bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation of Flow Interference Effects in Fixed and Vibrating Tandem Square Columns Using Hybrid RANS-LES Models
Authors: Gopalan Harish , Chandar Dominic Denver John , Pillamarri Narasimha Rao , Mengzhao Guan , Jaiman Rajeev K. , Ma Peifeng , Xu Haihua , Choudhary Ankit , Hussain Anis 
Published: October 2015

Investigation of flow past tandem and side-by-side circular and square columns is of interest in offshore engineering. Flow past fixed and vibrating circular columns has received a lot of focus in the literature. However, the studies focused on square columns, especially at high Reynolds numbers are very limited due to the computational cost of large eddy simulation (LES). Unsteady Reynolds-averaged Navier-Stokes (URANS) methods are limited by their accuracy, especially for tandem columns in the wake interference regime (spacing to diameter ratio: L=D ∼ 3:0). Hybrid URANS-LES models (URANS near the solid-wall and LES away from the wall) can overcome the drawbacks of the traditional URANS methods and can provide a reasonable prediction of the flow physics at a fraction of the cost of LES without significantly sacrificing numerical accuracy.
Arbitrary Lagrangian-Eulerian (ALE) methods fails when vibrating tandem bodies are in close proximity to each other or vibrate at high reduced velocities. Remeshing the domain can be expensive, especially at high Reynolds numbers (Re). Alternate strategies are necessary to efficiently simulation this problems. This study proposes the use of a non-linear URANS-LES model, coupled with an overset mesh method (for vibrating columns), for studying flow past tandem square columns. Simulations are performed at sub-critical Re to match the experimental Re. The initial results are encouraging for further investigation of fixed and vibrating tandem square column flow interference at high Reynolds numbers.
Extensions and Improvements to the Solutions for Linear Tank Dynamics
Authors: Ludvigsen Arild , Pan Zhi Yuan 
Published: October 2015

Linear solvers for the flow exterior to the hull may be used to solve for the fluid dynamics also in the interior of a tank, as discussed in Newman (2005) and Ludvigsen et al. (2013). This introduces extra, erroneous terms in the radiation part of the pressure in the tank, but due to cancellation in restoring and radiation terms, the total representation of the pressure and the global response is correctly obtained.
For some kinds of analysis, specific knowledge is needed of the radiation and restoring parts separately. The cancellation of the extra terms can then not be utilized.
Examples of this are stability analysis and eigenvalue analysis. In stability analysis we need to know the actual real global restoring coefficients. In eigenvalue analysis, we should have the separately correct representations of the added mass and restoring coefficients, respectively, to be able to conveniently use them as input to standard eigenvalue solvers.
Here, we develop the expressions for the corrected, actual terms of the total added mass and restoring coefficients for tanks. This is used in our computer program for performing eigenvalue analysis. Results for peak global response and natural periods of the structure with the influence of tank dynamics are presented. Comparisons are made with results obtained by a quasi-static method for an FPSO and a ship with more largely extensive tanks.
For a completely filled tank, the boundary value problem (BVP) for the velocity potential is reduced to Laplace equation in the fluid domain, subject to a Neuman condition on the fixed boundary and it is not closed. The extra condition of having zero pressure at some point in the tank is then added.
Direct re-use of the BVP solver for the external flow, gives an undetermined set of linear equations for the velocity potential in the tank fluid. A typical solver for sets of linear equations may still return a solution, but this will contain a random undetermined constant. After imposing zero pressure in the top of the tank, this solution is still unstable, contaminated by numerical noise.
An improved method is introduced by imposing algebraically, in the equation system, the constraint of zero pressure in the top of the tank. This gives a non-singular equation system with a stable solution holding zero pressure in some selected point in the tank.
Subsea Oil and Gas Production Assurance Using Artificial Lifts and Nodal Analysis
Authors: Okaro Ikenna A. , Tao Longbin 
Published: October 2015

This paper describes how the operation of deep, subsea oil wells can be analyzed and optimized using artificial lift systems. A modest explanation was offered about an enhanced Hubbert model for determining production targets at pre-feed phase of project. In addition, the impact of artificial lifts on the economics of subsea wells facing hyperbolic production decline was illustrated. The principle of Nodal analysis was highlighted and applied to optimize a proposed subsea oil production case. Configurations of a nominally rated rod pump, a multiphase pump and an electrical submersible pump were modelled in a steady-state flow using Pipesim software and the simulated results which were functions of liquid flow rate and pressure distribution across the production system exposed the behavior of the system.
The results showed that over 100% volumetric efficiency was achieved using a combination of electrical submersible pump at the bottom hole and a multiphase pump at riser base. A guide is presented on how to predict, analyze and enhance the recovery curve of subsea oil production using artificial lifts and nodal-system analysis. The benefit of this work is an enabling cost-effective approach for ensuring production assurance in deep water oil and gas production.
An Investigation of Riser Fairing Instability
Authors: Kristiansen Trygve , Braaten Henning , Lie Halvor , Baarholm Rolf , Skaugset Kjetil 
Published: October 2015

An analysis of galloping of two different types of riser fairings is presented. The first is named “long fairing” (LF) and the other “Short Crab Claw” (Short CC). The first one has a traditionally winged formed shape with a cord-to-diameter ratio of 2.43. The other one is more truncated in shape, and has cord-to-diameter ratio of only 1.4.
Results from two related experimental set-ups are included in the work; one 2D experiment with towing tests of fairings that are free to translate and rotate to investigate instability regions, and one 2D experiment with fixed fairings to obtain drag, moment and lift curves. The present analysis is based on two-degrees of freedom, linearized equations of motion, and predicts a range of velocities where instability occurs. Below and above this region, the fairing is stable. Damping complicates the analysis. An empirical damping model is included and discussed. The two fairing types inhibit appreciably different instability characteristics. In particular, the Short CC fairing has a narrower instability region than the long fairing, and is therefore less prone to instabilities.
An Anti-Recoil Control Design Using the New Riser Hybrid Tensioning System in Deepwater Drilling
Authors: Wu Yin 
Published: October 2015

A new riser anti-recoil control design is presented in this research paper using the novel riser hybrid tensioning system by combining a fast acting electrically powered riser tensioning system with existing conventional hydro-pneumatic tensioners. This work is the further development of a control system for the previous work presented in the framework proposal of riser hybrid tensioning system.
This innovation that we bring forward here is all designed to increase operating envelope of the vessel. A system model integrating both electrical and hydro-pneumatic tensioners and the riser string is built for anti-recoil control purpose. The main goal of this control design is a safer and more predictable position control of the riser string. A LQG control design technique is applied here. A feedback controller with Kalman estimator of the system state space variables is designed and implemented. The Matlab simulation helped to demonstrate the concept feasibility of this anti-recoil control strategy and to further verify that a more robust and accurate control performance could be achieved by this riser hybrid tensioning system.
This control technique increases the testability of the riser anti-recoil system; reduce potential damage and increase operator’s confidence. The new proposed data logging system improves the detectability of the anti-recoil system. And the position control, when the riser string “soft hang-off” on the tensioners, opens the possibility to extend the operability to other applications.
On the Occurrence of Higher Harmonics in the VIV Response
Authors: Wu Jie , Yin Decao , Lie Halvor , Larsen Carl M. , Baarholm Rolf J. , Jhingran Vikas , Liapis Stergios 
Published: October 2015

Vortex Induced Vibrations (VIV) can lead to fast accumulation of fatigue damage and increased drag loads on slender marine structures. A cylinder subjected to VIV can vibrate in both in-line (IL) and cross-flow (CF) directions. The CF response is dominated by the primary shedding frequency and the IL response frequency is often two times of the primary CF frequency. In addition, higher harmonics can also be present. The third order harmonics are more pronounced when the motion orbit of the cylinder is close to “figure 8″ shape and cylinder is moving against the flow at its largest transverse motion. Recent studies with flexible beam VIV tests have shown that higher harmonics can have significant contribution to the fatigue damage in addition to the loads at the primary shedding frequency. However, there is a lack of understanding of when and where higher harmonic loads occur. The fatigue damage due to the higher harmonics is not considered in the present VIV prediction tools.
In the present paper, the test data of selected cases subjected to linearly sheared flow profile from two test programs, the Shell high mode VIV test[11] and the Hanøytangen test[5] have been studied. The factors that may influence the occurrence of the higher harmonics, such as the bending stiffness, reduced velocity and orbits stability, have been studied. The importance of higher harmonics in VIV fatigue has also been investigated. Finally, a method to include higher harmonics in the fatigue calculation is presented.
Understanding Hybrid Subsea Foundation Design
Authors: Hossain M. Kabir , Shi Han , Abdalla Basel , Spari Markella K. 
Published: October 2015

Hybrid subsea foundations (HSF) are combined foundation systems of mudmats and piles. The primary motivation of combining these two foundation types is to provide greater resistance to large horizontal loads in addition to vertical loads, for which use of mudmats alone will require it to be of impractically large size. The contribution from the piles in the lateral capacity helps to limit the size of the mudmat, which is critical in subsea environment. In a brownfield situation, this is sometimes a hard limit with only limited space available to place a new mudmat in the existing field layout. Also, in some cases, the HSF may prove to be a more economical option for resisting large horizontal loads compared to, for example, to suction piles. While the authors are aware of some scattered project-specific design and use of subsea mudmat-pile hybrid foundations by individual contractors and operators, there is no industry-wide publicly known best practice currently available. These designs of HSF appear to be generally based on simplified analytical approach that require superimposition of conventional shallow and deep foundation capacity calculation methods, hence violates the static and kinematic compatibility requirements fundamental for a sound and robust prediction procedure.
This paper attempts to provide some insight into the behavior of mudmat-pile foundations as a hybrid integrated system numerically using finite element modeling and analysis (FEA). The interactions between the mudmat and the piles in an HSF are complex and hence a FEA-based approach is considered most suitable. The FEA model in this study included the mudmat, the corner piles, the pile-mudmat connections and the seabed soil. Sensitivity of the HSF capacity to the size of the piles (length and diameter), the connection type of the piles to the mudmat, and the number of piles are selectively investigated and the results presented. Based on these results some pertinent observations relevant to design of HSFs are also given.
While the study is of limited scope, it offers important insights into the effects of the primary design variables on HSF’s capacities. Therefore, the authors hope the information herein will be of benefit to practicing subsea engineers who might have to face choices to consider mudmat-pile hybrid foundations as a real option for their projects.
Full Scale Fairing Qualification Tests
Authors: Constantinides Yiannis , Liapis Stergios , Spencer Don , Islam Mohammed , Skaugset Kjetil , Batra Apurva , Baarholm Rolf 
Published: October 2015

Production risers as well as drilling risers are often subjected to Vortex-induced vibrations (VIV) when exposed to ocean currents. VIV have been observed in the field and can cause fatigue failure and excessive drag on the riser. In order to suppress VIV and reduce drag, fairings are often used. This paper presents hydrodynamic qualification tests for two types of fairings: the short crab claw (SCC) and a tapered dual fin design. The short crab claw fairing design is a novel design that was developed by the Norwegian Deepwater Programme (NDP). As will be detailed in this paper, the SCC design offers very low drag, completely suppresses VIV and reduces riser interference.
In 2012, a model test campaign was undertaken to understand and qualify the hydrodynamic performance of fairings at prototype conditions. The program consisted of testing the three fairing geometries and a strake to understand the stand-alone performance in VIV and the performance in interference. This was accomplished by utilizing a single pipe setup for the standalone test and a two-pipe setup for the interference tests. The paper reports the results of the program and draws conclusions on the hydrodynamic performance of the VIV suppression devices tested.
Overall, all VIV suppression devices tested were able to suppress VIV with the SCC fairing being the most effective. In all cases tested, the downstream fairings / strakes were very effective in suppressing VIV in an interference scenario where a fairing was placed upstream. Contrary to the well-documented case of two strakes in tandem, in this case the upstream fairings did not reduce the effectiveness of the downstream fairings/strakes.
Multipinhole SPECT helical scan parameters and imaging volume
Authors: Yao Rutao , Deng Xiao , Wei Qingyang , Dai Tiantian , Ma Tianyu , Lecomte Roger 
Published: October 2015

Purpose:The authors developed SPECT imaging capability on an animal PET scanner using a multiple‐pinhole collimator and step‐and‐shoot helical data acquisition protocols. The objective of this work was to determine the preferred helical scan parameters, i.e., the angular and axial step sizes, and the imaging volume, that provide optimal imaging performance.Methods:The authors studied nine helical scan protocols formed by permuting three rotational and three axial step sizes. These step sizes were chosen around the reference values analytically calculated from the estimated spatial resolution of the SPECT system and the Nyquist sampling theorem. The nine helical protocols were evaluated by two figures‐of‐merit: the sampling completeness percentage (SCP) and the root‐mean‐square (RMS) resolution. SCP was an analytically calculated numerical index based on projection sampling. RMS resolution was derived from the reconstructed images of a sphere‐grid phantom.Results:The RMS resolution results show that (1) the start and end pinhole planes of the helical scheme determine the axial extent of the effective field of view (EFOV), and (2) the diameter of the transverse EFOV is adequately calculated from the geometry of the pinhole opening, since the peripheral region beyond EFOV would introduce projection multiplexing and consequent effects. The RMS resolution results of the nine helical scan schemes show optimal resolution is achieved when the axial step size is the half, and the angular step size is about twice the corresponding values derived from the Nyquist theorem. The SCP results agree in general with that of RMS resolution but are less critical in assessing the effects of helical parameters and EFOV.Conclusions:The authors quantitatively validated the effective FOV of multiple pinhole helical scan protocols and proposed a simple method to calculate optimal helical scan parameters.
Genome Sequence of “
Candidatus
Thioglobus autotrophica” Strain EF1, a Chemoautotroph from the SUP05 Clade of Marine Gammaproteobacteria
Authors: Shah Vega , Morris Robert M. 
Published: October 2015

ABSTRACT

Chemoautotrophic marine bacteria from the SUP05 clade of marine gammaproteobacteria often dominate low-oxygen waters in upwelling regions, fjords, and hydrothermal systems. Here, we announce the complete genome sequence of “
Candidatus
Thioglobus autotrophica” strain EF1, the first cultured chemoautotrophic representative from the SUP05 clade.
Draft Genome Sequence of Thiostrepton-Producing Streptomyces azureus ATCC 14921
Authors: Sakihara Kengo , Maeda Jumpei , Tashiro Kosuke , Fujino Yasuhiro , Kuhara Satoru , Ohshima Toshihisa , Ogata Seiya , Doi Katsumi 
Published: October 2015

ABSTRACT

Streptomyces azureus
ATCC 14921 belongs to the
Streptomyces cyaneus
cluster and is known to be a thiostrepton producer. Here, we report a draft genome sequence for this strain, consisting of 350 contigs containing a total of 8,790,525 bp, 8,164 predicted coding sequences, and a G+C content of 70.9%.
Complete Genome Sequence of Spiroplasma kunkelii Strain CR2-3x, Causal Agent of Corn Stunt Disease in
Zea mays
L
Authors: Davis Robert E. , Shao Jonathan , Dally Ellen L. , Zhao Yan , Gasparich Gail E. , Gaynor Brady J. , Athey John C. , Harrison Nigel A. , Donofrio Nicole 
Published: October 2015

ABSTRACT

Spiroplasma kunkelii
causes corn stunt disease of
Zea mays
L. in the Americas. Here, we report the nucleotide sequence of the 1,463,926-bp circular chromosome and four plasmids of strain CR2-3x. This information will facilitate studies of
Spiroplasma
pathogenicity and evolutionary adaptations to transkingdom parasitism in plants and insect vectors.
Draft Genome Sequence of Bradyrhizobium japonicum Is-1, Which Is Incompatible with
Rj
2
Genotype Soybeans
Authors: Sakata Tomoyuki , Kanesaki Yu , Yoshikawa Hirofumi , Tsurumaru Hirohito , Yamakawa Takeo 
Published: October 2015

ABSTRACT

We report the draft genome sequence of
Bradyrhizobium japonicum
Is-1, which is incompatible with
Rj
2
genotype soybeans. The estimated genome size of this strain is 8.9 Mb. Genome sequence information of this strain will help to identify a causal gene for this incompatibility.
Complete Genome Sequence of
Southern tomato virus
Identified in China Using Next-Generation Sequencing
Authors: Padmanabhan Chellappan , Zheng Yi , Li Rugang , Sun Shu-E , Zhang Deyong , Liu Yong , Fei Zhangjun , Ling Kai-Shu 
Published: October 2015

ABSTRACT

The complete genome sequence of
Southern tomato virus
(STV), a double-stranded RNA virus that affects tomato in China, was determined using small RNA deep sequencing. This Chinese isolate shares 99% sequence identity to other isolates from Mexico, France, Spain, and the United States. This is the first report of STV infecting tomatoes in Asia.
Complete Genome Sequence of Spiroplasma cantharicola CC-1
T
(DSM 21588), a Bacterium Isolated from Soldier Beetle (
Cantharis carolinus
)
Authors: Lo Wen-Sui , Liu Po-Yu , Kuo Chih-Horng 
Published: October 2015

ABSTRACT

Spiroplasma cantharicola
CC-1
T
(DSM 21588) was isolated from the gut of a soldier beetle (
Cantharis carolinus
) collected in Maryland, USA. Here, we report the complete genome sequence of this bacterium to facilitate the investigation of its biology.
Draft Genome Sequence of
Achromobacter
sp. Strain DMS1, Capable of Degrading Polyaromatic Hydrocarbons Isolated from the Industrially Perturbed Environment of Amlakhadi Canal, India
Authors: Amin Shivani , Shah Binal , Jain Kunal , Patel Anand , Patel Namrata , Joshi Chaitanya G. , Madamwar Datta 
Published: October 2015

ABSTRACT

Here, we report the draft genome sequence of
Achromobacter
sp. strain DMS1, which is 4.9 Mbp and has 3,727 coding sequences (CDSs), and is capable of degrading xenobiotic compounds and harboring genes for aromatic hydrocarbon metabolism. Its genome will unravel the basic mechanism involved in bioremediation of anthropogens.
Induction of Kaposi's Sarcoma-Associated Herpesvirus-Encoded Viral Interleukin-6 by X-Box Binding Protein 1
Authors: Hu Duosha , Wang Victoria , Yang Min , Abdullah Shahed , Davis David A. , Uldrick Thomas S. , Polizzotto Mark N. , Veeranna Ravindra P. , Pittaluga Stefania , Tosato Giovanna , Yarchoan Robert 
Published: October 2015

ABSTRACT
Kaposi's sarcoma-associated herpesvirus (KSHV) is the causative agent for Kaposi sarcoma (KS), primary effusion lymphoma (PEL), and a subset of multicentric Castleman disease (MCD). The KSHV life cycle has two principal gene repertoires, latent and lytic. KSHV viral interleukin-6 (vIL-6), an analog of human IL-6, is usually lytic; production of vIL-6 by involved plasmablasts is a central feature of KSHV-MCD. vIL-6 also plays a role in PEL and KS. We show that a number of plasmablasts from lymph nodes of patients with KSHV-MCD express vIL-6 but not ORF45, a KSHV lytic gene. We further show that vIL-6 is directly induced by the spliced (active) X-box binding protein-1 (XBP-1s), a transcription factor activated by endoplasmic reticulum (ER) stress and differentiation of B cells in lymph nodes. The promoter region of vIL-6 contains several potential XBP-response elements (XREs), and two of these elements in particular mediate the effect of XBP-1s. Mutation of these elements abrogates the response to XBP-1s but not to the KSHV replication and transcription activator (RTA). Also, XBP-1s binds to the vIL-6 promoter in the region of these XREs. Exposure of PEL cells to a chemical inducer of XBP-1s can induce vIL-6. Patient-derived PEL tumor cells that produce vIL-6 frequently coexpress XBP-1, and immunofluorescence staining of involved KSHV-MCD lymph nodes reveals that most plasmablasts expressing vIL-6 also coexpress XBP-1. These results provide evidence that XBP-1s is a direct activator of KSHV vIL-6 and that this is an important step in the pathogenesis of KSHV-MCD and PEL.

IMPORTANCE
Kaposi sarcoma herpesvirus (KSHV)-associated multicentric Castleman disease (KSHV-MCD) is characterized by severe inflammatory symptoms caused by an excess of cytokines, particularly KSHV-encoded viral interleukin-6 (vIL-6) produced by lymph node plasmablasts. vIL-6 is usually a lytic gene. We show that a number of KSHV-MCD lymph node plasmablasts express vIL-6 but do not have full lytic KSHV replication. Differentiating lymph node B cells express spliced (active) X-box binding protein-1 (XBP-1s). We show that XBP-1s binds to the promoter of vIL-6 and can directly induce production of vIL-6 through X-box protein response elements on the vIL-6 promoter region. We further show that chemical inducers of XBP-1s can upregulate production of vIL-6. Finally, we show that most vIL-6-producing plasmablasts from lymph nodes of KSHV-MCD patients coexpress XBP-1s. These results demonstrate that XBP-1s can directly induce vIL-6 and provide evidence that this is a key step in the pathogenesis of KSHV-MCD and other KSHV-induced diseases.