bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effect of Power Take-Off System on S-Shaped Vertical Axis Autorotation Current Turbine
Authors: Soares Rodrigo B. , Fernandes Antonio Carlos , Sena Sales Junior Joel
Published: September 2023

This paper investigates the S-Shaped Vertical Axis Autorotation Current Turbine (VAACT) through experiments at the current flume from Laboratory of Waves and Currents (LOC-COPPE/UFRJ). The tests aim to obtain its efficiency curves varying the following parameters: Reynolds number, power takeoff (PTO) system, aspect ratio and tip speed ratio. The S-Shaped rotor is determined by Chan et al. [1] integrating genetic algorithm optimization to a bidimensional numerical model made in ANSYS®/Fluent®. Here, the optimized blade is made in 3D printer machine and subject to five different Reynolds numbers, four aspect ratios and seven PTO contributions. The power take-off system is based on lifting masses as explained in Fernandes & Rostami [2] where the power extracted is the time derivative of potential energy. The study shows the efficiency marginally changes with aspect ratio as this is a two-dimensional investigation. Moreover, the experiment provides the turbine efficiency is very sensitive to PTO configuration because it can significantly vary with that parameter. An uncertainty analysis has been carried out where that allows to realize the data into a given experimental assembly not only behave following up normal distribution but also have good repeatability. The maximum efficiency is about 14% and has been achieved at Reynolds number of 75,000, tip speed ratio of 1.44, aspect ratio of 1.5 and dimensionless Power Take-Off mass of 0.48.
Towards Functional Design for the Risk Management System of Maritime Accidents in Ice-Covered Arctic Waters From Resilience Perspectives
Authors: Fu Shanshan , Wu Mingyan , Zhang Mingyang , Han Bing , Wu Zhongdai
Published: September 2023

With emerging activities of Arctic shipping, the public pays more attention to risk management of maritime accidents and associated devastating consequences in Arctic waters. A risk management system is necessary so as to mitigate maritime accidents and promote the resilience of the Arctic maritime transportation systems. Consequently, this paper proposes a four-step functional design framework for risk assessment (risk identification, risk analysis, risk evaluation) and risk treatment of ships operating in ice-covered Arctic waters, concerning the four abilities (e.g., learn, anticipate, monitor, respond) for building resilient systems. First of all, we learn the accident scenarios and potential risk influencing factors (RIFs) of ice navigation from lessons and experiences. Secondly, we anticipate the navigational risks and associated critical RIFs for ice navigation in Arctic waters. Thirdly, we monitor the ship’s navigational status in the sea ice environment (including navigational speed, power system, and hull structure. Furthermore, under three steps, the risk management system can respond to the decision-making of the risk control options (RCOs) for the specific navigational risks in ice-covered waters. The proposed functional design framework and associated models may assist with risk management in Arctic shipping.
Numerical Investigation of Scoured Bridge Response Under Ship Collisions
Authors: Wang Zihao , Sha Yanyan , Ong Muk Chen
Published: September 2023

Bridges crossing navigable waterways may be subjected to scour within their service life. Scour has complex mechanisms due to its site- and time-dependent characteristics, making it challenging to predict the scour depth accurately. Local scour alters the soil support conditions around bridge foundations, which may ultimately lead to potential structural damage and failure. Accidental ship collisions also pose threats to the overall integrity of bridges with navigable channels. However, current bridge design specifications and guidelines treat these two hazards independently, where intact bridge configurations are adopted as the design and analysis basis for ship collisions. To date, there have been limited studies investigating the dynamic behavior of bridges with scour subjected to ship collision loads. In this study, comparisons are made among four empirical prediction models for the equilibrium local scour depth around cylindrical piles. The accuracy of each prediction model is evaluated by using historical laboratory test records. Then, a four-span continuous bridge is chosen as the representative structure to study the applicability of these prediction models. The effects of key parameters such as flow depth, flow velocity, pile diameter and bed sediment size are analyzed. To study the dynamic behavior of bridges with scour under ship collisions, detailed numerical models of both the bridge and the ship bow are developed in LS-DYNA. The soil-structure interaction is modeled as a nonlinear spring system considering the pile group effect. A selection of typical scour scenarios based on the optimal scour prediction model with the least estimation error is considered. The maximum displacements at the top of bridge piers and group piles are investigated. The obtained simulation results can provide bridge engineers with not only guidance on the accuracy of different scour prediction models, but also a better understanding of the structural behavior of bridges with scour under accidental ship collisions.
Working Load in a Container Stack Nonlinearity With Twist Lock Separation
Authors: Yanagimoto Fuminori , Ishibashi Kinya
Published: September 2023

Safe and high-efficient marine transportation needs accurate estimation of forces acting on each part of containers and related devices used for container securing system. Recent employment of the fully-automatic twist lock causes nonlinear behavior of force transmission in a container stack. This study is composed of two parts; first, a series of nonlinear 2D finite element analyses were carried out to investigate how the nonlinearity in the twist lock contributed to the force acting on the container and related devices. Second, a simplified model was developed to simulate the force based on the observation of above finite element analyses. The finite element analyses showed that the twist lock separation enhanced the contribution of the lashing rod to the strength of a container securing system, especially in the external lashing cases. The simple model was developed based on the finite element analyses. The nonlinearity was solved using the bisection method, and three conditions of the twist lock was employed to judge the convergence. The model successfully estimated the acting force in sufficiently small error compared to the finite element analyses.
Comparison of Ocean Wave Direction Spectra Estimated Using an Array of Three Optech Laser Sensors and a Directional Waverider Buoy
Authors: Jangir Pramod Kumar , Ewans Kevin C. , Young Ian R.
Published: September 2023

Accurate measurement of the directional properties of waves is needed for a variety of applications, including the safe and economical operation of offshore and shipping industries, climate monitoring, air-sea interaction, and sediment transport. Recent studies have indicated differences in significant wave heights (Hm0) estimated from Eulerian and Lagrangian measurement types of approximately 10%. Similar differences might be expected in measurements of directional properties due to the different measurement principles. Spatial arrays of wave sensors and Directional Waverider (pitch/roll) buoys are commonly used to measure direction wave spectra. This paper compares directional spectra estimated from wave measurements made with a spatial array of three Optech Lasers and a Directional Waverider Buoy operating at North Rankin A platform located on the northwest coast of Australia, using the maximum likelihood method (MLM). This comparison reveals the following: (a) the mean wave directions from the spatial array and the Waverider differ by up to approximately 20°; (b) the Waverider directional spreading at the spectra peak is narrower compared to the spatial array; however, (c) at frequencies above 1.3 times the peak frequency (f = 1.3fp), the directional spreading from the Laser array is narrower compared to the Waverider. (d) The directional spreading estimates of the Waverider at the spectral peak is a weak function of inverse wave age (U10CP), particularly at higher sea states; however, the Laser array measurements do not show such a dependence.
Pitch Motion Control of Spar-Type Floating Wind Turbines
Authors: Yu Shuang-Rui , Zhang Ming , Chen Ming-Lu , Yuan Zhi-Ming
Published: September 2023

Wave-induced pitch motion has adverse effects on the power generation of Floating Wind Turbines (FWTs). The traditional blade-pitch system, which is commonly used for regulating wind energy capture and power generation, can also be utilized to reduce the platform pitch motion. However, frequent active blade pitching can harm the wind turbine’s blade-pitch bearing and gear system, leading to inevitable deficiencies in controlling such wave-induced pitch motion. Many structural control methods have been proposed to mitigate the motion of floating substructures. The present study proposes an active structural control method utilizing a plate hinged at the bottom of a spar-type floating substructure as an external control device. The damping force provided by the hydraulic Power Take Off (PTO) system between the spar and the plate serves as the control force during optimization. The controller is developed under an optimal declutching control framework, in which the damping coefficient of the PTO system is set as a binary function. It is found that current optimal declutching control strategy can effectively minimize the pitch motion of the spar-type substructure and maximize the PTO’s power simultaneously. This indicates that more mechanical energy of the spar has been converted into electric energy. The proposed controller is able to reduce the wave-induced pitch motion by more than 21% and increase the PTO power capture by more than 370% at the platform’s natural frequency than without control.
Hydrodynamic Damping of an In-Line Oscillating Cylinder In-Line in Steady Flow
Authors: Ren Chengjiao , Cheng Liang , Tong Feifei
Published: September 2023

This study conducts a series of analysis to reconstruct the time-dependent in-line forces on an in-line oscillating cylinder in steady flow. The analysis involves reconstructing these forces from several approaches and comparing them with those obtained from the three-dimensional numerical simulations conducted at a fixed Reynolds number of 500 based on the incoming steady flow velocity. A range of velocity ratio r* (cylinder-oscillation-velocity to current velocity) from 0.1 to 1.83 at amplitude-to-diameter ratio A* = 1/π are considered. To quantify their performance, the reconstructed in-line force and damping force from the conventional Morison Equation (MOJS) with the relative and independent velocity models are examined. The results show that the independent velocity model outperforms the relative velocity model and provides a good fit at large r* where the wake is controlled by the cylinder oscillation. The study also demonstrates that the independent velocity model using a more general form of MOJS is superior to the conventional formula in predicting the in-line force. Recommendations are provided on selecting velocity models in force estimation at different r* ranges.
Methodology for Selection of Co-Simulation Platform for Digital Twin Development of Maritime Energy Systems
Authors: Gosala Vaidehi , Hachmeister Ludger , Stutz Sophie , Giering Jan-Erik , Ehlers Sören
Published: September 2023

Digital twins (DTs) are being increasingly considered in the maritime industry for the purposes of system design, monitoring, control, optimization, operational planning, maintenance, fault detection, and life cycle management. A system simulation can be utilized to enable many of these functionalities. Co-simulation based on the Functional Mock-up Interface (FMI) is typically used to interface component models independently developed in different modelling platforms, possibly having different supplier intellectual property restrictions. Currently, more than 170 software tools support FMI, a subset of which also support co-simulation. In this paper, a methodology for the selection of a co-simulation platform for a maritime DT is presented. The methodology is demonstrated for two maritime energy system case studies with different DT purposes and users, that represent different phases of a ship’s lifecycle. MATLAB/Simulink and Open Simulation Platform (OSP) are used as example co-simulation platforms. The DT’s purpose and its users are considered to understand the functional and interface requirements for a qualitative comparison of the platforms. Additionally, the platforms’ performance is compared quantitatively by co-simulating Functional Mock-up Units (FMUs) of the component models. The derived requirements, as well as the platforms’ capabilities and offerings, are then analyzed to select a suitable platform. It is shown that the choice of the co-simulation platform can be different according to the DT’s purpose, users, and phase of the ship’s and DT’s lifecycle.
Miniaturised Testing Device for the Qualitative Analysis of Gas Exsolution in Soil
Authors: Kaminski Pauline , Grabe Jürgen , Fatima Zeest
Published: September 2023

The presence of gas is a widespread phenomenon in marine and coastal soils, often accompanied by complications in engineering application. The characteristics of the gas phase in the pore space are relevant for the assessment of the soil mechanical implications. In granular soils the formation of capillary bridges between the soil particles can invoke cohesive forces. In fine-grained soils gas-induced fractures may weaken the soil structure. Additionally, an excessive gas production leads to a build-up of pore pressures and can thereby trigger a liquefaction failure in granular soils. To enable a differentiated investigation of these features, however, it is vital to look into the inner pore space of a gassy soil. For this purpose, a miniaturised experimental set-up was developed which allows for the documentation of gas bubble nucleation and growth in a soil’s pore space by means of the imaging technique X-ray computed tomography. Herein, gassy soil samples with a stationary grain structure are obtained by means of the axis-translation technique. The degree of saturation is adjusted by a controlled pressure relief. During image processing the three phases — soil particles, pore water and gas — are identified and thus, their interaction can be studied. The microscopic insights gained with the help of this experimental set-up will allow validation or falsification of the basic theoretical assumptions on gassy soils. Furthermore, the data bears great potential for the advancement of approaches for multiphase simulation.
Cuttings Bed Creation and Removal When Circulating Field Applied Oil-Based Drilling Fluids
Authors: Ytrehus Jan David , Lund Bjørnar , Taghipour Ali , Saasen Arild
Published: September 2023

Deviated well sections are common in modern well construction. In mature areas like the North Sea region, practically all producers or injector wells will have highly deviated sections. These wells must be drilled and completed in an optimal manner with respect to drill time, cost, risk and functionality. Most cuttings transport and hydraulic models are developed based on tests with model fluids and often in small diameter test sections. Hole cleaning and hydraulics with field fluids are different than the properties considered with most model fluids. Furthermore, results from small diameter tests with model fluids may not always be relevant for, nor scalable to, field applications due to time, length and other scales. Hence, there is a need for studies in controlled laboratory environments with various field application designed drilling fluids to improve engineering models and practices.

This paper presents results from laboratory studies with geometries that permits comparison with field operations when oil-based drilling fluids from Norwegian offshore operations are applied. The oil-based drilling fluids have densities and viscosities within the relevant shear rate range applied during drilling operations and in the tests. Previously published results with realistic fluids from this setup are with steady state conditions. Here characteristic transient behavior is presented and discussed.

The experiments have been performed in a flow loop that consists of a 10 meters long test section with 2” OD freely rotating steel drill string inside a 4” ID wellbore made of cement. Sand particles were injected while circulating the drilling fluids through the test section. Experiments were performed at different wellbore inclinations. The applied flow loop dimensions are designed so that the results are scalable to field applications; especially for the 12,25” and 8,5” sections. The selected setup is designed to provide correct shear rate ranges and equal Reynolds number to the field application when the same fluids are applied.

Results show that bed creation can be described as an alpha wave together with a bed thickness growth from start of drilling a highly deviated well section. The bed removal characteristics in presence of increased flow rate and/or increased drill string rotation are described.
Electrification of the Coastal Fishing Fleet Using Hydrogen and Ammonia-Fed Fuel Cells
Authors: Jafarzadeh Sepideh , Ladstein Jarle , Ødegård Anders , Sundseth Kyrre , Muñoz Ortiz Miguel , Høyli Randulf , Zenith Federico
Published: September 2023

In 2021, the Norwegian fishing fleet emitted approximately 855 000 tonnes of carbon dioxide-equivalents, which accounts for 1.3% of the total emissions in Norway. Converting to zero and low emission fuels is one of the measures that can significantly reduce GHG emissions of the fishing fleet. This study investigates the possibilities for using hydrogen and ammonia-fed fuel cells for powering a coastal fishing vessel (a 13 m longliner). The study is part of a Norwegian project where several stakeholders and research and industrial entities collaborated. General arrangements for the vessel are sketched for various trip lengths and configurations of power system using hydrogen, ammonia, batteries, and diesel. The effect of using alternative fuels on dimensions, specifications and stability are evaluated. Safety aspects for the vessel and bunkering are assessed. Using mathematical optimisation, the economic aspects of using alternative fuels onboard the vessel are studied. Finally, the environmental aspects of adopting alternative fuels on similar vessels and requirements for the infrastructure in ports are discussed. The results show that ammonia has the highest potential for reducing emissions for long trips; however, there are technical, economic and safety challenges with using ammonia. It is concluded that hydrogen-driven fishing vessels are feasible, but the Norwegian fish quota system, which among other aspects is based on vessel length, creates limitations for fuel storage and thus longer ranges.
Investigation on Residual Contact Pressure of Mechanically Lined Pipe With Partially Plastified Carrier Pipe Based on Tresca Criterion
Authors: Wei Rongzhi , Vaz Murilo Augusto , Hu Xuefeng , Guo Jianing
Published: September 2023

Mechanically Lined Pipe (MLP) refers to a bi-metal composite structure that consists of a carbon steel pipe internally lined with a thin coating of a Corrosion Resistance Alloy (CRA) to protect it against caustic substances from the internally transported fluid. Mechanical expansion is the most typically employed fabrication method. A major challenge for the installation and operation of MLP is the liner wrinkling caused by repeated bending during reeling installation and excessive axial compression due to thermal loads. Improving the interlayer gripping force is the key to avoiding wrinkling. The traditional fabrication process requires maintaining the outer carrier pipe completely elastic for production controllability. However, a moderate amount of plastification of the carrier pipe can further enhance the interlayer mechanical adhesion. The stress and strain analysis based on the Tresca criterion is performed for the hydraulic loading (expansion) and unloading process as a prelude to deriving the hoop strain compatibility equation. Both the models with nonhardening and linear-hardening carrier pipes partially plastified, and the closed-end solution to residual contact pressures are developed and compared. The results demonstrate that proper plastification of the linear-hardening carrier pipe is beneficial for increasing the residual contact pressure, namely, the MLP’s resistance to wrinkling.
Implementation of Industry 4.0 and its Effect on Human Element and Sustainable Development in the Blue Economy
Authors: Emad Gholam Reza , Shahbakhsh Mehrangiz , Abdussamie Nagi , Islam T. M. Rabiul
Published: September 2023

Industry 4.0 is revolutionising all industries including Blue Economy, and transforming different aspects of the way we live, work, and learn. Industry 4.0 has redefined entire services and processes through intelligent and integrated technologies such as Cyber-Physical-Systems (CPS), the Internet of Things (IoT), and artificial intelligence (AI). The Industry 4.0 has brought many positive changes and at the same time challenges that directly or indirectly involve the human element and sustainability. While the long-term strategy of the Blue Economy is aimed at unlocking the potential of ocean resources, a qualified and intelligent workforce in a sustainable environment can increase productivity and growth opportunities. So far, Industry 4.0 application in the Blue Economy industry has mainly addressed technological innovation. However, so far, the future role of the human and sustainability were not the focus of the R&D activities and thus under-researched. Understanding such a role is important, as industry 4.0, through digitalisation and automation, is redefining jobs, work activities, and the workplace itself. This entails not only the need for training a new breed of workforce who are able to operate novel systems but also affects the design of support equipment and systems for the offshore environment. This paper aims to explore the current status of human elements and sustainability associated with the application of Industry 4.0 on the Blue Economy programs such as aquaculture and renewable energy industries by utilising a systematic literature review. The paper will focus on issues that include changing the nature of jobs and its effect on the workforce in the Blue Economy industries and the need for training and upskilling of the workforce.
Experimental Study on the Hydrodynamic Performance of a U-Shaped Flexible Membrane Breakwater
Authors: Wu Jingping , Yi Xi , Zou Zaojian , Zhan Peng , Chen Changzhe
Published: September 2023

A new U-shaped flexible membrane breakwater is proposed, and its hydrodynamic performance of wave attenuation is experimentally studied in a physical wave flume with piston-type wavemaker. The physical breakwater model is consisted of two U-shaped flexible membranes and four slats. The four slats are stuck to the four ends of the two membranes and fixed near the free surface, and the flexible membranes are extended freely down and form the U-shaped inner and outer layers, with the bottom of the outer membrane lying flat on the flume bottom. The effects of the submerged or immerged depths of the four slats are studied; and a single membrane breakwater is compared with the two-membranes breakwater. A series of monochromatic regular waves are generated at a constant water depth and propagate normally to the breakwater models. The wave elevations on both the windward side and leeward side are recorded by the fixed wave probes respectively. The hydrodynamic performances including transmission coefficient, reflection coefficient and energy dissipation coefficient are calculated, and the variations of the three coefficients versus the relative width are presented. The results demonstrate that the two-membranes breakwater is obviously better than the single membrane breakwater; the slats positions have slight influence on the wave attenuation performances. Overall, the U-shaped flexible membrane breakwater shows a high performance of attenuating wave even for the waves with relatively long wavelength by dissipating the wave energy.
Study on Influencing Factors of Deep-Water Shallow Gas Jet Height via Numerical Simulation
Authors: Long Yang , Yang Jin , Yin Qishuai , Li Li , Xue Qianling
Published: September 2023

Actively releasing shallow gas operation is a drilling operation mode to release shallow gas from underground zone in advance, which is benefit in guaranteeing the security of the subsequent drilling operation. The shallow gas jet height is a key indicator to determine the safety of actively releasing shallow gas operation. The main influencing factors of shallow gas jet height include shallow gas reservoir pressure coefficient, pilot hole size, water depth and shallow gas reservoir buried depth. The increase of shallow gas reservoir pressure coefficient will stimulate higher jet height, while a certain degree of increase of water depth, shallow gas reservoir buried depth and pilot hole size will reduce the jet height of shallow gas, and the existence of sea current will accelerate the collapse and diffusion of shallow gas bubbles. The study of variation law of shallow gas jet height with each influencing factor is systematically carried out via numerical simulation, and the calculation results provide reference to predict the shallow gas jet height under corresponding parameters, which provides theoretical support and guiding significance for the decision of actively releasing shallow gas by pilot hole in deep-water sea.
Strength Assessment Methods for Adhesively Bonded Repair
Authors: Paboeuf Stéphane , Deydier Maxime , Sourisseau Quentin , Quéméré Marie-Odette , Court Jean-Philippe , Paillusseau Christophe
Published: September 2023

Bonding is an attractive assembly solution in many ways. Indeed, it is a non-intrusive and cold solution enables to assemble mono or multi-material structures. This assembly technique is particularly interesting for the installation of equipment or repairs when welding is prohibited, such as in ATEX-type risk areas.

For many years, COLD PAD has been developing bonded structural repair solutions and non-intrusive mechanical fasteners for marine environment. Their reinforcement product ColdShield™ [1], has been validated thanks to a previous collaboration with Bureau Veritas. From his side, Bureau Veritas is updating the guidance Note NI613 Adhesive Joints and Patch Repairs [2] to consider new development and innovation achieved in this technical domain.

The objective of this paper is initially to present the different methods for evaluating the resistance of bonded assemblies proposed by Bureau Veritas. Two application cases of bonded repair will be detailed with the associated lessons learnt in terms of reliability. The first one concerns a conventional steel-steel bonded repair, one of studied applications within the framework of the JIP Strength Bond Offshore [3]. For this application, the stress approach and the combined stress-energy method will be explained as well as the use of cohesive elements for numerical simulations. The second one is the design assessment of the ColdShield™ reinforcement solution [4], which contributes to hull girder strength for Floating Production Storage and Offloading (FPSO) hull repair, and for which a stress approach is possible due to the specificity of the design. Results of both applications are analysed, compared and commented. In conclusion, the paper will highlight the importance of the calculation methodology and its robustness to avoid a misinterpretation of the strength.
A Hybrid Numerical Framework for Engineering Design of Floating Offshore Wind Turbine Foundations
Authors: Tomaselli Pietro D. , Mandviwalla Xerxes , Jensen Bjarne
Published: September 2023

In addition to physical model tests, designers rely on numerical models to investigate the complex response of Floating Offshore Wind Turbine (FOWT) foundations to environmental conditions at sea. This paper presents a hybrid numerical framework for predicting the wave-induced motions of FOWT foundations. The framework combines the capabilities of three models, a wave propagation model, a potential flow solver, and a CFD solver. The developed framework can flexibly support different stages of the design process, from fast response assessment under several wave climates to detailed analyses in operational scenarios and extreme wave events. Wave and foundation response modelled with the framework are compared against laboratory measurements. Results are discussed and areas of improvement are identified.
Waste Heat Recovery by Binary Vapor Cycle for Gases From Marine Engines
Authors: Machado Kamille Vieira , Ordóñez Juan C. , Souza Jeferson Avila , Marques Crístofer Hood
Published: September 2023

The considerable energy waste in maritime transport and the need to obtain alternatives to reduce emissions of polluting gases are factors that have motivated the study of waste heat recovery systems for marine engines. The system studied herein relies on a binary vapor cycle that uses water for the topping cycle while three organic fluids were investigated for the bottoming cycle: R601a, R134a, and R22. Each of these belongs to a different category of fluid, namely dry fluid, isentropic fluid, and wet fluid, respectively. Two engines of different ratings and two different pressures of the heat recovery steam generator have been considered for each engine. Various outlet pressures for the topping turbine, which is the most liable to erosion and corrosion due to wet steam, have been investigated. The maximum efficiency achieved for the waste heat recovery system peaked at 21% while the maximum electric power accounted for 4.2% of engine brake power. Therefore, the employment of a waste heat recovery system based on a binary cycle seems a promising alternative to harnessing heat from the exhaust gases of marine engines.
A Decentralized Droop-Based Power Management System for Ship Power Systems Using Hybrid Dynamical Systems Framework
Authors: Reddy Namireddy Praveen , Skjetne Roger , Papageorgiou Dimitrios
Published: September 2023

In maritime transport, inspired by the automobile sector, autonomy is gaining traction in parallel with decarbonization. One of the numerous challenges in realizing fully autonomous operation in shipping is to design a resilient and fault-tolerant power system that preserves the survivability of ships during worst-case failures in unpredictable maritime weather conditions. In newly built ships, power systems are designed with a high number of sensors and communication equipment to enable remote control and condition monitoring in real time. In such power systems, the traditional concept of a centralized power management system (PMS) is not reliable during communication failures and cyberattacks. To address this issue a decentralized fault-tolerant droop-based PMS that does not rely on communication between energy sources is proposed. The droop curves are further designed for the derating operation of energy sources and energy storage devices. A ship power system exposed to faults represents a hybrid system that consists of interaction between continuous and discrete states. Hybrid dynamical systems theory is used to model the DC power system and implement the proposed PMS. The normal operation of energy sources, energy storage devices, and shiploads are modeled as continuous dynamics. The faults such as derating operation and disconnection of energy sources, energy storage devices, and shiploads are modeled as discrete events. The results demonstrate that the proposed PMS can keep the system parameters such as DC bus voltage within the limits permissible by class rules during the loss of power generation.
Influence of Propeller-Ice Loads on the Wear Development in Stern Tube Bearings of Marine Propulsion Systems and Identification of Critical Operating Conditions
Authors: Gilges Markus , Saleh Ahmed , Jain Mohit , Bekker Anriëtte , Lehmann Benjamin , Jacobs Georg
Published: September 2023

Increasing ship traffic in ice-covered waters leads to more frequent collisions between ship propellers and sea ice which causes extreme impulse loads on the propeller. Theses loads are transferred through the propeller shaft to the sliding bearings of the stern tube, especially, the aft stern tube bearings. Extreme bearing loads can lead to mixed-friction regimes which cause wear in the bearings and eventually results in a failure of the entire propulsion system. The effect of ice-induced loads on the contact conditions in the sliding bearings is widely unknown. Thus, a study of the influence of these loads on the contact conditions and wear behavior in stern tube bearings resulting from observed sea ice conditions and operating conditions of the ship is necessary. This paper aims to investigate the influence of ice collision loads on the contact conditions in the bearings of the stern tube of the research vessel SA Agulhas II. For this purpose, an elastohydrodynamic simulation and a multibody simulation based on field measurements were performed. As a result, this paper identifies the operating condition thresholds (i.e. propeller torque and rotational speed) during propeller-ice collisions that cause mixed-friction conditions in the bearings. On the basis of these conditions, a risk map is generated to assess the actual wear risk by including the frequency of occurrence of the corresponding mixed-friction condition over the duration of a voyage.
Roll Damping Simulations Using CFD for Offshore Wind Installation Operations
Authors: Devolder Brecht , Ramos Pedro , Stempinski Florian
Published: September 2023

In this work, the roll damping behavior of the offshore heavy lift DP3 installation vessel Orion from the DEME group is studied. Boundary element codes using potential flow theory require a roll damping coefficient to account for viscous effects. In this study, the roll damping coefficient is calculated using the Computational Fluid Dynamics (CFD) toolbox STAR-CCM+. Firstly, the CFD model setup is validated by performing roll decay tests and comparing the results with experimental scale model tests in a towing tank. Secondly, the roll damping is assessed by the Harmonic Excited Roll Motion (HERM) technique for various excitation frequencies and for different forward speeds. These high-fidelity full-scale simulations result in better estimations of roll damping coefficients for various conditions. This enhances the accuracy of efficient Boundary Element Methods (BEM) codes for wave-current-structure interactions simulations.
On the Digital Twin of the Ocean Cleanup Systems
Authors: Rakotonirina Andriarimina Daniel , Gonzalez Martin , Sainte-Rose Bruno
Published: September 2023

The Ocean Cleanup is introducing a Digital Twin (DT) describing the cleanup systems made with netted screens to concentrate marine litters and extract them from our oceans. Our DT aims at: i) avoiding over- or under-designing the system; ii) extrapolating from one system to a fleet of systems; and iii) estimating the costs of our offshore operations. These costs are evaluated as cost per kilogram of extracted plastic which is our Key Performance Indicator (KPI). One of the main contributing parameters to the KPI is the hydrodynamic load of our “U-shape” device that spans up to 630 meters and operates at a Speed Through Water (STW or ustw) up to 1.5 m/s equivalent to a twine Reynolds number of Ret* = 1600. The DT is built with OrcaFlex (OF) using lines and links, the Naumov’s drag correlation and on a no-wave assumption. Data collected from the Great Pacific Garbage Patch (GPGP) are utilised to increase the accuracy of our DT for estimating the loads and the system’s dynamic deformation. The DT is built using a three-cycle validation: i) initial guess applying the Naumov’s semi-empirical drag correlation to define OF drag coefficients which is excluding the influence of the local angles of attack (AoAs); ii) calibration of the OF drag coefficients using AquaSim (AS) with its twine-by-twine drag correlation for various AoAs; iii) re-calibration of the OF drag coefficients from two-dimensional CFD simulations using Direct Numerical Simulation (DNS) for a twine-by-twine establishment of a drag correlation on a one meter segment plane net to account for shielding effects at AoA < 24°. By doing so, we decrease the discrepancy of our OF model, on large spans, with an error less than 15% compared to the GPGP data. For a narrow span, mostly exhibiting very low AoAs, the first cycle shows a 300% discrepancy whereas at the end of the third cycle it shows a 50% discrepancy.
A Numerical Investigation on the Derivation of p-y Curves for Monopile Foundations Installed in Sand
Authors: Kronemberger Lopes Guilherme , Mendes de Sousa José Renato , Cascão Ferreira de Almeida Maria , de Souza Soares de Almeida Márcio
Published: September 2023

The design of monopile foundations for offshore wind turbines (OWTs) is usually performed using simplified (1D) models based on the p-y method. When deriving p-y curves, the main issues arise from the soil reaction profiles (p), commonly obtained by double differentiating the bending moment profiles. Several authors have proposed modified p-y curves for OWT applications derived from experimental analysis conducted using small-scale in-situ models, centrifuge models, or numerical analysis using three-dimensional finite element (3D FE) models. This paper presents a 3D FE model simulating a monopile installed in sand, which was used to derive monotonic p-y curves. Typical curve fitting methods adopted in the literature for the bending moment data were investigated, such as the High-Order Global Polynomial, the Piecewise polynomial, the Smoothing Cubic Spline, and the single-term Fourier series methods.

Moreover, a parametric study was conducted to quantify possible errors associated with the p-y curves. The number of points used to create the p-y curve, and the number of nonlinear soil springs adopted in the 1D model were varied. Finally, a guideline for deriving p-y curves from 3D FE models is provided.
Comparison of Vessel Motion Induced-VIV Response of Lazy-Wave and W-Shaped FOWT Power Cable Configurations
Authors: Fuglsang Alex , Kusangaya Anesu J. , Dillon-Gibbons Craig , Bauer Peter , Marcollo Hayden
Published: September 2023

As the Floating Offshore Wind Turbine (FOWT) industry expands from demonstrator to commercial projects, arrays of FOWTs with interconnected subsea power cables will be required in order to produce a competitive Levelized Cost of Energy (LCOE). The selection of subsea power cable configuration and design of the cable networks in a FOWT array will have a significant bearing on the reliability of the power cables, the availability of power from each turbine, and the LCOE produced by the array.

Two subsea cable configurations are considered in this paper and assessed for their exposure to VIV induced fatigue damage: A lazy-wave power cable attached to the seabed, and a W-Shaped cable directly connected between two FOWTs. The model is used to compare the lazy-wave and W-shape power cable configurations; identifying the propensity of each to experience direct, heave or surge/sway induced VIV, and where detected, compares the VIV responses of the two cable configurations. The Lazy-wave configuration decouples motions of the FOWT from the subsea cable termination, but due to length of cable required to reach the seabed, may be less cost-competitive, particularly in deeper water. The W-shaped cable could reduce the length of cable required to connect each FOWT, and in a farm of potentially 100’s of floaters, may present a significant LCOE reduction. However, the W-shaped configuration may also increase exposure of the cable to multiple VIV mechanisms: Direct wave and current, heave-induced, and potentially VIV induced through the translational motions (surge/sway) of the FOWT platforms.
A Parametric Study to Enhance the Design of Hydrokinetic Turbine
Authors: Ng Cheng Yee , Maldar Nauman Riyaz , Ean Lee Woen , Wong Bak Shiiun , Kang Hooi Siang
Published: September 2023

Many companies and governmental organizations have announced the aspiration to achieve Net Zero Carbon Emissions by 2050. Hence, electrification and low-carbon energy solutions are among the measures to reduce CO emissions. Seeing the fact that offshore platforms are in the middle of the ocean, and the ocean covers almost 80% of the earth surface, a high hydropower potential from the ocean with 29,000 MW is extractable from Malaysia. Many of the oil and gas companies are eyeing for an alternative marine energy source for electrification of the offshore platforms such as solar, wind and wave. Unfortunately, many yet seen the potential of the marine current energy by Marine Hydrokinetic Turbine (MHKT). Indeed, the high predictability of the resources and maturity of the MHKT technology have strengthened the feasibility of the deployment of this device. Although the strength of the MHKT has been highlighted, but the deployment of the on-shelf MHKT devices in Malaysia region is still a challenge, mainly due to the slow current flow within the region. Acknowledging this limitation and insufficient depth found in Malaysian waters, the present research focusses on parametric study to maximize efficiency of an existing hydrokinetic turbine. The study is based on numerical simulations which are carried out using the CFD software. Prior to parametric study, performance of the conventional turbine is evaluated with the existing results of the manufacturer’s experimental testing reports. Thereafter, the effect of modifications on each of the structural parameters such as blade profile and number of blades arrangement is analyzed. For every structural parameter, the most optimal configuration was identified by comparing the obtained power performance variables. The enhanced design turbine achieved at the end of modifications is subjected to performance assessment for the same flow velocities as the conventional one. As a result, with the ocean current flow of 1 m/s, the enhanced design turbine can generate 268 watts of power, meanwhile 165 watts from the conventional one at the rate of 1.62 times higher.
Dynamics of a Cold Water Intaking Pipe Subject to Internal Flow and Motion Excitation
Authors: Hisamatsu Ryoya , Utsunomiya Tomoaki
Published: September 2023

A cold water intaking pipe/riser is an important component of a floating Ocean Thermal Energy Conversion (OTEC) plant. Its dynamics subject to the large intake flow rate of seawater and motion excitation from a platform have not been definitively understood. This study experimentally investigates the dynamics with two experimental setups. The first setup uses a controllable pump and 4 m long pipe to investigate instability. The second setup uses a high capacity pump to investigate instability and forced vibration subject to top harmonic excitation. The results are compared with an analytical model considering the inlet flow effect. The analytical model predicts that a water intake pipe does not lose stability at any high flow velocity. The experiment newly confirmed that the pipe keeps stable up to 5.5 m/s which is the maximum velocity attainable in this experiment. The experiment and analytical model also highlight that a high internal flow velocity significantly increases the amplitude of inline vibration. Furthermore, the experiment also takes a new look on the dynamics such as long-period vibration and transverse vibration.
Real-Time Automatic Prediction, Detection, and Mitigation of Fluid Loss During Drilling Operation Employing Along String Measurement (ASM) Data Along Wired Drill Pipes by Using Digital Twin in Norwegian Continental Shelf
Authors: Gomar Mostafa , Elahifar Behzad
Published: September 2023

To automate drilling operations, reliable real-time down-hole data, as well as knowledge to extract information about the bottom hole environment, are essential. Numerous dynamics, such as drilling bits, fluid flow, and drill string dynamics, can be employed to monitor the downhole environment. Among the many drilling parameters measured by ASM and relevant to these dynamics, fluid pressure is the key measurement, conveying valuable information regarding drilling hydraulics in real-time operations. Using ASM data, the current study uses the digital twin technique for continually monitoring downhole conditions to discern the onset and progression of fluid loss.

An authentic real-time approach for monitoring and control of downhole fluid hydraulics should incorporate both model physics and downhole measurements. An innovative physics-based data analytics model has been developed to simulate fluid flow dynamics during drilling operations. Physical models are formulated as differential equations of mass and momentum conservation, which are discretized along the borehole utilizing finite element method. As a data analytics tool, the finite element solution is integrated with Kalman filtering to estimate downhole parameters in real-time. The combination of finite element and Kalman filtering algorithms (FE-KF) offers the most efficient way of dealing with fast and continuous streams of noisy ASM data.

Using this approach in conjunction with high-frequency ASM data, flow rate and pressure along the borehole domain can be predicted in real-time. Estimates of flow rate and pressure are compared to baseline values provided by surface facilities. By identifying all contributing factors to pressure drop across the annulus, an estimate of the quantity of fluid lost can be calculated online. In this approach, a series of ASM data from a well on the Norwegian Continental Shelf (NCS) is used to identify and monitor the initiation and progression of fluid loss far in advance of detection on the surface.

Current industry solutions for monitoring downhole pressure are based on assumptions (such as mono-bore wells, simple drill strings, and Newtonian drilling fluids) that result in an unrealistic perception of the downhole environment. Furthermore, all monitoring strategies are delayed and only informative to a single point, namely the location of the pressure sensor. As a complement to such approximate solutions, these methods often make use of unreliable surface data. An intriguing aspect of this research is using digital twin to introduce an algorithm capable of overcoming the shortcomings of previous methodologies while also employing an intelligent and delicate application of ASM data to predict and mitigate downhole drilling events in real-time.
On Implementing Cummins Equation to Represent Accurate Wave Radiation Forces in Modelica
Authors: Menon Ajay , Haider Ali Shahbaz , Bubbar Kush
Published: September 2023

This work explores the development of a Modelica™ compliant Ocean Engineering Toolbox (OET). Focusing on a symbolic solution to the Cummins equation for a floating, heaving body subject to polychromatic wave excitation forces, three formulations of the radiation convolution (symbolic, numerical, and state-space) are investigated and validated using the benchmark WEC-Sim. The presented formulation is tested using the model parameters of the Reference Model-3 (RM3) heaving point absorber Wave Energy Converter (WEC). For a preset excitation force, a 300-second simulation of the OET yields accurate results when compared to WEC-Sim. Computational speed measurements also indicate significant improvements in simulation efficiency compared to solving the radiation convolution integral numerically.