bluuebunny/crossref_metadata_2025_split huggingface dataset:
Retrieval of Ocean Wave Spectra From X-Band Marine Radar Images Using Inversion Schemes Based on Auto-Spectral Analysis
Authors: Radhakrishnan Gowtham , Leira Bernt J. , Gao Zhen , Sævik Svein , Christakos Konstantinos 
Published: September 2023

Abstract
Estimation of ocean wave conditions is extremely crucial for the planning and execution of demanding marine operations. Further, the Response Based Decision-Making requires accurate wave inputs to derive the responses using a numerical model. The X-band marine radars, installed on top of the vessels, are cost-effective means to assess the incoming wave field. Dedicated full-scale measurements were conducted using the research vessel Gunnerus in the Breisundet field, located on the west coast of Norway. After interaction with the ocean waves, the electromagnetic waves from the radar are backscattered based on the Bragg scattering mechanism. The radar digitizes the backscattered signal in the form of intensity images. 3-Dimensional (3-D) Fast Fourier Transform (FFT) was adopted to convert the temporal sequence of backscattered images to the wavenumber-frequency representations. The current velocity components estimated using the least-squares approach showed better agreement with the buoy-based current measurements. Then the wave-related components were extracted based on the linear wave dispersion relationship. Subsequently, the spectra were corrected for the shadowing effect using modulation transfer functions. Finally, the radar-based wave measurements were scaled using the nearby wave buoy records. The estimation of wave spectra improved considerably after the application of the Modulation Transfer Function (MTF). The spectra at the mid-range gave the best results when studying the effects due to range dependency. The spectra processed from radar images were validated using wave buoy measurements.
Visibility Enhancement in Turbid Water Based on Polarization and CLAHE
Authors: Liu Luping , Li Xin , Zhang Xiantao , Zhang Fan 
Published: September 2023

Abstract
Underwater visual distance is usually limited due to absorption and scattering of light, particularly in turbid water scenes. Currently, most underwater optical image processing algorithms are developed for the post-processing of static single-frame images taken in shallow water environments to achieve clear, color restoration images. Moreover, in turbid water scenes without ambient light, relying solely on post-processing algorithms to obtain ideal image quality can be challenging. In this study, we seek for underwater image quality recovery solution that can be applied during underwater vehicle operations. Polarization technology is used to remove the veiling light, which is the main cause of image degradation. The optical devices are fitted by polarizing filters through simple modifications. Additionally, a contrast limited adaptive histogram equalization (CLAHE) algorithm is employed to improve contrast and modify the color cast of images caused by direct signal attenuation. The proposed solution is tested and evaluated on underwater images acquired in laboratory experiments and the results are compared against other underwater post-processing methods. The study expects this approach will enhance the clarity and visual range of underwater targets, thereby improving target recognition in underwater operations.
New Developments and Capabilities Within WEC-Sim
Authors: Tom Nathan , Ruehl Kelley , Keester Adam , Forbush Dominic , Ogden David , Leon Jorge , Husain Salman , Grasberger Jeff , Topper Mathew B. R. , Yu Yi-Hsiang 
Published: September 2023

Abstract
WEC-Sim is an open-source software for simulating wave energy converters and has been actively developed and applied since its initial release in 2014 to simulate a wide variety of device archetypes. WEC-Sim is developed jointly by the National Renewable Energy Laboratory and Sandia National Laboratories within the MATLAB/SIMULINK environment. A general wave-to-wire model begins with a deployment site resource characterization, which is used to complete the hydrodynamic simulation of wave energy converters (WEC), with the power generation profile imported to a grid simulator to understand the influence on the local electrical network. While modeling the entire wave-to-wire is difficult and encompasses multiple time scales and physics, WEC-Sim is focused on the hydrodynamics simulation to predict, analyze, and optimize WEC dynamics and power performance. WEC-Sim simulations are performed in the time domain based on the radiation and diffraction method using hydrodynamics coefficients derived from boundary element method (BEM)-based frequency-domain potential flow solvers (e.g., WAMIT, NEMOH, Capytaine, or ANSYS-AQWA). With this level of modeling fidelity, WEC-Sim can handle floating body hydrodynamics, mechanical and electrical power generation methods, advanced control implementation, mooring systems, and other unique applications such as desalination. Additional WEC-Sim functionalities include pre-built Simulink blocks and MATLAB scripts that can simulate a wide range of floating systems and the corresponding auxiliary subsystems. The developers of WEC-Sim continue to release new versions of the software, at least annually, with the latest release in September 2022. These releases include bug fixes, updates to software documentation, as well as new features to expand WEC-Sim’s capabilities to model a wide range of WEC concepts. This publication will highlight the new features added to WEC-Sim between versions 4.1.0 to 5.0.1, which spans a 2-year period from June 2020 to September 2022. New features described here include topics such as continuous integration checks, revised Morison Element and nonlinear hydro implementations, run directly from Simulink (required for hardware-in-the-loop execution), BEMIO updates to import Capytaine BEM hydrodynamics, addition of cable blocks, and new wave visualization features.
Preliminary Investigation Into the Dynamic of Planing Hulls In Regular Waves Using the Smoothed Particle Hydrodynamics Method
Authors: Capasso Salvatore , Tagliafierro Bonaventura , Mancini Simone , De Luca Fabio , Martínez-Estévez Iván , Domínguez José Manuel , Altomare Corrado , Crespo Alejandro J. C. , Pensa Claudio , Viccione Giacomo 
Published: September 2023

Abstract
In this work a numerical investigation on a planing hull in regular waves is carried out by means of the Smoothed Particle Hydrodynamics (SPH) meshfree method. The simulation of the interaction of such vessels with wave trains features several challenging characteristics, from the complex physical interaction, due to large dynamic responses, to the likewise heavy numerical effort. A novel numerical wave flume implemented within the SPH-based DualSPHysics open-source solver fulfills both demands, guaranteeing comparable accuracy with established proprietary CFD code without sharpening the computational load. The numerical wave flume uses ad-hoc open boundary conditions to reproduce the flow characteristics encountered by the hull during its motion, combining current and waves while adjusting their characteristics with respect to the vessel experimental towing speed. It follows a relatively small three-dimensional domain, where the potentiality of the SPH method in modeling free-surface flows interacting with moving structures is unleashed. This novel application of the SPH method shows its feasibility proving an overall good agreement with the experiments; it is established, hence, an interesting alternative procedure to simulate seakeeping test in several marine conditions with reasonable effort and accuracy.
Slamming Effects on FPSO Balconies: Numerical and Experimental Analysis of Alternative Configurations for Impact Attenuation
Authors: e Silva Daniel Fonseca de Carvalho , Menezes Fabio Gouveia Telles de , Schmidt Dilnei , Mello Pedro Cardozo de 
Published: September 2023

Abstract
Wave slamming is a very complex physical phenomena that must be evaluated and analyzed during offshore structures design. Ship type offshore platforms like FPSOs (Floating, Production Storage and Offloading) take slamming effects into consideration by traditional standard recommendations and safety factors. However, FPSO may require additional deck area by using riser and mooring balconies and the slamming effects in such structures are not straightforward to be considered based on traditional approaches. This paper describes the analysis of a balcony structure that was found to be subjected to extreme impact loads and presents the numerical and experimental investigation of alternative configurations that may lead to impact loads attenuation. The alternatives include modifying the balcony flat-platted bottom by using wedge type elements, installation of cylindrical shape fender like structures and perforations on the balcony structure itself. The numerical analysis was carried out by prescribed motion short duration CFD (Computational Fluid Dynamics) calculations and the experiments were executed in USP (University of São Paulo) ocean basin considering the most relevant sea states expected. The balcony modifications were evaluated in several configurations by a single impact CFD simulations, and the most promising ones were tested for sea states realization in the ocean basin. The results, presented as impact force time series and as probability of exceedance curves, demonstrate the most promising balcony shape design alternatives to minimize wave impact loads and its effects on the hull structure.
Evaluation of Granite Deformation Through Non-Compliant Versus Compliant Indirect Tensile Strength Application
Authors: Abugharara Abdelsalam , Butt Stephen 
Published: September 2023

Abstract
Rock deformation evaluation as an essential approach for rock characterization and property determination has been examined via several methods through experimental and simulation studies. Such methods are reported to be conventional techniques applied to define the rock stress-strain relationship that consists of several regions including elastic and plastic regions. The load-displacement relationship also determines the yield and the breakage limits and shows the overall rock deformation behavior. The focus of this research is to evaluate the rock deformation behaviour through the implementation of compliant loading versus non-compliant. In this new approach and unconventional testing technique, the ultimate rock strength through rigid compression and the trend of the load-displacement curve were firstly determined. Secondly, Belleville springs were utilized in various stacks as per their full compression loads to determine the compression levels of 50% and 100% compression ranges of the non-compliant loading application. Results of testing about 150 samples of granite as high strength formation by indirect tensile tests, the compliant loading using Belleville conical disc springs compared with the non-compliant “rigid” loading was observed to influence the load-displacement curve to shift and the ultimate rock main failure to delay in the favor of compliant loading. Results also showed changes in granite fracture mode from pure and clean tensile in the case of non-compliant to a combination of tensile with rupture fractures in the 50% and the 100 compliant application. Such curve shift, rock failure delay, fracture modes, and overall deformation behaviour allow providing valuable data for controlling and predicting rock failure. This could also be used in optimally applying drilling parameters to evaluate rock fragmentation, improve the rate of penetration, and for safely designing civil structures.
Life Extension of Risers and Engineering Criticality Assessment
Authors: Mansour Ghiath (Guy) 
Published: September 2023

Abstract
Extending the service life of existing oil and gas offshore production structures beyond their original design life is on the rise as opposed to investing billions of dollars building new structures. Such structures typically include the floating platforms, topsides, subsurface and subsea equipment, moorings, risers, flowlines, pipelines, and umbilicals. As far as risers are concerned, industry codes and standards and government regulations for the official requirements of life extension are yet to be issued, albeit some are in the works. The general requirements for risers are essentially to be fit for service for the intended period of life extension utilizing the latest available codes, standards, and Metocean criteria at the time life extension is considered. This also includes taking into account the actual conditions of the risers as verified by inspection and the history of the risers as documented through the integrity management program. The fitness for service assessment of Steel catenary risers (SCRs) consists typically of assessment of strength, S-N fatigue from all contributing sources, interference with other risers, umbilicals, or objects, flow assurance, cathodic protection, etc. A less straight forward issue of life extension of is engineering criticality assessment (ECA). This paper discusses the different aspects of life extension of SCRs and perspectives on ECA in particular and provides strictly recommendations absent official requirements for life extension as noted earlier. The experts assessing life extension should evaluate these recommendations and determine whether to follow them.
Stochastic Vortex-Induced Vibration in Free-Stream Turbulence Using a Phenomenological Model
Authors: Badhurshah Rameez , Srinil Narakorn , Chaplin John R. , Thies Philipp , Johanning Lars , Borthwick Alistair G. L. , Venugopal Vengatesan 
Published: September 2023

Abstract
Underwater dynamic power cables connected to offshore floating energy devices are subject to ocean flow turbulence and, through eddy shedding, may experience vortex-induced vibration (VIV). A high level of turbulence intensity may cause fatigue damage to cables during the operation. The present preliminary study investigates the VIV response of a rigid circular cylinder in free-stream turbulence. A phenomenological reduced-order wake oscillator model is coupled with a stochastic differential equation that represents flow turbulence. The model consists of two coupled ordinary differential equations: a structure oscillator forced by the wake vortex shedding and a van der Pol oscillator coupled with the structural acceleration. Wake oscillator models have been extensively used in the past, with several application-specific versions having been developed. The stochastic differential equation accounts for random fluctuations in the fluid flow velocity. Here, we vary the turbulence intensity in the model up to a maximum of 20%. The cylinder response is not significantly affected by very low levels of turbulence, but amplitude modulations and beating phenomena are observed in a strongly turbulent flow. Lock-in, whereby the structure oscillation frequency synchronizes with the vortex shedding frequency, is also explored to study how the resonant frequencies differ in cases with and without the present turbulence. We also investigate the stochastic VIV response subject to the mass ratio variation. The model validation with selected empirical coefficients of the prediction model is also presented. The findings should be of benefit to researchers and design engineers who are concerned with the development of floating energy systems by better characterizing operational load conditions for new installations.
Finite Element Analysis of Composite Mooring Tensioner Springs in Wave Energy Converters
Authors: Cai Yuanzhen , Heitzmann Michael T. 
Published: September 2023

Abstract
Floating structures are widely used in the offshore oil and gas industry, in deep-sea wind farms, and ocean wave energy converters, where fixed-bottom designs are often uneconomical due to the water depth. The traditional way of positioning a floating platform is using a catenary mooring system. The mooring tensioner is a critical component of a mooring system and is responsible for station-keeping during different ocean wave conditions. Statistically, a disproportionate amount of offshore floating structure incidents can be attributed to premature mooring failures [1]. Therefore, a new concept of a taut leg mooring system that utilises a fibre-reinforced polymer (FRP) mooring tensioner will be introduced in this paper. FRP mooring tensioners not only can be used for station-keeping of offshore structures but also can be used for wave energy harvesting. This is due to its advantages compared to metal tensioners, such as corrosion resistance, high specific strain energy, and the ability to tailor the spring constant without changing the overall dimensions. In this paper, the operation envelope of the FRP mooring tensioner in a Wave Energy Converter (WEC) will be investigated through simulation. By doing a simulation, this paper will discuss the estimated amount of energy stored by the mooring tensioners made with different materials at the same torque. The analysis shows that UD S2 glass/epoxy mooring tensioners can store significantly more energy than a metal spring made with spring steel at the same wave conditions, and therefore generators inside the Power Take-Off (PTO) unities can convert more stored mechanical energy into electricity. This FRP mooring tensioner not only can be used in WECs, but also can be used in offshore oil, gas, offshore wind, and aquaculture industries. The generated electricity can power auxiliary equipment, such as feeding barges in the aquaculture industry. In the case of the wind farm industry, the FRP mooring tensioners integrated PTO systems can be the wave energy converter component of wind-wave multi-purpose renewable energy generation systems.
Minimum Operating Pressure to Prevent the Onset of Wrinkling Tendency in MLP During Transient Shutdown Condition
Authors: Rao Venu , Fernandez-Vega Jens 
Published: September 2023

Abstract
The use of mechanically bonded lined pipes (MLP) is a cost-effective option for sour service applications. It has been shown that reel-lay installation of MLPs with 30 bar nominal internal pressure would ensure the wrinkle-free installation of the MLP on the seabed. The internal pressure during the remaining phases of design life such as hydrotest, leak test, and operating conditions is relatively much higher than the internal pressure used in reel lay installation and hence, provides adequate constraint to disallow liner wrinkling for these conditions.
This paper presents the findings of a finite element based analysis study to see whether minimum threshold internal pressure is required during the cycling of transient operational loading of the MLP line to prevent the onset of wrinkling of the liner. It should be noted that the experimental work to back up FE analyses cannot be undertaken due to time and cost constraints related to the simulation of transient operating conditions.
Non-Linear and Survivable Experimental Modelling of a WEC Co-Located With an OWT
Authors: Crawford Jack , Gubesch Eric , Nader Jean-Roch 
Published: September 2023

Abstract
Ocean renewable sources of energy are to play a large role in mitigating the damaging future effects of climate change. Though, in becoming a viable alternative, greater work must be done in driving their capital costs down towards that of non-renewable technologies. An emerging solution is to combine offshore wind and wave energy devices within the same marine space, offering the potential benefits of increased power generation and shielding of structures in lee.
This paper presents the preliminary results of a novel experimental study into the linear and non-linear wave-structure interactions on a fixed WEC co-located with an OWT. The hydrodynamic response of the WEC was investigated for a range of regular wave sets, focusing particularly the effect of increasing wave amplitude on higher order wave-structure interactions. A process of harmonic decomposition was performed to capture higher order force components at multiple integers of the peak wave frequencies. The study revealed that non-linear contributions to the surge force became significant as wave amplitude increased, showing considerable variation at half the peak loading frequency. It followed that these experimental forces were found to be the sum of linear diffraction and total non-linear force components, with the first order component of the surge force fitting the numerical curve well. Second and third order force components were found to agree well with Stokes’ theory of wave amplitude proportionality. Finally, in maximising the hydrodynamic loading, focus wave tests were performed on the isolated WEC and co-located arrangement. With the OWT in lee, the WEC experienced a reduction in maximum surge force of approximately 23.2%.
A Preliminary Investigation of Risk Control Options for Maritime Accidents in Arctic Waters
Authors: Gu Siyuan , Fu Shanshan , Zhang Yue 
Published: September 2023

Abstract
Effective risk control options (RCOs) are the key issue for risk management of maritime accidents, especially for practical risk prevention and control in a rapidly changing environment in ice-covered Arctic waters. This paper conducts the identification of RCOs for maritime accidents in Arctic waters by using a text mining approach. First of all, we recognize the potential risk control measures (RCMs) for maritime accidents by deeply excavating from the global marine accident investigation reports (MAIR) in Arctic waters and the extensive ice-covered waters based on grounded theory. Second, we identify the critical RCMs considering the frequency of the potential RCMs in the existing MAIRs and related references, and the relationship between risk influencing factors (RIFs) from environmental, technical, human and organizational aspects. Third, we further analyze the dependencies among RCMs, RIFs and maritime accidents in Arctic waters. The text mining software NVivo is used to conduct preliminary text mining of the MAIRs. Furthermore, we propose RCOs for the typical maritime accidents (e.g., ship-ice collision, grounding, fire/explosion) in ice-covered waters based on the critical RCMs. The results can be used to make RCOs in Arctic shipping.
Investigating the Free Surface Effect on the Hydrodynamics of an ROV Moving Along a Straight Path at Design Speed
Authors: Guo Ruinan , Zan Yingfei , Huang Fuxiang , Han Duanfeng , Li Baozhong 
Published: September 2023

Abstract
The numerical models of a 1:3 open-frame Remote Operated Vehicle (ROV) model in drag simulations with various immersion ratios are established based on Reynolds-averaged Navier-Stokes equations and the Volume of Fluid method in software Star-CCM+ to investigate the free surface effectors. This paper aims to find a reasonable depth for constraint experiments of ROV, which should eliminate the free surface effect to a certain extent. The numerical drag towing tests with different depths in the design speed are performed. Two installing forms are adopted. One is that the ROV is installed in its upright state which means the strut is along the vertical direction of the body-fixed coordinate system, and the other is that the ROV rolls 90°, and the strut is along the lateral direction. Simulation results of hydrodynamic load in six degrees of freedom are analyzed to find the rules of the free surface effect. The flow structures of velocity in wake regions are studied. The reason why the hydrodynamic characteristics exist would be revealed. The results show that the hydrodynamic load will be affected significantly when the depth is less than half of the height of the ROV. And it should be noticed that there is also a considerable impact on the lateral forces and moments when the ROV is in the upright state.