bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Investigation of the Vertical Settlement of Seabed Pipelines Under Lateral Cyclic Loading in Clay
Authors: Jia Xu , Liu Yi , Jia Lusheng , Cheng Li , Wang Qi , Shen Zhichao
Published: August 2024

As exploration moves into deeper water, offshore pipelines, generally laid on the seabed, are an increasingly significant component of offshore hydrocarbon developments. Seabed pipelines are mainly subjected to the wave loading, which causes vertical settlement of pipelines. In this study, the vertical settlement of seabed pipelines under lateral cyclic loading in normally consolidated clay is investigated through the large deformation finite element (LDFE) analysis with the Coupled Eulerian Lagrangian (CEL) technique. The effects of strain rate dependency of the undrained shear strength and soil remoulding are considered by adopting an extended Tresca clay model during lateral cyclic loadings. Firstly, the LDFE results are compared with centrifuge test results and published LDFE data, showing a good agreement. Then, a series of LDFE cases are conducted to investigate the effects of pipe weight, lateral load amplitude, soil sensitivity, and the initial trench depth on the accumulated vertical settlement of pipelines under lateral cyclic loading. The LDFE results show that the affected clay zone around the pipeline due to the lateral cyclic loading is highly remoulded, and the initial trench depth has a great effect on the accumulated vertical settlement of pipelines. With the increasing number of lateral load cycles, the accumulated vertical settlement of pipelines first increases and then decreases. A modified expression is proposed to estimate the ultimate vertical settlement of pipelines in clay.
Ultimate Strength Test of Typical Joint of Composite Ship
Authors: Feng Guoqing , Li Kaiyan
Published: August 2024

Compared to metal materials, composite materials possess favorable properties such as high strength-to-weight ratio and high stiffness-to-weight ratio. They allow for a reduction in the overall weight of a ship while still meeting the requirements of ship design, aligning with the principles of energy efficiency and emission reduction. However, due to the anisotropy of composite materials, some components of composite ships are easily damaged in complex marine environment, which affects the safety and reliability of the entire hull structure. To understand the ultimate load-carrying capacity of vulnerable structures of composite ships under the influence of wave loads, structural response calculations for the target ship was conducted based on the design wave method in this paper. In cases where the target ship experiences overall longitudinal bending, areas with high compressive stress were identified. After screening, the box bracket structure at the joint of deck and transverse bulkhead was selected as the research object, and a typical joint specimen composed of transverse bulkhead, deck, cap girder and bracket was designed. Standard specimens of 0° uniorientational layering and 90° uniorientational layering were designed according to the relevant specifications, and tensile and compression tests were carried out, and the stiffness and strength data of the materials were measured for numerical analysis. In order to carry out the model test, the compressive ultimate strength test of typical joint specimens was carried out, and the displacement-loading force curve during the test was recorded. A shell element model was used to simulate the compression process of the ship typical joint specimen based on the 2D Hashin criterion as the failure criterion. By comparing numerical simulation results with experimental data, the accuracy of the numerical simulation method was validated.
CFD-DEM Modelling of Cuttings Transport With Power-Law Fluids in Horizontal Annulus
Authors: Sun Yi , Zhou Mengmeng , Song Xianzhi , Xu Zhengming , Ping Wanzhuo , Zhu Zhaopeng , Qi Yiqun , Jing Silin , Yao Xuezhe
Published: August 2024

For the horizontal wells, the cuttings deposition becomes a general question, as the cuttings are easy to deposit at the bottom of the wellbore to form a thick cuttings bed, which can easily cause drilling stuck and pumping accidents. Accurately characterizing the flow regimes and their transition of cuttings in complex multiphase flow in the wellbore becomes an important consideration, as the flow regimes and their transport directly affect the distribution of cuttings concentration. The drilling fluids exhibit typical power-law rheological properties, so it is necessary to study the influence of power-law rheological parameters on the flow characteristics of cuttings. A coupled Computational Fluid Dynamics (CFD) with Discrete Element Method (DEM) is applied here to describe the different flow regimes and their transition. The influences of power-law fluids’ rheological parameters on flow field characteristics and cuttings distribution are also discussed here. Based on these, the pressure gradient change in the wellbore is further described. The research results will lay a theoretical foundation for improving hole-cleaning efficiency and have practical significance for guiding the field construction of extended-reach horizontal wells.
The Load Bearing Mechanism and Holding Capacity of Helical Piles Subjected to Uplifting
Authors: Li Zeliang , Tian Yinghui , Maitra Shubhrajit , Cassidy Mark , Gaudin Christophe
Published: August 2024

Helical piles have been widely used onshore which can withstand compressive and tensile loads. As a promising foundation for offshore wind developments in deep water, helical pile has advantages of quiet installation and significant uplift capacity. In this paper, numerical analyses are conducted to investigate the load bearing mechanism considering the contributions from shaft and helical plate. The effects of helical plate embedment depth, interface roughness and shaft diameter ratio are studied. A discussion is presented on the terminology adoption depending on the contribution from the helical plate and the shaft.
Restoring Time Computation in Self-righting Process
Authors: Liu Jinbang , Hou Guoxiang
Published: August 2024

The excellent self-righting performance is important to guarantee the normal navigation of boats after overturning, and the restoring time is an important index in design requirements. Traditionally, the static stability method and experiments of full-scale vehicles were used to analyze the large angle stability of boats. However, when it comes to the analysis of self-righting performance, the traditional static stability method will cause improper integration, and experiments are not convenient. To solve these two problems, two new methods are proposed. An improved static stability method is proposed and a numerical simulation method is adopted. Firstly, a midpoint average method based on the static stability theory is proposed to compute the static restoring time, which has the advantage of convenience and can avoid improper integration. The results are compared with the references, which verifies the effectiveness of the midpoint average method. Then, a numerical simulation of a physical model in static water was finished and an experiment of the physical model in a towing tank was conducted. Comparing the restoring time of the midpoint average method, the numerical simulation and the experiment, the results show that the numerical simulation has high accuracy.
Numerical Investigation of Hydrogen Fuel Tank Skid Leakage on a Hydrogen-Powered Vessel
Authors: Fan Hongjun , Abdussamie Nagi , Harris Andrew , Chen Peggy Shu-Ling
Published: August 2024

Green hydrogen as a marine fuel can be crucial in decarbonising the maritime sector. More than 40 hydrogen-powered demonstration vessels are in operation worldwide, and numerous hydrogen-powered vessel projects are under development. Hydrogen gas exhibits a lower minimum ignition energy and a broader flammability range compared to other alternative fuels. In the event of a leak, there is a risk of fire and explosion, posing challenges for the safe design of hydrogen-powered vessels. Presently, rules and regulations for hydrogen-powered vessels are not yet fully developed. In many cases, classification societies recommend using risk-based design for such vessels. This paper is centered on the conceptual design of a hydrogen-powered offshore windfarm crew transfer vessel. It utilises the computational fluid dynamics (CFD) approach to simulate the dispersion behaviour of leaked hydrogen gas, taking into account environmental factors, vessel navigation speed, onboard obstacles, and other relevant parameters. Based on the CFD modelling results, this paper provides safety design recommendations for arranging hydrogen gas tanks on board the vessel.
Impacts of Vessel Motion on the Dynamic Response of ROV System in The Processes of Deployment and Recovery
Authors: Guo Yucheng , Yu Xiaoqi , Guo Shuangxi , Liu Xiangxu , Kong Yue , Chen Weimin
Published: August 2024

Remotely operated vehicles (ROVs) are frequently used in subsea explorations and exploitations, aiming to obtain not only traditional ocean oil and gas, but also other mineral resources, such as manganese, polymetallic nodules and sulfides. However, due to the interactions between ocean environmental loads, ROV, suspending cable and top-end vessel, the dynamic responses of ROV system have strong coupling and nonlinear characteristics. Especially, during the initial deployment and the final recovery stages, the cable length might be so short that the relative motion between the ROV and the vessel may cause a severe collision and even structural damage. In this study, based on the structural and dynamic characteristics of the ROV system during the initial deployment and the final recovery stages, numerical simulation and analytical method are employed to investigate the impacts of the top-end vessel motion on the ROV system. In the numerical simulations, vessel surge and hydrodynamic force on ROV, are considered, and the ROV responses and cable tensions under different vessel motion amplitudes and frequencies are presented. It is found that the ROV responses are larger than the vessel motion amplitudes in some cases owing to vessel surge. And, the governing equation of ROV with a horizontal moving boundary is developed. Then, in order to have a deeper understand of the behaviors of the ROV system and the mechanisms of our simulation results, the analytical method is used.
The Impact of Controller Parameters on the Maneuvering of Two Ships at Different Water Depths
Authors: Xu Chen , Zhou Xueqian , Ren Huilong , Guedes Soares C. , Sutulo Serge
Published: August 2024

This paper aims to investigate the impact of controller parameters on the performance of a PID controller in the maneuvering of two ships. In present work, a maneuvering model, which accounts the hydrodynamic interactions, is established using the MMG model. The shallow water effects on hydrodynamic derivatives are estimated by empirical formulas, and the hydrodynamic interaction forces between ships are evaluated by a 3D potential flow code. In the prediction of hydrodynamic interaction, the influence of fluid viscosity and the variation of free surface on hydrodynamic interaction are both neglected, and the double body model and mirror image technique are used to model the free surface and bottom, respectively. A conventional PID controller is used for course keeping, with the desired heading angle is determined via Line-of-Sight (LOS) guidance. The simulations of two ships overtaking are conducted at different ship speeds, initial lateral distances, water depths, and impact of PID controller parameters, such as lookahead distance, relative damping ratio, control bandwidth, on the performance of PID controller is revealed.
Transient Hole Cleaning Behaviour: What Can We Learn From Flow Loop Experiments
Authors: Lund Bjørnar , Taghipour Ali , Saasen Arild , Ytrehus Jan David
Published: August 2024

Ensuring adequate hole cleaning is important for safe, efficient and economic drilling operations. Most models and flow loop experiments assume steady-state conditions. However, drilling is an inherently transient process. Even in the steadiest situation, the drill bit position advances continuously. When inserting a new stand of drill-pipe there are transients in both string rotation speed and flow rate. Additional transients occur when the drill-pipe is rotated and reciprocated to clean the wellbore. When drilling wells with a narrow pressure margin it is important to control and limit such pressure peaks.

We have conducted flow loop experiments in a drilling fluid rig with a 10 m long inclinable test section to investigate hole cleaning performance of field applied oil-based and water-based drilling fluids. While the focus of the experiments has been on steady-state performance, the experiments also provide quantitative information about transient performance. Such information can be used for model closure development. Field applications could include analysis of transient responses from Along-String Measurement instruments, and thus provide additional information on cuttings accumulation, both with respect to location and quantity.

Transient data have been analysed using simple physics-based models. We have shown that the pressure peak due to onset of string rotation can be correlated with the cuttings entrainment rate. We further showed that a large fraction of the cuttings can be transported in suspended mode, even for laminar flow without string rotation.
Mooring Chains Out of Plane Bending Fatigue Analysis Clarifications
Authors: Barros Pedro , Storesund Walter , Skretting Ådne , Rahman Md. M. , Lillestøl Dag-Børre
Published: August 2024

Out of Plane Bending (OPB) fatigue of mooring chains has been the subject of several studies, of which the most comprehensive was the “Chain Out of Plane Bending” JIP completed in 2013. The currently applied fatigue damage calculation procedures are derived from the mentioned JIP. Following practical use of those procedures, it has been found that alternative procedures and updates can be considered. This paper describes alternative OPB fatigue damage calculation procedures, and the work performed to demonstrate their applicability and safety level with respect the JIP results most common applications.

A detailed implementation of the JIP test results with focus on interlink stiffness for wide angle amplitude cycles (cycles with sliding events) is presented. The resultant safety levels based on this methodology compared with a simplified interpretation of JIP test results is presented.

Alternative simplified procedures, for OPB fatigue damage estimation for mooring systems using OPB mitigation devices or for which very low OPB fatigue damage is expected, are presented and compared with the currently accepted procedures. In these systems it is demonstrated that the complex mooring analysis dedicated to OPB fatigue estimations, requiring mooring line angle estimations, may be waived and an indication of the conservativeness of the calculation results is presented.

Comparative analysis of the different interlink stiffness and fatigue damage calculation procedures were performed on several representative environmental states, demonstrating for different levels of procedural simplification the increasing level of safety.

It is demonstrated that different OPB fatigue damage calculation procedures can be used with different levels of required calculation effort, and therefore cost, according to the system optimization objective level. Simplified and easier to perform procedures for OPB fatigue calculation are presented and verified.
Deep Reinforcement Learning for Ship Collision Avoidance and Path Tracking
Authors: Singh Amar Nath , Vijayakumar Akash , Balasubramaniyam Shankruth , Somayajula Abhilash
Published: August 2024

This research focuses on collision avoidance between ships in the maritime industry, addressing human decision errors as a significant contributor to ship-to-ship collision. Emphasizing the crucial role of automation in maritime operations, the study employs advanced algorithms, specifically Deep Q Network, to enhance dynamic collision avoidance capabilities. By automating decision-making processes, the research aims to significantly reduce collision occurrences between ships, highlighting these algorithms as promising within the realm of deep reinforcement learning. Utilizing a three-degree-of-freedom dynamic model and Krisco field ship as a benchmark hull, rigorous numerical simulations validate the proposed model’s accuracy. The reinforcement learning agent, trained on this dynamic model, strives to optimize collision avoidance and waypoint tracking, demonstrated through numerical simulations and model experiments with a scaled version for a comprehensive evaluation of its maritime safety efficacy.
Using 3-P Weibull Distribution Evaluate Reliability of DDV and SPM Valve Hydraulic System of BOP
Authors: Cao Yang , Zhang Yu , An Chen
Published: August 2024

The direct drive valve and subplate mounted valve are critical components of the blowout preventer’s hydraulic system. The reliability analysis theory is used to analyze the service life of direct drive valve valves and subplate mounted valve valves in order to improve their reliability. The fault data is analyzed and Weibull probability plot is fitted, which is determined to follow the Weibull distribution of three parameters. The Weibull parameters are estimated by maximum likelihood estimation, and the optimal solution is obtained by particle swarm optimization. The probability density function reliability function and failure rate function are obtained. The results show that the direct drive valve and subplate mounted valve fault data follow the three-parameter Weibull distribution, and the average direct drive valve fault time is 2700 times, for subplate mounted valve is 6000 times.
Cnoidal Wave on a Long Elastic Floating Plate at Shallow Water Depth
Authors: Iijima Kazuhiro , Kyaw Soe Sandar , Maeda Takeru , Akira Tatsumi
Published: August 2024

This paper addresses the nonlinear waves propagating along a thin elastic plate floating in shallow water by using a numerical approach and by comparing with the analytical cnoidal wave theory. A numerical approach to simulate the nonlinear wave behavior on a floating plate is developed by incorporating the plate stiffness and inertia effects in the existing numerical method for free-surface waves. The accuracy and reliability of the newly developed numerical approach have been verified through comparisons with theoretical or experimental data from the literature. An analytical cnoidal wave solution for the propagation of cnoidal nonlinear waves along a floating plate is discussed and derived, too. This analytical approach aims to provide a foundational understanding of the complex wave dynamics exhibited by the floating plate. It turns out that the predictions from the analytical approach agree well with the numerical results in many cases while it still needs improvement.
Application of Data Analytics and Machine Learning in Analysing Result of Numerical Ship Manoeuvring Study
Authors: Hassani Vahid , Ross Andrew , Aspelund Leiv
Published: August 2024

We present the results of applying basic data analytic tools to data collected through an extensive high fidelity numerical simulation study focused on a vessel steering towards and passing through an enclosed ship tunnel in diverse weather conditions. While a companion paper [1] describes the simulation study that incorporates innovative developments in a numerical simulation tool, utilising results from geospatial modelling of the fjords and tunnel, shallow-water and confined-water hydrodynamics, extended modelling of ship hydrodynamics, both seakeeping and manoeuvring, collision-dynamics, the current paper focuses on application of tools from machine learning and data analytics to analyse the results from the above mentioned simulation study.
Lateral Displacement Control Challenges for Installation of Floating HDPE Pipeline
Authors: Jiwa M. Z.
Published: August 2024

HDPE pipe for marine application is commonly used for water intake, effluent outfall or water abstraction. The main reasons for this are PE has very high resistance to corrosion, low surface roughness which improves the hydraulic behaviour and excellent performance against the environmental force due to its flexibility properties. HDPE pipeline is normally installed by float-and-sink method. During the initial stage of installation, the string of HDPE pipeline will be floating for some period. A floating pipeline will be exposed to the current velocity and cause the pipeline to displace laterally. Therefore, it is necessary to introduce a method to hold the pipe while it is being installed offshore. This study presents method to manage the HDPE pipeline displacement during the float-and-sink method installation utilising the support boats.
Real-Time Recognition of Drill Bit Wear State Using Clustering Algorithm and GRU Neural Network
Authors: Zhang Qilong , Zheng Zeyu , Huang Zhongwei , Song Xianzhi , Wu Liwei , Zhang Ziyue
Published: August 2024

Drill bits are a critical factor influencing drilling efficiency. Due to the complexity of downhole conditions, it is challenging to achieve real-time and quantitative assessment of drill bit wear during the drilling process. Traditional approaches often rely on rate of penetration to assess downhole drill bit wear, which has inherent limitations and insufficient accuracy. To address the issues, this study presents a novel method for real-time identification of drill bit wear based on rock-breaking efficiency and mechanical specific energy, utilizing clustering algorithms and GRU neural networks. Initially, the working conditions of the drill bit, including bit sticking, vibration, bit bouncing, and bit balling, are annotated. Subsequently, an unsupervised clustering approach is employed to segment the drill bit wear process based on logging data, and the GRU neural network is used to establish a mapping relationship between surface drilling parameters and drill bit wear. This model was applied in Tianjin, China, where it monitored 18 drill bit trips. Among these, there were 3 instances with deviations, leading to an overall accuracy rate of 91.3%.
Investigation of Multiphase Flow Leak Detection in Pipeline Using Time Series Analysis Technique
Authors: Barooah Abinash , Khan Muhammad Saad , Ferroudji Hicham , Rahman Mohammad Azizur , Hassan Rashid , Hassan Ibrahim , Sleiti Ahmad K. , Gomari Sina Rezaei , Hamilton Matthew
Published: August 2024

Detecting chronic small leak sizes can be challenging because they may not produce significant or easily noticeable changes in flow rates or pressure differentials. Therefore, specialized techniques are often required to identify and locate chronic small leaks accurately in pipeline systems. The current study aims to address this gap by developing a method to identify multiphase flow leaks in pipelines using time series analysis techniques.

An experimental flow loop apparatus, featuring a 2-inch (0.0508 m) diameter and extending 22.6 feet (6.9 m) in length, has been employed to carry out our experiments. The experiments encompass a range of liquid flow rates varying between 170 and 350 kg/min and gas flow rates ranging from 10 to 60 g/min. The system was equipped with three distinct leak opening diameters, measuring 1.8 mm, 2.5 mm, and 3 mm, each separated by 90 mm. Data collected from four dynamic pressure sensors was subjected to time series analysis such as wavelet transforms to detect and pinpoint the location of pipeline leaks.

The obtained results indicate that dynamic pressure sensors are effective in detecting leak scenarios, as well as distinguishing between single and multiple leaks. However, for chronic small leaks, analyzing the standalone pressure response over time is generally not sufficient for detection. Time series analysis techniques play a crucial role in accurately identifying chronic small sized pipeline leaks. Discrete Wavelet Transform (DWT) was able to identify the point of leak opening and closing. Furthermore, DWT was able to reduce the false alarms for leak and no leak situations.

This study introduces the application of time series analysis on dynamic pressure to detect chronic small sized leaks in multiphase flow pipelines. Additionally, it explores the capacity of wavelet analysis to minimize the occurrence of false alarms for leak and non-leak scenarios thereby addressing crucial safety, environmental, and economic concerns.
Predicting Wave Propagation for Varying Bathymetry Using Conditional Convolutional Autoencoder Network
Authors: Deo Indu Kant , Vankateshwaran Akash , Jaiman Rajeev
Published: August 2024

In marine engineering applications, a crucial demand exists for the accurate and dependable prediction of far-field noise emanating from marine vessels. Traditional full-order models relying on the Navier-Stokes equations prove impractical, and advanced model reduction techniques can be inefficient for reliable far-field noise prediction. Recent advancements in deep learning-based reduced-order models have demonstrated effectiveness, achieving speeds several orders of magnitude faster than full-order simulations through the utilization of convolutional neural network architectures. Despite their effectiveness, existing models encounter considerable difficulties when forecasting wave propagation over extended time horizons and making predictions for distant locations. This research endeavors to enhance the predictive capacity of underwater radiated noise in far-field scenarios by refining the network architecture and integrating bathymetry information into the neural network input. Reduced-order models utilizing deep learning often rely on auto-regressive prediction, lacking information about far-field bathymetry. To overcome this limitation, we introduce a new range-conditional convolutional autoencoder network, which incorporates ocean bathymetry data into the input. To showcase the efficacy of our range-conditional convolutional autoencoder network, we examine a benchmark scenario involving far-field prediction over Dickin’s seamount. Our proposed architecture adeptly captures the transmission loss over a range-dependent, varying bathymetric profile. The architecture can be integrated into an adaptive management system for underwater radiated noise while providing real-time end-to-end mapping between near-field ship noise sources and marine mammals.
Robust CFD Analysis of Floating Wind Turbine Wave Responses With the FloatStepper Algorithm
Authors: Aliyar Sithik , Pierella Fabio , Roenby Johan , Tomaselli Pietro Danilo , Bredmose Henrik
Published: August 2024

In ocean environments, floating wind turbines are subject to both breaking waves and directional waves. While the response is often modelled through radiation-diffraction theory, the effects of higher-order wave loads are hereby limited to second order, and the damping often needs calibration against model tests. Better accuracy and full coverage of nonlinearity can be achieved through CFD. However, there is a limited robust Open Source CFD based six degrees of freedom (6-DOF) rigid body solvers, that can both generate different types of waves and also accurately simulate floating foundation motions. FloatStepper, a recent OpenFOAM-based rigid body motion algorithm, effectively addresses these differences, making it a good alternative to conventional body motion solvers. Its reliability and accuracy have been demonstrated in several benchmark cases, including single-phase and two-phase flows. The present study conducts a comprehensive examination the motion responses and mooring line tensions to unidirectional and multi-directional waves for a design variant of Stiesdal Offshore’s TetraSub floating foundation, using the FloatStepper algorithm. In particular, three categories of waves are investigated: 1) regular waves 2) unidirectional irregular and 3) multi-directional (3D) focusing waves. The numerical results are validated through comparison with experimental data from the 2023 test campaign of the Danish FloatLab project. The study contributes to the efficient use and validation of this robust CFD solver. It further extends the understanding of the multi-directional waves and wave-structure interaction for floating wind turbines, identifying potential limitations and areas for refinement in the modelling of this complex dynamics in CFD.
Vortex-Induced Motions of Floating Offshore Wind Turbines With Four Circular Columns: A Reduced Order Model Assessment of Small-Scale Experiments in a Towing Tank
Authors: Oliveira Éverton L. , Pesce Celso P. , Amaral Giovanni A. , Suzuki Hideyuki , Gonçalves Rodolfo T.
Published: August 2024

The complex movements caused by ocean currents affecting floating offshore platforms, specifically Vortex-Induced Motion (VIM), are the focus of this study. It examines VIM patterns observed in towing tank experiments involving a scaled model of a Floating Offshore Wind Turbine (FOWT) with a 4-circular-column platform and pontoons. A simplified mathematical model (ROM) was applied to analyze VIM, considering horizontal plane motions such as in-line, transverse, and yaw. The ROM model represented current forces using “wake variables”, adapting existing models initially developed for VIM of single-column platforms. It comprised eleven generalized coordinates, covering three for rigid body motion on the horizontal plane and a pair of wake variables for each column, resulting in an eleven-nonlinear second-order system of Ordinary Differential Equations (ODEs). The wake variable pairs followed van der Pol equations, incorporating hydrodynamic coefficients and parameters derived from prior experiments with low-draft cylinders. To simplify the numerical model, the hydrodynamic interactions among columns were not considered. Its accuracy was evaluated through a case study involving a small-scale experimental campaign. Simulations were performed at two different current incidence angles (0 and 45 degrees) across various reduced velocities. The simulations replicated the observed oscillations in the experimental trials, demonstrating fair agreement in transverse and yaw oscillations, including lock-in phenomena.
Wave-Structure-Seabed Interaction and Pore Pressure Measurements for Monopile Foundations: A 3D Experimental Study
Authors: Gkougkoudi-Papaioannou Maria , Pepi Yuri , Streicher Maximilian , Stuyts Bruno , Troch Peter
Published: August 2024

In the present study, 3D physical model tests have been performed at the Coastal & Ocean Basin (COB), in Ostend (Belgium) to investigate the wave-induced pore pressure development around a monopile foundation. The coupled hydrodynamic-geotechnical tests provide insight into the soil behaviour around the monopile foundation based on pore pressure measurements. Regular and irregular waves were generated to better simulate the engineering problem. Three different wave heights, wave periods and water depths were investigated. Differential pore pressure sensors were installed below the seabed surface in close proximity to the monopile to allow for the monitoring of the pore pressure in the soil directly adjacent to the structure, where the interaction between the monopile and the surrounding soil is most significant. The pore pressure sensors were positioned at varying depths below the seabed level to provide a broader perspective on how the soil’s response evolves with increasing depth from the seabed surface. First results show that increasing the wave height causes larger pore pressures at the seabed surface and, as a result, along the seabed foundation. On the other hand, the larger the water depth, the smaller the pore pressure development around the monopile foundation. These observations from the tests are in line with general expectations. This paper describes the experimental setup and presents the preliminary pore pressure results.
Vibration Analysis of Ship Shaft System Under Time-Varying Uncertainties Based on Interval Process Model
Authors: Shang Baoyou , Li Tianyun , Zhu Xiang , Wang Jianing
Published: August 2024

During navigation, the power system components (such as propeller, transmission shaft, etc.) on the ship will generate complex vibrations due to the action of various forms of excitation force. Due to the influence of the operating condition and the change of the wake field, the excitation force cannot be accurately measured and calculated, so the excitation force has the characteristics of uncertainty. In this paper, the non-random vibration response analysis method based on the convex model of non-probabilities is presented, which is used to solve the dynamic response limit of multi-degree of freedom system under time-varying uncertain excitation, and the expression for solving the dynamic response limit is given. The Monte Carlo simulation method is used to verify the reliability of the response boundary, which is the case with fewer excitation samples Improve the robustness of the dynamic response prediction of the shafting system to provide a useful reference.
ROP Calculation Methods Comparisons
Authors: Ma Shuai , Sui Dan
Published: August 2024

Efficiency in drilling operations is closely linked to the accurate estimation and control of the Rate of Penetration (ROP). This study presents a thorough comparative analysis of diverse ROP calculation methods, including Low Pass Filter, Kalman Filter, Sliding Mode Filter, and several others, all of which are utilized to extract ROP values from raw sensor measurements. The objective is to comprehensively evaluate the performance, advantages, and limitations of each method, specifically focusing on their ability to efficiently process and interpret drilling data in real-time. The work evaluates the accuracy of ROP calculations, the robustness of each method in handling noise, uncertainties and disturbances, and the computational efficiency required for their implementation. Case studies and comparative analyses provide valuable insights into the suitability of each technique.

The findings of this study hold significant implications for the drilling industry, offering valuable insights into the selection and deployment of ROP calculation methods. Engineers and developers can leverage this research to make informed decisions regarding the selection of the most appropriate ROP calculation method for their particular drilling operations. Moreover, this paper highlights the pivotal role of accurate measured ROP data in evaluating ROP models, impacting their accuracy, precision, and reliability. This paper offers a comprehensive and systematic evaluation of ROP calculation methods, providing a roadmap for the industry to process sensor measurements accurately and ultimately contribute to advancements in the field of offshore and marine engineering.
Experimental Investigation of Real-Scale Floating Solar Panel Assembly in Wind Tunnel
Authors: Arora Prince , Prasad Patel Badri , Ahmad Suhail , Kumar Jain Arvind , Joe Joe C. S.
Published: August 2024

Floating solar technology is gaining significant interest among researchers and on a commercial scale. FSPV (Floating Solar Photovoltaic) plants are being installed on water bodies such as thermal power plant reservoirs, balancing reservoirs, lakes, upstream of dams, backwaters, etc, from a small scale to utility scales. While this technology is gaining momentum due to its inherent advantages over the ground mount/rooftop solar system, its design requires further improvements and development to attain maturity. Wind-induced drag loads dominate the FSPV design, which is installed in relatively small reservoirs. On the other hand, wind-induced drag, wave, and current loading becomes critical when it is installed in the dam’s upstream reservoir where the open water area is in the range of 10 square Km.

The present study investigates the experimental wind tunnel test results of the real-scale dummy solar panel assembly used for FSPV parks. The testing was carried out at the National Wind Tunnel Facility (NWTF), IIT Kanpur. The test assembly includes five dummy solar panels of 2456 mm × 1134 mm, mounted on HDPE floaters in a 4+1 configuration. One dummy panel was instrumented for wind load measurement. The instrumented dummy panel was relocated from one position to another to get the wind load for each configuration. The tests were carried out for worst-case wind incidence angle, i.e. wind hitting the solar panel from the bottom at wind speed ranging from 0 Km/hr to 200 Km/hr. Drag and lift loads were obtained using load cells mounted underneath the panels. These results are useful for validating the numerical model.

The safety of the FSPV lies more in designing the anchoring and mooring system, which relies on wind load calculation. Realistic numerical models are required for the correct estimation of the wind load on the utility-scale FSPV, which can only be ensured after validating the numerical model with the experimental results on real-scale assembly. These well-established computational models can further be used for various changes in the study for which repeated experiments are not viable.
A Comparative Assessment of the Dynamic Responses of Solid Plate, Stiffened Plate, and Sandwich Plate of Equal Masses Under Explosive Loadings
Authors: Patel Murlidhar , Patel Shivdayal , Ahmad Suhail , Guedes Soares Carlos
Published: August 2024

For making a protective structure, the AL6XN steel has high ductility and excellent strength, and in the current study, it is used for making protective structures. The present work deals with a cost-effective numerical analysis of the protective structures’ blast performance. To investigate the significant effects on the air blast mitigation of a solid plate, a stiffened plate, and a sandwich plate of equal masses, their quarter parts are modeled. The use of quarter models significantly reduces the computation cost in terms of storage and computation time. The finite element models of a solid plate, a stiffened plate, and a sandwich plate are subjected to blast loads of 1–3 kg of TNT for a 0.1 m stand-off distance. To analyze the dynamic response of the modeled structures under blast loads, the Conventional Weapons Effects Program (CONWEP) module of Abaqus/Explicit is used. In air blast loadings, the structures are subjected to high impulse and deform with a high strain rate. To predict their plastic deformation behavior, the Johnson-Cook (J-C) plasticity model is used. This model is the most preferable for isotropic structures that are subject to large deformation with a high strain rate and high temperature. To verify the applicability of the numerical approach followed, the obtained results for solid plates’ deflection and impacted peak overpressures at applied blast conditions are compared with experimental data obtained from the literature. The blast performance comparison of the modeled structures deals with their deflection behavior, kinetic energy, energy absorption, and plastic deformations. The obtained results show that the sandwich plate has the greatest blast mitigation capacity, followed by the equivalent stiffened plate and the equivalent solid plate. Due to the sandwich plate’s smallest back face deflection and the highest capability to absorb energy, it is also applicable to the bulkhead, hull, and decks of ships.
Case Studies of Elastic Closed Fish Cage Concepts in Waves
Authors: Firoozkoohi Reza , Ravinthrakumar Senthuran
Published: August 2024

This paper demonstrate usage of a coupled linear hydrodynamic and structural model to assess the elastic response of closed fish cages in waves. From a design point of view it is important to avoid coupling between internal sloshing and the structure. This problem is addressed by assessing the elastic response of two closed fish cages made of an uniform elastic material. A vertical cylinder cage (bucket concept) and an ellipsoidal cage (egg concept inspired by Ovum AS design) with similar internal volume are investigated. WAMIT which is a software based on Boundary Element Method is used to compute hydrodynamic forces on rigid and elastic modes of motion. LSDYNA which is a Finite Element Method software is used to compute dry elastic mode shapes to be used as basis functions in the modal analysis. The computations were performed in frequency domain. The effective stress, i.e, Von Mises stress, is computed for the maximum responses in frequency domain to be compared with yield stress of the manufacturing material. The focus is on elastic cages for which the manufacturing material withstands bending. The effect of variation of stiffness on elastic response and its interaction with sloshing is addressed. The numerical method is explained briefly and its advantages and shortcomings are addressed. It is shown that the egg concept has a much smaller hydroelastic response than the bucket concept for the same material properties.
Typhoon Wave Prediction Using Long Short-Term Memory Networks for Offshore Windfarm on Western Coast of Taiwan
Authors: Chao Wei-Ting , Young Chih-Chieh , Hsu Tai-Wen
Published: August 2024

An accurate and efficient typhoon wave prediction model is important for improving the efficiency of offshore wind farm management. In the earlier studies, short-lead-time (i.e., 1 to 3 hours) typhoon wave prediction models were developed for the Taiwan coastal area. These models were constructed by BPNN with local meteorological information. However, Sufficient prediction lead-time is essential for early warning and response to offshore wind farms during typhoon events. Furthermore, past research on typhoon waves along the western coast of Taiwan often presented an underestimated tendency due to the structure of the typhoon being destroyed by the Central Mountain Range. This study aims to establish a novel long-lead-time typhoon wave prediction model using Long Shor-Term Memory (LSTM) networks while carefully considering typhoon parameters. The basic concept of LSTM is to utilize the memory cell to capture the features or vectors of time-related data, significantly enhancing prediction accuracy. The results of LSTM demonstrate high consistency with in-situ data for 1-hour lead time (i.e., the correlation coefficient is up to 0.98). For longer lead time (e.g., 6 hours), the method significantly improves learning and generalizing capability more than shallow learning methods. The correlation coefficients for training and validation reach 0.91 and 0.86, respectively.
Integrated Operation of Underwater Pipeline Inspection and Repair in Dry Cabin
Authors: Chen Jiawang , Li Miao , Guo Jin , Chen Junrong , Zhou Peng , Gao Qiaoling , Nan Liwen
Published: August 2024

Submarine pipelines are subject to complex working loads, environmental loads, and accident risks for a long time and have excellent failure probability. The underwater dry maintenance method can apply the land maintenance technology to the seabed and achieve the maintenance quality on the land. Therefore, we designed a dry cabin for underwater operations that can achieve pipeline inspection and repair. For pipeline inspection, a 3D laser scanning mechanism was designed to map the external features of the pipeline, and an ultrasonic non-destructive detection mechanism was designed to detect metal internal defects such as pipeline corrosion and cracks. For pipeline repair, a composite material winding mechanism was designed to wrap and reinforce the pipeline. Moreover, establishing a stable seal between the dry cabin and the pipeline is a prerequisite for safe underwater dry operations. Therefore, a new type D seal strip composed of rubber and EPDM foam was designed. The comprehensive optimal structure of seal strip was obtained based on the Response Surface Methodology. In the near future, we will carry out sea trial application to verify the functions of the device.
Photogrammetry and 3D Imaging System for Subsea Systems Inspection - Mooring Inspection on P-51
Authors: Heitich Leila Valladares , Batista Da Silva João Luis , Gomes dos Santos Christian Ramalho , dos Anjos Christiano Marino Lucas , de Souza Queiroz Wesley
Published: August 2024

Petrobras foresees a scenario, in 2025, of extensive utilization of FPSOs in production activities in the Brazilian pre-salt. Besides future installations, Petrobras has an extensive mature oil and gas production fleet, some of which will be decommissioning in the following years. Mooring line inspection quality and reliability are of utmost importance in assessing mooring systems integrity, supporting decision making and risk management during design life (e.g., anticipating line breakage, avoiding loss of position and disruptions in production). In more mature systems, accurate information can improve in the planning about parallel decommissioning projects. In this way more accurate and reliable inspection methods using 3D laser imaging and photogrammetry are being sought, enabling remote Diverless applications and creating highly accurate 3D models. In addition to improving result reliability, this technological innovation also makes it possible to evolve towards solutions with Digital Twins and artificial intelligence, further developing the integrity assessment of mooring systems. At the end of 2022, a pilot test with one of these technologies was conducted on one of mooring lines. This article aims to reveal the results and discusses next steps, bringing potential benefits as man-hours risk exposure reduction and result reliability.
Digital Twin for Offshore Windfarm Jacket Lifting Frame
Authors: Mali Vijaykumar
Published: August 2024

Wind turbine capacity is increasing every year with new innovations and so does the size of wind turbine jacket foundations. This paper presents the development of a Structural digital twin solution for a physical asset, namely the ‘lifting frame arrangement’ that is designed for up-righting wind farm jackets from a horizontally built condition to a vertical condition in a construction yard. The lifting frame arrangement is a crane-type structure with a fixed foundation, a fixed boom structure, and strand jacks mounted at the tip of the booms. The lifting frame is designed, fabricated, installed, operated, and maintained with strategic objectives to reduce the cost, schedule, and project risks.

The operational safety and structural integrity of the lifting frame system during the up-righting of jackets, were assured through several detailed design substantiation processes, which included certification by DNV. If we consider capital expenditure (CAPEX) cost as USD X Millions, then operating expenditure (OPEX) cost is about 0.05X Millions USD. OPEX cost of the lifting infrastructure increases at incremental rate year on year once the asset approaches its design life. Structural digital twin of the lifting frame has minimized OPEX costs by 50% while assuring the structural integrity of the complete system by near real time monitoring of asset health. This structural digital twin solution may also enable the enhancement in the capacity of the lifting frame, by revisiting the design safety factors based on the operational history and measured stresses and reactions, ensuring that the lifting frame becomes suitable for upending heavier jackets than designed.

This paper illustrates the stepwise details followed to develop the digital twin solution; the sensors used for monitoring operations as well as the status of the structural health of the lifting frame during operation. The reduced basis finite element analysis (RB-FEA-[2]) was followed using Akselos’ software for near real time integration of sensor data with analysis model.