bluuebunny/crossref_metadata_2025_split huggingface dataset:
Weather Window Analysis of Irish and Portuguese Wave Data With Relevance to Operations and Maintenance of Marine Renewables
Authors: O’Connor Michael , Lewis Tony , Dalton Gordon 
Published: November 2013

This paper presents the results of a weather window analysis of wave data from the west coast of Ireland and the Atlantic coast of Portugal in order to quantify the levels of access to ocean energy renewables, which may be deployed there, for operation and maintenance activities. In order to operate and maintain offshore marine renewables, a device will have to be accessible for a certain period of time. This will require a weather window consisting of a consecutive period of wave heights low enough and long enough for the device to be accessed. It is important to quantify what the levels of access are off the Irish west coast and Portuguese Atlantic coast given their high wind and wave resource.
Wave data from two wave buoys, the M3 buoy located 56km off the west coast of Ireland and the Leixoes buoy located 19km off the Portuguese coast, are analysed to quantify the levels of access that exist. The data is used to quantify the general regimes at both sites by presenting the wave energy resource, the mean annual exceedance and the wave height frequency at both sites. The levels of access are quantified at operations and maintenance (O/M) access limits of Hs 1.0, 1.5, 2.0 and 2.5m wave height, by presenting the number of windows and the percentage of the year that these windows make up as well as the total number of hours, monthly and annual, that the wave heights are below these limits. Also presented are the waiting periods between windows by showing both the longest individual waiting periods between windows in a year and also the total intervals between windows in a year. The levels of access observed off Ireland and Portugal are then compared to levels of access observed at other marine renewable locations, namely the North Sea, Irish East Coast and Pacific North-western US coast.
The results indicate that the levels of access off Ireland and Portugal are far below those observed at other marine renewable locations, and at the lower wave height access limits, there are very few suitable weather windows and considerable winter waiting periods between these windows. The implications of these low levels of access suggest that maintaining wave energy converters, off the west coast, may not be feasible and devices will need to be brought ashore for O/M activities.
Water-Driven Debris Impact Forces on Structures: Experimental and Theoretical Program
Authors: Riggs H. R. , Cox D. T. , Naito C. J. , Kobayashi M. H. , Piran Aghl P. , Ko H. T.-S. , Khowitar E. 
Published: November 2013

Water-driven debris generated during tsunamis and hurricanes can impose substantial impact forces on structures that are often not designed for such loads. This paper presents the design and results of an experimental and theoretical program to quantify these potential impact forces. Two types of prototypical debris are considered: a wood log and a shipping container.
Full-scale impact tests at Lehigh University were carried out with a wooden utility pole and a shipping container. The tests were carried out in-air, and were designed to provide baseline, full-scale results. A 1:5 scale shipping container model was used for in-water tests in the Oregon State University large wave flume. These tests were used to quantify the effect of the fluid on the impact forces.
Results from both experimental programs are presented and compared with theoretical predictions. The analytical predictions are found to be in sufficient agreement such that they can be used for design. A fundamental takeaway is that the impact forces are dominated by the structural impact, with a secondary affect provided by the fluid. Both forces are quantified in the paper.
Critical Assessment of PVDF Multilayer Barriers in Unbonded Flexible Risers: Applications and Benefits
Authors: Fernando Upul S. , Davidson Michelle , Sheldrake Terry 
Published: November 2013

The polymer barrier is the key component in a flexible pipe structure that is specifically designed to contain hydrocarbon media within the pipe. Maintaining the integrity of the barrier for the total service life of the pipe is therefore an essential requirement to prevent any leaking or spilling of the hydrocarbon into the external environment. For high temperature (> 100°C) service PVDF is commonly used as a barrier material, and the barrier designs are based on either single layer or multilayer (two or three layers) structures depending on design strategy, manufacturing constraints and service application.
This paper presents a critical review of the barrier design strategies, considering both single and multilayer structures. The main parameters in deciding a reliable barrier structure are discussed and the advantages/disadvantages of multilayers over single layers are highlighted. The different pipe failure modes/mechanisms that may be related to different barrier structures, the analyses and test requirements to evaluate and overcome these failures are discussed.
The West Africa Swell Project (WASP)
Authors: Forristall George Z. , Ewans Kevin , Olagnon Michel , Prevosto Marc 
Published: November 2013

The responses of floating systems are sensitive to the detailed shape of the swell portion of the wave spectrum. Knowledge of swell is particularly important for sites off West Africa. The West Africa Swell Project (WASP JIP) was formed to analyze the available data on West African swell. Measurements were obtained from Shell, Ifremer, Chevron and Marathon. Hindcast data came from Oceanweather and the NOAA Wavewatch model. Sites ranging from Nigeria to Namibia were considered.
Modeling the dispersion of swell over long distances indicates that the resulting power spectrum will have a triangular or lognormal shape. Sampling variability makes it difficult to distinguish between those shapes or Jonswap or Gaussian forms, but lognormal spectra generally provided good fits. The models also indicate that the width of the spectrum in both frequency and direction should be inversely related to the peak frequency. Fits to the measurements established detailed relationships for each location.
Calculating the response of single degree of freedom oscillators to the measured and hindcast spectra produces response spectra which give the maximum response as a function of natural period and damping. Extreme values of system response can be calculated from the response spectra. The largest responses come from uni-modal spectra, and design spectra can be estimated by inflating them.
Riser Base Jumper Slugging Analysis by CFD Simulations
Authors: Bakkouch Maya , Minguez Matthieu 
Published: November 2013

Slugging is one of the operational hazards of subsea pipelines associated with the transportation of multiphase fluids. Such phenomenon can results in cyclic loading in the lines, leading to fatigue damage or high stress (possible strength concern) that need to be considered in the design process. However, there is a real lack in the literature of clear guidance addressing the way of investigation of such possible Flow Induced Vibration (FIV) issue.
One solution is to perform Fluid Structure Interaction (FSI) analysis. However, for this purpose, it appears fundamental to recover at the best the main flow features that develop in characteristic piping systems. Depending on the flow conditions, on the line path configuration, slug can be disturbed, dissociated and consequently results in multi-scale flow that could become an additional source of fatigue. Riser Base Jumper (RBJ) in M-shape configuration, due to its complex geometry can be prone to such multi scale-flow and should be consequently treated with particular attention.
The proposed paper aims to improve the understanding of the main flow features that accompany slug flow in a RBJ. It is proposed to use Computational Multiphase Fluid Dynamic (CMFD) to this end. The main objective of the analysis is to characterise at the best the different expected pressure variations and the related excitation frequencies.
Numerical Tool for Automatic Identification of Free Spans on Submarine Pipelines
Authors: Jacovazzo Bruno M. , Jacob Breno P. 
Published: November 2013

It is well known that, after a submarine pipeline is laid over the seabed, free spans may appear due to the unevenness of the seafloor, associated to the relatively high bending stiffness of the pipe, and to the residual tension from the pipe laying process.
The identification of free spans along a given pipeline route is very important due to several factors. One of them is to allow the verification of design criteria related to fatigue induced by vortex induced vibrations (VIV), such as those presented on the DNV-RP-F105 code. Also, the number and length of free spans on a route may require extensive intervention works (e.g. rock dumping, digging, etc) to mitigate the spans and reduce unacceptable span lengths; or, alternatively, may require changes in the predetermined route of the pipeline.
In this context, this work describes the development of a numerical tool for the determination of the final equilibrium configuration of a pipeline after its laying by any given method, providing the automatic identification of free spans on submarine pipelines. The tool is based on global Finite Element models, and simulates the evolution of the pipe laying process along a predetermined route, using the actual seabottom bathymetry data. The objective is to allow an easier implementation of the verification of VIV induced fatigue, and the assessment of a given route in terms of the number and length of its free spans; for this purpose the tool may be associated to a program oriented towards the synthesis and optimization of submarine pipelines. A case study is presented to illustrate the use of the tool.
Efficient Dynamic Analysis of Floating Bodies Nonlinear Behavior in Wave Energy Conversion
Authors: Spanos P. D. , Richichi A. , Arena F. 
Published: November 2013

Floating oscillating-bodies are a kind of wave energy converter developed for harvesting the great amount of energy related to water waves; see Falcão [1] for a review.
In this paper a particular energy converter model is considered. A nonlinear analysis of its dynamic behavior is conducted both in the time and the frequency domains.
The model involves a tightly moored single-body floating wave energy converter. It captures motion in the horizontal and vertical directions. The nonlinear stiffness and damping forces are functions of the horizontal and vertical displacements and velocities and make the system a nonlinear one. In addition to the time-domain analysis of the nonlinear behavior of the system, the method of equivalent linearization is used to determine iteratively the effective linear stiffness and damping matrices and the response of the buoy in the frequency domain. The analysis pertains to the surge and the heave directions response of the wave energy converter under harmonic mono-frequency excitation (regular waves). The reliability of the linearization based approach is demonstrated by comparison with time domain integration data.
This approach offers the appealing feature of conducting efficiently a variety of parameter studies which can expedite preliminary evaluations, inter alia, of competing design scenarios for the energy converter. Suggestions for extending this approach to the case of fully nonlinear and random irregular waves are also included.
Large Diameter Pipeline PLEM Design for Remote, Arctic Application
Authors: Timmermans Jeroen , Luff Ian , Long Nicholas 
Published: November 2013

While subsea production template and manifold designs have come to be dominated by standardized solutions tailored for specific hardware, the design of Pipeline End Manifolds (PLEM) remains largely project-specific. Nevertheless, some trends in PLEM design for large-diameter pipelines in moderate water depths have emerged in the past years in the North Sea and elsewhere; namely, large stand-alone structures on suction pile foundations with diverless spoolpiece tie-ins. This arrangement has proven successful on numerous projects; however, the move to remote arctic fields of significant production capacity and long design life introduces new design drivers that warrant a “fresh approach” to PLEM design.
The developments currently being considered for the arctic will have to deal with:
- Remote location making mobilization of installation assets a significant cost driver such that separate installation of pipeline and PLEM is relatively unattractive
- Harsh conditions and short weather windows for installation favoring designs that reduce the number of separate installation steps and vessels
- Poorer access for maintenance and repair during the operating life favoring designs that are modular and that allow recovery of critical components using the smallest possible intervention vessels.
When combined with envisioned field production lives of 40 to 50 years, this means a very different set of design drivers will apply to the PLEM design. This paper presents an alternative PLEM design developed to overcome these challenges by:
- Integrating of the PLEM with the pipeline to work around current industry limitations for large diameter diverless tie-in connector systems and to minimize ROV rotated sealing surfaces subsea in normal operation,
- Introducing plug technology to remove the critical dependence on long-term trouble-free performance of large bore valves,
- Introducing driven pile foundations to reduce structure size, prevent long-term settlements and eliminate the need for separate pipeline support frames by maintaining the pipe centerline close to the mudline,
- Modularizing the system such that key components (all remaining valves) can be retrieved without complete shutdown of flow and such that installation / intervention can be performed using a wide range of vessels, and
- Incorporating lessons learned from the successful design of a North Sea vertical diverless pig launcher unit.
This paper presents an overview of the alternative PLEM design and discusses the status of the technologies required.
TLP Survivability Against Progressive Failure of Tendon and Foundation Systems in Offshore Western Australian Harsh Environment
Authors: Mansour Alaa M. , Gordon Brian J. , Ling Qi , Shen Qiang 
Published: November 2013

In this paper the design robustness of Tension Leg Platform (TLP) tendon and tendon foundation systems of a TLP that is located in offshore Western Australia is investigated.
A case study of a TLP that is self-stable (without tendons) has been considered. The study involves the numerical simulation of progressive failure of tendons in cyclonic events. The TLP response during the transition from a restrained TLP with all tendons to the free-floating condition has been numerically simulated. The numerical results from this simulation have been verified against physical model test measurements. The numerical simulation is repeated for a TLP with an optimized hull design that does not maintain stability when all tendons fail. Cost versus benefit in these two cases is quantified and compared.
The progressive failure of the TLP Gravity Base Foundation (GBF) system has also been investigated in this paper. One of the potential failure modes for this type of foundation is the loss of suction underneath the foundation. Increasing the amount of solid ballast in the GBF increases the net downward load on the soil and reduces the reliance on the soil suction. Numerical simulations of the progressive loss of suction are performed for two cases; 1) slightly over designed foundation to include extra ballast and 2) optimized foundation design that is highly rely on the soil suction. Again, cost versus benefit in these two cases is presented.
The paper provides clear insights supported by calculations and model tests for proposed design robustness that could be built in a TLP design at a relatively small additional cost to address uncertainties associated with designing TLP in offshore Western Australian harsh environment region.
Simplified Approach for Fracture Integrity Assessment of Bimetallic Girth Weld Joint
Authors: Bonora N. , Carlucci A. , Ruggiero A. , Iannitti G. 
Published: November 2013

Recent extensive use of Corrosion Resistance Alloy (CRA) as internal protection layer of standard carbon-steel pipes (clad and lined pipe) in the oil and gas industry requires an intensive use of bimetallic welds.
Since some degree of defects in welds is inevitable, and in codes and standards (such as BS7910) the case of bi-metallic joint is usually not considered, some R&D’s activities are ongoing to define specific design guidance for an Engineering Critical Assessment (ECA) aimed at determining flaw acceptance criteria for fabrication of bimetallic joints.
Based on the limited guidance in the literature, proposed procedures for ECA on CRA welds seem not cover the root/hot pass weld region, for which the requirement of “zero defect” became mandatory. As direct consequence, it penalizes the weld fabrication rate, particularly if “J-lay” or “S-Lay” methods are adopted. Furthermore, they are investigating on cases where weld material is overmatching the base metal or for a limited partial overmatching, despite for CRA welds, such conditions, seem quite difficult to be fully met, if current consumable materials present in the marked are selected.
Aim of present paper is to describe how any standard ECA procedure (ordinarily used to assess carbon-steel welds) may be alternatively adopted to assess CRA welds for clad & lined pipe material, if specific conditions are respected. For this purpose a few number of elastic-plastic Finite Element Analysis (FEA) is required to identify and/or extends the validity limits which have to be met in order to be conservative in the use of selected standard procedure. Outer, inner and under clad flaws, located along the weld fusion line, were investigated. Such approach, certainly leads to a quite conservatism, but gives the advantage to provide a safe flaws acceptance criterion in root/hot pass weld, and it may be also applied for any level of weld partial overmatching condition.
Despite proposed simplified approach is suitable until moderate plastic straining, it may be appropriated for any ECA on CRA pipe when “J-lay” or “S-lay” installation method is adopted, and/or for many riser’s configuration, and/or for several flowline routing also if exposed to post-buckling condition. It is demonstrated that the proposed simplified approach, when applied under moderate plastic strain conditions, provides accurate J-integral solutions compared to the complex method as proposed by current R&D.
Newer Frontiers in the Design of Steel Catenary Risers for Floating Production Systems
Authors: Mekha Basim , Bhat Shankar 
Published: November 2013

It is not uncommon nowadays to have a new floating production facility installed with steel catenary risers (SCRs) as the main method for receiving and exporting fluids. The use of steel catenary in deeper and shallower waters alike where it was challenging and even unthinkable some years back is now feasible. Advancements in the SCR technology cover not only design and software, but also manufacturing, installation methods and capabilities.
Since the first author’s OMAE 2001 paper “New Frontiers in the Design of Steel Catenary Risers for Floating Production Systems” [1] was published, a number of significant advances have been made in the design, manufacture and installation of steel catenary risers. In design aspects for example, the soil structure interaction and modeling of soil stiffness and trench formation has been the topic of many publications and research. The manufacturing capabilities of the pipe mills to produce and machine SCR pipe joints with upset ends has been advanced and implemented in recent projects. Advancement in the capability of Automated Ultrasonic Testing (AUT) systems to detect very small flaws in thick carbon steel and clad pipe welds is expanding the manufacturing envelop of SCRs while meeting design requirements. In addition, there is improvement in the capabilities of installation vessels; and more comprehensive material and fatigue test data have been accumulated providing data better basis to design and perform fracture mechanics analysis of SCRs. Lazy wave SCR configurations are being used to significantly expand the application of SCR technology to high motion vessels and more severe environments.
This paper contains a review of the current state of the art with a description of some of the important advancements that have extended the range of applicability of SCR technology. The SCR technology advancements presented and discussed in this paper include a better understanding of the soil behavior and trench formation with some analytical results, the use of upset ends and their manufacturing options, improvement in the AUT systems and flaw detection capabilities, CRA clad SCRs and Lazy Wave SCRs.
The Burkholderia pseudomallei Enoyl-Acyl Carrier Protein Reductase FabI1 Is Essential for
In Vivo
Growth and Is the Target of a Novel Chemotherapeutic with Efficacy
Authors: Cummings Jason E. , Kingry Luke C. , Rholl Drew A. , Schweizer Herbert P. , Tonge Peter J. , Slayden Richard A. 
Published: November 2013

ABSTRACT

The bacterial fatty acid biosynthesis pathway is a validated target for the development of novel chemotherapeutics. However, since
Burkholderia pseudomallei
carries genes that encode both FabI and FabV enoyl-acyl carrier protein (ACP) reductase homologues, the enoyl-ACP reductase that is essential for
in vivo
growth needs to be defined so that the correct drug target can be chosen for development. Accordingly, Δ
fabI1
, Δ
fabI2
, and Δ
fabV
knockout strains were constructed and tested in a mouse model of infection. Mice infected with a Δ
fabI1
strain did not show signs of morbidity, mortality, or dissemination after 30 days of infection compared to the wild-type and Δ
fabI2
and Δ
fabV
mutant strains that had times to mortality of 60 to 84 h. Although signs of morbidity and mortality of Δ
fabI2
and Δ
fabV
strains were not significantly different from those of the wild-type strain, a slight delay was observed. A FabI1-specific inhibitor was used to confirm that inhibition of FabI1 results in reduced bacterial burden and efficacy in an acute
B. pseudomallei
murine model of infection. This work establishes that FabI1 is required for growth of
Burkholderia pseudomallei
in vivo
and is a potential molecular target for drug development.