bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Assessment of Locally Thinned Areas Subject to a Hoop Stress and an Axial Stress: Background to the Guidance Given in Annex G of BS 7910:2013
Authors: Cosham Andrew , Andrews Robert 
Published: November 2019

Abstract
Annex G Assessment of locally thinned areas (LTAs) in BS 7910:2013 is applicable to LTAs in cylinder, a bend and a sphere or vessel end. It can be used to assess the longitudinally-orientated LTA in a cylinder subject to a hoop stress and a circumferentially-orientated LTA in a cylinder subject to an axial stress (due to axial force, in-plane bending moment and internal pressure), and also to assess an LTA subject to a hoop stress and an axial stress.
An outline of the origins of Annex G is given. A comparison with full-scale burst tests of pipes or vessels containing LTAs subject to a hoop stress and an axial stress is presented. It is demonstrated that the method in G.4.3 Hoop stress and axial stress is conservative.
A Numerical Evaluation of the Quadratic Transfer Function for a Floating Structure
Authors: Xie Zhitian , Liu Yujie , Falzarano Jeffrey 
Published: November 2019

Abstract
The second order force of a floating structure can be expressed in terms of a time independent quadratic transfer functions along with the incident wave elevation, through which it is possible to evaluate the second order wave exciting forces in the frequency domain. Newman’s approximation has been widely applied in approximating the elements of the quadratic transfer function matrix while numerically evaluating the second order wave induced force. Through Newman’s approximation, the off-diagonal elements can be numerically approximated with the diagonal elements and thus the numerical calculation efficiency can be enhanced. Newman’s approximation assumes that the off-diagonal elements do not change significantly with the wave frequency and that hydrodynamic phenomenon regarding the low difference frequency are usually of interest. However, it is obviously less satisfying when an element that is close to the diagonal line in the quadratic transfer function matrix shows an extremum if the corresponding wave frequency is close to the natural frequency of the certain motion. In this paper, the full derivation and expression of the second order wave forces and moments applied to a floating structure have been presented, through which the numerical results of the quadratic transfer function matrix including the diagonal and the off-diagonal elements will be illustrated. This work will present the basis of numerically evaluating the second order forces in the frequency domain. The comparisons among various approximations regarding the second order forces in deep water will also be presented as a meaningful reference.
On Signatures and Features of Modulational Instability in Ocean Waves
Authors: Babanin Alexander V. 
Published: November 2019

Abstract
Modulational instability of nonlinear waves in dispersive environments is known across a broad range of physical media, from nonlinear optics to waves in plasmas. Since it was discovered for the surface water waves in the early 60s, it was found responsible for, or able to contribute to the topics of breaking and rogue waves, swell, ice breakup, wave-current interactions and perhaps even spray production. Since the early days, however, the argument continues on whether the modulational instability, which is essentially a one-dimensional phenomenon, is active in directional wave fields (that is whether the realistic directional spectra are narrow enough to maintain such nonlinear behaviours). Here we discuss the distinct features of the evolution of nonlinear surface gravity waves, which should be attributed as signatures to this instability in oceanic wind-generated wave fields. These include: wave-breaking threshold in terms of average steepness; upshifting of the spectral energy prior to breaking; oscillations of wave asymmetry and skewness; energy loss from the carrier waves in the course of the breaking. We will also refer to the linear/nonlinear superposition of waves which is often considered a counterpart (or competing) mechanism responsible for breaking or rogue waves in the ocean. We argue that both mechanisms are physically possible and the question of in situ abnormal waves is a problem of their relative significance in specific circumstances.
Dynamic Response of Spar-Type Floating Offshore Wind Turbine in Freak Wave
Authors: Tang Yougang , Li Yan , Xie Peng , Qu Xiaoqi , Wang Bin 
Published: November 2019

Abstract
Simulations are conducted in time domain to investigate the dynamic response of a SPAR-type floating offshore wind turbine under the scenarios with freak wave. Towards this end, a coupled aero-hydro numerical model is developed. The methodology includes a blade-element-momentum model for aerodynamics, a nonlinear model for hydrodynamics, a nonlinear restoring model of SPAR buoy, and a nonlinear algorithm for mooring cables. The OC3 Hywind SPAR-type FOWT is chosen as an example to study the dynamic response under the freak conditions, while the time series of freak wave is generated by the Random Frequency Components Selection Phase Modulation Method. The motions of platform, the tensions in the mooring lines and the power generation performance are documented in different cases. According to the simulations, it shows that the power coefficient of wind turbine decreased rapidly at the moment when freak wave acted on the floating structure.
Achieving a High Accuracy Numerical Simulations of the Flow Around a Full Scale Ship
Authors: Pena Blanca , Muk-Pavic Ema , Ponkratov Dmitriy 
Published: November 2019

Abstract
The hydrodynamic performance of ships may be improved by the retrofit of Energy Saving Devices (ESDs). These devices are typically seen in the aft part of the ship hull and act by lowering the ship resistance, conditioning the fluid in front of the propeller and/or recovering energy from the rotational swirl of the fluid leaving the propeller.
In the case of a retrofit of an existing ship no straight forward solution exists. In order to find a beneficial design that will improve hydrodynamic performance, a successful and accurate initial assessment of the flow around a hull is of the most importance. Once the flow around the hull is scrutinized in detail, and required flow changes are determined, a ship designer can progress with designing an Energy Saving Device specifically tailored to have a desired effect.
This paper presents a high quality numerical evaluation of the flow around a ship hull in the full scale using a sophisticated DES model that was successfully validated against the sea trials. The findings from the numerical analysis will identify the potential improvements in the hydrodynamic performance of the ship that could be achieved by ESD.
The Characteristics of Numerical Solution of NDDE to Solve the Drill Pipe Stick-Slip
Authors: Katsui Tokihiro , Inoue Tomoya , Sogawa Daisuke , Notani Yusuke 
Published: November 2019

Abstract
The Stick-Slip is one of troublesome problems which happens in scientific drilling. In order to clarify the mechanism of Stick-Slip phenomenon, it is necessary to develop a reliable numerical model [1]-[4] to estimate drill bit motion for various drilling conditions.
We have investigated on an NDDE (Neutral Delay Differential Equation) [5] to solve Stick-Slip of drill pipe [6]-[8]. In order to solve this NDDE, it is necessary to determine the frictional torque acting on the drill bit. In the previous study, we have employed the Balanov’s [4] frictional torque model which is the function of drill bit rotation with four unknown model parameters. This numerical model calculates the Stick-Slip phenomena of the drill pipe model in the laboratory experiments correctly under the appropriate four model parameter settings. On the other hand, it is quite difficult to calculate the actual drill pipe Stick-Slip [9], because the calculated results change drastically depending on the four unknown parameter settings. In the present study, the frictional torque acting on the drill bit is defined as a periodic function and solved the NDDE to calculate the stick-slip of the actual drill pipe. The average, variation and period of the frictional torque on the drill bit were set under the consideration of measured top drive torques. The calculated numerical solutions of the drill bit motion and the top drive torque agreed qualitatively with the measured ones.
Numerical Simulation of Drifting and Run-Up Ice Floes Driven by Tsunami
Authors: Kioka Shinji , Ishida Maiko , Takeuchi Takahiro 
Published: November 2019

Abstract
In order to simulate drifting and run-up ice floes driven by tsunamis, we developed a quasi-3D Discrete Element Method (DEM) in which phenomena unique to granular solids, such as the arch action, jam and pile up of such solids, can be simulated with a small computation load. The validity of the simulation method was verified by hydraulic experiments using synthetic ice. Some numerical simulations of drifting and run-up ice floes driven by a tsunami were performed to investigate the fundamental characteristics of ice run-up and the applicability to actual seas. It was confirmed that the simulation results could estimate risk areas where ice pile up and jam form as well as hazardous areas showing the degree of damage to buildings. Such calculation was expected to be useful for the compilation of hazard maps and the development of disaster mitigation plans in the future.
Analysis of Polyester Reinforced Flexible Composite Pipe Under Internal Pressure
Authors: Sun Xinyu , Bai Yong , Zhang Xiaojie , Liu Chang , Zhao Jiannan 
Published: November 2019

Abstract
In recent years, petroleum and natural gas industry technology continues to develop, so the market demand for polyester fiber reinforced flexible composite pipe is increasing. Polyester reinforced flexible composite pipe is widely used in practical production, which is based on thermoplastic material and winded by polyester fiber. Based on the anisotropic uniformity of polyester reinforced flexible composite pipes, this paper focuses on the mechanical behavior of flexible composite pipes under internal pressure. By using numerical analysis method, the stress-strain change and burst pressure model of polyester reinforced pipe under internal pressure are established. The short-term burst pressure test is carried out to obtain the burst pressure of the reinforced pipe. The finite element analysis software ABAQUS is used to establish finite element model for simulation analysis. According to the generated test data, the correctness of the finite element analysis results is verified. The sensitivity of winding angle and diameter-thickness ratio to the pressure was studied to further understand the mechanical properties of polyester reinforced composite pipe.
Recent Advances in the Prediction and Mitigation of Flow Induced Pulsations in Flexible Risers and Flowlines
Authors: Belfroid S. P. C. , González Díez N. , Korst H. 
Published: November 2019

Abstract
Flow-induced pulsations in flexible risers and flowlines (FLIP) has been the subject of ongoing research roughly over the last two decades. This phenomenon, also called singing, can cause high vibration and cyclic stress levels in the attached up- and downstream pipe systems, thereby imposing serious limitations on the flowrates through the pipes. FLIP occurs when the flow velocity along the flexible is above a certain onset flow velocity. Large pressure pulsations can appear as a result of a feedback loop mechanism established between vortex shedding at the inner cavities and longitudinal acoustic standing waves. Since FLIP is recommended to be avoided in all cases, the main focus of the research has been to understand the phenomenon and build models to predict the onset velocity. An overview of the experiences in the behavior and prediction of onset data on a large number of field cases is given. Recent advances on the theory and prediction of the onset and behavior of flow induced pulsations are discussed. This ranges from new advanced test methods for acoustic source allocation to full large scale experiments. In addition, new and upcoming anti-FLIP technologies as well as possible mitigation actions available to operators are discussed, by introducing recent field experiences as well as large scale tests.
Application of Friction Fatigue Pile Driving Models in GRLWEAP
Authors: Milewski Henry , Kennedy Justin 
Published: November 2019

Abstract
Pile driveability analyses play a crucial part in pile installation planning (hammer sizing, anticipated driving time) and pile design (fatigue concerns). GRLWEAP is one of the predominant pile driving analysis software tools used globally. Traditionally, the offshore community has often wished to use specific SRD prediction methods in driveability analyses. Some of the most popular of these methods (e.g. Alm & Hamre, 2001) employ a ‘friction fatigue’ approach whereby side friction reduces with increasing pile penetration. A past limitation in GRLWEAP has been that friction fatigue methods could not be used in a full driveability analysis, since only a single SRD (valid only for a particular depth of penetration) can be input. This is prohibitive when outputs such as blowcounts are desired at each intermediate penetration depth (e.g. for fatigue analysis), rather than just the final depth.
With the introduction of GRLWEAP’s ‘friction fatigue’ module, a way of modelling friction fatigue is now provided, but the fatigue equations are formulated in a specific way that may not be directly applicable to various friction fatigue approaches. Using the Alm & Hamre (2001) friction fatigue method as an example, an approach is presented that shows how friction fatigue models that are not formulated in the same manner as GRLWEAP’s friction fatigue approach can be converted into a suitable form to allow full implementation in a GRLWEAP driveability analysis. This enables driveability analyses to capture the dynamic nature of the SRD as pile penetration increases, producing results that are valid for all penetrations and circumventing the need for alternative workarounds to capture friction fatigue. The general principles presented herein may be modified on similar principles for other friction fatigue models not explicitly captured within GRLWEAP.
Forced Vibration Tests for In-Line VIV to Assess Partially Strake-Covered Pipeline Spans
Authors: Wu Jie , Yin Decao , Passano Elizabeth , Lie Halvor , Peek Ralf , Sequeiros Octavio E. , Ang Sze Yu , Bernardo Chiara , Atienza Meliza 
Published: November 2019

Abstract
A series of experiments is performed in which a strake-covered rigid cylinder undergoes harmonic purely in-line motion while subject to a uniform “flow” created by towing the test rig along SINTEF Ocean’s towing tank. These tests are performed for a range of frequencies and amplitudes of the harmonic motion, to generate added-mass and excitation functions are derived from the in-phase and 90° out-of-phase components of the hydrodynamic force on the pipe, respectively.
Using these excitation- and added-mass functions in VIVANA together with those from experiments on bare pipe by Aronsen (2007), the in-line VIV response of partially strake-covered pipeline spans is calculated. It is found that as little as 10% strake coverage at the optimal location effectively suppresses pure in-line VIV.
Further advantages of strakes rather than intermediate supports to suppress in-line VIV include: strakes are not affected by the scour which can lower an intermediate support (in addition to creating the span in the first place). Further they do not prevent self-lowering of the pipeline or act as a point of concentration of VIV damage as the spans to each side of the intermediate support grow again.
A Study on the Validity of a One Degree of Freedom Model for Deepwater Subsea Lifts
Authors: Tommasini Rodrigo Batista , Carvalho Leonardo de Oliveira , Pavanello Renato 
Published: November 2019

Abstract
The lowering into deepwater phase of the installation of subsea equipment is analyzed by a one degree of freedom model and also by a multiple degree of freedom model in order to determine the scenarios where the simplified model can be used accurately. The one degree of freedom system is based on the assumption that the lifting cable has a length that varies throughout the time as a function of the payout speed. On the other hand, the multiple degree of freedom system is constructed using the commercial software Orcaflex which uses the line feeding feature to evaluate the continuous lowering of the equipment during the operation. Firstly, possible critical scenarios for the use of the simplified model are obtained by evaluating the total time for longitudinal pressure waves to travel inside the cable and by analyzing the resonance frequencies of the system for different water depths, types of cables, and equipment. Secondly, the one degree and the multiple degree of freedom systems are compared. The results show that high water depth and high mass ratio tends to lead to more critical scenarios for the use of the simplified model, especially when the excitation period is low. Further, the dynamics of the system for different payout speeds is assessed considering the most critical scenario for the use of the simplified model. In this case, the differences between the models are not affected by the speed. It is concluded that the one degree of freedom model should not be considered as an accurate method to analyze subsea lifts for scenarios of high mass ratio, high water depth and low excitation periods, independent of the payout speed considered for the operation. Finally, guidance for the selection between both models is provided.
Modeling a Non-Linear Mooring System for Floating Offshore Wind Using a Hydraulic Cylinder Analogy
Authors: Harrold Magnus J. , Thies Philipp R. , Newsam David , Bittencourt Ferreira Claudio , Johanning Lars 
Published: November 2019

Abstract
The mooring system for a floating offshore wind turbine is a critical sub-system that ensures the safe station keeping of the platform and has a key influence on hydrodynamic stability. R&D efforts have increasingly explored the benefits of nonlinear mooring systems for this application, as they have the potential to reduce the peak mooring loads and fatigue cycling, ultimately reducing the system cost. This paper reports on a hydraulic based mooring component that possesses these characteristics, attributable mostly to the non-linear deformation of a flexible bladder. This is not a typical hydraulic component and, as a consequence, modeling its dynamic performance is non-trivial. This paper addresses this by introducing an analogy to numerically model the system, in which the functionality of the mooring component is compared to that of a hydraulic cylinder. The development of a working model in Simscape Fluids is outlined, and is subsequently used to simulate the IMS in a realistic environment. It is found that the numerical model captures a number of the dynamic performance characteristics observed in a previously tested prototype of the IMS.
Development of 3-Dimensional Fully Nonlinear Potential Flow Planar Wave Tank in Framework of OpenFOAM
Authors: Lin Zaibin , Qian Ling , Bai Wei , Ma Zhihua , Chen Hao , Zhou Jian-Guo 
Published: November 2019

Abstract
A 3-Dimensional numerical wave tank based on the fully nonlinear potential flow theory has been developed in OpenFOAM, where the Laplace equation of velocity potential is discretized by Finite Volume Method. The water surface is tracked by the semi-Eulerian-Lagrangian method, where water particles on the free surface are allowed to move vertically only. The incident wave is generated by specifying velocity profiles at inlet boundary with a ramp function at the beginning of simulation to prevent initial transient disturbance. Additionally, an artificial damping zone is located at the end of wave tank to sufficiently absorb the outgoing waves before reaching downstream boundary. A five-point smoothing technique is applied at the free surface to eliminate the saw-tooth instability. The proposed wave model is validated against theoretical results and experimental data. The developed solver could be coupled with multiphase Navier-Stokes solvers in OpenFOAM in the future to establish an integrated versatile numerical wave tank for studying efficiently wave structure interaction problems.
On Deriving High Pressure Empirical Multiphase Forcing Functions From CFD Analysis
Authors: Macchion Olivier , Belfroid Stefan , Stachyra Leszek , Jensen Atle 
Published: November 2019

Abstract
Computational Fluid Dynamics (CFD) simulations are used to predict the flow-induced forcing in high-pressure multiphase pipe flow. Furthermore, empirical correlations from the literature is compared and validated against computational and experimental results. Based on the CFD results and in conjunction with the reference 6” (internal diameter (ID)) data, new scaling rules are proposed.
Fundamental CFD Study on the Hydrodynamic Performance of the DARPA SUBOFF Submarine
Authors: Takahashi Kenshiro , Sahoo Prasanta K. 
Published: November 2019

Abstract
This study attempts to examine the potential for computational fluid dynamics (CFD) as an estimation tool of the hydrodynamic performance of submarines. The DARPA SUBOFF model is adopted as a benchmark because of its availability of experimental data for validation. The computational modeling is based on the Reynolds Average Navier Stokes (RANS) equations solved by a finite volume method. Verification and validation of the straight-ahead resistance and the forces and moment exerted on the hull in steady translation and turn with a drift angle were conducted in accordance with the published methodology and procedure. The process to have determined the computational setups is described. Furthermore, the computational results as a function of velocity and drift angle are presented and compared with available experimental data. In conclusion, the present CFD method can be used as an estimation tool for the straight-ahead resistance at various velocities in model scale for multiple configurations.
Fatigue Assessment of “Corroded” Mooring Chain
Authors: Baker David A. , Li Zhen , Wang Sue , Zhang Xiying , Shao Yunliang , Li Harry , Zhan Xiaoqin , Zhu Linfang , Tao Xing (Terry) 
Published: November 2019

Abstract
Assessment of corroded mooring chain for continued service is a challenging task faced by industry. Current best practice relies heavily on qualitative inspection information collected during inspection campaign. There has been little investigation into this practice and whether it is an appropriate technique or can be improved. To address this issue, the Fatigue of Corroded Mooring Chains (FoCCs) Joint Industry Project (JIP), initiated in 2016 with fifteen (15) participating organizations, including oil majors, chain manufactures, consulting firms, and classification societies, to examine assessment methods for evaluating remaining fatigue life. JIP teams were formed to progress fatigue testing and finite element objectives. One such team, comprised of ExxonMobil, ABS and Asian Star Anchor Chain, has performed an additional series of fatigue tests beyond the core JIP work effort.
A fatigue test was conducted to 1) demonstrate the utility of finite element analysis in the assessment of fatigue life and 2) demonstrate performance of simulated damage. This unique fatigue test program was conducted on mooring chain with manufactured “corrosion pits” of different dimensions. All chain surface features were digitally recorded and converted into finite element models. These models were subsequently analyzed to compare with test results — both cycle count and failure location. This paper presents the findings from these fatigue tests and finite element analyses and how they can be utilized for assessment of remaining fatigue life.