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1

Current Concepts for Clean Air and Total Joint Arthroplasty: Laminar Airflow and Ultraviolet Radiation: A Systematic Review  

Microsoft Academic Search

Background  With the trend toward pay-for-performance standards plus the increasing incidence and prevalence of periprosthetic joint infection\\u000a (PJI), orthopaedic surgeons must reconsider all potential infection control measures. Both airborne and nonairborne bacterial\\u000a contamination must be reduced in the operating room.\\u000a \\u000a \\u000a \\u000a \\u000a Questions\\/purposes  Analysis of airborne bacterial reduction technologies includes evaluation of (1) the effectiveness of laminar air flow (LAF)\\u000a and ultraviolet light (UVL);

Richard P. Evans

2011-01-01

2

Airflow resistance in soybean  

NASA Astrophysics Data System (ADS)

Resistance of material to airflow is an important factor to consider in the design of a dryer or an aeration system. The airflow resistance of soybean was determined with the modified airflow resistance apparatus. It was found that pressure drop increased with increase in airflow rate, bulk density, bed depth and decreased with moisture content. Modified Shedd equation, Hukill and Ives equation and modified Ergun equation were examined for pressure drop prediction. Airflow resistance was accurately described by modified Shedd equation followed by Hukill and Ives equation and modified Ergun equation. The developed statistical model comprised of airflow rate, moisture content and bulk density could fit pressure drop data reasonably well.

Kenghe, R.; Nimkar, P.; Shirkole, S.; Shinde, K.

2012-04-01

3

NASA Dryden Fact Sheet - F-16XL Laminar Flow  

NASA Website

F-16XL Laminar Flow Research Aircraft Project Summary Two F-16XL aircraft were used by the Dryden Flight Research Center, Edwards, CA, in a NASA-wide program to improve laminar airflow on aircraft flying at sustained supersonic speeds.

4

Thermal Airflow Sensor.  

National Technical Information Service (NTIS)

Electronic fuel-injection systems for vehicles require precise airflow measurements. Thermal airflow sensors provide a direct measure of this quantity and respond rapidly to mass-flow changes. The article examines hot-wire and hot-film sensors. The constr...

K. Tanimoto Y. Ariyoshi M. Bessho S. Otani T. Yamakawa

1990-01-01

5

Assessing multizone airflow software  

SciTech Connect

Multizone models form the basis of most computer simulations of airflow and pollutant transport in buildings. In order to promote computational efficiency, some multizone simulation programs, such as COMIS and CONTAM, restrict the form that their flow models may take. While these tools allow scientists and engineers to explore a wide range of building airflow problems, increasingly their use has led to new questions not answerable by the current generation of programs. This paper, directed at software developers working on the next generation of building airflow models, identifies structural aspects of COMIS and related programs that prevent them from easily incorporating desirable new airflow models. The paper also suggests criteria for evaluating alternate simulation environments for future modeling efforts.

Lorenzetti, D.M.

2001-12-01

6

Oxygen stoichiometry of low-temperature synthesized metastable T?-La2CuO4  

NASA Astrophysics Data System (ADS)

We have investigated the oxygen stoichiometry of low-temperature synthesized metastable T?-La2CuO4 bulk samples by neutron scattering. T?-La2CuO4 is the parent compound of electron-doped high-temperature superconductors that is chemically closest to the parent compound of the hole-doped superconductor T-La2CuO4. While usually all electron-doped cuprates require strong reduction to approach stoichiometry, the low-temperature synthesis directly yields fully stoichiometric compounds. This result makes low-temperature grown T?-La2CuO4 the ideal material to perform a comparison of the two parent compounds of hole- and electron-doped cuprates.

Hord, R.; Pascua, G.; Hofmann, K.; Cordier, G.; Kurian, J.; Luetkens, H.; Pomjakushin, V.; Reehuis, M.; Albert, B.; Alff, L.

2013-10-01

7

Clothing in laminar-flow operating theatres  

Microsoft Academic Search

Bacterial shedding, wound contamination and clinical-infection rates in clean wounds are influenced by operating-theatre dress. The aim of this study was to clarify the relative contribution of hats, masks and clothing to the control of wound contamination in both ultraclean (enclosed vertical laminar-flow) and conventional (plenum ventilated) airflow theatres. Personnel wore varying combinations of dress in both types of theatre.

M. J. Hubble; A. E. Weale; J. V. Perez; K. E. Bowker; A. P. MacGowan; G. C. Bannister

1996-01-01

8

Genetic and biochemical analysis of the TLA1 gene in Chlamydomonas reinhardtii.  

PubMed

The Chlamydomonas reinhardtii genomic DNA database contains a predicted open reading frame (ORF-P) without an apparent stop-codon and unknown coding sequence, located in close proximity and immediately upstream of the TLA1 gene (GenBank Accession No. AF534570). The latter was implicated in the regulation of the light-harvesting chlorophyll antenna size of photosynthesis (Tetali et al. Planta 225:813-829, 2007). To provide currently lacking information on ORF-P and its potential participation in TLA1 gene expression, thus in the regulation of the chlorophyll antenna size, genetic and biochemical analyses were undertaken. The coding and UTR regions of the ORF-P were defined and delineated from those of the adjacent TLA1 gene. ORF-P is shown to encode a protein with a distinct RING-like zinc finger domain that is present in numerous eukaryotic proteins, believed to play a role in cellular ubiquitination, leading to regulation of cellular processes like signaling, growth, transcription, and DNA repair. It is further shown that the two genes share a 74-bp overlap between the 3' UTR region of ORF-P and the 5' UTR region of TLA1. However, they possess distinct start and stop codons and separate coding sequences, and transcribed as separate mRNAs without any trans-splicing between them. Complementation experiments showed that the TLA1 gene alone is sufficient to rescue the truncated chlorophyll antenna size phenotype of the tla1 mutant. Protein sequence alignments in C. reinhardtii and the colorless microalga Polytomella parva suggested that TLA1 defines the relationship between nucleus and organelle in microalgae, indirectly affecting the development of the chlorophyll antenna size. PMID:20012986

Mitra, Mautusi; Melis, Anastasios

2009-12-15

9

MBE growth and properties of T?-La2CuO4 thin films  

NASA Astrophysics Data System (ADS)

We prepared thin films of T?-La2CuO4, which usually crystallizes in the T structure, by MBE, and investigated their properties while systematically changing the post-reduction conditions with a view towards obtaining superconductivity along the lines of the parent compound superconductors we have recently reported (O. Matsumoto et al., Phys. Rev. B 79 (2009) 100508(R)). The results indicate that the optimal reduction window is very narrow, near which metallic conductivity is obtained down to 50 K. The resistivity of the T?-La2CuO4 films is in the range of 10-2-10-3 ? cm, which is several orders of magnitude lower than that of the counterpart T-La2CuO4, the implication of which is briefly discussed from the viewpoint of the difference in electronic structure induced by different oxygen coordination.

Yamamoto, H.; Matsumoto, O.; Tsukada, A.; Naito, M.

2010-11-01

10

Airflow dispersion in unsaturated soil  

Microsoft Academic Search

Dispersion data is abundant for water flow in the saturated zone but is lacking for airflow in unsaturated soil. However, for remediation processes such as soil vapour extraction, characterization of airflow dispersion is necessary for improved modelling and prediction capabilities. Accordingly, gas-phase tracer experiments were conducted in five soils ranging from uniform sand to clay at air-dried and wetted conditions.

T. Gidda; D. Cann; W. H. Stiver; R. G. Zytner

2006-01-01

11

Genetic and biochemical analysis of the TLA1 gene in Chlamydomonas reinhardtii  

Microsoft Academic Search

The Chlamydomonas reinhardtii genomic DNA database contains a predicted open reading frame (ORF-P) without an apparent stop-codon and unknown coding sequence, located in close proximity and immediately upstream of the TLA1 gene (GenBank Accession No. AF534570). The latter was implicated in the regulation of the light-harvesting chlorophyll antenna\\u000a size of photosynthesis (Tetali et al. Planta 225:813–829, 2007). To provide currently

Mautusi Mitra; Anastasios Melis

2010-01-01

12

Polyclonal antibodies against the TLA1 protein also recognize with high specificity the D2 reaction center protein of PSII in the green alga Chlamydomonas reinhardtii.  

PubMed

The Chlamydomonas reinhardtii DNA-insertional transformant truncated light-harvesting antenna 1 (tla1) mutant, helped identify the novel TLA1 gene (GenBank Accession # AF534570-71) as an important genetic determinant in the chlorophyll antenna size of photosynthesis. Down-regulation in the amount of the TLA1 23 kDa protein in the cell resulted in smaller chlorophyll antenna size for both photosystems (in Tetali et al. Planta 225:813-829, 2007). Specific polyclonal antibodies, raised against the recombinant TLA1 protein, showed a cross-reaction with the predicted 23 kDa TLA1 protein in C. reinhardtii protein extracts, but also showed a strong cross-reaction with a protein band migrating to 28.5 kDa. Questions of polymorphism, or posttranslational modification of the TLA1 protein were raised as a result of the unexpected 28.5 kDa cross-reaction. Work in this paper aimed to elucidate the nature of the unexpected 28.5 kDa cross-reaction, as this was deemed to be important in terms of the functional role of the TLA1 protein in the regulation of the chlorophyll antenna size of photosynthesis. Immuno-precipitation of the 28.5 kDa protein, followed by LC-mass spectrometry, showed amino acid sequences ascribed to the psbD/D2 reaction center protein of PSII. The common antigenic determinant between TLA1 and D2 was shown to be a stretch of nine conserved amino acids V-F-L(V)LP-GNAL in the C-terminus of the two proteins, constituting a high antigenicity "GNAL" domain. Antibodies raised against the TLA1 protein containing this domain recognized both the TLA1 and the D2 protein. Conversely, antibodies raised against the TLA1 protein minus the GNAL domain specifically recognized the 23 kDa TLA1 protein and failed to recognize the 28.5 kDa D2 protein. D2 antibodies raised against an oligopeptide containing this domain also cross-reacted with the TLA1 protein. It is concluded that the 28.5 kDa cross-reaction of C. reinhardtii protein extracts with antiTLA1 antibodies is due to antibody affinity for the GNAL domain of the D2 protein and has no bearing on the identity or function of the TLA1 protein. PMID:22442055

Mitra, Mautusi; Dewez, David; García-Cerdán, Jose Gines; Melis, Anastasios

2012-03-23

13

A Laminar-Flow, Water-Based Condensation Particle Counter (WCPC)  

Microsoft Academic Search

A new water-based condensation particle counter (WCPC) is presented. The WCPC is a thermally diffusive, laminar flow instrument. Condensational enlargement is achieved through the introduction of a saturated airflow into a “growth tube” with wetted walls held at a temperature higher than that of the entering flow. An unsheathed, 1 L\\/min instrument utilizing this principle has been evaluated with various

Susanne V. Hering; Mark R. Stolzenburg; Frederick R. Quant; Derek R. Oberreit; Patricia B. Keady

2005-01-01

14

Supersonic Laminar Flow Control Research.  

National Technical Information Service (NTIS)

The objective of the research is to understand supersonic laminar flow stability, transition, and active control. Some prediction techniques will be developed or modified to analyze laminar flow stability. The effects of supersonic laminar flow with distr...

C. F. Lo

1994-01-01

15

Supersonic Laminar Flow Control Research.  

National Technical Information Service (NTIS)

The objective of the research is to understand supersonic laminar flow stability, transition and active control. Some prediction techniques will be developed or modified to analyze laminar flow stability. The effects of super laminar flow with distributed...

C. F. Lo

1994-01-01

16

MICROPROCESSOR CONTROL OF ROTOGRAVURE AIRFLOWS  

EPA Science Inventory

The report discusses the technical and economic viability of using micro-processor-based control technology to collect volatile organic compound (VOC) emissions from a paper coating operation. The microprocessor-based control system monitors and controls both the airflow rate and...

17

AIRFLOW RESISTANCE OF OAT SEEDS: EFFECT OF AIRFLOW DIRECTION, MOISTURE CONTENT AND FOREIGN MATERIAL  

Microsoft Academic Search

Pressure drops through oat (Oat Sp.) beds were evaluated in the range of airflow rate from 0·0097 to 0·459 m\\/s-m using two airflow directions to determine the effect of grain moisture and foreign material on the resistance to airflow. Horizontal airflow resistance was lesser than vertical airflow resistance (e.g., for oat with 9·0% moisture content the pressure drop in horizontal

A. M. Pagano; D. E. Crozza; S. M. Nolasco

2000-01-01

18

Assembly of the light-harvesting chlorophyll antenna in the green alga Chlamydomonas reinhardtii requires expression of the TLA2-CpFTSY gene.  

PubMed

The truncated light-harvesting antenna2 (tla2) mutant of Chlamydomonas reinhardtii showed a lighter-green phenotype, had a lower chlorophyll (Chl) per-cell content, and higher Chl a/b ratio than corresponding wild-type strains. Physiological analyses revealed a higher intensity for the saturation of photosynthesis and greater P(max) values in the tla2 mutant than in the wild type. Biochemical analyses showed that the tla2 strain was deficient in the Chl a-b light-harvesting complex, and had a Chl antenna size of the photosystems that was only about 65% of that in the wild type. Molecular and genetic analyses showed a single plasmid insertion in the tla2 strain, causing a chromosomal DNA rearrangement and deletion/disruption of five nuclear genes. The TLA2 gene, causing the tla2 phenotype, was cloned by mapping the insertion site and upon complementation with each of the genes that were deleted. Successful complementation was achieved with the C. reinhardtii TLA2-CpFTSY gene, whose occurrence and function in green microalgae has not hitherto been investigated. Functional analysis showed that the nuclear-encoded and chloroplast-localized CrCpFTSY protein specifically operates in the assembly of the peripheral components of the Chl a-b light-harvesting antenna. In higher plants, a cpftsy null mutation inhibits assembly of both the light-harvesting complex and photosystem complexes, thus resulting in a seedling-lethal phenotype. The work shows that cpftsy deletion in green algae, but not in higher plants, can be employed to generate tla mutants. The latter exhibit improved solar energy conversion efficiency and photosynthetic productivity under mass culture and bright sunlight conditions. PMID:22114096

Kirst, Henning; García-Cerdán, Jose Gines; Zurbriggen, Andreas; Melis, Anastasios

2011-11-23

19

Input Data for Multizone Airflow and IAQ Analysis.  

National Technical Information Service (NTIS)

The use of multizone airflow and contaminant dispersal models requires a range of input data. In terms of airflow analysis, these data include leakage characteristics of airflow elements, wind pressure coefficients, ventilation system characteristics such...

A. K. Persily E. M. Ivy

2001-01-01

20

Calibration of a laminar flowmeter  

NASA Astrophysics Data System (ADS)

The parameters needed to describe the flow rate through a laminar flowmeter were investigated. Development of a laminar flow element standard is described, and a theory of laminar flowmeters based on the Poiseuille-Hagan law presented. Application of the theory to the laminar flow element standard is demonstrated. Better than 0.1% precision can be achieved, for short periods (days or longer) of less than six months.

Fain, D. E.

1981-01-01

21

Laminar cells and batteries  

SciTech Connect

A laminar battery comprising an end terminal formed with a pocket to accept internal components without requiring additional edge thickness in the seal area, incorporating as the separator in at least the cell immediately adjacent the pocketed end terminal a layer of cellophane together with a layer of paper on the side of the cellophane confronting the cathode.

Plasse, P.A.

1983-06-21

22

Laminar Multicell Lithium Batteries  

SciTech Connect

Laminar batteries of series connected cells comprising lithium anodes and an electrolyte containing a passivating solvent reactive with lithium in which the cells are electrically connected in series by intercell barriers comprising outer layers of electrochemically inert electronically conducting material in contact with the electrochemically active anode and cathode of adjacent cells and a layer of metal foil between the electrochemically inert layers.

Bruder, A. H.

1984-01-31

23

On Laminar Separation.  

National Technical Information Service (NTIS)

The laminar flow of an incompressible fluid in the vicinity of the separation point on a smooth surface of solid body is investigated. It is shown that the flow separation at large Reynolds number (R) occurs due to the action of large local positive press...

V. V. Sychev

1974-01-01

24

Numerical studies of Trichel pulses in airflows  

NASA Astrophysics Data System (ADS)

In this paper the Trichel pulse regime of corona discharge in airflows is numerically studied with a two-dimensional model. The model is based on the hydrodynamic drift-diffusion approximation, taking into consideration the flow of the air in the discharge gap. Both transverse and longitudinal airflows under different conditions have been investigated. The influences of airflows on the characteristics of the Trichel pulses were clearly observed and analysed. The simulation results proved to be compatible with experimental analysis reported in the literature.

Deng, F. C.; Ye, L. Y.; Song, K. C.

2013-10-01

25

Airflow resistance of selected biomass materials  

SciTech Connect

Pressure drop created when air was forced through beds of selected biomass materials was determined. Materials tested included peanut hulls, peanut hull pellets, maize cobs, and wood shavings, chips and bark. The data were presented as logarithmic plots and equations of pressure drop versus airflow. The airflow resistances of the biomass materials increased with an increase in bulk density and were found to be in the range between values for ear and shelled maize. 12 references.

Cooper, S.C.; Sumner, H.R.

1985-01-01

26

Homogeneous near surface activity distribution by double energy activation for TLA  

NASA Astrophysics Data System (ADS)

Thin layer activation (TLA) is a versatile tool for activating thin surface layers in order to study real-time the surface loss by wear, corrosion or erosion processes of the activated parts, without disassembling or stopping running mechanical structures or equipment. The research problem is the determination of the irradiation parameters to produce point-like or large area optimal activity-depth distribution in the sample. Different activity-depth profiles can be produced depending on the type of the investigated material and the nuclear reaction used. To produce activity that is independent of the depth up to a certain depth is desirable when the material removed from the surface by wear, corrosion or erosion can be collected completely. By applying dual energy irradiation the thickness of this quasi-constant activity layer can be increased or the deviation of the activity distribution from a constant value can be minimized. In the main, parts made of metals and alloys are suitable for direct activation, but by using secondary particle implantation the wear of other materials can also be studied in a surface range a few micrometers thick. In most practical cases activation of a point-like spot (several mm2) is enough to monitor the wear, corrosion or erosion, but for special problems relatively large surfaces areas of complicated spatial geometry need to be activated uniformly. Two ways are available for fulfilling this task, (1) production of large area beam spot or scanning the beam over the surface in question from the accelerator side, or (2) a programmed 3D movement of the sample from the target side. Taking into account the large variability of tasks occurring in practice, the latter method was chosen as the routine solution in our cyclotron laboratory.

Takács, S.; Ditrói, F.; Tárkányi, F.

2007-10-01

27

Truncated Photosystem Chlorophyll Antenna Size in the Green Microalga Chlamydomonas reinhardtii upon Deletion of the TLA3-CpSRP43 Gene1[C][W][OA  

PubMed Central

The truncated light-harvesting antenna size3 (tla3) DNA insertional transformant of Chlamydomonas reinhardtii is a chlorophyll-deficient mutant with a lighter green phenotype, a lower chlorophyll (Chl) per cell content, and higher Chl a/b ratio than corresponding wild-type strains. Functional analyses revealed a higher intensity for the saturation of photosynthesis and greater light-saturated photosynthetic activity in the tla3 mutant than in the wild type and a Chl antenna size of the photosystems that was only about 40% of that in the wild type. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western-blot analyses showed that the tla3 strain was deficient in the Chl a/b light-harvesting complex. Molecular and genetic analyses revealed a single plasmid insertion in chromosome 4 of the tla3 nuclear genome, causing deletion of predicted gene g5047 and plasmid insertion within the fourth intron of downstream-predicted gene g5046. Complementation studies defined that gene g5047 alone was necessary and sufficient to rescue the tla3 mutation. Gene g5047 encodes a C. reinhardtii homolog of the chloroplast-localized SRP43 signal recognition particle, whose occurrence and function in green microalgae has not hitherto been investigated. Biochemical analysis showed that the nucleus-encoded and chloroplast-localized CrCpSRP43 protein specifically operates in the assembly of the peripheral components of the Chl a/b light-harvesting antenna. This work demonstrates that cpsrp43 deletion in green microalgae can be employed to generate tla mutants with a substantially diminished Chl antenna size. The latter exhibit improved solar energy conversion efficiency and photosynthetic productivity under mass culture and bright sunlight conditions.

Kirst, Henning; Garcia-Cerdan, Jose Gines; Zurbriggen, Andreas; Ruehle, Thilo; Melis, Anastasios

2012-01-01

28

Measurement of airflow in residential furnaces  

SciTech Connect

In order to have a standard for furnaces that includes electricity consumption or for the efficiency of furnace blowers to be determined, it is necessary to determine the airflow of a furnace or furnace blower. This study focused on airflow testing, in order to determine if an existing test method for measuring blower airflow could be used to measure the airflow of a furnace, under conditions seen in actual installations and to collect data and insights into the operating characteristics of various types of furnace blowers, to use in the analysis of the electricity consumption of furnaces. Results of the measured airflow on furnaces with three types of blower and motor combinations are presented in the report. These included: (1) a forward-curved blower wheel with a typical permanent split capacitor (PSC) motor, (2) a forward-curved blower wheel with an electronically-commutated motor (ECM), and (3) a prototype blower, consisting of a backward-inclined blower wheel matched to an ECM motor prototype, which is being developed as an energy-saving alternative to conventional furnace blowers. The testing provided data on power consumption, static and total pressure, and blower speed.

Biermayer, Peter J.; Lutz, James; Lekov, Alex

2004-01-24

29

42 CFR 84.180 - Airflow resistance tests.  

Code of Federal Regulations, 2011 CFR

...DEVICES Non-Powered Air-Purifying Particulate...84.180 Airflow resistance tests. (a) Resistance to airflow will...a test fixture with air flowing at continuous...182. (b) The resistances for particulate...

2011-10-01

30

AIRFLOW CHARACTERISTICS IN A BABOON NASAL PASSAGE CAST  

EPA Science Inventory

Airflow patterns in the nasal Passages influence the distribution of air-pollutant-induced lesions in the airway mucosa. ittle is known about airflow characteristics or the complex nasopharyngeal airway of man and experimental animals. irflow characteristics in the nasopharyngeal...

31

Evaluation of airflow prediction methods in compact electronic enclosures  

Microsoft Academic Search

In forced convection cooled electronic enclosure design, one of the most important parameters is enclosure airflow. Enclosure airflow mainly depends upon enclosure pressure drop and fan characteristics. Fan curves are often used in conjunction with system pressure drop (impedance) characteristics to determine airflow. CFD tool accuracy depends mainly on accurate modeling of system pressure loss (grilles, filters, etc.) and fan

Rebecca Biswas; Raghu B. Agarwal; Avijit Goswami; Vivek Mansingh

1999-01-01

32

MEASURING AIRFLOW DISTRIBUTION IN PEANUT DRYING TRAILERS  

Technology Transfer Automated Retrieval System (TEKTRAN)

A method to measure airflow distribution within a filled peanut drying trailer was developed. Six 6.4-m peanut drying wagons were loaded with dry farmer stock peanuts at a local peanut processing facility. Three wagons had floors with 23% O.A. and three had floors with 40% O.A. Peanuts were level...

33

Tidal expiratory flow patterns in airflow obstruction  

Microsoft Academic Search

Tidal expiratory flow pattern was analysed in 99 subjects with a view to assessing it as a quantitative measurement of airflow obstruction. Fifteen normal volunteers, nine patients with dyspnoea referred for investigation in whom airway resistance was within normal limits, 24 patients with restrictive lung disorders, and 51 patients with airway obstruction were studied. The expiratory flow pattern against time

M J Morris

1981-01-01

34

Airflow obstruction in chalkpowder and sugar workers  

Microsoft Academic Search

Our aim was to investigate the relationship between suspected occupational hazards and airflow obstruction in industrial workers. The study was a cross-sectional survey of 314 male workers from a chalkpowder plant (n = 158) and from a sugar refinery (n = 156). Occupational exposure to chalkpowder and sugar dust was assessed by individual job classification. Outcome variables included respiratory symptoms

A. B. Bohadana; N. Massin; P. Wild; G. Berthiot

1996-01-01

35

AIRFLOW DISTRIBUTION IN EXHAUST VENTILATION SYSTEMS  

Microsoft Academic Search

The distribution of airflows converging at a junction can be estimated from the predicted pressures just upstream of the junction fitting. However, the total pressure approach requires iterative solutions at each junction, and the current implementation of the static pressure approach provides a poor fit to published empirical data. A model to predict pressures upstream of junctions is proposed and

Steven E. Guffey

1991-01-01

36

Flight Experiences with Laminar Flow.  

National Technical Information Service (NTIS)

A review of natural laminar flow (NLF) flight experiences over the period from the 1930's to the present has been given to provide information on the achievability and maintainability of NLF in typical airplane operating environments. Significant effects ...

B. J. Holmes

1986-01-01

37

Hybrid Mesh for Nasal Airflow Studies  

PubMed Central

The accuracy of the numerical result is closely related to mesh density as well as its distribution. Mesh plays a very significant role in the outcome of numerical simulation. Many nasal airflow studies have employed unstructured mesh and more recently hybrid mesh scheme has been utilized considering the complexity of anatomical architecture. The objective of this study is to compare the results of hybrid mesh with unstructured mesh and study its effect on the flow parameters inside the nasal cavity. A three-dimensional nasal cavity model is reconstructed based on computed tomographic images of a healthy Malaysian adult nose. Navier-Stokes equation for steady airflow is solved numerically to examine inspiratory nasal flow. The pressure drop obtained using the unstructured computational grid is about 22.6?Pa for a flow rate of 20?L/min, whereas the hybrid mesh resulted in 17.8?Pa for the same flow rate. The maximum velocity obtained at the nasal valve using unstructured grid is 4.18?m/s and that with hybrid mesh is around 4.76?m/s. Hybrid mesh reported lower grid convergence index (GCI) than the unstructured mesh. Significant differences between unstructured mesh and hybrid mesh are determined highlighting the usefulness of hybrid mesh for nasal airflow studies.

Zubair, Mohammed; Abdullah, Mohammed Zulkifly; Ahmad, Kamarul Arifin

2013-01-01

38

CFD studies on burner secondary airflow  

SciTech Connect

In many fossil power plants operating today, there is insufficient means to assure the proper balancing of the secondary airflows between the individual burners of wall-fired units. This mismatch leads to decreased boiler efficiency and increased emissions. In this study, a computational fluid dynamics (CFD) modeling of a fossil power plant wind box was performed. The model solved the three-dimensional Reynolds averaged Navier-Stokes equations with the k-epsilon turbulence model. The CFD results were validated by the experimental data taken from a 1/8th scale model of a wall-fired fossil unit. Simulations under various mass flow rates specified at inlet, various baffle positions and two opening conditions of the burners were obtained to identify the optimum design in terms of the equalization of the secondary airflow through the burners. This study demonstrated that the combination of experimental and CFD approach can be an effective tool in the research of burner secondary airflow balancing.

Purimetla, A.; Cui, J. [Tennessee Technology University, Cookeville, TN (United States). Dept. of Mechanical Engineering

2009-02-15

39

Aerodynamics of laminar separation flutter at a transitional Reynolds number  

NASA Astrophysics Data System (ADS)

Experimental observations of self-sustained pitch oscillations of a NACA 0012 airfoil at transitional Reynolds numbers were recently reported. The aeroelastic limit cycle oscillations, herein labelled as laminar separation flutter, occur in the range 5.0×104?Rec?1.3×105. They are well behaved, have a small amplitude and oscillate about ?=0°. It has been speculated that laminar separation leading to the formation of a laminar separation bubble, occurring at these Reynolds numbers, plays an essential role in these oscillations. This paper focuses on the Rec=7.7×104 case, with the elastic axis located at 18.6% chord. Considering that the experimental rig acts as a dynamic balance, the aerodynamic moment is derived and is empirically modelled as a generalized Duffing-van-der-Pol nonlinearity. As expected, it behaves nonlinearly with pitch displacement and rate. It also indicates a dynamically unstable equilibrium point, i.e. negative aerodynamic damping. In addition, large eddy simulations of the flow around the airfoil undergoing prescribed simple harmonic motion, using the same amplitude and frequency as the aeroelastic oscillations, are performed. The comparison between the experiment and simulations is conclusive. Both approaches show that the work done by the airflow on the airfoil is positive and both have the same magnitude. The large eddy simulation (LES) computations indicate that at ?=0°, the pitching motion induces a lag in the separation point on both surfaces of the airfoil resulting in negative pitching moment when pitching down, and positive moment when pitching up, thus feeding the LCO.

Poirel, D.; Yuan, W.

2010-10-01

40

Development of the light-harvesting chlorophyll antenna in the green alga Chlamydomonas reinhardtii is regulated by the novel Tla1 gene  

Microsoft Academic Search

The Chlamydomonas reinhardtii\\u000a tla1 (truncated light-harvesting chlorophyll antenna size) mutant was generated upon DNA insertional mutagenesis and shown to specifically possess a smaller than wild type\\u000a (WT) chlorophyll antenna size in both photosystems. Molecular and genetic analysis revealed that the exogenous plasmid DNA\\u000a was inserted at the end of the 5? UTR and just prior to the ATG start codon

Sarada D. Tetali; Mautusi Mitra; Anastasios Melis

2007-01-01

41

Impact of Airflow Communication between Nasal Cavities on Nasal Ventilation.  

PubMed

Objective: To investigate the impact of airflow communication between bilateral nostril sides on nasal ventilation. In addition, we try to validate the efficacy of the Draf III procedure from the aerodynamics perspective. Methods: One health model and two disease models were constructed. These included 2 patients with nasal septum perforation and 1 patient who received the Draf III procedure. With the computational fluid dynamics method, indices such as airflow velocity and wall shear stress in the nasal cavity were detected and compared among the 3 subjects. Results: The main pathway for airflow in the nasal cavity is the common meatus. Little airflow exchange occurred in the patient who underwent the Draf III procedure, and the wall shear stress around the communication site was as low as in the adjacent areas. However, when airflow communication occurred in the lower part of the nasal cavity, the airflow velocity and wall shear stress were obviously altered, and the ventilation function of the nasal cavity was impaired. Conclusion: Airflow communication in the upper part of the nasal cavity has little impact on nasal ventilation. Nonetheless, airflow communication occurring in the lower part of the nasal cavity disturbs the overall airflow distribution and a repair procedure is necessary. © 2013 S. Karger AG, Basel. PMID:24052029

Zhou, Bing; Huang, Qian; Cui, Shunjiu; Liu, Yingxi; Han, Demin

2013-09-17

42

Natural convection airflow measurement and theory  

SciTech Connect

Natural convection is a major mechanism for heat distribution in many passive solar buildings, especially those with sunspaces. To better understand this mechanism, observations of air velocities and temperatures have been made in 13 different houses that encompass a wide variety of one- and two-story geometries. This paper extends previous reports. Results from one house are described in detail, and some generalizations are drawn from the large additional mass of data taken. A simple mathematical model is presented that describes the general nature of airflow and energy flow through an aperture.

Balcomb, J.D.; Jones, G.F.; Yamaguchi, Kenjiro

1984-01-01

43

Laminar boundary layer over riblets  

Microsoft Academic Search

Laser doppler anemometry (LDA) measurements and numerical calculations have been made for a laminar boundary layer on triangular riblets. Calculated mean velocity distributions along the riblet contour are in good agreement with the measured ones. The results show that no transversal motion exists above and within the riblet valleys (e.g., no secondary motion). It is found that despite the large

L. Djenidi; F. Anselmet; J. Liandrat; L. Fulachier

1994-01-01

44

Airflow elicits a spider's jump towards airborne prey. I. Airflow around a flying blowfly  

PubMed Central

The hunting spider Cupiennius salei uses airflow generated by flying insects for the guidance of its prey-capture jump. We investigated the velocity field of the airflow generated by a freely flying blowfly close to the flow sensors on the spider's legs. It shows three characteristic phases (I–III). (I) When approaching, the blowfly induces an airflow signal near the spider with only little fluctuation (0.013 ± 0.006 m s?1) and a strength that increases nearly exponentially with time (maximum: 0.164 ± 0.051 m s?1 s.d.). The spider detects this flow while the fly is still 38.4 ± 5.6 mm away. The fluctuation of the airflow above the sensors increases linearly up to 0.037 m s?1 with the fly's altitude. Differences in the time of arrival and intensity of the fly signal at different legs probably inform the spider about the direction to the prey. (II) Phase II abruptly follows phase I with a much higher degree of fluctuation (fluctuation amplitudes: 0.114 ± 0.050 m s?1). It starts when the fly is directly above the sensor and corresponds to the time-dependent flow in the wake below and behind the fly. Its onset indicates to the spider that its prey is now within reach and triggers its jump. The spider derives information on the fly's position from the airflow characteristics, enabling it to properly time its jump. The horizontal velocity of the approaching fly is reflected by the time of arrival differences (ranging from 0.038 to 0.108 s) of the flow at different legs and the exponential velocity growth rate (16–79 s?1) during phase I. (III) The air flow velocity decays again after the fly has passed the spider.

Klopsch, Christian; Kuhlmann, Hendrik C.; Barth, Friedrich G.

2012-01-01

45

Airflow elicits a spider's jump towards airborne prey. I. Airflow around a flying blowfly.  

PubMed

The hunting spider Cupiennius salei uses airflow generated by flying insects for the guidance of its prey-capture jump. We investigated the velocity field of the airflow generated by a freely flying blowfly close to the flow sensors on the spider's legs. It shows three characteristic phases (I-III). (I) When approaching, the blowfly induces an airflow signal near the spider with only little fluctuation (0.013 ± 0.006 m s(-1)) and a strength that increases nearly exponentially with time (maximum: 0.164 ± 0.051 m s(-1) s.d.). The spider detects this flow while the fly is still 38.4 ± 5.6 mm away. The fluctuation of the airflow above the sensors increases linearly up to 0.037 m s(-1) with the fly's altitude. Differences in the time of arrival and intensity of the fly signal at different legs probably inform the spider about the direction to the prey. (II) Phase II abruptly follows phase I with a much higher degree of fluctuation (fluctuation amplitudes: 0.114 ± 0.050 m s(-1)). It starts when the fly is directly above the sensor and corresponds to the time-dependent flow in the wake below and behind the fly. Its onset indicates to the spider that its prey is now within reach and triggers its jump. The spider derives information on the fly's position from the airflow characteristics, enabling it to properly time its jump. The horizontal velocity of the approaching fly is reflected by the time of arrival differences (ranging from 0.038 to 0.108 s) of the flow at different legs and the exponential velocity growth rate (16-79 s(-1)) during phase I. (III) The air flow velocity decays again after the fly has passed the spider. PMID:22572032

Klopsch, Christian; Kuhlmann, Hendrik C; Barth, Friedrich G

2012-05-09

46

Impacts of fluid dynamics simulation in study of nasal airflow physiology and pathophysiology in realistic human three-dimensional nose models.  

PubMed

During the past decades, numerous computational fluid dynamics (CFD) studies, constructed from CT or MRI images, have simulated human nasal models. As compared to rhinomanometry and acoustic rhinometry, which provide quantitative information only of nasal airflow, resistance, and cross sectional areas, CFD enables additional measurements of airflow passing through the nasal cavity that help visualize the physiologic impact of alterations in intranasal structures. Therefore, it becomes possible to quantitatively measure, and visually appreciate, the airflow pattern (laminar or turbulent), velocity, pressure, wall shear stress, particle deposition, and temperature changes at different flow rates, in different parts of the nasal cavity. The effects of both existing anatomical factors, as well as post-operative changes, can be assessed. With recent improvements in CFD technology and computing power, there is a promising future for CFD to become a useful tool in planning, predicting, and evaluating outcomes of nasal surgery. This review discusses the possibilities and potential impacts, as well as technical limitations, of using CFD simulation to better understand nasal airflow physiology. PMID:23205221

Wang, De Yun; Lee, Heow Peuh; Gordon, Bruce R

2012-11-13

47

Factors Associated with Persistent Airflow Limitation in Severe Asthma  

Microsoft Academic Search

Persistent airflow limitation can develop in nonsmoking patients with asthma. However, the prevalence and risk factors for airways obstruction with incomplete reversibility in asthma are unknown. We assessed the prevalence of persistent airflow limitation (de- fined as postbronchodilator FEV 1 or FEV 1 \\/VC ? 75% predicted) in 132 nonsmoking outpatients with severe asthma visiting chest physicians in general hospitals

AEILKO H. ZWINDERMAN; PETER J. STERK; KLAUS F. RABE; ELISABETH H. BEL

48

Simulation of Effect of Wind Barriers on Airflow  

Microsoft Academic Search

ACK of a quantitative theory to explain airflow near Lw ind barriers in the atmospheric boundary layer has hindered experimental programs in barrier research and made optimum barrier design for practical applications difficult. Our objectives were to develop a quantitative, theoretical simulation of airflow normal to narrow wind barriers of various porosities and, when possible, verify the results using experimental

L. J. Hagen; E. L. Skidmore; P. L. Miller; J. E. Kipp

1981-01-01

49

Experimental Investigation of the Induced Airflow of Corona Discharge  

NASA Astrophysics Data System (ADS)

In order to improve the acceleration effect of corona discharge acting on air, we present an experimental study on the induced airflow produced by corona discharge between two parallel electrodes. The parameters investigated are the type of electrodes, actuation voltage and the distance in the absence of free airflow. The induced flow velocity is measured directly in the accelerated region using the particle image velocimetry technology. The results show that if corona discharge is not developed into arc discharge, the induced airflow velocity increases nearly linearly with the applied voltage and the maximum induced airflow velocity near the needle electrode reaches 36 m/s. It is expected that in the future, the result can be referred to in the research about effect of active flow control to reach much higher induced airflow speed.

Huang, Yong; Zhang, Xin; Wang, Xun-Nian; Wang, Wan-Bo; Huang, Zong-Bo; Li, Hua-Xing

2013-09-01

50

Airflow patterns in a human nasal model  

SciTech Connect

Nasal airflow patterns were studied by using xenon 133 gas to image the course taken by air as it flowed through a plastic model of the human nasal cavity. The model was produced from the head of a human cadaver, and was anatomically correct. A needle catheter was used to infuse the radioactive xenon into a continuous flow of room air maintained through the model by a variable vacuum source connected to the nasopharynx. The radioactive gas was infused at one of five release sites in the nostril, and the distribution of the radioactivity was imaged in the sagittal plane with a scintillation camera. The data were organized to show the activity in six contiguous regions of the midnose. For each catheter, release site activity patterns were determined for three flow rates. The results of this experiment showed that both catheter position and flow rate had significant and reproducible effects on the distribution of radioactivity within the model.

Hornung, D.E.; Leopold, D.A.; Youngentob, S.L.; Sheehe, P.R.; Gagne, G.M.; Thomas, F.D.; Mozell, M.M.

1987-02-01

51

Laminar electrical cells and batteries  

SciTech Connect

Laminar electrical cells and batteries of the Leclanche type are disclosed, in which the electrolyte comprises an aqueous solution containing from about 18 to about 22 percent of NH/sub 4/Cl and from about 25 to about 40 percent of ZnCl/sub 2/ by weight, based on the weight of solution. The electrolyte may contain a gelling agent, and may initially contain a minor amount of mercuric chloride.

Bruder, A.H.

1983-08-23

52

Laminar electrical cells and batteries  

SciTech Connect

Laminar electrical cells and batteries of the Leclanche type are disclosed that are especially adapted for service at high drain rates with variable duty cycles by the inclusion of cathodes formed as slurries of MnO/sub 2/ and carbon particles in an electrolyte comprising, by weight, about 2% of NH/sub 4/Cl, about 25% ZnCl/sub 2/, and the balance water with a minor amount of mercuric chloride.

Nel, P.E.; Pleskowicz, J.C.

1982-11-30

53

Neural Representations of Airflow in Drosophila Mushroom Body  

PubMed Central

The Drosophila mushroom body (MB) is a higher olfactory center where olfactory and other sensory information are thought to be associated. However, how MB neurons of Drosophila respond to sensory stimuli other than odor is not known. Here, we characterized the responses of MB neurons to a change in airflow, a stimulus associated with odor perception. In vivo calcium imaging from MB neurons revealed surprisingly strong and dynamic responses to an airflow stimulus. This response was dependent on the movement of the 3rd antennal segment, suggesting that Johnston's organ may be detecting the airflow. The calyx, the input region of the MB, responded homogeneously to airflow on. However, in the output lobes of the MB, different types of MB neurons responded with different patterns of activity to airflow on and off. Furthermore, detailed spatial analysis of the responses revealed that even within a lobe that is composed of a single type of MB neuron, there are subdivisions that respond differently to airflow on and off. These subdivisions within a single lobe were organized in a stereotypic manner across flies. For the first time, we show that changes in airflow affect MB neurons significantly and these effects are spatially organized into divisions smaller than previously defined MB neuron types.

Mamiya, Akira; Beshel, Jennifer; Xu, Chunsu; Zhong, Yi

2008-01-01

54

Analysis of the laminar flamelet concept for nonpremixed laminar flames  

SciTech Connect

The goal of this paper is to investigate the application of the laminar flamelet concept to the multidimensional numerical simulation of nonpremixed laminar flames. The performance of steady and unsteady flamelets is analyzed. The deduction of the mathematical formulation of flamelet modeling is exposed and some commonly used simplifications are examined. Different models for the scalar dissipation rate dependence on the mixture fraction variable are analyzed. Moreover, different criteria to evaluate the Lagrangian-type flamelet lifetime for unsteady flamelets are investigated. Inclusion of phenomena such as differential diffusion with constant Lewis number for each species and radiation heat transfer are also studied. A confined co-flow axisymmetric nonpremixed methane/air laminar flame experimentally investigated by McEnally and Pfefferle (Combust. Sci. Technol. 116-117 (1996) 183-209) and numerically investigated by Bennett, McEnally, Pfefferle, and Smooke (Combust. Flame 123 (2000) 522-546), Consul, Perez-Segarra, Claramunt, Cadafalch, and Oliva (Combust. Theory Modelling 7 (3) (2003) 525-544), and Claramunt, Consul, Perez-Segarra, and Oliva (Combust. Flame 137 (2004) 444-457) has been used as a test case. Results obtained using the flamelet concept have been compared to data obtained from the full resolution of the complete transport equations using primitive variables. Finite-volume techniques over staggered grids are used to discretize the governing equations. A parallel multiblock algorithm based on domain decomposition techniques running with loosely coupled computers has been used. To assess the quality of the numerical solutions presented in this paper, a verification process based on the generalized Richardson extrapolation technique and on the grid convergence index (GCI) has been applied. (author)

Claramunt, K.; Consul, R.; Carbonell, D.; Perez-Segarra, C.D. [Centre Tecnologic de Transferencia de Calor (CTTC), Universitat Politecnica de Catalunya (UPC), c/Colom 11, E-08222 Terrassa, Barcelona (Spain)

2006-06-15

55

Effect of Airflow Exposure on the Tear Meniscus  

PubMed Central

Purpose. To compare the effect of airflow exposure on the tear meniscus and blink frequency in normal and evaporative dry eye subjects. Methods. In 9 normal subjects and 9 short tear breakup time (SBUT) dry eye subjects, lower tear meniscus height (TMH) and area (TMA) and blink frequency were measured with anterior segment optical coherence tomography (OCT) before and after 5 minutes of airflow exposure (1.5 ± 0.5?m/s). Results. In SBUT dry eyes, both TMH and TMA decreased significantly (P = 0.027, P = 0.027) with a significant increase of blink frequency after airflow exposure, while significant increase in TMA was found in normal eyes. Conclusion. Measurement of the tear meniscus with anterior segment OCT seems to be useful as a noninvasive and objective method for evaluating the effect of airflow on tear film.

Koh, Shizuka; Tung, Cynthia; Kottaiyan, Ranjini; Zavislan, James; Yoon, Geunyoung; Aquavella, James

2012-01-01

56

Measuring rates of outdoor airflow into HVAC systems  

SciTech Connect

During the last few years, new technologies have been introduced for measuring the flow rates of outside air into HVAC systems. This document describes one particular technology for measuring these airflows, a system and a related protocol developed to evaluate this and similar measurement technologies under conditions without wind, and the results of our evaluations. We conclude that the measurement technology evaluated can provide a reasonably accurate measurement of OA flow rate over a broad range of flow, without significantly increasing airflow resistance.

Fisk, William J.; Faulkner, David; Sullivan, Douglas P.; Delp, Woody

2002-10-01

57

The way the wind blows: Implications of modeling nasal airflow  

Microsoft Academic Search

Nasal airflow is important for the many physiological functions of the nose, which include the warming and humidifying of\\u000a inspired air; the filtration of airborne pollutants; and the sense of smell and nasal pungency. Until recently, airflow properties\\u000a in the nose could only be understood using qualitative in vitro models of humans or in vivo studies in rodents. Recent advances

Kai Zhao; Pamela Dalton

2007-01-01

58

Effects of windbreaks on airflow, microclimates and crop yields  

Microsoft Academic Search

The mechanisms by which a porous windbreak modifies airflow, microclimates and hence crop yields are addressed, based upon\\u000a recent wind tunnel experiments, field observations and numerical modelling. This paper is thus an update to the excellent\\u000a reviews in Brandle (1988). It shows how a turbulent mixing layer initiated at the top of the windbreak dominates the airflow\\u000a behind a windbreak.

H. A. Cleugh

1998-01-01

59

Lithium batteries with laminar anodes  

SciTech Connect

This patent describes a laminar electrical cell, comprising an anode, a cathode, and an electrolyte permeable separator between the anode and the cathode. The anode consists essentially of a layer of lithium having at least one surface of unreacted lithium metal in direct contact with and adhered to a layer of conductive plastic with no intermediate adhesive promoting adjuncts. The cathode comprises a slurry of MnO/sub 2/ and carbon particles in a solution of a lithium salt in an organic solvent, the solution permeating the separator and being in contact with the lithium.

Bruder, A.H.

1986-11-04

60

Laminar Flow Control at High Speeds  

Microsoft Academic Search

Laminar flow control has always meant controlling the amplitude of linearly unstable waves before transition can occur. In many physical cases, the control of linear Tollmien-Schlichting (T-S) waves is sufficient to prevent transition and many successful demonstrations, including natural laminar flow airfoils, have occurred. Supersonic flight presents another set of challenges that complicates the control process. One has the possibilities

William Saric

2003-01-01

61

Stability criterion of a laminar flow  

Microsoft Academic Search

Conclusions 1.During flow in pipes roughness affects the hydraulic resistance coefficient in the entire laminar region. Relation (8) and other theoretical relations of laminar flow in pipes are valid only for smooth pipes.2.The lower critical value of the Reynolds number varies in wide limits depending on the pipe roughness. Its generally accepted value (1) is not universal and is valid

O. M. Aivazyan

1985-01-01

62

Laminar flamelet modelling of turbulent combustion  

Microsoft Academic Search

The incorporation of a laminar flamelet description into the presumed pdf approach to turbulent combustion modelling is reviewed. A significant advantage of this approach is that it permits the calculation of a library of strained laminar flame solutions, with realistic chemical kinetics included, separately from subsequent turbulent flow-field predictions. A unity of approach is identified between premixed and nonpremixed combustion

K. N. C. Bray

63

Study of laminar-jet diffusion flames  

Microsoft Academic Search

Based on the Shvab-Zeldovich formulation, the mass, momentum, and species equations for a laminar-jet diffusion flame are simplified. These equations are observed to be identical to those of a laminar hot jet and can be readily solved. Utilizing analytical results and general behaviors of experimental data, closed form correlations for flame height and flame shape are generated and shown to

Yuen

1980-01-01

64

Laminar and Turbulent Flow in Water  

ERIC Educational Resources Information Center

|There are many ways to visualize flow, either for laminar or turbulent flows. A very convincing way to show laminar and turbulent flows is by the perturbations on the surface of a beam of water coming out of a cylindrical tube. Photographs, taken with a flash, show the nature of the flow of water in pipes. They clearly show the difference between…

Riveros, H. G.; Riveros-Rosas, D.

2010-01-01

65

Natural Laminar Flow Nacelle for Transport Aircraft.  

National Technical Information Service (NTIS)

The potential of laminar flow nacelles for reducing installed engine/nacelle drag was studied. The purpose was twofold: to experimentally verify a method for designing laminar flow nacelles and to determine the effect of installation on the extent of lami...

M. Lamb W. K. Abeyounis J. C. Patterson R. J. Re

1986-01-01

66

Association of Radiographic Emphysema and Airflow Obstruction with Lung Cancer  

PubMed Central

Rationale: To study the relationship between emphysema and/or airflow obstruction and lung cancer in a high-risk population. Objective: We studied lung cancer related to radiographic emphysema and spirometric airflow obstruction in tobacco-exposed persons who were screened for lung cancer using chest computed tomography (CT). Methods: Subjects completed questionnaires, spirometry, and low-dose helical chest CT. CT scans were scored for emphysema based on National Emphysema Treatment Trial criteria. Multiple logistic regressions estimated the independent associations between various factors, including radiographic emphysema and airflow obstruction, and subsequent lung cancer diagnosis. Measurements and Main Results: Among 3,638 subjects, 57.5, 18.8, 14.6, and 9.1% had no, trace, mild, and moderate–severe emphysema, and 57.3, 13.6, 22.8, and 6.4% had no, mild (Global Initiative for Chronic Obstructive Lung Disease [GOLD] I), moderate (GOLD II), and severe (GOLD III–IV) airflow obstruction. Of 3,638 subjects, 99 (2.7%) received a lung cancer diagnosis. Adjusting for sex, age, years of cigarette smoking, and number of cigarettes smoked daily, logistic regression showed the expected lung cancer association with the presence of airflow obstruction (GOLD I–IV, odds ratio [OR], 2.09; 95% confidence interval [CI], 1.33–3.27). A second logistic regression showed lung cancer related to emphysema (OR, 3.56; 95% CI, 2.21–5.73). After additional adjustments for GOLD class, emphysema remained a strong and statistically significant factor related to lung cancer (OR, 3.14; 95% CI, 1.91–5.15). Conclusions: Emphysema on CT scan and airflow obstruction on spirometry are related to lung cancer in a high-risk population. Emphysema is independently related to lung cancer. Both radiographic emphysema and airflow obstruction should be considered when assessing lung cancer risk.

Wilson, David O.; Weissfeld, Joel L.; Balkan, Arzu; Schragin, Jeffrey G.; Fuhrman, Carl R.; Fisher, Stephen N.; Wilson, Jonathan; Leader, Joseph K.; Siegfried, Jill M.; Shapiro, Steven D.; Sciurba, Frank C.

2008-01-01

67

Minimum airflow reset of single-duct VAV terminal boxes  

NASA Astrophysics Data System (ADS)

Single duct Variable Air Volume (VAV) systems are currently the most widely used type of HVAC system in the United States. When installing such a system, it is critical to determine the minimum airflow set point of the terminal box, as an optimally selected set point will improve the level of thermal comfort and indoor air quality (IAQ) while at the same time lower overall energy costs. In principle, this minimum rate should be calculated according to the minimum ventilation requirement based on ASHRAE standard 62.1 and maximum heating load of the zone. Several factors must be carefully considered when calculating this minimum rate. Terminal boxes with conventional control sequences may result in occupant discomfort and energy waste. If the minimum rate of airflow is set too high, the AHUs will consume excess fan power, and the terminal boxes may cause significant simultaneous room heating and cooling. At the same time, a rate that is too low will result in poor air circulation and indoor air quality in the air-conditioned space. Currently, many scholars are investigating how to change the algorithm of the advanced VAV terminal box controller without retrofitting. Some of these controllers have been found to effectively improve thermal comfort, indoor air quality, and energy efficiency. However, minimum airflow set points have not yet been identified, nor has controller performance been verified in confirmed studies. In this study, control algorithms were developed that automatically identify and reset terminal box minimum airflow set points, thereby improving indoor air quality and thermal comfort levels, and reducing the overall rate of energy consumption. A theoretical analysis of the optimal minimum airflow and discharge air temperature was performed to identify the potential energy benefits of resetting the terminal box minimum airflow set points. Applicable control algorithms for calculating the ideal values for the minimum airflow reset were developed and applied to actual systems for performance validation. The results of the theoretical analysis, numeric simulations, and experiments show that the optimal control algorithms can automatically identify the minimum rate of heating airflow under actual working conditions. Improved control helps to stabilize room air temperatures. The vertical difference in the room air temperature was lower than the comfort value. Measurements of room CO2 levels indicate that when the minimum airflow set point was reduced it did not adversely affect the indoor air quality. According to the measured energy results, optimal control algorithms give a lower rate of reheating energy consumption than conventional controls.

Cho, Young-Hum

68

The effect of laminar air flow and door openings on operating room contamination.  

PubMed

We evaluate the association of laminar airflow (LAF) and OR traffic with intraoperative contamination rates. Two sterile basins were placed in each room during 81 cases, one inside and one outside the LAF. One Replicate Organism Detection and Counting (RODAC) plate from each basin was sent for culture at successive 30-minute intervals from incision time until wound closure. At successive 30-minute intervals more plates were contaminated outside than inside the LAF. A negative binomial model showed that the bacteria colony forming units (CFU) depended on whether there were any door openings (P=0.02) and the presence of LAF (P=0.003). LAF decreases CFU by 36.6%. LAF independently reduces the risk of contamination and microbial counts for surgeries lasting 90minutes or less. PMID:23890828

Smith, Eric B; Raphael, Ibrahim J; Maltenfort, Mitchell G; Honsawek, Sittisak; Dolan, Kyle; Younkins, Elizabeth A

2013-07-25

69

Self diagnosis for hot film airflow mass microsensors  

NASA Astrophysics Data System (ADS)

A self-diagnosis method for hot film airflow mass microsensor has been developed for the vehicle air intake. Based on the theory of heat transfer and airflow mass rate measurement for internal combustion engines, a hot film airflow mass microsensor with self-diagnosis capability is designed. It is composed of a heat sensing unit, a temperature sensing unit using a Heraeus silicon, a signal processor, a converters, a heater, a heating controller and a computer. The temperature sensing unit is split into a heater upstream temperature sensing resistor and a heater downstream temperature sensing resistor according to the air intake flow direction. From both theory and experiments, the relation between the heat transfer rate of the heater and the airflow mass rate at the air intake are deduced under the working conditions of a certain engine, and the temperature distribution rules in the heater surface, heater upstream and heater downstream are obtained. These relations are regarded as a reference model for the self-diagnosis in the microsensor. Finally, the failure of the microsensor can be detected by comparing the real-time measurement model with the reference model. Thus, this method can not only measure mass airflow rates in real time, but also inspect diagnosis faults of the heat sensing unit and the temperature sensing unit automatically.

Li, Lifu; Fan, Fan

2008-12-01

70

Evaluation of airflow patterns following procedures established by NUREG-1400.  

PubMed

The U.S. Nuclear Regulatory Commission's guide, NUREG-1400, addresses many aspects of air sampling in the work place. Here, we present detailed examples of the methodology used to conduct two qualitative airflow studies at different sites. In one test, smoke was used to evaluate the airflow patterns within a high-bay building for the purpose of determining appropriate locations for air monitoring equipment. The study revealed a stagnant layer of the air within the transfer area that made predicting movement of contamination within the transfer area difficult. Without conducting an airflow study, the stagnant layer may not have been identified and could have resulted in placement of samplers at inappropriate locations. In a second test, smoke was used to verify the effectiveness of an air space barrier curtain. The results showed that the curtain adequately separated the two air spaces. The methodology employed in each test provided sound, easy to interpret information that satisfied the requirements of each test. The methods described in this article can be applied at most facilities where determination of airflow patterns or the verification of suspected airflow patterns is required. PMID:16823267

Fritz, Brad G; Khan, Fenton; Mendoza, Donaldo P

2006-08-01

71

Research in natural laminar flow and laminar-flow control, part 3  

Microsoft Academic Search

Part 3 of the Symposium proceedings contains papers addressing advanced airfoil development, flight research experiments, and supersonic transition\\/laminar flow control research. Specific topics include the design and testing of natural laminar flow (NLF) airfoils, NLF wing gloves, and NLF nacelles; laminar boundary-layer stability over fuselage forebodies; the design of low noise supersonic\\/hypersonic wind tunnels; and boundary layer instability mechanisms on

J. N. Hefner; F. E. Sabo

1987-01-01

72

The way the wind blows: implications of modeling nasal airflow.  

PubMed

Nasal airflow is important for the many physiological functions of the nose, which include the warming and humidifying of inspired air; the filtration of airborne pollutants; and the sense of smell and nasal pungency. Until recently, airflow properties in the nose could only be understood using qualitative in vitro models of humans or in vivo studies in rodents. Recent advances in constructing three-dimensional geometric models of human nasal passages from CT scans, coupled with computational fluid dynamic modeling, has been a valuable tool for quantifying airflow and transport of gases, heat, particles, and aerosols in the human nose. Additionally, these techniques hold significant promise for evaluating and predicting the impact and successful remediation of a variety of clinical conditions on olfaction and nasal patency and setting guidelines for safe levels of exposure to inhaled materials. PMID:17437682

Zhao, Kai; Dalton, Pamela

2007-05-01

73

A laminar-flow heat exchanger  

NASA Astrophysics Data System (ADS)

The advantages of designing heat exchangers in the laminar flow regime are discussed from a theoretical standpoint. It is argued that laminar flow designs have the advantages of reducing thermodynamic and hydrodynamic irreversibilities and hence increasing system efficiency. More concretely, laminar flow heat exchangers are free from the turbulence-induced vibration common in conventional heat exchangers and can thus offer longer life and greater reliability. The problems of manufacturing heat exchangers suited to laminar flow are discussed. A method of manufacture which allows compact, modular design is outlined. Experience with this method of manufacture is described, and experimental results are presented. The problems of fouling and flow maldistribution are briefly discussed, and some possible applications are mentioned.

Doty, F. D.; Hosford, G.; Jones, J. D.; Spitzmesser, J. B.

74

Laminar Body Analysis Heat Plus Suction Stabilized.  

National Technical Information Service (NTIS)

An analytical investigation of the effectiveness of combined surface heating and suction in stabilizing a laminar boundary layer within a region of adverse pressure gradient was carried out. The study is of an applied nature in that two candidate vehicle ...

R. S. Scotti K. T. Corbett

1976-01-01

75

Computational Efficient Modelling of Laminar Separation Bubbles.  

National Technical Information Service (NTIS)

In predicting the aerodynamic characteristics of airfoils operating at low Reynolds numbers, it is often important to account for the effects of laminar (transitional) separation bubbles. Previous approaches to the modelling of this viscous phenomenon ran...

P. Dini M. D. Maughmer

1990-01-01

76

Laminar-Flow Wind Tunnel Experiments.  

National Technical Information Service (NTIS)

Although most of the laminar flow airfoils recently developed at the NASA Langley Research Center were intended for general aviation applications, low-drag airfoils were designed for transonic speeds and wind tunnel performance tested. The objective was t...

W. D. Harvey C. D. Harris W. G. Sewall J. P. Stack

1989-01-01

77

Active Control of Laminar Boundary Layer Disturbances  

Microsoft Academic Search

\\u000a Active suppression of the naturally occurring travelling wave disturbances that amplify in laminar boundary layers and cause\\u000a the transition from laminar to turbulent flow is considered. Both open-loop and closed-loop schemes are discussed. Numerical\\u000a predictions, based on linear stability theory, have been used to model the behaviour of the flow disturbances and the controlled\\u000a waves. Predictions based on these models

M. Gaster

78

Evolution of laminar mixing layer  

NASA Astrophysics Data System (ADS)

This investigation is directed at the analysis of the developing flow due to the mixing of two uniform incompressible fluid streams with different velocities. The asymptotic behavior of a laminar mixing layer is a similar solution of the boundary layer equations. Using the method of matched asymptotic expansions of the full Navier-Stokes equations for large Reynolds numbers, equations and solutions of the outer and inner expansions are presented. From the knowledge of asymptotic expansions, the governing Navier-Stokes equations evolve into the boundary layer equations downstream. The present formulation of the governing Navier-Stokes equations evolves gradually into the boundary layer equations downstream. Without imposing the similarity solution far downstream, the technique shows that the converged Navier-Stokes solution evolves into the laminar similarity solution downstream for reasonable velocity ratios. The Navier-Stokes solution is obtained based on the physical intuition of the interface trajectory which deflects monotonically downwards toward the slower moving stream, then gradually approaches an asymptotic value downstream without a wiggle. The downstream interface deflection naturally falls out from the Navier-Stokes solution and it is the information left over from the initial mixing region flow. This finding establishes the basis of the missing third boundary condition of the Blasius equation with the downstream interface deflection. This finding also reaffirms a unique third boundary condition for the Blasius equation that originated from the initial mixing flow region, an idea originally proposed by Klemp and Acrivos (1972) and first confirmed by Alston and Cohen (1992). Compared with the downstream interface deflection derived from other third boundary conditions, the present result falls between the von Karman condition and Alston and Cohen's result. The physical parameters evolve to their similarity form or their asymptotic forms at different rates with a given velocity ratio. It takes longer for the physical variables to evolve into their similarity profiles with decreasing velocity ratio. The longitudinal velocity always approaches the similarity form first. Calculation reveals that the nonsimilar solutions stretch out to a downstream Reynolds number of 103 to 104 for the velocity ratios studied (0.95--0.7).

Hwang, Din-Chih

79

STATISTICAL DATA ANALYSIS METHOD FOR MULTIZONAL AIRFLOW MEASUREMENT USING MULTIPLE KINDS OF PERFLUOROCARBON TRACER GAS  

Microsoft Academic Search

Conventional multiple types of perfluorocarbon tracers use the number of gases equal to the number of zones (n). The possible n×n+n airflows are solved from the mass balance of the gas and the airflow balance. However, some airflows may not occur because of the actual interzonal geometry, and the introduction of unnecessary, unknown parameters can impair the accuracy of the

Hiroyasu OKUYAMA; Yoshinori ONISHI; Shin-ichi TANABE; Seiichi KASHIHARA

80

A simple mathematical model of airflow in waving plant canopies  

Microsoft Academic Search

A simple mathematical model is proposed, which combines the effects of mean wind speed, plant spacing and the drag coefficients of individual plants to calculate the fluctuating airflow within a waving crop canopy. The model is non-linear and is only amenable to analytical treatment when linearized; however, the full non-linear version can be solved on an analogue computer.

J. J. Finnigan; P. J. Mulhearn

1978-01-01

81

Study of Airflow Out of the Mouth During Speech.  

ERIC Educational Resources Information Center

|Airflow outside the mouth is diagnostic of articulatory activities in the vocal tract, both total volume-velocity and the distribution of particle velocities over the flow-front being useful for this purpose. A system for recording and displaying both these types of information is described. This consists of a matrix of l6 hot-wire anemometer…

Catford, J.C.; And Others

82

Simple temperature compensation of thermal air-flow sensor  

Microsoft Academic Search

The thermal air-flow sensor, which is heated to a temperature with a constant degree of difference (?t) from that of the gas, provides power consumption according to the flow rates. The flow signal output of the sensor decreases depending on the rise in ambient temperature. This effect is easily compensated by inserting two identical compensation resistors (Rcom) in the Wheatstone

Kei Toda; Isao Sanemasa; Koichi Ishikawa

1996-01-01

83

Airflow characteristics in a baboon nasal passage cast.  

PubMed

Airflow patterns in the nasal passages influence the distribution of air-pollutant-induced lesions in the airway mucosa. Little is known about airflow characteristics of the complex nasopharyngeal airway of humans and experimental animals. Airflow characteristics in the nasopharyngeal airways of an adult male baboon (13.9 kg body wt) were investigated with thermistor probes and the findings compared with flow visualization, using a cinephotographic technique. A clear, acrylic, hollow cast of a baboon nose was made, and thermistor probes were inserted to record air velocity in the cast lumen using a wind tunnel to propel air through the cast. An identical cast was studied by passing water through the cast, with pulses of dye to reveal flow, and cinephotography was used for determination of flow velocities and flow patterns. Flow rates adjusted on the basis of a Reynolds conversion showed good correlations between the two methods, whereas cinephotography revealed areas of turbulence and vortex-like flow not detected by thermistor probes. These results suggest that water flow may provide useful information in complex airways where airflow cannot be determined by other methods. PMID:3782001

Patra, A L; Gooya, A; Morgan, K T

1986-11-01

84

Effect of aspirin on nasal resistance to airflow.  

PubMed

The effect of aspirin on nasal resistance to airflow was investigated by rhinomanometry in 25 healthy subjects before and after ingestion of aspirin or vitamin C in a double blind crossover trial. Aspirin caused a significant increase in nasal resistance compared with vitamin C. The effect of aspirin may be due to its inhibition of the synthesis of prostaglandins. PMID:3921141

Jones, A S; Lancer, J M; Moir, A A; Stevens, J C

1985-04-20

85

Airflow and air quality in a large enclosure  

Microsoft Academic Search

Knowledge of air flow patterns and thermal parameters are essential in the design of a ventilation system for large enclosures. The objective of this paper is to evaluate the possibility of using computer simulation to predict the airflow pattern and removal effectiveness of ventilation systems in large enclosures. The quality of air and thermal comfort in a three-floor shopping center

Z. Jiang; Qingyan Chen; F. Haghighat

1995-01-01

86

Pitot-tube flowmeter for quantification of airflow during sleep  

Microsoft Academic Search

The gold-standard pneumotachograph is not routinely used to quantify airflow during overnight polysomnography due to the size, weight, bulkiness and discomfort of the equipment that must be worn. To overcome these deficiencies that have precluded the use of a pneumotachograph in routine sleep studies, our group developed a lightweight, low dead space 'pitot flowmeter' (based on pitot-tube principle) for use

J. P. Kirkness; M. Verma; B. M. McGinley; M. Erlacher; A. R. Schwartz; P. L. Smith; J. R. Wheatley; S. P. Patil; T. C. Amis; H. Schneider

2011-01-01

87

Testing limits to airflow perturbation device (APD) measurements  

Microsoft Academic Search

BACKGROUND: The Airflow Perturbation Device (APD) is a lightweight, portable device that can be used to measure total respiratory resistance as well as inhalation and exhalation resistances. There is a need to determine limits to the accuracy of APD measurements for different conditions likely to occur: leaks around the mouthpiece, use of an oronasal mask, and the addition of resistance

Erika R. Lopresti; Arthur T. Johnson; Frank C. Koh; William H. Scott; Shaya Jamshidi; Nischom K. Silverman

2008-01-01

88

MODELING THE PERFORMANCE OF PERSONALIZED VENTILATION UNDER DIFFERENT ROOM AIRFLOWS  

Microsoft Academic Search

Personalized ventilation (PV) has the ability to improve inhaled air quality and accommodate the individual thermal preference. In this paper one kind of personalized ventilation system which supplies fresh air at the microphone position is investigated numerically. A numerical thermal manikin with the real geometry of human body is used to study the airflows around the occupant equipped with PV.

Naiping Gao; Jianlei Niu

89

Airflow in ducts: Measurement by perfluorocarbon (PFT) tracer  

Microsoft Academic Search

This paper describes the development of a tracer-gas system for measuring airflow in ducts, The fast-response system is capable of sampling different types of gases including a perfluorocarbon tracer (PFT) which was used for this siudy. The PFT, which is a liquid at room temperature, was injected into the duct using a thermostatically controlled heating block Tracer gas samples were

K. W. Cheong; S. B. Riffat

1994-01-01

90

Cough expired volume and airflow rates during sequential induced cough  

PubMed Central

Cough effectiveness is determined by a combination of volume of air expired and maximum expiratory airflow rate. Studies of cough sensitivity identify cough thresholds based on at least 2 or 5-cough re-accelerations to a stimulus, however, to date no study has examined the interplay between the distribution of cough expired air and cough airflow rates for these induced sequential coughs. The goal of this study was to investigate the relationship between reflex cough re-accelerations, cough airflow and cough inspired and expired volume. Twenty adults (18–40 years, four men) volunteered for study participation, and were outfitted with a facemask in-line with a pneumotachograph and a one-way valve for capsaicin delivery on inspiration. Cough inspired and expired volume (Liters of air) as well as airflow parameters (peak expiratory flow rates L/s) were measured for each cough response. Results demonstrate significant linear relationships between cough expired volume, flow rates, and the total number of coughs produced. Thus, as the number of coughs in an epoch increase, the mechanical effectiveness of coughs within the epoch may decrease according to peak expiratory flow rates and cough expired volume, particularly for coughs comprised of more than 3 re-accelerations.

Hegland, Karen W.; Troche, Michelle S.; Davenport, Paul W.

2013-01-01

91

Volume average technique for turbulent flow simulation and its application to room airflow prediction  

NASA Astrophysics Data System (ADS)

Fluid motion turbulence is one of the most important transport phenomena occurring in engineering applications. Although turbulent flow is governed by a set of conservation equations for momentum, mass, and energy, a Direct Numerical Simulation (DNS) of the flow by solving these equations to include the finest scale motions is impossible due to the extremely large computer resources required. On the other hand, the Reynolds Averaged Modelling (RAM) method has many limitations which hinder its applications to turbulent flows of practical significance. Room airflow featuring co- existence of laminar and turbulence regimes is a typical example of a flow which is difficult to handle with the RAM method. A promising way to avoid the difficulty of the DNS method and the limitation of the RAM method is to use the Large Eddy Simulation (LES) method. In the present thesis, the drawbacks of previously developed techniques for the LES method, particularly those associated with the SGS modelling, are identified. Then a new so called Volume Average Technique (VAT) for turbulent flow simulation is proposed. The main features of the VAT are as follows: (1) The volume averaging approach instead of the more common filtering approach is employed to define solvable scale fields, so that coarse- graining in the LES and space discretization of the numerical scheme are achieved in a single procedure. (2) All components of the SGS Reynolds stress and SGS turbulent heat flux are modelled dynamically using the newly proposed Functional Scale Similarity (FSS) SGS model. The model is superior to many previously developed SGS models in that it can be applied to highly inhomogeneous and/or anisotropic, weak or multi-regime turbulent flows using a relatively coarse grid. (3) The so called SGS turbulent diffusion is identified and modelled as a separate mechanism to that of the SGS turbulent flux represented by the SGS Reynolds stress and SGS turbulent heat flux. The SGS turbulent diffusion is defined in the coarse-graining procedure, and responsible for most of the energy dissipation. (4) A new 3-D collocated scheme for the solution of viscous incompressible fluid flow, based on the SIMPLE and fractional-step methods is developed for the LES. Benchmark tests of the VAT are performed based on 2-D and 3-D lid-driven and 3-D buoyancy-driven cavity flows. Finally, as an example of a practical calculation, the VAT is applied to the LES of airflow in an enclosed air- conditioned room with a wall-mounted cooling inlet and an outlet on the opposite wall.

Huang, Xianmin

92

COMPUTATIONAL FLUID DYNAMICS STUDY ON THE INFLUENCE OF AIRFLOW PATTERNS ON CARBON DIOXIDE DISTRIBUTION IN A SCALED LIVESTOCK BUILDING  

Microsoft Academic Search

Airflow patterns and airflow rate have an important influence on contaminant distribution in swine buildings. The objective of this paper is to model and evaluate the effect of airflow rates and airflow patterns on CO2 concentration distribution. Contaminant sources are assumed to be modeled as a constant concentration on the manure surface. Three different ventilation rates and three different deflector

Li Rong; Peter V. Nieslen; Guohong Tong; Peter Ravn; Guoqiang Zhang

93

Laminar Diffusion Flame Studies (Ground- and Space-Based Studies).  

National Technical Information Service (NTIS)

Laminar diffusion flames are of interest because they provide model flame systems that are far more tractable for analysis and experiments than more practical turbulent diffusion flames. Certainly, understanding flame processes within laminar diffusion fl...

Z. Dai A. M. El-Leathy K. C. Lin P. B. Sunderland F. Xu G. M. Faeth

2000-01-01

94

Laminar flame speeds of moist syngas mixtures  

SciTech Connect

This work experimentally investigates the effect of the presence of water vapor on the laminar flame speeds of moist syngas/air mixtures using the counterflow twin-flame configuration. The experimental results presented here are for fuel lean syngas mixtures with molar percentage of hydrogen in the hydrogen and carbon monoxide mixture varying from 5% to 100%, for an unburned mixture temperature of 323 K, and under atmospheric pressure. At a given equivalence ratio, the effect of varying amount of water vapor addition on the measured laminar flame speed is demonstrated. The experimental laminar flame speeds are also compared with computed values using chemical kinetic mechanisms reported in the literature. It is found that laminar flame speed varies non-monotonically with addition of water for the carbon monoxide rich mixtures. It first increases with increasing amount of water addition, reaches a maximum value, and then decreases. An integrated reaction path analysis is further conducted to understand the controlling mechanism responsible for the non-monotonic variation in laminar flame speed due to water addition. On the other hand, for higher values of H{sub 2}/CO ratio the laminar flame speed monotonically decreases with increasing water addition. It is shown that the competition between the chemical and thermal effects of water addition leads to the observed response. Furthermore, reaction rate sensitivity analysis as well as binary diffusion coefficient sensitivity analysis are conducted to identify the possible sources of discrepancy between the experimental and predicted values. The sensitivity results indicate that the reaction rate constant of H{sub 2}+OH = H{sub 2}O+H is worth revisiting and refinement of binary diffusion coefficient data of N{sub 2}-H{sub 2}O, N{sub 2}-H{sub 2}, and H{sub 2}-H{sub 2}O pairs can be considered. (author)

Das, Apurba K. [Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106 (United States); Kumar, Kamal; Sung, Chih-Jen [Department of Mechanical Engineering, University of Connecticut, Storrs, CT 06269 (United States)

2011-02-15

95

Lung Function in Young Adults Predicts Airflow Obstruction 20 Years Later  

PubMed Central

Rationale The burden of obstructive lung disease is increasing, yet there are limited data on its natural history in young adults. Objectives To determine in a prospective cohort of generally healthy young adults the influence of early adult lung function on the presence of airflow obstruction in middle age. Methods Longitudinal study of 2,496 adults who were 18-30 years of age at entry, did not report having asthma, and returned at Year 20. Airflow obstruction was defined as an FEV1/FVC ratio less than the lower limit of normal. Measurements and Main Results Airflow obstruction was present in 6.9% and 7.8% of participants at Years 0 and 20. Less than 10% of participants with airflow obstruction self-reported COPD. In cross sectional analyses airflow obstruction was associated with less education, smoking, and self-reported COPD. Low FEV1 and FEV1/FVC and airflow obstruction in young adults were associated with low lung function and airflow obstruction 20 years later. Of those with airflow obstruction at Year 0, 52% had airflow obstruction 20 years later. The FEV1/FVC at Year 0 was highly predictive of airflow obstruction 20 years later (c-statistic 0.91; 95% CI 0.89-0.93). The effect of cigarette smoking on lung function decline with age was most evident in young adults with pre-existing airflow obstruction. Conclusions Airflow obstruction is mostly unrecognized in young and middle age adults. A low FEV1, low FEV1/FVC and airflow obstruction in young adults, in addition to smoking, are highly predictive of low lung function and airflow obstruction in middle age.

Kalhan, Ravi; Arynchyn, Alexander; Colangelo, Laura A.; Dransfield, Mark T.; Gerald, Lynn B.; Smith, Lewis J.

2010-01-01

96

[Use of rooms with laminar air flow].  

PubMed

The paper deals with the problem of dependency of the reduction of microbial contamination and of dust pollution of the air mediu min the CAMERA-BOXES with a liminary flux on the aeration degree. It was shown that the degree of aeration in the camera-box constituted from 330 to 1060, with the rate of the air flux at the filter exit of from 0.2 to 0.6 m/sec. Vertical laminar flux provided release of the air from the microbes and dust. The use of the camera-box with a laminar flux for work requiring sterile conditions is recommended. PMID:1266473

Vashkov, V I; Alekseeva, M I; Gol'ts, M V; Morozov, P I; Mal'kov, O S

1976-02-01

97

Stretch in Premixed Laminar Flames Under IC Engine Conditions  

Microsoft Academic Search

Flamelet models for turbulent combustion provide an approach (via the laminar flame) to include detailed flame chemistry into fluid dynamic simulations of IC engines. The flamelet model postulates that a turbulent flame is a statistical distribution of premixed, laminar flames. However. turbulence affects the laminar flames through strain (a) and curvature. The effect of positive strains (outflow condition) on counter-flow

Richard J. Blint

1991-01-01

98

Response of Metal Core Piezoelectric Fibers to Unsteady Airflows  

NASA Astrophysics Data System (ADS)

In the previous study, possible applications of metal core piezoelectric fibers with a diameter of 200 to 250 µm as bionic airflow sensors mimicking the flow sensitive receptor hairs of crickets have been proposed. This study aims to investigate the dynamic responses of the metal core piezoelectric fibers to unsteady airflow. The metal core piezoelectric fiber is half coated on the outer surface and is used in the bending mode. Wind tunnel tests were carried out and the output voltage of the fiber under the excitation of the unsteady aerodynamic force during flow acceleration and deceleration was measured when the wind tunnel was suddenly closed or opened by a shutter. The relationship between the maximum voltage and the steady-state velocity and that between the voltage and the acceleration of flow were also obtained.

Qiu, J. H.; Ji, H. L.; Zhu, K. J.; Park, M. J.

99

Computational Investigation of Dynamic Glottal Aperture Effects on Respiratory Airflow  

NASA Astrophysics Data System (ADS)

The periodic movement of the glottal aperture (vocal folds) during tidal breathing has been long recognized as a factor in altering the airflow dynamics in the tracheobrnchial region. The potential influence from these altered flow structures on the transport and deposition of inhaled particles is not known. However, studies devoted to this dynamic physiological feature are scarce due to the complex anatomy in of the larynx and numerical challenges in simulating dynamic geometries. In this study, a high-fidelity immersed boundary solver is used to investigate this problem. A 3D human oral-larynx-lung model is firstly reconstructed from MRI data. The role of the vocal fold movement and associated airflow characteristics such as vortex shedding, Coanda effect etc. during inhalation and exhalation are then numerically studied.

Xi, Jinxiang; Yan, Hong; Dong, Haibo

2008-11-01

100

Efficient airflow design for cleanrooms improves business bottom lines  

SciTech Connect

Based on a review of airflow design factors and in-situ energy measurements in ISO Cleanliness Class-5 cleanrooms, this paper addresses the importance of energy efficiency in airflow design and opportunities of cost savings in cleanroom practices. The paper discusses design factors that can long lastingly affect cleanroom system performance, and demonstrates benefits of energy efficient cleanroom design from viewpoints of environmental control and business operations. The paper suggests that a high performance cleanroom should not only be effective in contamination control, but also be efficient in energy and environmental performance. The paper also suggests that energy efficient design practice stands to bring in immediate capital cost savings and operation cost savings, and should be regarded by management as a strategy to improve business bottom lines.

Xu, Tengfang

2003-01-05

101

Computational model of oscillatory airflow in a bronchial bifurcation.  

PubMed

Airflow distribution in the bronchial tree is an important factor that controls gas mixing in the lungs, especially, in diseased lungs or during high frequency ventilation. A nonlinear analog model has been developed to investigate the dependency of airflow distribution in asymmetric bronchial bifurcations on structural and physiological parameters. The system parameters (electrical analogs) are time-dependent and were extracted from laboratory studies of airway models and physiological measurements. The model was used to study flow distribution in peripheral pathways of normal and pathological airways during different modes of quiet breathing as well as high frequency ventilation. Model simulations revealed that (i) increasing of ventilation frequency or stroke volume increases the time and percentage of pendelluft in each cycle, (ii) diameter asymmetry between parallel pathways is more dominant than length asymmetry and enhances the degree of asynchronous ventilation to peripheral pathways, and (iii) asymmetry in the compliance of peripheral airways and lung parenchyma greatly increases the degree of asynchronous ventilation. PMID:9696286

Elad, D; Shochat, A; Shiner, R J

1998-04-01

102

Nanostructured optical fibre sensors for breathing airflow monitoring  

Microsoft Academic Search

A nanostructured optical fibre-based thin film sensor was designed for non-invasive, fast and reliable monitoring of respiratory airflow. Molecular-level self-assembly processing method was used to form multi-layered inorganic nanocluster and polymer thin films on the distal ends of optical fibres to form such sensors. In order to optimize the sensing performance, an analytical model based on the condensation of exhaled

Y. Kang; H. Ruan; Y. Wang; F. J. Arregui; I. R. Matias; R. O. Claus

2006-01-01

103

Nanostructured optical fiber sensors for breathing airflow monitoring  

Microsoft Academic Search

This paper presents recent progresses in the application of nanostructured optical fiber-based sensors for non-invasive, fast and reliable monitoring of respiratory airflow. Molecular-level self-assembly processing method is used to form multilayered inorganic nanocluster and polymer thin films on the distal ends of optical fibers to form such sensors. In order to optimize sensing performance, recent work has studies the synthesis

Y. Kang; H. Ruan; Jeffrey Mecham; Y. Wang; Francisco J. Arregui; Ignacio R. Matias; Richard O. Claus

2005-01-01

104

Natural convection airflow and heat transport in buildings: experimental results  

SciTech Connect

Observations of natural convection airflow in passive solar buildings are described. Particular results are given for two buildings supplementing other data already published. A number of generalizations based on the monitoring of the 15 buildings are presented. It is concluded that energy can be reasonably well distributed throughout a building by natural convection provided suitable openings are present and that the direction of heat transport is either horizontally across or upward.

Balcomb, J.D.; Jones, G.F.

1985-01-01

105

Nasal airflow resistance measurement: forced oscillation technique versus posterior rhinomanometry  

Microsoft Academic Search

This study was designed to determine whether nasal airflow resistance (Rn) which is nonlinear during tidal breathing, can be assessed by the forced oscilla- tion (FO) technique. Rn values obtained by the FO technique and extrapolated to 0 Hz (Rn,FO) were compared to those assessed by posterior rhinomanometry at maximal tidal inspira- tory flow (Rn,m), at a 0.5 L·s-1 flow

A. M. Lorino; F. Lofaso; F. Abi-Nader; I. Drogou; E. Dahan; F. Zerah; A. Harf; H. Lorino

106

Collecting aerosol in airflow with a magnetically stabilized fluidized bed.  

PubMed

A magnetically stabilized fluidized bed (MSB) is a highly efficient filter that takes the advantage of both fluidized beds and fixed beds. This paper presents the research to collect aerosol in airflow with a MSB. The filtering model of MSB is established with its parameters including magnetic field intensity, gas superficial velocity, average grain-size, and bed height on the collection efficiency of MSB. The model is verified by experiments. PMID:11723940

Gui, K T; Zhang, H; Shi, M H; Xu, Y Q

2001-10-01

107

Computed Tomography Structural Lung Changes in Discordant Airflow Limitation  

PubMed Central

Background There is increasing evidence that structural lung changes may be present before the occurrence of airflow limitation as assessed by spirometry. This study investigated the prevalence of computed tomography (CT) quantified emphysema, airway wall thickening and gas trapping according to classification of airflow limitation (FEV1/FVC <70% and/or < the lower limit of normal (LLN)) in (heavy) smokers. Methods A total number of 1,140 male former and current smokers participating in a lung cancer screenings trial (NELSON) were included and underwent chest CT scanning and spirometry. Emphysema was quantified by the 15th percentile, air way wall thickening by the square root of wall area for a theoretical airway with 10mm lumen perimeter (Pi10) and gas trapping by the mean lung density expiratory/inspiratory (E/I)-ratio. Participants were classified by entry FEV1/FVC: group 1>70%; group 2<70% but >LLN; and group 370% but FEV1 <80% predicted, were excluded. Multivariate regression analysis correcting for covariates was used to asses the extent of emphysema, airway wall thickening and gas trapping according to three groups of airflow limitation. Results Mean (standard deviation) age was 62.5 (5.2) years and packyears smoked was 41.0 (18.0). Group 2 subjects when compared to group 1 had a significantly lower 15th percentile, ?920.6 HU versus ?912.2 HU; a higher Pi10, 2.87 mm versus 2.57 mm; and a higher E/I-ratio, 88.6% versus 85.6% (all p<0.001). Conclusion Subjects with an FEV1/FVC<70%, but above the LLN, have a significant greater degree of structural lung changes on CT compared to subjects without airflow limitation.

Hoesein, Firdaus A. A. Mohamed; de Jong, Pim A.; Lammers, Jan-Willem J.; Mali, Willem PThM; Schmidt, Michael; de Koning, Harry J.; van der Aalst, Carlijn; Oudkerk, Matthijs; Vliegenthart, Rozemarijn; van Ginneken, Bram; van Rikxoort, Eva M.; Zanen, Pieter

2013-01-01

108

Modeling airflow and particle transport\\/deposition in pulmonary airways  

Microsoft Academic Search

A review of research papers is presented, pertinent to computer modeling of airflow as well as nano- and micron-size particle deposition in pulmonary airway replicas. The key modeling steps are outlined, including construction of suitable airway geometries, mathematical description of the air-particle transport phenomena and computer simulation of micron and nanoparticle depositions. Specifically, diffusion-dominated nanomaterial deposits on airway surfaces much

Clement Kleinstreuer; Zhe Zhang; Zheng Li

2008-01-01

109

Pressure Effect on the Structural Transition and Suppression of the High-Spin State in the Triple-Layered T'-La4Ni3O8  

NASA Astrophysics Data System (ADS)

We have carried out a comprehensive high-pressure study on the triple-layer T'-La4Ni3O8 with a suite of experimental probes, including structure determination, magnetic, and transport properties up to 50 GPa. Consistent with a recent ab inito calculation [1], application of hydrostatic pressure suppresses an insulator-metal spin-state transition at Pc ˜ 6 GPa. However, a low-spin metallic phase does not emerge after the high-spin state is suppressed to the lowest temperature. For P > 20 GPa, the ambient T' structure transforms gradually to a T'-type structure, which involves a structural reconstruction from fluorite La-O2-La blocks under low pressures to rock-salt LaO-LaO blocks under high pressures. Absence of the metallic phase under pressure has been discussed in terms of local displacements of O2- ions in the fluorite block under pressure before a global T* phase is established [2]. Ref. [1] V. Pardo and W. E. Pickett, Phys. Rev. B 85, 045111 (2012). [2] J.-G. Cheng, et al. Phys. Rev. Lett. 108, 236403(2012).

Cheng, J.-G.; Zhou, J.-S.; Goodenough, J. B.; Zhou, H. D.; Matsubayashi, K.; Uwatoko, Y.; Kong, P. P.; Jin, C. Q.; Yang, W. G.; Shen, G. Y.

2013-03-01

110

Pressure effect on the structural transition and suppression of the high-spin state in the triple-layer T'-La4Ni3O8.  

PubMed

We report a comprehensive high-pressure study on the triple-layer T'-La4Ni3O8 with a suite of experimental probes, including structure determination, magnetic, and transport properties up to 50 GPa. Consistent with a recent ab inito calculation, application of hydrostatic pressure suppresses an insulator-metal spin-state transition at P(c)?6??GPa. However, a low-spin metallic phase does not emerge after the high-spin state is suppressed to the lowest temperature. For P>20??GPa, the ambient T' structure transforms gradually to a T(†)-type structure, which involves a structural reconstruction from fluorite La-O2-La blocks under low pressures to rock-salt LaO-LaO blocks under high pressures. Absence of the metallic phase under pressure has been discussed in terms of local displacements of O2- ions in the fluorite block under pressure before a global T(†) phase is established. PMID:23003979

Cheng, J-G; Zhou, J-S; Goodenough, J B; Zhou, H D; Matsubayashi, K; Uwatoko, Y; Kong, P P; Jin, C Q; Yang, W G; Shen, G Y

2012-06-08

111

Qat-4 and Qat-5, new murine T-cell antigens governed by the Tla region and identified by monoclonal antibodies.  

PubMed

Two new lymphocyte antigens, provisionally designated Qat-4 and Qat-5 have been identified with two different hybridoma-derived, monoclonal AKR antiC57BL/6 antibodies. These antigens are governed by genes located to the right (distal) end of the H-2 complex, within the Qa-2,3 region. Qat-4 and Qat-5 antigens which do not seem to be identical with Qa-2,3 or TL antigens are absent from Ig/ lymphocytes and thymocytes. They are only present on a fraction of peripheral T cells. Thus, Qat-4 is expressed on 70%, and Qat-5 on 30% of splenic and lymph node T cells, Qat-4 is also found on the majority of Ig- cells from athymic nude mice. These findings illustrate the complexity of the chromosome segment between the H-2D and Tla loci and they emphasize the role of major histocompatibility complex-associated genes for the differentiation of T cells into different subpopulations with possibly distinct immunologic functions. PMID:312902

Hämmerling, G J; Hämmerling, U; Flaherty, L

1979-07-01

112

Airflow Simulations around OA Intake Louver with Electronic Velocity Sensors  

SciTech Connect

It is important to control outdoor airflow rates into HVAC systems in terms of energy conservation and healthy indoor environment. Technologies are being developed to measure outdoor air (OA) flow rates through OA intake louvers on a real time basis. The purpose of this paper is to investigate the airflow characteristics through an OA intake louver numerically in order to provide suggestions for sensor installations. Airflow patterns are simulated with and without electronic air velocity sensors within cylindrical probes installed between louver blades or at the downstream face of the louver. Numerical results show quite good agreements with experimental data, and provide insights regarding measurement system design. The simulations indicate that velocity profiles are more spatially uniform at the louver outlet relative to between louver blades, that pressure drops imposed by the sensor bars are smaller with sensor bars at the louver outlet, and that placement of the sensor bars between louver blades substantially increases air velocities inside the louver. These findings suggest there is an advantage to placing the sensor bars at the louver outlet face.

Han, Hwataik; Sullivan, Douglas P.; Fisk, William J.

2009-04-01

113

Wall Temperature Effects on Laminar Wakes.  

National Technical Information Service (NTIS)

An experimental investigation was made of the effects of cold wall conditions on the structure of the laminar near wake of a 7 degree half-angle right circular cone with a sharp nose at zero pitch and yaw. Free stream Mach number and Reynolds number were ...

A. R. Ahmadi M. Finston

1975-01-01

114

Passive laminar flow control of crossflow vorticity  

NASA Astrophysics Data System (ADS)

A passive laminar flow crossflow vorticity control system includes an aerodynamic or hydrodynamic surface having geometric perturbations. The perturbations include peaks and valleys having a predetermined spacing and aligned approximately in a streamline direction to force the formation of crossflow vortices. This minimizes amplification and growth of the vortices, thus delaying transition to turbulence and reducing overall drag.

Holmes, Bruce J.

1990-11-01

115

Some Laminar-Flame Modelling Problems.  

National Technical Information Service (NTIS)

In the paper the effect of radiation-heat loss on the structure and extinction limits of laminar CO/H2/N2 counterflow diffusion flames is investigated. From the fundamental integro-differential equation governing radiation transport a simplified radiation...

Y. Liu B. Rogg

1990-01-01

116

Flight research on natural laminar flow  

Microsoft Academic Search

Five decades of flight experiences with natural laminar flow (NLF) have provided a basis of understanding how this technology can be used for reduction of viscous drag on modern practical aircraft. The effects of cruise unit Reynolds number on NLF achievability and maintainability; compressibility effects on Tollmein-Schlichting growth; flight experiment on the Cessna Citation III business jet; flight instrumentation on

B. J. Holmes; C. C. Croom; E. C. Hastings Jr.; C. J. Obara; C. P. Vandam

1986-01-01

117

Laminar mixing in an SMX static mixer  

Microsoft Academic Search

Laminar mixing in an SMX static mixer was studied using experimental measurement techniques, particle image velocimetry and laser induced fluorescence, along with computational fluid dynamics. The effect of shear-thinning liquids and mixer element designs on pressure drop and mixing, as well as drop breakup mechanism in liquid-liquid dispersion were investigated. ^ Shear thinning fluids exhibited better mixing quality and lower

Shiping Liu

2005-01-01

118

Flight Research on Natural Laminar Flow.  

National Technical Information Service (NTIS)

Five decades of flight experiences with natural laminar flow (NLF) have provided a basis of understanding how this technology can be used for reduction of viscous drag on modern practical aircraft. The effects of cruise unit Reynolds number on NLF achieva...

B. J. Holmes C. C. Croom E. C. Hastings C. J. Obara C. P. Vandam

1986-01-01

119

Turbulent-Laminar Patterns in Shear Flows  

NASA Astrophysics Data System (ADS)

We study computationally turbulent-laminar patterns in very-large-aspect-ratio plane Couette flow. These states consist of large-scale alternations of turbulent and laminar flow oriented obliquely to the steamwise direction. Such flow patterns are now believed to be typical of many transitional shear flows when observed on long length scales. For a fixed pattern orientation of 24^circ, suggested by experiment, the basic scenario observed in computations as the Reynolds number is decreased is the following: From uniform turbulence there is a transition to intermittent patterns at Re˜420, then to steady, spatially periodic patterns at Re˜390. The wavelength increases as the Reynolds number is decreased until Re˜310, where the flow consists of localized turbulence within a laminar background. This scenario can depend on pattern orientation -- at 90^circ with respect to the flow direction, we observe spatio-temporal intermittency in which turbulent patches that repeatedly disappear abruptly and then re-nucleate gradually. We present an analysis of these flows in terms of mean quantities and discuss the difficulties of determining critical bifurcation parameters for such turbulent-laminar systems.

Barkley, Dwight

2007-03-01

120

Multilevel adaptive methods for laminar diffusion flames  

Microsoft Academic Search

A multilevel adaptive method is applied to the numerical simulation of laminar diffusion flames. A local fine grid is embedded near the jet inlet of the simulation to provide increased resolution and accuracy. Computational results confirm that the multilevel local refinement process substantially increases local and global accuracy with little added cost.

C. Liu; Z. Liu; S. McCormick

1993-01-01

121

CFD analysis of laminar oscillating flows  

SciTech Connect

This paper describes a numerical simulations of oscillating flow in a constricted duct and compares the results with experimental and theoretical data. The numerical simulations were performed using the computational fluid dynamics (CFD) code CFX4.2. The numerical model simulates an experimental oscillating flow facility that was designed to test the properties and characteristics of oscillating flow in tapered ducts, also known as jet pumps. Jet pumps are useful devices in thermoacoustic machinery because they produce a secondary pressure that can counteract an unwanted effect called streaming, and significantly enhance engine efficiency. The simulations revealed that CFX could accurately model velocity, shear stress and pressure variations in laminar oscillating flow. The numerical results were compared to experimental data and theoretical predictions with varying success. The least accurate numerical results were obtained when laminar flow approached transition to turbulent flow.

Booten, C. W. Charles W.); Konecni, S. (Snezana); Smith, B. L. (Barton L.); Martin, R. A. (Richard A.)

2001-01-01

122

Intrinsic Stability of a Body Hovering in an Oscillating Airflow  

NASA Astrophysics Data System (ADS)

We explore the stability of flapping flight in a model system that consists of a pyramid-shaped object hovering in a vertically oscillating airflow. Such a flyer not only generates sufficient aerodynamic force to keep aloft but also robustly maintains balance during free flight. Flow visualization reveals that both weight support and orientational stability result from the periodic shedding of vortices. We explain these findings with a model of the flight dynamics, predict increasing stability for higher center of mass, and verify this counterintuitive fact by comparing top- and bottom-heavy flyers.

Liu, Bin; Ristroph, Leif; Weathers, Annie; Childress, Stephen; Zhang, Jun

2012-02-01

123

Testing of air-flow windows for evaluation and application  

SciTech Connect

A description is given of how the performance of air-flow windows was assessed in comparison to a conventional window of good current design. Tests were performed in the University Building Environment and Energy Laboratory which allowed tests quite representative of actual application conditions in a variety of vertical orientations. The actual application condition requirement necessitated some approximations to the energy measurements which are not found in guarded hot box or calorimeter kinds of approaches to performance evaluations. The testing technique and required approximations are described. A possible type of solar-residential application is also described briefly.

Boehm, R.F.; Brandle, K.

1980-12-01

124

Prevalence of obstructive airflow limitation in Irish collegiate athletes  

Microsoft Academic Search

Background  Asthma prevalence in athletes is variable, depending on the sport and training conditions.\\u000a \\u000a \\u000a \\u000a Aims  To investigate the prevalence of obstructive airflow limitation, asthma control and lung volume differences in a control group\\u000a and five groups of collegiate athletes — outdoor field, indoor court, endurance, combat sports and swimming.\\u000a \\u000a \\u000a \\u000a Methods  Three hundred and five athletes completed a respiratory questionnaire and performed spirometry during

E. Smith; N. Mahony; B. Donne; M. O’Brien

2002-01-01

125

EFFECT OF AIRFLOW AND HEAT INPUT RATES ON DUCT EFFICIENCY.  

SciTech Connect

Reducing the airflow and heat input rates of a furnace that is connected to a duct system in thermal contact with unconditioned spaces can significantly reduce thermal distribution efficiency. This is a straightforward theoretical calculation based on the increased residence time of the air in the duct at the lower flow rate, which results in greater conduction losses. Experimental tests in an instrumented residential-size duct system have confirmed this prediction. Results are compared with the heat-loss algorithm in ASHRAE Standid 152P. The paper concludes with a discussion of possible remedies for this loss of efficiency in existing systems and optional design strategies in new construction.

ANDREWS,J.W.

2003-05-28

126

CFD modeling of pharmaceutical isolators with experimental verification of airflow.  

PubMed

Computational fluid dynamics (CFD) models have been developed to predict the airflow in a transfer isolator using a commercial CFD code. In order to assess the ability of the CFD approach in predicting the flow inside an isolator, hot wire anemometry measurements and a novel experimental flow visualization technique consisting of helium-filled glycerin bubbles were used. The results obtained have been shown to agree well with the experiments and show that CFD can be used to model barrier systems and isolators with practical fidelity. This indicates that CFD can and should be used to support the design, testing, and operation of barrier systems and isolators. PMID:17933207

Nayan, N; Akay, H U; Walsh, M R; Bell, W V; Troyer, G L; Dukes, R E; Mohan, P

127

Nasal resistance to airflow (its measurement, reproducibility and normal parameters).  

PubMed

A method of rhinomanometry is described for use in clinical research work. The statistical distribution of nasal resistance values is studied in a sample of 59 normal individuals. The variation of nasal resistance within two individuals is studied over a period of 7 hours. The choice of appropriate statistical tests to be used when comparing nasal resistance values is discussed. The reproducibility of nasal resistance measurements is assessed in 47 normal individuals. The results were used to define a normal range of values for total nasal resistance to airflow. PMID:3655533

Jones, A S; Lancer, J M; Stevens, J C; Beckingham, E

1987-08-01

128

Thermohydrodynamic analysis for laminar lubricating films  

Microsoft Academic Search

A Galerkin-type analysis to include thermal effects in laminar lubricating films was performed. The lubricant properties were assumed constant except for a temperature-dependent Newtonian viscosity. The cross-film temperature profile is established by collocation at the film boundaries and two interior Lobatto points. The interior temperatures are determined by requiring that the zeroth and first moment of the energy equation be

H. G. Elrod; D. E. Brewe

1986-01-01

129

Flight research on natural laminar flow  

NASA Astrophysics Data System (ADS)

Five decades of flight experiences with natural laminar flow (NLF) have provided a basis of understanding how this technology can be used for reduction of viscous drag on modern practical aircraft. The effects of cruise unit Reynolds number on NLF achievability and maintainability; compressibility effects on Tollmein-Schlichting growth; flight experiment on the Cessna Citation III business jet; flight instrumentation on Lear 28/29; OV-I NLF engine nacelle experiments; and viscous drag reduction are examined.

Holmes, B. J.; Croom, C. C.; Hastings, E. C., Jr.; Obara, C. J.; Vandam, C. P.

1986-12-01

130

Laminar separation bubbles: Dynamics and control  

Microsoft Academic Search

This work is an experimental investigation of the dynamics and control of the laminar separation bubbles which are typically\\u000a present on the suction surface of an aerofoil at a large angle of attack. A separation bubble is produced on the upper surface\\u000a of a flat plate by appropriately contouring the top wall of the wind tunnel. First, a basic (unforced)

Sourabh S. Diwan; O. N. Ramesh

2007-01-01

131

Laminar Smoke Points of Wax Candles  

Microsoft Academic Search

An experimental investigation of laminar smoke points of candle flames is presented. Adjustable wicks with diameters of 1.7–7.3 mm were used to measure smoke points in quiescent air for 14 different waxes. The measured smoke points increased with wick diameter. Smoke points interpolated to a wick diameter of 4.5 mm varied from 41–80 mm and increased from commercial waxes (candelilla, carnauba, beeswax, paraffin)

Kathryn M. Allan; John R. Kaminski; Jerry C. Bertrand; Jeb Head; Peter B. Sunderland

2009-01-01

132

Investigation of non-uniform airflow signal oscillation during high frequency chest compression  

PubMed Central

Background High frequency chest compression (HFCC) is a useful and popular therapy for clearing bronchial airways of excessive or thicker mucus. Our observation of respiratory airflow of a subject during use of HFCC showed the airflow oscillation by HFCC was strongly influenced by the nonlinearity of the respiratory system. We used a computational model-based approach to analyse the respiratory airflow during use of HFCC. Methods The computational model, which is based on previous physiological studies and represented by an electrical circuit analogue, was used for simulation of in vivo protocol that shows the nonlinearity of the respiratory system. Besides, airflow was measured during use of HFCC. We compared the simulation results to either the measured data or the previous research, to understand and explain the observations. Results and discussion We could observe two important phenomena during respiration pertaining to the airflow signal oscillation generated by HFCC. The amplitudes of HFCC airflow signals varied depending on spontaneous airflow signals. We used the simulation results to investigate how the nonlinearity of airway resistance, lung capacitance, and inertance of air characterized the respiratory airflow. The simulation results indicated that lung capacitance or the inertance of air is also not a factor in the non-uniformity of HFCC airflow signals. Although not perfect, our circuit analogue model allows us to effectively simulate the nonlinear characteristics of the respiratory system. Conclusion We found that the amplitudes of HFCC airflow signals behave as a function of spontaneous airflow signals. This is due to the nonlinearity of the respiratory system, particularly variations in airway resistance.

Sohn, Kiwon; Warwick, Warren J; Lee, Yong W; Lee, Jongwon; Holte, James E

2005-01-01

133

Laminar iridium coating produced by pulse current electrodeposition from chloride molten salt  

NASA Astrophysics Data System (ADS)

Laminar Ir coatings were prepared by pulse current electrodeposition in molten salt.Laminar Ir coating comprised a columnar nucleation layer and a laminar growth layer.Laminar Ir coating was much smoother (Ra: 1.01 ?m) and denser than columnar coating.The degree of <1 1 1> preferred orientation of laminar coating was extremely high.

Zhu, Li’an; Bai, Shuxin; Zhang, Hong; Ye, Yicong

2013-10-01

134

Trans-laminar-reinforced (TLR) composites  

NASA Astrophysics Data System (ADS)

A Trans-Laminar-Reinforced (TLR) composite is defined as composite laminate with up to five percent volume of fibrous reinforcement oriented in a "trans-laminar" fashion in the through-thickness direction. The TLR can be continuous threads as in "stitched laminates", or it can be discontinuous rods or pins as in "Z-FiberspTM" materials. Adding TLR to an otherwise two dimensional laminate results in the following advantages: substantially improved compression-after-impact response; considerably increased fracture toughness in mode I (double cantilever beam) and mode II (end notch flexure); and severely restricted size and growth of impact damage and edge delamination. TLR has also been used to eliminate catastrophic stiffener disbonding in stiffened structures. As little as one percent volume of TLR significantly alters the mechanical response of laminates. The objective of this work was to characterize the effects of TLR on the in-plane and inter-laminar mechanical response of undamaged composite laminates. Detailed finite element models were made of "unit cells," or representative volumes, and an inter-laminar dominated problem of practical interest. The work was limited to the linear response of undamaged material with at least one ply interface. Adding a few percent TLR had a small negative effect on the in-plane extensional and shear moduli, Esbx, Esby and Gsbxy, but had a large positive effect (up to 60 percent) on the thickness direction extensional modulus, Esbz. The out-of-plane shear moduli, Gsbxz and Gsbyz, were significantly affected only with the use of a TLR with a shear modulus an order of magnitude greater than that of the composite lamina. A simple stiffness averaging method for calculating the elastic constants was found to compare closely with the finite element results, with the greatest difference being found in the inter-laminar shear moduli, Gsbxz and Gsbyz. Delamination initiation was studied with a strength of materials approach in the unit cell models and the flanged skin models. It was concluded that if the formation of a transverse crack is included as a source of delamination initiation, the addition of TLR will not be effective at preventing or delaying the onset of delamination. The many benefits of TLR may be accounted for by an increased resistance to delamination growth.

Dickinson, Larry Charles

1997-11-01

135

Airflow control by non-thermal plasma actuators  

NASA Astrophysics Data System (ADS)

Active flow control is a topic in full expansion due to associated industrial applications of huge importance, particularly for aeronautics. Among all flow control methods, such as the use of mechanical flaps, wall synthetic jets or MEMS, plasma-based devices are very promising. The main advantages of such systems are their robustness, simplicity, low power consumption and ability for real-time control at high frequency. This paper is a review of the worldwide works on this topic, from its origin to the present. It is divided into two main parts. The first one is dedicated to the recent knowledge concerning the electric wind induced by surface non-thermal plasma actuators, acting in air at atmospheric pressure. Typically, it can reach 8 m s-1 at a distance of 0.5 mm from the wall. In the second part, works concerning active airflow control by these plasma actuators are presented. Very efficient results have been obtained for low-velocity subsonic airflows (typically U? <= 30 m s-1 and Reynolds number of a few 105), and promising results at higher velocities indicate that plasma actuators could be used in aeronautics.

Moreau, Eric

2007-02-01

136

Inspirational airflow patterns in deviated noses: a numerical study.  

PubMed

This study attempts to evaluate the effects of deviation of external nose to nasal airflow patterns. Four typical subjects were chosen for model reconstruction based on computed tomography images of undeviated, S-shaped deviated, C-shaped deviated and slanted deviated noses. To study the hypothetical influence of deviation of external nasal wall on nasal airflow (without internal blockage), the collapsed region along the turbinate was artificially reopened in all the three cases with deviated noses. Computational fluid dynamics simulations were carried out in models of undeviated, original deviated and reopened nasal cavities at both flow rates of 167 and 500 ml/s. The shape of the anterior nasal roof was found to be collapsed on one side of the nasal airways in all the deviated noses. High wall shear stress region was found around the collapsed anterior nasal roof. The nasal resistances in cavities with deviated noses were considerably larger than healthy nasal cavity. Patterns of path-line distribution and wall shear stress distribution were similar between original deviated and reopened models. In conclusion, the deviation of an external nose is associated with the collapse of one anterior nasal roof. The crooked external nose induced a larger nasal resistance compared to the undeviated case, while the internal blockage of the airway along the turbinates further increased it. PMID:22515677

Zhu, Jian Hua; Lee, Heow Pueh; Lim, Kian Meng; Lee, Shu Jin; Teo Li San, Lynette; Wang, De Yun

2012-04-19

137

IEA BESTEST Multi-Zone Non-Airflow In-Depth Diagnostic Cases: Preprint  

Microsoft Academic Search

This paper documents a set of in-depth diagnostic test cases for multi-zone heat transfer models that do not include the heat and mass transfer effects of airflow between zones. The multi-zone non-airflow test cases represent an extension to IEA BESTEST (Judkoff and Neymark 1995a).

J. Neymark; R. Judkoff; D. Alexander; C. Felsmann; P. Strachan; A. Wijsman

2011-01-01

138

Scanning LDV for Vibration Measurement of Filiform Hairs in Crickets in Response to Induced Airflow  

Microsoft Academic Search

Cercal hairs represent in cricket a wind sensitive escape system, able to detect the airflow generated from predating species. These sensors have been studied as a biomimetic concept to allow the development of MEMS for biomedical use. In particular, the behaviour of the hairs, including airflow response, resonant frequency and damping, has been investigated up to a frequency of 20

C. Santulli; T. J. Finn; R. Seidel; G. Jeronimidis

139

Randomised controlled trial of weightlifting exercise in patients with chronic airflow limitation  

Microsoft Academic Search

BACKGROUND PATIENTS: with chronic airflow obstruction are often limited by muscle fatigue and weakness. As exercise rehabilitation programmes have produced modest improvements at best a study was designed to determine whether specific muscle training techniques are helpful. METHODS: Thirty four patients with chronic airflow limitation (forced expiratory volume in one second (FEV1) 38% of predicted values) were stratified for FEV1

K Simpson; K Killian; N McCartney; D G Stubbing; N L Jones

1992-01-01

140

IEA BESTEST Multi-Zone Non-Airflow In-Depth Diagnostic Cases: Preprint  

SciTech Connect

This paper documents a set of in-depth diagnostic test cases for multi-zone heat transfer models that do not include the heat and mass transfer effects of airflow between zones. The multi-zone non-airflow test cases represent an extension to IEA BESTEST (Judkoff and Neymark 1995a).

Neymark, J.; Judkoff, R.; Alexander, D.; Felsmann, C.; Strachan, P.; Wijsman, A.

2011-11-01

141

Characterizing Indoor Airflow and Pollutant Transport using Simulation Modeling for Prototypical Buildings. I. Office Buildings  

Microsoft Academic Search

This paper describes the first efforts at developing a set of prototypical buildings defined to capture the key features affecting airflow and pollutant transport in buildings. These buildings will be used to model airflow and pollutant transport for emergency response scenarios when limited site-specific information is available and immediate decisions must be made, and to better understand key features of

M. D. Sohn; J. M. Daisey; H. E. Feustel

1999-01-01

142

42 CFR 84.155 - Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE...  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Airflow resistance test; Type C supplied-air respirator, continuous... § 84.155 Airflow resistance test; Type C supplied-air respirator, continuous...requirements. The resistance to air flowing from the...

2010-10-01

143

42 CFR 84.155 - Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE...  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Airflow resistance test; Type C supplied-air respirator, continuous... § 84.155 Airflow resistance test; Type C supplied-air respirator, continuous...requirements. The resistance to air flowing from the...

2009-10-01

144

42 CFR 84.155 - Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE...  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Airflow resistance test; Type C supplied-air respirator, continuous... § 84.155 Airflow resistance test; Type C supplied-air respirator, continuous...requirements. The resistance to air flowing from the...

2011-10-01

145

A Theoretical Study on Airflow Motive Force and Heat Transfer by the Water Spray  

NASA Astrophysics Data System (ADS)

On assuming the abscissa moving uniformly with the horizontal airflow in disregard of gravity, airflow motive force and heat transfer by the water spray have been easily analyzed theoretically. Here main results are as follows. The theoretical maximum airflow motive pressure is proportional to both the initial relative velocity of waterdrop and the relative water flow per unit cross-sectional area of the apparatus to the airflow or the moving abscissa but unrelated to the size of waterdrop. The airflow motive pressure approaches to the above maximum with an increase in the length of the apparatus. Making the waterdrop size smaller has an effect on the aparatus to get longer virtually. The initial velocity of waterdrop or the spraying nozzle pressure has little effect on the heat transfer between the air and the water.

Sakai, Yasuyuki

146

Hydrodynamic Suppression of Soot Formation in Laminar Coflowing Jet Diffusion Flames.  

National Technical Information Service (NTIS)

Effects of flow (hydrodynamic) properties on limiting conditions for soot-free laminar non-premixed hydrocarbon/air flames (called laminar soot-point conditions) were studied, emphasizing non-buoyant laminar coflowing jet diffusion flames. Effects of air/...

Z. Dai G. M. Faeth

2000-01-01

147

42 CFR 84.153 - Airflow resistance test, Type A and Type AE supplied-air respirators; minimum requirements.  

Code of Federal Regulations, 2010 CFR

... false Airflow resistance test, Type A and Type AE supplied-air respirators; minimum...DEVICES Supplied-Air Respirators § 84.153 Airflow resistance test, Type A and Type AE supplied-air respirators; minimum... (a) Airflow resistance will be...

2010-10-01

148

42 CFR 84.154 - Airflow resistance test; Type B and Type BE supplied-air respirators; minimum requirements.  

Code of Federal Regulations, 2011 CFR

... false Airflow resistance test; Type B and Type BE supplied-air respirators; minimum...DEVICES Supplied-Air Respirators § 84.154 Airflow resistance test; Type B and Type BE supplied-air respirators; minimum... (a) Airflow resistance shall be...

2011-10-01

149

42 CFR 84.153 - Airflow resistance test, Type A and Type AE supplied-air respirators; minimum requirements.  

Code of Federal Regulations, 2011 CFR

... false Airflow resistance test, Type A and Type AE supplied-air respirators; minimum...DEVICES Supplied-Air Respirators § 84.153 Airflow resistance test, Type A and Type AE supplied-air respirators; minimum... (a) Airflow resistance will be...

2011-10-01

150

42 CFR 84.153 - Airflow resistance test, Type A and Type AE supplied-air respirators; minimum requirements.  

Code of Federal Regulations, 2010 CFR

... false Airflow resistance test, Type A and Type AE supplied-air respirators; minimum...DEVICES Supplied-Air Respirators § 84.153 Airflow resistance test, Type A and Type AE supplied-air respirators; minimum... (a) Airflow resistance will be...

2009-10-01

151

42 CFR 84.154 - Airflow resistance test; Type B and Type BE supplied-air respirators; minimum requirements.  

Code of Federal Regulations, 2010 CFR

... false Airflow resistance test; Type B and Type BE supplied-air respirators; minimum...DEVICES Supplied-Air Respirators § 84.154 Airflow resistance test; Type B and Type BE supplied-air respirators; minimum... (a) Airflow resistance shall be...

2009-10-01

152

42 CFR 84.154 - Airflow resistance test; Type B and Type BE supplied-air respirators; minimum requirements.  

Code of Federal Regulations, 2010 CFR

... false Airflow resistance test; Type B and Type BE supplied-air respirators; minimum...DEVICES Supplied-Air Respirators § 84.154 Airflow resistance test; Type B and Type BE supplied-air respirators; minimum... (a) Airflow resistance shall be...

2010-10-01

153

Velocity profiles in laminar diffusion flames  

NASA Astrophysics Data System (ADS)

Velocity profiles in vertical laminar diffusion flames were measured by using laser Doppler velocimetry (LDV). Four fuels were used: n-heptane, iso-octane, cyclohexane, and ethyl alcohol. The velocity profiles were similar for all the fuels, although there were some differences in the peak velocities. The data compared favorably with the theoretical velocity predictions. The differences could be attributed to errors in experimental positioning and in the prediction of temperature profiles. Error in the predicted temperature profiles are probably due to the difficulty in predicting the radiative heat losses from the flame.

Lyons, Valerie J.; Margle, Janice M.

1986-05-01

154

Respiratory symptoms and airflow limitation in asphalt workers  

PubMed Central

Aims: To assess the occurrence of respiratory symptoms and signs of airflow limitations in a group of asphalt workers. Methods: All 64 asphalt workers and a reference group of 195 outdoor construction workers from the same company participated in a cross-sectional study. Spirometric tests and a questionnaire on respiratory symptoms and smoking habits were administered. Respiratory symptoms and lung function were adjusted for age and smoking. Results: The FEV1/FVC% ratio was significantly lower in the asphalt workers than in the referents. Symptoms of eye irritation, chest tightness, shortness of breath on exertion, chest wheezing, physician diagnosed asthma, and chronic obstructive pulmonary disease (COPD) were all significantly more prevalent among the asphalt workers. Conclusion: In asphalt workers there is an increased risk of respiratory symptoms, lung function decline, and COPD compared to other construction workers.

Randem, B; Ulvestad, B; Burstyn, I; Kongerud, J

2004-01-01

155

Slip-boundary equations for multicomponent nonequilibrium airflow  

NASA Astrophysics Data System (ADS)

Equations are presented for the surface-slip (or jump) values of species concentration, pressure, velocity, and temperature in the low Reynolds number, high-altitude flight regime of a space vehicle. These are obtained from closed-form solutions of the mass, momentum, and energy flux equations by using the Chapman-Enskog velocity distribution function. This function represents a solution of the Boltzmann equation in the Navier-Stokes approximation. The analysis, obtained for nonequilibrium multicomponent airflow, includes the finite-rare surface catalytic recombination and changes in the internal energy during reflection from the surface. Expressions for the various slip quantities have been obtained in a form which can readily be employed in flow-field computations. A consistent set of equations is provided for multicomponent and binary mixtures and single-species gas. An expression is also provided for the finite-rate species-concentration boundary condition for a multicomponent mixture in the absence of slip.

Gupta, R. N.; Scott, C. D.; Moss, J. N.

1985-11-01

156

Characterizing buildings for airflow models: What should we measure?  

SciTech Connect

Airflow models of buildings require dozens to hundreds of parameter values, depending on the complexity of the building and the level of fidelity desired for the model. Values for many of the parameters are usually subject to very large uncertainties (possibly an order of magnitude). Experiments can be used to calibrate or ''tune'' the model: input parameters can be adjusted until predicted quantities match observations. However, experimental time and equipment are always limited and some parameters are hard to measure, so it is generally impractical to perform an exhaustive set of measurements. Consequently, large uncertainties in some parameters typically remain even after tuning the model. We propose a method to help determine which measurements will maximally reduce the uncertainties in those input parameters that have the greatest influence on behavior of interest to researchers. Implications for experimental design are discussed.

Price, P.N.; Chang, S.C.; Sohn, M.D.

2004-06-01

157

Resistance of wood chips and sawdust to airflow  

SciTech Connect

Air flow resistance through variable height columns of wood chips and sawdust was evaluated by means of the pressure drop across an orifice plate. Input pressure to the bottom of the column was controlled by means of a sliding gate valve or damper on the supply fan air intake. Flow per unit of cross section plotted against input pressure per unit of bed depth yielded the expected straight line response on a log-log plot. The response for chips was similar in both actual value and slope to the flow characteristics of similar size products such as bean pods. The flow through sawdust was similar to the flow through fescue seed. Coefficients for the classical airflow equation were evaluated from the data. 7 references.

Suggs, C.W.; Lanier, A.

1985-01-01

158

Air-Flow Simulation in Realistic Models of the Trachea  

SciTech Connect

In this article we present preliminary results from a new technique for flow simulation in realistic anatomical airways. The airways are extracted by means of Level-Sets methods that accurately model the complex and varying surfaces of anatomical objects. The surfaces obtained are defined at the sub-pixel level where they intersect the Cartesian grid of the image domain. It is therefore straightforward to construct embedded boundary representations of these objects on the same grid, for which recent work has enabled discretization of the Navier- Stokes equations for incompressible fluids. While most classical techniques require construction of a structured mesh that approximates the surface in order to extrapolate a 3D finite-element gridding of the whole volume, our method directly simulates the air-flow inside the extracted surface without losing any complicated details and without building additional grids.

Deschamps, T; Schwartz, P; Trebotich, D

2004-12-09

159

Diffusion Flames Based on a Laminar Spray Flame Library  

Microsoft Academic Search

The present paper investigates the structure of turbulent spray diffusion flames by means of numerical simulations. The flamelet model for turbulent diffusion flames has recently been extended to turbulent spray diffusion flames. The model is suitable for considering detailed chemical reactions through use of a laminar flame library consisting of structures of laminar gas diffusion flamelets that are characterized by

C. Hollmann; E. Gutheil

1998-01-01

160

Long-Range LFC (Laminar Flow Control) Transport.  

National Technical Information Service (NTIS)

M = 0.83 Laminar Flow Control (LFC) transports, carrying large percentage payloads over a range of 20000 kilometers at cruise L/D's of 39 appear feasible with large space externally braced wings, external fuel pods, active controls, and 70 percent laminar...

W. Pfenninger

1987-01-01

161

Microwave Techniques for the Combustion Enhancement of Laminar Flames  

Microsoft Academic Search

An experimental technique for using microwave power to increase the flame speed of laminar premixed flames is discussed. The microwave energy is applied by means of a rectangular resonant cavity. A laminar flame burner is used to produce a free floating flame sheet within the confines of the rectangular cavity. Upon application of microwave power, the flame sheet is observed

Daniel J. Sullivan; S. H. Zaidi; S. O. Macheret

162

Roughness and waviness requirements for laminar flow surfaces  

Microsoft Academic Search

Many modern metal and composite airframe manufacturing techniques can provide surface smoothness which is compatible with natural laminar flow (NLF) requirements. An important consideration is manufacturing roughness of the surface in the form of steps and gaps perpendicular to the freestream. The principal challenge to the design and manufacture of laminar flow surfaces today appears to be in the installation

Clifford J. Obara; Bruce J. Holmes

1986-01-01

163

The vertical, laminar, isothermal free jet with buoyancy and diffusion  

Microsoft Academic Search

The flow of a vertical, laminar, isothermal jet with strong buoyancy and diffusion is treated numerically. Computational results are compared with Laser-Doppler and interferometric measurements performed in an axisymmetric jet of hydrogen. The close agreement indicates that the numerical procedure is also appropriate for investigating laminar diffusion flames.

D. Stirnberg; E. Ronkholz; W. Merzkirch

1983-01-01

164

Application of an integral method to modelling of laminar micromixing  

Microsoft Academic Search

Laminar mixing of very viscous liquids and its effect on the course of parallel chemical reactions have been studied theoretically and experimentally. An existing model of laminar micromixing, based on an integral transformation of material balance equations in a local frame of reference attached to the Lagrangian point has been extended to account for the effects of differential diffusion. Smooth

A. Ro?e?; R. A. Bakker; J. Ba?dyga

2001-01-01

165

Mean flow of turbulent laminar patterns in plane Couette flow  

Microsoft Academic Search

A turbulent-laminar banded pattern in plane Couette flow is studied numerically. This pattern is statistically steady, is oriented obliquely to the streamwise direction, and has a very large wavelength relative to the gap. The mean flow, averaged in time and in the homogeneous direction, is analysed. The flow in the quasi-laminar region is not the linear Couette profile, but results

Dwight Barkley; Laurette S. Tuckerman

2007-01-01

166

Computational Optimization of a Natural Laminar Flow Experimental Wing Glove.  

National Technical Information Service (NTIS)

Computational optimization of a natural laminar flow experimental wing glove that is mounted on a business jet is presented and discussed. The process of designing a laminar flow wing glove starts with creating a two-dimensional optimized airfoil and then...

F. Hartshom

2012-01-01

167

Design of fuselage shapes for natural laminar flow  

Microsoft Academic Search

Recent technological advances in airplane construction techniques and materials allow for the production of aerodynamic surfaces without significant waviness and roughness, permitting long runs of natural laminar flow (NLF). The present research effort seeks to refine and validate computational design tools for use in the design of axisymmetric and nonaxisymmetric natural-laminar-flow bodies. The principal task of the investigation involves fuselage

S. S. Dodbele; C. P. Vandam; P. M. H. W. Vijgen

1986-01-01

168

The Course of Persistent Airflow Limitation in Subjects with and without Asthma  

PubMed Central

Rationale Most patients who develop persistent airflow limitation do so either as a manifestation of chronic obstructive pulmonary disease that is largely related to smoking or as a consequence of persistent asthma. We sought to compare the natural course of lung function associated with persistent airflow limitation in subjects with and without asthma from early to late adult life. Methods We studied 2552 participants aged 25 or more who had multiple questionnaire and lung function data from the long-term prospective population-based Tucson Epidemiological Study of Airway Obstructive Disease. Persistent airflow limitation was defined as FEV1/FVC ratio consistently < 70% in all completed surveys subsequent to the first survey with airflow limitation. Participants were divided into nine groups based on the combination of their physician-confirmed asthma status (never, onset ? 25 years, or onset > 25 years) and the presence of airflow limitation during the study follow-up (never, inconsistent, or persistent). Results Among subjects with an asthma onset ? 25 years, blood eosinophilia increased significantly the odds of developing persistent airflow limitation (adjOR: 3.7, 1.4–9.5), whereas cigarette smoking was the strongest risk factor for persistent airflow limitation among non-asthmatics and among subjects with asthma onset after age 25 years. Among subjects with persistent airflow limitation, the natural course of lung function differed between subjects with asthma onset ? 25 years and non-asthmatics, with the former having lower FEV1 levels at age 25 (predicted value for a 175-cm tall male of 3,400 versus 4,090 ml, respectively; p<0.001) and the latter having greater FEV1 loss between age 25 and 75 (1,590 versus 2,140 ml; p=0.003). Conclusion In subjects who have asthma onset before 25 years of age and persistent airflow limitation in adult life, the bulk of the FEV1 deficit is already established before age 25 years.

Guerra, Stefano; Sherrill, Duane L; Kurzius-Spencer, Margaret; Venker, Claire; Halonen, Marilyn; Quan, Stuart F; Martinez, Fernando D

2008-01-01

169

Airflow attenuation and bed net utilization: observations from Africa and Asia  

PubMed Central

Background/Methods Qualitative studies suggest that bed nets affect the thermal comfort of users. To understand and reduce this discomfort the effect of bed nets on temperature, humidity, and airflow was measured in rural homes in Asia and Africa, as well as in an experimental wind tunnel. Two investigators with architectural training selected 60 houses in The Gambia, Tanzania, Philippines, and Thailand. Data-loggers were used to measure indoor temperatures in hourly intervals over a 12?months period. In a subgroup of 20 houses airflow, temperature and humidity were measured at five-minute intervals for one night from 21.00 to 6.00?hrs inside and outside of bed nets using sensors and omni-directional thermo-anemometers. An investigator set up a bed net with a mesh size of 220 holes per inch2 in each study household and slept under the bed net to simulate a realistic environment. The attenuation of airflow caused by bed nets of different mesh sizes was also measured in an experimental wind tunnel. Results The highest indoor temperatures (49.0?C) were measured in The Gambia. During the hottest months of the year the mean temperature at night (9?pm) was between 33.1?C (The Gambia) and 26.2?C (Thailand). The bed net attenuated the airflow from a minimum of 27% (Philippines) to a maximum of 71% (The Gambia). Overall the bed nets reduced airflow compared to un-attenuated airflow from 9 to 4?cm?sec-1 or 52% (p?airflow of 64% (range 55 - 71%) compared to un-attenuated airflow. As expected, airflow decreased with increasing net mesh size. Nets with a mesh of 136 holes inch-2 reduced airflow by 55% (mean; range 51 - 73%). A denser net (200 holes inch-2) attenuated airflow by 59% (mean; range 56 - 74%). Discussion Despite concerted efforts to increase the uptake of this intervention in many areas uptake remains poor. Bed nets reduce airflow, but have no influence on temperature and humidity. The discomfort associated with bed nets is likely to be most intolerable during the hottest and most humid period of the year, which frequently coincides with the peak of malaria vector densities and the force of pathogen transmission. Conclusions These observations suggest thermal discomfort is a factor limiting bed net use and open a range of architectural possibilities to overcome this limitation.

2012-01-01

170

The Tla protein of Porphyromonas gingivalis W50: a homolog of the RI protease precursor (PrpRI) is an outer membrane receptor required for growth on low levels of hemin.  

PubMed Central

The prpR1 gene of Porphyromonas gingivalis W50 encodes the polyprotein precursor (PrpRI) of an extracellular arginine-specific protease. PrpRI is organized into four distinct domains (pro, alpha, beta, and gamma) and is processed to a heterodimeric protease (RI) which comprises the alpha and beta components in a noncovalent association. The alpha component contains the protease active site, whereas the beta component appears to have a role in adherence and hemagglutination processes. DNA sequences homologous to the coding region for the RI beta component are present at multiple loci on the P. gingivalis chromosome and may represent a family of related genes. In this report, we describe the cloning, sequence analysis, and characterization of one of these homologous loci isolated in plasmid pJM7. The 6,041-bp P. gingivalis DNA fragment in pJM7 contains a major open reading frame of 3,291 bp with coding potential for a protein with an Mr 118,700. An internal region of the deduced sequence (V304 to N768) shows 98% identity to the beta domain of PrpRI, and the recombinant product of pJM7 is immunoreactive with an antibody specific to the RI beta component. The N terminus of the deduced sequence has regional similarity to TonB-linked receptors which are frequently involved in periplasmic translocation of hemin, iron, colicins, or vitamin B12 in other bacteria. We have therefore designated this gene tla (TonB-linked adhesin). In contrast to the parent strain, an isogenic mutant of P. gingivalis W50 in which the tla was insertionally inactivated was unable to grow in medium containing low concentrations of hemin (<2.5 mg liter(-1)), and hemin-depleted cells of this mutant failed to respond to hemin in an agar diffusion plate assay. These data suggest a role for this gene product in hemin acquisition and utilization. Furthermore, the mutant produced significantly less arginine- and lysine-specific protease activities than the parent strain, indicating that there may be a regulatory relationship between tla and other members of this gene family.

Aduse-Opoku, J; Slaney, J M; Rangarajan, M; Muir, J; Young, K A; Curtis, M A

1997-01-01

171

Thermohydrodynamic analysis for laminar lubricating films  

NASA Astrophysics Data System (ADS)

A Galerkin-type analysis to include thermal effects in laminar lubricating films was performed. The lubricant properties were assumed constant except for a temperature-dependent Newtonian viscosity. The cross-film temperature profile is established by collocation at the film boundaries and two interior Lobatto points. The interior temperatures are determined by requiring that the zeroth and first moment of the energy equation be satisfied across the film. The fluidity is forced to conform to a third--degree polynomial appropriate to the Lobatto-point temperatures. Preliminary indications are that the use of just two such sampling points enables satisfactory prediction of bearing performance even in the presence of substantial viscosity variation.

Elrod, H. G.; Brewe, D. E.

1986-09-01

172

Laminar Superlayer at the Turbulence Boundary  

NASA Astrophysics Data System (ADS)

In this Letter we present results from particle tracking velocimetry and direct numerical simulation that are congruent with the existence of a laminar superlayer, as proposed in the pioneering work of Corrsin and Kistler (NACA, Technical Report No. 1244, 1955). We find that the local superlayer velocity is dominated by a viscous component and its magnitude is comparable to the characteristic velocity of the smallest scales of motion. This slow viscous process involves a large surface area so that the global rate of turbulence spreading is set by the largest scales of motion. These findings are important for a better understanding of mixing of mass and momentum in a variety of flows where thin layers of shear exist. Examples are boundary layers, clouds, planetary atmospheres, and oceans.

Holzner, M.; Lüthi, B.

2011-04-01

173

Order parameter in laminar-turbulent patterns  

NASA Astrophysics Data System (ADS)

Over a century, and thousands of articles, after Reynolds' description of the transition to turbulence in pipe flow, a predictive theory of transition is still unavailable. One of the most intriguing phenomena observed near transition ishe coexistence of well-defined and long-lived laminar and turbulent regions, first observed in counter-rotating Taylor-Couette flow in the 1960s [1]. In the 2000s, Prigent & Dauchot [2] showed that these coexisting regions were part of a regular pattern of stripes, whose wavelength and orientation are Reynolds-number-dependent and reproducible. Analogous phenomena have been observed experimentally [2] and numerically [3] in plane Couette flow, in stator-rotor experiments (the flow between a stationary and a rotating disk) [4], in plane Poiseuille simulations [5], and, most recently, in simulations of pipe flow [6].

Tuckerman, L. S.; Barkley, D.; Moxey, D.; Dauchot, O.

174

On the evolution of laminar vortex rings  

NASA Astrophysics Data System (ADS)

Using Laser Doppler Anemometry (LDA) and Digital Particle Image Velocimetry (DPIV), the physical properties of laminar vortex rings are investigated in the Reynolds-number range 830 ? Re ? 1650. The measured initial circulations of the vortex rings are found to agree well with corrected versions of the vorticity-flux (slug-flow) model proposed by Didden and Pullin. The DPIV and LDA data show excellent agreement regarding local velocities and vortex-ring circulations. The DPIV data depict the distribution of the vorticity and circulation in the core regions, where the resulting vorticity distributions are found to be self-similar Gaussian profiles. The propagation velocity of the vortex rings is well approximated by an analytical model of Saffman for large core sizes. In the asymptotic limit t ? ?, the trajectories are in excellent agreement with the exact Stokes-dipole solution of Cantwell and Rott.

Weigand, A.; Gharib, M.

1997-04-01

175

Modeled velocity of airflow in the airways during various respiratory patterns.  

PubMed

Our modeling and simulation of the respiratory system with Weibel's morphometry shows that the average velocity of expiratory airflow is always greater than the average velocity of inspiratory airflow during tidal breathing when the intervals of inspiration and expiration are same. A nonlinear circuit model was developed comprised with the upper airway, the conducting airways (trachea approximately terminal bronchioles), and the lumped alveolar space. These compartments are established with known physiologic pulmonary characteristics that are represented by nonlinear resistors and capacitors. In this paper we set up the circuit model reflecting the geometric variation of airways during tidal breathing, and demonstrated computation results for the velocity of airflow along the airways based on 16 different respiratory patterns. The circuit model offers a convenient method that can be used to investigate the velocity of airflow and its interaction with mucus, as well as suggests a basic model for our future research on analyzing airway clearance techniques. PMID:17271155

Sohn, Kiwon; Holte, James; Phillips, James; Warwick, Warren

2004-01-01

176

Cost-Effectiveness of Increasing Airflow at Any Location in Underground Coal Mines. Volume 1.  

National Technical Information Service (NTIS)

This report presents the results of the economic analysis of several applicable alternatives to increase airflow in four underground coal mines. Pressure-quantity surveys were conducted underground and measurements were made at the main mine fans. The exi...

S. K. Mukherjee A. W. Laurito M. O. Rahim M. M. Singh

1983-01-01

177

Modeling Airflow Using Subject-Specific 4DCT-Based Deformable Volumetric Lung Models  

PubMed Central

Lung radiotherapy is greatly benefitted when the tumor motion caused by breathing can be modeled. The aim of this paper is to present the importance of using anisotropic and subject-specific tissue elasticity for simulating the airflow inside the lungs. A computational-fluid-dynamics (CFD) based approach is presented to simulate airflow inside a subject-specific deformable lung for modeling lung tumor motion and the motion of the surrounding tissues during radiotherapy. A flow-structure interaction technique is employed that simultaneously models airflow and lung deformation. The lung is modeled as a poroelastic medium with subject-specific anisotropic poroelastic properties on a geometry, which was reconstructed from four-dimensional computed tomography (4DCT) scan datasets of humans with lung cancer. The results include the 3D anisotropic lung deformation for known airflow pattern inside the lungs. The effects of anisotropy are also presented on both the spatiotemporal volumetric lung displacement and the regional lung hysteresis.

Ilegbusi, Olusegun J.; Li, Zhiliang; Seyfi, Behnaz; Min, Yugang; Meeks, Sanford; Kupelian, Patrick; Santhanam, Anand P.

2012-01-01

178

Compressible laminar streaks with wall suction  

NASA Astrophysics Data System (ADS)

The response of a compressible laminar boundary layer subject to free-stream vortical disturbances and steady mean-flow wall suction is studied. The theoretical frameworks of Leib et al. [J. Fluid Mech. 380, 169-203 (1999)] and Ricco and Wu [J. Fluid Mech. 587, 97-138 (2007)], based on the linearized unsteady boundary-region equations, are adopted to study the influence of suction on the kinematic and thermal streaks arising through the interaction between the free-stream vortical perturbations and the boundary layer. In the asymptotic limit of small spanwise wavelength compared with the boundary layer thickness, i.e., when the disturbance flow is conveniently described by the steady compressible boundary region equations, the effect of suction is mild on the velocity fluctuations and negligible on the temperature fluctuations. When the spanwise wavelength is comparable with the boundary layer thickness, small suction values intensify the supersonic streaks, while higher transpiration levels always stabilize the disturbances at all Mach numbers. At larger spanwise wavelengths, very small amplitudes of wall transpiration have a dramatic stabilizing effect on all boundary layer fluctuations, which can take the form of transiently growing thermal streaks, large amplitude streamwise oscillations, or oblique exponentially growing Tollmien-Schlichting waves, depending on the Mach number and the wavelengths. The range of wavenumbers for which the exponential growth occurs becomes narrower and the location of instability is significantly shifted downstream by mild suction, indicating that wall transpiration can be a suitable vehicle for delaying transition when the laminar breakdown is promoted by these unstable disturbances. The typical streamwise wavelength of these disturbances is instead not influenced by suction, and asymptotic triple deck theory predicts the strong changes in growth rate and the very mild modifications in streamwise wavenumber in the limit of larger downstream distance and small spanwise wavenumber.

Ricco, Pierre; Shah, Daniel; Hicks, Peter D.

2013-05-01

179

Effects of airflow on body temperatures and sleep stages in a warm humid climate  

NASA Astrophysics Data System (ADS)

Airflow is an effective way to increase heat loss—an ongoing process during sleep and wakefulness in daily life. However, it is unclear whether airflow stimulates cutaneous sensation and disturbs sleep or reduces the heat load and facilitates sleep. In this study, 17 male subjects wearing short pyjamas slept on a bed with a cotton blanket under two of the following conditions: (1) air temperature (Ta) 26°C, relative humidity (RH) 50%, and air velocity (V) 0.2 m s-1; (2) Ta 32°C, RH 80%, V 1.7 m s-1; (3) Ta 32°C; RH 80%, V 0.2 m s-1 (hereafter referred to as 26/50, 32/80 with airflow, and 32/80 with still air, respectively). Electroencephalograms, electrooculograms, and mental electromyograms were obtained for all subjects. Rectal (Tre) and skin (Ts) temperatures were recorded continuously during the sleep session, and body-mass was measured before and after the sleep session. No significant differences were observed in the duration of sleep stages between subjects under the 26/50 and 32/80 with airflow conditions; however, the total duration of wakefulness decreased significantly in subjects under the 32/80 with airflow condition compared to that in subjects under the 32/80 with still air condition ( P < 0.05). Tre, Tsk, Ts, and body-mass loss under the 32/80 with airflow condition were significantly higher compared to those under the 26/50 condition, and significantly lower than those under the 32/80 with still air condition ( P < 0.05). An alleviated heat load due to increased airflow was considered to exist between the 32/80 with still air and the 26/50 conditions. Airflow reduces the duration of wakefulness by decreasing Tre, Tsk, Ts, and body-mass loss in a warm humid condition.

Tsuzuki, Kazuyo; Okamoto-Mizuno, Kazue; Mizuno, Koh; Iwaki, Tatsuya

2008-03-01

180

Modelling the Effect of Tree Foliage on Sprayer Airflow in Orchards  

Microsoft Academic Search

The effect of tree foliage on sprayer airflow through pear trees in a fruit orchard was studied and modelled in detail. A\\u000a new three-dimensional (3-D) computational fluid dynamics model that integrates the 3-D canopy architecture with a local closure\\u000a model to simulate the effect of the stem and branches and leaves of trees separately on airflow was developed. The model

Ayenew Melese Endalew; Christof Debaer; Nick Rutten; Jef Vercammen; Mulugeta Admasu Delele; Herman Ramon; Bart M. Nicolaï; Pieter Verboven

2011-01-01

181

Effects of swirling airflow and divergence angle of airblast atomizer on atomization performance  

NASA Astrophysics Data System (ADS)

The effects of swirling airflow and divergence angle on the atomizing performance of an airblast atomizer were studied. Six different atomizers having three kinds of blade angle swirlers and three kinds of exit divergence angle have been tested, and the results have been analyzed. It is concluded that the swirling airflow and the divergence angle have little influence on the atomizing performance. Therefore atomizers may be designed chiefly according to the flow pattern needed in the combustor.

Zhao, Qishou; Lin, Lijun; Yuan, Quanchao

1987-04-01

182

Investigation on side-spray fluidized bed granulation with swirling airflow.  

PubMed

Top-spray fluidized bed granulation with axial fluidization airflow from the bottom of the granulator is well-established in the pharmaceutical industry. The application of swirling airflow for fluidized bed granulation was more recently introduced. This study examined the effects of various process parameters on the granules produced by side-spray fluidized bed with swirling airflow using the central composite and Box-Behnken design of experiment. Influence of the amount of binder solution, spray rate, and distance between spray nozzle and powder bed were initially studied to establish operationally viable values for these parameters. This was followed by an in-depth investigation on the effects of inlet airflow rate, atomizing air pressure and distance between spray nozzle and powder bed on granule properties. It was found that the amount of binder solution had a positive correlation with granule size and percentage of lumps but a negative correlation with size distribution and Hausner ratio of the granules. Binder solution spray rate was also found to affect the granules size. High drug content uniformity was observed in all the batches of granules produced. Both inlet airflow rate and atomizing air pressure were found to correlate negatively with granule size and percentage of lumps but correlate positively with the size distribution of the granule produced. Percentage of fines was found to be significantly affected by inlet airflow rate. Distance between spray nozzle and powder bed generally affected the percentage of lumps. PMID:23263750

Wong, Poh Mun; Chan, Lai Wah; Heng, Paul Wan Sia

2012-12-21

183

An investigation on airflow in disordered nasal cavity and its corrected models by tomographic PIV  

NASA Astrophysics Data System (ADS)

Knowledge of airflow characteristics in nasal cavities is essential to understand the physiology and pathology aspects of nasal breathing. Several studies have utilized physical models of the healthy nasal cavity to investigate the relationship between nasal anatomy and airflow. Since the final goal of these works is their contribution to the diagnosis and treatment of nasal diseases, therefore, the next step in this topic must be followed by the studies for disordered nasal cavities. In this paper, airflows in normal and abnormal nasal cavities and surgically created models, which simulate surgical treatment, are investigated experimentally by PIV. High-resolution computerized tomogram data and careful manipulation of the model surface by the ear, nose and throat doctor provide more sophisticated nasal cavity models. The correlation based correction PIV algorithm with window offset is used for PIV flow analysis. Average and RMS distributions in sagittal and coronal sections are obtained for inspiratory and expiratory nasal airflows. Comparisons in nasal airflows for both normal and abnormal cases are also examined. Airflow characteristics that are related to the abnormalities in the nasal cavity are proposed. In the case of simulations of surgical operations, velocity and RMS distributions in coronal section change locally, this may cause some difficulties in physiologic functions of noses and may hurt mucosal surface.

Kim, S. K.; Chung, S. K.

2004-06-01

184

Oscillating and star-shaped drops levitated by an airflow  

NASA Astrophysics Data System (ADS)

We investigate the spontaneous oscillations of drops levitated above an air cushion, eventually inducing a breaking of axisymmetry and the appearance of “star drops”. This is strongly reminiscent of the Leidenfrost stars that are observed for drops floating above a hot substrate. The key advantage of this work is that we inject the airflow at a constant rate below the drop, thus eliminating thermal effects and allowing for a better control of the flow rate. We perform experiments with drops of different viscosities and observe stable states, oscillations, and chimney instabilities. We find that for a given drop size the instability appears above a critical flow rate, where the latter is largest for small drops. All these observations are reproduced by numerical simulations, where we treat the drop using potential flow and the gas as a viscous lubrication layer. Qualitatively, the onset of instability agrees with the experimental results, although the typical flow rates are too large by a factor 10. Our results demonstrate that thermal effects are not important for the formation of star drops and strongly suggest a purely hydrodynamic mechanism for the formation of Leidenfrost stars.

Bouwhuis, Wilco; Winkels, Koen G.; Peters, Ivo R.; Brunet, Philippe; van der Meer, Devaraj; Snoeijer, Jacco H.

2013-08-01

185

Oscillating and star-shaped drops levitated by an airflow.  

PubMed

We investigate the spontaneous oscillations of drops levitated above an air cushion, eventually inducing a breaking of axisymmetry and the appearance of "star drops". This is strongly reminiscent of the Leidenfrost stars that are observed for drops floating above a hot substrate. The key advantage of this work is that we inject the airflow at a constant rate below the drop, thus eliminating thermal effects and allowing for a better control of the flow rate. We perform experiments with drops of different viscosities and observe stable states, oscillations, and chimney instabilities. We find that for a given drop size the instability appears above a critical flow rate, where the latter is largest for small drops. All these observations are reproduced by numerical simulations, where we treat the drop using potential flow and the gas as a viscous lubrication layer. Qualitatively, the onset of instability agrees with the experimental results, although the typical flow rates are too large by a factor 10. Our results demonstrate that thermal effects are not important for the formation of star drops and strongly suggest a purely hydrodynamic mechanism for the formation of Leidenfrost stars. PMID:24032934

Bouwhuis, Wilco; Winkels, Koen G; Peters, Ivo R; Brunet, Philippe; van der Meer, Devaraj; Snoeijer, Jacco H

2013-08-19

186

Structure of the Laminar Ablating Air-Teflon Boundary Layer.  

National Technical Information Service (NTIS)

Radiation profiles in an ablating flat plate air-teflon laminar boundary layer were studied both experimentally and theoretically. The experiments were conducted in a one atmosphere, 3000 - 6000K, subsonic free stream produced by an arc jet. Spatially res...

R. A. Greenberg N. H. Kemp K. L. Wray

1968-01-01

187

Frost Growth and Densification in Laminar Flow Over Flat Surfaces.  

National Technical Information Service (NTIS)

One-dimensional frost growth and densification in laminar flow over flat surfaces has been theoretically investigated. Improved representations of frost density and effective thermal conductivity applicable to a wide range of frost circumstances have been...

M. Kandula

2011-01-01

188

The laminar-turbulent transition in a fibre laser  

NASA Astrophysics Data System (ADS)

Studying the transition from a linearly stable coherent laminar state to a highly disordered state of turbulence is conceptually and technically challenging, and of great interest because all pipe and channel flows are of that type. In optics, understanding how a system loses coherence, as spatial size or the strength of excitation increases, is a fundamental problem of practical importance. Here, we report our studies of a fibre laser that operates in both laminar and turbulent regimes. We show that the laminar phase is analogous to a one-dimensional coherent condensate and the onset of turbulence is due to the loss of spatial coherence. Our investigations suggest that the laminar-turbulent transition in the laser is due to condensate destruction by clustering dark and grey solitons. This finding could prove valuable for the design of coherent optical devices as well as systems operating far from thermodynamic equilibrium.

Turitsyna, E. G.; Smirnov, S. V.; Sugavanam, S.; Tarasov, N.; Shu, X.; Babin, S. A.; Podivilov, E. V.; Churkin, D. V.; Falkovich, G.; Turitsyn, S. K.

2013-10-01

189

Laminar burning velocity of hydrogen–methane\\/air premixed flames  

Microsoft Academic Search

The laminar burning velocities of hydrogen–methane\\/air mixtures at NTP conditions were calculated using the CHEMKIN PREMIX code with the GRI kinetic mechanism. The equivalence ratio and the fuel composition were varied from lean to rich and from pure methane to pure hydrogen, respectively.The results show that the values of the blends laminar burning velocities are always smaller than those obtained

V. Di Sarli; A. Di Benedetto

2007-01-01

190

Flame\\/stretch interactions in laminar and turbulent premixed flames  

Microsoft Academic Search

The flame\\/stretch interactions of laminar and turbulent premixed flames are considered both experimentally and computationally. Potentially strong effects of flame\\/stretch interactions due to preferential-diffusion phenomena within practical turbulent premixed flames were suggested by experiments and numerical simulations of spherical outwardly propagating laminar premixed flames. These considerations were limited to conditions where ignition disturbances, pressure variations, intrinsic unsteadiness of propagating spherical

K. T. Aung; M. I. Hassan; S. Kwon; L.-K. Tseng; O.-C. Kwon; G. M. Faeth

2002-01-01

191

Laminar flow integration: Flight tests status and plans  

Microsoft Academic Search

Under the Aircraft Energy Efficiency - Laminar Flow Control Program, there are currently three flight test programs under way to address critical issues concerning laminar flow technology application to commercial transports. The Leading-Edge Flight Test (LEFT) with a JetStar aircraft is a cooperative effort with the Ames\\/Dryden Flight Research Facility to provide operational experience with candidate leading-edge systems representative of

R. D. Wagner; D. F. Fisher; M. C. Fischer; D. W. Bartlett; R. R. Meyer Jr.

1986-01-01

192

Numerische Simulation Laminarer Hyperschall-Stroemungen Um Ellipsoide (Numerical Simulation of Laminar Hypersonic Flows About an Ellipsoid).  

National Technical Information Service (NTIS)

The laminar hypersonic flow about a double ellipsoid, which idealizes the nose and cockpit of a spacecraft, were numerically simulated. The calculation method solves the three dimensional thin layer Navier-Stokes equations in a conservative formulation on...

S. Riedelbauch B. Mueller

1988-01-01

193

Can gestational Hypertension Be modified By Treating nocturnal airflow Limitation?  

PubMed Central

Objective: Recent evidence suggests that women with gestational hypertension (GH) have a high rate of sleep disordered breathing (SDB), and treatment for even marginal SDB may improve blood pressure control in women with GH. We assessed whether the application SDB treatment could improve blood pressure in women with GH. Methods: This was a single-center randomized study. Subjects underwent an unattended home-based diagnostic sleep study. The study was then repeated with subjects wearing one of two randomly assigned treatments: auto-titrating continuous positive airway pressure (auto-CPAP) or mandibular advancement device (MAD) + nasal strip. First morning blood pressure and blood for standard GH measures plus inflammatory markers were taken after each study. Subjects completed a series of questionnaires addressing sleep quality and tolerance of assigned therapy. Results: Twenty-four women completed the protocol—13 in the MAD group and 11 in auto-CPAP. The overall rate of SDB was 38%. Auto-CPAP was more effective at treating SDB than MAD + nasal strip, although the women randomized to MAD + nasal strip reported the greater comfort with therapy. First morning blood pressure was not consistently improved with either therapy. When subjects were stratified according to those whose blood pressure increased or decreased with therapy, an association was suggested between blood pressure improvement and reduced levels of tumour necrosis factor-?. Conclusion: We demonstrated that 38% of women with GH had concurrent SDB. We did not find an improvement in blood pressure or inflammatory markers with a single night of either the auto-CPAP or MAD + nasal strip interventions. However important lessons from this study may guide future investigations in this area. Citation: Reid J; Taylor-Gjevre R; Gjevre J; Skomro R; Fenton M; Olatunbosun F; Gordon JR; Cotton D. Can gestational hypertension be modified by treating nocturnal airflow limitation? J Clin Sleep Med 2013;9(4):311-317.

Reid, John; Taylor-Gjevre, Regina; Gjevre, John; Skomro, Robert; Fenton, Mark; Olatunbosun, Femi; Gordon, John R.; Cotton, David

2013-01-01

194

Rain-induced subsurface airflow and Lisse effect  

USGS Publications Warehouse

Water-level increase after rainfall is usually indicative of rainfall recharge to groundwater. This, however, may not be true if the Lisse effect occurs. This effect represents the water-level increase in a well driven by airflow induced by an advancing wetting front during highly intensive rains. The rainwater, which may behave like a low-permeability lid, seals the ground surface so that the air pressure beneath the wetting front is increased because of air compression due to downward movement of the wetting front. A rapid and substantial rise of the water level in the well screened below water table, which bears no relationship to groundwater recharge, can be induced when various factors such as soil properties and the rain-runoff condition combine favorably. A transient, three-dimensional and variably saturated flow model was employed to study the air and groundwater flows in the soil under rain conditions. The objectives of this paper are two-fold: to evaluate the reliability of the theory of the Lisse effect presented by Weeks to predict its magnitude in modeled situations that mimic the physical complexity of real aquifers, and to conduct parametric studies on the sensitivity of the water-level rise in the well to soil properties and the rain event. The simulation results reveal that the magnitude of the Lisse effect increases with the ponding depth. Soil permeability plays a key role in generating the Lisse effect. The water-level rise in the well is delayed relative to the air-pressure rise in the unsaturated zone when the soil permeability is low, and the maximum water-level rise is less than the maximum air pressure induced by rain infiltration. The simulation also explores the sensitivity of the Lisse effect to the van Genuchten parameters and the water table depth. Copyright 2008 by the American Geophysical Union.

Guo, H.; Jiao, J. J.; Weeks, E. P.

2008-01-01

195

Statistical data analysis method for multi-zonal airflow measurement using multiple kinds of perfluorocarbon tracer gas  

Microsoft Academic Search

Conventional multi-zonal ventilation measurement methods by multiple types of perfluorocarbon tracers use a number of different gases equal to the number of zones (n). The possible n×n+n airflows are estimated from the mass balance of the gases and the airflow balance. However, some airflows may not occur because of inter-zonal geometry, and the introduction of unnecessary, unknown parameters can impair

Hiroyasu Okuyama; Yoshinori Onishi; Shin-ichi Tanabe; Seiichi Kashihara

2009-01-01

196

A New Approach to Laminar Flowmeters  

PubMed Central

After studying the performance and characteristics of actual laminar flowmeters a new disposition for this type of sensors is proposed in such a way that the measurement errors introduced by the intrinsic nature of the device can be minimized. The preliminary study shows that the developing entry region introduces non-linearity effects in all these devices. These effects bring about not only errors, but also a change in the slope of the linear calibration respect of the Poiseuille relation. After a subsequent analysis on how these non-linearity errors can be reduced, a new disposition of this type of flowmeters is introduced. This device makes used of flow elements having pressure taps at three locations along its length and connected to three isolated chambers. In this way, the static pressure can be measured at three locations and contributed to by the pressure taps at the level of each chamber. Thus the linearization error is reduced with an additional advantage of producing a reduced pressure drop.

Pena, Fernando Lopez; Diaz, Alvaro Deibe; Lema, Marcos Rodriguez; Rodriguez, Santiago Vazquez

2010-01-01

197

Modelling the Effect of Tree Foliage on Sprayer Airflow in Orchards  

NASA Astrophysics Data System (ADS)

The effect of tree foliage on sprayer airflow through pear trees in a fruit orchard was studied and modelled in detail. A new three-dimensional (3-D) computational fluid dynamics model that integrates the 3-D canopy architecture with a local closure model to simulate the effect of the stem and branches and leaves of trees separately on airflow was developed. The model was validated with field observations made in an experimental orchard (pcfruit, Sint-Truiden, Belgium) in spring and summer 2008 and was used to investigate the airflow from three air-assisted orchard sprayers (Condor V, Duoprop and AirJet quatt). Velocity magnitudes were measured before and behind leafless and fully-leafed pear canopies across the row while the operating sprayers are passing along the row, and were compared with the simulations. The simulation results predicted the measured values well with all the local relative errors within 20%. The effect of foliar density on airflow from the three air assisted sprayers was manifested by changing the magnitude and direction of the sprayers' air velocity behind the canopy, especially at the denser regions of the canopy and by changing the pattern of velocity decay horizontally along the jet. The developed methodology will also allow a thorough investigation of atmospheric airflow in canopy structures.

Melese Endalew, Ayenew; Debaer, Christof; Rutten, Nick; Vercammen, Jef; Delele, Mulugeta Admasu; Ramon, Herman; Nicolaï, Bart M.; Verboven, Pieter

2011-01-01

198

Changes in nasal airflow and heat transfer correlate with symptom improvement after surgery for nasal obstruction.  

PubMed

Surgeries to correct nasal airway obstruction (NAO) often have less than desirable outcomes, partly due to the absence of an objective tool to select the most appropriate surgical approach for each patient. Computational fluid dynamics (CFD) models can be used to investigate nasal airflow, but variables need to be identified that can detect surgical changes and correlate with patient symptoms. CFD models were constructed from pre- and post-surgery computed tomography scans for 10 NAO patients showing no evidence of nasal cycling. Steady-state inspiratory airflow, nasal resistance, wall shear stress, and heat flux were computed for the main nasal cavity from nostrils to posterior nasal septum both bilaterally and unilaterally. Paired t-tests indicated that all CFD variables were significantly changed by surgery when calculated on the most obstructed side, and that airflow, nasal resistance, and heat flux were significantly changed bilaterally as well. Moderate linear correlations with patient-reported symptoms were found for airflow, heat flux, unilateral allocation of airflow, and unilateral nasal resistance as a fraction of bilateral nasal resistance when calculated on the most obstructed nasal side, suggesting that these variables may be useful for evaluating the efficacy of nasal surgery objectively. Similarity in the strengths of these correlations suggests that patient-reported symptoms may represent a constellation of effects and that these variables should be tracked concurrently during future virtual surgery planning. PMID:24063885

Kimbell, J S; Frank, D O; Laud, Purushottam; Garcia, G J M; Rhee, J S

2013-08-26

199

Airflow field around an operating tire and its effect on tire power loss  

SciTech Connect

The airflow direction, velocity, and turbulence level were measured aroung the left front tire of a passenger car operating on-road over the normal driving speed range. Both photographic and hot-wire anemometer techniques were employed. The measured airflow field, and other idealized ones, were used to select appropriate values for the tire heat transfer coefficient from previous GMR work. Tire power loss was then calculated with the GMR Combined Thermo-Mechanical Model to assess the importance of the airflow field on tire power loss. It was found that for the range of realistic flow conditios, tire power loss could be changed by up to 6% by the flow conditions alone.

Oswald, L.J.; Browne, A.L.

1981-01-01

200

Laminar flow integration: Flight tests status and plans  

NASA Astrophysics Data System (ADS)

Under the Aircraft Energy Efficiency - Laminar Flow Control Program, there are currently three flight test programs under way to address critical issues concerning laminar flow technology application to commercial transports. The Leading-Edge Flight Test (LEFT) with a JetStar aircraft is a cooperative effort with the Ames/Dryden Flight Research Facility to provide operational experience with candidate leading-edge systems representative of those that might be used on a future transport. In the Variable Sweep Transition Flight Experiment (VSTFE), also a cooperative effort between Langley and Ames/Dryden, basic transition data on an F-14 wing with variable sweep will be obtained to provide a data base for laminar flow wing design. Finally, under contract to the Boeing Company, the acoustic environment on the wing of a 757 aircraft will be measured and the influence of engine noise on laminar flow determined with a natural laminar flow glove on the wing. The status and plans for these programs are reported.

Wagner, R. D.; Fisher, D. F.; Fischer, M. C.; Bartlett, D. W.; Meyer, R. R., Jr.

1986-12-01

201

Inspiratory airflow dynamics during sleep in irritable bowel syndrome: a pilot study  

Microsoft Academic Search

Purpose  This study is a preliminary test of the hypothesis that the pathophysiology of irritable bowel syndrome (IBS) derives from\\u000a pharyngeal collapse during sleep.\\u000a \\u000a \\u000a \\u000a \\u000a Materials and methods  We studied inspiratory airflow dynamics during sleep in 12 lean females with IBS and 12 healthy female controls matched for\\u000a age and obesity. A standard clinical polysomnogram (airflow measured with a nasal\\/oral pressure catheter) was

Avram R. Gold; Joan E. Broderick; Mohammad M. Amin; Morris S. Gold

2009-01-01

202

The effect of lignocaine on nasal resistance and nasal sensation of airflow.  

PubMed

The effect of lignocaine on nasal sensation of airflow and nasal resistance was assessed in twenty-five subjects. A randomised crossover trial was conducted with lignocaine as the active drug and saline as the placebo. Both substances were delivered to the nasal mucosa as a nasal spray. Lignocaine caused a sensation of increased nasal patency in twenty-two of the twenty-five subjects studied. Saline had no such effect. The difference between this subjective effect of the two substances was highly significant (p less than 0.001). Neither spray had any significant effect on nasal resistance to airflow assessed objectively by rhinomanometry. PMID:3518333

Jones, A S; Lancer, J M; Shone, G; Stevens, J C

203

[Three dimensional reconstruction of the nasal cavity structure and numerical simulation of airflow].  

PubMed

The nasal cavity structure of one patient was reconstructed by the method of surface rendering based on his CT images. In a respiratory period the change of air flux in the nasal cavity was supposed based on the tidal volume and the respiratory period gained by statistical method. The digital simulation and the analysis of the airflow in the nasal cavity was made by the FEA method and the result was compared with the data from literatures. The comparison indicates that the result is confident. From the result we can observe the airflow distribution quantitatively in the nasal cavity in the period of respiration. PMID:17228700

Sun, Xiuzhen; Yu, Shen; Liu, Yingxi; Zheng, Zhaopan; Zhang, Jun

2006-12-01

204

42 CFR 84.157 - Airflow resistance test; Type C supplied-air respirator, pressure-demand class; minimum...  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Airflow resistance test; Type C supplied-air respirator, pressure-demand...84.157 Airflow resistance test; Type C supplied-air respirator, pressure-demand...c) The exhalation resistance to a flow of air at a rate of 85...

2011-10-01

205

42 CFR 84.156 - Airflow resistance test; Type C supplied-air respirator, demand class; minimum requirements.  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Airflow resistance test; Type C supplied-air respirator, demand...84.156 Airflow resistance test; Type C supplied-air respirator, demand...b) The exhalation resistance to a flow of air at a rate of 85...

2010-10-01

206

42 CFR 84.157 - Airflow resistance test; Type C supplied-air respirator, pressure-demand class; minimum...  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Airflow resistance test; Type C supplied-air respirator, pressure-demand...84.157 Airflow resistance test; Type C supplied-air respirator, pressure-demand...c) The exhalation resistance to a flow of air at a rate of 85...

2009-10-01

207

42 CFR 84.156 - Airflow resistance test; Type C supplied-air respirator, demand class; minimum requirements.  

Code of Federal Regulations, 2010 CFR

...2009-10-01 false Airflow resistance test; Type C supplied-air respirator, demand...84.156 Airflow resistance test; Type C supplied-air respirator, demand...b) The exhalation resistance to a flow of air at a rate of 85...

2009-10-01

208

42 CFR 84.157 - Airflow resistance test; Type C supplied-air respirator, pressure-demand class; minimum...  

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Airflow resistance test; Type C supplied-air respirator, pressure-demand...84.157 Airflow resistance test; Type C supplied-air respirator, pressure-demand...c) The exhalation resistance to a flow of air at a rate of 85...

2010-10-01

209

42 CFR 84.156 - Airflow resistance test; Type C supplied-air respirator, demand class; minimum requirements.  

Code of Federal Regulations, 2011 CFR

...2011-10-01 false Airflow resistance test; Type C supplied-air respirator, demand...84.156 Airflow resistance test; Type C supplied-air respirator, demand...b) The exhalation resistance to a flow of air at a rate of 85...

2011-10-01

210

Measurement of Airflow around the Human Body with Wide-cover Type Personal Air-conditioning with PIV  

Microsoft Academic Search

Many existing personal air-conditioning systems cool only specific portions of the human body in the form of spot cooling, using either cooled or fast airflow to control thermal sensation. This may cause various problems related to localized airflow, such as discomfort to the face and neck areas and dryness in the eyes. Therefore, a method is proposed in this research

Jeong-Hoon Yang; Shinsuke Kato; Ho-Tae Seok

2009-01-01

211

Study of Airflow around Occupants Seated in Desks Equipped with Upper and Lower Air Terminal Devices for Slightly Warm Environments  

Microsoft Academic Search

This paper will discuss the study of turbulent and mean airflow exiting air terminal devices and surrounding occupants seated in classroom desks for slightly warm environments equipped with personalized ventilation systems with upper and lower air terminal devices. In the turbulent airflow analysis the air root mean square, the air turbulence intensity, and the air velocity fluctuations frequencies are calculated,

Eusébio Z. E. Conceição; Sílvia P. Rosa; Ana L. V. Custódio; Renata L. Andrade; Maria J. P. A. Meira; M Manuela J. R. Lúcio

2010-01-01

212

Computational modeling of airflow patterns and heat transfer prediction through stacked layers' products in a vented box during cooling  

Microsoft Academic Search

Efficiency of forced-air cooling processes is measured by process time and product temperature uniformity. Ventilated packaging is required to achieve a rapid and uniform cooling process. Product type, produce positioning and orientation and container venting have significant effects on airflow patterns. To optimize the design, airflow patterns and temperature distributions inside a ventilated package should be known. The objective of

Mustafa Tutar; Ferruh Erdogdu; Burak Toka

2009-01-01

213

Examination of Thermal Adaptive Effect of the Adjustment of a Seated Human Body's Orientation to Spot Airflow  

Microsoft Academic Search

For a person exposed to spot airflow, his thermal sensation is considered to be greatly influenced by his posture relative to the spot airflow because of the change of the velocity distributions around his body caused by the posture adjustments. On the other hand, as one of the usual thermal adaptive activities, an office worker unconsciously alters his sitting posture

Shengwei Zhu; Shinsuke Kato; Ling Yang

214

Natural Laminar-Flow Blades for Vertical-Axis Wind Turbines.  

National Technical Information Service (NTIS)

Natural Laminar Flow (NLF) airfoils are those which can achieve significant extents of laminar flow (greater than 30% of chord) solely through favorable pressure gradients. A number of candidate airfoil sections were defined and then screened in a perform...

P. C. Klimas

1982-01-01

215

Roughness and waviness requirements for laminar flow surfaces  

NASA Astrophysics Data System (ADS)

Many modern metal and composite airframe manufacturing techniques can provide surface smoothness which is compatible with natural laminar flow (NLF) requirements. An important consideration is manufacturing roughness of the surface in the form of steps and gaps perpendicular to the freestream. The principal challenge to the design and manufacture of laminar flow surfaces today appears to be in the installation of leading-edge panels on wing, nacelle, and empennage surfaces. A similar challenge is in the installation of access panels, doors, windows, fuselage noses, and engine nacelles. Past work on roughness and waviness manufacturing tolerances and comparisons with more recent experiments are reviewed.

Obara, Clifford J.; Holmes, Bruce J.

1986-12-01

216

Production of plastic fuel tanks using Laminar barrier technology  

SciTech Connect

Automobiles from all parts of the world are now being built with plastic fuel tanks made from high density polyethylene (HPDE). The most difficult aspect of the current manufacturing process for meeting environmental regulations is the need to work with hazardous chemicals such as fluorine and sulfur trioxide to reduce hydrocarbon permeation. Laminar barrier technology is a barrier process under development which meets EPA requirements, reduces costs and eliminates environmental and employee safety concerns. Laminar technology is described in this paper. Its application for fuel tanks is discussed.

Bell, R.L.; Mehra, V.

1989-01-01

217

Banded laminar-turbulent patterns: mean flows, symmetries and statistics  

NASA Astrophysics Data System (ADS)

In large-aspect-ratio plane Couette flow, patterns of oblique bands, alternating between turbulent and laminar flow, are the intermediate regime between uniform turbulence and laminar Couette flow. The mean flows corresponding to these patterns, as well as the Reynolds stress force, are found to be represented almost perfectly by a single trigonometric function along the pattern wavevector, leading to a quantitative description in terms of six ODEs. The Fourier component corresponding to the pattern wavelength provides an order parameter for the transition, which can be described as a bifurcation in its probability distribution function.

Tuckerman, Laurette; Barkley, Dwight

2007-11-01

218

Measurement of laminar and turbulent density fields by means of speckle photography  

Microsoft Academic Search

A speckle photographic optical system is described, and its application to the visualization of laminar and turbulent density fields, by means of spatial filtering, is discussed. Two cases of heat and mass transfer are tested: a laminar axisymmetric jet of helium exhausting from a pipe into the ambient air, and the laminar free convection along a vertical heated plate. In

R. Erbeck; W. Merzkirch; U. Wernekinck

1987-01-01

219

Identification of the laminar-turbulent transition process in a plasma plume  

Microsoft Academic Search

This paper illustrates the complete dynamics of the laminar-turbulent transition process in a plasma plume using a simple measurement of the magnation-point heat flux correlated with acoustic, optical, and voltage drop fluctuations. In the laminar flow regime a steady jet is produced and the heat fluxes are accurately predicted hr laminar correlations. The initial stage of transition is characterized by

L. Krejci; V. Dolinek; B. Ruzicka; V. Chalupova; S. Russ

1993-01-01

220

Computational and experimental study of a forced, timevarying, axisymmetric, laminar diffusion flame  

Microsoft Academic Search

Forced, time-varying flames are laminar systems that help bridge the gap between laminar and turbulent combustion. In this study, we investigate computationally and experimentally the structure of an acousti- cally forced, axisymmetric laminar methane-air diffusion flame in which a cylindrical fuel jet is surrounded by a coflowing oxidizer jet. The flame is forced by imposing a sinusoidal modulation on the

Rahima K. Mohammed; Michael A. Tanoff; Mitchell D. Smooke; Andrew M. Schaffer; Marshall B. Long

1998-01-01

221

Heat transfer in all pipe flow regimes: laminar, transitional\\/intermittent, and turbulent  

Microsoft Academic Search

A predictive theory is presented which is capable of providing quantitative results for the heat transfer coefficients in round pipes for the three possible flow regimes: laminar, transitional, and turbulent. The theory is based on a model of laminar-to-turbulent transition which is also viable for purely laminar and purely turbulent flow. Fully developed heat transfer coefficients were predicted for the

J. P. Abraham; E. M. Sparrow; J. C. K. Tong

2009-01-01

222

Thermal sensation and comfort during exposure to local airflow to face or legs.  

PubMed

The present study examined the contribution of local airflow temperature to thermal sensation and comfort in humans. Eight healthy male students were exposed to local airflow to their faces (summer condition) or legs (winter condition) for 30 minutes. Local airflow temperature (Tf) was maintained at 18 degrees C to 36 degrees C, and ambient temperature (Ta) was maintained at 17.4 degrees C to 31.4 degrees C. Each subject was exposed to 16 conditions chosen from the combination of Tf and Ta. Based on the results of multiple regression analysis, the standardized partial regression coefficient of Tf and Ta were determined to be 0.93 and 0.13 in the summer condition, and 0.71 and 0.36 in the winter condition at the end of the exposure. Also, thermal comfort was observed to depend closely on the interrelation between Tf and Ta. The present data suggested that local airflow temperature is an important thermal factor regarding thermal sensation and comfort. PMID:15684546

Yamashita, Kazuaki; Matsuo, Juntaro; Tochihara, Yutaka; Kondo, Youichiro; Takayama, Shizuka; Nagayama, Hiroki

2005-01-01

223

Airflow Velocity Effects on Lightning Ignition of Aircraft Fuel Vent Efflux.  

National Technical Information Service (NTIS)

Studies of the effects of airflow, at aircraft holding velocities up to 250 knots, over the surface of an aircraft wingtip containing a recessed fuel vent showed that the probability of lightning ignition of the fuel vent efflux was greatly reduced by the...

M. M. Newman J. R. Stahmann J. D. Robb

1967-01-01

224

One-dimensional airflow in unsaturated zone induced by periodic water table fluctuation  

Microsoft Academic Search

This paper investigates the vertical airflow driven by fluctuating water table within the lower layer of a coastal two-layered system. The upper layer is unsaturated and semipermeable, while the lower is permeable. An analytical solution of the subsurface air pressure fluctuation is derived on the basis of model simplification assumptions, the reasonability of which was examined by numerical solutions of

Hailong Li; Jiu Jimmy Jiao

2005-01-01

225

Influence of airflow rate and substrate nature on heterogeneous struvite precipitation  

Microsoft Academic Search

In wastewater treatment plants a hard scale consisting of struvite crystals can be formed, in pipes and recirculation pumps, during anaerobic digestion of wastewater. This study was conducted to evaluate the effect of airflow rate and substrate nature on nucleation type, induction period and supersaturation coefficient during struvite precipitation. A crystallization reactor similar to that designed for calcium carbonate precipitation

H. Saidou; S. Ben Moussa; M. Ben Amor

2009-01-01

226

Propane–Air Mixture Combustion Assisted by MW Discharge in a Speedy Airflow  

Microsoft Academic Search

In this paper, results are presented from an experimental investigation of propane-air combustion in a stationary microwave (MW) discharge at different conditions. In these experiments, a deeply undercritical discharge is initiated in the base of an electromagnetic vibrator, which is immersed in cold supersonic airflow. Two schemes for mixing propane with air are considered. In the first scheme, a propane-air

Igor I. Esakov; Lev P. Grachev; Kirill V. Khodataev; Viacheslav A. Vinogradov; David M. Van Wie

2006-01-01

227

Assessment of Airflow Obstruction during CPAP by Means of Forced Oscillation in Patients with Sleep Apnea  

Microsoft Academic Search

The forced oscillation technique (FOT) is a noninvasive method to measure respiratory resistance (R rs ) potentially useful for monitoring upper airway obstruction in patients with obstructive sleep apnea\\/ hypopnea syndrome (SAHS). The aim of this work was to test the clinical suitability of FOT in assess- ing dynamic changes in airflow obstruction in patients with SAHS during continuous positive

DANIEL NAVAJAS; RAMÓN FARRÉ; MAR ROTGER; RAMÓN BADIA; MARINA PUIG-de-MORALES; JOSEP M. MONTSERRAT

1998-01-01

228

Characterization of turbulent airflow over evolving water-waves in a wind-wave tank  

NASA Astrophysics Data System (ADS)

Results of an experimental investigation of the turbulent boundary layer in airflow over evolving young wind-waves are presented. The experiments were conducted in a laboratory wind-wave flume consisting of a closed-loop wind tunnel capable of generating wind speed that may exceed 15 m/s, atop of a 5 m long wave tank. Simultaneous measurements of mean wind velocity and of instantaneous fluctuations of the horizontal and vertical air velocity components were carried out along the test section at different airflow rates and at numerous heights above the highest wave. Instantaneous surface elevation at the air sensors' location was simultaneously recorded. The friction velocities at all locations and for all airflow rates were determined by two independent methods: by fitting the logarithmic velocity profiles and by extrapolating the measured Reynolds shear stresses to mean water surface level. The variation with height and along the test section of the fluctuations of two velocity components, in the mean flow and in the vertical directions, was also studied and the results compared with flow behavior over rough and smooth plates. Wave-induced airflow parameters were then investigated by application of cross-spectral analysis. Results on the vertical extent of wave-induced boundary layer, on the phase relation between the wave-induced velocity fluctuations and the surface elevation, as well as on the wave-induced Reynolds shear stress are reported.

Zavadsky, Andrey; Shemer, Lev

2012-11-01

229

An analytical evaluation for airflow to inlet wells in vapor extraction systems under leaky conditions  

Microsoft Academic Search

Air inlet wells have been employed to enhance the fresh air flushing through the target-contaminated soils in many soil vapor extraction systems. The analytical solution presented here evaluates the efficiency of the airflow to these inlet wells under the conditions of leaky surface boundary, anisotropic soils, and partially screened extraction. Using the analytical solution, the efficiency of air inlet wells

Shemin Ge; Minru Liao

1996-01-01

230

Air-Flow Redistribution in Exhaust Ventilation Systems Using Dampers and Static Pressure Ratios  

Microsoft Academic Search

Ventilation manuals often heavily discourage use of dampers even though dampers offer the much-needed ability to change air-flow distribution to meet changing needs. If dampers can be adjusted accurately, quickly, and easily, there may be reason to discourage their use only for systems that transport particulates. A method is described for adjustment of ventilation flow dampers using only the ratio

Steven E. Guffey

1993-01-01

231

Computational Fluid Dynamics Simulation of Airflow and Aerosol Deposition in Human Lungs  

Microsoft Academic Search

Computational fluid dynamics (CFD) simulations of airflow and particle deposition in geometries representing the human tracheobronchial tree were conducted. Two geometries were used in this work: (1) based on the Weibel A model, and (2) based on a CT scan of a cadaver lung cast. Flow conditions used included both steady-state inhalation and exhalation conditions as well as time-dependent breathing

Natalya Nowak; Prashant P. Kakade; Ananth V. Annapragada

2003-01-01

232

Computational fluid dynamics modelling and validation of the isothermal airflow in a forced convection oven  

Microsoft Academic Search

This article discusses the application of computational fluid dynamics (CFD) to calculate the three-dimensional isothermal airflow in an industrial electrical forced-convection oven. The governing fluid flow equations were expanded with a fan model and a turbulence model. The standard and the renormalisation group (RNG) version of the k–? turbulence model produced comparable results. The performance of the CFD model was

Pieter Verboven; Nico Scheerlinck; Josse De Baerdemaeker

2000-01-01

233

Correlation of Systemic Superoxide Dismutase Deficiency to Airflow Obstruction in Asthma  

Microsoft Academic Search

Rationale: Increased oxidative stress and decreased superoxide dis- mutase (SOD) activity in the asthmatic airway are correlated to airflow limitation and hyperreactivity. We hypothesized that asth- matic individuals with higher levels of oxidative stress may have greater loss of SOD activity, which would be reflected systemically in loss of circulating SOD activity and clinically by development of severe asthma and\\/or

Suzy A. A. Comhair; Kristin S. Ricci; Mercedes Arroliga; Abigail R. Lara; Raed A. Dweik; Wei Song; Stanley L. Hazen; Eugene R. Bleecker; William W. Busse; Kian Fan Chung; Benjamin Gaston; Annette Hastie; Mark Hew; Nizar Jarjour; Wendy Moore; Stephen Peters; W Gerald Teague; Sally E. Wenzel; Serpil C. Erzurum

2005-01-01

234

Correlation of Systemic Superoxide Dismutase Deficiency to Airflow Obstruction in Asthma  

PubMed Central

Rationale: Increased oxidative stress and decreased superoxide dismutase (SOD) activity in the asthmatic airway are correlated to airflow limitation and hyperreactivity. We hypothesized that asthmatic individuals with higher levels of oxidative stress may have greater loss of SOD activity, which would be reflected systemically in loss of circulating SOD activity and clinically by development of severe asthma and/or worsening airflow limitation. Methods: To investigate this, serum SOD activity and proteins, the glutathione peroxidase/glutathione antioxidant system, and oxidatively modified amino acids were measured in subjects with asthma and healthy control subjects. Results: SOD activity, but not Mn-SOD or Cu,Zn-SOD protein, was lower in asthmatic serum as compared with control, and activity loss was significantly related to airflow limitation. Further, serum SOD activity demonstrated an inverse correlation with circulating levels of 3-bromotyrosine, a posttranslational modification of proteins produced by the eosinophil peroxidase system of eosinophils. Exposure of purified Cu,Zn-SOD to physiologically relevant levels of eosinophil peroxidase-generated reactive brominating species, reactive nitrogen species, or tyrosyl radicals in vitro confirmed that eosinophil-derived oxidative pathways promote enzyme inactivation. Conclusion: These findings are consistent with greater oxidant stress in asthma leading to greater inactivation of SOD, which likely amplifies inflammation and progressive airflow obstruction.

Comhair, Suzy A. A.; Ricci, Kristin S.; Arroliga, Mercedes; Lara, Abigail R.; Dweik, Raed A.; Song, Wei; Hazen, Stanley L.; Bleecker, Eugene R.; Busse, William W.; Chung, Kian Fan; Gaston, Benjamin; Hastie, Annette; Hew, Mark; Jarjour, Nizar; Moore, Wendy; Peters, Stephen; Teague, W. Gerald; Wenzel, Sally E.; Erzurum, Serpil C.

2005-01-01

235

A Dual Airflow Window for Indoor Air Quality Improvement and Energy Conservation in Buildings  

Microsoft Academic Search

This paper proposes a novel dual airflow window for use in residential buildings that tempers outdoor air with exhausted indoor air. The energy needed to condition outdoor air is reduced because of the counterflow heat exchange between the two flow streams. Experimentally validated computational fluid dynamics simulations have been used to optimize the window design and to estimate the benefits

Jennifer R. Gosselin; Qingyan Chen

2008-01-01

236

AIRFLOW-CONTAINED AEROPONIC NUTRIENT DELIVERY FOR A MICROGRAVITY PRANT GROWTH UNIT  

Microsoft Academic Search

HESSEL M. I., Jr., RICHERT G. E., Jr. and NEVILL G. E., Jr. Airflow-contained aeroponic nutrient deliveery for a microgravity plant growth unit. BIOTRONICS 21, 33-39, 1992. Paper presents a new approach to nutrient delivery and control for microgravity plant growth. Nutrients are delivered by aeroponic misting of roots and leakage is prevented by flowing air. Plant germination and growth

G. E. RICHERT; G. E. NEVILL

237

Computational fluid dynamics simulations of respiratory airflow in human nasal cavity and its characteristic dimension study  

NASA Astrophysics Data System (ADS)

To study the airflow distribution in human nasal cavity during respiration and the characteristic parameters of nasal structure, three-dimensional, anatomically accurate representations of 30 adult nasal cavity models were reconstructed based on processed tomography images collected from normal people. The airflow fields in nasal cavities were simulated by fluid dynamics with finite element software ANSYS. The results showed that the difference of human nasal cavity structure led to different airflow distribution in the nasal cavities and variation of the main airstream passing through the common nasal meatus. The nasal resistance in the regions of nasal valve and nasal vestibule accounted for more than half of the overall resistance. The characteristic model of nasal cavity was extracted on the basis of characteristic points and dimensions deduced from the original models. It showed that either the geometric structure or the airflow field of the two kinds of models was similar. The characteristic dimensions were the characteristic parameters of nasal cavity that could properly represent the original model in model studies on nasal cavity.

Zhang, Jun; Liu, Yingxi; Sun, Xiuzhen; Yu, Shen; Yu, Chi

2008-04-01

238

Pressure Field and Airflow at the Opening of a Naturally Ventilated Greenhouse  

Microsoft Academic Search

Direct estimation of airflow at the vent opening by means of differential pressure measurements were performed in a twin-span greenhouse equipped with a continuous vent at the gutter. Application of Bernoulli's equation provided a spatial estimate of mean air velocities and turbulent flows through the opening.In the particular case investigated, a wind blowing parallel to the greenhouse ridge gave rise

T. Boulard; C. Kittas; G. Papadakis; M. Mermier

1998-01-01

239

New approach for measuring airflows in buildings using a perfluorocarbon tracer  

Microsoft Academic Search

This paper describes a new approach for measuring airflows in buildings based on a perfluorocarbon tracer (PFT) technique. Ventilation measurements were carried out in a test room to examine the accuracy of the PFT technique. The PFT, which is a liquid at room temperature, was injected into the room at a constant rate using a thermostatically controlled heating unit. Tracer

K. W. Cheong; S. B. Riffat

1995-01-01

240

Airflow produced by dielectric barrier discharge between asymmetric parallel rod electrodes  

SciTech Connect

We observed a novel type of airflow produced by an atmospheric rf discharge between asymmetric parallel rod electrodes. The electrodes were a bare metal rod 1 mm in diameter and a glass-coated metal rod 3.2 mm in diameter. The thrust, measured by a pendulum, increased with discharge input power.

Hayashi, Kazuo; Tanaka, Motofumi; Yasui, Hiroyuki; Hashimoto, Kiyoshi [Power and Industrial Systems Research and Development Center, Toshiba Corporation, Power Systems Company, 20-1 Kansei-cho, Tsurumi-ku, Yokohama 230-0034 (Japan); Toshiba Business and Life Service Corporation, 7-1 Nisshin-cho, Kawasaki-ku, Kawasaki 210-0024 (Japan)

2007-09-15

241

Pulmonary anatomy in the Nile crocodile and the evolution of unidirectional airflow in Archosauria.  

PubMed

The lungs of birds have long been known to move air in only one direction during both inspiration and expiration through most of the tubular gas-exchanging bronchi (parabronchi). Recently a similar pattern of airflow has been observed in American alligators, a sister taxon to birds. The pattern of flow appears to be due to the arrangement of the primary and secondary bronchi, which, via their branching angles, generate inspiratory and expiratory aerodynamic valves. Both the anatomical similarity of the avian and alligator lung and the similarity in the patterns of airflow raise the possibility that these features are plesiomorphic for Archosauria and therefore did not evolve in response to selection for flapping flight or an endothermic metabolism, as has been generally assumed. To further test the hypothesis that unidirectional airflow is ancestral for Archosauria, we measured airflow in the lungs of the Nile crocodile (Crocodylus niloticus). As in birds and alligators, air flows cranially to caudally in the cervical ventral bronchus, and caudally to cranially in the dorsobronchi in the lungs of Nile crocodiles. We also visualized the gross anatomy of the primary, secondary and tertiary pulmonary bronchi of C. niloticus using computed tomography (CT) and microCT. The cervical ventral bronchus, cranial dorsobronchi and cranial medial bronchi display similar characteristics to their proposed homologues in the alligator, while there is considerable variation in the tertiary and caudal group bronchi. Our data indicate that the aspects of the crocodilian bronchial tree that maintain the aerodynamic valves and thus generate unidirectional airflow, are ancestral for Archosauria. PMID:23638399

Schachner, Emma R; Hutchinson, John R; Farmer, Cg

2013-03-26

242

Improving aviation safety with information visualization: Airflow hazard display for helicopter pilots  

NASA Astrophysics Data System (ADS)

Many aircraft accidents each year are caused by encounters with airflow hazards near the ground, such as vortices or other turbulence. While such hazards frequently pose problems to fixed-wing aircraft, they are especially dangerous to helicopters, whose pilots often have to operate into confined areas or under operationally stressful conditions. Pilots are often unaware of these invisible hazards while simultaneously attending to other aspects of aircraft operation close to the ground. Recent advances in aviation sensor technology offer the potential for aircraft-based sensors that can gather large amounts of airflow velocity data in real time. This development is likely to lead to the production of onboard detection systems that can convey detailed, specific information about imminent airflow hazards to pilots. A user interface is required that can present extensive amounts of data to the pilot in a useful manner in real time, yet not distract from the pilot's primary task of flying the aircraft. In this dissertation, we address the question of how best to present safety-critical visual information to a cognitively overloaded user in real time. We designed an airflow hazard visualization system according to user-centered design principles, implemented the system in a high fidelity, aerodynamically realistic rotorcraft flight simulator, and evaluated it via usability studies with experienced military and civilian helicopter pilots. We gathered both subjective data from the pilots' evaluations of the visualizations, and objective data from the pilots' performance during the landing simulations. Our study demonstrated that information visualization of airflow hazards, when presented to helicopter pilots in the simulator, dramatically improved their ability to land safely under turbulent conditions. Although we focused on one particular aviation application, the results may be relevant to user interfaces and information visualization in other safety-related applications where the user's primary task is something other than looking at the computer interface, such as emergency response, air traffic control, or operating a motor vehicle.

Aragon, Cecilia Rodriguez

243

Difference in airflow obstruction between Hispanic and non-Hispanic white female smokers  

PubMed Central

Rationale Smoking-related respiratory diseases are a major cause of morbidity and mortality. However, the relationship between smoking and respiratory disease has not been well-studied among ethnic minorities in general and among women in particular. Objective The objective of this cross-sectional study was to evaluate the risk of airflow obstruction and to assess lung function among Hispanic and non-Hispanic white (NHW) female smokers in a New Mexico cohort. Methods Participants completed a questionnaire detailing smoking history and underwent spirometry testing. Outcomes studied included airflow obstruction, selected lung function parameters, and chronic mucus hyper-secretion. Chi square, logistic, and linear regression techniques were utilized. Main findings Of the 1,433 eligible women participants, 248 (17.3%) were Hispanic; and 319 had airflow obstruction (22.3%). Hispanic smokers were more likely to be current smokers, and report lower pack-years of smoking, compared to NHW smokers (p < 0.05 for all analyses). Further, Hispanic smokers were at a reduced risk of airflow obstruction compared to NHW smokers, with an O.R. of 0.51, 95% C.I. 0.34, 0.78 (p = 0.002) after adjustment for age, BMI, pack-years and duration of smoking, and current smoking status. Following adjustment for covariates, Hispanic smokers also had a higher mean absolute and percent predicted post-bronchodilator FEV1/FVC ratio, as well as higher mean percent predicted FEV1 (p < 0.05 for all analyses). Principal conclusions Hispanic female smokers in this New Mexico-based cohort had lower risk of airflow obstruction and better lung function than NHW female smokers. Further, smoking history did not completely explain these associations.

Sood, Akshay; Stidley, Christine A.; Picchi, Maria A.; Celedon, Juan C.; Gilliland, P.H. Frank; Crowell, Richard E.; Belinsky, Steven A.; Tesfaigzi, Yohannes

2013-01-01

244

Equations of laminar and turbulent flows in general curvilinear coordinates  

Microsoft Academic Search

Recent developments in computational fluid mechanics and grid generation have made it possible to consider complex three dimensional laminar and turbulent flows using nonorthogonal coordinates. However, the necessary equations in generalized nonorthogonal coordinates are not readily available in a single reference. The purpose of this report is to present these equations for an incompressible fluid. Methods of curvilinear tensor analysis

M. C. Richmond; H. C. Chen; V. C. Patel

1986-01-01

245

Rapid preparation of monodispersed droplets with confluent laminar flows  

Microsoft Academic Search

We study the formation of micro droplets in confluent two-phase flows in a microfluidic system. Instability at the interface of two immiscible liquids undergoing laminar flow generates micro droplets of highly uniform size. Under high shear stress the droplets form rapidly, and more than 2000 droplets can be prepared of similar size. Droplet size can be controlled by varying the

Takasi Nisisako; T. Torii; Toshiro Higuchi

2003-01-01

246

Experimental Investigation on the Transition of Laminar Separated Layer  

Microsoft Academic Search

Transition of two-dimensional separated layer was investigated in detail. Mean velocity distribution of laminar layer shows a similar profile and agrees with Lin's calculation. In the transition region, hot-wire anemometer survey of velocity fluctuation revealed the existence of sinusoidal wave, the frequency of which lies in the unstable zone predicted by stability theory. Transition points determined by layer thickness and

Hiroshi Sato

1956-01-01

247

Laminar confined impinging jet into a porous layer  

Microsoft Academic Search

This work aims at studying laminar impinging jets on surfaces covered with a layer of a porous material. This contribution may provide insight into the design and optimization of heat and mass transfer processes over surfaces. Numerical simulations are presented and the porous substrate is treated as a rigid, homogeneous, and isotropic medium. Macroscopic transport equations are written for a

Daniel R. Graminho; Marcelo J. S. de Lemos

2008-01-01

248

Structure of the quasi-perpendicular laminar bow shock  

Microsoft Academic Search

It was found that low solar wind parameters M (less than or around 2.5) and beta (much less than 1) and high angles to the local shock normal, theta (greater than or around 65 deg), produced oblique laminar shock profiles as expected from theory, with marginal or vanishing upstream standing whistlers probably damped by acoustic or other plasma wave instabilities.

E. W. Greenstadt; F. L. Scarf; C. T. Russell; V. Formisano; M. Neugebauer

1975-01-01

249

Laminar flame speeds of hydrocarbon + air mixtures with hydrogen addition  

Microsoft Academic Search

Using the symmetrical, adiabatic, counterflow arrangement, the laminar flame speeds of methane + air and propane + air mixtures, with and without the addition of stoichiometrically small amounts of hydrogen, have been determined by first measuring the flame speeds with stretch and then linearly extrapolating these values to zero stretch. The results show that the flame speed is substantially increased

G. Yu; C. K. Law; C. K. Wu

1986-01-01

250

NASA Chat: Quest for the Holy Grail of Laminar Flow  

NASA Website

People who love flying are on a quest for aviation's holy grail – laminar flow. It's the absolutely uninterrupted flow of air over a wing and it's something you want but very hard to get. On Wed., March 30, NASA's Ethan Baumann ...

251

Airborne drug levels in a laminar-flow hood  

Microsoft Academic Search

The airborne levels of fluorouracil and cefazolin sodium injections after manipulation of these drug products inside a horizontal laminar-flow hood were measured. The Biotest RCS Centrifugal Air Sampler, generally used to measure microbial levels in air, was adapted with a paper filter to measure drug levels in air. In each of nine trials, five ampuls of fluorouracil were opened in

M. L. Kleinberg; M. J. Quinn

1981-01-01

252

Wall functions for numerical modeling of laminar MHD flows  

Microsoft Academic Search

A general wall function treatment is presented for the numerical modeling of laminar magnetohydrodynamic (MHD) flows. The wall function expressions are derived analytically from the steady-state momentum and electric potential equations, making use only of local variables of the numerical solution. No assumptions are made regarding the orientation of the magnetic field relative to the wall, nor of the magnitude

Ola Widlund

2003-01-01

253

Numerical simulation of laminar hypersonic flows about an ellipsoid  

Microsoft Academic Search

The laminar hypersonic flow about a double ellipsoid, which idealizes the nose and cockpit of a spacecraft, were numerically simulated. The calculation method solves the three dimensional thin layer Navier-Stokes equations in a conservative formulation on a surface oriented calculation grid using an implicit\\/explicit finite difference technique. The conservative formulation allows the correct calculation of embedded compression shocks, while the

S. Riedelbauch; B. Mueller

1988-01-01

254

Stabilization mechanisms of lifted laminar flames in axisymmetric jet flows  

Microsoft Academic Search

Stabilization mechanisms of lifted laminar propane flames are investigated in an axisymmetric jet flow configuration. Detailed mixing and flow fields upstream of the flame lift-off heights measured by Chung and coworkers [28–30] are calculated on a nonreacting flow basis. The local stoichiometric axial velocity, Ust, and scalar dissipation rate, ?st, are obtained at points that are upstream of the stabilization

Yung-Cheng Chen; Robert W. Bilger

2000-01-01

255

Laminar-turbulent transition in a bayonet tube  

Microsoft Academic Search

This paper provides the details of a numerical study of the bayonet tube during the laminar-turbulent transition. Attention is focused on the frictional characteristics of the tube. The results constitute a systematic investigation of the effect of the principal parameters on hydraulic resistance represented by an Euler number. Specifically discussed are the effects of fluid properties, tube length, and inner

Harpal Minhas; G. S. H. Lock

1996-01-01

256

The effect of riblets on laminar to turbulent transition  

Microsoft Academic Search

Experiments conducted on the effect of riblets on the laminar-to-turbulent transition of a flat plate in a water tunnel are reported. Transition was determined using a Laser Doppler Velocimeter (LDV). A smooth reference surface was compared to five riblet surfaces for a range of Reynolds numbers. Smooth surface transition Reynolds number was about 2.75 × 106. All of the five

D. M. Ladd; J. J. Rohr; L. W. Reidy; E. W. Hendricks

1993-01-01

257

Laminar Flow Tube Reactor interface with quadrupole mass spectrometer  

Microsoft Academic Search

Nucleation of supersaturated water vapor was studied using the Laminar Flow Tube Reactor (LFTR) technique. In order to check the presence of contaminants in the freshly nucleated water particles, the LFTR has been connected to a mass spectrometer. Trace amounts contaminants arising from the substances used as a circulating liquid to maintain temperatures of the LFTR have been detected. The

Vladimir B. Mikheev; Nels S. Laulainen; Viktor V. Pervukhin; Stephan E. Barlow

2000-01-01

258

Advanced Nucleation Study Using The Laminar Flow Tube Reactor (LFTR)  

Microsoft Academic Search

Quantitative measurements of homogeneous nucleation rates have been made using the laminar flow tube reactor experimental technique. Thorough computer calculations of the temperature, vapor concentration, supersaturation, and nucleation rate distributions in the reactor tube were made. The nucleation volume as well as the time of nucleation have been determined with high accuracy. The concentration of the particles formed in the

Vladimir Mikheev; Nels Laulainen

1998-01-01

259

Experimental nucleation studies with a laminar flow tube reactor  

Microsoft Academic Search

A Laminar Flow Tube Reactor (LFTR) has been used as a quantitative tool for nucleation measurements. It has been specially designed and constructed in order to minimize the potential experimental inaccuracies. Careful attention has been paid to the temperature conditions inside the LFTR. Other sources of experimental uncertainties, such as initial vapor concentration conditions, calculations of the parameters of the

Vladimir B. Mikheev; Nels S. Laulainen; Stephan E. Barlow

2000-01-01

260

Method for the Constrained Design of Natural Laminar Flow Airfoils  

Microsoft Academic Search

An automated iterative design method has been developed by which an airfoil with a substantial amount of natural laminar è ow can be designed while maintaining other aerodynamic and geometric constraints. Drag reductions have been realized using the design method over a range of Mach numbers, Reynolds numbers, and airfoil thicknesses. The key features of the method are the compressible

Bradford E. Green; John L. Whitesides; Richard L. Campbell; Raymond E. Mineck

1997-01-01

261

Laminar drag reduction in microchannels using ultrahydrophobic surfaces  

Microsoft Academic Search

A series of experiments is presented which demonstrate significant drag reduction for the laminar flow of water through microchannels using hydrophobic surfaces with well-defined micron-sized surface roughness. These ultrahydrophobic surfaces are fabricated from silicon wafers using photolithography and are designed to incorporate precise patterns of microposts and microridges which are made hydrophobic through a chemical reaction with an organosilane. An

Jia Ou; Blair Perot; Jonathan P. Rothstein

2004-01-01

262

Estimation of Laminar Burning Velocities by Direct Digital Photography  

ERIC Educational Resources Information Center

|The Bunsen burner flame, which is the most common flame in the laboratory, can be easily studied for its dynamics because of modern, economical digital technology available to student laboratories. Direct digital photography of Bunsen flames is used to obtain laminar burning velocities of selected gaseous hydrocarbon/air flames.|

Uske, J.; Barat, R.

2004-01-01

263

Laminar MoS2 membranes for molecule separation.  

PubMed

For the first time, a laminar separation membrane was assembled from atom-thick MoS2 sheets and exhibited a water permeance of 245 L h(-1) m(-2) bar(-1), which was 3-5 times higher than that of graphene oxide membranes without degradation of the rejection ratio (89%) for Evans blue molecules. PMID:24100417

Sun, Luwei; Huang, Hubiao; Peng, Xinsheng

2013-10-22

264

Electrostatic quadrupole focused particle accelerating assembly with laminar flow beam  

DOEpatents

A charged particle accelerating assembly provided with a predetermined ratio of parametric structural characteristics and with related operating voltages applied to each of its linearly spaced focusing and accelerating quadrupoles, thereby to maintain a particle beam traversing the electrostatic fields of the quadrupoles in the assembly in an essentially laminar flow throughout the assembly.

Maschke, Alfred W. (East Moriches, NY)

1985-01-01

265

Laminar epidermal hyperplasia and hyperkeratosis in an equine hoof.  

PubMed

A 6-year-old Canadian Warmblood gelding was presented for suspicion of keratoma growth, based on a history of recurring abscesses in the right front foot. Radiographic examination and computed tomography identified 2 bilaterally symmetrical, laminar epidermal ingrowths adhered to the hoof wall at the level of the lateral and medial heels. PMID:24155488

Tatarniuk, Dane M; Bracamonte, Joe L; Wilson, David G; Sharma, Ajay; Perry, Al W

2013-09-01

266

Electrostatic quadrupole focused particle accelerating assembly with laminar flow beam  

DOEpatents

A charged particle accelerating assembly provided with a predetermined ratio of parametric structural characteristics and with related operating voltages applied to each of its linearly spaced focusing and accelerating quadrupoles, thereby to maintain a particle beam traversing the electrostatic fields of the quadrupoles in the assembly in an essentially laminar flow through the assembly.

Maschke, A.W.

1984-04-16

267

Turbulent-laminar patterns in plane Couette flow  

NASA Astrophysics Data System (ADS)

We study turbulent-laminar patterns in large-aspect-ratio plane Couette flow. These states consist of regular alternations of turbulent and laminar flow over large length scales. We simulate these patterns by extending the minimal-flow-unit methodology to computational domains with one long dimension that can be tilted at any prescribed angle to the streamwise direction. At a tilt of 24 degrees, we reproduce experimentally observed oblique patterns. As Re is decreased from 420, uniform turbulence is succeeded by intermittency at Re=410 and then by three well-defined bands at Re=390 which persist to Re=320 and are replaced by two bands at Re=310. Surprisingly, during this entire evolution, the temporally averaged total kinetic energy remains constant. Thus, the turbulence in the bands (which occupy only a portion of the domain) is more intense than the uniform turbulence, in such a way as to compensate for the laminar regions. In a geometry with a long streamwise and a short spanwise direction, turbulent patches repeatedly disappear abruptly and then re-nucleate gradually, for Reynolds numbers as low as 220. When the spanwise direction is long and the streamwise direction short, transition occurs abruptly from uniform turbulence to laminar Couette flow at Re=400.

Tuckerman, Laurette; Barkley, Dwight

2005-11-01

268

Turbulent-laminar patterns in Couette flow: stripes and spots  

NASA Astrophysics Data System (ADS)

Large-scale turbulent-laminar spirals were first observed in counter-rotating Taylor-Couette flow by Coles (1965). Recently, Prigent and Dauchot (2001) discovered an analogous state in large-aspect-ratio plane Couette flow, consisting of turbulent-laminar bands oriented obliquely to the streamwise direction, while Cros and Le Gal (2002) observed large-scale turbulent spirals between stationary and rotating disks. We study these patterns numerically by extending the minimal flow unit methodology pioneered by Jimenez et al. (1991). Our periodic computational domains are of minimal size in one lateral direction but long (60 gaps) in the other, which can be tilted at any prescribed angle to the streamwise direction. Three types of patterned states are found as Re is decreased from uniform turbulence at Re=400. (1) Intermittent states occur near the turbulent-pattern threshold. (2) Periodic states have a well-defined wavelength which increases with decreasing Re. (3) Localized states are the manifestation in our computations of turbulent spots. This suggests that the basic physics of isolated turbulent spots can be captured without simulating two large lateral directions. Reversion to laminar Couette flow is inevitable when Re? 300. Mean and fluctuating fields for laminar-turbulent patterned flows are presented and shown to be out of phase with one another.

Barkley, Dwight; Tuckerman, Laurette

2004-11-01

269

Impulse response of laminar boundary layer and receptivity  

NASA Astrophysics Data System (ADS)

Impulse response of a laminar boundary layer of a flat plate to periodic surface suction and blowing is analyzed through a numerical computation based on parallel flow approximation. Bilateral Laplace transform is used to eliminate the problem of individually identifying the various eigen modes and contributions of other singularities.

Sengupta, Tapan K.

270

On the growth of turbulent regions in laminar boundary layers  

NASA Astrophysics Data System (ADS)

Turbulent spots evolving in a laminar boundary layer on a nominally zero pressure gradient flat plate are investigated. The plate is towed through an 18 m water channel, using a carriage that rides on a continuously replenished oil film giving a vibrationless tow. Turbulent spots are initiated using a solenoid valve that ejects a small amount of fluid through a minute hole on the working surface. A novel visualization technique that utilizes fluorescent dye excited by a sheet of laser light is employed. Some new aspects of the growth and entrainment of turbulent spots, especially with regard to lateral growth, are inferred from the present experiments. To supplement the information on lateral spreading, a turbulent wedge created by placing a roughness element in the laminar boundary layer is also studied both visually and with probe measurements. The present results show that, in addition to entrainment, another mechanism is needed to explain the lateral growth characteristics of a turbulent region in a laminar boundary layer. This mechanism, termed growth by destabilization, appears to be a result of the turbulence destabilizing the unstable laminar boundary layer in its vicinity. To further understand the growth mechanisms, the turbulence in the spot is modulated using drag-reducing additives and salinity stratification.

Gad-El-Hak, M.; Riley, J. J.; Blackwelder, R. F.

1981-09-01

271

A bypass wake induced laminar\\/turbulent transition  

Microsoft Academic Search

The process of laminar to turbulent transition induced by a von Karman vortex street wake, was studied for the case of a flat plate boundary layer. The boundary layer developed under zero pressure gradient conditions. The vortex street was generated by a cylinder positioned in the free stream. An X-type hot-wire probe located in the boundary layer, measured the streamwise

N. K. Kyriakides; E. G. Kastrinakis; S. G. Nychas; A. Goulas

1999-01-01

272

Laminar and non-laminar patterns of acetylcholinesterase activity in the marsupial lateral geniculate nucleus.  

PubMed

Acetylcholinesterase (AChE) distribution in the dorsal lateral geniculate nucleus (LGd) of 3 polyprotodont and 3 diprotodont marsupials has been compared with the cytoarchitecture and, as appropriate, with retinal terminal bands (RTBs) as demonstrated by tracers injected into the vitreous body. In this series those polyprotodont marsupials showing only partial segregation of retinal input (Virginia opossum and Tasmanian devil), display the least cell laminar differentiation. In them AChE staining is mainly diffuse but stronger in areas of greatest retinal terminal overlap. Segregation of visual input increases progressively in the remaining polyprotodont (eastern quoll) and in the diprotodonts (Tasmanian bettong, Tasmanian potoroo and brush-tailed possum), culminating in the last-named, in which segregation is most complete. Related to this development varying numbers of cell laminae/sublaminae appear and retinal terminal laminae/sublaminae (bands) are revealed. AChE activity can be correlated with both specific cell laminae/sublaminae and retinal terminal laminae/sublaminae in these complex LGds. Greatest AChE staining in every case is related to laminae/RTBs located in the medial part of the lateral (alpha) segment of LGd. Cytoarchitecturally, the ventral lateral geniculate nucleus (LGv), unlike the heterogeneous LGd, is remarkably homogeneous in the series of animals studied and shows well-stained AChE patches relating to areas receiving significant retinal input. PMID:2731033

Wilson, P M; Astheimer, L B

1989-05-01

273

A real-time restoring method for infrared images degraded by high-speed airflow  

NASA Astrophysics Data System (ADS)

Restoring images degraded by low speed airflow such as atmospheric turbulence was studied by many researchers a long time ago, and many methods were proposed. However, those methods proposed for low speed airflow generally can't meet this urgency mainly in two aspects: first, those methods are usually time-consuming, which fail time requisition; second, those deconvolution models designed for low speed airflow may not suit the case of high speed airflow, which leads to bad restoring effect. Because existent blind deconvolution methods are not competent for real-time restoring infrared images degraded by high speed airflow, a fast restoring method for that application is researched in this paper. Both the PSF estimation and the object estimation processes are constructed to improve the algorithm's efficiency. The simplified Weiner filter is adopted to fast estimate objects given PSF. For traditional methods, many computation methods, including iterative and non-iterative ones, can be used to resolve that problem. But we are more interested in non-iterative methods because of application background of our work, in which the speed of restoring algorithms is also an important factor that we must be concerned about. Therefore we choose here inverse-filtering method to estimate the object and use FFT to accelerate the computation. Gaussian-like function is used to approximate the PSF of degradation of high speed airflow. There are many papers on blur identification and was summarized well. However, those methods are either iterative, leading to slow estimation, or not feasible for Gaussian-like PSF. Therefore We figure out a new a frequency domain scheme to estimate the parameter of PSF quickly, and use both simulation and wind tunnel experiment infrared images to test its validation. Finally we compare our algorithm with other three blind algorithms, that is the Rechardson-Lucy method (RL), the maximum likelihood method (ML) and the primary component analysis method (PCA), and the results show that our algorithm not only gives much better result, but also consumes much less time.

Mi, Qiang; Fei, Jindong; Chen, Chen

2011-06-01

274

Stabilization of liquid hydrocarbon fuel combustion by using a programmable microwave discharge in a subsonic airflow  

NASA Astrophysics Data System (ADS)

Under conditions of a programmable discharge (a surface microwave discharge combined with a dc discharge), plasma-enhanced combustion of alcohol injected into a subsonic ( M = 0.3-0.9) airflow in the drop (spray) phase is stabilized. It is shown that the appearance of the discharge, its current-voltage characteristic, the emission spectrum, the total emission intensity, the heat flux, the electron density, the hydroxyl emission intensity, and the time dependences of the discharge current and especially discharge voltage change substantially during the transition from the airflow discharge to stabilized combustion of the liquid hydrocarbon fuel. After combustion stabilization, more than 80% of liquid alcohol can burn out, depending on the input power, and the flame temperature reaches ˜2000 K.

Kopyl, P. V.; Surkont, O. S.; Shibkov, V. M.; Shibkova, L. V.

2012-06-01

275

Characterizing Indoor Airflow and Pollutant Transport using Simulation Modeling for Prototypical Buildings. I. Office Buildings  

SciTech Connect

This paper describes the first efforts at developing a set of prototypical buildings defined to capture the key features affecting airflow and pollutant transport in buildings. These buildings will be used to model airflow and pollutant transport for emergency response scenarios when limited site-specific information is available and immediate decisions must be made, and to better understand key features of buildings controlling occupant exposures to indoor pollutant sources. This paper presents an example of this approach for a prototypical intermediate-sized, open style, commercial building. Interzonal transport due to a short-term source release, e.g., accidental chemical spill, in the bottom and the upper floors is predicted and corresponding HVAC system operation effects and potential responses are considered. Three-hour average exposure estimates are used to compare effects of source location and HVAC operation.

Sohn, M.D.; Daisey, J.M.; Feustel, H.E.

1999-06-01

276

The coupling influence of airflow and temperature on the wall-wetted fuel film distribution  

SciTech Connect

The coupling influence of airflow and temperature on the two-dimensional distribution of the film resulted from fuel spray impinging on a horizontal flat wall was studied with experiments. The horizontal airflow direction was perpendicular to the vertical axis of the injection spray. The results show that, as air velocity increases, the film shape turns from a circle to an oblong. As wall temperature increases, the film area shrinks. Film thickness decreases as wall temperature or air velocity increases. The boiling point of the fuel is an important temperature to affect the film area and the film thickness. Film center moves more far away in the downstream direction as air velocity increases. For a certain air velocity, film center moves less far away as wall temperature increases. (author)

Cheng, Yong-sheng [School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Shanghai 200240 (China); Deng, Kangyao; Li, Tao [Key Laboratory for Power Machinery and Engineering of Ministry of Education, Shanghai Jiao Tong University, Shanghai 200240 (China)

2010-02-15

277

Airway Resistance and Energy Budget of Airflow in a CT-Based Human Lung Model.  

NASA Astrophysics Data System (ADS)

An in-house characteristic-Galerkin finite element code is utilized to study airway resistance and energy budget of airflow in 5-7 generations of a CT-based human lung model. The energy budget of airflow in the trachea and main bronchi is further analyzed and compared with Pedley's airway resistance formula. The results show that most airways exhibit an asymptotic relationship of pressure drop proportional to mass flux with a power varying from 2 to 1.6. The maximum predicted airway resistance is found at the fourth airway generation with a value of 0.09 cm-H2O/l/s at peak inspiration. This is in excellent agreement with existing experimental data. According to the pressure drop-mass flux relationship, the five lobes have similar collective flow characteristics in the studied normal subject. The effect of turbulent laryngeal jet on the energy budget and airway resistance is also discussed.

Lin, Ching-Long; Tawhai, Merryn H.; Hoffman, Eric A.

2007-11-01

278

Stabilization of liquid hydrocarbon fuel combustion by using a programmable microwave discharge in a subsonic airflow  

SciTech Connect

Under conditions of a programmable discharge (a surface microwave discharge combined with a dc discharge), plasma-enhanced combustion of alcohol injected into a subsonic (M = 0.3-0.9) airflow in the drop (spray) phase is stabilized. It is shown that the appearance of the discharge, its current-voltage characteristic, the emission spectrum, the total emission intensity, the heat flux, the electron density, the hydroxyl emission intensity, and the time dependences of the discharge current and especially discharge voltage change substantially during the transition from the airflow discharge to stabilized combustion of the liquid hydrocarbon fuel. After combustion stabilization, more than 80% of liquid alcohol can burn out, depending on the input power, and the flame temperature reaches {approx}2000 K.

Kopyl, P. V.; Surkont, O. S.; Shibkov, V. M.; Shibkova, L. V. [Moscow State University, Faculty of Physics (Russian Federation)

2012-06-15

279

A combined PHREEQC-2\\/parallel fracture model for the simulation of laminar\\/non-laminar flow and contaminant transport with reactions  

Microsoft Academic Search

A combination of a parallel fracture model with the PHREEQC-2 geochemical model was developed to simulate sequential flow and chemical transport with reactions in fractured media where both laminar and turbulent flows occur. The integration of non-laminar flow resistances in one model produced relevant effects on water flow velocities, thus improving model prediction capabilities on contaminant transport. The proposed conceptual

Costantino Masciopinto; Angela Volpe; Domenico Palmiotta; Claudia Cherubini

2010-01-01

280

Source regions of lower-tropospheric airflow trajectories for the lower peninsula of Michigan: A 40-year air mass climatology  

Microsoft Academic Search

Airflow trajectories were used to create a long-term (40-year) air mass climatology for the lower peninsula of Michigan. The climatology provides a necessary baseline for evaluating the impact of changes in airflow on historical and potential future variations in temperature and precipitation. Five-day back trajectories were calculated four times per day at the 925 hPa level using wind data from

Ryan P. Shadbolt; Eleanor A. Waller; Joseph P. Messina; Julie A. Winkler

2006-01-01

281

Airflow elicits a spider's jump towards airborne prey. II. Flow characteristics guiding behaviour.  

PubMed

When hungry, the wandering spider Cupiennius salei is frequently seen to catch flying insect prey. The success of its remarkable prey-capture jump from its sitting plant into the air obviously depends on proper timing and sensory guidance. In this study, it is shown that particular features of the airflow generated by the insect suffice to guide the spider. Vision and the reception of substrate vibrations and airborne sound are not needed. The behavioural reactions of blinded spiders were examined by exposing them to natural and synthetic flows imitating the fly-generated flow or particular features of it. Thus, the different roles of the three phases previously identified in the fly-generated flow and described in the companion paper could be demonstrated. When exposing the spider to phase I flow only (exponentially increasing flow velocity with very little fluctuation and typical of the fly's approach), an orienting behaviour could be observed but a prey-capture jump never be elicited. Remarkably, the spider reacted to the onset of phase II (highly fluctuating flow) of a synthetically generated flow field with a jump as frequently as it did when exposed to natural fly-generated flows. In all cases using either natural or artificial flows, the spider's jump was triggered before its flow sensors were hit by phase III flow (steadily decreasing airflow velocity). Phase III may tell the spider that the prey has passed by already in case of no prey-capture reaction. Our study underlines the relevance of airflow in spider behaviour. It also reflects the sophisticated workings of their flow sensors (trichobothria) previously studied in detail. Presumably, the information contained in prey-generated airflows plays a similar role in many other arthropods. PMID:23427092

Klopsch, Christian; Kuhlmann, Hendrik C; Barth, Friedrich G

2013-02-20

282

Inflammatory Biomarkers Predict Airflow Obstruction After Exposure to World Trade Center Dust  

PubMed Central

Background: The World Trade Center (WTC) collapse on September 11, 2001, produced airflow obstruction in a majority of firefighters receiving subspecialty pulmonary evaluation (SPE) within 6.5 years post-September 11, 2001. Methods: In a cohort of 801 never smokers with normal pre-September 11, 2001, FEV1, we correlated inflammatory biomarkers and CBC counts at monitoring entry within 6 months of September 11, 2001, with a median FEV1 at SPE (34 months; interquartile range, 25-57). Cases of airflow obstruction had FEV1 less than the lower limit of normal (LLN) (100 of 801; 70 of 100 had serum), whereas control subjects had FEV1 greater than or equal to LLN (153 of 801; 124 of 153 had serum). Results: From monitoring entry to SPE years later, FEV1 declined 12% in cases and increased 3% in control subjects. Case subjects had elevated serum macrophage derived chemokine (MDC), granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor, and interferon inducible protein-10 levels. Elevated GM-CSF and MDC increased the risk for subsequent FEV1 less than LLN by 2.5-fold (95% CI, 1.2-5.3) and 3.0-fold (95% CI, 1.4-6.1) in a logistic model adjusted for exposure, BMI, age on September 11, 2001, and polymorphonuclear neutrophils. The model had sensitivity of 38% (95% CI, 27-51) and specificity of 88% (95% CI, 80-93). Conclusions: Inflammatory biomarkers can be risk factors for airflow obstruction following dust and smoke exposure. Elevated serum GM-CSF and MDC levels soon after WTC exposure were associated with increased risk of airflow obstruction in subsequent years. Biomarkers of inflammation may help identify pathways producing obstruction after irritant exposure.

Nolan, Anna; Naveed, Bushra; Comfort, Ashley L.; Ferrier, Natalia; Hall, Charles B.; Kwon, Sophia; Kasturiarachchi, Kusali J.; Cohen, Hillel W.; Zeig-Owens, Rachel; Glaser, Michelle S.; Webber, Mayris P.; Aldrich, Thomas K.; Rom, William N.; Kelly, Kerry; Prezant, David J.

2012-01-01

283

Bridge-output-to-frequency converter for smart thermal air-flow sensors  

Microsoft Academic Search

A fully integrated bridge-output-to-frequency converter has been realized as signal-conditioning circuitry for a one-chip smart thermal mass-flow sensor. The frequency converter reads out four separate resistor bridges of the air-flow sensor in order to realize high sensitivity and directional flow measurement over the full angle range of 360°. The converter selects the sensor bridges individually by means of a microprocessor-controlled

Gert J. A. van Dijk; Johan H. Huijsing

1995-01-01

284

Does submucosal diathermy to the inferior turbinates reduce nasal resistance to airflow in the long term?  

PubMed

The operation of submucosal diathermy is commonly performed for the relief of nasal obstruction due to mucosal swelling. In this study the effect of the procedure on nasal resistance to airflow is assessed by rhinomanometry. The results show that although the operation is effective in the short term (two months), there is no significant difference between the nasal resistances prior to surgery and at 15 months after surgery. PMID:3585157

Jones, A S; Lancer, J M

1987-05-01

285

IL10 polymorphisms are associated with airflow obstruction in severe alpha 1-antitrypsin deficiency  

Microsoft Academic Search

Severe a1-antitrypsin (AAT)deficiency is a provengeneticrisk factor for chronic obstructive pulmonary disease (COPD), especially in individuals who smoke. There is marked variability in the develop- ment of lung disease in individuals homozygous (PI ZZ) for this autosomalrecessivecondition,suggestingthatmodifiergenescould be important. We hypothesized that genetic determinants of ob- structive lung disease may be modifiers of airflow obstruction in individuals with severe AAT

Dawn L. DeMeo; Edward J. Campbell; Alan F. Barker; Mark L. Brantly; Edward Eden; N. Gerard McElvaney; Stephen I. Rennard; Robert A. Sandhaus; James M. Stocks; James K. Stoller; Charlie Strange; Gerard Turino; Edwin K. Silverman

2007-01-01

286

Combined simulation of airflow, radiation and moisture transport for heat release from a human body  

Microsoft Academic Search

This paper described a combined numerical simulation method of airflow, thermal radiation and moisture transport for predicting heat release from a human body. A human thermo-physiological model was also included to examine the sensible and latent heat transfer from the human body. Flow, temperature and moisture fields were investigated with three-dimensional Computational Fluid Dynamics (CFD). We used a low-Reynolds-number type

Shuzo Murakami; Shinsuke Kato; Jie Zeng

2000-01-01

287

Modeling of data center airflow and heat transfer: State of the art and future trends  

Microsoft Academic Search

An assessment of the current thermal modeling methodologies for data centers is presented, with focus on the use of computational\\u000a fluid dynamics and heat transfer as analysis tools, and model validation. Future trends in reduced or compact modeling of\\u000a data center airflow and heat transfer are presented to serve as an overview of integrating rack-level compact models into\\u000a full-scale facility

Jeffrey Rambo; Yogendra Joshi

2007-01-01

288

A complete 3D particle tracking algorithm and its applications to the indoor airflow study  

Microsoft Academic Search

While most research on particle tracking velocimetry (PTV) is devoted either to 2D flows or to small-scale 3D flows, this paper describes a complete 3D PTV algorithm and some applications to indoor airflow velocity measurements. A particle detection procedure especially adapted to the physical characteristics of neutrally buoyant helium-filled soap bubbles is described. To recover longer trajectories, a temporal tracking

Pascal Henry Biwole; Wei Yan; Yanhui Zhang; Jean-Jacques Roux

2009-01-01

289

Asymmetric surface dielectric barrier discharge in air at atmospheric pressure: electrical properties and induced airflow characteristics  

Microsoft Academic Search

The electrical properties of an asymmetric surface dielectric barrier discharge in atmospheric air have been investigated experimentally. The discharge is used for airflow production close to the dielectric surface, and the time-averaged flow velocity spatial profiles have been measured. Velocities of up to 3.5 m s-1 at heights of 1-2 mm are reached when filamentary discharges with current peaks up

Jérôme Pons; Eric Moreau; Gérard Touchard

2005-01-01

290

Nature of laminar-turbulence intermittency in shear flows.  

PubMed

In pipe, channel, and boundary layer flows turbulence first occurs intermittently in space and time: at moderate Reynolds numbers domains of disordered turbulent motion are separated by quiescent laminar regions. Based on direct numerical simulations of pipe flow we argue here that the spatial intermittency has its origin in a nearest neighbor interaction between turbulent regions. We further show that in this regime turbulent flows are intrinsically intermittent with a well-defined equilibrium turbulent fraction but without ever assuming a steady pattern. This transition scenario is analogous to that found in simple models such as coupled map lattices. The scaling observed implies that laminar intermissions of the turbulent flow will persist to arbitrarily large Reynolds numbers. PMID:23848777

Avila, M; Hof, B

2013-06-18

291

Laminar forced convection conjugate heat transfer over a flat plate  

NASA Astrophysics Data System (ADS)

Coupled heat transfer between laminar forced convection along and conduction inside a flat plate wall is theoretically studied. The laminar convective boundary layer is analyzed by employing the integral technique. The energy equations for the fluid and the plate wall are combined under the condition of the continuity in the temperature and heat flux at the fluid-solid interface. The analysis results in a simple formal solution. Expressions have been obtained for calculating local Nusselt number, wall heat flux and temperature along the plate, all are functions of the local Brun number, Brx, which is a measure of the ratio of the thermal resistance of the plate to that of the convective boundary layer. The results indicate that for Brx>=0.15, neglecting the plate resistance will results in an error of more than 5% in Nusselt number. Comparison of the present solution with other previous studies has been made. The solution may be of a considerable theoretical and practical interest.

Mosaad, M.

292

Design of minimum drag bodies in incompressible laminar flow  

Microsoft Academic Search

The problem of modifying the shape of a two-dimensional body to reduce its drag while maintaining its section area (volume per unit span) constant is addressed. Two-dimensional, incompressible, laminar flow governed by the steady-state Navier-Stokes equations is assumed about the body. In this study, a set of “adjoint” equations are solved which permits the calculation of the direction and relative

Jianchun Huan; Vijay Modi

1996-01-01

293

Laminar flame acceleration by neon enrichment in white dwarf supernovae  

Microsoft Academic Search

We explore how the laminar flame speed of degenerate C\\/O thermonuclear burning during a type Ia supernova depends on the composition of the white dwarf. Type Ia supernovae are currently the premier standard candle for measuring distances to redshift 1.6. The currently favored scenario for this supernovae is the thermonuclear incineration of a C\\/O white dwarf. Recent observations suggest that

David A. Chamulak; Edward F. Brown; Francis X. Timmes

2006-01-01

294

Asymptotic Analysis of Laminar Flame Propagation for General Lewis Numbers  

Microsoft Academic Search

The structure of a steady one-dimensional isobaric deflagration is examined for the case of a direct first-order one-step irreversible exothermic unimolecular decomposition under Arrhenius kinetics. In particular, the eigenvalue giving the speed of propagation of the laminar flame into the unburned gas is sought for constant Lewis number of order unity. The method of matched asymptotic expansion is invoked in

WILLIAM B. BUSH; FRANCIS E. FENDELL

1970-01-01

295

Numerical calculation of fully developed laminar flow in irregular annuli  

Microsoft Academic Search

Purpose – This study seeks to focus on the annular flow between rectangular and equilateral-triangular ducts under all possible arrangements. The aim of this work is to obtain accurate prediction of the friction factor of this flow using high-order finite element method. Design\\/methodology\\/approach – Steady and fully developed laminar flow of incompressible Newtonian fluid in an annulus of variable cross-sectional

O. M. Haddad; M. Q. Al-Odat

2006-01-01

296

Quenching of laminar iso-octane flames at cold walls  

Microsoft Academic Search

Quenching of laminar premixed iso-octane flames at cold walls is studied using detailed kinetics. Previous investigations of flame quenching used low-molecular-weight fuels such as methane, methanol, and acetylene. For these fuels postquench oxidation of hydrocarbons is very fast and the amount of intermediate hydrocarbons in the quench layer is low compared to the amount of unreacted fuel. However, this does

C. Hasse; M. Bollig; N. Peters; H. A. Dwyer

2000-01-01

297

Laminar source flow and heat transfer between naturally permeable disks  

NASA Astrophysics Data System (ADS)

Laminar source flow between two infinite parallel naturally permeable, fluid-saturated disks of very small permeability is considered with heat transfer. The solution is obtained by perturbing the source free flow solution and is valid for small values of reduced Reynolds number. Expression for velocity, shear stress, and temperature field are developed and the effects of the permeability on the velocity and the temperature field have been studied and discussed.

Jain, Shalini

2013-09-01

298

The Relationship of the Laminar Flame Width to Flame Speed  

Microsoft Academic Search

The width ( ? ) of a laminar flame is often characterized as a basic property of the flame and is sometimes used in turbulent combustion models to categorize the turbulence scale of the mixture. From computed flame speeds and temperature profiles of C3H8\\/Oa\\/Ns (ø=1) flames we have determined widths, using definitions based on ( dT*sol;dx)max, Q (the heat release

RICHARD J. BLINT

1986-01-01

299

The effect of riblets on laminar to turbulent transition  

Microsoft Academic Search

Experiments conducted on the effect of riblets on the laminar-to-turbulent transition of a flat plate in a water tunnel are reported. Transition was determined using a Laser Doppler Velocimeter (LDV). A smooth reference surface was compared to five riblet surfaces for a range of Reynolds numbers. Smooth surface transition Reynolds number was about 2.75 x 10 exp 6. All of

D. M. Ladd; J. J. Rohr; L. W. Reidy; E. W. Hendricks

1993-01-01

300

Dynamic Stall of a NACA 0012 Airfoil in Laminar Flow  

Microsoft Academic Search

The dynamic stall processes of a NACA 0012 airfoil oscillating sinusoidally in pitch and heave in laminar incompressible flow were investigated. The effects of changing the reduced frequency k from 0.6 to 1.2 and the pivot location x_0\\/c from 1\\/4 to 3\\/4 were calculated. The nominal angle of incidence on the airfoil oscillated between 6^circ and 18^circ about a mean

Sasi K. Digavalli

1994-01-01

301

Laminar Flow Tube Reactor interface with quadrupole mass spectrometer  

NASA Astrophysics Data System (ADS)

Nucleation of supersaturated water vapor was studied using the Laminar Flow Tube Reactor (LFTR) technique. In order to check the presence of contaminants in the freshly nucleated water particles, the LFTR has been connected to a mass spectrometer. Trace amounts contaminants arising from the substances used as a circulating liquid to maintain temperatures of the LFTR have been detected. The results of the mass spectroscopic analysis are in full agreement with the observed values of nucleation rate. .

Mikheev, Vladimir B.; Laulainen, Nels S.; Pervukhin, Viktor V.; Barlow, Stephan E.

2000-08-01

302

Numerical simulation of laminar flow past a circular cylinder  

Microsoft Academic Search

The present paper focuses on the analysis of two- and three-dimensional flow past a circular cylinder in different laminar flow regimes. In this simulation, an implicit pressure-based finite volume method is used for time-accurate computation of incompressible flow using second order accurate convective flux discretisation schemes. The computation results are validated against measurement data for mean surface pressure, skin friction

B. N. Rajani; A. Kandasamy; Sekhar Majumdar

2009-01-01

303

The transient response of strained laminar-premixed flames  

Microsoft Academic Search

Modeling and simulation of turbulent combustion in premixed gases, for relatively large-scale and low-intensity turbulence, have traditionally been based on the assumption that the flame response to strain is instantaneous. In this paper, we revisit the validity of this assumption by examining the time-dependent response of a premixed laminar flame when subjected to a sudden change in strain and a

Constantin A. Petrov; Ahmed F. Ghoniem

1995-01-01

304

Turbulent-Laminar Patterns in Plane Couette Flow  

Microsoft Academic Search

Regular patterns of turbulent and laminar fluid motion arise in plane Couette flow near the lowest Reynolds number for which\\u000a turbulence can be sustained. We study these patterns using an extension of the minimal flow unit approach to simulations of\\u000a channel flows pioneered by Jiménez and Moin. In our case computational domains are of minimal size in only two directions.

Dwight Barkley; Laurette S. Tuckerman

2005-01-01

305

Computational Study of Turbulent Laminar Patterns in Couette Flow  

Microsoft Academic Search

Turbulent-laminar patterns near transition are simulated in plane Couette flow using an extension of the minimal-flow-unit methodology. Computational domains are of minimal size in two directions but large in the third. The long direction can be tilted at any prescribed angle to the streamwise direction. Three types of patterned states are found and studied: periodic, localized, and intermittent. These correspond

Dwight Barkley; Laurette S. Tuckerman

2005-01-01

306

Computational Study of Turbulent Laminar Patterns in Couette Flow  

NASA Astrophysics Data System (ADS)

Turbulent-laminar patterns near transition are simulated in plane Couette flow using an extension of the minimal-flow-unit methodology. Computational domains are of minimal size in two directions but large in the third. The long direction can be tilted at any prescribed angle to the streamwise direction. Three types of patterned states are found and studied: periodic, localized, and intermittent. These correspond closely to observations in large-aspect-ratio experiments.

Barkley, Dwight; Tuckerman, Laurette S.

2005-01-01

307

Computational study of turbulent laminar patterns in couette flow.  

PubMed

Turbulent-laminar patterns near transition are simulated in plane Couette flow using an extension of the minimal-flow-unit methodology. Computational domains are of minimal size in two directions but large in the third. The long direction can be tilted at any prescribed angle to the streamwise direction. Three types of patterned states are found and studied: periodic, localized, and intermittent. These correspond closely to observations in large-aspect-ratio experiments. PMID:15698087

Barkley, Dwight; Tuckerman, Laurette S

2005-01-07

308

Ignition of Droplets in a Laminar Convective Environment  

Microsoft Academic Search

Numerical simulations of the ignition process of methanol and nheptane droplets in a laminar convective environment are performed\\u000a using detailed reaction mechanisms and detailed transport models. The ignition delay time of a single droplet is found to\\u000a decrease with increasing velocity of the convective gas flow. This decrease is attributed to the steepening of the spatial\\u000a gradients of the profiles

Rainer Stauch; Ulrich Maas

309

Chronic Endotoxin Exposure Produces Airflow Obstruction and Lung Dendritic Cell Expansion  

PubMed Central

Little is known about the mechanisms of persistent airflow obstruction that result from chronic occupational endotoxin exposure. We sought to analyze the inflammatory response underlying persistent airflow obstruction as a result of chronic occupational endotoxin exposure. We developed a murine model of daily inhaled endotoxin for periods of 5 days to 8 weeks. We analyzed physiologic lung dysfunction, lung histology, bronchoalveolar lavage fluid and total lung homogenate inflammatory cell and cytokine profiles, and pulmonary gene expression profiles. We observed an increase in airway hyperresponsiveness as a result of chronic endotoxin exposure. After 8 weeks, the mice exhibited an increase in bronchoalveolar lavage and lung neutrophils that correlated with an increase in proinflammatory cytokines. Detailed analyses of inflammatory cell subsets revealed an expansion of dendritic cells (DCs), and in particular, proinflammatory DCs, with a reduced percentage of macrophages. Gene expression profiling revealed the up-regulation of a panel of genes that was consistent with DC recruitment, and lung histology revealed an accumulation of DCs in inflammatory aggregates around the airways in 8-week–exposed animals. Repeated, low-dose LPS inhalation, which mirrors occupational exposure, resulted in airway hyperresponsiveness, associated with a failure to resolve the proinflammatory response, an inverted macrophage to DC ratio, and a significant rise in the inflammatory DC population. These findings point to a novel underlying mechanism of airflow obstruction as a result of occupational LPS exposure, and suggest molecular and cellular targets for therapeutic development.

Lai, Peggy S.; Fresco, Jennifer M.; Pinilla, Miguel A.; Macias, Alvaro A.; Brown, Ronald D.; Englert, Joshua A.; Hofmann, Oliver; Lederer, James A.; Hide, Winston; Christiani, David C.; Cernadas, Manuela

2012-01-01

310

COMIS -- an international multizone air-flow and contaminant transport model  

SciTech Connect

A number of interzonal models have been developed to calculate air flows and pollutant transport mechanisms in both single and multizone buildings. A recent development in multizone air-flow modeling, the COMIS model, has a number of capabilities that go beyond previous models, much as COMIS can be used as either a stand-alone air-flow model with input and output features or as an infiltration module for thermal building simulation programs. COMIS was designed during a 12 month workshop at Lawrence Berkeley National Laboratory (LBNL) in 1988-89. In 1990, the Executive Committee of the International Energy Agency`s Energy Conservation in Buildings and Community Systems program created a working group on multizone air-flow modeling, which continued work on COMIS. The group`s objectives were to study physical phenomena causing air flow and pollutant (e.g., moisture) transport in multizone buildings, develop numerical modules to be integrated in the previously designed multizone air flow modeling system, and evaluate the computer code. The working group supported by nine nations, officially finished in late 1997 with the release of IISiBat/COMIS 3.0, which contains the documented simulation program COMIS, the user interface IISiBat, and reports describing the evaluation exercise.

Feustel, H.E.

1998-08-01

311

Periodontitis is related to lung volumes and airflow limitation- a cross-sectional study.  

PubMed

This study aims to assess the potential association of periodontal diseases with lung volumes and airflow limitation in a general adult population.Based on a representative population sample of the Study of Health in Pomerania (SHIP), 1463 subjects aged 25-85 years were included. Periodontal status was assessed by clinical attachment loss (CAL), probing depth (PD), and number of missing teeth (NoMT). Lung function was measured using spirometry, body plethysmography, and diffusing capacity for carbon monoxide. Linear regression models using fractional polynomials were used to assess associations between periodontal disease and lung function. Fibrinogen and high-sensitive C-reactive protein (hs-CRP) were evaluated as potential intermediate factors.After full adjustment for potential confounders mean CAL was significantly associated with variables of mobile dynamic and static lung volumes, airflow limitation and hyperinflation (p<0.05). Including fibrinogen and hs-CRP did not change coefficients of mean CAL; associations remained statistically significant. Mean CAL was not associated with total lung capacity and diffusing capacity for carbon monoxide. Associations were confirmed for mean PD, extent measures of CAL/PD, and NoMT.Periodontal disease was significantly associated with reduced lung volumes and airflow limitation in this general adult population sample. Systemic inflammation did not provide a mechanism linking both diseases. PMID:23222882

Holtfreter, Birte; Richter, Stefanie; Kocher, Thomas; Dörr, Marcus; Völzke, Henry; Ittermann, Till; Obst, Anne; Schäper, Christoph; John, Ulrich; Meisel, Peter; Grotevendt, Anne; Felix, Stephan B; Ewert, Ralf; Gläser, Sven

2012-12-01

312

On intra- and intersubject variabilities of airflow in the human lungs.  

PubMed

The effects of intra- and intersubject variabilities in airway geometry on airflow in the human lungs are investigated by large eddy simulation. The airway models of two human subjects consisting of extra- and intrathoracic airways are reconstructed from CT images. For intrasubject study, airflows at two inspiratory flow rates are simulated on the airway geometries of the same subject with four different levels of truncation. These airway models are the original complete geometry and three geometries obtained by truncating the original one at the subglottis, the supraglottis, and the laryngopharynx, respectively. A comparison of the airflows in the complete geometry model shows that the characteristics of the turbulent laryngeal jet in the trachea are similar regardless of Reynolds number in terms of mean velocities, turbulence statistics, coherent structures, and pressure distribution. The truncated airway models, however, do not produce the similar flow structures observed in the complete geometry. An improved inlet boundary condition is then proposed for the airway model truncated at the laryngopharynx to improve the accuracy of solution. The new boundary condition significantly improves the mean flow. The spectral analysis shows that turbulent characteristics are captured downstream away from the glottis. For intersubject study, although the overall flow characteristics are similar, two morphological factors are found to significantly affect the flows between subjects. These are the constriction ratio of the glottis with respect to the trachea and the curvature and shape of the airways. PMID:19901999

Choi, Jiwoong; Tawhai, Merryn H; Hoffman, Eric A; Lin, Ching-Long

2009-10-13

313

On intra- and intersubject variabilities of airflow in the human lungs  

NASA Astrophysics Data System (ADS)

The effects of intra- and intersubject variabilities in airway geometry on airflow in the human lungs are investigated by large eddy simulation. The airway models of two human subjects consisting of extra- and intrathoracic airways are reconstructed from CT images. For intrasubject study, airflows at two inspiratory flow rates are simulated on the airway geometries of the same subject with four different levels of truncation. These airway models are the original complete geometry and three geometries obtained by truncating the original one at the subglottis, the supraglottis, and the laryngopharynx, respectively. A comparison of the airflows in the complete geometry model shows that the characteristics of the turbulent laryngeal jet in the trachea are similar regardless of Reynolds number in terms of mean velocities, turbulence statistics, coherent structures, and pressure distribution. The truncated airway models, however, do not produce the similar flow structures observed in the complete geometry. An improved inlet boundary condition is then proposed for the airway model truncated at the laryngopharynx to improve the accuracy of solution. The new boundary condition significantly improves the mean flow. The spectral analysis shows that turbulent characteristics are captured downstream away from the glottis. For intersubject study, although the overall flow characteristics are similar, two morphological factors are found to significantly affect the flows between subjects. These are the constriction ratio of the glottis with respect to the trachea and the curvature and shape of the airways.

Choi, Jiwoong; Tawhai, Merryn H.; Hoffman, Eric A.; Lin, Ching-Long

2009-10-01

314

Regulation of respiratory airflow during panting and feeding in the dog.  

PubMed

Cineradiographic study of the movement patterns of oropharyngeal and laryngeal structures during breathing and panting in dogs, correlated with recordings of expiratory and inspiratory airflow patterns (via thermocouples) at the nose and mouth show that the soft palate is the principal structural component regulating the path of respiratory in these animals. Cyclical movements of the soft palate during panting are accompanied by complementary movements of the posterior dorsum of the tongue (and epiglottis) to open and to close alternately the oropharynx and nasopharynx. The epiglottis appears to play a passive role during changes in airflow direction; its movements at this time being closely coupled to movements of the posterior tongue and hyoid. The dogs did not breathe during lapping or mastication, indicating the loss of functional separation of respiratory and feeding activities - a role traditionally held for the evolution of a secondary palate in mammals. Food stored in the posterior region of the oral cavity was observed to obstruct airflow via the nasopharynx during food transport and breakdown. Respiration commenced only after the food bolus had been swallowed. We suggest that specializations of the soft palate and epiglottis in dogs for thermal panting appear to restrict the formation of an adequate oropharyngeal seal during feeding. PMID:4048669

Biewener, A A; Soghikian, G W; Crompton, A W

1985-08-01

315

Numerical computation of buoyant airflows confined to attic spaces under opposing hot and cold wall conditions  

Microsoft Academic Search

The present paper addresses laminar natural convection of air confined to an isosceles triangular cavity representative of conventional attic spaces in houses and buildings with pitched roofs and horizontal suspended ceilings. Detailed experimental data in terms of velocities, temperatures and wall heat fluxes has become available for attic spaces under summer and winter conditions some time ago. However, the comparison

El Hassan Ridouane; Antonio Campo; Matthew McGarry

2005-01-01

316

Airflow-based PCO2 monitoring delivers O2 and removes CO2 from the monitored environment.  

PubMed

Previous investigation has suggested that the use of airflow-based gastrointestinal intraluminal PCO2 (GI PiCO2) monitoring systems may affect the local tissue microenvironment, making it not representative of the organ system as a whole. Therefore, we investigated the effects of using an airflow-based PCO2 monitoring system in a sealed environment. A 250-mL Erlenmeyer flask was filled with 10% CO2/90% N2 and was sealed with probes in place. Using a fiber-optic (Neotrend, Diametrix Medical, St. Paul, MN) system, the PCO2 and PO2 were continuously monitored with and without the airflow-based (Tonocap, Tonometrics, Datex-Ingstrom, Helsinki, Finland) system operating. PCO2 and PO2 remained constant when the airflow-based system was not in operation. PCO2 decreased 25.3 mmHg and PO2 increased 30 mmHg from a starting value of 0 mmHg when the airflow-based system was in operation for 12 h. The use of airflow-based methods for determining GI PiCO2 may influence the values obtained. Nonsample removing techniques such as fiber-optic methods for monitoring GI PiCO2 are preferable because they neither deliver O2 to nor remove CO2 from the local microenvironment. PMID:12166786

Vincent, Robert; Freeman, Brian; Weatherford, Eric; Henderson, LaRhee; Buising, Charisse; Wall, Piper

2002-08-01

317

Laminar flame acceleration by neon enrichment in white dwarf supernovae  

NASA Astrophysics Data System (ADS)

We explore how the laminar flame speed of degenerate C/O thermonuclear burning during a type Ia supernova depends on the composition of the white dwarf. Type Ia supernovae are currently the premier standard candle for measuring distances to redshift 1.6. The currently favored scenario for this supernovae is the thermonuclear incineration of a C/O white dwarf. Recent observations suggest that there may be more than one population of progenitor, and it has been suggested the peak luminosity may depend on the composition of the progenitor white dwarf. Of particular interest is 22 Ne, which is formed from CNO elements during core He burning of the progenitor star and therefore reflects the metallicity of the progenitor. We find that the laminar flame speed of a C/O mixture increases linearly with the abundance of 22 Ne when the abundance of 22 Ne is small. The faster and narrower laminar flame enlarges the lengthscale at which turbulent eddies can disrupt the burn. As a result, the addition of 22 Ne might lower the density at which a transition to distributed burning occurs.

Chamulak, David; Brown, Edward F.; Timmes, Francis X.

318

Laminar-turbulent cycles in inclined lock-exchange flows  

NASA Astrophysics Data System (ADS)

We consider strongly confined, stably stratified shear flows generated as a lock exchange in a tube inclined at an angle of ?=45?. This paper focuses on a transitional regime, in which the flow alternates between two distinct states: laminar, parallel shear flow and intense transverse motion characteristic of turbulence. Laminar-turbulent cycles were captured at Atwood numbers At?(?2-?1)/(?1+?2) ranging from 2.45×10-3 to 4.0×10-3, where (?1,?2) are the initial densities of the two fluids, with multiple cycles observed at At=2.55×10-3. The evolution of the density and velocity fields in these flows was measured simultaneously using laser-induced fluorescence and particle image velocimetry. During each laminar-turbulent cycle, the axial velocity exhibits a distinctive ramp-cliff pattern, indicating that the flow accelerates as it relaminarizes, then decelerates rapidly as the Kelvin-Helmholtz billows break down. Within the range of experimental conditions, transverse stratification does not directly determine the onset of instability. Instead, the data suggest that a necessary criterion for the onset of instability is for the local Reynolds number to exceed 2200, with only a weak dependence on the Richardson number.

Tanino, Yukie; Moisy, Frédéric; Hulin, Jean-Pierre

2012-06-01

319

The effects of gravity on wrinkled laminar flames  

SciTech Connect

Laminar and turbulent conical Bunsen type flames were used. The study compares results from normal gravity with the burner in an up-right orientation (+g), the burner inverted (-g), and in microgravity ({mu}g) by using the NASA Lewis drop tower facility. The primary diagnostic is a laser schlieren system and some LDA measurements were taken for the +g condition to measure the flow field. The +g laminar flame experiences a large amount of instabilities and results in an unsteady flame tip; cause is torroidal vortex rolling up between products and stagnate surrounding air. Comparison between LDA measurements in reactants and schlieren images shows that velocity fluctuation are induced at the same frequency as the roll up vortices are formed. This pumping of the reactant stream by the product/air interface instability in the +g case is also observed in the turbulent flames. In the -g arrangement the product/air interface is stable so there is no large pumping of the flame tip. At low flow rates the -g flames have flattened tips, but at higher flow rates they become conical in shape. When both flames. appear conical, the -g flames are longer for the same flow rate. In {mu}g the larger instabilities in the flame no longer exist as the product/air interface is believed to become stable. The laminar flames in {mu}g still show small instabilities over the entire flame.

Kostiuk, L.W.; Zhou, L.; Cheng, R.K.

1992-09-01

320

The effects of gravity on wrinkled laminar flames  

SciTech Connect

Laminar and turbulent conical Bunsen type flames were used. The study compares results from normal gravity with the burner in an up-right orientation (+g), the burner inverted (-g), and in microgravity ([mu]g) by using the NASA Lewis drop tower facility. The primary diagnostic is a laser schlieren system and some LDA measurements were taken for the +g condition to measure the flow field. The +g laminar flame experiences a large amount of instabilities and results in an unsteady flame tip; cause is torroidal vortex rolling up between products and stagnate surrounding air. Comparison between LDA measurements in reactants and schlieren images shows that velocity fluctuation are induced at the same frequency as the roll up vortices are formed. This pumping of the reactant stream by the product/air interface instability in the +g case is also observed in the turbulent flames. In the -g arrangement the product/air interface is stable so there is no large pumping of the flame tip. At low flow rates the -g flames have flattened tips, but at higher flow rates they become conical in shape. When both flames. appear conical, the -g flames are longer for the same flow rate. In [mu]g the larger instabilities in the flame no longer exist as the product/air interface is believed to become stable. The laminar flames in [mu]g still show small instabilities over the entire flame.

Kostiuk, L.W.; Zhou, L.; Cheng, R.K.

1992-09-01

321

Turbulent-Laminar Patterns in Pipes and Channels  

NASA Astrophysics Data System (ADS)

When fluid flows through a channel, pipe, or duct, there are two basic forms of motion: smooth laminar motion and complex turbulent motion. The discontinuous transition between these states is a fundamental problem that has been studied for more than 100 years. What has received far less attention is the large-scale nature of the turbulent flows near transition once they are established. We have carried out extensive numerical computations in pipes and channels to investigate the nature of transitional turbulence in these flow. We show the existence of three fundamentally different turbulent states separated by two distinct Reynolds numbers. In the case of pipe flow for example, below Re approximately 2200, turbulence takes the form of familiar equilibrium (or long-time transient) puffs. The turbulence is intensive -- puffs are localized and the ratio of turbulent to laminar flow is not dictated by system size but by factors such as initial conditions. At Re=2200 the flow makes a striking transition to extensive turbulence where the amount of turbulent flow scales with pipe length. The asymptotic state is an irregular (intermittent) alternation of turbulent and laminar flow whose complexity is inherent and does not result from random initial disturbances. Intermittency continues until Re=2500 where the intermittency factor, and other measures, reveal a continuous transition to a state of uniform turbulence along the pipe. We argue that these states are a manifestation of universal large-scale structures in transitional shear flows.

Barkley, Dwight

2010-03-01

322

Mean flow of turbulent laminar patterns in plane Couette flow  

NASA Astrophysics Data System (ADS)

A turbulent-laminar banded pattern in plane Couette flow is studied numerically. This pattern is statistically steady, is oriented obliquely to the streamwise direction, and has a very large wavelength relative to the gap. The mean flow, averaged in time and in the homogeneous direction, is analysed. The flow in the quasi-laminar region is not the linear Couette profile, but results from a non-trivial balance between advection and diffusion. This force balance yields a first approximation to the relationship between the Reynolds number, angle, and wavelength of the pattern. Remarkably, the variation of the mean flow along the pattern wavevector is found to be almost exactly harmonic: the flow can be represented via only three cross-channel profiles as U(x,y,z) = U_0(y) + U_c(y) cos(kz) + U_s(y) sin(kz). A model is formulated which relates the cross-channel profiles of the mean flow and of the Reynolds stress. Regimes computed for a full range of angle and Reynolds number in a tilted rectangular periodic computational domain are presented. Observations of regular turbulent-laminar patterns in other shear flows -- Taylor-Couette, rotor-stator, and plane Poiseuille -- are compared.

Barkley, Dwight; Tuckerman, Laurette S.

2007-03-01

323

Turbulent-laminar patterns in Couette flow: parameter dependence  

NASA Astrophysics Data System (ADS)

It now appears that large-scale turbulent-laminar patterns are inevitable intermediate states on the route from turbulent to laminar flow in large-aspect-ratio plane Couette flow. Computations in tilted periodic domains with one long lateral direction can access regimes which are not attainable experimentally. By fixing the pattern angle and wavelength, we determine the boundaries in parameter space within which each pattern can exist. The angle between the pattern and the streamwise direction can vary between 12^rc and 72^rc, a much larger range than has thus far been observed experimentally. The other parameter ranges 300? Re ? 400, 18 ? ? ? 33 (in gap widths) are close to those observed experimentally. When the computational domain is not tilted, i.e. ?=0^rc or 90^rc, we find only uniform turbulence or simple Couette flow. We show that turbulent-laminar transition in a domain with one long direction can occur quite differently from that in a traditional minimal flow unit.

Tuckerman, Laurette; Barkley, Dwight

2004-11-01

324

Laminar-turbulent cycles in inclined lock-exchange flows.  

PubMed

We consider strongly confined, stably stratified shear flows generated as a lock exchange in a tube inclined at an angle of ?=45(?). This paper focuses on a transitional regime, in which the flow alternates between two distinct states: laminar, parallel shear flow and intense transverse motion characteristic of turbulence. Laminar-turbulent cycles were captured at Atwood numbers At?(?(2)-?(1))/(?(1)+?(2)) ranging from 2.45×10(-3) to 4.0×10(-3), where (?(1),?(2)) are the initial densities of the two fluids, with multiple cycles observed at At=2.55×10(-3). The evolution of the density and velocity fields in these flows was measured simultaneously using laser-induced fluorescence and particle image velocimetry. During each laminar-turbulent cycle, the axial velocity exhibits a distinctive ramp-cliff pattern, indicating that the flow accelerates as it relaminarizes, then decelerates rapidly as the Kelvin-Helmholtz billows break down. Within the range of experimental conditions, transverse stratification does not directly determine the onset of instability. Instead, the data suggest that a necessary criterion for the onset of instability is for the local Reynolds number to exceed 2200, with only a weak dependence on the Richardson number. PMID:23005207

Tanino, Yukie; Moisy, Frédéric; Hulin, Jean-Pierre

2012-06-11

325

IFTS measurements of a laboratory scale laminar flame  

NASA Astrophysics Data System (ADS)

A point-and-shoot, passive remote sensing technology is highly desired to accurately monitor the combustion efficiency (CE) of petrochemical flares. A Phase II DOE-funded SBIR effort is being led by Spectral Sciences, Inc. to develop the methodologies needed to enable remote CE measurements via spectral remote sensing. Part of this effort entails standing up a laboratory-scale flare measurement laboratory to develop and validate CE measurements. This paper presents an overview and summarizes current progress of the Air Force Institute of Technology's (AFIT) contribution to this multi-organization, two-year effort. As a first step, a Telops Hyper-Cam longwave infrared (LWIR, 750-1300cm-1 or 7.7-13.3?m) imaging Fourier-transformspectrometer (IFTS) is used to examine a laminar, calibration flame produced by a Hencken burner. Ethylene and propane were combusted under several different fuel/air mixing ratios. For each event, 300 hyperspectral datacubes were collected on a 172(W)×200(H) pixel window at a 1.5cm-1 spectral resolution. Each pixel had approximately a 1.5×1.5mm2 instantaneous field-of-view (IFOV). Structured emission is evident throughout the combustion region with several lines arising from H2O; other lines have not yet been assigned. These first known IFTS measurements of a laminar Hencken-burner flame are presented along with some preliminary analysis. While the laminar flame appears stationary to the eye, significant flame flicker at a fundamental frequency of 17Hz was observed in the LWIR, and this is expected to complicate spectral interpretation for species concentrations and temperature retrieval. Changes to the fuel-air ratio (FAR) produced sizable changes in spectral intensity. Combustion spectra of ethylene and propane corresponding to ideal FAR were nearly identical.

Rhoby, Michael R.; Harley, Jacob L.; Gross, Kevin C.

2011-09-01

326

Experimental nucleation studies with a laminar flow tube reactor  

NASA Astrophysics Data System (ADS)

A Laminar Flow Tube Reactor (LFTR) has been used as a quantitative tool for nucleation measurements. It has been specially designed and constructed in order to minimize the potential experimental inaccuracies. Careful attention has been paid to the temperature conditions inside the LFTR. Other sources of experimental uncertainties, such as initial vapor concentration conditions, calculations of the parameters of the nucleation zone, and particle concentration measurements have been thoroughly analyzed as well. The nucleation rate dependence as a function of supersaturation and temperature has been measured for the dibutyl phthalate, ethylene glycol, and glycerol. The experimental results have been compared with the other experimental data and with the theoretical predictions. .

Mikheev, Vladimir B.; Laulainen, Nels S.; Barlow, Stephan E.

2000-08-01

327

Advanced Nucleation Study Using The Laminar Flow Tube Reactor (LFTR)  

NASA Astrophysics Data System (ADS)

Quantitative measurements of homogeneous nucleation rates have been made using the laminar flow tube reactor experimental technique. Thorough computer calculations of the temperature, vapor concentration, supersaturation, and nucleation rate distributions in the reactor tube were made. The nucleation volume as well as the time of nucleation have been determined with high accuracy. The concentration of the particles formed in the LFTR was measured at the outlet of the reactor tube using the ultrafine CPC TSI-3025A. Comparison of experimental data with theoretical predictions based on SCC-model has been made.

Mikheev, Vladimir; Laulainen, Nels

1998-03-01

328

Cortical laminar necrosis related to prolonged focal status epilepticus  

PubMed Central

Cortical laminar necrosis (CLN) is radiologically defined as high intensity cortical lesions on T1 weighted MRI images following a gyral distribution. Histopathologically, CLN is characterised by pannecrosis of the cortex involving neurones, glial cells, and blood vessels. It has been reported to be associated with hypoxia, metabolic disturbances, drugs, and infections. We present two patients who developed CLN and permanent neurological deficits after prolonged and repeated focal status epilepticus. The possible mechanisms leading to CLN in these patients are discussed, together with the implications of prompt and aggressive treatment in similar cases.

Donaire, A; Carreno, M; Gomez, B; Fossas, P; Bargallo, N; Agudo, R; Falip, M; Setoain, X; Boget, T; Raspall, T; Obach, V; Rumia, J

2006-01-01

329

Analysis of skin lesions using laminar optical tomography.  

PubMed

Evaluation of suspicious skin lesions by dermatologists is usually accomplished using white light examination and direct punch or surgical biopsy. However, these techniques can be imprecise for estimating a lesion's margin or level of dermal invasion when planning surgical resection. Laminar optical tomography (LOT) is an imaging technique capable of acquiring depth-sensitive information within scattering tissues. Here, we explore whether LOT data can be used to predict the depth and thickness of pigmented lesions using a range of simulations and phantom models. We then compare these results to LOT data acquired on normal and malignant skin lesions in vivo. PMID:22808439

Muldoon, Timothy J; Burgess, Sean A; Chen, Brenda R; Ratner, Désirée; Hillman, Elizabeth M C

2012-06-22

330

Unsteady Laminar CFD Simulation of Undulatory Rainbow Trout Swimming Hydrodynamics  

NASA Astrophysics Data System (ADS)

The propulsion mechanism of an undulatory swimming 10 cm rainbow trout (oncorhynchus mykiss) is studied using a laminar 2-D unsteady incompressible Navier-Stokes computational model with a moving adaptive mesh (Fluent 6.1). The wake mechanism is dominated by a reverse von Karman vortex street and compares well to previous experimental data. Thrust and drag forces are quantified and the equilibrium condition is satisfied within 5%. A method is developed to calculate hydrodynamic power using work, which results in a swimming efficiency of 62%. An investigation of the boundary layer shows incipient separation and highly unsteady velocity profiles.

Flanagan, Patrick; Hotchkiss, Rollin; Stock, David

2004-11-01

331

The incremental shuttle walking test in elderly people with chronic airflow limitation  

PubMed Central

Background: There is a concern that comorbidity or frailty in older people could limit the usefulness of currently available exercise tests for chronic lung disease. This study evaluated the feasibility and reproducibility of the incremental shuttle walking test (SWT) in people aged 70 years or over, compared exercise tolerance with other disability markers, and assessed whether the SWT is responsive to change after bronchodilators. Methods: Fifty elderly patients with chronic airflow limitation (CAL) and 32 controls without airflow limitation attempted the SWT before and after combined nebulised salbutamol/ipratropium bromide. Subjects also completed the Nottingham Extended Activities of Daily Living index (NEADL) and the London Handicap score (LHS). Results: Forty four subjects with CAL (88%) and 29 controls (84%) completed the SWT, including many with co-morbidities. Two week repeatability was good and the SWT was strongly associated with EADL (r=0.51, p<0.001) and LHS (r=0.43, p<0.004), but only weakly with forced expiratory volume in 1 second (FEV1) (r=0.31, p=0.05). Subjects with CAL walked a mean distance of 177.7 m compared with 243.3 m in controls (p<0.001); following bronchodilator therapy the distance walked increased in the CAL group by 13.2% (p=0.009). Conclusion: The SWT is a feasible and reproducible measure of exercise tolerance in elderly people with and without airflow obstruction and correlates with other markers of disability. It is sensitive to change following bronchodilation in subjects with CAL, although the change correlates less well with improvements in FEV1. Overall, these results suggest that the SWT might be an appropriate measure to assess interventions in elderly people.

Dyer, C; Singh, S; Stockley, R; Sinclair, A; Hill, S

2002-01-01

332

Diagnostic performance of single airflow channel recording (ApneaLink) in home diagnosis of sleep apnea  

Microsoft Academic Search

Background  ApneaLink is a novel single-channel screening device for sleep apnea detection which is based on pressure-transduced measurement\\u000a of oronasal airflow, summarised as respiratory disturbance index per hour of recording time (RDIApneaLink). We tested ApneaLink's diagnostic performance in a patient population with high prevalence of sleep apnea.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  ApneaLink was applied simultaneously with in-laboratory polysomnography (PSG) (n?=?102, 24 female, age 54.7 years) and

Regine Ragette; Yi Wang; Gerhard Weinreich; Helmut Teschler

2010-01-01

333

Inspiratory airflow dynamics during sleep in veterans with Gulf War illness: a controlled study  

Microsoft Academic Search

Purpose  To determine whether veterans with Gulf War Illness (GWI) are distinguished by sleep-disordered breathing, we compared inspiratory\\u000a airflow dynamics during sleep between veterans with GWI and asymptomatic veterans of the first Gulf War.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  We recruited 18 male veterans with GWI and 11 asymptomatic male veterans of the first Gulf War by advertisement. The two samples\\u000a were matched for age and

Mohammad M. Amin; Zuzana Belisova; Sayeed Hossain; Morris S. Gold; Joan E. Broderick; Avram R. Gold

334

Equine neutrophil elastase in plasma, laminar tissue, and skin of horses administered black walnut heartwood extract  

Microsoft Academic Search

Laminitis is a local manifestation of a systemic inflammatory response that is characterized by neutrophil activation and movement of neutrophils into the laminar tissues. Given the evidence for the involvement of neutrophils in the development of laminitis, we measured concentrations of neutrophil elastase, a serine protease released from the azurophilic granules of neutrophils, in plasma, skin and laminar tissues obtained

Geoffroy de la Rebière de Pouyade; Laura M. Riggs; James N. Moore; Thierry Franck; Ginette Deby-Dupont; David J. Hurley; Didier Serteyn

2010-01-01

335

Tabulated chemistry approaches for laminar flames: Evaluation of flame-prolongation of ILDM and flamelet methods  

Microsoft Academic Search

The present study considers the performance of tabulation methods for numerical simulation of complex chemical kinetics in laminar combusting flows and compares their predictions to results obtained by direct calculation. Two tabulation methods are considered: the Flame Prolongation of Intrinsic low-dimensional manifold (FPI) method and Steady Laminar Flamelet Model (SLFM). The FPI method is of current interest as it is

Pradeep K. Jha; Clinton P. T. Groth

2011-01-01

336

Tabulated chemistry approaches for laminar flames: Evaluation of flame-prolongation of ILDM and flamelet methods  

Microsoft Academic Search

The present study considers the performance of tabulation methods for numerical simulation of complex chemical kinetics in laminar combusting flows and compares their predictions to results obtained by direct calculation. Two tabulation methods are considered: the Flame Prolongation of Intrinsic low-dimensional manifold (FPI) method and Steady Laminar Flamelet Model (SLFM). The FPI method is of current interest as it is

Pradeep K. Jha; Clinton P. T. Groth

2012-01-01

337

Soot suppression by ferrocene in laminar ethylene\\/air nonpremixed flames  

Microsoft Academic Search

An experimental investigation is presented on the origin of the soot suppressing role of ferrocene additive in laminar, coannular, ethylene\\/air nonpremixed flames. The conditions examined involve laminar flames operating above and below their smoke point. In-flame diagnostics are employed to discern the interaction between the soot matrix and additive combustion products. The data presented in a previous study, as produced

Jie Zhang; Constantine M. Megaridis

1996-01-01

338

Laminar sources of synaptic input to cortical inhibitory interneurons and pyramidal neurons  

Microsoft Academic Search

The functional role of an individual neuron within a cortical circuit is largely determined by that neuron's synaptic input. We examined the laminar sources of local input to subtypes of cortical neurons in layer 2\\/3 of rat visual cortex using laser scanning photostimulation. We identified three distinct laminar patterns of excitatory input that correspond to physiological and morphological subtypes of

E. M. Callaway; J. L. Dantzker

2000-01-01

339

Laminar Flamelet Modelling of the Mean Reaction Rate in a Premixed Turbulent Flame,  

National Technical Information Service (NTIS)

The modelling of the mean reaction rate in a premixed turbulent flame is approached by means of a library of laminar flame solutions. A formulation of such a library is presented and the detailed data requirements are investigated. Laminar flame calculati...

R. S. Cant B. Rogg K. N. C. Bray

1989-01-01

340

On Laminar Flamelet Modelling of the Mean Reaction Rate in a Premixed Turbulent Flame  

Microsoft Academic Search

The modelling of the mean reaction rate in a premixed turbulent flame is approached by means of a library of laminar flame solutions. A formulation of such a library is presented and the detailed data requirements are investigated. Laminar flame calculations are performed in an asymmetrical counterflow configuration with a cold, reactive methane-air mixture flowing against the corresponding hot equilibrium

R. S. CANT; B. ROGG; K. N. C. BRAY

1990-01-01

341

An experimental and computational study on the propagation and kinetic structure of laminar premixed flames  

Microsoft Academic Search

The steady propagation and chemical kinetic structure of adiabatic planar, laminar premixed flames were experimentally and numerically studied with systematic and extensive variations of the effects of fuel, oxidizer, pressure, stoichiometry, and flame temperature. Experimentally, the laminar flame speeds were determined by using the counterflow twin-flame configuration with laser Doppler velocimetry probing and systematic elimination of flame stretch effects. Numerical

Egolfopoulos

1990-01-01

342

Experimental determination of laminar burning velocity for butanol and ethanol iso-octane blends  

Microsoft Academic Search

The potential of butanol as an additive in iso-octane used as gasoline fuel was characterized with respect to laminar combustion, and compared with ethanol. New sets of data of laminar burning velocity are provided by using the spherical expanding flame methodology, in a constant volume vessel. This paper presents the first results obtained for pure fuels (iso-octane, ethanol and butanol)

G. Broustail; P. Seers; F. Halter; G. Moréac; C. Mounaim-Rousselle

2011-01-01

343

LAMINAR FLAME SPEEDS OF ETHANOL, n-HEPTANE, ISO OCTANE AIR MIXTURES  

Microsoft Academic Search

One of the most important properties of premixed flames is burning velocity. Laminar burning velocities play essential roles in determining several important aspects of the combustion process in spark ignition engines; among these are the ignition delay, the thickness of the wall quench layers, and the minimum ignition energy. It is found that a detailed knowledge of laminar premixed flames

HARA Takashi; TANOUE Kimitoshi

344

Low Drag Airfoil Design Utilizing Passive Laminar Flow and Coupled Diffusion Control Techniques.  

National Technical Information Service (NTIS)

A two-dimensional high chord Reynolds number passive laminar airfoil was designed for a C sub l = 0.73 at a M at infinity = 0.6 and Re sub c = 4 times 10 to the 7th power providing an extremely high L/D = 240. This laminar airfoil design concept integrate...

R. L. Mask

1980-01-01

345

Laminar Burning Velocities for Hydrogen, Methane, Acetylene, and Propane-Nitrous Oxide Flames  

Microsoft Academic Search

Mixtures of four fuels (hydrogen, methane, acetylene and propane) with nitrous oxide were studied to experimentally and numerically determine the laminar flame speeds at near atmospheric pressure (0.8 atm). Using the flat flame method, laminar flame speeds for these nitrous oxide flames were determined for different levels of dilution with nitrogen. A comprehensive hydrocarbon oxidation mechanism in the literature was integrated

O. A. Powell; P. Papas; C. Dreyer

2009-01-01

346

Development of Quiet-Flow Supersonic Wind Tunnels for Laminar-Turbulent Transition Research.  

National Technical Information Service (NTIS)

This grant supported research into quiet-flow supersonic wind-tunnels, between May 1990 and December 1994. Quiet-flow nozzles operate with laminar nozzle-wall boundary layers, in order to provide low-disturbance flow for studies of laminar-turbulent trans...

S. P. Schneider

1994-01-01

347

The drag reduction in laminar and turbulent boundary layers by prepared surfaces with reduced momentum transfer  

Microsoft Academic Search

Similarity solutions for laminar boundary layer tangential momentum accomodation coefficient (TAC) slip flow are presented showing that the efficiency of a given slip coefficient is pressure-gradient dependent. Turbulent boundary layer flow is calculated applying an integral method. Slip produces a sort of laminarization. It is confirmed that a given TAC-value in turbulent flow corresponds to a Kn number about one

B. Gampert; K. Homann; H. B. Rieke

1980-01-01

348

An experimental study of laminar flow control airfoil with suction through perforated surface at low speed  

Microsoft Academic Search

An experimental study of a laminar flow control airfoil with suction through a perforated surface at low speed was made. The airfoil section was designed to be a natural laminar flow airfoil which can delay the boundary layer transition as far downstream as possible. The effects of suction quantity and position of sucked area on transition delay were examined. It

Yoji Ishida; Masayoshi Noguchi

1988-01-01

349

Structure and extinction of laminar ethanol-air spray flames  

NASA Astrophysics Data System (ADS)

A numerical study of structures of laminar ethanol-air spray flames in the counterflow configuration is presented. The model describes a thin spray where the gas phase is formulated in Eulerian coordinates and the spray is described through Lagrangian equations. The study presents structures and extinction conditions for atmospheric spray flames, and the focus is the fuel ethanol that has not been studied so far in the literature. Moreover, both mono- and bidisperse sprays are studied for strain rates that range from 55 s-1 up to extinction. The different droplet size groups that are considered in the discrete droplet model are treated completely separately from each other so that their individual history is represented by the model. The emphasis is the possible representation of bidisperse sprays through a Sauter mean radius for the above specified conditions which has a specific significance to the consideration of laminar spray flame structures in turbulent spray flame computations where a flamelet model may be employed. The results show that ethanol-air spray flames are more stable than methanol-air spray flames and their extinction flame temperature is above that of methanol-air spray flames all the way up to extinction. The extinction conditions of the bidisperse and the monodisperse ethanol-air spray flames with a Sauter mean radius differ considerably. This is attributable to the occurrence of droplet reversal and oscillation. The study also shows the effect of the spray dispersity on the species profiles.

Gutheil, E.

2001-06-01

350

Laminar cortical necrosis in adrenal crisis: sequential changes on MRI.  

PubMed

We describe the serial magnetic resonance imaging (MRI) findings in a six-year-old girl with congenital adrenal hyperplasia, who presented with seizures and unconsciousness during a hypoadrenal crisis. Initial neuroimaging revealed the presence of brain edema with high signal changes in the fronto-parietal cortex on diffusion-weighted MRI. The brain edema worsened four days into admission, and by day 14 low-density areas were seen over the frontal lobes bilaterally using computed tomography (CT). Follow-up MRI at between one and two months of admission revealed extensive white matter lesions with high intensity on T2-weighted images (T2WI) and fluid-attenuated inversion recovery (FLAIR) images, which extended into deep cortical layers. Additionally, linear lesions with high signal change on T1-weighted imaging developed in the superficial cortical layers, with frontal predominance. This layer appeared isointense on T2WI and high intensity on FLAIR images, suggesting laminar cortical necrosis. Two months later, linear, cavitary lesions appeared in the middle cortical layers between the aforementioned superficial laminar abnormality and deep cortex/white matter lesions. The high-intensity signals in the deep cortical layers remained contiguous with the white matter lesions. This unique type of multi-layered cortical lesion may have resulted from a complex combination of hypoglycemia and hypoxia/ischemia in the setting of adrenal insufficiency. PMID:17590301

Saito, Yoshiaki; Ogawa, Toshihide; Nagaishi, Jun-ichi; Inoue, Takehiko; Maegaki, Yoshihiro; Ohno, Kousaku

2007-06-21

351

Laminar flow of two miscible fluids in a simple network  

NASA Astrophysics Data System (ADS)

When a fluid comprised of multiple phases or constituents flows through a network, nonlinear phenomena such as multiple stable equilibrium states and spontaneous oscillations can occur. Such behavior has been observed or predicted in a number of networks including the flow of blood through the microcirculation, the flow of picoliter droplets through microfluidic devices, the flow of magma through lava tubes, and two-phase flow in refrigeration systems. While the existence of nonlinear phenomena in a network with many inter-connections containing fluids with complex rheology may seem unsurprising, this paper demonstrates that even simple networks containing Newtonian fluids in laminar flow can demonstrate multiple equilibria. The paper describes a theoretical and experimental investigation of the laminar flow of two miscible Newtonian fluids of different density and viscosity through a simple network. The fluids stratify due to gravity and remain as nearly distinct phases with some mixing occurring only by diffusion. This fluid system has the advantage that it is easily controlled and modeled, yet contains the key ingredients for network nonlinearities. Experiments and 3D simulations are first used to explore how phases distribute at a single T-junction. Once the phase separation at a single junction is known, a network model is developed which predicts multiple equilibria in the simplest of networks. The existence of multiple stable equilibria is confirmed experimentally and a criterion for existence is developed. The network results are generic and could be applied to or found in different physical systems.

Karst, Casey M.; Storey, Brian D.; Geddes, John B.

2013-03-01

352

Adsorptive Deformation of Organo-Substituted Laminar Silicates.  

PubMed

Deformations of organo-substituted laminar silicates (Pyzhevsk montmorillonite and synthetic fluorohectorite) upon water, hexane, and benzene vapor sorption have been studied. To solve this problem a dilatometer was used. Its main part was a line differential transformer, the core of which was connected to the sorbent by means of a rod. Any changes of the sorbent height caused a change in the core position in the transformer, which influenced the signal recorded from its secondary winding. The calibrated dilatometer was located in a liquid thermostat with a given temperature and was connected with the measurement unit (frequency meter, voltmeter, generator). Montmorillonite and synthetic fluorohectorite were modified by cetylpyridinium bromide and used in the form of tablets. As a result of the sample preparation conditions, the modified clay silicates swelled isotropically. These results were compared with the adsorption isotherms obtained gravimetrically. High sensitivity of the dilatometric method to the structural changes of the organo-substituted laminar silicates has been shown. The dilatometer used allowed the measurement of absolute deformations in the range 1 x 10(-4) to 3 mm. Copyright 1999 Academic Press. PMID:10092373

Tvardovski; Fomkin; Tarasevich; Zhukova

1999-04-15

353

Transmembrane semaphorin signaling controls laminar stratification in the mammalian retina  

PubMed Central

In the vertebrate retina, establishment of precise synaptic connections among distinct retinal neuron cell types is critical for processing visual information and for accurate visual perception. Retinal ganglion cells (RGCs), amacrine cells, and bipolar cells establish stereotypic neurite arborization patterns to form functional neural circuits in the inner plexiform layer (IPL)1–3: a laminar region that is conventionally divided into five major parallel sublaminae1,2. However, the molecular mechanisms governing distinct retinal subtype targeting to specific sublaminae within the IPL remain to be elucidated. Here, we show that the transmembrane semaphorin Sema6A signals through its receptor PlexinA4 (PlexA4) to control lamina-specific neuronal stratification in the mouse retina. Expression analyses demonstrate that Sema6A and PlexA4 proteins are expressed in a complementary fashion in the developing retina: Sema6A in most ON sublaminae and PlexA4 in OFF sublaminae of the IPL. Mice with null mutations in PlexA4 or Sema6A exhibit severe defects in stereotypic lamina-specific neurite arborization of tyrosine hydroxylase (TH)-expressing dopaminergic amacrine cells, intrinsically photosensitive RGCs (ipRGCs), and calbindin-positive cells in the IPL. Sema6A and PlexA4 genetically interact in vivo with respect to the regulation of dopaminergic amacrine cell laminar targeting. Therefore, neuronal targeting to subdivisions of the IPL in the mammalian retina is directed by repulsive transmembrane guidance cues present on neuronal processes.

Matsuoka, Ryota L.; Nguyen-Ba-Charvet, Kim T.; Parray, Aijaz; Badea, Tudor C.; Chedotal, Alain; Kolodkin, Alex L.

2010-01-01

354

Scanning PIV measurements of a laminar separation bubble  

NASA Astrophysics Data System (ADS)

Scanning PIV is applied to a laminar separation bubble to investigate the spanwise structure and dynamics of the roll-up of vortices within the bubble. The laminar flow separation with turbulent reattachment is studied on the suction side of an airfoil SD7003 at Reynolds numbers of 20,000-60,000. The flow is recorded with a CMOS high-speed camera in successive light-sheet planes over a time span of 1-2 s to resolve the temporal evolution of the flow in the different planes. The results show the quasi-periodic development of large vortex-rolls at the downstream end of the separation bubble, which have a convex structure and an extension of 10-20% chord length in the spanwise direction. These vortices possess an irregular spanwise pattern. The evolution process of an exemplary vortex structure is shown in detail starting from small disturbances within the separation bubble transforming into a compact vortex at the downstream end of the separation bubble. As the vortex grows in size and strength it reaches a critical state that leads to an abrupt burst of the vortex with a large ejection of fluid into the mean flow.

Burgmann, S.; Brücker, C.; Schröder, W.

2006-08-01

355

Development of Micro Rotary Reactor Causing Spiral Laminar Flow Interfaces  

NASA Astrophysics Data System (ADS)

Recently, research and development of the micro-fluidic systems such as ?TAS and Lab-on-chip have been activated in the field of chemical technology and biotechnology. Micro-fluidic systems are realized by micromachine technology and MEMS technology. These are essential elements for miniaturization of chemical analysis reaction systems. Furthermore, micro-fluidic systems can be applied to home medical care system. Micro mixing device is an essential element for a realization of these systems. Normally, mixing of different fluids depends on turbulent flow and diffusion. But it is difficult to generate turbulent flow in minute space. Micro mixer is important to improve reaction efficiency. The aim of this research is a development of a micro rotary reactor which will be built into micro-fluidic systems. The full length and the diameter of this reactor are 59mm and 15mm, respectively. This reactor is driven by an electromagnetic actuator. Therefore, the structure of this reactor becomes very simple and it is easy to miniaturize this reactor. This reactor aims at combing two liquids and forming spiral laminar flow interfaces. Forming spiral laminar flow interfaces increase reaction surface area and reaction distance of two liquids. This paper shows the structure and the characteristics of this reactor.

Furusawa, Hiroaki; Suzumori, Koichi; Kanda, Takefumi; Yamada, Yoshiaki; Sakata, Yusaku; Muto, Akinori

356

The effect of local anaesthesia of the nasal vestibule on nasal sensation of airflow and nasal resistance.  

PubMed

The effect of local anaesthesia of the nasal vestibule on nasal sensation of airflow and nasal resistance was assessed in 15 subjects. A single blind parallel group trial was undertaken in 30 subjects, with lignocaine as the active drug, and normal saline as the placebo. Fifteen subjects were included in each group. Both agents were infiltrated bilaterally into the floor of the nasal vestibule on each side via the sublabial route. Local anaesthesia of the nasal vestibule by infiltrating lignocaine produced a sensation of nasal obstruction in 9 out of 15 subjects (P less than 0.02). The infiltration of normal saline had no such effect. The difference between the effect of the 2 agents on nasal airflow sensation was significant (P less than 0.05). Neither injection had any significant effect on nasal resistance to airflow as assessed by active anterior rhinomanometry. PMID:3442947

Jones, A S; Crosher, R; Wight, R G; Lancer, J M; Beckingham, E

1987-12-01

357

Airflow velocity effects on air bearing with grooved disk surface in near-field optical disk drives  

NASA Astrophysics Data System (ADS)

By means of an air bearing, the pickup head slider of a near-field optical disk drive flies above data tracks on a rotating disk surface to achieve a stable flying height. The influence of airflow velocities of the air bearing on lift force deserves investigation, as the airflow velocity varies during track seeking or disk speed variation. In this study, a direct simulation Monte Carlo method is used to investigate three-dimensional nanoscale gas film lubrication at the air bearing between a slider and a rotating disk. This study aims to investigate air bearing behavior at different airflow velocities. Computational results show that faster flow generates larger pressure and lift force. Lower flying height reduces force variation caused by different velocities. This study also proposes a method for maintaining the flying height within the near-field range.

Wang, H. C.; Liu, T. S.

2006-05-01

358

Application of laminar flow control to high-bypass-ratio turbofan engine nacelles  

SciTech Connect

Recently, the concept of the application of hybrid laminar flow to modern commercial transport aircraft was successfully flight tested on a Boeing 757 aircraft. In this limited demonstration, in which only part of the upper surface of the swept wing was designed for the attainment of laminar flow, significant local drag reduction was measured. This paper addresses the potential application of this technology to laminarize the external surface of large, modern turbofan engine nacelles which may comprise as much as 5-10 percent of the total wetted area of future commercial transports. A hybrid-laminar-flow-control (HLFC) pressure distribution is specified and the corresponding nacelle geometry is computed utilizing a predictor/corrector design method. Linear stability calculations are conducted to provide predictions of the extent of the laminar boundary layer. Performance studies are presented to determine potential benefits in terms of reduced fuel consumption. 13 refs.

Wie, Y.S.; Collier, F.S. Jr.; Wagner, R.D. (High Technology Corp., Hampton, VA (United States) NASA, Langley Research Center, Hampton, VA (United States))

1991-09-01

359

Applications of Laminar Weak-Link Mechanisms for Ultraprecision Synchrotron Radiation Instruments  

SciTech Connect

Unlike traditional kinematic flexure mechanisms, laminar overconstrained weak-link mechanisms provide much higher structure stiffness and stability. Using a laminar structure configured and manufactured by chemical etching and lithography techniques, we are able to design and build linear and rotary weak-link mechanisms with ultrahigh positioning sensitivity and stability for synchrotron radiation applications. Applications of laminar rotary weak-link mechanism include: high-energy-resolution monochromators for inelastic x-ray scattering and x-ray analyzers for ultra-small-angle scattering and powder-diffraction experiments. Applications of laminar linear weak-link mechanism include high-stiffness piezo-driven stages with subnanometer resolution for an x-ray microscope. In this paper, we summarize the recent designs and applications of the laminar weak-link mechanisms at the Advanced Photon Source.

Shu, D.; Toellner, T. S.; Alp, E. E.; Maser, J.; Ilavsky, J.; Shastri, S. D.; Lee, P. L.; Narayanan, S.; Long, G. G. [Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439 (United States)

2007-01-19

360

Visualization of nasal airflow patterns in a patient affected with atrophic rhinitis using particle image velocimetry  

NASA Astrophysics Data System (ADS)

The relationship between airflow patterns in the nasal cavity and nasal function is poorly understood. This paper reports an experimental study of the interplay between symptoms and airflow patterns in a patient affected with atrophic rhinitis. This pathology is characterized by mucosal dryness, fetor, progressive atrophy of anatomical structures, a spacious nasal cavity, and a paradoxical sensation of nasal congestion. A physical replica of the patient's nasal geometry was made and particle image velocimetry (PIV) was used to visualize and measure the flow field. The nasal replica was based on computed tomography (CT) scans of the patient and was built in three steps: three-dimensional reconstruction of the CT scans; rapid prototyping of a cast; and sacrificial use of the cast to form a model of the nasal passage in clear silicone. Flow patterns were measured by running a water-glycerol mixture through the replica and evaluating the displacement of particles dispersed in the liquid using PIV. The water-glycerol flow rate used corresponded to an air flow rate representative of a human breathing at rest. The trajectory of the flow observed in the left passage of the nose (more affected by atrophic rhinitis) differed markedly from what is considered normal, and was consistent with patterns of epithelial damage observed in cases of the condition. The data are also useful for validation of computational fluid dynamics predictions.

Garcia, G. J. M.; Mitchell, G.; Bailie, N.; Thornhill, D.; Watterson, J.; Kimbell, J. S.

2007-10-01

361

[Effects of typhoon 'Haitang' airflow field on the northward migration route of rice brown planthopper].  

PubMed

Based on GIS, GrADS, and HYSPLIT-4.8 model, this paper analyzed the daily light-trap catches of rice brown planthopper at 42 pest monitoring stations of 10 provinces in China, the wind field on 850 hPa isobaric surface, and the migration tracks of rice brown planthopper at 20 pest monitoring stations during the occurrence of 0505 typhoon 'Haitang' from 19th to 21st July, 2005. After its landing on China, the typhoon 'Haitang' changed the southwest air flow, a flow which leads the northward migration of rice brown planthopper, and made the wind field converge in the southwest of the typhoon and swerve in larger areas. Accordingly, the northward migration of the rice brown planthopper was stopped, and the airborne populations were forced to descend in some areas. The shear line area nearby 850 hPa isobaric surface was the concentration and deposition area of the rice brown planthopper. There would be a mass migration area in the warm airflow shear area in the southeast of typhoon during the collapse of the typhoon. After the whole typhoon landed, the southwest airflow rebuilt, and a mass rice brown planthopper migrated to the north. PMID:20077712

Wang, Cui-Hua; Zhai, Bao-Ping; Bao, Yun-Xuan

2009-10-01

362

An experimental study of a plasma actuator in absence of free airflow: Ionic wind velocity profile  

NASA Astrophysics Data System (ADS)

In this study, we are interested in the direct current electrical corona discharge created between two wire electrodes. The experimental results are related to some electroaerodynamic actuators based on the direct current corona discharge at the surface of a dielectric material. Several geometrical forms are selected for the dielectric surface, such as a plate, a cylinder, and a NACA 0015 aircraft wing. The current density-electric field characteristics are presented for different cases in order to determine the discharge regimes. The corona discharge produces nonthermal plasma, so it is called plasma discharge. Plasma discharge creates a tangential ionic wind above the surface at the vicinity of the wall. The ionic wind induced by the corona discharge is measured in absence of free external airflow. The ionic wind velocity profiles and the maximum induced tangential force are given for different surface forms, so it is possible to compare the actuators effect based on the span of the ionic wind velocity and thrust values. The higher ionic wind velocity is obtained with the NACA profile, which shows the effectiveness of this actuator for the airflow control.

Mestiri, R.; Hadaji, R.; Ben Nasrallah, S.

2010-08-01

363

An experimental study of a plasma actuator in absence of free airflow: Ionic wind velocity profile  

SciTech Connect

In this study, we are interested in the direct current electrical corona discharge created between two wire electrodes. The experimental results are related to some electroaerodynamic actuators based on the direct current corona discharge at the surface of a dielectric material. Several geometrical forms are selected for the dielectric surface, such as a plate, a cylinder, and a NACA 0015 aircraft wing. The current density-electric field characteristics are presented for different cases in order to determine the discharge regimes. The corona discharge produces nonthermal plasma, so it is called plasma discharge. Plasma discharge creates a tangential ionic wind above the surface at the vicinity of the wall. The ionic wind induced by the corona discharge is measured in absence of free external airflow. The ionic wind velocity profiles and the maximum induced tangential force are given for different surface forms, so it is possible to compare the actuators effect based on the span of the ionic wind velocity and thrust values. The higher ionic wind velocity is obtained with the NACA profile, which shows the effectiveness of this actuator for the airflow control.

Mestiri, R.; Hadaji, R.; Ben Nasrallah, S. [Ecole Nationale d'Ingenieurs de Monastir, Monastir 5019 (Tunisia)

2010-08-15

364

Oscillatory Behavior of an Arc Airfoil in Low-Speed Airflow  

NASA Astrophysics Data System (ADS)

A computational investigation is conducted to study the oscillatory behavior of an arc airfoil situated in low-speed airflow. The present work is relevant to situations where the conventional rigid airfoils do not apply, such as the flight of bats. The outcome of this study is also beneficial in the design of micro air vehicles with flexible wings. The computations are performed using a deforming mesh to accommodate the airfoil oscillations. An unsteady, spatially second-order algorithm is employed to capture the time-variations of the lift and drag coefficients. A key feature of the present work is the flow response to airfoil oscillations. Fast Fourier Transform was applied to various parameters of the flow. For certain values of angle of attack for the non-oscillating airfoil, the flow has a dominant frequency and a well-defined vortex shedding. For other values of angle of attack, the flow around the non-oscillating airfoil contains many frequencies and has complex vortical structures. However, the oscillating airfoil in all cases makes the flow field periodic with well-defined patterns of vortex shedding. In this work, the flux of vorticity from the airfoil surface into the airflow is computed and compared with the pressure gradient along the surface of the airfoil. Effects of oscillations on magnitude and behavior of aerodynamic forces are also studied.

Molki, Majid; Sattari, Negin

2011-11-01

365

Experimental study of the effects of airflow and vocal fold stiffness on male and female voice production  

NASA Astrophysics Data System (ADS)

The effect of airflow in voice production is not fully understood, leading to difficulties when clinically diagnosing voice disorders. Many existing studies in this this area focus primarily on the male physiology. This study incorporates 2-layer, molded silicone vocal fold models whose geometry mimics the shape and dimensions of both male and female vocal folds. Measured quantities include subglottal and transglottal pressure, volume flow rate, and radiated sound. The results are used to clarify the relationship between glottal airflow and sound production. The Implications of the measurements for similarities and differences between male and phonation are discussed.

Campo, Elizabeth; Michael, Mcphail; Michael, Krane

2011-11-01

366

Goblet Cell Hyperplasia and Epithelial Inflammation in Peripheral Airways of Smokers with Both Symptoms of Chronic Bronchitis and Chronic Airflow Limitation  

Microsoft Academic Search

To quantify the number of goblet cells and inflammatory cells in the epithelium of peripheral airways in smokers with both symptoms of chronic bronchitis and chronic airflow limitation, we examined surgical specimens obtained from 25 subjects undergoing lung resection for localized pulmonary le- sions: 10 smokers with symptoms of chronic bronchitis and chronic airflow limitation, six asymptom- atic smokers with

MARINA SAETTA; GRAZIELLA TURATO; SIMONETTA BARALDO; ANNALISA ZANIN; FAUSTO BRACCIONI; CRISTINA E. MAPP; PIERO MAESTRELLI; GIORGIO CAVALLESCO; ALBERTO PAPI; LEONARDO M. FABBRI

367

A wind tunnel simulation of the effects of stoss slope on the lee airflow pattern over a two-dimensional transverse dune  

Microsoft Academic Search

Secondary airflow plays an important role in dune formation and development. The lee airflow pattern over transverse dunes is important in determining the shape, alignment, and spacing of dunes and is influenced significantly by the lee slope angle. In this paper we present the results of scaled wind tunnel simulations of the effects of stoss slope on the mean lee

Zhibao Dong; Guangqiang Qian; Wanyin Luo; Hongtao Wang

2007-01-01

368

Experimental study of Markstein number effects on laminar flamelet velocity in turbulent premixed flames  

SciTech Connect

Effects of turbulent flame stretch on mean local laminar burning velocity of flamelets, u{sub n}, were investigated experimentally in an explosion vessel at normal temperature and pressure. In this context, the wrinkling, A{sub t}/A{sub l}, and the burning velocity, u{sub t}, of turbulent flames were measured simultaneously. With the flamelet assumption the mean local laminar burning velocity of flamelets, u{sub n}=u{sub t} x (A{sub t}/A{sub l}){sup -1}, was calculated for different turbulence intensities. The results were compared to the influence of stretch on spherically expanding laminar flames. For spherically expanding laminar flames the stretched laminar burning velocity, u{sub n}, varied linearly with the Karlovitz stretch factor, yielding Markstein numbers that depend on the mixture composition. Six different mixtures with positive and negative Markstein numbers were investigated. The measurements of the mean local laminar burning velocity of turbulent flamelets were used to derive an efficiency parameter, I, which reflects the impact of the Markstein number and turbulent flame stretch - expressed by the turbulent Karlovitz stretch factor - on the local laminar burning velocity of flamelets. The results showed that the efficiency is reduced with increasing turbulence intensity and the reduction can be correlated to unsteady effects. (author)

Weiss, M.; Zarzalis, N. [Division of Combustion Technology, Engler-Bunte-Institute, University of Karlsruhe (TH), Karlsruhe (Germany); Suntz, R. [Institute for Chemical Technology, University of Karlsruhe (TH), Karlsruhe (Germany)

2008-09-15

369

Laminar flow of fine sediment-water mixtures  

NASA Astrophysics Data System (ADS)

Flows of sediment-water mixture (suspensions) are common superficial processes in nature. To investigate the possibility of predicting the behaviour of such flows, we study the free surface flow of a clay-water suspension down a slope, which may represent a simple realistic model for the flow of some concentrated sediment-water mixture in a natural environment. The hydrodynamic lubrication equations governing the flow are derived from the full Navier-Stokes equations, including an appropriate tensorial expression for the constitutive equation of the suspension (a Herschel-Bulkley fluid with a hysteresis in the yield strength). Results have been obtained for the free surface and length of an unsteady, laminar, isothermal flow of the suspension. The theory is in good agreement with laboratory experiments with fine clay suspensions.

Battaglia, M.; Borgia, A.

2000-03-01

370

Enhanced photocatalysis in a pilot laminar falling film slurry reactor  

SciTech Connect

Laminar falling film slurry (LFFS) photocatalytic reactors are one of the most efficient reactor configurations for conducting heterogeneous photocatalytic reactions, particularly for wastewater treatment. This paper presents a study on the oxidation of an aqueous salicylic acid waste in a pilot continuous flow LFFS photocatalytic reactor which has an optimum design for light absorption. In conducting the oxidation reaction, heterogeneous photocatalysis was supplemented with other photon-assisted processes. The effect of light intensity, radiation wavelength, oxidizing-enhancing agents, substrate and photocatalyst concentration, and exposure time were studied. A comparison of six different photon-based processes showed that higher oxidation rates of salicylic acid were obtained when there was concomitant photocatalysis, photolysis, and UV peroxidation. The oxidation rates of salicylic acid with this combined process were at least 1 order of magnitude higher in comparison with those for UVA photocatalysis and 3-fold higher in comparison with homogeneous UVC photolysis/UVC peroxidation.

Puma, G.L.; Yue, P.L. [Hong Kong Univ. of Science and Technology, Clear Water Bay, Kowloon (Hong Kong)

1999-09-01

371

Postfragmentation density function for bacterial aggregates in laminar flow  

NASA Astrophysics Data System (ADS)

The postfragmentation probability density of daughter flocs is one of the least well-understood aspects of modeling flocculation. We use three-dimensional positional data of Klebsiella pneumoniae bacterial flocs in suspension and the knowledge of hydrodynamic properties of a laminar flow field to construct a probability density function of floc volumes after a fragmentation event. We provide computational results which predict that the primary fragmentation mechanism for large flocs is erosion. The postfragmentation probability density function has a strong dependence on the size of the original floc and indicates that most fragmentation events result in clumps of one to three bacteria eroding from the original floc. We also provide numerical evidence that exhaustive fragmentation yields a limiting density inconsistent with the log-normal density predicted in the literature, most likely due to the heterogeneous nature of K. pneumoniae flocs. To support our conclusions, artificial flocs were generated and display similar postfragmentation density and exhaustive fragmentation.

Byrne, Erin; Bortz, David M.; Dzul, Steve; Solomon, Michael; Younger, John

2011-04-01

372

Laminar batteries and methods of making the same  

SciTech Connect

An end terminal web is described for use in manufacturing the end terminals of laminar batteries. The method comprises an elongated sheet of dimensionally stable thermal insulating material having a layer of adhesive adhered to one side thereof, and an array of battery terminal blanks each comprising a sheet of metal having a layer of conductive plastic adhered thereto over one side thereof and adhered to the elongated sheet on the other side thereof by the adhesive. Each battery terminal blank includes an index perforation, the array comprising a rectangular array of the blanks arranged in regular spaced rows across the elongated sheet and in parallel spaced columns extending along the elongated sheet in the direction of its elongation.

Sturgis, J.I.; Keene, R.G.

1987-05-12

373

Laminar batteries and methods of making the same  

SciTech Connect

A composite web is described for use in the manufacture of laminar batteries, the composite web comprising an elongated sheet of thermoplastic liquid impermeable electrically insulating material formed with a spaced array of apertures extending in rows across the sheet and in columns along the sheet, an electrode assembly adhered to the sheet around the peripheries of each of the apertures, each electrode assembly comprising a piece of electrically conducting electrochemically inert thermoplastic sheet material uniformly coated on one side opposite the side adjacent the elongated sheet with a layer of electrochemically active particles in a binder, and sheets of battery separator material each adhered to the elongated sheet over a different one of the electrode assemblies and confronting the electrode assembly. The separator sheet have peripheries extending beyond the boundaries of the electrode assemblies and each is secured to confronting regions of the elongated sheet by spaced strips of adhesive material.

Plasse, P.A.

1986-09-02

374

Laminar batteries and methods of making the same  

SciTech Connect

Laminar electrical cells and batteries, each cell of which comprises a first electrode formed as a porous layer of electrochemically active particles on an electrically conductive, electrochemically inactive substrate coextensive with the particle layer. The electrochemically inactive substrate is adhered around its periphery to the borders of an aperture in an electrically insulating frame. A separator for each cell overlies the active particle layer of the first electrode and has borders extending beyond the borders of the first electrode and within the borders of the insulating frame. A second electrode for each cell comprises a slurry of electrochemically active particles in contact with the other side of the separator. Methods of making the above cells and batteries from elongated webs of electrically insulating ones of the constituent materials of the cells.

Plasse, P. A.

1985-09-03

375

Calculation of hypersonic laminar boundary layers with chemical kinetics  

NASA Astrophysics Data System (ADS)

CLIM, a computer program developed to calculate the laminar boundary layer in axisymmetric steady hypersonic flows such as those on reentry vehicles, is described and demonstrated. CLIM takes into account the effects of transverse or longitudinal curvature, wall injection, and chemical reactions of equilibrium or nonequilibrium gases, permitting the treatment of ablation phenomena. The basic hypotheses are outlined; the program equations are derived; the finite-difference discretization is explained; and results are presented graphically for test problems involving a 10-deg-half-angle cone, a Shuttle-like hyperboloid, and the ablation of a carbon wall. When programmed on an IBM 3081, CLIM comprises about 3000 lines and can compute the wall stresses and the boundary-layer thickness, velocity, temperature, density, and concentration profiles for a 50-section body and 10 gas species in less than 1 min for nondissociated air, about 1 min for equilibrium air, and less than 10 min for nonequilibrium air.

Noel, F.; Boukhobza, P.

1986-11-01

376

Comparison of several models of the laminar/turbulent transition  

NASA Astrophysics Data System (ADS)

The contribution deals with modelling of the laminar/turbulent transition using several transition models. Transition models of various types were tested: a) the model with the algebraic equation for the intermittency coefficient according to Straka and Pøíhoda; b) the three-equation transition model with the transport equation for the energy of non-turbulent fluctuations proposed by Walters and Cokljat; c) the ?-Re? model with the transport equation forthe intermittency coefficient of Langtry and Menter. The transition models were compared by means of test cases covering both flat-plate boundary-layer flows with various free stream turbulence and the flow over an airfoil including the effect of foregoing wake on the transition. The agreement of numerical results with experimental data is in all cases quite satisfactory.

Fürst, V.; Straka, J.; P?íhoda, P.; Šimurda, J.

2013-04-01

377

Laminar profile of visual response properties in ferret superior colliculus.  

PubMed

In the superior colliculus (SC), visual afferent inputs from various sources converge in a highly organized way such that all layers form topographically aligned representations of contralateral external space. Despite this anatomical organization, it remains unclear how the layer-specific termination of different visual input pathways is reflected in the nature of visual response properties and their distribution across layers. To uncover the physiological correlates underlying the laminar organization of the SC, we recorded multiunit and local field potential activity simultaneously from all layers with dual-shank multichannel linear probes. We found that the location of spatial receptive fields was strongly conserved across all visual responsive layers. There was a tendency for receptive field size to increase with depth in the SC, with superficial receptive fields significantly smaller than deep receptive fields. Additionally, superficial layers responded significantly faster than deeper layers to flash stimulation. In some recordings, flash-evoked responses were characterized by the presence of gamma oscillatory activity (40-60 Hz) in multiunit and field potential signals, which was strongest in retinorecipient layers. While SC neurons tended to respond only weakly to full-field drifting gratings, we observed very similar oscillatory responses to the offset of grating stimuli, suggesting gamma oscillations are produced following light offset. Oscillatory spiking activity was highly correlated between horizontally distributed neurons within these layers, with oscillations temporally locked to the stimulus. Together, visual response properties provide physiological evidence reflecting the laminar-specific termination of visual afferent pathways in the SC, most notably characterized by the oscillatory entrainment of superficial neurons. PMID:23803328

Stitt, Iain; Galindo-Leon, Edgar; Pieper, Florian; Engler, Gerhard; Engel, Andreas K

2013-06-26

378

Numerical Prediction of Laminar Instability Noise for NACA 0012 Aerofoil  

NASA Astrophysics Data System (ADS)

Aerofoil self-generated noise is recognized to be of fundamental importance in the frame of applied aeroacoustics and the use of computational methods to assess the acoustic behaviour of airframe components challenges an even larger community of engineers and scientists. Several noise generation mechanisms can be found which are mainly related to the physical development of turbulence over the boundary layer. They can be classified in 3 main categories: the Turbulent Boundary Layer--Trailing Edge noise (TBL-TE), the Laminar Boundary Layer--Vortex Shedding (LBL-VS) noise and the Separation Stall (S-S) noise. The TBL-TE is mainly related to the noise generated by turbulent eddies which develop into the boundary layer and usually exhibits a broadband spectrum. The LBL-VS is related to laminar instabilities that can occur within the boundary layer which are responsible for a very late transition and generate a typical peaked tonal noise, while the S-S noise mainly results from the development of large vortices after the separation point. In this paper we propose a numerical analysis targeted to the simulation the LBL-VS noise mechanisms on a NACA 0012 aerofoil, tested at a Reynolds number of 1.1 M and Mach number of 0.2. The aerodynamic simulation is performed with a 2D transient RANS approach using the k-? transitional turbulence model, while the acoustic computations are performed with the FfowcsWilliams-Hawkings (FW-H) acoustic analogy and with a Finite Element (FE) approach solving Lighthill's wave equation. Computed noise spectra are compared with experimental data published by NASA showing a good agreement both for peak location as well as for the predicted noise level.

de Gennaro, Michele; Hueppe, Andreas; Kuehnelt, Helmut; Kaltenbacher, Manfred

2011-09-01

379

The Body-Mass Index, Airflow Obstruction, Dyspnea, and Exercise Capacity Index in Chronic Obstructive Pulmonary Disease  

Microsoft Academic Search

background Chronic obstructive pulmonary disease (COPD) is characterized by an incompletely re- versible limitation in airflow. A physiological variable — the forced expiratory volume in one second (FEV 1 ) — is often used to grade the severity of COPD. However, patients with COPD have systemic manifestations that are not reflected by the FEV 1 . We hypoth- esized that

Bartolome R. Celli; Claudia G. Cote; Jose M. Marin; Ciro Casanova; Maria Montes de Oca; Reina A. Mendez; Victor Pinto Plata; Howard J. Cabral

2004-01-01

380

Corticosteroid trials in non-asthmatic chronic airflow obstruction: a comparison of oral prednisolone and inhaled beclomethasone dipropionate  

Microsoft Academic Search

One hundred and twenty seven adults considered on clinical grounds to have non-asthmatic chronic airflow obstruction entered a randomised, double blind, placebo controlled, crossover trial comparing the physiological response to inhaled beclomethasone dipropionate 500 micrograms thrice daily with oral prednisolone 40 mg a day, both given for two weeks. One hundred and seven patients completed the study. Response was assessed

D C Weir; R I Gove; A S Robertson; P S Burge

1990-01-01

381

Partial Reversibility of Airflow Limitation and Increased Exhaled NO and Sputum Eosinophilia in Chronic Obstructive Pulmonary Disease  

Microsoft Academic Search

We investigated the relationship between the reversibility of air- flow limitation, the concentration of nitric oxide (NO) in exhaled air, and the inflammatory cells in the sputum of patients with sta- ble chronic obstructive pulmonary disease (COPD). We examined nine normal healthy control subjects and 20 nonatopic patients with COPD. Ten patients had no reversibility of airflow limitation (increase in

ALBERTO PAPI; MICAELA ROMAGNOLI; SIMONETTA BARALDO; FAUSTO BRACCIONI; IPPOLITO GUZZINATI; MARINA SAETTA; ADALBERTO CIACCIA; LEONARDO M. FABBRI

2000-01-01

382

Airflow modeling report for vapor extraction operations at the 200-ZP-2 operable unit (carbon tetrachloride expedited response action).  

National Technical Information Service (NTIS)

The primary objective of constructing a numerical airflow model of the 200-ZP-2 vapor extraction well field is to estimate the zone of influence of the soil vapor extraction systems. The zone of influence will be used to estimate the location and volume o...

V. J. Rohay W. J. McMahon

1996-01-01

383

Persistent airflow limitation in adult-onset nonatopic asthma is associated with serologic evidence of Chlamydia pneumoniae infection  

Microsoft Academic Search

Background: Persistent airflow limitation may develop in patients with asthma, particularly in adults with nonatopic (intrinsic) disease. Although the underlying mechanisms are still unknown, respiratory infections might be involved. Objective: We investigated the annual loss of lung function in relation to seropositivity to Chlamydia pneumoniae in different subgroups of patients with severe asthma according to age at onset of asthma

Anneke ten Brinke; Jaap T. van Dissel; Peter J. Sterk; Aeilko H. Zwinderman; Klaus F. Rabe; Elisabeth H. Bel

2001-01-01

384

Study on airflow characteristics inside and outside a cross-ventilation model, and ventilation flow rates using wind tunnel experiments  

Microsoft Academic Search

The internal airflow characteristics in a cross-ventilation model were investigated using split-film probes capable of measuring directional velocity components. The penetrating flow entered the inlet at steep declining angles due to the front eddy and flowed downwards to the floor. The internal turbulence spectrum of the main stream penetrating the inlet remained the same as that of the oncoming flow,

M. Ohba; K. Irie; T. Kurabuchi

2001-01-01

385

Behavior of Spiral Flow Structures Along the Trailing Edges of E-Block Arms Under Increasing Airflow Velocities  

Microsoft Academic Search

The behavior of spiral flow structures along the trailing edges of the E-block arm has been investigated under increasing airflow velocities. These coherent structures in the flow are commonly believed to be closely associated with the flow induced vibrations on the E-block arms. The experiments showed that vortex shedding is detected in a hard disk drive (HDD) model when the

T. H. Yip; C. K. Tan; Y. K. Kuan

2006-01-01

386

The behavior of spiral flow structures along the trailing edges of E-block arms under increasing airflow velocities  

Microsoft Academic Search

The behavior of spiral flow structures along the trailing edges of the E-block arm has been investigated under increasing airflow velocities. These coherent structures in the flow are commonly believed to be closely associated with the flow induced vibrations on the E-block arms. The experiments showed that vortex shedding is detected in a HDD model when the motor speed is

T. Yip; C. Tan; Y. Kuan

2006-01-01

387

Carbon monoxide lung diffusion capacity improves risk stratification in patients without airflow limitation: evidence for systematic measurement before lung resection  

Microsoft Academic Search

Objective: In many centers, carbon monoxide lung diffusion capacity (DLCO) is still not routinely measured in all patients but only in patients with airflow limitation. The objective of the study was to assess the degree of correlation between forced expiratory volume in 1s (FEV1) and DLCO, and verify whether a low predicted postoperative DLCO (ppoDLCO) could have a role in

Alessandro Brunelli; Majed Al Refai; Michele Salati; Armando Sabbatini; Nicholas J. Morgan-Hughes; Gaetano Rocco

2006-01-01

388

Airflow in a slot-ventilated enclosure partially filled with porous boxes: Part II – Measurements and simulations within porous boxes  

Microsoft Academic Search

The present study will give rise to better understanding of the airflow behaviour in a ceiling-slot ventilated enclosure partially filled with slotted porous boxes under isothermal conditions. Boxes were filled randomly with spheres of the same diameter. Laser Doppler velocimetry (LDV) measurements and computational fluid dynamics (CFD) predictions were carried out to characterize air velocity inside packed vented boxes. An

Jean Moureh; Mitoubkieta Tapsoba; Denis Flick

2009-01-01

389

The effects of simultaneous electrophoresis and thermophoresis on particulate contamination of an inverted EUVL photomask surface in parallel airflow  

NASA Astrophysics Data System (ADS)

The combined influences of electrophoresis and thermophoresis on particle deposition on the inverted critical surface of a flat plate in parallel airflow were investigated by employing the statistical Lagrangian particle tracking approach in an effort to assess the degree of particulate contamination of EUVL photomasks during horizontal transport in cleanroom environments. The numerical method was validated through the comparison with the experimental data, found in the literature, about particle deposition velocity onto a wafer in vertical airflow with and without electrophoresis or thermophoresis. In addition, the validation of the present model was performed via the comparison with the theoretical prediction of particle deposition velocity onto a flat plate under no phoretic forces in parallel airflow. Then, the particle deposition velocity onto the face-down surface of a flat plate in parallel airflow was obtained by varying the temperature of the inverted critical surface in different strengths of uniform electric fields. Injected particles were assumed to be charged with -1 , 0, or +1 elementary unit of charge, in order to consider attractive or repulsive electric force. The degree of particulate contamination of the inverted critical surface was found to be significantly influenced by the combination of electrophoretic and thermophoretic effects.

Lee, Handol; Yook, Se-Jin; Young Han, Seog

2012-10-01

390

Airflow Dynamics of Coughing in Healthy Human Volunteers by Shadowgraph Imaging: An Aid to Aerosol Infection Control  

PubMed Central

Cough airflow dynamics have been previously studied using a variety of experimental methods. In this study, real-time, non-invasive shadowgraph imaging was applied to obtain additional analyses of cough airflows produced by healthy volunteers. Twenty healthy volunteers (10 women, mean age 32.2±12.9 years; 10 men, mean age 25.3±2.5 years) were asked to cough freely, then into their sleeves (as per current US CDC recommendations) in this study to analyze cough airflow dynamics. For the 10 females (cases 1–10), their maximum detectable cough propagation distances ranged from 0.16–0.55 m, with maximum derived velocities of 2.2–5.0 m/s, and their maximum detectable 2-D projected areas ranged from 0.010–0.11 m2, with maximum derived expansion rates of 0.15–0.55 m2/s. For the 10 males (cases 11–20), their maximum detectable cough propagation distances ranged from 0.31–0.64 m, with maximum derived velocities of 3.2–14 m/s, and their maximum detectable 2-D projected areas ranged from 0.04–0.14 m2, with maximum derived expansion rates of 0.25–1.4 m2/s. These peak velocities were measured when the visibility of the exhaled airflows was optimal and compare favorably with those reported previously using other methods, and may be seen as a validation of these previous approaches in a more natural setting. However, the propagation distances can only represent a lower limit due to the inability of the shadowgraph method to visualize these cough airflows once their temperature cools to that of the ambient air, which is an important limitation of this methodology. The qualitative high-speed video footage of these volunteers coughing into their sleeves demonstrates that although this method rarely completely blocks the cough airflow, it decelerates, splits and redirects the airflow, eventually reducing its propagation. The effectiveness of this intervention depends on optimum positioning of the arm over the nose and mouth during coughing, though unsightly stains on sleeves may make it unacceptable to some.

Tang, Julian W.; Nicolle, Andre; Pantelic, Jovan; Koh, Gerald C.; Wang, Liang De; Amin, Muhammad; Klettner, Christian A.; Cheong, David K. W.; Sekhar, Chandra; Tham, Kwok Wai

2012-01-01

391

Increased platelet aggregate formation in patients with chronic airflow obstruction and hypoxaemia.  

PubMed Central

Platelet aggregate formation in vivo was assessed by means of the platelet aggregate ratio and from platelet release products (beta thromboglobulin, platelet factor 4, thromboxane B2) in 23 patients with chronic airflow obstruction with and without hypoxaemia and in 10 control subjects without respiratory disease. Eight of the 11 hypoxaemic patients were having long term oxygen therapy. The platelet aggregate ratio was lower in the hypoxaemic patients (0.88 (SE 0.03] than in the non-hypoxaemic (0.97 (0.01] and control groups (1.00 (0.02], and there was a trend to lower aggregate ratios in the more hypoxaemic patients. Platelet release products in the peripheral venous blood were not increased in the patients or control subjects. Platelet behaviour is altered in chronic hypoxaemia and this enhanced platelet activity could contribute to the pulmonary vascular damage found in these patients through direct effects or mediator release.

Wedzicha, J A; Syndercombe-Court, D; Tan, K C

1991-01-01

392

Inter-flat airflow and airborne disease transmission in high-rise residential buildings.  

PubMed

1. A virus-spread mechanism is related to inter-flat or interzonal airflow through open windows caused by buoyancy effects. 2. Both on-site measurements and numerical simulations quantify the amount of the exhaust air that exits the upper part of the window of a floor and re-enters the lower part of the open window of the immediately upper floor. 3. Ventilation air could contain up to 7% (in terms of mass fraction) of the exhaust air from the lower floor.4. In high-rise buildings, windows flush with the façade are a major route for the vertical spread of pathogen-containing aerosols, especially those<1 ?m in diameter. PMID:22311361

Niu, J; Tung, C W; Gao, N

2012-02-01

393

Numerical investigation of airflow in an idealized human extra-thoracic airway: a comparison study.  

PubMed

Large eddy simulation (LES) technique is employed to numerically investigate the airflow through an idealized human extra-thoracic airway under different breathing conditions, 10, 30, and 120 l/min. The computational results are compared with single and cross hot-wire measurements, and with time-averaged flow field computed by standard [Formula: see text] and [Formula: see text]-SST Reynolds-averaged Navier-Stokes (RANS) models and the Lattice Boltzmann method (LBM). The LES results are also compared to root-mean-square (RMS) flow field computed by the Reynolds stress model (RSM) and LBM. LES generally gives better prediction of the time-averaged flow field than RANS models and LBM. LES also provides better estimation of the RMS flow field than both the RSM and the LBM. PMID:23619907

Chen, Jie; Gutmark, Ephraim

2013-04-26

394

Decreased activation of inflammatory networks during acute asthma exacerbations is associated with chronic airflow obstruction  

PubMed Central

Asthma exacerbations are associated with subsequent deficits in lung function. Here, we tested the hypothesis that a specific pattern of inflammatory responses during acute exacerbations may be associated with chronic airway obstruction. Gene coexpression networks were characterized in induced sputum obtained during an acute exacerbation, from asthmatic children with or without chronic airflow limitation. The data showed that activation of Th1-like/cytotoxic and interferon signalling pathways during acute exacerbations was decreased in asthmatic children with deficits in baseline lung function. These associations were independent of the identification of picornaviruses in nasal secretions or the use of medications at the time of the exacerbation. Th2-related pathways were also detected in the responses, but variations in these pathways were not related to chronic airways obstruction. Our findings demonstrate that decreased activation of Th1-like/cytotoxic and interferon pathways is a hallmark of acute exacerbation responses in asthmatic children with evidence of chronic airways obstruction.

Bosco, Anthony; Ehteshami, Samira; Stern, Debra A.; Martinez, Fernando D.

2010-01-01

395

Real-time monitoring for alpha emitters in high-airflow environments  

SciTech Connect

Key problems in detecting alpha contamination for site characterization and decontamination and decommissioning that remain to be solved include measurement of airborne contamination, material holdup within pipes, and leakage of material containers. These problems are very difficult using traditional alpha detectors and systems. The ionization detection method (long-range alpha detection of LRAD) offers a number of specific advantages for these environmental measurements. An LRAD system detects the air molecules ionized by alpha-emitting contamination rather than the alpha particles. Thus, LRAD-based detectors are not limited by the short range of alpha particles and can be used to detect contamination anywhere that air can penetrate. Extending this technology to large enclosures of long pipes requires a system optimized for large airflows. In this paper we will present designs and preliminary results for high-volume flow-through air monitors based on the LRAD technique. In addition, we will discuss the behavior of the monitors and their potential applications.

Koster, J.E.; MacArthur, D.W.; Bounds, J.A.; Rawool-Sullivan, M; Whitley, C.R.; Conaway, J.G.; Steadman, P.A.

1996-07-01

396

Influence of near-wall airflow traversing crater in target on thermal effects of laser irradiation  

NASA Astrophysics Data System (ADS)

In this paper, fluid-solid thermal coupled computational models have been set up to simulate the subsonic nearwall airflow traversing a crater in target and heat transfer in target solid without phase transition in order to predict wall shear, heat flux and heat transfer coefficient on target surface and temperature field in the target under laser irradiation. The prototype of the model is the experiment zone of a flow simulation experiment facility, and the model was verified by the measured flow field data in it. The turbulence is modeled with Reynolds stress transport model. Laser irradiation is simulated with a beam of direct irradiation applied to the exterior boundary of the computational domain.

Xu, Rangshu; Zhang, Nana; Lin, Xinwei; Zhao, Changyu; Li, Guowen

2013-05-01

397

Unsteady laryngeal airflow simulations of the intra-glottal vortical structures.  

PubMed

The intra-glottal vortical structures developed in a static divergent glottis with continuous flow entering the glottis are characterized. Laryngeal airflow calculations are performed using the Large Eddy Simulation approach. It has been shown that intra-glottal vortices are formed on the divergent wall of the glottis, immediately downstream of the separation point. Even with non-pulsatile flow entering the glottis, the vortices are intermittently shed, producing unsteady flow at the glottal exit. The vortical structures are characterized by significant negative static pressure relative to the ambient pressure. These vortices increase in size and strength as they are convected downstream by the flow due to the entrained air from the supra-glottal region. The negative static pressures associated with the intra-glottal vortical structures suggest that the closing phase during phonation may be accelerated by such vortices. The intra-glottal negative pressures can affect both vocal fold vibration and voice production. PMID:20058989

Mihaescu, Mihai; Khosla, Sid M; Murugappan, Shanmugam; Gutmark, Ephraim J

2010-01-01

398

Phonation threshold pressure estimation using electroglottography in an airflow redirection system  

PubMed Central

Objectives/Hypothesis The present study proposed to estimate phonation threshold pressure (PTP) non-invasively using airflow redirection into a pneumatic capacitance system. Study Design Prospective study. Methods Subjects phonated into the device, which interrupts airflow mechanically and redirects the flow into a pneumatic capacitor. Five interruptions were effected per trial. PTP was estimated as the difference between subglottal pressure (SGP) and transglottal pressure at phonation offset. The novel method was tested for consistency in 20 normal human subjects at low (75 dB) and high (85 dB) sound pressure levels. The device was tested for validity on a tracheotomy patient. Results Mean SGP was 9.02 ± 3.27 cm H2O and mean PTP was 3.68 ± 1.41 cm H2O. Intrasubject coefficient of variation, a measure of intrasubject consistency, was 0.33 ± 0.23. Statistically significant differences existed between the means of SGP but not PTP at 75 dB and 85 dB. The correlation coefficient between accepted and experimental SGP in a tracheotomy patient was 0.947 (p<0.001). Conclusions Measurements corresponded well to previously reported values, and intrasubject variability was low, indicating the device was consistent. Testing on a tracheotomy patient demonstrated validity. More research is needed to determine the sensitivity and specificity of the device in differentiating between normal and pathological voices. This device may have clinical application as a non-invasive and reliable method of estimating PTP and indicating that laryngeal health is likely abnormal.

Rieves, Adam L.; Regner, Michael F.; Jiang, Jack J.

2009-01-01

399

Hair receptor sensitivity to changes in laminar boundary layer shape.  

PubMed

Biologists have shown that bat wings contain distributed arrays of flow-sensitive hair receptors. The hair receptors are hypothesized to feedback information on airflows over the bat wing for enhanced stability or maneuverability during flight. Here, we study the geometric specialization of hair-like structures for the detection of changes in boundary layer velocity profiles (shapes). A quasi-steady model that relates the flow velocity profile incident on the longitudinal axis of a hair to the resultant moment and shear force at the hair base is developed. The hair length relative to the boundary layer momentum thickness that maximizes the resultant moment and shear-force sensitivity to changes in boundary layer shape is determined. The sensitivity of the resultant moment and shear force is shown to be highly dependent on hair length. Hairs that linearly taper to a point are shown to provide greater output sensitivity than hairs of uniform cross-section. On an order of magnitude basis, the computed optimal hair lengths are in agreement with the range of hair receptor lengths measured on individual bat species. These results support the hypothesis that bats use hair receptors for detecting changes in boundary layer shape and provide geometric guidelines for artificial hair sensor design and application. PMID:20157224

Dickinson, B T

2010-02-16

400

The Application of a Nonsimilar Laminar Boundary Layer Analysis to Hypersonic Inlet Compression Surfaces.  

National Technical Information Service (NTIS)

The report presents the results of an investigation in which the Smith and Clutter nonsimilar laminar boundary layer analysis is compared to experimental data and a modified linearized similar solution on typical hypersonic two-dimensional and axisymmetri...

D. Sedlock

1966-01-01

401

Improved laminar predictions using a stabilised time-dependent simple scheme  

NASA Astrophysics Data System (ADS)

A new scheme which can solve unsteady incompressible flows is described in this paper. The scheme is a variant of the SIMPLE methodology. Typically, a scheme of this type tends to suffer from stability problems, which this new scheme overcomes by taking small intermediate steps within a time step. The calculations made in the intermediate steps are damped to enhance the stability of the scheme. The new stabilised scheme is evaluated for laminar flow around a square cylinder, impulsively started laminar flow over a backward-facing step and fluctuating laminar flow over a backward-facing step. Comparisons are made with other numerical predictions and experimental data. In general, good agreement is found, except for the fluctuating laminar flow over a backward-facing step problem. The new scheme is found to have the same level of accuracy, stability and efficiency in comparison with the PISO scheme, but it is easier to code.

Barton, I. E.

1998-10-01

402

Modeling Bituminous Coal Devolatilization in the Electric Grid and Laminar Entrained Flow Research Reactors.  

National Technical Information Service (NTIS)

Bituminous coal devolatilization data from an electric grid reactor and a laminar entrained flow reactor are modeled using two separate analytical derivations. The analyses are based on the assumption that the reactive volatile component of the pulverized...

K. M. Sprouse

1986-01-01

403

Advanced Natural Laminar Flow Airfoil with High Lift to Drag Ratio.  

National Technical Information Service (NTIS)

An experimental verification of a high performance natural laminar flow (NLF) airfoil for low speed and high Reynolds number applications was completed in the Langley Low Turbulence Pressure Tunnel (LTPT). Theoretical development allowed for the achieveme...

J. K. Viken W. Pfenninger R. J. McGhee

1986-01-01

404

Fuel-dilution effect on differential molecular diffusion in laminar hydrogen diffusion flames  

Microsoft Academic Search

Laminar flame calculations have been made for a Tsuji counterflow geometry to investigate salient features caused by the differential diffusion effect in nitrogen-diluted hydrogen diffusion flames. A strong dependence of the differential diffusion parameter \\</p

Yung-cheng Chen; Jyh-Yuan Chen

1998-01-01

405

Laminar Flow in a Two-Dimensional Channel with a Right Angle Corner.  

National Technical Information Service (NTIS)

Laminar, steady, incompressible flow in a two-dimensional channel with a right angle corner was investigated by numerical analysis and experimental measurement. The problem was used as a vehicle to compare a finite differencing method with an upwind diffe...

R. M. Wilson J. A. Owczarek

1973-01-01

406

Controlled Heat Transfer in a Laminar Boundary Layer along the Penetrable Surface of a Blunt Body  

Microsoft Academic Search

The problem on the determination of distributed forced injection from the surface of a blunt body subjected to flow for attaining preassigned characteristics of heat transfer is treated within the framework of the model of laminar boundary layer.

A. I. Borodin

2003-01-01

407

Development of Advanced High Lift Leading Edge Technology for Laminar Flow Wings.  

National Technical Information Service (NTIS)

This paper describes the Advanced High Lift Leading Edge (AHLLE) task performed by Northrop Grumman Systems Corporation, Aerospace Systems (NGAS) for the NASA Subsonic Fixed Wing project in an effort to develop enabling high-lift technology for laminar fl...

A. Korntheuer J. C. Lin M. M. Bright S. Komadina

2013-01-01

408

Design and operation of a laminar-flow electrostatic-quadrupole-focused acceleration column  

SciTech Connect

This report deals with the design principles involved in the design of a laminar-flow electrostatic-quadrupole-focused acceleration column. In particular, attention will be paid to making the parameters suitable for incorporation into a DC MEQALAC design.

Maschke, A.W.

1983-06-20

409

Technology Developments for Laminar Boundary Layer Control on Subsonic Transport Aircraft.  

National Technical Information Service (NTIS)

Since the beginning of the NASA Aircraft Energy Efficiency (ACEE) program in 1976, significant progress has been made in the development of laminar flow technology for commercial transports. Exploitation of new materials, fabrication methods, analysis tec...

R. D. Wagner D. V. Maddalon M. C. Fischer

1984-01-01

410

Micro-Composite Fabrication via Field-Aided Laminar Composite (FALCom) Processing.  

National Technical Information Service (NTIS)

A novel composite fabrication process is used to create multi- functional micro-composites, which can be tailored for specific end-use applications. The Field-Aided Laminar Composite (FALCom) process uses specifically focused electric fields to align nano...

J. L. Holmes

2012-01-01

411

Freiflugexperimente MIT Einem Laminarfluegel-Handschuh (Free Flight Experiment with a Laminar Wing Glove).  

National Technical Information Service (NTIS)

The CPM3 (Computational Preston Tube) method and the piezo array technique are compared in terms of functionality for laminar turbulent boundary layer transition investigations. The CPM3 technique is based on static pressure measurement from three wall Pi...

N. Weiser W. Nitsche

1991-01-01

412

Effects of Curvature and Dilution on Unsteady, Premixed, Laminar Flame Propagation.  

National Technical Information Service (NTIS)

We have used a time-dependent, one-dimensional, Lagrangian model to study laminar flames in stoichiometric hydrogen-oxygen mixtures diluted with nitrogen. For stoichiometric hydrogen-air mixtures we have seen that spherically expanding flame first deceler...

K. Kailasanath E. S. Oran

1985-01-01

413

A Study of Fineblanking for the Manufacture of Flueric Laminar Proportional Amplifiers.  

National Technical Information Service (NTIS)

A nonconventional stamping process, known as fineblanking, is investigated for use in high-volume production of flueric laminar proportional amplifiers. The investigation includes the standard deviation of critical dimensions, supply and control flow meas...

R. M. Phillippi

1977-01-01

414

Investigation of Radiative Interaction in Laminar Flows Using Monte Carlo Simulation.  

National Technical Information Service (NTIS)

The Monte Carlo method (MCM) is employed to study the radiative interactions in fully developed laminar flow between two parallel plates. Taking advantage of the characteristics of easy mathematical treatment of the MCM, a general numerical procedure is d...

J. Liu S. N. Tiwari

1993-01-01

415

Measurements of laminar burning velocities for natural gas–hydrogen–air mixtures  

Microsoft Academic Search

Laminar flame characteristics of natural gas–hydrogen–air flames were studied in a constant-volume bomb at normal temperature and pressure. Laminar burning velocities and Markstein lengths were obtained at various ratios of hydrogen to natural gas (volume fraction from 0 to 100%) and equivalence ratios (? from 0.6 to 1.4). The influence of stretch rate on flame was also analyzed. The results

Zuohua Huang; Yong Zhang; Ke Zeng; Bing Liu; Qian Wang; Deming Jiang

2006-01-01

416

Optimal product distribution from laminar flow reactors: Newtonian and other power-law fluids  

Microsoft Academic Search

In tubular reactors viscous fluids are in laminar flow. For reactions in series this gives a product distribution different from either plug flow or mixed flow. More importantly, laminar flow depresses the maximum amount of intermediate that can be obtained when compared to plug flow. Here we treat the simple case of an elementary two-step mechanism:(1)[A?R?S]Three special cases of the

Keith L. Levien; Octave Levenspiel

1999-01-01

417

High-pressure laminar flame speeds and kinetic modeling of carbon monoxide\\/hydrogen combustion  

Microsoft Academic Search

Laminar flame speeds were accurately measured for CO\\/H2\\/air and CO\\/H2\\/O2\\/helium mixtures at different equivalence ratios and mixing ratios by the constant-pressure spherical flame technique for pressures up to 40 atmospheres. A kinetic mechanism based on recently published reaction rate constants is presented to model these measured laminar flame speeds as well as a limited set of other experimental data. The

Hongyan Sun; S. I. Yang; G. Jomaas; C. K. Law

2007-01-01

418

Effects of hydrogen addition on laminar and turbulent premixed methane and iso-octane–air flames  

Microsoft Academic Search

The effect of adding hydrogen to methane and iso-octane–air premixtures has been investigated under both laminar and turbulent conditions. Five percent by mass of hydrogen was added the to base fuel. Measurements were performed at 5bar and the equivalence ratio was varied from the lean ignition limit to either the rich ignition or sooting\\/buoyancy limit. The laminar burning velocity, ul,

C. Mandilas; M. P. Ormsby; C. G. W. Sheppard; R. Woolley

2007-01-01

419

On the effect of riblets in fully developed laminar channel flows  

NASA Astrophysics Data System (ADS)

The effect of longitudinal riblet surfaces on viscous drag in fully developed laminar channel flows was investigated. Unlike turbulent flows, drag reduction was not obtained in the laminar flows. Results were independent of Reynolds number. Wall-shear rates on most regions of the cross-sectional perimeter of riblets were smaller than that of corresponding plane channel flow even though the net drag was increased.

Choi, Haecheon; Moin, Parviz; Kim, John

1991-08-01

420

An Experimental Study of Thermophoretic Deposition of Aerosol Particles in Laminar Tube Flow with Mixed Convection  

Microsoft Academic Search

The thermophoretic deposition of aerosol particles in mixed-convection, laminar tube flow with a cooled wall is considered. The presence of free convection alters the velocity and temperature profiles for laminar tube flow relative to the constant-properties case. Previous modeling results (Walsh, Weimer, and Hrenya, in press), show that the modified flow fields lead to changes in the cumulative deposition-efficiency profiles

J. K. Walsh; A. W. Weimer; C. M. Hrenya

2006-01-01

421

Morphometric trajectory analysis for the C2 crossing laminar screw technique  

Microsoft Academic Search

This paper reports a morphometric study of the C2 laminae to provide quantitative anatomical data for safe crossing laminar\\u000a screw placement. A valid trajectory is essential for C2 crossing laminar screw placement. Although several clinical technique\\u000a notes and modifications to define a safe screw trajectory have been introduced in the recent years, no morphometric analysis\\u000a has been performed to confirm

Bin Yue; Dai-Soon Kwak; Moon-Kyu Kim; Seong-Oh Kwon; Seung-Ho Han

2010-01-01

422

Bone laminarity in the avian forelimb skeleton and its relationship to flight mode: testing functional interpretations.  

PubMed

Wing bone histology in three species of birds was characterized in order to test hypotheses related to the relationship between skeletal microstructure and inferred wing loading during flight. Data on the degree of laminarity (the proportion of circular vascular canals) and the occurrence of secondary osteons were obtained from three species that utilize different primary flight modes: the Double-crested cormorant, a continuous flapper; the Brown pelican, a static soarer; and the Laysan albatross, a dynamic soarer. Laminarity indices were calculated for four quadrants for each of the three main wing elements. Ulnae and carpometacarpi were predicted to exhibit quadrant specific patterns of laminarity due to hypothesized differences in locally applied loads related to the attachment of flight feathers. However, few differences among the quadrants were identified. No significant differences were identified among the three elements, which is notable as different bones are likely experiencing different loading conditions. These results do not support the concept of bone functional adaptation in the primary structure of the wing elements. Significant differences in laminarity were found among the three primary flight modes. The dynamic soaring birds exhibited significantly lower laminarity than the flapping and static soaring birds. These results support the proposed hypothesis that laminarity is an adaptation for resisting torsional loading. This may be explained by overall wing shape: whereas dynamic soaring birds have long slender wings, flappers and static soaring birds have broader wings with a larger wing chord that would necessarily impart a higher torsional moment on the feather-bearing bones. PMID:22241723

Simons, Erin L R; O'connor, Patrick M

2012-01-12

423

Premixed laminar flame propagation in a rotating vessel  

NASA Astrophysics Data System (ADS)

Combustion in a swirling flow is devoted to burn lean mixture in spark ignition engines since it provides fuel economy and exhaust emission reduction. Therefore it is important to know the flame behavior under centrifugal forces. The flame in a rotating gas is modified by an aerodynamic mechanism due to action of centrifugal forces instead the laminar burning velocity due to chemical kinetics. The paper deals with important characteristics of eddy combustion mechanism such as: flame shape and propagation as a function of the rotation rate. Therefore pictures captured by a video camera are treated with the image processing toolbox from Matlab in order to establish the main characteristics of the flame kernel of a mixture propane -- air at different rotation rates ranging from 500 to 4000 rpm. It is observed that the flame propagates along the rotation axis and that the extinguishing of the flame is involved with the heat losses as soon the flame reaches the wall of the chamber. In addition, the flame shape is quite similar to the intrusion head of a light fluid penetrating into a stagnated heavy fluid.

Parra, Teresa; Gorczakowski, Andrzej; Chomiak, Jerzy; Jarosinski, Jozef

2008-11-01

424

Cooperative phenomena in laminar fluids: Observation of streamlines  

SciTech Connect

Complex plasmas are an ideal model system to investigate laminar fluids as they allow to study fluids at the kinetic level. At this level we are able to identify streamlines particle by particle. This gives us the ability to research the behaviour of these streamlines as well as the behaviour of each individual particle of the streamline.We carried out our experiments in a modified GEC-RF-Reference cell. We trapped the particles within two glass rings and forced them to form a circular flow by using several stripe electrodes. In this flow the particles behave like an ideal fluid and form streamlines. By putting an obstacle into the flow we reduce the cross-section. To pass through this constricted cross-section some streamlines have to reconnect. After the obstacle the streamlines split up again. An analysis how streamlines split up and reconnect as result of external pressure on the fluid in our system is presented here.Streamlines also occur if two clouds of particles penetrate each other. We call this 'Lane formation'. Results from our PK-4 experiment are presented here also.

Fink, Martin A.; Kretschmer, M.; Hoefner, H.; Konopka, U.; Morfill, G.E.; Ratynskaia, S. [Max Planck Institute for extraterrestrial Physics, Giessenbachstrasse, 85741 Garching (Germany); Fortov, V.; Petrov, O.; Usachev, A.; Zobnin, A. [Institute for High Energy Density, Russian Academy of Sciences, ul. Izhorskaya 13/19, 125412 Moscow (Russian Federation)

2005-10-31

425

Numerical simulation of laminar flow in a curved duct  

NASA Astrophysics Data System (ADS)

This paper describes numerical simulations that were performed to study laminar flow through a square duct with a 900 bend. The purpose of this work was two fold. First, an improved understanding was desired of the flow physics involved in the generation of secondary vortical flows in three-dimensions. Second, adaptive gridding techniques for structured grids in three- dimensions were investigated for the purpose of determining their utility in low Reynolds number, incompressible flows. It was also of interest to validate the commercial computer code CFD-ACE. Velocity predictions for both non-adaptive and adaptive grids are compared with experimental data. Flow visualization was used to examine the characteristics of the flow though the curved duct in order to better understand the viscous flow physics of this problem. Generally, moderate agreement with the experimental data was found but shortcomings in the experiment were demonstrated. The adaptive grids did not produce the same level of accuracy as the non-adaptive grid with a factor of four more grid points.

Lopez, Amalia R.; Oberkampf, William L.

1995-04-01

426

Transient Measurements at the laminar -- Karman Vortex Street Transition  

NASA Astrophysics Data System (ADS)

Here we examine the hysteretic behavior that appears in the generation of a von Karman vortex street produced by a rigid rod that penetrates a vertically flowing soap film (related papers: http://karman.phyast.pitt.edu/). The mean flow velocity is adjusted so that the system is in the hysteretic gap. Then the velocity field is perturbed, and the response of the flow is investigated by laser Doppler velocimetry. To reduce three dimensional effects, the rod was replaced by a disk having a thickness roughly eight times that of the film. The replacement of the rod by a disk increases the gap width and the shedding frequency. In this gap, the perturbation for both obstacles generates a noisy state that is neither laminar nor temporally periodic. In this unexpected state, the spectrum of the fluctuations is broad, with a mean frequency that is slightly lower than the sharply defined frequency of the periodic state.

Vörös, Zoltán; Goldburg, Walter; Horváth, Viktor

1999-11-01

427

Laminar and weakly turbulent oceanic gravity currents performing inertial oscillations  

NASA Astrophysics Data System (ADS)

The small scale dynamics of a weakly turbulent oceanic gravity current is determined. The gravity current considered is initially at rest and adjusts by performing inertial oscillations to a geostrophic mean flow. The dynamics is explored with a hierarchy of mathematical models. The most involved are the fully 3-D Navier-Stokes equations subject to the Boussinesq approximation. A 1-D and 0-D mathematical model of the same gravity current dynamics are systematically derived. Using this hierarchy and the numerical solutions of the mathematical models, the turbulent dynamics at the bottom and the interface is explored and their interaction investigated. Three different regimes of the small scale dynamics of the gravity current are identified, they are characterised by laminar flow, coherent roll vortices and turbulent dynamics with coherent streaks and bursts. The problem of the rectification of the turbulent fluxes, that is, how to average out the fluctuations and calculate their average influence on the flow, is considered. It is shown that two different regimes of friction are superposed, an Ekman friction applies to the average geostrophic flow and a linear friction, not influenced by rotation, to the inertial oscillations. The combination of the two makes the bulk friction non-local in time for the 0-D model. The implications of the results for parametrisations of the Ekman dynamics and the small scale turbulent fluxes in the planetary boundary layer are discussed.

Wirth, A.

2012-05-01

428

The ignition of methanol droplets in a laminar convective environment  

SciTech Connect

Numerical simulations of the ignition of methanol droplets in a laminar convective environment are performed using detailed reaction mechanisms and detailed transport models. The flow velocities of the forced convection ranges from 0.01 up to 5 m/s, whereas the ambient gas temperature is varied between 1300 and 1500 K. The ignition delay time of a single droplet is found to decrease with increasing velocity of the convective gas flow. This decrease is attributed to the steepening of the spatial gradients of the profiles of physical variables, such as species mass fractions or temperature. This steepening is originated by a stronger gas flow and leads to a speed-up of the physical transport processes. For the studied flow conditions, an acceleration of the gas flow on the order of the gravitational acceleration does not show a significant influence on the ignition delay time. A downstream movement of the local ignition point with increasing flow velocity is observed. For higher flow velocities, an ignition in the wake of the droplet followed by an upstream flame propagation is found. After ignition, the formation of an envelope flame is detected. The structure of this envelope flame is studied. (author)

Stauch, R.; Maas, U. [Institut fuer Technische Thermodynamik, Universitaet Karlsruhe, Kaiserstrasse 12, D-76128 Karlsruhe (Germany)

2008-04-15

429

Numerical study of ethylene and acetylene laminar flame speeds  

SciTech Connect

Detailed chemical kinetic computations for ethylene-air and acetylene-air mixtures have been performed to simulate laminar flame speeds. Sensitivity analysis was applied to determine those reactions which strongly influence flame propagation. In ethylene-air mixtures, the C{sub 2}H{sub 3} + O{sub 2} = CH{sub 2}CHO + O reaction was one of the most sensitive reactions in the C{sub 2}H{sub 4}/C{sub 2}H{sub 3} submechanism and therefore this reaction was very important to ethylene flame propagation. This reaction was not considered in previously reported mechanisms used to model ethylene-air flame propagation. In acetylene-air mixtures, the C{sub 2}H{sub 2}+O {yields} Products, HCCO+H=CH{sub 2}(s)+CO, HCCO+O{sub 2}=CO{sub 2}+CO+H, H+C{sub 2}H{sub 2}(+M) = C{sub 2}H{sub 3}(+M) and CH{sub 2}(s)+C{sub 2}H{sub 2} = H{sub 2}CCCH+H were the most sensitive reactions in the C{sub 2}H{sub 2}/HCCO / CH{sub 2}(s) reaction set.

Marinov, N.M.; Pitz, W.J.; Westbrook, C.K.

1995-03-01

430

Acoustic receptivity of laminar boundary layers over wavy walls  

NASA Astrophysics Data System (ADS)

Acoustic receptivity of laminar boundary layers over surfaces with nonlocalized low-amplitude periodic waviness is experimentally investigated. An array of 2D strips is used to simulate continuous wall waviness. Particular attention to measurement techniques is required to minimize facility-dependent flow and acoustic field anomalies. Balanced arrays of acoustic sources upstream and downstream of the test section are used to generate a traveling acoustic mode, effectively eliminating the standing modes that would distort the results of continuous receptivity measurements. Hot-wire measurements of Tollmien-Schlichting (T-S) mode shapes arc shown to be in excellent agreement with theory. By increasing the number of wall wavelengths, it is demonstrated that an effectively infinite wavy wall can be produced by a small region near lower branch. It is also shown that the ratio between receptivity at distributed waviness and at localized surface inhomogeneities is of O(10). The effect of mismatching the T-S wavelength with the geometric wall wavelength is investigated by changing the free stream velocity at a constant forcing frequency. Strong receptivity occurs only over a narrow band where the wall wavelength and the T-S wavelength are matched. The results of this experiment are shown to match trends as well as absolute amplitudes predicted by receptivity theory.

Wiegel, M.; Wlezien, R. W.

1993-07-01

431

Computational sensitivity analysis of geometric parameters in laminar superhydrophobic microchannels  

NASA Astrophysics Data System (ADS)

This talk presents 3-D numerical simulations of laminar flow through a microchannel of height h containing superhydrophobic surfaces (SHS) along the top and bottom walls. The SHS is modelled as an array of longitudinal shear-free surfaces having width w and inclination angle ?. The simulations allow for a phase offset l between the shear-free surfaces on the top and bottom walls. The sensitivity of velocity, wall shear stress, and slip-length with respect to infinitesimal changes in the geometrical design parameters (w, ?, l, and h) was examined using the Sensitivity Equation Method and Complex Step Differentiation. These techniques differ from traditional parametric studies in that sensitivities are obtained more accurately by direct numerical solution of a separate set of PDEs for the sensitivity derivatives. In this manner, the present sensitivity results can be used to reliably predict the percent drag savings achievable for a unit increase in w and h. Sensitivity results also indicate that an increase in ? translates into enhanced mixing, albeit with a drag penalty. Finally, the talk discusses how the present sensitivity results may be incorporated in to a gradient-based optimization algorithm toward improved microchannel design.

Yarahmadi, Asghar; Metzger, Meredith

2010-11-01

432

Pulsating laminar fully developed channel and pipe flows.  

PubMed

Analytical investigations are carried out on pulsating laminar incompressible fully developed channel and pipe flows. An analytical solution of the velocity profile for arbitrary time-periodic pulsations is derived by approximating the pulsating flow variables by a Fourier series. The explicit interdependence between pulsations of velocity, mass-flow rate, pressure gradient, and wall shear stress are shown by using the proper dimensionless parameters that govern the flow. Utilizing the analytical results, the scaling laws for dimensionless pulsation amplitudes of the velocity, mass-flow rate, pressure gradient, and wall shear stress are analyzed as functions of the dimensionless pulsation frequency. Special attention has been given to the scaling laws describing the flow reversal phenomenon occurring in pulsating flows, such as the condition for flow reversal, the dependency of the reversal duration, and the amplitude. It is shown that two reversal locations away from the wall can occur in pulsating flows in pipes and channels and the reversed amount of mass per period reaches a maximum at a certain dimensionless frequency for a given amplitude of mass-flow rate fluctuations. These analyses are numerically conducted for pipe and channel flows over a large frequency range in a comparative manner. PMID:20365456

Haddad, Kais; Ertunç, Ozgür; Mishra, Manoranjan; Delgado, Antonio

2010-01-08

433

Conjugate heat and mass transfer in a desiccant-airflow system: A numerical solution method  

SciTech Connect

An effective numerical method was developed for analyzing, as a conjugate problem, transient two-dimensional heat and mass transfer between a solid desiccant and a humid laminar airstream. The method is also more generally applicable to conjugate problems of heat and mass transfer between solids and flowing fluids. The alternating direction implicit (ADI) procedure with an upwind scheme is used for solving both the energy and mass transfer equations. The secant method is applied to solve the local equilibrium relationship between the water content and the water vapor concentration in the silica gel bed. Comparison with conventional, nonconjugate problem solutions has shown that such solutions produce unacceptably large errors in thick-bed (of the order of 2 cm) desiccant systems; for example, they overpredict the water absorption rates by 53%.

Fujii, Yoshihisa; Lior, N. [Univ. of Pennsylvania, Philadelphia, PA (United States). Dept. of Mechanical Engineering and Applied Mechanics

1996-05-24

434

Do chronic changes in nasal airflow have any physiological or pathological effect on the nose and paranasal sinuses? A systematic review.  

PubMed

.A reduction in nasal airflow associated with anatomical defects of the nose such as nasal septal deviation has been proposed to cause nasal pathology. . The majority of animal experiments where one nasal passage is surgically closed over several months report only minor changes in the histology of the nasal epithelium and no rhinitis or sinusitis. .Complete abolition of nasal airflow associated with laryngectomy or the treatment of atrophic rhinitis is not associated with the development of rhinitis or sinusitis. . Radiological studies have shown a lack of association between the degree of nasal septal deviation and evidence of rhinosinusitis. .Such studies provide evidence that reduced nasal airflow causes no significant nasal disease. . There is no convincing evidence that a reduction in nasal airflow is a causative factor for rhinitis or sinusitis. PMID:16441795

Boyce, J; Eccles, R

2006-02-01

435

Effects of alcohol-partitioning type and airflow on cosolvent flooding to benzene-LNAPL saturated porous media.  

PubMed

This study fundamentally investigated the swelling and distribution of benzene-light nonaqueous phase liquid (LNAPL) in porous media while cosolvent was flushed to the benzene-partially saturated system. Furthermore, the effects of simultaneous injection of cosolvent and air on the LNAPL behavior were visualized and thus quantified within a two-dimensional transparent porous medium. Partitioning types of alcohols affected dissolution of benzene entrapped in porous media. Tert-butanol (TBA) and 1-propanol floods apparently increased the LNAPL area, while a 70% ethanol flood reduced the LNAPL area by dissolution. Airflow facilitates mobilization of the swollen LNAPL by TBA and 1-propanol, while it facilitates dissolution of non-swollen LNAPL by ethanol. Therefore, LNAPL behavior during cosolvent flooding would be determined by partitioning type of alcohols and the presence of airflow. PMID:19131164

Jeong, Seung-Woo; Ju, Byung-Kyu; Lee, Byung-Jin

2008-12-03

436

The incidence of airflow obstruction in bronchial carcinoma, its relation to breathlessness, and response to bronchodilator therapy  

Microsoft Academic Search

Breathlessness is a common symptom in patients with primary bronchial carcinoma and is often not well-controlled. Most patients are ex- or current smokers, and therefore are at high risk for co-existing chronic obstructive pulmonary disease (COPD). The incidence of airflow obstruction in patients with bronchial carcinoma, its relation to breathlessness, and response to bronchodilator therapy was examined prospectively. Fifty-seven consecutive

J. Congleton; M. F. Muers

1995-01-01

437

Mathematical Modeling Procedures for Airflow, Heat and Mass Transfer During Forced Convection Cooling of Produce: A Review  

Microsoft Academic Search

The aim of this review paper is to give comprehensive and detailed mathematical modeling procedures for the airflow, heat\\u000a and mass transfer occurred during forced convection cooling of produce in order to optimize the cooling process. First, a\\u000a brief explanation of forced-air precooling process and its importance in improving produce market quality will be given. Then,\\u000a two main modeling procedures

Jalal Dehghannya; Michael Ngadi; Clement Vigneault

2010-01-01

438

Genome-Wide Association Studies Identify CHRNA5/3 and HTR4 in the Development of Airflow Obstruction  

PubMed Central

Rationale: Genome-wide association studies (GWAS) have identified loci influencing lung function, but fewer genes influencing chronic obstructive pulmonary disease (COPD) are known. Objectives: Perform meta-analyses of GWAS for airflow obstruction, a key pathophysiologic characteristic of COPD assessed by spirometry, in population-based cohorts examining all participants, ever smokers, never smokers, asthma-free participants, and more severe cases. Methods: Fifteen cohorts were studied for discovery (3,368 affected; 29,507 unaffected), and a population-based family study and a meta-analysis of case-control studies were used for replication and regional follow-up (3,837 cases; 4,479 control subjects). Airflow obstruction was defined as FEV1 and its ratio to FVC (FEV1/FVC) both less than their respective lower limits of normal as determined by published reference equations. Measurements and Main Results: The discovery meta-analyses identified one region on chromosome 15q25.1 meeting genome-wide significance in ever smokers that includes AGPHD1, IREB2, and CHRNA5/CHRNA3 genes. The region was also modestly associated among never smokers. Gene expression studies confirmed the presence of CHRNA5/3 in lung, airway smooth muscle, and bronchial epithelial cells. A single-nucleotide polymorphism in HTR4, a gene previously related to FEV1/FVC, achieved genome-wide statistical significance in combined meta-analysis. Top single-nucleotide polymorphisms in ADAM19, RARB, PPAP2B, and ADAMTS19 were nominally replicated in the COPD meta-analysis. Conclusions: These results suggest an important role for the CHRNA5/3 region as a genetic risk factor for airflow obstruction that may be independent of smoking and implicate the HTR4 gene in the etiology of airflow obstruction.

Shrine, Nick R. G.; Loehr, Laura R.; Zhao, Jing Hua; Manichaikul, Ani; Lopez, Lorna M.; Smith, Albert Vernon; Heckbert, Susan R.; Smolonska, Joanna; Tang, Wenbo; Loth, Daan W.; Curjuric, Ivan; Hui, Jennie; Latourelle, Jeanne C.; Henry, Amanda P.; Aldrich, Melinda; Bakke, Per; Beaty, Terri H.; Bentley, Amy R.; Borecki, Ingrid B.; Brusselle, Guy G.; Burkart, Kristin M.; Chen, Ting-hsu; Couper, David; Crapo, James D.; Davies, Gail; Dupuis, Josee; Franceschini, Nora; Gulsvik, Amund; Hancock, Dana B.; Harris, Tamara B.; Hofman, Albert; Imboden, Medea; James, Alan L.; Khaw, Kay-Tee; Lahousse, Lies; Launer, Lenore J.; Litonjua, Augusto; Liu, Yongmei; Lohman, Kurt K.; Lomas, David A.; Lumley, Thomas; Marciante, Kristin D.; McArdle, Wendy L.; Meibohm, Bernd; Morrison, Alanna C.; Musk, Arthur W.; Myers, Richard H.; North, Kari E.; Postma, Dirkje S.; Psaty, Bruce M.; Rich, Stephen S.; Rivadeneira, Fernando; Rochat, Thierry; Rotter, Jerome I.; Artigas, Maria Soler; Starr, John M.; Uitterlinden, Andre G.; Wareham, Nicholas J.; Wijmenga, Cisca; Zanen, Pieter; Province, Michael A.; Silverman, Edwin K.; Deary, Ian J.; Palmer, Lyle J.; Cassano, Patricia A.; Gudnason, Vilmundur; Barr, R. Graham; Loos, Ruth J. F.; Strachan, David P.; London, Stephanie J.; Boezen, H. Marike; Probst-Hensch, Nicole; Gharib, Sina A.; Hall, Ian P.; O'Connor, George T.; Tobin, Martin D.; Stricker, Bruno H.

2012-01-01

439

Numerical simulations of island-scale airflow and the Maui vortex under summer trade-wind conditions  

Microsoft Academic Search

The fifth-generation Pennsylvania State University-NCAR Mesoscale Model (MM5) coupled with the Noah Land Surface Model (LSM) is used to simulate island-scale airflow and the Maui Vortex during summer trade-wind conditions (1 July-31 August 2005). The model is initialized by the Global Forecast System (GFS) as the boundary conditions. The MM5-LSM is validated with observations (i.e. 2-m temperature, 2-m dew point

Dana Lamar Carlis

2007-01-01

440

Air-flow patterns and heat fluxes in roof-ventilated multi-span greenhouse with insect-proof screens  

Microsoft Academic Search

Experiments were performed in a semi-commercial, roof-ventilated, four-span greenhouse with insect-proof screens over its openings, to determine the air-flow patterns, heat fluxes and ventilation rates. The ventilation rate in leeward ventilation increased with wind velocity. A comparison between ventilation rates measured by the tracer gas and energy-balance methods showed good correlation between the two. An indication of the influence of

E Shilo; M Teitel; Y Mahrer; T Boulard

2004-01-01

441

Laminar fluid flow and mass transfer in a standard field and laboratory emission cell  

Microsoft Academic Search

The field and laboratory emission cell (FLEC) is becoming a standard method of characterizing pollutant emissions from building materials. Based on this method, the material and the inner surface of the FLEC cap form a cone-shaped cavity. The airflow is distributed radially inward over the test surface through a slit in a circular-shaped channel at the perimeter of the chamber.

L. Z Zhang; J. L Niu

2003-01-01

442

Inhaled corticosteroids reduce the progression of airflow limitation in chronic obstructive pulmonary disease: a meta-analysis  

PubMed Central

Background: Chronic obstructive pulmonary disease (COPD) is a syndrome of chronic progressive airflow limitation which occurs as a result of chronic inflammation of the airways and lung parenchyma. However, the role of inhaled corticosteroids in the treatment of COPD is controversial. We hypothesised that inhaled corticosteroids reduce the progression of airflow limitation in COPD. Methods: A comprehensive literature search was conducted and data were analysed using random effects methodology. The effect of inhaled steroids on annual change in forced expiratory volume in 1 second (FEV1) was determined for all trials, for trials with high dose treatment regimens, and for trials in subjects with moderate to severe airflow limitation. Results: Data from eight controlled clinical trials of ?2 years were included (n=3715 subjects). Meta-analysis of all study data revealed that inhaled corticosteroids reduce the rate of FEV1 decline by 7.7 ml/year (95% confidence interval (CI) 1.3 to 14.2, p=0.02). Meta-analysis of studies with high dose regimens revealed a greater effect of 9.9 ml/year (95% CI 2.3 to 17.5, p=0.01) compared with the meta-analysis of all studies. Conclusions: Inhaled corticosteroid treatment for ?2 years slows the rate of lung function decline in COPD. The effect observed with high dose regimens is greater than that with all regimens combined. These data suggest a potential role for inhaled corticosteroids in modifying the long term natural history of COPD.

Sutherland, E; Allmers, H; Ayas, N; Venn, A; Martin, R

2003-01-01

443

Large eddy simulation of the pharyngeal airflow associated with obstructive sleep apnea syndrome at pre and post-surgical treatment.  

PubMed

Obstructive Sleep Apnea Syndrome (OSAS) is the most common sleep-disordered breathing medical condition and a potentially life-threatening affliction. Not all the surgical or non-surgical OSAS therapies are successful for each patient, also in part because the primary factors involved in the etiology of this disorder are not completely understood. Thus, there is a need for improving both diagnostic and treatment modalities associated with OSAS. A verified and validated (in terms of mean velocity and pressure fields) Large Eddy Simulation approach is used to characterize the abnormal pharyngeal airflow associated with severe OSAS and its interaction with the airway wall in a subject who underwent surgical treatment. The analysis of the unsteady flow at pre- and post-treatment is used to illustrate the airflow dynamics in the airway associated with OSAS and to reveal as well, the changes in the flow variables after the treatment. At pre-treatment, large airflow velocity and wall shear stress values were found at the obstruction site in all cases. Downstream of obstruction, flow separation generated flow recirculation regions and enhanced the turbulence production in the jet-like shear layers. The interaction between the generated vortical structures and the pharyngeal airway wall induced large fluctuations in the pressure forces acting on the pharyngeal wall. After the surgery, the flow field instabilities vanished and both airway resistance and wall shear stress values were significantly reduced. PMID:21700289

Mihaescu, Mihai; Mylavarapu, Goutham; Gutmark, Ephraim J; Powell, Nelson B

2011-06-22

444

Magnetic resonance imaging and computational fluid dynamics (CFD) simulations of rabbit nasal airflows for the development of hybrid CFD/PBPK models  

PubMed Central

The percentages of total airflows over the nasal respiratory and olfactory epithelium of female rabbits were calculated from computational fluid dynamics (CFD) simulations of steady-state inhalation. These airflow calculations, along with nasal airway geometry determinations, are critical parameters for hybrid CFD/physiologically based pharmacokinetic models that describe the nasal dosimetry of water-soluble or reactive gases and vapors in rabbits. CFD simulations were based upon three-dimensional computational meshes derived from magnetic resonance images of three adult female New Zealand White (NZW) rabbits. In the anterior portion of the nose, the maxillary turbinates of rabbits are considerably more complex than comparable regions in rats, mice, monkeys, or humans. This leads to a greater surface area to volume ratio in this region and thus the potential for increased extraction of water soluble or reactive gases and vapors in the anterior portion of the nose compared to many other species. Although there was considerable interanimal variability in the fine structures of the nasal turbinates and airflows in the anterior portions of the nose, there was remarkable consistency between rabbits in the percentage of total inspired airflows that reached the ethmoid turbinate region (~50%) that is presumably lined with olfactory epithelium. These latter results (airflows reaching the ethmoid turbinate region) were higher than previous published estimates for the male F344 rat (19%) and human (7%). These differences in regional airflows can have significant implications in interspecies extrapolations of nasal dosimetry.

Corley, R. A.; Minard, K. R.; Kabilan, S.; Einstein, D. R.; Kuprat, A. P.; Harkema, J. R.; Kimbell, J. S.; Gargas, M. L.; Kinzell, John H.

2010-01-01

445

Measurement of tidal breath by determination of chest wall volume displacement in patients with airflow obstruction.  

PubMed

We compared tidal volume (VT) measured from the integrated airflow signal of a pneumotachygraph (PNTG) in ten patients, seated comfortably, with airway obstruction to VT, recorded simultaneously, by three chest-wall volume-displacement methods: two-channel magnetometer, isovolume calibration (mag-isov); respiratory inductance plethysmograph, isovolume calibration (rip-isov); and, inductance plethysmograph, least squares calibration (rip-l sq). There was no difference between VT, measured without PNTG, with each of the methods. When mouthpiece, noseclips, PNTG, and finally, dead space were included in a breathing circuit, VT increased to approximately one and one-half times that measured without the mouthpiece. Inspiratory volumes were measured with similar error by each method (mag-isov, 8.61 +/- 5.73 percent SD; rip-isov, 9.30 +/- 6.12 percent SD; rip-l sq, 8.43 +/- 6.27 percent SD). We conclude that in airway obstruction patients seated in a constant position, over the range of inspiratory volumes studied, error associated with chest wall volume-displacement methods is no greater than in normal subjects. PMID:4028853

Dadzie, C; Simpser, M; Lavietes, M H

1985-09-01

446

Changes in airflow dynamics after creation of pharyngeal flaps in nonsyndromic children.  

PubMed

Velopharyngeal insufficiency is a common problem in the cleft palate population that may require a pharyngeal flap. Sleep disordered breathing is a common complication of this surgery and a baseline sleep study is often performed before undergoing the procedure. Few postoperative sleep studies are ever done and little is known about the effects that pharyngeal flaps have on airflow dynamics.Preoperative and postoperative nasometry and polysomnographic data were reviewed and compared from nonsyndromic children requiring pharyngeal flap since 2009. Eighteen children having undergone pharyngeal flap were identified. Of those 18, Nadir oxygen saturations were worsened in 10, improved in 7, and remained the same in 1. Snoring was caused or made worse in 8. Sleep efficiency was worse in 11, improved in 6, and remained the same in 1. Apnea/hypopnea events increased in 9 and decreased in the other 9. Hypernasality was improved in varying degrees in 17 patients, but all required additional speech therapy. Diagnosed preoperative sleep apnea remained in 1 patient. No patient's postpharyngeal flap had any significant sleep disturbance that would warrant continuous positive airway pressure. No flaps required division or takedown.This preliminary study suggests that pharyngeal flaps may increase snoring and apnea/hypopnea events without causing diagnosable sleep disordered breathing and the resultant clinical sequelae. Nasometry shows evidence of nasal airway diversion without complete obstruction. Speech improves more subjectively than nasometry would predict after pharyngeal flap. PMID:23542857

Griner, Devan; Sargent, Larry A; Overmeyer, Claire Lee

2013-05-01

447

Investigation on oblique shock wave control by arc discharge plasma in supersonic airflow  

NASA Astrophysics Data System (ADS)

Wedge oblique shock wave control by arc discharge plasma in supersonic airflow was investigated theoretically, experimentally, and numerically in this paper. Using thermal choking model, the change in oblique shock wave was deduced, which refer that the start point of shock wave shifts upstream, the shock wave angle decreases, and its intensity weakens. Then the theoretical results were validated experimentally in a Mach 2.2 wind tunnel. On the test conditions of arc discharge power of ~1 kW and arc plasma temperature of ~3000 K, schlieren photography and gas pressure measurements indicated that the start point of shock wave shifted upstream of ~4 mm, the shock wave angle decreased 8.6%, and its intensity weakened 8.8%. The deduced theoretical results match the test results qualitatively, so thermal mechanism and thermal choking model are rational to explain the problem of oblique shock wave control by arc discharge plasma. Finally, numerical simulation was developed. Based on thermal mechanism, the arc discharge plasma was simplified as a thermal source term that added to the Navier-Stokes equations. The simulation results of the change in oblique shock wave were consistent with the test results, so the thermal mechanism indeed dominates the oblique shock wave control process.

Wang, Jian; Li, Yinghong; Xing, Fei

2009-10-01

448

Numerical investigation of wind-induced airflow and interunit dispersion characteristics in multistory residential buildings.  

PubMed

Compared with the buoyancy-dominated upward spread, the interunit dispersion of pollutants in wind-dominated conditions is expected to be more complex and multiple. The aim of this study is to investigate the wind-induced airflow and interunit pollutant dispersion in typical multistory residential buildings using computational fluid dynamics. The mathematical model used is the nonstandard k-? model incorporated with a two-layer near-wall modification, which is validated against experiments of previous investigators. Using tracer gas technique, the reentry of exhaust air from each distinct unit to other units on the same building, under different practical conditions, is quantified, and then, the possible dispersion routes are revealed. The units on the floor immediately below the source on the windward side, and vertically above it on the leeward side, where the reentry ratios are up to 4.8% and 14.9%, respectively, should be included on the high-infection list. It is also found that the presence of balconies results in a more turbulent near-wall flow field, which in turn significantly changes the reentry characteristics. Comparison of the dispersion characteristics of the slab-like building and the more complicated building in cross (#) floorplan concludes that distinctive infectious control measures should be implemented in these two types of buildings. PMID:23495766

Ai, Z T; Mak, C M; Niu, J L

2013-04-18

449

Numerical investigation of airflow inside a 1-in hard disk drive  

NASA Astrophysics Data System (ADS)

The increasing application of the hard disk drive in consumer electronic devices has pushed the usage of the small form factor hard drives. At the same time, the data storage industry continues to enhance the capacity and performance of computer hard disk drive. The concerns of track mis-registration caused by various runout still remain with the form factor change. The objective of the current study is to numerically investigate the airflow characteristic inside a 1 in hard disk drive. The simulation model is constructed based on the currently available 1-in micro-drive in the market, with 3600 rpm disk rotation speed, thus the flow Reynolds number based on the disk tip radius is around 4.8×103. Two models with different actuator arm positions (outside and middle-disk) were studied. The simulation results show that the standard k-epsilon model used allows us to extract similar information and understanding as that from more developed numerical model. Good agreement in normalized velocity magnitude and flow pattern is observed between the numerical and experimental results. At different actuator arm positions, streamlines and velocity vectors plots show the effect of the actuator arm position to the flow pattern, especially around the arm. This arm position also affects the radial and tangential shear stress values over the disk, which may help to estimate the wind loss and power consumption.

Suriadi, M. A.; Tan, C. S.; Zhang, Q. D.; Yip, T. H.; Sundaravadivelu, K.

2006-08-01

450

Incipient air entrainment in a translating axisymmetric plunging laminar jet  

NASA Astrophysics Data System (ADS)

Air entrainment due to a translating axisymmetric laminar water jet plunging into an otherwise quiescent pool of water was studied experimentally. The jet impact diameter, Dj, and velocity, Vj, ranged from 0.33 to 1.21 cm and 104 to 365 cm/s, respectively. For all of these jet flow conditions, the water surface around the jet impact site of the stationary jet is smooth and no air is entrained. When the jet is moving horizontally with velocity Vt, a depression of the free surface forms directly downstream of the jet. In any set of experiments with constant Vj and Dj, as Vt is increased, the depth and streamwise length of this depression increases and a cusp forms at the bottom of its upstream edge. Air entrainment first occurs in the form of discrete small bubbles with diameters of about 0.05 cm that are injected from the cusp when the Froude number (Fr=Vt/gDj, where g is the acceleration of gravity) exceeds a critical value of about 1.4 for Vj/Vt>5. At higher values of Vt, a separate mode of entrainment occurs where large pockets of air are injected from the cusp into the flow in the form of intermittent bursts. At still higher values of Vt, the high-entrainment-rate condition occurs continuously. High-speed flow visualization movies of the entrainment process show that in all entrainment regimes, the bubbles enter the water when vortices from the jet shear layer pass over the leading-edge cusp of the depression and that these bubbles are initially trapped within the vortices. The boundaries between the three entrainment regimes are determined and presented on a plot of Froude number versus velocity ratio (Vj/Vt).

Chirichella, D.; Gomez Ledesma, R.; Kiger, K. T.; Duncan, J. H.

2002-02-01

451

Method and applications of fiber synthesis using laminar flow  

NASA Astrophysics Data System (ADS)

A Laminar Flow Reactor (LFR) using the principles of hydrodynamic focusing was created and used to fabricate functional composite polymer fibers. These fibers had the ability to conduct or serve as a carrier for singlet oxygen-generating molecules. Critical to the process was designing an easy-to-fabricate, inexpensive device and developing a repeatable method that made efficient use of the materials. The initial designs used a planar layout and hydrodynamically focused in only one dimension while later versions switched to a two-fluid concentric design. Modeling was undertaken and verified for the different device layouts. Three types of conductive particles were embedded in the formed polymer: silver, indium tin oxide (ITO) and polyaniline. The polymer was also used as a carrier to two singlet oxygen generating molecules: Methylene Blue (MB) and perylene. Both were effective in killing Bacillus thuringiensis but MB leached from the fiber into the tested cell suspension. Perylene, which is not water soluble, did not leach out and was just as effective as MB. Research that was performed at ITT is also presented. A critical need exists to detect, identify, quantify, locate, and track virus and toxin aerosols to provide early warning during both light and dark conditions. The solution presented is a remote sensing technology using seeding particles. Seeding particles developed during this program provide specific identification of threat cloud content. When introduced to the threat cloud the seeders will bind specifically to the analyte of interest and upon interrogation from a stand off laser source will fluoresce. The fluorescent signal is detected from a distance using a long-range microscope and collection optics that allow detection of low concentrations of threat aerosols.

Burns, Bradley Justin

452

Rich methane premixed laminar flames doped with light unsaturated hydrocarbons  

SciTech Connect

The structure of three laminar premixed rich flames has been investigated: a pure methane flame and two methane flames doped by allene and propyne, respectively. The gases of the three flames contain 20.9% (molar) of methane and 33.4% of oxygen, corresponding to an equivalence ratio of 1.25 for the pure methane flame. In both doped flames, 2.49% of C{sub 3}H{sub 4} was added, corresponding to a ratio C{sub 3}H{sub 4}/CH{sub 4} of 12% and an equivalence ratio of 1.55. The three flames have been stabilized on a burner at a pressure of 6.7 kPa using argon as dilutant, with a gas velocity at the burner of 36 cm/s at 333 K. The concentration profiles of stable species were measured by gas chromatography after sampling with a quartz microprobe. Quantified species included carbon monoxide and dioxide, methane, oxygen, hydrogen, ethane, ethylene, acetylene, propyne, allene, propene, propane, 1,2-butadiene, 1,3-butadiene, 1-butene, isobutene, 1-butyne, vinylacetylene, and benzene. The temperature was measured using a PtRh (6%)-PtRh (30%) thermocouple settled inside the enclosure and ranged from 700 K close to the burner up to 1850 K. In order to model these new results, some improvements have been made to a mechanism previously developed in our laboratory for the reactions of C{sub 3}-C{sub 4} unsaturated hydrocarbons. The main reaction pathways of consumption of allene and propyne and of formation of C{sub 6} aromatic species have been derived from flow rate analyses. (author)

Gueniche, H.A.; Glaude, P.A.; Dayma, G.; Fournet, R.; Battin-Leclerc, F. [Departement de Chimie-Physique des Reactions, Nancy University, CNRS, ENSIC, 1 rue Grandville, BP 20451, 54001 Nancy Cedex (France)

2006-09-15

453

Spraying Powder Materials by the High-Enthalpy Laminar Plasma Flow  

SciTech Connect

One of the most promising engineering solutions of the problem of spraying powder materials is the proposed method of plasma spraying by the laminar plasma jet. Laminar plasma flow is characterized by small jet angle divergence; the powder particles are penetrated and accelerated mainly in the axial direction. The molten powder particles are transported almost to the surface of a treated work-piece inside the laminar plasma flow in an atmosphere of the plasma-forming gas with the acceleration on the entire transfer area, which leads to an increase in the particles velocity, a decrease of their oxidability, an increase in the powder deposition efficiency, density, adhesion strength with the surface to be coated.

Khutsishvili, M.; Kikvadze, L. [Plasma Spray Laboratory, Georgian Technical University, M. Kostava street 77, Tbilisi 0175 (Georgia)

2008-03-19

454

Acoustic effect on stall hysteresis for low Reynolds number laminar flow  

NASA Astrophysics Data System (ADS)

An experimental investigation was conducted in the Virginia Tech Stability Wind Tunnel to determine the effect of sound waves on the separated laminar boundary layer of a wing at low Reynolds numbers. Also studied was the effect of Reynolds number on the stall hysteresis behavior of the airfoil at Reynolds numbers between 100,000 and 300,000. It was found that increasing the Reynolds number changed the location and magnitude of the maximum lift coefficient. The stall hysteresis loop, a phenomenon that occurs only at low Re, in which the alpha at flow separation and that at reattachment are not identical, was also found to change with increasing Reynolds numbers. It was found that sound could be used to excite turbulence in a separated laminar boundary layer and cause flow reattachment via a laminar bubble. The required sound frequency and level were found to vary with Reynolds number and angle of attack.

Schaefer, C. G., Jr.

455

Spraying Powder Materials by the High-Enthalpy Laminar Plasma Flow  

NASA Astrophysics Data System (ADS)

One of the most promising engineering solutions of the problem of spraying powder materials is the proposed method of plasma spraying by the laminar plasma jet. Laminar plasma flow is characterized by small jet angle divergence; the powder particles are penetrated and accelerated mainly in the axial direction. The molten powder particles are transported almost to the surface of a treated work-piece inside the laminar plasma flow in an atmosphere of the plasma-forming gas with the acceleration on the entire transfer area, which leads to an increase in the particles velocity, a decrease of their oxidability, an increase in the powder deposition efficiency, density, adhesion strength with the surface to be coated.

Khutsishvili, M.; Kikvadze, L.

2008-03-01

456

Statistical analysis of the transition to turbulent-laminar banded patterns in plane Couette flow  

NASA Astrophysics Data System (ADS)

The transition between uniform turbulence in plane Couette flow and turbulent-laminar banded patterns is studied using numerical computations. Timeseries of the velocity along a line in the midplane along the pattern wavevector are Fourier transformed. When averaged in time, these spectra show diffuse maxima corresponding to streaks and longitudinal rolls with a wavelength near 4, and a sharper, higher, maximum corresponding to the turbulent-laminar pattern with wavelength 40. Probability distribution functions are computed for the Fourier component corresponding to wavelength 40. It is shown that this PDF is a Gaussian centered at 0 for a a uniform turbulent flow and that this maximum shifts to a finite value when a turbulent-laminar banded pattern appears.

Tuckerman, Laurette S.; Barkley, Dwight; Dauchot, Olivier

2008-11-01

457

Response of cricket and spider motion-sensing hairs to airflow pulsations.  

PubMed

Closed-form analytical solutions are presented for the angular displacement, velocity and acceleration of motion-sensing filiform hairs exposed to airflow pulsations of short time duration. The specific situations of interest correspond to a spider intentionally moving towards a cricket, or an insect unintentionally moving towards or flying past a spider. The trichobothria of the spider Cupiennius salei and the cercal hairs of the cricket Gryllus bimaculatus are explored. Guided by earlier work, the spatial characteristics of the velocity field due to a flow pulsation are approximated by the local incompressible flow field due to a moving sphere. This spatial field is everywhere modulated in time by a Gaussian function represented by the summation of an infinite Fourier series, thus allowing an exploration of the spectral dependence of hair motion. Owing to their smaller total inertia, torsional restoring constant and total damping constant, short hairs are found to be significantly more responsive than long hairs to a flow pulsation. It is also found that the spider trichobothria are underdamped, while the cercal hairs of the cricket are overdamped. As a consequence, the spider hairs are more responsive to sudden air motions. Analysis shows that while two spiders of different characteristic sizes and lunge velocities can generate pulsations with comparable energy content, the associated velocity fields display different patterns of spatial decay with distance from the pulsation source. As a consequence, a small spider lunging at a high velocity generates a smaller telltale far-field velocity signal than a larger spider lunging at a lower velocity. The results obtained are in broad agreement with several of the observations and conclusions derived from combined flow and behavioural experiments performed by Casas et al. for running spiders, and by Dangles et al. for spiders and a physical model of spiders lunging at crickets. PMID:19324674

Kant, R; Humphrey, J A C

2009-02-19

458

Gaseous oxygen uptake in porous media at different moisture contents and airflow velocities.  

PubMed

The presence and distribution of water in the pore space is a critical factor for flow and transport of gases through unsaturated porous media. The water content also affects the biological activity necessary for treatment of polluted gas streams in biofilters. In this research, microbial activity and quantity of inactive volume in a porous medium as a function of moisture content and gas flow rate were investigated. Yard waste compost was used as a test medium, and oxygen uptake rate measurements were used to quantify microbial activity and effective active compost volume using batch and column flow-through systems. Compost water contents were varied from air-dry to field capacity and gas flows ranged from 0.2 to 2 L x min(-1). The results showed that overall microbial activity and the relative fraction of active compost medium volume increased with airflow velocity for all levels of water content up to a certain flow rate above which the oxygen uptake rate assumed a constant value independent of gas flow. The actual value of the maximum oxygen uptake rate was controlled by the water content. The oxygen uptake rate also increased with increasing water content and reached a maximum between 42 and 48% volumetric water content, above which it decreased, again likely because of formation of inactive zones in the compost medium. Overall, maximum possible oxygen uptake rate as a function of gas flow rate across all water contents and gas flows could be approximated by a linear expression. The relative fraction of active volume also increased with gas flow rate and reached approximately 80% for the highest gas flows used. PMID:19603735

Sharma, Prabhakar; Poulsen, Tjalfe G; Kalluri, Prasad N V

2009-06-01

459

Predictors of survival in a group of patients with chronic airflow obstruction.  

PubMed

This article shows the results of a 10-year follow-up study conducted on a cohort of 870 patients affected by severe chronic airflow obstruction (CAO) on spirometric tests. The main aims of the study were to identify those factors associated with reduced survival in CAO patients and to evaluate the effectiveness of a care program on patients' survival. The analysis compared the survival time and causes of death between patients who showed adherence and patients who did not show adherence to the care program. The most important results can be summarized as follows: (1) CAO patients have a high mortality rate for acute respiratory failure, cor-pulmonale, and lung cancer; (2) patient's age at the time of selection to enter follow-up influences the death hazard; (3) patients who need long-term oxygen treatment (LTOT) have a higher death hazard than those who don't need it; (4) the higher is FEV1 or PaO2 value at the time of selection, the lower the death hazard; (5) patients who need, and regularly take, long-term oxygen treatment have a lower death hazard compared to those who need it, but do not take it properly; and (6) patients with a partial reversible airway obstruction (pRAO) who regularly attend the clinic for planned check-ups, have a lower death hazard compared to those who have the same characteristics, but do not show adherence to the care program. These results indicate that an organized program to treat severe CAO patients may improve their survival. PMID:9674661

Piccioni, P; Caria, E; Bignamini, E; Forconi, G; Nebiolo, F; Arossa, W; Bugiani, M

1998-07-01

460

Chronic airflow limitation in a rural Indian population: etiology and relationship to body mass index  

PubMed Central

Purpose Respiratory conditions remain a source of morbidity globally. As such, this study aimed to explore factors associated with the development of airflow obstruction (AFO) in a rural Indian setting and, using spirometry, study whether underweight is linked to AFO. Methods Patients > 35 years old attending a rural clinic in West Bengal, India, took a structured questionnaire, had their body mass index (BMI) measured, and had spirometry performed by an ancillary health care worker. Results In total, 416 patients completed the study; spirometry was acceptable for analysis of forced expiratory volume in 1 second in 286 cases (69%); 16% were noted to exhibit AFO. Factors associated with AFO were: increasing age (95% confidence interval (CI) 0.004–0.011; P = 0.005), smoking history (95% CI 0.07–0.174; P = 0.006), male gender (95% CI 0.19–0.47; P = 0.012), reduced BMI (95% CI 0.19–0.65; P = 0.02), and occupation (95% CI 0.12–0.84; P = 0.08). The mean BMI in males who currently smoked (n = 60; 19.29 kg/m2; standard deviation [SD] 3.46) was significantly lower than in male never smokers (n = 33; 21.15 kg/m2 SD 3.38; P < 0.001). AFO was observed in 27% of subjects with a BMI <18.5 kg/m2, falling to 13% with a BMI ?18.5 kg/m2 (P = 0.013). AFO was observed in 11% of housewives, 22% of farm laborers, and 31% of cotton/jute workers (P = 0.035). Conclusion In a rural Indian setting, AFO was related to advancing age, current or previous smoking, male gender, reduced BMI, and occupation. The data also suggest that being under-weight is linked with AFO and that a mechanistic relationship exists between low body weight, smoking tobacco, and development of AFO.

Chakrabarti, Biswajit; Purkait, Sabita; Gun, Punyabrata; Moore, Vicky C; Choudhuri, Samadrita; Zaman, MJ; Warburton, Christopher J; Calverley, Peter MA; Mukherjee, Rahul

2011-01-01

461

Mass Airflow Cabinet for Control of Airborne Infection of Laboratory Rodents  

PubMed Central

A mass airflow cabinet for handling and housing of laboratory rodents has been developed and tested. The unit consists of a high-efficiency particulate air filter and uniform distribution of air at a vertical velocity of 19 cm per s. Animals are maintained without bedding in mesh-bottomed cages that rest on rollers for rotation inside the cabinet. There is an air barrier of 90 cm per s separating the cabinet air from room air. Sampling for airborne bacteria yielded an average of 0.03 colony-forming units (CFU) per ft3 of air inside the cabinet, whereas 28.8 CFU per ft3 was simultaneously detected outside the cabinet during housekeeping, a reduction of almost three logs. The efficiency of the air barrier was tested by aerosolization of T3 phage. When phage was aerosolized 5 cm outside the cabinet, no phage could be detected 5 cm inside when the fans were operating; with the fans off an average of 1.6 × 104 plaque-forming units (PFU) per ft3 was detected in six tests. Aerosolization of phage inside the cabinet yielded an average of 9 × 10 PFU per ft3 outside; an average of 4.1 × 106 PFU per ft3 were detected with the fans not in operation, a reduction of more than four logs. In-use studies on effectiveness showed that the cabinet significantly reduced the incidence of mice originally titer-free to Reo-3 virus. Hemagglutination inhibition antibodies to Reo-3 were detected in 9/22 (42%) mice housed in a conventionally ventilated animal laboratory while no seroconversion was detected in any of 22 mice housed in the mass air flow cabinet in the same laboratory. Images

McGarrity, Gerard J.; Coriell, Lewis L.

1973-01-01

462

Airflow and nanoparticle deposition in rat nose under various breathing and sniffing conditions  

PubMed Central

Accurate prediction of nanoparticle (1~100 nm) deposition in the rat nasal cavity is important for assessing the toxicological impact of inhaled nanoparticles as well as for potential therapeutic applications. A quasi-steady assumption has been widely adopted in the past investigations on this topic, yet the validity of such simplification under various breathing and sniffing conditions has not been carefully examined. In this study, both steady and unsteady computational fluid dynamics (CFD) simulations were conducted in a published rat nasal model under various physiologically realistic breathing and sniffing flow rates. The transient airflow structures, nanoparticle transport and deposition patterns in the whole nasal cavity and the olfactory region were investigated and compared with steady state simulation of equivalent flow rate. The results showed that (1) the quasi-steady flow assumption for cyclic flow was valid for over 70% of the cycle period during all simulated breathing and sniffing conditions in the rat nasal cavity, or the unsteady effect was only significant during the transition between the respiratory phases; (2) yet the quasi-steady assumption for nanoparticle transport was not valid, except in the vicinity of peak respiration. In general, the total deposition efficiency of nanoparticle during cyclic breathing would be lower than that of steady state due to the unsteady effect on particle transport and deposition, and further decreased with the increase of particle size, sniffing frequency, and flow rate. In the contrary, previous study indicated that for micro-scale particles (0.5~4?m), the unsteady effect would increase deposition efficiencies in rat nasal cavity. Combined, these results suggest that the quasi-steady assumption of nasal particle transport during cycling breathing should be used with caution for an accurate assessment of the toxicological and therapeutic impact of particle inhalation. Empirical equations and effective steady state approximation derived in this study are thus valuable to estimate such unsteady effects in future applications.

Jiang, Jianbo; Zhao, Kai

2010-01-01

463

Type I planet migration in weakly magnetized laminar discs  

NASA Astrophysics Data System (ADS)

The migration of low-mass planets, or type I planetary migration, has been studied in hydrodynamical disc models for more than three decades. For a long time, it was thought to be very rapid and directed inwards due to Lindblad torques. More recently, it has been shown that the corotation torque, linked to the horseshoe motion of the gas near the planet, may slow down or even reverse migration. How is this picture modified by the expected presence of a magnetic field in the protoplanetary disc? When the magnetic field is strong enough to prevent horseshoe motion, the corotation torque is replaced by a torque arising from magnetic resonances which may significantly alter the migration rate. In the case of a weaker magnetic field, the magnetic field is not strong enough to prevent horseshoe motion and a corotation torque then exists. In this regime, recent turbulent magnetohydrodynamical (MHD) simulations have reported the existence of an additional component of the corotation torque due to the presence of the magnetic field. The aim of this paper is to investigate the physical origin and the properties of this additional corotation torque. We performed MHD simulations of a low-mass planet embedded in a 2D laminar disc threaded by a weak toroidal magnetic field, where the effects of turbulence are modelled by a viscosity and a resistivity. We confirm that the interaction between the magnetic field and the horseshoe motion of the gas results in an additional corotation torque on the planet, which we dub the MHD torque excess. We demonstrate that it is caused by the accumulation of the magnetic field along the downstream separatrices of the horseshoe region, which gives rise to an azimuthally asymmetric underdense region at that location. The properties of the MHD torque excess are characterized by varying the slope of the density, temperature and magnetic field profiles, as well as the diffusion coefficients and the strength of the magnetic field. The sign of the torque excess and its radial distribution are found to be in agreement with the earlier full magnetorotational instability simulations. This sign depends on the density and temperature gradients only and is positive for profiles expected in protoplanetary discs. The magnitude of the torque excess is in turn mainly determined by the strength of the magnetic field and the turbulent resistivity. It can be strong enough to reverse migration even when the magnetic pressure is less than 1 per cent of the thermal pressure. The MHD torque excess can therefore lead to outward planetary migration in the radiatively efficient outer parts of protoplanetary discs, where the hydrodynamical corotation torque is too weak to prevent fast inward migration.

Guilet, Jérôme; Baruteau, Clément; Papaloizou, John C. B.

2013-04-01

464

Numerical investigation of the tone noise mechanism over laminar airfoils  

NASA Astrophysics Data System (ADS)

This paper presents the first numerical investigation via direct numerical simulation of the tone noise phenomenon occurring in the flow past laminar airfoils. This phenomenon corresponds to the radiation of discrete acoustic tones in some specific flow conditions, and has received much attention since the 1970s, and several experimental studies have been carried out to identify and understand the underlying physical mechanisms. However, several points remain to be clarified in order to provide a complete explanation of its origin. The flow around a two-dimensional NACA0012 airfoil is considered in order to have a deeper understanding of the tone noise phenomenon. Consistently with previous experimental studies, it is shown that depending on the Reynolds number and angle of attack, two different types of acoustic spectrum are observed: one which exhibits a broadband contribution with a dominant frequency together with a sequence of regularly spaced discrete frequencies, while the other one is only characterized by a simple broadband contribution. The first configuration is typical of the tone noise phenomenon. The present work shows that in this case, the mean flow on the pressure side of the airfoil exhibits a separation bubble near the trailing edge and the main tone frequency is close to the most amplified frequency of the boundary layer. The mechanism proposed in previous works for the main tone generation is therefore validated by numerical simulation. On the other hand, the analysis of the suction side boundary layer reveals that there is no separation and that the most amplified frequency is different from the main tonal one. However, the suction side boundary layer is highly receptive to the tone frequency. Finally, an original explanation for the existence of the secondary discrete frequencies observed in the radiated pressure spectrum is given. They are associated to a bifurcation of the airfoil wake from a symmetric to a non-symmetric vortex pattern. A possible explanation for the existence of this bifurcation is the interaction between the disturbances which are the most amplified by the suction side boundary layer and those originating in the forcing of the suction side flow by the main tone noise mechanism.

Desquesnes, G.; Terracol, M.; Sagaut, P.

465

Eddy genesis and manipulation in plane laminar shear flow  

NASA Astrophysics Data System (ADS)

Eddy formation and presence in a plane laminar shear flow configuration consisting of two infinitely long plates orientated parallel to each other is investigated theoretically. The upper plate, which is planar, drives the flow; the lower one has a sinusoidal profile and is fixed. The governing equations are solved via a full finite element formulation for the general case and semianalytically at the Stokes flow limit. The effects of varying geometry (involving changes in the mean plate separation or the amplitude and wavelength of the lower plate) and inertia are explored separately. For Stokes flow and varying geometry, excellent agreement between the two methods of solution is found. Of particular interest with regard to the flow structure is the importance of the clearance that exists between the upper plate and the tops of the corrugations forming the lower one. When the clearance is large, an eddy is only present at sufficiently large amplitudes or small wavelengths. However, as the plate clearance is reduced, a critical value is found, which triggers the formation of an eddy in an otherwise fully attached flow for any finite amplitude and arbitrarily large wavelength. This is a precursor to the primary eddy to be expected in the lid-driven cavity flow, which is formed in the limit of zero clearance between the plates. The influence of the flow driving mechanism is assessed by comparison with corresponding solutions for the case of gravity-driven fluid films flowing over an undulating substrate. When inertia is present, the flow generally becomes asymmetrical. However, it is found that for large mean plate separations the flow local to the lower plate becomes effectively decoupled from the inertia dominated overlying flow if the wavelength of the lower plate is sufficiently small. In such cases the local flow retains its symmetry. A local Reynolds number based on the wavelength is shown to be useful in characterizing these large-gap flows. As the mean plate separation is reduced, the form of the asymmetry caused by inertia changes and becomes strongly dependent on the plate separation. For lower plate wavelengths which do not exhibit a kinematically induced secondary eddy, an inertially induced secondary eddy can be created if the mean plate separation is sufficiently small and the global Reynolds number is sufficiently large.

Scholle, M.; Haas, A.; Aksel, N.; Wilson, M. C. T.; Thompson, H. M.; Gaskell, P. H.

2009-07-01

466

History of Suction-Type Laminar-Flow Control with Emphasis on Flight Resrearch. Monographs in Aerospace History Number 13.  

National Technical Information Service (NTIS)

Table of Contents: Foreword; Preface; Laminar-Flow Control Concepts and Scope of Monograph; Early Research on Suction-Type Laminar-Flow Control (Research from the 1930s through the War Years; Research from after World War II to the Mid-1960s); Post X-21 R...

A. L. Braslow

1999-01-01

467

Flight Test Measurement Techniques for Laminar Flow. Volume 23(Les techniques de mesure en vol des ecoulements laminaires).  

National Technical Information Service (NTIS)

The advantages of laminar flow technology have been well known for decades. Experiments in Germany, the United Kingdom, and the United States date back to the 1930's. One application of some of the early research was the use of a laminar flow airfoil on t...

D. Fisher K. H. Horstmann H. Riedel

2003-01-01

468

Incompressible boundary layer transition flight experiments over a nonaxisymmetric fuselage forebody and comparisons with laminar boundary layer stability theory  

Microsoft Academic Search

Analyses of previous boundary-layer transition experiments over axisymmetric bodies indicates a potential for achieving substantial amounts of laminar flow over such shapes. Achievement of natural laminar flow over portions of nonlifting aircraft geometries, such as fuselage to forebodies, tip tanks or engine nacelles, could significantly contribute to the reduction of total aircraft viscous drag. A modern surface-panel method, a streamwise

Paul M. H. W. Vijgen

1990-01-01

469

Calculation of heat transfer in pipes to gases with variable properties with allowance for the laminar transition of flow  

Microsoft Academic Search

Based on experimental data in the literature, an engineering method for calculating heat transfer in pipes during the heating of turbulent flows of gases with variable properties is developed which allows for the laminar transition of the flow in the region of high thermal loads and moderate and low inlet Reynolds numbers. The effect of the laminar transition is treated

V. A. Kurganov

1987-01-01

470

Computation of unsteady laminar boundary layers subject to traveling-wave freestream fluctuations  

NASA Astrophysics Data System (ADS)

Simple modifications to the boundary conditions for an unsteady boundary-layer calculation method developed by Cebeci and Carr (1978) are developed to accomodate both standing-wave and traveling-wave free stream fluctuations. Calculations using the modified procedure are presented for both types of fluctuations. The calculations are conducted for a laminar boundary layer developing on a flat plate in air. Comparisons are made with available experimental and analytical results. It is found that, depending on whether the free stream perturbations consist of a standing wave or traveling waves, unsteady laminar boundary layers exhibit quite different behavior.

Evans, R. L.

1989-11-01

471

Effect of laminar velocity profile variation on mixing in microfluidic devices: The sigma micromixer  

NASA Astrophysics Data System (ADS)

The effect of the laminar velocity profile and its variation on mixing phenomena at the reduced scale is studied. It is shown that the diffusive mass flux between two miscible streams, flowing laminar in a microchannel, is enhanced if the velocity at their diffusion interface is increased. Based on this idea, an in-plane passive micromixing concept is proposed and implemented in a working device (sigma micromixer). This mixer shows considerable mixing performance by periodically varying the flow velocity profile, such that the maximum of the profile coincides with the transversely progressing diffusion fronts repeatedly throughout the mixing channel.

Yakhshi Tafti, Ehsan; Kumar, Ranganathan; Cho, Hyoung J.

2008-10-01

472

A modeling study of the effect of gravity on airflow distribution and particle deposition in the lung.  

PubMed

Inhalation of particles generated as a result of thermal degradation from fire or smoke, as may occur on spacecraft, is of major health concern to space-faring countries. Knowledge of lung airflow and particle transport under different gravity environments is required to addresses this concern by providing information on particle deposition. Gravity affects deposition of particles in the lung in two ways. First, the airflow distribution among airways is changed in different gravity environments. Second, particle losses by sedimentation are enhanced with increasing gravity. In this study, a model of airflow distribution in the lung that accounts for the influence of gravity was used for a mathematical description of particle deposition in the human lung to calculate lobar, regional, and local deposition of particles in different gravity environments. The lung geometry used in the mathematical model contained five lobes that allowed the assessment of lobar ventilation distribution and variation of particle deposition. At zero gravity, it was predicted that all lobes of the lung expanded and contracted uniformly, independent of body position. Increased gravity in the upright position increased the expansion of the upper lobes and decreased expansion of the lower lobes. Despite a slight increase in predicted deposition of ultrafine particles in the upper lobes with decreasing gravity, deposition of ultrafine particles was generally predicted to be unaffected by gravity. Increased gravity increased predicted deposition of fine and coarse particles in the tracheobronchial region, but that led to a reduction or even elimination of deposition in the alveolar region for coarse particles. The results from this study show that existing mathematical models of particle deposition at 1 G can be extended to different gravity environments by simply correcting for a gravity constant. Controlled studies in astronauts on future space missions are needed to validate these predictions. PMID:16603478

Asgharian, Bahman; Price, Owen; Oberdörster, Gunter

2006-06-01

473

Nonlinear Formulation of the Bulk Surface Stress over Breaking Waves: Feedback Mechanisms from Air-flow Separation  

NASA Astrophysics Data System (ADS)

Historically, our understanding of the air-sea surface stress has been derived from engineering studies of turbulent flows over flat solid surfaces, and more recently, over rigid complex geometries. Over the ocean however, the presence of a free, deformable, moving surface gives rise to a more complicated drag formulation. In fact, within the constant-stress turbulent atmospheric boundary layer over the ocean, the total air-sea stress not only includes the traditional turbulent and viscous components but also incorporates surface-wave effects such as wave growth or decay, air-flow separation, and surface separation in the form of sea-spray droplets. Because each individual stress component depends on and alters the sea state, a simple linear addition of all stress components is too simplistic. In this paper we present a model of the air-sea surface stress that incorporates air-flow separat