bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Study of Underwater Inflatable Co-Prime Sonar Array (UICSA)
Authors: Li Yanjun , Thomas Jordan , Ouyang Bing , Su Tsung-chow , Ahmad Fauzia 
Published: December 2020

Abstract
Underwater Inflatable Co-Prime Sonar Array (UICSA) is a compact sonar array assembly that can be deployed in the ocean then morph into a predetermined length to work. As a sonar array, it is critical to reduce the structural deflection and maintain sensor spacing under external forces like ocean currents. The array, like the mooring system, is affected by ocean currents. In this paper, we conduct the numerical study of the morphed UICSA made of different materials in different current conditions using OrcaFlex. The results can evaluate the performance of different UICSA systems and determine the optimal UICSA design.
Retracted: “On the Role That the End Shape of an Underwater Vehicle Plays on Wave-Induced Vertical Forces” [ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering, Volume 6B: Ocean Engineering, Virtual, Online, August 3–7, 2020, Conference Sponsors: Ocean, Offshore and Arctic Engineering Division, ISBN: 978-0-7918-8438-6, Copyright © 2020 by ASME. Paper No. OMAE2020-18400, V06BT06A048; 10 pages; doi: 10.1115/OMAE2020-18400]
Authors: ASME  
Published: December 2020

Abstract
This paper was removed from publication at the author’s request. January 15, 2021.
Copyright © 2021 by ASME
Dynamic Load Analysis of the Tower Structure of a Floating Wind Turbine Under Random Wind and Wave Excitation by Detuning Blade Pitch Controller Proportional Gains
Authors: Shilun Zhao 
Published: December 2020

Abstract
This paper carried out coupled non-linear aero-hydro-servo-elastic simulations of a semisubmersible floating wind turbine under normal and severe sea states at various wind speeds. The NREL 5MW turbine was modeled by the SIMO-RIFLEX module in SESAM with hydrodynamic gathered by the WADAM code. A taut leg mooring system with redundancy was applied to account for the relatively shallow water site in the South China Sea. By detuning KP, the proportional gain coefficient of the blade-pitch controller, the platform motions and dynamic load effects on tower structure were investigated. It was found that the reduction of KP mitigates the load effects on tower top and base connections in certain load conditions. The motion performance of the platform was improved to some extent. The generator power output, as well as the fluctuation, were analyzed. Finally, suggestion on detailed blade pitch gains tuning according to specific wind speed and sea state was given.
Real-Time Evaluation of Structural Integrity of Tubulars in Directional Wellbores
Authors: Ramba Viswanth , Selvaraju Senthil , Subbaih Senthilmurugan , Palanisamy Muthukumar , Gauba Sanjaykumar , Jandial Suresh 
Published: December 2020

Abstract
The actual forces acting on the drill string in directional drilling is relatively complex than vertical drilling. In this work, the different forces acting on the drill string during directional drilling are analyzed using actual drilling data. The calculation of such forces can help driller to predict downhole complications that are caused due to drill string failures. The estimation of effective tension force at the top of the drill string requires both true tension forces and buckling stability forces acting on the drill string. True tension is a function of weight component of the drill string, the forces acting on BHA due to change in cross-sectional area and bottom pressure force acting on the drill bit and the drag forces acting on the string. The buckling stability force is defined as the difference between the internal and external force acting on the drill string. The effective tension is used to calculate the hookload and normal forces acting on the drill string. The calculation of the hookload at the deadline can help the driller to compare with actual hookload and take corrective action before the complication occurs. Further, that requires the relationship between the effective tension force at the top of the drill string and the hookload measured at the deadline. Such a relationship can be established by knowing the efficiency of the rig components such as sheave, block and tackle system, hydraulic lines and weight parameter for remaining components.
Considering the unavailability of the efficiency of these components, the following model parameters are introduced: sheave efficiency, correction factor for efficiency of block and tackle system, hydraulic lines and weight parameter for the remaining components.
All the three parameters are estimated by tuning the model with actual directional drilling data.
In another aspect, the true tension is used to locate the position of neutral point by calculating the axial stress along the drill string. The proposed model is capable of predicting the hookload at the deadline, position of neutral point and normal forces acting along the drill string. The abnormal behavior of the normal forces along the drill string is used to locate the key-seating zones. Further, the model is validated with actual directional drilling data and successfully implemented in real-time monitoring platform and the model is found to be capable of predicting downhole complications such as drill string parting and improper hole cleaning. This study is expected to provide theoretical bases for understanding the stability regions of directional well.
Capturing Wake Stiffness in Wake-Induced Vibration of Tandem Cylinders
Authors: Soares Bruno , Srinil Narakorn 
Published: December 2020

Abstract
When a downstream circular cylinder is in the vicinity of the disturbed wake flow which is originated from the presence of an upstream cylinder, fluid-structure interactions due to vortex- and wake-induced vibrations may coexist. Their combined effects are of practical concern for offshore structures deployed in an array or proximity such as marine risers, pipelines and mooring lines. The wake flow deficit law and wake-induced drag and lift hydrodynamic forces are modelled based on the boundary layer theory, which is modified to account for the oscillation of the upstream cylinder. Unsteady drag and lift forces associated with the vortex-induced vibration (VIV) and wake-induced vibration (WIV) are represented dynamically by van der Pol-type wake oscillators. The present paper proposes a new modelling concept and framework capable of evaluating the combined WIV-VIV of tandem circular cylinders in comparison with experimental data, capturing a key feature of the wake stiffness associated with WIV. An equivalent natural frequency based on the wake stiffness mechanism behaves equivalently to the WIV frequency. Numerical studies show that the downstream cylinder may respond in a multi-frequency scenario at specific reduced velocities. The prediction model captures the wake stiffness trend similar to the experimental observation. The correlation to the wake stiffness concept allows the identification of situations for which the downstream cylinder is mainly governed by the WIV mechanism resulting in largest vibration amplitudes.
Motion Decay Simulations of a Moored Wave Energy Converter
Authors: Jiang Changqing , el Moctar Ould , Schellin Thomas E. , Paredes Guilherme Moura 
Published: December 2020

Abstract
Significant cost reductions are required for marine renewable energy to become competitive. Aside from the deployment of arrays, one key area that has been identified as having potential for cost reductions is the mooring system. A challenge, therefore, is to design mooring systems which can satisfy their primary role of station keeping while being affordable and durable.
This paper presents the effects of three different mooring configurations on the motion behavior of a buoy type wave energy convertor, considering nonlinear mooring-induced fluid-structure interactions, such as the associated viscous effects. To simulate motion decay, an overset mesh method that coupled a dynamic mooring model with the Navier-Stokes equations flow solver OpenFOAM was adopted. The mooring configurations comprised an all catenary system, a catenary system with buoys, and a catenary system with buoys and clump weights. The favorable agreement between the simulations and experimental measurements validated the coupled numerical approach for simulating different mooring configurations. The mooring systems influenced not only restoring force characteristics, but also total damping of the system, which demonstrated the importance of considering mooring-induced damping when investigating moored offshore structures.
A Simple and Effective Method to Predict the Generation of Black Carbon in Oilfields
Authors: Dai Guohua , Wan Yufei , Liu Chunyu , Sang Jun , Wang Wenguang , Qian Xin , Hao Ming , Liu Renwei 
Published: December 2020

Abstract
As an important safety discharge facility in petrochemical industry, flare is widely used in offshore and onshore oil and gas fields to relieve pressure, vent unwanted gases. This open-air combustion system oxidizes the fuel gases into carbon dioxide and water vapor and hence avoids the contamination of air with harmful gases that cause air pollution and climate change. With the increasingly strict requirements of environmental protection and the implementation of low-carbon development policy, the black carbon (soot) caused by incomplete combustion from the flare will be strictly controlled. At present, there is no simple and effective method to determine whether the flare produces visible black carbon which exacerbates the pollution. According to the investigation on site, there are different degrees of black carbon emission from the flares both in the onshore and offshore oilfield, which brings some troubles to the petroleum corporation. Based on a flare tip and the associated gas from an oilfield in Bohai Bay of China, a simulation model, which in accordance with the actual situation, was established with the Computational Fluid Dynamics software. The Non-Premixed Combustion model was used to simulate the Combustion, the P-1 model was adopted to calculate the thermal radiation and the Moss-Brookes model was selected to compute the generation of black carbon. The feasibility of the model was demonstrated by comparing the simulation results with the field test results. Then the limitation of current conventional practice to predict whether the soot is produced, was demonstrated with the model. At the same time, the production rate of black carbon under different conditions of components and fraction were calculated. After a comprehensive analysis and comparison, a simple, directly and effective method to predict the soot was proposed. When the C-to-H ratio of fuel gas is greater than 0.273, it tends to visible soot, and when the C-to-H ratio is greater than 0.285, it tends to heavy soot, which is in line with the actual in site. Therefore, the method can be applied to predict the level of the generation of black carbon in the engineering.
Hull Structural Strength Evaluation Based on Fiber Bragg Gratings Pressure Sensors to Measure Spatial Pressure Distribution on Ship’s Hull in Waves
Authors: Komoriyama Yusuke , Ota Daichi , Ma Chong , Sawada Hiroshi , Oka Masayoshi , Matsui Sadaoki , Houtani Hidetaka 
Published: December 2020

Abstract
In this study, the feasibility of Fiber Bragg Gratings (FBG) pressure sensors is verified for hull structural strength evaluation. To investigate the effectiveness of FBG pressure sensors for the strength evaluation, the towing tank test is carried out with a pure hydro-structural (PHS) ship model, which is capable of elastic deformation. FBG pressure sensors are installed on the outer hull surface and FBG strain sensors are installed inside the hull to calculate a vertical bending moment (VBM). Measured water pressure is interpolated on the whole hull surface by using the weighted average approach based on relative distance. Finite Element Analysis (FEA) is carried out based on interpolated water pressure. In FEA, inertia force is considered according to the inertia relief method, and VBM is calculated by FEA results. The strain measured by FBG strain sensors is transformed to VBM based on the calibration coefficient obtained by the vertical bending test. Finally, VBM obtained by the measured water pressure and strain are compared. As a result, VBM obtained by the measured water pressure is consistent with ones obtained by the measured strain. Therefore, the availability of water pressure measured by the FBG pressure sensors is validated for the hull structural strength evaluation in terms of VBM.
Transient Response of the Steel Plate to Underwater Explosion Bubble
Authors: Chen Yingyu , Yao Xiongliang , Liu Liangtao , Gan Ning , Cui Xiongwei 
Published: December 2020

Abstract
In this paper, a coupling eulerian langarian method (CEL) is used to study the interaction between a collapsing underwater explosion bubble and a steel plate. The VOF method is used to simulate the physical process of bubble growth, contraction and collapse, while the finite element method is used to calculate dynamic response of the steel plate. By establishing the three dimensional numerical model, the study reveals the interesting insights into the complex problem of interaction a underwater explosion bubble and a steel plate, including the physical process of bubble growth, contraction and collapse, the dynamic response of the steel plate, as well as the wall pressure induced by the bubble dynamic. The results indicate that the elastic-plastic plate will generate permanent deformation loaded by the water jet; owing to the deformation of the nearby structure, the bubble shows as a “hazel” in the bubble contraction phase and forms toroidal jet which leads the bubble into several toroidal bubbles in the bubble collapse phase. This paper aim at proposing an effective numerical method which can be useful for the problem of strong interaction between bubble and structure.
Research on the Obstacle Avoidance Strategy for the Wave Glider in the Maritime Environment Containing Dynamic Obstacles Based on the Improved Artificial Potential Field Method
Authors: Wang Daoyong , Tian Xinliang , Zhang Xiantao , Guo Xiaoxian , Wang Peng 
Published: December 2020

Abstract
As a wave-propelled and persistent unmanned surface vehicle, wave glider has been widely applied in marine monitoring. Due to its long voyage, the wave glider inevitably encounters various obstacles at sea, which may cause collision accidents. However, considering the characteristics of weak maneuverability and underactuation of it, the obstacle avoidance for the wave glider is challenging. In this paper, the dynamic obstacle avoidance strategy for the wave glider based on an improved artificial potential field (IAPF) is proposed. The IAPF is committed to addressing the local minimum in the traditional artificial potential field and the obstacle avoidance difficulties caused by the weak maneuverability of the wave glider. Various simulations are conducted to demonstrate the feasibility of the proposed strategy by adopting an eight-degree-of-freedom mathematical model of the wave glider. The simulation results show that the wave glider can accomplish the obstacle avoidance task with the proposed IAPF algorithm when facing with different dynamic obstacles under various marine environments.
Autonomous Surface Vessel Obstacle Avoidance Based on Hierarchical Reinforcement Learning
Authors: Zhou Chang , Wang Lei , Yu Shangyu , He Huacheng 
Published: December 2020

Abstract
The obstacle avoidance problem of autonomous surface vessels (ASV) has attracted the attention of the marine control research community for long years. Out of safety consideration, it is important for ASV to avoid all kinds of obstacles like shores, cliffs, floaters and other vessels. Developing a heading and path planning strategy for ASV is the main task and the remaining challenge. Traditional obstacle avoidance algorithms lead to too much computing in working environment. The issue of computation cost can be solved by training obstacle avoidance models with reinforcement learning (RL). By using the RL method, the ASV will choose the most efficient action according to the ASV’s experience it learned from the past. In this paper, RL is adopted to design a decision-making agent for obstacle avoidance. To train the obstacle avoidance model under a sparse feedback environment, hierarchical reinforcement learning (HRL) method is applied. Using this algorithm, better obstacle avoidance performance and longer survival time can be achieved. Memory pool modification and target network modification are also used to smooth the training process of the ASV. Simulation results demonstrate that HRL can make the learning process of un-manned ship’s obstacle avoidance smoother and more effective. Also, the living time of ASVs is improved.
Modeling Fluid Flow in Tight Unconventional Reservoirs: Micro/Nano Scale Approach
Authors: Qaddoura Rabab , Aldhuhoori Mohammed , Alkuwaiti Hamda , Belhaj Hadi 
Published: December 2020

Abstract
The need for a tool to predict transport phenomena in petroleum unconventional tight reservoirs is placing more stringent demand on establishing more realistic models beyond the currently used viscous and inertial dependent models.
Since diffusion is the principal mechanism in tight unconventional reservoirs that take place in both Micro and Nano scales, a diffusive term was added to the diffusivity model that operates both viscous and inertial forces, introduced by (Belhaj, et al., 2003).
This diffusive term is a modified Fick’s 1st Law. It counts for the flow velocity caused by the diffusion process. Using the three-term model as a rate equation, in addition to the continuity equation and the EOS, a new model (a form of PDE) has been developed.
The new model works ideally in unconventional tight reservoirs where oil and/or gas flow. The model has been numerically solved and tested. A comprehensive parametric study has been conducted and revealed clear trends. It has been concluded that diffusion mechanism contribution to flow increases with low permeability of the medium and low viscosity of the flowing fluid. An index (a combination of permeability and viscosity) has been developed and used to verify the influence and impact of the diffusion forces.
Experimental Study of Wave Loading by Internal Solitary Waves on a Submerged Slender Body
Authors: Ji Meng , Chen Ke , You Yunxiang , Zhang Ruirui 
Published: December 2020

Abstract
Although ocean structures are complex, they all can be disassembled into a number of simple-shaped parts. One common shape is the slender body mentioned in this paper, and we focus on studying the mechanism of this shape. Experiments were carried out to study features of wave loads exerted by internal solitary waves (ISWs) on a submerged slender body. ISWs were generated by a piston-type wave maker in a large-type density stratified two-layer fluid wave flume. Using a three-component force transducer, the force variation of three degree of freedom (DOF) on the model was recorded. A satisfactory prediction method is established for ISWs on a submerged slender body based on internal solitary wave theory, Morison equation and pressure integral. Calculations based on this new prediction method are in good agreement with the experimental results. The experimental results and calculations show that, different incident angles, wave amplitude and layer thickness ratio have great effects on the wave loads, especially transverse incident waves bring much more severely influence. Besides the forces increase linearly with the wave amplitude becoming larger, and the maximums of the horizontal forces increase with the layer thickness ratio increasing.
Comparison Between ERA5 and CFS Datasets of Extratropical Cyclones Associated With Extreme Wave Events in the Atlantic Ocean
Authors: Gramcianinov C. B. , Campos R. M. , Guedes Soares C. , de Camargo R. 
Published: December 2020

Abstract
Atmospheric and ocean datasets using numerical modeling allied to data assimilation are valuable tools for planning and maintaining marine activities, particularly due to their spatial coverage and resolution. However, even modern analyses and reanalyses present critical errors where cyclonic winds are often underestimated in some locations, leading to issues in wind-wave climate hindcasts and forecasts. This work aims to evaluate two of the newest datasets available regarding their ability to reproduce extratropical cyclone tracks associated with extreme waves in the Atlantic Ocean. The analysis is focused on the storm track position and cyclone intensity, two important features that control the wave climate. The datasets used are the ECMWF’s ERA5 and NCEP’s CFSv2. The cyclones are identified and compared between 2011 and 2018 using the relative vorticity at 850hPa and the intensity is measured through the 10-meters wind speed. The results show that the differences in track density exist mainly in coastal areas and they can be related to the coarser resolution of CFSv2 compared to ERA5. CFSv2 presents a higher number of cyclones associated with extreme wave events in the South and North Atlantic, corresponding to 87.1% and 89.2% of the cyclones identified, while ERA5 presents 66.6% and 59.5% respectively. The maximum intensity distribution shows that CFSv2 tends to produce more intense cyclones than ERA5, even for identical storms in the datasets. The distances of matching cyclones in the two datasets are around 0.5°.
Characterization and Modeling of Asphaltenes for Complex Reservoirs in Venezuela: State of the Art
Authors: Rodriguez M. Fernancelys 
Published: December 2020

Abstract
Asphaltenes are complex hydrocarbon molecules that are in suspension in the oil, stabilized by resins, which may cause severe production issues at reservoir and surface conditions. High asphaltene and resin contents is one of the main characteristics of the Venezuelan unconventional oils (highly viscous oils) in the Orinoco Oil Belt. This high concentration of resins in the oil maintains the aggregates of asphaltenes dissolved in the continue oil phase avoiding asphaltene precipitation/ flocculation/deposition issues at field conditions as some Venezuelan conventional oil reservoirs located in northern Monagas State in which unfavorable resins/asphaltene (R/A) ratios promote the precipitation of asphaltenes.
Conventional oil reservoirs in northern Monagas show gravitational segregation, this is the case of Carito-Mulata and Santa Barbara Field, varying from an upper zone of critical fluid behavior to a black oil zone in the lowest part of the structure in which the current pressure levels induce asphaltene precipitation, causing problems by plugging reservoirs, wells and pipelines, severely affecting oil and gas production. This causes increased production costs (chemical cleaning) and/or irreversible formation damage when reservoir pressures are less than asphaltene precipitation/flocculation onset pressures. Therefore it is necessary to characterize the asphaltene thermodynamic behavior and include this in reservoir numerical-simulation models, with the aim of increasing the reliability of the results and optimizing production strategies.
Reproducing the thermodynamic behavior of asphaltenes is very complex, both experimentally and in numerical simulation, especially in terms of description and measurement of the degree of asphaltene-porous media interaction and the effect of injected fluids into the reservoir (EOR methods such as miscible/non-miscible gas injection or chemical flooding). Nevertheless, efforts have been done by the Venezuelan National Oil Company and collaborators, both at laboratory and simulation scales, to study the asphaltene thermodynamic behavior and the effect of permeability reduction in the porous media and its impact on the production profiles for complex Venezuelan reservoirs.
This article presents a literature review of the Venezuelan experience for the characterization and modeling of asphaltenes for conventional and heavy oil reservoirs.