bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nonlinear Dynamic Feature of the Fluid Resonance in a Recessing-Type Moonpool
Authors: Song Zhiwei , Tang Guoqiang , Lu Lin 
Published: September 2023

Abstract
Two-dimensional fully nonlinear potential flow numerical analyses on the fluid resonance within moonpool are systemically performed in the time domain with the varied incident wave amplitudes and a wide range of the incident wave frequency covering the natural frequency of the piston mode. The super-harmonic resonances are found around half and one-third of the first sloshing mode natural frequency in the recessing-type moonpool, where the higher-order harmonics rather than first-order harmonic dominate the responses, and the frequencies of higher-order harmonics are almost identical to the first sloshing mode natural frequency. Such a nonlinear phenomenon, however, disappears in the response of fluid oscillation within a traditional clean moonpool. The harmonic analysis illustrates that the introduction of recess leads to the energy transferring to the sloshing mode, thus exciting the sloshing motions. The joint works of the asymmetry due to recess and the free-surface nonlinearity results in the super-harmonic resonances inside the recessing-type moonpool. The evolutions of fluid oscillations in the recessing-type moonpool, being a complex nonlinear dynamic process, are further examined through the phase dynamics by performing Hilbert Transformation on the time series. Phase trapping and phase slipping states are confirmed in the responses of fluid in the recessing-type moonpool, which reflects the nonlinear evolutions of response developing from partial synchronization to de-synchronization.
Floating Nuclear Power Plants, a Safe Way Out of the Energy and Climate Conundrum
Authors: Lim Soon Heng 
Published: September 2023

Abstract
Climate scientists are alarmed at the rate global temperatures are rising and its knock-on effect on biodiversity. Some believe we are in the midst of the sixth mass extinction. Even as the evidence is apparent, the extraction of coal, oil and gas continues unabated to feed an insatiable demand for energy.
Global initiatives such as COP 27 and COP15 have not made as much headway as needed. Carbon sequestration is too costly. Solar and wind energy are not the silver bullet they have been made up to be.
The deployment of solar panels and wind turbines on land and over oceans desecrates the world’s biodiversity. Its impact is no less than that of wild forest fires and droughts.
The best tool to date to produce energy is by nuclear fission. It has zero emission, virtually zero impact on climate change and biodiversity owing to its high capacity factor and energy density and hence small spatial footprint. The spent fuel is also dense and hence easy to manage compared to CO2 and carbon particulates.
Floating nuclear power plants overcome many of the challenges that land based nuclear power plants face including construction and geotechnical issues and the loss of water replenishment source.
The proposal here is to build a lagoon to surround the floating plant. This would enhance security and provide other benefits including storing spent fuel and provide a benign environment for operation and maintenance. Within the lagoon, desalination and green hydrogen production may also be carried out.
Propagation of Hydrodynamic Wave Past Two Vertically Submerged Flexible Barriers of Non-Uniform Thickness
Authors: Singh Mansi , Gayen R. 
Published: September 2023

Abstract
In the literature related to linear water waves, most of the works have considered thin structures to have constant or uniform thickness. This assumption is based on the fact that the thickness variations in structures that are thin have no significant impact on the hydrodynamic quantities. But in the present work, we have shown that it is not so; even for thin structures, thickness variations can cause major changes in the physical quantities like plate deflection and the hydrodynamic force experienced by the structure. Also, in general, for an intensive study of the fluid-structure interaction problems, it is necessary to include the structural variations in the models for a better understanding of the phenomena. The transition from one barrier to a pair of barriers might be interesting because they enclose a water column which leads to near-resonant motion. This feature might be helpful to engineers for the purpose of construction of breakwaters. Thus in the present paper, we assess the hydrodynamic response of a pair of completely submerged vertical flexible barriers of non-uniform thickness to incoming surface gravity waves using hypersingular integral equations. The fluid domain is considered to be of infinite depth, and further, both the barriers are assumed to have clamped-free ends. By considering Kirchhoff’s thin plate theory, the described problem is reduced into a boundary value problem, which is solved by converting it into a system of coupled Fredholm integral equations using the classical method of integration and Green’s integral theorem. Further, the obtained integral equations system is converted to a matrix system of linear equations using appropriate approximations for the unknown quantities to obtain numerical solutions. With the help of MATLAB software the matrix system is solved, whose solutions are then used to determine numerical estimates of various physical quantities. The method used and the numerical results are validated by comparing them in the limiting cases of dual flexible barriers of constant thickness which are already available in the literature. Some selective graphical results are depicted in order to show the effect of the non-uniform thickness of the two flexible barriers on their hydrodynamic response by choosing certain thickness profiles.
A Study on Tsunami Disaster Prevention Measures by Floating Tsunami Mooring Bitts for a Vessel Moored at a Wharf
Authors: Tsutsui Chiaki , Minami Kiyokazu , Masuda Mitsuhiro 
Published: September 2023

Abstract
The tsunami triggered by the 2011 Great East Japan Earthquake caused severe maritime accidents to moored vessels in Japanese ports. Some researchers have proposed the floating tsunami protection wharf (FTPW) as a new tsunami protection measure for moored vessels in wharves. FTPW is a useful tool that can prevent breaking of mooring lines and grounding at a wharf by the leading waves of a tsunami. However, it may be difficult to place the FTPW in existing ports because it occupies a large area of the port, depending on the size of moored vessels. Additionally, some concerns exist about negative effects on cargo works because cargo handling equipment is placed on the floating body of the FTPW, which can sway. In this study, we proposed the use of floating tsunami mooring bitts (FTMB) to address these FTPW problems. FTMB are pillared floating mooring bitts placed inside the digging of a wharf so that they occupy less port area compared with the FTPW and minimize negative effects on cargo works. The FTMB float when the water level increases as a result of a tsunami, preventing the vessel from grounding at the wharf and breaking of the mooring lines. In this study, we performed tsunami simulations to verify the floating and disaster prevention performance of the FTMB using the 3-dimensional moving particle simulation (MPS) method. Our study demonstrates the tsunami disaster prevention and mitigation performances of the FTMB. The pillar and slit types FTMB, which are smaller than the existing FTPW, were able to prevent the breaking of mooring lines and grounding at the wharf by the tsunami. Furthermore, the FTMB showed the effect of delay of the tsunami inflow time to the land area. In the future, the FTMB will be one of the effective tsunami disaster prevention measures to reduce tsunami damage to vessels moored at the wharf.
Two-Sided Wave Generation in a High-Order Spectral Numerical Wave Tank
Authors: Aertsens Tim , Ducrozet Guillaume , Toffoli Alessandro , Monbaliu Jaak 
Published: September 2023

Abstract
The Coastal & Ocean Basin (COB) is a brand-new wave-current basin in Ostend (Belgium). The basin is 30m long and 30m wide, and it is equipped with modular wavemakers on two adjacent sides. This allows generation of multi-modal seas (including the so-called crossing-sea states). A system of multiple pumps will also be installed to allow generation of currents propagating at an arbitrary angle relative to the dominant wave field. To optimally utilize this new facility, an efficient numerical equivalent of the COB has been coded based on the High-Order Spectral Method (HOSM). The first step is the addition of a secondary wavemaker to the open-source High-Order Spectral Numerical Wave Tank (HOS-NWT). This was done by calculating an additional potential for each of the wavemakers in two separate additional domains and then using them as forcing terms on the two sides of the basin where the physical wavemakers are present. The implementation was done in a generic way and is made open-source. The effectiveness of the implemented method is demonstrated by comparing three base cases: only the x-wavemaker, only the y-wavemakers and both wavemakers together. However, there still remain challenges when it comes to wave generation in the y-direction and accurately modelling the corner between the two wavemakers.
Developing an Optimal Shape for Dynamically Installed Anchor
Authors: Bae Junsik , Kim Youngho , Hossain Muhammad Shazzad 
Published: September 2023

Abstract
Dynamically installed anchors (DIAs) have been identified as the most cost-effective anchoring solutions for mooring floating facilities because of its simple (free-fall) installation procedure. Due to the impressive concept of DIAs, many attractive shapes of the anchor have been proposed. However, the influence of the various geometric parameters on the performance of the anchor during installation and under operational loadings is yet to be explored. This paper assesses the potential of changing each component of the geometry and through that optimising the shape aiming at reducing fabrication cost and increasing efficiency in terms of tip embedment depth during installation and diving behavior under operational loadings. Large-deformation finite element analyses were performed using the Coupled Eulerian-Lagrangian (CEL) approach with the simple elastic-perfectly plastic Tresca soil model modified incorporating strain softening and strain-rate dependency of the shear strength. Parametric analyses were conducted varying the configurations of the shaft, fins and padeye. The anchor drag coefficient during free-fall in the water column was also assessed through computational fluid dynamics (CFD) analyses. Thus far, it has been found that an anchor with (i) a 1:2 sloped cylindrical shaft, (ii) padeye offset ratio within 0.2 &lt; ηp &lt; 1, and (iii) enhanced middle main two fins show better performance in terms of tip embedment depth and diving upon loading. A critical factor to dive is the alignment of the loading direction at the padeye with the anchor resistance centroid.
Jellyfish Deflection From Marine Fish Pens Using Bubbler Technology
Authors: Thodi Premkumar , Talimi Vandad , Liu Lei , Thijssen Jan , Gauthier David , Paris Mario 
Published: September 2023

Abstract
Increased jellyfish blooms have been identified as a major cause of caged fish damage in marine aquaculture facilities as well as clogging of seawater intake systems of nuclear power plant cooling stations and desalination plants. Bubbler technology has shown great promise for protecting marine facilities from jellyfish impacts. This paper focuses on the design of apparatus, planning and execution of large scale tests using simulated silicone jellyfish in a controlled environment. The following parameters were varied during testing: water current (0.1–0.6 m/s), bubble curtain angle (5°, 30° and 45°), air flow rate (0.1, 0.3 and 0.6 cfm/ft), number of curtains (1, 2 and 3), jellyfish size (5 and 18 cm diameter), curtain spacing (15, 50, 100 and 400 cm) and jellyfish release methods (surface and subsurface). From the test results, it was concluded that effective deflection of jellyfish in marine environment with currents upto 0.6 m/s was achievable. Also, the curtain angle, number of curtains, larger spacing between curtains and air flow rate through bubbler were observed to have a positive impact on the deflection efficiency for high current speeds. A CFD model developed was used to estimate the deflection efficiency, which provided a good agreement with test results.
Decommissioning of Umbilicals and Flexible Pipes - A Sensitivity Analysis in Decision-Making Process
Authors: Nogueira Soares Luisa , Lourenço Marcelo Igor , Paranhos Pasqualino Ilson , Ribeiro Nicolosi Eduardo , Violante Ferreira Claudio 
Published: September 2023

Abstract
The decommissioning of subsea equipment is a reality in Brazil and worldwide, highlighting the need for the development of decision-making methodologies for application in decommissioning projects. In Brazil, the volume of umbilicals and flexible pipes to be decommissioned in the future is huge and an analysis of the best decommissioning alternative would be desirable. Based on a decision-making methodology developed by a COPPE/UFRJ research group, this work aims to present the technical criterion for decommissioning decision-making process and a sensitivity analysis regarding the approach developed for this criterion. Among five different criteria, the proposed technical approach is composed of two sub-criteria — Complexity of Operations and Technological Risk — allowing us to assess the complexity of execution and operational activities of decommissioning alternatives and the technological risk associated with them. The decommissioning alternatives were divided into two groups — leave in situ and removal — and a total of six alternatives were considered in this study. The analyses developed to show the influence of different parameters in the methodology results emphasizes the robustness of the proposed methodology. Also, this work presents a preliminary indication for various decommissioning scenarios, varying combinations of water depth, structural integrity, cleaning status, and other factors. The results obtained in this work contribute to the consolidation of a robust methodology for the application and foundation of decision-making in decommissioning projects for flexible and umbilical lines.
An Irregular Wave Approach to Fatigue Life Capacity for Flexible Risers With Severed or Corroded Tensile Armors
Authors: Doynov Krassimir , Cooke Nathan , Pasala Dharma , Majed Arya 
Published: September 2023

Abstract
A novel simulation-based approach for assessing the remaining fatigue life of flexible risers with damaged or broken tensile armors has been developed that can be used to challenge the need for premature replacement, and to modify risers’ Integrity Management to ensure safe operation. A series of potential corrosion or damage scenarios, such as generalized loss of thickness or number of broken wires, are evaluated using high-fidelity finite element models and computationally efficient irregular wave simulations. Results from the various damage scenarios are used to construct curves showing the timeline of the remaining fatigue life of the flexible riser as a function of the number of broken wires. These timeline curves can then be used to modify riser Integrity Management via scheduling periodic NDT inspections to check the evolution of broken wires and provide advanced warning for approaching end-of-life conditions to operation engineers.
This novel approach is demonstrated through a case study involving a 7” ID flexible riser with a known history of annulus breach and subsequent repairs near the splash zone, with the potential for tensile armor corrosion to have occurred. Several hypothetical damage configurations involving combinations of severed (broken) tensile armors are evaluated under 100-year design loading to identify the minimum number of wires lost which increases the stress utilization of both the pressure and tensile armors up to a limit that can be considered a pre-cursor of upcoming rupture or loss of containment. The results from these analyses are used to construct a timeline of the remaining fatigue life of the flexible riser as a function of the number of broken wires.
This comprehensive demonstration of accurate capture of flexible pipe damaged wire kinematics by high fidelity finite element models and nonlinear simulations has direct applications to flexible pipe integrity management and remnant life assessments. Given that the nonlinear NDS framework allows highly efficient accelerated computation, it is now feasible to execute real-time irregular wave local fatigue simulations with finite element models that include damaged wire data from physical inspections to more accurately predict remnant life.
Application of the Yield Stress Concept in Drilling Fluid Engineering
Authors: Saasen Arild , Ytrehus Jan David , Lund Bjørnar 
Published: September 2023

Abstract
The yield stress appears as a quantity that is frequently used to describe drilling fluid rheological properties. For the driller it is important to use a simple model to predict the pressure losses in the total fluid circulation system. A very simple model, to which good prediction models exists, is the Bingham model using the yield point (YP) and plastic viscosity (PV) as determined following API procedures. This is acceptable for the driller when looking for the drill pipe and bottom hole assembly conditions as most of the pressure losses are to be found in these components and the bit nozzles where the shear rate is high.
In the flow phenomena occurring in the annulus is different. The concept of YP and PV cannot generally be used to describe the necessary properties of the fluid. A low shear yield point (LSYP) is frequently used by drilling engineers to describe the yield stress of a Herschel-Bulkley fluid. When the LSYP is used it is possible to select measurement data from relevant shear rate regions to be able to produce estimates of frictional pressure losses and to determine the fluids equivalent circulating density (ECD) during circulation.
In oscillatory tests yield stresses are determined as the stress where the linear viscoelastic strain region ends. Also, a flow point is measured, being the stress at the amplitude where the viscoelastic loss modulus becomes equal to the elastic storage modulus. These two viscoelastic yield stress properties relate to interactions in particle suspensions, emulsions and polymer solutions. Thus, these properties are of importance when dealing with shelf life of fluid properties.
In the article the different application of the yield stress concept is outlined. It is shown that these values have a real significance for any flow phenomenon when used correctly. It is also shown that there is no reason for these different yield stress estimates to be equal. Still, none of these estimates are incorrect or correct, but reflects the physical conditions the yield stress is meant to describe.
Experimental Observation on Chaotic Vortex-Induced Vibration of Circular Cylinder in Turbulent Flow
Authors: Aye Yan Naung , Srinil Narakorn 
Published: September 2023

Abstract
The subject of vortex-induced vibration (VIV) in a steady flow has been extensively studied throughout the past decades. There is limited experimental research presenting the influence of incoming turbulent flow on the VIV of circular cylinders which may be useful in studying real-life structural responses in ocean currents. In this study, we experimentally investigate the effect of the incoming turbulence on VIV through a pivoted rigid circular cylinder with an elastically mounted pendulum and universal joint setup in a water flume at Newcastle University, where repeatable turbulent flow can be generated. The measured flow turbulence intensity is about 13–15%. This experimental system allows the vertical cylinder’s free movement in two degrees of freedom with the horizontal springs attached to the in-line (X) and cross-flow (Y) directions, with an aspect ratio (submerged length over diameter) of 22.67, a mass ratio of 4.38, a damping ratio of 0.06 and a maximum reduced velocity of 20 associated with the Reynolds number of about 11,100. The cylinder X-Y motions and the influence of cylinder inclination during VIV are captured using the Qualisys motion capture, and the load cells are equipped to monitor the spring dynamic forces. The effects of flow turbulence are observed through the measured response time histories exhibiting chaotic features with high modulations, especially in the in-line responses and at higher flow velocities. Although a typical transition of response amplitudes from an initial branch to an upper and then lower branch with a jump and hysteresis phenomenon as well as a 2:1 dual resonance is found when varying the flow velocities, chaotic responses with irregular X-Y trajectories and highly fluctuating frequencies associated with the lower branch are remarked. Wavelet signals are used to quantify the time-varying and dominant oscillation frequencies. Understanding of such chaotic VIV features in free-stream turbulent flow may be useful in estimating structural fatigue or in enhancing the renewable energy harvesting from natural flow-induced vibration phenomena.
FSI Simulations and Analyses of a Non-Resonant Buoyant Wave Energy Converter
Authors: Shao Xinyuan , Yao Hua-Dong , Ringsberg Jonas W. , Skjöldhammer Jan , Lin Jianfeng 
Published: September 2023

Abstract
Deploying wave energy converters (WECs) in wave parks into the ocean requires detailed planning and numerical analyses to maximize the wave energy capture and keep the LCoE at the lowest possible level. High-fidelity simulation models can accurately simulate the fluid-structure interaction (FSI) between the WECs and the ocean’s waves. However, the computation cost is too high for simulations and analyses of large-scale WEC parks. This study presents fully coupled hydrodynamic-structure response simulations and analyses using the high-fidelity CFD software STAR-CCM+, which is compared with the DNV software package SESAM that adopts potential flow theory to model environmental loads. A novel non-resonant heave-point buoyant WEC called NoviOcean is investigated. The first case study, where only one WEC was modelled, showed that both simulation approaches/software gave comparable WEC motion results for moderate sea state conditions, but the SESAM software required significantly less computation cost. Hence, the SESAM model was used in systematic simulations of two WECs to investigate the effect of FSI on the energy capture by both WECs by varying the distance between the WECs and the wave direction. The results show which WEC distances and wave directions should be preferred to maximize the wave energy capture.