and lift of the coupling system were investigated and a significant drag reduction was found. In addition, The time-averaged lift directly depended on the symmetry of the filament and rapidly changed with a sudden alteration in symmetry. Our research is helpful to understand the change of motion behavior of this coupling system at low Reynolds numbers.
A Review: DC Microgrids for Sustainable Power Delivery in Offshore Industries
Authors: Indrajith Bawantha , Gunawardane Kosala , Jayasinghe Hasith 
Published: September 2023

Abstract
Legacy Alternating Current (AC) based power systems, coupled with bulk-generated electrical energy from fossil fuels, are working against the achievement of sustainable development. Worldwide integration of renewable energy in power generation is growing rapidly. This is making a major contribution to the achievement of sustainable development goals and affordable clean energy. Direct Current (DC) operable products are becoming the most common type of internal power architecture in many application domains in both land and marine based systems. In these systems, power supplied from AC form is internally converted to DC within the appliance. Renewable-based power generation, including solar photovoltaics (PVs), wind, wave, and tidal generators, can generate DC power intrinsically or can be converted to DC power. In addition to that the supportive novel technologies developing around renewable energy generation such as hydrogen storages, fuel cells and associated other alternative energy storage technologies such as battery and supercapacitors all are intrinsically in DC form. Therefore, both the supply and the demand sides of power systems are in favor of moving towards DC systems called DC microgrids. With the elimination of DC/AC and AC/DC converter stages in DC grids, they create a highly efficient, low-cost platform. Also impacts such as skin effect, reactive power usage, power quality issues and grid synchronization are comprehensively reduced too. Since renewable sources like photovoltaics generate on-site DC power, eliminating the need for long distance AC transmission facilities, they are particularly attractive for remote communities and industrial and commercial sites. Since the minimum interaction on main power grids, offshore systems are more attractive to be operated as low voltage DC distribution. DC microgrids have the potential to revolutionize power systems by offering a versatile solution for a wide range of power applications. These microgrids can support various power applications including small-scale generation, energy storage backup, data centers, marine operations, and industrial facilities. With the details provided about the objectives behind the trend towards DC microgrids, their benefits and some issues, a comprehensive discussion about DC microgrid standards, components and controlling are also presented. Furthermore, this paper discusses application of offshore industries like aquaculture, oil and gas. These offshore industries are rapidly integrating with DC microgrids to have low-emission operations with reduced impact on nature. With the information illustrated on this paper, it is desirable to indicate that system and control architecture for a desired offshore application can be designed uniquely from any another industrial application to have sustainable power delivery arrangements.
A Dry Monitoring System of Mooring Lines Utilizing Artificial Intelligence
Authors: Sidarta Djoni E. , Tcherniguin Nicolas , Bouchard Philippe 
Published: September 2023

Abstract
Detection of mooring line failure of a floating vessel without any inputs of environmental conditions and/or directions can be made possible by measuring and analyzing vessel positions and headings, and also drafts in the case of an FPSO. This approach simplifies the required monitoring equipment and certainly helps in reducing cost and required maintenance.
In addition to changing a vessel’s mean positions and headings, mooring line failure changes natural periods of the system. Therefore, to determine the condition of mooring lines and to detect mooring line failure, a dry monitoring system can (or needs to) detect subtle changes of natural periods of the system and variations in vessel headings as a function of vessel position and draft (or mass) for an FPSO. This task that can be categorized as pattern recognition and classification is very difficult to carry out with human visualization or conventional methods/tools to get to a reasonable detection rate. Although challenging, solving this task can be rewarding. This is an area that Artificial Intelligence (AI) is very good at, and AI can be an essential component of a reliable dry monitoring system.
This paper presents several AI models, including Artificial Neural Networks (ANN), that can be used to determine the condition of mooring lines and to detect mooring line failure. This paper compares the performance of these AI models for a vessel’s loading condition (draft) that has not been included in the training of the models. This paper also discusses a method to enable an ANN model to be more tolerant and adaptive to new conditions and its applicability for other AI models.
AI models can be used in combination with conventional digital methods (numerical algorithms) to determine the condition of mooring lines and to detect mooring line failure. This approach of combining AI models and conventional digital methods for a dry monitoring system requires knowing how and when to use AI models and conventional digital methods. This important aspect is illustrated in the presented examples on how the monitoring system detects mooring line failure in real time. These examples show the importance of AI and conventional digital methods and the significant contribution from each of them.
This paper demonstrates that AI can be an important tool for a dry monitoring system of mooring lines and can be used in conjunction with conventional digital methods to increase the robustness of the solution. This application of AI is an example of the potential of AI in solving an engineering problem, which is otherwise difficult to solve using conventional methods/tools.
Reducing Containership Greenhouse Gas Emission Through Speed Optimisation by Coupling a Fast Time Manoeuvring Solver to a One-Dimensional Propulsion Model and Under Keel Clearance Predicting System in Shallow Water Under Environmental Forcing
Authors: Kazerooni Reza , Karatvuo Helena , Harkin Alex , Womersley Timothy , Jensen Bugge 
Published: September 2023

Abstract
Deciding the target speed profiles within harbor approach and navigational channels requires a trade-off between sufficient under keel clearance and control of the ship in different weather conditions. Rudder as the main type of steering system for conventional ocean-going vessels is considered as a passive control device leading to decreased steering performance when ship speed through water decreases. On the shallow sections of navigational channels, the ship needs to slow down to maintain safe bottom clearance margins (due to squat effects). However, once combined with strong wind or currents, this speed reduction may limit the ship controllability and course-keeping which becomes a challenge to navigation. In response to the recent pressures on the climate, another dimension has been added to this transit planning balance. It is now also important to optimize target speed profiles to minimize emissions while ensuring safety in manoeuvering and reducing grounding risk. A fast time manoeuvering solver using a PID controller for steering the ship is developed based on SimFlex 4 manoeuvering model and linked to a one-dimensional model of the ship propulsion system to estimate the actual loading on the propeller and engine during the manoeuvers. Consequently, the fuel consumption and emission of green-house gases from the engine is predicted. The ship under keel clearance is calculated based on empirical squat, turning and wind induced heel methods, and a second order panel method for evaluating vessel frequency response incorporating implicitly the effect of vessel forward speed and varying depth for the ship responses in waves. Consolidated as commercial package, NCOS ONLINE, it is of the modern generation of operational tools for navigation optimization in shallow and confined waterways. The tool is then used to find the optimum target speed resulting in minimum emissions from the main propulsor, while the manoeuvring performance and under keel clearance remain within the acceptable thresholds for safe navigation of large commercial ships.
Experimental and Numerical Analysis of Ice Crushing Tests With Different Shaped Ice Specimens
Authors: Müller Franciska , Böhm Angelo , Herrnring Hauke , von Bock und Polach Rüdiger U. Franz , Ehlers Sören 
Published: September 2023

Abstract
Ships operating in ice covered waters are exposed to the risk of colliding with an iceberg or ice floe. Predicting the loads in ice-structure interaction is crucial for the safety of existing ships and the optimization of the ship structures in the future. The ice geometry and the interaction velocity are two parameters, among others, that have a high influence on the acting forces and pressures. There has not been much research on the influence of the ice geometry in ice-structure interaction tests in the past. This paper analyzes the failure mode, peak forces, and energy of different ice specimen geometries at different interaction velocities in small-scale crushing tests and identifies shape-dependent effects. Furthermore, a first attempt is made to numerically simulate these experiments with the Mohr-Coulomb Nodal Split (MCNS) ice model in order to extend the applicability of the model to more general ice-structure interaction problems. Overall 21 different ice shapes were tested in crushing experiments with a hydraulic piston and drop tower experiments and were simulated with the MCNS model. In addition, the influence of the interaction velocity was analyzed for 13 shapes at interaction velocities of 10, 100 and 2000 mm/s. The specimen shapes included among others a cylinder, cones, truncated cones, elliptical, dome-shaped and wedge-shaped. In the experiments, the load, the displacement, and the failure behavior were recorded. Especially the peak force, energy, and failure mode were used for the analysis and comparison with the simulation results. The results show a high dependency of the failure mode and peak forces on the specimen shape, initial contact area, and interaction velocity. The MCNS model is capable to predict trends of the peak load depending on the initial contact area and generated different failure behaviors depending on the ice geometry to some extent. However, there is potentially room for improvement, especially considering the triaxiality and the influence of the interaction velocity.
Numerical Study of the Lateral Blockage Effect on the Performance of a Novel Vertical-Axis Turbine
Authors: Wu Hao , Cao Renjing , Wang Enhao 
Published: September 2023

Abstract
Regarding to a novel vertical axis auto-rotation current turbine (VAACT), a detailed three-dimensional (3D) numerical study was carried out on the influence of lateral blockage on its performance using detached eddy simulation (DES) combined with the slide mesh. Firstly, time series of angular velocities during the power production stage of the turbine are given, and it is demonstrated that the increase of blockage ratio is beneficial to stabilize its rotation and power output. Also, it is found that as the lateral blockage ratio decreases, the efficiency of the turbine decreases. The fitted curve of mean power coefficient (Cp¯) as a function of lateral blockage ratio is presented. Based on the fitted curve, it is roughly predicted that Cp¯ will be about 0.145 without the lateral blockage effect. Finally, detailed flow field characteristics such as limiting streamlines and 3D vortical structures are displayed in this paper. The two rows of side-by-side vortexes are observed to periodically fall off in the wake, and the onset vortexes behind the turbine are almost two-dimensional in the spanwise direction. All in all, this study deepens the understanding of this novel vertical-axis turbine, and can provide references for its future industrial applications.
An Approximate Method for Predicting Nonlinear Time Domain Motion of Ship Taking Motion Attitude Change at Large Amplitude Into Account
Authors: Duan Fei , Ma Ning , Shi Qiqi , Gu Xiechong , Zhou Yaohua 
Published: September 2023

Abstract
The large amplitude motion of a ship in rough sea will lead to obvious nonlinear characteristics of the hydrodynamic loads acting on the hull, especially for shallow draft ships. Therefore, the fast and accurate prediction of nonlinear motion of the ship needs to be solved. The transformation from frequency domain to time domain is realized based on impulse response function method. And the nonlinear restoring force is calculated through pressure integration on instantaneous wetted surfaces. The instantaneous radiation and diffraction force considering the nonlinearity of hull surface are pre-calculated and stored in a database. The database includes the added mass, damping coefficient and diffraction force at different relative position of wave and the hull. According to the height of the instantaneous average wave surface on the hull at the last moment, the instantaneous value of the added mass, damping coefficient and diffraction force of the hull are obtained by invoking the corresponding steady-state solution in the database. The radiation force and diffraction force change along with the motion attitude of the ship are considered in this method. The model test has been carried out to verify the proposed method. Compared with model test, the method proposed in this paper can obtain accurate results of ship nonlinear hydrodynamic forces in a relatively short time, which is effective for prediction of the ship’s large motion response.
HDD Borehole Pull-In Analysis of Offshore CCS Pipeline
Authors: Yu Yi , Duplenskiy Stanislav 
Published: September 2023

Abstract
In recent years, with the increasing demand of reducing CO2 emissions, offshore pipeline found its new application in transporting CO2 offshore. Carbon capture and storage (CCS) is an effective method in the fight against climate change. This technology allows CO2 to be “captured” from large sources such as power plants and prevents release of greenhouse gas to the atmosphere. The captured CO2 has to be compressed and then transported to a safe and durable storage location, such as depleted subsea oil reservoirs. The captured CO2 is then locked away deeply under the sea floor so that it cannot escape into the atmosphere and contribute to global warming.
To facilitate the connection between an offshore pipeline and an onshore plant, a robust landfall method must be adopted. The benefits of using horizontal direction drilling (HDD) for offshore pipeline landfall include longer durability, potentially lower project cost, less community and environmental disruption, and fewer authorization issues.
In this paper, the analysis methods and the results of an HDD pull-in case study are presented. An analytical method for pull-in force is discussed first and then a global finite element (FE) model is developed. In the global model, a 10 km long pipeline is included. The pipeline, the pull wire and HDD borehole are simulated by using beam elements. The tube-to-tube elements are used to simulate the contact between the pipeline/wire and the borehole. The global model is used for both the pull-in and the hang-off analysis. To prevent corrosion of the pipeline in case of the coating damage, circular anodes are installed on the pipeline. In the HDD borehole, the anodes are installed for all the pipe joints. Since the anode pitch is small enough, the anodes are also used as centralisers during pull-in installation. To study of the effect of anodes on pull-in load, a local FE model is also developed. In the local model, a short pipe section and an anode with detailed geometry are included. The pipe and the HDD borehole are modelled using shell elements and the anode is modelled with solid elements. The additional pull-in load caused by the anode is predicted by using the local model. The loads acting on the hang-off structure in different phases are also obtained from the analysis, which are used as design input data for the hang-off structural design. The finite element analysis (FEA) results are compared with the results obtained from the simplified analytic calculation. It is concluded that the results obtained from the proposed FEA method are more accurate and more reliable than those from the simplified methods. In future, the proposed numerical analysis method can be used as reference or go-by for projects with HDD pull-in.
Derivation of Adapted Soil Springs for the Buckling Analysis of Suction Caissons During Installation
Authors: Ramos Juan Pablo , Widerspan Viktor , Heinrich Dariya , Böhm Manuela 
Published: September 2023

Abstract
The buckling capacity of suction caissons during installation must be investigated, as these are sensitive to buckling due to their thin-walled structure. A geometric material nonlinear analysis with imperfections, in which the soil is modeled using continuum elements, provides the most realistic results. Nonetheless, the modeling of the nonlinear material behavior of the soil as well as the consideration of multiple imperfection shapes are associated with a high modeling and computational effort. To avoid this, springs are often used to model the soil. However, the common approaches for determining lateral soil springs were developed experimentally for flexible piles and not short caissons. In this work finite element models are created to derive adapted soil springs for large scale tests on suction caissons. The comparison of the implemented soil springs with the soil springs from the guidelines shows that an adjustment of the commonly used springs is necessary. A factor that allows the springs to approximate the behavior of the continuum elements is formulated. Additional models that analyze the supporting effect of the soil on the buckling capacity of the suction caisson using continuum finite elements and soil springs foundations are developed. These models also compare the effect of the embedment depth and the soil bearing capacity.
Numerical Simulation to Collapse of a Carcass of a Flexible Riser Using a Dynamic Model With Quasi-Static Behavior Through of an Explicit Solve Method
Authors: Párraga Quispe José Luis , Ribeiro Rodrigo , Drumond Geovana , Nogueira Soares Luisa , Igor Lourenço Marcelo , Barata Anderson , Ramalho dos Santos Ferreira Lucas , dos Santos Cordeiro Alexandre 
Published: September 2023

Abstract
A flexible pipe riser is a flowline to oil transport from a subsea well to a floating unit, and it is composed of layers between these a carcass, a pressure sheath, a pressure vault, tensile armors, and anti-wear layers. A carcass or interlocked carcass is more internal layer and is projected to support radial forces. High radial forces can produce a collapse failure of an interlocked carcass. The interlocked carcass has a helical section geometry, so the pitch provides an interlock between its surfaces. These interactions between surfaces using a finite element model with an implicit method produce high non-linearity of the numerical problem for convergence of results. Therefore, a numerical model is proposed using a dynamic model with a quasi-static behavior and explicit solve method for the collapse analysis of an interlocked carcass. Numerical analysis is carried out in two steps. In the first step, the carcass pipe is generated by an angle of revolution applied to the section considering the pitch of the spiral. Therefore, a numerical model is developed to insert an imperfection in the perfect pipe. In the second step, an external vessel with stoppers is modeled where the carcass pipe is positioned internally, thus representing the pressure test with a hyperbaric chamber.
Incorporating Empirical Nonlinear Efficiency Into Control Co-Optimization of a Real World Heaving Point Absorber Using WecOptTool
Authors: Gaebele Daniel T. , Michelén Ströfer Carlos A. , Devin Michael C. , Grasberger Jeff T. , Coe Ryan G. , Bacelli Giorgio 
Published: September 2023

Abstract
The open-source WecOptTool was developed to make wave energy converter (WEC) control co-design accessible. WecOptTool is based on the pseudo-spectral method which is capable of efficiently dealing with any linear or nonlinear constraints and nonlinear dynamics by solving the WEC optimal control problem in the time domain using a gradient based optimization algorithm. This work1 presents a control co-optimization study of the AquaHarmonics Inc. heaving point absorber WEC sized for ocean deployment to solve practical industry design problems. Components such as the specific type of generator, the hull shape, and the displaced volume are pre-determined. We co-optimize the WEC’s mass versus mooring line pretension in conjunction with the controller. The optimization is subject to the power-take-off (PTO) dynamics and the rated constraints of the components. In particular, the continuous torque rating is implemented as an explicit constraint, a novel approach for WEC optimization. The PTO dynamics are incorporated into the optimization algorithm via a combination of first principle methods (linear drivetrain model) and empirical efficiency maps (electrical generator) represented as a power loss map. This is a practical method applicable to a variety of PTO architectures and transferable to other WECs. A discussion between using an efficiency coefficient versus a power loss map and their implication for the optimization method is presented. This application of WecOptTool represents a real world WEC by combining simplified models with empirical efficiency data. The WEC, as a dynamically coupled, oscillatory system, requires consideration of the time trajectory dependent power loss for optimizing the average electrical power. This objective function, the modelling approach, and the realistic loss terms makes the common practice of artificially penalizing the reactive power needless.