bluuebunny/crossref_metadata_2025_split huggingface dataset:
Design and Evaluation of Wellbore Strengthening Materials for Fractured Reservoirs
Authors: Gargılı Uğur , Gücüyener İ. Hakkı , Durgut İsmail , Ay Ahmet , Doğan H. Ali 
Published: October 2022

Abstract
Fractured formations are commonly encountered while drilling carbonate reservoirs. Drilling of fractured formations usually results in lost circulation. In some cases, target zones cannot be reached due severe to lost circulation incidents.
Fractures encountered before reaching target zones can be sealed off by using wellbore strengthening materials (WSM). WSM are drilling fluid additives which are specially sized and designed particulates. They are generally used to strengthen the wellbore and to prevent the occurrence of losses by propping and sealing the fractures while drilling. In this study, experiments were carried out to determine optimum concentration and particle size distribution (PSD) of WSM to seal off fractures with certain sizes.
A non-damaging water-based polymer drill-in fluid with acid soluble marble particles having different concentrations and PSD were used in this study. Plugging efficiency of different blends were tested using modified Permeability Plugging Apparatus by pushing WSM-imbedded drill-in fluid through fracture widths of 400, 800 and 1200 μm manufactured on metal disks. Different WSM blends were compared with each other with regards to sealing time required to reach target pressure of 2000 psi and volume lost until the seal is achieved.
During the study, tests were run to investigate the effect of different PSD, concentration, and fracture width on sealing efficiency. Results were interpreted to determine optimum WSM formulations for different fracture sizes by taking into account continuous particle addition strategy while drilling together with downhole tools limitations. Optimum WSM blends were determined to seal off the mentioned fracture widths successfully.
Bottom Lateral Pressure Effect on the Ultimate Bending Moment of the Scaled Hull Girders
Authors: Ma Hongyang , Wan Qi , Wang Deyu 
Published: October 2022

Abstract
Scaled models are designed as alternatives to true ship structures in ultimate strength experiments. In this paper, a series of true ship hull girders of a 10,000TEU container ship under different scale combinations of geometric length and plate thickness are modeled. At the same time, the scale ratio of bottom water pressure is designed based on the scale ratio of geometric length. The relevant scaling characteristics of hull girders’ ultimate strength and collapse behaviors are investigated based on the nonlinear finite element analysis. Most of all, the effect of bottom water pressure on the ultimate bending moment is explored in detail. Aiming at presenting the mechanism of the bottom water pressure on the scale models. Results show that the bottom water pressure has a significant effect on the ultimate bending moment when the scaling factor of geometric length is close to one. By contrast, the effect of bottom water pressure on the ultimate bending moment is weak when the scaling factor of geometric length is relatively small. The effect of the bottom lateral pressure is to reduce the ultimate bending moment carrying capacity by changing the bending rigidity of the hull girder. The presence of lateral pressure makes the hull girder be more prone to buckle.
Digital Twin of a Maneuvering Ship: Real-Time Estimation of Drift And Resistance Coefficients Based on Ship Motion and Rudder and Propeller Commands
Authors: Uehara Sasaki Humberto A. , Cardozo de Mello Pedro , Aoun Tannuri Eduardo 
Published: October 2022

Abstract
The present work tackles the modeling problem concerning the initial steps of a Digital Twin (DT) application in a maneuvering ship. To envision a real implementation, further problems need to be solved, such as architecture design, communication network, digitalization purpose, etc., subjects which will not be aborded here. Instead, we concentrated on developing a well-rounded general system model that will enable the future employment of DT technology. Some examples can include performance analysis due to degradation of the hull, rudder, or thruster; decision support for maintenance scheduling; or even distance monitoring.
The paper focuses on real-time estimation of the main vessel hydrodynamic coefficients — namely the drift and resistance coefficients — through ship motion measurements (obtained from GNSS and Gyrocompass) and the input commands to the propeller and rudder.
Compared to the previous (OMAE2021-62899), we included proper propeller and rudder models; replaced the Extended Kalman Filter (EKF) with the Unscented Kalman Filter (UKF) and estimated the coefficients directly instead of its linear approximation.
Some maneuvers were tested within a simulated environment called pyDyna — a ship maneuvering simulator implemented on python based on the mathematical model adopted in the TPN-USP Ship Maneuvering Simulation Center. Data from motion sensors were mimicked by inducing a Gaussian white noise in the data retrieved from the simulator in real-time intending to better represent a real-world scenario.
Preliminary results show good adherence and low computational, possibly presenting as a convenient preliminary parameter assessment until more precise and time-consuming methods such as CFD are evoked.
CFD Modelling of Flexible Concrete Mattress Hydrodynamic Forces
Authors: Griffiths Terry , Griggs Randall , Khiadani Mehdi 
Published: October 2022

Abstract
While flexible concrete mattresses have been used extensively in the offshore industry for many decades, relatively little peer-reviewed published data exists to define the hydrodynamic forces and failure modes of these structures.
This paper presents a series of 3D CFD models which provide the predicted hydrodynamic force coefficients for a typical subsea bidirectionally-flexible concrete mattress. In addition, the CFD models also provide insight into the flow dynamics between and within the concrete blocks, allowing an understanding of the relative hydrodynamic forces on each block. The model results provide useful insight when interpreted in conjunction with physical model tests and field data to provide the potential for new design guidance to be developed.
Application of Recurrent Neural Network Long Short-Term Memory Model on Early Kick Detection
Authors: Wang Junzhe , Ozbayoglu Evren M. 
Published: October 2022

Abstract
Long-short term memory [1] (LSTM) is an artificial Recurrent Neural Network (RNN) architecture capable of performing deep learning tasks. With the special feedback feature, the LSTM network is suitable for processing a sequence of data and making a sequence of predictions. It has been successfully applied to many disciplines such as speech recognition, language translation, time series forecasting, and anomaly detection. In this paper, the RNN-LSTM network is applied to real-time drilling data to study the complex dependencies between multiple drilling parameters and common kick indicators. A well-trained model will use the concept of the sliding window to continuously predict the unforeseen value of sensitive kick indicators. With proper analysis, the predicted result is helpful to detect kicks ahead of time. This paper also proposed a general workflow to easily visualize the prediction results. Compared with other time series prediction methods, the LSTM network has the advantages of more accurate multi-step prediction, more physical, and more flexible. The proposed LSTM network uses accelerated GPU computing, the fast computational speed makes both online and offline learning possible. It is concluded that this approach is capable of accurately predicting kick indicators under certain circumstances. It may provide innovative guidance for the application of the LSTM network in early kick detection and future study.
Numerical Investigations on Plastic Responses of Strain-Rate Sensitive Panels Under the Lateral Impact
Authors: Zhou Hongyu , Wang Deyu 
Published: October 2022

Abstract
In the present study, the influence of the stiffening effect and the scale effect of material strain rate sensitivity on the lateral impacted panels is investigated. Rigid-plastic analysis for the collision scenario which fully clamped panels made of strain rate sensitive material struck by the blunt impact mass are conducted. A relationship is suggested to characterize the material strain rate sensitivity through the dynamic flow stress, defined by introducing a related factor n1 based on the theoretical analysis. Numerical simulations of low-velocity impact tests examining dynamic responses of clamped panels struck transversely by an impact block with a hemispherical indenter are presented. The dynamic behaviors obtained by numerical simulations are compared to reveal the influence of dynamic material characteristics on the impact behavior of steel panels. The great consistency between simulation results and predictions of the rigid-plastic analysis illustrates that the proposed rigid-plastic methods are effective to deal with the collision problem taking strain rate sensitivity into account. Moreover, the scale effect of the material strain rate effect on dynamic behaviors included the maximum permanent displacement and the peak impact force of panels is described quantitatively. The quantitative summarizations for the effect of the strain rate sensitivity are given. The maximum permanent displacement and the peak impact force are confirmed to be a power function of the related factor n1.
Fatigue Strength of Fixed Offshore Structures Under Variable Amplitude Loading Due to Wind, Wave, and Ice Action
Authors: Braun Moritz , Dörner Alfons , Willems Tom , Seidel Marc , Hendrikse Hayo , Høyland Knut V. , Fischer Claas , Ehlers Sören 
Published: October 2022

Abstract
Fixed offshore wind turbines are increasingly developed for high latitude areas where not only wind and wave loads need to be considered, but also moving sea ice. Current structural design rules do not adequately consider the effect of ice loading on fatigue life, due to missing studies on fatigue strength of welded joints under combined wind, wave, and ice action. Thus, a methodology to determine combined variable-amplitude loading (VAL) spectra was developed in a previous study. The stress state time-history at an exemplarily selected point in the support structure of an offshore wind energy monopile was translated into a VAL sequence. This sequence is used as an input for fatigue tests of butt-welded joints in the current study. The current study presents the VAL spectrum and the corresponding VAL time series, the results of the fatigue tests and compares them to typical fatigue damage sums for other stress spectra.
Verification of Inverse Propeller Moment Estimation Using a Scale Laboratory Rig
Authors: Nickerson Brendon M. , Laas Jaco , Bekker Anriëtte 
Published: October 2022

Abstract
There has been increasing interest in the loads caused during interaction between ship propellers and ice. Recent research into propeller ice interaction has produced inverse models that can be used to estimate the propeller moment induced by ice impacts. These models rely on the measurement of the output response of the propulsion shaft, which is inverted to obtain the input propeller load. Though these models have been validated numerically and used with full-scale response data, they have not been validated using simultaneous input and output measurements. Reliable full-scale simultaneous measurements can be difficult to obtain due to the harsh conditions experienced during propeller-ice interactions, and the cost involved with direct measurement of propeller loads. Thus, the use of a laboratory rig to verify the inverse method is investigated. An inverse model based on the use of modal superposition to represent the propulsion shaft as a continuous system has been implemented alongside a laboratory scale rig. The input loads and output responses are measured simultaneously during experiments with the scale model. These output responses are provided to the inverse model, and its estimation of the input load are compared to the measured loads. The comparison provides information about the accuracy of the estimations provided by the inverse model. It is found that improvements should be made to the rig in order to conduct more accurate comparisons.
Operational Planning and Power Management System for Offshore Platform With Wind Energy Supply – Impacts on CO2 Reduction and Power Quality
Authors: Svendsen Harald G. , Holdyk Andrzej , Vrana Til Kristian , Mosgren Idun Runde , Wiik Jan 
Published: October 2022

Abstract
This paper considers the operation of offshore oil and gas platform energy systems with energy supply from wind turbines to reduce CO2 emissions. The study is conducted through simulations of a case that reflects a “typical” oil and gas platform on the Norwegian Continental Shelf, with energy demand for gas lift and gas export compressors, separator train, oil export pump, water injection pumps, accommodation and utilities.
The study case with wind energy is compared to a base case with only gas turbines, and both cases have been implemented and analysed in multiple simulation tools. Results have been compared and used to assess the impact of wind integration on CO2 emissions, gas turbine fuel usage and wear and tear, power system frequency stability and other key indicators.
The results are consistent between the modelling tools, and indicate a potential for CO2 emission reduction of 20–25 % for this case with a wind energy share of 26 %. There is some variation depending on the amount of reserve power required and the rules for when to start up and shut down gas turbine generators.
Hydrodynamic Performance Evaluation of a Semi-Submersible Floater Using Open-Source Tools
Authors: Hassani Milad , Li Lin , Kalofotias Filippos , Jiang Zhiyu 
Published: October 2022

Abstract
Floating structures are viable alternatives for supporting wind turbines in deep water. Design of floating support structures is a challenging task, and a design evaluation requires considerations of costs and system performance.
An approach for evaluation of semi-submersible floaters has been developed in this paper. A braceless semi-submersible floater is selected and this floater is designed to support a 5-MW wind turbine in the North Sea. The evaluation framework consists of automatic modeling and numerical simulations in open-source tools. A Python-SALOME-NEMOH interface is used to obtain the hydrodynamic properties for geometries defined by various variables. The geometries are subjected to three performance constraints related to the static platform pitch, metacentric height, nacelle acceleration and wind loads in operating and parked conditions. Finally, the geometries are evaluated using two combined objective functions related to material cost and nacelle acceleration, and the Pareto Fronts are discussed. This work contributes to developing efficient design optimization methods for floating structures.
Water-Depth Identification From Free-Surface Data Using the KdV-Based Nonlinear Fourier Transform
Authors: de Koster Pascal , Brühl Markus , Wahls Sander 
Published: October 2022

Abstract
We propose a novel method to determine the average water depth from shallow, weakly nonlinear water waves that are approximated by the Korteweg-de Vries equation. Our identification method only requires free-surface measurements from two wave gauges aligned in the direction of wave propagation. The method we propose is based on comparing solitonic components in wave packets, which are computed using the nonlinear Fourier transform (NFT) (typical time-series data often contains at least some solitonic components, even when these components are not directly visible). When the correct water depth is used for the normalisation of the wave, the solitonic components found by the NFT remain constant as the wave packet propagates, whereas any other water depth will result in solitonic components that do not remain constant. The basic idea is thus to iteratively determine the water depth that leads to a best fit between the solitonic components of time series measurements at two different gauge positions. We present a proof-of-concept on experimental bore data generated in a wave flume, where the identified water depth is within 5% of the measured value.
Motion Response Prediction of Marine Vessels Based on Hydrodynamic Models Updated Through On-Site Measurements
Authors: Radhakrishnan Gowtham , Leira Bernt J. , Gao Zhen , Sævik Svein , Gomola Alojz 
Published: October 2022

Abstract
Decision support systems in offshore vessels utilize wave parameters in combination with physics-based vessel models to predict the vessel behavior prior to the initiation and execution of a marine operation. These predictions are, usually, accompanied by significant uncertainties inherent in the estimation of wave statistical parameters, idealized parametric spectra, and system variables. Consequently, the predictions may deviate considerably from the real behavior of the vessel. Therefore, this study uses numerical wave spectra corresponding to a site in the North Sea in conjunction with a hydrodynamic model adapted to measurements to make more accurate intermediate-term response predictions. Considering a weather-restricted marine operation, the intermediate-term predictions involve simulating the responses for any time window within the upcoming 72 hours. The vessel model’s uncertainty is minimized by calibrating the influential parameters utilizing the full-scale response measurements within an optimization framework. The subsequent Roll predictions based on calibrated parameters exhibit better alignment with the measured Roll motions. The application of recursive optimization showed a significant reduction in prediction errors in an actual marine operation.
Influence of Aerodynamic Loads on a Dual-Spar Floating Offshore Wind Farm With a Shared Line in Parked Conditions
Authors: Liang Guodong , Jiang Zhiyu , Merz Karl 
Published: October 2022

Abstract
The concept of a shared mooring system, in which adjacent wind turbines are coupled by sharing mooring lines, has been proposed to reduce the mooring costs of floating offshore wind farms. This work investigates the influence of aerodynamic loads on a floating offshore wind farm of two spar wind turbines connected with a shared line in extreme environmental conditions. A case study is performed for the floating offshore wind farm under parked conditions using a numerical simulation tool. The environmental conditions are determined from environmental contours with a return period of 50 years. Turbulent wind and irregular waves are simulated in dynamic analyses. Wind and waves are aligned and two loading directions are considered. Floater motions and structural response are analyzed. The influence of aerodynamic loads is studied by comparing the simulation results under both wind and waves with those under wave-only. It is concluded that the aerodynamic loads affect the horizontal motions of floating offshore wind turbines, the mooring response and the tower-base bending moment significantly in extreme environmental conditions, especially when the loading direction is 90 deg. The findings from this study improve understanding of the design loads of shared mooring systems.
A Numerical Scheme to Investigate Ice Fracture in Level Ice-Ship Interaction
Authors: Xu Ying , Wu Jiameng , Wang Zeping 
Published: October 2022

Abstract
Ice load is a major threat to the structural safety of polar ships. Accurate prediction of ice loads is inseparable from the good presentation of sea ice fractures by using numerical methods. However, sea ice fracture is a typical discontinuity problem and has been a thorny issue.
This paper uses extended finite element method to study the fracture mechanism of level ice when interacts with a rigid plate, which is a simplified structure of ships, to help gain better understanding of the ice load. The numerical simulations are performed based on ABAQUS. The transversely isotropic material model and failure criterion are adopted for the numerical simulation of the level ice. The deformation and stress distribution of the level ice, as well as the location of initial crack and the path of the crack propagating are discussed.
The results of the study show that the level ice fracture is closely related to the local tensile failure. The ice failure mode and ice load are closely related to the impact velocity and inclination. As the cracking process of level ice can be well simulated and the stress state can be well presented, extended finite element method is proved to be an effective method to investigate the ice fracture mechanism.
Axial In-Place Behaviour of Unbonded Flexible Pipes
Authors: Norland Kristian , Larsen Anders A. , de la Cour Dorthe , Larsen Henrik Ø. , Pedersen Tommy , Eriksen Morten 
Published: October 2022

Abstract
The axial behaviour of an unbonded flexible pipe is highly non-linear and may change throughout the load history and along the pipe. The axial stiffness and expansion coefficients (pressure and temperature) of a flexible pipe are given as two sets: one for the tension state and one for the compression state. Previously the typical interpretation has been that this tension/compression classification referred to the true wall axial force in the pipe. However, this approach is incomplete in several aspects:
• The determining physical factor is whether the tensile armour layers are in contact with the underlying layers.
• An unbonded flexible pipe consists of different layers with different axial force and orientation. It can be argued that the term “true wall axial force” does not make sense for an unbonded flexible pipe.
• To determine the axial force for a given condition, a set of expansion coefficients and axial stiffness must be selected. Hence, it becomes a circular argument.
Based on detailed analysis by the product supplier, a transition plane can be defined. The “Transition Plane Concept” offers an efficient way of implementing a realistic axial behaviour in the in-place design (incl. upheaval buckling). The axial behaviour during the in-place phase can be consistently defined by a transition plane and this can be implemented in the in-place analysis. Reduced risk for upheaval buckling of flexible pipes and removal of excessive conservatism can be achieved.
Numerical Simulations for Impacts of Offshore Wind Power Facilities on Currents and Water Quality
Authors: Miki Koki , Tabeta Shigeru , Mizuno Katsunori 
Published: October 2022

Abstract
When selecting a suitable site for offshore wind farm, the impact on the marine environment is one of the most important issues. However, in most cases of the suitable sites selection, the distances from protected areas, spawning and wintering grounds of marine creatures are taken into account as environmental indicators, and there are few which explicitly consider the impact of the offshore windfarm on marine ecosystem including current field and water quality which could be affected by the construction of offshore power plants. In this study, the impacts of offshore wind farms on the flow field and water quality were investigated by numerical simulations, introducing models of offshore wind farms facilities and sessile organism on the structure into a three-dimensional coupled hydrodynamic-ecosystem models. A nesting grid system were employed which combines a farm-scale grid and a local-scale grid. The large-scale simulation results showed that the changes in current due to a foundation structure of wind turbine could affect the flow field around the downstream structures. It is also found that water quality change in this scale is mainly caused by the changes in current field and the effects of sessile organisms on the structures are small. On the other hand, the small-scale results shows that the effects of sessile organisms may also appear in the very near vicinity of the structure. By using the developed model, it is possible to visualize the extent of the changes in currents and water quality caused by the offshore wind farm facilities.