bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transition Criteria for Laminar to Turbulent Flow for Yield Power Law (YPL) Fluids Based on Stability Analysis
Authors: Kalayci Goktug , Ozbayoglu Evren M. , Miska Stefan Z. , Yu Mengjiao , Takach Nicholas , Saasen Arild , May Roland 
Published: December 2013

It is well known that a Newtonian fluid with the presence of solid particles in suspension behaves non-Newtonian. Higher the solid content, more significant the yield stress of the fluid. Determination of the hydraulic behavior of fluids having a significant yield stress is a challenging task. For engineering purposes, pressure drop within the system, during pipeline transportation, has to be estimated carefully and accurately. Flow regime plays a vital role during hydraulic calculations. The inaccurate determination of flow regime can lead us to large errors in frictional pressure drop calculations and ultimately leads to error in designing and flow assurance point of view, since hydraulic calculations are including a friction factor term, which is a direct function of flow regime. In general, Reynolds number is the main parameter used by the industry for determining the flow regime, and the friction factor. This approach works reasonably accurate for Newtonian fluids. However, as the yield stress of the fluid increases, this conventional technique for determining the flow regime is not as accurate. Although many approaches have been introduced for estimating the flow regime for non-Newtonian fluids, there exists a lack of information and confidence of such predictions for fluids having high yield stress, such as Yield Power Law (YPL) fluids (i.e., Herchel-Bulkley). (1)τ=τy+Kγm
This study presents an analytical solution for predicting the transition from laminar to non-laminar flow regime based on Ryan & Johnson’s approach using the stability analysis and equation of motion for YPL fluids. Comparing with the experimental results for YPL fluids under different flow conditions, including laminar and non-laminar flow regimes, show that presented approach gives a better estimation of the transition from laminar to non-laminar flow regime than conventional Reynolds number approach. In some cases, it is observed that although the Reynolds number is high, flow is still laminar, which is predicted accurately using the presented model. This study provides a higher accuracy in estimating the flow regime, which leads to a higher confidence in hydraulic designs and determining limitations of the system in concern.
Development of a Low Cost Particle Image Velocimetry System for Fluids Engineering Research and Education
Authors: Ring Brock P. , Atkinson Daniel K. , Henderson Andrew W. , Lemley Evan C. 
Published: December 2013

Particle image velocimetry (PIV) has transformed fluid mechanics research in recent years. PIV also holds the possibility to transform fluids engineering undergraduate education with the ability of students to get hands-on experience in visualization of real flow fields. One barrier to use of PIV is the cost of a system. Research grade systems are often over $100,000 and inaccessible to many undergraduate students. Recent availability of low-cost high-frame-rate digital cameras, lasers, and public domain software offer potential accessibility for PIV for many labs at academic institutions.
In this paper we describe the development of a PIV system for under $1000 including specific components and their costs. In our lab this system is currently being used for several liquid flow experiments including obtaining the flow field in and near small bifurcations. Although we are using the system for liquid flows, it may be used for gas flows as well. One issue that is addressed is the cost of flow seeding — this has been solved by using pulverized green algae as seed particles with a strong reflection by a 532 nm green laser.
The system is small and portable and is useful for observing flow in locations that are not of direct interest for experiments, but may have a bearing on flow conditions in experimental measurements; such as upstream of test sections. We describe some examples of how we have used the lost-cost PIV system in our lab and how it can be used for fluids engineering education and research. The current research application of this system is performing loss coefficient calculations in a test section using the energy dissipation.
Teaching Heat Exchanger Design in Mechanical Engineering With CFD
Authors: Teixeira José C. , Teixeira Senhorinha F. C. , Oliveira António 
Published: December 2013

Technologies for energy recovery and conversion are at the forefront of any mechanical engineering curricula. Heat exchangers are often found in various industries and, therefore, deserve a special dedication to the effort in under and post graduate education.
The Integrated Masters degree in Mechanical Engineering at the University of Minho includes a semester (out of 10) dedicated to the thermal analysis of heat exchangers. Traditionally such subject would follow the route of application of the NTU charts and the efficiency method. Although this approach is still of great relevance both as a calculation methodology and as a method to develop the physical insight into the subject, the application of advanced computation tools has been introduced into the course with great acceptance by the students. In brief, the course provides an excellent opportunity to integrate various subjects.
This paper details the rationale for the application of CFD techniques in heat exchanger design and calculations. It frames this approach within the overall education in mechanical engineering, and integrates the methodology with traditional design methodologies. Various test cases are detailed (constant wall temperature heat exchanger, double pipe and shell and tube) and the results are compared with integral methods. The local heat transfer coefficients are discussed with regard to the empirical correlations.
Performance Characteristics and Flow Conditions of High Pressure and Large Flow Rate Cooling Fan
Authors: Shigemitsu Toru , Fukutomi Junichiro , Agawa Takuya 
Published: December 2013

Data center has been built with spread of cloud computing. Further, electric power consumption of it is growing rapidly. High pressure and large flow rates small-sized cooling fans are used for servers in the data center and there is a strong demand to increase pressure and flow rate of it because of increase of quantity of heat from the servers. Contra-rotating rotors have been adopted for some of the high pressure and large flow rate cooling fans to meet the demand of it. There is limitation of space for servers and geometrical restriction for cooling fan because spokes to support the fan motor, electrical power cables and so on should be installed in the cooling fan. It is important to clarify performance of each front and rear rotor of contra-rotating small-sized cooling fan and internal flow condition to achieve the high performance cooling fans.
In the present paper, detailed performance and the flow condition around the rotor of the high pressure and large flow rate contra-rotating small-sized axial fan with 40mm square casing are investigated. Pressure, shaft power and efficiency curves of each front and rear rotor are clarified by the experimental and the numerical results. Furthermore, the internal flow condition of the rear rotor is clarified by the numerical analysis results and design guideline to improve the performance is discussed by these results.
Lattice Boltzmann Simulation of the Flow Field in Pump Intakes: A New Approach
Authors: Schneider Andreas , Conrad Daniel , Böhle Martin 
Published: December 2013

In recent years Lattice Boltzmann Methods have become popular for solving fluid flow problems of engineering interest. Reasons for this popularity are due to the advantages of this method which are for example the simplicity to handle complex geometries and the high efficiency in calculating transient flows.
For the operational reliability and efficiency of pumps and pump systems the incoming flow conditions are crucial. Since the efficiency and reliability requirements of pumps are rising and must be guaranteed by the pump and plant manufacturer, the flow conditions in pump intakes need to be evaluated during plant planning. Recent trends show that pump intakes are built more and more compact which makes the flow in the intake even more complex and holds a higher risk for unacceptable pump inflow conditions. If the inflow conditions of the pump are not according to the demand of the pump manufacturer or to international standards, optimization needs to be done.
In this contribution a numerical scheme for the simulation of pump intakes based on a Lattice Boltzmann-LES approach is presented and the ability to capture the flow phenomena of the intake flow is analyzed.
Experimental Investigation on Unstable Flow in Multi-Stage Centrifugal Blower With Inlet Guide Vane
Authors: Hiradate Kiyotaka , Sakamoto Kiyohide , Kanno Toshio , Shinkawa Yasushi , Joukou Satoshi , Suzuki Katsunari 
Published: December 2013

This study experimentally examines unstable flow phenomena occur in a five-stage centrifugal blower equipped with inlet guide vanes (IGVs) before the first stage.
High response pressure transducers were mounted on a suction nozzle, an U-turn bend between a diffuser and return channel in the second stage, and a discharge nozzle to detect surge. Moreover, at a vaneless space between an impeller and a vaned diffuser in the second stage, three pressure transducers were located thirty degrees apart in the circumferential direction to distinguish rotating stall in the diffuser from surge. Measurements were performed at several flowrates changing the IGVs from fully opening condition to partially opening conditions.
We confirmed three types of pressure fluctuation in low flowrate region. The first is the fluctuation showing the largest amplitude and the lowest frequency (about 7–9 percent of impeller rotation frequency) and observed at all the sensors. This appears in the positive slope region of the total system head curve. The second is the spike-like fluctuation intermittently observed only in the vaneless space. This occurs at the IGVs partially opening conditions and shows observed time lag among the three sensors. The last is the fluctuation with smaller amplitude and higher frequency (about 14–23 percent of impeller rotation frequency) than that of the first and observed at all the sensors. This occurs at the IGVs partially opening conditions. At 4.5 percent IGVs opening, this fluctuation is observed in the steep negative slope region of the total system head curve, where the whole compression system is supposed to be stable. Moreover, this fluctuation is measured at the same phase in the vaneless space.
We concluded that the first-mentioned fluctuation is deep surge and the second-mentioned fluctuation is rotating stall in the diffuser. On the other hand, we have considered the last-mentioned fluctuation to be mild surge and the reason why this occurs in the negative slope region to be as follows. At 4.5 percent IGVs opening, slope of the first stage head curve becomes steeply negative by prewhirl and this negative slope stabilizes the system. By contrast, at the second to the last stage, the slope of the head curve becomes positive in low flowrate region and this positive slope destabilizes the system. Therefore, even if the total system head curve maintains a steep negative slope, the system operating point oscillates slightly (mild surge situation) due to a balance of these stabilization and destabilization effects.
Hydroelastic Stability and Vibration of a Large Reactor Pendulum Structure
Authors: Meyer Gregory A. , Banyay Gregory A. , Maeby Samuel A. , Sidener Scott E. , Schwirian Richard E. 
Published: December 2013

Parallel-flow induced vibrations of both large and small reactor internal structures have been analyzed in the past for multiple reactor types. In parallel flows relating to annular and leakage flows, the possibility for significant wear issues can arise and need to be assessed as has been shown throughout the literature. With parallel flow induced vibration, a particular fluid-structure interaction known as hydroelastic instability can arise. If hydroelastic instability occurs, damage to components can be severe and/or catastrophic. This particular phenomenon has been studied in the literature and a few empirically derived methodologies have been published to evaluate the potential for hydroelastic instability to occur in both a limited number of specific geometries and some generic geometries. However, as structural components and their associated flow field characteristics can vary significantly and because of the potential for catastrophic damage to reactor components and the associated costs, a more detailed first principles approach may be warranted to further determine if hydroelastic instability is not only possible, but probable.
A potential design for a reactor internals test in which part of the upper internals would exhibit significant annular parallel flow velocities is analyzed for the potential onset of hydroelastic instability. In particular, the upper core plate, which is attached to the rest of the upper internals via support columns in a pendulum setup with the attachment/pivot point at the upper pressure vessel head flange, is temporarily designed to carry a significant non-prototypic pressure drop causing significant upper core plate to core barrel gap flow velocities and potential instability issues. Due to the different geometry of this hardware configuration compared to those found in the literature, both an empirically-based stability analysis from the literature and a first-principles based hydroelastic stability analysis are conducted. The first-principles analysis derives and solves the time-dependent equations of motion and mass conservation for both the fluid and structure and compares the results proximity to stability limits found in the literature. A comparison of the empirically based stability assessment with the first-principles stability analysis is made. Furthermore, an assessment of the probability for the onset of hydroelastic instability of the upper internals assembly is made via a Monte Carlo simulation using the first-principles analysis methodology.
Numerical Simulation and Experimental Study of Cabin-Airflow and Transport of Gas-Mixtures in Aircraft Cargo Compartments: Model Validation
Authors: Zur Malte , Otremba Frank , Klippel Alexander , Leder Alfred 
Published: December 2013

Dangerous goods are transported as air freight in commercial aircrafts. Using plastic jerrycans or plastic containers, liquids or gases can escape by leakage or permeation effects. Prior research by the German Federal Institute for Materials Research and Testing (BAM) showed that the lower explosion limit can be reached when transporting dangerous goods in sea-freight containers under normal transportation situations. This motivated the presented study of the transportation situation of dangerous goods in cargo compartments of commercial airplanes. The scope of this paper is to present the experimental method used for validating a numerical model for CFD (Computational Fluid Dynamics) simulations. The CFD model will be used in a future study to evaluate the potential risk from transporting dangerous goods.
The objective of this paper is to present the model mock-up of an aircraft cargo compartment and some examples of three dimensional velocity profiles of the air flow in the mock-up. The velocity profiles are calculated using numerical simulations and measured by Laser-Doppler-Anemometry (LDA) experiments. The mock-up is a generic model of a wide-body aircraft lower deck cargo compartment in a 1:10 scale. Geometry, air exchange rates and inlet as well as outlet flow conditions in the cargo compartment are modeled using realistic boundary conditions. The commercial CFD (Computational Fluid Dynamics) code ANSYS CFX 14 is used for numerical flow simulations applying RANS (Reynolds-Averaged-Navier-Stokes) equations and turbulence models. The turbulence models studied are the renormalization group k-ε-model (RNG), the Reynolds-Stress model by Launder, Reece and Rodi (LRR) and the SST-k-ω-model by Menter (SST).
The flow measurement with LDA in the mock-up of a cargo compartment proves to be a feasible method for producing data to validate CFD simulations. Qualitative evaluation of the results shows a good overall agreement between numerical and experimental results. The experimental validation indicates that the implemented CFD model is capable of reproducing the flow situation in the model mock-up.
Large-Scale Prospective T Cell Function Assays in Shipped, Unfrozen Blood Samples: Experiences from the Multicenter TRIGR Trial
Authors: Hadley David , Cheung Roy K. , Becker Dorothy J. , Girgis Rose , Palmer Jerry P. , Cuthbertson David , Krischer Jeffrey P. , Dosch Hans-Michael 
Published: December 2013

ABSTRACTBroad consensus assigns T lymphocytes fundamental roles in inflammatory, infectious, and autoimmune diseases. However, clinical investigations have lacked fully characterized and validated procedures, equivalent to those of widely practiced biochemical tests with established clinical roles, for measuring core T cell functions. The Trial to Reduce Insulin-dependent diabetes mellitus in the Genetically at Risk (TRIGR) type 1 diabetes prevention trial used consecutive measurements of T cell proliferative responses in prospectively collected fresh heparinized blood samples shipped by courier within North America. In this article, we report on the quality control implications of this simple and pragmatic shipping practice and the interpretation of positive- and negative-control analytes in our assay. We used polyclonal and postvaccination responses in 4,919 samples to analyze the development of T cell immunocompetence. We have found that the vast majority of the samples were viable up to 3 days from the blood draw, yet meaningful responses were found in a proportion of those with longer travel times. Furthermore, the shipping time of uncooled samples significantly decreased both the viabilities of the samples and the unstimulated cell counts in the viable samples. Also, subject age was significantly associated with the number of unstimulated cells and T cell proliferation to positive activators. Finally, we observed a pattern of statistically significant increases in T cell responses to tetanus toxin around the timing of infant vaccinations. This assay platform and shipping protocol satisfy the criteria for robust and reproducible long-term measurements of human T cell function, comparable to those of established blood biochemical tests. We present a stable technology for prospective disease-relevant T cell analysis in immunological diseases, vaccination medicine, and measurement of herd immunity.
Comparison of the Cerebrospinal Fluid (CSF) Toluidine Red Unheated Serum Test and the CSF Rapid Plasma Reagin Test with the CSF Venereal Disease Research Laboratory Test for Diagnosis of Neurosyphilis among HIV-Negative Syphilis Patients in China
Authors: Zhu Lin , Gu Xin , Peng Rui-Rui , Wang Cuini , Gao Zixiao , Zhou Pingyu , Gao Ying , Shi Mei , Guan Zhifang , Seña Arlene C. 
Published: December 2013

ABSTRACT

In this study, we aimed to investigate the performance of nontreponemal antibody tests in cerebrospinal fluid (CSF) specimens from syphilis patients. From September 2009 to September 2012, CSF specimens were collected at the Shanghai Skin Disease Hospital in Shanghai, China, from 1,132 syphilis patients without HIV infection, including 154 with symptomatic and 56 with asymptomatic neurosyphilis. All of the CSF specimens underwent testing with a rapid plasma reagin (RPR) test, an RPR-V (commercial RPR antigen diluted 1:2 in 10% saline) test, the toluidine red unheated serum test (TRUST), and the Venereal Disease Research Laboratory (VDRL) test. Specificities, sensitivities, positive predictive values (PPVs), negative predictive values (NPVs), and kappa values were calculated to determine the performances of the tests. We compared results of the CSF-VDRL, CSF-RPR, CSF-RPR-V, and CSF-TRUST among patients with symptomatic and asymptomatic neurosyphilis who had reactive CSF-
Treponema pallidum
particle agglutination (TPPA) test results. Overall, the CSF-VDRL test was reactive in 261 patients (23.1%). There were no cases in which the CSF-VDRL was nonreactive and CSF-RPR, CSF-RPR-V, or CSF-TRUST was reactive. Agreement between the results of CSF-TRUST and CSF-RPR was almost perfect (κ = 0.861), with substantial agreement between the results of CSF-RPR and CSF-RPR-V (κ = 0.740). The sensitivities of CSF-VDRL, CSF-RPR, CSF-RPR-V, and CSF-TRUST were 81.4%, 76.2%, 79.5%, and 76.2%, respectively. Compared to CSF-VDRL, CSF-RPR, CSF-RPR-V, and CSF-TRUST had comparable PPVs and NPVs. However, the specificity of CSF-VDRL (90.3%) was significantly lower than those of the other tests (92.7 to 93.4%). Therefore, CSF-RPR, CSF-RPR-V, and CSF-TRUST can be considered alternative tests for neurosyphilis diagnosis in HIV-negative populations, particularly when the CSF-VDRL is not available.
A Cost-Effective Approach for Detection of Toxigenic Clostridium difficile: Toxigenic Culture Using ChromID Clostridium difficile Agar
Authors: Luk Shik , To Wing Kin , Ng Tak Keung , Hui Wai Ting , Lee Wing Keung , Lau Florence , Ching Almond Man Wai 
Published: December 2013

ABSTRACT
We evaluated the performance and the cost of toxigenic culture using a commercial chromogenic medium (CDIF) for 538 stool specimens. Compared with real-time PCR, this method was found to detect an additional 9% of positive specimens and result in 61% reduction in material costs, with a trade-off increase in turnaround time of 1 day.