bluuebunny/crossref_metadata_2025 huggingface dataset:
CFD Simulation of Hydrodynamic Interaction Between a Ship and a Podded Propeller Using Body Force Method
Authors: Seo Dong Cheol , Jahra Fatima , Wang Jungyong
Published: August 2024

This paper presents an application example of the body force propeller method to consider hydrodynamic interaction between the hull, pod and propeller blades; and predict the overall propulsion performance without implementing the actual rotating propeller model. As a test case, a tugboat with twin puller-pod units is selected, and a series of simulations, from a stand-alone propeller operation to a fully equipped hull under propeller overload conditions, are conducted. To evaluate the simulation performance improvement, two different modelling options in the body force propeller model, inflow sampling and induced velocity correction, are investigated. The estimated thrust, torque and tow force are then compared with the model test results. Finally, it is proposed to adopt the varying inflow sampling technique to enhance the simulation accuracies of the body force propeller method, particularly for propeller overload test cases.
Analysis of Nonlinear Hydrodynamic Properties of Shallow-Draft Floating Photovoltaic Structure
Authors: Cao Hangyu , Du Junfeng , Zhao Shujie , Zhang Deqing , Chang Anteng
Published: August 2024

As the global energy industry evolves and renewable energy rapidly advances, offshore floating photovoltaic (FPV) technology is garnering increasing attention. Unlike conventional water surface FPVs, ocean-based FPVs exhibit a more complex dynamic response to wave action. Traditional approaches, such as linear restoring stiffness and linear wave excitation forces used in marine structures, may not accurate for dynamic response prediction of FPVs due to their significant instantaneous wet surface changes attributed to their light weight, large span, and shallow draft. This research focuses on a novel type of shallow draft offshore photovoltaic floating structure, examining the variation of nonlinear restoring force in the FPV module under different offsets by an inhouse code. Additionally, the variation of the Froude-Krylov force on the FPV module in response to instantaneous changes in the wet surface area is explored. This investigation is crucial for understanding and optimizing the performance and design of such innovative floating photovoltaic systems.
Hydrodynamic Analysis of the Side-by-Side Moored FLNG-LNGC System
Authors: Di Shang , Ju Fan , Chen Tianwen
Published: August 2024

Considering the mooring systems, second-order wave forces and potential nonlinear gap resonance, the intricate relative motions between Floating Liquefied Natural Gas (FLNG) and Liquified Natural Gas Carrier (LNGC) during the offloading operation of Liquified Natural Gas (LNG) significantly increase the risk of collision. The present research mainly focuses on the numerical analysis of the forces of the side-by-side offloading system. Based on the three-dimensional potential theory modified by the Damping Lid Method, hydrodynamic coefficients such as the added mass, the quadratic transfer function (QTF) of drift forces and so on in the frequency domain are calculated. The Damping Lid is added to the free surface to suppress the overestimated wave elevation between two floating bodies in the close proximity. Using the Frequency to Time-Domain Transformation Method, the time-domain simulation can then be performed, through which the forces and the relative motions are subsequently obtained. The numerical calculation results indicate that if the incident wave frequency is close to the resonant frequency of the gap, a violent resonance phenomenon will occur in the liquid surface motion. Similarly, when the frequency of the low-frequency drift force is close to the natural frequency of the system’s horizontal movement, it can also cause resonance. The hydrodynamic coefficients and the motions of the side-by-side system, as well as the tensions of the mooring system, exhibit significant variations near both types of resonance frequencies.
Estimation and Experimental Validation of Extreme Waves and Loads on a Large Monopile
Authors: Pakozdi Csaba , Alsos Hagbart S. , Ravinthrakumar Senthuran , Nyboe Synne , Rolland Louise Ankerstjerne , Nordheim Knut
Published: August 2024

Numerical wave analyses of extreme sea states have been performed for a large monopile subjected to 50 year and 500 year hurricane conditions. The numerical analyses have been established using the REEF3D::FNPF software. The wave kinematics has then been combined with a Morison type load model containing a modified inertia term, KC dependent drag and a Weynberg-Campbell slamming term. The line loads generated from the numerical hydrodynamic analyses are then implemented into the SIMA FE solver to establish the extreme WTG responses.

The extreme statistics of hydrodynamic and structural response has been investigated and compared with results from model tests. The model test data sample is considerable and consist of 20 × 3h series of seed variations, including variations between sea states and mudline boundary conditions. When evaluating parameters such as crest height, steepness, we observe that the numerical wave tank approach allows for similar extreme behaviour as the observed in model tests.

In general, the numerical and experimental results agree well when comparing the extreme statistics. Beyond this, we also compare the extreme events in the slamming zone. This implies that we sequence the max. load events for both experiments and numerical analyses and sort them by magnitude before making a direct time domain comparison of each of the sorted extreme events. The correspondence between model tests and numerics for the splash zone loads, is also observed for the overall response statistics.

Finally, we conduct a comparison of waves between the REEF3D::FNPF-based models and more conventional constrained wave methods as outlined in IEC61400-3-1.
FIV Assessment of Piping Systems Using Vibration Screening and Advanced Analysis Methodologies
Authors: Skarlas Panagiotis , Ibrahimi Deborah , Varelis George E. , Peng Deng-Jr
Published: August 2024

Structural vibrations of piping systems due to internal fluid flow are common when the system contains flow domain variations, such as elbows, tee-joints, control valves, small bore connections and reducers. In this paper, the applicability of the Likelihood of Failure (LOF) screening methodology, as proposed by the Energy Institute (EI) guidelines, is investigated for a water injection piping system with complex geometry. The system comprises 16″–18″ piping and a manifold that distributes the flow to seven 6″ risers. The system flow rates were checked against the EI guidelines, resulting in a sub-critical LOF (≤ 0.5).

A combination of computational fluid dynamics (CFD) and finite element (FE) analyses in ANSYS Workbench software package is also employed for the assessment of the flow-induced vibrations (FIV) of the piping system, considering 1-way fluid-structure interaction (FSI) effects. The resulting pipe vibrations are post-processed to assess their acceptability in the Velocity RMS – Frequency domain, according to the EI methodology. FIV-induced stresses and fatigue damage are also assessed against structural limits.

For both models, the flowrates corresponding to sub-critical conditions (LOF ≤ 0.5) cause vibrations that fall into the problematic zone according to the EI Vibration Assessment methodology, and they result in a low fatigue life. Alternative support configurations are analysed, aiming at rectifying the system response in terms of vibrations and fatigue performance.

The results presented in this work indicate that even though the LOF screening is widely used for efficiently assessing the flow capacity of piping systems for safe operation, for systems with complex geometries the LOF screening may not be sufficient to ensure no FIV failures will take place. In such cases it is recommended that the assessment should be complemented with more advanced CFD/FE analyses.
Sensitivity of Ship Voyage Optimizations to Various Energy Cost Models
Authors: Chen Yuhan , Mao Wengang
Published: August 2024

A ship’s energy performance model describing the relationship between ship speed and energy consumption is an essential component in her voyage optimization system, since it is required to evaluate the energy costs associated with different voyage plannings. For energy-efficient voyage planning, such a ship model estimates the corresponding energy consumption of each feasible route/sub-route based on her sailing speeds and encountering environmental conditions. Thus, the reliability of a ship’s energy performance model is expected to have a great influence on the ship’s voyage optimization results. Various approaches have been widely researched to construct the ship performance model, such as empirical white-box models based on experimental tests and physical knowledge, data-driven black-box models using machine learning methods, and gray-box models combining the above two approaches, etc. In addition, various energy cost functions are used for the ship voyage optimizations, such as the total power or fuel consumption, etc. The objective of this study is to investigate the sensitivity of ship voyage optimizations due to different energy cost functions from different modeling techniques. A chemical tanker with full-scale measurement is used in the case study to study the sensitivity of voyage optimizations in terms of energy efficiency. Some insights into employing different energy cost functions and models are discussed in detail to provide good recommendation practices for optimal voyage planning.
Composite Repair of Corroded Pipelines
Authors: Takahashi Goes Tami , Drumond Geovana , Pinheiro Bianca , Pasqualino Ilson
Published: August 2024

Recent studies have demonstrated that composite materials can be used with practicality, agility, economy, and effectiveness in the execution of repairs of corroded steel tubes. Thus, the present work aims to study the behavior of metallic pipes repaired with composite materials manufactured in polymeric matrix reinforced by glass fibers submitted to internal pressure tests. For this, an externally corroded pipe was modeled in software Abaqus with a 50% reduction of the wall and repaired with composite material. The repaired pipe was submitted to internal pressure and the burst pressure was compared with experimental results from literature with an error of 3%. The numerical-experimental correlation validated the numerical model, which can be used with reliability and safety by industry.
Modeling Thermal-Hydrological-Mechanical (THM) Processes for CO2 Sequestration in Depleted Gas Reservoirs
Authors: Zhao Xinrui , Winterfeld Philip , Wu Yu-Shu
Published: August 2024

Over the past two decades, researchers have devoted enormous efforts into developing numerical models for simulating CO2 geo-sequestrations. Due to the large temporal and spatial scales associated with such processes, numerical modeling has proven to be the most cost-effective to evaluate them. Presently, the majority of the existing models were developed for CO2 sequestration in saline aquifers. In contrast, the number of models for depleted gas reservoirs is relatively small, and only a fraction of them have the capability to consider geomechanical and thermal coupling or complicated natural gas compositions.CO2 sequestration in depleted gas reservoirs is considered a promising technique for combating global warming. The use of depleted gas reservoirs has several advantages over saline aquifers, such as the availability of existing facilities and the proven capacity and stability of gas storage. It is believed that storing CO2 in depleted petroleum reservoirs can serve as an interim solution for storage until large-scale storage in saline aquifers reaches maturity. Here we propose an Equation of State (EOS) module for CO2 sequestration in depleted gas reservoirs or CO2-enhanced gas recovery. It takes into consideration the mutual solubilities in the CO2-hydrocarbon gas-brine system based on the equality of the chemical potentials of the aqueous and non-aqueous phases. In such a way, it can properly address CO2 dissolution into brine when hydrocarbon gas is present. Hydrocarbon gas includes methane, ethane, and propane. It employs well-recognized approaches to calculate the thermodynamic properties of the gaseous and aqueous phases. This EOS module has been applied to our in-house simulator, TOUGH2-CSM, to enable thermalhydrological-mechanical modeling. Our research could fill the gap and provide a reference for future studies in this regard.
Level Ice-Structure Interaction Simulations Using Solid and Shell Elements
Authors: Körgesaar Mihkel , Tabri Kristjan , Avi Eero
Published: August 2024

This article contributes to the design of ice-going vessels by presenting computationally efficient simulations of a rigid ship crossing level ice field for ice resistance estimation. First, the ice material model is calibrated against the existing four-point bending (4PB) experiments conducted in the Baltic Sea. The ice beam is modelled both with detailed solid and coarse continuum shell elements. Solid element simulations are used to verify the accuracy of the coarse shell modeling approach. Mesh size sensitivity of the shell element solutions is presented. Using the calibrated model the ice resistance of a passenger ferry operating in the Baltic Sea is assessed. Ice is modelled both with solid and shell elements to compare the differences in response. While solid model results provide a more realistic estimate of the ice forces, shell element simulations are 5 times faster. However, shell element results give about 20% lower load and thus can be less conservative, thus further calibration of model could be beneficial.
Multi-Objective Ship Voyage Optimization Framework for Underwater Noise Emission
Authors: Venkateshwaran Akash , Deo Indu Kant , Jaiman Rajeev K. , Jelovica Jasmin
Published: August 2024

Anthropogenic noise from marine shipping and other sources poses a serious threat to marine mammals and the ocean ecosystem. This paper aims to enhance a ship’s adaptability to varying ocean conditions, with the primary objective of reducing its contribution to underwater radiated noise (URN) along with fuel consumption. A new multi-objective optimization framework (MOOF) is developed that optimizes the ship’s sailing speed using a non-dominated sorting genetic algorithm (NSGA-II) to mitigate URN. Two objective functions: i) total noise intensity levels and ii) total fuel consumption are minimized under some voyage constraints. Subsequently, the Pareto solutions obtained from NSGA-II are further processed using a Euclidean-based multiple-criteria decision-making method to find the trade-off solution. To illustrate the efficacy of the MOOF, we consider a practical case study of a 6900 TEU containership in a voyage scenario. The proposed framework has shown a 94% reduction in the total intensity of URN, with a notable drop of 1.22 dB. Nevertheless, this accomplishment is accompanied by a slight increase in fuel consumption of 3.25 MT, or 0.4%. Thus, in the case of a realistic shipping route, MOOF quantitatively demonstrates its efficacy in significantly reducing URN intensity levels without enforcing a major compromise on fuel consumption. Further discussion on the optimized speed profiles and prospects is presented.
Subsea Lifting Operations Considering Taut-Slack Cable Conditions and KC-Dependent Hydrodynamic Coefficients
Authors: de Andrade Emerson M. , Fernandes Antonio C. , Sales Junior Joel S.
Published: August 2024

The assessment of the dynamic behavior of vessel-cable-equipment systems can be complex due to the various involved parameters. For this kind of system, the practical point of view is commonly interested in maintaining the taut cable condition, avoiding the slack one. Compared to models with constant hydro-dynamic coefficients, the ones that consider Keulegan-Carpenter number (KC) dependent hydrodynamic coefficients in subsea lifting operations have different dynamical behaviors. However, there is no evidence of how the taut-slack limits change when considering KC-dependent hydrodynamic coefficients. To better understand this issue, the present study assesses three cable-equipment dynamic models with constant and KC-dependent hydrodynamic coefficients: (1) a single-degree-of-freedom, (2) a multi-degrees-of-freedom, and (3) a continuous model. Herein, we demonstrate that for a given model, at low-frequency ratios, considering KC-dependent hydrodynamic coefficients increases the region for slack in the (Λ, τ) domain, where Λ and τ stands for displacement and frequency ratios, respectively. In contrast, for high-frequency ratios, there are no significant differences. Also, we found that the taut-slack regions may differ significantly between the models, for example, surpassing a 20% difference in the frequency ratio. Furthermore, increasing the equipment mass or damping coefficients reduces the region for slack in the (Λ, τ) domain, while the opposite occurs when increasing the added mass coefficients. This study sheds light on the dynamical behavior of subsea lifting operations contrasting models with constant hydrodynamic coefficients and models considering KC-dependent hydrodynamic coefficients, showing that the response of the models may change significantly depending on the assumptions, which impacts the maintenance of taut cable conditions in subsea lifting operations.
A Digital Twin to Estimate the Remaining Fatigue Life of Risers
Authors: Mendes de Sousa Fernando Jorge , Queija de Siqueira Marcos , Kronemberger Lopes Guilherme , Gonçalves de Lacerda Thiago Ângelo , Carneiro Campello George , Figueira de Souza Rodolfo , Brun Coser Tiago , Cardoso de Almeida Ricardo , Souza de Oliveira Felipe Eduardo
Published: August 2024

Digital Twins can be defined as virtual models of physical systems, used to create simulations to predict the performance of equipment or processes. In offshore production systems, Digital Twins have been employed to increase operational efficiency and enhance safety. They can provide real time data to support structural integrity management decisions, such as life extension of submarine structures. The objective of this work is to present a Digital Twin application aiming to predict the remaining fatigue life of risers connected to floating production units, focusing on the top region and on tensile armors. This tool captures real-time monitored internal pressures and movement data from sensors installed on the vessels and automatically calculates the fatigue damages and remaining lives. The Riser Fatigue Digital Twin employs hybrid methods to perform global and local analyses quickly, and then calculates damage for each sea state to which the production unit and the risers are subjected. The consideration of actual measured motions at the platforms reduces uncertainties associated to traditional fatigue life evaluation methods that typically rely on vessel motions derived from Response Amplitude Operators (RAOs) and wave spectra. The presented case study illustrates the fatigue life calculation for two risers employing the proposed approach. The obtained results are compared to results referent to a simplified and traditional design method. It is expected that the Digital Twin will be very useful in providing real-time information regarding the structural integrity of the risers in operation, reducing the overall time spent on such analyses, and facilitating data-driven decision-making for integrity managers.
Uncertainty in the Extreme Waves in the North Atlantic Ocean and Ship Responses
Authors: Waseda Takuji , Sasmal Kaushik , Miratsu Rei , Kodaira Tsubasa , Zhu Tingyao , Fukui Tsutomu , Fujimoto Wataru , Ishibashi Kinya , Vukovic Vladan
Published: August 2024

The statistics of the waves in the North Atlantic Ocean have been used as the basis of ship design for decades. Recently, there have been efforts to update the scatter diagram of wave height and period based on the numerical hindcast data combined with AIS data. However, the validation of the extreme wave distribution is problematic due to the lack of observational data. In this study, we have compared the extreme value estimates of the wave height among a 25-year hindcast simulation and satellite-derived products from 1994 to 2018 sampled in the Global Wave Statistics areas 8, 9, 15, and 16. The comparison revealed that both epistemic and aleatory uncertainties affect the detected annual maxima (AM). Nevertheless, the difference in the estimated return period wave heights was within the statistical uncertainty. The locations and timing of the detected events can differ largely between wave hindcast and satellite observation (aleatory), and the AMs vary among satellite products for the same event (epistemic). The Atlantic wave model is based on NOAA Wave Watch III and was forced by NCEP CFSR (TodaiWW3-NK) at a relatively high horizontal (20km) and spectral resolution (10 degrees). Two curated satellite products, Ribal & Young (2019) and the CCI dataset (Dodet et al. 2020) were used.
Harnessing Uncertainty: a Generalized Polynomial Chaos Approach to Mooring Load Analysis in Offshore Floating Wind Turbines
Authors: Rafiee Ashkan , Repalle Nitin
Published: August 2024

This study investigates the efficacy of Generalized Polynomial Chaos (gPCE) and Bayesian Optimisation in the analysis of mooring loads for offshore floating wind turbines. Amidst inherent uncertainties, these methodologies provide robust frameworks for optimizing design and assessing mooring system fatigue. By leveraging advanced statistical techniques, the research identifies key variables influencing system performance, thereby facilitating cost-effective and resilient design strategies. The paper demonstrates the potential of gPCE and Bayesian methods to enhance predictive accuracy and streamline the optimisation process, setting a precedent for future applications in marine renewable energy systems.
Development of MMG (Maneuvering Modeling Group) Simulation Using MATLAB-Simulink
Authors: Kim Do-Kyun , Kim Jung-Hyeon , Son Hui-Hun , Choi Si-Woong , Kim Dong-Han , Yeo Chan-Young , Park Jong-Yong
Published: August 2024

In this paper, the Maneuvering Modeling Group (MMG) [1] model is implemented in MATLAB-Simulink [2]. By developing in MATLAB-Simulink, various variables and algorithms such as ship specifications, guidance, control, and environmental disturbances can be easily managed in block form. The similarity of the implemented model was verified by turning and zig-zag tests. Based on the developed dynamics model, various sea tests proposed by the International Maritime Organization (IMO) were automatically configured to be performed. To summarize, the results of various complex ship sea tests can be easily predicted and managed.
Geotechnical Analysis of Jack-Up Leg Mounted on Spudcan for Offshore Wind Turbines Considering Installation and Operation
Authors: Lee Min Jy , Gilo Angelica , Choo Yun Wook
Published: August 2024

Recently, the size of offshore wind generators and blades are increasing for more efficient energy production. Larger offshore wind turbine foundations are also required for higher vertical and lateral capacities against significant loads and bending moments. In addition, construction costs have become serious issues for developing offshore wind farms in Korea because of critical soil conditions and insufficient supply-chain for construction. Thus, the reduction of LCOE (Levelized Cost of Energy) has been highlighted in Korean market. This has obviously led to the motivation for developing a new substructure system for this purpose. This study investigates the effect of soil conditions on the foundation penetration behavior using centrifuge model tests, ISO (2016), InSafeJIP and numerical analysis using the software ABAQUS. The penetration for installation and vertical and lateral behavior for operation of the foundation was analyzed using ISO (2016), SNAME (2018) and LPile program 2013. This study showed that guidelines and test results showed quite similar penetration behavior. Additionally, lateral pile deflection of the legs will not occur significantly in this substructure, but it is necessary to check the structural stability of jack-up units.
Dynamic Simulation Procedure of Mooring System for a Floating Offshore Wind Turbine Platform
Authors: Huang Jun-Hui , Yang Shun-Han
Published: August 2024

Mounting a wind turbine on a floating platform allows the wind power generation more efficient and economically feasible in deeper water areas. For a floating offshore wind turbine (FOWT) system, a suitable mooring system is essential to ensure a safe and reliable operation of the entire system. However, during the design phase of a mooring system, various designs and its detailed parameters can quickly rack up the total number of simulations needed. In this study, a design procedure was proposed to capture various simulation stages and critical checkpoints for design validations of mooring systems. After identifying relevant design and evaluation parameters for the mooring system, the design procedure begins with free decay analyses and restoring performance assessments of the moored FOWT system to evaluate the intrinsic characteristics of each design candidates. In the second stage of the design workflow, 1-hr time domain simulations of the entire system were performed to eliminate design candidates that are prone to mooring slack events or any other vulnerable responses. Finally, the most suitable design of the mooring system was selected based on 3-hr simulations for the environmental conditions of 50-year return period. In the present study, design of a mooring system for the University of Maine VolturnUS-S reference platform supporting the International Energy Agency 15-MW reference wind turbine was chosen as the case study to demonstrate the proposed design procedure. The initial design matrix consists of two mooring patterns, four mooring chain diameters, and five mooring line lengths. The simulated results showed that the proposed procedure can be used as a guideline to quickly narrow down to a smaller group of feasible designs. The design process will also contribute to form the basis to develop a semi-automated mooring design tool in the future.
Development of a Simulation Performance Laboratory for Assessing DP and MASS Controllers in Complex Wave and Ice Environments
Authors: Islam Mohammed , Pearson Wayne , Gash Robert , Mills Jason
Published: August 2024

Activities like shipping and harvesting ocean energy are increasingly being conducted in harsh, ice-rich waters. Analytical and numerical models, validated against full-scale and model testing results, are vital to developing new technologies and understanding issues posed by operating in such environments. This paper presents the development and initial validations of a simulation performance laboratory, SPLASH, for modelling complex ice, wave and current interactions with dynamic positioning (DP) platforms and marine autonomous surface ships (MASS). SPLASH has a modular architecture, with components with well-defined interfaces tied together by a central controller. The core component is the numerical engine that models the floating system (e.g., a ship), with active propulsion and steering systems, and the complex environments, including current, waves and rigid-body ice pieces. The central controller can interface with external controllers to govern the movement of the floating system.

In the current research, two case studies were carried out: the first aimed to model and validate a complex ice-structure interaction scenario involving an ice field comprised of over 75,000 ice pieces, including brash ice, and a DP-controlled ship operating under various configurations; the second focused on modelling wave-ice-DP-ship interaction scenarios, where both regular and irregular wave are modelled in the presence of an ice field with a large number of ice pieces. The preliminary results show promise in offering a platform for accurately and efficiently assessing advanced control systems for DP/MASS operations in complex ice-wave-current environments.
Experimental Investigation of the Radiation Loads of a Heave Plate With Tilt Angle
Authors: Han Seung-Yoon , Bouscasse Benjamin , Leroy Vincent , Delacroix Sylvain , Bonnefoy Félicien , Le Touzé David
Published: August 2024

Installing a heave plate is a practical solution to reduce the responses of a floating system. In the case of a wind turbine, the platform is often tilted by the wind effect on the structure.

The paper presents an experimental campaign dedicated to evaluating the effect of the tilt angle on the radiation loads for a free-surface piercing circular cylinder with a circular heave plate. The horizontal and vertical loads are measured by a force transducer mounted on the bottom of a specifically designed beam. Tests in forced surge and forced heave are performed with a plate with a disk-to-column ratio of 2.9 at a single submerged draft with a draft-to-disk ratio of 0.775.

The methodology to retrieve added mass and damping from the loads measured in the tests is presented, and some results are given with a specific focus on the effect of the tilt angle on the loads. Some elements are given on how the tilt angle affects the typical hydrodynamic coefficients used in the frequency domain solvers in the presence of heave plates.
Offshore Support Structures for Green Hydrogen Systems: Overview and Perspectives
Authors: Rodriguez Claudio A. , Collu Maurizio , Brennan Feargal
Published: August 2024

The goals for zero-carbon sustainable industries and the demand for diverse energy matrix have triggered the research for alternative energy sources. Due to its enormous potential, ocean renewables have become the preferred choice, and several works are devoted to the study of offshore hydrogen production systems powered by offshore wind turbines. Although numerous ocean technologies are available, the choice for offshore wind turbines is a direct consequence of the maturity level of this technology without more elaborate technical criteria. The aim of the present work is to review the technologies and the state-of-the art on offshore hydrogen productions systems from a broader perspective. The design key-drivers of this system will be identified and discussed, followed by a multicriteria analysis to assess, and rank each of the available and/or promising technologies for the support structures of the offshore hydrogen production system. A strength, weaknesses, opportunities, and threats (SWOT) analysis is also provided to aid in the discussion of the challenges and opportunities for the design of offshore “green” hydrogen floating systems.
Experimental Investigation of the Influence of PDC Bit With Stinger on Drilling Performance Under Different Hole Cleaning Efficiencies
Authors: Abugharara Abdelsalam N. A. , Futheiz Ibrahim , Alwaar Abourawi , Butt Stephen D.
Published: August 2024

The original design of the hole opener was a stinger without a bit and was meant to guide the hole along a previously drilling pilot hole and to keep drill cuttings from falling back into the pilot hole and efficiently transport them to the surface. Later hole opener designs included and end-of-stinger bit, initially a roller cone bit and later a PDC bit. Previous research conducted at the Drilling Technology Laboratory (DTL) involved using a PDC bit at the end of the stinger for drilling experiments in both field and lab settings. These experiments revealed improved drilling performance compared to using a flat base or a passive end-of-stinger bit. Building on this research, our study focuses on drilling with a PDC bit at the stinger, but at varying distances from the base. Our aim is to examine how the distance between the stinger bit and the base bit affects drilling performance and to establish correlations that can help optimize the length of the end-of-stinger bit for optimal drilling performance. We conducted experiments drilling various types of rocks under different Weight on Bit (WOB) and Revolution Per Minute (RPM) conditions.

Experimental results indicated that drilling with and without the stinger had similar drilling performance in terms of ROP and drilling torque at low WOB. However, as WOB increased the founder point for drilling with the stinger was pushed to higher WOB and the drilling performance using the stinger was improved compared to drilling without the stinger. Drilling performance for all stinger lengths used were similar with no specific configuration performing better than the others.
A Deep Learning Method for UUV to Detect Undersea Landform Features
Authors: Xiao Yao , Huang Shuang , Wang Hongjian , Yu Dan , Chu Ling , Huang Yutong , Tian Jinmu
Published: August 2024

Marine topography refers to the configuration and composition of underwater landscapes, which holds significant importance for marine resource exploration and environmental research. However, conventional methods for detecting terrain and geomorphology in marine environments often struggle to accurately identify these features due to the intricate nature of the marine setting and data interference. To tackle this challenge, a proposal is made to leverage deep learning techniques for exploring ocean terrain and geomorphology. As the utilization of Side-scan Sonar (SSS) in underwater settings becomes increasingly prevalent, the study of sonar image processing is becoming more comprehensive. This study introduces a feature extraction approach for Unmanned Underwater Vehicle (UUV) SSS images based on a multi-layer feature fusion structure of a lightweight Fully Convolutional Network (FCN). The method aims to address issues such as low precision in feature extraction, inadequate boundary coherence, and suboptimal edge detail in existing methods for extracting features from SSS images. Recognizing the abundance of convolution parameters in the fully connected layer leading to network model complexity and information loss, a lightweight FCN is devised to reduce computational load, simplify the network model, and prevent information loss due to large dimension spans. Experimental findings demonstrate that this method not only ensures adequate network training but also leverages information correlation across different convolution layers to enhance the network’s ability to capture and fuse effective feature information, thereby improving the integrity of feature extraction edges in SSS images.
Hydrokinetic Energy Harnessing Using Two Tandem Cylinders With Large Turbulence Stimulation and Nonlinear Damping in Flow-Induced Oscillations
Authors: Congpuong Nipit , Sadiq Salman , Sun Hai , Bernitsas Michael M.
Published: August 2024

Large Passive Turbulence Control (PTC) and nonlinear adaptive damping are used together to improve the efficiency and power-to-volume ratio of the VIVACE converter at the Marine Renewable Energy Laboratory (MRELab) of the University of Michigan. A large PTC is attached to two cylinders in tandem. Linear damping is used on the upstream cylinder and adaptive damping on the downstream cylinder. With this configuration, the flow-induced oscillation (FIO) of the leading cylinder starts at water speed of 0.36 m/s. FIO initiates as linear resonance leading to VIV. Then VIV and galloping coexist until a water speed of 0.9 m/s before reaching pure galloping with no gap in FIO. The mechanical power of each cylinder is calculated based on experimental measurements. The combined mechanical power of the two cylinders increases quadratically with the flow speed. This new PTC along with adaptive damping modify the efficiency curve to be maximum over the range of water speed between 0.5 and 0.9 m/s regardless of stiffness and damping. This extension of the optimal efficiency to a wider flow speed range allows the converter to work well in real environment where the water flow has nonuniform speed.
Influence of Wave Spreading on Offshore Wind Turbine Design: a Monopile Supported DTU 10-MW Turbine Case Study
Authors: Ryan Gerard V. , McAdam Ross A. , Adcock Thomas A. A.
Published: August 2024

Offshore ocean waves are directionally spread, whereby the propagation of energy travels in different directions. Despite this multi-directionality, the use of 3-dimensional wave models for loading on fixed offshore wind turbines has been limited. This is partially due to the common assumption that uni-directional sea states are conservative within a design philosophy. This may not always be true given that in operating conditions the amount of aerodynamic damping in the side-side direction is much lower than the fore-aft direction.

This paper aims to address this issue by providing the influence of wave spreading on various offshore wind turbine design scenarios: fatigue, ultimate and service limit state design. This study demonstrates that wave spreading indeed results in more fatigue damage for operating load cases. Despite this increase in operating cases, the overall fatigue and ultimate limit state utilisation is still reduced when a wave spreading is adopted.
Analytical and Numerical Modeling of the Wall Scraper for Horizontal Wells
Authors: Gao Xiang , Hao Xiao , Zhou Mengmeng , Song Xianzhi , Yuan Guohai , Xu Zhengming , Zhu Zhaopeng , Qi Yiqun , Jiang Dan
Published: August 2024

Horizontal wells are being widely used with the increase of oil and gas demand and the development of extraction technology. During the drilling process of horizontal wells, cuttings are easily deposited on the bottom of the annulus to form cuttings bed due to the gravity, which may lead to safety accidents, such as, high friction and high torque, and pipe sticking. In recent years, downhole tools have been innovatively proposed to use to improve the hole cleaning efficient. There are many factors that affect the effectiveness of the downhole tools. This paper establish the model of the wall scraper and utilizes a Computational Fluid Dynamics (CFD) to obtain hole cleaning efficiency with different parameters. The simulations were conducted at steady state and the results for maximum cutting concentrations in the annulus were analyzed. The results shows that the flow rate, drillpipe rotation speed, cuttings size, and cuttings concentration have significant impact on cuttings transport. This study could provide theoretical support for the subsequent development and application of downhole tools.
Experimental Investigation of the Buffer Blocks on the Extreme Flows Generated Using Dam-Break Mechanism
Authors: Percy V. P. Golda , Sriram V. , Sundar V. , Schüttrumpf Holger
Published: August 2024

The flows resulting from extreme events are bound to create devastating social, environmental, and economic consequences in the coastal regions. The earthquake-triggered tsunami in 2004 awakened the importance of the protective measures along the coast. This study focusses on the effectiveness of buffer blocks in dissipating the extreme flows for the less vulnerable regions in which the extreme flows are generated using dam-break mechanism. At an instant of time, the gate opens in a radial direction leading to a sudden flow thereby replicating surges due to an extreme event over a dry bed. The buffer blocks are positioned at 10m from the gate which acts as the coastal defensive elements thus attenuating the flow. Initially, single row of buffer blocks is investigated in detail. The downstream flow characteristics such as flow depth, flow velocity, and momentum flux are analyzed for various reservoir water depths and the results are summarized.
Dynamic Performance of a Land-Based OWC Wave Energy Converter Under Focused Wave Conditions
Authors: Wang Rongquan , Hu Yuxuan , Cong Peiwen , Ning Dezhi
Published: August 2024

The survivability and energy conversion efficiency of the wave energy conversion device are the two very important factors that need to be considered in the device design process. Many researches have been carried out to improve the efficiency of the oscillation water column (OWC) device. However, there is little study on the survivability of the device. Therefore, it is very important to study the dynamic characteristics of OWC wave energy device under extreme wave conditions to get more information about the survivability of the device. In this paper, the dynamic characteristics of OWC wave energy device under the action of focused waves is experimentally investigated in a wave flume at the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. It is found that the peak value of air pressure in the air chamber is smaller than its trough value, which means that the negative pressure generated by the water column falling is greater than the positive pressure generated by the water column rising under the action of the focused wave. The high speed down motion of the water surface at the front wall makes the waver column inside the chamber unstable due to the violent interaction between the focused wave and the OWC device. As a result, the oscillating of air pressure inside the chamber and the horizontal wave force on the device are induced. The peak value of the dimensionless total horizontal wave force almost stays the same with the increase of wave amplitude in the present research range, while the oscillating peak value decreasing with the focus amplitude. Although the oscillation value is smaller than the peak value, the value of wave force will be maintained at a relatively large level, threatening the safety of the device.
Preliminary Investigation on the Effects of Gusty Wind Forcing on Steep Unidirectional Waves
Authors: Zhang Zitan , Li Ye
Published: August 2024

In air-sea interaction, wind, the driving force that generates surface waves, exchanges energy and momentum with waves. However, the airflow with high turbulence intensity above the waves leads to the evolution of nonlinear waves being more complex. Therefore, it is crucial to investigate the role of wind-wave interaction in wave evolution and consequent extreme wave generation. In this paper, the parametric laboratory experiments were carried out at Shanghai Jiao Tong University to investigate the effect of wind-wave interaction on nonlinear wave evolution and extreme wave generation. Here, we are concerned with wave-by-wave local interactions different from the existing work on wind energy transfer in the spectral wave model. We considered three sets of random waves generated from the JONSWAP spectrum with different initial steepness. The wind with high turbulence intensity is generated by a movable fan array in the large-scale open wave tank. We investigate the long-time nonlinear wave evolution with wind and discuss the statistical properties of waves. We find that the gusty wind forcing enhances the ‘heavy tail’ effect in the exceedance probability of wave height. It suggests that the gusty wind forcing leads the nonlinear waves to deviate from equilibrium, increasing the probability of extreme events.
A Scenario Optimization Approach to the Prediction of Extreme Structural Responses to Environmental Loading
Authors: Crespo Luis G. , Agrell Christian , Vanem Erik
Published: August 2024

This paper proposes a data-driven approach to characterize the extreme response of a wind turbine subject to both uncertain properties and random loading. Whereas the loading is driven by environmental conditions measured in situ, the response is evaluated by computationally intensive simulations. The training data used to build the computational model might be given by the greatest simulated responses or by high quantiles of fitted worst-case distributions. Worst-case and chance-constrained optimization are used to learn functions that bound the data. We may choose to bound all the data in order to obtain a conservative prediction, or we can deliberately exclude a few outliers from the dataset in order to obtain a more informative but riskier prediction. In addition, we use scenario theory to rigorously bound the probability of future data exceeding the predicted extreme response.
Adhesive Influence on the Liner Detachment of Mechanically Lined Pipes Subjected to Bending and Internal Pressure
Authors: Caire Marcelo , Luis Martinez Fernández Jorge , Augusto Vaz Murilo , Hu Xuefeng
Published: August 2024

Mechanically lined pipes (MLPs) employ a thin-walled corrosion resistant alloy (CRA) liner to avoid corrosion in offshore pipelines. During reeling installation, the liner may wrinkle in the compression side due to reverse elasto-plastic bending cycles. This problem can be avoided by either increasing the liner thickness or applying internal pressure during the installation but both solutions lead to a cost increase. A proposed alternative is to manufacture the pipe with an adhesive layer between the carrier pipe and the liner to avoid wrinkle formation and potentially reduce the laying costs. Its effectiveness depends on a number of factors, including the adhesive properties and the resulting residual contact pressure from the manufacture process. In this work, a uniform ovalization finite element model is employed to assess the bending behaviour of tight-fit and snug-fit lined pipes, respectively denoted TFP and SFP, with three different types of adhesives. Three dimensional solid elements are employed for both the carrier pipe and the liner with elasto-plastic response and the adhesive is represented by a contact surface. The uniform ovalization model, while unable to capture wrinkling effects, reveals the adhesive’s significant influence on liner detachment and stress distribution.
Investigation of Hydrodynamic Effects on Large Floating Structure Using a 2D-Time Domain Hydrodynamic Solver Based on Strip Theory
Authors: P. P. Vijith , Rajendran Suresh , Zhou Xueqian
Published: August 2024

The hydrodynamic effects stemming from waves interacting with large floating structures are important due to these structures’ flexibility. This flexibility induces wave-induced vibrations termed hydroelasticity, resulting in higher-order harmonics within the overall hydrodynamic force acting upon the structure. This paper outlines an investigation into the hydrodynamic effects on a very large floating structure utilizing a 2D-time domain code. The performance of the seakeeping solver is tested by comparing the results with the 3D solver. The hydrodynamic coefficients derived from the 2D Code are compared with results obtained from NEMOH, a 3D frequency domain open-source solver. Rigid motions are estimated, and RAOs are compared with NEMOH and WAMIT solvers. Furthermore, this study explores the impact of elastic response on the vertical bending moment of a very large floating structure using the 2D-time domain code.
Repeated Low-Velocity Impacts on Dynamic Failure Mechanisms of Composite Sandwich Panels With PVC Foam Cores
Authors: Cai Wei , Li Shuxin , Zhu Ling
Published: August 2024

Composite sandwich structures have been widely used in naval architecture and ocean engineering field, thanks to their excellent properties like high strength to weight and stiffness to weight ratios, favourable energy-absorbing capacity, reduced corrosion tendency and design flexibility. Due to complex service conditions such as collisions, ice impacts, aircraft landing impacts and falling object impacts, composite sandwich structures in marine engineering field are commonly subjected to repeated low-energy impacts at localized sites during complex service conditions, and its resultant damage may seriously affect their mechanical performance and structural safety. Therefore, to provide insight into dynamic failure behaviours, this paper performed a series of repeated low-velocity impact tests on the orthogonal woven glass fibre laminated sandwich panels with a PVC foam core layer. The variations of the mechanical characteristics and failure behaviours of composite sandwich panels against impact numbers are explored, such as peak force, dent depth, structural stiffness, failure modes and energy absorption. It is found that the accumulated impact-induced damage has a significant negative effect on the structural stiffness, failure mode, and energy absorption characteristics of composite sandwich panels. The PVC foam cores show a good energy absorption ability to protect the integrity of the bottom face sheet from repeated impacts. This research provides a detailed understanding of the damage mechanisms of composite sandwich panels under repeated impacts.