bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue Analysis of a Diffuser-Augmented Fiber-Composite Tidal Turbine
Authors: Rotor Mark Anthony , Genita Jeff David , Nacario Jericho Lance
Published: August 2024

This study investigates the structural performance of the diffuser-augmented horizontal axis tidal turbine (DATT) by examining the fatigue performance of its blades on different hydrofoil diffuser design parameters. While the diffuser augmentation relieves the issue of requiring a larger turbine to produce the same amount of power, it also increases the structural load on the turbine blades due to increased power performance. Currently, there is little literature on the structural response to increased load in DATT systems. Hence, this study examines the diffuser hydrofoil design parameters, namely, camber and orientation angle, for the fatigue performance of the turbine blades. In the first phase, the Finite Element (FE) model is created and verified, and the spectrum load cases are generated to simulate dynamic loading. Secondly, the FE model undergoes a static test, and various load spectra are applied for fatigue analysis. Glass Fiber Reinforced Polymer (GFRP) and Carbon Fiber Reinforced Polymer (CFRP) composite materials show satisfactory fatigue performance. Lastly, the third phase determines the level of sensitivity of the angle diffuser and camber to the fatigue performance, wherein the former results in a Sobol index of around 0.95, indicating a high significance level, while the latter parameter results in around 0.05, indicating non-significance. This study concludes that using fiber-reinforced polymer materials is satisfactory in tidal fatigue load application. The understanding of the fatigue behavior of DATT enables the development of better designs and saves on the cost of prototype development. Future work on more design parameters is recommended for optimization and sensitivity studies investigation.
Characterization and Performance Evaluation of Various Types of Polymers Based Latexes for Water Based Drilling Fluids Applications
Authors: Al-Yami Abdullah , Khan Majad , Tahir Muhammed Nawaz , Almulhim Sara , Alsafran Ali , Wagle Vikrant
Published: August 2024

Polymer based latex chemicals are primarily used as fluid loss additive in drilling fluids. They are used to prepare a thin filter cake on the wellbore formation and reduce filtrate loss into the formation. A thin filter cake reduces or eliminates incidences of differential stuck drill pipes.

The objective of this study is to look into two different polymer latexes for the use of water-based drilling fluids applications. The first polymer is based on Styrene-butadiene latex. The second polymer is based on Polyvinyl Acetate emulsion, (PVA).

Analytical techniques such as nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared analysis (FTIR), differential scanning calorimeter (DSC), and thermogravimetric analysis (TGA) were used to help in elucidating the structures and physical properties of different latexes. Tests such as for density, rheology, HT/HP filtration and thermal stability were conducted to compare the performance of different latexes in drilling fluid formulations.

Intensive analytical and performance evaluation were done on different types of latexes to find proper way of latex optimization for application for water-based drillings fluids. Styrene butadiene polymer latex outperforms several polymers due to the strong anionic interaction with formation compared to other mechanisms.
Tank Test of Flexible Acrylic Ship Model in Waves for Extreme Response Prediction
Authors: Komoriyama Yusuke , Houtani Hidetaka , Takami Tomoki , Matsui Sadaoki , Fujimoto Wataru
Published: August 2024

In this study, the Most Probable Wave Episodes (MPWEs) for given target Vertical Bending Moments (VBMs) are estimated considering the nonlinearities in the wave and VBM, and the tank tests using a flexible acrylic ship model in the MPWEs are carried out to discuss the effect of body nonlinearity in VBMs on the MPWEs. Although whipping was not considered in this study, this is the first study on MPWEs that considers the body nonlinearity in VBMs in addition to wave nonlinearity. The nonlinearity in waves is considered by using the Higher Order Spectral Method (HOSM), while the body nonlinearity including slamming forces in the VBM is considered by a simplified model incorporating nonlinear correction factors together with the transfer function (TF) of VBM. The MPWEs are estimated by using the HOSM and First Order Reliability Method (FORM), in combination with the simplified VBM model. The VBM nonlinear effects on the HOSM+FORM results are discussed by using the tank test results in MPWEs.
Modified Passive Nonlinear Observer for Multiple Full-Actuated Ships Cooperative Towing
Authors: Li Ze , Wang Lei , Wang Yiting
Published: August 2024

Multi-ship cooperative towing mission is one of the application scenarios of dynamic positioning ships. Dynamic positioning ship can achieve high-precision towing and improve the safety of towing mission. And the observer provides filtered low-frequency motion data for the dynamic positioning system during towing. Passive nonlinear observer is one of widely-used observers in dynamic positioning system. However, the first-order Markov process in passive nonlinear observer cannot accurately describe the interaction forces between ships when it comes to multi-ship cooperative towing mission. This paper discusses the variation character of positioning errors after implementing the estimated value of interaction force into the observer in numerical simulation. The influence of different estimation models and estimation accuracy on positioning errors is considered. By comparing the positioning errors of the adjusted passive nonlinear observer with passive nonlinear observer and alpha-beta observer, the results show that the adjusted passive nonlinear observer helps the dynamic positioning ship to reach a steady state faster than passive nonlinear observer and has a certain improvement in positioning accuracy, and the adjusted passive nonlinear observer can also select the appropriate parameters faster than alpha-beta observer. In conclusion, this paper gives concluding remarks when using passive nonlinear observer in multi-ship cooperative towing mission.
Comparative Study of Different Reduced Order Methods for Fluid-Structure Interaction and Validation With Experimental Results for a LNG Carrier
Authors: Chhoeung Sovanna , Fallet Cedric , Hartmann Moritz , Desmars Nicolas , Klein Marco
Published: August 2024

Ships and offshore structures are constantly exposed to wave loads during their lifetime. The detailed knowledge of their hydrodynamic properties is necessary to ensure the safety of the crew, structure and loading during operation. Therefore, wave loads are crucial to consider in the structural and seakeeping analysis of marine structures during their design process. The assessment of the hydrodynamic behaviour is obtained by numerical simulations accompanied by model tests for validation purposes. Reduced-order methods based on potential flow theory are mostly applied due to its computational efficiency. The aim of this study is to provide an overview on different established reduced order models discussing the theoretical foundation as well as limitations and applications. For this purpose, the sea-keeping behaviour of a LNG carrier is adressed as an application example in this study. The response amplitude operator (RAO) of the LNG carrier is determined with three different established numerical programs and validated by experimental results.
Study on the Vibration of a Cylindrical Shell Structure Using Energy Variational Principle
Authors: Han Xinyi , Li Tianyun , Zhu Xiang , Zhang Cheng , Peng Kehui
Published: August 2024

Numerous investigations have focused on the vibration of cylindrical shells, and achieved fruitful research outcomes [1,2]. However, most of these studies have primarily addressed general boundary conditions, leaving a gap in the analysis of the vibration characteristics of cylindrical shells under complex boundary conditions, which are prevalent in practical applications. Hence, it is necessary to delve into the vibration characteristics of cylindrical shells under various complex boundaries.

This research derives a solution model for cylindrical shells under both general and complex boundary conditions, utilizing the Energy Variational Principle and LOVE Thin Shell Theory. Through this approach, the free and forced vibration characteristics of cylindrical shells have been analyzed. Furthermore, numerical data obtained from the theoretical solution are compared with Finite Element Method (FEM) results to verify the reliability of the proposed method. Additionally, the study investigates the influences of different boundary conditions on the vibration characteristics of the structure.
Acoustic Radiation Study of Wind-Induced Aerodynamic Noise From a Large Cruise Ship Chimney Based on the CAS-RTM Method
Authors: Feng Xiliang , Zhu Yue , Chen Ziheng , Wu Haolong , Liu Ziyang , Gan Jin
Published: August 2024

The cruise ship’s chimney, situated at the highest position of the top deck, is susceptible to aerodynamic noise induced by the sea’s wind field, thus affecting the comfort of passengers on the open deck. This study conducted real measurements on wind-induced aerodynamic noise from a large cruise ship chimney. Based on offshore wind conditions, CFD simulations were conducted to derive the surface pulsation pressure, which in turn was input to the acoustic boundary elements and translated into a compact sound source. Then, employing the Compact Acoustic Source combined with the Ray Tracing Method (CAS-RTM), the acoustic radiation impact of the aerodynamic sound source on the open deck was predicted and analyzed. The predicted outcomes were validated through comparison with measured results, and finally, the aerodynamic shapes of the chimney were optimized. The results highlighted the effectiveness of the CAS-RTM method in obtaining a directional aerodynamic noise source and realizing sound propagation in an open acoustic environment. The directivity of the aerodynamic noise source primarily manifests on the left and right sides of the chimney, with radiated sound pressure exhibiting an increase and then decrease with rising frequency, peaking at 315 Hz. Both aerodynamic optimization schemes enhanced flow separation and vortex shedding while mitigating pulsation pressure distribution. Optimization I demonstrated the largest reduction of 3.172 dB, mainly at position 1 on the front side of the chimney. Conversely, Optimization II exhibited the greatest reduction, measuring 4.414 dB, at position 6 on the rear side of the chimney. This study can provide some instructive insights for the prediction and control of aerodynamic noise from cruise ship chimneys.
An Improved Interface Coupling Computational Fluid Dynamics With Potential Theory-Based Wave Descriptions
Authors: Pakozdi Csaba , Gutsch Martin , Sajan Joseph C. , Fouques Sébastien
Published: August 2024

This study employs the Steady Surface Gravity Wave (SSGW) theory and the periodic High-Order Spectrum (HOS) method to define the wave environment. Unlike traditional streamfunction wave theories, SSGW theory has the advantage of being valid across all water depths. This method allows for the simulation of nonlinear high-order waves with a steepness beyond what is achievable with 5th-order Stokes wave theory, and it also enables simulations in shallow water using the same theory.

A novel technique has been developed to reduce the computational cost of generating wave kinematics in Computational Fluid Dynamics (CFD) simulations. The key innovation in this technique is using bi-cubic interpolation to calculate velocity from the velocity potential, resulting in significant reductions in data volume. A similar technique is applied to link the HOS solution with CFD simulations. The commercial CFD software STAR-CCM+, used in this study, is based on the finite volume method with a segregated flow solver, using the multiphase Volume Of Fluid (VOF) model offering different motion modeling capabilities.

Verification studies employ regular waves, beginning with validating the SSGW interface by comparing it to the inbuilt Fenton’s Stokes 5th-order wave theory and the 5th-order Cnoidal wave theory. This assessment is conducted in both standing and moving frames. Additionally, regular waves defined by HOS are coupled with CFD. Both interfaces demonstrate high efficiency in terms of computational cost and a substantial reduction in the required data volume at the HOS interface.
Experimental Investigations on a Highly Flexible Submerged Structure in Waves
Authors: León Hernando Ignacio , Kosleck Sascha , Black Suzanne
Published: August 2024

In the wave tank facilities at the Technical University of Berlin, a series of comprehensive experiments were conducted to evaluate the feasibility of an innovative offshore fish cage design. This pioneering structure comprises several distinct cylindrical sections, each fully submerged and constructed from highly flexible membranes and fish netting. The different sections are fixed with a flexible but more rigid structure. This model is used to determine the feasibility of a full-scale model, that due to its large dimensions and near-the-surface operation, will be subjected to heavy responses and forces in demanding sea states.

The experimental setup consists of a motion capture system, that coupled with other sensors such as force gauges, allowed to track and evaluate the motion of the submerged structure as well as the wave hydrodynamical loads that it was subjected to. The primary objective of this experimental campaign was to evaluate the dynamic response of this flexible body to various wave conditions, encompassing both single regular waves and wave spectra. Different angles of attack of the body were tested with the aim of being able to cover as much variety of responses of the body as possible. Finally, the research assesses the applicability of conventional rigid-body motion analysis techniques, such as the response amplitude operator to this intricate flexible system. This paper presents the first results of what will be an in-depth analysis of these body motions in waves. Identifying, as a result, the heave motion of the mentioned underwater flexible body.
The Effect of Directional Spreading on Extreme Sea State Response for Floating Wind Turbines
Authors: Moalemi Aref , H. Wagner Mathilde , Aliyar Sithik , Ghadirian Amin , Jensen Bjarne , Bredmose Henrik
Published: August 2024

Empirical investigations have consistently demonstrated the multi-directional nature of actual ocean waves, a phenomenon that has been paid relatively limited attention in the research field of floating wind turbines. The present study seeks to reduce this knowledge gap by experimentally investigating the response of a novel 15 MW floating wind turbine design when subjected to multi-directional wave conditions.

The experimental work was carried out in the deep water basin at DHI A/S (DHI), at a scale of 1:40. In this investigation, the wind turbine rotor was simplistically modeled as a point mass, allowing for a focused examination of the hydrodynamic performance of the floater and mooring system.

The investigation of the concept’s behavior involved wave-only tests for irregular multi-directional waves with two spreading angles and across several sea states. The effect of swell waves was also examined through standalone tests as well as the combined motion response when they were superposed with directionally spread wind wave spectra.

While the effects of directional spreading and swell are well understood for small amplitude waves, the nonlinear interactions and load effects are less explored in the literature. The study therefore also covers severe wave conditions, both in terms of long sea state realizations and three-dimensional focusing waves. For all tests, the low-frequency response that is outside of the linear wave spectrum has special interest, since the natural frequencies of the floating structure are placed here. The outcomes of the experiments are presented through comparison of time series, power spectra, exceedance probability plots, and harmonic separation.
Extraction of Ship Collision Avoidance Patterns From AIS Data
Authors: Vijayakumar Akash , Singh Amar Nath , Somayajula Abhilash
Published: August 2024

The maritime industry faces constant challenges in preventing ship collisions and ensuring adherence to the Convention on the International Regulations for Preventing Collisions at Sea (COLREGs). This paper presents a comprehensive analysis of ship collision avoidance patterns utilizing Automatic Identification System (AIS) data. By examining AIS data parameters, including vessel speed, course, heading and the dynamic change in position, crucial insights into the avoidance of collision can be extracted. In this paper the encounters are extracted from the AIS data collected near Los Angeles Port. The raw data is preprocessed and visualised in a relative distance domain from the own ship. The encounters are filtered using a collision risk model and the encounter situations are labeled and classified into multiple classes using GRU-RNN deep learning technique.
Design and Motion Analysis of a Floating Water Channel Platform With Wave Energy Converters
Authors: Kim Jeongrok
Published: August 2024

This study performed stability and motion analysis for the basic design of a floating water channel platform (FWCP). This structure has a Y-shaped and is equipped with three wave energy converters (WECs). Such a system enhances the wave energy capture through reflection, incident wave energy collection, and fluid resonance in a closed region. The challenge is to ensure the stability and lies in accurately predicting the motion of the platform owing to fluid resonance. Thus, this study proposed four models to design a platform, and evaluated stability according to large angle through GZ curve. In addition, the motions of the platform were analyzed in the frequency domain using WAMIT and OrcaWAVE commercial codes, and compared with the model experiment results. The motion of the platform was found to be slightly overestimated at the fluid resonance frequency. Thus, further research is necessary to obtain a more accurate estimate.
Filter Units for Cable Stabilisation: The Effect of Fill Material and Volumetric Filling Ratio on Performance
Authors: Griffiths Terry , Li Frank , George Christo , Draper Scott , Clayton Jay , Pistani Fabrizio , An Hongwei , White David
Published: August 2024

Fiter units (sometimes called rock bags) are a very popular solution to improve the stability of subsea cables and cable protection systems (CPS) in the offshore wind industry. They are easily filled quay-side from local rock quarries and installed from vessels that are already mobilized as part of a windfarm construction spread. However, very limited data and research has been presented on the hydrodynamic properties and stability limit states for these mesh bags. No prior known literature describes the influence of filter material properties on their lateral resistance and stability, especially in the typical case where they are placed over a cable and are subjected to external loading from the cable or CPS.

This paper presents results from a parametric study involving scaled physical model tests at scale factor of around 1:10. The tests explore the performance of the bags when filled with different materials to different levels of filling. The results show that bag material and filling level have strong influence on the filter unit and cable stability due to their strong influence on the filter bag weight distribution between the cable and the adjacent seabed. Empirical models for use in engineering design are proposed based on the experimental data.
Ultra-Deep Drilling Wellbore Temperature Model Considering Thermophysical Properties of Different Lithology
Authors: Yao Xuezhe , Song Xianzhi , Zhou Mengmeng , Xu Zhengming , Cui Yueqi , Wang Haobo , Zhu Zhaopeng , Duan Shiming
Published: August 2024

Deep and ultra-deep drilling encounters high-temperature and high-pressure formation, and the state of wellbore flow and heat transfer is complicated, so the wellbore temperature is difficult to describe accurately. The conventional wellbore-formation heat transfer model holds that the formation lithology is uniform and the thermophysical parameters are constant value. However, a variety of lithologies are drilled during the drilling, and the thermophysical parameters of the formation vary with lithology and temperature. In this paper, a wellbore-formation heat transfer model of the ultra-deep well is developed by considering the thermophysical properties of different formation lithologies. A mathematical model of wellbore-formation heat transfer is constructed based on the law of energy conservation. Then the lithology of the formation is extracted, and the thermophysical parameters matrix of the lithology is constructed, to be embedded into the heat transfer mathematical model. Finally, the finite difference method is used to solve the mathematical model. The real data of an ultra-deep well is used to verify the model. The results show that the error between the predicted results of the model and the measured is only 3%. The wellbore-formation heat transfer model established in this paper can accurately describe the evolution law of the wellbore temperature field.
Study on Practical Fatigue Assessment Considering Hull Vibration Based on the EWP Concept
Authors: Takeuchi Takaaki , Osawa Naoki , Fukutake Natsumi , Hirakawa Shinichi , Kawajiri Yoshitaka , Yoshida Tomomi
Published: August 2024

Onboard multi-position hull monitoring (HM) is carried out on an 8,600 TEU container ship. The relationship between the characteristics of hull vibration (HV) superimposed stress waveforms and the fatigue damage enlargement ratio resulting from HV (Cvib) is studied. Based on this analysis, a methodology for estimating Cvib throughout the entire ship from HM data at a select few reference positions (RP) is proposed. By integrating the proposed whole-ship Cvib estimation technique with the concept of equivalent wave probability (EWP), which allows for the assessment of whole-ship fatigue damage due to wave-induced fluctuating stress (excluding HV) solely via HM data at a limited number of RP, an EWP-based comprehensive ship fatigue assessment approach that accounts for HV is developed. The effectiveness of this developed method is validated using long-term HM data. It is ascertained that the statistical attributes of Cvib throughout the entire ship can be reasonably approximated by those of the RPs with the same structural types (hatch side coaming or bottom of a cargo hold). Furthermore, it is demonstrated that the accuracy of HV superimposed fatigue damage can be improved through the estimation of Cvib’s statistical characteristics using exclusively HM data in the short seas where whipping is significantly occurring.
Local Structural Response of Concrete Shells due to Wave Impact: Calculated Responses From Measured Slamming Pressures Vs. Hydroelastic Measurements
Authors: Abrahamsen Bjørn Christian , Søreide Tore Helge , Hellan Øyvind
Published: August 2024

Design of concrete columns as part of offshore structures exposed to wave slamming, relies on finite element, (FE), analysis. Measured slamming forces obtained from model tests are often used as input to the analysis. This process of calculating the structural response is not straightforward, and in practical applications, it typically does not consider hydro-elastic effects, except for possibly incorporating added mass. So, how effective are these FEA calculations? Here FE analysis of a concrete shell covering a section of a monopile is carried out. The wave impact pressures used as input to the FE calculations were measured on slamming panels fixed to a circular monopile in SINTEF’s Ocean basin. The calculated utilizations are compared statistically with directly measured utilizations of elastic shells installed in the same monopile. The results show that in most cases the calculated design utilizations of the concrete shells are significantly higher than measured utilizations. Hence, the FE analysis is conservative in most cases, even though significant non-conservative simplifications were introduced in the calculation procedure.
A Practical Summation Method of Tolerances for Misalignment and SCF Calculation for Girth Welds
Authors: Hørte Torfinn , Fjeldstad Arne , Wormsen Anders , Kalvig Ragnhild Birgitte Hidle , Berg Espen
Published: August 2024

In conventional fatigue analysis of girth welds of risers and pipelines, misalignment with corresponding estimates of stress concentration factors need consideration. This is most important for cracks starting from the weld toe. The three most important sources for the misalignment are: i) diameter tolerances, ii) out-of-roundness (or ovality) tolerances and iii) thickness tolerances. In fatigue analysis of subsea wellhead systems, the most fatigue utilized girth welds are usually between machined components such as the wellhead or conductor housing and extension pipes or between two pipes. In this context, we have seen different industry practices on combining misalignment from the different sources of tolerances, leading to different stress concentration factors and correspondingly different fatigue lives. Both simple and somewhat complex combination methods can be rather conservative, resulting in high stress concentration factors and consequently, unacceptable low fatigue lives. There appears to be a lack of detailed guidance for combining these tolerances, and different engineers make different evaluations. We see the need for a common methodology, and in this paper, we present a practical approach, based on geometrical considerations and simplified statistical summation methods, to assess the resulting misalignment from tolerances. The applicable stress concentration factor is then calculated as a function of the misalignment using a standard formula. The method is applicable for specific tolerances provided in the relevant fabrication specification or standard. It can also be used in combination with measured so-called high/low values from the outside or inside of the pipe.

Application of the proposed methodology is demonstrated for fabrication tolerances provided in API 5L, and example results are calculated and presented as a function of pipe diameter for different pipe wall thicknesses. Results are computed for girth welds connecting a pipe to a machined component and for pipe-to-pipe connections. Different tolerances for seamless and welded pipes as given in API 5L are considered. Intermediate results are provided, such that it is transparent to see the contribution to the total misalignment from the different tolerance sources. It is likely that the method leads to somewhat lower stress concentration factors than what are most commonly used today by the industry for wellhead fatigue analyses. Although some conservatism is removed, the method is still judged to be on the conservative side which is also supported with reference to a large database of actual measured misalignments generally being less than 1 mm (OMAE2018-78408), indicating that the actual misalignment is generally well within typical fabrication requirements.
Evaluating and Optimising the Overset Solver in OpenFOAM for Complex Wave-Structure Interaction Problems
Authors: Rai Ranjodh S. , Qian Ling , Ma Zhihua , Bai Wei
Published: August 2024

In this paper, the latest overset mesh solver, updated in ESI-OpenCFD OpenFOAM v2212, is evaluated for two complex wave-structure interaction problems; namely, fifth-order Stokes wave interaction with a 2-D T-shaped floating body and focused wave interaction with a 3-D hemispherical wave energy converter. In particular, it is established whether the updated hole-cutting procedure improves the accuracy of solutions and reduces computational time. It is found that the accuracy of solutions for both problems are improved, but only for the T-shaped floating body case is this down to the new hole-cutting procedure. No discernible difference is made to the computational efficiency for either case. In addition, the primary bottleneck of the overset procedure in terms of efficiency is also identified with a vision of improving the overall efficiency of the solver and reducing computational time for modelling complex wave-structure interaction problems. It is found that the ‘markDonors’ function, called during the overset grid assembly procedure, is the primary bottleneck in efficiency, with the function’s parallel efficiency and scalability also shown to be poor.
The Impact of Considering the Commissioning Inspection When Defining Optimal Inspection Plans for Subsea Equipment
Authors: Maturana Marcos C. , Schleder Adriana M. , Martins Marcelo R. , de Barros Leonardo O. , Orlowski Rene T. C.
Published: August 2024

Cost optimization of asset management is a central issue in the offshore oil and gas strategy, and risk-based approaches has been more and more employed to assist the segment in the concretization of that goal. In this sense, the use of Risk Based Inspection by the petroleum industry has significantly increased. The inspection procedure aims mitigating the uncertainty related to the asset degradation state, enabling a better quantification of the actual damage, and, consequently, increases the accuracy of remaining life projections. Since the costs involved in offshore subsea inspections are considerable, inspection plans optimization plays a crucial role in the balance of an asset management program.

The present paper discusses the impact of considering the commissioning inspection when defining optimal inspection plans for subsea equipment. A genetic algorithm, an optimization technique inspired in the concepts of evolutionary genetics is used to obtain the optimal inspection plans. The genes are defined in terms of two variables: the type of inspection to be done and in which period it occurs, considering a finite window of opportunities for inspection occurrences. The optimization process considers a multicriteria objective function, consisting in the dimensions time, cost, and risk. Finally, the application of the proposed methodology is illustrated by means of the elaboration of the inspection plans for an Emergency Shutdown Valve and the effects of considering commissioning in the preparation of inspection plans are discussed. This study aims to contribute to improve the decision-making process concerning inspection policies.
Optimizing Northern Sea Route Transportation Times: A Comprehensive Study From Chinese Shipper’s Perspective
Authors: Gao Xinjia , Ge Wenhan , Yu Qifeng , Zhao Xintong
Published: August 2024

The Arctic Sea Route has long intrigued shippers and shipping companies for its potential to shorten the distance between the Atlantic and Pacific Oceans. With Arctic Sea ice melting, the Northern Sea Route’s navigational conditions have improved, revealing the growing prospects of commercial shipping. This study primarily focuses on the perspective of Chinese shippers, exploring the categories of goods that enjoy advantages on the Northern Sea Route and conducting a comparative analysis between the Northern Sea Route and the traditional Suez Canal route. Through quantitative analysis, it has been observed that as the navigational time of the Northern Sea Route increases, its position in the global maritime industry is progressively strengthening. Moreover, the article underscores the impact of transportation costs and time on profitability, providing specific cargo selection recommendations based on the effects of shortened transportation time. While emphasizing the potential advantages of the Northern Sea Route, the paper also puts forward long-term strategic recommendations to assist Chinese shippers and shipping companies in better harnessing the development opportunities provided by the Northern Sea Route and enhancing their competitiveness in the international shipping market.
Coastal Protection Measures for a Barrier Island Along East Coast of India - Physical Modelling
Authors: Mallela Mounika , Saha Nilanjan , Alluri Satya Kiran Raju , M. V. Ramana Murthy
Published: August 2024

Barrier islands are shore parallel sand deposits formed by the action of waves and winds and are separated from the mainland by tidal creeks, bays, and lagoons. These narrow strip of sand bars are most vulnerable to sea level rise and storm surges which are the consequences of changing Earth’s climate. As barrier islands are formed because of wind and waves, which shift according to weather patterns and local geographical features, they are most dynamic and complex in nature. As a case study, the barrier island of Sriharikota along East Coast of India stretching about 44 km parallel to pullicat lake (second largest lagoon in India) and Bay of Bengal is chosen as the study location.

From the last two decades, the shore front of the island is experiencing rapid erosion causing high risk to the infrastructure on the island. So, there is an immense need of long-term shoreline management strategies which are environmentally friendly and sustainable solutions.

The present study pertains to an experimental study on submerged rubble mound breakwater with a scaled model of 1:21 for three water depths of 0.4 m, 0.45 m, and 0.5 m. The wave heights are varied in the range of 0.05 m to 0.2 m with corresponding wave periods of 1.0 to 2.4 seconds. The performance of the submerged breakwater has been assessed by analyzing the hydrodynamic coefficients (i.e., wave reflection, transmission and loss characteristics) using two probe method. The results of the experimental study showed the significant impact of relative submergence, crest width, wave steepness and sea bed slope on the hydrodynamic performance of the structure.
Theoretical Modeling Toolbox for Diffraction Problems of Common Shaped Bodies
Authors: Nguyen Nhu
Published: August 2024

The present study aims to develop an open-source Python-based toolbox for the theoretical modeling of diffraction problems in commonly shaped bodies. The project has dual objectives: 1) to offer a quick and efficient means for design exploration during the initial project phase and 2) to serve as a tool for code comparison and benchmarking for numerical models. While numerical solvers are commonly employed due to the complexity of obtaining exact solutions, our prior work on OSWEC modeling has demonstrated the advantages of an analytical approach, characterized by a simple setup and significantly quick computational time (typically less than a second for a hundred cases). This analytical approach is well-suited for early stages of project development, encompassing design space exploration and device geometry optimization. The current phase of the toolbox includes diffraction solutions for three fundamental cylindrical bodies: bottom-seated surface-piercing cylinder, truncated cylinder, and bottom-seated surface-piercing elliptical cylinder. The outputs encompass domain velocity potentials, excitation forces, and moments, all validated using Capytaine (a Boundary Element Method modeling program). The project is ongoing and is planned for expansion to provide solutions for other shapes. Additionally, an extension of the program to include radiation problems is also scheduled.
Procedure to Include the Dynamic Loads of Catenary Shaped Risers on FPSO Roll Motion Assessments
Authors: Chads Carlos Eduardo , de Tarso Esperança Paulo
Published: August 2024

This work describes a procedure to include dynamic loads of catenary shaped risers to the roll motion response calculation of a Floating Production Storage and Offloading (FPSO) unit in the frequency domain. The procedure involves the application of an asymptotic solution for the dynamic tension at the top of risers based on the work of Aranha & Pinto [1]. It is assumed, as an approximation, that the riser dynamic tensions are sinusoidal when the FPSO is under the action of regular waves (this hypothesis is related to the assumption that the quadratic hydrodynamic damping is linearized in the chosen formulation). Since the dynamic tension expression is amplitude dependent, the described procedure is iterative. This work is restricted to the heave and roll motions, but focused on the roll response analyses. The roll response was analyzed for the case study FPSO under beam regular waves coming from portside and starboard, with 60 catenary shaped flexible risers connected. The roll RAOs calculated with the described procedure have presented a good agreement with the roll motions calculated with a coupled time-domain model in OrcaFlex™. From the hull “point of view”, the effect of the riser loads can be considered as equivalent to additional inertia, damping and stiffness effects, which are quantified for the case study of this work.
Vertical Axis Autorotation Current Turbine (VAACT) Analysis With Power Take-Off System
Authors: Soares Rodrigo B. , Fernandes Antonio C. , S. Sales Junior Joel
Published: August 2024

This research paper examines the effectiveness of the Vertical Axis Autorotation Current Turbine (VAACT) by conducting simulations using a two-dimensional Computational Fluid Dynamics (CFD) model. The verification and validation are carried out using the recommended practices from the International Towing Tank Conference (ITTC) [1]. The verification process includes checking the domain, grid, and time-step, and the model results are compared to tests at the Laboratory of Waves and Currents (LOC-COPPE/UFRJ) using an S-shaped VAACT profile. In the CFD environment, the power take-off (PTO) system is modeled by adding an external torque due to the PTO system and the damping coefficient (Kt) into a User-Defined Function (UDF). The validation is performed at Reynolds numbers ranging from 70,000 to 135,000. The time series analysis indicates that both lift and drag forces play a crucial role in the turbine’s performance. Although the instantaneous efficiency is in phase with the drag force, the lift is responsible for driving the device at smaller drag magnitudes. Additionally, the torque coefficient is in phase with the lift force, which implies that the hydrodynamic performance can be governed by it. The analysis also reveals that the returning blade adds a resisting torque on the turbine, which may impact its performance, as represented by high-pressure points at this blade.
Validation of Local Structural Loads Computed by OpenFAST Against Measurements From the FOCAL Experimental Campaign
Authors: Carmo Lucas , Bergua Roger , Wang Lu , Robertson Amy
Published: August 2024

This work presents the validation of the local structural load modeling capability in OpenFAST for floating substructures based on data from the FOCAL experimental campaign. Previously, OpenFAST could only represent the floating substructure as a rigid body, and though this approach can model the global response of the floater in most cases, it is not able to capture the structural loads within the floater’s individual members. Consideration of local substructure loads is important for some floating designs, because the pursuit of cost reduction often results in lighter and more flexible structures. To address this limitation, the HydroDyn (hydrodynamics) and SubDyn (substructure dynamics) modules of OpenFAST have been recently extended to account for the flexibility of floating substructures. To validate this new capability, we compare the results obtained by OpenFAST with data measured during the FOCAL experimental campaign, which analyzed a 1:70 scale performance-matched model of the IEA 15-MW reference turbine atop a modified University of Maine VolturnUS-S semisubmersible in a wave basin under the action of both wind and waves. For the purposes of the present work, the most important feature of the experiment is the presence of load cells at the root of each pontoon, and our objective is to assess how well those loads are reproduced by OpenFAST. To model the distributed hydrodynamic and hydrostatic loads along the floating substructure, we adopt a strip-theory approach based on the Morison equation, and we discuss the impact of different hydrodynamic modeling options (wave stretching, MacCamy-Fuchs correction, and second-order wave kinematics) on both motions and loads. For simplicity, we focus on wave-only conditions, both regular and irregular. The results demonstrate good overall agreement for the loads at the root of the pontoons for the waves analyzed in this work, especially given the assumptions and simplifications inherent to a simple strip-theory model.
Optimizing Subsea Rock Installation for Cost Savings: A Norwegian Shelf Case Study
Authors: Xie Xiyang , Vermeulen Otilia , Gao Hao , Nazari Moeen , Asklund Per Olav , Lunde Bjørn , Rasmussen Stian Laland
Published: August 2024

In offshore engineering, Subsea Rock Installation (SRI) is a cost-intensive process. This study focuses on a pipe-in-pipe project in the Norwegian Continental Shelf (NCS), addressing the challenges posed by a soft-clay seabed and deep iceberg scars. Traditional 2D limit equilibrium methods (LEM) often fail to capture the complex realities of these environments, particularly in terms of 3D seabed and rock geometry, and comprehensive material behavior. The rock volume based on 2D LEM design is also over conservative. Recognizing these limitations, this research advocates for the adoption of a 3D finite element method (FEM), which offers a more accurate analysis. By employing FEM, particularly for the stability of free-span infills in deep iceberg scars, it aims to optimize rock volume usage. The results suggest potential cost reductions up to 16%, underscoring the value of embracing more comprehensive design and simulation processes. These insights offer valuable guidance for future offshore engineering projects, paving the way for more efficient and confident design strategies.
Digital Twin Modelling for Full-Electric Harbour Craft: An Integrated Hydrodynamics and Systems Model
Authors: Hadi Januwar , Zhi Yung Tay , Kudupudi Ravindra , Taskar Bhushan , Tan Ching Eng , Singh Chopra Prabjot , Peng Neil , Konovessis Dimitrios
Published: August 2024

Marine vessels have undergone a significant transformation with the advent of digital twin technology. Digital twins, which are virtual replicas of physical vessels, have revolutionized the maritime industry by enhancing decision-making processes that manifest in operational efficiency and better ship design. This paper presents an overview of digital twins for a marine vessel, a full-electric harbour craft, highlighting their key components, creation & validation, applications, and future potential. Furthermore, the paper discusses the integration of the hydrodynamics model as a comprehensive digital twin model. The application of digital twins is beneficial, but not limited to planning, training, and safety. It is by inferring the digital twin model for simulation to predict range & speed, crew training and stress tests respectively. The digital twin model may eventually contribute to cost savings, environmental sustainability, improved overall vessel performance, and subsequent designs.

This paper also explores the challenges and limitations of digital twins in the maritime domain, such as power & operational envelopes, interoperability, and the need for skilled personnel. Addressing these challenges is crucial for the widespread adoption and success of digital twin technology in the marine industry. The adoption of digital twins offers to redefine the way marine vessels are designed & operated, leading to a more efficient, and environmentally friendly maritime industry.
A Thermal-Electromagnetic Assessment of Dynamic Umbilicals for Ultra Deep Waters
Authors: Cestari Coutinho Filipe , Morini Rafael Giovane , Camporez Danieli
Published: August 2024

Subsea Umbilicals are design to supply different functions, according to the needs of subsea production systems. These needs can include power distribution, monitoring, hydraulic and electric control.

Ultra deep waters already present a challenge to the mechanical design of the product, demanding a high-performance structural behavior but keeping important properties such as its weight and bending stiffness.

Besides the mechanical aspects to the design of subsea umbilical, when the umbilical functions include in same cross section power function, electrical control and optical monitoring, a care shall be taken to the thermal and electromagnetic aspects.

Prysmian performed a study to assess the behavior of a dynamic umbilical applied to ultra deep water scenarios, considering the mechanical, thermal and electromagnetic aspects of design.

The study presented results that shown that the positioning of the components has a significant influence on the efficiency of the subsea umbilical under application, both in thermal and electromagnetic aspects.
A new numerical method for linear rheology of living polymers
Authors: Love Claire , Peterson Joseph D.
Published: August 2024

Living polymers such as wormlike micelles have attracted considerable experimental and theoretical interest over the past three decades, but the differential-integral equations that describe the joint processes of reversible scission and stress relaxation were only recently developed and have not yet been solved. Here, we introduce a numerical method that is simple, stable, accurate, flexible, and fast compared to alternatives. After validating the method and its predictions, we provide a preliminary discussion on previously unquantified sources of uncertainty in a popular stochastic approach to modeling the same problem.
Mental Fatigue in Sport—From Impaired Performance to Increased Injury Risk
Authors: Schampheleer Emilie , Roelands Bart
Published: August 2024

The literature describing the effects of mental fatigue (MF) has grown tremendously. This is accompanied by identification of a host of performance-determining parameters affected by MF. MF results from prolonged cognitive effort and predominantly affects physical, technical, tactical, and perceptual–cognitive dimensions of sport, while physiological parameters (eg, heart rate, lactate) and physical aspects of maximal and supramaximal efforts are predominantly unaffected. The aim of this paper was to provide an overview of the parameters described in the literature as influenced by MF. By identifying the different parameters, we not only see how they affect the performance of athletes but also raise concerns about the potentially increased injury risk due to MF. Preliminary evidence suggests that subsequent disturbances in balance, motor skills, and decision-making processes could potentially increase the vulnerability to injury. An abundance of lab-based studies looked into the effects of MF on performance; however, many questions remain about the mechanisms of origin and neurophysiological causes of MF, and only small steps have been taken to translate this knowledge into practice. Thus, there is a need for more research into the underlying mechanisms of MF and the role of the brain, as well as more applied research with a high ecological validity that also takes into account the potential increased risk of injury due to MF.