bluuebunny/crossref_metadata_2025_split huggingface dataset:
An Ecology Friendly, Closed-Cage Fish Farm. Computational Model Validation Against Results From Field Measurements
Authors: Iwanowski Bogdan , Myrholt Jim-Roger , Ovesen Glenn , Hanssen Finn-Christian W. , Brask Annette Kristin , Latif Adil 
Published: August 2024

Abstract
A closed-cage fish farm was built at a rather sheltered location in northern Norway. The closed-cage solution is more ecology friendly than the frequently used net cage fish farms, since the fish breeding water is separated from the outside ocean space, thus preventing entry of the parasitic sea lice. Moreover, the fish food, waste, applied chemicals and medicines are under control and do not contaminate the outside sea water.
The fish farm structure was designed to be sound mechanically under local environmental loads occurring at the installation site. To verify initial estimates of the environmental loads due to current and waves, two sensors that measure vertical current speed profile and directional wave parameters were placed in the fish farm neighborhood.
The structural response was measured as well. Sensors that recorded forces in mooring lines, internal structural forces and motions (accelerations) of the fish farm moving components were placed at critical positions, based on foreknowledge obtained from numerical simulations.
The measurement campaign lasted for one year, thus covering all weather seasons. The acquired large data sets were analyzed statistically, but also an effort was made to find individual extreme environmental load occurrences. It is underlined that the measurements were made in full scale conditions (geometry and environment), and not on the geometrically scaled model as in a laboratory or experimental tank.
A detailed hydro-mechanical model of the fish farm was created. Numerical calculations of the structure’s response were performed with the OrcaFlex software. The detected individual extreme environmental load events were reproduced numerically, and the corresponding structural response was simulated in time domain. Acomparison of the field-measured data with the computational results is presented in the paper, followed by a discussion and conclusions.
Hydrodynamic and Dynamic Analysis of a Multi-Module Semi-Submersible Photovoltaic Platform Considering Tidal Variation
Authors: Tang Yichang , Chen Mingsheng , Jiang Yanlin , Li Tingqiu , Zhang Kai , Zhou Hao 
Published: August 2024

Abstract
Floating Photovoltaic (FPV) systems are considered a novel method to generate electricity. The semi-submersible platform which has been studied mature to exploit renewable energy in the deep sea was built for generating power by photovoltaic systems in recent years. With the development of multi-module designation and various arrangements of mooring systems, the motion response with correcting viscous damping of the semi-submersible platform and the stiffness of the mooring system in the deep sea are significant problems. This paper presents an efficient multi-module coupled hydrodynamic and structural based on the Cummins equation to study the nonlinear multi-body hydrodynamic interference of the semi-submersible platform of FPV systems. Connections between modules are modeled as linear springs with certain stiffness to release all Degrees of Freedom (DoF) of the module. Furthermore, supporting members of modules are modeled as Morison bars. The motion response with hydrodynamic interference of every module is calculated accurately and different design types of mooring systems are studied in this paper, discussing vibration behaviors in low frequency. The diverse layout scenarios are obtained by altering the spacing of the FPV system when deployed adjacent to each other as well as the configurations of the mooring systems. The results suggest that arranging the layout scenario of the mooring system to increase the global stability and the FPV system built as a rectangle with four semi-submersible modules has a lower motion response.
Experimental Study on the Slamming Loads on Inclination Bulwark of a Cylindrical FPSO
Authors: Hu Haifeng , Deng Shi , Cai Yuanlang , Qiao Xiaoguo , Zhang Wenbo 
Published: August 2024

Abstract
Slamming loads on the inclined bulwark of a cylindrical floating production storage and offloading (CFPSO) unit are studied experimentally with respect to sea states and distances from mean sea level. From model test result, the maximum load is obtained at the lower part, and the load decreases with the height increasing. Lasting period of load is short at the lower and upper positions but it is a little longer at the medium position due to wave surface properties. Empirical mode decomposition method is an alternative to remove sensor resonance and dynamic amplification effect in the test result postprocessing in addition to the conventional statistical analysis. Moreover, from pure wave test cases, larger slamming loads are obtained coincidently with the larger vertical motions (heave and roll/pitch). However, in coupled wave-current cases, smaller slamming loads are observed even though the vertical motions are amplified. Findings in the paper provide basic understandings on slamming loads distribution on a CFPSO in extreme sea state and propose an alternative method in the slamming loads design at the same time.
Unlocking the Flow: A Comparison of Off-Bottom Plug Placement Techniques in Well Abandonment
Authors: Shakeri Amin , Ghazal Abdallah , Karimfazli Ida 
Published: August 2024

Abstract
Plug and abandonment (P&A) of oil and gas wells are essential for the protection of the environment and public safety. In Western Canada, a common abandonment technique involves placing cement plugs along the wellbore, utilizing either the balanced-plug or the dump-bailing methods. The balanced-plug technique employs a constant injection flow rate, whereas the dump-bailing method relies on gravity to release cement slurry above a mechanical barrier. Ensuring minimal mixing of cement slurry with wellbore fluids is critical for the integrity of the abandonment process.
In this study we develop three-dimensional hydrodynamic models of the two placement methods to compare the flow dynamics and mixing of the slurry and wellbore fluids. The primary difference between the placement methods is the slurry flow rate during the placement process. Our results reveal that the dump bailing approach leads to more extensive mixing of the slurry and wellbore fluids, especially as the distance between the cement release level and the barrier increases. The balanced plug method typically leads to the accumulation of a cement slurry with water content close to target specifications, contrasting with the dump bailing method, where the water content can vary significantly from the intended design.
Preparation of Transparent Soil and its Application in Model Tests for Offshore Geotechnical Engineering
Authors: Zhang Chunhui , Zheng Xiaoming , Tian Yinghui , Wang Le , Zhang Wenlong , Zhang Bowei 
Published: August 2024

Abstract
The characteristics and mechanism of the interaction between seabed foundations and seabed soil are crucial for comprehending the bearing capacity mechanism of seabed foundations. To observe the movement of foundations in seabed soil and the deformation mechanisms of seabed soil, transparent clay and transparent sand with similar mechanical properties to seabed soft clay and sand were prepared in this paper. A transparent soil-PIV model test system was developed to investigate the interaction between seabed foundations and seabed soil. The test system comprises an actuator, a charge-coupled device camera, a control system and two laser devices. The T-bar penetration test and the plate anchor keying test were conducted in transparent clay and transparent sand, respectively, using the developed model test system. The soil flow mechanism during T-bar penetration and the keying behavior of the plate anchor were observed. Results indicated that during the penetration of T-bar, a trapped cavity is formed above the T-bar. The trapped cavity hinders the soil flow and prevents it from entering the full-flow mechanism. The peak load is reached when the anchor rotates to an angle of 24 ° from the horizontal plane during the keying process. The soil deformation is classified as a shallow failure mechanism, with the affected area extending from the anchor to the sand surface. This study provides a novel approach to investigate the interaction mechanism between seabed foundations and seabed soil.
Mooring Anchor Radius and Spread-Angle Optimization for a 2 MW Semi-Submersible Floating Wind Turbine in Taiwan Strait
Authors: Lai Zhao-Yu , Ivanov Glib , Chen Jui-Chen , Chen DongHui , Ma Kai-Tung 
Published: August 2024

Abstract
Floating Offshore Wind Turbines (FOWTs), especially the semi-submersible type, have gained significant attention due to their potential to produce energy in deeper water. Nevertheless, the design of such floaters in the typhoon-prone and shallow water environmental conditions of the Taiwan Strait poses some challenges, particularly concerning their mooring systems, which are pivotal to the FOWT’s reliability and cost-effectiveness. The study focuses on the method to find the best combination of anchor radii and spreading angles, which directly impact the behavior of mooring lines, using a 2MW semi-submersible FOWT, TaidaFloat Demo. Critical factors such as mooring line tension and platform motion are investigated to ensure the robustness of the design. The study is conducted by applying optimization techniques to minimize mooring line costs while meeting Class Rules required for the specific environmental conditions of the Taiwan Strait. The result shows that the combination of a spreading angle of 10 degrees and an anchor radius of 17.5 times of water depth is the most cost-effective considering material usage in Taiwan Strait condition. This research contributes insights into the method of design and optimization of semi-submersible floating offshore wind turbines under challenging environmental conditions.
Standardizing Second-Order Roll Analyses for FPSOs in Brazilian Deep and Ultra-Deep Waters: Approximations and Damping Evaluation
Authors: C. Oliveira Allan , P. Carvalho Luiz Felipe , G. T. Menezes Fabio 
Published: August 2024

Abstract
Evolution in the design of FPSOs for Brazilian deep and ultra-deep waters has resulted in larger platforms with increased weight and footprint. Consequently, the dynamics of FPSOs, particularly in terms of rolling motions, have been affected, leading to an observed increase in the natural periods of rolling motion in recent years. While the increase in the natural period of roll motion significantly reduces the observed first-order motion, platforms are still subject to second-order excitations, resulting in responses at their resonance periods.
The analysis of second-order motions is more complex and typically requires substantial computational power for accurate assessment. Approximations are often used to evaluate second-order loads and motions, with the level of approximation complexity depending on the natural period being assessed. To meet design schedules, a tradeoff between computational cost and the quality of the approximation may be necessary since second-order motions are input for riser and structural analyses.
Assessment of roll damping in second-order motions is also crucial due to its impact on roll motion levels. The use of roll damping devices remains important in controlling and reducing second-order platform response. This paper discusses different approaches to assess second-order loads and responses, aiming to establish the minimum requirements for a reliable assessment of second-order roll motion.
Experimental and Numerical Investigation of the Inlet Effect on the Dynamics of a Water Intake Pipe
Authors: Hisamatsu Ryoya , Yamaguchi Yusei , Riveros-Jerez Carlos A. , Utsunomiya Tomoaki 
Published: August 2024

Abstract
A water intake pipe/riser is an important component in deep seawater utilization technologies. Regarding the issue of flow-induced vibration, the concern of instability due to the internal flow has received considerable interest. A key question, particularly in the water-aspirating pipes, is the effect of the inlet flow on the dynamics. This study experimentally investigates the internal flow and inlet effects on the dynamics of a hang-off water intake pipe under top-end excitations. The results indicate that the internal flow effect increases inline response. In particular, it suggests the existence of a bifurcation phenomenon, where the amplitude significantly increases under excitation at slightly shorter periods than the natural period. The experiments further compare different inlet shapes: bellmouth, T-shape and L-shape; however, no significant differences in their response characteristics are observed. The second part of this paper provides a discussion based on CFD simulations stressing the contribution of the contracted jet formed inside the pipe and the sink flow in the vicinity outside the inlet to the dynamics of the water intake pipes.
Experimental Investigation on Stress Components of the Sealing Structure of Subsea Connectors Under Axial Preloads
Authors: Zhang Kang , An Weizheng , Wei Pengyu , Yi Qi , Wang Haining 
Published: August 2024

Abstract
The sealing performance of subsea connectors plays a vital role in the safe operation of subsea oil and gas production systems, which is directly determined by compression deformations of the gasket of the subsea connector. Therefore, the changing rules of the sealing structural deformations under various axial loads are key problems when designing subsea connector products. In this paper, experimental measurements are performed in order to investigate the structural stresses of the sealing structure of the subsea connector, i.e. the hub and the gasket. As for the real products of the hub and gasket structures, test solutions are designed. Structural stress components of some representative points are observed when the axial preloads are loaded. Test results show the maximum tensile stress of the outer wall is more than that of the inner wall, which indicates the weak point of the hub is on the outer wall surface nearby the joint region between the hub’s shoulder and the thick-walled cylinder. The maximum tensile stress of the outer wall is less than that of the inner wall, which indicates the weak point of the hub is on the inner wall surface.
Numerical Simulation of Pulsating Slurry Flow in a Jumper for Subsea Mining
Authors: Masanobu Sotaro , Takano Satoru , Yamamoto Marcio 
Published: August 2024

Abstract
For the design and operation of a subsea mining system, it is important to predict pressure loss due to the hydraulic transport of solid particles in the lifting system.
The lifting system has a short flexible jumper to connect the seafloor mining tool to the lifting pump and a vertical riser pipe connecting this pump to the production support vessel. The configuration of the flexible jumper shall have an inclined part so that the mining tool can move freely on the seafloor.
In the actual mining system, the slurry flow in the pipe system is expected to be unsteady. Then, the time-domain simulation is required for safe and reliable ore lifting. In the present paper, we develop the numerical model for the time-domain simulation for pulsating slurry flow in a jumper. The model is validated by comparison with the experimental results we carried out in the previous work using alumina beads, of which densities are almost the same as those of seafloor polymetallic sulphides ore, as solid particles. Next, we investigate the slurry flow in a jumper with steep wave configuration using the model developed. We assume the 100 m long flexible jumper of which outer and inner diameters are 0.254 m and 0.200 m, respectively. Seafloor polymetallic sulphides ore, whose density and diameter are 3,440 kg/m3 and 0.03 m respectively, are assumed as the solid particles. We vary the pulsating conditions of slurry flow and jumper configuration, and discuss the effects of slurry parameters, such as slurry flow pulsation on water velocity, solid velocity, solid concentration and pressure loss in the jumper system. As a result, the total time-averaged pressure loss increases as the top end of jumper is away from the neutral position. The amplitude of pressure loss pulsation is almost uniformly distributed along the jumper although the amplitude of solid concentration pulsation is ununiformly distributed. The slurry parameters should not be estimated using straight pipe simulation results for the neutral or near position of the jumper system.
SPH Simulation of Hydrodynamic Response of a Semi-Submersible Aquaculture Platform
Authors: Liu Jiaming , Wang Kai , Han Ruolang , Huang Shuo , Xiao Yue 
Published: August 2024

Abstract
The drastic dynamic response of a floating aquaculture platform serving in the deep sea would endanger the safety and integrity of the system due to the extreme environments. Therefore, it is essential to simulate and analyze the motion of a semi-submersible deep-sea aquaculture platform in real sea states. This study introduced a new concept of a semi-submersible aquaculture platform named Zhuhaiqin, and the computational domain was built for numerical simulations via the open-source code DualSPHysics. The interaction between the platform and the waves was discretized by the smoothed particle hydrodynamics (SPH) method, while information on the net structures and the mooring system was obtained based on the lumped-mass approach. Moored floating box and flexible net deformation tests were used to demonstrate the reliability and validity of the numerical model used in this work. Subsequently, the dynamic response of the simplified real-scale model based on “Zhuhaiqin “ was analyzed under different wave conditions. The results indicate that wave heights and net structures significantly affect the motion response of the aquaculture platform. In particular, the mooring forces on the fairleads on the waveward side of the platform are more sensitive to wave height than on the other side. In addition, the nets significantly increase the forces on the fairleads. It is recommended to optimize the platform profile and mooring strength concerning the results presented in this work to avoid accidents.
Pipe-Soil Interaction for VIV of Free Spans in Carbonate Silty Sand
Authors: Papavasileiou Vasileios , Bransby Fraser , Hou Zhechen , O’Neill Michael , Watson Phil , Low Han Eng , Peek Ralf , Rathbone Andrew 
Published: August 2024

Abstract
Pipeline free-spans are sections of the pipeline that are not supported by the seabed, and can occur either due to natural processes such as seabed undulations and scour, or exist as engineered sections including pipeline crossings or buckle initiators. Free-spans can leave the pipeline susceptible to inline (horizontal) or cross-flow (vertical) Vortex-Induced-Vibrations (VIV) that could potentially result in fatigue failure. For spans deemed to have a high probability of failure, i.e. critical spans, or for spans evolving over time due to seabed mobility, expensive mitigation can be required. To assess the remaining fatigue life of a free-span, the system response must be quantified, including interactions with the seabed at the span shoulders, which are usually defined in terms of dynamic soil spring stiffness and soil damping values.
The paper presents findings from an experimental study to determine soil stiffness and damping during simulated VIV motions for pipeline ‘elements’ (representing parts of the free-span ‘shoulder’) at varied pipeline vertical pressures and installation modelling scenarios. Testing was performed in a carbonate silty sand sample. The paper focuses on in-line VIV, although selected results for cross-flow VIV are also presented.
The results indicate that the initial embedment, amplitude of the cyclic motion and pipeline self-weight significantly affect the soil response. These findings will improve understanding of Pipe-Soil-Interaction (PSI) for free-span shoulder sections, resulting in increased confidence in the selection of non-linear soil springs and dashpots, and contributing to more informed assessment of free-span behavior.
Fatigue Assessment and Resonance Effects in an Inter Array Cable due to Global Dynamic Deflections in a Bottom Fixed Monopile Wind Turbine Foundation
Authors: Li Henan , Arnholm Carsten , Siddiqui Mohd Atif , Farnes Knut-Aril , Midttveit Steinar , Rolland Louise Ankerstjerne , Nordheim Knut 
Published: August 2024

Abstract
Inter Array Cable (IAC) hanging through the Monopile (MP) are critical components for fixed offshore wind turbines. Here, fatigue analysis for IAC is performed with focus on resonance modes of the IAC. The IAC is modelled using a specialized time-domain solver for offshore marine systems (OrcaFlex) with imposed motion time-series at IAC hang-off location. The IAC responses (tension and curvature time series) are extracted for further computation of component stress time series. The IAC cross-section is further modelled in detail considering friction between components using a tailor-made cross-section analysis tool (Uflex2D) for extracting stresses under various tension and curvature combinations. Finally, cable fatigue is calculated using an in-house tool, Flexstress for Umbilicals (FFU). FFU allows both non-linear stress calculations and processing a relatively large amount of load cases with significant computational efficiency. FFU further calculates fatigue damage based on Rainflow counting using appropriate SN curves. It is found for the current cable configuration that the most critical component with regards to fatigue damage is the copper tape screen with fatigue service life of 31 years considering a safety factor of 10. During fatigue assessment it is also observed that IAC resonance modes can be excited. The resonance effect is further investigated, and mitigation methods are discussed.
Impacts of Small Gaps and Embedment Depths on Forces of a Circular Cylinder Near a Plane Wall
Authors: Liu Zinan , Cheng Liang , Ren Chengjiao , Tong Feifei 
Published: August 2024

Abstract
Numerical simulations of a cylinder placed on or near a plane wall are often required in engineering design of offshore structures to determine hydrodynamic forces, such as a power cable laid directly on the seabed. Generation of computational mesh around such a configuration has been a challenge of conducting simulations, primarily due to the narrow gaps formed between the cylinder and the plane wall. Extremely fine meshes are often required around the narrow gaps to achieve reliable numerical results, leading to additional computational costs. To alleviate this problem, this study examines the hydrodynamic features of two alternative geometric configurations, namely (1) a near-wall cylinder with sealed gap and (2) a cylinder shallowly embedded in the plane wall, whose meshing and simulation are less challenging than that would otherwise be needed for a cylinder placed on the wall. A series of three-dimensional numerical simulations for a constant Reynolds number 3900 and a range of narrow gap distances / embedment depths from 0.001 to 0.1 cylinder diameters are conducted. The possibility of employing the three configurations to determine the hydrodynamic forces on a cylinder placed on a wall is examined in this study.