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1

F-16XL Ship #1 in flight - used for laminar airflow studies  

NASA Technical Reports Server (NTRS)

One of two F-16XL prototype aircraft, on loan from the Air Force, was used by NASA's Dryden Flight Research Center, Edwards, California, in a program to investigate laminar flow technology and help improve the flow of air over an aircraft's wing at sustained supersonic speeds. A small, perforated titanium wing glove with a turbo compressor was tested on the F-16XL to determine if air suction can remove a small part of the boundary-layer air flowing over the wing and thereby achieve laminar (smooth) flow over a portion of the wing. The flight research program on ship #1 ended in 1996. It was then conducted with NASA's two-seat F-16XL, ship #2 employing a larger glove.

1992-01-01

2

A mobile laminar airflow unit to reduce air bacterial contamination at surgical area in a conventionally ventilated operating theatre.  

PubMed

The aim of this study was to evaluate the efficacy of a mobile laminar airflow (LAF) unit in reducing bacterial contamination at the surgical area in an operating theatre supplied with turbulent air ventilation. Bacterial sedimentation was evaluated during 76 clean urological laparotomies; in 34 of these, a mobile LAF unit was added. During each operation, settle plates were placed at four points in the operating theatre (one at the patient area and three at the perimeter), a nitrocellulose membrane was placed on the instrument table and an additional membrane near the wound. During four operations, particle counting was performed to detect particles > or =0.5 microm. Mean bacterial sedimentation on the nitrocellulose membrane on the instrument table was 2730 cfu/m(2)/h under standard ventilation conditions, whereas it decreased significantly to a mean of 305 cfu/m(2)/h when the LAF unit was used, i.e. within the suggested limit for ultraclean operating theatres (P=0.0001). The membrane near the wound showed a bacterial sedimentation of 4031 cfu/m(2)/h without the LAF unit and 1608 cfu/m(2)/h with the unit (P=0.0001). Particle counts also showed a reduction when the LAF unit was used. No significant difference was found at the four points in the operating theatre between samplings performed with, and without, the LAF unit. Use of a mobile LAF unit with turbulent air ventilation can reduce bacterial contamination at the surgical area in high-risk operations (e.g. prosthesis implant). PMID:17669550

Pasquarella, C; Sansebastiano, G E; Ferretti, S; Saccani, E; Fanti, M; Moscato, U; Giannetti, G; Fornia, S; Cortellini, P; Vitali, P; Signorelli, C

2007-08-01

3

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

4

Does a mobile laminar airflow screen reduce bacterial contamination in the operating room? A numerical study using computational fluid dynamics technique  

PubMed Central

Background Air-borne bacteria in the operating room (OR) may contaminate the surgical wound, either by direct sedimentation from the air or indirectly, by contaminated sterile instruments. Reduced air contamination can be achieved with an efficient ventilation system. The current study assesses the additive effect of a mobile laminar airflow (MLAF) unit on the microbiological air quality in an OR supplied with turbulent-mixing air ventilation. Methods A recently designed OR in NKS (Nya Karolinska Sjukhuset, Stockholm, Sweden) was the physical model for this study. Simulation was made with MLAF units adjacent to the operating table and the instrument tables, in addition to conventional turbulent-mixing ventilation. The evaluation used numerical calculation by computational fluid dynamics (CFD). Sedimentation rates (CFU/m2/h) were calculated above the operating table and two instrument tables, and in the periphery of the OR. Bacterial air contamination (CFU/m3) was simulated above the surgical and instrument tables with and without the MLAF unit. Results The counts of airborne and sedimenting, bacteria-carrying particles downstream of the surgical team were reduced to an acceptable level for orthopedic/implant surgery when the MLAF units were added to conventional OR ventilation. No significant differences in mean sedimentation rates were found in the periphery of the OR. Conclusions The MLAF screen unit can be a suitable option when the main OR ventilation system is unable to reduce the level of microbial contamination to an acceptable level for orthopedic implant surgery. However, MLAF effect is limited to an area within 1 m from the screen. Increasing air velocity from the MLAF above 0.4 m/s does not increase the impact area.

2014-01-01

5

Timeline analysis program (TLA-1), appendices  

NASA Technical Reports Server (NTRS)

Appendices for the Timeline Analysis Program (TLA-1) were given. The appendices contain the Atlanta terminal area scenarios, the task catalog and the control and display configurations for the forward and aft flight decks of the NASA 515 aircraft, and the event/procedure, phase, mission, and subsystem catalogs.

Miller, K. H.

1976-01-01

6

Laminar flow control laminarization  

NASA Technical Reports Server (NTRS)

A practical aerodynamically and structurally reasonably efficient laminar flow control (LFC) suction method, removing the slowest boundary layer particles through many closed spaced fine slots, was developed and subsequently applied to a second F94 LFC wing glove in flight: 100 percent laminar flow was observed up to the F94 test limit. Laminar flow on LFC wings in flight is thus possible at a much higher Reynold's number than even in the best low turbulence tunnels as a result of the negligible influence of the atmospheric microscale turbulence on transition. The F94 LFC glove comparison experiments, with suction starting at 0.03c and 0.4c, verified the theoretically predicted boundary layer stabilization by suction starting at 0.08c, thus maintaining laminar flow at substantially higher C sub L numbers as compared to boundary layer stabilization by flow acceleration; i.e., geometry alone without suction upstream of 0.4c.

Pfeminger, W.

1977-01-01

7

Surgical area contamination – comparable bacterial counts using disposable head and mask and helmet aspirator system, but dramatic increase upon omission of head-gear: an experimental study in horizontal laminar air-flow  

Microsoft Academic Search

The effect of different head coverings on air-borne transmission of bacteria and particles in the surgical area was studied during 30 strictly standardized sham operations performed in a horizontal laminar air flow (LAF) unit. The operating team members wore disposable gowns plus either a non-sterile head covering consisting of a squire type disposable hood and triple laminar face mask, a

B. Friberg; S. Friberg; R. Östensson; L. G. Burman

2001-01-01

8

F-16XL Supersonic Laminar Flow Test Flight  

NASA Video Gallery

An F-16XL aircraft was used by the Dryden Flight Research Center, Edwards, California, in a NASA-wide program to improve laminar airflow on aircraft flying at sustained supersonic speeds. It was th...

9

Numerical study of variations of airflow induced by a moving automatic guided vehicle in a cleanroom  

Microsoft Academic Search

The variations of airflow induced by a moving automatic guided vehicle (AGV) in a vertical laminar flow cleanroom are studied numerically. From a viewpoint of fluid mechanics, the characteristic of the variations of the airflow induced by a moving object is dynamic and is classified as a moving boundary problem. A Galerkin finite element formulation with an arbitrary Lagrangian?Eulerian (ALE)

2002-01-01

10

Portable Airflow Meter  

NASA Technical Reports Server (NTRS)

Compact hand-held instrument measures airflow. Consists of hot-wire anemometer probe in flow-straightening tube that reduces swirling. Configuration developed empirically to reduce length of instrument to practical dimension for use and storage in confined space. Two versions of new straightener only 17 and 18 in. long. Weighs less than 8 lb. and readily stored on Space Shuttle, developed to measure airflow in waster-collection system during flight. Used on Earth to measure airflow in ventilation systems, vacuum cleaners, and the like.

Burgett, Frank A.; Hardwick, Donald R.; Porter, Johnny L.

1988-01-01

11

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

12

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

13

Embryonal Carcinoma Cells Express Qa and Tla Class I Genes of the Major Histocompatibility Complex  

Microsoft Academic Search

The murine major histocompatibility complex encodes H-2K and H-2D transplantation antigens and other class I-like proteins called Qa and Tla molecules; the functions of the Qa\\/Tla molecules are not known. That they may participate in embryonic cell--cell interactions and\\/or play a role in immune responses against tumors has been speculated. We have studied two murine embryonal carcinoma tumors, 402AX and

Suzanne Ostrand-Rosenberg; Deborah A. Nickerson; Virginia K. Clements; Elizabeth P. Garcia; Esi Lamouse-Smith; Leroy Hood; Iwona Stroynowski

1989-01-01

14

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

15

Laminar Air Purge of Microorganisms in Dental Aerosols: Prophylactic Procedures with the Ultrasonic Scaler  

Microsoft Academic Search

Studies of 50 patients undergoing prophylaxis in a dental operatory equipped with laminar airflow showed that from more than 40,400 viable particles containing one or more microbes collected from dental aerosols, about 40,267 were recovered when laminar air was not in use. Airborne contamination reductions of 99.7% were effected in the dental office when a vertical downflow of laminar, high

George H. Williams; Nicholas L. Pollok; Donald E. Shay; Charles E. Barr

1970-01-01

16

Accuracy evaluation of a numerical simulation model of nasal airflow.  

PubMed

Abstract Conclusion: Our numerical simulation model provides an accurate reflection of nasal airflow, and the results were validated by clinical measurements. Objectives: To evaluate the accuracy of a numerical simulation model of nasal airflow. Methods: Ten volunteers with normal nasal cavities underwent CT, acoustic rhinometry, and rhinomanometry. CT data were uploaded into Mimics, ICEM-CFD, Fluent, and CFD-Post software for three-dimensional modeling, finite element grid division, transient calculations, and analysis, respectively. Velocity and pressure data of airflow were obtained during the normal respiratory cycle. The accuracy of the simulation was evaluated by two methods: acoustic rhinometry measurements were used to evaluate the accuracy of the anatomic model, and rhinomanometry measurements were used to evaluate the accuracy of the nasal resistance values obtained by numerical simulation. Results: There were no significant differences between the values describing the model and the acoustic rhinometry measurements, the nasal resistance values obtained by numerical simulation. The airflow through the nasal cavity was mainly laminar. The maximum velocities were measured at the nasal valve, the amplitudes of all velocity curves at locations beyond the nasal valve were reduced. The amplitudes of the pressure curves increased from the front to the back of the airway. PMID:24702230

Lu, Jiuxing; Han, Demin; Zhang, Luo

2014-05-01

17

Laminar Flow Aircraft Certification  

NASA Technical Reports Server (NTRS)

Various topics telative to laminar flow aircraft certification are discussed. Boundary layer stability, flaps for laminar flow airfoils, computational wing design studies, manufacturing requirements, windtunnel tests, and flow visualization are among the topics covered.

Williams, Louis J. (compiler)

1986-01-01

18

Modulation of the light-harvesting chlorophyll antenna size in Chlamydomonas reinhardtii by TLA1 gene over-expression and RNA interference  

PubMed Central

Truncated light-harvesting antenna 1 (TLA1) is a nuclear gene proposed to regulate the chlorophyll (Chl) antenna size in Chlamydomonas reinhardtii. The Chl antenna size of the photosystems and the chloroplast ultrastructure were manipulated upon TLA1 gene over-expression and RNAi downregulation. The TLA1 over-expressing lines possessed a larger chlorophyll antenna size for both photosystems and contained greater levels of Chl b per cell relative to the wild type. Conversely, TLA1 RNAi transformants had a smaller Chl antenna size for both photosystems and lower levels of Chl b per cell. Western blot analyses of the TLA1 over-expressing and RNAi transformants showed that modulation of TLA1 gene expression was paralleled by modulation in the expression of light-harvesting protein, reaction centre D1 and D2, and VIPP1 genes. Transmission electron microscopy showed that modulation of TLA1 gene expression impacts the organization of thylakoid membranes in the chloroplast. Over-expressing lines showed well-defined grana, whereas RNAi transformants possessed loosely held together and more stroma-exposed thylakoids. Cell fractionation suggested localization of the TLA1 protein in the inner chloroplast envelope and potentially in association with nascent thylakoid membranes, indicating a role in Chl antenna assembly and thylakoid membrane biogenesis. The results provide a mechanistic understanding of the Chl antenna size regulation by the TLA1 gene.

Mitra, Mautusi; Kirst, Henning; Dewez, David; Melis, Anastasios

2012-01-01

19

Laminar Soot Processes  

NASA Technical Reports Server (NTRS)

Soot processes within hydrocarbon-fueled flames affect particle emissions from combustion processes, thermal loads of combustor components, hazards of unwanted fires, and capabilities for computational combustion. Thus, soot processes within laminar nonpremixed (diffusion) and premixed flames are being studied, using both space-based (flight) experiments at MicroGravity (MG) and supporting ground-based experiments at Normal Gravity (NG). The study is limited to laminar flames due to their experimental and computational tractability, noting the relevance of these results to practical turbulent flames based on laminar flamelet concepts. Unfortunately, buoyancy affects soot processes in laminar diffusion flames while effects of buoyancy are small for most practical flames; therefore, present observations of laminar diffusion flames involve either particular flame conditions where effects of buoyancy are small during ground-based experiments at ng or truly nonbuoyant flames during planned flight experiments at mg. Laminar premixed flames are also being considered during ground-based experiments at ng because soot processes are easier to interpret and less affected by buoyancy in laminar premixed flames than in laminar diffusion flames.

Xu, F.; Sunderland, P. B.; Lin, K.-C.; Faeth, G. M.

1997-01-01

20

Surface laminar circuit packaging  

Microsoft Academic Search

Discusses the SLC (surface laminar circuit), a component carrier technology which satisfies various requirements for packaging of small computers through its surface laminar structure, which is similar to semiconductor wiring. By utilizing photo via holes instead of plated through holes for signal line connection, SLC has a high wiring density which allows it to carry bare chips directly attached on

Yutaka Tsukada; Syuhei Tsuchida; Yohko Mashimoto

1992-01-01

21

Visual Exploration of Nasal Airflow  

Microsoft Academic Search

Rhinologists are often faced with the challenge of assessing nasal breathing from a functional point of view to derive effective therapeutic interventions. While the complex nasal anatomy can be revealed by visual inspection and medical imaging, only vague information is available regarding the nasal airflow itself: Rhinomanometry delivers rather unspecific integral information on the pressure gradient as well as on

Stefan Zachow; Philipp Muigg; Thomas Hildebrandt; Helmut Doleisch; Hans-christian Hege

2009-01-01

22

Laminar soot processes  

NASA Technical Reports Server (NTRS)

Soot processes within hydrocarbon fueled flames are important because they affect the durability and performance of propulsion systems, the hazards of unwanted fires, the pollutant and particulate emissions from combustion processes, and the potential for developing computational combustion. Motivated by these observations, the present investigation is studying soot processes in laminar diffusion and premixed flames in order to better understand the soot and thermal radiation emissions of luminous flames. Laminar flames are being studied due to their experimental and computational tractability, noting the relevance of such results to practical turbulent flames through the laminar flamelet concept. Weakly-buoyant and nonbuoyant laminar diffusion flames are being considered because buoyancy affects soot processes in flames while most practical flames involve negligible effects of buoyancy. Thus, low-pressure weakly-buoyant flames are being observed during ground-based experiments while near atmospheric pressure nonbuoyant flames will be observed during space flight experiments at microgravity. Finally, premixed laminar flames also are being considered in order to observe some aspects of soot formation for simpler flame conditions than diffusion flames. The main emphasis of current work has been on measurements of soot nucleation and growth in laminar diffusion and premixed flames.

Sunderland, P. B.; Lin, K.-C.; Faeth, G. M.

1995-01-01

23

Power requirement of rotating rods in airflow  

NASA Technical Reports Server (NTRS)

Experiments were performed to determine the power required for rotating a rotor disc fitted with a number of radially arranged rods placed into a ducted airflow. An array of stationary rods, also radially arranged, were placed upstream close to the rotor with a small gap between the rods to cause wake interference. The results show that power increased with increasing airflow and the rate of increase varied considerably. At lower values of airflow the rate of increase was larger than at higher airflow and definite power peaks occurred at certain airflow rates, where the power attained a maximum within the test airflow range. During the test a maximum blade passage frequency of 2037 Hz was attained.

Barna, P. S.; Crossman, G. R.

1974-01-01

24

Visualizing full-scale ventilation airflows  

SciTech Connect

The patterns of airflow are central to almost everything associated with HVAC. However, since these patterns are normally invisible, it is difficult to know how the airflow is behaving and the possibility of error is significant. In many studies no attempt is made to visualize the airflow, and only conceptual sketches are drawn of how one thinks it behaves. This is partly due to the traditional difficulty of clearly visualizing air currents.

Settles, G.S. [Pennsylvania State Univ., University Park, PA (United States). Dept. of Mechanical Engineering

1997-07-01

25

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

2012-02-01

26

Airflow Characteristics in a Baboon Nasal Passage Cast.  

National Technical Information Service (NTIS)

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 man and experimental animals. Airflow characteri...

A. L. Patra A. Gooya K. T. Morgan

1986-01-01

27

Supersonic laminar flow control research  

NASA Technical Reports Server (NTRS)

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 distributed heating and cooling on active control will be studied. The primary tasks of the research applying to the NASA/Ames Proof of Concept (POC) Supersonic Wind Tunnel and Laminar Flow Supersonic Wind Tunnel (LFSWT) nozzle design with laminar flow control are as follows: (1) predictions of supersonic laminar boundary layer stability and transition, (2) effects of wall heating and cooling for supersonic laminar flow control, and (3) performance evaluation of POC and LFSWT nozzles design with wall heating and cooling effects applying at different locations and various length.

Lo, Ching F.

1994-01-01

28

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

29

Laminar Soot Processes (LSP)  

NASA Technical Reports Server (NTRS)

This is the final report of a research program considering the structure and the soot surface reaction properties of laminar nonpremixed (diffusion) flames. The study was limited to ground-based measurements of buoyant laminar jet diffusion flames at pressures of 0.1-1.0 atm. The motivation for the research is that soot formation in flames is a major unresolved problem of combustion science that influences the pollutant emissions, durability and performance of power and propulsion systems, as well as the potential for developing computational combustion. The investigation was divided into two phases considering the structure of laminar soot-containing diffusion flames and the soot surface reaction properties (soot surface growth and oxidation) of these flames, in turn. The first phase of the research addressed flame and soot structure properties of buoyant laminar jet diffusion flames at various pressures. The measurements showed that H, OH and O radical concentrations were generally in superequilibrium concentrations at atmospheric pressure but tended toward subequilibrium concentrations as pressures decreased. The measurements indicated that the original fuel decomposed into more robust compounds at elevated temperatures, such as acetylene (unless the original fuel was acetylene) and H, which are the major reactants for soot surface growth, and that the main effect of the parent fuel on soot surface growth involved its yield of acetylene and H for present test conditions. The second phase of the research addressed soot surface reaction properties, e.g., soot surface growth and surface oxidation. It was found that soot surface growth rates in both laminar premixed and diffusion flames were in good agreement, that these rates were relatively independent of fuel type, and that these rates could be correlated by the Hydrogen-Abstraction/Carbon-Addition (HACA) mechanisms of Colket and Hall (1994), Frenklach et al. (1990,1994), and Kazakov et al. (1995). It was also found that soot surface oxidation rates were relatively independent of fuel type, were not correlated with O2, CO2, H2O and O collision rates but were correlated with the collision rates of OH with a collision efficiency of 0.14, in agreement with the early measurements in premixed flames of Neoh et al. (1980), after allowing for oxidation by O2 via the classical rate expression of Nagle and Strickland-Constable (1962).

Dai, Z.; El-Leathy, A. M.; Kim, C. H.; Krishnan, S. S.; Lin, K.-C.; Xu, F.; Faeth, G. M.

2002-01-01

30

Truncated photosystem chlorophyll antenna size in the green microalga Chlamydomonas reinhardtii upon deletion of the TLA3-CpSRP43 gene.  

PubMed

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. PMID:23043081

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

2012-12-01

31

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

32

Laminar Soot Processes  

NASA Technical Reports Server (NTRS)

Interior of the Equipment Module for the Laminar Soot Processes (LSP-2) experiment that fly in the STS-107 Research 1 mission in 2002 (LSP-1 flew on Microgravity Sciences Lab-1 mission in 1997). The principal investigator is Dr. Gerard Faeth of the University of Michigan. LSP uses a small jet burner (yellow ellipse), similar to a classroom butane lighter, that produces flames up to 60 mm (2.3 in) long. Measurements include color TV cameras and a radiometer or heat sensor (blue circle), and laser images whose darkness indicates the quantity of soot produced in the flame. Glenn Research in Cleveland, OH, manages the project.

2001-01-01

33

Structure of laminar sooting inverse diffusion flames  

SciTech Connect

The flame structure of laminar inverse diffusion flames (IDFs) was studied to gain insight into soot formation and growth in underventilated combustion. Both ethylene-air and methane-air IDFs were examined, fuel flow rates were kept constant for all flames of each fuel type, and airflow rates were varied to observe the effect on flame structure and soot formation. Planar laser-induced fluorescence of hydroxyl radicals (OH PLIF) and polycyclic aromatic hydrocarbons (PAH PLIF), planar laser-induced incandescence of soot (soot PLII), and thermocouple-determined gas temperatures were used to draw conclusions about flame structure and soot formation. Flickering, caused by buoyancy-induced vortices, was evident above and outside the flames. The distances between the OH, PAH, and soot zones were similar in IDFs and normal diffusion flames (NDFs), but the locations of those zones were inverted in IDFs relative to NDFs. Peak OH PLIF coincided with peak temperature and marked the flame front. Soot appeared outside the flame front, corresponding to temperatures around the minimum soot formation temperature of 1300 K. PAHs appeared outside the soot layer, with characteristic temperature depending on the wavelength detection band. PAHs and soot began to appear at a constant axial position for each fuel, independent of the rate of air flow. PAH formation either preceded or coincided with soot formation, indicating that PAHs are important components in soot formation. Soot growth continued for some time downstream of the flame, at temperatures below the inception temperature, probably through reaction with PAHs. (author)

Mikofski, Mark A.; Fernandez-Pello, A. Carlos [Microgravity Combustion Laboratory, University of California Berkeley, Berkeley, CA 94720 (United States); Williams, Timothy C.; Shaddix, Christopher R.; Blevins, Linda G. [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550 (United States)

2007-06-15

34

An electromagnetic energy scavenger from direct airflow  

NASA Astrophysics Data System (ADS)

This paper presents two types of electromagnetic power generators exploiting direct conversion of airflow into mechanical vibration: (1) a windbelt-based vibratory linear energy scavenger targeting strong airflows and (2) a Helmholtz-resonator-based generator capable of scavenging energy from weaker airflows, i.e. environmental airflows. Both devices consist of two tightly coupled parts: a mechanical resonator, which produces high-frequency mechanical oscillation from quasi-constant airflow, and a permanent magnet/coil system, which generates electrical power from the resonator's motion. The proposed energy scavengers obviate the typically required matching of the resonant frequencies of the scavenger and the ambient energy sources it taps. This enables a device that is simpler, smaller and higher-frequency than the previously reported resonant power generator. The windbelt-based energy scavenger demonstrated a peak-to-peak output voltage of 81 mV at 0.53 kHz, from an input pressure of 50 kPa. The Helmholtz-resonator-based energy scavenger achieved a peak-to-peak output voltage of 4 mV at 1.4 kHz, from an input pressure of 0.2 kPa, which is equivalent to 5 m s-1 (10 mph) of wind velocity.

Kim, Seong-Hyok; Ji, Chang-Hyeon; Galle, Preston; Herrault, Florian; Wu, Xiaosong; Lee, Jin-Ho; Choi, Chang-Auk; Allen, Mark G.

2009-09-01

35

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...

36

A Prototype Flight-Deck Airflow Hazard Visualization System  

NASA Technical Reports Server (NTRS)

Airflow hazards such as turbulence, vortices, or low-level wind shear can pose a threat to landing aircraft and are especially dangerous to helicopters. Because pilots usually cannot see airflow, they may be unaware of the extent of the hazard. We have developed a prototype airflow hazard visual display for use in helicopter cockpits to alleviate this problem. We report on the results of a preliminary usability study of our airflow hazard visualization system in helicopter-shipboard operations.

Aragon, Cecilia R.

2004-01-01

37

Overview of Laminar Flow Control  

NASA Technical Reports Server (NTRS)

The history of Laminar Flow Control (LFC) from the 1930s through the 1990s is reviewed and the current status of the technology is assessed. Early studies related to the natural laminar boundary-layer flow physics, manufacturing tolerances for laminar flow, and insect-contamination avoidance are discussed. Although most of this publication is about slot-, porous-, and perforated-suction LFC concept studies in wind tunnel and flight experiments, some mention is made of thermal LFC. Theoretical and computational tools to describe the LFC aerodynamics are included for completeness.

Joslin, Ronald D.

1998-01-01

38

Computer simulation of airflow and particle transport in cleanrooms  

Microsoft Academic Search

A review of existing airflow and particle transport simulation methods is presented, and some recent applications of the methods to cleanroom airflow prediction are discussed. The advantages of numerical simulation of cleanrooms over corresponding experimental measurement include the ability to cover a wide variety of design options easily (such as bench configuration, dimensions, airflow rate, and particle source generation rate),

Thomas H. Kuehn

1988-01-01

39

Airflow Resistance Monitoring in Laryngotracheal Stenosis  

Microsoft Academic Search

Thirty-seven patients with laryngotracheal stenosis were treated within the last 3 years at the ENT Department of the Semmelweis University of Medicine in Budapest. Unilateral laser arytenoidectomy was performed in the group with pure vocal cord paralysis. Airflow resistance of the upper respiratory tract was measured with a modified Rhinotest MP 500 active anterior rhinomanometer through the tracheostomal orifice before

Andor Hirschberg; Ottó Ribári; György Szabó; Gábor Élö

1995-01-01

40

Statistics for Laminar Flamelet Modeling.  

National Technical Information Service (NTIS)

Statistical information required to support modeling of turbulent premixed combustion by laminar flamelet methods is extracted from a database of the results of Direct Numerical Simulation of turbulent flames. The simulations were carried out previously b...

R. S. Cant C. J. Rutland A. Trouve

1990-01-01

41

Assembly of the Light-Harvesting Chlorophyll Antenna in the Green Alga Chlamydomonas reinhardtii Requires Expression of the TLA2-CpFTSY Gene1[C][W][OA  

PubMed Central

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 Pmax 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.

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

2012-01-01

42

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

43

The association between airflow obstruction and radiologic change by tuberculosis  

PubMed Central

Introduction Cigarette smoking is the most commonly encountered risk factor for chronic obstructive pulmonary disease (COPD). However, it is not the only one and there is consistent evidence from epidemiologic studies that nonsmokers may develop chronic airflow limitation. A history of tuberculosis has recently been found to be associated with airflow obstruction in adults older than 40 years. The aim of this study was to evaluate the association between the radiologic changes by tuberculosis and airflow obstruction in a population based sample. Methods A nationwide COPD prevalence survey was conducted. We compared the prevalence of airflow obstruction according to the presence of the radiologic change by the tuberculosis. Results We analyzed 1,384 subjects who participated in the nationwide Korean COPD survey. All subjects were older than 40 years and took the spirometry and simple chest radiography. We defined the airflow obstruction as FEV1/FVC <0.7. A total of 149 (10.8%) subjects showed airflow obstruction. A total of 167 (12.1%) subjects showed radiologic change by tuberculosis. Among these 167 subjects, 44 (26.3%) had airflow obstruction. For the subjects without radiologic change by tuberculosis, the prevalence of airflow obstruction was only 8.6%. The unadjusted odds ratio for airflow obstruction according to the radiologic change was 3.788 (95% CI: 2.544-5.642). Conclusions The radiologic change by tuberculosis was associated with airflow obstruction.

Hwang, Yong Il; Kim, Joo Hee; Lee, Chang Youl; Park, Sunghoon; Park, Yong Bum; Jang, Seung Hun; Kim, Cheol Hong; Shin, Tae Rim; Park, Sang Myun; Sim, Yun Su; Kim, Dong-Gyu; Lee, Myung-Goo; Hyun, In-Gyu

2014-01-01

44

Considerations for efficient airflow design in cleanrooms  

SciTech Connect

A high-performance cleanroom should provide efficient energy performance in addition to effective contamination control. Energy-efficient designs can yield capital and operational cost savings, and can be part of a strategy to improve productivity in the cleanroom industry. Based upon in-situ measurement data from ISO Class 5 clean rooms, this article discusses key factors affecting cleanroom air system performance and benefits of efficient airflow design in clean rooms. Cleanroom HVAC systems used in the semiconductor, pharmaceutical, and healthcare industries are very energy intensive, requiring large volumes of cleaned air to remove or dilute contaminants for satisfactory operations. There is a tendency, however, to design excessive airflow rates into cleanroom HVAC systems, due to factors such as design conservatism, lack of thorough understanding of airflow requirements, concerns about cleanliness reliability, and potential design and operational liabilities. Energy use of cleanroom environmental systems varies with system type and design, cleanroom functions, and the control of critical parameters such as temperature and humidity. In particular, cleanroom cleanliness requirements specified by cleanliness class have an impact on overall energy use. A previous study covering Europe and the US reveals annual cleanroom electricity usage for cooling and fan energy varies significantly depending on cleanliness class, and may account for up to three-quarters of total annual operating costs. A study on a semiconductor cleanroom in Japan found air delivery systems account for more than 30% of total power consumption. It is evident that the main factors dictating cleanroom operation energy include airflow rates and HVAC system efficiency. Improving energy efficiency in clean rooms may potentially contribute to significant savings in the initial costs of the facilities as well as operation and maintenance costs. For example, energy consumption by a typical chip manufacturer can be cut 40% or more, and the associated greenhouse emissions even more. Cleanroom HVAC systems provide huge opportunities for energy savings in the semiconductor industry. In addition to direct cost reductions in cleanroom investment and operation, energy-efficient designs can reduce maintenance costs, increase power reliability, improve time-to-market in cleanroom production, and improve environmental quality. Companies that use energy efficiency to lower costs and increase productivity can gain a competitive advantage and achieve a higher return on investment. In addition, energy-efficient cleanroom systems conserve energy and natural resources, heightening the company's reputation as an environmentally conscious leader in the community and the industry. A significant portion of energy use in cleanroom environmental systems is associated with recirculating air systems. We will review and analyze design factors and operational performance of airflow systems in ISO Class 5 clean rooms. We will also discuss benefits of efficient cleanroom airflow designs in conjunction with effective cleanroom contamination control. We will consider the following common recirculating air system designs: fan-tower (FT) with pressurized-plenum; distributed air handler unit (AHU); and fan-filter unit (FFU).

Xu, Tengfang

2004-07-29

45

Laminar-flow flight experiments  

NASA Technical Reports Server (NTRS)

The flight testing conducted over the past 10 years in the NASA laminar-flow control (LFC) will be reviewed. The LFC program was directed towards the most challenging technology application, the high supersonic speed transport. To place these recent experiences in perspective, earlier important flight tests will first be reviewed to recall the lessons learned at that time.

Wagner, Richard D.; Maddalon, Dal V.; Bartlett, D. W.; Collier, F. S., Jr.; Braslow, A. L.

1989-01-01

46

Process for making laminar batteries  

Microsoft Academic Search

This patent describes the process of making laminar cells, which consists of perforating a first elongated web of liquid impervious, electrically nonconducting thermoplastic material with a spaced rectangular array of apertures arranged in rows across the direction of elongation of the web and in columns parallel to the direction of elongation of the web adding patches of electrically conductive material.

Plasse

1986-01-01

47

What defines airflow obstruction in asthma?  

PubMed

Asthma guidelines from the Global Initiative for Asthma (GINA) and from the National Heart, Lung, and Blood Institute provide conflicting definitions of airflow obstruction, suggesting a fixed forced expiratory volume in 1 s (FEV(1))/forced vital capacity (FVC) cut-off point and the lower limit of normality (LLN), respectively. The LLN was recommended by the recent American Thoracic Society/European Respiratory Society guidelines on lung function testing. The problem in using fixed cut-off points is that they are set regardless of age and sex in an attempt to simplify diagnosis at the expense of misclassification. The sensitivity and specificity of fixed FEV(1)/FVC ratios of 0.70, 0.75 and 0.80 versus the LLN were evaluated in 815 subjects (aged 20-44 yrs) with a diagnosis of asthma within the framework of the European Community Respiratory Health Survey. In males, the 0.70 ratio showed 76.5% sensitivity and 100.0% specificity, the 0.75 ratio 100.0% sensitivity and 92.4% specificity, and the 0.80 ratio 100.0% sensitivity but 58.1% specificity. In females, the 0.70 ratio showed 57.3% sensitivity and 100.0% specificity, the 0.75 ratio 91.5% sensitivity and 95.9% specificity, and the 0.80 ratio 100.0% sensitivity but 72.9% specificity. The fixed cut-off points cause a lot of misidentification of airflow obstruction in young adults, with overestimation with the 0.80 ratio and underestimation with the 0.70 ratio. In conclusion, the GINA guidelines should change their criteria for defining airflow obstruction. PMID:19720808

Cerveri, I; Corsico, A G; Accordini, S; Cervio, G; Ansaldo, E; Grosso, A; Niniano, R; Tsana Tegomo, E; Antó, J M; Künzli, N; Janson, C; Sunyer, J; Svanes, C; Heinrich, J; Schouten, J P; Wjst, M; Pozzi, E; de Marco, R

2009-09-01

48

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

49

FEM Analysis of Micro-machined Airflow Accelerometer's Sensitive Mechanism  

Microsoft Academic Search

The sensitive mechanism of micro- machined airflow accelerometer is explained. Using the finite element method, the stream field by heat source, with different input accelerations, has been obtained. The numerical results are as follows: Without acceleration, the velocities of airflow at two thermistors are equal, so the current of both thermistors are also equal. The output of the bridge circuit

Li Yan-jie; Piao Lin-hua; Li Bai-hua; Zhang Fu-xue

2009-01-01

50

System for measuring intake airflow rate in an engine  

SciTech Connect

A system is described for measuring intake airflow rate in an engine for a motor vehicle having an intake passage to the engine, and a throttle valve in the intake passage, the intake passage including a first intake passage upstream of the throttle valve and a second intake passage between the throttle valve and cylinders of the engine, the system comprising: an airflow meter disposed in the first intake passage for measuring a first intake airflow rate of flow passing in the first intake passage; first means for calculating a second intake airflow rate of flow into the second intake passage not entering into the cylinders during opening or closing of the throttle valve; and second means for producing a signal representing intake airflow rate of flow actually admitted into the cylinders in accordance with the difference between the first intake airflow rate and the second intake airflow rate; the first means comprises their means for calculating the second intake airflow rate based on opening degree of the throttle valve.

Sogawa, Y.

1989-01-17

51

Review on airflow in unsaturated zones induced by natural forcings  

NASA Astrophysics Data System (ADS)

Subsurface airflow in unsaturated zones induced by natural forcings is of importance in many environmental and engineering fields, such as environmental remediation, water infiltration and groundwater recharge, coastal soil aeration, mine and tunnel ventilation, and gas exchange between soil and atmosphere. This review synthesizes the published literature on subsurface airflow driven by natural forcings such as atmospheric pressure fluctuations, topographic effect, water table fluctuations, and water infiltration. The present state of knowledge concerning the mechanisms, analytical and numerical models, and environmental and engineering applications related to the naturally occurring airflow is discussed. Airflow induced by atmospheric pressure fluctuations is studied the most because of the applications to environmental remediation and transport of trace gases from soil to atmosphere, which are very important in understanding biogeochemical cycling and global change. Airflow induced by infiltration is also an extensively investigated topic because of its implications in rainfall infiltration and groundwater recharge. Airflow induced by water table fluctuations is important in coastal areas because it plays an important role in coastal environmental remediation and ecological systems. Airflow induced by topographic effect is studied the least. However, it has important applications in unsaturated zone gas transport and natural ventilation of mines and tunnels. Finally, the similarities and differences in the characteristics of the air pressure and airflow are compared and future research efforts are recommended.

Kuang, Xingxing; Jiao, Jiu Jimmy; Li, Hailong

2013-10-01

52

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

53

Co-Articulatory Airflow Characteristics of Intervocalic Voiceless Plosives  

ERIC Educational Resources Information Center

A pneumotachographic investigation of intervocalic /p/, /t/ and /k/ was undertaken to isolate physiological parameters responsible for coarticulatory air-flow phenomena. Airflow was most sensitive during the /k/ closure phase. The dynamics of the closure phase for each place of articulation and their implications for pneumotachography are…

Barry, William; Kuenzel, Hermann

1975-01-01

54

Impacts of Fluid Dynamics Simulation in Study of Nasal Airflow Physiology and Pathophysiology in Realistic Human Three-Dimensional Nose Models  

PubMed Central

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.

Lee, Heow Peuh; Gordon, Bruce R.

2012-01-01

55

Efficient, physiologically realistic lung airflow simulations.  

PubMed

One of the key challenges for computational fluid dynamics (CFD) simulations of human lung airflow is the sheer size and complexity of the complete, multiscale geometry of the bronchopulmonary tree. Since 3-D CFD simulations of the full airway tree are currently intractable, researchers have proposed reduced geometry models in which multiple airway paths are truncated downstream of the first few generations. This paper investigates a recently proposed method for closing the CFD model by application of physiologically correct boundary conditions at truncated outlets. A realistic, reduced geometry model of the lung airway based on CT data has been constructed up to generation 18, including extrathoracic, bronchi, and bronchiole regions. Results indicate that the new method yields reasonable results for pressure drop through the airway, at a small fraction of the cost of fully resolved simulations. PMID:21768041

Walters, D Keith; Burgreen, Greg W; Lavallee, David M; Thompson, David S; Hester, Robert L

2011-10-01

56

Effect of magnetic field, airflow or combination of airflow with magnetic field on hollow needle-to-cylinder discharge regimes  

NASA Astrophysics Data System (ADS)

For the hollow needle-to-cylinder dc discharge in air at atmospheric pressure we studied the effect of magnetic field, airflow and combination of airflow with magnetic field on transitions between various discharge regimes. We showed that application of magnetic field on the discharge in static air does not substantially change the discharge characteristics. In contrast with this finding, application of airflow through the needle increases the range of current of the discharge pulseless regime in comparison with the discharge in static air. A similar but more significant effect was obtained for combination of the airflow and magnetic field on the discharge. It was also shown that for the discharge in static air, discharge in static air in magnetic field, discharge with airflow and discharge in magnetic field with airflow for the filamentary streamer regime, the duration of the discharge voltage pulses decreases with increasing current. Using the combination of the airflow and magnetic field we were therefore able to stabilize the discharge and to increase the volume of the discharge chamber occupied by the non-equilibrium plasma.

Pekárek, Stanislav

2013-12-01

57

NASA Flight Tests Explore Supersonic Laminar Flow  

NASA Video Gallery

In partnership with Aerion Corporation of Reno, Nevada, NASA's Dryden Flight Research Centerâ??s tested supersonic airflow over a small experimental airfoil design on its F-15B Test Bed aircraft du...

58

Patient specific CFD models of nasal airflow: overview of methods and challenges.  

PubMed

Respiratory physiology and pathology are strongly dependent on the airflow inside the nasal cavity. However, the nasal anatomy, which is characterized by complex airway channels and significant individual differences, is difficult to analyze. Thus, commonly adopted diagnostic tools have yielded limited success. Nevertheless, with the rapid advances in computer resources, there have been more elaborate attempts to correlate airflow characteristics in human nasal airways with the symptoms and functions of the nose by computational fluid dynamics study. Furthermore, the computed nasal geometry can be virtually modified to reflect predicted results of the proposed surgical technique. In this article, several computational fluid mechanics (CFD) issues on patient-specific three dimensional (3D) modeling of nasal cavity and clinical applications were reviewed in relation to the cases of deviated nasal septum (decision for surgery), turbinectomy, and maxillary sinus ventilation (simulated- and post-surgery). Clinical relevance of fluid mechanical parameters, such as nasal resistance, flow allocation, wall shear stress, heat/humidity/NO gas distributions, to the symptoms and surgical outcome were discussed. Absolute values of such parameters reported by many research groups were different each other due to individual difference of nasal anatomy, the methodology for 3D modeling and numerical grid, laminar/turbulent flow model in CFD code. But, the correlation of these parameters to symptoms and surgery outcome seems to be obvious in each research group with subject-specific models and its variations (virtual- and post-surgery models). For the more reliable, patient-specific, and objective tools for diagnosis and outcomes of nasal surgery by using CFD, the future challenges will be the standardizations on the methodology for creating 3D airway models and the CFD procedures. PMID:23261244

Kim, Sung Kyun; Na, Yang; Kim, Jee-In; Chung, Seung-Kyu

2013-01-18

59

Effect of airflow exposure on the tear meniscus.  

PubMed

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. PMID:22570766

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

2012-01-01

60

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

61

Laminar Jet Diffusion Flame Burning  

NASA Technical Reports Server (NTRS)

Study of the downlink data from the Laminar Soot Processes (LSP) experiment quickly resulted in discovery of a new mechanism of flame extinction caused by radiation of soot. Scientists found that the flames emit soot sooner than expected. These findings have direct impact on spacecraft fire safety, as well as the theories predicting the formation of soot -- which is a major factor as a pollutant and in the spread of unwanted fires. This sequence, using propane fuel, was taken STS-94, July 4 1997, MET:2/05:30 (approximate). LSP investigated fundamental questions regarding soot, a solid byproduct of the combustion of hydrocarbon fuels. The experiment was performed using a laminar jet diffusion flame, which is created by simply flowing fuel-like ethylene or propane -- through a nozzle and igniting it, much like a butane cigarette lighter. The LSP principal investigator was Gerard Faeth, University of Michigan, Arn Arbor. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). LSP results led to a reflight for extended investigations on the STS-107 research mission in January 2003. Advanced combustion experiments will be a part of investigations planned for the International Space Station. (983KB, 9-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300184.html.

2003-01-01

62

Burning Laminar Jet Diffusion Flame  

NASA Technical Reports Server (NTRS)

Study of the downlink data from the Laminar Soot Processes (LSP) experiment quickly resulted in discovery of a new mechanism of flame extinction caused by radiation of soot. Scientists found that the flames emit soot sooner than expected. These findings have direct impact on spacecraft fire safety, as well as the theories predicting the formation of soot -- which is a major factor as a pollutant and in the spread of unwanted fires. This sequence was taken July 15, 1997, MET:14/10:34 (approximate) and shows the ignition and extinction of this flame. LSP investigated fundamental questions regarding soot, a solid byproduct of the combustion of hydrocarbon fuels. The experiment was performed using a laminar jet diffusion flame, which is created by simply flowing fuel -- like ethylene or propane -- through a nozzle and igniting it, much like a butane cigarette lighter. The LSP principal investigator was Gerard Faeth, University of Michigan, Arn Arbor. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). LSP results led to a reflight for extended investigations on the STS-107 research mission in January 2003. Advanced combustion experiments will be a part of investigations planned for the International Space Station. (518KB, 20-second MPEG, screen 160 x 120 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300182.html.

2003-01-01

63

Chevrons formation in laminar erosion  

NASA Astrophysics Data System (ADS)

When eroded by laminar free-surface flows, granular substrates may generate a rich variety of natural patterns. Among them are dunes, similar to the ones observed by Charru and Hinch in a Couette cell (Charru F, Hinch EJ ; Ripple formation on a particle bed sheared by a viscous liquid. Part 1. Steady flow ; JOURNAL OF FLUID MECHANICS 550: 111-121 MAR 10 2006). Chevron-shaped instabilities as those found on the sea-shore, can also be observed, sometimes in competition against dunes formation. These were first pointed out by Daerr et al. when pulling a plate covered with granular material out of a bath of water (Daerr A, Lee P, Lanuza J, et al. ; Erosion patterns in a sediment layer ; PHYSICAL REVIEW E 67 (6): Art. No. 065201 Part 2 JUN 2003). Both instabilities can grow in laminar open-channel flows, an experimental set-up which is more easily controlled. The mechanisms leading to the formation of these patterns are investigated and compared. Whereas dunes formation requires vertical inertia effects, we show that chevrons may result from the non-linear evolution of bars instability, which may grow even in purely viscous flows.

Devauchelle, Olivier; Josserand, Christophe; Lagree, Pierre-Yves; Zaleski, Stephane; Nguyen, Khanh-Dang; Malverti, Luce; Lajeunesse, Eric

2007-11-01

64

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

65

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

66

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

67

Laminar-flow wind tunnel experiments  

NASA Technical Reports Server (NTRS)

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 to extend the technology of laminar flow to higher Mach and Reynolds numbers and to swept leading edge wings representative of transport aircraft to achieve lower drag and significantly improved operation costs. This research involves stabilizing the laminar boundary layer through geometric shaping (Natural Laminar Flow, NLF) and active control involving the removal of a portion of the laminar boundary layer (Laminar-Flow Control, LFC), either through discrete slots or perforated surface. Results show that extensive regions of laminar flow with large reductions in skin friction drag can be maintained through the application of passive NLF boundary-layer control technologies to unswept transonic wings. At even greater extent of laminar flow and reduction in the total drag level can be obtained on a swept supercritical airfoil with active boundary layer-control.

Harvey, William D.; Harris, Charles D.; Sewall, William G.; Stack, John P.

1989-01-01

68

Statistics for laminar flamelet modeling  

NASA Technical Reports Server (NTRS)

Statistical information required to support modeling of turbulent premixed combustion by laminar flamelet methods is extracted from a database of the results of Direct Numerical Simulation of turbulent flames. The simulations were carried out previously by Rutland (1989) using a pseudo-spectral code on a three dimensional mesh of 128 points in each direction. One-step Arrhenius chemistry was employed together with small heat release. A framework for the interpretation of the data is provided by the Bray-Moss-Libby model for the mean turbulent reaction rate. Probability density functions are obtained over surfaces of the constant reaction progress variable for the tangential strain rate and the principal curvature. New insights are gained which will greatly aid the development of modeling approaches.

Cant, R. S.; Rutland, C. J.; Trouve, A.

1990-01-01

69

Endurance of hyperventilation in chronic airflow limitation.  

PubMed

The capacity to sustain an increase in ventilation (VE) sufficient to decrease the end-tidal partial pressure of carbon dioxide (PETCO2) by about 10 mm Hg was studied in six hypercapnic patients with moderate to severe chronic airflow limitation (CAL). Patients could continue such an increased VE for a finite time (range 5 to 54 minutes). During hyperventilation (H), ventilation was approximately doubled and represented 77.1 +/- 8.4 (mean +/- SE) percent of maximum voluntary ventilation, mean oxygen consumption (VO2) increased 44 percent (p less than 0.005) and mean inspiratory pleural pressure (Ppl) swings were 43.8 +/- 10.5 percent of maximum Ppl. Four patients achieved reductions of PETCO2 less than 10 mm Hg, and two patients achieved or exceeded the target decrease in PETCO2. The decrease in PaCO2 was correlated with the wasted ventilation ratios (VD/VT) during H, the greatest decrease in PaCO2 being related to the lowest VD/VT (p less than 0.05). Electromyographic (EMG) evidence of inspiratory muscle fatigue developed in four of the six patients during H. Five normal subjects achieved an equal or greater decrease in PETCO2, and none showed EMG evidence of inspiratory muscle fatigue. We conclude that, although impaired gas exchange limits the capacity to voluntarily reduce the PaCO2, the development of respiratory muscle fatigue in some patients with CAL may also contribute by limiting the capacity to sustain the substantial increase in respiratory muscle work done in the attempt. PMID:6404605

Pardy, R L; Roussos, C

1983-05-01

70

Respiratory airflow patterns in ponies at rest and during exercise.  

PubMed Central

The exercise-induced changes in the equine breathing pattern were studied by analyzing tidal breathing flow-volume loops recorded in ten ponies both at rest and during a standardized exercise. Airflow, tidal volume, esophageal pressure and mask pressure were simultaneously recorded before, during and after a treadmill exercise. From the collected data, respiratory frequency and total pulmonary resistance were calculated, tidal breathing flow-volume loops were retraced using a computerized method and loop indices were measured for each period of the experimental protocol. For each pony, results of three consecutive daily measurements were averaged. The exercise loop indices were compared with the corresponding resting values using a one-way analysis of variance. The significantly changed indices were correlated with respiratory frequency and total pulmonary resistance. Several types of respiratory patterns were observed at rest as well as during exercise, although each pony was relatively constant in its own pattern of breathing. Most resting inspiratory and expiratory airflow curves were found to be biphasic. When ponies started running, the airflow developed an increasingly rectangular pattern. During strenuous exercise, both inspiratory and expiratory airflow curves showed a substantial increase of the volume acceleration and tended to a plateau. The loop indices relating the expiratory to the inspiratory airflow were significantly increased compared with their rest values. Correlations of these indices with respiratory frequency and total pulmonary resistance were weak.(ABSTRACT TRUNCATED AT 250 WORDS)

Art, T; Lekeux, P

1988-01-01

71

Research in Natural Laminar Flow and Laminar-Flow Control, part 3  

NASA Technical Reports Server (NTRS)

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 swept leading edges at supersonic speeds.

Hefner, Jerry N. (compiler); Sabo, Frances E. (compiler)

1987-01-01

72

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

SciTech Connect

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 swept leading edges at supersonic speeds.

Hefner, J.N.; Sabo, F.E.

1987-12-01

73

Metal-metal reinforced laminar composites  

NASA Technical Reports Server (NTRS)

Two prototype laminar composites have shown potential for high strength and high temperature applications. These composites might be made with less in-place anisotropy and be less expensive than comparable fiber composites.

Weeton, J. W.; Hoffman, C. A.

1973-01-01

74

Three-Dimensional Laminar Boundary Layers.  

National Technical Information Service (NTIS)

This grant, devoted to the subject of laminar flows in three dimensions. During this period, efforts were first focused on settling the fundamental question of three dimensional separation. New evidences continue to lend support to our open separation con...

K. C. Wang

1985-01-01

75

Airflow Hazard Visualization for Helicopter Pilots: Flight Simulation Study Results  

NASA Technical Reports Server (NTRS)

Airflow hazards such as vortices or low level wind shear have been identified as a primary contributing factor in many helicopter accidents. US Navy ships generate airwakes over their decks, creating potentially hazardous conditions for shipboard rotorcraft launch and recovery. Recent sensor developments may enable the delivery of airwake data to the cockpit, where visualizing the hazard data may improve safety and possibly extend ship/helicopter operational envelopes. A prototype flight-deck airflow hazard visualization system was implemented on a high-fidelity rotorcraft flight dynamics simulator. Experienced helicopter pilots, including pilots from all five branches of the military, participated in a usability study of the system. Data was collected both objectively from the simulator and subjectively from post-test questionnaires. Results of the data analysis are presented, demonstrating a reduction in crash rate and other trends that illustrate the potential of airflow hazard visualization to improve flight safety.

Aragon, Cecilia R.; Long, Kurtis R.

2005-01-01

76

Unidirectional pulmonary airflow patterns in the savannah monitor lizard.  

PubMed

The unidirectional airflow patterns in the lungs of birds have long been considered a unique and specialized trait associated with the oxygen demands of flying, their endothermic metabolism and unusual pulmonary architecture. However, the discovery of similar flow patterns in the lungs of crocodilians indicates that this character is probably ancestral for all archosaurs--the group that includes extant birds and crocodilians as well as their extinct relatives, such as pterosaurs and dinosaurs. Unidirectional flow in birds results from aerodynamic valves, rather than from sphincters or other physical mechanisms, and similar aerodynamic valves seem to be present in crocodilians. The anatomical and developmental similarities in the primary and secondary bronchi of birds and crocodilians suggest that these structures and airflow patterns may be homologous. The origin of this pattern is at least as old as the split between crocodilians and birds, which occurred in the Triassic period. Alternatively, this pattern of flow may be even older; this hypothesis can be tested by investigating patterns of airflow in members of the outgroup to birds and crocodilians, the Lepidosauromorpha (tuatara, lizards and snakes). Here we demonstrate region-specific unidirectional airflow in the lungs of the savannah monitor lizard (Varanus exanthematicus). The presence of unidirectional flow in the lungs of V.?exanthematicus thus gives rise to two possible evolutionary scenarios: either unidirectional airflow evolved independently in archosaurs and monitor lizards, or these flow patterns are homologous in archosaurs and V.?exanthematicus, having evolved only once in ancestral diapsids (the clade encompassing snakes, lizards, crocodilians and birds). If unidirectional airflow is plesiomorphic for Diapsida, this respiratory character can be reconstructed for extinct diapsids, and evolved in a small ectothermic tetrapod during the Palaeozoic era at least a hundred million years before the origin of birds. PMID:24336209

Schachner, Emma R; Cieri, Robert L; Butler, James P; Farmer, C G

2014-02-20

77

CFD modelling and wind tunnel validation of airflow through plant canopies using 3D canopy architecture  

Microsoft Academic Search

The efficiency of pesticide application to agricultural fields and the resulting environmental contamination highly depend on atmospheric airflow. A computational fluid dynamics (CFD) modelling of airflow within plant canopies using 3D canopy architecture was developed to understand the effect of the canopy to airflow. The model average air velocity was validated using experimental results in a wind tunnel with two

A. Melese Endalew; M. Hertog; M. A. Delele; K. Baetens; T. Persoons; M. Baelmans; H. Ramon; B. M. Nicolaï; P. Verboven

2009-01-01

78

Airflow Obstruction after Myeloablative Allogeneic Hematopoietic Stem Cell Transplantation  

Microsoft Academic Search

Despite advances in the management of myeloablative allogeneic hematopoietic stem cell transplants, airflow obstruction (AFO) re- mains a significant complication. We conducted a 12-year study to examine the recent epidemiology of AFO and its associated mortality. Using the rate of percent predicted FEV1 decline after transplant, we defined AFO as a more than 5% per year decline in percent predicted

Jason W. Chien; Paul J. Martin; Ted A. Gooley; Mary E. Flowers; Susan R. Heckbert; W. Garrett Nichols; Joan G. Clark

2003-01-01

79

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

80

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 flow…

Catford, J.C.; And Others

81

Cough expired volume and airflow rates during sequential induced cough.  

PubMed

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. PMID:23847546

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

2013-01-01

82

Airflow Hazard Visualization for Helicopter Pilots: Flight Simulation Study Results  

Microsoft Academic Search

Airflow hazards such as vortices or low level wind shear have been identified as a primary contributing factor in many helicopter accidents. US Navy ships generate airwakes over their decks, creating potentially hazardous conditions for shipboard rotorcraft launch and recovery. Recent sensor developments may enable the delivery of airwake data to the cockpit, where visualizing the hazard data may improve

Cecilia R. Aragon; Kurtis R. Long

83

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

84

Laminar Heating Validation of the OVERFLOW Code  

NASA Technical Reports Server (NTRS)

OVERFLOW, a structured finite difference code, was applied to the solution of hypersonic laminar flow over several configurations assuming perfect gas chemistry. By testing OVERFLOW's capabilities over several configurations encompassing a variety of flow physics a validated laminar heating was produced. Configurations tested were a flat plate at 0 degrees incidence, a sphere, a compression ramp, and the X-38 re-entry vehicle. This variety of test cases shows the ability of the code to predict boundary layer flow, stagnation heating, laminar separation with re-attachment heating, and complex flow over a three-dimensional body. In addition, grid resolutions studies were done to give recommendations for the correct number of off-body points to be applied to generic problems and for wall-spacing values to capture heat transfer and skin friction. Numerical results show good comparison to the test data for all the configurations.

Lillard, Randolph P.; Dries, Kevin M.

2005-01-01

85

Wing Leading Edge Joint Laminar Flow Tests  

NASA Technical Reports Server (NTRS)

An F-104G aircraft at NASA's Dryden Flight Research Center has been equipped with a specially designed and instrumented test fixture to simulate surface imperfections of the type likely to be present near the leading edge on the wings of some laminar flow aircraft. The simulated imperfections consisted of five combinations of spanwise steps and gaps of various sizes. The unswept fixture yielded a pressure distribution similar to that of some laminar flow airfoils. The experiment was conducted at cruise conditions typical for business-jets and light transports: Mach numbers were in the range 0.5-0.8, and unit Reynolds numbers were 1.5-2.5 million per foot. Skin friction measurements indicated that laminar flow was often maintained for some distance downstream of the surface imperfections. Further work is needed to more precisely define transition location and to extend the experiments to swept-wing conditions and a broader range of imperfection geometries.

Drake, Aaron; Westphal, Russell V.; Zuniga, Fanny A.; Kennelly, Robert A., Jr.; Koga, Dennis J.

1996-01-01

86

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

87

Flow/Soot-Formation Interactions in Nonbuoyant Laminar Diffusion Flames  

NASA Technical Reports Server (NTRS)

This is the final report of a research program considering interactions between flow and soot properties within laminar diffusion flames. Laminar diffusion flames were considered because they provide model flame systems that are far more tractable for theoretical and experimental studies than more practical turbulent diffusion flames. In particular, understanding the transport and chemical reaction processes of laminar flames is a necessary precursor to understanding these processes in practical turbulent flames and many aspects of laminar diffusion flames have direct relevance to turbulent diffusion flames through application of the widely recognized laminar flamelet concept of turbulent diffusion flames. The investigation was divided into three phases, considering the shapes of nonbuoyant round laminar jet diffusion flames in still air, the shapes of nonbuoyant round laminar jet diffusion flames in coflowing air, and the hydrodynamic suppression of soot formation in laminar diffusion flames.

Dai, Z.; Lin, K.-C.; Sunderland, P. B.; Xu, F.; Faeth, G. M.

2002-01-01

88

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

89

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

90

Transient airflow structures and particle transport in a sequentially branching lung airway model  

NASA Astrophysics Data System (ADS)

Considering oscillatory laminar incompressible three-dimensional flow in triple planar and nonplanar bifurcations representing generations three to six of the human respiratory system, air flow fields and micron-particle transport have been simulated under normal breathing and high-frequency ventilation (HFV) conditions. A finite-volume code (CFX4.3 from AEA Technology, Pittsburgh, PA) and its user-enhanced FORTRAN programs were validated with experimental velocity data points for a single bifurcation. The airflow structures and micron-particle motion in the triple bifurcations were analyzed for a representative normal breathing cycle as well as HFV condition. While both the peak inspiratory and expiratory velocity profiles for the low Womersley case (?=0.93) agree well with those of instantaneously equivalent steady-state cases, some differences can be observed between flow acceleration and deceleration at off-peak periods or near flow reversal, especially during inspiratory flow. Similarly, the basic features of instantaneous particle motion closely resemble the steady-state case at equivalent inlet Reynolds numbers. The preferential concentration of particles caused by the coherent vortical structures was found in both inhalation and exhalation; however, it is more complicated during expiration. The effects of Womersley number and non-planar geometries as well as the variations in secondary flow intensity plus pressure drops across various bifurcations under normal breathing and HFV conditions were analyzed as well. This work may elucidate basic physical insight of aerosol transport relevant in dosimetry-and-health-effect studies as well as for drug aerosol delivery analyses.

Zhang, Z.; Kleinstreuer, C.

2002-02-01

91

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

92

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

93

Axial Flow in Laminar Trailing Vortices.  

National Technical Information Service (NTIS)

The structure of laminar trailing vortices behind a lifting wing is considered. The inviscid roll up of the trailing vortex sheet is examined, and the nature of the singularity at the centre of the spiral is determined. It is shown that viscosity removes ...

D. W. Moore P. G. Saffman

1972-01-01

94

Approaches for improving airflow uniformity in unidirectional flow cleanrooms  

Microsoft Academic Search

Airflow behavior inside a cleanroom with vertical unidirectional flow has been investigated. The design parameters, such as porosity and height of raised floor, width of cleanroom and inlet velocity profile, which affect the uniformity of air velocity distribution inside the cleanroom have been studied computationally. The Reynolds-averaged Navier–Stokes equations governing the flow are solved using a finite-volume code STAR-CD. The

M. Cheng; G. R. Liu; K. Y. Lam W. J. Cai; E. L. Lee

1998-01-01

95

Percent Emphysema, Airflow Obstruction, and Impaired Left Ventricular Filling  

PubMed Central

BACKGROUND Very severe chronic obstructive pulmonary disease causes cor pulmonale with elevated pulmonary vascular resistance and secondary reductions in left ventricular filling, stroke volume, and cardiac output. We hypothesized that emphysema, as detected on computed tomography (CT), and airflow obstruction are inversely related to left ventricular end-diastolic volume, stroke volume, and cardiac output among persons without very severe lung disease. METHODS We measured left ventricular structure and function with the use of magnetic resonance imaging in 2816 persons who were 45 to 84 years of age. The extent of emphysema (expressed as percent emphysema) was defined as the percentage of voxels below ?910 Hounsfield units in the lung windows on cardiac computed tomographic scans. Spirometry was performed according to American Thoracic Society guidelines. Generalized additive models were used to test for threshold effects. RESULTS Of the study participants, 13% were current smokers, 38% were former smokers, and 49% had never smoked. A 10-point increase in percent emphysema was linearly related to reductions in left ventricular end-diastolic volume (?4.1 ml; 95% confidence interval [CI], ?3.3 to ?4.9; P<0.001), stroke volume (?2.7 ml; 95% CI, ?2.2 to ?3.3; P<0.001), and cardiac output (?0.19 liters per minute; 95% CI, ?0.14 to ?0.23; P<0.001). These associations were of greater magnitude among current smokers than among former smokers and those who had never smoked. The extent of airflow obstruction was similarly associated with left ventricular structure and function, and smoking status had similar modifying effects on these associations. Percent emphysema and airflow obstruction were not associated with the left ventricular ejection fraction. CONCLUSIONS In a population-based study, a greater extent of emphysema on CT scanning and more severe airflow obstruction were linearly related to impaired left ventricular filling, reduced stroke volume, and lower cardiac output without changes in the ejection fraction.

Barr, R. Graham; Bluemke, David A.; Ahmed, Firas S.; Carr, J. Jeffery; Enright, Paul L.; Hoffman, Eric A.; Jiang, Rui; Kawut, Steven M.; Kronmal, Richard A.; Lima, Joao A.C.; Shahar, Eyal; Smith, Lewis J.; Watson, Karol E.

2010-01-01

96

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

97

Numerical Simulations and Observations of Airflow through the Alenuihaha Channel  

NASA Astrophysics Data System (ADS)

Airflow characteristics in the coastal waters of the Hawaiian archipelago, particular the Alenuihaha Channel between the island of Hawaii and the Island of Maui, are examined using observations and model simulations from the Advanced Research WRF (ARW) Modeling System. Airflow features related to interaction with the archipelago, including seasonal and diurnal changes, are presented using data from the QuikSCAT satellite, various buoys and ship data gathered in the Alenuihaha Channel. Verifications of the WRF model is made through comparisons of several years of buoy data with respective years of a WRF model hindcast. Special attention is paid to the Alenuihaha Channel, the site of two historical buoys, where a notable acceleration of wind occurs in conjunction with a sinking of the trade-wind inversion. WRF simulations for July 2005 provides model support for the existence of accelerated winds, a lowering of the trade-wind inversion and a hydraulic jump within the channel, delineating their magnitude, degree of deflection, diurnal variations, and placement while elucidating their mechanics. Topographical influences of Maui on the airflow through the Alenuihaha Channel are explored by comparing WRF runs with Maui County with those in which it has been removed. These influences include island blocking/orographic lifting on the windward side and adiabatic descent on the lee side, which augment the pressure gradient through the channel.

Chen, Y.; Hitzl, D.; Nguyen, H.

2013-12-01

98

Airflow calibration of a bellmouth inlet for measurement of compressor airflow in turbine-powered propulsion simulators  

NASA Technical Reports Server (NTRS)

The development of turbine-powered propulsion simulators for high-speed wind tunnel models requires a bellmouth inlet which can accurately measure compressor-inlet airflow. A bellmouth inlet was instrumented with total pressure probes, static pressure probes, and thermocouples for airflow measurement. The bellmouth flowmeter against a critical venturi flowmeter was calibrated. The calibration was done at four inlet pressures ranging from 58 to 114 kPa. The bellmouth discharge coefficient varied as a function of bellmouth-throat Mach number. Over the range of Reynolds number and Mach number tested the Reynolds number was not a significant influence on the discharge coefficient. The overall accuracy of the bellmouth inlet as a flowmeter was estimated to be + or - 0.5% of the flowmeter reading.

Smith, S. C.

1985-01-01

99

Investigation of a Laminar Flow Leading Edge  

NASA Technical Reports Server (NTRS)

The recent resurgence of interest in utilizing laminar flow on aircraft surfaces for reduction in skin friction drag has generated a considerable amount of research in natural laminar flow (NLF) and hybrid laminar flow control (HLFC) on transonic aircraft wings. This research has focused primarily on airfoil design and understanding transition behavior with little concern for the surface imperfections and manufacturing variations inherent to most production aircraft. In order for laminar flow to find wide-spread use on production aircraft, techniques for constructing the wings must be found such that the large surface imperfections present in the leading edge region of current aircraft do not occur. Toward this end, a modification to existing leading edge construction techniques was devised such that the resulting surface did not contain large gaps and steps as are common on current production aircraft of this class. A lowspeed experiment was first conducted on a simulation of the surface that would result from this construction technique. Preston tube measurements of the boundary layer downstream of the simulated joint and flow visualization using sublimation chemicals validated the literature on the effects of steps on a laminar boundary layer. These results also indicated that the construction technique was indeed compatible with laminar flow. In order to fully validate the compatibility of this construction technique with laminar flow, thus proving that it is possible to build wings that are smooth enough to be used on business jets and light transports in a manner compatible with laminar flow, a flight experiment is being conducted. In this experiment Mach number and Reynolds number will be matched in a real flight environment. The experiment is being conducted using the NASA Dryden F-104 Flight Test Fixture (FTF). The FTF is a low aspect ratio ventral fin mounted beneath an F-104G research aircraft. A new nose shape was designed and constructed for this experiment. This nose shape provides an accelerating pressure gradient in the leading edge region. By flying the aircraft at appropriate Mach numbers and altitudes, this nose shape simulates the leading edge region of a laminar flow wing for a business jet or light transport. Manufactured into the nose shape is a spanwise slot located approximately four inches downstream of the leading edge. The slot, which is an inch wide and one-eighth of an inch deep allows the simulation of surface imperfections, such as gaps and steps at skin joints, which will occur on aircraft using this new construction technique. By placing strips of aluminum of various sizes and shapes in the slot, the effect on the boundary layer of different sizes and shapes of steps and gaps will be examined. It is planned to use five different configurations, differing primarily in the size and number of gaps. Downstream of the slot, the state of the boundary layer is determined using hot film gages and Stanton gages. Agreement between these two very different techniques of measuring boundary layer properties is considered important to being able to state with confidence the effects on the boundary layer of the simulated manufacturing imperfections. To date, the aircraft has not flown. First flights of the aircraft are on schedule to begin October 4, 1993. Low-speed, preliminary experiments at matching Reynolds numbers have been completed.

Drake, Aaron; Kennelly, Robert A., Jr.; Koga, Dennis J.; Westphal, Russell V.; Zuniga, Fanny

1994-01-01

100

Numerical Simulations of Laminar Air-Water Flow of a Non-linear Progressive Wave at Low Wind Speed  

NASA Astrophysics Data System (ADS)

A numerical simulation for two-dimensional laminar air-water flow of a non-linear progressive water wave with large steepness is performed when the background wind speed varies from zero to the wave phase speed. It is revealed that in the water the difference between the analytical solution of potential flow and numerical solution of viscous flow is very small, indicating that both solutions of the potential flow and viscous flow describe the water wave very accurately. In the air the solutions of potential and viscous flows are very different due to the effects of viscosity. The velocity distribution in the airflow is strongly influenced by the background wind speed and it is found that three wind speeds, , (the maximum orbital velocity of a water wave), and (the wave phase speed), are important in distinguishing different features of the flow patterns.

Wen, X.; Mobbs, S.

2014-03-01

101

Three-Dimensional Engineered High Fidelity Normal Human Lung Tissue-Like Assemblies (TLA) as Targets for Human Respiratory Virus Infections  

NASA Technical Reports Server (NTRS)

Unlike traditional two-dimensional (2D) cell cultures, three-dimensional (3D) tissue-like assemblies (TLA) (Goodwin et aI, 1992, 1993, 2000 and Nickerson et aI. , 2001,2002) offer high organ fidelity with the potential to emulate the infective dynamics of viruses and bacteria in vivo. Thus, utilizing NASA micro gravity Rotating Wall Vessel (RWV) technology, in vitro human broncho-epithelial (HBE) TLAs were engineered to mimic in vivo tissue for study of human respiratory viruses. These 3D HBE TLAs were propagated from a human broncho-tracheal cell line with a mesenchymal component (HBTC) as the foundation matrix and either an adult human broncho-epithelial cell (BEAS-2B) or human neonatal epithelial cell (16HBE140-) as the overlying element. Resulting TLAs share several characteristic features with in vivo human respiratory epithelium including tight junctions, desmosomes and cilia (SEM, TEM). The presence of epithelium and specific lung epithelium markers furthers the contention that these HBE cells differentiate into TLAs paralleling in vivo tissues. A time course of infection of these 3D HBE TLAs with human respiratory syncytial virus (hRSV) wild type A2 strain, indicates that virus replication and virus budding are supported and manifested by increasing virus titer and detection of membrane-bound F and G glycoproteins. Infected 3D HBE TLAs remain intact for up to 12 days compared to infected 2D cultures that are destroyed in 2-3 days. Infected cells show an increased vacuolation and cellular destruction (by transmission electron microscopy) by day 9; whereas, uninfected cells remain robust and morphologically intact. Therefore, the 3D HBE TLAs mimic aspects of human respiratory epithelium providing a unique opportunity to analyze, for the first time, simulated in vivo viral infection independent of host immune response.

Goodwin, T. J.; Deatly, A. M.; Suderman, M. T.; Lin, Y.-H.; Chen, W.; Gupta, C. K.; Randolph, V. B.; Udem, S. A.

2003-01-01

102

Insect contamination protection for laminar flow surfaces  

NASA Technical Reports Server (NTRS)

The ability of modern aircraft surfaces to achieve laminar flow was well-accepted in recent years. Obtaining the maximum benefit of laminar flow for aircraft drag reduction requires maintaining minimum leading-edge contamination. Previously proposed insect contamination prevention methods have proved impractical due to cost, weight, or inconvenience. Past work has shown that insects will not adhere to water-wetted surfaces, but the large volumes of water required for protection rendered such a system impractical. The results of a flight experiment conducted by NASA to evaluate the performance of a porous leading-edge fluid discharge ice protection system operated as an insect contamination protections system are presented. In addition, these flights explored the environmental and atmospheric conditions most suitable for insect accumulation.

Croom, Cynthia C.; Holmes, Bruce J.

1986-01-01

103

Coupling of wrinkled laminar flames with gravity  

NASA Technical Reports Server (NTRS)

The overall objective of our research is to understand flame-gravity coupling processes in laminar and low turbulent Reynolds number, Re(sub l), premixed flames (i.e. wrinkled- laminar flames). The approach we have developed is to compare the flowfields and mean flame properties under different gravitational orientations. Key to our study is the investigation of microgravity (mu g) flames. These mu g experiments provide vital information to reconcile the differences between flames in normal gravity (+g, flame pointing upward) and reverse gravity (-g, flame pointing downwards). Traditionally, gravity effects are assumed to be insignificant or circumvented in the laboratory, therefore, not much is available in the literature on the behavior of -g flames.

Bedat, Benoit; Kostiuk, Larry W.; Cheng, Robert K.

1995-01-01

104

Laminar Flow Control at High Speeds  

NASA Astrophysics Data System (ADS)

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 of T-S waves, Goertler vortices, crossflow vortices, and attachment-line contamination. Choices range from using 2-D wings instead of 3-D wings, subsonic or supersonic leading edges, and passive or active control methods. Goertler and crossflow vortices exhibit early nonlinear growth and saturation and require solutions outside of the usual linear stability analysis. As a result, one brings to bear coordinated wind-tunnel tests, flight tests, DNS, and nonlinear PSE. All of these efforts are reviewed with special attention paid to the use of distributed roughness to modulate the nonlinear growth of crossflow waves.

Saric, William

2003-11-01

105

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

106

Correlated Variability in Laminar Cortical Circuits  

PubMed Central

SUMMARY Despite the fact that strong trial-to-trial correlated variability in responses has been reported in many cortical areas, recent evidence suggests that neuronal correlations are much lower than previously thought. Here, we used multicontact laminar probes to revisit the issue of correlated variability in primary visual (V1) cortical circuits. We found that correlations between neurons depend strongly on local network context—whereas neurons in the input (granular) layers showed virtually no correlated variability, neurons in the output layers (supragranular and infragranular) exhibited strong correlations. The laminar dependence of noise correlations is consistent with recurrent models in which neurons in the granular layer receive intracortical inputs from nearby cells, whereas supragranular and infragranular layer neurons receive inputs over larger distances. Contrary to expectation that the output cortical layers encode stimulus information most accurately, we found that the input network offers superior discrimination performance compared to the output networks.

Hansen, Bryan J.; Chelaru, Mircea I.; Dragoi, Valentin

2012-01-01

107

Laminar nanofluid flow in microheat-sinks  

Microsoft Academic Search

In response to the ever increasing demand for smaller and lighter high-performance cooling devices, steady laminar liquid nanofluid flow in microchannels is simulated and analyzed. Considering two types of nanofluids, i.e., copper-oxide nanospheres at low volume concentrations in water or ethylene glycol, the conjugated heat transfer problem for microheat-sinks has been numerically solved. Employing new models for the effective thermal

J. Koo; C. Kleinstreuer

2005-01-01

108

Laminar Flow in the Ocean Ekman Layer  

NASA Astrophysics Data System (ADS)

INTRODUCTION THE EFFECT OF A STABLE DENSITY GRADIENT THE FATAL FLAW FLOW VISUALIZATION THE DISCOVERY OF LAMINAR FLOW FINE STRUCTURE WAVE-INDUCED SHEAR INSTABILITY BILLOW TURBULENCE REVERSE TRANSITION REVISED PARADIGM ONE-DIMENSIONAL MODELLING OF THE UPPER OCEAN DIURNAL VARIATION BUOYANT CONVECTION BILLOW TURBULENCE IN THE DIURNAL THERMOCLINE CONSEQUENCES FOR THE EKMAN CURRENT PROFILE SOLAR RADIATION APPLICATIONS Slippery Seas of Acapulco Pollution Afternoon Effect in Sonar Patchiness Fisheries Climate DISCUSSION CONCLUSION REFERENCES

Woods, J. T. H.

109

Prevalence of airflow obstruction in smokers and never-smokers in Switzerland.  

PubMed

The aim of the present study was to measure age-specific prevalence of airflow obstruction in Switzerland in smokers and never-smokers using pulmonary function tests and respiratory symptoms from 6,126 subjects participating in the Swiss Cohort Study on Air Pollution and Lung Diseases in Adults. The lower limit of normal of the forced expiratory volume in 1 s/forced vital capacity ratio was used to define airflow obstruction. Severity of airflow obstruction was graded according to the recommendations of the Global Initiative for Chronic Obstructive Lung Disease. Prevalence of airflow obstruction ranged from 2.5% in subjects aged 30-39 yrs to 8.0% in those aged ? 70 yrs. In multivariate analysis, age (OR 2.8, ? 70 yrs versus 30-39 yrs), smoking (OR 1.8) and asthma (OR 6.7) were associated with airflow obstruction. Never-smokers constituted 29.3% of subjects with airflow obstruction. Never-smokers with airflow obstruction were younger, more likely to be male and reported asthma more frequently than obstructive smokers. Obstructive smokers and never-smokers had similar level of symptoms and quality of life impairment. The prevalence of airflow obstruction in Switzerland is similar to other developed countries. Never-smokers account for a third of the prevalence, which is higher proportion than elsewhere. Airflow obstruction in never-smokers deserves attention because of its frequency and its similar health impact to that in smokers. PMID:20413537

Bridevaux, P-O; Probst-Hensch, N M; Schindler, C; Curjuric, I; Felber Dietrich, D; Braendli, O; Brutsche, M; Burdet, L; Frey, M; Gerbase, M W; Ackermann-Liebrich, U; Pons, M; Tschopp, J-M; Rochat, T; Russi, E W

2010-12-01

110

Real-time visualization and analysis of airflow field by use of digital holography  

NASA Astrophysics Data System (ADS)

The measurement and analysis of airflow field is very important in fluid dynamics. For airflow, smoke particles can be added to visually observe the turbulence phenomena by particle tracking technology, but the effect of smoke particles to follow the high speed airflow will reduce the measurement accuracy. In recent years, with the advantage of non-contact, nondestructive, fast and full-field measurement, digital holography has been widely applied in many fields, such as deformation and vibration analysis, particle characterization, refractive index measurement, and so on. In this paper, we present a method to measure the airflow field by use of digital holography. A small wind tunnel model made of acrylic glass is built to control the velocity and direction of airflow. Different shapes of samples such as aircraft wing and cylinder are placed in the wind tunnel model to produce different forms of flow field. With a Mach-Zehnder interferometer setup, a series of digital holograms carrying the information of airflow filed distributions in different states are recorded by CCD camera and corresponding holographic images are numerically reconstructed from the holograms by computer. Then we can conveniently obtain the velocity or pressure information of the airflow deduced from the quantitative phase information of holographic images and visually display the airflow filed and its evolution in the form of a movie. The theory and experiment results show that digital holography is a robust and feasible approach for real-time visualization and analysis of airflow field.

Di, Jianglei; Wu, Bingjing; Chen, Xin; Liu, Junjiang; Wang, Jun; Zhao, Jianlin

2013-04-01

111

Optimal Determination of Respiratory Airflow Patterns Using a Nonlinear Multicompartment Model for a Lung Mechanics System  

PubMed Central

We develop optimal respiratory airflow patterns using a nonlinear multicompartment model for a lung mechanics system. Specifically, we use classical calculus of variations minimization techniques to derive an optimal airflow pattern for inspiratory and expiratory breathing cycles. The physiological interpretation of the optimality criteria used involves the minimization of work of breathing and lung volume acceleration for the inspiratory phase, and the minimization of the elastic potential energy and rapid airflow rate changes for the expiratory phase. Finally, we numerically integrate the resulting nonlinear two-point boundary value problems to determine the optimal airflow patterns over the inspiratory and expiratory breathing cycles.

Li, Hancao; Haddad, Wassim M.

2012-01-01

112

Improved prediction of laminar leading edge separation  

NASA Technical Reports Server (NTRS)

Research was conducted to provide a definite criterion for the prediction of the bubble burst on airfoils typical of those used for fighter wings. The approach taken was to correlate existing airfoil bubble burst data using various parameters at the laminar separation point. The method due to Weber was modified to provide a continuous analytic solution for the velocity distribution around the airfoil leading edge. Coupling the modified Weber method with the Stratford laminar separation prediction method leads to a universal chart giving the conditions at separation as a function of stagnation location and leading edge radius. Application of the combined method to available two-dimensional airfoil data resulted in an empirical criterion presenting the limiting local velocity gradient at separation as a function of the boundary layer momentum thickness at separation for bubble burst. The correlation leads as well to the qualitative explanation of two types of laminar stall: thin airfoil and leading edge. The validity of the correlation is demonstrated by predicting the lift coefficient and angle of attack for stall on airfoils with leading edge or trailing edge flaps.

Herring, R. N.; Ely, W. L.

1979-01-01

113

Vapor-Generator Wand Helps To Reveal Airflow Patterns  

NASA Technical Reports Server (NTRS)

In vapor-generator wand, liquid propylene glycol flows into electrically heated stainless-steel tube. Liquid boils in heated tube, and emerging vapor forms dense, smoke-like fog used to make airflow patterns visible. Built in variety of sizes, suitable for uses ranging from tabletop demonstrations to research in wind tunnels. For best viewing, plume illuminated by bright, focused incandescent spotlight at right angle to viewing direction. Viewing further enhanced by coating walls of test chamber with flat, dark color to minimize reflections and increase contrast.

Robelen, David B.

1993-01-01

114

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

115

Intrinsic stability of a body hovering in an oscillating airflow.  

PubMed

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. PMID:22401125

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

2012-02-10

116

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

117

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

118

Numerical Simulation of the Bursting of a Laminar Separation Bubble  

Microsoft Academic Search

Numerical simulations of laminar separation bubbles are carried out to investigate the so-called bubble bursting, i.e. the\\u000a changeover from a short to a long bubble by means of very small variation of one governing parameter. A laminar separation\\u000a bubble is formed if a laminar boundary layer separates in a region of adverse pressure gradient on a flat plate and undergoes

Olaf Marxen; Dan Henningson

119

Forced-air patient warming blankets disrupt unidirectional airflow.  

PubMed

We have recently shown that waste heat from forced-air warming blankets can increase the temperature and concentration of airborne particles over the surgical site. The mechanism for the increased concentration of particles and their site of origin remained unclear. We therefore attempted to visualise the airflow in theatre over a simulated total knee replacement using neutral-buoyancy helium bubbles. Particles were created using a Rocket PS23 smoke machine positioned below the operating table, a potential area of contamination. The same theatre set-up, warming devices and controls were used as in our previous study. This demonstrated that waste heat from the poorly insulated forced-air warming blanket increased the air temperature on the surgical side of the drape by > 5°C. This created convection currents that rose against the downward unidirectional airflow, causing turbulence over the patient. The convection currents increased the particle concentration 1000-fold (2 174 000 particles/m(3) for forced-air warming vs 1000 particles/m(3) for radiant warming and 2000 particles/m(3) for the control) by drawing potentially contaminated particles from below the operating table into the surgical site. Cite this article: Bone Joint J 2013;95-B:407-10. PMID:23450029

Legg, A J; Hamer, A J

2013-03-01

120

Airflow modelling over aeolian bedforms, Proctor Crater, Mars  

NASA Astrophysics Data System (ADS)

The presence of multiple dune forms inside Martian craters is evident on much of the recent HiRISE imagery available. Typically multiple length scales are present with progressively smaller bedform features superimposed on larger dunes, giving rise to complex but regular topographical patterns. There is a need to understand the airflow behaviour over these features to investigate if the formational pattern and orientation of the bedforms correspond to localised wind flow forcing. Using computational fluid dynamics (OpenFoam) we present preliminary findings within Mars' Proctor Crater, examining a dune area of 4.5km x 5.0km running with a computational cell resolution of 5m x 5m. A range of wind speed and directions are investigated and results are compared to bedform orientation and length scale. Superimposed over recent HiRISE imagery, results reveal a distinctive relationship between steered airflow and localised bedform orientation, mapping orthogonally onto the crestal ridges and dune troughs present. This work has important implications for the reconstruction of aeolian dunes within craters on Mars and can help lend further support to studies examining recent activity of Martian dune migration.

Jackson, D. W. T.; Smyth, T.; Bourke, M.

2012-04-01

121

CFD simulation of turbulent airflow around wind turbine airfoils  

NASA Astrophysics Data System (ADS)

The airflow around wind turbines has proved to be a difficult problem to approach by means of today's Computational Fluid Dynamics (CFD) codes. One reason for this difficulty lies within the stall characteristics of turbine airfoils. For the purposes of this research, the popular commercial CFD code, FLUENT was employed to facilitate the understanding of airflow around wind turbines through the study of various turbulence models. Parallel processing was employed to enhance computational performance as well as lower simulation times. The system used for simulation is the National Renewable Energy Laboratory (NREL) Phase VI Wind Turbine. The coefficients of pressure for the airfoil were extracted from the simulated data and compared against data obtained during the NREL Phase VI Wind Turbine data campaign. Since power is a driving factor of the design of wind turbine blades, the aspect of power was also examined and compared. After the completion of the baseline study, a parametric study was carried out to examine the effects of rotor speed downstream of the turbine blades.

Halbrooks, David N.

122

Near surface airflow modelling over dunes in Proctor Crater, Mars  

NASA Astrophysics Data System (ADS)

Multiple dune forms inside Martian craters is evident on much of the recent Hi-Rise imagery available. Typically, multiple length scales are present with progressively smaller bedform features superimposed on larger dunes. This has produced complex but regular topographical aeolian-driven patterns. Understanding the airflow conditions over and around these features will help in our understanding of the formational patterns and orientation of the aeolian bedforms relative to localised wind flow forcing. Here we use computational fluid dynamics modelling and present preliminary findings within Mars' Proctor Crater over a dune area measuring 4.5km x 5.0km running with a computational cell resolution of 5m x 5m. A range of wind speed and directions are investigated and results are compared to bedform orientation, length scale and migration of ripples evident from recent HiRise imagery. Results reveal a distinctive relationship between steered airflow and localised bedform orientation, mapping orthogonally onto the crestal ridges present. This work has important implications for evolutionary reconstruction of aeolian dunes within craters on Mars and helps lend further support to studies examining recent activity of Martian dune migration.

Jackson, Derek; Bourke, Mary; Smyth, Thomas

2014-05-01

123

Nanostructured optical fiber sensors for breathing airflow monitoring  

NASA Astrophysics Data System (ADS)

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 process and the fundamental mechanisms for the change in optical reflection, specifically caused by exhaled air condensation on the coating surface. The physically small sensors fabricated by varying thin film chemistry, offer a full range of environmental relative humidity sensing from 0% to 100% with response times of microseconds, and mostly important, provide much higher sensitivity to breathing air, over 6 times larger than 100% relative humidity. The sensor performances in comparison with a medical nasal thermistor suggest such a thin film sensor an excellent device for advanced breathing airflow monitoring. All the features are appealing to clinical respiratory diagnosis and related sensor instrumentation design, and in good agreement with our analytical model.

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

2005-05-01

124

Numerical Simulations of Airflow at Gemini Telescope Sites  

NASA Astrophysics Data System (ADS)

In order to determine the optimum location of the Gemini 8 meter telescopes it is desirable to know the airflow characteristics at the proposed sites. Similarly, a determination of the height of the telescope pier requires some knowledge of the thickness of the turbulent boundary layer under various conditions at the proposed sites. On site testing provides valuable data but over a limited range of wind conditions and only at specific points. In order to better understand the ambient wind flow at the proposed sites, three dimensional hydrodynamic simulations of the airflow over the top of Mauna Kea and over Cerro Pachon in Chile were carried out with the facilities at the San Diego Supercomputer Center. The results of these calculations will be presented. They show that the summit ridge at Mauna Kea to be an excellent site, though the off ridge locations are less desirable, and that either of the proposed sites on Cerro Pachon will meet the desired criteria. They also show that a telescope pier height of 15-20m will place the telescopes above the turbulent boundary layer under almost all conditions.

Charles, Richard; De Young, David S.

1993-12-01

125

Flame Structure and Scalar Properties in Microgravity Laminar Fires  

NASA Technical Reports Server (NTRS)

Recent results from microgravity combustion experiments conducted in the Zero Gravity Facility (ZGF) 5.18 second drop tower are reported. Emission mid-infrared spectroscopy measurements have been completed to quantitatively determine the flame temperature, water and carbon dioxide vapor concentrations, radiative emissive power, and soot concentrations in a microgravity laminar ethylene/air flame. The ethylene/air laminar flame conditions are similar to previously reported experiments including the Flight Project, Laminar Soot Processes (LSP). Soot concentrations and gas temperatures are in reasonable agreement with similar results available in the literature. However, soot concentrations and flame structure dramatically change in long duration microgravity laminar diffusion flames as demonstrated in this paper.

Feikema, D. A.; Lim, J.; Sivathanu, Y.

2006-01-01

126

Estimating Engine Airflow in Gas-Turbine Powered Aircraft with Clean and Distorted Inlet Flows  

NASA Technical Reports Server (NTRS)

The P404-GF-400 Powered F/A-18A High Alpha Research Vehicle (HARV) was used to examine the impact of inlet-generated total-pressure distortion on estimating levels of engine airflow. Five airflow estimation methods were studied. The Reference Method was a fan corrected airflow to fan corrected speed calibration from an uninstalled engine test. In-flight airflow estimation methods utilized the average, or individual, inlet duct static- to total-pressure ratios, and the average fan-discharge static-pressure to average inlet total-pressure ratio. Correlations were established at low distortion conditions for each method relative to the Reference Method. A range of distorted inlet flow conditions were obtained from -10 deg. to +60 deg. angle of attack and -7 deg. to +11 deg. angle of sideslip. The individual inlet duct pressure ratio correlation resulted in a 2.3 percent airflow spread for all distorted flow levels with a bias error of -0.7 percent. The fan discharge pressure ratio correlation gave results with a 0.6 percent airflow spread with essentially no systematic error. Inlet-generated total-pressure distortion and turbulence had no significant impact on the P404-GE400 engine airflow pumping. Therefore, a speed-flow relationship may provide the best airflow estimate for a specific engine under all flight conditions.

Williams, J. G.; Steenken, W. G.; Yuhas, A. J.

1996-01-01

127

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

Microsoft Academic Search

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.

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

2007-01-01

128

Partitioning the work-sparing effects of partial ventilatory support in airflow obstruction  

PubMed Central

Sweeping conclusions regarding the utility or nonutility of elevating expiratory pressure are not warranted. The effects of manipulating airway pressure in the setting of airflow obstruction depend heavily on the nature and severity of disease, as well as on the presence of airflow limitation during tidal breathing.

Marini, John J

2004-01-01

129

Use of a Helium Bubble Generator to Evaluate the Role of Entrained Airflow in Dust Generation.  

National Technical Information Service (NTIS)

A study of dust generation by free falling powders in a test chamber prompted an interest in the role of induced airflow in dust generation. A helium bubble generator was used to study the airflow patterns caused by dropping powders in a large test chambe...

W. A. Heitbrink

1993-01-01

130

THE DEVELOPMENT OF TECHNIQUES FOR ASSESSING THE COMBINED ACOUSTIC AND AIRFLOW PERFORMANCE OF NATURAL VENTILATION STRATEGIES  

Microsoft Academic Search

The potential to use natural ventilation for buildings in busy urban areas affected by high levels of road traffic noise can be limited by excessive noise entering through ventilation openings. This paper is concerned with techniques to reduce noise ingress into naturally ventilated buildings while minimizing airflow path resistance. A method is proposed for quantifying the acoustic and airflow performance

D. J. Oldham; M. H. de Salis; S. Sharples

131

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

132

Air-flow limitation in myasthenia gravis. The effect of acetylcholinesterase inhibitor therapy on air-flow limitation.  

PubMed

In a survey of 21 patients with myasthenia gravis receiving regular acetylcholinesterase inhibitor therapy, 8 were found to have air-flow limitation associated with their antimyasthenic therapy. In 6 of these subjects, detailed assessments were made of the effect of antimyasthenic therapy on airways function. Pyridostigmine was given together with either placebo or the anticholinergic bronchodilator ipratropium bromide (72 micrograms) by inhalation administered double blind on 2 consecutive days. Airways resistance (Raw) increased significantly after pyridostigmine and placebo inhaler (0.49 +/- 0.13 kPa/L/s basal versus 0.60 +/- 0.13 kPa/L/s at 2 h; mean +/- SEM, p less than 0.05), whereas a significant decrease in Raw followed the combination of pyridostigmine with ipratropium bromide (0.57 +/- 0.08 kPa/L/s basal versus 0.41 +/- 0.07 kPa/L/s at 2 h, p less than 0.05). Thus, acetylcholinesterase inhibitor therapy in subjects with myasthenia gravis with airflow limitation led to significant increase in airways resistance that could be completely reversed by the inhalation of the muscarinic receptor blocker ipratropium bromide. PMID:6226224

Shale, D J; Lane, D J; Davis, C J

1983-10-01

133

Velocity profiles in laminar diffusion flames  

NASA Technical Reports Server (NTRS)

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.

1986-01-01

134

Laminar natural convection under nonuniform gravity.  

NASA Technical Reports Server (NTRS)

Laminar natural convection is analyzed for cases in which gravity varies with the distance from the leading edge of an isothermal plate. The study includes situations in which gravity varies by virtue of the varying slope of a surface. A general integral solution method which includes certain known integral solutions as special cases is developed to account for arbitrary position-dependence of gravity. A series method of solution is also developed for the full equations. Although it is more cumbersome it provides verification of the integral method.

Lienhard, J.; Eichhorn, R.; Dhir, V.

1972-01-01

135

Airflow structures and nano-particle deposition in a human upper airway model  

NASA Astrophysics Data System (ADS)

Considering a human upper airway model, or equivalently complex internal flow conduits, the transport and deposition of nano-particles in the 1-150 nm diameter range are simulated and analyzed for cyclic and steady flow conditions. Specifically, using a commercial finite-volume software with user-supplied programs as a solver, the Euler-Euler approach for the fluid-particle dynamics is employed with a low-Reynolds-number k- ? model for laminar-to-turbulent airflow and the mass transfer equation for dispersion of nano-particles or vapors. Presently, the upper respiratory system consists of two connected segments of a simplified human cast replica, i.e., the oral airways from the mouth to the trachea (Generation G0) and an upper tracheobronchial tree model of G0-G3. Experimentally validated computational fluid-particle dynamics results show the following: (i) transient effects in the oral airways appear most prominently during the decelerating phase of the inspiratory cycle; (ii) selecting matching flow rates, total deposition fractions of nano-size particles for cyclic inspiratory flow are not significantly different from those for steady flow; (iii) turbulent fluctuations which occur after the throat can persist downstream to at least Generation G3 at medium and high inspiratory flow rates (i.e., Qin?30 l/min) due to the enhancement of flow instabilities just upstream of the flow dividers; however, the effects of turbulent fluctuations on nano-particle deposition are quite minor in the human upper airways; (iv) deposition of nano-particles occurs to a relatively greater extent around the carinal ridges when compared to the straight tubular segments in the bronchial airways; (v) deposition distributions of nano-particles vary with airway segment, particle size, and inhalation flow rate, where the local deposition is more uniformly distributed for large-size particles (say, dp=100 nm) than for small-size particles (say, dp=1 nm); (vi) dilute 1 nm particle suspensions behave like certain (fuel) vapors which have the same diffusivities; and (vii) new correlations for particle deposition as a function of a diffusion parameter are most useful for global lung modeling.

Zhang, Z.; Kleinstreuer, C.

2004-07-01

136

Numerical simulation of normal nasal cavity airflow in Chinese adult: a computational flow dynamics model.  

PubMed

Our purpose is to simulate the airflow inside the healthy Chinese nose with normal nasal structure and function by computational fluid dynamics (CFD) method and to analyze the relationship between the airflow and physiological function. In this study, we used the software MIMICS 13.0 to construct 20 3-dimensional (3-D) models based on the computer tomography scans of Chinese adults' nose with normal nasal structure and function. Thereafter, numerical simulations were carried out using the software FLUENT 6.3. Then the characteristics of airflow inside the airway and sinuses were demonstrated qualitatively and quantitatively in steady state. We found that during the inhalation phase, the vortices and turbulences were located at anterior part and bottom of the nasal cavity. But there is no vortex in the whole nasal cavity during the expiratory phase. The distributions of pressure and wall shear stress are different in two phases. The maximum airflow velocity occurs around the plane of palatine velum during both inspiratory and expiratory phases. After the airflow passed the nasal valve, the peak velocity of inhaled airflow decreases and it increases again at the postnaris. Vice versa, the exhaled airflow decelerates after it passed the postnaris and it accelerates again at nasal valve. The data collected in this presentation validates the effectiveness of CFD simulation in the study of airflow in the nasal cavity. Nasal airflow is closely related to the structure and physiological functions of the nasal cavity. CFD may thus also be used to study nasal airflow changes resulting from abnormal nasal structure and nasal diseases. PMID:21938528

Tan, Jie; Han, Demin; Wang, Jie; Liu, Ting; Wang, Tong; Zang, Hongrui; Li, Yunchuan; Wang, Xiangdong

2012-03-01

137

Deterministic Particle Trapping in Laminar Microvortices  

NASA Astrophysics Data System (ADS)

We present a method of deterministic trapping of particles larger than a critical size in laminar microscale vortices. This novel phenomenon is observed in microchannels containing a straight channel with periodic expansion and contraction arrays. High fluid flow rates in the laminar regime create a detached boundary layer in each array producing two symmetric fluid recirculation zones. Particles introduced into the straight channel experience two lateral lift forces due to shear gradient and wall effect when inertia is important. As particles approach the expansion, larger shear gradient lift induces larger particles to migrate laterally across streamlines and into the vortex, since the balancing wall-effect lift is no longer significant immediately after the expansion. Smaller particles are maintained in streamlines that flow out of the device because they experience less shear gradient lift--scaling with particle diameter cubed. We identify the hydrodynamic forces responsible for the trapping mechanism, determine the critical particle size for trapping and present potential biological applications in concentrating cells from complex samples using this phenomenon.

Mach, Albert; di Carlo, Dino

2010-11-01

138

A Series of Laminar Jet Flame  

NASA Technical Reports Server (NTRS)

Study of the downlink data from the Laminar Soot Processes (LSP) experiment quickly resulted in discovery of a new mechanism of flame extinction caused by radiation of soot. Scientists found that the flames emit soot sooner than expected. These findings have direct impact on spacecraft fire safety, as well as the theories predicting the formation of soot -- which is a major factor as a pollutant and in the spread of unwanted fires. This sequence, using propane fuel, was taken STS-94, July 4 1997, MET:2/05:30 (approximate). LSP investigated fundamental questions regarding soot, a solid byproduct of the combustion of hydrocarbon fuels. The experiment was performed using a laminar jet diffusion flame, which is created by simply flowing fuel-like ethylene or propane -- through a nozzle and igniting it, much like a butane cigarette lighter. The LSP principal investigator was Gerard Faeth, University of Michigan, Arn Arbor. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). LSP results led to a reflight for extended investigations on the STS-107 research mission in January 2003. Advanced combustion experiments will be a part of investigations planned for the International Space Station. (249KB JPEG, 1350 x 1524 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300185.html.

2003-01-01

139

Series of Laminar Soot Processes Experiment  

NASA Technical Reports Server (NTRS)

Study of the downlink data from the Laminar Soot Processes (LSP) experiment quickly resulted in discovery of a new mechanism of flame extinction caused by radiation of soot. Scientists found that the flames emit soot sooner than expected. These findings have direct impact on spacecraft fire safety, as well as the theories predicting the formation of soot -- which is a major factor as a pollutant and in the spread of unwanted fires. This sequence was taken July 15, 1997, MET:14/10:34 (approximate) and shows the ignition and extinction of this flame. LSP investigated fundamental questions regarding soot, a solid byproduct of the combustion of hydrocarbon fuels. The experiment was performed using a laminar jet diffusion flame, which is created by simply flowing fuel -- like ethylene or propane -- through a nozzle and igniting it, much like a butane cigarette lighter. The LSP principal investigator was Gerard Faeth, University of Michigan, Arn Arbor. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). LSP results led to a reflight for extended investigations on the STS-107 research mission in January 2003. Advanced combustion experiments will be a part of investigations planned for the International Space Station. (189KB JPEG, 1350 x 1517 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300183.html.

2003-01-01

140

Gliding Swifts Attain Laminar Flow over Rough Wings  

PubMed Central

Swifts are among the most aerodynamically refined gliding birds. However, the overlapping vanes and protruding shafts of their primary feathers make swift wings remarkably rough for their size. Wing roughness height is 1–2% of chord length on the upper surface—10,000 times rougher than sailplane wings. Sailplanes depend on extreme wing smoothness to increase the area of laminar flow on the wing surface and minimize drag for extended glides. To understand why the swift does not rely on smooth wings, we used a stethoscope to map laminar flow over preserved wings in a low-turbulence wind tunnel. By combining laminar area, lift, and drag measurements, we show that average area of laminar flow on swift wings is 69% (n?=?3; std 13%) of their total area during glides that maximize flight distance and duration—similar to high-performance sailplanes. Our aerodynamic analysis indicates that swifts attain laminar flow over their rough wings because their wing size is comparable to the distance the air travels (after a roughness-induced perturbation) before it transitions from laminar to turbulent. To interpret the function of swift wing roughness, we simulated its effect on smooth model wings using physical models. This manipulation shows that laminar flow is reduced and drag increased at high speeds. At the speeds at which swifts cruise, however, swift-like roughness prolongs laminar flow and reduces drag. This feature gives small birds with rudimentary wings an edge during the evolution of glide performance.

Lentink, David; de Kat, Roeland

2014-01-01

141

Gliding Swifts Attain Laminar Flow over Rough Wings.  

PubMed

Swifts are among the most aerodynamically refined gliding birds. However, the overlapping vanes and protruding shafts of their primary feathers make swift wings remarkably rough for their size. Wing roughness height is 1-2% of chord length on the upper surface-10,000 times rougher than sailplane wings. Sailplanes depend on extreme wing smoothness to increase the area of laminar flow on the wing surface and minimize drag for extended glides. To understand why the swift does not rely on smooth wings, we used a stethoscope to map laminar flow over preserved wings in a low-turbulence wind tunnel. By combining laminar area, lift, and drag measurements, we show that average area of laminar flow on swift wings is 69% (n?=?3; std 13%) of their total area during glides that maximize flight distance and duration-similar to high-performance sailplanes. Our aerodynamic analysis indicates that swifts attain laminar flow over their rough wings because their wing size is comparable to the distance the air travels (after a roughness-induced perturbation) before it transitions from laminar to turbulent. To interpret the function of swift wing roughness, we simulated its effect on smooth model wings using physical models. This manipulation shows that laminar flow is reduced and drag increased at high speeds. At the speeds at which swifts cruise, however, swift-like roughness prolongs laminar flow and reduces drag. This feature gives small birds with rudimentary wings an edge during the evolution of glide performance. PMID:24964089

Lentink, David; de Kat, Roeland

2014-01-01

142

Microphone Detects Waves In Laminar Boundary-Layer Flow  

NASA Technical Reports Server (NTRS)

Simple noninvasive acoustical technique effective in measurement of instability waves, which precede onset of turbulence in laminar boundary layer flows. Microphone mounted below surface detects pressure waves indicative of instabilities in laminar flow. Relatively insensitive to long-wavelength background noise. Such measurements important in research on aerodynamic flows and potential applications in control of turbulence (with consequent reduction of drag) on aircraft.

Kendall, James M.

1990-01-01

143

Windtunnel as a Tool for Laminar Flow Research.  

National Technical Information Service (NTIS)

Testing laminar airfoils or wings in the wind tunnel, entails some specific experimental problems. These problems are discussed in the paper using the (limited) experience of laminar flow tests made in the High Speed Wind Tunnel HST of NLR. Special measur...

A. Elsenaar

1990-01-01

144

Airflow design for cleanrooms and its economic implications  

SciTech Connect

A cleanroom is designed to control the concentration of airborne particles. As a result, large amount of cleaned air is often required to remove or dilute contaminants for satisfactory operations in critical cleanroom environment. Cleanroom environmental systems (HVAC systems) in semiconductor, pharmaceutical, and healthcare industries are much more energy intensive compared to their counterparts (HVAC systems) serving commercial buildings such as typical office buildings. There is a tendency in cleanroom design and operation, however, to provide excessive airflow rates by HVAC systems, largely due to design conservatism, lack of understanding in airflow requirements, and more often, concerns such as cleanliness reliability, design and operational liabilities. A combination of these likely factors can easily result in HVAC systems' over-design. Energy use of cleanroom environmental systems varies with the system design, cleanroom functions, and critical parameter control including temperatures and humidities. In particular, cleanroom cleanliness requirements specified by ''cleanliness class'' [1],[2] often cast large impact on energy use. A review of studies on cleanroom operation costs indicated that energy costs could amount to 65-75% of the total annual cost associated with cleanroom operation and maintenance in some European countries[3]. Depending on cleanroom cleanliness classes, annual cleanroom electricity use for cooling and fan energy ranged approximately between 1,710 kWh/m{sup 2} and 10,200 kWh/m{sup 2} (or 160 kWh/ft{sup 2} and 950 kWh/ft{sup 2}) in California[4], USA. Cleanroom fan energy use typically consumed half of total HVAC energy use in three states in the USA[5]. For cleanrooms in a wafer-process semiconductor factory in Japan[6], HVAC systems used 43% of power consumption of an entire cleanroom factory, while air delivery systems account for 30% of the total power consumption. Fan energy use for cleanrooms of ISO Classes 3,4,5 collectively account for approximately 80% of the fan energy use for cleanrooms of all classes[7]. It is evident that biggest factors dictating cleanroom operating energy costs often include the magnitude of cleanroom airflow and how efficiently the HVAC systems deliver the cleaned and conditioned air to cleanrooms. Since energy generally represents a significant operating cost for cleanroom facilities, improving energy efficiency in cleanrooms can potentially contribute to significant cost savings. Because the number of cleanrooms in the world has been growing rapidly in the last decade and involves many industries, improvement in energy efficiency is becoming more important. Even during economy downturns, with industry profit margins lessening, the ratio of cleanroom energy costs to a company's profits naturally increases. This can lead to a higher return of investment if cleanroom owners and engineers effectively take appropriate energy efficiency measures. While effective contamination control is the main purpose to operate a cleanroom, how to achieve efficient contamination control operations in cleanrooms presents constant challenges to many engineers in the industries. This paper examines how the real environmental systems in ISO Cleanliness Class-5 cleanrooms actually performed, in terms of airflow and energy use required by fan systems, and presents opportunities and benefits in energy efficient cleanroom designs. The objectives of this paper are to (1) present performance analysis for HVAC systems in seven ISO Cleanliness Class-5 cleanrooms; (2) identify ways to increase cleanroom energy efficiency, while achieving effective cleanroom contamination control; and (3) illustrate benefits of energy efficient cleanroom designs.

Xu, Tengfang

2002-08-20

145

Airflow pattern around a worker in a uniform freestream.  

PubMed

The effect of boundary layer separation on worker exposure is an important factor in the design of local exhaust ventilation. Three-dimensional airflow around a mannequin is examined by using flow visualization techniques and hot-film anemometry. Above the chest, a downwash effect is noted; from the chest to the elbows, a combination of downwash and vortex shedding is observed; and from the waist to the hip, vortex shedding appears to be dominant. A coherent vertical flow structure is observed close to the body. Vortex shedding frequency is determined by using hot-film anemometry. The dimensions of the reverse flow region and the area of the vortices are estimated from flow visualization videos. PMID:1835278

Kim, T; Flynn, M R

1991-07-01

146

Gas turbine airflow control for optimum heat recovery  

SciTech Connect

Gas turbines furnished with heat recovery equipment generally have maximum cycle efficiency when the gas turbine is operated at its ambient capability. At reduced gas turbine output the cycle performance can fall off rapidly as gas turbine exhaust temperature drops, which reduces the heat recovery equipment performance. This paper reviews the economic gains which can be realized through use of several control modes which are currently available to optimize the cycle efficiency at part load operation. These include variable inlet guide vane (VIGV) control for singleshaft units, and combined VIGV and variable high-pressure set (compressor) speed control for two-shaft units. In addition to the normal control optimization mode to maintain the maximum exhaust temperature, a new control mode is discussed which allows airflow to be modulated in response to a process signal while at constant part load. This control feature is desirable for gas turbines which supply preheated combustion air to fired process heaters.

Rowen, W.I.; Van Housen, R.L.

1983-01-01

147

Simulation of Airflow in Kashmir Valley for a Summer Day.  

NASA Astrophysics Data System (ADS)

The airflow over the Kashmir Valley for a summer day was studied using a numerical mesoscale model. Srinagar observations were used as initial data. The surface orography, soil moisture variations, cloud cover, and vegetation effects were included in the computations. The combined effect of these factors on the development of atmospheric circulations in the valley was obtained quantitatively, and the three-dimensional model simulated results are compared with available observations. The following principal results were obtained. (a) The simulated surface temperature pattern shows a close correlation with the terrain elevations and prevailing atmospheric stabilities, (b) the intensities of katabatic and anabatic winds developed at the slopes are governed by terrain asymmetries and aspect ratio of the slopes, (c) the boundary layer depths developed at different locations in the valley are found to be nonuniform, and (d) the convergence zone formed during nighttime shows an irregular distribution.

Ramanathan, N.; Srinivasan, K.

1998-05-01

148

Thermal signatures help deduce evaporative fluxes into turbulent airflows  

NASA Astrophysics Data System (ADS)

Evaporative fluxes and energy balance of terrestrial surfaces are affected by interplay between water availability, energy input, and exchange across the air boundary layer. Commonly occurring turbulent airflows impose complex and highly dynamic boundary conditions that challenge prediction of surface evaporation rates. During stage-I evaporation where the vaporization plane is at the surface, intermittent turbulent interactions with the surface give rise to distinct thermal signatures that could be recorded using infrared thermography (IRT). The study links measured thermal signatures with spatio-temporal distribution of eddy-induced localized evaporation rates towards characterization of turbulent momentum field and estimation of overall evaporative fluxes. Results highlight potential of the approach for remote quantification of interactions between turbulent eddies and evaporating surfaces. Surface thermal inertia present a challenge to high resolution implementation, and strategies for overcoming these are presented including applications to plant canopies (low thermal inertia surfaces). Applications for larger scales will be discussed.

Haghighi, E.; Or, D.

2013-12-01

149

Effect of airflow on biodrying of gardening wastes in reactors.  

PubMed

Biodrying consists of reducing moisture by using the heat from aerobic bio-degradation. The parameters that control the process are: aeration, temperature during the process, initial moisture of biowaste, and temperature and relative humidity of the input air. Lawn mowing and garden waste from the gardens of the University Jaume I, Castellón (Spain) were used as a substrate. Biodrying was performed in 10 reactors with known air volumes from 0.88 to 6.42 L/(min x kg dry weight). To promote aeration, 5 of the reactors had 15% of a bulking agent added. The experiment lasted 20 days. After the experiments it was found that the bulking agent led to greater weight loss. However, the increased airflow rate was not linearly proportional to the weight loss. PMID:24218815

Colomer-Mendoza, F J; Herrera-Prats, L; Robles-Martínez, F; Gallardo-Izquierdo, A; Piña-Guzmán, A B

2013-05-01

150

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

151

The role of the olfactory recess in olfactory airflow.  

PubMed

The olfactory recess - a blind pocket at the back of the nasal airway - is thought to play an important role in mammalian olfaction by sequestering air outside of the main airstream, thus giving odorants time to re-circulate. Several studies have shown that species with large olfactory recesses tend to have a well-developed sense of smell. However, no study has investigated how the size of the olfactory recess relates to air circulation near the olfactory epithelium. Here we used a computer model of the nasal cavity from a bat (Carollia perspicillata) to test the hypothesis that a larger olfactory recess improves olfactory airflow. We predicted that during inhalation, models with an enlarged olfactory recess would have slower rates of flow through the olfactory region (i.e. the olfactory recess plus airspace around the olfactory epithelium), while during exhalation these models would have little to no flow through the olfactory recess. To test these predictions, we experimentally modified the size of the olfactory recess while holding the rest of the morphology constant. During inhalation, we found that an enlarged olfactory recess resulted in lower rates of flow in the olfactory region. Upon exhalation, air flowed through the olfactory recess at a lower rate in the model with an enlarged olfactory recess. Taken together, these results indicate that an enlarged olfactory recess improves olfactory airflow during both inhalation and exhalation. These findings add to our growing understanding of how the morphology of the nasal cavity may relate to function in this understudied region of the skull. PMID:24577441

Eiting, Thomas P; Smith, Timothy D; Perot, J Blair; Dumont, Elizabeth R

2014-05-15

152

High-dose inhaled albuterol in severe chronic airflow limitation.  

PubMed

Higher doses of inhaled albuterol have been shown to cause slightly more bronchodilatation than standard doses from a metered-dose inhaler in patients with severe chronic airflow limitation. Higher doses, however, carry an increased risk of side effects, and the optimum dose balancing benefit and adverse effects have yet to be established. We have therefore looked at objective and subjective evidence of beneficial and adverse effects after 4 doses of albuterol in 30 patients with chronic bronchitis, severe airflow limitation, and less than 200 ml increase in FEV1 after 200 micrograms inhaled albuterol. Subjects were given placebo, 400 micrograms, 1 mg, 2 mg, and 4 mg albuterol by dry powder inhaler in random order on separate days in a double-blind study, and FEV1, relaxed VC, PEFR, 12-min walk distance, finger tremor, oxygen saturation, heart rate, and arrhythmias were measured at intervals over 6 h. With increasing doses of albuterol, there was a significant dose-related increase in FEV1, VC, and PEFR, the maximal mean changes being 196 ml, 480 ml, and 50 L/min, respectively. The duration of effect was longer with the higher doses. There was a dose-related increase in heart rate, tremor amplitude, and supraventricular ectopic beats and a dose-related fall in oxygen saturation. There was no drug-related effect on the frequency of ventricular ectopic beats either at rest or during the walk tests. The largest increases in walk distance occurred after the 1 and 2 mg doses and the least after the 4 mg dose.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2462383

Vathenen, A S; Britton, J R; Ebden, P; Cookson, J B; Wharrad, H J; Tattersfield, A E

1988-10-01

153

Laminar Premixed and Diffusion Flames (Ground-Based Study)  

NASA Technical Reports Server (NTRS)

Ground-based studies of soot processes in laminar flames proceeded in two phases, considering laminar premixed flames and laminar diffusion flames, in turn. The test arrangement for laminar premixed flames involved round flat flame burners directed vertically upward at atmospheric pressure. The test arrangement for laminar jet diffusion flames involved a round fuel port directed vertically upward with various hydrocarbon fuels burning at atmospheric pressure in air. In both cases, coflow was used to prevent flame oscillations and measurements were limited to the flame axes. The measurements were sufficient to resolve soot nucleation, growth and oxidation rates, as well as the properties of the environment needed to evaluate mechanisms of these processes. The experimental methods used were also designed to maintain capabilities for experimental methods used in corresponding space-based experiments. This section of the report will be limited to consideration of flame structure for both premixed and diffusion flames.

Dai, Z.; El-Leathy, A. M.; Lin, K.-C.; Sunderland, P. B.; Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

2000-01-01

154

Data Visualization of Invisible Airflow Hazards During Helicopter Takeoff and Landing Operations  

NASA Technical Reports Server (NTRS)

Many aircraft accidents each year are caused by encounters with unseen airflow hazards near the ground such as vortices, downdrafts, wind shear, microbursts, or other turbulence. While such hazards frequently pose problems to fixed-wing airplanes, they are especially dangerous to helicopters, which often have to operate in confined spaces and under operationally stressful conditions. We are developing flight-deck visualizations of airflow hazards during helicopter takeoff and landing operations, and are evaluating their effectiveness with usability studies. Our hope is.that this work will lead to the production of an airflow hazard detection system for pilots that will save lives.

Aragon, Cecilia R.

2004-01-01

155

Quantification of reactive mixing in laminar microflows  

NASA Astrophysics Data System (ADS)

We propose numerical methods for the estimation of the yield of reaction in laminar flows. The methods are based on backward tracking of tracer particles. In the case of fast reaction (high Damköhler number) the degree of mixing at a particular point can be calculated by a backward random-walk Monte Carlo simulation. This procedure is applicable for both chaotic and nonchaotic regions. In a chaotic flow the reaction-diffusion equation can be approximated by a one-dimensional equation in Lagrangian coordinates along the stable manifold of a fluid element. An adaptive tracking technique of the stable manifold allows the numerical quantification of the effect of the flow on a finite rate chemistry.

Vikhansky, A.

2004-12-01

156

On the combustion of a laminar spray  

NASA Technical Reports Server (NTRS)

A spray combustor, with flow velocities in the laminar range, exhibits a unique operating mode where large amplitude, self-induced oscillations of the flame shape occur. The phenomenon, not previously encountered, only occurs when fuel is supplied in the form of fine liquid droplets and does not occur when fuel is supplied in gaseous form. Several flow mechanisms are coupled in such a fashion as to trigger and maintain the oscillatory motion of the flame. These mechanisms include heat transfer and evaporation processes, dynamics of two-phase flows, and effects of gravity (buoyancy forces). An interface volume, lying above the fuel nozzle and below the flame was found to be the most susceptible to gravity effects and postulated to be responsible for inducing the oscillatory motion. Heptane fuel was used in the majority of the tests. Tests performed with iso-octane also showed similar results.

Levy, Yeshayahou; Bulzan, Daniel L.

1993-01-01

157

Base pressure in laminar supersonic flow.  

NASA Technical Reports Server (NTRS)

An asymptotic description is proposed for supersonic laminar flow over a wedge or a backward-facing step, for large Reynolds number and for a base or step height which is small compared with the boundary-layer length. The analysis is carried out for adiabatic wall conditions and a viscosity coefficient proportional to temperature. In a particular limit corresponding to a very thick boundary layer, a similarity law is obtained for the base pressure. For a thinner boundary layer an asymptotic form for the base pressure is obtained which shows the dependence on the parameters explicitly and which permits good agreement with experiment. This latter result is based on an inviscid-flow approximation for the corner expansion and for reattachment with viscous forces important primarily in a thin sublayer about the dividing streamline. A prediction of the pressure distribution at reattachment is given and the result is compared with experimental pressure distributions.

Messiter, A. F.; Hough, G. R.; Feo, A.

1973-01-01

158

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

159

Laminar superlayer at the turbulence boundary.  

PubMed

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. PMID:21517388

Holzner, M; Lüthi, B

2011-04-01

160

Laminar flow control perforated wing panel development  

NASA Technical Reports Server (NTRS)

Many structural concepts for a wing leading edge laminar flow control hybrid panel were analytically investigated. After many small, medium, and large tests, the selected design was verified. New analytic methods were developed to combine porous titanium sheet bonded to a substructure of fiberglass and carbon/epoxy cloth. At -65 and +160 F test conditions, the critical bond of the porous titanium to the composite failed at lower than anticipated test loads. New cure cycles, design improvements, and test improvements significantly improved the strength and reduced the deflections from thermal and lateral loadings. The wave tolerance limits for turbulence were not exceeded. Consideration of the beam column midbay deflections from the combinations of the axial and lateral loadings and thermal bowing at -65 F, room temperature, and +160 F were included. Many lap shear tests were performed at several cure cycles. Results indicate that sufficient verification was obtained to fabricate a demonstration vehicle.

Fischler, J. E.

1986-01-01

161

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

162

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

163

Current Laminar Flow Control Experiments at NASA Dryden  

NASA Technical Reports Server (NTRS)

An experiment to demonstrate laminar flow over the swept wing of a subsonic transport is being developed. Discrete Roughness Elements are being used to maintain laminar flow over a substantial portion of a wing glove. This passive laminar flow technology has only come to be recognized as a significant player in airliner drag reduction in the last few years. NASA is implementing this experiment and is planning to demonstrate this technology at full-scale Bight cruise conditions of a small-to-medium airliner.

Bowers, Al

2010-01-01

164

Inductively coupled plasma torch with laminar flow cooling  

DOEpatents

An improved inductively coupled gas plasma torch. The torch includes inner and outer quartz sleeves and tubular insert snugly fitted between the sleeves. The insert includes outwardly opening longitudinal channels. Gas flowing through the channels of the insert emerges in a laminar flow along the inside surface of the outer sleeve, in the zone of plasma heating. The laminar flow cools the outer sleeve and enables the torch to operate at lower electrical power and gas consumption levels additionally, the laminar flow reduces noise levels in spectroscopic measurements of the gaseous plasma.

Rayson, Gary D. (Las Cruces, NM); Shen, Yang (Las Cruces, NM)

1991-04-30

165

Laminar Flow Control Leading Edge Systems in Simulated Airline Service  

NASA Technical Reports Server (NTRS)

Achieving laminar flow on the wings of a commercial transport involves difficult problems associated with the wing leading edge. The NASA Leading Edge Flight Test Program has made major progress toward the solution of these problems. The effectiveness and practicality of candidate laminar flow leading edge systems were proven under representative airline service conditions. This was accomplished in a series of simulated airline service flights by modifying a JetStar aircraft with laminar flow leading edge systems and operating it out of three commercial airports in the United States. The aircraft was operated as an airliner would under actual air traffic conditions, in bad weather, and in insect infested environments.

Wagner, R. D.; Maddalon, D. V.; Fisher, D. F.

1988-01-01

166

Effects of high-speed airflows on a surface dielectric barrier discharge  

NASA Astrophysics Data System (ADS)

A detailed study of the interaction between high-speed gas flows and surface dielectric barrier discharges (DBD) is presented. In the present paper, it is demonstrated that a DBD can be sustained in transonic airflows, up to isentropic Mach numbers of 1.1. The plasma is characterized electrically, as well as optically with a CCD camera and a photomultiplier tube. Different airflow velocities, plasma excitation frequencies and voltages are investigated. The airflow has a significant influence on the plasma characteristics: the glow component is reduced, the discharge becomes more filamentary and most importantly, the light emission duration from individual microdischarges is reduced by more than a factor of ten at high flow velocities. Large edge effects play a key role in the interaction between the flow and the plasma. These results offer new perspectives for the use of dielectric barrier discharges in transonic and supersonic gas flows and their applications to airflow control and to plasma-assisted combustion.

Pavon, S.; Dorier, J.-L.; Hollenstein, Ch; Ott, P.; Leyland, P.

2007-03-01

167

42 CFR 84.1149 - Airflow resistance tests; all dust, fume, and mist respirators; minimum requirements.  

Code of Federal Regulations, 2010 CFR

...RESPIRATORY PROTECTIVE DEVICES Dust, Fume, and Mist; Pesticide; Paint...Airflow resistance tests; all dust, fume, and mist respirators; minimum...in the facepiece, mouthpiece, hood, or helmet of a dust, fume, or mist respirator mounted...

2009-10-01

168

42 CFR 84.1149 - Airflow resistance tests; all dust, fume, and mist respirators; minimum requirements.  

Code of Federal Regulations, 2010 CFR

...RESPIRATORY PROTECTIVE DEVICES Dust, Fume, and Mist; Pesticide; Paint...Airflow resistance tests; all dust, fume, and mist respirators; minimum...in the facepiece, mouthpiece, hood, or helmet of a dust, fume, or mist respirator mounted...

2010-10-01

169

Fabrication, characterization, and simulation of a cantilever-based airflow sensor integrated with optical fiber.  

PubMed

In this paper, we present the fabrication and packaging of a cantilever-based airflow sensor integrated with optical fiber. The sensor consists of a micro Fabry-Perot (FP) cavity including a fiber and a micro cantilever that is fabricated using the photolithography method. Airflow causes a small deflection of the micro cantilever and changes the cavity length of the FP, which makes the fringe shift. The pressure distribution and velocity streamlines across the cantilever resulted from the airflow in the channel have been simulated by the finite element method. The experimental results demonstrate that the sensor has a linear sensitivity of 190 [fringe shift (pm)] per (l/min) and a minimum detectable airflow change of 0.05 (l/min). PMID:23669859

Cheri, M Sadegh; Latifi, Hamid; Aghbolagh, F Beygi Azar; Naeini, O R Ranjbar; Taghavi, Majid; Ghaderi, Mohammadamir

2013-05-10

170

Airflow and Hail Growth in Supercell Storms and Some Implications for Suppression.  

National Technical Information Service (NTIS)

Multiple radar and aircraft observations of a damaging supercell hailstorm in northeastern Colorado are synthesized to show that the airflow and hail growth conformed in many respects to earlier models derived by the lead author. Some features that before...

K. A. Browning G. B. Foote

1975-01-01

171

Contribution of laminar myofiber architecture to load- dependent changes in mechanics of LV myocardium  

Microsoft Academic Search

THE VENTRICULAR MYOCARDIUM consists of a syncytium of myocytes organized into branching transmurally ori- ented laminar sheets approximately four cells thick (14). Recent evidence indicates that this laminar struc- ture contributes importantly to systolic function. When systolic deformation is expressed in an axis system determined by the anatomy of the laminar architec- ture, laminar sheets of myocytes shear and laterally

YASUO TAKAYAMA; KEVIN D. COSTA; JAMES W. COVELL

2002-01-01

172

In Vitro Experiments and Numerical Simulations of Airflow in Realistic Nasal Airway Geometry  

Microsoft Academic Search

Pressure–flow relationships measured in human plastinated specimen of both nasal cavities and maxillary sinuses were compared to those obtained by numerical airflow simulations in a numerical three-dimensional reconstruction issued from CT scans of the plastinated specimen. For experiments, flow rates up to 1500 ml\\/s were tested using three different gases: HeO2, Air, and SF6. Numerical inspiratory airflow simulations were performed for

Céline Croce; Redouane Fodil; Marc Durand; Gabriela Sbirlea-Apiou; Georges Caillibotte; Jean-François Papon; Jean-Robert Blondeau; André Coste; Daniel Isabey; Bruno Louis

2006-01-01

173

Bioinspired carbon nanotube fuzzy fiber hair sensor for air-flow detection.  

PubMed

Artificial hair sensors consisting of a piezoresistive carbon-nanotube-coated glass fiber embedded in a microcapillary are assembled and characterized. Individual sensors resemble a hair plug that may be integrated in a wide range of host materials. The sensors demonstrate an air-flow detection threshold of less than 1 m/s with a piezoresistive sensitivity of 1.3% per m/s air-flow change. PMID:24665067

Maschmann, Matthew R; Ehlert, Gregory J; Dickinson, Benjamin T; Phillips, David M; Ray, Cody W; Reich, Greg W; Baur, Jeffery W

2014-05-01

174

Experimental study of airflow and particle characteristics of a 300-mm POUP\\/LPU minienvironment system  

Microsoft Academic Search

This study examines the airflow and particle characteristics of a front opening unified pod\\/load port unit (FOUP\\/LPU) minienvironment system. The airflow and particle number were measured by using a three-dimensional ultrasonic anemometer and an He-Ne laser airborne particle counter, respectively. A large vortex is produced below an extracted wafer in the minienvironment. This vortex extends to the lower part of

Shih-Cheng Hu; Tzong-Ming Wu

2003-01-01

175

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

176

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

177

Evaluation of circumferential airflow uniformity entering combustors from compressors. Volume 2: Data supplement  

NASA Technical Reports Server (NTRS)

A study of the airflow uniformity leaving compressors and entering combustors was made using compressors from two advanced engines, the J58 and F100/F401. The data used in the analysis of each case is presented in tabular form and computer-generated profile plots. A plot of the square root of the dynamic pressure ratio, which is similar to airflow deviation, is also presented.

Shadowen, J. H.; Egan, W. J., Jr.

1972-01-01

178

Chronic airflow limitation in developing countries: burden and priorities  

PubMed Central

Respiratory disease has never received priority in relation to its impact on health. Estimated DALYs lost in 2002 were 12% globally (similar for industrialized and developing countries). Chronic airflow limitation (due mainly to asthma and COPD) alone affects more than 100 million persons in the world and the majority of them live in developing countries. International guidelines for management of asthma (GINA) and COPD (GOLD) have been adopted and their cost-effectiveness demonstrated in industrialized countries. As resources are scarce in developing countries, adaptation of these guidelines using only essential drugs is required. It remains for governments to set priorities. To make these choices, a set of criteria have been proposed. It is vital that the results of scientific investigations are presented in these terms to facilitate their use by decision-makers. To respond to this emerging public health problem in developing countries, WHO has developed 2 initiatives: “Practical Approach to Lung Health (PAL)” and the Global Alliance Against Chronic Respiratory Diseases (GARD)”, and the International Union Against Tuberculosis and Lung Diseases (The Union) has launched a new initiative to increase affordability of essential asthma drugs for patients in developing countries termed the “Asthma Drug Facility” (ADF), which could facilitate the care of patients living in these parts of the world.

Ait-Khaled, Nadia; Enarson, Donald A; Ottmani, Salah; Sony, Asma El; Eltigani, Mai; Sepulveda, Ricardo

2007-01-01

179

Evaluation of airflow patterns following procedures established by NUREG-1400  

SciTech Connect

The U.S. Nuclear Regulatory Commission's NUREG-1400 addresses many aspects of air sampling in the work place. Here, we present two detailed examples of the implementation of qualitative air flow studies at different scales using guidelines established by NUREG-1400. In one test, smoke was used to evaluate the airflow patterns within the transfer area of the 105 KE Basin, located on the Hanford Site, Richland, Washington. The purpose of the study was to determine appropriate locations for air monitoring equipment in support of sludge water pumping activities. 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 air flow study, the stagnant layer would not have been identified, and could have resulted in locating 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.

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

2006-07-26

180

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

2013-08-01

181

Cigarette smoke potentiates asbestos-induced airflow abnormalities  

SciTech Connect

It has been suggested that exposure to both asbestos and cigarette smoke can produce worse parenchymal lung disease than exposure to asbestos alone. Using a guinea pig model of asbestos administration that produces primarily airway disease and associated airflow abnormalities, we showed previously that the combination of asbestos and smoke acts synergistically to produce more marked increases in tissue collagen, fibrosis of airway walls, and early interstitial fibrosis than are seen with asbestos alone. To investigate the functional effects of these morphological and biochemical abnormalities, pulmonary function tests for volumes and flows, including lung volumes, pressure-volume curves, and flow-volume curves, were performed. By themselves, both smoke and asbestos produced increases in total lung capacity (TLC), residual volume (RV), and functional residual capacity (FRC); the two agents together made all these changes worse than either one alone. Both smoking and asbestos moved the pressure-volume curve upward, and the effects of the two agents together were again greater than either alone. Similarly, both smoke and asbestos decreased flows, and the two agents produced more severe impairment than either one by itself. The changes in volumes, pressure-volume curve, and flows correlated with both increased thickness of small airway walls and increases in airspace size. These observations indicate that, at least in this guinea pig model, cigarette smoke can potentiate the functional consequences of asbestos exposure.

Wright, J.L.; Tron, V.; Wiggs, B.; Churg, A.

1988-01-01

182

A miniature airflow energy harvester from piezoelectric materials  

NASA Astrophysics Data System (ADS)

This paper describes design, simulation, fabrication, and testing of a miniature wind energy harvester based on a flapping cantilevered piezoelectric beam. The wind generator is based on oscillations of a cantilever that faces the direction of the airflow. The oscillation is amplified by interactions between an aerofoil attached on the cantilever and a bluff body placed in front of the aerofoil. A piezoelectric transducer with screen printed PZT materials is used to extract electrical energy. To achieve the optimum design of the harvester, both computational simulations and experiments have been carried out to investigate the structure. A prototype of the wind harvester, with the volume of 37.5 cm3 in total, was fabricated by thick-film screen printing technique. Wind tunnel test results are presented to determine the optimum structure and to characterize the performance of the harvester. The optimized device finally achieved a working wind speed range from 1.5 m/s to 8 m/s. The power output was ranging from 0.1 to 0.86 ?W and the open-circuit output voltage was from 0.5 V to 1.32 V.

Sun, H.; Zhu, D.; White, N. M.; Beeby, S. P.

2013-12-01

183

Effect of airflow setting on the organic composition of woodheater emissions.  

PubMed

Fine particle emissions from woodheaters are large contributors to ambient atmospheric pollution in a number of regional centers in Australia. The health impact of woodsmoke is not limited to the particle loading alone, and a wide range of toxic inorganic and organic compounds are also emitted as gases or adsorbed onto particles. The organic composition of woodsmoke was determined from two heater models operated using different airflow settings. Particle emission factors varied between 3 and 36 g per kg dry wood burned, with higher burn rates (open airflow) producing significantly less particle mass per kg wood burned than the low burn rates (closed airflow). Over 90 organic compounds were quantified from the vapor- and particle-phases, including furans, methoxyphenols, and other substituted aromatics, PAHs, maltols, and the sugar levoglucosan. Emission factors for the majority of the particle-phase compounds increased as the airflow was progressively closed, but decreased for some PAHs and other compounds found predominantly in the vapor-phase. Levoglucosan was the single most abundant compound, contributing 5-16% of the total particle mass. Although there was some variation in levoglucosan emissions between heater models, the fact that levoglucosan emissions vary relatively little between airflow conditions for a given heater provides the potential to use it as a general tracer for woodsmoke. In contrast, the mass fractions of many other particle-phase compounds were considerably higher when operated with a closed airflow. PMID:15952364

Jordan, Timothy B; Seen, Andrew J

2005-05-15

184

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

185

Structure, propagation, and stabilization of laminar premixed flames. Final report.  

National Technical Information Service (NTIS)

The primary objective of the funded program was to qualitatively understand and quantitatively determine the structure and dynamics of laminar premixed flames. The investigation ws conducted using laser-based experimentation, computational simulation with...

C. K. Law

1999-01-01

186

Assessment of the National Transonic Facility for Laminar Flow Testing  

NASA Technical Reports Server (NTRS)

A transonic wing, designed to accentuate key transition physics, is tested at cryogenic conditions at the National Transonic Facility at NASA Langley. The collaborative test between Boeing and NASA is aimed at assessing the facility for high-Reynolds number testing of configurations with significant regions of laminar flow. The test shows a unit Reynolds number upper limit of 26 M/ft for achieving natural transition. At higher Reynolds numbers turbulent wedges emanating from the leading edge bypass the natural transition process and destroy the laminar flow. At lower Reynolds numbers, the transition location is well correlated with the Tollmien-Schlichting-wave N-factor. The low-Reynolds number results suggest that the flow quality is acceptable for laminar flow testing if the loss of laminar flow due to bypass transition can be avoided.

Crouch, Jeffrey D.; Sutanto, Mary I.; Witkowski, David P.; Watkins, A. Neal; Rivers, Melissa B.; Campbell, Richard L.

2010-01-01

187

Numerical modelling of one-dimensional laminar pulverized coal combustion.  

National Technical Information Service (NTIS)

A model for laminar, premixed pulverized-coal flame propagation has been developed which includes particle radiation, conduction between gas and particles, and combustion of volatiles and char. Radiative heat transfer between particles is described by the...

Chinh Minh Trinh

1995-01-01

188

Combined Forced and Free Laminar Convection in Horizontal Tubes.  

National Technical Information Service (NTIS)

The report describes an experimental study of the effects of property variations, particularly density and viscosity, on fully-developed laminar flow heat transfer and pressure drop in horizontal tubes. Electrically heated glass and stainless-steel tubes ...

S. M. Morcos A. E. Bergles

1974-01-01

189

Laminar Wave Train Structure of Collisionless Magnetic Slow Shocks.  

National Technical Information Service (NTIS)

The laminar wave train structure of collisionless magnetic slow shocks is investigated using two fluid hydromagnetics with ion cyclotron radius dispersion. For shock strengths less than the maximally strong switch-off shock, in the shock leading edge disp...

F. V. Coroniti

1970-01-01

190

On Strong Slot Injection Into a Subsonic Laminar Boundary Layer.  

National Technical Information Service (NTIS)

This paper is concerned with the problem of strong slot injection into a subsonic laminar boundary layer at asymptotically high Reynolds number. The problem is formulated and the governing equations are presented within the context of triple deck theory. ...

M. Napolitano R. E. Messick

1978-01-01

191

Design of fuselage shapes for natural laminar flow  

NASA Technical Reports Server (NTRS)

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 body shaping using a computational design procedure. Analytical methods were refined and exploratory calculations conducted to predict laminar boundary-layer on selected body shapes. Using a low-order surface-singularity aerodynamic analysis program, pressure distribution, boundary-layer development, transition location and drag coefficient have been obtained for a number of body shapes including a representative business-aircraft fuselage. Extensive runs of laminar flow were predicted in regions of favorable pressure gradient on smooth body surfaces. A computational design procedure was developed to obtain a body shape with minimum drag having large extent of NLF.

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

1986-01-01

192

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

193

Prediction of laminar flame properties of propane-air mixtures  

Microsoft Academic Search

A numerical model including a detailed chemical kinetic reaction mechanism is used to study laminar flame propagation in propane-air mixtures. The effects of variations in pressure and fuel-oxidizer equivalence ratio are examined. Propane-air flames are compared with methane-air, methanol-air, and ethylene-air laminar flames. Quenching of propane-air flames in thermal boundary layers is examined, and the results are compared with previous

C. K. Westbrook; W. J. Pitz

1985-01-01

194

Prediction of laminar flame properties of propane-air mixtures  

Microsoft Academic Search

A numerical model including a detailed chemical kinetic reaction mechanism is used to study laminar flame propagation in propane-air mixtures. The effects of variations in pressure and fuel-oxidizer equivalence ratio are examined. Propane-air flames are compared with methane-air, methanol-air, and ethylene-air laminar flames. Quenching of propane-air flames in thermal boundary layers is examined, and the results are compared with previous

C. K. Westbrook; W. J. Pitz

1983-01-01

195

Clinical application of C2 laminar screw technique  

Microsoft Academic Search

C2 laminar screws have become an increasingly used alternative method to C2 pedicle screw fixation. However, the outcome of\\u000a this technique has not been thoroughly investigated. A total of 35 cases with upper cervical spinal instability undergoing\\u000a C2 laminar screw fixation were reviewed. All cases had symptoms of atlantoaxial instability, such as craniocervical junction\\u000a pain, and were fixed with the

Weihu Ma; Leling Feng; Rongming Xu; Xiaochen Liu; Alan H. Lee; Shaohua Sun; Liujun Zhao; Yong Hu; Guanyi Liu

2010-01-01

196

Natural laminar-turbulent transition delay by dielectric barrier discharge  

NASA Astrophysics Data System (ADS)

The use dielectric barrier discharge for the delay of laminar turbulent transition excited by natural flow disturbances in a quiet wind-tunnel was investigated experimentally. Optimal electrodes location and the operational regime of high-voltage impulse generator provided maximal downstream shift of transition location were found. It was demonstrated that the 10% increase of the laminar part of boundary layer can be obtained using barrier discharge with the cross-flow electrodes. This gives up to 20% friction drag reduction.

Ustinov, Maxim; Kogan, Mikhail; Litvinov, Vladimir; Uspensky, Alexander

2011-12-01

197

Natural laminar flow airfoil analysis and trade studies  

NASA Technical Reports Server (NTRS)

An analysis of an airfoil for a large commercial transport cruising at Mach 0.8 and the use of advanced computer techniques to perform the analysis are described. Incorporation of the airfoil into a natural laminar flow transport configuration is addressed and a comparison of fuel requirements and operating costs between the natural laminar flow transport and an equivalent turbulent flow transport is addressed.

1979-01-01

198

Analysis and circuit realization of intermittency with multiple laminar states  

NASA Astrophysics Data System (ADS)

In this Letter, an electrical circuit is built for realizing the multi-state intermittency generated by a simple force-driven chaotic system. The intermittency phenomenon and its underlaying mechanism are analyzed, and the experimental results are discussed. It is shown that, with two classes of invariant subspaces, the number of the laminar states and the distance between the adjacent laminar states of the created multi-state on-off intermittency can be arbitrarily changed by manipulating the control parameters.

Chen, Qingfei; Hong, Yiguang; Chen, Guanrong; Cang, Shijian; Zhong, Qiuhai

2008-02-01

199

Thermodynamics of the Laminar Donnan System.  

PubMed

Thermodynamic quantities of a polyelectroyte immersed in salt solution are derived modeling the polyelectrolyte by a sequence of charged parallel flat plates. The starting point for the analysis is the derivation of the Gibbs free enthalpy in its canonic variables pressure (p) and temperature (T), i.e., as a thermodynamic potential. From this, further thermodynamic quantities such as Helmoltz free energy, entropy, internal energy, compressibility, isobar and isochor heat capacities, and expansive force are derived in analytical expressions by differentiation. All these formulas contain the parameter plate surface charge density (sigma) that provides a measure of the discontinuity of the polymer charge distribution that can be used to fit the theory to experimental data. Thermodynamic quantities are also known from the classical Donnan equilibrium that treats the polyelectroyte charge network as a charge continuum. A limiting process is used to perform the transition from the laminar Poisson- Boltzmann model to the continuous Donnan equilibrium. In general, the expressions of the Donnan system are recovered for plate charge density sigma-->0, number of plates Z-->infinity, and sigma Z=constant. Copyright 2000 Academic Press. PMID:10926461

Dähnert; Huster

2000-08-15

200

A simplified approach to laminar separation bubbles  

NASA Astrophysics Data System (ADS)

A simple method is developed for modeling the flow and heat transfer in steady two-dimensional laminar boundary layer flows containing thin separation bubbles. The boundary layer in the local interactive region is divided into two1 layers: a viscous region near the wall and a quasi-inviscid rotational layer. The streamline which divides these two regions is somewhat arbitrary at the outset; but numerous calculations and comparisons with interacting boundary layer and triple-deck results show that, within a certain range based on the length scale of the problem, the results are insensitive to its choice. The viscous layer establishes a simple relationship between the pressure distribution and either the wall shear stress or streamline variation. Investigions of solutions to these equations show that certain constraints must be satisfied by a pressure distribution at and between separation and reattachment, thus demonstrating why difficulties are encountered in calculating through separation with a fixed pressure distribution. Furthermore, the general features of the solutions which can be obtained through an inverse method of solution be qualitatively typical of separated flows. When this model is applied to several basic geometries, solution of the nonlinear ordinary differential equation for the pressure and that for the outer elliptic flow which includes the displacement effect of the boundary layer requires only several seconds of computation time yet yields results for the boundary layer quantities of interest that agree well with results of detailed numerical investigations.

Poslusny, C. M.

1985-12-01

201

Intratracheal Bleomycin Causes Airway Remodeling and Airflow Obstruction in Mice  

PubMed Central

Introduction In addition to parenchymal fibrosis, fibrotic remodeling of the distal airways has been reported in interstitial lung diseases. Mechanisms of airway wall remodeling, which occurs in a variety of chronic lung diseases, are not well defined and current animal models are limited. Methods We quantified airway remodeling in lung sections from subjects with idiopathic pulmonary fibrosis (IPF) and controls. To investigate intratracheal bleomycin as a potential animal model for fibrotic airway remodeling, we evaluated lungs from C57BL/6 mice after bleomycin treatment by histologic scoring for fibrosis and peribronchial inflammation, morphometric evaluation of subepithelial connective tissue volume density, TUNEL assay, and immunohistochemistry for transforming growth factor ?1 (TGF?1), TGF?2, and the fibroblast marker S100A4. Lung mechanics were determined at 3 weeks post-bleomycin. Results IPF lungs had small airway remodeling with increased bronchial wall thickness compared to controls. Similarly, bleomycin treated mice developed dose-dependent airway wall inflammation and fibrosis and greater airflow resistance after high dose bleomycin. Increased TUNEL+ bronchial epithelial cells and peribronchial inflammation were noted by 1 week, and expression of TGF?1 and TGF?2 and accumulation of S100A4+ fibroblasts correlated with airway remodeling in a bleomycin dose-dependent fashion. Conclusions IPF is characterized by small airway remodeling in addition to parenchymal fibrosis, a pattern also seen with intratracheal bleomycin. Bronchial remodeling from intratracheal bleomycin follows a cascade of events including epithelial cell injury, airway inflammation, pro-fibrotic cytokine expression, fibroblast accumulation, and peribronchial fibrosis. Thus, this model can be utilized to investigate mechanisms of airway remodeling.

Polosukhin, Vasiliy V.; Degryse, Amber L.; Newcomb, Dawn C.; Jones, Brittany R.; Ware, Lorraine B.; Lee, Jae Woo; Loyd, James E.; Blackwell, Timothy S.; Lawson, William E.

2014-01-01

202

Exercise performance following a carbohydrate load in chronic airflow obstruction.  

PubMed

We evaluated the effects of a large (920 cal) liquid carbohydrate (CHO) load on the maximum exercise capacity of 18 patients with chronic airflow obstruction [forced expiratory volume at at 1 s (FEV1) = 1.27 +/- 0.48 liters; FEV1/forced vital capacity = 0.41 +/- 0.11]. Patients underwent duplicate incremental cycle ergometer exercise tests to a symptom-limited maximum following CHO and a liquid placebo in single-blind fashion. Expired gas measurements were obtained during each power output. In 12 patients arterial blood gases were measured, and in six patients venous blood was obtained for measurement of glucose, electrolytes, and osmolality. With CHO, the maximum power output decreased from 86 +/- 30 to 76 +/- 31 W (P less than 0.001), whereas the ventilation at exhaustion was nearly identical (47.6 +/- 13.2 and 46.8 +/- 12.5 l/min). Arterial partial pressure of CO2 (PaCO2) at exhaustion decreased (P less than 0.025), arterial partial pressure of O2 (PaO2) increased (P less than 0.01), and the ventilatory equivalent for CO2 (VE/VCO2) increased (P less than 0.005) with CHO. At equivalent power outputs, CHO resulted in significant increases in VE (P less than 0.001) and VCO2 (P less than 0.001); PaCO2 was unchanged, whereas PaO2 increased (P less than 0.01). CHO increased the serum glucose at rest and during exercise. No changes in serum osmolality or electrolytes occurred during exercise following CHO. After CHO loading, the majority of patients appeared to reach their limiting level of ventilation at a lower power output. In contrast, there was no significant difference in the mean maximum power output with CHO in six normal control subjects.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3921518

Brown, S E; Wiener, S; Brown, R A; Marcarelli, P A; Light, R W

1985-04-01

203

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

NASA Technical Reports Server (NTRS)

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 flames must precede understanding these processes in more complex turbulent diffusion flames. In addition, many properties of laminar diffusion flames are directly relevant to turbulent diffusion flames using laminar flamelet concepts. Laminar jet diffusion flame shapes (luminous flame boundaries) have been of particular interest since the classical study of Burke and Schumann because they are a simple nonintrusive measurement that is convenient for evaluating flame structure predictions. Thus, consideration of laminar flame shapes is undertaken in the following, emphasizing conditions where effects of gravity are small, due to the importance of such conditions to practical applications. Another class of interesting properties of laminar diffusion flames are their laminar soot and smoke point properties (i.e., the flame length, fuel flow rate, characteristic residence time, etc., at the onset of soot appearance in the flame (the soot point) and the onset of soot emissions from the flame (the smoke point)). These are useful observable soot properties of nonpremixed flames because they provide a convenient means to rate several aspects of flame sooting properties: the relative propensity of various fuels to produce soot in flames; the relative effects of fuel structure, fuel dilution, flame temperature and ambient pressure on the soot appearance and emission properties of flames; the relative levels of continuum radiation from soot in flames; and effects of the intrusion of gravity (or buoyant motion) on emissions of soot from flames. An important motivation to define conditions for soot emissions is that observations of laminar jet diffusion flames in critical environments, e.g., space shuttle and space station facilities, cannot involve soot emitting flames in order to ensure that test chamber windows used for experimental observations are not blocked by soot deposits, thereby compromising unusually valuable experimental results. Another important motivation to define conditions where soot is present in diffusion flames is that flame chemistry, transport and radiation properties are vastly simplified when soot is absent, making such flames far more tractable for detailed numerical simulations than corresponding soot-containing flames. Motivated by these observations, the objectives of this phase of the investigation were as follows: (1) Observe flame-sheet shapes (the location of the reaction zone near phi=1) of nonluminous (soot free) laminar jet diffusion flames in both still and coflowing air and use these results to develop simplified models of flame-sheet shapes for these conditions; (2) Observe luminous flame boundaries of luminous (soot-containing) laminar jet diffusion flames in both still and coflowing air and use these results to develop simplified models of luminous flame boundaries for these conditions. In order to fix ideas here, maximum luminous flame boundaries at the laminar smoke point conditions were sought, i.e., luminous flame boundaries at the laminar smoke point; (3) Observe effects of coflow on laminar soot- and smoke-point conditions because coflow has been proposed as a means to control soot emissions and minimize the presence of soot in diffusion flames.

Dai, Z.; El-Leathy, A. M.; Lin, K.-C.; Sunderland, P. B.; Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

2000-01-01

204

Laminar flame propagation in a stratified charge  

NASA Astrophysics Data System (ADS)

The propagation of laminar flame from a rich or stoichiometric mixture to a lean mixture in a stratified methane-air charge was investigated experimentally and numerically. Emphasis was on the understanding of the flame behavior in the transition region; in particular, on the mechanism of burning velocity enhancement in this region. In the experimental setup, mixtures of two different equivalence ratios were separated by a soap bubble in a spherical constant volume combustion vessel. The richer mixture inside the bubble was ignited by a focused laser beam. The flame development was observed by Schlieren technique and flame speeds were measured by heat release analysis of the pressure data. An one-dimensional, time- dependant numerical simulation of the flame propagation in a charge with step-stratification was used to interpret the experimental results. Both the experimental and numerical studies showed that the instantaneous flame speed depended on the previous flame history. Thus a `strong' (with mixture equivalence ratio close to stoichiometric) flame can sustain propagation into finite regions of substantially lean equivalence ratio. Both thermal and chemical effects were crucial for explaining the mechanism of the flame speed enhancement in the transition period. Because of the presence of this `back- support' effect, the usual concept of specifying the burning velocity as a function of the end gas state is inadequate for a stratified charge. A simple correlation for instantaneous flame velocity based on the local burned gas temperature is developed. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617-253-5668; Fax 617-253- 1690.)

Ra, Youngchul

205

The stability of laminar symmetric separated wakes  

NASA Astrophysics Data System (ADS)

Time-dependent computations of the two-dimensional incompressible uniform-velocity laminar flow past a normal flat plate (of unit half-width) in a channel are presented. Attention is restricted to cases in which the well-known anti-symmetric (von Kármán-type) vortex shedding is suppressed by the imposition of a symmetry plane on the downstream plate centreline. With a further symmetry plane at the channel's upper boundary, the only two governing parameters in the problem are the channel half-width, H, and the Reynolds number, Re (based on the body half-width and the upstream velocity, U). The former is restricted to the range 3 {?} H {?} 30 and the interest lies in determining the nature of the initial instability which occurs in the separated wake as Re is gradually increased. It is found that for sufficiently large H and at a critical Re, a long-time-scale global (supercritical) instability is initiated, which in its saturated (limit) state takes the form of ‘lumps’ of vorticity being periodically shed from the tail end of the separated bubble. Stability calculations of corresponding mean flow profiles (typical of those found in the separated wake) are undertaken by examining the impulse response of particular profiles via appropriate solution of the Orr Sommerfeld equation. The results of this analysis extend those available from related published work and are consistent with the behaviour found from the numerical computations. Taken together, all the results suggest that this type of global instability may be generic to many kinds of separated wakes and, indeed, may provide the fundamental explanation for the very low-frequency oscillations often noticed in fully turbulent wake bubbles.

Castro, Ian P.

2005-06-01

206

Acoustics of laminar boundary layers breakdown  

NASA Astrophysics Data System (ADS)

Boundary layer flow transition has long been suggested as a potential noise source in both marine (sonar-dome self noise) and aeronautical (aircraft cabin noise) applications, owing to the highly transient nature of process. The design of effective noise control strategies relies upon a clear understanding of the source mechanisms associated with the unsteady flow dynamics during transition. Due to formidable mathematical difficulties, theoretical predictions either are limited to early linear and weakly nonlinear stages of transition, or employ acoustic analogy theories based on approximate source field data, often in the form of empirical correlation. In the present work, an approach which combines direct numerical simulation of the source field with the Lighthill acoustic analogy is utilized. This approach takes advantage of the recent advancement in computational capabilities to obtain detailed information about the flow-induced acoustic sources. The transitional boundary layer flow is computed by solving the incompressible Navier-Stokes equations without model assumptions, thus allowing a direct evaluation of the pseudosound as well as source functions, including the Lighthill stress tensor and the wall shear stress. The latter are used for calculating the radiated pressure field based on the Curle-Powell solution of the Lighthill equation. This procedure allows a quantitative assessment of noise source mechanisms and the associated radiation characteristics during transition from primary instability up to the laminar breakdown stage. In particular, one is interested in comparing the roles played by the fluctuating volume Reynolds stress and the wall-shear-stresses, and in identifying specific flow processes and structures that are effective noise generators.

Wang, Meng

1994-12-01

207

Acoustics of laminar boundary layers breakdown  

NASA Technical Reports Server (NTRS)

Boundary layer flow transition has long been suggested as a potential noise source in both marine (sonar-dome self noise) and aeronautical (aircraft cabin noise) applications, owing to the highly transient nature of process. The design of effective noise control strategies relies upon a clear understanding of the source mechanisms associated with the unsteady flow dynamics during transition. Due to formidable mathematical difficulties, theoretical predictions either are limited to early linear and weakly nonlinear stages of transition, or employ acoustic analogy theories based on approximate source field data, often in the form of empirical correlation. In the present work, an approach which combines direct numerical simulation of the source field with the Lighthill acoustic analogy is utilized. This approach takes advantage of the recent advancement in computational capabilities to obtain detailed information about the flow-induced acoustic sources. The transitional boundary layer flow is computed by solving the incompressible Navier-Stokes equations without model assumptions, thus allowing a direct evaluation of the pseudosound as well as source functions, including the Lighthill stress tensor and the wall shear stress. The latter are used for calculating the radiated pressure field based on the Curle-Powell solution of the Lighthill equation. This procedure allows a quantitative assessment of noise source mechanisms and the associated radiation characteristics during transition from primary instability up to the laminar breakdown stage. In particular, one is interested in comparing the roles played by the fluctuating volume Reynolds stress and the wall-shear-stresses, and in identifying specific flow processes and structures that are effective noise generators.

Wang, Meng

1994-01-01

208

The fluid dynamics of canine olfaction: unique nasal airflow patterns as an explanation of macrosmia  

PubMed Central

The canine nasal cavity contains hundreds of millions of sensory neurons, located in the olfactory epithelium that lines convoluted nasal turbinates recessed in the rear of the nose. Traditional explanations for canine olfactory acuity, which include large sensory organ size and receptor gene repertoire, overlook the fluid dynamics of odorant transport during sniffing. But odorant transport to the sensory part of the nose is the first critical step in olfaction. Here we report new experimental data on canine sniffing and demonstrate allometric scaling of sniff frequency, inspiratory airflow rate and tidal volume with body mass. Next, a computational fluid dynamics simulation of airflow in an anatomically accurate three-dimensional model of the canine nasal cavity, reconstructed from high-resolution magnetic resonance imaging scans, reveals that, during sniffing, spatially separate odour samples are acquired by each nostril that may be used for bilateral stimulus intensity comparison and odour source localization. Inside the nose, the computation shows that a unique nasal airflow pattern develops during sniffing, which is optimized for odorant transport to the olfactory part of the nose. These results contrast sharply with nasal airflow in the human. We propose that mammalian olfactory function and acuity may largely depend on odorant transport by nasal airflow patterns resulting from either the presence of a highly developed olfactory recess (in macrosmats such as the canine) or the lack of one (in microsmats including humans).

Craven, Brent A.; Paterson, Eric G.; Settles, Gary S.

2010-01-01

209

Biostabilization-biodrying of municipal solid waste by inverting air-flow.  

PubMed

The process of biodrying could be a good solution for municipal solid waste management, allowing the production of fuel with an interesting energy content. Previous work (Adani, F., Baido, D., Calcaterra, E., Genevini, P.L., 2002. The influence of biomass temperature on biostabilization-biodrying of municipal solid waste. Bioresource Technology 83 (3), 173-179) has indicated that appropriate management of the processing parameters (air-flow rate and biomass temperatures) could achieve biomass drying in very short times (8-9 days). However, the data of that work also evidenced that if the conditions do not consider pile turning, and the air-flow is always from one direction, temperature gradients arise within the biomass, resulting in a lack of homogeneity in the moisture and energy content of the final product. Therefore, a new laboratory study was conducted on municipal solid waste biodrying-biostabilization in an effort to obtain homogeneous final products. Our proposal to solve this lack of homogeneity is to periodically invert the air-flow direction. Thus, in line with a previous study, two trials, A and B, were carried out, dividing the biomass into three layers to study temperature and moisture gradients throughout the process, and a third trial (C) simulating air-flow inversion at regular intervals was introduced. The results suggest that the daily inversion of air-flow eliminates marked temperature differences and leads to a homogeneous final product. PMID:15792579

Sugni, Mara; Calcaterra, Enrico; Adani, Fabrizio

2005-08-01

210

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

2013-10-18

211

Laminar Soot Processes (LSP) Experiment: Findings From Space Flight Measurements  

NASA Technical Reports Server (NTRS)

The present experimental study of soot processes in hydrocarbon-fueled laminar nonbuoyant and nonpremixed (diffusion) flames at microgravity within a spacecraft was motivated by the relevance of soot to the performance of power and propulsion systems, to the hazards of unwanted fires, and to the emission of combustion-generated pollutants. Soot processes in turbulent flames are of greatest practical interest, however, direct study of turbulent flames is not tractable because the unsteadiness and distortion of turbulent flames limit available residence times and spatial resolution within regions where soot processes are important. Thus, laminar diffusion flames are generally used to provide more tractable model flame systems to study processes relevant to turbulent diffusion flames, justified by the known similarities of gas-phase processes in laminar and turbulent diffusion flames, based on the widely-accepted laminar flamelet concept of turbulent flames. Unfortunately, laminar diffusion flames at normal gravity are affected by buoyancy due to their relatively small flow velocities and, as discussed next, they do not have the same utility for simulating the soot processes as they do for simulating the gas phase processes of turbulent flames.

Sunderland, P. B.; Urban, D. L.; Yuan, Z. G.; Aalburg, C.; Diez, F. J.; Faeth, G. M.

2003-01-01

212

Soot Formation in Freely-Propagating Laminar Premixed Flames  

NASA Technical Reports Server (NTRS)

Soot formation within hydrocarbon-fueled flames is an important unresolved problem of combustion science. Thus, the present study is considering soot formation in freely-propagating laminar premixed flames, exploiting the microgravity environment to simplify measurements at the high-pressure conditions of interest for many practical applications. The findings of the investigation are relevant to reducing emissions of soot and continuum radiation from combustion processes, to improving terrestrial and spacecraft fire safety, and to developing methods of computational combustion, among others. Laminar premixed flames are attractive for studying soot formation because they are simple one-dimensional flows that are computationally tractable for detailed numerical simulations. Nevertheless, studying soot-containing burner-stabilized laminar premixed flames is problematical: spatial resolution and residence times are limited at the pressures of interest for practical applications, flame structure is sensitive to minor burner construction details so that experimental reproducibility is not very good, consistent burner behavior over the lengthy test programs needed to measure soot formation properties is hard to achieve, and burners have poor durability. Fortunately, many of these problems are mitigated for soot-containing, freely-propagating laminar premixed flames. The present investigation seeks to extend work in this laboratory for various soot processes in flames by observing soot formation in freely-propagating laminar premixed flames. Measurements are being made at both Normal Gravity (NG) and MicroGravity (MG), using a short-drop free-fall facility to provide MG conditions.

Lin, K.-C.; Hassan, M. I.; Faeth, G. M.

1997-01-01

213

Assessment of LAURA for Laminar Supersonic Shallow Cavities  

NASA Technical Reports Server (NTRS)

The ability of the Laura flow solver to predict local heating augmentation factors for shallow cavities is assessed. This assessment is part of a larger e ort within the Space Shuttle return-to-flight program to develop technologies to support on-orbit tile repair decisions. The comparison is made against global phosphor thermography images taken in the Langley Aerothermodynamic Laboratory 20-Inch Mach 6 Air Tunnel. The cavities are rectangular in shape, with lengths L/H of 14 20 and depths H/ of 1.1 5.2. The fully laminar results, for Re = 300, show good agreement between the data sets. For Re = 503, the wind tunnel data indicates boundary layer transition with turbulent flow both within and downstream of the cavity. The turbulent flow structures are significantly di erent from the laminar predictions, with order of magnitude increases in the heating augmentations. Because of the di erent flow structures, no simple bump factor can be used to correct the laminar calculations to account for the turbulent heating levels. A fine gradation in wind tunnel cases will be required to clearly delineate the laminar-to-turbulent transition point, and hence the limits of applicability of the laminar numerical approach.

Wood, William A.; Pulsonetti, Maria V.; Everhart, Joel L.; Bey, Kim S.

2004-01-01

214

Laminarization of Turbulent Boundary Layer on Flexible and Rigid Surfaces  

NASA Technical Reports Server (NTRS)

An investigation of the control of turbulent boundary layer flow over flexible and rigid surfaces downstream of a concave-convex geometry has been made. The concave-convex curvature induces centrifugal forces and a pressure gradient on the growth of the turbulent boundary layer. The favorable gradient is not sufficient to overcome the unfavorable; thus, the net effect is a destabilizing, of the flow into Gortler instabilities. This study shows that control of the turbulent boundary layer and structural loading can be successfully achieved by using localized surface heating because the subsequent cooling and geometrical shaping downstream over a favorable pressure gradient is effective in laminarization of the turbulence. Wires embedded in a thermally insulated substrate provide surface heating. The laminarized velocity profile adjusts to a lower Reynolds number, and the structure responds to a lower loading. In the laminarization, the turbulent energy is dissipated by molecular transport by both viscous and conductivity mechanisms. Laminarization reduces spanwise vorticity because of the longitudinal cooling gradient of the sublayer profile. The results demonstrate that the curvature-induced mean pressure gradient enhances the receptivity of the flow to localized surface heating, a potentially viable mechanism to laminarize turbulent boundary layer flow; thus, the flow reduces the response of the flexible structure and the resultant sound radiation.

Maestrello, Lucio

2001-01-01

215

Computational Analysis of the G-III Laminar Flow Glove  

NASA Technical Reports Server (NTRS)

Under NASA's Environmentally Responsible Aviation Project, flight experiments are planned with the primary objective of demonstrating the Discrete Roughness Elements (DRE) technology for passive laminar flow control at chord Reynolds numbers relevant to transport aircraft. In this paper, we present a preliminary computational assessment of the Gulfstream-III (G-III) aircraft wing-glove designed to attain natural laminar flow for the leading-edge sweep angle of 34.6deg. Analysis for a flight Mach number of 0.75 shows that it should be possible to achieve natural laminar flow for twice the transition Reynolds number ever achieved at this sweep angle. However, the wing-glove needs to be redesigned to effectively demonstrate passive laminar flow control using DREs. As a by-product of the computational assessment, effect of surface curvature on stationary crossflow disturbances is found to be strongly stabilizing for the current design, and it is suggested that convex surface curvature could be used as a control parameter for natural laminar flow design, provided transition occurs via stationary crossflow disturbances.

Malik, Mujeeb R.; Liao, Wei; Lee-Rausch, Elizabeth M.; Li, Fei; Choudhari, Meelan M.; Chang, Chau-Lyan

2011-01-01

216

Laminar flow integration: Flight tests status and plans  

NASA Technical Reports Server (NTRS)

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.

1986-01-01

217

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

218

Atomization of water jets and sheets in axial and swirling airflows  

NASA Technical Reports Server (NTRS)

Axial and swirling airflows were used to break up water jets and sheets into sprays of droplets to determine the overall effects of orifice diameter, weight flow of air, and the use of an air swirler on fineness of atomization as characterized by mean drop size. A scanning radiometer was used to determine the mean drop diameter of each spray. Swirling airflows were produced with an axial combustor, 70 deg blake angle, air swirling. Water jets were injected axially upstream, axially downstream and cross stream into the airflow. In addition, pressure atomizing fuel nozzles which produced a sheet and ligament type of breakup were investigated. Increasing the weight flow rate of air or the use of an air swirling markedly reduced the spray mean drop size.

Ingebo, R. D.

1977-01-01

219

Simultaneous real-time measurements of mastication, swallowing, nasal airflow, and aroma release.  

PubMed

Mastication, swallowing, breath flow, and aroma release were measured simultaneously in vivo using electromyography, electroglottography, a turbine air flow meter, and the MS-Nose, respectively. Signals were synchronized either electronically or by aligning the nasal airflow data with the breath by breath release of acetone. Chewing affected nasal airflow, with the flow fluctuations following the mastication pattern. Data analysis suggested that air was pumped out of the mouth into the throat with each chew, and the mean volume was 26 mL. Aroma release was associated with the pulses of air pumped from the mouth with each chew. During swallowing, there was no nasal airflow, but after swallowing, aroma release was evident. The volume of the retronasal route was estimated at 48 mL when swallowing and 72 mL when samples were chewed. The combination of techniques shows the effects of physiological processes on aroma release. PMID:12903969

Hodgson, M; Linforth, R S T; Taylor, A J

2003-08-13

220

Competition between pressure effects and airflow influence for the performance of plasma actuators  

NASA Astrophysics Data System (ADS)

The present work addresses the combined influence of pressure variations and different airflow velocities on the discharge intensity of plasma actuators. Power consumption, plasma length, and discharge capacitance were investigated systematically for varying pressure levels (p = 0.1-1 bar) and airflow velocities (U?=0-100 m/s) to characterize and quantify the favorable and adverse effects on the discharge intensity. In accordance with previous reports, an increasing plasma actuator discharge intensity is observed for decreasing pressure levels. At constant pressure levels, an adverse airflow influence on the electric actuator performance is demonstrated. Despite the improved discharge intensity at lower pressure levels, the seemingly improved performance of the plasma actuators is accompanied with a more pronounced drop of the relative performance. These findings demonstrate the dependency of the (kinematic and thermodynamic) environmental conditions on the electric performance of plasma actuators, which in turn affects the control authority of plasma actuators for flow control applications.

Kriegseis, J.; Barckmann, K.; Frey, J.; Tropea, C.; Grundmann, S.

2014-05-01

221

The Granite Mountain Atmospheric Sciences Testbed (GMAST): A Facility for Long Term Complex Terrain Airflow Studies  

NASA Astrophysics Data System (ADS)

This presentation describes a new facility at Dugway Proving Ground (DPG), Utah that can be used to study airflow over complex terrain, and to evaluate how airflow over a mountain barrier affects wind patterns over adjacent flatter terrain. DPG's primary mission is to conduct testing, training, and operational assessments of chemical and biological weapon systems. These operations require very precise weather forecasts. Most test operations at DPG are conducted on fairly flat test ranges having uniform surface cover, where airflow patterns are generally well-understood. However, the DPG test ranges are located alongside large, isolated mountains, most notably Granite Mountain, Camelback Mountain, and the Cedar Mountains. Airflows generated over, or influenced by, these mountains can affect wind patterns on the test ranges. The new facility, the Granite Mountain Atmospheric Sciences Testbed, or GMAST, is designed to facilitate studies of airflow interactions with topography. This facility will benefit DPG by improving understanding of how mountain airflows interact with the test range conditions. A core infrastructure of weather sensors around and on Granite Mountain has been developed including instrumented towers and remote sensors, along with automated data collection and archival systems. GMAST is expected to be in operation for a number of years and will provide a reference domain for mountain meteorology studies, with data useful for analysts, modelers and theoreticians. Visiting scientists are encouraged to collaborate with DPG personnel to utilize this valuable scientific resource and to add further equipment and scientific designs for both short-term and long-term atmospheric studies. Several of the upcoming MATERHORN (MountAin TERrain atmospHeric mOdeling and obseRvatioNs) project field tests will be conducted at DPG, giving an example of GMAST utilization and collaboration between DPG and visiting scientists.

Zajic, D.; Pace, J. C.; Whiteman, C. D.; Hoch, S.

2011-12-01

222

Airflow obstruction in bronchiectasis: correlation between computed tomography features and pulmonary function tests  

PubMed Central

BACKGROUND—An obstructive defect is usual in bronchiectasis, but the pathophysiological basis of airflow obstruction remains uncertain. High resolution computed tomographic (CT) scanning now allows quantitation of static morphological abnormalities, as well as dynamic changes shown on expiratory CT scans. The aim of this study was to determine which static and dynamic structural abnormalities on the CT scan are associated with airflow obstruction in bronchiectasis.?METHODS—The inspiratory and expiratory features on the CT scan of 100 patients with bronchiectasis undergoing concurrent lung function tests were scored semi-quantitatively by three observers.?RESULTS—On univariate analysis the extent and severity of bronchiectasis, the severity of bronchial wall thickening, and the extent of decreased attenuation on the expiratory CT scan correlated strongly with the severity of airflow obstruction; the closest relationship was seen between decreased forced expiratory volume in one second (FEV1) and the extent of decreased attenuation on the expiratory CT scan (Rs = -0.55, p<0.00005). On multivariate analysis bronchial wall thickness and decreased attenuation were consistently the strongest independent determinants of airflow obstruction. The extent of decreased attenuation was positively associated with the severity of bronchial wall thickness, but was not independently linked to gas transfer levels. Endobronchial secretions seen on CT scanning had no functional significance; the severity of bronchial dilatation was negatively associated with airflow obstruction after adjustment for other morphological features.?CONCLUSIONS—These findings indicate that airflow obstruction in bronchiectasis is primarily linked to evidence of intrinsic disease of small and medium airways on CT scanning and not to bronchiectatic abnormalities in large airways, emphysema, or retained endobronchial secretions.??

Roberts, H; Wells, A; Milne, D; Rubens, M; Kolbe, J; Cole, P; Hansell, D

2000-01-01

223

Prevalence of airflow limitation in outpatients with cardiovascular diseases in Japan  

PubMed Central

Background and objectives Cardiovascular disease (CVD) and chronic obstructive pulmonary disease (COPD) commonly coexist and share common risk factors. The prevalence of COPD in outpatients with a smoking history and CVD in Japan is unknown. The aim of this study was to determine the proportion of Japanese patients with a smoking history being treated for CVD who have concurrent airflow limitation compatible with COPD. A secondary objective was to test whether the usage of lung function tests performed in the clinic influenced the diagnosis rate of COPD in the patients identified with airflow limitation. Methods In a multicenter observational prospective study conducted at 17 centers across Japan, the prevalence of airflow limitation compatible with COPD (defined as forced expiratory volume (FEV)1/FEV6 <0.73, by handheld spirometry) was investigated in cardiac outpatients ?40 years old with a smoking history who routinely visited the clinic for their CVD. Each patient completed the COPD Assessment Test prior to spirometry testing. Results Data were available for 995 patients with a mean age of 66.6±10.0 years, of whom 95.5% were male. The prevalence of airflow limitation compatible with COPD was 27.0% (n=269), and 87.7% of those patients (n=236) did not have a prior diagnosis of COPD. The prevalence of previously diagnosed airflow limitation was higher in sites with higher usage of lung function testing (14.0%, 15.2% respectively) compared against sites where it is performed seldom (11.1%), but was still low. Conclusion The prevalence of airflow limitation in this study indicates that a quarter of outpatients with CVD have COPD, almost all of whom are undiagnosed. This suggests that it is important to look routinely for COPD in CVD outpatients.

Onishi, Katsuya; Yoshimoto, Daisuke; Hagan, Gerry W; Jones, Paul W

2014-01-01

224

Laminar flow control, 1976 - 1982: A selected annotated bibliography  

NASA Technical Reports Server (NTRS)

Laminar Flow Control technology development has undergone tremendous progress in recent years as focused research efforts in materials, aerodynamics, systems, and structures have begun to pay off. A virtual explosion in the number of research papers published on this subject has occurred since interest was first stimulated by the 1976 introduction of NASA's Aircraft Energy Efficiency Laminar Flow Control Program. The purpose of this selected bibliography is to list available, unclassified laminar flow (both controlled and natural) research completed from about 1975 to mid 1982. Some earlier pertinent reports are included but listed separately in the Appendix. Reports listed herein emphasize aerodynamics and systems studies, but some structures work is also summarized. Aerodynamic work is mainly limited to the subsonic and transonic sped regimes. Because wind-tunnel flow qualities, such as free stream disturbance level, play such an important role in boundary-layer transition, much recent research has been done in this area and it is also included.

Tuttle, M. H.; Maddalon, D. V.

1982-01-01

225

Laminar and Turbulent Gaseous Diffusion Flames. Appendix C  

NASA Technical Reports Server (NTRS)

Recent measurements and predictions of the properties of homogeneous (gaseous) laminar and turbulent non-premixed (diffusion) flames are discussed, emphasizing results from both ground- and space-based studies at microgravity conditions. Initial considerations show that effects of buoyancy not only complicate the interpretation of observations of diffusion flames but at times mislead when such results are applied to the non-buoyant diffusion flame conditions of greatest practical interest. This behavior motivates consideration of experiments where effects of buoyancy are minimized; therefore, methods of controlling the intrusion of buoyancy during observations of non-premixed flames are described, considering approaches suitable for both normal laboratory conditions as well as classical microgravity techniques. Studies of laminar flames at low-gravity and microgravity conditions are emphasized in view of the computational tractability of such flames for developing methods of predicting flame structure as well as the relevance of such flames to more practical turbulent flames by exploiting laminar flamelet concepts.

Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

2001-01-01

226

Method for laminar boundary layer transition visualization in flight  

NASA Technical Reports Server (NTRS)

Disclosed is a method of visualizing laminar to turbulent boundary layer transition, shock location, and laminar separation bubbles around a test surface. A liquid crystal coating is formulated using an unencapsulated liquid crystal operable in a temperature bandwidth compatible with the temperature environment around the test surface. The liquid crystal coating is applied to the test surface, which is preferably pretreated by painting with a flat, black paint to achieve a deep matte coating, after which the surface is subjected to a liquid or gas flow. Color change in the liquid crystal coating is produced in response to differences in relative shear stress within the boundary layer around the test surface. The novelty of this invention resides in the use of liquid crystals which are sensitive to shear stress to show aerodynamic phenomena such as a boundary layer transition, shock location, and laminar separation bubbles around a test surface.

Holmes, Bruce J. (inventor); Gall, Peter D. (inventor)

1988-01-01

227

Lockheed laminar-flow control systems development and applications  

NASA Technical Reports Server (NTRS)

Progress is summarized from 1974 to the present in the practical application of laminar-flow control (LFC) to subsonic transport aircraft. Those efforts included preliminary design system studies of commercial and military transports and experimental investigations leading to the development of the leading-edge flight test article installed on the NASA JetStar flight test aircraft. The benefits of LFC on drag, fuel efficiency, lift-to-drag ratio, and operating costs are compared with those for turbulent flow aircraft. The current activities in the NASA Industry Laminar-Flow Enabling Technologies Development contract include summaries of activities in the Task 1 development of a slotted-surface structural concept using advanced aluminum materials and the Task 2 preliminary conceptual design study of global-range military hybrid laminar flow control (HLFC) to obtain data at high Reynolds numbers and at Mach numbers representative of long-range subsonic transport aircraft operation.

Lange, Roy H.

1987-01-01

228

Method and apparatus for detecting laminar flow separation and reattachment  

NASA Technical Reports Server (NTRS)

The invention is a method and apparatus for detecting laminar flow separation and flow reattachment of a fluid stream by simultaneously sensing and comparing a plurality of output signals, each representing the dynamic shear stress at one of an equal number of sensors spaced along a straight line on the surface of an airfoil or the like that extends parallel to the fluid stream. The output signals are concurrently compared to detect the sensors across which a reversal in phase of said output signal occurs, said detected sensors being in the region of laminar separation or reattachment. The novelty in this invention is the discovery and use of the phase reversal phenomena to detect laminar separation and attachment of a fluid stream from any surface such as an airfoil supported therein.

Stack, John P. (inventor); Mangalam, Sivaramakrishnan M. (inventor)

1989-01-01

229

Aerodynamic-wave break-up of liquid sheets in swirling airflows and combustor modules  

NASA Technical Reports Server (NTRS)

Experimental mean drop diameter data were obtained for the atomization of liquid sheets injected axially downstream in high velocity swirling and nonswirling airflow. Conventional simplex pressure atomizing fuel nozzles and splash type fuel injectors were studied under simulated combustor inlet airflow conditions. A general empirical expression relating recirprocal mean drop diameter to airstream mass velocity was obtained and is presented. The finest degree of atomization, i.e., the highest value of the coefficient C, was obtained with swirl can combustor modules (C = 15) as compared with pressure atomizing nozzles (C = 12).

Ingebo, R.

1983-01-01

230

Method and apparatus for detecting laminar flow separation and reattachment  

NASA Technical Reports Server (NTRS)

The invention is a method and apparatus for simultaneously detecting laminar separation and reattachment of a fluid stream such as an airstream from and to the upper surface of an airfoil by simultaneously sensing and comparing a plurality of output signals. Each signal represents the dynamic shear stress at one of an equal number of sensors spaced along a straight line on the surface of the airfoil that extends parallel to the airstream. The output signals are simultaneously compared to detect the sensors across which a reversal in phase of said output signal occurs, said detected sensors being in the region of laminar separation or reattachment.

Stack, John P. (inventor); Mangalam, Sivaramakrishnan M. (inventor)

1990-01-01

231

A model for predicting laminar gas flow through micropassages  

NASA Astrophysics Data System (ADS)

An theoretical investigation was conducted to detect the gas-solid interface effect on laminar flow characteristics for gas flowing through micropassages. In the wall-adjacent region, the change in viscosity of fluid vs the distance from the wall surface, as derived from the kinetic theory of gases result in significant influence on the flow characteristics in micropassages. A model was proposed to account for the wall effect. Analytical expressions for velocity profiles and pressure drop were derived, respectively, for laminar flow of gases in microtubes and in extremely narrow parallel plates. The Knudsen number, Kn, as a criterion, that the flow can be treated reasonably as flow in macrochannels, is discussed.

Li, Jun-Ming; Wang, Bu-Xuan; Peng, Xiao-Feng

1997-12-01

232

A numerical study on airflow and dynamic cross-contamination in the super cleanroom for photolithography process  

Microsoft Academic Search

We performed the numerical study on the characteristics of airflow and cross-contamination in the photolithography process cleanroom. The nonuniformity, the deflection angle and the global cross-contamination were used to analyze the characteristics and performances of cleanroom. From the numerical results, we found that the airflow characteristics of the cleanroom are largely affected by the porosity of the access panel and

Kwang-Chul Noh; Myung-Do Oh; Seung-Chul Lee

2005-01-01

233

An arbitrary Lagrangian–Eulerian finite element method for interactions of airflow and a moving AGV in a cleanroom  

Microsoft Academic Search

The motions of the airflow induced by the movement of an automatic guided vehicle (AGV) in a cleanroom are numerically studied. This subject is an important issue of microcontamination control for the semiconductor process. The characteristics of the airflow induced by the movement of the AGV are dynamic and are classified as a type of moving boundary problems. An arbitrary

Suh-Jenq Yang

2003-01-01

234

Effect of a plasma actuator on an airflow along an inclined wall: P.I.V. and wall pressure measurements  

Microsoft Academic Search

In this work, we propose to analyse experimentally the ability of a DC surface corona discharge to modify an airflow along an inclined wall. The goal is to fully detach an airflow which is naturally attached along the inclined wall. Two sets of experiments conducted in a wind tunnel up to 10m\\/s have been done. First, pressure measurements along the

Alexandre Labergue; Luc Leger; Eric Moreau; Gérard Touchard

2005-01-01

235

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

Code of Federal Regulations, 2012 CFR

... 2012-10-01 2012-10-01 false Airflow resistance test; Type C supplied-air respirator, pressure-demand class... Supplied-Air Respirators § 84.157 Airflow resistance test; Type C supplied-air respirator, pressure-demand...

2012-10-01

236

The Toughness of High Hardness Laminar Composite Steel as Influenced by Specimen and Crack Orientation.  

National Technical Information Service (NTIS)

The purpose of the present paper is to extend the study of high hardness laminar composite steel and establish the orientation influence using static and dynamic toughness measurements. The toughness behavior of high hardness laminar composite steel (high...

C. F. Hickey P. T. Lum R. Chait

1974-01-01

237

F-16XL-2 Supersonic Laminar Flow Control Flight Test Experiment  

NASA Technical Reports Server (NTRS)

The F-16XL-2 Supersonic Laminar Flow Control Flight Test Experiment was part of the NASA High-Speed Research Program. The goal of the experiment was to demonstrate extensive laminar flow, to validate computational fluid dynamics (CFD) codes and design methodology, and to establish laminar flow control design criteria. Topics include the flight test hardware and design, airplane modification, the pressure and suction distributions achieved, the laminar flow achieved, and the data analysis and code correlation.

Anders, Scott G.; Fischer, Michael C.

1999-01-01

238

Measurement of laminar burning speeds and Markstein lengths using a novel methodology  

Microsoft Academic Search

Three different methodologies used for the extraction of laminar information are compared and discussed. Starting from an asymptotic analysis assuming a linear relation between the propagation speed and the stretch acting on the flame front, temporal radius evolutions of spherically expanding laminar flames are postprocessed to obtain laminar burning velocities and Markstein lengths. The first methodology fits the temporal radius

Toni Tahtouh; Fabien Halter; Christine Mounaïm-Rousselle

2009-01-01

239

Design and commissioning of a laminar soil container for use on small shaking tables  

Microsoft Academic Search

This paper describes the design, fabrication and commissioning of a single axis laminar shear box for use in seismic soil–structure interaction studies. A laminar shear box is a flexible container that can be placed on a shaking table to simulate vertical shear-wave propagation during earthquakes through a soil layer of finite thickness. The laminar shear box described in this paper

Alper Turan; Sean D. Hinchberger; Hesham El Naggar

2009-01-01

240

Airborne Dust Capture and Induced Airflow of Various Spray Nozzle Designs  

Microsoft Academic Search

Water spray characteristics, including droplet size and velocity, airborne dust capture potential, and induced airflow quantity for various spray nozzle designs were evaluated to provide basic information for improving spray applications. Water droplet size and velocity characteristics were initially measured by a Phase Doppler Particle Analyzer (PDPA) for hollow cone, full cone, flat fan, and air atomized spray nozzles at

Douglas Pollock; John Organiscak

2007-01-01

241

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

242

A numerical investigation of effects of a moving operator on airflow patterns in a cleanroom  

Microsoft Academic Search

The variations of the airflow induced by a moving operator in a cleanroom installed with a curtain were studied numerically. This situation is cataloged to a class of the moving boundary problems. An arbitrary Lagrangian–Eulerian kinematic description method is utilized to describe the flow field and a penalty finite element formulation with moving meshes is adopted to solve this problem.

Suh-Jenq Yang; Wu-Shung Fu

2002-01-01

243

EMI from airflow aperture arrays in shielding enclosures-experiments, FDTD, and MoM modeling  

Microsoft Academic Search

Aperture arrays designed to provide airflow through shielding enclosures can provide part of the coupling path from interior sources to external electromagnetic interference (EMI). In this work, radiation through aperture arrays is investigated numerically and experimentally. FDTD modeling is compared with measurements on aperture arrays in a test enclosure. The method of moments (MoM) is also utilized to study radiation

Min Li; Joe Nuebel; James L. Drewniak; Richard E. DuBroff; Todd H. Hubing; Thomas P. Van Doren

2000-01-01

244

Detection of Mouse Cough Based on Sound Monitoring and Respiratory Airflow Waveforms  

PubMed Central

Detection for cough in mice has never yielded clearly audible sounds, so there is still a great deal of debates as to whether mice can cough in response to tussive stimuli. Here we introduce an approach for detection of mouse cough based on sound monitoring and airflow signals. 40 Female BALB/c mice were pretreated with normal saline, codeine, capasazepine or desensitized with capsaicin. Single mouse was put in a plethysmograph, exposed to aerosolized 100 µmol/L capsaicin for 3 min, followed by continuous observation for 3 min. Airflow signals of total 6 min were recorded and analyzed to detect coughs. Simultaneously, mouse cough sounds were sensed by a mini-microphone, monitored manually by an operator. When manual and automatic detection coincided, the cough was positively identified. Sound and sound waveforms were also recorded and filtered for further analysis. Body movements were observed by operator. Manual versus automated counts were compared. Seven types of airflow signals were identified by integrating manual and automated monitoring. Observation of mouse movements and analysis of sound waveforms alone did not produce meaningful data. Mouse cough numbers decreased significantly after all above drugs treatment. The Bland-Altman and consistency analysis between automatic and manual counts was 0.968 and 0.956. The study suggests that the mouse is able to present with cough, which could be detected by sound monitoring and respiratory airflow waveform changes.

Chen, Liyan; Lai, Kefang; Lomask, Joseph Mark; Jiang, Bert; Zhong, Nanshan

2013-01-01

245

Atomization of water jets and sheets in axial and swirling airflows  

NASA Technical Reports Server (NTRS)

Axial and swirling airflows were used to break up water jets and sheets into sprays of droplets to determine the overall effects of orifice diameter, weight flow of air, and the use of an air swirler on fineness of atomization as characterized by mean drop size. A scanning radiometer was used to determine the mean drop diameter of each spray. Swirling airflows were produced with an axial combustor, 70 deg blake angle, air swirling. Water jets were injected axially upstream, axially downstream and cross stream into the airflow. In addition, pressure atomizing fuel nozzles which produced a sheet and ligament type of breakup were investigated. Increasing the weight flow rate of air or the use of an air swirling markedly reduced the spray mean drop size. Test conditions included a water flow rate of 68.0 liter per hour and airflow rates (per unit area) of 3.7 to 25.7 g per square cm per sec, at 293 K and inlet-air static pressures of 1.01 x 10 to the 5th to 1.98 x 10 to the 5th N/sq m.

Ingebo, R. D.

1979-01-01

246

Airflow and autonomic responses to stress and relaxation in asthma: The impact of stressor type  

Microsoft Academic Search

The impact of stress on respiratory airflow in asthmatics is unclear. Part of the uncertainty may spring from the different physiological effects of different stressors. Given their potential to elicit increases in parasympathetic vagal activity, stressful situations that present few opportunities for coping (passive coping stressors) may be particularly problematic for people with asthma. Thirty-one adult asthmatics participated in a

David Aboussafy; Tavis S. Campbell; Kim Lavoie; Frances E. Aboud; Blaine Ditto

2005-01-01

247

ENVIRONMENTAL TECHNOLOGY VERIFICATION, TEST REPORT OF CONTROL OF BIOAEROSOLS IN HVAC SYSTEMS, AIRFLOW PRODUCTS AFP30  

EPA Science Inventory

The Environmental Technology Verification report discusses the technology and performance of the AFP30 air filter for dust and bioaerosol filtration manufactured by Airflow Products. The pressure drop across the filter was 62 Pa clean and 247 Pa dust loaded. The filtration effici...

248

Measuring Airflow in Local Exhaust Ventilation Systems. Module 23. Vocational Education Training in Environmental Sciences.  

ERIC Educational Resources Information Center

This module, one of 25 on vocational education training for careers in environmental health occupations, contains self-instructional materials on measuring airflow in local exhaust ventilation systems. Following guidelines for students and instructors and an introduction that explains what the student will learn are three lessons: (1) naming each…

Consumer Dynamics Inc., Rockville, MD.

249

The selection of the most appropriate airflow model for designing indoor air sensor systems  

Microsoft Academic Search

Current indoor air sensor system design is mostly by intuition or experience rather than by design. Sensor systems that are intended to ensure the safety and well-being of building occupants should be systematically designed and their performance evaluated. The literature shows that selection of an airflow model for sensor system design has been either out of convenience (thus choosing a

Y. Lisa Chen; Jin Wen

250

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

251

Evaluation of Airflow Patterns in the Transfer Area of the 105 KE Basin  

SciTech Connect

This report is a qualitative study of airflow patterns within a building at the transfer area of the 105 KE Basin on the Hanford Site in Washington State. The purpose of the study was to determine the appropriate location for air monitoring equipment.

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

2003-03-07

252

Braking of expiratory airflow in obese pigs during wakefulness and sleep.  

PubMed

Braking of expiratory airflow is a phenomenon prominently seen in neonates where it is thought to defend end-expiratory lung volume. This paper describes pronounced expiratory braking in an adult animal, the obese Vietnamese pot-bellied pig. Three obese pigs were chronically instrumented for recording of intrapleural pressure and bioelectric signals related to sleep. Airflow was measured by a pneumotachograph attached to a facemask. Expiratory airflow resistance was calculated for 10 consecutive expirations during wakefulness, NREM, and REM sleep. All animals demonstrated a biphasic expiratory flow pattern characterized by an initial plateau in flow at a low value followed by a rapid increase later in expiration. Airflow resistance during early expiration was on average four-fold higher than during late expiration. A striking observation was the maintenance of pronounced expiratory braking during NREM and REM sleep. Expiratory braking in these animals is likely due to laryngeal mechanisms and may serve to preserve end-expiratory lung volume or improve hemodynamics. PMID:11812389

Tuck, S A; Dort, J C; Remmers, J E

2001-11-01

253

Computational and experimental study of airflow around a fan powered UVGI lamp  

NASA Astrophysics Data System (ADS)

The quality of indoor air environment is very important for improving the health of occupants and reducing personal exposure to hazardous pollutants. An effective way of controlling air quality is by eliminating the airborne bacteria and viruses or by reducing their emissions. Ultraviolet Germicidal Irradiation (UVGI) lamps can effectively reduce these bio-contaminants in an indoor environment, but the efficiency of these systems depends on airflow in and around the device. UVGI lamps would not be as effective in stagnant environments as they would be when the moving air brings the bio-contaminant in their irradiation region. Introducing a fan into the UVGI system would augment the efficiency of the system's kill rate. Airflows in ventilated spaces are quite complex due to the vast range of length and velocity scales. The purpose of this research is to study these complex airflows using CFD techniques and validate computational model with airflow measurements around the device using Particle Image Velocimetry measurements. The experimental results including mean velocities, length scales and RMS values of fluctuating velocities are used in the CFD validation. Comparison of these data at different locations around the device with the CFD model predictions are performed and good agreement was observed.

Kaligotla, Srikar; Tavakoli, Behtash; Glauser, Mark; Ahmadi, Goodarz

2011-11-01

254

Plasma actuators for airflow control: measurement of the non-stationary induced flow velocity  

Microsoft Academic Search

This paper deals with the measurement of the instantaneous flow velocity induced by surface plasma actuators in air at atmospheric pressure. More accurately, experiments with Laser Doppler Velocimetry (LDV) are conducted with two different types of plasma actuators in order to determine the establishment time of the induced airflow. DC corona discharges and AC dielectric barrier discharges are investigated in

Maxime Forte; Luc Leger; Jérôme Pons; Eric Moreau; Gérard Touchard

2005-01-01

255

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

256

Airflow and hail growth in supercell storms and some implications for suppression. Technical note  

Microsoft Academic Search

Multiple radar and aircraft observations of a damaging supercell hailstorm in northeastern Colorado are synthesized to show that the airflow and hail growth conformed in many respects to earlier models derived by the lead author. Some features that before had inferred indirectly are now substantiated and elaborated upon by direct observations.

K. A. Browning; G. B. Foote

1975-01-01

257

HEAT TRANSFER BETWEEN MATERIALS AND UNSTEADY AIRFLOW FROM A HELMHOLTZ TYPE COMBUSTOR  

Microsoft Academic Search

Although pulse combustion devices exhibit a high thermal efficiency and low pollutant emission when used in a drying process, a broad application of these dryers has been limited because of a lack of understanding of the fundamental controlling heat and mass transfer. This paper reports the results of an experimental investigation of heat transfer between unsteady airflow and a brass

X. D. Liu; C. W. Cao; Z. H. Lang

2001-01-01

258

Application of porous materials for laminar flow control  

NASA Technical Reports Server (NTRS)

Fairly smooth porous materials were elected for study Doweave; Fibermetal; Dynapore; and perforated titanium sheet. Factors examined include: surface smoothness; suction characteristics; porosity; surface impact resistance; and strain compatibility. A laminar flow control suction glove arrangement was identified with material combinations compatible with thermal expansion and structural strain.

Pearce, W. E.

1978-01-01

259

Fluerics 36: Large-Scale Modeling of Laminar Flueric Devices.  

National Technical Information Service (NTIS)

The purpose of this report is to investigate large-scale modeling of laminar flueric flow phenomena. A test facility using silicone oil as the working fluid and Reynolds number as the modeling parameter was designed, constructed, and instrumented. The tes...

C. E. Spyropoulos

1974-01-01

260

Interactions between a laminar flame and end gas autoignition  

Microsoft Academic Search

A numerical model combining one dimensional fluid mechanics and detailed chemical kinetics is used to examine the interactions between laminar flame propagation and end gas autoignition at high temperatures and pressures of approximately 30 atmospheres. The flame is found to have very little influence on the computed rates of fuel-air autoignition in the end gas, but the subsequent high rate

W. J. Pitz; C. K. Westbrook

1985-01-01

261

Soot Formation in Hydrocarbon/Air Laminar Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

Soot processes within hydrocarbon/air diffusion flames are important because they affect the durability and performance of propulsion systems, the hazards of unwanted fires, the pollutant and particulate emissions from combustion processes, and the potential for developing computational combustion. Motivated by these observations, this investigation involved an experimental study of the structure and soot properties of round laminar jet diffusion flames, seeking an improved understanding of soot formation (growth and nucleation) within diffusion flames. The present study extends earlier work in this laboratory concerning laminar smoke points (l) and soot formation in acetylene/air laminar jet diffusion flames (2), emphasizing soot formation in hydrocarbon/air laminar jet diffusion flames for fuels other than acetylene. In the flame system, acetylene is the dominant gas species in the soot formation region and both nucleation and growth were successfully attributed to first-order reactions of acetylene, with nucleation exhibiting an activation energy of 32 kcal/gmol while growth involved negligible activation energy and a collision efficiency of O.53%. In addition, soot growth in the acetylene diffusion flames was comparable to new soot in premixed flame (which also has been attributed to first-order acetylene reactions). In view of this status, a major issue is the nature of soot formation processes in diffusion flame involving hydrocarbon fuels other than acetylene. In particular, information is needed about th dominant gas species in the soot formation region and the impact of gas species other than acetylene on soot nucleation and growth.

Sunderland, P. B.; Faeth, G. M.

1994-01-01

262

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

263

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

264

Experimental investigation of nanofluids in confined laminar radial flows  

Microsoft Academic Search

This paper presents an experimental investigation of heat transfer enhancement capabilities of coolants with suspended nanoparticles (Al2O3 dispersed in water) inside a radial flow cooling device. Steady, laminar radial flow of a nanofluid between a heated disk and a flat plate with axial coolant injection has been considered. An experimental test rig was built. Results show that heat transfer enhancements

Iulian Gherasim; Gilles Roy; Cong Tam Nguyen; Dinh Vo-Ngoc

2009-01-01

265

Computational Optimization of a Natural Laminar Flow Experimental Wing Glove  

NASA Technical Reports Server (NTRS)

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 lofting it into a three-dimensional wing glove section. The airfoil design process does not consider the three dimensional flow effects such as cross flow due wing sweep as well as engine and body interference. Therefore, once an initial glove geometry is created from the airfoil, the three dimensional wing glove has to be optimized to ensure that the desired extent of laminar flow is maintained over the entire glove. TRANAIR, a non-linear full potential solver with a coupled boundary layer code was used as the main tool in the design and optimization process of the three-dimensional glove shape. The optimization process uses the Class-Shape-Transformation method to perturb the geometry with geometric constraints that allow for a 2-in clearance from the main wing. The three-dimensional glove shape was optimized with the objective of having a spanwise uniform pressure distribution that matches the optimized two-dimensional pressure distribution as closely as possible. Results show that with the appropriate inputs, the optimizer is able to match the two dimensional pressure distributions practically across the entire span of the wing glove. This allows for the experiment to have a much higher probability of having a large extent of natural laminar flow in flight.

Hartshom, Fletcher

2012-01-01

266

Laminar flow in a porous tube with uniform mass injection  

Microsoft Academic Search

Laminar flows in a cylindrical porous tube with uniform mass injection through the porous wall are studies. The full Navier-Stokes equations are solved numerically by employing some finite-difference schemes. Solutions for velocity profiles and frictional pressure drops are obtained by the use of vorticity and stream function approach. The results indicate: 1) The fully developed velocity profiles do exist after

J. Ku; W. Leidenfrost

1981-01-01

267

Sensitivity analysis of transfer functions of laminar flames  

Microsoft Academic Search

The sensitivity of laminar premixed methane\\/air flames responses to acoustic forcing is investigated using direct numerical simulation to determine which parameters control their flame transfer function. Five parameters are varied: (1) the flame speed sL, (2) the expansion angle of the burnt gases ?, (3) the inlet air temperature Ta, (4) the inlet duct temperature Td and (5) the combustor

F. Duchaine; F. Boudy; D. Durox; T. Poinsot

268

Flight Tests of a Supersonic Natural Laminar Flow Airfoil  

NASA Technical Reports Server (NTRS)

A flight test campaign of a supersonic natural laminar flow airfoil has been recently completed. The test surface was an 80-inch (203 cm) chord and 40-inch (102 cm) span article mounted on the centerline store location of an F-15B airplane. The wing was designed with a leading edge sweep of effectively 0 deg to minimize boundary layer crossflow. The test article surface was coated with an insulating material to avoid significant heat transfer to and from the test article structure to maintain a quasi-adiabatic wall. An aircraft-mounted infrared camera system was used to determine boundary layer transition and the extent of laminar flow. The tests were flown up to Mach 2.0 and chord Reynolds numbers in excess of 30 million. The objectives of the tests were to determine the extent of laminar flow at high Reynolds numbers and to determine the sensitivity of the flow to disturbances. Both discrete (trip dots) and 2-D disturbances (forward-facing steps) were tested. A series of oblique shocks, of yet unknown origin, appeared on the surface, which generated sufficient crossflow to affect transition. Despite the unwanted crossflow, the airfoil performed well. The results indicate the sensitivity of the flow to the disturbances, which can translate into manufacturing tolerances, were similar to that of subsonic natural laminar flow wings.

Frederick, M. A.; Banks, D. W.; Garzon, G. A.; Matisheck, J. R.

2014-01-01

269

Laminar Wave-Train Structure of Collisionless Magnetic Slow Shocks.  

National Technical Information Service (NTIS)

The laminar wave-train structure of collisionless magnetic slow shocks is investigated using two-fluid hydromagnetics with ion-cyclotron-radius dispersion. For shock strengths less than the maximally strong switch-off shock, in the shock-leading edge, dis...

F. V. Coroniti

1970-01-01

270

Supersonic laminar flow development in a square duct  

NASA Technical Reports Server (NTRS)

Supersonic laminar flow development in a constant-area square duct exhibits as one of its distinguishing features the formation of two contrarotating secondary flow vortices centered about the corner bisector. This phenomenon does not occur in unbounded corner flow. The secondary flow causes an outward bulging of total pressure contours in the vicinity of the corner bisector for wholly attached flow conditions.

Davis, D. O.; Gessner, F. B.; Kerlick, G. D.

1987-01-01

271

Theory for Aerosol Generation in Laminar Flow Condensers  

Microsoft Academic Search

Generation of aerosols in laminar flow condensers is investigated theoretically. A model is developed for simultaneous heat and vapor mass transfer, aerosol nucleation, condensation, coagulation, thermophoresis, and diffusion representing the aerosol size distribution by a lognormal function throughout the process. The importance of the above physical phenomena and the effect of process parameters (reheater and boiler temperature, seed nuclei concentration)

Gautam M. Phanse; Sotiris E. Pratsinis

1989-01-01

272

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

273

Laminar epidermal hyperplasia and hyperkeratosis in an equine hoof  

PubMed Central

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.

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

2013-01-01

274

Application of laminar flow control to supersonic transport configurations  

NASA Technical Reports Server (NTRS)

The feasibility and impact of implementing a laminar flow control system on a supersonic transport configuration were investigated. A hybrid laminar flow control scheme consisting of suction controlled and natural laminar flow was developed for a double-delta type wing planform. The required suction flow rates were determined from boundary layer stability analyses using representative wing pressure distributions. A preliminary design of structural modifications needed to accommodate suction through a perforated titanium skin was carried out together with the ducting and systems needed to collect, compress and discharge the suction air. The benefits of reduced aerodynamic drag were weighed against the weight, volume and power requirement penalties of suction system installation in a mission performance and sizing program to assess the net benefits. The study showed a feasibility of achieving significant laminarization of the wing surface by use of a hybrid scheme, leading to an 8.2 percent reduction in the cruise drag. This resulted in an 8.5 percent reduction in the maximum takeoff weight and a 12 percent reduction in the fuel burn after the inclusion of the LFC system installation penalties. Several research needs were identified for a resolution of aerodynamics, structural and systems issues before these potential benefits could be realized in a practical system.

Parikh, P. G.; Nagel, A. L.

1990-01-01

275

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

276

Laminar recurrences, maxline, unstable singularities and biological dynamics  

Microsoft Academic Search

Recurrence quantification analysis can reveal subtle aspects of dynamics not easily appreciated by other methods such as the Fourier transform. Laminarity and maxline are two RQA variables that can demonstrate the presence of unstable singularities which are often found in biological dynamics. Examples are presented and their implications are discussed relative to deterministic dynamics and stochastic processes.

J. P. Zbilut; C. L. Webber Jr.

2008-01-01

277

Numerical Simulation of an Enclosed Laminar Jet Diffusion Flame in Microgravity Environment: Comparison with ELF Data  

NASA Technical Reports Server (NTRS)

Enclosed diffusion flames are commonly found in practical combustion systems, such as the power-plant combustor, gas turbine combustor, and jet engine after-burner. In these systems, fuel is injected into a duct with a co-flowing or cross-flowing air stream. The diffusion flame is found at the surface where the fuel jet and oxygen meet, react, and consume each other. In combustors, this flame is anchored at the burner (i.e., fuel jet inlet) unless adverse conditions cause the flame to lift off or blow out. Investigations of burner stability study the lift off, reattachment, and blow out of the flame. Flame stability is strongly dependent on the fuel jet velocity. When the fuel jet velocity is sufficiently low, the diffusion flame anchors at the burner rim. When the fuel jet velocity is increased, the flame base gradually moves downstream. However, when the fuel jet velocity increases beyond a critical value, the flame base abruptly jumps downstream. When this "jump" occurs, the flame is said to have reached its lift-off condition and the critical fuel jet velocity is called the lift-off velocity. While lifted, the flame is not attached to the burner and it appears to float in mid-air. Flow conditions are such that the flame cannot be maintained at the burner rim despite the presence of both fuel and oxygen. When the fuel jet velocity is further increased, the flame will eventually extinguish at its blowout condition. In contrast, if the fuel jet velocity of a lifted flame is reduced, the flame base moves upstream and abruptly returns to anchor at the burner rim. The fuel jet velocity at reattachment can be much lower than that at lift off, illustrating the hysteresis effect present in flame stability. Although there have been numerous studies of flame stability, the controlling mechanisms are not well understood. This uncertainty is described by Pitts in his review of various competing theories of lift off and blow out in turbulent jet diffusion flames. There has been some research on the stability of laminar flames, but most studies have focused on turbulent flames. It is also well known that the airflow around the fuel jet can significantly alter the lift off, reattachment and blow out of the jet diffusion flame. Buoyant convection is sufficiently strong in 1-g flames that it can dominate the flow-field, even at the burner rim. In normal-gravity testing, it is very difficult to delineate the effects of the forced airflow from those of the buoyancy-induced flow. Comparison of normal-gravity and microgravity flames provides clear indication of the influence of forced and buoyant flows on the flame stability. The overall goal of the Enclosed Laminar Flames (ELF) investigation (STS-87/USMP-4 Space Shuttle mission, November to December 1997) is to improve our understanding of the effects of buoyant convection on the structure and stability of co-flow diffusion flame, e.g., see http://zeta.lerc.nasa.gov/expr/elf.htm. The ELF hardware meets the experiment hardware limit of the 35-liter interior volume of the glovebox working area, and the 180x220-mm dimensions of the main door. The ELF experiment module is a miniature, fan-driven wind tunnel, equipped with a gas supply system. A 1.5-mm diameter nozzle is located on the duct's flow axis. The cross section of the duct is nominally a 76-mm square with rounded corners. The forced air velocity can be varied from about 0.2 to 0.9 m/s. The fuel flow can be set as high as 3 std. cubic centimeter (cc) per second, which corresponds to a nozzle exit velocity of up to 1.70 m/s. The ELF hardware and experimental procedure are discussed in detail in Brooker et al. The 1-g test results are repeated in several experiments following the STS-87 Mission. The ELF study is also relevant to practical systems because the momentum-dominated behavior of turbulent flames can be achieved in laminar flames in microgravity. The specific objectives of this paper are to evaluate the use reduced model for simulation of flame lift-off and blowout.

Jia, Kezhong; Venuturumilli, Rajasekhar; Ryan, Brandon J.; Chen, Lea-Der

2001-01-01

278

Relationship between oxygen transfer rate and airflow for fine-pore aeration under process conditions.  

PubMed

Although feedback systems that control the air supply to aeration tanks inherently incorporate some assumption about oxygen transfer response to changes in airflow, it is rare to measure this relationship under process conditions. This paper reports measurements of oxygen mass-transfer curves (MTCs) for a tank at the Tillman Water Reclamation Plant in Los Angeles, California. The curves were obtained by measuring the oxygen transfer efficiency (OTE) at selected points for several set values of airflow while the plant was operating. They approximate inverted parabolas because increasing the airflow increases the amount of oxygen supplied by the blowers, but decreases the OTE, which is the fraction of the supplied oxygen that actually enters the water. Data were recorded from both recently cleaned diffusers and ones that were moderately to severely fouled. The peaks in the curves from the fouled diffusers are at or below the midpoints of the observed ranges of airflows. Hence, there is only a narrow range of usable airflows between the lower limit, determined by the manufacturer of the diffusers, and the peak of the MTC, which is the maximum amount of oxygen that can be supplied. The peaks for the cleaned diffusers are higher, which allows more ability to adjust to changing biological loads. These results show that existing dissolved oxygen control systems may not be adequate and that fouling may reduce not only the overall efficiency of an aeration system but its ability to respond to changes in the biological load. The measurements also provide some insight to the limitations of using sparsely distributed dissolved oxygen sensors to control the aeration process and the excess costs that are incurred by the consequent need to compensate for uncertainty with extra air. However, additional testing is needed to determine whether the present results are aberrant or typical of tanks with fouled or cleaned diffusers. PMID:11561585

Iranpour, R; Stenstrom, M K

2001-01-01

279

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

PubMed Central

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.

Hutchinson, John R.; Farmer, CG

2013-01-01

280

Usability Evaluation of a Flight-Deck Airflow Hazard Visualization System  

NASA Technical Reports Server (NTRS)

Many aircraft accidents each year are caused by encounters with unseen airflow hazards near the ground, such as vortices, downdrafts, low level wind shear, microbursts, or turbulence from surrounding vegetation or structures near the landing site. These hazards can be dangerous even to airliners; there have been hundreds of fatalities in the United States in the last two decades attributable to airliner encounters with microbursts and low level wind shear alone. However, helicopters are especially vulnerable to airflow hazards because they often have to operate in confined spaces and under operationally stressful conditions (such as emergency search and rescue, military or shipboard operations). Providing helicopter pilots with an augmented-reality display visualizing local airflow hazards may be of significant benefit. However, the form such a visualization might take, and whether it does indeed provide a benefit, had not been studied before our experiment. We recruited experienced military and civilian helicopter pilots for a preliminary usability study to evaluate a prototype augmented-reality visualization system. The study had two goals: first, to assess the efficacy of presenting airflow data in flight; and second, to obtain expert feedback on sample presentations of hazard indicators to refine our design choices. The study addressed the optimal way to provide critical safety information to the pilot, what level of detail to provide, whether to display specific aerodynamic causes or potential effects only, and how to safely and effectively shift the locus of attention during a high-workload task. Three-dimensional visual cues, with varying shape, color, transparency, texture, depth cueing, and use of motion, depicting regions of hazardous airflow, were developed and presented to the pilots. The study results indicated that such a visualization system could be of significant value in improving safety during critical takeoff and landing operations, and also gave clear indications of the best design choices in producing the hazard visual cues.

Aragon, Cecilia R.

2004-01-01

281

Thermal Infrared Imaging: A Novel Method to Monitor Airflow During Polysomnography  

PubMed Central

Study Objectives: This is a feasibility study designed to evaluate the accuracy of thermal infrared imaging (TIRI) as a noncontact method to monitor airflow during polysomnography and to ascertain the chance-corrected agreement (?) between TIRI and conventional airflow channels (nasal pressure [Pn], oronasal thermistor and expired CO2 [PECO2]) in the detection of apnea and hypopnea. Design: Subjects were recruited to undergo polysomnography for 1 to 2 hours, during which simultaneous recordings from electroencephalography, electrooculography, electromyography, respiratory impedance plethysmography, conventional airflow channels, and TIRI were obtained. Setting: University-affiliated, American Academy of Sleep Medicine-accredited sleep disorders center. Patients or Participants: Fourteen volunteers without a history of sleep disordered breathing and 13 patients with a history of obstructive sleep apnea were recruited. Measurements and Results: In the detection of apnea and hypopnea, excellent agreement was noted between TIRI and thermistor (? = 0.92, Bayesian Credible Interval [BCI] 0.86, 0.96; p? = 0.99). Good agreement was noted between TIRI and Pn (? = 0.83, BCI 0.70, 0.90; p? = 0.98) and between TIRI and PECO2(? = 0.80, BCI 0.66, 0.89; p? = 0.94). Conclusions: TIRI is a feasible noncontact technology to monitor airflow during polysomnography. In its current methodologic incarnation, it demonstrates a high degree of chance-corrected agreement with the oronasal thermistor in the detection of apnea and hypopneas but demonstrates a lesser degree of chance-corrected agreement with Pn. Further overnight validation studies must be performed to evaluate its potential in clinical sleep medicine. Citation: Murthy JN; van Jaarsveld J; Fei J; Pavlidis I; Harrykissoon R; Lucke JF; Faiz S; Castriotta RJ. Thermal infrared imaging: a novel method to monitor airflow during polysomnography. SLEEP 2009;32(11):1521-1527.

Murthy, Jayasimha N.; van Jaarsveld, Johan; Fei, Jin; Pavlidis, Ioannis; Harrykissoon, Rajesh I; Lucke, Joseph F.; Faiz, Saadia; Castriotta, Richard J.

2009-01-01

282

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

283

A simulation study of the changes in PM2.5 concentrations due to interzonal airflow variations caused by internal door opening patterns  

NASA Astrophysics Data System (ADS)

Short-term variations in interzonal airflows can cause significant fluctuations in gaseous or particulate matter concentrations in indoor environments and therefore, interzonal airflow variations need careful consideration when modelling indoor pollutant concentrations. This study investigates the potential accuracy of modelling interzonal airflow variations and assesses the effect of interzonal airflow variations on indoor pollutant concentrations. A variable interzonal airflow is compared with a time-weighted average interzonal airflow, and the differences in the resulting estimates of indoor pollutant concentrations are analysed. Interzonal airflow variations were simulated by the opening/closing of internal doors for periods of 1, 2, 5, 10, 15 and 30 min. Based on experimental comparison, it can be concluded that the modelling approach used, accurately predicts PM2.5 concentrations for interzonal airflow variations for durations of 10 min or greater, with increasing accuracy for longer durations. The simulations demonstrate that both the time of occurrence and duration of the interzonal airflow variations are critical in determining indoor concentrations, and indicating that a time-weighted average interzonal airflow is not a suitable substitute for modelling interzonal airflow variations, as it under-predicts mean PM2.5 concentrations by up to 28%.

McGrath, J. A.; Byrne, M. A.; Ashmore, M. R.; Terry, A. C.; Dimitroulopoulou, C.

2014-04-01

284

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

285

Hydrodynamic Fluctuations in Laminar Fluid Flow. II. Fluctuating Squire Equation  

NASA Astrophysics Data System (ADS)

We use fluctuating hydrodynamics to evaluate the enhancement of thermally excited fluctuations in laminar fluid flow using plane Couette flow as a representative example. In a previous publication (J. Stat. Phys. 144:774, 2011) we derived the energy amplification arising from thermally excited wall-normal fluctuations by solving a fluctuating Orr-Sommerfeld equation. In the present paper we derive the energy amplification arising from wall-normal vorticity fluctuation by solving a fluctuating Squire equation. The thermally excited wall-normal vorticity fluctuations turn out to yield the dominant contribution to the energy amplification. In addition, we show that thermally excited streaks, even in the absence of any externally imposed perturbations, are present in laminar fluid flow.

Ortiz de Zárate, José M.; Sengers, Jan V.

2013-02-01

286

Laminar/turbulent oscillating flow in circular pipes  

NASA Technical Reports Server (NTRS)

A two-dimensional oscillating flow analysis was conducted simulating the gas flow inside Stirling engine heat exchangers. Both laminar and turbulent oscillating pipe flow were investigated numerically for Re(max) = 1920 (Va = 80), 10,800 (Va = 272), 19,300 (Va = 272), and 60,800 (Va = 126). The results are compared with experimental results of previous investigators. Predictions of the flow regime are also checked by comparing velocity amplitudes and phase difference with those from laminar theory and quasi-steady profile. A high Reynolds number k-epsilon turbulence model was used for turbulent oscillating pipe flow. Finally, the performance of the k-epsilon model was evaluated to explore the applicability of quasi-steady turbulent models to unsteady oscillating flow analysis.

Ahn, Kyung H.; Ibrahim, Mounir B.

1992-01-01

287

Preliminary aerodynamic design considerations for advanced laminar flow aircraft configurations  

NASA Technical Reports Server (NTRS)

Modern composite manufacturing methods have provided the opportunity for smooth surfaces that can sustain large regions of natural laminar flow (NLF) boundary layer behavior and have stimulated interest in developing advanced NLF airfoils and improved aircraft designs. Some of the preliminary results obtained in exploratory research investigations on advanced aircraft configurations at the NASA Langley Research Center are discussed. Results of the initial studies have shown that the aerodynamic effects of configuration variables such as canard/wing arrangements, airfoils, and pusher-type and tractor-type propeller installations can be particularly significant at high angles of attack. Flow field interactions between aircraft components were shown to produce undesirable aerodynamic effects on a wing behind a heavily loaded canard, and the use of properly designed wing leading-edge modifications, such as a leading-edge droop, offset the undesirable aerodynamic effects by delaying wing stall and providing increased stall/spin resistance with minimum degradation of laminar flow behavior.

Johnson, Joseph L., Jr.; Yip, Long P.; Jordan, Frank L., Jr.

1986-01-01

288

Laminar/turbulent oscillating flow in circular pipes  

NASA Astrophysics Data System (ADS)

A two-dimensional oscillating flow analysis was conducted simulating the gas flow inside Stirling engine heat exchangers. Both laminar and turbulent oscillating pipe flow were investigated numerically for Re(max) = 1920 (Va = 80), 10,800 (Va = 272), 19,300 (Va = 272), and 60,800 (Va = 126). The results are compared with experimental results of previous investigators. Predictions of the flow regime are also checked by comparing velocity amplitudes and phase difference with those from laminar theory and quasi-steady profile. A high Reynolds number k-epsilon turbulence model was used for turbulent oscillating pipe flow. Finally, the performance of the k-epsilon model was evaluated to explore the applicability of quasi-steady turbulent models to unsteady oscillating flow analysis.

Ahn, Kyung H.; Ibrahim, Mounir B.

1992-12-01

289

Numerical study of the laminar shock-boundary layer interaction  

NASA Astrophysics Data System (ADS)

The interaction of an oblique shock wave with a laminar boundary layer on an adiabatic flat plane was analyzed numerically with solutions of the two dimensional Navier-Stokes equations using McCormack's explicit finite volume method. The agreement between numerical calculations and experimental results is good. Local and global properties of the interaction region are discussed regarding shock strength, separation bubble length using a similarity law, and separation environment. The assymmetrical structure inside the separation bubble produces an assymmetrical shape of the wall shear stress distribution. The calculation speed was increased by algorithm vectorization on a CRAY 1S supercomputer. Further investigations for determination of a similarity law in interaction with turbulent boundary layer, of the physical mechanisms of the laminar interaction, and for study of the wall temperature transfer are recommended.

Katzer, E.

1986-04-01

290

Numerical study of the laminar shock boundary layer interaction  

NASA Astrophysics Data System (ADS)

The interaction of an oblique shock wave with a laminar boundary layer on an adiabatic flat plate was analyzed numerically with solutions of the two dimensional Navier-Stokes equations using McCormack's explicit finite volume method. The agreement between numerical calculations and experimental results is good. Local and global properties of the interaction region are discussed regarding shock strength, separation bubble length using a similarity law, and separation environment. The asymetrical structure inside the separation bubble produces an asymetrical shape of the wall shear stress distribution. The calculation speed was increased by algorithm vectorization on a CRAY 1S supercomputer. Further investigations for determination of a similarity law in interaction with turbulent boundary layer, of the physical mechanisms of the laminar interaction, and for study of the wall temperature transfer are recommended.

Katzer, E.

1985-02-01

291

Some observations regarding steady laminar flows past bluff bodies.  

PubMed

Steady laminar flows past simple objects, such as a cylinder or a sphere, have been studied for well over a century. Theoretical, experimental and numerical methods have all contributed fundamentally towards our understanding of the resulting flows. This article focuses on developments during the past few decades, when mostly numerical and asymptotical advances have provided insights also for steady, although unstable, high-Reynolds-numbers flow regimes. PMID:24936017

Fornberg, Bengt; Elcrat, Alan R

2014-07-28

292

Drag reduction in laminar and turbulent flows past superhydrophobic surfaces  

Microsoft Academic Search

A series of experiments and direct numerical simulations (DNS) will be presented which demonstrate significant drag reduction for both laminar and turbulent flows of water through channels using superhydrophobic surfaces with well-defined micron-sized surface roughness. The surfaces are fabricated from PDMS to incorporate precise patterns of ridges or posts that can support a shear-free air-water interface. A flow cell is

Jonathan P. Rothstein

2009-01-01

293

Computational sensitivity analysis of geometric parameters in laminar superhydrophobic microchannels  

Microsoft Academic Search

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 alpha. The simulations allow for a phase offset l between the shear-free surfaces on the top and bottom

Asghar Yarahmadi; Meredith Metzger

2010-01-01

294

Flame\\/Wall Interactions: Laminar Study of Unburnt HC Formation  

Microsoft Academic Search

This work presents a numerical study dedicated to the formation of unburnt hydrocarbon. Two configurations: head-on quenching\\u000a (HOQ) on a planar wall and in crevices, are considered. It is well known that they contribute for an important part to the\\u000a sources of hydrocarbon (HC) emission in a combustion chamber. The aim of this work is to use laminar flame simulations

Marc Chauvy; Bruno Delhom; Julien Reveillon; Francois-Xavier Demoulin

2010-01-01

295

Unsteady Laminar CFD Simulation of Undulatory Rainbow Trout Swimming Hydrodynamics  

Microsoft Academic Search

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

Patrick Flanagan; Rollin Hotchkiss; David Stock

2004-01-01

296

An experimental investigation of an acoustically excited laminar premixed flame  

Microsoft Academic Search

A two-dimensional laminar premixed flame is stabilized over a burner in a confined duct and is subjected to external acoustic forcing from the downstream end. The equivalence ratio of the flame is 0.7. The flame is stabilized in the central slot of a three-slotted burner. The strength of the shear layer of the cold reactive mixture through the central slot

S. Kartheekeyan; S. R. Chakravarthy

2006-01-01

297

Rich methane premixed laminar flames doped with light unsaturated hydrocarbons  

Microsoft Academic Search

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 C3H4 was

Hadj-Ali Gueniche; Pierre-Alexandre Glaude; Guillaume Dayma; René Fournet; F. Battin-Leclerc

2006-01-01

298

Rich methane premixed laminar flames doped with light unsaturated hydrocarbons  

Microsoft Academic Search

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 CâHâ was

H. A. Gueniche; P. A. Glaude; G. Dayma; R. Fournet; F. Battin-Leclerc

2006-01-01

299

Laminar natural convection along vertical corners and rectangular channels  

NASA Astrophysics Data System (ADS)

Laminar natural convection along a vertical right angle corner and in rectangular ducts has been analyzed. Solutions for isothermal and constant heat flux walls have been obtained by a coupled strongly implicit procedure. The effect of Prandtl number on the corner flow behavior is examined. It is also shown that rectangular ducts entrain a larger amount of mass than do square ducts of equal length.

Ramakrishna, K.; Khosla, P. K.; Rubin, S. G.

300

Experimental investigation of oxide nanofluids laminar flow convective heat transfer  

Microsoft Academic Search

In the present investigation nanofluids containing CuO and Al2O3 oxide nanoparticles in water as base fluid in different concentrations produced and the laminar flow convective heat transfer through circular tube with constant wall temperature boundary condition were examined. The experimental results emphasize that the single phase correlation with nanofluids properties (Homogeneous Model) is not able to predict heat transfer coefficient

S. Zeinali Heris; S. Gh. Etemad; M. Nasr Esfahany

2006-01-01

301

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

302

On stability of free laminar boundary layer between parallel streams  

NASA Technical Reports Server (NTRS)

An analysis and calculations on the stability of the free laminar boundary layer between parallel streams were made for an incompressible fluid using the Tollmien-Schlichting theory of small disturbances. Because the boundary conditions are at infinity, two solutions of the Orr-Sommerfeld stability equations need not be considered, and the remaining two solutions are exponential in character at the infinite boundaries. The calculations show that the flow is unstable except for very low Reynolds numbers.

Lessen, Martin

1950-01-01

303

Flame Shapes of Nonbuoyant Laminar Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

The shapes (flame-sheet and luminous-flame boundaries) of steady nonbuoyant round hydrocarbon-fueled laminar-jet diffusion flames in still and coflowing air were studied both experimentally and theoretically. Flame-sheet shapes were measured from photographs using a CH optical filter to distinguish flame-sheet boundaries in the presence of blue CO2 and OH emissions and yellow continuum radiation from soot. Present experimental conditions included acetylene-, methane-, propane-, and ethylene-fueled flames having initial reactant temperatures of 300 K, ambient pressures of 4-50 kPa, jet exit Reynolds number of 3-54, initial air/fuel velocity ratios of 0-9 and luminous flame lengths of 5-55 mm; earlier measurements for propylene- and 1,3-butadiene-fueled flames for similar conditions were considered as well. Nonbuoyant flames in still air were observed at micro-gravity conditions; essentially nonbuoyant flames in coflowing air were observed at small pressures to control effects of buoyancy. Predictions of luminous flame boundaries from soot luminosity were limited to laminar smokepoint conditions, whereas predictions of flame-sheet boundaries ranged from soot-free to smokepoint conditions. Flame-shape predictions were based on simplified analyses using the boundary layer approximations along with empirical parameters to distinguish flame-sheet and luminous flame (at the laminar smoke point) boundaries. The comparison between measurements and predictions was remarkably good and showed that both flame-sheet and luminous-flame lengths are primarily controlled by fuel flow rates with lengths in coflowing air approaching 2/3 lengths in still air as coflowing air velocities are increased. Finally, luminous flame lengths at laminar smoke-point conditions were roughly twice as long as flame-sheet lengths at comparable conditions due to the presence of luminous soot particles in the fuel-lean region of the flames.

Xu, F.; Dai, Z.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z. G. (Technical Monitor)

2001-01-01

304

Flame Shapes of Nonbuoyant Laminar Jet Diffusion Flames. Appendix K  

NASA Technical Reports Server (NTRS)

The shapes (flame-sheet and luminous-flame boundaries) of steady nonbuoyant round hydrocarbon-fueled laminar-jet diffusion flames in still and coflowing air were studied both experimentally and theoretically. Flame-sheet shapes were measured from photographs using a CH optical filter to distinguish flame-sheet boundaries in the presence of blue C02 and OH emissions and yellow continuum radiation from soot. Present experimental conditions included acetylene-, methane-, propane-, and ethylene-fueled flames having initial reactant temperatures of 300 K, ambient pressures of 4-50 kPa, jet exit Reynolds number of 3-54, initial air/fuel velocity ratios of 0-9 and luminous flame lengths of 5-55 mm; earlier measurements for propylene- and 1,3-butadiene-fueled flames for similar conditions were considered as well. Nonbuoyant flames in still air were observed at micro-gravity conditions; essentially nonbuoyant flames in coflowing air were observed at small pressures to control effects of buoyancy. Predictions of luminous flame boundaries from soot luminosity were limited to laminar smoke-point conditions, whereas predictions of flame-sheet boundaries ranged from soot-free to smoke-point conditions. Flame-shape predictions were based on simplified analyses using the boundary layer approximations along with empirical parameters to distinguish flame-sheet and luminous-flame (at the laminar smoke point) boundaries. The comparison between measurements and predictions was remarkably good and showed that both flame-sheet and luminous-flame lengths are primarily controlled by fuel flow rates with lengths in coflowing air approaching 2/3 lengths in still air as coflowing air velocities are increased. Finally, luminous flame lengths at laminar smoke-point conditions were roughly twice as long as flame-sheet lengths at comparable conditions due to the presence of luminous soot particles in the fuel-lean region of the flames.

Xu, F.; Faeth, G. M.; Urban, D. L. (Technical Monitor); Yuan, Z.-G. (Technical Monitor)

2000-01-01

305

Topological Charge and the Laminar Structure of the QCD Vacuum  

SciTech Connect

Monte Carlo studies of pure glue SU(3) gauge theory using the overlap-based topological charge operator have revealed a laminar structure in the QCD vacuum consisting of extended, thin, coherent, locally 3-dimensional sheets of topological charge embedded in 4D space, with opposite sign sheets interleaved. In this talk I discuss the interpretation of these Monte Carlo results in terms of our current theoretical understanding of theta-dependence and topological structure in asymptotically free gauge theories.

Thacker, H. B. [University of Virginia, Charlottesville, VA 22904 (United States)

2007-02-27

306

Ground vibration test of the laminar flow control JStar airplane  

NASA Technical Reports Server (NTRS)

A ground vibration test was conducted on a Lockheed JetStar airplane that had been modified for the purpose of conducting laminar flow control experiments. The test was performed prior to initial flight flutter tests. Both sine-dwell and single-point-random excitation methods were used. The data presented include frequency response functions and a comparison of mode frequencies and mode shapes from both methods.

Kehoe, M. W.; Cazier, F. W., Jr.; Ellison, J. F.

1985-01-01

307

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

308

Laminar flow past a sphere rotating in the transverse direction  

Microsoft Academic Search

Laminar flow past a sphere rotating in the transverse direction is numerically investigated in order to understand the effect\\u000a of the rotation on the characteristics of flow over the sphere. Numerical simulations are performed at Re = 100, 250 and 300,\\u000a where the Reynolds number is based on the free-stream velocity and the sphere diameter. The rotational speeds considered are

Dongjoo Kim

2009-01-01

309

Laminar recurrences, maxline, unstable singularities and biological dynamics  

Microsoft Academic Search

Recurrence quantification analysis can reveal subtle aspects of dynamics not easily\\u000a appreciated by other methods such as the Fourier transform. Laminarity and maxline are two RQA variables that can demonstrate\\u000a the presence of unstable singularities which are often found in biological dynamics. Examples are presented and their implications\\u000a are discussed relative to deterministic dynamics and stochastic processes.

J. P. Zbilut; C. L. Webber

2008-01-01

310

Drag reduction in laminar and turbulent flows past superhydrophobic surfaces  

NASA Astrophysics Data System (ADS)

A series of experiments and direct numerical simulations (DNS) will be presented which demonstrate significant drag reduction for both laminar and turbulent flows of water through channels using superhydrophobic surfaces with well-defined micron-sized surface roughness. The surfaces are fabricated from PDMS to incorporate precise patterns of ridges or posts that can support a shear-free air-water interface. A flow cell is used to measure the pressure drop and velocity profile as a function of the flow rate for a series of channel geometries and superhydrophobic surface designs. DNS are performed for flow past superhydrophobic surfaces which both complement and extend the range of geometries and Reynolds number obtained in the experiments. We will show that drag reductions up to 75% and slip lengths up to 150?m can be obtained in turbulent flows past superhydrophobic surfaces. Additionally, we will show that slip along the air water interface forestalls the transition from laminar to turbulent flow. The drag reduction is found to increases with increasing post/ridge spacing and the fraction of air-water interface. In turbulent flows, the drag reduction increases with Reynolds number before eventually reaching a plateau. These results suggest that in turbulent flows, the drag reduction scales with the thickness of the viscous sublayer and not the overall channel height as in laminar flows.

Rothstein, Jonathan P.

2009-11-01

311

Co-laminar flow cells for electrochemical energy conversion  

NASA Astrophysics Data System (ADS)

In this review, we present the major developments in the evolution of ‘membraneless’ microfluidic electrochemical cells which utilize co-laminar flow to minimize reactant mixing while producing electrical power in a compact form. Categorization of devices according to reactant phases is suggested, with further differentiation being subject to fabrication method and function, namely multi-layer sandwich structures for medium-power cell stacks and single-layer monolithic cells for low-power on-chip applications. Power density metrics reveal that recent co-laminar flow cells compare favourably with conventional membrane-based electrochemical cells and that further optimization of device architecture could be expedited through standardized testing. Current research trends indicate that co-laminar flow cell technology for power generation is growing rapidly and finding additional use as an analytical and education tool. Practical directions and recommendations for further research are provided, with the intention to guide scientific advances and technology development toward ultimate pairing with commercial applications.

Goulet, Marc-Antoni; Kjeang, Erik

312

Enhanced mixing in laminar flows with ultrahydrophobic surfaces  

NASA Astrophysics Data System (ADS)

Ultrahydrophobic surfaces have recently been shown to produce significant drag reduction in laminar flows. In this presentation, we will talk about current research aimed at engineering these ultrahydrophobic surfaces to produce mixing enhancement in laminar flows. Our research utilizes the slip velocity along the shear-free air-water interface formed between the surface structures to produce secondary flows which stretch and fold fluid elements to produce enhanced mixing. The surfaces are fabricated with PDMS casted from silicon mold with hydrophobic patterns of microridges in different spacing and at various angles to the flow direction. The effectiveness of the surfaces is tested in micro mixing flow cell using a confocal microscope to track fluorescent die. At the inlet, to streams of fluid are brought together at a y-junction, one stream is tagged with fluorescent die. The normalized fluorescence intensity is used in experiments to calculate the degree of mixing and compared directly to the mixing predictions from numerical simulations. The kinematical mechanism of this laminar mixing enhancement method is studied though both experimental and simulations. The mixing length is shown to be dramatically reduced when compared to smooth channels and can be optimized through the design of the microridges.

Ou, Jia; Moss, Geoffrey; Rothstein, Jonathan

2006-11-01

313

Detection of Cortical Laminar Architecture Using Manganese-Enhanced MRI  

PubMed Central

Changes in Manganese-Enhanced MRI (MEMRI) contrast across the rodent somatosensory cortex were compared to the cortical laminae as identified by tissue histology and administration of an anatomical tracer to cortex and thalamus. Across the cortical thickness, MEMRI signal intensity was low in layer I, increased in layer II, decreased in layer III until mid-layer IV, and increased again, peaking in layer V, before decreasing through layer VI. The reeler mouse mutant was used to confirm that the cortical alternation in MEMRI contrast was related to laminar architecture. Unlike in wild-type mice, the reeler cortex showed no appreciable changes in MEMRI signal, consistent[ACS1] with absence of cortical laminae in histological slides. The tract-tracing ability of MEMRI was used to further confirm assignments and demonstrate laminar specificity. Twelve to sixteen hours after stereotaxic injections of MnCl2 to the ventroposterior thalamic nuclei, an overall increase in signal intensity was detected in primary somatosensory cortex compared to other brain regions. Maximum intensity projection images revealed a distinctly bright stripe located 600 ? 700 ?m below the pial surface, in layer IV. The data show that both systemic and tract-tracing forms of MEMRI are useful for studying laminar architecture in the brain.

Silva, Afonso C.; Lee, Junghee; Wu, Carolyn W.-H.; Tucciarone, Jason; Pelled, Galit; Aoki, Ichio; Koretsky, Alan P.

2008-01-01

314

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

315

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

316

Type I planet migration in nearly laminar disks  

SciTech Connect

We describe two-dimensional hydrodynamic simulations of the migration of low-mass planets ({<=}30 M{sub {circle_plus}}) in nearly laminar disks (viscosity parameter {alpha} < 10{sup -3}) over timescales of several thousand orbit periods. We consider disk masses of 1, 2, and 5 times the minimum mass solar nebula, disk thickness parameters of H/r = 0.035 and 0.05, and a variety of {alpha} values and planet masses. Disk self-gravity is fully included. Previous analytic work has suggested that Type I planet migration can be halted in disks of sufficiently low turbulent viscosity, for {alpha} {approx} 10{sup -4}. The halting is due to a feedback effect of breaking density waves that results in a slight mass redistribution and consequently an increased outward torque contribution. The simulations confirm the existence of a critical mass (M{sub {alpha}} {approx} 10M{sub {circle_plus}}) beyond which migration halts in nearly laminar disks. For {alpha} {approx}> 10{sup -3}, density feedback effects are washed out and Type I migration persists. The critical masses are in good agreement with the analytic model of Rafikov. In addition, for {alpha} {approx}> 10{sup -4} steep density gradients produce a vortex instability, resulting in a small time-varying eccentricity in the planet's orbit and a slight outward migration. Migration in nearly laminar disks may be sufficiently slow to reconcile the timescales of migration theory with those of giant planet formation in the core accretion model.

Li, Hui [Los Alamos National Laboratory; Li, Shengtai [Los Alamos National Laboratory; Lubow, S H [STSI; Lin, D [UCSC

2008-01-01

317

Plasma and lipoprotein lipids and apolipoproteins AI, AII and B in patients with chronic airflow limitation.  

PubMed Central

Plasma and lipoprotein cholesterol and triglycerides, and plasma apolipoproteins AI, AII and B were compared in patients with chronic airflow limitation, and normal controls matched for body mass index. The controls were non-smokers, and free from respiratory disease. High-density lipoprotein (HDL) cholesterol concentration was significantly elevated in the patients, due mainly to a raised HDL2 cholesterol level. HDL triglyceride was significantly lower in the patients. All other lipids were not different from normal. Apolipoprotein AI levels were significantly raised in the patients but other apolipoproteins were unchanged. The changes found may account in part for the fact that patients with chronic airflow limitation have a lower incidence of atherosclerotic heart disease.

Bolton, C H; Mulloy, E; Harvey, J; Downs, L G; Hartog, M

1989-01-01

318

Modeling the acoustical and airflow performance of natural ventilation inlet and outlet units  

NASA Astrophysics Data System (ADS)

One aspect of the trend towards designing green buildings has been the increasing use of natural ventilation for buildings which otherwise might have required mechanical ventilation or even full air conditioning. However, the pressure differentials available to drive the natural ventilation process are small and hence relatively large inlets and outlets with low resistance to flow are required. These apertures constitute significant acoustic weak points on building facades and hence need to be treated to reduce noise ingress. Although there are a number of natural ventilation units available they have frequently been designed from the application of simple principles without any attempt to optimise both their airflow and acoustical performance. In this paper the results of a series of computer modeling exercises are described using acoustic FEM and BEM plus Computational Fluid Dynamics (CFD) which seeks to establish recommendations for the optimum design of natural ventilation inlet and outlet devices for both acoustical and airflow performance.

Oldham, David J.; Kang, Jian; Brocklesby, Martin

2005-04-01

319

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

320

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

321

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

322

Acute Effect of Cigarette Smoke and Nicotine on Airway Blood Flow and Airflow in Healthy Smokers  

Microsoft Academic Search

Cigarette smoke contains irritants and vasoactive substances. We wanted to determine the effect of smoking a cigarette and\\u000a of nasally or orally inhaled nicotine on airway blood flow (Qaw) and airflow in smokers. In ten healthy current smokers, Qaw, FEV1, and FEF25–75 were measured before and at 5, 30, and 180 min after smoking a cigarette. The effects of systemic

Kanwaldeep Randhawa; Eliana Mendes; Adam Wanner

2006-01-01

323

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

PubMed Central

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.

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

2013-01-01

324

Microfabricated airflow nozzle for microencapsulation of living cells into 150 micrometer microcapsules  

Microsoft Academic Search

Microencapsulation of genetically engineered cells has attracted much attention as an alternative nonviral strategy to gene\\u000a therapy. Though smaller microcapsules (i.e. less than 300 ?m) theoretically have various advantages, technical limitations\\u000a made it difficult to prove this notion. We have developed a novel microfabricated device, namely a micro-airflow-nozzle (MAN),\\u000a to produce 100 to 300 ?m alginate microcapsules with a narrow size distribution.

Shinji Sugiura; Tatsuya Oda; Yasuyuki Aoyagi; Ryota Matsuo; Tsuyoshi Enomoto; Kunio Matsumoto; Toshikazu Nakamura; Mitsuo Satake; Atsushi Ochiai; Nobuhiro Ohkohchi; Mitsutoshi Nakajima

2007-01-01

325

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

326

Emphysema Predicts Hospitalisation and Incident Airflow Obstruction among Older Smokers: A Prospective Cohort Study  

PubMed Central

Background Emphysema on CT is common in older smokers. We hypothesised that emphysema on CT predicts acute episodes of care for chronic lower respiratory disease among older smokers. Materials and Methods Participants in a lung cancer screening study age ?60 years were recruited into a prospective cohort study in 2001–02. Two radiologists independently visually assessed the severity of emphysema as absent, mild, moderate or severe. Percent emphysema was defined as the proportion of voxels ? ?910 Hounsfield Units. Participants completed a median of 5 visits over a median of 6 years of follow-up. The primary outcome was hospitalization, emergency room or urgent office visit for chronic lower respiratory disease. Spirometry was performed following ATS/ERS guidelines. Airflow obstruction was defined as FEV1/FVC ratio <0.70 and FEV1<80% predicted. Results Of 521 participants, 4% had moderate or severe emphysema, which was associated with acute episodes of care (rate ratio 1.89; 95% CI: 1.01–3.52) adjusting for age, sex and race/ethnicity, as was percent emphysema, with similar associations for hospitalisation. Emphysema on visual assessment also predicted incident airflow obstruction (HR 5.14; 95% CI 2.19–21.1). Conclusion Visually assessed emphysema and percent emphysema on CT predicted acute episodes of care for chronic lower respiratory disease, with the former predicting incident airflow obstruction among older smokers.

McAllister, David A.; Ahmed, Firas S.; Austin, John H. M.; Henschke, Claudia I.; Keller, Brad M.; Lemeshow, Adina; Reeves, Anthony P.; Mesia-Vela, Sonia; Pearson, G. D. N.; Shiau, Maria C.; Schwartz, Joseph E.; Yankelevitz, David F.; Barr, R. Graham

2014-01-01

327

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

2009-10-01

328

Airflow and autonomic responses to stress and relaxation in asthma: the impact of stressor type.  

PubMed

The impact of stress on respiratory airflow in asthmatics is unclear. Part of the uncertainty may spring from the different physiological effects of different stressors. Given their potential to elicit increases in parasympathetic vagal activity, stressful situations that present few opportunities for coping (passive coping stressors) may be particularly problematic for people with asthma. Thirty-one adult asthmatics participated in a protocol including a widely used passive coping stressor (the cold pressor test), an active coping stressor (mental arithmetic), an interview about an upsetting asthma-related incident (viewed as a potential passive coping stressor given the exposure to unpleasant memories), and progressive muscle relaxation. Repeated measurements of airflow (via peak expiratory flow), vagal tone (via heart rate variability), and other variables were obtained. The cold pressor test, asthma interview and progressive muscle relaxation produced significant decreases in airflow compared to the baseline period. The cold pressor test and progressive muscle relaxation produced significant, complementary increases in vagal tone. These results suggest that passive coping stressors and other stimuli (e.g., certain forms of relaxation) that elicit increased vagal tone may be associated with poorer asthma control, a view consistent with a significant negative correlation between the participant's mean vagal tone response to the tasks and score on a measure of asthma self-efficacy. PMID:15975675

Aboussafy, David; Campbell, Tavis S; Lavoie, Kim; Aboud, Frances E; Ditto, Blaine

2005-09-01

329

Rupatadine improves nasal symptoms, airflow and inflammation in patients with persistent allergic rhinitis: a pilot study.  

PubMed

Nasal obstruction is the main symptom in patients with allergic rhinitis and may be measured by rhinomanometry. Rupatadine is a new antihistamine with potential antiallergic activities. The aim of this pilot study is to evaluate nasal symptoms, nasal airflow and nasal mediators in patients with persistent allergic rhinitis, before and after treatment with rupatadine. Twenty patients with persistent allergic rhinitis were evaluated, 15 males and 5 females (mean age 35 +/- 9.1 years), all of whom received rupatadine (10 mg/daily) for 3 weeks. Nasal and ocular symptoms (measured by VAS), rhinomanometry, and nasal mediators (ECP and tryptase) were assessed in all subjects before and after treatment. Rupatadine treatment induced significant symptom relief (both nasal and ocular, respectively p=0.005 and p=0.0004), including obstruction (p=0.0015) and significant increase of nasal airflow (p=0.0025). Moreover, there was a significant difference of nasal mediators. In conclusion, this pilot study demonstrates the effectiveness of rupatadine treatment in: i) improving nasal and ocular symptoms, ii) increasing nasal airflow, iii) exerting antiallergic activity in patients with persistent allergic rhinitis. These positive results could explain the effectiveness of rupatadine in the treatment of persistent allergic rhinitis, as reported in a previous study Further controlled studies need to be conducted to confirm these preliminary findings. PMID:20487631

Ciprandi, Giorgio; Cirillo, I

2010-01-01

330

Airflow influence on the discharge performance of dielectric barrier discharge plasma actuators  

NASA Astrophysics Data System (ADS)

In the present work, the effect of the airflow on the performance of dielectric barrier discharge plasma-actuators is investigated experimentally. In order to analyze the actuator's performance, luminosity measurements have been carried out simultaneously with the recording of the relevant electrical parameters. A performance drop of about 10% is observed for the entire measured parameter range at a flow speed of M = 0.145 (U?=50 m/s). This insight is of particular importance, since the plasma-actuator control authority is already significantly reduced at this modest speed level. The results at higher Mach numbers (0.4airflow velocities. Two non-dimensional scaling numbers are proposed to characterize and quantify the airflow influence. It is demonstrated that these numbers span a universal performance drop diagram for the entire range of investigated operating parameters.

Kriegseis, J.; Grundmann, S.; Tropea, C.

2012-07-01

331

Hair sensor using a photoelectronic principle for sensing airflow and its direction  

NASA Astrophysics Data System (ADS)

Many organisms have diverse hair cells to instantaneously perceive the change of surroundings so that they can keep away from threats. These organs can precisely detect the tiny variations of airflow, water flow, sound, or pressure, and also resolve their affecting directions. Through this brilliant inspiration by the insects' cilia, we decided to design and develop a hair sensor for detecting two-dimensional airflow and pressure waves by using photoelectronic principles. The hair sensor inherently consists of an artificial cilium supported by an elastic membrane. A light-emitting diode and a quadrant photodiode are used as the photoelectronic sensor. The airflow or pressure wave directly stimulates the cilium to sway, and this motion contributes to let the projected light beam shift over the quadrant photodiode, whose four photodiodes produce then corresponding output signals. Because of dynamic and high-sensitive properties of the photoelectronic sensor, the hair sensor we developed possesses a high measurement resolution to be able to detect very tiny stimulation and its affecting direction. According to its multifaceted characteristics and simple structure, the hair sensor can be applied in numerous potential application fields, such as intrusion alarm system, noise detection system, as well as a tactile sensor.

Huang, Kuang-Yuh; Huang, Chien-Tai

2011-01-01

332

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

333

Sleep position and the ocular surface in a high airflow environment  

PubMed Central

Purpose To study the relationship between sleep position and ocular surface symptoms and signs in an high air flow environment. Methods Prospective observational study of new patients attending the dry eye clinic was performed. Patients with pre-existing ocular history, relevant systemic history (e.g. Sjogren’s syndrome) or who were using topical or systemic therapy for dry eye were not included. Data were collected from the patient to document their dry eye symptoms; preferred dependent sleeping side and their bedroom airflow. All patients were examined by a clinician blind to the patient’s responses where Schirmer’s test and slit lamp examination were performed looking for the presence of lagophthalmos and corneal epitheliopathy. Results 48 patients enrolled into the study of which 23 were males and 25 were females with a normal and comparable age distribution. The study found a strong association between patients’ preferred sleeping side and the incidence of corneal epitheliopathy in the contralateral eye particularly in patients with evidence of lagophthalmos. Dry eye symptoms were found to be worse and tear production lower on the contralateral side to the preferred sleeping side particularly in patients who sleep in a high airflow environment. Conclusion In patients sleeping in a high airflow environment with nocturnal lagophthalmos, this study observed an association between preferred dependent sleep position and increased dry eye symptoms, lower Schirmer’s scores and increased corneal epitheliopathy in the contralateral eye.

Gauba, Vinod; Curtis, Zoe J.

2013-01-01

334

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

PubMed

This study aimed 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 25-86 years were included. Periodontal status was assessed by clinical attachment loss (CAL), probing depth and number of missing teeth. Lung function was measured using spirometry, body plethysmography and diffusing capacity of the lung for carbon monoxide. Linear regression models using fractional polynomials were used to assess associations between periodontal disease and lung function. Fibrinogen and high-sensitivity 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 of the lung for carbon monoxide. Associations were confirmed for mean probing depth, extent measures of CAL/probing depth and number of missing teeth. 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

2013-12-01

335

Flight-measured laminar boundary-layer transition phenomena including stability theory analysis  

NASA Technical Reports Server (NTRS)

Flight experiments were conducted on a single-engine turboprop aircraft fitted with a 92-in-chord, 3-ft-span natural laminar flow glove at glove section lift coefficients from 0.15 to 1.10. The boundary-layer transition measurement methods used included sublimating chemicals and surface hot-film sensors. Transition occurred downstream of the minimum pressure point. Hot-film sensors provided a well-defined indication of laminar, laminar-separation, transitional, and turbulent boundary layers. Theoretical calculations of the boundary-layer parameters provided close agreement between the predicted laminar-separation point and the measured transition location. Tollmien-Schlichting (T-S) wave growth n-factors between 15 and 17 were calculated at the predicted point of laminar separation. These results suggest that for many practical airplane cruise conditions, laminar separation (as opposed to T-S instability) is the major cause of transition in predominantly two-dimensional flows.

Obara, C. J.; Holmes, B. J.

1985-01-01

336

The effect of debris accumulation on and filter resistance to airflow for four commercially available vacuum cleaners.  

PubMed

Mortar removal with right-angle grinders can cause excessive exposure to respirable crystalline silica. To control this dust exposure, vacuum cleaners need to exhaust 2.3 m(3)/min (80 cubic feet per minute) from the grinder's exhaust hood. Maintaining this airflow while collecting as much as 15.9 kg (35 lb) of debris in the vacuum cleaner has been problematic. A laboratory study was conducted to evaluate how mortar debris affects vacuum cleaner airflow and filter pressure loss. Four vacuum cleaners were tested. Two of the vacuum cleaners used vacuum cleaner bags as a prefilter; the other two vacuum cleaners used cyclones to reduce the amount of debris that reaches the filter. Test debris was collected by a masonry restoration contractor during actual mortar removal using a grinder fitted with a hood. The hood is attached to a vacuum cleaner with cyclonic pre-separation. The vacuum cleaner fan curves were obtained experimentally to learn how pressure loss affects vacuum cleaner airflows. Then, 15.9 kg (35 lb) of mortar removal debris was sucked into the vacuum cleaner in 2.27-kg (5-lb) increments. Before and after adding each 2.27-kg (5-lb) increment of debris, vacuum cleaner airflows were measured with a venturi meter, and vacuum cleaner static pressures were measured at the inlet to the vacuum cleaner motor, and before and after each filter. The vacuum cleaners equipped with cyclonic pre-separation were unaffected by the mass of debris collected in the vacuum cleaner and were able to maintain airflows in excess of 1.98 m(3)/min (70 cfm) throughout the testing program. As debris accumulated in the vacuum cleaners that used bags, airflow decreased from 2.3 m(3)/min (80 cfm) to as little as 0.85 m(3)/min (30 cfm). This airflow loss is caused by the increased airflow resistance of the bags that increased from less 0.03 kPa/m(3)/min (0.1 inches of water per cfm) to 16.7 kPa/m(3)/min (1.9 inches of water/cfm). Apparently, vacuum cleaners using bags should be used in applications where adequate dust control can be achieved at airflows less than 0.85 m(3)/min (30 cfm). Vacuum cleaners with cyclonic pre-separators provided superior and cost-effective dust control compared with vacuums with bags when dust loading was high and when more than 30 cfm of airflow is needed for dust control. PMID:19360515

Heitbrink, William A; Santalla-Elias, Javier

2009-06-01

337

Axisymmetric thermoviscoelastoplastic state of branched laminar shells, taking account of transverse-shear and torsional deformation  

SciTech Connect

The nonaxisymmetric thermoelastic stress-strain state (SSS) of branched laminar orthotropic shells was considered; the axisymmetric thermoviscoelastic SSS of branched laminar orthotropic shells was considered; and the axisymmetric thermoviscoelastoplastic SSS of branched laminar isotropic shells was considered, taking into account of the transverse-shear deformation. In the present work, in contrast, the axisymmetric thermoviscoelastoplastic SSS of branched laminar isotropic shells is considered, taking account of transverse-shear and torsional deformation. Layers that are made from orthotropic materials and deform in the elastic region may be present.

Galishin, A.Z. [S.P. Timoshenko Institute of Mechanics, Kiev (Ukraine)

1995-10-01

338

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

339

Laminar circuit organization and response modulation in mouse visual cortex  

PubMed Central

The mouse has become an increasingly important animal model for visual system studies, but few studies have investigated local functional circuit organization of mouse visual cortex. Here we used our newly developed mapping technique combining laser scanning photostimulation (LSPS) with fast voltage-sensitive dye (VSD) imaging to examine the spatial organization and temporal dynamics of laminar circuit responses in living slice preparations of mouse primary visual cortex (V1). During experiments, LSPS using caged glutamate provided spatially restricted neuronal activation in a specific cortical layer, and evoked responses from the stimulated layer to its functionally connected regions were detected by VSD imaging. In this study, we first provided a detailed analysis of spatiotemporal activation patterns at specific V1 laminar locations and measured local circuit connectivity. Then we examined the role of cortical inhibition in the propagation of evoked cortical responses by comparing circuit activity patterns in control and in the presence of GABAa receptor antagonists. We found that GABAergic inhibition was critical in restricting layer-specific excitatory activity spread and maintaining topographical projections. In addition, we investigated how AMPA and NMDA receptors influenced cortical responses and found that blocking AMPA receptors abolished interlaminar functional projections, and the NMDA receptor activity was important in controlling visual cortical circuit excitability and modulating activity propagation. The NMDA receptor antagonist reduced neuronal population activity in time-dependent and laminar-specific manners. Finally, we used the quantitative information derived from the mapping experiments and presented computational modeling analysis of V1 circuit organization. Taken together, the present study has provided important new information about mouse V1 circuit organization and response modulation.

Olivas, Nicholas D.; Quintanar-Zilinskas, Victor; Nenadic, Zoran; Xu, Xiangmin

2012-01-01

340

Laminar circuit organization and response modulation in mouse visual cortex.  

PubMed

The mouse has become an increasingly important animal model for visual system studies, but few studies have investigated local functional circuit organization of mouse visual cortex. Here we used our newly developed mapping technique combining laser scanning photostimulation (LSPS) with fast voltage-sensitive dye (VSD) imaging to examine the spatial organization and temporal dynamics of laminar circuit responses in living slice preparations of mouse primary visual cortex (V1). During experiments, LSPS using caged glutamate provided spatially restricted neuronal activation in a specific cortical layer, and evoked responses from the stimulated layer to its functionally connected regions were detected by VSD imaging. In this study, we first provided a detailed analysis of spatiotemporal activation patterns at specific V1 laminar locations and measured local circuit connectivity. Then we examined the role of cortical inhibition in the propagation of evoked cortical responses by comparing circuit activity patterns in control and in the presence of GABAa receptor antagonists. We found that GABAergic inhibition was critical in restricting layer-specific excitatory activity spread and maintaining topographical projections. In addition, we investigated how AMPA and NMDA receptors influenced cortical responses and found that blocking AMPA receptors abolished interlaminar functional projections, and the NMDA receptor activity was important in controlling visual cortical circuit excitability and modulating activity propagation. The NMDA receptor antagonist reduced neuronal population activity in time-dependent and laminar-specific manners. Finally, we used the quantitative information derived from the mapping experiments and presented computational modeling analysis of V1 circuit organization. Taken together, the present study has provided important new information about mouse V1 circuit organization and response modulation. PMID:23060751

Olivas, Nicholas D; Quintanar-Zilinskas, Victor; Nenadic, Zoran; Xu, Xiangmin

2012-01-01

341

The coupling of conical wrinkled laminar flames with gravity  

SciTech Connect

This work explores the influences that gravity has on conical premixed laminar and mildly turbulent flames (i.e., wrinkled laminar flames). The approach is to compare overall flame characteristics in normal (+g) reverse ({minus}g), and micro-gravity ({micro}g). Laser schlieren is the principal diagnostic for the {micro}g experiments. Laboratory investigation of +g and {minus}g flames also include two components laser doppler anemometry. The results obtained in a wide range of flow, mixture and turbulence conditions show that gravity has a profound effect on the lean stabilization limits, features of the flowfield, and mean flame heights. in +g and {micro}g do not flicker. analysis of the flame flickering frequencies produces in an empirical relationship St*{sup 2}/Ri = 0.0018 Re{sup 2/3} (where St*, Ri, and Re are, respectively, the Strouhal number normalized by the heat release ratio, the Richardson number, and the Reynolds number). This correlation would be useful for theoretical prediction of buoyancy induced flame instabilities. Comparison of mean flame heights shows that +g, {minus}g, {micro}g flame properties do not converge with increased flow momentum. Velocity measurements in laminar flames show that in +g, the flow generated by the rising products plum is almost non-divergent, slightly turbulent and unstable. In {minus}g, the flow becomes divergent but is stable and non-turbulent in the region surrounding the flame cone. The change from a nondivergent to divergent flow field seems to account for the differences in the observed mean flame heights. The schlieren images and the velocity measurements in +g and {minus}g also provide some insight into the overall flowfield features of {micro}g flames.

Kostiuk, L.W.; Cheng, R.K. [Lawrence Berkeley Lab., CA (United States)] [Lawrence Berkeley Lab., CA (United States)

1995-10-01

342

Distributed educated throat stability bypass to increase the stable airflow range of a Mach 2.5 inlet with 60-percent internal contraction  

NASA Technical Reports Server (NTRS)

The results of an experimental investigation to increase the stable airflow operating range of a supersonic mixed-compression inlet are presented. A distributed educated throat stability-bypass entrance configuration was tested. In terms of diffuser-exit corrected airflow, a large inlet stable airflow range of about 16.1 percent was obtained if a constant pressure was maintained in the bypass plenum. Limited unstart angle of attack data are presented.

Shaw, R. J.; Mitchell, G. A.; Sanders, B. W.

1974-01-01

343

Forward slanted slot throat stability bypass to increase the stable airflow range of a Mach 2.5 inlet with 60 percent internal contraction  

NASA Technical Reports Server (NTRS)

The results of an experimental investigation to increase the stable airflow operating range of a supersonic mixed-compression inlet are presented. Two forward-slanted slot stability-bypass entrance configurations were tested. In terms of diffuser-exit corrected airflow, a large inlet stable airflow range of 18.5 percent was obtained with the superior configuration if a constant pressure was maintained in the bypass plenum. Limited unstart angle-of-attack data are presented.

Shaw, R. J.; Mitchell, G. A.; Sanders, B. W.

1974-01-01

344

Experimental investigation of recirculating cells in laminar coaxial jets.  

NASA Technical Reports Server (NTRS)

Utilizing several unique means of introducing smoke into the flow field for careful visualization in addition to hot-wire techniques, experiments are performed in a specially designed facility producing laminar flows up to considerably high Reynolds numbers. Characteristics of the cells and the flow conditions that bring them about are documented by smoke photographs in the Reynolds number velocity ratio plane and the results are compared to previous analytical predictions. The cells are found to fall into three categories with different flow characteristics involving unsteadiness in position, and shear layer instabilities which result in higher mixing with the outer streams.-

Warpinski, N. R.; Nagib, H. M.; Lavan, Z.

1972-01-01

345

Analytical Study of Gravity Effects on Laminar Diffusion Flames  

NASA Technical Reports Server (NTRS)

A mathematical model is presented for the description of axisymmetric laminar-jet diffusion flames. The analysis includes the effects of inertia, viscosity, diffusion, gravity and combustion. These mechanisms are coupled in a boundary layer type formulation and solutions are obtained by an explicit finite difference technique. A dimensional analysis shows that the maximum flame width radius, velocity and thermodynamic state characterize the flame structure. Comparisons with experimental data showed excellent agreement for normal gravity flames and fair agreement for steady state low Reynolds number zero gravity flames. Kinetics effects and radiation are shown to be the primary mechanisms responsible for this discrepancy. Additional factors are discussed including elipticity and transient effects.

Edelman, R. B.; Fortune, O.; Weilerstein, G.

1972-01-01

346

Cortical laminar necrosis related to prolonged focal status epilepticus.  

PubMed

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. PMID:16361606

Donaire, A; Carreno, M; Gómez, B; Fossas, P; Bargalló, N; Agudo, R; Falip, M; Setoaín, X; Boget, T; Raspall, T; Obach, V; Rumiá, J

2006-01-01

347

Acute Hepatic Encephalopathy Presenting as Cortical Laminar Necrosis: Case Report  

PubMed Central

We report on a 55-year-old man with alcoholic liver cirrhosis who presented with status epilepticus. Laboratory analysis showed markedly elevated blood ammonia. Brain magnetic resonance imaging (MRI) showed widespread cortical signal changes with restricted diffusion, involving both temporo-fronto-parietal cortex, while the perirolandic regions and occipital cortex were uniquely spared. A follow-up brain MRI demonstrated diffuse cortical atrophy with increased signals on T1-weighted images in both the basal ganglia and temporal lobe cortex, representing cortical laminar necrosis. We suggest that the brain lesions, in our case, represent a consequence of toxic effect of ammonia.

Choi, Jong Mun; Roh, Sook Young

2013-01-01

348

Aircraft energy efficiency laminar flow control wing design study  

NASA Technical Reports Server (NTRS)

An engineering design study was performed in which laminar flow control (LFC) was integrated into the wing of a commercial passenger transport aircraft. A baseline aircraft configuration was selected and the wing geometry was defined. The LFC system, with suction slots, ducting, and suction pumps was integrated with the wing structure. The use of standard aluminum technology and advanced superplastic formed diffusion bonded titanium technology was evaluated. The results of the design study show that the LFC system can be integrated with the wing structure to provide a structurally and aerodynamically efficient wing for a commercial transport aircraft.

Bonner, T. F., Jr.; Pride, J. D., Jr.; Fernald, W. W.

1977-01-01

349

Manufacturing tolerances for natural laminar flow airframe surfaces  

NASA Technical Reports Server (NTRS)

Published aircraft surface waviness and boundary layer transition measurements imply that currently achievable low levels of surface waviness are compatible with the natural laminar flow (NLF) requirements of business and commuter aircraft, in the cases of both metallic and composite material airframes. The primary challenge to the manufacture of NLF-compatible surfaces is two-dimensional roughness in the form of steps and gaps at structural joints. Attention is presently given to recent NASA investigations of manufacturing tolerance requirements for NLF surfaces, including flight experiment results.

Holmes, B. J.; Obara, C. J.; Martin, G. L.; Domack, C. S.

1985-01-01

350

Analysis of skin lesions using laminar optical tomography  

PubMed Central

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.

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

2012-01-01

351

Laminar Boundary Layer Behind a Strong Shock Moving into Air  

NASA Technical Reports Server (NTRS)

The laminar wall boundary layer behind a strong shock advancing into stationary air has been determined. Numerical results have been obtained for shock Mach numbers up to 14 using real gas values for density and viscosity and assuming Prandtl and Lewis numbers of 0.72 and 1, respectively. The numerical results for shear and heat transfer agree, within 4 percent, with a previously presented approximate analytical expression for these quantities. A slight modification of this expression results in agreement with the numerical data to within 2.5 percent. Analytical expressions for boundary-layer thickness and displacement thickness, correct to within 4 percent for the present data, have also been obtained.

Mirels, Harold

1961-01-01

352

Hybrid laminar flow control applied to advanced turbofan engine nacelles  

NASA Technical Reports Server (NTRS)

The potential application of hybrid laminar flow control (HLFC) to the external surface of an advanced, high bypass ratio turbofan engine nacelle with a wetted area that approaches 15 percent of the wing total wetted area of future commercial transports is presented. A pressure distribution compatible with HLFC is specified and the corresponding nacelle geometry is computed employing a predictor/corrector design technique. Performance evaluations on an advanced twin-engine transport configuration are discussed to determine potential benefits in terms of reduced fuel consumption.

Collier, F. S., Jr.; Arcara, P. C., Jr.; Wie, Y. S.

1992-01-01

353

Hair Receptor Sensitivity to Changes in Laminar Boundary Layer Shape (Postprint).  

National Technical Information Service (NTIS)

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 s...

B. T. Dickinson

2010-01-01

354

Inspiratory airflow limitation after exercise challenge in cold air in asthmatic children.  

PubMed

Methacholine and histamine can lead to inspiratory flow limitation in asthmatic children and adults. This has not been analyzed after indirect airway stimuli, such as exercise. The aim of the study was to analyze airflow limitation after exercise in cold, dry air. 72 asthmatic children with mild to moderate asthma (mean age 13.2 ± 2.2 yrs) performed a treadmill exercise challenge. A fall of >10% in FEV(1) was the threshold for expiratory flow limitation and a fall of >25% of MIF(50) was the threshold for inspiratory flow limitation. The occurrence of wheeze, stridor and cough were quantified before and after exercise. After exercise, the mean fall in FEV(1) was 17.7 ± 14.6%, while the mean fall in MIF(50) was 25.4 ± 15.8%; no correlation was found between fall in FEV(1) and MIF(50) (R(2): 0.04; p = 0.717). 53 of the 72 children showed an inspiratory and/or expiratory airflow limitation. 38% (20/53) of these children showed an isolated expiratory flow limitation, 45% (24/53) showed both expiratory and inspiratory flow limitation and 17% (9/53) showed an isolated inspiratory flow limitation. The fall in FEV(1) peaked 9 min after exercise and correlated to expiratory wheeze. The fall in MIF(50) peaked 15 min after exercise and correlated to inspiratory stridor. The time difference in peak fall between FEV(1) and MIF(50) was statistically significant (5.9 min; p < 0.001, 99% CI: 2.3-9.5 min). In conclusion, this study shows that an exercise challenge in asthmatic children can give rise to inspiratory airflow limitation, which may give rise to asthma like symptoms. PMID:22789953

Driessen, Jean M; van der Palen, Job; van Aalderen, Wim M; de Jongh, Frans H; Thio, Boony J

2012-10-01

355

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

356

C-reactive protein levels, airflow obstruction, and chronic kidney disease  

Microsoft Academic Search

Objectives  There is some evidence that chronic obstructive pulmonary disease and chronic kidney disease (CKD) may be related, perhaps\\u000a through systemic inflammation, which is common to both. However, this relationship has not yet been clearly demonstrated.\\u000a The aim of this study was to investigate the association between airflow obstruction, CKD, and C-reactive protein (CRP) levels\\u000a in Japanese men.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  The study included

Yayoi Funakoshi; Hisamitsu Omori; Shuichi Mihara; Ayumi Onoue; Yasuhiro Ogata; Hisamichi Aizawa; Takahiko Katoh

357

High resolution measured and modelled three-dimensional airflow over a coastal bowl blowout  

NASA Astrophysics Data System (ADS)

Blowouts are common landforms found within coastal dunes. Their dynamics are primarily driven by aeolian transport caused by surface wind stress, though patterns of deflation and deposition within blowouts are poorly understood as near surface wind flow is complex. Three-dimensional wind flows around blowouts have yet to be properly quantified, especially within zones of separation, re-attachment and acceleration. This has been largely due to inadequate measurement of airflow and a lack of suitable airflow models. With this in mind, we present results from a study that has quantified alongshore and oblique onshore wind flow dynamics over a bowl blowout on the Belmullet Peninsula, Ireland. Using ultrasonic three-dimensional anemometry (measuring at 50 Hz) and three-dimensional computational fluid dynamic (CFD) modelling, we measure and model for the first time in 3D a detailed picture of the heterogeneity of wind flow over this type of terrain. During alongshore wind conditions, wind speeds within the deflation basin were retarded by 50% compared to the foredune zone and flow separation restricted to a small zone in lee of the windward rim. Wind was directed into the deflation basin through a gap in a western erosional wall, termed the blowout throat. In oblique onshore wind, airflow orientated with the blowout throat remained unchanged in direction and slowed by only 30% compared to wind speed on the foredune. In lee of the erosional wall adjacent to the blowout throat, small zones of flow separation occurred close to the erosional wall. In both cases, the highest variation in wind speed and direction occurred in zones of separation and attachment whilst flow increased in steadiness with height over the erosional walls. The results illustrate that wind is manipulated according to localised topography within the bowl blowout itself. Resulting zones of potential sediment transport (erosion and deposition) are spatially complex and alter with wind direction. The presence of a blowout throat has a significant influence on airflow patterns within a deflation basin. Modelled (CFD) and measured anemometer data demonstrated excellent comparisons for wind direction and speed, allowing much greater spatial measurement resolution than physical instrumentation. Simulated turbulence did not correlate well with measured data, highlighting the requirement for high frequency, three-dimensional anemometry in areas of complex flow.

Smyth, Thomas A. G.; Jackson, Derek W. T.; Cooper, J. Andrew G.

2012-12-01

358

Measurement of effective pulmonary blood flow by soluble gas uptake in patients with chronic airflow obstruction.  

PubMed Central

A study was designed to assess the accuracy and reproducibility of rebreathing and single breath soluble gas uptake measurements of effective pulmonary blood flow (Q) in patients with airways obstruction. Both rebreathing (RB) and single breath (SB) estimates of Q were compared with direct Fick and thermodilution (TD) measurements of cardiac output at rest and during exercise in eight patients with chronic, poorly reversible airflow obstruction with mean FEV1 65% predicted and mean FEV1/FVC 53%. The mean (SD) resting values obtained were QRB 3.47 (0.46), QSB 4.75 (1.15), QFick 4.77 (0.97), and QTD 5.15 (0.98). QRB was significantly lower than the other three estimates, which did not differ significantly from each other. Exercise produced significant increases in all four estimates for the group. The mean exercise values were QRB 6.23 (1.19), QSB 7.62 (1.97), QFick 8.97 (1.96), and QTD 9.09 (1.00), both QRB and QSB being significantly less than QFick and QTD. Analysis of variance of the rest, exercise, and combined data showed highly significant relationships with the TD and Fick measurements for both QRB and QSB over the range of values studied. In addition, the reproducibility of QRB and QSB was assessed in 15 other patients with chronic airflow obstruction (mean FEV1 42% predicted, FEV1/FVC 43%) and in 10 normal subjects. The coefficients of intrasubject variability for a single measurement for QRB were 8.7% in normal subjects and 10.2% in patients and for QSB were 11.7% in normal subjects and 16.1% in patients. The group differences from morning to afternoon, between days, and over a month were not significant in the normal subjects. In the patients QRB was slightly higher in the afternoon than in the morning of the same day, but the differences between days and over a month were not significant for either test. Although both tests detected the increase in pulmonary blood flow during exercise, the single breath test was more accurate at rest. Some underestimation was present for rebreathing at rest and for both tests during exercise, but this can be allowed for. In patients with mild airflow obstruction the reproducibility of the soluble gas uptake methods was similar to that of invasive catheter methods of cardiac output estimation. The single breath test in particular was, however, less reproducible in patients with more severe airflow obstruction, and the rebreathing method may be more useful for detecting increases in pulmonary blood flow in these patients.

Pierce, R J; McDonald, C F; Thuys, C A; Rochford, P D; Barter, C E

1987-01-01

359

Single-stage electrohydraulic servosystem for actuating on airflow valve with frequencies to 500 hertz  

NASA Technical Reports Server (NTRS)

An airflow valve and its electrohydraulic actuation servosystem are described. The servosystem uses a high-power, single-stage servovalve to obtain a dynamic response beyond that of systems designed with conventional two-stage servovalves. The electrohydraulic servosystem is analyzed and the limitations imposed on system performance by such nonlinearities as signal saturations and power limitations are discussed. Descriptions of the mechanical design concepts and developmental considerations are included. Dynamic data, in the form of sweep-frequency test results, are presented and comparison with analytical results obtained with an analog computer model is made.

Webb, J. A., Jr.; Mehmed, O.; Lorenzo, C. F.

1980-01-01

360

Bayesian Modeling of Exposure and Airflow Using Two-Zone Models  

PubMed Central

Mathematical modeling is being increasingly used as a means for assessing occupational exposures. However, predicting exposure in real settings is constrained by lack of quantitative knowledge of exposure determinants. Validation of models in occupational settings is, therefore, a challenge. Not only do the model parameters need to be known, the models also need to predict the output with some degree of accuracy. In this paper, a Bayesian statistical framework is used for estimating model parameters and exposure concentrations for a two-zone model. The model predicts concentrations in a zone near the source and far away from the source as functions of the toluene generation rate, air ventilation rate through the chamber, and the airflow between near and far fields. The framework combines prior or expert information on the physical model along with the observed data. The framework is applied to simulated data as well as data obtained from the experiments conducted in a chamber. Toluene vapors are generated from a source under different conditions of airflow direction, the presence of a mannequin, and simulated body heat of the mannequin. The Bayesian framework accounts for uncertainty in measurement as well as in the unknown rate of airflow between the near and far fields. The results show that estimates of the interzonal airflow are always close to the estimated equilibrium solutions, which implies that the method works efficiently. The predictions of near-field concentration for both the simulated and real data show nice concordance with the true values, indicating that the two-zone model assumptions agree with the reality to a large extent and the model is suitable for predicting the contaminant concentration. Comparison of the estimated model and its margin of error with the experimental data thus enables validation of the physical model assumptions. The approach illustrates how exposure models and information on model parameters together with the knowledge of uncertainty and variability in these quantities can be used to not only provide better estimates of model outputs but also model parameters.

Zhang, Yufen; Banerjee, Sudipto; Yang, Rui; Lungu, Claudiu; Ramachandran, Gurumurthy

2009-01-01

361

Experimental investigation of flow instabilities in a laminar separation bubble  

NASA Astrophysics Data System (ADS)

The present paper reports the results of a detailed experimental study aimed at investigating the dynamics of a laminar separation bubble, from the origin of separation up to the breakdown to turbulence of the large scale coherent structures generated as a consequence of the Kelvin-Helmholtz instability process. Measurements have been performed along a flat plate installed within a double contoured test section, designed to produce an adverse pressure gradient typical of Ultra-High-Lift turbine blade profiles, which induces the formation of a laminar separation bubble at low Reynolds number condition. Measurements have been carried out by means of complementary techniques: hot-wire (HW) anemometry, Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV). The high accuracy 2-dimensional LDV results allow investigating reverse flow magnitude and both Reynolds normal and shear stress distributions along the separated flow region, while the high frequency response of the HW anemometer allows analyzing the amplification process of flow oscillations induced by instability mechanisms. PIV results complement the flow field analysis providing information on the generation and evolution of the large scale coherent structures shed as a consequence of the separated shear layer roll-up, through instantaneous velocity vector maps. The simultaneous analysis of the data obtained by means of the different measuring techniques allows an in depth view of the instability mechanisms involved in the transition/reattachment processes of the separated shear layer.

Simoni, D.; Ubaldi, M.; Zunino, P.

2014-06-01

362

Airborne drug levels in a laminar-flow hood  

SciTech Connect

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 the hood and transferred to empty vials. Likewise, in each of nine trials, 50 vials of cefazolin sodium 1 g were reconstituted and transferred to small-volume i.v. solutions. Drug manipulations were performed between the hood's filter and the Biotest, which was placed inside the hood. Drug collected on the filter in the Biotest was assayed with ultraviolet spectrophotometry after extraction. The range of fluorouracil collected by the Biotest was from 0 to 14 microgram, corresponding to 0-0.07 microgram/liter of sample air. Recovered cefazolin sodium ranged from 28 to 131 microgram, or 0.02-0.11 microgram/liter of sampled air. Following routine manipulation of drug products in a laminar-flow hood, the drug can contaminate, the air flowing over the product.

Kleinberg, M.L.; Quinn, M.J.

1981-09-01

363

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

364

Streamwise Vorticity Generation in Laminar and Turbulent Jets  

NASA Technical Reports Server (NTRS)

Complex streamwise vorticity fields are observed in the evolution of non-circular jets. Generation mechanisms are investigated via Reynolds-averaged (RANS), large-eddy (LES) and direct numerical (DNS) simulations of laminar and turbulent rectangular jets. Complex vortex interactions are found in DNS of laminar jets, but axis-switching is observed only when a single instability mode is present in the incoming mixing layer. With several modes present, the structures are not coherent and no axis-switching occurs, RANS computations also produce no axis-switching. On the other hand, LES of high Reynolds number turbulent jets produce axis-switching even for cases with several instability modes in the mixing layer. Analysis of the source terms of the mean streamwise vorticity equation through post-processing of the instantaneous results shows that, complex interactions of gradients of the normal and shear Reynolds stresses are responsible for the generation of streamwise vorticity which leads to axis-switching. RANS computations confirm these results. k - epsilon turbulence model computations fail to reproduce the phenomenon, whereas algebraic Reynolds stress model (ASM) computations, in which the secondary normal and shear stresses are computed explicitly, succeeded in reproducing the phenomenon accurately.

Demuren, Aodeji O.; Wilson, Robert V.

1999-01-01

365

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

366

Spatial distribution of laminar flow-assisted dendritic amplification.  

PubMed

In this paper, we report spatial distribution of laminar flow-assisted dendritic amplification (LFDA) product. LFDA is a recently invented signal amplification method dedicated to biomolecular binding events on microchannel walls. Onto the bound biomolecule, a dendritic structure is constructed by supplying two building blocks from laminar streams produced by a Y-shaped microchannel. In view of the extension of LFDA to simultaneous amplification of multiple binding spots, we have investigated the distribution of the LFDA product across and along the microchannel with the course of time. We fabricated a Y-shaped microchannel with a cross section of 110 microm x 22 microm using poly(dimethylsiloxane). As the LFDA building blocks, FITC-labeled streptavidin and biotinylated anti-streptavidin were injected from the two inlets of the microchannel at a mean flow velocity of 6.2 mm s(-1) (after the confluence). Nonspecific adsorption of the building blocks formed the seed layer of LFDA. The progress of LFDA was monitored with a fluorescence microscope up to 10.1 mm of microchannel length. After 5 min or later, the fluorescence intensity profile across the microchannel showed a peak at the center of the channel. With the course of time, the peak height grew exponentially except for slight saturation, but the peak width was almost constant. Along the microchannel, the peak height decreased almost linearly with the increasing logarithm of the distance, and the peak width was broadened in accordance with the 1/3 power law. PMID:19156297

Hosokawa, Kazuo; Maeda, Mizuo

2009-02-01

367

Laminar flow control leading edge glove flight test article development  

NASA Technical Reports Server (NTRS)

A laminar flow control (LFC) flight test article was designed and fabricated to fit into the right leading edge of a JetStar aircraft. The article was designed to attach to the front spar and fill in approx. 70 inches of the leading edge that are normally occupied by the large slipper fuel tank. The outer contour of the test article was constrained to align with an external fairing aft of the front spar which provided a surface pressure distribution over the test region representative of an LFC airfoil. LFC is achieved by applying suction through a finely perforated surface, which removes a small fraction of the boundary layer. The LFC test article has a retractable high lift shield to protect the laminar surface from contamination by airborne debris during takeoff and low altitude operation. The shield is designed to intercept insects and other particles that could otherwise impact the leading edge. Because the shield will intercept freezing rain and ice, a oozing glycol ice protection system is installed on the shield leading edge. In addition to the shield, a liquid freezing point depressant can be sprayed on the back of the shield.

Pearce, W. E.; Mcnay, D. E.; Thelander, J. A.

1984-01-01

368

Discussion of test results in the design of laminar airfoils for competition gliders  

NASA Technical Reports Server (NTRS)

The deformation of flow in the boundary layer and the local separation of a laminar layer (laminar bubbles) from various airfoils were investigated. These phenomena were classified and their influence is discussed. Various aerodynamic characteristics are discussed and the principles for prescribing pressure distribution to attain a high value of c sub z max with a possibly low drag coefficient are described.

Ostrowski, J.; Skrzynski, S.; Litwinczyk, M.

1980-01-01

369

Three-dimensional EHD simulation for point corona electrostatic precipitator based on laminar and turbulent models  

Microsoft Academic Search

The three-dimensional flow interaction for tuft or point corona for industrial electrostatic precipitators was investigated using both laminar and turbulent flow models. The secondary flow distribution based on laminar flow model forms a pair of organized donut-shaped rings generated from every corona or tuft points, while a pair of rings is less organized for turbulent flow model. When the primary

Toshiaki Yamamoto; Yoshifumi Morita; Hidekatsu Fujishima; Masaaki Okubo

2006-01-01

370

Nonlinear effects in the extraction of laminar flame speeds from expanding spherical flames  

Microsoft Academic Search

Various factors affecting the determination of laminar flames speeds from outwardly propagating spherical flames in a constant-pressure combustion chamber were considered, with emphasis on the nonlinear variation of the stretched flame speed to the flame stretch rate, and the associated need to nonlinearly extrapolate the stretched flame speed to yield an accurate determination of the laminar flame speed and Markstein

A. P. Kelley; C. K. Law

2009-01-01

371

A Novel Microfluidic Platform for Continuous DNA Extraction and Purification using Laminar Flow Magnetophoresis  

Microsoft Academic Search

We present a novel microfluidic platform using laminar-flow magnetophoresis for combined continuous extraction and purification of DNA. All essential unit operations (DNA binding, sample washing and DNA elution) are integrated on one single chip. The key function is the motion of magnetic beads given by the interplay of laminar flow and time-varying magnetic field. The time for extraction was 1

M. Karle; J. Miwa; G. Roth; R. Zengerle; F. von Stetten

2009-01-01

372

Laminar plasma jets: Generation, characterization, and applications for materials surface processing  

Microsoft Academic Search

Nontransferred dc laminar plasma jets of pure argon were generated at atmospheric pressure, with a generator having an interelectrode insert. Associated with the experimental investigation, similarity theory was adopted to examine the arc voltage characteristics, ther- mal efficiency, and jet length change of the laminar plasma. Jet flow temperature and veloc- ity were evaluated by various methods. The jet shows

W. X. Pan; G. Li; X. Meng; W. Ma; C. K. Wu

2005-01-01

373

Laminarization of a boundary layer in a supersonic nozzle by cooling of the surface  

NASA Technical Reports Server (NTRS)

The concept of cooling of the surface of wind tunnel walls in order to laminarize the boundary layer, and thereby eliminate perturbations in the working area, is discussed. Equations are given, which are used to calculate the temperature conditions under which the flow in the boundary layer will be stably laminar.

Maksimov, V. P.; Maslov, A. A.

1983-01-01

374

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

Microsoft Academic Search

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

Y. S. Wie; F. S. Jr. Collier; R. D. Wagner

1991-01-01

375

Aerodynamic design of a natural laminar flow nacelle and the design validation by flight testing  

Microsoft Academic Search

The laminar flow technology is one of the key technologies in aeronautics offering substantial improvements in the areas of economy and ecology. This paper describes the aerodynamic design methodology for a natural laminar flow (NLF) nacelle and the subsequent verification of the design quality by flight tests with a subsonic transport aircraft. The aerodynamic design was a contribution within the

H. Riedel; K.-H. Horstmann; A. Ronzheimer; M. Sitzmann

1998-01-01

376

Transport Coefficients for Laminar and Turbulent Flow Through a Four-Cusp Channel.  

National Technical Information Service (NTIS)

The heat transfer coefficients for laminar and turbulent flow in a four-cusp channel were determined. A numerical solution was developed for laminar flow an and experimental study for turbulent flow was carried out. Systematic variations of the Reynolds n...

A. Souza Dutra J. A. R. Parise P. R. Souza Mendes

1986-01-01

377

The Effects of Axial Conduction in the Wall on Heat Transfer with Laminar Flow.  

National Technical Information Service (NTIS)

Wall conduction effects on steady-state laminar flow heat-transfer experiments are examined, and an analysis of heat transfer with axial conduction in the wall bounding a fluid in laminar flow is developed to determine the effects of the conduction in the...

E. J. Davis W. N. Gill

1969-01-01

378

Exploring Roughness Effect on Laminar Internal Flow–Are We Ready for Change?  

Microsoft Academic Search

Laminar flow is often encountered in the channels of microdevices as a result of the small hydraulic diameters. The roughness introduced on the walls of these channels through various fabrication techniques, such as etching, micromachining, laser drilling, etc., results in a high value of relative roughness (defined as the wall surface roughness to channel hydraulic diameter ratio). Laminar flow in

Satish G. Kandlikar

2008-01-01

379

Combustion characteristics of the end burning hybrid rockets in laminar flow  

Microsoft Academic Search

In this study, we aim to clarify the blowoff mechanism for flame spreading in an opposed laminar flow in narrow solid fuel ducts. To clarify this mechanism we conducted two experiments. First, we observed the changes of the flame spread rate at various oxygen velocities, ambient pressures, and port diameters. For flame spreading in laminar flow, combustion modes could be

Tsuneyoshi Matsuoka; Harunori Nagata

2011-01-01

380

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

381

Laminarization of minimal plane Couette flow: Going beyond the basin of attraction of turbulence  

NASA Astrophysics Data System (ADS)

Laminarization of minimal plane Couette turbulence is achieved numerically through short-time imposition of weak spanwise system rotation. A laminarization strategy presented in this Letter is inspired by investigation of the phase-space structure in the vicinity of a recently found unstable periodic orbit [G. Kawahara and S. Kida, ``Periodic motion embedded in plane Couette turbulence: regeneration cycle and burst,'' J. Fluid Mech. 449, 291 (2001)]. The periodic orbit, which a turbulent state occasionally approaches, and its local stable manifold are found to form the separatrix between the basin of attraction of turbulent and laminar flows. The introduction of the slight rotation during its approach to the periodic orbit enables the state to go beyond the basin of attraction of the turbulence toward the laminar flow. The global stabilization of the unstable periodic orbit by the method of controlling chaos is also performed to accomplish the laminarization without waiting until the natural approach.

Kawahara, Genta

2005-04-01

382

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

383

A smart, intermittent driven particle sensor with an airflow change trigger using a lead zirconate titanate (PZT) cantilever  

NASA Astrophysics Data System (ADS)

This paper reports on a smart, intermittent driven particle sensor with an airflow trigger. A lead zirconate titanate cantilever functions as the trigger, which detects an airflow change without requiring a power supply to drive the sensing element. Because an airflow change indicates that the particle concentration has changed, the trigger switches the optical particle counter from sleep mode to active mode only when the particle concentration surrounding the sensor changes. The sensor power consumption in sleep mode is 100 times less than that in the active mode. Thus, this intermittent driven method significantly reduces the total power consumption of the particle sensor. In this paper, we fabricate a prototype of the particle sensor and demonstrate that the optical particle counter can be switched on by the fabricated trigger and thus that the particle concentration can be measured.

Takahashi, Hidetoshi; Tomimatsu, Yutaka; Kobayashi, Takeshi; Isozaki, Akihiro; Itoh, Toshihiro; Maeda, Ryutaro; Matsumoto, Kiyoshi; Shimoyama, Isao

2014-02-01

384

Field characterization of three-dimensional lee-side airflow patterns under offshore winds at a beach-dune system  

NASA Astrophysics Data System (ADS)

Characterization of three-dimensional (3D) airflow remains elusive within a variety of environments and is particularly challenging over complex dune topography. Previous work examining airflow over and in the lee of dunes has been restricted to two-dimensional studies and has concentrated on dune shapes containing angle of repose lee sides only. However, the presence of vegetation in coastal dunes creates topographic differences and irregular shapes that interfere with flow separation at the crest and significantly modify lee-side airflow patterns and potential transport. This paper presents the first 3D field characterization of airflow patterns at the lee side of a subaerial dune. Flow information was obtained using an array of 3D ultrasonic anemometers deployed over a beach surface during seven offshore wind events. Data were used to measure cross-shore and alongshore lee-side airflow patterns using the three dimensions of the wind vector. Distances to re-attachment were similar to previous studies, but the range of transverse incident wind directions resulting in flow separation (0+/-35°) was almost twice that previously reported (0+/-20°). Airflow reversal took place with winds as slow as 1 m s-1. Transverse offshore winds generated areas of opposing wind directions both within the reversed zone and beyond re-attachment, contrary to consistent deflection in only one direction found in transverse desert dunes. Patterns of flow convergence-divergence have been reported in fluvial studies. However, while convergence was associated with weak reversal in fluvial settings, it appeared to be related to strong flow reversal here and could be produced by pressure differentials at the dune crest.

Delgado-Fernandez, Irene; Jackson, Derek W. T.; Cooper, J. Andrew G.; Baas, Andreas C. W.; Beyers, J. H. Meiring; Lynch, Kevin

2013-06-01

385

A Numerical Model of Viscoelastic Layer Entrainment by Airflow in Cough  

NASA Astrophysics Data System (ADS)

Coughing is an alternative mode of ensuring mucus clearance in the lung when normal cilia induced flow breaks down. A numerical model of this process is presented with the following aspects. (1) A portion of the airway comprising the first three bronchus generations is modeled as radially reinforced elastic tubes. Elasticity equations are solved to predict airway deformation under effect of airway pressure. (2) The compressible, turbulent flow induced by rapid lung contraction is modeled by direct numerical simulation for Reynolds numbers in the range 5,000-10,000 and by Large Eddy Simulation for Reynolds numbers in the range 5,000-40,000. (3) A two-layer model of the airway surface liquid (ASL) covering the airway epithelial layer is used. The periciliary liquid (PCL) in direct contact with the epithelial layer is considered to be a Newtonian fluid. Forces modeling cilia beating can act upon this layer. The mucus layer between the PCL and the interior airflow is modeled as an Oldroyd-B fluid. The overall computation is a fluid-structure interaction simulation that tracks changes in ASL thickness and airway diameters that result from impulsive airflow boundary conditions imposed at bronchi ends. In particular, the amount of mucus that is evacuated from the system is computed as a function of cough intensity and mucus rheological properties.

Mitran, Sorin M.

2008-07-01

386

Mechanical Design of a Performance Test Rig for the Turbine Air-Flow Task (TAFT)  

NASA Technical Reports Server (NTRS)

To support development of the Boeing-Rocketdyne RS84 rocket engine, a fill-flow, reaction turbine geometry was integrated into the NASA-MSFC turbine air-flow test facility. A mechanical design was generated which minimized the amount of new hardware while incorporating all test and instrUmentation requirements. This paper provides details of the mechanical design for this Turbine Air-Flow Task (TAFT) test rig. The mechanical design process utilized for this task included the following basic stages: Conceptual Design. Preliminary Design. Detailed Design. Baseline of Design (including Configuration Control and Drawing Revision). Fabrication. Assembly. During the design process, many lessons were learned that should benefit future test rig design projects. Of primary importance are well-defined requirements early in the design process, a thorough detailed design package, and effective communication with both the customer and the fabrication contractors. The test rig provided steady and unsteady pressure data necessary to validate the computational fluid dynamics (CFD) code. The rig also helped characterize the turbine blade loading conditions. Test and CFD analysis results are to be presented in another JANNAF paper.

Xenofos, George; Forbes, John; Farrow, John; Williams, Robert; Tyler, Tom; Sargent, Scott; Moharos, Jozsef

2003-01-01

387

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

388

Airflow reduction during cold weather operation of residential heat recovery ventilators  

SciTech Connect

Laboratory measurements of the performance of residential heat recovery ventilators have been carried out for the R-2000 Energy Efficient Home Program. This work was based on a preliminary test procedure developed by the Canadian Standards Association, part of which calls for testing the HRV under cold weather conditions. An environmental chamber was used to simulate outdoor conditions. Initial tests were carried out with an outdoor temperature of -20/sup 0/C; subsequent tests were carried out at a temperature of -25/sup 0/C. During the tests, airflows, temperatures, and relative humidities of airstreams entering and leaving the HRV, along with electric power inputs, were monitored. Frost buildup in the heat exchangers and defrost mechanisms, such as fan shutoff or recirculation, led to reductions in airflows. The magnitude of the reductions is dependent on the design of the heat exchanger and the defrost mechanism used. This paper presents the results of tests performed on a number of HRVs commercially available in Canada at the time of the testing. The flow reductions for the various defrost mechanisms are discussed.

McGugan, C.A.; Edwards, P.F.; Riley, M.A.

1987-06-01

389

Effects of surface roughness on evaporation from porous surfaces into turbulent airflows  

NASA Astrophysics Data System (ADS)

The ubiquitous and energy intensive mass transfer between wet porous surfaces and turbulent airflows is of great importance for various natural and industrial applications. The roughness of natural surfaces is likely to influence the structure of adjacent boundary layer and thus affecting heat and mass fluxes from surfaces. These links were formalized in a new model that considers the intermittent turbulence-induced boundary layer with local mass and energy exchange rates. We conducted experiments with regular surface roughness patterns subjected to constant turbulent airflows and monitored mass loss and thermal signatures of localized evaporative fluxes using infrared thermography. The resulting patterns were in good agreement with model predictions for local and surface averaged turbulent exchange rates. Preliminary results obtained for evaporation from sinusoidal wavy soil surfaces reveal that evaporative fluxes can be either enhanced or suppressed (relative to a flat surface) owing to relative contribution of downstream (separation zone) and rising (reattachment zone) surfaces of the wave with thick and thin viscous sublayer thicknesses, respectively. For isolated roughness elements (bluff bodies) over a flat evaporating surface, the resulting fluxes are enhanced (relative to a smooth surface) due to formation of vortices that induce thinner boundary layer. Potential benefits of the study for interpretation and upscaling of evaporative and heat fluxes from natural (rough) terrestrial surfaces will be discussed. Keywords: Turbulent Evaporation, Porous Media, Surface Roughness, Infrared Thermography.

Haghighi, Erfan; Or, Dani

2014-05-01

390

Measurement method of multi-zone airflow rate using human expiration flow rate using human expiration low rate using human expiration  

Microsoft Academic Search

Investigation of ventilation measurement method was of ventilation measurement method was of ventilation measurement method was ventilation measurement method was measurement method was was carried out in a full-scale test house. The aim of this study was to examine the ventilation rate via human expiration. The adopted method is able to measure multi- zone airflow rates. Airflow rate between rooms

H. Yoshino; M. Fujikawa; R. Takaki; H. Okuyama; M. Hayashi; M. Sugawara

391

Computational wing design studies relating to natural laminar flow  

NASA Technical Reports Server (NTRS)

Two research studies are described which directly relate to the application of natural laminar flow (NLF) technology to transonic transport-type wing planforms. Each involved using state-of-the-art computational methods to design three-dimensional wing contours which generate significant runs of favorable pressure gradients. The first study supported the Variable Sweep Transition Flight Experiment and involves design of a full-span glove which extends from the leading edge to the spoiler hinge line on the upper surface of an F-14 outer wing panel. A wing was designed computationally for a corporate transport aircraft in the second study. The resulting wing design generated favorable pressure gradients from the leading edge aft to the mid-chord on both upper and lower surfaces at the cruise design point. Detailed descriptions of the computational design approach are presented along with the various constraints imposed on each of the designs.

Waggoner, Edgar G.

1986-01-01

392

Investigation B: Laminar confined coaxial entrance flow with heat generation  

NASA Technical Reports Server (NTRS)

The results of a parametric study on the entrance flow region in a gas core nuclear reactor are presented. The physical system is modeled as laminar confined, coaxial flow with heat generation in the inner fluid. The governing equations include the boundary layer approximations and the assumptions of only radial radiative transport of energy represented as an energy diffusion term. The Von Mises transformation and a zeta transformation are used to transform the equations into nonlinear nonhomogeneous convective-diffusion equations. A unique combination of forward and backward difference equations which yields accurate results at moderate computational times, is used in the numerical method. Results show that the rapidly accelerating, heat generating inner stream actually shrinks in radius as it expands axially.

Bobba, G. K. M.; Weinstein, H.

1975-01-01

393

Asymptotic structure of laminar diffusion flames at high pressure  

NASA Astrophysics Data System (ADS)

We analyze the structure of laminar diffusion flames at high pressure in the limit of large activation energy for the particular configuration of a steady flame in counterflow. We consider a dense fluid in which normal Fickian diffusion of the fuel is limited, and thermal diffusion, i.e., the Soret effect, is the dominant mechanism for fuel mass transport. Temperature and species profiles, as well as flame temperature and location, are determined as a function of Damköhler number and Soret diffusion coefficient. In particular, we find that oxidant is entirely consumed by the flame, while some fuel leaks through. For light fuels, the fuel profile is found to have a local peak on the oxidant side as a result of thermal diffusion. Our analysis includes a description of extinction phenomena, including explicit criteria in terms of the Soret diffusion coefficient, ratio of temperature of the two streams, and the Damköhler number at extinction.

Fong, D.; Bechtold, J. K.; Law, C. K.

2012-09-01

394

A computationally efficient modelling of laminar separation bubbles  

NASA Technical Reports Server (NTRS)

The goal is to accurately predict the characteristics of the laminar separation bubble and its effects on airfoil performance. Toward this end, a computational model of the separation bubble was developed and incorporated into the Eppler and Somers airfoil design and analysis program. Thus far, the focus of the research was limited to the development of a model which can accurately predict situations in which the interaction between the bubble and the inviscid velocity distribution is weak, the so-called short bubble. A summary of the research performed in the past nine months is presented. The bubble model in its present form is then described. Lastly, the performance of this model in predicting bubble characteristics is shown for a few cases.

Dini, Paolo; Maughmer, Mark D.

1989-01-01

395

A computationally efficient modelling of laminar separation bubbles  

NASA Technical Reports Server (NTRS)

The goal of this research is to accurately predict the characteristics of the laminar separation bubble and its effects on airfoil performance. To this end, a model of the bubble is under development and will be incorporated in the analysis section of the Eppler and Somers program. As a first step in this direction, an existing bubble model was inserted into the program. It was decided to address the problem of the short bubble before attempting the prediction of the long bubble. In the second place, an integral boundary-layer method is believed more desirable than a finite difference approach. While these two methods achieve similar prediction accuracy, finite-difference methods tend to involve significantly longer computer run times than the integral methods. Finally, as the boundary-layer analysis in the Eppler and Somers program employs the momentum and kinetic energy integral equations, a short-bubble model compatible with these equations is most preferable.

Maughmer, Mark D.

1988-01-01

396

Oblique laminar-turbulent interfaces in plane shear flows.  

PubMed

Localized structures such as turbulent stripes and turbulent spots are typical features of transitional wall-bounded flows in the subcritical regime. Based on an assumption for scale separation between large and small scales, we show analytically that the corresponding laminar-turbulent interfaces are always oblique with respect to the mean direction of the flow. In the case of plane Couette flow, the mismatch between the streamwise flow rates near the boundaries of the turbulence patch generates a large-scale flow with a nonzero spanwise component. Advection of the small-scale turbulent fluctuations (streaks) by the corresponding large-scale flow distorts the shape of the turbulence patch and is responsible for its oblique growth. This mechanism can be easily extended to other subcritical flows such as plane Poiseuille flow or Taylor-Couette flow. PMID:23373928

Duguet, Yohann; Schlatter, Philipp

2013-01-18

397

Some optimal body shapes for laminar film condensation  

NASA Astrophysics Data System (ADS)

The geometry of the condensing surface affects the thermal performance of a condenser. Optimizing the surface shape to maximize the condensation heat transfer offers potential for increased performance and/or reduced condenser cost. Thus, the condensation model developed by Dhir and Lienhard (1971, 1973) for bodies of arbitrary shape is used in the present study to determine two-dimensional and axisymmetric body shapes that maximize the rate of heat transfer by laminar film condensation, subject to certain constraints. The optimal body shapes are obtained as solutions of classical isoperimetric problems in the calculus of variations using both indirect and direct (Rayleigh-Ritz) techniques. Extensions of the present results to film boiling and natural convection are discussed.

Krane, R. J.; Haines, J. R.

1985-11-01

398

Flame height measurement of laminar inverse diffusion flames  

SciTech Connect

Flame heights of co-flowing cylindrical ethylene-air and methane-air laminar inverse diffusion flames were measured. The luminous flame height was found to be greater than the height of the reaction zone determined by planar laser-induced fluorescence (PLIF) of hydroxyl radicals (OH) because of luminous soot above the reaction zone. However, the location of the peak luminous signals along the centerline agreed very well with the OH flame height. Flame height predictions using Roper's analysis for circular port burners agreed with measured reaction zone heights when using values for the characteristic diffusion coefficient and/or diffusion temperature somewhat different from those recommended by Roper. The fact that Roper's analysis applies to inverse diffusion flames is evidence that inverse diffusion flames are similar in structure to normal diffusion flames. (author)

Mikofski, Mark A. [Microgravity Combustion Laboratory, University of California, Berkeley, CA 94720 (United States); Williams, Timothy C.; Shaddix, Christopher R.; Blevins, Linda G. [Combustion Research Facility, Sandia National Laboratories, Livermore, CA 94550 (United States)

2006-07-15

399

Flame height measurement of laminar inverse diffusion flames.  

SciTech Connect

Flame heights of co-flowing cylindrical ethylene-air and methane-air laminar inverse diffusion flames were measured. The luminous flame height was found to be greater than the height of the reaction zone determined by planar laser-induced fluorescence (PLIF) of hydroxyl radicals (OH) because of luminous soot above the reaction zone. However, the location of the peak luminous signals along the centerline agreed very well with the OH flame height. Flame height predictions using Roper's analysis for circular port burners agreed with measured reaction zone heights when using values for the characteristic diffusion coefficient and/or diffusion temperature somewhat different from those recommended by Roper. The fact that Roper's analysis applies to inverse diffusion flames is evidence that inverse diffusion flames are similar in structure to normal diffusion flames.

Shaddix, Christopher R.; Williams, Timothy C.; Blevins, Linda Gail; Mikofski, Mark A. (University of California Berkeley)

2005-09-01

400

Analysis and Optimization Laminar Viscous Flow Through a Channel  

NASA Astrophysics Data System (ADS)

Optimizing of laminar viscous flow through a pipe by two dimensionless values is investigated analytically. Dimensionless entropy generation and pumping power to heat transfer rate ratio are used as basis for constant viscous and the temperature dependence on the viscosity. For this matter we calculate entropy generation and pumping power for a fully developed in a pipe subjected to constant wall temperature for either constant viscosity and the variable viscosity. The variation entropy generation increase along the pipe length for viscous fluid is drawn, either the variation summation dimensionless entropy generation and the pumping power to heat transfer rate ratio are varying the fluid inlet temperature for fixed pipe length and are varying pipe length for fixed fluid inlet temperature are drawn. For low heat transfer conditions the entropy generation due to viscosity friction becomes dominant and the dependence of viscosity with the temperature becomes essentially important to be considered.

Langeroudi, H. G.; Aghanajafi, C.

2006-12-01

401

F-16XL Ship #2 Laminar Flow Glove mounting  

NASA Technical Reports Server (NTRS)

NASA's two-seat F-16XL research aircraft is shown in the modification hangar at NASA's Dryden Flight Research Center, Edwards, California, during installation of a titanium 'glove' on the upper surface of its modified left wing. The aircraft subsequently carried out a 13-month-long, 45-flight research program which investigated drawing off a small part of the boundary-layer air in order to provide laminar--or smooth--flow over a major portion of a wing flying at supersonic speeds. A turbo-compressor in the aircraft's fuselage provided suction to draw air through more than 10 million tiny laser-drilled holes in the glove via a manifold system employing 20 valves. Data obtained during the program could assist designers of future aircraft in developing a more efficient high-speed civil transport.

1995-01-01

402

High-flaps for natural laminar flow airfoils  

NASA Technical Reports Server (NTRS)

A review of the NACA and NASA low-drag airfoil research is presented with particular emphasis given to the development of mechanical high-lift flap systems and their application to general aviation aircraft. These flap systems include split, plain, single-slotted, and double-slotted trailing-edge flaps plus slat and Krueger leading-edge devices. The recently developed continuous variable-camber high-lift mechanism is also described. The state-of-the-art of theoretical methods for the design and analysis of multi-component airfoils in two-dimensional subsonic flow is discussed, and a detailed description of the Langley MCARF (Multi-Component Airfoil Analysis Program) computer code is presented. The results of a recent effort to design a single- and double-slotted flap system for the NASA high speed natural laminar flow (HSNLF) (1)-0213 airfoil using the MCARF code are presented to demonstrate the capabilities and limitations of the code.

Morgan, Harry L.

1986-01-01

403

Stability theory applications to laminar-flow control  

NASA Technical Reports Server (NTRS)

In order to design Laminar Flow Control (LFC) configurations, reliable methods are needed for boundary-layer transition predictions. Among the available methods, there are correlations based upon R sub e, shape factors, Goertler number and crossflow Reynolds number. The most advanced transition prediction method is based upon linear stability theory in the form of the e sup N method which has proven to be successful in predicting transition in two- and three-dimensional boundary layers. When transition occurs in a low disturbance environment, the e sup N method provides a viable design tool for transition prediction and LFC in both 2-D and 3-D subsonic/supersonic flows. This is true for transition dominated by either TS, crossflow, or Goertler instability. If Goertler/TS or crossflow/TS interaction is present, the e sup N will fail to predict transition. However, there is no evidence of such interaction at low amplitudes of Goertler and crossflow vortices.

Malik, Mujeeb R.

1987-01-01

404

Metal-metal laminar composites for high temperature applications  

NASA Technical Reports Server (NTRS)

A study was conducted to obtain indications of the potentialities of laminar metal-metal composites for elevated temperature use. Most of the composites consisted of multiple layers or laminae of tungsten alternated with laminae of Nichrome V, a ductile, weaker but oxidation-resistant alloy. Composites with 50 volume percent of each phase were tested in tension and stress rupture at temperatures of 871 and 1093 C (1600 and 2000 F) and in impact at 23 and 524 C (73 and 975 F). A tension and a short time stress-rupture test was conducted on specimens of 77 v/o W-Re-Hf-C/23 v/o Inconel alloy 600 at 1093 C (2000 F).

Hoffman, C. A.; Weeton, J. W.

1972-01-01

405

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

406

A theoretical study of a laminar diffusion flame  

NASA Technical Reports Server (NTRS)

Theoretical models of an axisymmetric laminar diffusion flame are discussed, with an emphasis on the behavior of such flames at increasing pressures. The flame-sheet or Burke-Schumann model (in terms of Bessel functions) and various boundary layer numerical solutions are presented and their results compared with experimental data. The most promising theoretical model combines the numerical flow field solution of the Patankar-Spalding computer code with the Pratt-Wormeck chemical reaction subroutine. The flame shapes for pressures of 1, 5, 10, 20, and 50 atmospheres were computed and agree remarkably well with experimental data. There is a noticeable shape change with pressure, believed to be a result of buoyancy effects. The chemical concentration profiles do not exhibit much dependence on pressure, a reflection of the fact that only one chemical mechanism was utilized at all pressures.

Frair, K. L.

1978-01-01

407

Thermal Induced Processes in Laminar System of Stainless Steel Beryllium  

NASA Astrophysics Data System (ADS)

The paper reports on investigation of the laminar system ‘stainless steel 12Cr18Ni10Ti Be’ at thermal treatment. There have been determined sequences of phase transformations along with relative amount of iron-containing phases in the samples subjected to thermal beryllization. It has been revealed that thermal beryllization of stainless steel thin foils results in ??? transformation and formation of the beryllides NiBe and FeBe2. It has also been revealed that direct ???- and reverse ???-transformations are accompanied by, correspondingly, formation and decomposition of the beryllide NiBe. It is shown that distribution of the formed phases within sample bulk is defined by local concentration of beryllium. Based on obtained experimental data there is proposed a physical model of phase transformations in stainless steel at thermal beryllization.

Zhubaev, A. K.; Kadyrzhanov, K. K.; Rusakov, V. S.; Turkebaev, T. E.

2005-07-01

408

On strong slot injection into a subsonic laminar boundary layer  

NASA Astrophysics Data System (ADS)

This paper is concerned with the problem of fluid injection into a steady, subsonic, laminar, boundary layer flow over a flat plate at zero angle of attack. The problem is formulated within the context of the triple deck theory for asymptotic analysis of strong slot injection for large Reynolds number. The lower deck, linearized problem for small injection velocity is solved analytically using Fourier transform techniques. Graphical results are given for a wide range of slot lengths. A numerical technique for the lower deck non-linear problem is presented together with results for various injection velocities. In contrast to the supersonic case, separation is found to first occur downstream of the slot, where a recirculating flow bubble is formed.

Napolitano, M.; Messick, R. E.

1980-06-01

409

Laminar air flow versus barrier nursing in marrow transplant recipients.  

PubMed

Forty-eight patients with acute leukaemia in relapse (n = 14), acute leukaemia in complete remission (n = 19), chronic myeloid leukaemia (n = 8) or severe aplastic anaemia (n = 7) received a marrow transplant. The first 26 patients were nursed in laminar-air-flow plastic isolators while the next 22 patients were treated in barrier nursing rooms. Gnotobiotic parameters and morbidity in the 2 groups are compared. Good decontamination of the gastro-intestinal tract was obtained using either of the 2 isolation techniques. The incidence of bacterial and mycotic infections, as well as the supportive care required by the patients was almost equal in both groups. Our results also suggest that the incidence of graft versus host disease may decrease with efficient decontamination of the patients. PMID:6388667

Mahmoud, H K; Schaefer, U W; Schüning, F; Schmidt, C G; Bamberg, M; Haralambie, E; Linzenmeier, G; Hantschke, D; Grosse-Wilde, H; Luboldt, W

1984-11-01

410

On the Oscillation of Combustion of a Laminar Spray  

NASA Technical Reports Server (NTRS)

A spray combustor, with flow velocities in the laminar range, exhibits a unique operating mode where large amplitude, self-induced oscillations of the flame shape occur. The phenomenon, not previously encountered, only occurs when fuel is supplied in the form of fine liquid droplets and does not occur when fuel is supplied in gaseous form. Several flow mechanisms are coupled in such a fashion as to trigger and maintain the oscillatory motion of the flame. These mechanisms include heat transfer and evaporation processes, dynamics of two-phase flows, and effects of gravity (buoyancy forces). An interface volume, lying between the fuel nozzle and the flame was found to be the most susceptible to gravity effects, and postulated to be responsible for inducing the oscillatory motion. Heptane fuel was used in the majority of the tests.

Levy, Yeshayahou; Bulzan, Daniel L.

1995-01-01

411

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

412

Laminar flow control research at TsAGI: Past and present  

NASA Astrophysics Data System (ADS)

This paper presents a brief review of activities in laminar flow control being performed at the Central Aerohydrodynamic Institute named after Prof. N.E. Zhukovsky (TsAGI). These efforts are focused on the improvement of the existing laminar flow control methods and on the development of new ones. The investigations have demonstrated the effectiveness of aircraft surface laminarization applications with the aim of friction drag reduction. The opportunity of considerable delaying of laminar-turbulent transition due to special wing profile geometry and using boundary layer suction and surface cooling has been verified at sub- and supersonic speeds through various wind tunnel testing at TsAGI and during flying laboratory experiments at the Flight Research Institute (LII). The investigations on using hybrid laminar flow control systems for friction drag reduction were also carried out. New techniques of laminar flow control were proposed, in particular, the method of local heating of the wing leading edge, boundary layer laminarization by means of receptivity control, and electrohydrodynamic methods of boundary layer stability control.

Chernyshev, S. L.; Kiselev, A. Ph.; Kuryachii, A. P.

2011-04-01

413

Technology developments for laminar boundary layer control on subsonic transport aircraft  

NASA Technical Reports Server (NTRS)

The development of laminar flow technology for commercial transport aircraft is discussed and illustrated in a review of studies undertaken in the NASA Aircraft Energy Efficiency (ACEE) program since 1976. The early history of laminar flow control (LFC) techniques and natural laminar flow (NLF) airfoil designs is traced, and the aims of ACEE are outlined. The application of slotted structures, composites, and electron beam perforated metals in supercritical LFC airfoils, wing panels, and leading edge systems is examined; wind tunnel and flight test results are summarized; studies of high altitude ice effects are described; and hybrid (LFC/NLF designs are characterized. Drawings and photographs are provided.

Wagner, R. D.; Maddalon, D. V.; Fischer, M. C.

1984-01-01

414

A perspective of laminar-flow control. [aircraft energy efficiency program  

NASA Technical Reports Server (NTRS)

A historical review of the development of laminar flow control technology is presented with reference to active laminar boundary-layer control through suction, the use of multiple suction slots, wind-tunnel tests, continuous suction, and spanwise contamination. The ACEE laminar flow control program is outlined noting the development of three-dimensional boundary-layer codes, cruise-noise prediction techniques, airfoil development, and leading-edge region cleaning. Attention is given to glove flight tests and the fabrication and testing of wing box designs.

Braslow, A. L.; Muraca, R. J.

1978-01-01

415

Control of supersonic wind-tunnel noise by laminarization of nozzle-wall boundary layer  

NASA Technical Reports Server (NTRS)

One of the principal design requirements for a quiet supersonic or hypersonic wind tunnel is to maintain laminar boundary layers on the nozzle walls and thereby reduce disturbance levels in the test flow. The conditions and apparent reasons for laminar boundary layers which have been observed during previous investigations on the walls of several nozzles for exit Mach numbers from 2 to 20 are reviewed. Based on these results, an analysis and an assessment of nozzle design requirements for laminar boundary layers including low Reynolds numbers, high acceleration, suction slots, wall temperature control, wall roughness, and area suction are presented.

Beckwith, I. E.; Harvey, W. D.; Harris, J. E.; Holley, B. B.

1973-01-01

416

Summary of past experience in natural laminar flow and experimental program for resilient leading edge  

NASA Technical Reports Server (NTRS)

The potential of natural laminar flow for significant drag reduction and improved efficiency for aircraft is assessed. Past experience with natural laminar flow as reported in published and unpublished data and personal observations of various researchers is summarized. Aspects discussed include surface contour, waviness, and smoothness requirements; noise and vibration effects on boundary layer transition, boundary layer stability criteria; flight experience with natural laminar flow and suction stabilized boundary layers; and propeller slipstream, rain, frost, ice and insect contamination effects on boundary layer transition. The resilient leading edge appears to be a very promising method to prevent leading edge insect contamination.

Carmichael, B. H.

1979-01-01

417

Evaluation of FIDAP on some classical laminar and turbulent benchmarks. [FluId Dynamics Analysis Package  

NASA Technical Reports Server (NTRS)

The numerical accuracy of the fluid-dynamics code FIDAP is investigated by means of test computations on two-dimensional flows. The theoretical basis of the algorithm is briefly reviewed, and results for laminar flow in a wall-driven cavity and for both laminar and turbulent flows over a backward-facing step are presented in extensive tables and graphs and characterized in detail. Good agreement with published experimental data and previous computations is obtained for laminar flows using a version of FIDAP without streamlined upwinding (STU). For turbulent flows, the addition of STU is found to be useful, although it causes separation-zone reattachment length to be underpredicted.

Sohn, J. L.

1988-01-01

418

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

2010-03-01

419

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

420

Three-phase traveling wave surface discharge along an insulating flat plate in air: application to electrohydrodynamically airflow control  

Microsoft Academic Search

Several studies have shown that a surface corona discharge may be used as an air-moving actuator in order to control the airflow around an obstacle, such as a plane wing to reduce the drag for example. For few years, our laboratory has been working on this subject, especially in the case of a DC corona discharge. The present paper deals

E. Moreau; L. Leger; G. Touchard

2002-01-01

421

Enhanced performance of heat recovery ventilator by airflow-induced film vibration (HRV performance enhanced by FIV)  

Microsoft Academic Search

Heat recovery of air ventilation is a means of energy conversation in buildings. In the present paper, a plastic film heat recovery ventilator that works under cross-flow mode was developed. The thin film vibrates when airflow passes through the channels, which enhances heat exchange performance. Experiments, as well as theoretical analyses, were carried out to study the performance of such

Yanhua Lu; Yiping Wang; Li Zhu; Qi Wang

2010-01-01

422

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

Code of Federal Regulations, 2012 CFR

...Airflow resistance shall not exceed 38 mm. (1.5 inches) of water-column height to air drawn at the flow rate of 85 liters...exhalation resistance shall not exceed 25 mm. (1 inch) of water-column height at this flow...

2012-10-01

423

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

424

Using a Swinging Vane Anemometer to Measure Airflow. Module 14. Vocational Education Training in Environmental Health Sciences.  

ERIC Educational Resources Information Center

This module, one of 25 on vocational education training for careers in environmental health occupations, contains self-instructional materials on using a swinging vane anemometer to measure airflow. Following guidelines for students and instructors and an introduction that explains what the student will learn are three lessons: (1) naming each…

Consumer Dynamics Inc., Rockville, MD.

425

Regional airflow and particle distribution in the lung with a 3D-1D coupled subject-specific boundary condition  

NASA Astrophysics Data System (ADS)

Correct prediction of regional distribution of inhaled aerosol particles is vital to improve pulmonary medicine. Physiologically consistent regional ventilations of airflow and aerosol particles are simulated with a 3D-1D coupled subject-specific boundary condition (BC). In 3D CT-resolved 7-generation airways, large eddy simulations are performed to capture detailed airflow characteristics and Lagrangian particle simulations are carried to track the particle transport and deposition. Results are compared with two traditional outlet BCs: uniform velocity and uniform pressure. Proposed BC is eligible for physiologically consistent airflow distribution in the lung, while the others are not. The regional ventilation and deposition of particles reflect the regional ventilation of airflow. In this study, two traditional BCs yield up to 98% (334%) over-prediction in lobar particle ventilation (deposition) fraction. Upper to lower particle ventilation ratios of both left and right lungs read ˜0.4 with the proposed BC, while those for the other two BCs vary with the error up to 73%.

Choi, Jiwoong; Yin, Youbing; Hoffman, Eric; Tawhai, Merryn; Lin, Ching-Long

2010-11-01

426

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

2014-01-01

427

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

428

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

429

A theoretical study on accurate measurements of thoron with airflow-through scintillation cell method.  

PubMed

For accurate measurements of (220)Rn concentration with airflow-through scintillation cell method, a theoretical study was performed for discussing the influences of sampling flow rate, volumes of sampling tube and scintillation cell on the measurements. It is found that a high flow rate and a large inner volume of scintillation cell as well as a small inner volume of sampling tube are not only preferable for measuring low levels of (220)Rn, but also helpful for enhancing the measurement accuracy. In calibration experiments, both the sampling flow rate and the sampling tube volume should be noted. The variations of the flow rate and tube volume should be considered for accurate measurements in the fields. PMID:20876070

Tang, F; Zhuo, W; Zhao, C; Chen, B; Xu, Y; He, L

2010-10-01

430

Comparison between effects of various partial inferior turbinectomy options on nasal airflow: a computer simulation study.  

PubMed

Partial inferior turbinectomy is typically performed on patients suffering from chronic nasal obstruction due to hypertrophy of inferior turbinates and is refractory to other more conservative treatments. The effects of the various options of incision performed on the inferior turbinate in terms of the resulting nasal airflow pattern are examined using computational fluid mechanics. The pressure drops across the severely blocked nose and healthy nose models were found to be 32.3 and 12.3 Pa, respectively, whereas the pressure drops across the nasal cavity following one-third turbinate resection, total turbinate resection and front-end resection were obtained as 5.8, 6.1 and 30.5 Pa correspondingly. Based on the total pressure drop results, the one-third resection option seems to be better than the front-end surgery and the total turbinate resection. PMID:21916676

Lee, Heow Pueh; Garlapati, Revanth Reddy; Chong, Vincent Fook Hin; Wang, De Yun

2013-01-01

431

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

NASA Astrophysics Data System (ADS)

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 to 20 mA are produced along the surface. In terms of powers, mechanical powers (output) of a few milliwatts are obtained for electrical powers (input) up to 10 W. Variation laws or behaviour with several discharge parameters (applied voltage waveform, distance between electrodes, dielectric thickness and permittivity) have been experimentally determined.

Pons, Jérôme; Moreau, Eric; Touchard, Gérard

2005-10-01

432

Airway responsiveness and bronchial-wall thickness in asthma with or without fixed airflow obstruction.  

PubMed

To determine whether asthmatic subjects have an increase in airway wall thickness that could enhance airway narrowing during bronchoprovocation, we examined the relationship between airway responsiveness and bronchial wall thickness measured by high-resolution computed tomography (HRCT). We studied 24 nonsmokers with asthma, of whom 13 had a fixed component of airflow obstruction (Group 1) and 11 had an optimal FEV1 of 80% or more of the predicted value (Group 2). These subjects were compared with a control group of 10 nonasthmatic subjects (Group 3). Measurements were taken of each subject's expiratory flows, bronchodilator response, lung volumes, and methacholine responsiveness. All subjects used an inhaled beta 2-agonist on demand, and 19 also used inhaled steroids (13 in a Group 1 and six in Group 2). HRCT sections were obtained at the top and base of the lung and at the level of the intermediary bronchus (IB), although only this last level was found adequate for analysis. The ratio of IB wall thickness to outer diameter (T/D) showed a negative relationship with the outer diameter in Group 1 only. The mean T/D ratio of IB was not significantly different in Groups 1, 2, and 3, with respective values of 0.16 +/- 0.01, 0.15 +/- 0.01, and 0.18 +/- 0.01 at TLC, and 0.16 +/- 0.01, 0.20 +/- 0.01, and 0.19 +/- 0.01 at FRC. In subjects with a fixed component of airflow obstruction, the thicker the airway wall in relation to its diameter, the lower was the PC20 for methacholine. This was not observed in the other study groups. No correlation was found between the T/D ratio and baseline FEV1.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7663797

Boulet, L; Bélanger, M; Carrier, G

1995-09-01

433

Effects of single-sided inferior turbinectomy on nasal function and airflow characteristics.  

PubMed

Knowledge of airflow characteristics in the nasal cavity is essential to understanding the physiologic and pathologic aspects of nasal breathing.