bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flexible Riser Response Induced by Combined Slug Flow and Wave Loads
Authors: Ortega Arturo , Rivera Ausberto , Larsen Carl M. 
Published: November 2013

Flexible risers provide optimum solutions for deep water offshore fields. Reliable dynamic analysis of this kind of slender structure is crucial to ensure safety against long time fatigue failure. Beyond the effects from wave loads, the influence from transient internal slug flow on the slender structure dynamics should also be taken into account.
In this study two coupled in-house codes were used in order to identify and quantify the effects of an internal slug flow and wave loads on the flexible riser dynamics. One code carries out a global dynamic analysis of the slender structure displacements using a finite element formulation. The other program simulates the behaviour of the internal slug flow using a finite volume method. The slug flow is influenced by the dynamic shape of the riser, while the time varying forces from internal slug flow plus external waves will influence the shape. Hence, a fully coupled analysis is needed in order to solve the coupled problem. By means of the distributed simulation these two programs run synchronously and exchange information during the time integration process.
A test case using hydrodynamic forces according to the linear Airy wave theory, coupled with an internal unstable slug flow was analysed and the results show: amplification of the dynamic response due to the interaction between the two load types, effects on the effective tension caused by the internal two-phase flow, and influence on the internal slug flow caused by the wave induced response.
Inclusion of Crack Face Pressure in Reference Stress for Thick Walled Risers and Flowlines
Authors: Cerkovnik Mark , Akhtar Wasy 
Published: November 2013

A methodology is developed to account for the effect of crack face pressure on the reference stress in high pressure, thick walled, flowlines and risers. Risers and flowlines in production service may be exposed to corrosive attack resulting in pitting. In such cases, cracks can initiate and fitness for service assessment, including fatigue crack growth and fracture analysis, is required. For such thick walled lines, the effect of high internal pressure on the crack face is significant and must be taken into account. Current industry standards, including API-RP-579 [1] and BS7910 [2], are silent on the effects of crack face pressure on the reference stress.
Reference stress, a quantity similar to the net section stress, can be used to predict the local plastic failure of the remaining ligament ahead of the crack tip, or the collapse of the full cross section. The reference stress is also used in the abscissa on the Failure-Assessment-Diagram (FAD) to determine the allowable stress intensity ratio for fracture assessment.
The methodology described in the paper follows from systematic detailed finite element analysis (FEA) conducted using linear material properties. The analysis is conducted over a range of pipe thickness ratios (D/t), crack depths (a/t) and crack aspect ratios (c/a). The results presented permit an accurate calculation of the effect of crack face pressure that can be implemented within the framework of existing methods of fitness for service analysis without the use of FEA. This paper presents a detailed analysis of the effect of crack face pressure on the reference stress for axial and circumferential internal flaws. The results from this study provide expressions to estimate the reference stress with crack face pressure loading, thus, allowing an improved fracture prediction for high pressure risers and flowlines.
Numerical Simulation of Hydrodynamics of a Circular Disk Oscillating Near a Seabed
Authors: Garrido-Mendoza Carlos A. , Souto-Iglesias Antonio , Thiagarajan K. P. 
Published: November 2013

This paper studies how the hydrodynamics coefficients of added mass and damping varies when an oscillating disk approaches a seabed. Analysis was performed by OpenFOAM code using the ‘PIMPLE’ algorithm. The simulations considered the flow as laminar and hence no turbulence model was used. Simulations were conducted for a solid disk of 200 mm diameter, 2 mm thick, oscillating at amplitudes varying from 1–48 mm and elevation ‘h’ of the disk from the seabed varying from 0.2–2 times the disk radius. The geometry and parameters used here were the same as that of Wadhwa et al. (2010) [1] and Vu et al. (2008) [2]. The forces on the disk were calculated using a Tool for post-processing force/lift/drag data with function tool available in OpenFOAM. The motions of the disk were restricted to axial (heave) direction. The calculated forces and displacement were analyzed using a Fourier projection to separate the added mass and damping effects. Numerical results were compared with the experiments conducted by Wadhwa et al. (2010) [1] with a sandy bottom.
Results show that the added mass and damping increase monotonically with the Keulegan-Carpenter number (KC) up to a critical value, beyond which the behavior becomes random. The critical KC increases linearly with increasing distance from the seabed. The hydrodynamic problem has important applications in structures such as foundation templates and subsea structures oscillating in proximity to the seabed. The computations show vortex lines of the flow, and the influence of the seabed on the flow around the structure.
Simulation of Wave-Body Interaction Using a Single-Phase Level Set Function in the SWENSE Method
Authors: Reliquet Gabriel , Drouet Aurélien , Guillerm Pierre-Emmanuel , Jacquin Erwan , Gentaz Lionel , Ferrant Pierre 
Published: November 2013

The purpose of this paper is to present combination of the SWENSE (Spectral Wave Explicit Navier-Stokes Equations – [1]) method — an original method to treat fully nonlinear wave-body interactions — and a free surface RANSE (Reynolds Averaged Navier-Stokes Equations) solver using a single-phase Level Set method to capture the interface. The idea is to be able to simulate wave-body interactions under viscous flow theory with strong deformations of the interface (wave breaking in the vicinity of the body, green water on ship decks…), while keeping the advantages of the SWENSE scheme.
The SWENSE approach is based on a physical decomposition by combining incident waves described by a nonlinear spectral scheme based on potential flow theory and an adapted Navier-Stokes solver where only the diffracted part of the flow is solved, incident flow parameters seen as forcing terms.
In the single-phase Level Set method [2, 3], the air phase is neglected. Thus, only the liquid phase is solved considering a fluid with uniform properties. The location of the free surface is determined by a Level Set function initialised as the signed distance. The accuracy of simulation depends essentially on the pressure scheme used to impose free surface dynamic boundary condition.
Comparisons of numerical results with experimental and numerical data for US navy combatant DTMB 5415 in calm water and in head waves are presented.
COBRA Riser Concept for Ultra Deepwater Condition
Authors: Nurwanto Tomy , Karunakaran Daniel , Franciss Ricardo 
Published: November 2013

Offshore ultra deepwater field is being promising as the future of oil and gas reserves. However, the development of ultra deepwater field posed many challenges, in particular, on the selection of the riser concept. Long suspended length of riser will significantly increase the vessel payload. High external hydrostatic pressure on the riser will increase the probability of collapse failure. Large dynamic motions of the vessel and large vessel offset yields potential buckling issues at the touch-down-point (TDP). In addition, potential fatigue problems due to vessel motions and soil-riser interactions also present at TDP area. Large current speed in deepwater field might also lead to vortex induced vibration (VIV) which eventually will contribute to significant fatigue damage for particular riser sections. By looking into these challenges, it is very important to select the most appropriate riser concept for the ultra deepwater field.
Catenary Offset Buoyant Riser Assembly (COBRA) as newly developed hybrid riser concept offers a solution to overcome the challenges in ultra deepwater field. In general, COBRA consists of a catenary riser section with a long-slender sub-surface buoyancy module on top which is tethered down to sea bed via two mooring lines. The catenary section from top of the sub-surface buoy is connected to the floater by a flexible jumper. This flexible jumper can effectively absorb the floater motions, which give significant improvements for both strength and fatigue performance on the overall system. As a hybrid riser concept, this concept offers cost effective solution by avoiding all the expensive bottom assemblies that normally needed for a hybrid riser concept.
This paper focuses on COBRA riser concept specifically for Santos Basin Central Cluster region at 2200 m water depth. It is observed that there is common sudden change phenomenon on the current direction in Santos Basin area. The effect of bidirectional current is analyzed, and the comparison with unidirectional current is discussed thoroughly. The analyses are focused on the global strength design performance under extreme environmental load and global fatigue design performance of the riser due to wave induced and VIV induced.
The results clearly indicate that COBRA riser concept has a robust design and it is feasible for 2200 m water depth, in particular for Santos Basin Cluster Region area. It is also shows that COBRA riser has sufficient strength performance even for extreme bidirectional current.
A Surface Ice Module for Wind Turbine Dynamic Response Simulation Using FAST
Authors: Yu Bingbin , Karr Dale G. , Song Huimin , Sirnivas Senu 
Published: November 2013

The simulation software FAST is an open source CAE package maintained by the National Renewable Energy Laboratory. A new module of FAST for assessing the dynamic response of offshore wind turbines subjected to ice forcing is presented. This paper describes the recent addition of capabilities for analyzing the response of wind turbines subjected forces resulting from ice impact on the turbine support structure. Several models are presented which involve both prescribed forcing and coupled response. For conditions in which the ice forcing is essentially decoupled from the structural response, ice forces are established from existing models for brittle and ductile ice failure modes. For conditions in which the ice failure and the structural response are coupled, such as lock-in conditions, a rate-dependent ice model is described, which is developed in conjunction with a new modularization framework for FAST.
The ice loading module includes ice mechanics models, that incorporate ice floe forcing, deformation, and failure. For lower speeds, forces slowly build until the ice strength is reached and ice fails resulting in a quasi-static condition where the frequency of the forcing is about an order of magnitude lower than the response of the structure. For intermediate speeds, the ice failure response can be coupled with the structural response resulting in response where the ice feature failure period and the response period of the structure approximately coincide. A third response regime occurs at high speeds of encounter in which brittle fracturing of the ice feature in contact with the structure occur in a more or less random pattern, which results in random vibration excitation of the structure. These three conditions are specifically addressed in the ISO standard 19906:2010 for consideration in the design of arctic offshore structures. Special consideration of lock-in vibrations is required due to the detrimental effects of such response with regard to fatigue and foundation/soil response. The use of FAST for transient, time domain simulation with the new ice module is well suited for such analyses.
Case Study of Tsunami Bore Impact on RC Wall
Authors: Robertson Ian N. , Carden Lyle P. , Chock Gary Y. K. 
Published: November 2013

The Tohoku Tsunami of March 11, 2011 caused tremendous damage to many coastal buildings, bridges and port facilities. During field surveys following this event, the authors documented a number of structures that were damaged to a near-collapse condition as a result of hydrodynamic loading. Analysis of survivor videos provided information on the tsunami flow characteristics at these locations, allowing for an assessment of current hydrodynamic loading expressions under full-scale conditions.
Based on laboratory experiments performed at Oregon State University, the lead author and colleagues developed a new hydrodynamic loading expression for a broken bore striking a vertical wall [1]. This expression was applied to a case study of a large vertical reinforced concrete (RC) wall damaged by an incoming bore strike during the Tohoku Tsunami. The damaged wall is on the seaward side of a high-bay building in the Minami Gamou Sewage Treatment plant near the Sendai coastline. A non-linear finite element model of the building was subjected to the hydrodynamic pressure distribution derived from the laboratory experiments. It is shown by structural analysis of the wall that using this loading expression generates the same yielding response in the wall as observed in the field, as reflected in the deflected shape measured by LiDAR. Similar analysis using current Japan Tsunami design provisions indicates that these provisions are considerably more conservative from a structural perspective than is necessary to resist hydrodynamic loading from a tsunami bore.
This paper presents the application of hydrodynamic loading by the leading edge of a bore, determined based on laboratory experiments, to the non-linear analysis of a reinforced concrete building damaged during the Tohoku Tsunami.
Simulation of the Gap Resonance Between Two Rectangular Barges in Regular Waves by a Free Surface Viscous Flow Solver
Authors: Elie B. , Reliquet G. , Guillerm P.-E. , Thilleul O. , Ferrant P. , Gentaz L. , Ledoux A. 
Published: November 2013

This paper compares numerical and experimental results in the study of the resonance phenomenon which appears between two side-by-side fixed barges for different sea-states.
Simulations were performed using SWENSE (Spectral Wave Explicit Navier-Stokes Equations) approach and results are compared with experimental data on two fixed barges with different headings and bilges.
Numerical results, obtained using the SWENSE approach, are able to predict both the frequency and the magnitude of the RAO functions.
Potential Fate of Ingested Lactobacillus plantarum and Its Occurrence in Human Feces
Authors: Costa Giselle Nobre , Marcelino-Guimarães Francismar Corrêa , Vilas-Bôas Gislayne Trindade , Matsuo Tiemi , Miglioranza Lucia Helena S. 
Published: November 2013

ABSTRACT

Lactobacillus
plantarum
has been used in human clinical trials to promote beneficial effects in the immune system, to alleviate intestinal disorders, and to reduce the risk of cardiovascular disease. It is also involved in many fermentation processes in the food industry. However, information on the fate of ingested
L. plantarum
is limited. In this study, 61 subjects received daily doses of fermented milk containing 2 × 10
11
cells of
L. plantarum
Lp115 for different periods of time. The target microorganism was monitored in the fecal microbiota via quantitative PCR (qPCR).
L. plantarum
was detected and quantified in all of the subjects during the ingestion periods. The differences between the
L. plantarum
levels at time zero and during all the different ingestion periods were statistically significant (
P
= 0.001). However, at 15 and 45 days after discontinuing supplementation, the number of lactobacilli was reduced to the baseline level (those at time zero). A longer period with
L. plantarum
in the diet did not result in increased levels of this bacterium in the stool, based on postconsumption evaluations (
P
= 0.001). The qPCR method was specific and sensitive for
L. plantarum
quantification in such a complex microbial environment as the gastrointestinal tract.
RNA Sequencing Reveals Differences between the Global Transcriptomes of Salmonella enterica Serovar Enteritidis Strains with High and Low Pathogenicities
Authors: Shah Devendra H. 
Published: November 2013

ABSTRACT

Salmonella enterica
serovar Enteritidis is one of the important causes of bacterial food-borne gastroenteritis worldwide. Field strains of
S
. Enteritidis are relatively genetically homogeneous; however, they show extensive phenotypic diversity and differences in virulence potential. RNA sequencing (RNA-Seq) was used to characterize differences in the global transcriptome between several genetically similar but phenotypically diverse poultry-associated field strains of
S
. Enteritidis grown in laboratory medium at avian body temperature (42°C). These
S
. Enteritidis strains were previously characterized as high-pathogenicity (HP;
n
= 3) and low-pathogenicity (LP;
n
= 3) strains based on both
in vitro
and
in vivo
virulence assays. Using the negative binomial distribution-based statistical tools edgeR and DESeq, 252 genes were identified as differentially expressed in LP strains compared with their expression in the HP strains (
P
< 0.05). A majority of genes (235, or 93.2%) showed significantly reduced expression, whereas a few genes (17, or 6.8%) showed increased expression in all LP strains compared with HP strains. LP strains showed a unique transcriptional profile that is characterized by significantly reduced expression of several transcriptional regulators and reduced expression of genes involved in virulence (e.g.,
Salmonella
pathogenicity island 1 [SPI-1], SPI-5, and fimbrial and motility genes) and protection against osmotic, oxidative, and other stresses, such as iron-limiting conditions commonly encountered within the host. Several functionally uncharacterized genes also showed reduced expression. This study provides a first concise view of the global transcriptional differences between field strains of
S
. Enteritidis with various levels of pathogenicity, providing the basis for future functional characterization of several genes with potential roles in virulence or stress regulation of
S
. Enteritidis.
Planctomycetes in Lakes: Poor or Strong Competitors for Phosphorus?
Authors: Pollet Thomas , Humbert Jean-François , Tadonléké Rémy D. 
Published: November 2013

ABSTRACT

Experiments were conducted with water samples from two perialpine lakes with differing eutrophication status in order to examine the effects of inorganic-nutrient amendments (nitrogen as NO
3
−
or NH
4
+
and phosphorus as PO
4
3−
) on the dynamics, structure, and composition of
Planctomycetes
and to test the hypothesis that the community structure of
Planctomycetes
members and that of the other bacteria (without
Planctomycetes
, here referred to as bacteria-wP, the most represented groups within the community) would be similarly impacted by nutrient additions. Initial samples were characterized by high total nitrogen-to-total phosphorus ratios (range, 39 to 55), suggesting P rather than N was the limiting nutrient for microbial communities. Consistent with this, P additions stimulated phytoplankton growth and affected the community structure of bacteria-wP but, surprisingly, not that of
Planctomycetes
. N additions did not significantly affect the community structures of bacteria-wP and
Planctomycetes
or the
Planctomycetes
phylotype composition. The estimated generation time of
Planctomycetes
was 123 h. These findings could suggest that the generally well-accepted statement that bacteria (as a whole) are superior to phytoplankton in the ability to obtain phosphorus under P limitation might actually not hold for
Planctomycetes
.
Planctomycetes
might be poor competitors for P that do not respond quickly to the nutrient supply, which may help explain why their abundance is low in aquatic systems. The alternative view that
Planctomycetes
could be strong competitors for P (storing it) is also discussed. Our findings highlight the need for further studies examining
Planctomycetes
-phosphorus relationships in aquatic ecosystems.
Impacts of Sample Preparation Methods on Solubility and Antilisterial Characteristics of Essential Oil Components in Milk
Authors: Chen Huaiqiong , Davidson P. Michael , Zhong Qixin 
Published: November 2013

ABSTRACT

Essential oil components (EOCs) have limited water solubility and are used at much higher concentrations in complex food matrices than in growth media to inhibit pathogens. However, the correlation between solubility and activity has not been studied. The objective of this work was to characterize the solubility of EOCs in solvents and milk and correlate solubility with antilisterial activity. The solubilities of four EOCs, thymol, carvacrol, eugenol, and
trans
-cinnamaldehyde, in water was significantly increased in the presence of 5% (vol/vol) ethanol. In milk, the solubility of EOCs was lower than in water, with lower solubility in higher-fat milk. EOCs applied to milk as stock solutions (in 95% aqueous ethanol) enabled quicker dissolution and higher solubility in milk serum than other methods of mixing, such as end to end, and greater reductions of
Listeria monocytogenes
Scott A after 0 and 24 h. When the EOC concentration detected in milk serum was above the minimum bactericidal concentration, complete inhibition of
L. monocytogenes
in tryptic soy broth resulted. Therefore, the antilisterial properties in milk could be correlated with the solubility by comparison to the minimum inhibitory or bactericidal concentrations of EOCs. While the EOCs applied using ethanol generally had solubility and activity characteristics superior to those of other mixing methods, ethanol is not used to a great extent in nonfermented foods. Therefore, mixing methods without an organic solvent may be more readily adaptable to enhancing the distribution of EOCs in complex food systems.
Lactobacillus buchneri Genotyping on the Basis of Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR) Locus Diversity
Authors: Briner Alexandra E. , Barrangou Rodolphe 
Published: November 2013

ABSTRACT

Clustered regularly interspaced short palindromic repeats (CRISPR) in combination with associated sequences (
cas
) constitute the CRISPR-Cas immune system, which uptakes DNA from invasive genetic elements as novel “spacers” that provide a genetic record of immunization events. We investigated the potential of CRISPR-based genotyping of
Lactobacillus buchneri
, a species relevant for commercial silage, bioethanol, and vegetable fermentations. Upon investigating the occurrence and diversity of CRISPR-Cas systems in
Lactobacillus buchneri
genomes, we observed a ubiquitous occurrence of CRISPR arrays containing a 36-nucleotide (nt) type II-A CRISPR locus adjacent to four
cas
genes, including the universal
cas1
and
cas2
genes and the type II signature gene
cas9
. Comparative analysis of CRISPR spacer content in 26
L. buchneri
pickle fermentation isolates associated with spoilage revealed 10 unique locus genotypes that contained between 9 and 29 variable spacers. We observed a set of conserved spacers at the ancestral end, reflecting a common origin, as well as leader-end polymorphisms, reflecting recent divergence. Some of these spacers showed perfect identity with phage sequences, and many spacers showed homology to
Lactobacillus
plasmid sequences. Following a comparative analysis of sequences immediately flanking protospacers that matched CRISPR spacers, we identified a novel putative protospacer-adjacent motif (PAM), 5′-AAAA-3′. Overall, these findings suggest that type II-A CRISPR-Cas systems are valuable for genotyping of
L. buchneri
.