bluuebunny/crossref_metadata_2025 huggingface dataset:
Co-Simulation of a Marine Offshore Vessel in DP-Operations Including Hardware-In-the-Loop (HIL)
Authors: Skjong Stian , Pedersen Eilif
Published: October 2017

In this work, a co-simulation case study of a marine offshore surface vessel in Dynamic Positioning (DP) operation, where the DP-controller is placed on an Arduino® micro-controller, is presented. The reasons for using co-simulation are that it is possible to distribute the model among different cores in one computer as well as among different computing members over a local area network. Also, it is possible to export submodels from different software and connect them together in a common simulation. This enables the use of suited modeling software for different types of dynamical systems, as well as hardware, such as micro-controllers for Hardware-In-the-Loop testing. Such an integrated and open simulation method facilitates the development of new products as well as shortening the iterative process in design phases. As for co-simulation standard, the Functional Mock-up Interface (FMI) for co-simulation will be used in this work, and a communication Functional Mock-up Unit (FMU) that communicates with hardware and handles the signal flow between the hardware and the co-simulation will be developed. In the case study, a DP-controller is implemented on the microcontroller and connected to a filter, a position reference system and an offshore vessel model, all implemented as FMUs in the total co-simulation. For simulation master algorithm, the open source software “Coral”, that was developed in the knowledge building project “Virtual Prototyping of Maritime Systems and Operations” (ViProMa), will be used. The simulation results show that even though the micro-controller is set to communicate with a lower frequency than the rest of the co-simulation submodels, the total c-simulation is stable and produces good results. It also show that the FMI standard facilitates hardware in the loop in the co-simulation, and that the co-simulation master algorithm Coral is suited for such simulation cases.
Ductile Damage Study of Defective Girth Welds for Oil and Gas Pipeline: A Tailored Numerical and Finite Element Method Calibration From SENT Fracture Mechanics Test
Authors: Bruschi Roberto , Rossi Marco , Di Michele Alex , Scarsciafratte Daniele , Torselletti Enrico
Published: October 2017

In this paper, the evolution of ductile damage in pipe girth welds for offshore pipelines application is studied with the use of Finite Element Analysis. To this purpose, the Gurson-Tvergaard-Needlmen (GTN) model is calibrated and applied to different finite element simulations. Saipem internally developed software, written in Matlab® environment, is used to automatically calibrate the Gurson model from experimental data and run several Finite Element Models of the pipe with different flaws in the girth weld.

The objective of this paper is to present and discuss this numerical tool, developed by Saipem coupling a Matlab® GUI and the ABAQUS FE solver. The tool allows speeding up and automatizing the calibration procedure of the Gurson model and making a rapid evaluation in terms of the Crack Driving Force (CDF) for defective girth weld. The tool allows also a quick and efficient model preparation, full FE analysis and post-processing, with saving of engineering hours.
A Winch Reference Control System for Semi-Pelagic Triple Trawling: With Full-Scale Sea Trials
Authors: Haugen Joakim , Grimaldo Eduardo , Gjøsund Svein H.
Published: October 2017

Multi-rig bottom trawling can negatively impact the seabed, and the bottom contact forces contribute to the total towing resistance. Lifting the doors from the seabed can reduce some of the trawl gear’s influence on the seabed and save fuel costs. In this study we evaluated a simple reference controller designed to control a trawl door’s distance from the seabed. This was achieved by providing desired warp lengths to a controller, which then regulated the distance via a low-pressure hydraulic winch. The reference controller algorithm uses an anti-windup proportional-integral controller with saturation of winch acceleration and speed. Herein, we present results of a full-scale sea trial conducted using a triple shrimp trawl with trawl doors towed close to the seabed. Our results demonstrate the feasibility of controlling the trawl doors’ altitude above the seabed using only winch-actuated feedback.
Subsea Pipeline Lateral Buckling Design: Strain Concentration or Strain Reduction Factors
Authors: Liu M.
Published: October 2017

Strain based design is normally applied for HPHT pipelines when the conventional stress based method becomes impractical. In addition to a design safety factor, a strain concentration factor is typically incorporated in the lateral buckling assessment to account for non-uniform stiffness or plastic bending moment due to geometry and material strength mismatch between adjacent pipe joints. Increased strain concentration can compromise pipeline low cycle fatigue and lateral buckling capacity, leading to an early onset of local buckling failure. In this paper, the philosophy of local buckling mitigation using the strain concentration factor is examined. The local buckling behaviour is evaluated in relation to strain concentration. Global strain reduction and evolution against buckling is analysed with respect to varying joint mismatch level derived according to a structural reliability analysis.

The concept of a strain reduction factor due to mismatch is developed and proposed based on the global strain capacity reduction with reference to the uniform configuration. It is demonstrated that the strain reduction factor is a unique characteristic parameter. As opposed to strain concentrations it is an invariant insensitive to evaluation methods and the design strain demand level, hence more representative as a limiting design metric to maintain the safety margin. The use of the strain reduction factor is thus put forward in strain based lateral buckling design as an alternative to using the strain concentration factor. The method for obtaining the strain reduction factor and its application is developed. The rationale for its introduction is outlined and some of its benefits are established. The discernible difference and scenarios for application of either factors are discussed, including low and high cycle fatigue, linearity and stress concentration (SNCF from SCF for welds), ECA and lateral buckling. Additional causal factors giving rise to mismatch such as pipe schedule transition and buckler arrestor are also discussed. Iterations of FE analyses are performed for a pipe-in-pipe configuration in a case study.
Communications Challenges in the Arctic: Oil and Gas Operations Perspective
Authors: Ho Tu Dac , Fjørtoft Kay
Published: October 2017

Challenges when operating offshore systems in the Arctic were addressed and analyzed from general data communications systems to distress communications systems. Two methodologies were developed with tools for estimating: a) Rainfall rate in the worst case as well as the degradation due to the highest rainfall rate to link budget of typical satellite links; b) Performance of any service at a given geographical area or location. The evaluations were for diversified inputs such as geographical locations were ranging from further south to high North; the most typical satellite communications systems in the region; and an abundant list of services dedicated to offshore Oil and Gas industry, the paper has provided a wide range list of results and recommendations when analyzing services performances from low to high latitudes and west to east longitudes. An important conclusion was that voice-relevant services were not working fine for both Inmarsat and VSAT from the latitude of 73.5 degree North regardless of the bandwidth of the satellite when assuming the deadline for these voice packets was one second. These services can be partially of fully satisfied by Inmarsat or VSAT depends on the bandwidth provided if working below that latitude. For file transfer services, it is possible to guarantee a certain satisfactory ratio at high latitude provided a compensation for bandwidth. The paper1 also provides other numerical results in regarding of link compensation that can be used for new satellite link purpose.
Simulating Riser VIV in Current and Waves Using an Empirical Time Domain Model
Authors: Thorsen Mats J. , Sævik Svein
Published: October 2017

The theoretical background of an empirical model for time domain simulation of VIV is reviewed. This model allows the surrounding flow to be time varying, which is in contrast to the traditional frequency domain tools. The hydrodynamic load model consists of Morison’s equation plus an additional term representing the oscillating effect of vortex shedding. The magnitude of the vortex shedding force is given by a dimensionless coefficient, and this force is assumed to act perpendicular to the relative velocity between the cylinder and the fluid. The time variability of the vortex shedding force is described by a synchronization model, which captures how the instantaneous frequency reacts to cylinder motion.

The parameters in the time domain load model are calibrated against a commonly used frequency domain VIV analysis tool, VIVANA. To do this, a finite element model of a vertical tensioned riser is established, and the structure is exposed to a linearly sheared flow. Key results such as cross-flow displacements along the riser, frequency content, r.m.s. of bending stresses and mean in-line displacements are compared, and it is shown that the frequency and time domain methods are close to equivalent in this simple case with stationary flow.

Finally, the time domain model is utilized to study VIV of a riser subjected to regular waves. The characteristics of wave induced VIV are discussed in light of the simulation results. It is seen that VIV is excited in the zone close to the surface, and the energy is transported downwards as traveling waves. The vibrations typically build up as the horizontal water particle velocity is high, and die out as the velocity decreases. The effect of varying the wave amplitude and period is investigated, and it is found that the dominating frequency, mode and r.m.s. stresses increase together with the wave height. The effect of the wave period is however more complicated. For example, reducing the wave period increases the dominating mode but decreases the displacements. Hence the stress may increase or decrease, depending on which of these effects are strongest.
Automated System for Fleet Benchmarking and Assessment of Technical Condition
Authors: Mo Brage , Dehli Petter , Steinebach Christian , Lim Tow Foong , Perera Lokukaluge P.
Published: October 2017

On-board Energy systems in vessels have to use fuel efficiently to maintain ship speed at lowest possible costs. This paper describes how to use ship operational data to improve and maintain efficiency of the vessel’s power production with respect to the condition and performance of equipment. The paper describes an overview of an automated Technical Operations Performance (TOP) Monitoring service. TOP monitors the performance of marine main and auxiliary diesel engines by use of the information collected onboard vessels at regular intervals. Performance data are stored in xml-reports sent as email attachments from ship to shore. This communication is reliable and cost efficient for merchant ships that are on-line only for shorter periods. Load, ISO and environmental corrections make results valid for benchmarking and trending. The service aggregates the hierarchical information obtained from different sources by transferring measurement readings into unified indicators, the Technical Condition Index (TCI) [1]. Experts manually check the automatically generated performance reports and add additional guidance on options to improve power production and machinery conditions analyzing the available data with respect to different targets, such as low engine degradation and high fuel efficiency. The performance reports then influence business processes indicating possible causes for loss of performance in equipment and possible erroneous instrumentation, and the need for maintenance actions. The obtained TCI values show the performance of individual units, or for a fleet/class of equipment and vessels.
Validation of Open-Source SPH Code DualSPHysics for Numerical Simulations of Water Entry and Exit of a Rigid Body
Authors: Buruchenko Sergei K. , Canelas Ricardo B.
Published: October 2017

Water entry and exit of a body is an important topic in naval hydrodynamics as these phenomena play relevant roles both for offshore structures and vessels. Water entry and exit events are intrinsically transient and represent intense topological changes in the system, with large amounts of momentum exchange between phases. At its onset, they can be characterized by highly localized, both in space and time, loads on the vessel, influencing both the local structural safety of the structure and the global loads acting on it.

The DualSPHysics code is proposed as a numerical tool for the simulation of fluid and floating object interaction. The numerical model is based on a Smoothed Particle Hydrodynamics discretization of the Navier-Stokes equations and Newton’s equations for rigid body dynamics. This paper examines the water impact, fluid motions, and movement of objects in the conventional case studies of object entry and exit from still water. A two dimensional body drop analysis was carried out demonstrating acceptable agreement of the movement of the object with published experimental and numerical results. The velocity field of the fluid is also captured and analyzed. Simulations for water entry and exit of a buoyant and neutral density cylinder compares well with previous experimental, numerical, and empirical studies in penetration, free surface evolution and object kinematics. These results provide a good foundation to evaluate the accuracy and stability of the DualSPHysics implementation for modeling the interaction between free surface flow and free moving floating objects.
Test to Determine Hydrodynamic Interaction Between Drilling Riser, Drill String and Mud
Authors: Li Songcheng , Campbell Mike , Russo Massimiliano , Katla Erling
Published: October 2017

Drilling riser damping can have a significant effect on the dynamic response of the drilling system, especially the fatigue response of the wellhead and conductor system. The presence of any drilling riser damping helps to diminish the transfer of riser motions into the wellhead system, which can improve any wellhead fatigue issues.

One of the little studied contributors to the system damping is the hydrodynamic damping effect of the interaction between the drill pipe and drilling fluid inside the riser. As part of the ongoing Structural Well Integrity Joint Industry Project (JIP), finite element analysis (FEA) with a wide range of drag and inertia coefficients is conducted to simulate the mud drag and inertia on the drill string and the riser. These sensitivity studies demonstrate that the mud drag and inertia on the drill string could be one of the key driving factors in riser system damping. To verify the FEA work, the Structural Well Integrity JIP conducted a laboratory test to determine the drag coefficient and added mass coefficient of drill pipe inside a marine drilling riser with and without flowing mud and water in the riser annulus.

In this paper, the test setup and the test matrix are introduced, and the methodology for determining drag coefficient and added mass coefficient are explained. The test results are also presented and compared with published test data for open water.
Geopolymers As an Alternative for Oil Well Cementing Applications: A Review of Advantages and Concerns
Authors: Khalifeh Mahmoud , Saasen Arild , Hodne Helge , Godøy Rune , Vrålstad Torbjørn
Published: October 2017

Geopolymers, being inorganic polymers created from rock sources, were evaluated as an alternative to Portland cement. To evaluate their usability some properties of a selected geopolymer were measured and compared with those from a neat class G Portland cement. The geopolymeric slurries showed a non-Newtonian viscosity behavior with a measurable, albeit low, yield stress. The pumpability measurements using atmospheric and pressurized consistometer showed an adequate set profile for both the geopolymer and cement sample. Static fluid loss test show that the geopolymeric slurries experienced a lower fluid loss compared to that of the Portland cement. The shrinkage factor for the geopolymers was reduced (expanded) as the downhole temperature was ramped up. The shrinkage of the Portland cement sample proceeded only with a lower rate. Tensile strength of the geopolymers was approximately 5% of their compressive strength; however, this value for Portland cement was approximately 10% of its compressive strength. Finally, shear bond strength of geopolymers would benefit from improvement.
Experimental and Numerical Analysis of Hybrid 3kW Ocean Wave-Power Generation System Subjected to Regular and Irregular Wave Forces
Authors: Jeongsoo Kim , Min-Su Park , Youn-Ju Jeong , Yoon-Koog Hwang
Published: October 2017

In particular of coastal area, needs of ocean energy development have emerged with global demands on non-pollution energy. Although there are several types of wave-power generation systems, such as an attenuator and an overtopping device, these have problems related to frequent damages or limited applicable area. This study is concerned with development of a new hybrid wave-power system, which is expected to provide higher power efficiency than the previous system, and experimental and numerical estimations on performance of the new system. The proposed wave power absorber is composed of a generator embedded in the floating shield cylinder, pendulum plate to accelerate rotation of generator, self-dynamic positioning devices, and a support column to fix the entire power generation system to the seabed. To determine major design parameters and to conduct a specific concept design of the proposed power generation system, hydrodynamic tests of the floating shield cylinder were carried out. The cylinder was scaled with a scale factor 0.12. Several test specimens were fabricated to examine effects of the following physical characteristics on the system performance: draft depth of the cylinder, diameter of the cylinder, longitudinal projective area of the cylinder, a number of blades attached on the cylinder, blade length. Each specimen was subjected to 8 regular and 4 irregular wave loads for 5 minutes; an extreme water wave condition was also included. In the hydrodynamic tests, rotation numbers of the cylinder per a minute were measured. Although consistent patterns of the angular velocity of the cylinder was not observed from the experimental results, the results showed that the ratio of draft depth to diameter mainly effects on the angular velocity of the cylinder, and that the cylinder quickly rotates at the crest of an incident wave while it inversely and slowly rotates at the through. Furthermore, to supplement the above tests and to analyze mechanical behaviors of the support system, numerical simulations of the system were also conducted. To calculate water pressure on the cylinder and the support column, the commercial computational program ANSYS AQWA was used. The distribution and the magnitude of the predicted water pressure were then mapped into the finite element model of the cylinder and the support structure to examine the structural responses and stability against overturning.
Optimization of the Superstructure and Forecastle Fairing of a Container Ship
Authors: Rui Deng , Chao Li , Guo-xiang Dong , Wen-shan Cai , Ze-hua Lu , Xu Xiang
Published: October 2017

Wind resistance is an important part of the container ship compared with the other types of commercial vessels because of the containers piled on the deck, and it is significant to investigate the wind load of the container ship and the approach to minimize it in order to reduce the wind resistance and save energy. Two approaches are adopted in the investigation to minimize the wind load, the first one of which is smoothing the corners of the superstructure while the second one is adding a forecastle fairing in the front of the deck. Three different superstructures and six different fairings are designed and tested with the ship in the wind tunnel. It is suggested by the comparison of the experimental results that the optimization of the superstructure and forecastle fairing is helpful in wind resistance reduction.
Further Advances on Concrete Coating Impact on Pipeline Strength
Authors: Battistini Alberto , Catena Luca , Mancini Adelina , Marchionni Lorenzo , Parrella Antonio , Vitali Luigino
Published: October 2017

Concrete Weight Coating is used in offshore industry to provide for pipeline vertical and lateral stability against waves and currents and to guarantee protection against fishing activities. Reinforced concrete coating of adequate strength, especially in case of thick coatings for stringent in-place stability requirements, entails additional bending stiffness and consequently strain concentration at field joints, thus significantly affecting the state of stress and strain on the pipe steel during laying firstly, and then during operations.

Attention of the offshore pipeline industry has been focused in the development of experimental and theoretical activities in a more scientific way, which aimed to satisfy the need of a better knowledge in this field. Both analytical and FEM solutions are available in the free literature and relevant standards to predict the contribution of concrete coating layer on global pipeline strength and deformation capacity and simplified threshold values for the concrete damage are provided, as well.

Generally, for installation analysis purpose, a pipeline with equivalent mechanical behavior (bending moment-curvature relationship) and physical (weight) properties is used in installation and operation analyses. No assumptions are typically made on concrete damage evolution to evaluate the decay of pipe capacity beyond the elastic range.

In this paper new advances in modelling the mechanical behavior of concrete coated joints are discussed. In particular an advanced ABAQUS finite element model is proposed to take into account the effect of concrete coating damage on the overall capacity. The following effects have been accounted:

• Non-linear stress-strain relationship of the steel at large usage factors/curvatures on the strain concentration at the field joint.

• Concrete coating damage evolution on global pipeline bending stiffness.

In this paper:

• The state-of-the-art about published materials, numerical studies and design approaches on concrete material modelling and concrete coated pipes is briefly presented;

• A FEM based analysis methodology is drawn and proposed for the strength and deformation capacity assessment of a concrete coated pipe;

• The FEM model is calibrated on available full scale tests;

• The results of a project case study performed with ABAQUS FE Model are given.
Maintenance Regime Minimum (MRM): State of the Art — Maintaining Offshore Platforms Before Decommissioning
Authors: Kumar Kundan , Ratnayake R. M. Chandima
Published: October 2017

It is a mandatory requirement to maintain offshore oil and gas (O&G) production and process platforms during the engineering down period (i.e. the period from the end of the design/operational life to decommissioning). Decommissioning of the offshore production and process (OP&PPs) involves cessation of operations, withdrawal of the facility from service, transformation into an out-of-service state, deactivation and removal. There are several energy sources (i.e. pressure, chemical substances, electrical and mechanical instrumentation, telecom equipment, navigation radar system, gravity, heat/cold, biological substances, etc.), which need to be maintained and/or deactivated until the platform is decommissioned. This manuscript first maps the current state of the art in relation to the maintenance of OP&PSs before decommissioning. Then, the ‘Maintenance Regime Minimum’ (MRM) approach is proposed to perform comparative analysis in order to identify and select the optimal maintenance hours within the decommissioning strategy, based on cost (e.g. man hours required), safety, and environmental challenges. The manuscript also illustrates how the MRM approach focuses on potential decommissioning alternatives in relation to the optimization of maintenance hours and challenges involved in different tags throughout the functional hierarchy. The results of a case study on two topside systems (i.e. in relation to two alternatives) are also presented.
The Influence of SiO2 and TiO2 Nanoparticles on the Properties of Water-Based Mud
Authors: Mijić Petar , Gaurina-Međimurec Nediljka , Pašić Borivoje
Published: October 2017

About 75% of all formations drilled worldwide are shale formations and 90% of all wellbore instability problems occur in shale formations. This increases the overall cost of drilling. Therefore, drilling through shale formations, which have nanosized pores with nanodarcy permeability still need better solutions since the additives used in the conventional drilling fluids are too large to plug them. One of the solutions to drilling problems can be adjusting drilling fluid properties by adding nanoparticles. Drilling mud with nanoparticles can physically plug nanosized pores in shale formations and thus reduce the shale permeability, which results in reducing the pressure transmission and improving wellbore stability. Furthermore, the drilling fluid with nanoparticles, creates a very thin, low permeability filter cake resulting in the reduction of the filtrate penetration into the shale. This thin filter cake implies high potential for reducing the differential pressure sticking. In addition, borehole problems such as too high drag and torque can be reduced by adding nanoparticles to drilling fluids.

This paper presents the results of laboratory examination of the influence of commercially available nanoparticles of SiO2 (dry SiO2 and water-based dispersion of 30 wt% of silica), and TiO2 (water-based dispersion of 40 wt% of titania) in concentrations of 0.5 wt% and 1 wt% on the properties of water-based fluids. Special emphasis is put on the determination of lubricating properties of the water-based drilling fluids. Nanoparticles added to the base mud without any lubricant do not improve its lubricity performance, regardless of their concentrations and type. However, by adding 0.5 wt% SiO2-disp to the base mud with lubricant, its lubricity coefficient is reduced by 4.6%, and by adding 1 wt% TiO2-disp to the base mud with lubricant, its lubricity coefficient is reduced by 14.3%.
Advanced 3-D FEA Modelling for a Modern and Multidisciplinary Pipeline Design Approach
Authors: Bartolini Lorenzo Maria , Marchionni Lorenzo , Spinazzè Maurizio , Vignati Giulio Claudio , Vitali Luigino
Published: October 2017

In the last thirty years the attention of the offshore pipeline industry has been strongly focused on submarine pipelines crossing harsh environments and subject to severe operating conditions of temperature and pressure.

Pipeline structural integrity may be threaten by large free-spanning sections between rocky peaks and deep depressions that may be coupled with the pipeline propensity to develop lateral/vertical deflection due to severe service conditions (high pressure/high temperature). For short flowlines, pipeline walking is an additional issue to be verified and faced during design and the application of an integrated approach between flow assurance, installation, geotechnics and pipeline design is a must.

All these features characterize new load scenarios for which intervention works are mandatory to control the development of excessive loads and deformations within acceptance criteria. 3-Dimensional Finite Element Models permit to anticipate the pipeline global response under design loads taking into account the expected (during design phase) and/or actual (after measurements of the as-built) 3-Dimensional pipeline configuration. In case that mitigation measures are to be installed along the pipeline route, their effectiveness can be verified and optimized. Potential failure events in the most promising mitigation measure strategy can be investigated and anticipated at design stage. This paper describes the most relevant capability of the pre- and post-processing tools developed in MATLAB environment and based on ABAQUS Finite Element.
Investigation of Free Surface Damping Models With Applications to Gap Resonance Problems
Authors: Markeng Kevin , Vada Torgeir , Pan Zhi Yuan
Published: October 2017

In this paper two methods for modelling the damping in a narrow gap are investigated. The first method is called the Pressure Damping Model. This method has been used in studies of wave energy devices. An attractive feature of this model is that the modified input is directly related to the energy dissipation in the gap, which means that if this dissipation is estimated the input to the model can be obtained directly. The idea of the method is to add a pressure input in the gap to suppress the resonant motion. A challenge with the method is that it contains a non-linear term.

The second method is the Newtonian Cooling damping model. The method is based on introducing a dissipation term in the free surface boundary condition. This dissipation term contains a coefficient which is not directly related to the energy dissipation. Hence this method is not so easy to relate directly to the estimated energy dissipation. An advantage with this method is that it is linear and hence can be expected to be more robust.

In the first part of the paper a 2-dimensional problem is investigated using both methods. In addition to the numerical performance and robustness, much focus is put on investigation of the energy balance in the solution, and we attempt to relate both models to the energy dissipation in the gap.

In the second part the Newtonian cooling method is implemented in a 3-dimensional potential flow solver and it is shown that the method provides a robust way to handle the resonance problem. The method will give rise to a modified set of equations which are described.

Two different problems are investigated with the 3D solver. First we look at a side-by-side problem, where the 3D results are also compared with 2D results. Finally, the moonpool problem is investigated by two different 3D solvers, a classical Green’s function based method and a Rankine solver. It is also shown how this damping model can be combined with a similar model on the internal waterplane to remove irregular frequencies.
Pipeline Loads and a Design Approach in Areas of Seabed Subsidence
Authors: Reed Knut , Moshagen Hermann
Published: October 2017

Seabed subsidence may sometimes be a consequence of the drainage of the oil and gas reservoir. The subsidence process results in changes of the seabed level as well as displacements of the seabed horizontally. The horizontal displacements may impose significant axial compression or tension loads on seabed pipelines installed in the area.

This paper focuses on the engineering challenges of pipelines subject to seabed subsidence. The paper deals with the design issues of the pipelines. It will be seen that for pipelines in areas of seabed subsidence an overall design approach applies where pipeline integrity management may be an important part of the solution.

The present paper describes the phenomenon of seabed subsidence including a typical subsidence field and the time history of vertical and horizontal displacements of the seabed. An example pipeline route is defined for the purpose of illustration of displacements along the route.

A pipeline to be designed and installed in the subsidence area is defined. The load transfer mechanism from seabed to pipeline is described and the resulting compression or tension loads from seabed subsidence on the pipeline are then derived.

An approach for designing a solution for the pipeline to accommodate the loads from seabed subsidence is established and discussed. The discussion involves spool design, mitigation measures and integrity management issues. The paper concludes by recommendations for future applications in actual design cases.
Flow Induced Pulsations (FLIP) in Rough Bore Gas Flexible Pipes, Tests and Model
Authors: Legeay S. , Decuupere M. , Charliac D.
Published: October 2017

Since the early 2000’s singing risers phenomenon has been encountered. The so called Flow Induced Pulsations (FLIP) phenomenon occurs in dry gas risers (such as Gas Export lines) and may generate high tonal noises up to 110 dB but may also lead to high vibration of adjacent equipment leading to significant fatigue failure.

This publication presents the recently developed model that aims at performing FLIP assessment for rough bore gas flexible pipes. The developed model provides the FLIP onset velocity and frequency for a given rough bore. It will also describe the main contributing factors such as the inner layer corrugation profile, the operating conditions (pressure, temperature and flow rate) and adjacent equipment’s acoustic reflection contributions.

In addition, a Flow Induced Pulsation test carried out in 2003 to 2006 will be presented. Test outcomes will be compared to model presented in the first part.

Finally, reliability of the model will be presented detailing benchmark with past tests and FLIP experienced on fields.

To conclude, the model enables predictions and recommendations to avoid FLIP at an early stage prior to project execution.
Experimental Investigation of the Green Water Loads on a Wave-Piercing Tumblehome Ship
Authors: Li Hui , Deng Bao-Li , Sun Shu-Zheng , Du Wen-Lei , Zhao Hao-Dong
Published: October 2017

This paper presents the results of an experimental investigation of green water loads on a wave-piercing tumblehome ship. A water tank experiment was carried out in head regular waves by using a self-propelling segmented ship model. Wave probes and pressure sensors were arranged on the bow deck along the longitudinal and transverse directions. The height of water and the impact pressure on the deck were measured and their distributions in different wave conditions studied. The motion of the water flowing on the deck was recorded by a high-speed video system. Based on the experimental results, it was found that the green water is more serious with the increase of incident wave height and ship speed. The bow shape has little effects on the occurrence of green water, but it influences the green water loads to some extent. The distribution of green water pressure is different from that of green water height due to the strong nonlinearity of green water pressure.
A Fast and Practical Method for Predicting the Fatigue Life of Offshore Wind Turbine Jacket Support Structures
Authors: Han Chaoshuai , Ma Yongliang , Qu Xianqiang , Qin Peijiang , Qiu Binbin
Published: October 2017

Fatigue assessment is a very important part in the design process of offshore wind turbine support structures subjected to wind and wave loads. Fully coupled time domain simulations due to wind and wave loads can potentially provide reliable fatigue predictions, however, it will take high computational effort to carry out fatigue analysis of the simultaneous wind and wave response of the support structure in time domain. For convenience and reducing computational efforts, a fast and practical method is proposed for predicting the fatigue life of offshore wind turbine jacket support structures. Wind induced fatigue is calculated in the time domain using ANSYS based on rainflow counting, and wave induced fatigue is computed in frequency domain using SACS based on a linear spectral analysis. Fatigue damage of X-joints and K-joints under combined environmental loads of wind and wave is estimated by using the proposed method. To verify the accuracy of the proposed formula, fatigue damage based on time domain rainflow cycle counting is calculated and can be considered as a reference. It is concluded that the proposed method provides reasonable fatigue damage predictions and can be adopted for evaluating the combined fatigue damage due to wind and wave loads in offshore wind turbine.
Key Techniques in Simulating Comprehensive Anchor Behaviors by Large Deformation Finite Element Analysis
Authors: Zhao Yanbing , Liu Haixiao
Published: October 2017

With the application of innovative anchor concepts and advanced technologies in deepwater moorings, anchor behaviors in the seabed are becoming more complicated, such as 360-degree rotation of the anchor arm, gravity installation of anchors with high soil strain rate, and keying and diving (or penetration) of anchors. As a very important component of the installation or mooring system, anchor line connects the anchor and the anchor handling vessel (AHV) or floating moored platform. With moving of the AHV or platform, anchor line produces a space movement, and forms a reverse catenary shape and even a three-dimensional profile in the soil. Numerical analysis on the behaviors of anchor lines and deepwater anchors requires techniques that can deal with large strains and deformations of the soil, track changes in soil strength due to soil deformation, strain rate and strain softening effects, appropriately describe anchor-soil friction, and construct structures with connector elements to conform to their characteristics. Being an effective tool of large deformation finite element analysis, the coupled Eulerian-Lagrangian (CEL) method is advantageous in handling geotechnical problems with large deformations, where a traditional Lagrangian analysis is coupled with an Eulerian phase of material advection. This paper gives an overview of several key techniques in the CEL analysis of comprehensive behaviors of deepwater anchors, including construction of the embedded anchor line and the anchor line in the water, installation of gravity installed anchors (GIAs), keying or diving of drag anchors and GIAs, and implementation of the omni-directional arm of GIAs. Numerical probe tests and comparative studies are also presented to examine the robustness and accuracy of the proposed techniques. The aim of this paper is to provide a numerical framework to analyze the comprehensive behaviors of anchor lines and deepwater anchors.
A Two-Dimensional Model of Predicting Sand Erosion in Elbows for Liquid Flow
Authors: Kang Rong , Liu Haixiao , Liu Mingyang
Published: October 2017

A two-dimensional theoretical procedure is proposed in this study to estimate sand particle erosion in 90-degree elbows for liquid flow. The two-dimensional model adequately describes the erosion occurring along the centerline of the elbow extrados and to an extent reflects the erosion level on the whole elbow. The sand erosion prediction procedure is divided into three steps: building a two-dimensional liquid flow model, tracking the particle trajectories and predicting the penetration depth. First, a motion expression of the fluid streamline in an elbow is deduced from the continuity equation and the Euler equations, supposing the incompressible flow in the elbow is steady and inviscid. The radial velocity is introduced into the present model to reflect the effect of secondary flow on the symmetry plane. Second, particle trajectories are computed using the Lagrange approach based on the obtained expression of flow field distributions. The effects of the fluid drag force and the virtual mass force are considered as the main factors, and the particle impact velocity and angle are predicted through this method. Third, the penetration depth can be calculated from erosion correlations and the erosion profile along the centerline of the 90-degree elbow can also be worked out. Several typical experiments are selected to verify the two-dimensional theoretical model by comparing the predicted erosion results with the measured data.
Best Practice Guidance for Establishing the Design Fatigue Capacity of Subsea Well Intervention System Connectors
Authors: Wormsen Anders , Kirkemo Finn , Muff Anthony David
Published: October 2017

This paper presents a best practice guidance for establishing the design fatigue capacity of subsea connectors, both for air and for seawater with cathodic protection. The design fatigue capacity is established based on analysis and in-air full-scale connector fatigue testing. This best practice guidance is based on experience with the use of API 17G since 2006, recent updates of the fatigue design codes DNVGL-RP-C203 and BS 7608 and a review of a large number of in-air full-scale connector fatigue tests. This best practice guidance has been proposed to be included in Annex D of the 3rd edition of API 17G and in Annex B of the 5th edition of NORSOK U-001.
Design Aspects of Breakwaters for Cold Climate Oil and Gas Terminals
Authors: Jimenez Puente Isabel , Gudmestad Ove Tobias
Published: October 2017

This paper focuses on design aspects regarding breakwaters for cold climate terminals, in particular, the different types of berm breakwaters, their stability, armour mobility criteria and armour size.

A methodology is analyzed in order to determine the mean weight of the heaviest armour class as a function of wave parameters such as the significant wave height and the mean wave period, both for non-reshaping and reshaping stable berm breakwaters. The influence of the wave period on the stone mass required will be of special importance in the discussion. This methodology will enable us to determine the required median armour weight for a specific wave parameter, being easily able to compare the feasibility of different concepts or availability of the required stone size at the location.

As a case study, the breakwater selection for the Melkøya terminal in the Norwegian Barents Sea, is assessed through a comparison of the necessary armour unit masses for the different berm breakwaters. The armour mobility criteria currently established is reviewed and a recommendation for an updated criterion for the statically stable non-reshaped berm breakwater category is proposed.
Fatigue Testing of Used Mooring Chain
Authors: Gabrielsen Øystein , Larsen Kjell , Reinholdtsen Svein-Arne
Published: October 2017

In Statoil mooring chains have been inspected since the first floaters were installed in the 1990’s, and replacement of top chain started as early as year 2000. Background for replacement has been wear, surface corrosion, end of design fatigue life and check of condition for lifetime extension evaluation. For seabed chains in site inspection has been, and still are, difficult and expensive. High quality inspection data is limited. Technology development the last years has allowed for cost efficient seabed chain replacements, and presently even seabed chains have been retrieved to investigate integrity and remaining fatigue life.

Statoil started full scale fatigue testing of chains in 2011, and the results from the first tests, presented in Fredheim et al (2013), indicates that the surface condition of the chain is vital for the fatigue capacity. Fatigue test show that chain fatigue capacity varies significantly.

The surface conditions of the chains are site dependent. To ensure timely replacement, it is vital to know the remaining fatigue capacity of the chains. An extensive fatigue test program was thus initiated, and is still ongoing. As testing has proceeded, different degrading mechanisms and fatigue capacity dependencies have been revealed. Further testing is still required, and more tests are scheduled for the following years.

The paper sums up testing so far (Dec 2016), and presents the most important findings and results.
CFD Analysis of Performance of Hydrocyclone for SMS Ore Separation on Seafloor
Authors: Yamazaki Tetsuo , Takeda Yosuke , Arai Rei , Nakatani Naoki
Published: October 2017

These days, many seafloor massive sulfide (SMS) deposits have been discovered in Japan’s exclusive economic zones. They have many kinds of useful metals, and are expected to be future metal resources. However, SMS mining faces an economic problem for the reason that disposal of unnecessary parts of SMS ores is very expensive in Japan. Adding a function of primary ore separation on seafloor is necessary for economical SMS mining. Some small scale model experiments were conducted by the authors. In this study, CFD analysis is applied for the results of the model hydrocyclone. From the analysis, the fundamental flow condition good for the ore separation in the cyclone is recognized.
Simulating Ice-Structure Interaction With the Material Point Method
Authors: Wang Yaomei , Yang Biye , Zhang Guiyong , Jiang Yichen , Zong Zhi
Published: October 2017

The process of ice-structure interaction is a complex problem which is influenced by the properties of both ice and the structure. In this paper, the material point method (MPM) is introduced to simulate the interaction between an ice sheet and a cylinder structure. MPM is efficient in solving history dependent and large deformation problems and has shown advantage in hyper-velocity impact and landslide issues, etc..

The constitutive relation of ice is based on elasto-viscous-plastic model with the Drucker-Pragers yield criterion. Ice follows the Maxwell elasto-viscous model before the yield criterion is reached and fails when the plastic strain surpasses the failure strain. Meanwhile, the constitutive model used in this work considers the effect of the Young’s modulus, Poisson’s ratio, density, temperature, cohesive force and internal friction angle of ice.

A series of simulations are conducted and the results are in accord with existing theories. According to the comparison, the influences of ice temperature and penetration speed of the structure on the global ice load are testified. The numerical tests have proven the feasibility of MPM in simulating the interaction between an ice sheet and a cylinder structure. Future work in ice-structure interaction problems with MPM is also discussed.
Estimation of Elastic Buckling Strength of a Non-Spherical Tank in the Partially Filled Condition
Authors: Sano Atsushi , Matsubara Naoya , Izumi Naruyoshi , Fujikubo Masahiko
Published: October 2017

A method of estimating elastic buckling strength of a non-spherical tank intended for the use in LNG carriers is presented. Partially filled condition that causes combined meridional tension and circumferential compression is considered. Analytical expression of pre-buckling stress distributions is derived based on membrane shell theory. These stresses are applied to the elastic buckling strength analysis employing Hutchinson’s solution for a toroidal shell segment under similar stress condition. The buckling strength of a spherical shell is highly sensitive to initial shape imperfections, but these are not considered as a most fundamental case. The predicted stress distributions and elastic buckling strength are compared with those calculated by the 3D shell finite element analysis.
Outcomes From a Study of Validation of Ship Specific Models for Shiphandling Simulator
Authors: Berg Tor E. , Selvik Ørjan
Published: October 2017

This paper presents some outcomes from a four years (2013 – 2016) long research project investigating validation of ship specific simulation models. In contrast to the other initiatives such as SIMMAN 2008 [1] and SIMMAN 2014 [2], the R&D project “Sea Trials and Model Tests for Validation of Shiphandling Simulation Models” (SIMVAL [3]) investigates model development and validation methods for specific vessels. For these vessels, the yard’s documentation of manoeuvring characteristic was available for the researchers. In addition, the project has been given permission to perform different sets of sea trials on selected case vessels. As far as possible, these sea trials were designed to document vessel-specific operations such as low-speed manoeuvres and dynamic positioning. Other papers presenting results from the SIMVAL project will be given in a separate session, Session 12–14, in the Torgeir Moan Symposium at OMAE2017.