bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural Response of Subsea Pipe Elbows Under Monotonic and Cyclic Loading
Authors: Varelis George E. , Dib Elie , Karamanos Spyros A. 
Published: October 2022

Abstract
Pipe bends (elbows) are commonly used components in subsea piping systems. They are quite flexible compared to the corresponding straight pipes and are used to reduce the reaction forces and moments at the supports and the bending moments within the piping system, as well as to accommodate pipeline thermal expansion requirements. Because of their flexibility though, they develop significant deformations, mainly in the form of cross-sectional deformation (ovalization), which are associated with the development of local stresses and strains, significantly larger than those in the corresponding straight pipe, and may cause either buckling or rupture of the elbow pipe wall.
Several works have been reported on the structural performance and integrity of elbows in piping systems, in power plants or process industries. Under extreme loading conditions, e.g. seismic, or under shutdown/startup conditions, those elbows are subjected to bending under internal pressure, which may cause either plastic collapse or fracture due to low-cycle fatigue. On the other hand, the response of externally pressurised thick-walled elbows used in subsea systems, has received much less attention. The main feature in those elbows is the presence of external pressure, which has a destabilizing effect, especially in deep water applications. Under monotonic load, in the presence of external pressure, elbow ovalization is accentuated leading to pipe collapse at relatively low levels of structural loading. Under cyclic loading, progressive ovalization of the elbow occurs due to accumulation of plastic deformation, which may also result in rapid collapse due to the presence of external pressure.
The present paper, motivated by the use of steel elbows in subsea systems, describes a finite element simulation of elbow response under static and cyclic loading, in the presence of external pressure. Particular emphasis is given on the constitutive model, which should be capable of simulating the response of steel material under cyclic loading, and primarily, the accumulation of plastic strain over the loading cycles. The numerical results are compared with the design provisions in DNVGL-ST-F101.
FRyFAST : A Coupling Between FRyDoM and OpenFAST for the Simulation of Floating Offshore Wind Turbines With High Complexity Platforms
Authors: Chauvigné Camille , Letournel Lucas , Rongère François , Wuillaume Pierre-Yves , Castro Casas Natalia , Maréchal Benjamin , Kerkeni Sofien 
Published: October 2022

Abstract
The present paper describes the coupling between two open source software packages, OpenFAST and FRyDoM (named FRyFAST), dedicated to the floating offshore wind turbine (FOWT) dynamics simulation. FRyDoM (Flexible and Rigid body Dynamic modelling for Marine operations) is a multi-body and multi-physics framework, mainly dedicated to complex offshore systems, developed by D-ICE Engineering and Ecole Centrale Nantes. This framework is coupled with OpenFAST in order to simulate FOWT with advanced platform system, corresponding to multi-body system, platform with high interaction with other bodies in close environment or in contact with those bodies. This coupling enables also the used of an advanced Finite Element Model (FEM) based on an iso-geometric representation of the mooring lines. A lot of dedicated models for the platform can also be added through this coupling thanks to the FRyDoM API. In the first part, the coupling between OpenFAST and FRyDoM is presented. Particular attention has been paid to the integration of the added mass term to enable stability of this coupling, and to the synchronization between the two time integration schemes. Verification and validation results of this coupling will be presented. Tension in the mooring lines, dynamic behaviour of the FOWT in different wind and sea conditions have been analysed and show the capacity of this model to perform FOWT design.
The Impact of Climate Change on Offshore Operations and Design Considerations for Offshore Vessels and Installations
Authors: Rosen Jordan , Kilner Andrew , Gumley Jonathan , Jayasinghe Kanishka , Thurumella Hemant 
Published: October 2022

Abstract
This paper investigates the impact on the availability, uptime, and design conditions of offshore facilities and operations due to climate change. As the physical processes that generate ocean waves are intrinsically linked to atmospheric conditions, the ocean wave climate will change as global temperatures increase and global winds change. The impacts on offshore facilities have been investigated by studying and comparing wave climate predictions for a range of climate change scenarios, considering both the magnitude of temperature increase and the time horizon of the scenario. This paper relies on the scenarios generated in multiple revisions of the Coupled Model Intercomparison Project (CMIP).
This paper presents the impacts of climate change in a series of case studies:
• Changing design wave conditions for several potential offshore wind farm developments around Australia.
• The predicted change in the availability and uptime of five Single Point Mooring (SPM) terminals around South America.
• The predicted change in durations of offshore platform decommissioning activities and the duration of operations to install new floating facilities.
Wave Attenuation Performance of Arranging a Rectangular Buoy in a Perforated Caisson Using Quadratic Pressure Drop Condition
Authors: Wang Yuhan , Dong Sheng 
Published: October 2022

Abstract
Integrating a rectangular buoy type wave energy converter (WEC) inside the perforated caisson can be advantageous to the wave attenuation performance as well as the stability of the WEC. As a preliminary study on such integration system, a theoretical model was established to investigate the wave attenuation performance of the integration system with a fixed buoy inside a perforated caisson. The methods of separation of variables and eigenfunction function expansion were used to determine the velocity potentials in different fluid domains. Instead of the traditional linear pressure drop condition for perforated walls, a quadratic condition, which is more consistent with the practical truth, was used in this study. The proposed model was validated by results in a former research. The wave attenuation performance was then investigated and discussed through a parametric study.
Load Capacity of Sandwich Panel With Core Foam Evaluated by 3-Point Bending Test
Authors: Josefson B. L. , Paboeuf S. , Anyfantis K. , Zamarin A. , Oddy C. , Collier B. , Ntouni K. , Bolf D. 
Published: October 2022

Abstract
The classification society Bureau Veritas requires a structural assessment of composite materials structures to confirm the compliance with applicable rules, like 3-point bending tests. However, for sandwich panels with a low-density foam core, local phenomena like indentation and wrinkling may occur in the upper face sheet at the loading punch, thus the intended load capacity of the sandwich panel will not be reached. It is then proposed to perform complementary shear tests to capture the behaviour of the core of the sandwich panel.
In the present paper, the load capacity in a 3-point bending test is simulated with emphasis on the influence of the constitutive modelling of the core foam, as calibrated against experimental results for shear tests. It is carried out as a benchmark exercise, with participation from three universities.
The FE-simulations show that the shear test can be used to accurately model the load capacity of the core foam. However, for the 3-point bending test using specimen with a very high panel length / thickness ratio a large part of the load transfer is done in the upper face sheet with less involvement of shear in the core. Although core fracture is observed in the experiments, both the FE-simulated and experimentally found maximum load agree well with the load capacity as determined from analytical formula for local failure in the upper face sheet. The FE-simulated vertical displacement at maximum load differs though.
Topology Optimization of Joints Between Prismatic Sandwich Panels and Girders Under In-Plane and Bending Loads
Authors: Yan Shengyu , Jelovica Jasmin 
Published: October 2022

Abstract
Prismatic sandwich structures offer improved mechanical properties over traditional structures used in ships and other vehicles. While research on their response and strength under local and hull girder loads has been advancing, insufficient attention has been placed on their joints, i.e. connections to surrounding structure, such as girders and bulkheads. It is important to seek appropriate topology of the joints to minimize stress they experience. We conduct this investigation via topology optimization, minimizing stress for a given volume fraction of a material. Aggregation approach is used where a p-norm function approximates the maximum stress in the finite element analysis to reduce the number of iterations to reach converged solution. Optimization is performed using sequential convex approximations via Method of Moving Asymptotes (MMA). The optimization is performed in Matlab. Maximum stress of optimized designs is validated using Abaqus. Joints are optimized for three load cases, combining moment on the joint (coming from lateral pressure on the panel) with in-plane tension and compression. Several topologies of the joint were found which feature 2–3 times smaller maximum stress than the conventional joint, even for lower structural weight (material volume fraction). However, the complexity of the joint is increased, which can be controlled effectively by the filter radius and passive elements.
Validation of a Simplified Numerical FLNG-Carrier Side-by-Side Offloading Model With Experiment
Authors: Wang Yutao , Wolgamot Hugh , Zhao Wenhua , Draper Scott , Milne Ian 
Published: October 2022

Abstract
One of the key challenges associated with an FLNG facility is to optimise its offloading operability. LNG offloading operations typically use a side-by-side (SBS) configuration, where a carrier is moored parallel to the FLNG, leaving only a relatively small gap between the two vessels. In this paper, a numerical model for predicting the relative motion between an FLNG vessel and LNG carrier during offloading is developed using potential flow theory, and compared to wave basin experiments on simplified box geometries.
In particular, this study addresses the prediction of roll motion, which is critical to SBS operation but difficult to model within the potential theory framework due to its dependence on viscous damping. The Ikeda method, which is an industry standard method for calculating ship roll damping, is applied in the model. However, since the Ikeda method was developed for a single hull, a modification is proposed to deliver improved performance in the context of the SBS offloading operation. More specifically, the small clearance between the vessels will influence the flow field and subsequently modify the fluid velocity around the bilge. This study suggests that the relative velocity between the fluid and hull roll motion is a better input for the original Ikeda method.
Flow Around Curved Tandem Cylinders
Authors: Aasland Tale E. , Pettersen Bjørnar , Andersson Helge I. , Jiang Fengjian 
Published: October 2022

Abstract
The flow around curved tandem cylinders of equal diameter has been investigated for the first time, by means of direct numerical simulations. A convex configuration was used. The nominal gap ratio was L/D = 3.0 and a Reynolds number of 500 was chosen. Due to the change in effective gap ratio along the cylinder axis, there is a variation of tandem flow regimes, from alternating overshoot/reattachment, via stable reattachment, to co-shedding, in this case called gap shedding. The combination of reattachment and gap shedding gives near-zero drag and vertical forces for the downstream cylinder, whereas the corresponding forces on the upstream cylinder are comparable to single curved cylinders. Meanwhile, the opposite is true for the lift forces. A low-frequency variation of horizontal and vertical forces is seen, and this is attributed to a slow variation of the position where gap shedding commences. Finally, the concept of a critical angle is proposed to describe the transition to gap shedding, for a given combination of nominal gap ratio and Reynolds number.
An Evaluation of Consequence Severity of Ship Evacuations in the Canadian Arctic
Authors: Browne Thomas , Kennedy Allison , Piercey Caitlin , Power Jonathan , Veitch Brian 
Published: October 2022

Abstract
Ship evacuations in Arctic waters expose crew and passengers to the potential for severe life-safety consequences. Effective planning and allocation of Arctic SAR services should be supported by evidence-based assessments of the consequence severity of ship evacuations. This paper provides an evaluation of life-safety consequence severity for ship evacuation scenarios in the Canadian Arctic. Exposure time is a predominant factor influencing consequence severity of Arctic ship evacuations. The study integrates existing models for exposure time estimation [1,2] and life-safety consequence [3]. Exposure time is estimated for air- and marine-based SAR assets, considering associated capacities, speeds, and operating ranges. Evacuation scenario factors include ship type, number of POB, and geographic location. The methodology provides Arctic SAR service providers with a tool for planning effective resource allocation and response efforts. As a base case, exposure times and consequence severities are estimated for SAR response with a single asset. The effect of deploying multiple SAR assets is demonstrated. Results indicate that the deployment of air-based SAR assets contributes to reduced exposure times and mitigation of life-safety consequence severity. Evacuation of a passenger vessel is a worst-case scenario. Evacuations of high POB vessels require the deployment of multiple SAR assets to prevent potential disastrous life-safety consequences.
Optimizing Models for Predicting Torque on Bit Using Data From the Volve Field in Norway
Authors: Höhn Patrick , Bashara Ahmed Rahim Kreem , Paz Carlos , Oppelt Joachim 
Published: October 2022

Abstract
Torsional oscillations can cause severe damage to downhole tools and may result in expensive fishing and sidetracking operations. The drilling industry is aware of this problem and still looking for suitable solutions to determine the drivers of the oscillations, and to quantify their effects. The mitigation of this problem requires a detailed knowledge of the parameters controlling the drilling process. Nowadays, modeling is a useful tool for describing the downhole processes using the stream of data acquired from the sensors installed in the drilling equipment.
This paper focuses on torque on bit which is directly connected with torsional oscillations. The model generation is performed, either by fitting empirical models with measured data or by creating new machine learning models. Five empirical literature models are parametrized using the optimization module of the Python library SciPy. Machine learning models are generated using Scikit-learn with measurement data from the Volve field in Norway. For the current testing dataset Random Forest showed the highest accuracy with a R2-score of 0.767. Other machine learning algorithms showed a comparable accuracy. However, empirical models failed to achieve reliable results. In future, the generated models can be used to optimize drilling parameters to prevent technical drilling problems.
Simulation of a Moored Multibody Offshore Structure Articulated by Different Joints in Waves
Authors: Jiang Changqing , el Moctar Ould , Zhang Guiyong , Schellin Thomas E. 
Published: October 2022

Abstract
Within the framework of the Space@Sea project, a modular floating structure (MFS) was developed to serve as building blocks for artificial islands. The modularity was one of the key elements, intended to provide the desired flexibility of additional deck space at sea. Depending on the purpose of a modular floating concept, various articulation techniques, such as hinge, prismatic, cylindrical and screw joints can be applied to connect MFSs. This paper presents numerical simulations of moored and articulated multibody offshore structures in waves, via a coupled mooring-joint-viscous flow solver accounting for mooring dynamics, joint restrictions, nonlinear rigid body motions, and viscous flow effects. The considered concepts consisted of two MFSs connected by two kinds of connections, namely a rigid joint and a flexible joint, and positioned by four symmetrical catenary mooring lines. The analyzed responses comprised multibody motions as well as associated forces acting in the hinged joints and the mooring lines. Results indicated that surge motions of the articulated bodies were almost identical to each other, whereas the effects of the joint on heave motions were not pronounced. However, highly dynamic pitch motions between two hinged MFSs were observed. Apart from motion responses, forces acting on the hinge joint and the mooring lines were considered. The coupled mooring-joint-viscous flow solver demonstrated its ability to predict responses of moored and articulated offshore structures in waves.
The Comparison of Two Kinematic Motion Models for Autonomous Shipping Maneuvers
Authors: Wang Yufei , Perera Lokukaluge P. , Batalden Bjørn-Morten 
Published: October 2022

Abstract
Autonomous shipping with adequate decision support systems is widely considered as a high-potential development direction in the maritime industry in the upcoming years. Prediction technologies are one of the key components in these decision support systems and they usually require a large number of data sets to estimate vessel states. Certain vessel motion models are generally implemented with the above-mentioned prediction technologies to improve the accuracy and robustness of the estimated states. In contrast to wider research studies of different motion models for the applications of ground vehicles, the studies of appropriate motion models for maritime transport applications are still insufficient. Therefore, it is necessary to develop reliable motion models for vessels, and that can improve the decision supporting capabilities in future vessels, especially in autonomous shipping.
In this paper, two kinematic motion models which can be used to estimate various vessel maneuvering states are examined and compared. In the current stage, the proposed models are used to investigate ship maneuvers produced by a ship bridge simulator. Two nonlinear filter algorithms combined with Monte Carlo-based simulation tests are applied to estimate the respective vessel states. In the conclusion, a comprehensive comparison of the estimation algorithms is presented with the estimated vessel states. Hence, this study provides robust and convenient estimation algorithms that can support autonomous shipping navigation in the future.
Development of Guar Gum Fracturing Fluid With Temperature Resistance of 150°C and Specific Gravity of 1.0~1.2g/m3
Authors: Xue Meng , Liyan Zhu , Yongchang Zhao , Zhishuo Chen , Abulimiti Waili , Erdong Yao 
Published: October 2022

Abstract
For major high temperature and deep reservoir in West China, hydraulic stimulation confronts challenges of true vertical depth more than 6000 m and bottom hole temperature beyond 150°C. The long injection path from surface to stimulated formation induces significant friction. It commonly leads to very high ground pressure, which will exceed the limit of ground pumping equipment. In addition, conventional fracture fluid systems lost their fracturing ability and sand carrying capacity under high temperature. Therefore, it is urgent to develop a novel fracture fluid system with adjustable specific gravity and high temperature resistance for high temperature deep reservoir fracturing.
In this article, the basic properties of guar gum were determined at first, and a high temperature and salt resistant organic boron crosslinking agent was synthesized. The optimal dosage and the optimal crosslinking pH, and the delayed time for crosslinking was studied. Then, the relationship between fluid density and weighting agent dosage is measured, which will facilitate the fracturing fluid density adjustment in the field. Three specific gravity formulas of fracturing fluid, that is 1.10, 1.15 and 1.20g/cm3, is optimized. Finally, the performance of fracturing fluid was evaluated comprehensively, and its gel-breaking and formation damage performance were tested.
The apparent viscosity of 0.5wt% guar gum solution was 57.2mPa · s at room temperature (25 °C), and 29.1mPa · s at 150 °C. The synthesized high-temperature boron crosslinking agent YP-4 is colorless, transparent, and miscible with water. The optimal crosslinking concentration is 0.65wt%. The crosslinking occurred in the range of pH = 9∼12. The crosslinking time can be controlled within 3∼10min by adjusting the dosage and pH value. NaCl weighting fluid formulas with a density of 1.0∼1.2g/cm3 was optimized. The optimal fracturing fluid formulation was 0%∼26.4wt% NaCl brine +0.5wt% hydroxypropyl guar gum +0.3wt% alkaline pH regulator +0.65wt% crosslinking agent YP-4. This fracturing fluid can stable for more than 60min at 150 °C and 170s−1, and the final viscosity was high than 100 mPa·s. If the guar gum concentration was increased to 0.55wt%, the viscosity would exceed 260 mPa·s. 0.2wt% amine persulfate can be used to break the fracturing fluid, and the viscosity after breaking is less than 4mPa·s. What’s more, the fracturing fluid has good compatibility with various additives, and no flocculation or precipitation occurs within 24h. The average damage of gel breaking liquid to the core is 24.81%, which is relatively small. High temperature resistance and adjustable weight density have great advantages in field applications. Equipment constraints can be met while fracturing can be performed at minimal cost. This fluid system will provide beneficial support for high temperature and deep well fracturing.
A Deep Learning Model for Rate of Penetration Prediction and Drilling Performance Optimization Using Genetic Algorithm
Authors: Erge Oney , Ozbayoglu Murat , Ozbayoglu Evren 
Published: October 2022

Abstract
In this study, a deep learning model is proposed that can accurately predict the rate of penetration during geothermal or oil and gas well construction operations. Also, a genetic algorithm is applied and used together with the deep learning model to determine the optimum values for the drilling parameters: weight on bit (WOB) and drillstring rotation rate (RPM).
It is vital to estimate the optimal set of values for drilling parameters to construct wellbores quickly and efficiently. Traditionally, drill-off tests are conducted by halting the normal drilling operation and manually changing the WOB and RPM values to search for the highest ROP output. This operation can be repetitive and can lead to an inaccurate estimation of parameters because only a few different parameters are tried. The proposed learning algorithm estimates the optimum WOB and RPM, based on the historical values and can keep learning as the drilling proceeds, which is essential for fully automated well construction.
The proposed deep learning model is trained with actual drilling datasets that showed an accurate prediction of the rate of penetration and mechanical specific energy (MSE). This model is used together with the genetic algorithm and the optimum drilling parameters are determined that yield minimum MSE. The results showed a significant performance improvement compared to the historical values.
The proposed model can be used as an advisory system to the driller or the output can be used within the control system to automate the drilling process. The proposed learning model showed the capability to further optimize the drilling-rate and mitigate any invisible lost time (ILT) and potential nonproductive time (NPT) by completing the well as soon as possible.