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1

Laminar-airflow equipment certification: what the pharmacist needs to know.  

PubMed

The basic information pharmacy practitioners need to determine the suitability and applicability of laminar-airflow equipment test standards and procedures is presented. The operative guideline for any laminar-flow clean bench (LFCB) certification is the cleanroom and work station requirements for controlled environments as defined by the federal government under Federal Standard 209b (FS 209b). FS 209b outlines the tests, test procedures, and acceptable performance ranges for all LFCB equipment. National Sanitation Foundation Standard Number 49 (NSF 49) is used in the certification of biological-safety cabinets (BSCs). NSF 49 covers those aspects of safety, maintenance, performance, and testing that are unique BSCs. To monitor certification properly, practitioners should be familiar with these standards and the air-velocity profile, high-efficiency particulate air filter performance, noise output, light, and electrical test procedures. A review of the requisite knowledge, experience, and reputation of certifying agents is presented, along with an outline of all the necessary procedures, equipment, and documentation to be used in the process. A thorough test report should be issued upon unit certification. As pharmacy practitioners are responsible for all other aspects of quality assurance, they should also be capable of auditing these certifications to ensure the aseptic quality of products compounded in the laminar-airflow environment. PMID:6465148

Bryan, D; Marback, R C

1984-07-01

2

Timeline Analysis Program (TLA-1)  

NASA Technical Reports Server (NTRS)

The Timeline Analysis Program (TLA-1) was described. This program is a crew workload analysis computer program that was developed and expanded from previous workload analysis programs, and is designed to be used on the NASA terminal controlled vehicle program. The following information is described: derivation of the input data, processing of the data, and form of the output data. Eight scenarios that were created, programmed, and analyzed as verification of this model were also described.

Miller, K. H.

1976-01-01

3

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 1m from the screen. Increasing air velocity from the MLAF above 0.4m/s does not increase the impact area. PMID:25006349

2014-01-01

4

Lazy Caching in TLA Peter Ladkin Leslie Lamport Bryan Olivier  

E-print Network

Lazy Caching in TLA Peter Ladkin Leslie Lamport Bryan Olivier Denis Roegel Tue 13 Apr 1999 [12 of the lazy caching algorithm of Afek, Brown, and Merritt is sequen- tially consistent. We specify;Contents 1 Introduction 1 2 Lazy Caching in TLA+ 3 2.1 TLA and TLA

Rajamani, Sriram K.

5

Lazy Caching in TLA Peter Ladkin Leslie Lamport Bryan Olivier  

E-print Network

Lazy Caching in TLA Peter Ladkin Leslie Lamport Bryan Olivier Denis Roegel Tue 13 Apr 1999 [12 of the lazy caching algorithm of Afek, Brown, and Merritt is sequen­ tially consistent. We specify; Contents 1 Introduction 1 2 Lazy Caching in TLA + 3 2.1 TLA and TLA

Lamport ,Leslie

6

Lazy Caching in TLA Peter Ladkin Leslie Lamport Bryan Olivier  

E-print Network

Lazy Caching in TLA Peter Ladkin Leslie Lamport Bryan Olivier Denis Roegel Mon 8 Feb 1999 [08 of the lazy caching algorithm of Afek, Brown, and Merritt is sequen- tially consistent. We specify;Contents 1 Introduction 1 2 Lazy Caching in TLA+ 3 2.1 TLA and TLA

Roegel, Denis

7

Specifying and Verifying Systems With TLA + Leslie Lamport  

E-print Network

Specifying and Verifying Systems With TLA + Leslie Lamport Microsoft Research John Matthews HP Labs; Specifying and Verifying Systems With TLA + Leslie Lamport Microsoft Research John Matthews HP Labs Cambridge

Tuttle, Mark R.

8

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

9

Formal But Lively Buffers in TLA+ Peter B. Ladkin  

E-print Network

Formal But Lively Buffers in TLA+ Peter B. Ladkin omitted. We specify in TLA a buffer implemented as an array, a dou- ble buffer implemented as two arrays in series, and an abstract buffer which uses a sequence. We prove, formally and rigorously

Ladkin, Peter B.

10

Formal But Lively Buffers in TLA + Peter B. Ladkin  

E-print Network

Formal But Lively Buffers in TLA + Peter B. Ladkin Universit¨at Bielefeld, Technische Fakult­ stood, our example needs only the trivial invariant, which is simply omitted. We specify in TLA a buffer implemented as an array, a dou­ ble buffer implemented as two arrays in series, and an abstract buffer which

Ladkin, Peter B.

11

TLA markers and nuclear scanning method for wear rate monitoring  

NASA Astrophysics Data System (ADS)

Two new extensions of the TLA-direct measuring method are presented: the TLA-markers for wear control and the nuclear scanning method for monitoring wear non-uniformity on large surfaces. Both methods were applied to measure the material loss on the surface of railway car brake disks.

Stan-Sion, C.; Plostinaru, D.; Ivan, A.; Ivanov, E.; Dudu, D.; Catana, M.; Roman, M.

1994-08-01

12

TLA - markers and nuclear scanning method for wear rate monitoring  

Microsoft Academic Search

Two new extensions of the TLA-direct measuring method are presented: the TLA-markers for wear control and the nuclear scanning method for monitoring wear non-uniformity on large surfaces. Both methods were applied to measure the material loss on the surface of railway car brake disks.

C. Stan-Sion; D. Plostinaru; A. Ivan; E. Ivanov; D. Dudu; M. Catana; M. Roman

1994-01-01

13

Steam boiler control speci cation problem: A TLA solution  

E-print Network

Steam boiler control speci cation problem: A TLA solution Frank Le ke and Stephan Merz Institut fur of the state of the steam boiler, detect failures, and model message transmission. We give a more detailed between the physi- cal state of the steam boiler and the model maintained by the controller and discuss

14

Steam boiler control specification problem: A TLA solution  

E-print Network

Steam boiler control specification problem: A TLA solution Frank Le?ke and Stephan Merz Institut f of the state of the steam boiler, detect failures, and model message transmission. We give a more detailed between the physi­ cal state of the steam boiler and the model maintained by the controller and discuss

Merz, Stephan

15

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...

16

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

17

Natural laminar flow and laminar flow control  

NASA Technical Reports Server (NTRS)

The present volume discusses the development history and basic concepts of laminar flow control, laminar flow flight experiments, subsonic laminar-flow airfoils, and a design philosophy for long-range laminar flow-control commercial transports with advanced supercritical airfoils. Also discussed are the relationship of wave-interaction theory to laminar flow control, supersonic laminar flow control, and the NASA-Langley 8-ft Transonic Pressure Tunnel.

Barnwell, R. W. (editor); Hussaini, M. Y. (editor)

1992-01-01

18

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

19

Multizone Airflow Model in Modelica  

Microsoft Academic Search

We present the implementation of a library of multi- zone airflow models in Modelica and a comparative model validation with CONTAM. Our models have a similar level of detail as the models in CONTAM and COMIS. The multizone airflow models allow model- ing the flow between rooms through doors, staircases or construction cracks. The flow can be caused by buoyancy

Michael Wetter

2006-01-01

20

AIRFLOW NETWORK MODELING IN ENERGYPLUS  

Microsoft Academic Search

The airflow network model in EnergyPlus provides the ability to simulate multizone wind-driven airflows. The model is also able to simulate the impacts of forced air distribution systems, including supply and return air leaks. The air distribution system portion of the model is currently applicable for constant-air-volume systems. Future enhancements will include adding hybrid ventilation control and possible extension to

Lixing Gu

2007-01-01

21

NASA supercritical laminar flow control airfoil experiment  

NASA Technical Reports Server (NTRS)

The design and goals of experimental investigations of supercritical LFC airfoils conducted in the NASA Langley 8-ft Transonic Pressure Tunnel beginning in March 1982 are reviewed. Topics addressed include laminarization aspects; flow-quality requirements; simulation of flight parameters; the setup of screens, honeycomb, and sonic throat; the design cycle; theoretical pressure distributions and shock-free limits; drag divergence and stability analysis; and the LFC suction system. Consideration is given to the LFC airfoil model, the air-flow control system, airfoil-surface instrumentation, liner design and hardware, and test options. Extensive diagrams, drawings, graphs, photographs, and tables of numerical data are provided.

Harvey, W. D.

1982-01-01

22

Airflow models gaining clout  

SciTech Connect

Move over, mock-ups. So long, smoke bombs. Take a walk, wind tunnels. Computational fluid dynamics, a spaceage simulation technique, is gaining velocity in the building community. And the design of inner spaces may never be the same. CFD is an equation-intensive computer modeling method that can simulate transient and steady-state airflow patterns and temperature gradients, indoors or out. CFD is used to downsize heating, ventilating and air conditioning systems, locate air outlets, and in general, create spaces that offer creature comfort, provide quality air and use less energy. The method is good for new construction, retrofits and forensic work, for example to investigate a building fire or a contaminant. In a room, CFD helps engineers consider, over a period of time, the combined impacts of ventilation, size, shape, contents, weather, even fenestration. For its first decade or two, CFD stayed the near-exclusive domain of aerospace, defense and electronics. With few exceptions, the building community could not afford the supercomputers that were needed to run the tens of thousands of equations involved. However, in the past few years, thanks to the increasing power and decreasing cost of computers, CFD simulation became practical. Curtain wall designers are even using it, though not without some controversy. Indoor air quality specialists, smoke and fire-spread researchers, laboratory designers, energy engineers, code writers, architects, and plant and building engineers are uncharacteristically upbeat about the tool. {open_quotes}CFD modeling is so many light years ahead of design tools that exist,{close_quotes} says Mariano Rodriguez, director of research and development for architect The Hillier Group, Princeton, N.J. {open_quotes}It`s the next step up from a wind tunnel test, and you don`t need a $300,000 wind tunnel.{close_quotes}

Post, N.M.

1994-10-10

23

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

24

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. PMID:23148270

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

2012-01-01

25

Aircraft Laminar Flow Control  

Microsoft Academic Search

Aircraft laminar flow control (LFC) from the 1930s through the 1990s is reviewed and the current status of the technology is assessed. Examples are provided to demonstrate the benefits of LFC for subsonic and supersonic aircraft. Early studies related to the laminar boundary-layer flow physics, manufacturing tolerances for laminar flow, and insect-contamination avoidance are discussed. LFC concept studies in wind-tunnel

Ronald D. Joslin

1998-01-01

26

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

PubMed

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

Mitra, Mautusi; Dewez, David; Garca-Cerdn, Jose Gines; Melis, Anastasios

2012-04-01

27

Numerical simulation of airflow in the human nasal cavity.  

PubMed

An anatomically correct finite element mesh of the right human nasal cavity was constructed from CAT scans of a healthy adult nose. The steady-state Navier-Stokes and continuity equations were solved numerically to determine the laminar airflow patterns in the nasal cavity at quiet breathing flow rates. In the main nasal passages, the highest inspiratory air speed occurred along the nasal floor (below the inferior turbinate), and a second lower peak occurred in the middle of the airway (between the inferior and middle turbinates and the septum). Nearly 30 percent of the inspired volumetric flow passed below the inferior turbinate and about 10 percent passed through the olfactory airway. Secondary flows were induced by curvature and rapid changes in cross-sectional area of the airways, but the secondary velocities were small in comparison with the axial velocity through most of the main nasal passages. The flow patterns changed very little as total half-nasal flow rate varied between resting breathing rates of 125 m/s and 200 ml/s. During expiration, the peaks in velocity were smaller than inspiration, and the flow was more uniform in the turbinate region. Inspiratory streamline patterns in the model were determined by introducing neutrally buoyant point particles at various locations on the external naris plane, and tracking their path based on the computed flow field. Only the stream from the ventral tip of the naris reached the olfactory airway. The numerically computed velocity field was compared with the experimentally measured velocity field in a large scale (20x) physical model, which was built by scaling up from the same CAT scans. The numerical results showed good agreement with the experimental measurements at different locations in the airways, and confirmed that at resting breathing flow rates, airflow through the nasal cavity is laminar. PMID:8748525

Keyhani, K; Scherer, P W; Mozell, M M

1995-11-01

28

Aircraft Laminar Flow Control  

NASA Technical Reports Server (NTRS)

Aircraft laminar flow control (LFC) from the 1930's through the 1990's is reviewed and the current status of the technology is assessed. Examples are provided to demonstrate the benefits of LFC for subsonic and supersonic aircraft. Early studies related to the laminar boundary-layer flow physics, manufacturing tolerances for laminar flow, and insect-contamination avoidance are discussed. LFC concept studies in wind-tunnel and flight experiments are the major focus of the paper. LFC design tools are briefly outlined for completeness.

Joslin, Ronald D.

1998-01-01

29

Laminar-flow airfoil  

NASA Technical Reports Server (NTRS)

An airfoil having a fore airfoil element, an aft airfoil element, and a slot region in between them. These elements induce laminar flow over substantially all of the fore airfoil element and also provide for laminar flow in at least a portion of the slot region. The method of the invention is one for inducing natural laminar flow over an airfoil. In the method, a fore airfoil element, having a leading and trailing edge, and an aft airfoil element define a slot region. Natural laminar flow is induced over substantially all of the fore airfoil element, by inducing the pressures on both surfaces of the fore airfoil element to decrease to a location proximate the trailing edge of the fore airfoil element using pressures created by the aft airfoil element.

Somers, Dan M. (Inventor)

2005-01-01

30

Laminar Soot Processes  

NASA Technical Reports Server (NTRS)

Soot formation within hydrocarbon-fueled flames is an important unresolved problem of combustion science for several reasons: soot emissions are responsible for more deaths than any other combustion pollutant, thermal loads due to continuum radiation from soot limit the durability of combustors, thermal radiation from soot is mainly responsible for the growth and spread of unwanted fires, carbon monoxide associated with soot emissions is responsible for most fire deaths, and limited understanding of soot processes is a major impediment to the development of computational combustion. Thus, soot processes within laminar nonpremixed (diffusion) flames are being studied, emphasizing space-based experiments at microgravity. The study is limited to laminar flames due to their experimental and computational tractability, noting the relevance of these results to practical flames through laminar flamelet concepts. The microgravity environment is emphasized because buoyancy affects soot processes in laminar diffusion flames whereas effects of buoyancy are small for most practical flames. Results discussed here were obtained from experiments carried out on two flights of the Space Shuttle Columbia. After a brief discussion of experimental methods, results found thus far are described, including soot concentration measurements, laminar flame shapes, laminar smoke points and flame structure. The present discussion is brief.

Lin, K. -C.; Dai, Z.; Faeth, G. M.

1999-01-01

31

[Phonatory airflow in the supraglottal space].  

PubMed

The phonatory airflow can be measured by means of a hot wire tube placed in the supraglottic space without tying down the tongue. The velocity of airflow above the glottis reaches values around c = 50 to 150 cm/s. The variations in airflow oscillations were recorded. The voice of the person under examination was picked up by a condenser microphone (Bruel & Kjaer No. 2112). According to D'Alembert's wave equation, the sound intensity is related to the velocity of the phonatory air stream. The validity of this statement has been confirmed by repeated testing. The fundamental frequency of voice and of the airflow were analysed synchronously by means of the Nicolet analyser. The air consumption is not utilized for sound production in phonation by breathing. A "hard" or "pressed" voice is associated with diminished or irregular air consumption. The method can be employed in assessing the conditions of phonetic airflow in normal and dysphonic voices. PMID:6865619

Msebeck, K; Rosenberg, H

1983-05-01

32

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 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 POC and LFSWT's nozzle design with laminar flow control are as follows: (1) supersonic laminar boundary layer stability and transition prediction; (2) effects of heating and cooling for supersonic laminar flow control; and (3) POC and LFSWT nozzle design with heating and cooling effects combining wall contour and length changes.

Lo, C. F.

1994-01-01

33

Supersonic laminar flow control research  

Microsoft Academic Search

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)

Ching F. Lo

1994-01-01

34

Development of Power-head based Fan Airflow Station  

E-print Network

Development of Power-head Based Fan Airflow Station Gang Wang Research associate University of Nebraska, Lincoln Mingsheng Liu Professor University of Nebraska, Lincoln Abstract Fan airflow measurement is critical for heating... under partial loads. On the other hand, in most of airflow range, the power curve varies exquisitely. Wang and Liu developed the VFD airflow station to obtain the fan airflow using the power and speed based on the power curve. Both the fan...

Wang, G.; Liu, M.

2005-01-01

35

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

36

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

37

Supersonic Laminar Flow Control Research  

NASA Technical Reports Server (NTRS)

The objective of this 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 distributed heating and cooling as an active boundary layer control technique will be studied. The primary tasks of the research apply to the NASA/Ames PoC and LFSWT's nozzle design with laminar flow control and are listed as follows: Predictions of supersonic laminar boundary layer stability and transition; Effects of wall heating and cooling on supersonic laminar flow control on a flat plate; Performance evaluation of the PoC and LFSWT nozzle designs with wall heating and cooling applied at different locations and various lengths; Effects of a conducted-vs-pulse wall temperature distribution for the LFSWT; and Application of wall heating and/or cooling to laminar boundary layer and flow separation control of airfoils and investigation of related active control techniques.

Lo, Ching F.; Wiberg, Clark G.

1996-01-01

38

Supersonic laminar flow control research  

NASA Technical Reports Server (NTRS)

The objective 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 distributed heating and cooling as an active boundary layer control technique will be studied. The primary tasks of the research apply to the NASA/Ames Proof of Concept (PoC) and Laminar Flow Supersonic Wind Tunnel's (LFSWT's) nozzle design with laminar flow control and are listed as follows: (1) predictions of supersonic laminar boundary layer stability and transition, (2) effects of wall heating and cooling on supersonic laminar flow control, (3) performance evaluation of the PoC and LFSWT nozzle designs with wall heating and cooling applied at different locations and various lengths, and (4) effects of a conducted versus pulse wall temperature distribution for the LFSWT.

Lo, Ching F.; Wiberg, Clark G.

1995-01-01

39

Overview of Laminar Flow Control  

Microsoft Academic Search

The history of Laminar Flow Control (LFC) from the 1930s through the1990s is reviewed and the current status of the technology is assessed. Early studiesrelated to the natural laminar boundary-layer flow physics, manufacturingtolerances for laminar flow, and insect-contamination avoidance are discussed.Although most of this publication is about slot-, porous-, and perforated-suctionLFC concept studies in wind tunnel and flight experiments, some

Ronald D. Joslin

1998-01-01

40

Tuberculosis, bronchiectasis and chronic airflow obstruction.  

PubMed

Both tuberculosis and bronchiectasis carry a significant burden worldwide in terms of morbidity and mortality, as well as financial, especially in the developing world. Epidemiological data for tuberculosis are now more readily available since the World Health Organisation declared it 'a global emergency' in 1993. The global prevalence of bronchiectasis, a recognized sequel of tuberculosis, is unknown, but is by no means insignificant. The pathophysiology of chronic airflow obstruction in both of these diseases is poorly understood, but it is associated with an accelerated rate of loss in pulmonary function. This article examines the global burden of tuberculosis and bronchiectasis, and focuses on the interrelation with chronic airflow obstruction. PMID:20409028

Jordan, Toni S; Spencer, Elspeth M; Davies, Peter

2010-05-01

41

Doping of Ce in T-La2CuO4 : Rigorous test for electron-hole symmetry for high- Tc superconductivity  

NASA Astrophysics Data System (ADS)

We report that Ce doping was achieved in La2CuO4 with the K2NiF4(T) structure for the first time by molecular beam epitaxy. A synthesis temperature of as low as 630C and an appropriate substrate choice, i.e. , (001)LaSrGaO4(as=3.843) , enabled us to incorporate Ce into the K2NiF4 lattice and to obtain Ce-doped T-La2-xCexCuO4 up to xtilde 0.06 . The doping of Ce makes T-La2CuO4 more insulating, which is in sharp contrast to Sr (or Ba) doping in T-La2CuO4 , which makes the compound metallic and superconducting. The observed smooth increase in resistivity from the hole-doped side (T-La2-xSrxCuO4) to the electron-doped side (T-La2-xCexCuO4) indicates that the electron-hole symmetry is broken in the T -phase materials.

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

2006-11-01

42

Laminar flames in premixed gases  

NASA Technical Reports Server (NTRS)

Numerical simulation of laminar flames in premixed gases is addressed. Various efforts to solve the laminar flame problem are briefly described, and basic equations to be modeled in a comprehensive description of laminar flames are discussed along with the physical and chemical processes represented by these equations and the numerical requirements to model them. Two flame methods are discussed in some detail: a numerical model for studying transient phenomena and its 2D counterpart method. The various input parameters needed for the models are addressed, and the use of the models is illustrated in several studies of laminar flames in premixed gases. Flammability limits and multidimensional flame propagation are also examined.

Kailasanath, K.

1991-01-01

43

Optimal Airflow Control for Laboratory Air Handling Unit (LAHU) Systems  

E-print Network

An optimal airflow control method and procedure have been developed for laboratory air handing unit (LAHU) systems using linear optimization theories. The optimal airflow control minimizes the thermal energy consumption and the cost, and improves...

Cui, Y.; Liu, M.; Conger, K.

2002-01-01

44

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...

45

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

46

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

47

Laminar Soot Processes  

NASA Technical Reports Server (NTRS)

The Laminar Soot Processes (LSP) experiment under way during the Microgravity Sciences Lab-1 mission in 1997. LSP-2 will fly in the STS-107 Research 1 mission in 2001. The principal investigator is Dr. Gerard Faeth of the University of Michigan. LSP uses a small jet burner, similar to a classroom butane lighter, that produces flames up to 60 mm (2.3 in) long. Measurements include color TV cameras and a temperature sensor, 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

48

Laminar Soot Processes  

NASA Technical Reports Server (NTRS)

Image of soot (smoke) plume made for the Laminar Soot Processes (LSP) experiment during the Microgravity Sciences Lab-1 mission in 1997. LSP-2 will fly in the STS-107 Research 1 mission in 2002. The principal investigator is Dr. Gerard Faeth of the University of Michigan. LSP uses a small jet burner, similar to a classroom butane lighter, that produces flames up to 60 mm (2.3 in) long. Measurements include color TV cameras and a temperature sensor, 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

49

The natural history of chronic airflow obstruction  

Microsoft Academic Search

A prospective epidemiological study of the early stages of the development of chronic obstructive pulmonary disease was performed on London working men. The findings showed that forced expiratory volume in one second (FEV1) falls gradually over a lifetime, but in most non-smokers and many smokers clinically significant airflow obstruction never develops. In susceptible people, however, smoking causes irreversible obstructive changes.

C Fletcher; R Peto

1977-01-01

50

LARGE EDDY SIMULATION OF NATURAL AND MIXED CONVECTION AIRFLOW INDOORS  

E-print Network

1 LARGE EDDY SIMULATION OF NATURAL AND MIXED CONVECTION AIRFLOW INDOORS WITH TWO SIMPLE FILTERED simulation of natural and mixed convection airflow indoors with two simple filtered dynamic subgrid scale, and can provide more flow information than other CFD models. Typical indoor airflow includes natural

Chen, Qingyan "Yan"

51

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. PMID:23043081

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

2012-01-01

52

Flight experiences with laminar flow  

NASA Technical Reports Server (NTRS)

A review of natural laminar flow (NLF) flight experiences over the period from the 1930's to the present has been given to provide information on the achievability and maintainability of NLF in typical airplane operating environments. Significant effects of loss of laminar flow on airplane performance have been observed for several airplanes, indicating the importance of providing information on these changes to laminar flow airplane operators. Significant changes in airplane stability and control and maximum lift were observed in flight experiments with the loss of laminar flow. However, these effects can be avoided by proper selection of airfoils. Conservative laminar flow airfoil designs should be employed which do not experience significant loss of lift (caused by flow separation) upon the loss of laminar flow. Mechanisms have been observed for the effects of insect accumulation, flight through clouds and precipitation, and propeller slipstreams on laminar flow behavior. Fixed transition testing, in addition to free transition testing, is recommended as a new standard procedure for airplanes with surfaces designed to support laminar flow.

Holmes, Bruce J.

1986-01-01

53

Laminar flow control - viscous simulation  

Microsoft Academic Search

Laminar flow control which offers the possibility of major reductions in aircraft drag is described. The theoretical background for the possible stabilizations of the laminar boundary layer due to shaping, suction and cooling is presented. The effects of vehicle and environmental factors on the implementation of that technology are examined. Viscous simulation is the technology of adjusting boundary layer conditions

E. Reshotko

1984-01-01

54

Supersonic laminar flow control research  

NASA Technical Reports Server (NTRS)

The objective of this 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 distributed heating and cooling as an active boundary layer control technique will be studied. The primary tasks of the research apply to the NASA/Ames PoC and LFSWT's nozzle design with laminar flow control and are listed as follows: (1) predictions of supersonic laminar boundary layer stability and transition; (2) effects of wall heating and cooling on supersonic laminar flow control; (3) performance evaluation of the PoC and LFSWT nozzle designs with wall heating and cooling applied at different locations and various lengths; and (4) effects of a conducted -vs- pulse wall temperature distribution for the LFSWT.

Lo, Ching F.; Wiberg, Clark G.

1995-01-01

55

Convection warmers--a possible source of contamination in laminar airflow operating theatres?  

PubMed

This work results from concerns that forced-air convection heaters applied to patients in the operating theatre might interfere with ultra-clean ventilation system and thus be a potential source of wound contamination. Air samples were taken in the operative field and the bacterial load calculated by estimating the number of colony forming units per cubic metre of air (cfu/m(3)). Six tests were carried out, two in empty theatres and four during standard orthopaedic operating lists. Differences were seen between empty theatres and those standing empty for short periods during busy operating lists. Increases were seen on entry to theatre of staff and patients with the convection heaters off. A further small rise was seen after the convection heaters were turned on when applied to patients. This study showed that use of warm air convection heaters on patients produced a small increase in the number of colony forming units in ultra-clean air theatres but the levels were unlikely to have clinical significance. By far the greatest effect on numbers was movement and presence of the patient and theatre staff in the theatre. PMID:12419268

Tumia, N; Ashcroft, G P

2002-11-01

56

Preliminary Report on Laminar-Flow Airfoils and New Methods Adopted for Airfoil and Boundary-Layer Investigations  

NASA Technical Reports Server (NTRS)

Recent developments in airfoil-testing methods and fundamental air-flow investigations, as applied to airfoils, are discussed. Preliminary test results, obtained under conditions relatively free from stream turbulence and other disturbances, are presented. Suitable airfoils and airfoil-design principles were developed to take advantage of the unusually extensive laminar boundary layers that may be maintained under the improved testing conditions. The results are of interest mainly in range of below 6,000,000.

Jacobs, Eastman N.

1939-01-01

57

Supersonic Laminar Flow Control Research  

NASA Technical Reports Server (NTRS)

The objective of this research is to understand supersonic laminar flow stability, transition and active control. Some prediction techniques are developed or modified to analyze laminar flow stability. The effects of distributed heating and cooling as an active boundary layer control technique are studied. The primary tasks of the research apply to the NASA/Ames Proof-of-Concept (PoC) and the Laminar Flow Supersonic Wind Tunnel's (LFSWT's) nozzle design with laminar flow control and are listed as follows: (1) Predictions of supersonic laminar boundary layer stability and transition; (2) Effects of wall heating and cooling on supersonic laminar flow control on a flat plate; (3) Performance evaluation of the PoC and LFSWT nozzle designs with wall heating and cooling applied at different locations and various lengths; (4) Effects of a conducted -vs- pulse wall temperature distribution for the LFSWT; and (5) Application of wall heating and/or cooling to laminar boundary layer and flow separation control of airfoils and investigation of related active control techniques.

Lo, C. F.; Wiberg, Clark G.

1996-01-01

58

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. PMID:23983811

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

2013-01-01

59

Ce doping in T-La2CuO4 films: Broken electron-hole symmetry in high-Tc superconductivity  

NASA Astrophysics Data System (ADS)

We attempted Ce doping in La2CuO4 with the K2NiF4 (T) structure by molecular beam epitaxy. With low growth temperature and appropriate substrate choice, we found that Ce can be incorporated into the K2NiF4 lattice up to x 0.06, which has not yet been realized in bulk synthesis. The doping of Ce made T-La2-xCexCuO4 more insulating, which is in sharp contrast to Ce doping in La2CuO4 with the Nd2CuO4 structure, which made the compounds superconducting. The observed smooth increase in resistivity from hole-doped side (T-La2-xSrxCuO4) to electron-doped side (T-La2-xCexCuO4) indicates that electron-hole symmetry is broken in the T-phase materials. We propose that the nature of the insulating state in T-La2-xCexCuO4 is of a Kondo insulator instead of a Mott insulator. The insulating mechanism based on Kondo interaction between Cu3d spins and O2p holes explains the global evolution of the resistivity and also the pseudo gap phenomenon from hole-doping to electron doping.

Tsukada, Akio; Naito, Michio

2005-03-01

60

Effects of the ambient temperature on the airflow across a Caucasian nasal cavity.  

PubMed

We analyse the effects of the air ambient temperature on the airflow across a Caucasian nasal cavity under different ambient temperatures using CFD simulations. A three-dimensional nasal model was constructed from high-resolution computed tomography images for a nasal cavity from a Caucasian male adult. An exhaustive parametric study was performed to analyse the laminar-compressible flow driven by two different pressure drops between the nostrils and the nasopharynx, which induced calm breathing flow rates???5.7?L/min and???11.3?L/min. The inlet air temperature covered the range?-?10(o) C ? To ?50(o) C. We observed that, keeping constant the wall temperature of the nasal cavity at 37(o) C, the ambient temperature affects mainly the airflow velocity into the valve region. Surprisingly, we found an excellent linear relationship between the ambient temperature and the air average temperature reached at different cross sections, independently of the pressure drop applied. Finally, we have also observed that the spatial evolution of the mean temperature data along the nasal cavity can be collapsed for all ambient temperatures analysed with the introduction of suitable dimensionless variables, and this evolution can be modelled with the help of hyperbolic functions, which are based on the heat exchanger theory. PMID:24574201

Burgos, M A; Sanmiguel-Rojas, E; Martn-Alcntara, A; Hidalgo-Martnez, M

2014-03-01

61

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

62

F-16XL Ship #2 during last flight showing titanium laminar flow glove on left wing  

NASA Technical Reports Server (NTRS)

Dryden research pilot Dana Purifoy bends NASA F-16 XL #848 away from the tanker on the 44th flight in the Supersonic Laminar Flow Control program recently. The flight test portion of the program ended with the 45th and last data collection flight from NASA's Dryden Flight Research Center, Edwards, California, on Nov. 26, 1996. The project demonstrated that laminar--or smooth--airflow could be achieved over a major portion of a wing at supersonic speeds. The flight tests at Dryden involved use of a suction system which drew boundary-layer air through millions of tiny laser-drilled holes in a titanium 'glove' that was fitted to the upper surface of the F-16XL's left wing.

1996-01-01

63

F-16XL Ship #2 during last flight showing titanium laminar flow glove on left wing  

NASA Technical Reports Server (NTRS)

The perforated titanium overlay mounted on the upper surface of the left wing is clearly evident on this view of NASA 848, a highly modified F-16XL aircraft flown by NASA's Dryden Flight Research Center in the Supersonic Laminar Flow Control (SLFC) research program. The two-seat, single-engine craft, one of only two 'XL' F-16s built, recently concluded the SLFC project with its 45th data collection mission. The project demonstrated that laminar--or smooth--airflow could be achieved over a major portion of a wing at supersonic speeds by use of a suction system. The system drew a small part of the boundary-layer air through millions of tiny laser-drilled holes in the 'glove' fitted to the upper left wing.

1996-01-01

64

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

PubMed Central

The hunting spider Cupiennius salei uses airflow generated by flying insects for the guidance of its prey-capture jump. We investigated the velocity field of the airflow generated by a freely flying blowfly close to the flow sensors on the spider's legs. It shows three characteristic phases (IIII). (I) When approaching, the blowfly induces an airflow signal near the spider with only little fluctuation (0.013 0.006 m s?1) and a strength that increases nearly exponentially with time (maximum: 0.164 0.051 m s?1 s.d.). The spider detects this flow while the fly is still 38.4 5.6 mm away. The fluctuation of the airflow above the sensors increases linearly up to 0.037 m s?1 with the fly's altitude. Differences in the time of arrival and intensity of the fly signal at different legs probably inform the spider about the direction to the prey. (II) Phase II abruptly follows phase I with a much higher degree of fluctuation (fluctuation amplitudes: 0.114 0.050 m s?1). It starts when the fly is directly above the sensor and corresponds to the time-dependent flow in the wake below and behind the fly. Its onset indicates to the spider that its prey is now within reach and triggers its jump. The spider derives information on the fly's position from the airflow characteristics, enabling it to properly time its jump. The horizontal velocity of the approaching fly is reflected by the time of arrival differences (ranging from 0.038 to 0.108 s) of the flow at different legs and the exponential velocity growth rate (1679 s?1) during phase I. (III) The air flow velocity decays again after the fly has passed the spider. PMID:22572032

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

2012-01-01

65

Suction laminarization of highly swept supersonic laminar flow control wings  

NASA Technical Reports Server (NTRS)

An evaluation is made of a suction-based method for the laminarization of highly-swept supersonic wings at cruise Mach numbers in the 2.0-2.5 range, in the interest of the reduction of wave drag due to lift. The laminar boundary layer development, as well as Tollmien-Schlichting and crossflow instabilities, have been analyzed for the case of an X66 supercritical airfoil at 60 and 72 deg sweep, for Mach numbers of 1.56 and 2.52, respectively. Strong suction is found to be needed at the front part of the upper surface and both the upper and lower rear pressure-rise areas.

Pfenninger, W.; Vemuru, C. S.

1988-01-01

66

Laminar flow control is maturing  

NASA Technical Reports Server (NTRS)

Recent research demonstrates that laminar flow (LF) can be reliable in flight and that the support system need not be complex. Shaping produces favorable pressure gradients for maintaining natural laminar flow (NLF), and laminar flow control (LFC) techniques such as full chord suction promise a fuel-saving payoff of up to 30 percent on long-range missions. For large aircraft, current research is concentrated on hybrid LFC concepts which combine suction and pressure-gradient control. At NASA Ames, an F-14 with variable wing sweep has been flight tested with smooth surface gloves on the wings; preliminary results indicate high transition Reynolds numbers to sweep angles as large as 25 deg. In addition, a 757 was flight tested with an NLF glove on the right wing just outboard of the engine pylon; and the LF was found to be suprisingly robust.

Wagner, Richard D.; Bartlett, Dennis W.; Maddalon, Dal V.

1988-01-01

67

Terminal Box Airflow Reset: An Effective Operation and Control Strategy for Comfort Improvement and Energy Conservation  

E-print Network

A new terminal box operation and control strategy, airflow reset, is developed to improve building comfort and energy efficiency during unoccupied and lightly occupied hours. The airflow reset lowers the minimum airflow possibility to zero...

Liu, M.; Abbas, M.; Zhu, Y.; Claridge, D. E.

2002-01-01

68

Hybrid laminar flow control study  

NASA Technical Reports Server (NTRS)

Hybrid laminar flow control (HLFC) in which leading edge suction is used in conjunction with wing pressure distribution tailoring to postpone boundary layer transition and reduce friction drag was examined. Airfoil design characteristics required for laminar flow control (LFC) were determined. The aerodynamic design of the HLFC wing for a 178 passenger commercial turbofan transport was developed, and a drag was estimated. Systems changes required to install HLFC were defined, and weights and fuel economy were estimated. The potential for 9% fuel reduction for a 3926-km (2120-nmi) mission is identified.

1982-01-01

69

Supersonic laminar-flow control  

NASA Technical Reports Server (NTRS)

Detailed, up to date systems studies of the application of laminar flow control (LFC) to various supersonic missions and/or vehicles, both civilian and military, are not yet available. However, various first order looks at the benefits are summarized. The bottom line is that laminar flow control may allow development of a viable second generation SST. This follows from a combination of reduced fuel, structure, and insulation weight permitting operation at higher altitudes, thereby lowering sonic boom along with improving performance. The long stage lengths associated with the emerging economic importance of the Pacific Basin are creating a serious and renewed requirement for such a vehicle. Supersonic LFC techniques are discussed.

Bushnell, Dennis M.; Malik, Mujeeb R.

1987-01-01

70

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

71

Data center TCO benefits of reduced system airflow  

Microsoft Academic Search

New blade chassis designs, with banks of aggregate fans and system-level thermal architectures which precisely manage airflow, have enabled a new level of energy savings for enterprise customers that extends beyond the system and offers an opportunity for new system thermal design principles. By reducing system airflow rate to an absolute minimum, system fan power is minimized. More significantly, lowering

Christopher G. Malone; Wade Vinson; Cullen E. Bash

2008-01-01

72

Laminar flow control for transport aircraft applications  

NASA Technical Reports Server (NTRS)

The incorporation of laminar flow control into transport aircraft is discussed. Design concepts for the wing surface panel of laminar flow control transport aircraft are described. The development of small amounts of laminar flow on small commercial transports with natural or hybrid flow control is examined. Techniques for eliminating the insect contamination problem in the leading-edge region are proposed.

Wagner, R. D.

1986-01-01

73

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. PMID:23205221

Lee, Heow Peuh; Gordon, Bruce R.

2012-01-01

74

The Laminar Soot Processes (LSP)  

NASA Technical Reports Server (NTRS)

The Laminar Soot Processes (LSP) Experiment Mounting Structure (EMS) was used to conduct the LSP experiment on Combustion Module-1. The EMS was inserted into the nozzle on the EMS and ignited by a hot wire igniter. The flame and its soot emitting properties were studied.

2004-01-01

75

Laminar flow: Challenge and potential  

NASA Technical Reports Server (NTRS)

Commercial air transportation has experienced revolutionary technology advances since WWII. These technology advances have resulted in an explosive growth in passenger traffic. Today, however, many technologies have matured, and maintaining a similar growth rate will be a challenge. A brief history of laminar flow technology and its application to subsonic and supersonic air transportation is presented.

Kirchner, Mark E.

1987-01-01

76

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

77

Operational considerations for laminar flow aircraft  

NASA Technical Reports Server (NTRS)

Considerable progress has been made in the development of laminar flow technology for commercial transports during the NASA Aircraft Energy Efficiency (ACEE) laminar flow program. Practical, operational laminar flow control (LFC) systems have been designed, fabricated, and are undergoing flight testing. New materials, fabrication methods, analysis techniques, and design concepts were developed and show much promise. The laminar flow control systems now being flight tested on the NASA Jetstar aircraft are complemented by natural laminar flow flight tests to be accomplished with the F-14 variable-sweep transition flight experiment. An overview of some operational aspects of this exciting program is given.

Maddalon, Dal V.; Wagner, Richard D.

1986-01-01

78

Airflow monitor: An effective approach to protecting assets and increasing safety in automated test equipment  

Microsoft Academic Search

Testing high power sophisticated avionics equipment requires accurate cooling airflow monitoring to protect the operator and expensive avionics equipment. This paper introduces an airflow monitor design that monitors cooling airflow, warns the operator when cooling airflow is below minimum requirements and automatically terminates testing prior to thermal failure. A method to accurately measure the cooling air flowing to a unit

C. P. Heagney

2008-01-01

79

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

80

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. PMID:22570766

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

2012-01-01

81

Optimization of VAV AHU Terminal Box Minimum Airflow  

E-print Network

Determining the optimal terminal box airflow is a complex process which is influenced by various factors, such as weather condition, supply air temperature, primary air fraction and internal load. A guideline for determination of a cost efficient...

Wang, Wei

2011-10-21

82

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

83

Computerised acoustical respiratory phase detection without airflow measurement  

Microsoft Academic Search

A simple, non-invasive acoustical method is developed to detect respiratory phases in relationship to swallows without the\\u000a direct measurement of airflow. In 21 healthy subjects (451 years) breath sounds are recorded at the trachea and at five different\\u000a recording locations at the chest wall, with simultaneous recording of airflow by a pneumotachograph. The chest signal with\\u000a the grestest inspiratoryexpiratory power

Z. K. Moussavi; M. T. Leopando; H. Pasterkamp; G. Rempel

2000-01-01

84

Air-flow regulation system for a coal gasifier  

Microsoft Academic Search

An improved air-flow regulator for a fixed-bed coal gasifier is provided which allows close air-flow regulation from a compressor source even though the pressure variations are too rapid for a single primary control loop to respond. The improved system includes a primary controller to control a valve in the main (large) air supply line to regulate large slow changes in

Fasching

1984-01-01

85

Air-flow regulation system for a coal gasifier  

Microsoft Academic Search

An improved air-flow regulator for a fixed-bed coal gasifier is provided which allows close air-flow regulation from a compressor source even though the pressure variations are too rapid for a single primary control loop to respond. The improved system includes a primary controller to control a valve in the main (large) air supply line to regulate large slow changes in

Fasching

2009-01-01

86

Supersonic laminar flow control on commercial transports  

NASA Technical Reports Server (NTRS)

This paper provides an overview of the status of supersonic laminar flow control. Existing research into the aerodynamic problems of subsonic and supersonic laminar flow control is first reviewed to provide a prospective for subsequent discussions of recent studies to evaluate the potential performance benefits of the application of laminar flow control to supersonic transports. A flight research program to provide a realistic assessment of the technical feasibility is then described.

Wagner, R. D.; Fischer, M. C.; Collier, F. S., Jr.; Pfenninger, W.

1990-01-01

87

NASA Flight Tests Explore Supersonic Laminar Flow  

NASA Video Gallery

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

88

Laminar vortex shedding behind a cooled circular cylinder  

NASA Astrophysics Data System (ADS)

This paper addresses the functional demonstration of a hot air flow generator driven by convective heat transfer and the airflow behind a cooled circular cylinder in cross flow in the low velocity range. The wake flow was investigated experimentally using flow visualization, hot-wire anemometry, and laser Doppler anemometry. An evaluation of the free-stream velocity from the vortex shedding frequency was derived for the isothermal and non-isothermal cases and demonstrated using simple stroboscope measurements. The results confirm that cylinder cooling destabilizes the wake flow in air, i.e., the laminar steady regime can be changed into the vortex shedding regime, and the vortex shedding frequency increases as the cylinder temperature decreases. This thermal effect of cylinder cooling is consistent with its counterpart, the known effect of flow stabilization by cylinder heating. The effective temperature and effective Reynolds number concept have been further quantitatively evaluated, and the extension of their validity to the case of cooled cylinders has been confirmed.

Trvn?ek, Zden?k; Wang, An-Bang; Tu, Wen-Yun

2014-02-01

89

F-16XL Ship #2 during last flight viewed from tanker showing titanium laminar flow glove on left win  

NASA Technical Reports Server (NTRS)

Dryden research pilot Dana Purifoy drops NASA F-16XL #848 away from the tanker in the 44th flight in the Supersonic Laminar Flow Control program recently. The flight test portion of the program ended with the 45th and last data collection flight Nov. 26, 1996. The project demonstrated that laminar--or smooth--airflow could be achieved over a major portion of a wing at supersonic speeds by use of a suction system. The system drew turbulent boundary-layer air through millions of tiny laser-drilled holes in a titanium 'glove' fitted to the upper left wing. About 90 hours of flight time were logged by the unique aircraft during the 13-month flight research program, much of it at speeds of Mach 2. Data acquired during the program will be used to develop a design code calibration database which could assist designers in reducing aerodynamic drag of a proposed second-generation supersonic transport.

1996-01-01

90

Airflow characteristics of jet expansion for nonisothermal flow conditions  

SciTech Connect

Proper distribution of conditioned air plays an important role in both the comfort of the occupants and the air quality of ventilated or air-conditioned spaces. Airflow patterns and distributions of velocity, temperature, and turbulence intensity are the primary factors that affect room air movement and the comfort of occupants in the occupied zone. However, these factors are dependent upon the characteristics of the diffuser air jet, i.e., expansion, mixing, and entrainment of room air. Therefore, understanding the characteristics of the diffuser air jet and its effects on the airflow conditions in the occupied zone is essential to modeling of room air movement and selection and design of air supply outlets. Data were collected in a large test room (24 by 16 by 9 ft [7.3 by 4.9 by 2.7 m]) with a high sidewall grille. The airflow characteristics at the centerline of the room for 21 test cases for both isothermal and nonisothermal flow conditions were investigated. The results show that both airflow rate and heat load strongly affect airflow patterns and air velocity and air temperature inside the room. As the airflow rate increases and/or heat load decreases, the air jet travels further along the ceiling and lessens the chance of dropping into the occupied zone. On the other hand, as the airflow rate decreases and/or heat load increases, the air jet separates from the ceiling and moves down toward the occupied zone, causing air at higher velocities and lower temperatures to reach occupants, resulting in a possible sensation of draft (coolness). Furthermore, stagnant areas form due to the lack of air circulation.

Hosni, M.H.; Abu-El-Hassan, M.B. [Kansas State Univ., Manhattan, KS (United States). Dept. of Mechanical Engineering; Miller, P.L. [National Renewable Energy Lab., Golden, CO (United States)

1996-12-31

91

Association of Radiographic Emphysema and Airflow Obstruction with Lung Cancer  

PubMed Central

Rationale: To study the relationship between emphysema and/or airflow obstruction and lung cancer in a high-risk population. Objective: We studied lung cancer related to radiographic emphysema and spirometric airflow obstruction in tobacco-exposed persons who were screened for lung cancer using chest computed tomography (CT). Methods: Subjects completed questionnaires, spirometry, and low-dose helical chest CT. CT scans were scored for emphysema based on National Emphysema Treatment Trial criteria. Multiple logistic regressions estimated the independent associations between various factors, including radiographic emphysema and airflow obstruction, and subsequent lung cancer diagnosis. Measurements and Main Results: Among 3,638 subjects, 57.5, 18.8, 14.6, and 9.1% had no, trace, mild, and moderatesevere emphysema, and 57.3, 13.6, 22.8, and 6.4% had no, mild (Global Initiative for Chronic Obstructive Lung Disease [GOLD] I), moderate (GOLD II), and severe (GOLD IIIIV) airflow obstruction. Of 3,638 subjects, 99 (2.7%) received a lung cancer diagnosis. Adjusting for sex, age, years of cigarette smoking, and number of cigarettes smoked daily, logistic regression showed the expected lung cancer association with the presence of airflow obstruction (GOLD IIV, odds ratio [OR], 2.09; 95% confidence interval [CI], 1.333.27). A second logistic regression showed lung cancer related to emphysema (OR, 3.56; 95% CI, 2.215.73). After additional adjustments for GOLD class, emphysema remained a strong and statistically significant factor related to lung cancer (OR, 3.14; 95% CI, 1.915.15). Conclusions: Emphysema on CT scan and airflow obstruction on spirometry are related to lung cancer in a high-risk population. Emphysema is independently related to lung cancer. Both radiographic emphysema and airflow obstruction should be considered when assessing lung cancer risk. PMID:18565949

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

2008-01-01

92

Minimum airflow reset of single-duct VAV terminal boxes  

NASA Astrophysics Data System (ADS)

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

Cho, Young-Hum

93

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

94

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

95

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

96

LAMINAR: PRACTICAL FINE-GRAINED DECENTRALIZED INFORMATION  

E-print Network

LAMINAR: PRACTICAL FINE-GRAINED DECENTRALIZED INFORMATION FLOW CONTROL (DIFC) Indrajit Roy, Donald... Security breach ! #12;Security model Decentralized Information Flow Control (DIFC) [Myers and Liskov '97} {} Information flow in a lattice #12;In this talk: Laminar A practical way to provide end-to-end security

Witchel, Emmett

97

Laminar Flow Control at High Speeds  

Microsoft Academic Search

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

William Saric

2003-01-01

98

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

99

Airflow studies in a forced ventilated chamber with low partitions  

SciTech Connect

A climate chamber was used to study experimentally the airflow characteristics in a ventilated space with low partitions. Two types of commonly used air distribution devices were selected for the study--a ceiling diffuser and side grille systems. A total of 16 tests were performed using the two diffusers with partition heights varying up to 1.8 m (5.91 ft) above floor level. From the measured results, the thermal comfort indices were assessed. A stabilization effect of airflow was found when the partition height reached 1.8 m (5.91 ft). Local draft risk was located in the occupied zone. Also, the modified Archimedes number proposed by Jackman (1990) was used to describe the indoor airflow in the absence of a workable design guide for partitioned spaces.

Chow, W.K.; Tsui, K.F. [Hong Kong Polytechnic Univ. (Hong Kong). Dept. of Building Services Engineering

1995-12-31

100

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

101

Airflow induced vibration of the Si-IT prototype  

E-print Network

In this note we present the results of air-flow induced vibration tests performed on mechanical prototypes of the Si option of the Inner Tracker upgrade. We made a modal analyze where we observed the eigenfrequency of the Si-ladder structure at ?30 Hz as previously measured at CERN. Flowing dry-air to cool the prototypes we do not observe a lock-in state of the vortex induced vibration (VIV). The maximum observed vibration amplitude is calculated. We conclude that the VIV excites the eigenfrequency almost independently from the air-flow speed, and with an amplitude which does not damage the structure.

Dijkstra, H; De Aguiar, V; Rigo, V

2014-01-01

102

Considerations for Efficient Airflow Design in Cleanrooms Tengfang Xu, Ph.D., PE,  

E-print Network

such as design conservatism, lack of thorough understanding of airflow requirements, concerns about cleanliness such as temperature and humidity. In particular, cleanroom cleanliness requirements specified by cleanliness class1 two goals: effective contamination control and efficient airflow delivery. Effective contamination

103

Studies of inspiratory airflow patterns in the nasal passages of the F344 rat and rhesus monkey using nasal molds: relevance to formaldehyde toxicity.  

PubMed

For highly water soluble and reactive gases, such as formaldehyde, the reported distribution of nasal lesions in rats and rhesus monkeys following inhalation exposure may be attributable, at least in part, to regional gas uptake patterns that are a consequence of nasal airflow characteristics. Inspiratory nasal airflow was studied at flow rates across the physiologic range using a unidirectional dynamically similar water-dye siphon system in clear acrylic molds of the nasal airways of F344 rats and rhesus monkeys. In both species there were complex and inspiratory flow streams, exhibiting regions of simple laminar, complex secondary (vortices, eddies, swirling), and turbulent flows, with only minor effects of the volumetric flow rates studied on these flow patterns. There was a precise association between points of dye intake at the nostril with complex but generally coherent streaklines throughout the nose, indicating the potential for sensitive dependence of nasal airflow on nostril geometry. On the basis of these studies, a classification for the major airways (meatuses) in the nasal passages of rats and rhesus monkeys was proposed. The spiral shape of the anterior nasal airway of the rat was considered to play an important role in local mixing of inspired airstreams. In the rhesus monkey, the complex geometry of the nasal vestibule contributed to the formation of secondary flows and turbulence in the anterior nose, which represents a potentially important difference between rheusus monkeys and humans. There was a good correlation between routes of flow, regional secondary flows, turbulence, and impaction of airstreams on the airway wall, with the reported distribution of formaldehyde-induced nasal lesions in rats and rhesus monkeys. These studies support the proposal that nasal airflow patterns play an important role in the distribution of lesions induced by formaldehyde. PMID:1891770

Morgan, K T; Kimbell, J S; Monticello, T M; Patra, A L; Fleishman, A

1991-09-01

104

Distributed Manipulation of Flat Objects With Two Airflow Sinks  

Microsoft Academic Search

Distributed manipulation systems induce motions on objects through the application of forces at many points of contact. Current forms of distributed manipulation include multiple mobile robots, vibrating plates, actively controlled arrays of air jets, and planar micro- and macro-mechanical arrays of actuators. The authors have presented a new form of distributed manipulation using passive airflow fields. This paper lays out

Hyungpil Moon; Jonathan E. Luntz

2006-01-01

105

Estimation of Airflow in Livestock Buildings Rasmus Larsen  

E-print Network

to the airflow introduced by a given ventilation system. By introducing particles (e.g. smoke or soapbubles. On the other hand, for image sequence neighborhoods that exhibit two dimensional spatial structures [2] used the curvature of the match surface, [18] investigated the use of second order spatial

106

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 (1840 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

107

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

108

Air-flow regulation system for a coal gasifier  

DOEpatents

An improved air-flow regulator for a fixed-bed coal gasifier is provided which allows close air-flow regulation from a compressor source even though the pressure variations are too rapid for a single primary control loop to respond. The improved system includes a primary controller to control a valve in the main (large) air supply line to regulate large slow changes in flow. A secondary controller is used to control a smaller, faster acting valve in a secondary (small) air supply line parallel to the main line valve to regulate rapid cyclic deviations in air flow. A low-pass filter with a time constant of from 20 to 50 seconds couples the output of the secondary controller to the input of the primary controller so that the primary controller only responds to slow changes in the air-flow rate, the faster, cyclic deviations in flow rate sensed and corrected by the secondary controller loop do not reach the primary controller due to the high frequency rejection provided by the filter. This control arrangement provides at least a factor of 5 improvement in air-flow regulation for a coal gasifier in which air is supplied by a reciprocating compressor through a surge tank.

Fasching, George E. (Morgantown, WV)

1984-01-01

109

Pitot-tube flowmeter for quantification of airflow during sleep  

Microsoft Academic Search

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

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

2011-01-01

110

STATE OF CALIFORNIA HSPP/PSPP INSTALLATION; COOLING COIL AIRFLOW & FAN WATT DRAW TEST  

E-print Network

STATE OF CALIFORNIA HSPP/PSPP INSTALLATION; COOLING COIL AIRFLOW & FAN WATT DRAW TEST CEC-CF-6R/PSPP Installation; Cooling Coil Airflow & Fan Watt Draw Test (Page 1 of 3) Site Address: Enforcement Agency: Permit1R )indicates Cooling Coil Airflow or Fan Watt Draw verification are required, HSPP or PSPP

111

STATE OF CALIFORNIA HSPP/PSPP INSTALLATION; COOLING COIL AIRFLOW & FAN WATT DRAW TEST  

E-print Network

STATE OF CALIFORNIA HSPP/PSPP INSTALLATION; COOLING COIL AIRFLOW & FAN WATT DRAW TEST CEC- CF-4R TESTING CF-4R-MECH-22 HSPP/PSPP Installation; Cooling Coil Airflow & Fan Watt Draw Test (Page 1 of 3) Site When the Certificate of Compliance (CF1R )indicates Cooling Coil Airflow or Fan Watt Draw verification

112

Simultaneous solutions of coupled thermal airflow problem for natural ventilation in buildings  

Microsoft Academic Search

Natural and hybrid ventilation can be sustainable building ventilation strategies, where airflow is driven naturally by thermal buoyancy and\\/or wind forces other than pure mechanical means. The simulation and design of these systems need to consider the combined impact of thermal and airflow transport behaviors. The numerical solution of such combined thermal airflow problems often employs a segregate and iterative

Liangzhu Wang; W. Stuart Dols; Steven J. Emmerich

2012-01-01

113

CHAMBERS FOR STUDYING THE EFFECTS OF AIRFLOW VELOCITY ON PLANT GROWTH  

Microsoft Academic Search

KORTHALS R. L., KNIGHT S. L., CHRISTLANSON L. L. and SPOMER L. ART Chambers for studying the effects of airflow velocity on plant growth. BIOTRONICS 23, 113-119, 1994. Three plant growth chambers were developed for studying the effect of airflow velocity on plant growth and development. Airflow delivery design was based on ASHRAE Standard 51-1985 (l) for fan testing. Each

R. L. KORTHALS; S. L. KNIGHT; L. L. CHRISTIANSON; L. ART SPOMER

114

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

115

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

Microsoft Academic Search

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

J. N. Hefner; F. E. Sabo

1987-01-01

116

Effect of forced-air warming on the performance of operating theatre laminar flow ventilation.  

PubMed

Forced-air warming exhaust may disrupt operating theatre airflows via formation of convection currents, which depends upon differences in exhaust and operating room air temperatures. We investigated whether the floor-to-ceiling temperatures around a draped manikin in a laminar-flow theatre differed when using three types of warming devices: a forced-air warming blanket (Bair Hugger); an over-body conductive blanket (Hot Dog); and an under-body resistive mattress (Inditherm). With forced-air warming, mean (SD) temperatures were significantly elevated over the surgical site vs those measured with the conductive blanket (+2.73 (0.7) C; p<0.001) or resistive mattress (+3.63 (0.7) C; p<0.001). Air temperature differences were insignificant between devices at floor (p=0.339), knee (p=0.799) and head height levels (p=0.573). We conclude that forced-air warming generates convection current activity in the vicinity of the surgical site. The clinical concern is that these currents may disrupt ventilation airflows intended to clear airborne contaminants from the surgical site. PMID:22321079

Dasari, K B; Albrecht, M; Harper, M

2012-03-01

117

Soot Formation in Laminar Premixed Flames  

NASA Technical Reports Server (NTRS)

Soot processes within hydrocarbon-fueled flames affect emissions of pollutant soot, thermal loads on combustors, hazards of unwanted fires and capabilities for computational combustion. In view of these observations, the present study is considering processes of soot formation in both burner-stabilized and freely-propagating laminar premixed flames. These flames are being studied in order to simplify the interpretation of measurements and to enhance computational tractability compared to the diffusion flame environments of greatest interest for soot processes. In addition, earlier studies of soot formation in laminar premixed flames used approximations of soot optical and structure properties that have not been effective during recent evaluations, as well as questionable estimates of flow residence times). The objective of present work was to exploit methods of avoiding these difficulties developed for laminar diffusion flames to study soot growth in laminar premixed flames. The following description of these studies is brief.

Xu, F.; Krishnan, S. S.; Faeth, G. M.

1999-01-01

118

Laminar Flow Control Flight Experiment Design  

E-print Network

this envelope, flight conditions are determined which meet evaluation criteria for minimum lift coefficient and crossflow transition location. The angle of attack data band is determined, and the natural laminar flow characteristics are evaluated. Finally, DRE...

Tucker, Aaron 1975-

2012-11-29

119

Evolution of laminar mixing layer  

NASA Astrophysics Data System (ADS)

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

Hwang, Din-Chih

120

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

121

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

122

Climate chamber for environmentally controlled laboratory airflow experiments.  

PubMed

Climate chambers have been widely used in in vitro and in vivo studies which require controlled environmental temperature and humidity conditions. This article describes a new desktop climate chamber that was developed for application of respiratory airflows on cultured nasal epithelial cells (NEC) under controlled temperature and humidity conditions. Flow experiments were performed by connecting the climate chamber to an airflow generator via a flow chamber with cultured NEC. Experiments at two controlled climate conditions, 25 degrees C and 40% relative humidity (RH) and 37 degrees C and 80%RH, were conducted to study mucin secretion from the cultures inresponse to the flow. The new climate chamber is a relatively simple and inexpensive apparatus which can easily be connected to any flow system for climate controlled flow experiments. This chamber can be easily adjusted to various in vitro experiments, as well as to clinical studies with animals or human subjects which require controlled climate conditions. PMID:20639592

Even-Tzur, Nurit; Zaretsky, Uri; Grinberg, Orly; Davidovich, Tomer; Kloog, Yoel; Wolf, Michael; Elad, David

2010-01-01

123

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. PMID:23785411

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

124

Non-steady airflow measurement using pressure differential techniques  

Microsoft Academic Search

A method is presented for the direct measurement of small airflows in particular physiological situations, with especial reference\\u000a to flow in the avian lung. The Pitot principle of flow-induced pressure differentials is incorporated into a non-linear device.\\u000a Its properties, calibration and linearization are discussed. The general problem is considered of identification, explanation\\u000a and practical reduction of artefacts incident upon the

J. H. Brackenbury

1972-01-01

125

CFD Studies of Indoor Airflow and Contaminant Particle Transportation  

Microsoft Academic Search

This article presents a numerical study of indoor airflows and contaminant particle transportation in three ventilated rooms. The realizable k?? model is employed to model the air-phase turbulence, while the Lagrangian particle tracking model is utilized for the particle-phase simulation. The predicted air-phase velocities and contaminant particle concentrations are validated against the experimental data obtained from the literature. In the

Z. F. Tian; J. Y. Tu; G. H. Yeoh

2007-01-01

126

Control of nasal vasculature and airflow resistance in the dog.  

PubMed Central

Nasal vascular and airflow resistances have been measured in dogs, simultaneously on both sides separately. Vascular resistance was measured either by constant flow perfusion of the terminal branch of the maxillary artery (which supplies, via the sphenopalatine artery, the nasal septum, most of the turbinates and the nasal sinuses) or by measuring blood flow through this artery, maintained by the dog's own blood pressure. Airflow resistance was assessed by inserting balloon-tipped endotracheal catheters into the back of each nasal cavity via the nasopharynx, and measuring transnasal pressure at constant airflow through each side of the nose simultaneously. Preliminary experiments indicated that there was 5-10% collateral anastomosis between the two sides. Close-arterial injection of drugs showed different patterns of response. Adrenaline, phenylephrine, chlorpheniramine and low doses of prostaglandin F2 alpha increased vascular resistance and lowered airway resistance. Salbutamol, methacholine and histamine lowered vascular resistance and increased airway resistance. Dobutamine decreased airway resistance with a small increase in vascular resistance. Prostaglandins E1, E2 and F2 alpha (high dose) decreased both vascular and airway resistances. Substance P, eledoisin-related peptide and vasoactive intestinal polypeptide lowered vascular resistance with little change in airway resistance. The results are interpreted in terms of possible drug actions on precapillary resistance vessels, sinusoids and venules, and arteriovenous anastomoses. It is concluded that nasal airway resistance cannot be correlated with vascular resistance or blood flow, since the latter has a complex and ill-defined relationship with nasal vascular blood volume. PMID:6204040

Lung, M A; Phipps, R J; Wang, J C; Widdicombe, J G

1984-01-01

127

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

128

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

129

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

130

Multiscale laminar flows with turbulentlike properties.  

PubMed

By applying fractal electromagnetic force fields on a thin layer of brine, we generate steady quasi-two-dimensional laminar flows with multiscale stagnation point topology. This topology is shown to control the evolution of pair separation (Delta) statistics by imposing a turbulentlike locality based on the sizes and strain rates of hyperbolic stagnation points when the flows are fast enough, in which case Delta(2) approximately t(gamma) is a good approximation with gamma close to 3. Spatially multiscale laminar flows with turbulentlike spectral and stirring properties are a new concept with potential applications in efficient and microfluidic mixing. PMID:17155255

Rossi, Lionel; Vassilicos, J C; Hardalupas, Yannis

2006-10-01

131

Laminar flow control - Introduction and overview  

NASA Technical Reports Server (NTRS)

A development history and a development-trends evaluation are presented for laminar flow controlled airfoil technologies and design concepts, including the search for 'natural' laminar flow and actively controlled flow via suction through small pores on the airfoil surface. While most NASA activities in this field have been concerned with subsonic aircraft, it has been projected that the control of boundary layer turbulence may be even more critical to the aerodynamic efficiency of supersonic aircraft. Developmental programs for these techniques have been conducted with several modified conventional aircraft.

Hefner, Jerry N.

1992-01-01

132

Undoped and Hole-Doped Superconductors T'-La1.8-xEu0.2SrxCuO4 (x = 0 and 0.05) Prepared by Solid-State Reaction  

NASA Astrophysics Data System (ADS)

We have successfully synthesized La1.8-xEu0.2SrxCuO4 (x = 0 and 0.05) with the Nd2CuO4-type (T'-type) structure by means of the structural transformation at low temperatures from the K2NiF4-type (T-type) structure via the Sr2CuO3-type (S-type) structure. Superconductivity has appeared by postannealing T'-La1.8-xEu0.2SrxCuO4 in vacuum at 700 C for the removal of excess oxygen. The superconducting transition temperatures are 20 and 13 K for x = 0 and 0.05, respectively. T'-La1.8-xEu0.2SrxCuO4 with x = 0.05 is, at least nominally, the first hole-doped superconducting cuprate with the T'-type structure.

Takamatsu, Tomohisa; Kato, Masatsune; Noji, Takashi; Koike, Yoji

2012-07-01

133

The Timetable of Laminar Neurogenesis Contributes to the Specification of  

E-print Network

The Timetable of Laminar Neurogenesis Contributes to the Specification of Cortical Areas in Mouse on either side of the 17-18 border suggesting that there might be different timetables of laminar compute the timetable of laminar histogenesis from birthdating experiments. Here we report the results

Polleux, Franck

134

AIAA 2004-2311 Toward Practical Laminar Flow Control--  

E-print Network

AIAA 2004-2311 Toward Practical Laminar Flow Control-- Remaining Challenges William S. Saric Arizona State University Tempe AZ 85287-6106 ABSTRACT Different laminar flow control strategies instability has been the primary challenge for laminar flow control. Favorable pressure gradients used

135

Research in natural laminar flow and laminar-flow control, part 1  

SciTech Connect

Since the mid 1970's, NASA, industry, and universities have worked together to conduct important research focused at developing laminar flow technology that could reduce fuel consumption for general aviation, commuter, and transport aircraft by as much as 40 to 50 percent. The symposium was planned in view of the recent accomplishments within the areas of laminar flow control and natural laminar flow, and the potential benefits of laminar flow technology to the civil and military aircraft communities in the United States. Included were technical sessions on advanced theory and design tool development; wind tunnel and flight research; transition measurement and detection techniques; low and high Reynolds number research; and subsonic and supersonic research.

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

1987-12-01

136

Research in Natural Laminar Flow and Laminar-Flow Control, part 1  

NASA Technical Reports Server (NTRS)

Since the mid 1970's, NASA, industry, and universities have worked together to conduct important research focused at developing laminar flow technology that could reduce fuel consumption for general aviation, commuter, and transport aircraft by as much as 40 to 50 percent. The symposium was planned in view of the recent accomplishments within the areas of laminar flow control and natural laminar flow, and the potential benefits of laminar flow technology to the civil and military aircraft communities in the United States. Included were technical sessions on advanced theory and design tool development; wind tunnel and flight research; transition measurement and detection techniques; low and high Reynolds number research; and subsonic and supersonic research.

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

1987-01-01

137

Transition caused by the laminar flow separation  

NASA Technical Reports Server (NTRS)

An experimental investigation of the effects of the geometry of body surface, Reynolds number, stream turbulence, and a roughness element (wire) on the reattachment of separated laminar boundary-layer flow on a bent flat plate is presented and discussed. The flow mechanisms determining reattachment of the boundary layer are analyzed and discussed.

Maekawa, T; Atsumi, Shoichi

1952-01-01

138

Numerical Study of Laminar Wall Quenching.  

National Technical Information Service (NTIS)

Laminar flame quenching at the cold wall of a combustion chamber has been studied, using a numerical model to describe the reactive flow. The model combines an unsteady treatment of the fluid mechanics and a detailed chemical kinetic reaction mechanism. F...

C. K. Westbrook, A. A. Adamczyk, G. A. Lavoie

1979-01-01

139

Passive laminar flow control of crossflow vorticity  

Microsoft Academic Search

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

Bruce J. Holmes

1990-01-01

140

Stability theory for laminar flow control design  

Microsoft Academic Search

Both passive and active techniques of laminar-flow control (LFC) require reliable methods for prediction of boundary layer transitions, as well as for quantification of LFC sensitivity to such control parameters as Mach number, pressure gradient, wall temperature, angle of attack, sweep, flow history, surface curvature, volume rotation, and flow chemistry. An account is presently given to a linear stability theory-based

Mujeeb R. Malik

1990-01-01

141

Laminar flamelet modeling of turbulent diffusion flames  

NASA Technical Reports Server (NTRS)

In modeling turbulent combustion, decoupling the chemistry from the turbulence is of great practical significance. In cases in which the equilibrium chemistry model breaks down, laminar flamelet modeling (LFM) is a promising approach to decoupling. Here, the validity of this approach is investigated using direct numerical simulation of a simple chemical reaction in two-dimensional turbulence.

Mell, W. E.; Kosaly, G.; Planche, O.; Poinsot, T.; Ferziger, J. H.

1990-01-01

142

Helicity in laminar and turbulent flow  

Microsoft Academic Search

A general theoretical review of helicity in flows that are laminar or turbulent is presented with references to corresponding experimental investigations. The topological nature of the helicity invariant is examined, and the turbulent dynamo mechanism is discussed in relation to the phenomenon of helicity. Helicity is also discussed in terms of being a topological constraint in relaxation to equilibrium, and

H. K. Moffatt; A. Tsinober

1992-01-01

143

Spiral Laminar Flow: A revolution in understanding?  

E-print Network

Blood Flow Spiral laminar flow #12;Spiral flow in the Aorta (MRI) Computational Fluid Dynamics 0 10 20 = Stent failure Turbulence associated with: - Altered wall shear stress - Damage lining artery - Cellular downstream intimal thickening Results -Downstream Disease Progression #12;Summary Spiral Stent Turbulence

Greenaway, Alan

144

Laminar Instability of Cylindrical Liquid Jets  

Microsoft Academic Search

Interfacial instability of slightly miscible, laminar, cylindrical liquid jets in another fluid is examined. A general explicit dispersion equation is derived using an integro-differential approach. Under appropriate conditions, the resultant equation reduces to the dispersion relationships of Rayleigh, Weber, and Bogy, and matches Tomotika's equation for both limiting and non-limiting cases. The influence of jet and ambient fluid properties, mass

Ho. Teng

1994-01-01

145

Evaluation of different airflow sensors at the WIPP facility  

SciTech Connect

The Waste Isolation Pilot Plant (WIPP) is an US Department of Energy underground disposal facility designed to permanently and safely isolate US defense-generated transuranic radioactive waste. The underground ventilation system is engineered to minimize the release of radioactive contamination to the environment in the event of an accident. During 1994 an extensive ventilation remote monitoring and control system was installed. It consists of fifteen air velocity sensors, eight differential pressure stations, automated control features on key underground air regulators, and eight psychrometric stations. The airflow monitoring component of the system has been a problem since the original installation. Due to the WIPP's variable airflow capabilities, the air velocity sensors required extensive and time-consuming re-calibration to make the sensors read out volumetric flow, rather than the point or line values, which they were factory calibrated for. Problems with the hardware made the process difficult. Furthermore, once re-calibrated the durability and reliability of the units were inconsistent, and often unacceptable. Two new types of airflow sensors were tested; one or both of which will ultimately replace the old units. The tested sensors were an ultrasonic-type device (FloSonic), and a warm body, mass flow unit (Airboss*200W) (a re-engineered version of the previous units). Recommendations were made regarding which type of sensor to install at specific locations. These decisions were based on the conditions at each sensor location and the relative strengths of the two sensor types. Installation, field calibration methodology, test procedures, main results and recommendations are discussed.

McDaniel, K.; Duckworth, I.J.; Prosser, B.S.

1999-07-01

146

Masks for influenza patients: measurement of airflow from the mouth.  

PubMed

In case of a new influenza pandemic, provision of masks to coughing patients could be used to slow expansion of the epidemic. To quantitatively assess the efficacy of different masks, we used an ultrasonic anemometer to measure the velocity of airflow from the mouth in coughing. We found that even the cheapest paper masks reduced the air speed to less than 1/10, implicating their effectiveness in decreasing viral spread. We therefore propose that governments provide free masks to coughing patients in the general population upon the emergence of a new human influenza virus. PMID:16785699

Inouye, Sakae; Matsudaira, Yasuaki; Sugihara, Yoshibumi

2006-06-01

147

CFD modeling of pharmaceutical isolators with experimental verification of airflow.  

PubMed

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

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

2007-01-01

148

Testing of air-flow windows for evaluation and application  

SciTech Connect

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

Boehm, R.F.; Brandle, K.

1980-12-01

149

Evaluation of airflow patterns in 2706-T and 2706-TA  

SciTech Connect

The purpose of this study was to evaluate the adequacy of the current placement of fixed head air samplers and continuous air monitors (CAMs) in the 2706-T and 2706-TA Complex. The airflow study consisted of 6 configurations of facility HVAC and HEPA filtration equipment to determine impacts on CAM location. The results of this study provide recommendations based on guidance in DOE G 411.1-8 and NUREG-1400 for placement of fixed head air samplers or CAMS within 2706-T and 2706-TA.

DEROSA, D.C.

1999-08-26

150

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

151

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

152

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.

153

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

154

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

155

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

156

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. PMID:15025768

Marini, John J

2004-01-01

157

Particle Image Velocimetry measurement of indoor airflow field: A review of the technologies and applications  

E-print Network

Particle Image Velocimetry measurement of indoor airflow field: A review of the technologies with point-wise anemometry. Therefore, using Particle Image Velocimetry (PIV) is a promising technique. "Particle image velocimetry measurement of indoor airflow field: A review of the technologies

Chen, Qingyan "Yan"

158

Simplified Models for Exhaled Airflow from a Cough with the Mouth Covered  

E-print Network

1 Simplified Models for Exhaled Airflow from a Cough with the Mouth Covered Chun Chen1 , Chao: (765) 496-0539, Email: yanchen@purdue.edu Abstract Covering a cough can be useful in reducing for predicting the exhaled airflow from a cough with the mouth covered. This investigation used smoke

Chen, Qingyan "Yan"

159

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

E-print Network

One-dimensional airflow in unsaturated zone induced by periodic water table fluctuation Hailong Li1 zone induced by periodic water table fluctuation, Water Resour. Res., 41, W04007, doi:10.1029/2004WR airflow driven by fluctuating water table within the lower layer of a coastal two-layered system

Jiao, Jiu Jimmy

160

Improving Aviation Safety with Information Visualization: Airflow Hazard Display for Helicopter Pilots  

E-print Network

Improving Aviation Safety with Information Visualization: Airflow Hazard Display for Helicopter Pilots by Cecilia Rodriguez Aragon B.S. (California Institute of Technology) 1982 M.S. (University with Information Visualization: Airflow Hazard Display for Helicopter Pilots by Cecilia Rodriguez Aragon Doctor

Hearst, Marti

161

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

162

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

163

Laminar flow instability in nuclear rockets  

SciTech Connect

Laminar flow instability (LFI) is a rarely encountered phenomenon, occurring in gaseous heated channels with high exit-to-inlet temperature ratios and a laminar Reynolds Number at the channel exit, as may be experienced in a nuclear rocket. Analytical techniques were developed and programmed for parametric evaluation that had been previously validated by comparison with available experimental data. The four types of transients associated with LFI are described in terms of the governing equations. Parametric evaluations of solid core prismatic and particle bed fuel configurations were made to determine their sensitivities to LFI from temperature ratio, flow rate, orificing, transition Reynolds Number, pressure level, presence of an exit sonic nozzle, power density and heat flux shape. The flow rate at the point of neutral stability and the growth rate of the excursive transient are calculated. The full power design point and the cooldown phases of operation were both evaluated.

Black, D.L. (628 C Street, S. E., Washington, DC 20003-4302 (United States))

1993-01-20

164

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

Code of Federal Regulations, 2010 CFR

...2010-10-01 false Airflow resistance test; Type C supplied-air respirator, pressure-demand class; minimum requirements... 84.157 Airflow resistance test; Type C supplied-air respirator, pressure-demand class; minimum...

2010-10-01

165

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.

166

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

167

Laminar Flow Control and Aerodynamic Shape Optimization  

Microsoft Academic Search

Summary A gradient-based optimization method used to minimize the total drag of airfoils is presented. The viscous drag is minimized by delaying the laminar-turbulent transition. The gradients are obtained solving the adojoint of the Euler, boundary-layer and stability equations. The optimization is subjected to constraints such as restriction on geometry, lift and pitch moment. The geometry is parametrised using radial

A. Hani; O. Amoignon; M. Chevalier

168

Laminar flow control SPF\\/08 feasibility demonstration  

Microsoft Academic Search

The feasibility of applying superplastic forming\\/diffusion bonding (SPF\\/DB) technology to laminar flow control (LFC) system concepts was demonstrated. Procedures were developed to produce smooth, flat titanium panels, using thin -0.016 inch sheets, meeting LFC surface smoothness requirements. Two large panels 28 x 28 inches were fabricated as final demonstration articles. The first was flat on the top and bottom sides

R. C. Ecklund; N. R. Williams

1981-01-01

169

Trans-Laminar-Reinforced (TLR) Composites  

NASA Technical Reports Server (NTRS)

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-Fiber(TM) materials. It has been repeatedly documented in the literature that 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 1 (double cantilever beam) and mode 2 (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. TLR directly supports the 'Achilles heel' of laminated composites, that is delamination. 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 of 'unit cells', or representative volumes, were used to study the effects of adding TLR on the elastic constants; the in-plane strength; and the initiation of delamination. Parameters investigated included TLR material, TLR volume fraction, TLR diameter, TLR through-thickness angle, ply stacking sequence, and the microstructural features of pure resin regions and curved in-plane fibers. The work was limited to the linear response of undamaged material with at least one ply interface. An inter-laminar dominated problem of practical interest, a flanged skin in bending, was also modeled.

Hinders, Mark; Dickinson, Larry

1997-01-01

170

Role of interphase processes in styrene vapor removal from airflow under the action of a pulsed electron beam  

Microsoft Academic Search

The conversion of styrene vapor in airflow under the action of a pulsed electron beam has been studied. It is demonstrated that the main processes leading to the removal of styrene from airflow involve reactive oxygen species and yield styrene oxidation products, which are characterized by low vapor pressures and are removed from airflow in a condensed state. This experimental

Yu. N. Novoselov; I. E. Filatov

2009-01-01

171

Building and Environment 42 (2007) 203217 Model-based analysis and simulation of airflow control systems of  

E-print Network

temperature and airflow are indispensable in the design of the entire control system. In our airflow model, we the ductwork to room. These situations will require controlling the supply air temperature and the exhaustedBuilding and Environment 42 (2007) 203­217 Model-based analysis and simulation of airflow control

Melnik, Roderick

172

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

173

Slip-boundary equations for multicomponent nonequilibrium airflow  

NASA Technical Reports Server (NTRS)

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

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

1985-01-01

174

Characterizing buildings for airflow models: What should we measure?  

SciTech Connect

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

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

2004-06-01

175

Resistance of wood chips and sawdust to airflow  

SciTech Connect

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

Suggs, C.W.; Lanier, A.

1985-01-01

176

Induced airflow in flying insects II. Measurement of induced flow.  

PubMed

The flapping wings of insects and birds induce a strong flow over their body during flight. Although this flow influences the sensory biology and physiology of a flying animal, there are very little data on the characteristics of this self-generated flow field or its biological consequences. A model proposed in the companion paper estimated the induced flow over flying insects. In this study, we used a pair of hot wire anemometers to measure this flow at two locations near the body of a tethered flapping hawk moth, Manduca sexta. The axial inflow anemometer measured the airflow prior to its entry into the stroke plane, whereas the radial outflow anemometer measured the airflow after it crossed the stroke plane. The high temporal resolution of the hot wire anemometers allowed us to measure not only the mean induced flow but also subtle higher frequency disturbances occurring at 1-4 times the wing beat frequency. These data provide evidence for the predictions of a mathematical model proposed in the companion paper. Specifically, the absolute value of the measured induced flow matches the estimate of the model. Also, as predicted by the model, the induced flow varies linearly with wing beat frequency. Our experiments also show that wing flexion contributes significantly to the observed higher frequency disturbances. Thus, the hot wire anemometry technique provides a useful means to quantify the aerodynamic signature of wing flexion. The phasic and tonic components of induced flow influence several physiological processes such as convective heat loss and gas exchange in endothermic insects, as well as alter the nature of mechanosensory and olfactory stimuli to the sensory organs of a flying insect. PMID:16354777

Sane, Sanjay P; Jacobson, Nathaniel P

2006-01-01

177

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

178

Laminar Flow Control by Suction at Mach 2  

Microsoft Academic Search

\\u000a Laminar flow control by suction of crossflow-dominated laminar-turbulent transition at Mach 2 was studied experimentally and\\u000a numerically as part of the EU project SUPERTRAC. The measurements were performed in the Ludwieg Tube Facility (RWG) at DLR\\u000a Gttingen. With a suction panel manufactured from porous sinter material a significant delay of laminar-turbulent transition\\u000a could be achieved. Transition N-factors in the range

S. Hein; E. Schlein; A. Hanifi; J. Sousa; D. Arnal

2010-01-01

179

Fault tolerant attitude control for small unmanned aircraft systems equipped with an airflow sensor array.  

PubMed

Inspired by sensing strategies observed in birds and bats, a new attitude control concept of directly using real-time pressure and shear stresses has recently been studied. It was shown that with an array of onboard airflow sensors, small unmanned aircraft systems can promptly respond to airflow changes and improve flight performances. In this paper, a mapping function is proposed to compute aerodynamic moments from the real-time pressure and shear data in a practical and computationally tractable formulation. Since many microscale airflow sensors are embedded on the small unmanned aircraft system surface, it is highly possible that certain sensors may fail. Here, an adaptive control system is developed that is robust to sensor failure as well as other numerical mismatches in calculating real-time aerodynamic moments. The advantages of the proposed method are shown in the following simulation cases: (i) feedback pressure and wall shear data from a distributed array of 45 airflow sensors; (ii) 50% failure of the symmetrically distributed airflow sensor array; and (iii) failure of all the airflow sensors on one wing. It is shown that even if 50% of the airflow sensors have failures, the aircraft is still stable and able to track the attitude commands. PMID:25405953

Shen, H; Xu, Y; Dickinson, B T

2014-01-01

180

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

181

Research in natural laminar flow and laminar-flow control, part 2  

SciTech Connect

Part 2 of the Symposium proceedings includes papers addressing various topics in basic wind tunnel research/techniques and computational transitional research. Specific topics include: advanced measurement techniques; laminar flow control; Tollmien-Schlichting wave characteristics; boundary layer transition; flow visualization; wind tunnel tests; flight tests; boundary layer equations; swept wings; and skin friction.

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

1987-12-01

182

Research in natural laminar flow and laminar-flow control, part 2  

Microsoft Academic Search

Part 2 of the Symposium proceedings includes papers addressing various topics in basic wind tunnel research\\/techniques and computational transitional research. Specific topics include: advanced measurement techniques; laminar flow control; Tollmien-Schlichting wave characteristics; boundary layer transition; flow visualization; wind tunnel tests; flight tests; boundary layer equations; swept wings; and skin friction.

J. N. Hefner; F. E. Sabo

1987-01-01

183

Research in Natural Laminar Flow and Laminar-Flow Control, part 2  

NASA Technical Reports Server (NTRS)

Part 2 of the Symposium proceedings includes papers addressing various topics in basic wind tunnel research/techniques and computational transitional research. Specific topics include: advanced measurement techniques; laminar flow control; Tollmien-Schlichting wave characteristics; boundary layer transition; flow visualization; wind tunnel tests; flight tests; boundary layer equations; swept wings; and skin friction.

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

1987-01-01

184

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

185

Experimental design of laminar proportional amplifiers  

NASA Technical Reports Server (NTRS)

An experimental program was initiated at Langley Research Center to study the effects of various parameters on the design of laminar proportional beam deflection amplifiers. Matching and staging of amplifiers to obtain high-pressure gain was also studied. Variable parameters were aspect ratio, setback, control length, receiver distance, receiver width, width of center vent, and bias pressure levels. Usable pressure gains from 4 to 19 per stage can now be achieved, and five amplifiers were staged together to yield pressure gains up to 2,000,000.

Hellbaum, R. F.

1976-01-01

186

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

187

Transition to turbulence in laminar hypersonic flow  

NASA Technical Reports Server (NTRS)

Progress in a recently started project aimed at the prediction of transition to turbulence in hypersonic flow is briefly discussed. The prediction of transition to turbulence is a very important issue in the design of space vessels. Two space vehicles currently under investigation, namely the aeroassisted transfer vehicle (AOTV) and the trans-atmospheric vehicle (TAV), suffer from strong aerodynamic heating. This heating is strongly influenced by the boundary layer structure. These aerospace vehicles fly in the upper atmospheric layer at a Mach number between 10 and 30 at very low atmospheric pressures. At very high altitudes the flow is laminar, but when the space vessel returns to a lower orbit, the flow becomes turbulent and the heating is dramatically increased. The prediction of this transition process is commonly done by means of experiments. The experimental facilities available nowadays cannot model the hypersonic flow field accurately enough by limitations in Mach and Reynolds number. These facilities also have a large free stream disturbance level which makes it very difficult to investigate transition accurately. An alternative approach is to study transition by theoretical means. Up to now numerical studies of hypersonic flow only discussed steady laminar or turbulent flow. This theoretical approach is extended to the study of transition in hypersonic flow by means of direct numerical simulations and additional theoretical investigations to explain the mechanisms leading to transition. A brief outline of how this research is to be performed is given.

Vandervegt, Jaap

1989-01-01

188

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

189

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

190

Coupling of a multizone airflow simulation program with computational fluid dynamics for indoor environmental analysis  

E-print Network

Current design of building indoor environment comprises macroscopIC approaches, such as CONT AM multizone airflow analysis tool, and microscopic approaches that apply Computational Fluid Dynamics (CFD). Each has certain ...

Gao, Yang, 1974-

2002-01-01

191

Evaluation of circumferential airflow uniformity entering combustors from compressors. Volume 1: Discussion of data and results  

NASA Technical Reports Server (NTRS)

The compressor discharge airflow uniformity of two compressors from advanced engines, the J58 and F100/F401, was studied. Compressor discharge pressures and temperatures at up to 33 circumferential rake locations allowed the airflow distribution to be ascertained and computer plotted. Several flight conditions and compressor variables, i.e., inlet distortion, modified seals, etc., were analyzed. An unexpectedly high nonuniform airflow was found for both compressors. Circumferential airflow deviation differences of up to 52% from maximum to minimum were found for the J58, and up to 40% for the F100/F401. The effects of aerodynamic and thermal distortion were found to be additive. The data were analyzed for influence of exit guide vane wakes and found free of any effect. Data system errors were small in relation to the measured pressure and temperature variations.

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

1972-01-01

192

Airflow and nanoparticle deposition in a 16-generation tracheobronchial airway model  

EPA Science Inventory

In order to achieve both manageable simulation and local accuracy of airflow and nanoparticle deposition in a representative human tracheobronchial (TB) region, the complex airway network was decomposed into adjustable triple-bifurcation units, spreading axially and laterally. Gi...

193

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 12% of chord length on the upper surface10,000 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 durationsimilar 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

194

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

195

Optimized Natural-Laminar-Flow Airfoils and D. W. Zingg  

E-print Network

Optimized Natural-Laminar-Flow Airfoils J. Driver and D. W. Zingg University of Toronto Institute-averaged Navier-Stokes equations. The algorithm is applied to the design of airfoils with maximum lift-drag ratio natural-laminar-flow airfoils. In particular, the optimization algorithm is able to design an airfoil

Zingg, David W.

196

Numerical and experimental studies on laminar flow control  

Microsoft Academic Search

This paper gives an overview of numerical and experimental investigations performed in the framework of laminar flow control studies. After a description of the transition mechanisms that are likely to occur on swept wings, different techniques to delay the onset of laminar-turbulent transition are presented. Application of these techniques is illustrated by numerical results, wind tunnel experiments and free flight

Daniel Arnal

1999-01-01

197

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

Microsoft Academic Search

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.

M. H. Tuttle; D. V. Maddalon

1982-01-01

198

Durability of hybrid laminar flow control (HLFC) surfaces  

Microsoft Academic Search

As a part of the European Commission sponsored HYLTEC (Hybrid Laminar Flow Technology) project, a SAAB 2000 aircraft fitted with a number of small laser drilled panels on the wing leading edge completed 20 months of routine service; the objective being to investigate contamination and durability aspects of Hybrid Laminar Flow Control (HLFC) suction surfaces. A post-flight test

Trevor Young; Brian Mahony; Bryan Humphreys; Ernst Totland; Alan McClafferty; Julie Corish

2003-01-01

199

Roughness and waviness requirements for laminar flow surfaces  

Microsoft Academic Search

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

Clifford J. Obara; Bruce J. Holmes

1986-01-01

200

Propulsion system optimization for suction laminar flow control bodies  

Microsoft Academic Search

Equations are derived for comparing propulsion systems for a suction laminar flow control (LFC) vehicle such as a torpedo when propelled by: (1) suction pump efflux only, and (2) suction pump augmented by external propeller. In an example, with nonlaminar\\/laminar drag ratio J = 0.43, the drag of a suction LFC vehicle is 17 percent of the drag of a

K. H. Rogers

1979-01-01

201

Laminar\\/Turbulent Plasma Jets Generated at Reduced Pressure  

Microsoft Academic Search

Laminar DC plasma jets are attractive for precisely controlled plasma-material processing. The design of a novel nontransferred plasma torch enabled the switching between turbulent and laminar plasma flows by simply changing the plasma generation parameters. Images of the plasma flows generated at different conditions are presented.

Heji Huang; Wenxia Pan; Zhiying Guo; Chengkang Wu

2008-01-01

202

COMISan international multizone air-flow and contaminant transport model  

Microsoft Academic Search

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

Helmut E. Feustel

1999-01-01

203

An instrumented sample holder for time-lapse microtomography measurements of snow under advective airflow  

NASA Astrophysics Data System (ADS)

An instrumented sample holder was developed for time-lapse microtomography of snow samples to enable in situ nondestructive spatial and temporal measurements under controlled advective airflows, temperature gradients, and air humidities. The design was aided by computational fluid dynamics simulations to evaluate the airflow uniformity across the snow sample. Morphological and mass transport properties were evaluated during a 4-day test run. This instrument allows the experimental characterization of metamorphism of snow undergoing structural changes with time.

Ebner, P. P.; Grimm, S. A.; Schneebeli, M.; Steinfeld, A.

2014-09-01

204

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. Nicola; Pieter Verboven

2011-01-01

205

Neural control of airflow profile during hypoxia in sleep and wakefulness  

Microsoft Academic Search

Airflow profile is often overlooked when characterizing respiratory pattern, although some profiles are theoretically more efficient than others. We studied airflow profiles, diaphragmatic activity (DIA) and the activity of augmenting inspiratory (IAUG) neurons in the ventral medulla of unanesthetized cats breathing either 21% O2 or 10-12% O2 in N2 during wakefulness (W), non-rapid eye movement (NREM) and rapid eye movement

A. T. Lovering; W. Dunin-Barkowski; E. H. Vidruk; J. M. Orem

2002-01-01

206

Eosinophils, bronchitis and asthma: pathogenesis of cough and airflow obstruction.  

PubMed

Eosinophilic airway inflammation is commonly observed in chronic cough in patients with asthma and non-asthmatic eosinophilic bronchitis. Indeed asthma and non-asthmatic eosinophilic bronchitis are amongst the commonest causes of chronic cough accounting for about 25 and 10% of cases respectively. In most cases the trigger that causes the cough is uncertain; however removal of potential triggers is important to consider in particular with respect to occupational exposure to known sensitizers. In both conditions the cough improves subjectively and objectively following treatment with corticosteroids. This improvement is associated with the presence of an airway eosinophilia, but whether eosinophilic inflammation is the cause of cough or an epiphenomenon is uncertain. The success of anti-IL5 to reduce eosinophilic inflammation and asthma exacerbations contrasts with the lack of efficacy to modify cough in asthma and therefore challenges a causal association. Both asthma and non-asthmatic eosinophilic bronchitis can lead onto airway remodeling and result in persistent airflow obstruction. However, response to corticosteroid therapy in both conditions is generally very good and the limited long term data available suggests that both usually have a benign course. Interestingly, improvement in airway remodeling in response to anti-IL5 observed using CT imaging and analysis of sub-epithelial matrix deposition does suggest that the eosinophil may play a causal role in airway remodeling. PMID:21074631

Brightling, C E

2011-06-01

207

Oscillating and star-shaped drops levitated by an airflow  

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

208

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

209

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

PubMed

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

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

2013-03-01

210

Measurement of the resistivity of porous materials with an alternating air-flow method.  

PubMed

Air-flow resistivity is a main parameter governing the acoustic behavior of porous materials for sound absorption. The international standard ISO 9053 specifies two different methods to measure the air-flow resistivity, namely a steady-state air-flow method and an alternating air-flow method. The latter is realized by the measurement of the sound pressure at 2 Hz in a small rigid volume closed partially by the test sample. This cavity is excited with a known volume-velocity sound source implemented often with a motor-driven piston oscillating with prescribed area and displacement magnitude. Measurements at 2 Hz require special instrumentation and care. The authors suggest an alternating air-flow method based on the ratio of sound pressures measured at frequencies higher than 2 Hz inside two cavities coupled through a conventional loudspeaker. The basic method showed that the imaginary part of the sound pressure ratio is useful for the evaluation of the air-flow resistance. Criteria are discussed about the choice of a frequency range suitable to perform simplified calculations with respect to the basic method. These criteria depend on the sample thickness, its nonacoustic parameters, and the measurement apparatus as well. The proposed measurement method was tested successfully with various types of acoustic materials. PMID:21361434

Dragonetti, Raffaele; Ianniello, Carmine; Romano, Rosario A

2011-02-01

211

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

212

Laminar flow control SPF/08 feasibility demonstration  

NASA Technical Reports Server (NTRS)

The feasibility of applying superplastic forming/diffusion bonding (SPF/DB) technology to laminar flow control (LFC) system concepts was demonstrated. Procedures were developed to produce smooth, flat titanium panels, using thin -0.016 inch sheets, meeting LFC surface smoothness requirements. Two large panels 28 x 28 inches were fabricated as final demonstration articles. The first was flat on the top and bottom sides demonstrating the capability of the tooling and the forming and diffusion bonding procedures to produce flat, defect free surfaces. The second panel was configurated for LFC porous panel treatment by forming channels with dimpled projections on the top side. The projections were machined away leaving holes extending into the panel. A perforated titanium sheet was adhesively bonded over this surface to complete the LFC demonstration panel. The final surface was considered flat enough to meet LFC requirements for a jet transport aircraft in cruising flight.

Ecklund, R. C.; Williams, N. R.

1981-01-01

213

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

214

Progress in natural laminar flow research  

NASA Technical Reports Server (NTRS)

For decades, since the earliest attempts to obtain natural laminar flow (NLF) on airplanes, three classical objections to its practicality have been held in the aeronautical community. These objectives concerned first, the capability to manufacture practical airframe surfaces smooth enough for NLF; second, the apparent inherent instability and sensitivity of NLF; and third, the accumulation of contamination such as insect debris in flight. This paper explains recent progress in our understanding of the achieveability and maintainability of NLF on modern airframe surfaces. This discussion explains why previous attempts to use NLF failed and what has changed regarding the three classical objections to NLF practicality. Future NASA research plans are described concerning exploring the limits of NLF usefulness, production tolerances, operational considerations, transition behavior and measurement methods, and NLF design applications.

Holmes, B. J.

1984-01-01

215

Rain-induced subsurface airflow and Lisse effect  

NASA Astrophysics Data System (ADS)

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

Guo, Haipeng; Jiao, Jiu J.; Weeks, Edwin P.

2008-07-01

216

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

217

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

218

CFD validation of a supersonic laminar flow control concept  

NASA Technical Reports Server (NTRS)

A three-dimensional Navier-Stokes code is used in conjunction with a linear compressible stability analysis code to develop a numerical procedure for prediction of laminar flow transition. The procedure is applied to a modified F-16XL fighter with a laminar flow control glove at supersonic speed. Details of boundary layer stability analysis indicate that, computationally, laminar flow could be realized on the highly swept wing in the absence of the leading edge attachment-line contamination. Effects of the three-dimensionality of the flow were shown to be important in the boundary layer stability analysis. The numerically predicted surface pressures compare favorably with the flight test data.

Woan, Chung-Jin; Gingrich, Philip B.; George, Michael W.

1991-01-01

219

Role of interphase processes in styrene vapor removal from airflow under the action of a pulsed electron beam  

Microsoft Academic Search

The conversion of styrene vapor in airflow under the action of a pulsed electron beam has been studied. It is demonstrated\\u000a that the main processes leading to the removal of styrene from airflow involve reactive oxygen species and yield styrene oxidation\\u000a products, which are characterized by low vapor pressures and are removed from airflow in a condensed state. This experimental

Yu. N. Novoselov; I. E. Filatov

2009-01-01

220

Surface Pressure and Mountain Drag for Transient Airflow over a Mountain Ridge.  

NASA Astrophysics Data System (ADS)

The linear problem of rotating, stratified, adiabatic, hydrostatic, Boussinesq airflow over a mountain ridge is solved analytically for the case where the spatially uniform, normally incident airflow is the sum of a steady and sinusoidally varying component. The mountain generates a response at the fundamental frequency of the wind and all higher harmonics.During flow acceleration, the evanescent (vertically decaying) modes deepen and broaden the high-low pressure asymmetry across the ridge and increase the mountain drag. In contrast, the evanescent modes for steady airflow product only a symmetric mountain anticyclone that generates no drag. The influence of the acceleration is more pronounced for mesoscale and synoptic-scale ridges (i.e., ridges whose Rossby number is order unity or smaller) and when the fundamental period is near the inertial period.The transience also amplifies the magnitude of the maximum wave drag over its value predicted from steady airflow theory using the instantaneous wind speed. The total acceleration reaction due to both evanescent and wave modes can be larger than this steady airflow drag.

Bannon, Peter R.; Zehnder, Joseph A.

1985-12-01

221

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

PubMed Central

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.

2014-01-01

222

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

PubMed

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). PMID:20007171

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

2010-06-01

223

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

224

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

225

Ignition in laminar and turbulent nonpremixed counterflow  

NASA Astrophysics Data System (ADS)

Investigations into nonpremixed ignition were conducted to examine the influence of complex chemistry and flow turbulence as found in practical combustion systems. The counterflow configuration, where a hot air jet ignited a cold (298K) fuel jet, was adopted in experiments and calculations. The study of the ignition of large alkane hydrocarbons focused on the effects of fuel structure by investigating the reference fuels n-heptane and iso-octane. The ignition response of these fuels was similar to smaller fuels with similar molecular structures. This conclusion was reinforced by showing that the ignition temperature became nearly insensitive to fuel molecule size above C4, but continued to depend on whether the structure was linear or branched. The effects of turbulence were studied by adding perforated plates to the burner to generate controlled levels of turbulence. This configuration was examined in detail experimentally and computationally without reaction, and subsequently the effects of turbulence on ignition were studied with hydrogen as the fuel. The results indicated that at low turbulence intensities, ignition is enhanced relative to laminar ignition, but as the turbulence intensity increases the ignition temperature also increases, demonstrating that optimal conditions for ignition exist at low turbulence intensities. At high pressures, where HO2 chemistry is important, all turbulent ignition temperatures were higher than laminar ones, and the increasing temperature trend with turbulence intensity was still observed. At low fuel concentrations, a different ignition mode was observed where the transition from a weakly reacting state to a flame occurred over a range of temperatures where the flame was repeatedly ignited and extinguished. Turbulent ignition was modeled by solving a joint scalar PDF equation using a Monte Carlo technique. The absence of significant heat release prior to ignition enabled the use of a frozen flow solution, solved separately, in the scalar calculation. The results did not reproduce the qualitative trends noted in the experiments and the influence of turbulence intensity was not apparent in the calculated results. These discrepancies were attributed to shortcomings in the molecular mixing models in low turbulent Reynolds number flows and where reaction rates are much lower than in a flame.

Blouch, John Dewey

2002-01-01

226

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

227

Laminar diffusion flames under micro-gravity conditions  

NASA Technical Reports Server (NTRS)

Laminar methane and propane gas-jet diffusion flames have been theoretically and experimentally studied at NASA-Lewis under microgravity conditions. It is noted that laminar diffusion flames are strongly affected by the combined effects of kinetics, radiation, and such transient phenomena as flame ignition, stabilization, and extinction. Observations on the distinctive nature of the flame color and luminosity parameters in microgravity are presented, and flame behavior under transient, high-deceleration rates is discussed. Test hardware and instrumentation design are described.

Edelman, Raymond B.; Bahadori, Yousef; Olson, Sandra L.; Stocker, Dennis P.

1988-01-01

228

Simultaneous analysis of vocal fold vibration and transglottal airflow: exploring a new experimental setup.  

PubMed

The purpose of this study was to develop an analysis system for studying the relationship between vocal fold vibration and the associated transglottal airflow. Recordings of airflow, electroglottography (EGG), oral air pressure, and acoustic signals were performed simultaneously with high-speed imaging at a rate of approximately 1900 frames/s. Inverse filtered airflow is compared with the simultaneous glottal area extracted from the high-speed image sequence. The accuracy of the synchronization between the camera images and the foot pedal synchronization pulse was examined, showing that potential synchronization errors increase with time distance to the synchronization pulse. Therefore, analysis was limited to material near the synchronization pulse. Results corroborate previous predictions that air flow lags behind area, but also they reveal that relationships between these two entities may be complex and apparently varying with phonation mode. PMID:14513955

Granqvist, Svante; Hertegrd, Stellan; Larsson, Hans; Sundberg, Johan

2003-09-01

229

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

230

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

231

Radiative interactions in laminar duct flows  

NASA Technical Reports Server (NTRS)

Analyses and numerical procedures are presented for infrared radiative energy transfer in gases when other modes of energy transfer occur simultaneously. Two types of geometries are considered, a parallel plate duct and a circular duct. Fully developed laminar incompressible flows of absorbing-emitting species in black surfaced ducts are considered under the conditions of uniform wall heat flux. The participating species considered are OH, CO, CO2, and H2O. Nongray as well as gray formulations are developed for both geometries. Appropriate limiting solutions of the governing equations are obtained and conduction-radiation interaction parameters are evaluated. Tien and Lowder's wide band model correlation was used in nongray formulation. Numerical procedures are presented to solve the integro-differential equations for both geometries. The range of physical variables considered are 300 to 2000 K for temperature, 0.1 to 100.0 atm for pressure, and 0.1 to 100 cm spacings between plates/radius of the tube. An extensive parametric study based on nongray formulation is presented. Results obtained for different flow conditions indicate that the radiative interactions can be quite significant in fully developed incompressible flows.

Trivedi, P. A.; Tiwari, S. N.

1990-01-01

232

A new approach to laminar flowmeters.  

PubMed

After studying the performance and characteristics of actual laminar flowmeters a new disposition for this type of sensors is proposed in such a way that the measurement errors introduced by the intrinsic nature of the device can be minimized. The preliminary study shows that the developing entry region introduces non-linearity effects in all these devices. These effects bring about not only errors, but also a change in the slope of the linear calibration respect of the Poiseuille relation. After a subsequent analysis on how these non-linearity errors can be reduced, a new disposition of this type of flowmeters is introduced. This device makes used of flow elements having pressure taps at three locations along its length and connected to three isolated chambers. In this way, the static pressure can be measured at three locations and contributed to by the pressure taps at the level of each chamber. Thus the linearization error is reduced with an additional advantage of producing a reduced pressure drop. PMID:22163486

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

2010-01-01

233

Soot formation in laminar diffusion flames  

SciTech Connect

Laminar, sooting, coflow diffusion flames at atmospheric pressure have been studied experimentally and theoretically as a function of fuel dilution by inert nitrogen. The flames have been investigated with laser diagnostics. Laser extinction has been used to calibrate the experimental soot volume fractions and an improved gating method has been implemented in the laser-induced incandescence (LII) measurements resulting in differences to the soot distributions reported previously. Numerical simulations have been based on a fully coupled solution of the flow conservation equations, gas-phase species conservation equations with complex chemistry, and the dynamical equations for soot spheroid growth. The model also includes the effects of radiation reabsorption through an iterative procedure. An investigation of the computed rates of particle inception, surface growth, and oxidation, along with a residence time analysis, helps to explain the shift in the peak soot volume fraction from the centerline to the wings of the flame as the fuel fraction increases. The shift arises from changes in the relative importance of inception and surface growth combined with a significant increase in the residence time within the annular soot formation field leading to higher soot volume fractions, as the fuel fraction increases.

Smooke, M.D.; Long, M.B.; Connelly, B.C. [Department of Mechanical Engineering, Yale University, P.O. Box 208284, New Haven, CT 06520-8284 (United States); Colket, M.B.; Hall, R.J. [United Technologies Research Center, East Hartford, CT (United States)

2005-12-01

234

A New Approach to Laminar Flowmeters  

PubMed Central

After studying the performance and characteristics of actual laminar flowmeters a new disposition for this type of sensors is proposed in such a way that the measurement errors introduced by the intrinsic nature of the device can be minimized. The preliminary study shows that the developing entry region introduces non-linearity effects in all these devices. These effects bring about not only errors, but also a change in the slope of the linear calibration respect of the Poiseuille relation. After a subsequent analysis on how these non-linearity errors can be reduced, a new disposition of this type of flowmeters is introduced. This device makes used of flow elements having pressure taps at three locations along its length and connected to three isolated chambers. In this way, the static pressure can be measured at three locations and contributed to by the pressure taps at the level of each chamber. Thus the linearization error is reduced with an additional advantage of producing a reduced pressure drop. PMID:22163486

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

2010-01-01

235

Relationships among Smoking Habits, Airflow Limitations, and Metabolic Abnormalities in School Workers  

PubMed Central

Background Chronic obstructive pulmonary disease is caused mainly by habitual smoking and is common among elderly individuals. It involves not only airflow limitation but also metabolic disorders, leading to increased cardiovascular morbidity and mortality. Objective We evaluated relationships among smoking habits, airflow limitation, and metabolic abnormalities. Methods Between 2001 and 2008, 15,324 school workers (9700 males, 5624 females; age: ?30 years) underwent medical checkups, including blood tests and spirometry. They also responded to a questionnaire on smoking habits and medical history. Results Airflow limitation was more prevalent in current smokers than in ex-smokers and never-smokers in men and women. The frequency of hypertriglyceridemia was higher in current smokers in all age groups, and those of low high-density-lipoprotein cholesterolemia and diabetes mellitus were higher in current smokers in age groups ? 40 s in men, but not in women. There were significant differences in the frequencies of metabolic abnormalities between subjects with airflow limitations and those without in women, but not in men. Smoking index was an independent factor associated with increased frequencies of hypertriglyceridemia (OR 1.015; 95% CI: 1.0121.018; p<0.0001) and low high-density-lipoprotein cholesterolemia (1.013; 1.0101.016; p<0.0001) in men. Length of smoking cessation was an independent factor associated with a decreased frequency of hypertriglyceridemia (0.984; 0.9750.994; p?=?0.007). Conclusions Habitual smoking causes high incidences of airflow limitation and metabolic abnormalities. Women, but not men, with airflow limitation had higher frequencies of metabolic abnormalities. PMID:24312268

Horie, Masafumi; Noguchi, Satoshi; Tanaka, Wakae; Goto, Yasushi; Yoshihara, Hisanao; Kawakami, Masaki; Suzuki, Masaru; Sakamoto, Yoshio

2013-01-01

236

Automating the Solar DRYERAIRFLOW Control Utilizing Pressure Diffrence Concept  

NASA Astrophysics Data System (ADS)

The presence of a chimney in natural convective solar dryer has proven its benefit in accelerated transport of moist air from the drying compartment and thus shortening the drying time for intended crops. The experiment and simulation studies done by various parties have guaranteed increases in the airflow in relation to the physical height of chimney. A simple automated control system is proposed to assist the controls of airflow rate so that a near optimum mass flow rate could be achieved for the best possible dried product quality in the shortest possible drying period.

Luk, T. B.; Vakhguelt, A.

2009-08-01

237

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

238

Applications of a Coupled Multizone and CFD Model to Calculate Airflow and Contaminant Dispersion in Built Environment for Emergency  

E-print Network

is multizone network model, e.g. CONTAM (Walton and Dols 2003) and COMIS (Feustel 1999). Kowalski et al. (20031 Applications of a Coupled Multizone and CFD Model to Calculate Airflow and Contaminant Dispersion airflow network models are fast but cannot provide detailed flow and contaminant transport information

Chen, Qingyan "Yan"

239

An aerodynamically efficient sphere anemometer with integrated hot-film sensors for 2-D environmental airflow monitoring  

Microsoft Academic Search

This paper reports a novel anemometer configuration for airflow measurement. The flow over a sphere provides an ideal flow geometry. Four micro hot-film sensors are orthogonally mounted on the circumference of a sphere. The airflow speed distribution on the sphere as well as flow separation point will affect heat dissipation of the hot-film sensors, and result in variance of resistance

X. M. Jing; J. Y. Lu; J. M. Miao; H. Hans; H. A. Rahman; S. S. Pan; L. Norford

2011-01-01

240

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

241

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

242

Brief history of laminar flow clean room systems  

SciTech Connect

This paper reviews the development and evolution of laminar flow clean rooms and hoods and describes the underlying principles and rationales associated with development of this type of clean room system and Federal Standard No. 209. By the mid 1970's, over a thousand hospitals in the US had installed laminar flow equipment in operating rooms. During the past several years a great deal of attention has been focused on conserving energy in clean rooms. Some gains in energy conservation have been achieved by improved design, off hours shutdown, and closer evaluation of requirements for clean rooms. By the early 1970's, the laminar flow principle had been carried from the Laboratory and applied to production hardware to create a mature industry producing and marketing a variety of laminar flow equipment in less than 10 years time. This achievement was made possible by literally dozens of persons in industry, government, military, and private individuals who developed hardware, added numerous innovations, and had the foresight to apply the technology to many fields other than industrial clean rooms. Now, with laminar flow devices available, class 100 levels are readily achievable and maintained, and at the same time require fewer operating restrictions than previously possible.

Whitfield, W J

1981-01-01

243

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

244

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

245

Performance of Supply Airflow Entrainment for Particles in an Underfloor Air Distribution System  

E-print Network

comfort conditions and energy conservation. However, the supply air outlet of UFAD system is set on the floor, such that the supply airflow may entrain the dust particles settled on the floor or suspended near the floor. This creates problems that need...

Li, C.; Li, N.

2006-01-01

246

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

247

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.

248

Usability evaluation of a flight-deck airflow hazard visualization system  

Microsoft Academic Search

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

Cecilia R. Aragon

2004-01-01

249

Turbine Air-Flow Test Rig CFD Results for Test Matrix  

NASA Technical Reports Server (NTRS)

This paper presents the Turbine Air-Flow Test (TAFT) rig computational fluid dynamics (CFD) results for test matrix. The topics include: 1) TAFT Background; 2) Design Point CFD; 3) TAFT Test Plan and Test Matrix; and 4) CFD of Test Points. This paper is in viewgraph form.

Wilson, Josh

2003-01-01

250

Airflow and pressure during canary song: direct evidence for mini-breaths  

Microsoft Academic Search

Male canaries (Serinus canaria) produce songs of long duration compared to the normal respiratory cycle. Each phrase in a song contains repetitions of a particular song syllable, with repetition rates for different syllables ranging from 3 to 35 notes\\/s. We measured tracheal airflow and air sac pressure in order to investigate respiratory dynamics during song.

Rebecca Schurr Hartley; Roderick A. Suthers

1989-01-01

251

An air-flow based wafer bake system for improved temperature uniformity  

Microsoft Academic Search

This paper presents an innovative apparatus for wafer baking\\/chilling using a stream of temperature controlled air-flow. This apparatus takes the form of a baking chamber on which the wafer is placed. A stream of hot air is passed through the chamber below the wafer. Heat is transferred from the hot air to the wafer from the bottom surface of the

Lan Wang; Ai Poh Loh; Zhi Ming Gong; Siew Loong Chow

2008-01-01

252

Study on heat and mass transfer characteristics of humid air-flow in a fin bundle  

Microsoft Academic Search

This paper deals with the heat and mass transfer characteristics of humid air-flow under frosting conditions. A slit fin bundle was used for the simulation of fins of a heat exchanger. The effects of the cooling block temperature, air humidity and air velocity on the frosting characteristics were experimentally investigated. The frosted mass was affected considerably by the cooling block

Dong-Hwi Kim; Shigeru Koyama; Ken Kuwahara; Jeong-Tae Kwon; Byung-Duck Park

2010-01-01

253

Optimisation of air-flow conditions during the chilling and storage of carcasses and meat products  

Microsoft Academic Search

In the meat industry investment and running costs for chillers are determined mainly by the chilling time and the weight losses associated with chilling or storage. The aim of this study was to assess the consequences of the spatial heterogeneity of air-flow properties in rooms and to optimise the multi-stage low air temperature chilling process used to reduce weight losses.

A. Kondjoyan; J. D. Daudin

1997-01-01

254

Physical Modeling of Airflow-Walls Interactions to Understand the Sleep Apnea Syndrome  

E-print Network

is the most vulnerable to obstruction from loss of muscle tone during sleep. On physical exam, a long and widePhysical Modeling of Airflow-Walls Interactions to Understand the Sleep Apnea Syndrome Yohan Payan1, France {pelorson,perrier}@icp.inpg.fr Abstract. Sleep Apnea Syndrome (SAS) is defined as a partial

Payan, Yohan

255

Mathematical modeling and simulation of batch drying of foods in fixed beds with airflow reversal  

Microsoft Academic Search

A mathematical model based on the heat and mass transfer mechanisms between the air and the product was developed in order to simulate the fixed bed drying process of foods conducted with and without periodical reversals of the airflow direction. The proposed model considers the fixed bed of the product as a series of ideal stirred stages connected in series,

I. I. Ruiz-Lpez; C. E. Martnez-Snchez; R. Cobos-Vivaldo; E. Herman-Lara

2008-01-01

256

USABILITY EVALUATION OF A FLIGHT-DECK AIRFLOW HAZARD VISUALIZATION SYSTEM  

E-print Network

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 indications of the best design choices in producing the hazard visual cues. Introduction Turbulence and other

Hearst, Marti

257

Contam airflow models of three large buildings: Model descriptions and validation  

Microsoft Academic Search

Airflow and pollutant transport models are useful for several reasons, including protection from or response to biological terrorism. In recent years they have been used for deciding how many biological agent samplers are needed in a given building to detect the release of an agent; to figure out where those samplers should be located; to predict the number of people

Douglas R. Black; Phillip N. Price

2009-01-01

258

Airflow mechanics in models of equine obstructive airway disease under conditions simulating exercise  

Microsoft Academic Search

Effects of respiratory tract obstructions on ventilatory mechanics in horses exercising at high speeds were tested with a fibreglass replica of the airways (nares to mainstem bronchi) of an adult horse. Segmental pressures were recorded at six sites along the model at four different unidirectional flows (1300 4100 litre min?1), and the respective resistances (R) to airflow were calculated.

R. F Slocombe

1997-01-01

259

Assessment of the clinical usefulness of nebulised ipratropium bromide in patients with chronic airflow limitation  

Microsoft Academic Search

The effect of adding nebulised ipratropium bromide to bronchodilator treatment was studied in 20 patients with severe chronic airflow limitation. Maintenance theophylline with or without a steroid preparation was continued and comparison made between placebo, nebulised salbutamol, and a combination of nebulised salbutamol and ipratropium. Although the mean FEV1 values showed the combination to produce a small but significant increase

I G Brown; C S Chan; C A Kelly; A G Dent; P V Zimmerman

1984-01-01

260

Nasal Obstruction in Patients with Seasonal Allergic Rhinitis: Relationships between Allergic Inflammation and Nasal Airflow  

Microsoft Academic Search

Background: Nasal obstruction is a typical symptom of allergic rhinitis. Allergic rhinitis is characterized by a Th2-dependent inflammation. The aim of this study was to evaluate the possible relationships between allergic inflammation, including inflammatory cells and cytokine pattern, and nasal airflow in patients with nasal obstruction due to seasonal allergic rhinitis. Methods: Fifty patients (31 males and 19 females, mean

Giorgio Ciprandi; Ignazio Cirillo; Andrea Vizzaccaro; Manlio Milanese; Maria Angela Tosca

2004-01-01

261

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

PubMed

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

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

2005-01-01

262

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

263

Airflow produced by dielectric barrier discharge between asymmetric parallel rod electrodes  

SciTech Connect

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

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

2007-09-15

264

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

NASA Astrophysics Data System (ADS)

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

Aragon, Cecilia Rodriguez

265

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

266

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

267

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

268

Design of a hybrid laminar flow control nacelle  

NASA Technical Reports Server (NTRS)

Consideration is given to the potential application of hybrid-laminar-flow control to the external surface of a modern, high-bypass-ratio (HBR) turbofan engine nacelle. With the advent of advanced ultra-HBR fans (with bypass ratios of 10-15), the wetted areas of these nacelles approach 10 percent of the total wetted area of future commercial transports. A hybrid-laminar-flow-control 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 on an advanced twin-engine transport configuration are presented to determine potential benefits in terms of reduced fuel consumption.

Wie, Yong-Sun; Collier, Fayette S., Jr.; Wagner, Richard D.; Viken, Jeffery K.; Pfenninger, Werner

1992-01-01

269

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

270

Laminar-turbulent transition prediction module for LOGOS package  

NASA Astrophysics Data System (ADS)

The present work is devoted to a description and substantiation of an original module for computing the location of laminar-turbulent transition in subsonic boundary layer flows, which is based on the e N -method and enables more accurate computations of the flow around bodies in the presence of the so-called natural transition to turbulence in the boundary layer. A combined work of the module and the RANS solver from the aerodynamic part of the LOGOS package is demonstrated by the example of the flow past a flat plate. The obtained computed locations of the beginning and the end of the laminar-turbulent transition coincide with known reference values.

Boiko, A. V.; Nechepurenko, Yu. M.; Zhuchkov, R. N.; Kozelkov, A. S.

2014-04-01

271

Roughness and waviness requirements for laminar flow surfaces  

NASA Astrophysics Data System (ADS)

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

Obara, Clifford J.; Holmes, Bruce J.

1986-12-01

272

Computational Evaluation of a Transonic Laminar-Flow Wing Glove Design  

E-print Network

The aerodynamic benefits of laminar flow have long made it a sought-after attribute in aircraft design. By laminarizing portions of an aircraft, such as the wing or empennage, significant reductions in drag could be achieved, reducing fuel burn...

Roberts, Matthew William

2012-07-16

273

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

274

Development and test of an inlet and duct to provide airflow for a wing boundary layer control system  

NASA Technical Reports Server (NTRS)

The boundary layer control (BLC) system of the quiet short-haul research airplane (QSRA) requires significant amounts of pressurized airflow for successful operation. An inlet and duct were successfully developed which removed airflow from the engine fan duct for the BLC system at or above the required total pressure of 99% of the average fan duct total pressure. The design was constrained by the tight space limitations of the QSRA nacelle. Potential flow with boundary layer analysis techniques were used as an aid to select the inlet and duct geometries. Airflow and total pressure profile data were obtained during development tests.

Gunnarson, D. W.; Mcardle, J. C.

1978-01-01

275

Further experiments on the stability of laminar and turbulent hydrogen-air flames at reduced pressures  

NASA Technical Reports Server (NTRS)

Stability limits for laminar and turbulent hydrogen-air burner flames were measured as a function of pressure, burner diameter, and composition. On the basis of a simple flame model, turbulent flashback involved a smaller effective penetration distance than laminar flashback. No current theoretical treatment predicts the observed pressure and diameter dependence of laminar and turbulent blowoff.

Fine, Burton

1957-01-01

276

EulerianEulerian two-phase numerical simulation of nanofluid laminar forced convection in a microchannel  

E-print Network

Eulerian­Eulerian two-phase numerical simulation of nanofluid laminar forced convection August 2010 Accepted 5 August 2010 Keywords: Nanofluid Microchannel Two-phase Laminar Heat transfer a b s t r a c t In this paper, laminar forced convection heat transfer of a copper­water nanofluid inside

Harting, Jens

277

Laminar flow control research at TsAGI: Past and present  

Microsoft Academic Search

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

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

2011-01-01

278

Natural-Laminar-Flow Airfoil and Wing Design by Adjoint Method and Automatic Transition Prediction  

E-print Network

describes the application of optimization technique based on control theory for natural-laminar-flow airfoilNatural-Laminar-Flow Airfoil and Wing Design by Adjoint Method and Automatic Transition Prediction that an airfoil can be designed to have the desired favorable pressure gradient for laminar flow and the new

Jameson, Antony

279

Characterization of laminar jet impingement cooling in portable computer applications  

Microsoft Academic Search

A thermal characterization study of laminar air jet impingement cooling of electronic components within a geometry representative of the CPU compartment of a typical portable computer is reported. A finite control volume technique was used to solve for the velocity and temperature fields. Convection, conduction and radiation effects were included in the simulations. The range of jet Reynolds numbers considered

John R. Guarino; Vincent P. Manno

2002-01-01

280

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

281

Turbulent-Laminar Patterns in Pipes and Channels  

Microsoft Academic Search

When fluid flows through a channel, pipe, or duct, there are two basic forms of motion: smooth laminar motion and complex turbulent motion. The discontinuous transition between these states is a fundamental problem that has been studied for more than 100 years. What has received far less attention is the large-scale nature of the turbulent flows near transition once they

Dwight Barkley

2010-01-01

282

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

283

Studies of Origin of Three-Dimensionality in Laminar Wakes.  

National Technical Information Service (NTIS)

Wind tunnel experiments, using hot-wire anemometry and smoke-wire flow visualization, were conducted to study the process of transition from laminar to turbulent flow of parallel and oblique vortex streets from circular cylinders. It was found that the or...

M. Gharib

1993-01-01

284

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

285

DEPARTMENT OF ENGINEERING SCIENCE High Pressure Laminar Burning  

E-print Network

of : Temperature gradient in burned gas Change in gas properties e.g. cp Effects of residuals Normally use 10 zones Baffle Plate Max initial pressure 4 bar Max initial temperature 470 K Max pressure 34 bar Max unburned temperature 725 K High Pressure Laminar Burning Velocity Measurements October 27, 2008 Page 3 #12;System

286

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

287

Contamination control in semiconductor industry using laminar barrier inerting technology  

Microsoft Academic Search

Laminar Barrier Inerting is a new and effective method of preventing air infiltration into semiconductor process equipment. Air infiltration during loading and unloading is a major source of contamination within semiconductor process furnaces. During these steps, cooler clean room air can replace hot process nitrogen due to buoyant forces. Many fabrication processes are quite sensitive to oxygen and moisture resulting

E. Quilantang; A. Sharif; A. Hosein; T. Yokum; R. Cartwright

1994-01-01

288

Detailed Structure and Stabilization Mechanism of Lifted Laminar Methane Flame  

Microsoft Academic Search

The present study has numerically investigated the lifted flame field frequently encountered in the actual fire situations. This study employs the physical submodels including the detailed chemical kinetics, the variable transport properties, and the radiation model. A lifted laminar CH4\\/air flame with a central diluted fuel jet and a surrounding fuel-lean coflow is chosen as a validation case. Computations are

Hoo-Joong Kim; Yong-Mo Kim

2002-01-01

289

Laminar conjugated forced convection heat transfer in curved rectangular channels  

Microsoft Academic Search

This paper examines fully developed laminar flow and conjugated forced convection heat transfer in curved rectangular channels. The wall average Nusselt number, Nu, is presented as a function of the wall conduction parameter, ?, the Dean number, De, and the channel aspect ratio, ?. Secondary flow streamlines for the case of ?=1\\/2 are presented to illustrate the enhanced stability in

T. W. Gyves; T. F. Irvine

2000-01-01

290

Hydromagnetic Laminar Flow through Conducting Parallel Porous Walls  

Microsoft Academic Search

The steady state solution for the laminar flow of an electrically conducting liquid in the presence of transverse magnetic field has been investigated in detail. Taking into account the porosity of the walls we have obtained the velocity profiles for the induced magnetic and electric fields. Consideration has also been given to the rectangular channels in the following two cases:

P. Govinda Reddy; M. K. Jain

1967-01-01

291

A perturbation approach for suction laminar flow control applications  

Microsoft Academic Search

A new method for computing the hydrodynamic stability eigenvalue problem in the presence of wall suction by using the eigenvalue and eigenfunctions of the no-suction problem is presented. The perturbation approach is computationally efficient in comparison with the direct approach; it is potentially applicable in various ways to hydrodynamic stability, particularly in laminar flow control.

Jamal A. Masad; Mujeeb R. Malik

1994-01-01

292

Laminar: Practical Fine-Grained Decentralized Information Flow Control  

E-print Network

Laminar: Practical Fine-Grained Decentralized Information Flow Control Indrajit Roy Donald E information flow control (DIFC) is a promising model for writing programs with powerful, end-to-end security information flow control using a single set of abstrac- tions for OS resources and heap-allocated objects

McKinley, Kathryn S.

293

Boundary layer receptivity mechanisms relevant to laminar flow control  

Microsoft Academic Search

Receptivity processes by which free-stream acoustic waves generate instability waves in boundary layers are investigated. Concentration is placed on mechanisms associated with local regions of short scale variation in wall suction or admittance distribution. These mechanisms are relevant to laminar flow control technology, in which suction is utilized to control the growth of boundary layer instabilities. The receptivity process requires

Meelan Choudhari

1990-01-01

294

An overview of recent subsonic laminar flow control flight experiments  

NASA Technical Reports Server (NTRS)

This paper presents an overview of wind-tunnel investigations and flight research activities in the United States and Europe devoted to advancing the state-of-the-art and reducing the risk associated with the application of laminar flow control (LFC) technology. The paper highlights LFC research conducted within the last five years.

Collier, F. S., Jr.

1993-01-01

295

Advanced stability theory analyses for laminar flow control  

Microsoft Academic Search

Recent developments of the SALLY computer code for stability analysis of laminar flow control wings are summarized. Extensions of SALLY to study three dimensional compressible flows, nonparallel and nonlinear effects are discussed. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Keywords (in text query field) Abstract Text Return: Query Results

S. A. Orszag

1980-01-01

296

A fundamental study of suction for Laminar Flow Control (LFC)  

Microsoft Academic Search

This report covers the period forming the first year of the project. The aim is to experimentally investigate the effects of suction as a technique for Laminar Flow Control. Experiments are to be performed which require substantial modifications to be made to the experimental facility. Considerable effort has been spent developing new high performance constant temperature hot-wire anemometers for general

Jonathan H. Watmuff

1992-01-01

297

Laminar flame speeds of hydrocarbon + air mixtures with hydrogen addition  

Microsoft Academic Search

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

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

1986-01-01

298

Self-pumping suction/propulsion for laminar flow bodies  

NASA Astrophysics Data System (ADS)

An analysis is presented to investigate the feasibility of a self-pumping suction system for a very low drag suction laminar flow control (SLFC) underwater test body. The nose and afterbody of a torpedo-like body are contoured such that a prominent low-pressure region in the aft part of the body can serve as a suction pump to suck the boundary layer fluid through the circumferential surface-slots and thus laminarize the entire body length forward of the aft low-pressure peak. The results indicate that it is feasible to laminarize a test body in this fashion at a design speed, such as 40 knots; but that the laminarization of a particular configuration is limited to a band of speeds at and near the design speed. If an SLFC test body with a wide range of speed capability is desired, then a controllable-speed suction pump and controllable suction distribution along the body are indicated. The analysis includes a suction system design calculation example and should be a useful reference for future development of undersea SLFC vehicles.

Rogers, K. H.; King, D. A.

1984-06-01

299

Combustion Module-1 with Laminar Soot Process (LSP)  

NASA Technical Reports Server (NTRS)

Technicians install the Laminar Soot Processes (LSP) experiment into the combustion chamber of Combustion Module-1. CM-1 was one of the most complex and technologically sophisticated pieces of hardware ever to be included as a part of a Spacelab mission.

2004-01-01

300

Preconditioned Multigrid Simulation of an Axisymmetric Laminar Diffusion Flame \\Lambda  

E-print Network

diffusion flames. We con­ sider a flame sheet problem with one­step chemical reaction. The governingPreconditioned Multigrid Simulation of an Axisymmetric Laminar Diffusion Flame \\Lambda Samir Karaa of an elliptic flame sheet problem. By selecting the generalized minimum residual method as the linear smoother

Zhang, Jun

301

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

302

Transverse Diffusion of Laminar Flow Profiles To Produce Capillary Nanoreactors  

E-print Network

for mixing two or more reactants inside capillaries. Conceptually, solutions of reactants are injected inside the capillary by pressure as a series of consecutive plugs. Due to the laminar nature of flow inside mixtures inside the capillary, TDLFP lowers reagent consumption to nanoliters (microliters are required

Krylov, Sergey

303

Surface wave transition before breakup on a laminar liquid jet  

Microsoft Academic Search

Problems of liquid jet breakup are very fundamental in the fluid-dynamics and application fields of atomization. Instability theories of the surface wave were usually used to describe the breakup phenomena. In these theories, it was assumed that the surface wave was a regular sinusoidal wave. However, irregular surface waves were frequently observed even though a liquid jet was laminar. In

M Arai; K Amagai

1999-01-01

304

Numerical studies of laminar and turbulent drag reduction, part 2  

NASA Technical Reports Server (NTRS)

The flow over wave shaped surfaces is studied using a Navier Stokes solver. Detailed comparisons with theoretical results are presented, including the stability of a laminar flow over wavy surfaces. Drag characteristics of nonplanar surfaces are predicted using the Navier-Stokes solver. The secondary instabilities of wall bounded and free shear flows are also discussed.

Balasubramanian, R.; Orszag, S. A.

1983-01-01

305

LAMINAR BURNING VELOCITY OF GASOLINES WITH ADDITION OF ETHANOL  

E-print Network

1 LAMINAR BURNING VELOCITY OF GASOLINES WITH ADDITION OF ETHANOL P. Dirrenberger1 , P.A. Glaude*1 of Combustion Physics, Lund University, Lund, Sweden *Corresponding author: Email: pierre WITH ADDITION OF ETHANOL P. Dirrenberger1 , P.A. Glaude*1 , R. Bounaceur1 , H. Le Gall1 , A. Pires da Cruz2 , A

Boyer, Edmond

306

Laminar burning speeds of ethanol\\/air\\/diluent mixtures  

Microsoft Academic Search

Laminar burning speed of ethanol\\/air\\/diluent mixtures have been measured over a wide range of temperature, pressure, fuel air equivalence ratio and diluent. Experimental facilities include a cylindrical vessel with two large end windows and a spherical vessel with capability to withstand pressures up to 425atm. Both of these vessels are heated for having initial temperatures of unburned gas up to

Kian Eisazadeh-Far; Ali Moghaddas; Jalal Al-Mulki; Hameed Metghalchi

2011-01-01

307

Development of In-Situ Fan Curve Measurement with One Airflow Measurement  

E-print Network

3:50 pm 4:10 pm Fan Head (in WG) 2.44 3.13 3.61 Fan Speed (Hz) 34.8 (58%) 39 (65%) 45.7 (76.2%) Airflow (CFM) 14637 14786 N/A Supply air temp.(F) 55.7 55.9 56.0 Table3 presents the measured fan speed, fan head, and fan... curve coefficient Method I Method II a0 3.238 5.005 a1 0.0003993 0.0002846 a2 -9.503E-09 -7.75E-09 3 4 5 6 7 8 10 15 20 25 30 35 40 Airflow [103CFM] F a n h e a d [ i n. w . g. ] Method II Method I Figure 3. Compares the Fan Curves...

Liu, G.; Joo, I. S.; Song, L.; Liu, M.

2003-01-01

308

Effects of feedstock, airflow rate, and recirculation ratio on performance of composting systems with air recirculation.  

PubMed

The thermodynamics, kinetics, and energy use of composting systems with air recirculation were determined for feedstocks comprising paper mill sludge and biosolids. Results were developed by simulating the composting system using a two-dimensional finite difference numerical model. Incorporated into the simulation model was independent regulation of temperature and oxygen using a closed loop feedback control system with a two-stage fan setting. Results showed that at low airflows and high recirculation ratios, heat removal by the exhaust gas was insufficient to maintain set point temperatures with the result that process temperatures increased and eventually limited the reaction rate. Types of feedstock, magnitude of airflow and recirculation ratio all affected the energy use of the system. Although recirculation leads to high energy use, it can produce high quality compost by having a temperature gradient of less than 2 degrees C across the bed. PMID:15963715

Ekinci, K; Keener, H M; Akbolat, D

2006-05-01

309

Numerical Modelling of Airflow and Temperature Distribution in a Living Room with Different Heat Exchange Conditions  

NASA Astrophysics Data System (ADS)

Numerical mathematical modelling of the indoor thermal conditions and of the energy losses for separate rooms is an important part of the analysis of the heat-exchange balance and energy efficiency in buildings. The measurements of heat transfer coefficients for bounding structures, the air-tightness tests and thermographic diagnostics done for a building allow the influence of those factors to be predicted more correctly in developed numerical models. The temperature distribution and airflows in a typical room (along with the heat losses) were calculated for different heater locations and solar radiation (modelled as a heat source) through the window, as well as various pressure differences between the openings in opposite walls. The airflow velocities and indoor temperature, including its gradient, were also analysed as parameters of thermal comfort conditions. The results obtained show that all of the listed factors have an important influence on the formation of thermal comfort conditions and on the heat balance in a room.

Gendelis, S.; Jakovi?s, A.

2010-01-01

310

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 full-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.

Forbes, John C.; Xenofos, George D.; Farrow, John L.; Tyler, Tom; Williams, Robert; Sargent, Scott; Moharos, Jozsef

2004-01-01

311

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

312

Computational model of airflow in upper 17 generations of human respiratory tract.  

PubMed

Computational fluid dynamics (CFD) studies of airflow in a digital reference model of the 17-generation airway (bronchial tree) were accomplished using the FLUENT computational code, based on the anatomical model by Schmidt et al. [2004. A digital reference model of the human bronchial tree. Computerized Medical Imaging and Graphics 28, 203-211]. The lung model consists of 6.744 x 10(6) unstructured tetrahedral computational cells. A steady-state airflow rate of 28.3L/min was used to simulate the transient turbulent flow regime using a large eddy simulation (LES) turbulence model. This CFD mesh represents the anatomically realistic asymmetrical branching pattern of the larger airways. It is demonstrated that the nature of the secondary vortical flows, which develop in such asymmetric airways, varies with the specific anatomical characteristics of the branching conduits. PMID:18501360

Gemci, T; Ponyavin, V; Chen, Y; Chen, H; Collins, R

2008-01-01

313

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

314

Thermal Comfort under Transient Metabolic and Dynamic Localized Airflow Conditions Combined with Neutral and Warm Ambient Temperatures  

E-print Network

, in practice, people move between spaces, and thermal conditions such as metabolic rate, surface temperatures, airflow speed and direction vary in a typical day. A human subject test was designed to determine the transient relationship between the people...

Ugursal, Ahmet

2012-02-14

315

Unique airflow visualization techniques for the design and validation of above-plenum data center CFD models  

E-print Network

One cause for the substantial amount of energy used for data center cooling is poor airflow effects such as hot-aisle to cold-aisle air recirculation. To correct these and to investigate innovative designs that will notably ...

Lloyd, Michael David, S.M. Massachusetts Institute of Technology

2010-01-01

316

Unique Airflow Visualization Techniques for the Design and Validation of Above-Plenum Data Center CFD Models  

E-print Network

One cause for the substantial amount of energy used for data center cooling is poor airflow effects such as hot-aisle to cold-aisle air recirculation. To correct these and to investigate innovative designs that will notably ...

Lloyd, Michael

317

Design, fabrication, and control of MEMS-based actuator arrays for air-flow distributed micromanipulation  

Microsoft Academic Search

This paper reports the design, fabrication and control of arrayed microelectromechanical systems (MEMS)-based actuators for distributed micromanipulation by generation and control of an air-flow force field. The authors present an original design of pneumatic microactuator, improving reliability and durability of a distributed planar micromanipulator described in the previous study. The fabrication process is based on silicon-on-insulator (SOI) wafer and HF

Yamato Fukuta; Yves-Andre Chapuis; Yoshio Mita; Hiroyuki Fujita

2006-01-01

318

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. PMID:23427092

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

2013-01-01

319

Development and verification of a high-fidelity computational fluid dynamics model of canine nasal airflow.  

PubMed

The canine nasal cavity contains a complex airway labyrinth, dedicated to respiratory air conditioning, filtering of inspired contaminants, and olfaction. The small and contorted anatomical structure of the nasal turbinates has, to date, precluded a proper study of nasal airflow in the dog. This study describes the development of a high-fidelity computational fluid dynamics (CFD) model of the canine nasal airway from a three-dimensional reconstruction of high-resolution magnetic resonance imaging scans of the canine anatomy. Unstructured hexahedral grids are generated, with large grid sizes ((10-100) x 10(6) computational cells) required to capture the details of the nasal airways. High-fidelity CFD solutions of the nasal airflow for steady inspiration and expiration are computed over a range of physiological airflow rates. A rigorous grid refinement study is performed, which also illustrates a methodology for verification of CFD calculations on complex unstructured grids in tortuous airways. In general, the qualitative characteristics of the computed solutions for the different grid resolutions are fairly well preserved. However, quantitative results such as the overall pressure drop and even the regional distribution of airflow in the nasal cavity are moderately grid dependent. These quantities tend to converge monotonically with grid refinement. Lastly, transient computations of canine sniffing were carried out as part of a time-step study, demonstrating that high temporal accuracy is achievable using small time steps consisting of 160 steps per sniff period. Here we demonstrate that acceptable numerical accuracy (between approximately 1% and 15%) is achievable with practical levels of grid resolution (approximately 100 x 10(6) computational cells). Given the popularity of CFD as a tool for studying flow in the upper airways of humans and animals, based on this work we recommend the necessity of a grid dependence study and quantification of numerical error when presenting CFD results in complicated airways. PMID:19725691

Craven, Brent A; Paterson, Eric G; Settles, Gary S; Lawson, Michael J

2009-09-01

320

Unsteady-state airflow and particle deposition in a three-generation human lung geometry.  

PubMed

The study of particle transport and deposition in the human lung is critical in health risk assessment of air pollutants and in pharmaceutical drug delivery. Several computational fluid dynamics (CFD) studies have investigated particle deposition in the lung for simplified airflow scenarios. A shortcoming with most CFD studies is uncertainty regarding flow boundary conditions, which directly impacts airflow and particle deposition. The influence of inlet and outlet conditions on airflow and particle deposition in lung common airways was assessed here. Common airways consisted of nine airways of the human lung ahead of lobes: the trachea, main, and lobar bronchi connected as a network of cylindrical tubes with dimensions based on morphometric measurements. Three different boundary conditions were used: (1) prescribed constant flow rate at the trachea entrance and atmospheric pressure at terminal branch exits, (2) atmospheric pressure at the trachea inlet and prescribed outlet flow rates corresponding to uniform lobar expansion, and (3) the same as case (2) with exit flow rates according to nonuniform lobar expansion. Unsteady airflow fields were numerically solved for a 2-s inhalation. Spherical particles of 1 nm to 10 microm diameter were injected at the trachea inlet, and particle deposition patterns during inhalation were evaluated. A Lagrangian particle tracking method was used that included particle inertia, gravity, and Brownian motion. Predicted flows showed similar trends but with a notable difference in magnitude. Lower particle deposition was found in case (1) for all particle sizes. The differences among these cases indicated the significance of realistic boundary conditions for accurate assessment of the flow field and particle deposition. PMID:18444012

Nazridoust, Kambiz; Asgharian, Bahman

2008-04-01

321

Measurement of airflow of air-conditioning in a car with PIV  

Microsoft Academic Search

In the present study, a model experiment is performed in order to clarify the airflow characteristics of a car cabin. In addition,\\u000a this study provides high precision data for a benchmark test using the CFD (Computational Fluid Dynamics) analysis method.\\u000a Initially, the study focuses on the ventilation mode that describes the flow field in the car cabin obtained from an

Jeong-Hoon Yang; Shinsuke Kato; Hideaki Nagano

2009-01-01

322

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

Microsoft Academic Search

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

Jrme Pons; Eric Moreau; Grard Touchard

2005-01-01

323

Indices of Upper Airway Obstruction in Patients with Simultaneous Chronic Airflow Limitation  

Microsoft Academic Search

In patients with chronic airflow limitation (CAL), the detection of upper airway obstruction (UAO) by analysis of forced flows can be difficult due to the masking of conventional UAO indices. We analyzed five indices: maximum inspiratory flow at 50% of forced vital capacity (FIF50), the ratio of maximum expiratory to inspiratory flow at 50% of forced vital capacity (FEF50\\/FIF50), the

Eduardo Garca-Pachn; Pere Casan; Joaqun Sanchis

1994-01-01

324

Respiratory-triggered electron beam CT with integrated spirometry for evaluation of dynamic airflow  

Microsoft Academic Search

The purpose is to integrate time-attenuation curves from Electron-Beam CT with flow-time curves from spirometry in the analysis of airflow obstruction. A pressure-sensitive switch was connected between a spirometer mouthpiece and a modified EBCT scanner keyboard. The onset of expiratory flow causes pressure changes which simultaneously trigger EBCT and spirometric acquisitions. Subjects performed a forced expiratory maneuver, during which EBCT

Michael F. McNitt-Gray; Jonathan Goldin; Mike Welch; Oded Szold; Michael Levine; Denise R. Aberle

1996-01-01

325

Vibration characteristics of micromachined piezoelectric diaphragms with a standing beam subjected to airflow  

Microsoft Academic Search

This paper presents a novel configuration consisting of a micromachined diaphragm and a standing beam for sensing airflow. A piezoelectric Pb(Zr,Ti)O3 (PZT) film is deposited by spin-coating on the diaphragm to actuate and sense the vibration at its resonant frequency. A standing and extruded beam built on the diaphragm responds to the aerodynamic drag force, inducing mechanical strain, increasing the

X. M. Jing; J. M. Miao; T. Xu; M. Olfatnia; L. Norford

2010-01-01

326

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

PubMed Central

Background: The World Trade Center (WTC) collapse on September 11, 2001, produced airflow obstruction in a majority of firefighters receiving subspecialty pulmonary evaluation (SPE) within 6.5 years post-September 11, 2001. Methods: In a cohort of 801 never smokers with normal pre-September 11, 2001, FEV1, we correlated inflammatory biomarkers and CBC counts at monitoring entry within 6 months of September 11, 2001, with a median FEV1 at SPE (34 months; interquartile range, 25-57). Cases of airflow obstruction had FEV1 less than the lower limit of normal (LLN) (100 of 801; 70 of 100 had serum), whereas control subjects had FEV1 greater than or equal to LLN (153 of 801; 124 of 153 had serum). Results: From monitoring entry to SPE years later, FEV1 declined 12% in cases and increased 3% in control subjects. Case subjects had elevated serum macrophage derived chemokine (MDC), granulocyte-macrophage colony-stimulating factor (GM-CSF), granulocyte colony-stimulating factor, and interferon inducible protein-10 levels. Elevated GM-CSF and MDC increased the risk for subsequent FEV1 less than LLN by 2.5-fold (95% CI, 1.2-5.3) and 3.0-fold (95% CI, 1.4-6.1) in a logistic model adjusted for exposure, BMI, age on September 11, 2001, and polymorphonuclear neutrophils. The model had sensitivity of 38% (95% CI, 27-51) and specificity of 88% (95% CI, 80-93). Conclusions: Inflammatory biomarkers can be risk factors for airflow obstruction following dust and smoke exposure. Elevated serum GM-CSF and MDC levels soon after WTC exposure were associated with increased risk of airflow obstruction in subsequent years. Biomarkers of inflammation may help identify pathways producing obstruction after irritant exposure. PMID:21998260

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

2012-01-01

327

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

Microsoft Academic Search

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

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

2006-01-01

328

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

Microsoft Academic Search

Objective:Inmanycenters,carbonmonoxidelungdiffusioncapacity(DLCO)isstillnotroutinelymeasuredinallpatientsbutonlyinpatients with airflow limitation. The objective of the study was to assess the degree of correlation between forced expiratory volume in 1 s (FEV1) and DLCO, and verify whether a low predicted postoperative DLCO (ppoDLCO) could have a role in predicting complications in patients without airflow limitation. Methods: We analyzed 872 patients submitted to lung resection between January 2000 and

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

2010-01-01

329

Coolant pressure and airflow distribution in a strut-supported transpiration-cooled vane for a gas turbine engine  

NASA Technical Reports Server (NTRS)

An analysis to predict pressure and flow distribution in a strut-supported wire-cloth vane was developed. Results were compared with experimental data obtained from room-temperature airflow tests conducted over a range of vane inlet airflow rates from 10.7 to 40.4 g/sec (0.0235 to 0.0890 lb/sec). The analytical method yielded reasonably accurate predictions of vane coolant flow rate and pressure distribution.

Kaufman, A.; Poferl, D. J.; Richards, H. T.

1972-01-01

330

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

PubMed

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

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

1985-08-01

331

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; Drr, Marcus; Vlzke, Henry; Ittermann, Till; Obst, Anne; Schper, Christoph; John, Ulrich; Meisel, Peter; Grotevendt, Anne; Felix, Stephan B; Ewert, Ralf; Glser, Sven

2013-12-01

332

Chronic Endotoxin Exposure Produces Airflow Obstruction and Lung Dendritic Cell Expansion  

PubMed Central

Little is known about the mechanisms of persistent airflow obstruction that result from chronic occupational endotoxin exposure. We sought to analyze the inflammatory response underlying persistent airflow obstruction as a result of chronic occupational endotoxin exposure. We developed a murine model of daily inhaled endotoxin for periods of 5 days to 8 weeks. We analyzed physiologic lung dysfunction, lung histology, bronchoalveolar lavage fluid and total lung homogenate inflammatory cell and cytokine profiles, and pulmonary gene expression profiles. We observed an increase in airway hyperresponsiveness as a result of chronic endotoxin exposure. After 8 weeks, the mice exhibited an increase in bronchoalveolar lavage and lung neutrophils that correlated with an increase in proinflammatory cytokines. Detailed analyses of inflammatory cell subsets revealed an expansion of dendritic cells (DCs), and in particular, proinflammatory DCs, with a reduced percentage of macrophages. Gene expression profiling revealed the up-regulation of a panel of genes that was consistent with DC recruitment, and lung histology revealed an accumulation of DCs in inflammatory aggregates around the airways in 8-weekexposed animals. Repeated, low-dose LPS inhalation, which mirrors occupational exposure, resulted in airway hyperresponsiveness, associated with a failure to resolve the proinflammatory response, an inverted macrophage to DC ratio, and a significant rise in the inflammatory DC population. These findings point to a novel underlying mechanism of airflow obstruction as a result of occupational LPS exposure, and suggest molecular and cellular targets for therapeutic development. PMID:22517795

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

2012-01-01

333

Human-Mediated Dispersal of Seeds by the Airflow of Vehicles  

PubMed Central

Human-mediated dispersal is known as an important driver of long-distance dispersal for plants but underlying mechanisms have rarely been assessed. Road corridors function as routes of secondary dispersal for many plant species but the extent to which vehicles support this process remains unclear. In this paper we quantify dispersal distances and seed deposition of plant species moved over the ground by the slipstream of passing cars. We exposed marked seeds of four species on a section of road and drove a car along the road at a speed of 48 km/h. By tracking seeds we quantified movement parallel as well as lateral to the road, resulting dispersal kernels, and the effect of repeated vehicle passes. Median distances travelled by seeds along the road were about eight meters for species with wind dispersal morphologies and one meter for species without such adaptations. Airflow created by the car lifted seeds and resulted in longitudinal dispersal. Single seeds reached our maximum measuring distance of 45 m and for some species exceeded distances under primary dispersal. Mathematical models were fit to dispersal kernels. The incremental effect of passing vehicles on longitudinal dispersal decreased with increasing number of passes as seeds accumulated at road verges. We conclude that dispersal by vehicle airflow facilitates seed movement along roads and accumulation of seeds in roadside habitats. Dispersal by vehicle airflow can aid the spread of plant species and thus has wide implications for roadside ecology, invasion biology and nature conservation. PMID:23320077

von der Lippe, Moritz; Bullock, James M.; Kowarik, Ingo; Knopp, Tatjana; Wichmann, Matthias

2013-01-01

334

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

PubMed Central

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

2009-01-01

335

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

336

Comparative analysis of realistic CT-scan and simplified human airway models in airflow simulation.  

PubMed

Efforts to model the human upper respiratory system have undergone many phases. Geometrical proximity to the realistic shape has been the subject of many research projects. In this study, three different geometries of the trachea and main bronchus were modelled, which were reconstructed from computed tomography (CT) scan images. The geometrical variations were named realistic, simplified and oversimplified. Realistic refers to the lifelike image taken from digital imaging and communications in medicine format CT scan images, simplified refers to the reconstructed image based on natural images without realistic details pertaining to the rough surfaces, and oversimplified describes the straight wall geometry of the airway. The characteristics of steady state flows with different flow rates were investigated, simulating three varied physical activities and passing through each model. The results agree with previous studies where simplified models are sufficient for providing comparable results for airflow in human airways. This work further suggests that, under most exercise conditions, the idealised oversimplified model is not favourable for simulating either airflow regimes or airflow with particle depositions. However, in terms of immediate analysis for the prediction of abnormalities of various dimensions of human airways, the oversimplified techniques may be used. PMID:23521065

Johari, Nasrul Hadi; Osman, Kahar; Helmi, Nor Harris N; Abdul Kadir, Mohammed A Rafiq

2015-01-01

337

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. Sjogrens 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 patients responses where Schirmers 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 Schirmers scores and increased corneal epitheliopathy in the contralateral eye. PMID:24526862

Gauba, Vinod; Curtis, Zoe J.

2013-01-01

338

Influence of airflow intensity on phytase production by solid-state fermentation.  

PubMed

Phytase production by Aspergillus niger F3 by solid state fermentation (SSF) on citrus peel was evaluated at pilot scale under different aeration conditions. The best airflow intensity was 1 VkgM (Lair kg medium(-1) min(-1)), which allowed to produce 65 units of phytases per gram in dry basis (65 Ug(-1) d.b.) as it removed the metabolic heat generated by the microorganism, Agitation did not improve heat removal. Airflow intensity was considered as scale-up criterion. When the airflow intensity was maintained at 1 VkgM for SSF with 2 and 20 kg of medium, the kinetics parameters for biomass and enzyme concentration at the end of fermentation differed by less than 2. The air flow intensity was required to maintain the temperature and cool the SSF and to provide oxygen for microbial growth. Air flow intensity is a key a factor that must be considered when scale-up of SSF is attempted. PMID:22704830

Rodrguez-Fernndez, D E; Rodrguez-Len, J A; de Carvalho, J C; Karp, S G; Sturm, W; Parada, J L; Soccol, C R

2012-08-01

339

Simplified models for exhaled airflow from a cough with the mouth covered.  

PubMed

Covering a cough can be useful in reducing the transmission of airborne infectious diseases. However, no simple method is available in the literature for predicting the exhaled airflow from a cough with the mouth covered. This investigation used smoke to visualize the airflow exhaled by 16 human subjects. Their mouths were covered by a tissue, a cupped hand, a fist, and an elbow with and without a sleeve. This study then developed simplified models for predicting the airflow on the basis of the smoke visualization data. In addition, this investigation performed numerical simulations to assess the influence of mouth coverings on the receptor's exposure to exhaled particles. It was found that covering a cough with a tissue, a cupped hand, or an elbow can significantly reduce the horizontal velocity and cause the particles to move upward with the thermal plumes generated by a human body. In contrast with an uncovered cough, a covered cough or a cough with the head turned away may prevent direct exposure. PMID:24628862

Chen, C; Lin, C-H; Jiang, Z; Chen, Q

2014-12-01

340

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

341

Nature of laminar-turbulence intermittency in shear flows.  

PubMed

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

Avila, M; Hof, B

2013-06-01

342

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

343

Correlations of laminar combustion data for alternative SI engine fuels  

SciTech Connect

Most of the spark ignition engine cycle simulations use turbulent burning models which require a knowledge of laminar burning velocity of the fuel-air mixture as a function of mixture strength, unburned mixture temperature and pressure. Burning velocity data of different alternative spark ignition engine fuels obtained by various workers have been compared and critically evaluated. Empirical and semi-empirical correlations, suitable for cycle simulation studies, are presented for laminar burning velocity as a function of mixture strength, unburned mixture temperature, pressure, and residual gas fraction. Fuels considered include ethanol, methanol, alcohol/water blends, isooctane/alcohol blends, propane and isooctane. Experimental data obtained by the present author constitute the major part of the data used in correlations. Published data of other workers and the predictions of theoretical thermo-kinetic models have also been considered in correlations.

Gulder, O.L.

1984-01-01

344

Gyrotactic trapping in laminar and turbulent Kolmogorov flow  

E-print Network

Phytoplankton patchiness, namely the heterogeneous distribution of microalgae over multiple spatial scales, dramatically impacts marine ecology. A spectacular example of such heterogeneity occurs in thin phytoplankton layers (TPLs), where large numbers of photosynthetic microorganisms are found within a small depth interval. Some species of motile phytoplankton can form TPLs by gyrotactic trapping due to the interplay of their particular swimming style (directed motion biased against gravity) and the transport by a flow with shear along the direction of gravity. Here we consider gyrotactic swimmers in numerical simulations of the Kolmogorov shear flow, both in laminar and turbulent regimes. In the laminar case, we show that the swimmer motion is integrable and the formation of TPLs can be fully characterized by means of dynamical systems tools. We then study the effects of rotational Brownian motion or turbulent fluctuations (appearing when the Reynolds number is large enough) on TPLs. In both cases we show that TPLs become transient, and we characterize their persistence.

Francesco Santamaria; Filippo De Lillo; Massimo Cencini; Guido Boffetta

2014-10-07

345

Gyrotactic trapping in laminar and turbulent Kolmogorov flow  

E-print Network

Phytoplankton patchiness, namely the heterogeneous distribution of microalgae over multiple spatial scales, dramatically impacts marine ecology. A spectacular example of such heterogeneity occurs in thin phytoplankton layers (TPLs), where large numbers of photosynthetic microorganisms are found within a small depth interval. Some species of motile phytoplankton can form TPLs by gyrotactic trapping due to the interplay of their particular swimming style (directed motion biased against gravity) and the transport by a flow with shear along the direction of gravity. Here we consider gyrotactic swimmers in numerical simulations of the Kolmogorov shear flow, both in laminar and turbulent regimes. In the laminar case, we show that the swimmer motion is integrable and the formation of TPLs can be fully characterized by means of dynamical systems tools. We then study the effects of rotational Brownian motion or turbulent fluctuations (appearing when the Reynolds number is large enough) on TPLs. In both cases we show t...

Santamaria, Francesco; Cencini, Massimo; Boffetta, Guido

2014-01-01

346

Natural laminar flow and airplane stability and control  

NASA Technical Reports Server (NTRS)

Location and mode of transition from laminar to turbulent boundary layer flow have a dominant effect on the aerodynamic characteristics of an airfoil section. The influences of these parameters on the sectional lift and drag characteristics of three airfoils are examined. Both analytical and experimental results demonstrate that when the boundary layer transitions near the leading edge as a result of surface roughness, extensive trailing-edge separation of the turbulent boundary layer may occur. If the airfoil has a relatively sharp leading-edge, leading-edge stall due to laminar separation can occur after the leading-edge suction peak is formed. These two-dimensional results are used to examine the effects of boundary layer transition behavior on airplane longitudinal and lateral-directional stability and control.

Vandam, Cornelis P.

1986-01-01

347

Observations on streamwise vortices in laminar and turbulent boundary layers  

NASA Technical Reports Server (NTRS)

The frequent but often unsuspected presence of streamwise vortices in nominally two dimensional laminar and turbulent boundary layers and some of their consequences are described. Since there is no body of systematic information on streamwise vortices imbedded in boundary layers, a number of issues concerning their occurrence and behavior are discussed in the form of a set of succinct observations. Desirable experimental and numerical research to remedy the current lack of knowledge is recommended.

Morkovin, M. V.

1979-01-01

348

Aerodynamic Design for Swept-wing Laminar Flow  

E-print Network

Improvement (AFRL/NGC) AFRL Air Force Research Laboratory ATTAS Advanced Technologies Testing Aircraft System (German Aerospace Center) BL Wing buttock line, measured in inches from aircraft centerline CAD Computer-aided design CC Complex conjugate CFD... PSE Parabolized stability equations xi RMS Root-mean-square SARGE Subsonic Aircraft Roughness Glove Experiment SCRAT Subsonic Research Aircraft Testbed SWIFT Swept-Wing In-Flight Testing (AFRL/TAMU) SWLFC Swept-wing laminar flow control TAMU Texas A...

Belisle, Michael Joseph

2013-11-08

349

Laminar Flow Supersonic Wind Tunnel primary air injector  

NASA Technical Reports Server (NTRS)

This paper describes the requirements, design, and prototype testing of the flex-section and hinge seals for the Laminar Flow Supersonic Wind Tunnel Primary Injector. The supersonic atmospheric primary injector operates between Mach 1.8 and Mach 2.2 with mass-flow rates of 62 to 128 lbm/s providing the necessary pressure reduction to operate the tunnel in the desired Reynolds number (Re) range.

Smith, Brooke Edward

1993-01-01

350

Design of minimum drag bodies in incompressible laminar flow  

Microsoft Academic Search

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

Jianchun Huan; Vijay Modi

1996-01-01

351

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

352

Determining the mechanical properties of equine laminar corium tissue  

E-print Network

as that of the modulus data. Since the laminar corium is actually composed of two separate, macroscopically distinguishable layers, video-based image analysis was explored as a means of obtaining mechanical properties for each layer, defined as the dermal... and the epidermal regions. Ten images of adjacent sides of a single sample were taken and the preliminary results are encouraging. The uniaxial modulus determined from the crosshead load-displacement data for this specimen was 1348 psi, whereas the dermal region...

Hallab, Nadim James

2012-06-07

353

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

354

Conceptual design for a laminar-flying-wing aircraft  

E-print Network

Conceptual Design for a Laminar-Flying-Wing Aircraft Tariq Issam Saeed Trinity Hall University of Cambridge A thesis submitted for the degree of Doctor of Philosophy February 2012 Declaration Described in this dissertation is worked performed... indebted to him for the many useful discussions on aircraft jet propulsion. Thanks also go to Dr Keith Seffen for the useful discussions on structural design and Dr Jerome Jarrett for his general advice. Finally, I would like to acknowledge Jeremy Eastwood...

Saeed, Tariq Issam

2012-06-12

355

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

356

Distributed acoustic receptivity in laminar flow control configurations  

Microsoft Academic Search

A model problem related to distributed receptivity to free-stream acoustic waves in laminar flow control (LFC) configurations is studied, within the Orr-Sommerfield framework, by a suitable extension of the Goldstein-Ruban theory for receptivity due to localized disturbances on the airfoil surface. The results, thus, complement the earlier work on the receptivity produced by local variations in the surface suction and\\/or

Meelan Choudhari

1992-01-01

357

Distributed acoustic receptivity in laminar flow control configurations  

Microsoft Academic Search

A model problem related to distributed receptivity to free-stream acoustic waves in laminar flow control (LFC) configurations is studied within the OrrSommerfeld framework, by developing a suitable extension of the GoldsteinRuban theory for receptivity due to localized disturbances on the airfoil surface. One advantage of the proposed method is that it easily permits the prediction of receptivity due to a

Meelan Choudhari

1994-01-01

358

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

359

DNS Study of spatial discrete suction for Laminar Flow Control  

Microsoft Academic Search

By means of spatial direct numerical simulations (DNS) based on the complete Navier-Stokes equations the effect of three-dimensional\\u000a discrete suction on the spatial development of a laminar boundary-layer flow generic for the front part of a swept-back airliner\\u000a wing has been investigated. The baseflow is an accelerated Falkner-Skan-Cooke boundary layer, on a swept wedge with semi-opening\\u000a angle of 45 (Hartree

Ralf Messing; Markus Kloker

360

Making Large Suction Panels For Laminar-Flow Control  

NASA Technical Reports Server (NTRS)

Perforated titanium panels used to identify and resolve issues related to manufacture. Recently, relatively large suction panels with aerodynamically satisfactory surface perforations and with surface contours and smoothness characteristics necessary for Laminar-Flow Control (LFC) designed, fabricated, and tested. Requirements of production lines for commercial transport airplanes carefully considered in development of panels. Sizes of panels representative of what is used on wing of commercial transport airplane. Tests of perforated panels in transonic wind tunnel demonstrated aerodynamic stability at flight mach numbers.

Maddalon, Dal V.

1991-01-01

361

Smart Suction for Laminar Flow Control on Swept Wings  

Microsoft Academic Search

Results of high-order direct numerical simulations are summarized for the evolution of crossflow disturbances in incompressible wing-generic boundary-layers with suction at the wall. The concept of smart suction, an adapted combination of the upstream-flow-deform- ation (UFD) technique and suction, is presented for laminar flow control. In the UFD technique, relatively tightly spaced, useful crossflow vortices (CFVs) are excited once, grow

Tillmann A. Friederich; Markus J. Kloker

2008-01-01

362

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

363

Structure and Soot Formation Properties of Laminar Flames  

NASA Technical Reports Server (NTRS)

Soot formation within hydrocarbon-fueled flames is an important unresolved problem of combustion science for several reasons: soot emissions are responsible for more deaths than any other combustion-generated pollutant, thermal loads due to continuum radiation from soot limit the durability of combustors, thermal radiation from soot is mainly responsible for the growth and spread of unwanted fires, carbon monoxide emissions associated with soot emissions are responsible for most fire deaths, and limited understanding of soot processes in flames is a major impediment to the development of computational combustion. Motivated by these observations, soot processes within laminar premixed and nonpremixed (diffusion) flames are being studied during this investigation. The study is limited to laminar flames due to their experimental and computational tractability, noting the relevance of these results to practical flames through laminar flamelet concepts. Nonbuoyant flames are emphasized because buoyancy affects soot processes in laminar diffusion flames whereas effects of buoyancy are small for most practical flames. This study involves both ground- and space-based experiments, however, the following discussion will be limited to ground-based experiments because no space-based experiments were carried out during the report period. The objective of this work was to complete measurements in both premixed and nonpremixed flames in order to gain a better understanding of the structure of the soot-containing region and processes of soot nucleation and surface growth in these environments, with the latter information to be used to develop reliable ways of predicting soot properties in practical flames. The present discussion is brief, more details about the portions of the investigation considered here can be found in refs. 8-13.

El-Leathy, A. M.; Xu, F.; Faeth, G. M.

2001-01-01

364

Laminar shocks in high power laser plasma interactions  

E-print Network

We propose a theory to describe laminar ion sound structures in a collisionless plasma. Reflection of a small fraction of the upstream ions converts the well known ion acoustic soliton into a structure with a steep potential gradient upstream and with downstream oscillations. The theory provides a simple interpretation of results dating back more than forty years but, more importantly, is shown to provide an explanation for recent observations on laser produced plasmas relevant to inertial fusion and to ion acceleration.

Cairns, R A; Norreys, P; Trines, R

2014-01-01

365

The Effects of Gravity on Wrinkled Laminar Flames  

NASA Technical Reports Server (NTRS)

The effects of gravity are significant to the dynamics of idealized unconfined open premixed flames. Moderate to low turbulence Reynolds number flames, i.e., wrinkled laminar flames, of various unconfined geometries have been used extensively for investigating fundamental processes of turbulent flame propagation and to validate theoretical models. Without the wall constraints, the flames are free to expand and interact with surrounding ambient air. The flow field in which the flame exists is determined by a coupling of burner geometry, flame orientation and the gravity field. These complex interactions raise serious questions regarding the validity of comparing the experimental data of open flames with current theoretical and numerical models that do not include the effects of gravity nor effects of the larger aerodynamic flowfield. Therefore, studies of wrinkled laminar flame in microgravity are needed for a better understanding of the role of gravity on flame characteristics such as the orientation, mean aerodynamics stretch, flame wrinkle size and burning rate. Our approach to characterize and quantify turbulent flame structures under microgravity is to exploit qualitative and quantitative flow visualization techniques coupled with video recording and computer controlled image analysis technologies. The experiments will be carried out in the 2.2 second drop tower at the NASA Lewis Research Center. The longest time scales of typical wrinkled laminar flames in the geometries considered here are in the order of 10 msec. Hence, the duration of the drop is sufficient to obtain the amount of statistical data necessary for characterize turbulent flame structures.

Kostiuk, Larry W.; Zhou, Liming; Cheng, Robert K.

1993-01-01

366

Turbulent-Laminar Patterns in Pipes and Channels  

NASA Astrophysics Data System (ADS)

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

Barkley, Dwight

2010-03-01

367

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

368

Laminar and Connectional Organization of a Multisensory Cortex  

PubMed Central

The transformation of sensory signals as they pass through cortical circuits has been revealed almost exclusively through studies of the primary sensory cortices, where principles of laminar organization, local connectivity and parallel processing have been elucidated. In contrast, almost nothing is known about the circuitry or laminar features of multisensory processing in higher-order, multisensory cortex. Therefore, using the ferret higher-order multisensory rostral posterior parietal (PPr) cortex, the present investigation employed a combination of multichannel recording and neuroanatomical techniques to elucidate the laminar basis of multisensory cortical processing. The proportion of multisensory neurons, the share of neurons showing multisensory integration, and the magnitude of multisensory integration were all found to differ by layer in a way that matched the functional or connectional characteristics of the PPr. Specifically, the supragranular layers (L23) demonstrated among the highest proportions of multisensory neurons and the highest incidence of multisensory response enhancement, while also receiving the highest levels of extrinsic inputs, exhibiting the highest dendritic spine densities, and providing a major source of local connectivity. In contrast, layer 6 showed the highest proportion of unisensory neurons while receiving the fewest external and local projections and exhibiting the lowest dendritic spine densities. Coupled with a lack of input from principal thalamic nuclei and a minimal layer 4, these observations indicate that this higher-level multisensory cortex shows unique functional and organizational modifications from the well-known patterns identified for primary sensory cortical regions. PMID:23172137

Foxworthy, W. Alex; Clemo, H. Ruth; Meredith, M. Alex

2012-01-01

369

Natural laminar flow experiments on modern airplane surfaces  

NASA Technical Reports Server (NTRS)

Flight and wind-tunnel natural laminar flow experiments have been conducted on various lifting and nonlifting surfaces of several airplanes at unit Reynolds numbers between 0.63 x 10 to the 6th power/ft and 3.08 x 10 to the 6th power/ft, at Mach numbers from 0.1 to 0.7, and at lifting surface leading-edge sweep angles from 0 deg to 63 deg. The airplanes tested were selected to provide relatively stiff skin conditions, free from significant roughness and waviness, on smooth modern production-type airframes. The observed transition locations typically occurred downstream of the measured or calculated pressure peak locations for the test conditions involved. No discernible effects on transition due to surface waviness were observed on any of the surfaces tested. None of the measured heights of surface waviness exceeded the empirically predicted allowable surface waviness. Experimental results consistent with spanwise contamination criteria were observed. Large changes in flight-measured performance and stability and control resulted from loss of laminar flow by forced transition. Rain effects on the laminar boundary layer caused stick-fixed nose-down pitch-trim changes in two of the airplanes tested. No effect on transition was observed for flight through low-altitude liquid-phase clouds. These observations indicate the importance of fixed-transition tests as a standard flight testing procedure for modern smooth airframes.

Holmes, B. J.; Obara, C. J.; Yip, L. P.

1984-01-01

370

Lift-to-drag ratio and laminar flow control of a morphing laminar wing in a wind tunnel  

Microsoft Academic Search

A new hardware-in-the-loop control strategy to enhance the aerodynamic performance of a two-dimensional morphing laminar wing prototype was developed and tested. The testing was performed in a wind tunnel under cruise flight flow conditions: Mach number ranging from 0.2 to 0.3 and angle of attack from - 1 to 0.5. For each set of flow conditions, the shape of the

Daniel Coutu; Vladimir Brailovski; Patrick Terriault; Mahmoud Mamou; Youssef Mbarki; ric Laurendeau

2011-01-01

371

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 13.22.2yrs) 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 17.714.6%, while the mean fall in MIF(50) was 25.415.8%; 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 9min after exercise and correlated to expiratory wheeze. The fall in MIF(50) peaked 15min after exercise and correlated to inspiratory stridor. The time difference in peak fall between FEV(1) and MIF(50) was statistically significant (5.9min; p<0.001, 99% CI: 2.3-9.5min). 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

372

Instrumentation and measurement of airflow and temperature in attics fitted with ridge and soffit vents  

SciTech Connect

This study established a research facility where airflow velocities, temperature, and differential pressures could be measured at the ridge of an attic. Following the construction of a test building, sensors were constructed, calibrated, and installed inside the attic. Paired tests were performed for three different ridge vent treatments; two were rolled type vents and one was a baffled vent. When both attics were fitted with the same ridge vent, the airspeed and differential pressure profiles at the ridge were very similar for both attics, indicating that any observed differences in airspeed and differential pressure were caused by the ridge vent treatment used. The baffled vent and rolled vents were then installed on the ridge of the west and east attics, respectively. The data demonstrated that the baffled ridge vent provided a minimum of twice the ridge airspeed of the rolled vents, when all wind conditions were considered. On the day selected to study the direction of the airflows at the ridge, the baffled vent had airflow speeds at the ridge similar to the rolled vent without fabric backing. The baffled vent allowed air to come out of the attic through both sides of the ridge (negative differential pressures on both sides), while the rolled vent without fabric backing caused air to enter through the south side of the ridge and exit through the north side (positive differential pressure on the south side and negative differential pressure on the north), in effect short-circuiting the vent. The fabric-backed rolled vent allowed attic air to come out of the attic through both sides of the ridge, as did the baffled vent, but the airspeed was slower. The baffled vent was the one with the highest airspeed at the ridge and also had both sides of the vent under negative differential pressure, providing the most effective ventilation.

Romero, M.I.; Brenner, R.J. [USDA-ARS, Gainesville, FL (United States). Center for Medical Agricultural and Veterinary Entomology

1998-12-31

373

Effect of air-flow on the evaluation of refractive surgery ablation patterns.  

PubMed

An Allegretto Eye-Q laser platform (Wavelight GmbH, Erlangen, Germany) was used to study the effect of air-flow speed on the ablation of artificial polymer corneas used for testing refractive surgery patterns. Flat samples of two materials (PMMA and Filofocon A) were ablated at four different air flow conditions. The shape and profile of the ablated surfaces were measured with a precise non-contact optical surface profilometer. Significant asymmetries in the measured profiles were found when the ablation was performed with the clinical air aspiration system, and also without air flow. Increasing air-flow produced deeper ablations, improved symmetry, and increased the repeatability of the ablation pattern. Shielding of the laser pulse by the plume of smoke during the ablation of plastic samples reduced the central ablation depth by more than 40% with no-air flow, 30% with clinical air aspiration, and 5% with 1.15 m/s air flow. A simple model based on non-inertial dragging of the particles by air flow predicts no central shielding with 2.3 m/s air flow, and accurately predicts (within 2 ?m) the decrease of central ablation depth by shielding. The shielding effects for PMMA and Filofocon A were similar despite the differences in the ablation properties of the materials and the different full-shielding transmission coefficient, which is related to the number of particles ejected and their associated optical behavior. Air flow is a key factor in the evaluation of ablation patterns in refractive surgery using plastic models, as significant shielding effects are found with typical air-flow levels used under clinical conditions. Shielding effects can be avoided by tuning the air flow to the laser repetition rate. PMID:21369297

Dorronsoro, Carlos; Schumacher, Silvia; Prez-Merino, Pablo; Siegel, Jan; Mrochen, Michael; Marcos, Susana

2011-02-28

374

Airflow and Precipitation Fields within Deep Alpine Valleys Observed by Airborne Doppler Radar(.  

NASA Astrophysics Data System (ADS)

Although airborne Doppler radar is increasingly relied upon to provide detailed descriptions of mesoscale precipitation systems in remote and complex meteorological settings, the utility of these observations has often been limited by the considerable difficulty in their manual processing to remove ground clutter and other sources of contamination, which is a prerequisite to synthesis of reliable airflow and reflectivity fields. This difficulty is further magnified over mountainous terrain, where these sources of contamination take on increased spatial extent and geometric complexity. Removal of such contamination has traditionally required tedious and time-consuming manual editing. As such, routine retrieval of near-surface airflow and precipitation characteristics over steep orography and within hydrologically critical zones, such as deep valleys cutting through mountainous regions (along which population and transportation corridors are frequently concentrated), has been impractical. A new approach is described that largely automates this data-editing procedure for airborne radar platforms, achieving reliable elimination of corrupted data with minimal loss of meteorological signal. Subjective decisions are minimized through a judicious combination of data renavigation, pattern recognition, and reliance upon high-resolution digital terrain information. This technique is applied to data obtained over the Alps by the NCAR Electra and NOAA P-3 aircraft during the recent Mesoscale Alpine Programme field campaign. Three-dimensional airflow and reflectivity fields are shown to illustrate the power and fidelity of this new approach by capitalizing on data collected near, and even beneath, the aircraft track to provide a unique and highly illuminating description of airflow deep within Alpine river valleys and their tributaries during two contrasting orographic precipitation events. The validity of these results is explored through quantitative comparison of this output with independent kinematic measures obtained from ground-based Doppler radar. The utility of airborne radar to provide comprehensive and near-simultaneous views reaching into multiple valleys hidden from the view of ground-based radars is highlighted for a notable case of `down valley' flow, more comprehensively illustrating the nature and extent of low-level upstream blocking during a widespread orographic precipitation event.

Bousquet, Olivier; Smull, Bradley F.

2003-10-01

375

Gas crossflow effects on airflow through a wire-form transpiration cooling material  

NASA Technical Reports Server (NTRS)

An experimental analysis was conducted to determine the effects of gas stream flow parallel to the discharging surface on the flow characteristics of a wire-form porous material. Flow data were obtained over a range of transpiration airflow rates from 0.129 to 0.695/grams per second-centimeter squared and external gas stream Mach numbers from 0 to 0.46. The conclusion was drawn that the flow characteristics of the wire cloth were not significantly affected by the external gas flows.

Kaufman, A. S.; Russell, L. M.; Poferl, D. J.

1972-01-01

376

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

Microsoft Academic Search

ObjectivesThere 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 MethodsThe study included

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

377

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

378

Detailed predictions of particle aspiration affected by respiratory inhalation and airflow  

NASA Astrophysics Data System (ADS)

The effects of air pollution found in the atmosphere and exposure to airborne particles are an important problem in the interest of public health. Exposure to contaminated air under different flow conditions is studied using the latest computational fluid dynamics models. For the first time the upper respiratory airway is integrated into a human body and placed inside a room, facing different airflow speeds (0.05-0.35 m s-1). It was found that the airflow streamlines diverged as it approached the human body, at the torso and accelerated upwards past the face and head before separating at the rear of the head, forming recirculating regions in the wake behind the body. Inhaled particles were tracked backwards to determine its origins. At a plane upstream from the face the locations of particles inhaled form a region known as the critical area, which is presented. This study establishes a better understanding of particle inhalability and provides a step towards a more holistic approach in determining inhalation toxicology effects of exposure to atmospheric particles.

Inthavong, Kiao; Ge, Qin Jiang; Li, Xiang Dong; Tu, Ji Yuan

2012-12-01

379

Evaluation of an experimental short-length annular combustor: One-side-entry dilution airflow concept  

NASA Technical Reports Server (NTRS)

A test program was conducted to evaluate an experimental short-length annular combustor that uses a one-side-entry dilution airflow concept. The combustor design features scoops on the outer liner for controlling the primary- and secondary-zone airflow distribution. Combustor inlet total pressures were limited to 62 N/sq cm (90 psia) with inlet-air temperatures from 590 K (600 F) to 890 K (1150 F). At a diffuser inlet Mach number of 0.25, the exit temperature pattern factor was 0.44 with an average exit temperature of 1436 K (2124 F) and a total pressure loss of 4.3 percent. At a diffuser inlet Mach number of 0.31, the exit temperature pattern factor was reduced to 0.29 with an average exit temperature of 1450 K (2151 F) and a total pressure loss of 6.1 percent. Nominal combustion efficiencies of 100 percent were obtained with the ASTM A-1 fuel. Exhaust gas emissions, smoke, and altitude relight data are included with exit-temperature profiles and distribution patterns.

Humenik, F. M.; Biaglow, J. A.

1973-01-01

380

Oscillatory Behavior of an Arc Airfoil in Low-Speed Airflow  

NASA Astrophysics Data System (ADS)

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

Molki, Majid; Sattari, Negin

2011-11-01

381

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

382

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

383

Laminar flow control leading edge systems in simulated airline service  

NASA Technical Reports Server (NTRS)

The feasibility of two candidate leading-edge flow laminarization systems applicable to airline service was tested using representative airline operational conditions with respect to air traffic, weather, and airport insect infestation. One of the systems involved a perforated Ti alloy suction surface with about 1 million 0.0025-in. diameter holes drilled by electron beam, as well as a Krueger-type flap that offered protective shielding against insect impingement; the other supplied surface suction through a slotted Ti alloy skin with 27 spanwise slots on the upper and lower surface.

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

1988-01-01

384

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

385

Unsteady Laminar CFD Simulation of Undulatory Rainbow Trout Swimming Hydrodynamics  

NASA Astrophysics Data System (ADS)

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

Flanagan, Patrick; Hotchkiss, Rollin; Stock, David

2004-11-01

386

Analysis of Laminar Incompressible Flow on Semiporous Channels  

NASA Technical Reports Server (NTRS)

Perturbation solutions for laminar incompressible flow in semiporous and fully porous channels are compared. The perturbation parameter measures the amount of suction or blowing at the porous wall. The velocity profile and the wall friction parameter are more affected by suction or blowing for the semiporous channel than for the fully porous channel. For blowing through the wall, the pressure decreases in channel direction for both channels; with sufficiently high suction rates, the analysis showed that the pressure rises in flow direction for the fully porous channel.

Donoughe, Patrick L

1956-01-01

387

Effects of diluents on laminar premixed hydrogen flames in microgravity  

NASA Astrophysics Data System (ADS)

An experimental and computational study of the effects of diluents on the properties of laminar premixed hydrogen flames in microgravity was carried out during the present investigation. The microgravity experiments made use of a short-drop free-fall laboratory facility that provided at least 450 ms of 10-2 g conditions. Outwardly propagating spherical flames were used to measure laminar burning velocities at fuel-equivalence ratios of 1.0 and 1.8, and at pressures of 0.5, 0.7 and 1.0 atm, containing varying concentrations of He, Ar, N2 and CO2 as fire suppressants. Burning velocities were also computed using the steady, one-dimensional laminar premixed flame code PREMIX with detailed chemical kinetics, transport properties, and radiative heat loss. Measured and computed results both showed the suppressant effectiveness (based on the reduction of burning velocity for a given concentration) to increase in the order He, Ar, N2 and CO2. This is attributed to two different physical effects: quenching of chain reaction due to the lower temperatures produced by the suppressant effects on the specific heats of the gases, and changes in the transport rates in the flame reaction zone. However the suppressants can also decrease the Markstein number, especially for CO2, causing the flames to become more susceptible to preferential-diffusion instability. The resulting increase in flame surface wrinkling increases the burning velocity, thus counteracting the desired effect of the flame suppressant. Far from the flammability limit, the agreement between measured and computed laminar burning velocities was found to be good. For near-limit flames, however, the computed and measured burning velocities deviated noticeably, with the observed differences being substantially larger than the measured uncertainties. Sensitivity analyses suggest that inaccuracies in three-body termination rates for H+O2+M=HO2+M reactions, particularly in the third-body chaperon efficacy of various species M, and in mass diffusion coefficients, particularly for H2 diffusion, are the most likely explanation for these near-limit differences.

Qiao, Li

388

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

389

Air Flow in a Separating Laminar Boundary Layer  

NASA Technical Reports Server (NTRS)

The speed distribution in a laminar boundary layer on the surface of an elliptic cylinder, of major and minor axes 11.78 and 3.98 inches, respectively, has been determined by means of a hot-wire anemometer. The direction of the impinging air stream was parallel to the major axis. Special attention was given to the region of separation and to the exact location of the point of separation. An approximate method, developed by K. Pohlhausen for computing the speed distribution, the thickness of the layer, and the point of separation, is described in detail; and speed-distribution curves calculated by this method are presented for comparison with experiment.

Schubauer, G B

1936-01-01

390

Transient radiative energy transfer in incompressible laminar flows  

NASA Technical Reports Server (NTRS)

Analysis and numerical procedures are presented to investigate the transient radiative interactions of nongray absorbing-emitting species in laminar fully-developed flows between two parallel plates. The particular species considered are OH, CO, CO2, and H2O and different mixtures of these. Transient and steady-state results are obtained for the temperaure distribution and bulk temperature for different plate spacings, wall temperatures, and pressures. Results, in general, indicate that the rate of radiative heating can be quite high during earlier times. This information is useful in designing thermal protection systems for transient operations.

Tiwari, S. N.; Singh, D. J.

1987-01-01

391

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

392

Application of laminar flow control to the High Speed Civil Transport - The NASA Supersonic Laminar Flow Control Program  

NASA Technical Reports Server (NTRS)

The NASA Supersonic Laminar Flow Control (SLFC) program encompasses the development of refined CFD methods and boundary layer stability codes for the highly 3D supersonic flow conditions encountered by the F-16XL technology demonstration aircraft and the prospective High Speed Civil Transport (HSCT). While the F-16XL-1 aircraft continues to gather SLFC data, work is under way on the F-16XL-2 aircraft: which will furnish attach-line design criteria, code-calibration data, and an improved understanding of the flowfield over a wing that will add confidence to the design of HSCTs' boundary layer-controlling air-suction panels.

Fischer, Michael C.; Vemuru, Chandra S.

1991-01-01

393

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

394

Laminar flow of two miscible fluids in a simple network  

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

395

Topology of advective-diffusive scalar transport in laminar flows.  

PubMed

The present study proposes a unified Lagrangian transport template for topological description of advective fluid transport and advective-diffusive scalar transport in laminar flows. The key to this unified description is the expression of scalar transport as purely advective transport by the total scalar flux. This admits generalization of the concept of transport topologies known from laminar mixing studies to scalar transport. The study is restricted to two-dimensional systems and the fluid and scalar transport topologies, as a consequence, prove to be Hamiltonian. The unified Lagrangian transport template is demonstrated and investigated for a heat-transfer problem with nonadiabatic boundaries, representing generic scalar transport with permeable boundaries. The fluid and thermal transport topologies under steady conditions both accommodate islands (constituting isolated flow and thermal regions) that undergo Hamiltonian disintegration into chaotic seas upon introducing time periodicity. The thermal transport topology invariably comprises transport conduits that connect the nonadiabatic boundaries and facilitate wall-wall and wall-fluid heat transfer. For steady conditions these transport conduits are regular; for time-periodic conditions these conduits may, depending on degree of diffusion, be regular or chaotic. Regular conduits connect nonadiabatic walls only with specific flow regions; chaotic heat conduits establish connection (and thus heat exchange) of the nonadiabatic walls with the entire flow domain. PMID:18352124

Speetjens, M F M

2008-02-01

396

Air-breathing laminar flow-based microfluidic fuel cell.  

PubMed

This communication reports the design and characterization of an air-breathing laminar flow-based microfluidic fuel cell (LFFC). The performance of previous LFFC designs was cathode-limited due to the poor solubility and slow transport of oxygen in aqueous media. Introduction of an air-breathing gas diffusion electrode as the cathode addresses these mass transfer issues. With this design change, the cathode is exposed to a higher oxygen concentration, and more importantly, the rate of oxygen replenishment in the depletion boundary layer on the cathode is greatly enhanced as a result of the 4 orders of magnitude higher diffusion coefficient of oxygen in air as opposed to that in aqueous media. The power densities of the present air-breathing LFFCs are 5 times higher (26 mW/cm2) than those for LFFCs operated using formic acid solutions as the fuel stream and an oxygen-saturated aqueous stream at the cathode ( approximately 5 mW/cm2). With the performance-limiting issues at the cathode mitigated, these air-breathing LFFCs can now be further developed to fully exploit their advantages of direct control over fuel crossover and the ability to individually tailor the chemical composition of the cathode and anode media to enhance electrode performance and fuel utilization, thus increasing the potential of laminar flow-based fuel cells. PMID:16316201

Jayashree, Ranga S; Gancs, Lajos; Choban, Eric R; Primak, Alex; Natarajan, Dilip; Markoski, Larry J; Kenis, Paul J A

2005-12-01

397

A computationally efficient modelling of laminar separation bubbles  

NASA Technical Reports Server (NTRS)

In order to predict the aerodynamic characteristics of airfoils operating at low Reynolds numbers, it is necessary to accurately account for the effects of laminar (transitional) separation bubbles. Generally, the greatest difficulty comes about when attempting to determine the increase in profile drag that results from the presence of separation bubbles. While a number of empirically based separation bubble models have been introduced in the past, the majority assume that the bubble development is fully predictable from upstream conditions. One way of accounting for laminar separation bubbles in airfoil design is the bubble analog used in the design and analysis program of Eppler and Somers. A locally interactive separation bubble model was developed and incorporated into the Eppler and Somers program. Although unable to account for strong interactions such as the large reduction in suction peak sometimes caused by leading edge bubbles, it is able to predict the increase in drag and the local alteration of the airfoil pressure distribution that is caused by bubbles occurring in the operational range which is of most interest.

Dini, Paolo; Maughmer, Mark D.

1989-01-01

398

Numerical solution of the Navier-Stokes equations for laminar, transonic flows  

Microsoft Academic Search

An implicit finite difference solution of the Navier-Stokes equations yielded time histories of the transonic laminar flow development about a circular cylinder and NACA-0018 airfoil. Reynolds numbers ranged from those corresponding to purely laminar flow to those corresponding to significant turbulence in the boundary layer. Body thermal conditions of an adiabatic wall and a specified body temperature were considered. Versatility

L. Turner III

1979-01-01

399

Small is beautiful: Upscaling from microscale laminar to natural turbulent rivers  

E-print Network

Small is beautiful: Upscaling from microscale laminar to natural turbulent rivers L. Malverti,1 E; published 9 October 2008. [1] The use of microscale experimental rivers (with flow depths of the order the experimental microscale at which flow is laminar to the scale of natural turbulent rivers. We address

Lajeunesse, Eric

400

A LEAN METHANE PREMIXED LAMINAR FLAME DOPED WITH COMPONENTS OF DIESEL FUEL  

E-print Network

A LEAN METHANE PREMIXED LAMINAR FLAME DOPED WITH COMPONENTS OF DIESEL FUEL PART I: N-BUTYLBENZENE E better understand the chemistry involved during the combustion of components of diesel fuel flow rate analyses. Keywords: Premixed laminar flame, methane, n-butylbenzene, modelling, diesel fuel

Boyer, Edmond

401

Flame stabilization in the far field of a laminar round jet diffusion flame  

Microsoft Academic Search

A lifted flame stabilized in the far field of a round laminar jet is considered. Using recent developments in the theory of triple flames, and, the Landau-Squire solution for a nonreacting laminar round jet, a transcendental equation is derived for the lift-off height. This equation is shown to have stable solutions if the Schmidt number is greater than unity but

Sandip Ghosal

1999-01-01

402

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

403

Optimal control of the cylinder wake in the laminar regime by Trust-Region methods and  

E-print Network

Optimal control of the cylinder wake in the laminar regime by Trust-Region methods and POD Reduced In this paper, optimal control theory is used to minimize the total mean drag for a circular cylinder wake flow in the laminar regime (Re = 200). The control parame- ters are the amplitude and the frequency of the time

Bergmann, Michel

404

CONTROL AND SUPPRESSION OF LAMINAR VORTEX SHEDDING OFF TWO-DIMENSIONAL BLUFF BODIES  

E-print Network

CONTROL AND SUPPRESSION OF LAMINAR VORTEX SHEDDING OFF TWO-DIMENSIONAL BLUFF BODIES A DISSERTATION #12;Abstract The focus of this research is on the control and suppression of vortex shedding of flow instabilities in the laminar shedding regime. Both bounded and unbounded flow conditions are examined

Stanford University

405

Passive and Active Device for Laminar Flow Control of Swept Wing  

Microsoft Academic Search

Summary Laminar flow control of aircraft gains importance due to both economic and environmental aspects. In this paper several solutions for passive devices and one proposal for an active device for laminar flow control on swept wings are presented. The passive devices concern the anti contamination devices (ACD) which are capable to stop the spanwise propagation of fuselage-induced contaminated flow

J. V. Krier; T. Sucipto; J. P. Godard; R. Donelli; D. Arnal

406

Optimal control of the cylinder wake in the laminar regime by Trust-Region methods and  

E-print Network

drag for a circular cylinder wake flow in the laminar regime (Re = 200). The control parame- tersOptimal control of the cylinder wake in the laminar regime by Trust-Region methods and POD Reduced control theory [1] has emerged as a new approach to solve active flow control and aerodynamic shape design

Paris-Sud XI, Université de

407

Computations for laminar flow control in swept-wing boundary layers  

Microsoft Academic Search

The laminarization of a swept-wing boundary layer by the introduction of passive spanwise-periodic roughness elements (DRE) near the leading edge is modeled by linear stability theory and nonlinear parabolized stability equations. Studies predict that, for chord Reynolds numbers of 8 million and with an appropriate pressure coefficient design, the crossflow instability can be stabilized and laminar flow achieved. Sensitivity to

Helen Reed; Richard Rhodes; William Saric

2007-01-01

408

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

Microsoft Academic Search

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

Yoji Ishida; Masayoshi Noguchi

1988-01-01

409

Pressure-Driven Laminar Flow in Tangential Microchannels: an Elastomeric Microfluidic  

E-print Network

Pressure-Driven Laminar Flow in Tangential Microchannels: an Elastomeric Microfluidic Switch Rustem, Massachusetts 02138 This paper describes laminar fluid flow through a three- dimensional elastomeric-to-face (typically at a 90° angle), with the fluid flows in tangential contact. There are two ways to control fluid

Prentiss, Mara

410

Active Control of Instabilities in Laminar BoundaryLayer Flow--Part I: An Overview  

E-print Network

Active Control of Instabilities in Laminar Boundary­Layer Flow-- Part I: An Overview Ronald D laminar flow in a region of the flow in which the natural instabilities, if left unattended, lead the phenomena by­which the automated studies can be used to expand knowledge of flow control. 1 This research

Erlebacher, Gordon

411

The Phase Relationship in Laminar Channel Flow Controlled by Traveling Wave-Like Blowing/Suction  

E-print Network

The Phase Relationship in Laminar Channel Flow Controlled by Traveling Wave-Like Blowing (2006)] in a two-dimensional laminar Poiseuille flow is investigated. The investigation is done disturbances in- duced by a traveling wave-like blowing/suction control [T. Min et al., J. Fluid Mech. 558, 309

Hoepffner, Jérôme

412

Application of the e sup N method to calculations of laminar flow control  

Microsoft Academic Search

The e sup N method was applied to two-dimensional, incompressible laminar boundary layers with and without suction with the aim of developing an aerodynamic design method for a laminar flow control airfoil. The method consisted of an airfoil, boundary layer and e sup N codes, respectively. The airfoil code used the vortex singularity method and the boundary layer code Keller's

Y. Ishida; N. Itoh

1985-01-01

413

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

Microsoft Academic Search

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

HARA Takashi; TANOUE Kimitoshi

414

A temperature-based variable for monitoring outdoor coil airflow in an air-source heat pump during frost-forming conditions  

SciTech Connect

Frost-buildup tests were conducted on a 3-ton (10.6kW) nominal cooling capacity air-source heat pump with an orifice expansion device. This study was conducted to determine if a simple temperature-based control variable could be used to determine the amount of degradation in the outdoor airflow (and heating capacity) of the unit. Refrigerant pressures and temperatures were monitored through-out the system in addition to power requirements and airflow rates. A temperature-based variable was developed that could be used to predict airflow degradation across the outdoor heat exchanger. This variable was defined using the difference between ambient air temperature and a measured refrigerant temperature. Eight refrigerant temperatures in the system were recorded and evaluated. Plots of airflow as a function of this temperature variable, along with plots of the absolute value percent changes of this temperature variable and airflow, were evaluated to determine which refrigerant temperatures could best be used in the variable to predict degradation in airflow. The best fit between the temperature-based variable and airflow degradation occurred with the inclusion of the refrigerant temperature at the outlet from the evaporator. Calculations of percent changes based on values sampled after a defrost showed a polynomial or linear relationship between airflow and the temperature-based variable. Data from two previously tested heat pumps were also used to compare changes in the outdoor airflow to changes in the temperature-based variable. The base-case heat pump and another heat pump both used an orifice as the expansion device in the heating mode. A third heat pump, which used a thermostatic expansion valve (TXV) as the expansion device in the heating mode, failed to show the same goodness of fit between airflow and the temperature-based variable.

Payne, W.V. II; O`Neal, D.L. [Texas A and M Univ., College Station, TX (United States). Energy Systems Lab.

1994-12-31

415

Overview of supersonic laminar flow control research on the F-16XL ships 1 and 2  

NASA Technical Reports Server (NTRS)

NASA is directing research to develop technology for a high-speed civil transport. Supersonic laminar flow control has been identified as a program element, since it offers significant drag-reduction benefits and is one of the more promising technologies for producing an economically viable aircraft design. NASA is using two prototype F-16XL aircraft to research supersonic laminar flow control. The F-16XL planform is similar to design planforms of high-speed civil transports. The planform makes the aircraft ideally suited for developing technology pertinent to high-speed transports. The supersonic laminar flow control research programs for both aircraft are described. Some general results of the ship-1 program demonstrate that significant laminar flow was obtained using laminar flow control on a highly swept wing at supersonic speeds.

Anderson, Bianca T.; Bohn-Meyer, Marta

1992-01-01

416

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

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

417

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

418

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.

419

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

Microsoft Academic Search

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

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

2006-01-01

420

Unsteady thermal performance analysis of a room with serial and parallel duct radiant floor heating system using hot airflow  

Microsoft Academic Search

In this study, the unsteady thermal performance of a test room heated by circulating hot airflow under the floor was analyzed with a developed mathematical model based on heat transfer equilibrium among the air flow, the floor and the indoor air. The time variations in the indoor air temperature for the serial duct floor heating system were investigated theoretically and

O?uz Bozk?r; Suat Canbazo?lu

2004-01-01

421

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

Code of Federal Regulations, 2010 CFR

...RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators 84.154 Airflow...test; Type B and Type BE supplied-air respirators; minimum requirements...inches) of water-column height to air drawn at the flow rate of 85 liters (3 cubic...

2010-10-01

422

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

Code of Federal Regulations, 2011 CFR

...RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators 84.154 Airflow...test; Type B and Type BE supplied-air respirators; minimum requirements...inches) of water-column height to air drawn at the flow rate of 85 liters (3 cubic...

2011-10-01

423

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

Code of Federal Regulations, 2012 CFR

...RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators 84.154 Airflow...test; Type B and Type BE supplied-air respirators; minimum requirements...inches) of water-column height to air drawn at the flow rate of 85 liters (3 cubic...

2012-10-01

424

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

Code of Federal Regulations, 2013 CFR

...RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators 84.154 Airflow...test; Type B and Type BE supplied-air respirators; minimum requirements...inches) of water-column height to air drawn at the flow rate of 85 liters (3 cubic...

2013-10-01

425

Using CFD Capabilities of CONTAM 3.0 for Simulating Airflow and Contaminant Transport In and Around Buildings  

E-print Network

a single CFD zone within a CONTAM network model has also been implemented. This enables the detailed a generic residential house model to show how these two new CFD features enhance the existing CONTAM1 Using CFD Capabilities of CONTAM 3.0 for Simulating Airflow and Contaminant Transport

Chen, Qingyan "Yan"

426

Using CFD Capabilities of CONTAM 3.0 for Simulating Airflow and Contaminant Transport in and around Buildings  

Microsoft Academic Search

CONTAM is a multizone building airflow and contaminant transport computer program often used for ventilation and indoor air quality analysis. The program was recently enhanced to incorporate CFD capabilities for both outdoor and indoor environmental analysis. This paper introduces the CFD features implemented within the most recent version, CONTAM 3.0. The outdoor or external CFD link predicts wind pressure coefficients

Liangzhu Leon Wang; W. Stuart Dols; Qingyan Chen

2010-01-01

427

Influence of porous media, airflow rate, and air channel spacing on benzene NAPL removal during air sparging  

SciTech Connect

To study the effects of porous media type, airflow rate, and air channel spacing on NAPL removal, air sparging of a benzene NAPL was performed in a lab-scale reactor with two isolated vertical air channels on either side of the NAPL. Experimental conditions included three discrete air channel distances, three types of saturated porous media, and five airflow rates. Benzene NAPL removal efficiency was shown to increase from 7.5% to 16.2% with increasing porous media mean particle size over the 168 h of operation. Initial change in the airflow rate had an effect on contaminant removal rate, but further change in the airflow rate had little effect. Benzene NAPL removal efficiency was shown to decrease with increasing channel spacing, but the mere presence of air channels was shown to suppress lateral contaminant migration. Benzene removal efficiency was shown to be highly correlated with the mean particle diameter, the square root of the uniformity coefficient, and the inverse of the square of the distance between the NAPL and the air channel.

Rogers, S.W.; Ong, S.K.

2000-03-01

428

Measurement of airflow velocity in half-scale car model using PIV - In case of foot-mode air conditioning  

Microsoft Academic Search

SUMMARY Compared to architecture, automobiles are somewhat more susceptible to external thermal influences. Therefore, keeping the internal atmosphere comfortable is extremely important from the standpoint of the passengers' health and comfort. In the present study, a half-scale car model is created by the Society of Automotive Engineers of Japan (JSAE) to clarify the airflow properties inside the car using particle

Hiroki Takahashi; Hideaki Nagano; Masahiro Terada; Shinsuke Kato

429

Tracer Gas Measurement of Airflow Rates in Spaces with Several Air-Handling Units, Recirculation, or Large Time Constants  

Microsoft Academic Search

Methods to measure airflow rates using tracer gas in single air-handling units are well known. In some buildings, however, in particular in Singapore, rooms are often ventilated with two or more units and present large recirculation rates. Large recirculation ratios homogenize the concentrations, so concentrations in supply and extract ducts are close to each other. In addition, these spaces often

C.-A. Roulet; M. S. Zuraimi; S. C. Sekhar; K. W. Tham

2006-01-01

430

Experimental and Numerical Study on Effects of Airflow and Aqueous Ammonium Solution Temperature on Ammonia Mass Transfer Coefficient  

Microsoft Academic Search

This paper reports the results of an investigation, based on fundamental fluid dynamics and mass transfer theory, carried out to obtain a general understanding of ammonia mass transfer from an emission surface. The effects of airflow and aqueous ammonium solution temperature on ammonia mass transfer are investigated by using computational fluid dynamics (CFD) modeling and by a mechanism modeling using

Li Rong; Peter V. Nielsen; Guoqiang Zhang; Glauber Mariano; Ani Torres; Wellington Jesus; Walter Nakaema; Maria Jorge; Rauda Mariani; Klara Slezakova; Dionsia Castro; Maria Pereira; Simone Morais; Cristina Delerue-Matos; Maria Alvim-Ferraz; Catherine Barton; Charles Zarzecki; Mark Russell; Marjaleena Aatamila; Pia Verkasalo; Maarit Korhonen; Marja Viluksela; Kari Pasanen; Pekka Tiittanen; Aino Nevalainen; Yi-Ming Kuo; Juu-En Chang; Kun-Yu Chang; Chih-C. Chao; Yeu-Juin Tuan; Guo-Ping Chang-Chien; Yongping Li; Guohe Huang; Arhontoula Chatzilazarou; Evangelos Katsoyannos; Olga Gortzi; Stavros Lalas; Yiannis Paraskevopoulos; Euthalia Dourtoglou; John Tsaknis; Tarek Abichou; Jeremy Clark; Sze Tan; Jeffery Chanton; Gary Hater; Roger Green; Doug Goldsmith; Morton Barlaz; Nathan Swan; Gang Sun; Huiqing Guo; Jonathan Peterson; Zhengmin Qian; Hung-Mo Lin; Walter Stewart; Nirav Shah; Linli Kong; Fen Xu; Denjin Zhou; Zhicao Zhu; Qingci He; Shengwen Liang; Weiqing Chen; Chungsying Lu; Hsunling Bai; Fengsheng Su; Wenfa Chen; Jyh Hwang; Hsiu-Hsia Lee; Judith Chow; John Watson; Douglas Lowenthal; Lung-Wen Chen; Nehzat Motallebi

2010-01-01

431

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

PubMed Central

Cough airflow dynamics have been previously studied using a variety of experimental methods. In this study, real-time, non-invasive shadowgraph imaging was applied to obtain additional analyses of cough airflows produced by healthy volunteers. Twenty healthy volunteers (10 women, mean age 32.212.9 years; 10 men, mean age 25.32.5 years) were asked to cough freely, then into their sleeves (as per current US CDC recommendations) in this study to analyze cough airflow dynamics. For the 10 females (cases 110), their maximum detectable cough propagation distances ranged from 0.160.55 m, with maximum derived velocities of 2.25.0 m/s, and their maximum detectable 2-D projected areas ranged from 0.0100.11 m2, with maximum derived expansion rates of 0.150.55 m2/s. For the 10 males (cases 1120), their maximum detectable cough propagation distances ranged from 0.310.64 m, with maximum derived velocities of 3.214 m/s, and their maximum detectable 2-D projected areas ranged from 0.040.14 m2, with maximum derived expansion rates of 0.251.4 m2/s. These peak velocities were measured when the visibility of the exhaled airflows was optimal and compare favorably with those reported previously using other methods, and may be seen as a validation of these previous approaches in a more natural setting. However, the propagation distances can only represent a lower limit due to the inability of the shadowgraph method to visualize these cough airflows once their temperature cools to that of the ambient air, which is an important limitation of this methodology. The qualitative high-speed video footage of these volunteers coughing into their sleeves demonstrates that although this method rarely completely blocks the cough airflow, it decelerates, splits and redirects the airflow, eventually reducing its propagation. The effectiveness of this intervention depends on optimum positioning of the arm over the nose and mouth during coughing, though unsightly stains on sleeves may make it unacceptable to some. PMID:22536332

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

2012-01-01

432

Unsteady laryngeal airflow simulations of the intra-glottal vortical structures  

PubMed Central

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

433

QUANTITATIVE CT ANALYSIS, AIRFLOW OBSTRUCTION AND LUNG CANCER IN THE PITTSBURGH LUNG SCREENING STUDY  

PubMed Central

Background To study the relationship between emphysema, airflow obstruction and lung cancer in a high risk population we performed quantitative analysis of screening computed tomography (CT) scans. Methods Subjects completed questionnaires, spirometry and low-dose helical chest CT. Analyses compared cases and controls according to automated quantitative analysis of lung parenchyma and airways measures. Results Our case-control study of 117 matched pairs of lung cancer cases and controls did not reveal any airway or lung parenchymal findings on quantitative analysis of screening CT scans that were associated with increased lung cancer risk. Airway measures including wall area %, lumen perimeter, lumen area and average wall HU, and parenchymal measures including lung fraction < ?910 Hounsfield Units (HU), were not statistically different between cases and controls. Conclusions The relationship between visual assessment of emphysema and increased lung cancer risk could not be verified by quantitative analysis of low-dose screening CT scans in a high risk tobacco exposed population. PMID:21610523

Wilson, David O; Leader, Joseph K; Fuhrman, Carl R; Reilly, John J; Sciurba, Frank C.; Weissfeld, Joel L

2011-01-01

434

Suppression of Soot Formation and Shapes of Laminar Jet Diffusion Flames  

NASA Technical Reports Server (NTRS)

Laminar nonpremixed (diffusion) flames are of interest because they provide model flame systems that are far more tractable for analysis and experiments than practical turbulent flames. In addition, many properties of laminar diffusion flames are directly relevant to turbulent diffusion flames using laminar flamelet concepts. Finally, laminar diffusion flame shapes have been of interest since the classical study of Burke and Schumann because they involve a simple nonintrusive measurement that is convenient for evaluating flame shape predictions. Motivated by these observations, the shapes of round hydrocarbon-fueled laminar jet diffusion flames were considered, emphasizing conditions where effects of buoyancy are small because most practical flames are not buoyant. Earlier studies of shapes of hydrocarbon-fueled nonbuoyant laminar jet diffusion flames considered combustion in still air and have shown that flames at the laminar smoke point are roughly twice as long as corresponding soot-free (blue) flames and have developed simple ways to estimate their shapes. Corresponding studies of hydrocarbon-fueled weakly-buoyant laminar jet diffusion flames in coflowing air have also been reported. These studies were limited to soot-containing flames at laminar smoke point conditions and also developed simple ways to estimate their shapes but the behavior of corresponding soot-free flames has not been addressed. This is unfortunate because ways of selecting flame flow properties to reduce soot concentrations are of great interest; in addition, soot-free flames are fundamentally important because they are much more computationally tractable than corresponding soot-containing flames. Thus, the objectives of the present investigation were to observe the shapes of weakly-buoyant laminar jet diffusion flames at both soot-free and smoke point conditions and to use the results to evaluate simplified flame shape models. The present discussion is brief.

Xu, F.; Dai, Z.; Faeth, G. M.

2001-01-01

435

Gravity-induced reorientation of the interface between two liquids of different densities flowing laminarly through a microchannel  

E-print Network

These applications all rely on multistream laminar flow, which enables control over local chemical composition within­liquid interface between fluids of different densities flowing side-by-side in pressure-driven laminar flow growing number of microchemical systems that utilize multistream laminar flow for performing spatially

Kenis, Paul J. A.

436

An investigation of surfactant and enzyme formulations for the alleviation of insect contamination on Hybrid Laminar Flow Control (HLFC) surfaces  

Microsoft Academic Search

Hybrid Laminar Flow Control (HLFC) is an active drag reduction technique that requires a small amount of air to be sucked through a porous skin surface, thus stabilising the boundary layer and permitting extended laminar flow along the wing surface. Contamination of the laminar flow surfaces by insects is a major concern for this technology. An overview of insect contamination

D O'Donoghue; T. M Young; J. T Pembroke; T. F O'Dwyer

2002-01-01

437

Phonation threshold pressure estimation using electroglottography in an airflow redirection system  

PubMed Central

Objectives/Hypothesis The present study proposed to estimate phonation threshold pressure (PTP) non-invasively using airflow redirection into a pneumatic capacitance system. Study Design Prospective study. Methods Subjects phonated into the device, which interrupts airflow mechanically and redirects the flow into a pneumatic capacitor. Five interruptions were effected per trial. PTP was estimated as the difference between subglottal pressure (SGP) and transglottal pressure at phonation offset. The novel method was tested for consistency in 20 normal human subjects at low (75 dB) and high (85 dB) sound pressure levels. The device was tested for validity on a tracheotomy patient. Results Mean SGP was 9.02 3.27 cm H2O and mean PTP was 3.68 1.41 cm H2O. Intrasubject coefficient of variation, a measure of intrasubject consistency, was 0.33 0.23. Statistically significant differences existed between the means of SGP but not PTP at 75 dB and 85 dB. The correlation coefficient between accepted and experimental SGP in a tracheotomy patient was 0.947 (p<0.001). Conclusions Measurements corresponded well to previously reported values, and intrasubject variability was low, indicating the device was consistent. Testing on a tracheotomy patient demonstrated validity. More research is needed to determine the sensitivity and specificity of the device in differentiating between normal and pathological voices. This device may have clinical application as a non-invasive and reliable method of estimating PTP and indicating that laryngeal health is likely abnormal. PMID:19688842

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

2009-01-01

438

Respiratory-triggered electron beam CT with integrated spirometry for evaluation of dynamic airflow  

NASA Astrophysics Data System (ADS)

The purpose is to integrate time-attenuation curves from Electron-Beam CT with flow-time curves from spirometry in the analysis of airflow obstruction. A pressure-sensitive switch was connected between a spirometer mouthpiece and a modified EBCT scanner keyboard. The onset of expiratory flow causes pressure changes which simultaneously trigger EBCT and spirometric acquisitions. Subjects performed a forced expiratory maneuver, during which EBCT images of the lung were obtained every 500 ms using 130 kVp, 630 mA, 100 ms scan time and 3 mm collimation. From EBCT images, time-attenuation curves were generated for each of three zones (non-dependent, middle and dependent lung) using small ROIs (12 mm2) placed over approximately the same anatomic regions of lung. The resulting time- attenuation curves and flow-time curves were then superimposed. Two normal subjects, two subjects with emphysema and three lung transplant subjects have been studied to date. In normal subjects, lung attenuation increases steadily during the first 4 - 6 seconds of expiration, whereas in patients with emphysema, lung attenuation was relatively constant over the course of expiration. Lung transplant subjects show both of these characteristics--normal characteristics for the transplant lung and emphysematous characteristics for the native lung. Lung transplant subjects may also demonstrate some dynamics between transplant and diseased lung. Respiratory-triggered EBCT can be used to simultaneously acquire time-attenuation and flow-time data. This has been used to characterize dynamic airflow patterns in patients with respiratory disease.

McNitt-Gray, Michael F.; Goldin, Jonathan G.; Welch, Mike; Szold, Oded; Levine, Michael; Aberle, Denise R.

1996-04-01

439

Peripheral resistance: a link between global airflow obstruction and regional ventilation distribution.  

PubMed

Airflow obstruction and heterogeneities in airway constriction and ventilation distribution are well-described prominent features of asthma. However, the mechanistic link between these global and regional features has not been well defined. We speculate that peripheral airway resistance (R(p)) may provide such a link. Structural and functional parameters are estimated from PET and HRCT images of asthmatic (AS) and nonasthmatic (NA) subjects measured at baseline (BASE) and post-methacholine challenge (POST). Conductances of 35 anatomically defined proximal airways are estimated from airway geometry obtained from high-resolution computed tomography (HRCT) images. Compliances of sublobar regions subtended by 19 most distal airways are estimated from changes in regional gas volume between two lung volumes. Specific ventilations (sV) of these sublobar regions are evaluated from 13NN-washout PET scans. For each pathway connecting the trachea to sublobar region, values of R(p) required to explain the sV distribution and global airflow obstruction are computed. Results show that R(p) is highly heterogeneous within each subject, but has average values consistent with global values in the literature. The contribution of R(p) to total pathway resistance (R(T)) increased substantially for POST (P < 0.0001). The fraction R(p)/R(T) was higher in AS than NA at POST (P < 0.0001) but similar at BASE (range: 0.960-0.997, median: 0.990). For POST, R(p)/R(T) range was 0.979-0.999 (NA) and 0.981-0.995 (AS). This approach allows for estimations of peripheral airway resistance within anatomically defined sublobar regions in vivo human lungs and may be used to evaluate peripheral effects of therapy in a subject specific manner. PMID:23123354

Wongviriyawong, C; Harris, R S; Greenblatt, E; Winkler, T; Venegas, J G

2013-02-15

440

Response characteristics for thermal and pressure devices commonly used for monitoring nasal and oral airflow during sleep studies.  

PubMed

We examined thermocouple and pressure cannulae responses to oral and nasal airflow using a polyester model of a human face, with patent nasal and oral orifices instrumented with a dual thermocouple (F-ONT2A, Grass) or a dual cannula (0588, Braebon) pressure transducer ( 10 cm H2O, Celesco) system. Tidal airflow was generated using a dual compartment facemask with pneumotachographs (Fleisch 2) connected to the model orifices. During nasal breathing: thermocouple amplitude = 0.38 Ln [pneumotachograph amplitude] + 1.31 and pressure cannula amplitude = 0.93 [pneumotachograph amplitude](2.15); during oral breathing: thermocouple amplitude = 0.44 Ln [pneumotachograph amplitude] + 1.07 and pressure cannula amplitude = 0.33 [pneumotachograph amplitude](1.72); (all range ? 0.1-? 4.0 L s(-1); r(2) > 0.7). For pneumotachograph amplitudes <1 L s(-1) (linear model) change in thermocouple amplitude/unit change in pneumotachograph amplitude was similar for nasal and oral airflow, whereas nasal pressure cannula amplitude/unit change in pneumotachograph amplitude was almost four times that for oral. Increasing oral orifice area from 0.33 cm(2) to 2.15 cm(2) increased oral thermocouple amplitude/unit change in pneumotachograph amplitude by ? 58% but decreased pressure cannula amplitude/unit change in pneumotachograph amplitude by 49%. For pneumotachograph amplitudes up to 1 L s(-1), alterations in inspiratory/expiratory ratios or total respiratory time did not affect the sensitivity of either nasal or oral pressure cannulae or the nasal thermocouple, but the oral thermocouple sensitivity was influenced by respiratory cycle time. Different nasal and oral responses influence the ability of these systems to quantitatively assess nasal and oral airflow and oro-nasal airflow partitioning. PMID:24557006

Gehring, J M; Cho, J-G; Wheatley, J R; Amis, T C

2014-03-01

441

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

442

Nonlinear transient growth and detecting the laminar-turbulent boundary  

NASA Astrophysics Data System (ADS)

The area of transition to turbulence has experienced a spurt of activity recently in wall-bounded shear flows where transition is triggered by finite amplitude disturbances. This has been stimulated by the discovery of new solutions to the governing equations which are disconnected from the steady unidirectional ``base'' flow in, for example, pipe flow and plane Couette flow. Understanding how all this new (nonlinear) work fits together with transient growth ideas which focus on linear mechanisms based around the base state presents an interesting challenge. In this talk, we attempt to bridge the gap from linear optimals to the (very nonlinear) laminar-turbulent boundary in phase space which determines whether a given disturbance will trigger turbulence or not.

Kerswell, Rich; Pringle, Chris

2009-11-01

443

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

444

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

445

GASP cloud encounter statistics - Implications for laminar flow control flight  

NASA Technical Reports Server (NTRS)

The cloud observation archive from the NASA Global Atmospheric Sampling Program (GASP) is analyzed in order to derive the probability of cloud encounter at altitudes normally flown by commercial airliners, for application to a determination of the feasability of Laminar Flow Control (LFC) on long-range routes. The probability of cloud encounter is found to vary significantly with season. Several meteorological circulation features are apparent in the latitudinal distribution of cloud cover. The cloud encounter data are shown to be consistent with the classical midlatitude cyclone model with more clouds encountered in highs than in lows. Aircraft measurements of route-averaged time-in-clouds fit a gamma probability distribution model which is applied to estimate the probability of extended cloud encounter, and the associated loss of LFC effectiveness along seven high-density routes. The probability is demonstrated to be low.

Jasperson, W. H.; Nastrom, G. D.; Davis, R. E.; Holdeman, J. D.

1984-01-01

446

Turbulence and Laminar Structures: Can They Co-Exist?  

NASA Technical Reports Server (NTRS)

Schwarzschild first suggested that the laminar structures observed in the high Reynolds number Re = UL/nu approx. = (10(exp 12)) solar photosphere are the result of turbulence rather than a proof of its absence. He reasoned that since turbulence generates large turbulent viscosities nu(sub t) much greater than nu, the "effective" Reynolds number Re = UL/nu(sub t) approx. = O(1). Schwarzschild's argument is, however, incomplete for it assumes that the entire role of the non-linear interactions is to "enhance" viscosity. While this is not true in general, we present a proof of how and why it may occur, thus completing Schwarzschild's argument. We further discuss the fact that the same model non-local turbulence models have been shown to reproduce LES data for a variety of flows pertaining to astrophysics, geophysics and laboratory situations (at a fraction of the time).

Canuto, V. M.

2000-01-01

447

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

448

Enhanced photocatalysis in a pilot laminar falling film slurry reactor  

SciTech Connect

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

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

1999-09-01

449

Laminar mixed convection in a radially rotating semiporous channel  

NASA Astrophysics Data System (ADS)

Flow and heat transfer characteristics of laminar mixed convection in a radially rotating semiporous channel with a uniform transpiration and a constant wall temperature gradient are examined. The buoyancy effect is taken into account through the consideration of the density variation in the centrifugal force term. A similarity solution is sought; and then the effects of rotation, transpiration and wall heating on the velocity and temperature fields, the skin friction, the pressure drop and the heat transfer rate are investigated by the solution of the two coupled quasilinear equations. Flow-reversal phenomena can be caused by the transpiration and buoyancy effects. Two modes of flow reversal and the related critical conditions are studied in detail to explore the mechanism of the mixed convection.

Soong, C. Y.; Hwang, G. J.

1990-09-01

450

Laminar boundary-layer flow of non-Newtonian fluid  

NASA Technical Reports Server (NTRS)

A solution for the two-dimensional and axisymmetric laminar boundary-layer momentum equation of power-law non-Newtonian fluid is presented. The analysis makes use of the Merk-Chao series solution method originally devised for the flow of Newtonian fluid. The universal functions for the leading term in the series are tabulated for n from 0.2 to 2. Equations governing the universal functions associated with the second and the third terms are provided. The solution together with either Lighthill's formula or Chao's formula constitutes a simple yet general procedure for the calculation of wall shear and surface heat transfer rate. The theory was applied to flows over a circular cylinder and a sphere and the results compared with published data.

Lin, F. N.; Chern, S. Y.

1979-01-01

451

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

452

Flight Tests of a Supersonic Natural Laminar Flow Airfoil  

NASA Technical Reports Server (NTRS)

IR thermography was used to characterize the transition front on a S-NLF test article at chord Reynolds numbers in excess of 30 million Changes in transition due to Mach number, Reynolds number, and surface roughness were investigated - Regions of laminar flow in excess of 80% chord at chord Reynolds numbers greater than 14 million IR thermography clearly showed the transition front and other flow features such as shock waves impinging upon the surface A series of parallel oblique shocks, of yet unknown origin, were found to cause premature transition at higher Reynolds numbers. NASA has a current goal to eliminate barriers to the development of practical supersonic transport aircraft Drag reduction through the use of supersonic natural laminar flow (S-NLF) is currently being explored as a means of increasing aerodynamic efficiency - Tradeoffs work best for business jet class at M<2 Conventional high-speed designs minimize inviscid drag at the expense of viscous drag - Existence of strong spanwise pressure gradient leads to crossflow (CF) while adverse chordwise pressure gradients amplifies and Tollmien-Schlichting (TS) instabilities Aerion Corporation has patented a S-NLF wing design (US Patent No. 5322242) - Low sweep to control CF - dp/dx < 0 on both wing surfaces to stabilize TS - Thin wing with sharp leading edge to minimize wave drag increase due to reduction in sweep NASA and Aerion have partnered to study S-NLF since 1999 Series of S-NLF experiments flown on the NASA F-15B research test bed airplane Infrared (IR) thermography used to characterize transition - Non-intrusive, global, good spatial resolution - Captures significant flow features well

Frederick, Mike; Banks, Dan; Garzon, Andres; Matisheck, Jason

2014-01-01

453

Periodic and Chaotic Modes in Premixed Laminar Flames  

NASA Astrophysics Data System (ADS)

In this thesis, we report the discoveries of many periodic and chaotic modes of laminar premixed flames on porous plug burners. This report is the first confirmation of predictions of a number of recent theoretical studies on the dynamics of premixed flames. The experimental innovations and techniques presented in section 3.6 are at the heart of the discoveries of these dynamical modes. In our experiments, a flame front is stabilized on a porous plug burner enclosed within a pyrex chamber. By varying the total flow rate, the stoichiometry of the combustible mixture, and the chamber pressure, we discovered many periodic and chaotic modes. We show that different fuels and/or oxidizers as well as the symmetries of the system can affect the dynamics of the flame front. Experimental evidence is presented that shows that laminar premixed flames exhibit low-dimensional, deterministic chaos. The largest Liapunov exponent and the pointwise dimension calculations are used to confirm that chaos exists in certain regions of parameter space. We also describe a power spectrum technique that can be used to identify deterministic dynamics in real time. With the help of a spectrum analyzer, an experimentalist can map the dynamics (simple and complex) of the system under investigation in a relatively short time. As far as we know, this is the first time that nonlinear dynamics techniques are used to analyze experimental data from combustion. All the nonperiodic modes that we have discovered exhibit low-dimensional deterministic chaos and we believe that this result is a general one for propagating fronts. The implication of our work is that such nonperiodic states can be described by a tractable set of ordinary differential equations.

El-Hamdi, Mohamed Abbes

1991-06-01

454

Forced response of a laminar shock-induced separation bubble  

NASA Astrophysics Data System (ADS)

The source of unsteadiness in shock-wave/boundary-layer interactions is currently disputed. This paper considers a two-dimensional separation bubble induced by an oblique shock wave interacting with a laminar boundary layer at a free-stream Mach number of 1.5. The global response of the separated region to white noise forcing is analyzed for different interaction strengths, which generate small and large separation bubbles. Forcing location and amplitude effects have been examined. For both interaction strengths and for forcing both upstream and inside the bubble, the wall-pressure spectra downstream of the separation show a high-frequency peak that is demonstrated to be a Kelvin-Helmholtz instability. A low-frequency response at the separation point is also found when the separation bubble is only forced internally, therefore with a disturbance-free upstream boundary layer. For low-amplitude internal forcing, the low-frequency response at the separation point and downstream of the bubble is linear. However, when forced upstream the low-frequency unsteadiness of the large separation bubble is found to be driven by nonlinearities coming from the downstream shedding. The same nonlinear behavior is found when the separation bubble is internally forced over a narrow band around the shedding frequency, without low-frequency disturbances. This analysis for a laminar interaction is used to interpret the low-frequency unsteadiness found at the foot of the shock of turbulent interactions. Here, the low-frequency unsteadiness occurs in the absence of upstream disturbances and a linear relationship is found between the internal forcing and the response near the separation point. When low-frequencies are not present in the forcing they are generated from weak nonlinearities of the shear-layer instability modes.

Sansica, A.; Sandham, N. D.; Hu, Z.

2014-09-01

455

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

SciTech Connect

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

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

2008-09-15

456

The effect of glycine-powder airflow and hand instrumentation on peri-implant soft tissues: a split-mouth pilot study.  

PubMed

Fifteen edentulous patients with overdentures supported by two implants in the mandibular canine regions received periodontal therapy using both hand instrumentation with Teflon curettes and a glycine-based airflow system. Periodontal probing depth (PPD), bleeding on probing (BOP), and bacterial content (BC) within the gingival sulcus were analyzed. A significant effect modification of the glycine airflow with respect to time was found for PPD (P = .01), BOP (P < .001), and BC (P = .004), which were treated as ordered categorical variables. Glycine airflow may be more effective than Teflon curettes for the maintenance of periimplant soft tissues. PMID:23342332

Mussano, Federico; Rovasio, Stefania; Schierano, Gianmario; Baldi, Ileana; Carossa, Stefano

2013-01-01

457

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

458

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

459

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

460

Hybrid laminar flow control tests in the Boeing Research Wind Tunnel  

NASA Technical Reports Server (NTRS)

The hybrid laminar flow control (HLFC) concept has undergone wind tunnel testing at near full-scale Reynolds number on an infinite wing of 30-deg sweep on which boundary-layer suction was furnished over the first 20 percent of chord of the upper surface. Depending on the external pressure distribution, the HLFC extended the laminarity of the boundary layer as far back as 45 percent of chord; this corresponds to a transition Reynolds number of about 11 million. The maximum chordwise extent of laminar run was found to be insensitive to the suction level over a wide range.

Parikh, P. G.; Lund, D. W.; George-Falvy, D.; Nagel, A. L.

1990-01-01

461

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

462

Aircraft energy efficiency laminar flow control glove flight conceptual design study  

NASA Technical Reports Server (NTRS)

A laminar flow control glove applied to the wing of a short to medium range jet transport with aft mounted engines was designed. A slotted aluminum glove concept and a woven stainless steel mesh porous glove concept suction surfaces were studied. The laminar flow control glove and a dummy glove with a modified supercritical airfoil, ducting, modified wing leading and trailing edges, modified flaps, and an LFC trim tab were applied to the wing after slot spacing suction parameters, and compression power were determined. The results show that a laminar flow control glove can be applied to the wing of a jet transport with an appropriate suction system installed.

Wright, A. S.

1979-01-01

463

Visualization of the Airflow around a Life-Sized, Heated, Breathing Mannequin at Ultralow Windspeeds  

PubMed Central

During the past two decades, there has been considerable progress in developing particle size-selective criteria for aerosol sampling and exposure assessment that relate more realistically to actual human exposures than previously. An important aspect has been the aspiration efficiencythe inhalabilitywith which particles enter through the nose and mouth of aerosol-exposed individuals during breathing. Most of the reported experiments to determine inhalability have been conducted in wind tunnels with life-sized, breathing mannequins, for windspeeds from 0.5 m s?1 and above. A few experiments have been reported for calm air. However, nothing has been reported for the intermediate range from 0.5 m s?1 downward, and it so happensas we now knowthat this corresponds to most industrial workplaces. The research described in this paper represents a first step toward filling this knowledge gap. It focuses on identifying the features of the airflow near the mannequin at such low windspeeds that might have important influences on the nature of particle transport, and hence on inhalability, and eventually the performances of personal aerosol samplers mounted in the breathing zone. We have carried out flow visualization experiments for the realistic range of windspeeds indicated, investigating specifically the effect of the air jet released into the freestream during expiration and the effect of the upward-moving boundary layer near the body associated with the buoyancy of air in that region as a result of heat received from the warm body. We set out to identify the combinations of conditionsexternal windspeed, breathing mode (nose versus mouth breathing), breathing rate and body temperaturewhere such factors need to be taken into account. We developed an experimental system that allowed the visualization of smoke traces, providing very good observation of how the flow was modified as conditions changed. From inspection of a large number of moving pictures, we developed a matrix of regimescategorized by windspeed and breathing ratewhere the effect of the expired air is sufficient to permanently and seriously destabilize the airflow approaching the mannequin. It was found that the effect of body temperature was minimal. Such results will be important in the interpretation of current and future inhalability experiments carried out at realistic low windspeeds. PMID:18497432

Schmees, Darrah K.; Wu, Yi-Hsuan; Vincent, James H.

2008-01-01