bluuebunny/crossref_metadata_2025_split huggingface dataset:
Prediction of Scour Around Subsea Shallow Foundations Under Time-Varying Currents
Authors: Qu Lili , Draper Scott , An Hongwei , Watson Phil , Cheng Liang , Harris John M. , Whitehouse Richard J. S. 
Published: August 2024

Abstract
This paper describes the development of a framework to predict scour and undermining around squat, shallowly embedded structures under time-varying currents. Squat structures, with height equal to or smaller than their horizontal dimensions, are frequently employed offshore for a range of purposes, including pipeline and cable infrastructure, offshore substations, and innovative applications like offshore data centers and artificial reefs. These structures typically feature a rectangular base with a seabed-embedded skirt to increase the geotechnical capacity of the foundation and guard against the risk of local scour compromising the foundation. To investigate scour development at these structures, and to develop a framework to predict scour and undermining, experiments have been conducted using a generic squat structure with a shallow skirt foundation placed on a sandy bed within uniform grain size. Initially four experiments with different unidirectional currents were performed. For each of these experiments scour was initiated by the flow at the corners of the structure and scour holes developed, eventually leading to the undermining of the structure. The flow conditions were run until an equilibrium profile was observed, and the equilibrium scour depth, the equilibrium extent of undermining, and the associated timescales of these processes were obtained. These values were then used in a STEP model (Scour Time Evolution Predictor) scheme to predict how scour would evolve in time-varying currents. Comparisons of the STEP model with an additional experiment simulating a time-varying unidirectional current show that the time-history of scour depth, extent and the undermining area can be predicted reasonably well, indicating that the STEP model can be applied to scour assessment in time-varying currents.
Integrity of Drilling Fluid As Primary Barrier for CCS Wells
Authors: N'Gouamba Elie , Feneuil Blandine , Skogestad Jan Ole , Linga Harald , Skår Gjertrud , Roggeband Serge M. , Nedrum Jack , Ødegård Sven Inge 
Published: August 2024

Abstract
The primary barrier in the well during drilling is the drilling fluid, both in terms of hydrostatic pressure from the fluid column, its frictional pressure drop resistance and the influence from the drilling fluid for mitigating reservoir fluid influx. Accordingly, it is of crucial importance that threats to this barrier are understood. When drilling infill wells for carbon capture and storage (CCS), a potential threat to this barrier is the risk of influx of already stored CO2 from the formation. This is a situation that must be understood as the geological storage of CO2 is scaled up in order to contribute to achieving climate goals.
While there is substantial experience and knowledge in the industry on interactions between natural gas and drilling fluids, far less is known about the effects of CO2 of the drilling fluids and how this affects the barrier properties of the fluid. In order to increase the understanding of the risk of primary barrier collapse, laboratory studies of drilling fluids exposed to CO2 are performed. Challenges to the primary barrier integrity and possible mitigations are discussed in light of the results.
Technology Development for Offshore Emission Reductions in Order to Reach Emission Reduction Targets
Authors: Skorpa Ragnhild , Ytrehus Jan David , Gardarsdottir Stefania 
Published: August 2024

Abstract
Norway has committed to ambitious greenhouse gas reduction targets over the coming decades. Reducing emissions linked to oil and gas exploitation on the Norwegian continental shelf (NCS) is crucial to reaching those goals. Oil and gas exploitation accounts for 27 percent of Norwegian greenhouse gas emissions and are the second largest source of such emissions in the country, after the transportation sector. In particular, Norway has set targets for 55% emission reductions on the Norwegian Continental Shelf by 2030 and to move towards zero emission activities on the Norwegian Continental Shelf by 2050.
In this paper we present and discusses how a solution-portfolio approach is required to reach emission reduction targets on the Norwegian Continental Shelf.
Assessment of Nonlinear Loads and Motions Through Response Conditioned Design Waves: Practical Application and Limits
Authors: Bouscasse Benjamin , Dermatis Athanasios , Kim Shinwoong , Ducrozet Guillaume , de Hauteclocque Guillaume , Lasbleis Marine 
Published: August 2024

Abstract
Assessment of the extreme responses that offshore structures will experience within their life-cycle, involves numerous long-duration calculations for various weather and service conditions. The response distribution of any quantity driven by wave-structure interaction can be obtained efficiently with linear theory. However, the accuracy of that method is known to quickly deteriorate in severe sea states and for highly nonlinear quantities. In those cases, simulations with a high-fidelity solver or experiments are necessary which, although accurate, imply a significant cost (computational or experimental time) and in several cases become unfeasible. For this reason, the concept of response-conditioned waves (RCW) has been developed, as a way of investigating solely wave patterns of short duration, which can be considered tantamount to brute-force simulations. This approach consists of computing short-time wave episodes, that induce a given target response of the studied quantity. At a later stage, these waves can be generated and propagated in a computational domain, so that the fully nonlinear responses are obtained, by using only brief high-fidelity numerical simulations. The present paper demonstrates the relevance of such an approach, designed as a two-step method. First, the RCW is computed with a low-fidelity surrogate model, based on a nonlinear High Order Spectral (HOS) potential flow solver for wave modeling and a linear wave-structure interaction model. The method has been validated for two distinct response cases, namely the prediction of the vertical bending moment (VBM) of a zero-speed containership and the nacelle acceleration of a floating wind turbine. An overview of those applications is provided and the principal strengths, as well as the potential limitations of the method, are identified and discussed.
Non-Metallic Clamp for Flexible Risers
Authors: Doynov Krassimir , Iwicki Rachel , Henneke Brandon 
Published: August 2024

Abstract
A novel non-metallic clamp for flexible risers with breached outer sheath in the splash zone has been developed, qualified, and installed to restore annulus integrity and enable riser lifetime extension.
Flexible riser outer sheath breaches in the splash zone or aerial riser portion have been experienced by operators and reported to occur by Sureflex JIP, due to natural degradation (i.e., UV aging and fatigue), dropped objects, or blocked vent ports of riser end fittings terminated topside. An outer sheath breach in the splash zone or aerial riser portion exposes the structural carbon steel wires to rapid corrosion due to oxygen inflow at the breach location, and because existing cathodic protections are not effective above the mean seawater level. Rapid corrosion in turn decreases both riser strength resistance to pressure and tensile loads, and riser corrosion fatigue resistance, which over relatively short period of time may lead to loss of riser containment. Clamping of the breached outer sheath location has been historically used to mitigate that risk of loss of containment with the use of steel clamps of various design.
Three steel clamps were installed over a longitudinal-seam-weld-outer-sheath repair performed at riser installation over the course of a few years, with a new leakage discovered after each clamp installation. This experience has led to the realization the outer-sheath stiffness transition in the vicinity of the steel clamp edge and clamp tightening have driven initiation of new breaches nearby due to the degraded outer-sheath-seam-weld repair. This realization in turn inspired the development of a novel, cost effective non-metallic clamp that eliminates the sharp stiffness transition caused by metallic clamps.
This paper describes the development, qualification and installation of a novel non-metallic clamp to enable the lifetime extension of a flexible riser described in OMAE 2023-101167 [1]. The paper presents the transition from technology readiness level TRL-0 (basic research) to TRL-6 (system installation). It presents the logic of material and component functionality selection, failure mode identification, prototyping, validation testing, system integration, installation, and lessons learned. It concludes with recommendation on scalability of the non-metallic clamp use and further development on adding venting functionality.
Data-Driven Generation of Tailored Wave Sequences
Authors: Klein Marco , Wedler Mathies , Pick Marc-André , Seifried Robert , Ehlers Svenja , Stender Merten , Hoffmann Norbert 
Published: August 2024

Abstract
This paper explores the applicability of machine learning techniques for the generation of tailored wave sequences. For this purpose, a fully convolutional neural network was implemented for relating the target wave sequence at the target location in time domain to the respective control signal of the wave board. The database was generated by means of extensive wave tank tests. The experimental campaign focused on the generation of very steep wave groups including wave breaking which cannot be covered by the simplified wave generation methods. The extensive experimental campaign was performed in a small wave tank with an fully automated approach including determination and control of the wave maker motion as well as data measurement. The training data set features wave groups of short duration based on JONSWAP spectra, where the parameters wave steepness, peak wave period and enhancement factor were systematically varied. At the end of the training process, the trained models are able to predict the wave maker control signal based on time series of the target wave defined for a specific target location in the wave tank. The accuracy of the trained models are evaluated by means of unseen validation data. In addition, the predictive accuracy of the trained models is compared with the classical linear transformation approach.
Simulation Analysis of Critical Loads of Cylindrical Pressure Hulls With Initial Defects
Authors: Yuan Siming , Han Enquan , Han Husha 
Published: August 2024

Abstract
Pressure hull is an important part of underwater unmanned vehicle, which is the main provider of buoyancy force and withstands immense seawater pressure. Initial geometric defects will lead to the reduction of the ultimate strength of the structure, and the first-order mode is often used as the initial geometric defects in finite element analysis to study the ultimate strength of the structure. In this paper, based on ABAQUS finite element simulation software, an internal corrugated pressure hull model is established, and first, linear eigenvalue buckling analysis is performed on the internal corrugated pressure hull to obtain the first 30 order linear buckling modes of the pressure hull. Then, each order of buckling modes and the superposition of multi-order modes are respectively taken as the initial defects, and the nonlinear buckling analysis of the inner corrugated pressure hull is performed to obtain the critical buckling load. The results show that: for single-mode defects, the most unfavorable geometric defects are generally low-order modes. When considering the defects of the superposition of multi-order modes, with the increase of combined orders, the critical buckling load shows a decreasing tendency, and the decreasing amplitude changes from large to small and then large again. When the combination of orders from 1-8 to 1-24, the critical buckling load shows a slowly decreasing tendency, that the variation is within 3.28%.
Seabed Response Around a Partially Buried Pipeline Subjected to the Combined Ocean Waves and Currents Loads in a Trench Layer
Authors: Sun Ke , Gao Yuan , Zhang Jisheng 
Published: August 2024

Abstract
The widespread co-existence of the wave and ocean currents is a common phenomenon in coastal environment, nevertheless, the relevant work for seabed response was primarily restricted to either wave-alone or waves and a following/opposing co-directional current conditions. Unlike the previous studies, the oblique currents, ranging from perpendicular incidence to parallel incidence, are considered in the present study for fluid-pipeline-seabed interactions, which might be claimed that a two-dimension simulation was no longer applicable. An integrated model is proposed to examine the soil behavior from a three dimension prospective, in which the RANS equation is applied to govern the fluid domain, while the Biot’s poro-elastic theory is employed for the solid domain description. Results show that a fully/partially-backfilled pipeline in a trench layer has a remarkable resistance to the seabed momentary liquefaction in comparison with one positioned on the seabed surface. Under the presence of the counter-current waves, the transient pore pressure would be strengthened, whereas the co-current waves would weaken the pore pressure oscillation. The momentary liquefaction depth surrounding the undersea pipeline increases with the declination in the obliquity between the waves and current. Moreover, as the backfill thickness reduce and trench gradient decline, the instantaneous instability of the subsea pipeline and its underlying seabed would be compromised.
Experimental Assessment of Drilling Fluid and Wall Slippage for Wellbore Displacement
Authors: Johnson John , Wojtanowicz Andrew K. 
Published: August 2024

Abstract
In the ideal plug-flow mode Bingham-type drilling fluids display strong frontal displacement potential at a very low flowrate. The rate may be significantly increased with the fluid’s wall slippage so that maximum size of the fluid’s plug is maintained. Based on this concept the study qualifies the wall slippage effect as a rheological property to be used in fluid’s selection and evaluation for the purpose of wellbore displacement. The effect is analyzed using a conceptual model of fluid motion between two parallel plates to define the relationship between velocity of undisturbed fluid plug (slip velocity) and shearing rate for the maximum slippage effect. Applying the analysis to coaxial geometry gives practical formulas and a simplified procedure for fluid testing using either modified or conventional rotational viscometer. Also defined are new parameters of the fluid’s displacement performance: Maximum Slip Velocity and Plug Displacement Index. The study evaluates a variety of water-base drilling fluids such as high-molecular-weight polymer solutions, dispersed clay suspensions and suspensions flocculated with different electrolytes. The results show that the best-performing displacement fluid is a prehydrated bentonite suspension flocculated with sodium chloride.
Model Test of a Semi-Submersible Floating Wind Turbine: Hydrodynamic Motions and Internal Loads
Authors: Jiang Yucong , Zheng Xiang Yuan , Wang Shuaishuai , Zhao Mengyang , Zhang Sheng , Moan Torgeir , Gao Zhen , Li Wei 
Published: August 2024

Abstract
A semi-submersible floating wind turbine (FWT) similar to OO-STAR in geometry has been developed by the authors from the Department of Marine Technology of Norwegian University of Science and Technology (NTNU). This study is dedicated to experimentally fathoming its dynamic performance of motions and internal loads under wind and wave loads. Model tests are conducted in the ocean basin at Tsinghua Shenzhen International Graduate School. First, a physical model with a scale ratio of 1/28 is designed and fabricated, comprising an aluminum floating model, steel ballast, a small wind turbine, and a spread mooring system. A 6-axis force sensor is purposely placed at the root of central column for measuring the cross-sectional loads between the column and the floating foundation. Second, a series of model tests, including free-decay tests, wind-only tests, wave-only tests, and wind-wave tests, are carried out to investigate the primary dynamic performance of the floating system. The test results not only demonstrate the effectiveness and reliability of such an experimental method of measuring the internal loads, but also reveal important dynamic characteristics of this floating wind turbine. Under wave loads, the foundation exhibits low-frequency motion responses in pitch, heave, and surge, primarily concentrated at the corresponding natural frequencies. Moreover, there are both low-frequency and high-frequency responses induced by the natural vibrations of the tower in the cross-sectional loads, including the shear force, the axial fore and the bending moment. However, the contribution of the high-frequency component is relatively small. When wind loads are applied in combination of random wave loads, high-frequency responses induced by the natural vibrations of the tower could be observed in pitch, heave, and surge motion responses. Besides, the contribution of the high-frequency component in the section-crossing load becomes much more significant. Non-Gaussian effects are not significant for the shear force, the axial force and the bending moment in the tests.
Prevention of Flow-Induced Pulsations in Unbonded Flexible Pipes Using a Carcass Insert Technology
Authors: González Díez Néstor , Belfroid Stefan P. C. 
Published: August 2024

Abstract
Flow-induced pulsations (FLIP) originated from flexible pipes, when used in deepwater applications, can cause large vibrations and dynamic stress levels in the attached topside or subsea pipe systems. The pulsations are characterized by high frequencies that can cause fatigue failures within a short time, leading to loss of containment.
To prevent the appearance of FLIP, a new technology has been developed that involves manufacturing a T-shaped insert to cover the inner spiral cavity of the carcass, making the pipe bore relatively smooth. Smoothing the pipe bore with this insert delays and prevents the onset of flow-induced pulsations during dry gas transportation by minimizing the strength of pressure pulsations caused by local vortex flow and created in the spiral cavity. The use of this insert allows higher gas flow rates to be achieved in flexible pipes without introducing FLIP, thereby eliminating all FLIP-related structural integrity issues of the systems attached to the flexible. The smoothing of the pipe bore also reduces friction and improves flow assurance of pipe, reducing the pressure drop.
This paper describes the merits of new insert technology using the FLIP prevention mechanism including the theoretical work related to analyzing flow and pressure pulsation. An acoustic energy balance framework is used to determine the onset velocity of pulsations originated at residual cavities left by the implementation of the insert. A shallow cavity is formed between two adjacent windings of the spiral insert. An aerodynamic analysis of these shallow cavities is described to determine whether self-sustained acoustic oscillations are possible. Other risks are introduced by the absence of the insert near end-fittings. Finally, in-situ conditions leading to non-uniformity such as bending of the flexible and pipe ovality are addressed. FLIP risks can be fully eliminated with the new insert technology in its nominal design and within its manufacturing tolerances.
Full-Scale Testing on Corrosion Resistant Alloy-Mechanically Lined Pipes (CRA-MLPs) for Submarine Pipeline Applications
Authors: Reda Ahmed , Kaspary Tiago , Montague Paul , A. Shahin Mohamed , Menezes Eduardo 
Published: August 2024

Abstract
Corrosion-resistant alloy (CRA) mechanically lined pipes (MLPs) have long been known as a cost-reduction alternative compared to CRA-clad (metallurgically bonded) pipes. Additional advantages also exist, including improved fit-up and installability, a wider choice of CRA materials, pipe dimensions and a lower carbon footprint. MLPs provide at least the same corrosion resistance as the CRA-clad pipes; however, as the liner is not metallurgically bonded to the carbon steel outer pipe, there is an additional failure mechanism of liner buckling during installation or strain associated with lateral buckling. Despite this, MLPs have been successfully installed in the subsea by reeling on several projects and many are currently in service without concerns. For any submarine pipeline, fatigue damage may be accrued from the loads incurred by fabrication, transportation, installation, pipeline spanning, thermal cyclic loading, instability, and interference loads such as fishing. As such, fatigue cracking can occur at both the girth weld and the triple point. Currently, the triple point is not classified in the fatigue design of many standards and there is limited data in the literature regarding the fatigue performance of the triple point. In this paper, full-scale bending testing was conducted on a 273.1 mm outside diameter MLP before a full-scale fatigue resonance testing. The full-scale bending testing was undertaken to replicate the through-life stresses experienced by the triple point, whereas the full-scale fatigue resonance testing was undertaken to understand the fatigue performance of the triple point. A periodic inspection of the liner was also performed during the full-scale fatigue testing as there is always a concern that the liner might crack before the back steel.
Research on USV Smooth Path Planning Method Based on IAC-QPSO Algorithm
Authors: Li Chengfeng , Wang Hongjian , Huang Yutong , Zhong Bo , Chi Zhikang , Tian Jinmu , Luo Naifu 
Published: August 2024

Abstract
Aiming at the problem of unmanned surface vehicle (USV) smooth path planning in complex obstacle environment, a USV smooth path planning method based on improved ant colony and quantum particle swarm optimization (IAC-QPSO) algorithm is proposed. An improved ant colony (IAC) algorithm is used to plan the global optimal polyline path, and the optimal turning regions are obtained by redundant optimization and merging strategies. The particle dimension is determined adaptively according to the number of optimal turning regions, which avoids the blindness and redundancy of size determination. To improve the quality of the initial solution, particle position initialization is carried out in the turning regions, so that it is easier to find the global optimal path. The boundary constraint is determined according to the extension of the optimal path turning regions, which greatly reduces the solution space, thus reducing the solution difficulty, and improving the search efficiency. Additionally, Levy flight, random particle and spiral search are introduced into quantum particle swarm optimization (QPSO) to enhance the optimization ability of the algorithm. Using the weighted sum of path length, safety degree and smoothness as fitness function, the optimal smooth path is obtained by the improved quantum particle swarm optimization (IQPSO) algorithm and cubic spline interpolation. Simulation results show the effectiveness of the proposed algorithm.