bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation on the Effects of Diffuser Inlet Opening Angles on the Performance of a Drag-Based Hydrokinetic Turbine
Authors: Ng Cheng Yee , Riyaz Nauman Maldar , Ong Muk Chen 
Published: August 2024

Abstract
The potential of ocean energy as a renewable source is widely acknowledged. Ocean currents energy is one of the ocean energies, which is harnessed by using hydrokinetic turbines (HKTs). Despite continuous efforts on the optimization of HKTs’ energy conversion performance, challenges remain in regions with slow flow velocities. This study aims to investigate the effects of incorporating a diffuser into a HKT design on the power output performance. Numerical simulations using the Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations and renormalized group (RNG) k-ε turbulence model is conducted by varying the diffuser inlet opening angles (θi = 15°, 20°, 25°, 30°, and 35°). The results show that the highest flow velocity is measured at the diffuser throat for all angles, which a deceleration flow effect is also observed here. This decelerated flow zone is found to be extended from the diffuser wall to its midline. The optimal configuration for power and torque coefficients is found in inlet opening angle of 20°. Overall, incorporating a diffuser with the optimum inlet opening angle in the HKT design improves the power generation efficiency compared to the HKT configurations without a diffuser.
Estimating the Most Likely Extreme Nacelle Acceleration of a Floating Offshore Wind Turbine From Physical Model Tank Testing
Authors: McMillan Ailsa , McDonald Alasdair , Pillai Ajit C. , Yuan Zhiming , Davey Thomas 
Published: August 2024

Abstract
The floating platforms on which floating offshore wind turbines are mounted introduce considerable complexity in terms of dynamic motion. Understanding the extreme response of these marine structures is important. One such extreme response is the nacelle accelerations, which can cause damage to nacelle components, such as the generator, and should therefore be kept to a minimum. Tank testing is a tool which can be used to understand the behaviour of these structures, and to determine extreme response. Here, a method of estimating the most likely extreme nacelle accelerations from a tank testing programme is shown, using a 1:100 scaled model of the IEA 15 MW turbine with the Volturn-US semi-submersible platform. The results showed that the most likely extreme nacelle accelerations within the chosen 50-year return sea state are 0.195 g in the fore-aft direction, with a typical safety limit of 0.2–0.4 g. Extreme statistical analysis was carried out on the data obtained by a 3-DOF accelerometer, using the peaks-over-threshold (POT) method fitted to a generalised Pareto distribution (GPD). Threshold selection and declustering of data are also discussed. The results may be applied to further test programmes, aiding in the development and design of current or novel floating platforms in any programmable sea state.
Bending Stiffness of Unbonded Flexible Pipes and its Application in Installation
Authors: Zhu Linfa , Zhou Yan , Hou Yucheng , Reuter Jason , Yuan Jiabei , Tan Zhimin , Roberts Andrew 
Published: August 2024

Abstract
The bending hysteresis behavior of unbonded flexible pipe is well known and fully implemented in flexible riser system design and analysis, for example, extreme, interference and fatigue analysis. However, in some quasi-static applications, the inclusion of the full bending hysteresis loop sometimes leads to noticeable deviations from configurations observed in the field.
To address the issue, this paper intends to interpret these differences from the nature of the internal friction, which is the main mechanism governing the pipe bending hysteresis behavior. Two operation cases are presented for the study: 1) a flowline installation, and 2) a flexible riser wet storage. The pipes in both cases are not subjected to any significant wave excitations. Therefore they are considered quasi-static applications. The flowline installation involves a camelback configuration at the end fitting-gooseneck connection. The riser wet storage case involves wave configuration with installation ballasts, considering about a 1-year wet parking period. The paper presents a configuration sensitivity study with different bending stiffnesses and identifies the one that produces the best agreement between the predicted and measured configuration in the survey. Based on the findings, the paper also recommends the most appropriate use of pipe bending stiffness in designing quasi-static jumpers, which predicts accurate configuration and associated support interfacing loads thus avoiding excessive conservatism.
Research on Temperature Field Distribution of Helical Carcass Supported Composite Flexible Cryogenic Pipe for LNG
Authors: Bu Yufeng , Yan Jun , Yin Yuanchao , Yang Zhixun , Fu Ying , Hailong Lu 
Published: August 2024

Abstract
Helical carcass supported composite flexible cryogenic pipe (hc-FCP) for LNG is one of the key equipment of floating liquefied natural gas (FLNG) storage and offloading device system. Hc-FCP cross-sectional form is complex, and the operation needs to withstand −163 °C cryogenic, which causes a change in the properties of the material inside the pipe. Therefore, obtaining the temperature field distribution of a pipe structure is essential for predicting its mechanical properties. In this paper, a two-dimensional axisymmetric steady-state heat transfer numerical model of the hc-FCP is constructed, and the accuracy of the numerical model is verified through prototype experiments, and the temperature field distribution at the actual working temperature of the pipe is characterized by a gradient distribution along the radial direction and a corrugated type distribution along the axial direction. The influence law of outside environmental factors on the temperature field distribution characteristics of the pipe is also discussed. The results show that the temperature gradient between the inner and outer surfaces of the pipe increases as the ambient temperature rises; the temperature change between the inner and outer surfaces of the pipe increases as the ambient wind speed increases, and the effect of wind speed on the change of the pipe temperature field becomes smaller and smaller as the wind speed increases.
Numerical Study on Tip-Gap Flow of a Hydrofoil
Authors: Takahashi Kenshiro 
Published: August 2024

Abstract
Ducted propellers are expected to provide significant hydrodynamic and hydracoustic benefits for underwater vehicles. However, ducted propellers typically have a tip gap between the blades and duct surface, which can cause flow instabilities and cavitation resulting in undesirable noise. Therefore, understanding the tip-gap flow mechanism is critical for managing the hydroacoustics of these propulsors. This study focused on a fundamental analysis of a tip-gap flow of a hydrofoil using computational fluid dynamics. The Reynolds-averaged Navier-Stokes (RANS) turbulence model was primarily used to compute the mean global features of the tip-gap vortices, whereas a large-eddy simulation (LES) was used to resolve the crucial turbulent structures. A mesh refinement study was performed by decreasing the mesh size in the tip-gap region. The computed vortex topology in the tip-gap region was similar to that obtained in an experiment. Further analysis of the tip-gap flow was conducted, and several remarks are discussed regarding the formations of tip-separation vortex, tip-leakage vortex, and induced vortex yielded. The LES computed the complex vortex structures, and the result was compared with that obtained with the RANS simulation.
Parametric Study on Tip-Gap Flow of a Hydrofoil Using Computational Fluid Dynamics
Authors: Takahashi Kenshiro 
Published: August 2024

Abstract
Ducted propellers are expected to provide significant hydrodynamic and hydroacoustic benefits for underwater vehicles. However, ducted propellers typically have a tip gap between the blades and duct surface, which can cause flow instabilities and cavitation, resulting in undesirable noise. Therefore, understanding the tip-gap flow mechanism is critical for managing the hydroacoustics of these propulsors. In this work, a parametric study on the tip-gap flow of a hydrofoil was performed using computational fluid dynamics. The tip-gap height, incident angle, Reynolds number, and section profile were the investigated parameters. The extensions of the tip-leakage vortex (TLV) and tip-separation vortex (TSV) decreased for smaller tip-gap heights. The isosurface of vapour pressure in the TLV was not observed for the largest tip-gap height, whereas it remained near the leading edge for the smallest tip-gap height. The TSV and TLV were mitigated for smaller incident angles, although a lower pressure region was yielded at the leading edge even for no incident angle. The global features of the TLV and TSV were similar for different Reynolds numbers. However, a greater leakage flow was observed for a higher Reynolds number. Enlarged TLVs and expanded lower pressure regions were observed for the thinner and cambered hydrofoils.
Impact of Roll Waves in Mudflow on Hydraulic Structures
Authors: Yu Boyuan , Chu Vincent H. 
Published: August 2024

Abstract
Mudflow is destructive because the flow’s tendency to become unstable at a small Froude number, leading to roll waves of a steep front that can strike an obstacle with great force. We conducted simulations of roll waves in mudflow down an inclined open channel to determine the impact force of the waves against hydraulic structures of various shapes and orientations using a depth-averaged shallow-mudflow model. The roll waves increase in amplitude with distance from a local disturbance. The rate of the increase depends on the Froude number of the undisturbed flow, and the rheological properties of the mud. The wave-impact force could reach a peak of more than an order of magnitude greater than the force on the structure without the roll waves. However, an obstacle with a sharp and pointy front can deflect the incident waves, significantly reducing the impact force.
A Sensitivity Analysis of the Voyage Adjustment for Sailing in Ice of the Carbon Intensity Indicator Regulation
Authors: Tran Trung Tien , Browne Thomas , Veitch Brian 
Published: August 2024

Abstract
The Carbon Intensity Indicator (CII) regulation came into force in 2023 with the objective of reducing greenhouse gas emissions in the maritime industry. Ice-classed vessels sailing in ice have been granted a voyage adjustment in the CII regulation. The voyage adjustment allows ice-classed vessels to exclude from the calculation of CII the part of any voyage that constitutes sailing in ice. The current study examines a sensitivity analysis of definitions for sailing in ice conditions. Sailing in ice is defined in the current regulation as an ice-classed vessel operating in a sea area within the ice edge. Alternative definitions have been considered which are more specific in terms of concentration and thickness of the ice field where the vessel operates. We present a case study of a conventional diesel-powered bulk carrier with ice class IA Super on a voyage in the Canadian Arctic. Routing of the vessel is optimized based on an assumed rewards function, a routing algorithm, and a ship performance model. We compare the routes selected under different definitions of “sailing in ice conditions”. The results show that different definitions of sailing in ice conditions lead to different optimal routes for the vessel, some of which are more effective than others in meeting the IMO’s strategic objective of reducing emissions.
The Influence of Current Profile on On-Bottom Stability of Subsea Cable
Authors: Hao Mingxuan , Longva Vegard , Ye Naiquan , Ji Guomin , Sævik Svein 
Published: August 2024

Abstract
With the development of offshore wind industry towards deeper water depth, the demands for transferring electricity through subsea power cables over long distance across uneven seabed have increased. An important design criterion in subsea cables is to ensure that the cable can remain stable on the seabed when exposed to complex hydrodynamic loads induced by waves and currents. Accurate current profile is critical in assessing the hydrodynamic loads property on the cable. The current profile near seabed is significantly affected by the boundary layer effect above the sea bottom. According to common practice, the boundary layer related to the wave kinematics at the seabed, is usually neglected. This is known to have a marginal effect for large diameter subsea pipelines. However, the diameter of the subsea cable may be in the same order as the boundary layer thickness and its impact on the on-bottom stability can therefore not be ignored.
DNV-RP-F109 includes the ability to take the effect from waves onto the current profile into account. In the present study, time-domain dynamic on-bottom stability analysis of a subsea cable is performed by using a tailor-made finite element program SIMLA to investigate the influence of the boundary layer. The case study is conducted on a 300-mm-diameter cable, which is placed on a sandy soil in shallow water, exposed to irregular waves and two different current profiles, however, by respectively excluding and including the wave effect on the current profile. Sensitivity study regarding different diameter and submerged weight of soil has been carried out and validated against published paper.
Conceptual Design of a Hybrid Floating Offshore Wind Turbine Integrated With Hydrogen Production and Storage System
Authors: Pham Thanh Dam , Trinh Luan Cong , Dinh Van Nguyen , Leahy Paul 
Published: August 2024

Abstract
The shift towards renewable energy requires sustainable energy carriers, with hydrogen emerging as a crucial player in creating a lasting and stable decarbonized energy sector. Floating offshore wind turbines are expected to become a major contributor to renewable electricity because they can harness wind energy over a vast area of the ocean, areas which fixed-bottom wind turbines cannot reach. Combining floating offshore wind turbines with hydrogen production and storage potentially creates a powerful solution to address the variability of wind energy and allows the production of zero-carbon “green” hydrogen from wholly renewable sources. Additionally, integrating hydrogen systems with large floating offshore wind turbines allows for decentralized and easily-scalable energy production and storage. This approach not only boosts energy security in coastal and island states but also reduces dependence on existing energy networks.
This paper introduces a conceptual design of a hybrid system. It integrates a 15 MW semi-submersible floating offshore wind turbine with a hydrogen production and storage unit, both mounted on the same semi-submersible floating platform. The system mass properties are modeled in Catia, and its dynamic behaviors are analyzed using the OpenFAST software. Essential tests performed include free decay tests and response amplitude operator analysis to observe the platform’s movements. The primary goal is to verify the system stability during different operational events and varying environmental factors. The analysis emphasizes the advantages and potential of combining offshore wind turbine technology with hydrogen storage and production systems.
A Novel Approach for Assessing the Accuracy of Prediction Models
Authors: Wang Hexian , Guo Lingyun 
Published: August 2024

Abstract
Currently, prediction models universally contend with model errors and lack a method for assessing their accuracy. Based on statistics, this paper proposes a novel approach that involves estimating the feature parameters of the database, determining the best-fit distribution and calculating the recommendation factor. Based on this approach, we developed an intelligent characterization extraction machine (ICEM) containing three processors: the Feature Parameter Extractor (FPE), the Fitted Distribution Processor (FDP), and the Recommendation Factor Processor (RFP). Firstly, a detailed database consisting of prediction accuracy needs to be inputted into ICEM; secondly, the FPE estimates the characteristic parameters of the database, and the FDP determines the best-fit distribution; finally, the RFP will give the recommendation factor. In this paper, an example is designed to show the ICEM’s application in evaluating the prediction accuracy of failure assessment model for pipes with axial cracks on the outer surface. The results show that: the software can compute the characteristic parameters and determine the best-fit distribution of the database which can quantify predicted performance and provide recommended safety factors.
Experimental Modelling of Wave-Structure-Soil Interaction of a Floating Offshore Wind Turbine at Large Scale
Authors: Windt Christian , Goseberg Nils , Schimmels Stefan , Kudella Matthias , Shanmugasundaram Ranjith , Rusche Henrik , Sumer B. Mutlu , Kirca V. S. Özgür , Yilmaz S. Utku , Vanjakula Vinay , Adam Frank , Smyczynski Marcin , Kazimierowicz-Frankowska Krystyna 
Published: August 2024

Abstract
The understanding of the wave-structure-soil interaction around marine structures is important in order to drive design decisions towards lean, yet resilient marine infrastructure. In particular, in the light of the increasing use of the marine environment for renewable energy generation, analysis of the wave-structure-soil interaction becomes increasingly relevant. While most experimental studies on wave-structure-soil interaction are conducted at small to medium scale, this paper presents the initial results of an experimental test campaign on the wave-structure-soil interaction of a floating offshore wind turbine at large scale. The data of the period averaged pore pressure reveal a significant buildup of pore pressure beyond the onset of liquefaction, which can be attributed to the additional structural loading when comparing results to similar, isolated wave-soil interaction cases in the absence of a structure.
Evaluating Position Control for Real-Time Hydrodynamic Motion Response in a Robotized Dry Test Rig With a Point-Absorber WEC
Authors: Salar Dana , Hultman Erik 
Published: August 2024

Abstract
A robotized dry test rig in six degrees of freedom, for emulating the influence of hydrodynamic forces on and the resulting motion response of different types of point absorbing wave energy converters has been developed at Uppsala University. In the past we have investigated and shown that the dry test rig works with both force and position control methods.
In this article we further examine the position control method, as we have not been able to use it for rougher wave movements. This is due to the fact that there has been a control lag in the system which contributed to the system becoming unbalanced in some emulation scenarios. A solution for an updated position control method, with significantly reduced control lag, is demonstrated in robot simulations and compared with both hydrodynamic model simulations and physical robot experiments for two buoy sizes in regular waves.
The results show a clear positive solution for avoiding control lag problems, making the position control method fully possible to use in the field. Future work is to implement the updated method on the physical robot test rig.
AI-Based Surrogate Model for the Prediction of Ship Fuel Consumption Reflecting Hydrometeorological Conditions
Authors: Zhang Mingyang , Tsoulakos Nikolaos , Kujala Pentti , Hirdaris Spyros 
Published: August 2024

Abstract
Accurate prediction of ship fuel consumption is essential for optimizing ship performance and minimizing environmental impact. This study presents the development and validation of an artificial intelligence (AI)-based surrogate model specifically designed to predict Ship Fuel Consumption (SFC) in the case of a bulk carrier. The surrogate model employs a cutting-edge approach by combining deep learning techniques, specifically incorporating attention mechanisms into Bidirectional Long Short-Term Memory (Bi-LSTM) networks. This advanced model leverages a rich and diverse dataset comprising crucial operational parameters, including ship navigation, ship operational conditions, engine operational status, and Metocean data, to achieve highly accurate predictions of SFC. The dataset used for training and validation is sourced directly from realistic bulk carrier operations, ensuring the relevance and practical applicability of the model. Extensive generalization tests were conducted to evaluate the performance of the developed surrogate model. The results indicate that the AI-based surrogate model achieves long-term high accuracy in predicting ship fuel consumption under varying operational conditions. The developed surrogate model may serve as a valuable tool for bulk carrier operators, offering insights into fuel efficiency improvements and enhancing the overall sustainability of ship operations.
Experimental Research of Innovative Composite Offshore Structure for Umbilicals Transportation and Installation
Authors: Atutis Mantas 
Published: August 2024

Abstract
Sustainable design and manufacturing of low-carbon structures is a major concern for the offshore renewables industry. Fiber reinforced polymer (FRP) composite materials are seen as a suitable alternative to traditional structural materials due to their high strength and light weight. Due to the high potential of offshore windfarms and high expectations from the industry mentioned benefits provide significant savings in subsea and offshore applications of FRP composite materials. Safety, structural integrity, and corrosion resistance are essential factors to consider aggressive offshore and subsea environments. Current research presents a comparative experimental investigation and introduces a new type of composite structure considering glass fiber reinforced polymers (GRP) in lieu of conventional carbon steel for umbilical or cable storage, sea transportation and subsea installation. Due to lack of standard and experimental results, a new prototype is experimentally tested on site based on large scale experimental program. Identified priorities reflected to this research work by promising application of GRP composite material may find innovative use in offshore environment.
Experimental Study of Shielding Effects of Aluminum Alloy Net Panel in Waves
Authors: Lei Yu , Zheng Xiang Yuan , Liu Xin , Yan Shu , Cai Xiao , Zhang Sheng 
Published: August 2024

Abstract
For the traditional polyethylene and nylon nets, lots of studies have been carried out to study their hydrodynamic characteristics in waves and currents. However, the studies of the metal nets which also have wide application prospect in marine aquaculture are rare, especially on their performance in waves. In this study, a series of laboratory experiments are conducted to investigate the hydrodynamic characteristics of the chain-link type aluminum alloy nets. Two net panels of identical dimensions are placed in the ocean basin. They are parallel to each other, with a certain length of gap. The wave forces on the net panels under different wave heights, wave periods and immersion depths are measured. The wave elevations at different downstream positions of the nets and the wave forces on both upstream and downstream net panels are measured to investigate the shielding effects. The wave transmission coefficient and shielding coefficient of the horizontal wave force are therefore derived. The experimental results show that both two coefficients are around 1 under different wave conditions which indicates that the shielding effects of the chain-link type aluminum alloy nets can be ignored. Thereby, in the calculation of wave loads on upstream and downstream fish nets, it is reasonable to neglect the wave attenuation inside the nets.