bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct Simulations of Turning Circle Maneuver in Waves Using RANS-Overset Method
Authors: Wang Jianhua , Wan Decheng
Published: September 2018

In the present work, a RANS-overset method is used to numerically investigate turning circle maneuver in waves for a twin-screw ship. CFD solver naoe-FOAM-SJTU is used for the numerical computations of the fully appended ONR Tumblehome ship model. Overset grids are used to fully discretize the ship hull, twin propellers and rudders. The simulation of turning circle maneuver is carried out at constant propeller rotational speed with 35° rudder deflection. Open source toolbox waves2Foam is utilized to generate desired waves for the moving computational domain. Predicted ship trajectory and 6DoF motions, hydrodynamic forces and moments acting on the ship and the moving components are presented. The main parameters of the turning circle maneuver, such as the advance, the transfer, the tactical diameter, and the turning diameter, are presented and compared with the available experiment. Wave effects on the free running turning circle maneuver are discussed through detailed flow visualizations. The trajectory and main parameters agree well with the experiment, which show that the present RANS-overset method is a reliable approach to directly simulate turning circle maneuver in waves.
Fully Coupled Analysis of Ship Motion and Sloshing Tanks in Regular and Irregular Waves
Authors: Zhuang Yuan , Wan Decheng
Published: September 2018

Fully coupled analysis of ship motion and sloshing tank in waves is essential for floating structures which store and transports natural gas. For partially filled tanks would generate violent sloshing due to external wave excitation, and the sloshing flow can consequently affect ship motion. Therefore, how to evaluate ship motion and sloshing phenomenon in tank is of great importance, especially under real sea state, when wave induced sloshing would be more complex than that under linear wave condition.

In the present work, a CFD-based method is applied to simulate both external wave field and inner sloshing tank field in regular waves and irregular waves. The ship is a simplified FPSO, with two LNG tanks.

All the numerical simulations are carried out by the in-house CFD code naoe-FOAM-SJTU, which is developed on the open source platform OpenFOAM. The regular and irregular wave condition is simulated based on open source toolbox waves2Foam. The main parameters of coupling effect of ship motion and sloshing tank, such as the time history of ship motion, sloshing phenomenon in tanks are obtained by our computations. The predicted results for the coupling effects of ship motion and sloshing tank in regular waves are compared with the corresponding experimental data. The comparison is satisfactory and shows that the CFD method has the ability to simulate coupling effects of ship motion and sloshing tank in waves.
CFD Study of Added Resistance and Motion of DTC in Short and Long Waves
Authors: Liu Cong , Chen Gang , Wan Decheng
Published: September 2018

In the present work, in-house CFD code naoe-FOAM-SJTU is used to investigate the added resistance and motion of DTC ship at Fr = 0.052 and 0.138 in short and long head waves. The time history and Fourier series of resistance and motion is given. Validation against the experimental results shows that the computation agrees well with EFD data in high speed cases. Then, the time-averaged and the Fourier transform of hydrodynamic pressure on ship are analyzed. The time-averaged pressure shows the added resistance is mainly caused by the high pressure at the upper bow. The distribution of second harmonic pressure on the bow demonstrates the bow relative motion is closely related with the nonlinearity of resistance. It can be explained as the large bow relative motion induces the stronger non-linear change of instantaneous wetness at flare bow. The wave patterns are plotted and show that the angle which wave diverged from the ship increases as the ship speed decrease and wave length increase.
On the Uncertainties of Estimating JONSWAP Spectrum Peak Parameters
Authors: Ewans Kevin , McConochie Jason
Published: September 2018

A spectral description of the wave spectrum is usually required in the design of offshore structures, and a generalised form of the JONSWAP spectrum is often used. The JONSWAP spectrum involves parameters that allow flexibility in the specification of the spectral peak, which is important for the response of both fixed and floating structures, but particularly for the floating structures. The peak of the wave spectrum is also important in nonlinear effects that for example contribute to the probability of a large crest occurring in a sea state time series realisation in a model basin, used to test a design platform.

There has been a number of studies focused on the uncertainties of JONSWAP parameter estimates. We review these to establish an overview of the present understanding of the uncertainties, and we undertake further analyses to investigate the sensitivity of the uncertainties to the method of analysis and the types of data typically available for analysis, including both time series and spectral data.
The Rationale for Update of S-N Curves for Single Sided Girth Welds for Risers and Pipelines in DNV GL RP C-203 Based on Fatigue Performance of More Than 1700 Full Scale Fatigue Test Results
Authors: Horn Agnes Marie , Lotsberg Inge , Orjaseater Oddvin
Published: September 2018

Deep-water tendon and riser systems are often subjected to severe fatigue loading from waves, currents and vessel movements. The girth welds between successive lengths of pipe or at pipe terminations represent fatigue-critical features where failure would be catastrophic. Hence, validation fatigue testing by full scale pipes of the most critical welds are often performed to ensure adequate quality and/or to document a better S-N curves than those available in standards today like DNVGL-RP-C203 [1] and BS7608 [2]. To better understand the fatigue performance with respect to identify trends, dependencies and critical features that influence the fatigue performance, a JIP on Fatigue of Girth Welds were initiated in 2011. Two phases have been conducted and a total of 1700 full scale one sided girth welds, mostly run by Stress Engineering, have been statistically analyzed. The test data has been interrogated to investigate the effect of as-welded condition, OD ground, OD/ID ground, un-reeled pipe, reeled pipe, thickness and effect of misalignment. Based on these analyses, new S-N curves for risers and pipelines have been included in DNVGL-RP-C203 for non-reeled girth welds. This paper presents the findings and trends from the JIP work which has been the rationale for the updates of girth welds in section 2.10 in DNVGL-RP-C203 2016 edition.
Green Water Assessment for Marine and Offshore Applications: Structural Response of the ULCS Breakwater
Authors: Malenica Šime , Lee Byung Hyuk , Vladimir Nikola , Gatin Inno , Monroy Charles , De Lauzon Jerome
Published: September 2018

Green water loading which occurs during the floating body operations in heavy weathers can be very dangerous for the structural integrity of the superstructures and the equipment’s located at the upper decks. The correct modeling of the green water loading and the corresponding structural response is far from trivial and many different physical aspects need to be taken into account at the same time. Depending on the type of the floating body, the overall procedure involves the use of the different numerical tools at different steps. For off-shore type structures the procedure is slightly more complicated than for ships because, in addition to the classical seakeeping simulations, the mooring software also needs to be used. In all cases the final design conditions should be modeled using the complex hydro-structure interaction tools.

In the present work the overall methodology is demonstrated and applied to the case of the evaluation of the structural response of the breakwater on the Ultra Large Container Ship (ULCS).
Optimising Ship Manoeuvring in Narrow Waterways Under Wind Disturbances
Authors: Ahmed Yaseen Adnan , Hannan Mohammed Abdul , Kamal Iwan Mustaffa
Published: September 2018

This paper focuses on getting optimised ship trajectories in narrow waterways under wind disturbances considering time as an objective function, i.e. the ship tends to sail by taking the optimised rudder output for minimum time manoeuvre. Non-linear programming (NLP) has been proposed to use with weighted sigmoid function as non-equality constraints to follow up the reference line if it is necessary. Problems with different boundary conditions and disturbance values have been investigated to justify the effectiveness of the proposed method. The problem regarding the initial value for the start-up of the optimisation process has also been resolved by applying a systematic technique for this method.
TurkStream Collapse Test Program
Authors: Timms Chris , Swanek Doug , DeGeer Duane , Meijer Arjen , Liu Ping , Jurdik Erich , Chaudhuri Jay
Published: September 2018

The TurkStream pipeline project is designed to transport approximately 32 billion cubic meters of natural gas annually from Russia to Turkey under the Black Sea, with more than 85% of the deep-water route being deeper than 2000 m. The offshore section is intended to consist of two parallel lines, each approximately 900 km long. The preliminary stages of the front end engineering design (pre-FEED) phase was managed by INTECSEA. To support the analyses and design of the deepest portions, a full scale collapse test program was performed by C-FER Technologies (C-FER). This collapse test program, which included 62 full-scale collapse and pressure+bend tests, 54 medium-scale ring collapse tests, and hundreds of small-scale tests, was primarily aimed at measuring, quantifying and documenting the increase in pipe strength and collapse resistance resulting from the thermal induction heat treatment effect (thermal ageing) that arises during the pipe coating process. Two grades of 32-inch (813 mm) outside diameter (OD) line-pipe, SAWL450 and SAWL485 with wall thicknesses of 39.0 mm or 37.4 mm, respectively, were supplied from various mills for testing. The collapse test program objectives were as follows:

• Determine the collapse resistance of line pipes originating from various pipe mills;

• Determine the pressure+bend performance of line pipes originating from various pipe mills;

• Measure the effect of thermal ageing on material and collapse testing results, including the impact of multiple thermal cycles; and

• Evaluate the results of medium-scale ring collapse tests as compared to full-scale tests.

This paper presents selected results of this work, along with some comparisons to predictive equations.
Improved FPSO Offloading Strategy Based on Analysis Including DP System
Authors: Gundersen Gerhard , Stuberg Petter , Kendon Timothy Edward , Reinholdtsen Svein-Arne
Published: September 2018

Direct offloading operations from turret moored FPSOs are traditionally performed with dynamic positioned (DP) shuttle tankers with a bow loading hose and hawser line connected to the stern of the production facility. The hawser line restricts the mobility of the shuttle tanker which is often forced to point towards the FPSO. The inherent increased risk of collision in case of a forward drive-off incident has motivated a study for a hawser-less tandem offloading operation. The structural limits of the flexible loading hose allows for larger operational sector and heading flexibility which enables the shuttle tanker to point away from the FPSO and hence reduces the probability of collision. An analysis model with two representative vessels for offloading operations in the North Sea has been developed in order to investigate the new concept. The model includes a compiled version of the DP system core algorithm, extracted from the real time system of both vessels. The new offloading strategy, with heading offset away from the FPSO, has been implemented in an updated control algorithm for the shuttle tanker. Time-domain analysis of the complete tandem offloading system has been simulated with measured wind, waves and current from a HindCast data base. Heading and relative motion between FPSO and shuttle tanker has been extracted and statistically evaluated in order to determine the time for which the shuttle tanker is directed towards the FPSO. The paper demonstrates how a marine simulation model, including core algorithm of the actual DP system and numerous simulations based on historical measured environment, can be used to document the feasibility of a new offloading operation control strategy.
Simulations on Hydrodynamic Coefficients of Stationary Cactus-Shaped Cylinders at a Low Reynolds Number
Authors: Wang J. , Shi C. , Liu Y. , Bao X.
Published: September 2018

Flexible cylinders, such as marine risers, often experience sustained vortex-induced vibration (VIV). Both helical strakes and fairings are demonstrated to be effective in suppressing VIV, while, helical strakes result in large drag, which increases the rotational angle and bending moment at the riser hang-off location and, fairings are cumbersome in term of storage, installation and maintenance. This study was inspired by the giant Saguaro Cacti which grow in desert region. Saguaro Cacti have shallow root system, but can grow up to fifty feet in height and can withstand very high wind velocities. In this study, numerical simulations of flow past a stationary cactus-shaped cylinder are performed in two-dimensional field at a low Reynolds number of 200. The hydrodynamic coefficients and the vortex-shedding patterns of a cactus-shaped cylinder are compared with those of a circular cylinder. In addition, a set of two cactus-shaped cylinders of tandem arrangement are also studied to investigate the effects of wake. Results showed that a cactus-shaped cylinder can reduce the drag, lift, and Strouhal number, which suggests its potential as an alternative technology to suppress VIV of a riser.
Stress Analysis of Post-Buckled Sandwich Panels
Authors: Romanoff Jani , Jelovica Jasmin , Goncalves Bruno Reinaldo , Remes Heikki
Published: September 2018

The paper presents a method to assess stresses in sandwich plates with periodic microstructure in the post-buckling region. The fundamental assumption is that the microstructure is linear elastic and von Karman non-linearity is present only at macro-, i.e. panel-scale. This enables response evaluation by equivalent homogenous continuum with constant stiffness properties. It is shown that the homogenization cancels shear-induced, odd-terms in microstructural field variables such as displacements and stresses. These are of fundamental importance when strength of the panel must be assessed. The localization approach utilised here neglects the actual position of the microstructure and thus is able to capture only the maximum values of these stress fluctuations. The validation of the present approach is carried out with 3D FE analyses and a good agreement is shown. The shear-induced periodic stresses are of fundamental importance when the strength in the post-buckling region is assessed based on linear elastic basis.
The Application of Fuzzy-Ball Drilling Fluid to Deepwater Drilling to Deal With Highly Mineralized Formation Brines and Low-Temperature Environment
Authors: Wei Panfeng , Zheng Lihui , Yang Mingzheng , Chen Yuanhang
Published: September 2018

For deepwater oil and gas well drilling with the issue of highly mineralized formation brines, it is required that the drilling fluid properties are not affected by the high salinity formation fluid and the low-temperature environment. A novel drilling fluid mainly consists of fuzzy-ball fluid, which has an excellent tolerance to salinity and low temperature, has the potential to be applied for deepwater drilling to achieve safe and efficient drilling tasks.

Experimental studies and field tests have been carried out to characterize the rheological properties of fuzzy-ball drilling fluid under different conditions of brine salinity and test temperature. In the experimental test, fuzzy-ball fluids with different densities are prepared with brines of varying salinity mineralized by Ca2+ and Mg2+. The rheological curves are plotted from different apparent viscosities and shear stresses under different shear rates measured by a rheometer under 10 ∼ 80°C and a six-speed viscometer at 0°C.

The results positively showed that the yield stress of fuzzy-ball fluid is stable at a relatively high value with the variation of fluid salinity and temperature. The apparent viscosity slightly increases with the decrease of salinity and temperature. It can be claimed that the rheological properties of fuzzy-ball drilling fluid are stable within the range of salinity and temperature investigated experimentally.

Field tests have been conducted during several workover jobs, the rheological properties of fuzzy-ball drilling fluid were stable at temperatures and salinities on site. Thus, it can be proved that the novel fuzzy-ball drilling fluid could be applied in deepwater drilling under the high salinity formation fluid and low-temperature environment.
Learnings From Strain Measurements on an In-Field Conductor and Wellhead System
Authors: Shankaran Rohit , Rimmer Alexander , Haig Alan
Published: September 2018

In recent years due to use of drilling risers with larger and heavier BOP/LMRP stacks, fatigue loading on subsea wellheads has increased, which poses potential restrictions on the duration of drilling operations. In order to track wellhead and conductor fatigue capacity consumption to support safe drilling operations a range of methods have been applied:

• Analytical riser model and measured environmental data;

• BOP motion measurement and transfer functions;

• Strain gauge data.

Strain gauge monitoring is considered the most accurate method for measuring fatigue capacity consumption. To compare the three approaches and establish recommendations for an optimal approach and method to establish fatigue accumulation of the wellhead, a monitoring data set is obtained on a well offshore West of Shetland. This paper presents an analysis of measured strain, motions and analytical predictions with the objective of better understanding the accuracy, limitations, or conservatism in each of the three methods defined above.

Of the various parameters that affect the accuracy of the fatigue damage estimates, the paper identifies that the selection of analytical conductor-soil model is critical to narrowing the gap between fatigue life predictions from the different approaches. The work presented here presents the influence of alternative approaches to model conductor-soil interaction than the traditionally used API soil model.

Overall, the paper presents the monitoring equipment and analytical methodology to advance the accuracy of wellhead fatigue damage measurements.
Time-Domain Coupled Dynamic Analysis of Mooring Systems in Extreme Sea Condition
Authors: Han Xuliang , Wang ShiSheng , Xie Bin , Xie Wenhui , Zhou Weiwei
Published: September 2018

In order to predict the coupled motion and external wave load for the design of deepwater floating structure system, based on the three-dimensional time-domain potential flow theory, this paper present the indirect time-domain dynamic coupling method and the body nonlinear dynamic coupling method. The perturbation expansion theory is adopted to evaluate hydrodynamic on the fixed mean wetted body surface for the former method. The transient free surface Green function has been extended and applied to calculate the nonlinear hydrodynamic on the instantaneous wetted exact body surface for the latter method. The finite element model is employed to solve dynamic response of mooring line. Then asynchronous coupled method is adopted to achieve the coupled dynamic analysis of platform and mooring lines. The time-domain motion responses and spectrum analysis of Spar platform are verified and compared with the traditional indirect time-domain coupling dynamic method when the mooring system is completed. Also the time-domain motion responses and statistical characteristic of Spar platform are investigated with one mooring line broken in extreme sea condition. Some conclusions are obtained, that is, dynamic coupling effects are significant and transient position hydrodynamic calculation of platform has a great influence on the low frequency motion. The results also show that the influence on the global performance of mooring system is different when the broken line is in different place. A remarkable influence occurs when the broken mooring line is in the head-wave direction.
Permanent Plug and Abandon of a Subsea Well With Obstructed Well Access: A Success Story
Authors: Stanislawek Mikolaj
Published: September 2018

Permanent Plug and Abandon (PP&A) operations of the existing production and exploration wells continue to have a higher focus in drilling and well operations for Oil & Gas Companies. It is expected that they will play an important role in the future, and their further optimization and simplification is even more important. This paper describes a successful approach and execution of a challenging Permanent Plug and Abandon operation of a subsea well in the Norwegian Sea by Statoil.

A subsea well at over 350 m water depth was being drilled, when a casing running tool was stuck at the subsea wellhead when running an intermediate casing string. This led to a temporary well abandonment, before permanent P&A operations could be resumed at a later stage. Several concepts and contingency scenarios were evaluated and risk assessed in the planning phase, which required implementation of nonstandard and innovative P&A solutions and equipment. They were developed in the planning phase and reviewed with planning and execution teams, and tested before the operational start-up. Main P&A operational goals were established in the planning phase, and successfully implemented during the operations: 1) well control — confirm there is no gas and no well control risk in the well before resuming P&A operations, 2) gain access to the well by retrieving stuck tool from subsea wellhead, and 3) establish permanent P&A barriers in the well.

Both planning and execution of this operation is described in this paper, which includes main planned operations, and also a strategical approach with several contingency scenarios prepared in order to be able to P&A this well permanently.
Station-Keeping Trials in Ice: Numerical Modelling
Authors: Serre Nicolas , Kerkeni Sofien , Sapelnikov Dmitry , Akuetevi Cyrille , Sukhorukov Sergiy , Guo Fengwei , Metrikin Ivan , Liferov Pavel
Published: September 2018

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia with two anchor handling supply vessels; Magne Viking and Tor Viking. The data collection included monitoring of ice conditions and response of Magne Viking during ice interaction events. The present paper describes numerical simulations of broken ice and intact ice interaction events with single point moored Magne Viking.
Station-Keeping Trials in Ice: Marine Spread
Authors: Kjøl Andreas , Liferov Pavel , Almkvist Erik , Lindvall Joakim K. , McKeever Thomas
Published: September 2018

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia with two anchor handling tug supply vessels. The vessels Tor Viking and Magne Viking were used as Support vessel and Moored vessel, respectively. This paper describes the above mentioned marine assets, mooring analysis, mooring configuration, mooring and unmooring procedures, including quick disconnection system design and operation.
Multi-Objective Design Optimization of Drilling Riser Operability Envelope for Ultra-Deep Water
Authors: Yang Hezhen , Koh Chan Ghee , Low Ying Min , Adaikalaraj Peter Francis Bernad
Published: September 2018

This paper presents an efficient methodology for multi-objective design optimization of drilling riser in ultra-deep water considering maximum operability window and minimum weight of drilling riser system. As exploration activity moves to ultra-deep waters, the associated drilling cost increases, putting pressure on the operators to expand the drilling operability and reduce costs. Drilling systems are an integral part of oil and gas exploration particularly in deep waters. The drilling riser design requires a time-consuming design loops and scenarios analyzed with different FEM models, such as connected mode, drift-off, hang-off, recoil analysis, emergency disconnection, etc. The main purposes of this work is to improve the safety and cost-effective for drilling riser design by employing multi-objective optimization based on metamodel. The Radial Basis Function (RBF) metamodel is constructed by the design of experiment sampling and is utilized to solve the problem of time-consuming analyses. In the optimization module, multi-objective optimization by a non-dominated sorting genetic algorithm II is performed. Thereby, RBF optimum solutions forming a Pareto set are obtained and compared with accuracy analysis to determine their validity. The optimization results indicate that the proposed optimization strategy is valid and provide an efficient optimization design method for drilling riser in ultra-deep water.
Improving the Safety of Fishing Vessels Through Roll Motion Analysis
Authors: Santiago Caamaño Lucía , Míguez González Marcos , Díaz Casás Vicente
Published: September 2018

Fishing sector is one of the most dangerous worldwide. Accidents are usually related to stability failures that can be due to static or dynamic phenomena. Their main cause is the crew lack of training in stability matters, especially in small-medium sized fishing vessels. The vast majority of fishermen assess the risk level of their ship carrying out a subjective analysis, based on their previous experience.

In order to reduce the number of stability-related accidents, onboard guidance systems were proposed in the last years as a tool that helps the skippers to evaluate the ship stability in an easy and understandable way.

The authors of this work have proposed their own alternative, which consists on a simplified stability guidance software installed on a touchable-screen computer.

In its initial version, this software relied in data manually introduced by the crew and only considered static stability for the evaluation of the vessel safety index. In the version presented in this paper, the authors have tried to solve the need for manual data applying a methodology for the real-time estimation of the roll natural frequency of the vessel. In addition to this, environmental conditions and the evaluation of dynamic stability vulnerabilities based on the IMO Second Generation of Intact Stability Criteria have also been included.
Station-Keeping Trials in Ice: Overview of Ice Management Support
Authors: Neville Mike , Almkvist Erik , Scibilia Francesco , Lindvall Joakim K. , Liferov Pavel
Published: September 2018

In March 2017, Statoil performed station-keeping trials in drifting ice in the Bay of Bothnia. The anchor handling tug supply vessel Magne Viking, performed station keeping operations in various ice conditions, including managed and non-managed ice. Physical ice management was used to manage the approaching ice to a target condition suitable for the station keeping tests, and to enable other essential operations including deployment and retrieval of the mooring spread and other equipment. Given the objective of the trials, physical ice management activities were performed in such a way to allow investigation of various relevant parameters that influence the managed ice condition. Additional tests were also performed for the sole purpose to assist with validation of Aker Arctic’s ice management software “AIMS”, including tests designed to estimate the performance of the vessels under different ice conditions.

This paper focuses on the physical ice management operations performed by the ice management vessel Tor Viking (TV) during the Station Keeping Trials in ice (SKT). Also included is a discussion on how AIMS was used in the planning phase and how simulations compared with actual observations.
Analysis of Semi-Submersible Under Combined High Waves and Current Conditions Compared With Model Tests
Authors: Yang Limin , Nestegård Arne , Falkenberg Erik
Published: September 2018

Viscous effects on the low-frequency excitation force on column based platforms are significant in extreme waves. The wave drift force as calculated by a zero-current potential flow radiation/diffraction code becomes negligible for such waves. In the present study, the effect of current and viscous contributions on the slowly varying wave forces are adjusted by a formula developed in the Exwave JIP, see e.g. [1], which is validated against model test results.

This paper presents numerical predictions of low frequency horizontal motions of a semi-submersible in combined high waves and current condition. In the simulation model, frequency dependent wave drift forces from radiation/diffraction code are modified by the formula. Static current forces and viscous damping are modelled by the drag term in Morison load formula using relative velocity between current and floater and with force coefficients as recommended by DNVGL-RP-C205 [2]. Low frequency surge responses calculated by the simulation model are compared with model tests for waves only and for combined collinear and noncollinear wave and current conditions.
Experimental Study on Crack Propagation and Strain Accumulation of Cracked Stiffened Plate Under Cyclic Load
Authors: Jiang Wei , Yang Ping , Peng Ziya
Published: September 2018

Stiffened plates with cracked damage are often subjected to constant amplitude and/or variable amplitude cyclic loads in sea environment. Under the stress-controlled asymmetric low-cycle fatigue loads, the coupling effect of low-cycle fatigue crack propagation and accumulative plasticity contributes to the increase of accumulative mean strain of cracked structures. Low-cycle fatigue crack growth and the increase of whole strain of cracked structures will change the bearing capacity of cracked structures. In this paper, experimental study on crack propagation and strain accumulation of cracked stiffened plate under low cycle fatigue load has been conducted. AH32 steel is used to make stiffened plate specimen with crack symmetrically located about stiffener. The accumulative strain of the cracked stiffened plate specimens during low-cycle fatigue crack propagation was obtained. From the experiments for cracked stiffened plates under the low-cycle fatigue loading, it is found out that the crack propagates firstly in the weld and then also gradually takes place in the stiffener. The stress ratio of low-cycle fatigue load and stiffener stiffness have been investigated in the experimental study and it is found out that these parameters significantly affect the low-cycle fatigue crack growth life and accumulation strain of the cracked stiffened plate specimens.
Numerical Investigation of Energy Saving Device Effects on Ships With Propeller-Hull Interactions
Authors: Mysa Ravi Chaithanya , Tuyen Le Quang , Shengwei Ma , Nguyen Vinh-Tan
Published: September 2018

Energy saving devices (ESD) such as propeller ducts, pre-swirl stators, pre-nozzles, etc have been explored as a more economic and reliable approach to reduce energy consumption for both in-operation and newly design ships over the past decades. Those energy saving devices work in the principle of reducing ship resistance and improving propulsion efficiency as well as hull-propeller interactions. Potential saving from various types of ESD have been reported in literature from the range of 3–9% [1] for propulsion efficiency dependent on different measures. Deployment of those devices on actual full-scale ships has been limited over the past years. One of the key obstacles in application of ESD is the lack of confidence in measuring its efficiency on full-scale ships in actual operational conditions. Advances in computational fluid dynamics (CFD) has provided an alternative approach from model scale test to better understand uncertainties in prediction of ESD efficiency in full-scale ship operations [Shin et al, 2013]. In this work a high fidelity CFD model is presented for investigation effects of pre-nozzles on propulsion efficiency and ship resistance. The model is based on the Reynolds Average Navier-Stokes (RANS) solver with different turbulent models including a hybrid detached eddy simulation (DES) approach for predictions of complex near body flow features as well as in the wake regions from hull and propeller. The model is validated with model test for both towing and self-propulsion conditions. Finally a study of pre-nozzle effects on propeller efficiency as well as hull-propeller interaction is presented and compared with available experimental data (Tokyo 2015 Workshop). The current work constitutes a fundamental approach towards designing more efficient ESD for a specific hull form and propeller.
Retracted: “Kinematic Analysis of the Motion of a Six Degrees of Freedom Wave Energy Converter Based on the Concept of the Stewart-Gough Platform” [ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering, Volume 10: Ocean Renewable Energy, Madrid, Spain, June 17–22, 2018, Conference Sponsors: Ocean, Offshore and Arctic Engineering Division, ISBN: 978-0-7918-5131-9. Paper No. OMAE2018-78601, pp. V010T09A047; 10 pages, doi:10.1115/OMAE2018-78601]
Authors: ASME
Published: September 2018

This paper was withdrawn. ASME does not hold the copyright. December 21, 2018.

Copyright © 2018 by ASME
Parameter Estimation for Synthetic Rope Models
Authors: Weller S. D. , Banfield S. J. , Canedo J.
Published: September 2018

With widespread market penetration in the offshore sector, synthetic rope materials offer a range of axial compliance that can be exploited for mooring design, ranging from stiff (e.g. high modulus polyethylene) to soft (e.g. nylon). For new applications, such as the marine renewable energy (MRE) sector synthetic ropes are potentially an enabling technology due to their load reduction properties and relative low cost compared to conventional mooring component materials.

Existing design, test and certification procedures for ropes were developed for the station keeping of large offshore equipment. Arrays of small, reactive MRE devices will have an entirely different set of mooring load cases with the mooring system potentially an integral part of the power take off system. Larger devices are also likely to be subjected to complex loading as MRE deployment sites are typically highly energetic in terms of wind, wave and/or tidal energy. Consequently devices and associated subsystems are subjected to dynamic load cases in a wide range of complex environmental and operating conditions. Underpinning research is therefore required to understand the behaviour of synthetic materials subjected to highly dynamic loading regimes in terms of operational performance and long-term durability as these factors could have a significant impact on coupled device performance and availability. At present conventional mooring analyses is based on the use of simplified rope characteristics, although several studies including a Joint Industry Project (Syrope) have investigated these aspects. However, at present an industry-standard method to account for the time-varying behaviour of synthetic ropes for offshore equipment moorings does not exist.

The SynMaRE (Synthetic ropes for Marine Renewable Energy mooring systems) project aims to develop a time domain analytical model that can adequately represent the time dependent and non-trivial behaviour of synthetic ropes. Instead of being a stand-alone tool, it is intended that the model will be adopted for incorporation in (or with) commercial mooring system software allowing the prediction of mooring loads and device responses to an increased level of accuracy. This paper will present findings from an initial assessment of parameter estimation techniques utilising a simplified viscoelastic and viscoplastic model and validation scenarios based on physical tension-tension test data featuring load cases relevant to MRE mooring systems.
Estimation of Residual Stresses in Steel Welded Joints Using Three Dimensional Finite Element Analysis
Authors: Patel Shivdayal , Patel B. P. , Ahmad Suhail
Published: September 2018

Welding is one of the most used joining methods in the ship industry. However, residual stresses are induced in the welded joints due to the rapid heating and cooling leading to inhomogenously distributed dimensional changes and non-uniform plastic and thermal strains. A number of factors, such as welding speed, boundary conditions, weld geometry, weld thickness, welding current/voltage, number of weld passes, pre-/post-heating etc, influence the residual stress distribution. The main aim of this work is to estimate the residual stresses in welded joints through finite element analysis and to investigate the effects of boundary conditions, welding speed and plate thickness on through the thickness/surface distributions of residual stresses. The welding process is simulated using 3D Finite element model in ABAQUS FE software in two steps: 1. Transient thermal analysis and 2. Quasi-static thermo-elasto-plastic analysis. The normal residual stresses along and across the weld in the weld tow region are found to be significant with nonlinear distribution. The residual stresses increase with the increase in the thickness of the plates being welded. The nature of the normal residual stress along the weld is found to be tensile-compressive-tensile and the nature of normal residual stress across the weld is found to be tensile along the thickness direction.
Kinematic Formulation of Mooring Platform During Collisions Based on Multi-Body Dynamic Theory
Authors: Duan Qiuwan , Yang Yang
Published: September 2018

When a platform is operating in a mooring, various vessels that frequently pass by result in severe accidental collisions of the platform. Thus, the kinematic response of the mooring platform should be investigated. A new analytical method, including a load analysis and kinematics analysis, is proposed in this paper. In the load analysis, the impact force is calculated using finite element method (FEM). In the kinematic analysis, closed-form analytical expressions based on multi-body dynamics are derived with the impact force as an input. Furthermore, the expressions are improved considering the fluid effect. A series of collision cases are implemented to validate the proposed method by FEM. The kinematic results solved by the proposed method agree well with FEM, which illustrates that the method is feasible and accurate. However, the proposed method taking around 30s, which is much shorter than 7200s by FEM, is proved to be more efficient.
Numerical Analysis of the Pendulous Installation Method in Deep Water
Authors: Hou Zhicheng , Sun Liping , Zhu Xiaomeng
Published: September 2018

This paper mainly studies the numerical analysis of the Pendulous Installation Method of a pump module in 1,500 meter water. A nonlinear time-domain coupled vessel and the pump installation system is established using ORCAFLEX riser program to simulate the pendulous free-fall motion of the pump module. The analysis studies the effect of environmental loads and vessel’s dynamic response on the entire installation system. Different directions of environmental loads and a series of sea-states defined using significant wave heights are taken into consideration. The results show that the optimum direction of the environmental loads is taken as 180 degrees (aganist vessel length), and the dynamic response of the vessel has a great impact on the entire system and should not be neglected.
Numerical Study of Phase Change Influence on Wave Impact Loads in LNG Tanks on Floating Structures
Authors: Ancellin Matthieu , Brosset Laurent , Ghidaglia Jean-Michel
Published: September 2018

Understanding the physics of sloshing wave impacts is necessary for the improvement of sloshing assessment methodology based on sloshing model tests, for LNG membrane tanks on floating structures. The phase change between natural gas and liquefied natural gas is one of the physical phenomena involved during a LNG wave impact but is not taken into account during sloshing model tests.

In this paper, some recent numerical and analytical works on the influence of phase change are summarized and discussed. For the impact of an ideally shaped wave, phase change influences two different steps of the impact in different ways: during the gas escape phase, phase change leads to a higher impact velocity; for entrapped gas pockets, phase change causes a reduction of the pressure in the gas pocket. However, this influence is quantitatively small.

The generalization to more realistic wave shapes (including e.g. liquid aeration) should be the focus of future works.
Development of a New Methodology for Riser Deformed Shape Prediction/Monitoring
Authors: Choi Junho , Kim Joseph Moo-Hyun
Published: September 2018

Ocean environmental conditions, such as waves, winds, and currents, are getting harsher due to climate change. This means that oil and gas production platforms in the ocean may experience unexpectedly large environmental loads bigger than previous design loads. Also, many platforms are reaching the end of their design lives. Ensuring riser integrity is one of the most important issues for platform safety and service-life extension. Currently, monitoring sensors are deployed on risers, and structural evaluation methods are utilized to examine riser integrity. However, there are some limitations to the structural evaluation methods. Furthermore, platform operators continue to seek for more direct and cost-effective riser monitoring method due to the low price of oil. In this study, the MultiSensor Fusion (MSF) system is proposed to surmount technical and economic obstacles in real-time riser-monitoring technology. The MSF system is validated for TLP (tension-leg platform) risers by using numerical sensors and numerical-simulation tools.
Elasto-Plastic Beam Afloat on Water Subjected to Waves
Authors: Iijima Kazuhiro , Tatsumi Akira , Fujikubo Masahiko
Published: September 2018

This paper addresses development of a mathematical model which describes the behavior of an elasto-plastic beam afloat on water surface. The mathematical model is valid for predicting the collapse of a Very Large Floating Structure (VLFS) subjected to extreme wave-induced vertical bending moment. It is a follow-up of the previous work in which the collapse behavior of a VLFS is pursued by adopting a segmented beam approach. In this research, the whole VLFS is modelled with elasto-plastic beam elements. The hydrodynamic behavior is modeled by using Rankine source panel method based on time-domain potential theory. It is shown that the elasto-plastic beam approach gives almost the same result as the segmented beam approach for predicting the one-element collapse behavior. The elastoplastic beam approach is extensively used to predict the progressive collapse spread over multiple sections, which cannot be followed by the segmented beam approach.
Dynamic Response Analysis of Floating Storage Tank System Considering Hydrodynamic and Mechanical Interactions
Authors: Wan Ling , Zhang Chi , Magee Allan Ross , Jin Jingzhe , Han Mengmeng , Ang Kok Keng , Hellan Øyvind
Published: September 2018

For better utilization of ocean and coastal space, hydrocarbon products can be stored in the floating tanks, which can be enclosed by barge system. The barge system can be moored through pile foundations. The tanks are moored through marine fenders connected to barges. In the system, hydrodynamic and mechanical interaction problems are involved. Different scenarios including two barge, three barge and four barge systems are investigated. In addition, one tank plus four barge system are also studied. Hydrodynamic interactions between different bodies are firstly studied to investigate the significance of interaction. Different barge configurations are then considered in terms of mechanical interaction significance. Tank dynamic responses with and without hydrodynamic interaction are evaluated.
Decision Making Through the Application of Bayesian Network for Internal Corrosion Assessment of Pipelines
Authors: Ayello Francois , Liu Guanlan , Zhang Jiana
Published: September 2018

Decision making for a new pipeline’s design and provision of the most effective maintenance or repair measures for a pipeline in operation can be a long and costly process. The final decision made, whether during design or operation, may not always reduce the risk or remediate the threat. This is mainly due to the uncertainty and missing information regarding the field chemistry for current and future pipeline operating conditions, that were not considered and quantified during the assessment.

In this paper, two case studies of pipeline internal corrosion risk are presented, one for pipeline in design and the latter for pipeline in operation. Both cases were assessed using Bayesian Networks. Bayesian Networks (BN) have been used to quantify the value of information of uncertain and missing data. BN displays the cause-effect relationships of these data in the form of conditional probabilities to describe how one’s data is influencing internal corrosion rates probability. Thus, predicting the pipeline’s conditions over the design life. Operators can visualize the development of internal corrosion within a pipeline over time and gain clearer understanding of the causal relationships that could lead to pipeline failure. The results allowed operators to confirm the effects of the parameter and followed by a sensitivity analysis to find out which data to prioritize in acquisition and validation before proceeding to decide on how the pipeline should be designed and maintained/inspected in future.
An Overview of Strain-Based Fracture Assessment of Pipelines
Authors: Wu Guiyi , Wang Longjie
Published: September 2018

Development of remote energy requires large pipeline networks to be placed in more challenging environments such as offshore in deeper waters or on land in Arctic or near-Arctic locations. Pipeline installed and operated in such regions may be subjected to large plastic strains. Engineering critical assessments (ECA) are commonly carried out during design, installation and operation of offshore pipelines to determine acceptable flaw sizes in pipeline girth welds. A number of fracture mechanics-based procedures are available for ECA of pipeline girth welds. Most of these methods are primarily stress-based assessments and are therefore not directly applicable to cases where the displacement-/strain-controlled loading generates large amounts of plastic deformation. For such cases, strain-based fracture assessment for pipeline/girth welds should be carried out instead. However, limited guidance on strain-based assessment is available in the current codes and standards used primarily by the oil and gas industries. This paper reviews the existing strain-based fracture assessment methods, and reports the results of preliminary studies performed to compare the methods reviewed with the available full-scale pipe test data.