bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental Study on Void Fractions and Pressure Drops in Three-Phase Flow for Deep Sea Mining
Authors: Takano Satoru , Masanobu Sotaro , Kanada Shigeo , Ono Masao 
Published: October 2021

Abstract
Subsea minerals exist in the deep water within Japan’s exclusive economic zone. There are many technical issues which should be addressed for subsea mining.
The air-lift pumping systems are one of promising methods for subsea minerals transport. Flow assurance for three-phase flow is important to design the air-lift pumping system for subsea mining. It is important to establish methods for estimating void fractions and frictional pressure drops.
To establish the methods for three-phase flow, we reviewed previous studies for two- or three-phase flow. There are some models to estimate the void fractions such as slip flow model and drift flux model. There are also some models to estimate the frictional pressure drops such as homogeneous model and separated flow model. We calculated void fractions and frictional pressure drops by existing correlation and compared calculated results with experimental data in two- or three-phase flow.
In addition, we proposed the methods for estimating the void fractions and frictional pressure drops in three-phase flow. These had fewer number of experimental constants than existing correlations, these could calculate void fractions and frictional pressure drops in more various conditions than existing correlations.
A Combined Vortex Lattice Lifting Line Method for Unsteady Propeller Calculations
Authors: Büsken Andreas , Krüger Stefan 
Published: October 2021

Abstract
This paper presents a Combined Method for the calculation of propeller forces in inhomogeneous inflow. It consists of an extended Goldstein approach based on Lifting Line Theory and a Vortex Lattice Method. After a brief overview of both methods is given, the coupling strategy is described and the additional modifications are explained. A correction factor accounting for the vortex which develops under a separated and later reattached flow on the suction side of the propeller blade is implemented as the first modification. Further, the Lamb-Oseen vortex model is used for the vortices in the free vortex system of the propeller. Finally, some results achieved with the described method are presented and compared to measured values.
A CFD Approach for Modelling the Fluid-Structure Interaction of Offshore Aquaculture Cages and Waves
Authors: Martin Tobias , Bihs Hans 
Published: October 2021

Abstract
Open ocean aquaculture cages became recently a promising alternative to traditional fish cage designs. The offshore environment implies larger loads on the structures and higher risk of fish loss. Floating rigid aquaculture cages with stiff nets are considered as a possible solution to cope with these new challenges. Their design process requires more advanced tools to account for the non-linear fluid-structure interaction. This paper presents a suitable numerical approach for analysing the interaction of offshore aquaculture cages and waves using Computational Fluid Dynamics. Here, a numerical wave tank accounts for the accurate propagation of the waves, and structural dynamics solutions are utilised for the cage system. Two-way coupling is enabled by accounting for the influence of the net on the fluid. The numerical model is validated against measurements for the loads on and the responses of a mobile floating fish farm in waves and current.
A Framework for Condition Monitoring and Risk-Based Decision Support Involving a Vessel State Observer
Authors: Han Xu , Leira Bernt J. , Sævik Svein , Radhakrishnan Gowtham , Skjong Stian , Kyllingstad Lars T. 
Published: October 2021

Abstract
Digital twins have attracted significant attention across different domains for decades. In the maritime and the energy industries, digital twins have been mainly used for system condition monitoring, project visualization, crew training, real-time decision making/support, and predictive maintenance based on onsite measurement data from onboard sensors. Such a digital twin normally presumes the vessel’s operational condition by assistance from sensors and engineering judgement. However, a vessel’s operational condition and loading state may shift quite often due to the frequently changing operational scenarios, tasks, and environmental conditions. In addition, the true vessel state (e.g., inertia distribution) may deviate from the intended one according to planning due to possible engineering errors. Even though there are sensors helping to monitor vessel condition such as draft monitoring systems and ballast systems, several important vessel parameters are difficult to measure directly, e.g., moment of inertia, center of gravity, and nonlinear hydrodynamic damping. This paper proposes a framework for monitoring vessel condition and providing decision support based on quantitative risk assessment, through a vessel state observer which is able to self-tune the important but uncertain vessel parameters by utilizing the available prior knowledge, vessel measurements, and information about the associated sea states. The tuned vessel parameters improve the information about the real-time vessel condition and consequently assist to improve the prediction accuracy of vessel seakeeping performance in the near future for the emerging wave conditions. Furthermore, the tuned results and the response prediction can then be applied to a decision support system, quantitatively evaluating potential risk and providing suggestions. The framework consists of 5 modules, i.e., wave data acquisition and processing, vessel data acquisition and processing, vessel seakeeping model tuning, real-time vessel motion and critical structural response prediction, and risk awareness and avoidance. Details of each module are described in the paper. The proposed framework can also assist in the development of autonomous ships.
Study on the Mechanism of Sand-Carrying and Comprehensive Performance of Viscous Slickwater
Authors: Bai Hao , Zhou Fujian , Wang Jie , Zhang Mengchuan 
Published: October 2021

Abstract
From the using history, we can see that conventional slickwater and guar fracturing fluid will be widely replaced by viscous slickwater in unconventional oil/gas fracturing. The viscous slickwater combines the advantages of slickwater and guar fracturing fluid but avoids the disadvantages of both, that includes drag reduction and good sand carrying capacity. This paper will analyze the viscous reducer’s molecular structure and viscoelasticity to find out the sand carrying mechanism. Using Haake RS6000 rheometer to test the elastic modulus and viscous modulus of conventional slickwater and viscous slickwater, reveal the sand-carrying performance from the perspective of viscoelasticity; using JEM 2100 LaB6 transmission electron microscope to test the molecular structure of two polymers, from the molecular space structure to analysis of its drag reduction performance. Finally, systematically evaluated the viscosity, drag reduction rate, sand-carrying, and gel-breaking properties of the viscous slickwater. The polymer enhances the viscous slickwater’s sand carrying performance by increasing the elastic modulus of fluid and reduces the drag in the flow through the intermolecular framework structure. The comprehensive performance evaluation results show that: 1) The apparent viscosity of the 0.6 wt% viscous slickwater is 80 mPa.s, which is close to conventional guar gum fracturing fluid; 2) When the linear flow rate reaches 5 m/s, the viscous slickwater drag reduction rate is greater than 75 %; 3) The viscous slickwater fluid static and dynamic sand carrying performance is better than conventional slickwater, which is close to guar gum fracturing fluid; 4) When the breaker concentration is equal to 50 ppm, the gel breaking time of viscous slickwater is about 35 mins and the residue content is less than 45 ppm. The conventional fracturing fluid will be more and more replaced by viscous slickwater during the fracturing of unconventional oil and gas reservoirs. This article provides a reference for researchers to understand its drag reduction and sand carrying performance.
Dynamic Failure Probability Evaluation of Subsea High Integrity Pressure Protection System by Bayesian Networks
Authors: Wang Chuan , Gou Jun , Yu Chao , Liu Yupeng , Luo Jianjun , Chen Qiufan 
Published: October 2021

Abstract
Safety instrument system is composed of sensor, logic solver and final actuator. It is widely used in process industry, such as oil and gas industry, chemical industry, metallurgy and electric power industry. It is an important measure to ensure the safety of production, which can effectively avoid the potential danger to people, equipment and the environment. However, when it breaks down, the consequences can be expected to be extremely serious. Therefore, HIPPS requires low risk, so it is necessary to quantitatively evaluate the dynamic performance of HIPPS to ensure the high safety of HIPPS during the design life cycle.
In this paper, a Bayesian network based method is proposed to evaluate the dynamic performance of HIPPS. The effects of different detection methods and maintenance methods on the dynamic performance of HIPPS were analyzed quantitatively. The results show that the performance of the system has been improved obviously after maintenance. Compared with the traditional method, the performance of HIPPS is improved by introducing partial stroke test. The sensitivity analysis shows that the failure rate has a great influence on the risk of HIPPS valve. Increased coverage of PST may improve the performance of HIPPS.
Dynamic Model Development of Wind Turbine Drivetrains by Using Sensor Measurements
Authors: van Binsbergen Diederik , Nejad Amir R. , Helsen Jan 
Published: October 2021

Abstract
This paper aims to analyze the feasibility of establishing a dynamic drivetrain model from condition monitoring measurements. In this study SCADA data and further sensor data is analyzed from a 1.5MW wind turbine, provided by the National Renewable Energy Laboratory. A multibody model of the drivetrain is made and simulation based sensors are placed on bearings to look at the possibility to obtain geometrical and modal properties from simulation based vibration sensors. Results show that the axial proxy sensor did not provide any usable system information due to its application purpose. SCADA data did not meet the Nyquist frequency and cannot be used to determine geometrical or modal properties. Strain gauges on the shaft can provide the shaft rotational frequency, while torque and angular displacement sensors can provide the torsional eigenfrequency of the system. Simulation based vibration sensors are able to capture gear mesh frequencies, harmonics, sideband frequencies and shaft rotational frequencies.
Performance of a Near Shore Oscillating Wave Surge Converter With Variable Flap Configurations in Various Sea Conditions
Authors: Sugar Landon , Filho Faete , Abdel-Salam Tarek , Muglia Michael , Duba Kurabachew 
Published: October 2021

Abstract
Oscillating Wave Surge Converters (OWSCs) are designed to enter survival mode during extreme wave conditions where they forego the opportunity to extract energy to preserve structural integrity. While this is a good tradeoff, it is important that OWSC technology progresses to a point where energy is constantly extracted as long as waves are present. This work addresses the need for an OWSC that can extract wave energy in a wide range of sea conditions while minimizing structural overloading by regulating the fluid-structure interaction. The OWSC being studied here was conceptually designed and patented by researchers at NREL. It consists of a flap face that resembles household blinds, where the flaps can be opened or closed to accommodate the sea conditions. The performance of this variable geometry OWSC in various, shallow wave states was studied in two numerical modeling programs. Of particular interest were the flap’s hydrodynamic coefficients and potential power generation at a specific reference site. This configuration was predicted to mitigate wave forces by allowing some of the wave energy to pass through the device, thus preserving its structural integrity.
Estimation of Wind Turbine Gearbox Loads for Online Fatigue Monitoring Using Inverse Methods
Authors: Mehlan Felix C. , Nejad Amir R. , Gao Zhen 
Published: October 2021

Abstract
In this article a novel approach for the estimation of wind turbine gearbox loads with the purpose of online fatigue damage monitoring is presented. The proposed method employs a Digital Twin framework and aims at continuous estimation of the dynamic states based on CMS vibration data and generator torque measurements from SCADA data. With knowledge of the dynamic states local loads at gearbox bearings are easily determined and fatigue models are be applied to track the accumulation of fatigue damage. A case study using simulation measurements from a high-fidelity gearbox model is conducted to evaluate the proposed method. Estimated loads at the considered IMS and HSS bearings show moderate to high correlation (R = 0.50–0.96) to measurements, as lower frequency internal dynamics are not fully captured. The estimated fatigue damage differs by 5–15 % from measurements.
Residual Strength of Tubular Columns With Localized Thickness Loss
Authors: Atteya Mostafa , Mikkelsen Ove , Oma Narve , Ersdal Gerhard 
Published: October 2021

Abstract
This paper provides a comprehensive finite element analysis to investigate the ultimate capacity of corroded members under concentric axial loads. The paper investigates previous experimental work on stocky and slender tubular columns with simulated patch corrosion and provides a numerical model that can estimate the columns capacities. Further, a parametric study is performed to investigate the effect of geometric parameters such as location, height, and width of corrosion patch on the ultimate capacity of corroded columns. Finally, the paper presents a comparison between laboratory tests to the formulae of superseded standards and numerical analysis using nonlinear finite element methods. The numerical model proposed in this paper show good agreement with the results from the experimental work.
The Impact of Cyclic Loading on the Flexural Strength of Ice
Authors: Kaplan Ihsan , von Bock und Polach R. U. Franz 
Published: October 2021

Abstract
Flexural strength measurements of sea ice in far inlying regions can experience continuous cyclic loading due to wave interactions. Furthermore, global warming leads to a continuous decrease of the Polar ice masses, resulting in an increased vulnerability of the integrity of the ice and its exposure to wave interactions and in consequence a growth of the marginal ice zone. In order to investigate the impact of cyclic loading on the flexural strength of ice, experiments with periodically loaded and previously unloaded ice samples is performed and analyzed. Previous research indicated both a weakening and a strengthening of the ice and the scope of this paper is also to enhance the understanding of the impact of cyclic loading of ice. This is relevant as ice might be subjected to several loading cycles before wave induced break-up and the question is whether the impact of cyclic loading needs to be accounted for in models. of its impact is addressed. The results show that the flexural strength of periodically loaded samples increases instead of fatigueing. Furthermore the ice has a very dynamic behaviour even at very low loading frequencies and small displacement-amplitudes in the micrometre range.
Modeling Relation Between Forward Speed and Propeller Speed of the Cruising AUV Using Multiple Regression Analysis
Authors: Umeda Jun , Fujiwara Toshifumi 
Published: October 2021

Abstract
This study addresses predicting the relationship between forward speed and propeller speed of an autonomous underwater vehicle (AUV) with a towed flexible cable using multiple regression analysis. Accurate prediction of the propeller speed corresponding to forward speed is important. The prediction requires considering various factors such as the dynamic behavior of a flexible cable, tidal currents, and AUV motions. The regression analysis based on in-service data of the AUV, therefore, established the relation between the forward speed and propeller speed considering the other factors. On the other hand, minimal independent variables in the regression model are desirable to avoid multicollinearity and overfitting. Variable selection based on the t-Test and sparse modeling was carried out to remove insignificant variables. We confirmed that the regression model presented in this study was in agreement with the observed data sufficiently, and the residuals of the regression model followed a normal distribution. The propeller speed predicted by the regression model considering only the forward speed of the AUV was comparable to the result predicted by the CFD calculation, not including the other factors. The result indicates the regression analysis can validate the results based on experiments and a numerical simulation.
State Estimation and Slug Control of the Subsea Multiphase Pipeline
Authors: Yu Chao , Wang Chuan , Deng Xin , Zhang XueLiang , Sun HaiFang , Peng WeiMing , Liu YuPeng 
Published: October 2021

Abstract
The simulation and control of the severe slugging flow in the subsea multiphase pipeline is the focus of research in the production and exploitation of oil companies. Severe slug flow results in severe fluctuations of pressure and flow rate at both the wells end and the receiving host processing facilities, causing safety and shutdown risks. To prevent the severe slugging flow regime in multiphase transport pipelines, an Ordinary Differential Equation (ODE) model is established by using the mass conservation law for individual phases in the pipeline and the riser sections. Then, the proposed model is compared to the results from the OLGA simulation. A comparative study of different slugging flow control solutions is conducted. Unscented Kalman Filter (UKF), Wavelet Neural Network (WNN) and UKF&WNN are used for state estimation and combined with PI controller. The UKF and WNN are good nonlinear filters. However, when the nominal choke opening is increased, they work unsatisfying. The UKF&WNN observer shows slightly better results than UKF and WNN when the system has high input disturbance.
Minimum Miscibility Pressure of CO2/Hydrocarbon Systems Within Nanopores
Authors: Yang Gang , Li Xiaoli 
Published: October 2021

Abstract
Minimum miscibility pressure (MMP), as a key parameter for the miscible gas injection enhanced oil recovery (EOR) in unconventional reservoirs, is affected by the dominance of nanoscale pores. The objective of this work is to investigate the impact of nanoscale confinement on MMP of CO2/hydrocarbon systems and to compare the accuracy of different theoretical approaches in calculating MMP of confined fluid systems. A modified PR EOS applicable for confined fluid characterization is applied to perform the EOS simulation of the vanishing interfacial tension (VIT) experiments. The MMP of multiple CO2/hydrocarbon systems at different pore sizes are obtained via the VIT simulations. Meanwhile, the multiple mixing cell (MMC) algorithm coupled with the same modified PR EOS is applied to compute the MMP for the same fluid systems. Comparison of these results to the experimental values recognize that the MMC approach has higher accuracy in determining the MMP of confined fluid systems. Moreover, nanoscale confinement results in the drastic suppression of MMP and the suppression rate increases with decreasing pore size. The drastic suppression of MMP is highly favorable for the miscible gas injection EOR in unconventional reservoirs.
Buoyant Miscible Jets in the Plug and Abandonment of Oil and Gas Wells
Authors: Hassanzadeh Hossein , Eslami Ali , Taghavi Seyed Mohammad 
Published: October 2021

Abstract
The plug and abandonment (P&A) operation is the final stage in the life cycle of oil and gas wells. The aims of the P&A operation are to seal the well and permanently maintain the well-integrity similar to that of the original natural caprock. Using this approach, it is possible to isolate fluids movement between different strata, to prevent environmental disasters. Generally, the main steps in the P&A operation are (i) accessing the annulus section of the well, (ii) cleaning the defected area, and (iii) placing the cement plug barriers into the target area. To prepare the target area and avoid cement plug contamination, a cleaning process is required inside and outside the casing. The jet cleaning process is one of the effective methods for the cleaning step, in which a liquid of a higher density is usually injected into the target area to displace a lighter ambient fluid. During the jet cleaning process, several forces affect the cleaning efficiency, including inertial, viscous and buoyancy forces.
In this work, we analyze a fundamental component of the jet cleaning process in the P&A operation, via experimentally studying the characteristics of a miscible positively buoyant jet. In our work, a heavy fluid is injected downwards into a large rectangular tank filled with a light ambient fluid. Due to the large dimensions of the experimental tank, the wall effects on the flow are neglected, i.e. we consider a free jet. We investigate some of the parameters affecting the behaviour of our positively buoyant jets, such as the injection velocity, the nozzle diameter, and the ratio between the viscosity of the jet fluid to that of the ambient fluid. In the parameter ranges of our interest, the jet flow exhibits certain critical flow features, such as the laminar length (i.e. the initial stable part of the jet where the injection fluid remains laminar and does not mix with the ambient fluid) and the spread angle (i.e. the area occupied by the jet). Our results show that both the laminar length and the spread angle decrease by increasing the injection velocity. In addition, increasing the viscosity ratio results in increasing the maximum laminar length and decreasing the spread angle. These results can help to better design an efficient cleaning in the P&A operation of oil and gas wells.
Benchmark Study and Uncertainty Assessment of Planar Motion Mechanism Tests on KVLCC2 in a Circulating Water Channel
Authors: Ma Chengqian , Ma Ning , Gu Xiechong 
Published: October 2021

Abstract
The benchmark experiment research for the maneuverability of a small-scaled ship model is critical for investigating the scaled effect on the maneuvering hydrodynamic derivatives, and validating the CFD technology. Till now, there is little research on the benchmark study and uncertainty analysis for the small-scaled ship which is frequently used in the Circulating Water Channel (CWC). Therefore, an experimental study of the planar motion mechanism (PMM) tests is performed in the CWC of the SJTU. The PMM tests performed in the CWC can avoid some disadvantages of those in the towing tank, such as the limitations on the acquisition time and frequency due to the size of the towing tank, interference of the carriage on the signal acquisition. In addition, the flow field visualization for the tests in the CWC is easier to achieve compared with the experiments in the towing tank, which helps the scholars to understand the characteristic of the wake field during maneuvers. The benchmark ship is the KVLCC2 with a scaled ratio of 1/128.77. The hull forces are recorded and processed to obtain the maneuvering hydrodynamic derivatives. To assess the quality of the acquired data, randomness analysis, stationarity analysis, normality analysis, and statistical convergence are performed for the PMM tests in the CWC for the first time. Finally, the uncertainty analysis (UA) method for the PMM tests performed in the CWC is also developed.