bluuebunny/crossref_metadata_2025_split huggingface dataset:
Advanced Pipeline Impact Design
Authors: Igland Ragnar T. , Alsos Hagbart S. , Kvarme Stig Olav 
Published: October 2016

The safety of pipelines and subsea structures are key elements in subsea field developments. As part of the safety engineering, protection from dropped objects and third party impact actions is required. This article addresses this aspect.
Dropped object from a platform or a vessel is one of the design scenarios. The fall-pattern of the object is essential for the impact velocity and corresponding energy, model of the path and the effects of hydrodynamic behavior is outlined.
In lieu of accurate information, the design code use energy band for energy estimates and may give extremely conservative impact energy. The falling objects structural flexibility and properties are discussed and evaluated regarding the energy dissipation and possible damage of the pipeline.
The pipeline combined response from global deflection and denting regarding impacts are investigated. Analysis and testing methods applied in pipeline design are presented. Focus is placed on the overall interaction between the impacting object, the deformed pipeline and energy dissipation by coating and soil.
Typically, pipeline damage from design codes provides conservative cross sectional damage estimates. This is confirmed from both simplified and detailed FE analyses, as well as fullscale impact experiments performed by REINERTSEN AS.
One of the main objectives promoted by the authors is the importance of both impact velocity and mass during impact, and not only the kinetic energy of the impact. The kinetic energy from a dropped object is unlikely to be fully dissipated as cross sectional deformation of the pipeline.
Global deformations will be triggered, which implies that the dissipated energy going into local denting is reduced to a fractional value. The effect is more pronounced for small diameter pipelines than for pipelines with large diameter. This paper discusses the impact mechanics and seeks to estimate the fractional value by using simplified element analysis.
Fatigue Assessment of Pipeline With Plain Dents Under Cyclic Pressure Loading Using Finite Element Method
Authors: Durowoju Michael , Pu Yongchang , Benson Simon , Race Julia 
Published: October 2016

One of the major challenges faced in fatigue assessment today is determining the stress concentration factor ‘SCF’ associated with the dents, which are used with appropriate SN curves to determine the fatigue life. This historically has been determined empirically or by using finite element analysis.
This paper presents finite element analysis on a parametric range of industry pipes (both offshore and onshore) to extract SCF data used for fatigue assessment. The parametric dataset focuses on the effects of pipe geometry, dent geometry, material properties and pressure cycling on the prediction of the fatigue life. This parametric dataset will eventually be used to develop an algorithm for fatigue prediction using an artificial neural network.
Two types of indenters (Dome and Bar) are used to simulate circumferential and longitudinal dents. Four different dent depths ranging from 2% d/D to 10% d/D are also simulated to investigate the effect of dent geometry. Four different pipe grades (X42, X65, X80 and X100) are analyzed to investigate the effect of pipe materials on dent fatigue. Similarly, eight pipes with different diameter to thickness ratio D/t ranging from 18–96 are analyzed to investigate the effect of pipe geometry. Stresses are computed at both 50% SMYS and 72% SMYS to investigate the effect of pressure variation.
The results from this study indicate that longitudinal dents have higher stress concentrations compared to circumferential dents of similar dent depth. Results also indicate that the re-round dent depth (i.e. dent depth after pressurization) increases with increasing D/t and increasing dent depth. Similarly, the pipe material has a major effect on the fatigue life. Pipes with higher material strength have higher stress concentration compared to pipes with lower strength of similar dent depth. The stress concentration factors SCF associated with the dents are then computed.
Multi-Scale Numerical Analysis of the Field Efficiency of an Ocean Plastic Cleanup Array
Authors: Sainte-Rose Bruno , Lebreton Laurent , de Lima Rego Joao , Kleissen Frank , Reisser Julia 
Published: October 2016

The impact of plastic pollution on marine ecosystems and global economy has been drawing public concern since the end of the 20th century. To mitigate this issue, The Ocean Cleanup (TOC) Foundation is developing technologies to extract, prevent, and intercept plastic debris from coastal and oceanic environments. The core technology being optimized is the use of floating booms placed perpendicular to the main ocean plastic flow so it can concentrate plastic debris to a point where it can be extracted, shipped and processed in a cost-effective manner.
In order to optimize the system’s field efficiency (i.e. mass of ocean plastic captured per length of floating boom), a multi-scale approach has been elaborated, where temporal and spatial scales span over several orders of magnitude. Here we introduce this general multi-scale method alongside its assumptions and multi-scale models. We then describe two application examples, the first corresponding to our coastal pilot in the Japanese island of Tsushima and the second related to our main cleanup target area: the so-called Great Pacific Garbage Patch, situated between Hawaii and the US west coast.
Airgap and Wave in Deck Impact Statistics
Authors: Hagen Øistein , Johannessen Thomas B. , Birknes-Berg Jørn 
Published: October 2016

As offshore reservoirs are depleted, the seabed may subside. Bottom fixed installations which have previously had sufficient clearance between the deck and the sea surface may be in a situation where wave impact with the deck must be considered at relevant probability levels. Some statistical aspects associated with the calculation of a deck impact load with a prescribed probability of occurrence are the subject of the present paper.
The Short Crest JIP addressed the distribution of the crest height in extreme sea states, the properties of the largest crests and the deck impact loading on a closed deck. It was concluded that the largest waves in the sea may be in the process of breaking and thus have properties which deviate significantly from estimates found from weakly nonlinear irregular or regular wave theory.
The present paper addresses findings from the Short Crest JIP regarding
• long-term analysis of wave heights and crest, including the effect of wave breaking
• air gap analysis for jacket, TLP and semisubmersible using 2nd order time domain simulations over the platform area
• statistics for horizontal wave-in-deck impacts for short crested sea versus for long crested sea
• structural reliability analysis of jackets for some simple limit states that are governed by loads caused by impact of extreme crests
Fundamental Study on Elastic Behavior of Large-Scale Floating Coal Stockyard
Authors: Eto Hiroaki , Sato Chiaki , Masuda Koichi , Ikoma Tomoki , Kishida Tomoyuki , Kubota Mitsuru 
Published: October 2016

This paper proposes a large-scale floating coal stockyard (LFCS) and discusses its elastic behavior. Indonesia has recently become the main country supplying coal in the Asia-Pacific region. However, there is concern that export to Japan will decrease as coal demand increases. Therefore, the trend of coal transport in Indonesia is a very important matter in ensuring the continued stable import of coal to Japan. It is difficult for bulk carriers to traverse the shallow terrain of the seabed of the Markham River in East Kalimantan to reach coastal areas. Additionally, an LFCS can be operated as a relay base for barges, and large coal carriers have been proposed for use in offshore areas. The LFCS is capable of loading, storing, and offloading coal. Installing an LFCS offshore Kalimantan is expected to improve coal transport productivity in the region.
Under such circumstances, the design plan proposed in this paper can simultaneously perform independent loading and unloading without interference. The partial mass distribution and local rigidity of the LFCS varies depending on the coal loading conditions. In addition, because the structure has a planar shape, the response of the LFCS showed elastic behavior. Design example of such a huge floating structure with the great difference of the displacement is unparalleled, it is very important to clarify a design fundamental subject.
The objectives of this study are to provide a preliminary LFCS design and investigate the impact of varying the mass distribution and local rigidity on not only the distribution of the distortion and internal stress but also on the dynamic hydroelastic motion of the LFCS when it is impacted by waves. Therefore, the wave response of the LFCS was analyzed under different loading conditions.
Reeling Analysis and Limit State Criteria
Authors: Xu Jianfeng , Vishnubhotla Srinivas , Aamlid Olav , Collberg Leif 
Published: October 2016

Reeling has been an attractive offshore installation method for rigid flowlines and steel catenary risers due to its fast speed, cost effectiveness and reliability. Over years of evolution, it has become a proven technology, and the understanding to the engineering fundamentals is greatly improved as well. Due to the reeling process, the pipeline is plastically deformed; residual stresses, pipe ovality, and pipe out of straightness are increased. The strength, fatigue, and fracture performance of the pipe and the girth weld have to be closely evaluated to insure the pipeline integrity during and after the installation. As part of the installation design, different types of analyses are generally carried out to demonstrate the reelability, and the pipeline responses against all limit states. However, the methods adopted by different contractors can vary greatly.
In this paper, the engineering fundamentals of reeling process are reviewed. A few typical reeling analyses, both analytical and finite element based, are demonstrated with examples. The local buckling limit state criteria based on DNV-OS-F101 for different stages of reeling are also illustrated.
An Experimental Consideration on Accuracy of Inverse Super Short Baseline Underwater Positioning Using Acoustic Data Transmission
Authors: Watanabe Yoshitaka 
Published: October 2016

Authors are developing a test system of new type acoustic positioning system (APS) using inverse super short baseline (ISSBL) method. In this method, the vehicle is equipped with hydrophone array. Direction of arrival (DOA) of acoustic signal from mother ship is detected, and relative position between the mother ship and the vehicle is calculated with the measured DOA and the depth. Information of ship’s position is included in the transmitted acoustic signal, then absolute position of the vehicle can be calculated with the relative position and the included information. The vehicle position can be obtained in the vehicle in real-time and be used directly to navigate. No reply from the vehicle is necessary.
Five ocean experiments were conducted in various depth points. In the experiments, an experimental device was moored at sea bottom, and the ship cruised around above the moored device with transmitting acoustic signal including the ship’s information.
In consideration about random scattering of positioning result, followings were found. Random scattering is much suppressed with EKF using high rate symbol value. On the other hand, estimation error of ship’s position, which is about 0.5–1 meter, is not negligible. When the DOA measurement for each symbol is accurate, the estimation error of the ship’s position becomes dominant in output of EKF as a consequence of random scattering suppression. Therefore, this method is more advantageous in case the DOA measurement have larger random error. Then this method is useful in deeper case and small array can be adopted to the system. On the other hand, this method do not perform well when the elevation angle from the target to the ship is shallow. Moreover convergence percentage seems to touch the lowest value at around 10%.
Recent Advances in Pipeline Free Span Design: A New Revision of DNV-RP-F105
Authors: Vedeld Knut , Sollund Håvar , Fyrileiv Olav 
Published: October 2016

Pipeline free span design has evolved from basic avoidance criteria in the DNV ’76 rules [1], to fatigue and ultimate limit state considerations in Guideline no. 14 [2]. Modern multimode, multi-span free span design is predominantly performed according to DNV-RP-F105 [3].
In 2006, the latest revision of DNV-RP-F105 [3] was written as a direct result of extensive research, performed due to significant free span challenges in the Ormen Lange pipeline project. DNV-RP-F105 was at the time, and still is, the only pipeline design code giving contemporary design guidance for vortex induced vibrations (VIV) and direct wave loading design for pipelines in free spans.
The last revision of DNV-RP-F105 included a few, but highly important advances, particularly the consideration for multi-mode and multi-span pipeline dynamic response behavior. In the 10 years that have followed, no breakthroughs of similar magnitude have been achieved for pipeline free spans, but a large number of incremental improvements to existing calculation methods, and some novel advances in less critical aspects of VIV understanding have been made. As a result, DNV-RP-F105 has recently been revised to account for these advances, which include improved frequency-domain analyses of wave-induced fatigue, a new response model for cross-flow VIV in low Keulegan-Carpenter (KC) regimes in pure waves, new analytical methods for dynamic response calculations of short spans in harsh conditions, and extensive guidance on how to apply the recommended practice for assessment of fatigue and extreme environmental load effects on curved structural members such as spools, jumpers and manifold flexloops.
This paper gives an overview of most of the important changes and updates to the new revision of DNV-RP-F105. Case studies are used to demonstrate the importance and effects of the changes made, and to some extent how the revision of DNV-RP-F105 can enhance its applicability and ease of use.
Crack Extension Effects on Welding Residual Stress in Fitness for Service Assessment of Crack-Like Defect in Weld
Authors: Hong Jeong K. 
Published: October 2016

The current industry code and standard fitness-for-service assessment (ICS FFSA) procedures ignore the release of the welding residual stress (WRS) in defect assessment of a crack growing in a WRS field. Doing so can result in overly restrictive results in the ICS FFSA of an engineering component. The current ICS FFSA procedures have produced compendiums of WRS distributions and stress intensity factor (SIF) solutions that are characterized by the joint geometry and welding parameters. It is also known that these distributions are based on extensive numerical analyses and provide upper bound estimates; therefore, these types of solutions do not necessarily satisfy the self-equilibrating state.
In this investigation, through-wall WRS distributions from the literature data, including measurements and finite element analysis (FEA) results for girth welded pipes, are compared to the representative ICS FFSA WRS procedures.
Also, the WRS and SIF solutions using the proposed procedure are compared to those using the ICS FFSA procedures employing 2D and 3D models.
From the investigation, it is observed that the ICS FFSA procedures show discrepancies for certain conditions and the levels of conservatism are dependent on the model geometry, boundary constraint condition, crack size, and crack shape.
For some cases, the estimations provided from the ICS FFSA procedures are not conservative compared to the reference solutions from literatures and FEA simulations.
As a continuous study of the previous investigation [OMAE 2015-41319], the objective of the present paper is to motivate the industry to improve ICS FFSA procedures by clarifying the ambiguous technical issues of crack-like defect assessment in weld regions.
Numerical Study on Flap Style Rudder Hydrodynamic Characteristics With Different Connections
Authors: Dong Zhenwei , Xiao Zhijian , Gong Shiqi , Zhang Zhiguo , Feng Dakui 
Published: October 2016

The flow field characteristics of 2-D flap style rudders with and without gap are analyzed through 4 models. To explore the influence of different filling styles, one flap rudder with gap and three flap rudders without gap are simulated from 0 to 30 degrees angle of attack with k-omega SST turbulence model.
Validation is done by comparing the results with EFD data from reference and the mesh independence verification is also made. Then lift and drag coefficients are compared among four models. Pressure, velocity distributions are given to explain the difference on hydrodynamic characteristics among them. Unsteady computation method is used to investigate the fluctuation characteristics of drag coefficients at large angle of attack. Stream lines are shown to better understand the vortex system on the suction surface.
Numerical Study of Flow Around a Smooth Circular Cylinder at Reynold Number=3900 With Large Eddy Simulation Using CFD Code
Authors: Khan Niaz B. , Jameel Mohammed , Mohamad Badry Ahmad Badarudin Bin , Ibrahim Zainah B. 
Published: October 2016

The study of flow around circular cylinders is one of the challenges in marine hydrodynamics. Many offshore structures are of cylindrical shape such as spar hull, risers and pipelines. Furthermore, the flow around cylinder open the path for studying more complex shape structures like ellipses, flat plat and other complex geometries. The aim of the study is to understand the flow field around these structures and calculation of forces acting on them. In current study, flow over a circular cylinder is investigated numerically using the turbulent model Large Eddy simulation (LES) and SIMPLE pressure-velocity coupling. In LES option, Smagorinksy-lilly subgrid scale model with dynamic stress is used. Mesh is generated using ICEM CFD tool and analysis is performed using ANSYS fluent. Velocity profiles are investigated in the cylinder wake up to ten diameters and compared with the experimental results. Hydrodynamic values and pressure distribution on the cylinder wall are also analyzed.
The numerical results extracted from the simulation agreed well with the experimental results available in the literature. Furthermore, the spanwise mesh resolution study shows that flow around cylinder at Reynold number Re = 3900 is highly 3dimensional study and 2D study or coarse mesh in spanwise direction will deteriorate the results.
Multiphase Transient Slugging Flow in Subsea Oil and Gas Production
Authors: Zhang Zhenhua , Tao Longbin 
Published: October 2016

Slug flow in horizontal pipelines and riser systems in deep sea has been proved as one of the challenging flow assurance issues. Large and fluctuating gas/liquid rates can severely reduce production and, in the worst case, shut down, depressurization or damage topside equipment, such as separator, vessels and compressors.
Previous studies are primarily based on experimental investigations of fluid properties with air/water as working media in considerably scaled down model pipes, and the results cannot be simply extrapolated to full scale due to the significant difference in Reynolds number and other fluid conditions. In this paper, the focus is on utilizing practical shape of pipe, working conditions and fluid data for simulation and data analysis. The study aims to investigate the transient multiphase slug flow in subsea oil and gas production based on the field data, using numerical model developed by simulator OLGA and data analysis.
As the first step, cases with field data have been modelled using OLGA and validated by comparing with the results obtained using PIPESYS in steady state analysis. Then, a numerical model to predict slugging flow characteristics under transient state in pipeline and riser system was set up using multiphase flow simulator OLGA. One of the highlights of the present study is the new transient model developed by OLGA with an added capacity of newly developed thermal model programmed with MATLAB in order to represent the large variable temperature distribution of the riser in deep water condition. The slug characteristics in pipelines and temperature distribution of riser are analyzed under the different temperature gradients along the water depth. Finally, the depressurization during a shut-down and then restart procedure considering hydrate formation checking is simulated. Furthermore, slug length, pressure drop and liquid hold up in the riser are predicted under the realistic field development scenarios.
An Innovative FPSO Design Hosting SCRs in the North Sea Harsh Environment
Authors: Mansour Alaa M. , Zuccolo Ricardo , Peng Cheng , Wu Chunfa , Greiner Bill , Kumar Dhiraj , Azevedo Jefferson 
Published: October 2016

Floating Production Storage and Offloading (FPSO) floaters have the advantages of providing the required storage in the hull and direct offloading to tankers of opportunity in deep and ultra-deep water in areas lacking infra-structure.
Steel Catenary Risers (SCRs) are the preferred solution in wet-tree applications due to their simplicity, robustness and low Capital costs (CAPEX) and Operational costs (OPEX) compared to other riser options. However, due to its relatively high dynamic motions, FPSO is not a feasible host for SCRs in most environments and especially so in the North Sea very harsh environment. Also, for efficient production from rich reservoirs, large diameter and number of risers are typically required. This makes it more challenging to find a robust and commercially attractive riser solution.
In this paper a novel design for an FPSO with the ability to host SCRs in the North Sea very harsh environment is presented and evaluated. The novel design, namely, Low Motion FPSO (LM-FPSO), has a hull form with a generally rectangular cross-section. The platform is moored in-place using a conventional mooring system. The LM-FPSO performance is enhanced with the robust low-tech feature, namely, free-hanging solid ballast tank (SBT). The SBT is located certain distance below hull keel and connected to the hull through four groups of short tendons. All tendon components are the same as those used in conventional TLPs. Through the mass and added mass of the SBT, the LM-FPSO provides significantly improved heave, roll and pitch responses.
The paper presents detailed description of the novel North Sea LM-FPSO design and its in-service performance. The SCR’s feasibility is discussed. The identified risks and associated mitigations for the new design compared to the conventional FPSO are investigated and reported. The paper concludes with discussions on the project execution plan and cost benefit when developing fields using this novel design.
A Study on Small Scale Associated Gas FLNG Utilizing Small Scale LNG Carriers to Near-By Onshore LNG Plant
Authors: Nguyen X. C. , Miheaye Komla , Kim Mun-gyu , Newman Howard , Yoo Dong-hoon , Cho Ho-young , de Regt Cees , Kim Jin-ki , Lee Wang-keun 
Published: October 2016

This study describes a FLNG specifically designed to monetize Associated Gas (AG) of producing oil fields located within convenient distance of an existing LNG Plant or Port with LNG storage facility.
Limited production capacity combined with short range small capacity shuttles and limited LNG storage capacity, provide a cost effective means for LNG production.
This FLNG is designed to service an existing industry and does not require development of stranded gas discoveries.