bluuebunny/crossref_metadata_2025_split huggingface dataset:
Risk Assessment and Countermeasure on Drilling and Production Process of Deep Water Gas Hydrate in the South China Sea
Authors: Yuan Zhu , Kang Liu , Guoming Chan 
Published: December 2020

Abstract
Deep-water natural gas hydrate has high environmental risk and high technical difficulty in drilling and production. In order to promote the development of gas hydrate, we develop the assessment methods and control technologies for the operation risk during hydrate drilling and production. The work completed includes:
(1) Safety analysis of conductor and wellhead for the hydrate drilling and production
Establish a pipe-wellhead stability model to determine the drilling and working conditions under different working conditions.
(2) Risk assessment of wellbore blockage in hydrate drilling and production
Construct a wellbore multiphase flow analysis model to determine the amount of drilling inhibitor injection; obtain the location and extent of the hydrate blockage.
(3) Risk assessment of wellbore instability in hydrate production
Combined with hydrate formation properties, ground stress distribution and casing mechanics model, the position of the formation instability, and the damage of casing crushing is determined.
(4) Gas diffusion risk assessment due to hydrate decomposition in water
Study the distribution of underwater gas diffusion formed by large-area decomposition of hydrate to get the overflow flow risk.
(5) Safety model and process risk assessment of hydrate drilling operations
Conduct hazard identification and operation safety analysis of hydrate drilling operations, determine the risk level of each operation stage, and support the drilling operation.
Design for Flexible Connector of Multi-Floating Structure
Authors: Hongtao Yuan , Gang Chen , Wei Zhang , Yan Yin , Yuhan Wang , Chao Wang 
Published: December 2020

Abstract
For the connector between the modules of a regular hexagonal multi-floating structure, it designed a flexible connector based on hinge joints and spin joints, which allowed part of rolling, pitching and torsion between adjacent modules to release bending moment and strain. A 221m multi-floating structure hydrodynamic calculation model was modeled in this paper. Firstly, the connector loads under the regular waves were calculated by ANSYS Aqwa. Secondly, structural model of a flexible connector was built by SolidWorks basing on the finite element theory. It analyzed structural strength of the flexible connectors under different load conditions of a series of wave direction angles by ANSYS Static Structral. Lastly, the results show that the design of the multi-floating structure connectors met the design requirements in different working conditions.
Application of Peak Distribution Method for Response Based Analysis of Mooring Lines Under Tropical Storms
Authors: Ghasemi A. , Drobyshevski Y. , Kimiaei M. , Efthymiou M. 
Published: December 2020

Abstract
Response based analysis (RBA) is a comprehensive approach for the prediction of extreme responses and design metocean conditions of offshore facilities. For RBA, the structural system needs to be modelled, and its behavior analyzed when subjected to large metocean datasets, usually comprising thousands of different sea states. Due to the dynamic and nonlinear behavior of mooring systems in floating structures, application of conventional time domain analysis for RBA of these systems is a computationally demanding process. Hence, investigation of faster solvers and more efficient methods for the RBA is inevitable. Peak distribution method (PDM), which has recently been introduced and used for response analysis of mooring systems under extreme design conditions, is a possible solution to reduce the computational efforts in RBA by reducing the number of simulations.
This study explores the utilization of the PDM for RBA of the mooring system of a turret-moored large FPSO subjected to tropical storms. Large variability of metocean parameters within such storms limits the applicability of intuitive judgement for the selection of governing sea states. The results are compared through both time-domain and frequency-domain simulations and a computationally efficient methodology is proposed. It provides a general robust framework of computing the extreme value distribution of the system response. The proposed methodology can be used for RBA of mooring lines tension under storm conditions comprising large number of sea states.
Numerical Study on the Performance Analysis and Vibration Characteristics of Flexible Marine Propeller
Authors: Ashok Kumar S. , Anantha Subramanian V. , Vijayakumar R. 
Published: December 2020

Abstract
This paper addresses the hydro-elastic performance of two composite marine propellers at operating condition and compares the results with conventional materials. The study involves three stages namely, design and development of a B series propeller, hydrodynamic and structural performance analysis in uniform flow and free vibration test both in dry and wet condition. In order to perform the hydro-elastic based fluid structure interaction (FSI), Co-Simulation method was adopted to couple Reynolds Averaged Navier-Strokes Equation (RANSE) based Computational Fluid Dynamics (CFD) solver and finite element method (FEM) solvers. The open water characteristics such as thrust coefficient (KT), torque coefficient (KQ), and open water efficiency (ηO) were analyzed as a function of advance velocity (J) of the propeller. A detailed study of the various blade materials by varying mechanical properties are presented. The results obtained show the variation of stress and deflection on the blade, along with the influence of the blade deformation on the performance of propeller. The vibration behaviour of the propellers were also analysed by Block-Lanczos method in FEM solver to obtain the natural frequencies and the mode shapes using Acoustic Fluid-Structure Coupling method for both dry and wet condition. Results showed that composite propeller have better hydro-dynamic property and lower vibration than metal propeller.
Development of Closed Formula of Wave Load Based Upon Long-Term Prediction: Heave Acceleration and Pitch Angle
Authors: Shinomoto Kyohei , Matsui Sadaoki , Sugimoto Kei , Ashida Shinsaku 
Published: December 2020

Abstract
In order to ensure the structural safety of a ship, the most severe sea states she is expected to encounter throughout her service life need to be given consideration. This is the reason why the maximum loads corresponding to such sea states are typically specified in classification society structural rules such as the Common Structural Rules (CSR) of the International Association of Classification Societies (IACS). The maximum loads used for the structural design of a ship can have a significant impact on not only her structural safety, but also her hull construction cost; therefore, it is very important that the loads be accurately estimated. The linear term of the maximum loads typically specified in some classification society rules is equivalent to a long-term predicted value with an exceedance probability of 10−8. Since the maximum loads specified in classification society rules such as the CSR were developed specifically for specific ship types, their effective application to other ship types may be somewhat limited.
Aim of our larger study is to develop a closed formula of long-term prediction for maximum loads. The formula has high accuracy and can be applied to any ship size and type. This paper focused on the heave acceleration and pitch angle, which are used for the calculation of internal loads and so on. A formula which takes into account such as the standard deviation of the hull response in irregular waves and the directional distribution of irregular waves was proposed. Main ship parameters such as ship length L, breadth B, draft d, block coefficient Cb, and water line area coefficient Cw were used for formulating the long-term prediction. The accuracy and effectiveness of the proposed formula were confirmed through various numerical calculations using a linear seakeeping analysis code developed by ClassNK. The calculation covers 154 ship models (77 existing ships × 2 loading conditions per ship).
Vortex-Induced Vibration of a Spherical Body With Free Surface Effects: Application to Tugboats With Low Length-to-Beam Ratio
Authors: Chizfahm A. , Joshi V. , Jaiman R. K. 
Published: December 2020

Abstract
Flow-structure interactions of submerged or floating bodies can lead to undesired behavior in many marine and offshore engineering applications. In this paper, we consider a complex nonlinear dynamical system of unsteady wake flow interacting with a freely moving tugboat in open water. To meet the operational demands of compact, agile, and high power ship-handling, new hull forms of tugboats are designed with low length-to-beam ratios and rounded sterns. While the hydrodynamic design with low length-to-beam ratios provides improved directional controllability, it can be challenging for tractor tugboats due to the massively separated wake flow with the vortex shedding. These wake vortices can cause large fluctuating yaw moments and possibly a strong fluid-structure coupling via synchronization or lock-in. Of particular interest, the proposed study will focus on the physical mechanism and control of flow-induced oscillations with free-surface effects via our in-house fully-coupled three-dimensional fluid-structure-free-surface interaction solver. Stabilized finite element based methods will be employed to discretize the partial differential equations that arise from the mathematical modeling of the physical phenomena considered. We will begin with a fundamental understanding of coupled dynamics of a canonical geometry of a freely vibrating sphere at free-surface. The physical insight gained will then be applied to a realistic tugboat configuration. We aim to understand the fundamentals of vortex-shedding modes and the coupled dynamics pertaining to the flow-induced vibration (FIV) response of a freely vibrating sphere (a prototypical problem for a rounded tugboat) in all three spatial directions. To predict and analyze the vortex synchronization regimes and the wake patterns, the FIV response of the sphere at a low mass ratio is investigated over a broad range of reduced velocities and Reynolds numbers. We find that the sphere begins to move along a linear trajectory with hairpin vortex-shedding mode, eventually transforming into a circular trajectory with spiral mode in its stationary state for Re ∈ [2000–6000]. We systematically examine these mode transitions and the motion trajectories in the three degrees-of-freedom for higher Reynolds number up to 15,000 which has not been studied in detail in the literature. Finally, we will look into the effect of free surface on the FIV response of the sphere piercing the free surface and will link our fundamental results with a realistic configuration of tugboat undergoing vortex-induced oscillation with free surface effects.
Retracted: “Nonlinear Integrated Simulation of Dropped Container Impact With Platform Deck” [Proceedings of the ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering, Volume 2A: Structures, Safety, and Reliability, Virtual, Online, August 3–7, 2020, Conference Sponsors: Ocean, Offshore and Arctic Engineering Division, ISBN: 978-0-7918-8432-4, Copyright © 2020 by ASME. Paper No. OMAE2020-18581, V02AT02A012; 10 pages; doi: 10.1115/OMAE2020-18581]
Authors: ASME  
Published: December 2020

Abstract
This paper was removed from publication at the author’s request, August 30, 2021.
Copyright © 2021 by ASME
Direct Numerical Simulations on the Flow Normal to a Plate With Transit Shape From Circular Disk to Triangle
Authors: Wang Huaicheng , Tian Xinliang , Zhao Yakun , Li Jun , Li Xin , Lu Wenyue 
Published: December 2020

Abstract
This paper presents a numerical study of the flow normal to a triangular plate. A total of four plates with the same frontal area Ar and different curved edges are used. The curvature of edges is determined by the compression ratio k (k = 0.3, 0.4, 0.5, 0.8; the large value of k corresponds to the large curvature of the edges). A disk of χ = 50 (χ is the diameter-thickness aspect ratio) is used as the reference disk. The Reynolds number Re based on the characteristic length is up to 250. Four states are observed and denoted as: (I) steady and geometric symmetry state (SG); (II) steady and reflectional symmetry state (SR); (III) reflectional symmetry breaking with periodic flow (RSB); (IV) chaotic state (CS). The critical Reynolds numbers at the first two stages (Rec1, Rec2) decrease with the increasing k, indicating that flow of the plates with a larger curvature is more unstable. Therefore, we believe that the flow around a triangular plate is more stable than that around a circular disk.
Effect of Multiple Fracture Initiation on the Accuracy of Hydraulic Fracturing Simulation
Authors: Bennour Ziad , Mahmud Walid Mohamed , Ermila Mansur 
Published: December 2020

Abstract
Hydraulic fracturing is a stimulation technique in which the formation is fractured using high pressure exerted by a fluid. The induced fracture increases the permeability of the formation by providing conductive channels to the formation which results in improved fluids productivity.
Hydraulic fracturing is a common practice in oil and gas, particularly in the development of unconventional low porosity and low permeability reservoirs. However, as the hydraulic fracturing technique is costly, considerable preparations efforts must be made before executing the fracturing operation including simulating the intended fracture model.
A simulation model of a hydraulic fracturing assists in forecasting and controlling the intended fractures that are to be induced. Although the simulation model can be helpful, it may not exactly mimic or predict the actual initiated fractures due to the complex nature of the actual fracturing process. Thus, the simulated model and the actual fracture might differ in many ways which results in an uncertainty in the simulated fracture model.
Therefore, in order to reduce uncertainty, initial data input and assumptions made before and during the fracturing simulation need to be precise in order to obtain accurate simulation results. The growth of a single fracture is often assumed during the simulation of hydraulic fracturing which maybe incorrect as multiple fractures may initiate at the start or middle of the actual fracturing treatment and can have significant effect on the simulated fracturing results.
This paper proposes a method to minimize the difference between fracturing simulation and actual fracture treatment results by utilizing sensitivity tests to the main fracturing parameters. Thus, the initial actual fracturing results were used to detect the occurrence of multiple fractures where the latter was considered to enhance the upcoming simulation accuracy of the proposed treatments. The analysis of high net pressure data during the actual treatment indicates the possible presence of multiple fractures where history matching between actual treatment and simulation results data can give an estimate on when and how many multiple fractures were initiated during the fracturing treatment.
As a result, the data analysis showed that multiple fractures initiation had a significant effect on the fracture simulation results and the assumption of a single fracture during hydraulic fracturing should be discarded unless it is confirmed to be the case. Geological settings of the reservoir and the presence of natural fractures were also found to cause multiple fractures initiation during the treatments, and therefore, the reservoir data and description need to be determined properly before attempting the simulation of a fracturing treatment.
Experimental and Numerical Investigations on VIV Response of a Pipe in Shear Flow
Authors: Karanjai Dipanjan , Nallayarasu S. , Bhattacharya S. K. 
Published: December 2020

Abstract
The vortex induced vibration of slender cylindrical structures is common in offshore structures and marine applications such as risers, towing cables, etc. The VIV response of such slender elements in steady uniform current has been investigated in the past using numerical and experimental studies. Though few numerical studies exist for varying current (sheared flow), experimental studies are limited. Hence, the experimental studies are an essential part of VIV investigation, especially for sheared flow.
The experiments were conducted using a specially fabricated circular steel tank of diameter 2.4 m with a central hinge to rotate the pipe horizontally in a water pool of depth 0.7 m. Shear current is simulated by rotating the pipe about the hinge. A pipe of diameter 25 mm (= D) and length 1 m (= L) was fixed at one end of the rotating cable support, and the other end was passed over a pulley inside a rotating cylinder. The rotating cylinder is provided with a pulley at the top to tension the pipe. A shear current with a maximum velocity of 1.3 m/s and a minimum velocity of 0.1 m/s is generated using the set up. The VIV response of the pipe was measured using electrical resistance-type strain gauges pasted along the length. The measured axial strain was used to obtain transverse displacements, which was used to determine the response frequency, amplitudes, and forces. The Strouhal number was calculated. The VIV response and the fluid force coefficients obtained from the experiments were compared with Shear7 results.
Motion Characteristics of a Spar-Buoy With Ring-Fin Motion Stabilizer in Deep Sea
Authors: Katayama Toru , Yamamoto Yusuke , Morimoto Taishi , Goto Masahiro 
Published: December 2020

Abstract
The main topics of this paper is the investigation of motion characteristics of the spar-buoy with ring fin motion stabilizer, which is developed to use as a platform for wind observation with a doppler lidar in shallow sea, some mooring conditions to apply it for deep sea. Four different mooring conditions are applied the spar-buoy and it motion in a designed sever wave condition are measured in the towing tank of Osaka Prefecture University.
The results show that the amplitude of pitching in deep sea is smaller than the results in shallow sea, even if the wave condition in deep sea are severer than that in shallow sea. From further investigation about the effects of four different mooring conditions on motion characteristics, it has that the center of pitching at four mooring conditions are almost same but the amplitude of pitching is smaller by changing the mooring point and the intermediate sinker position.
Experimental Investigation of Vortex Induced Vibration of Cross Flow Response for a Flexible Cable Under Uniform Current
Authors: R Prethiv Kumar , Nallayarasu S. 
Published: December 2020

Abstract
Vortex Induced Vibration (VIV) of slender cylindrical structures subjected to uniform flow is subject interest since the use of such elements is common in the offshore and naval industry. The numerical and experimental investigation of VIV for slender, flexible cable member in uniform current has been carried out in this study. The experiments were conducted in a towing tank of 85 m length and 2.8 m water depth mounted with the facility to control speed, The carriage has a range of velocity up to 5 m/s. A flexible cable of diameter 15 mm with an aspect ratio of approximately 100 has been used for the present study. The lateral displacement of cable has been measured using the strain gauges mounted along the length. The strain gauges measure the axial strain due to lateral bending of the cable and in turn, converted to lateral displacement. Experiments were carried out for a wide range of Reynolds number (Re) ranging from 3000 to 15000. From the measured responses, the Strouhal number (St) is back calculated. It is observed that the Strouhal number for flexible cable ranges from 0.13 to 0.17 for low Reynolds number from 3000 to 15000 and it falls within the expected range. The normalized RMS displacements (RMS A/D) have been obtained for specified range of Re. The lift coefficient (CL) attains a stable value of around 0.10 to 0.25 for reduced velocity (Vr) greater than 5.33 for different locations. The lift coefficient follows a similar trend along the span for different Vr. Numerical simulation has been carried out using Shear7 software with results matching reasonably well.
Experimental and Numerical Assessment of Both Slug and Vortex Induced Vibrations on a Spool Model
Authors: Minguez Matthieu , Le Prin Kevin , Liné Alain , Lafon Vincent , Pétrié François , Rippol Thierry 
Published: December 2020

Abstract
The paper addresses the flow-induced response of a rigid spool/jumper. It mainly focuses on its mechanical response resulting from internal intermittent slug flows but also addresses potential coupling with an external excitation due to vortex shedding. These works provide quantitative experimental data that match quite well with existing empirical correlations in terms of slug flow properties. The repeatability of the measurement system has been experienced and underlines promising capabilities. The tests provide exhaustive complementary data regarding the slug flow properties (e.g. pocket length) which will be reused for numerical modelling purpose. The mechanical response of the spool is exhaustively addressed for different regular slug flows. Some correlations are proposed aiming at describing the mechanical responses. The coupling with an additional external current solicitation and Vortex Induced Vibrations (VIV) is discussed and characterized for some conditions. Finally, a discussion on the current Industry Best Practices is introduced in order to challenge the capability of the proposed approaches to described and recover such complex phenomenon. The comparisons underline the weak agreement between experiments and numerical models, opening discussion on the best way to address this physics and the next developments.
Sensitivity Analysis of Parameters for FPSO Model Updating
Authors: Wu Qihao , Zhang Min , Yang Tian’en , Xu Nuoya , Wang Junrong , Du Junfeng , Fonseca Nuno , Tahchiev Galin 
Published: December 2020

Abstract
This paper presents parameter sensitivity analysis for a FPSO numerical model updating. Generally, model test data are considered a better presentation of physical phenomena than its numerical counterpart. To minimize the discrepancy, model updating is of pragmatically importance. Model updating of a certain FPSO can be achieved by specific steps. In each step, the required properties of numerical model and test results are matched by means of tuning of the related parameters.
To avoid inefficiency and physical meaning loss resulting from large modification of parameters which are insensitive to objective properties, parameter sensitivity analyses using the direct method are conducted in this paper. The investigated parameters mainly are the FPSO’s mooring line length, mooring line mass per unit length, mooring line cross-sectional area, fairlead position, FPSO hydrostatic stiffness, FPSO mass properties, linear and quadratic damping coefficients. According to the different stages of FPSO model updating, the objective functions are set to be the FPSO’s mooring line pretension, mooring system horizontal restoring force, the natural periods of the FPSO’s 6 degree of freedom motions and the standard deviation of motion response spectra under irregular waves.