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Sample records for laminar airflow tla

  1. Economic analysis of temperature-controlled laminar airflow (TLA) for the treatment of patients with severe persistent allergic asthma

    PubMed Central

    Brazier, Peter; Schauer, Uwe; Hamelmann, Eckard; Holmes, Steve; Pritchard, Clive; Warner, John O

    2016-01-01

    Introduction Chronic asthma is a significant burden for individual sufferers, adversely impacting their quality of working and social life, as well as being a major cost to the National Health Service (NHS). Temperature-controlled laminar airflow (TLA) therapy provides asthma patients at BTS/SIGN step 4/5 an add-on treatment option that is non-invasive and has been shown in clinical studies to improve quality of life for patients with poorly controlled allergic asthma. The objective of this study was to quantify the cost-effectiveness of TLA (Airsonett AB) technology as an add-on to standard asthma management drug therapy in the UK. Methods The main performance measure of interest is the incremental cost per quality-adjusted life year (QALY) for patients using TLA in addition to usual care versus usual care alone. The incremental cost of TLA use is based on an observational clinical study monitoring the incidence of exacerbations with treatment valued using NHS cost data. The clinical effectiveness, used to derive the incremental QALY data, is based on a randomised double-blind placebo-controlled clinical trial comprising participants with an equivalent asthma condition. Results For a clinical cohort of asthma patients as a whole, the incremental cost-effectiveness ratio (ICER) is £8998 per QALY gained, that is, within the £20 000/QALY cost-effectiveness benchmark used by the National Institute for Health and Care Excellence (NICE). Sensitivity analysis indicates that ICER values range from £18 883/QALY for the least severe patients through to TLA being dominant, that is, cost saving as well as improving quality of life, for individuals with the most severe and poorly controlled asthma. Conclusions Based on our results, Airsonett TLA is a cost-effective addition to treatment options for stage 4/5 patients. For high-risk individuals with more severe and less well controlled asthma, the use of TLA therapy to reduce incidence of hospitalisation would be a cost

  2. Improved asthma control in patients with severe, persistent allergic asthma after 12 months of nightly temperature-controlled laminar airflow: an observational study with retrospective comparisons

    PubMed Central

    Schauer, Uwe; Bergmann, Karl-Christian; Gerstlauer, Michael; Lehmann, Sylvia; Gappa, Monika; Brenneken, Amelie; Schulz, Christian; Ahrens, Peter; Schreiber, Jens; Wittmann, Michael; Hamelmann, Eckard

    2015-01-01

    Introduction Continuous or episodic allergen exposure is a major risk factor of frequent symptoms and exacerbations for patients with allergic asthma. It has been shown that temperature-controlled laminar airflow (TLA) significantly reduced allergen exposure and airway inflammation and improved quality of life of patients with poorly controlled allergic asthma. Objective The objective was to evaluate the effects of nighttime TLA when used during real-life conditions for 12 consecutive months in addition to the patients’ regular medication. Methods This multicenter, pre- and postretrospective observational study included patients with inadequately controlled moderate-to-severe allergic asthma who received add-on treatment with TLA for 12 consecutive months. Data on medication use, asthma control, asthma symptoms, lung function, use of hospital resources, and exacerbations were collected after 4 and 12 months and compared with corresponding data collected retrospectively from medical records during the year prior to inclusion in the study. Results Data from 30 patients (mean age 28; range 8–70) completing 4 months and 27 patients completing 12 months of TLA use are presented. The mean number of exacerbations was reduced from 3.6 to 1.3 (p<0.0001), and the ratio of asthma-related emergency room visits or hospitalizations diminished from 72.4 to 23.3% (p=0.001) or from 44.8 to 20.0% (p<0.05), respectively, after 12 months of TLA use. The Asthma Control Test index increased from 14.1 to 18.5 (p<0.0001). After 4 months of TLA use, clear improvements can be shown for most variables in line with the data collected after 12 months. Conclusions The addition of TLA to the patients’ regular medication significantly reduced exacerbations, asthma symptoms, and the utilization of hospital resources. The data support that TLA may be an important new non-pharmacological approach in the management of poorly controlled allergic asthma. PMID:26557252

  3. Effect of a novel temperature-controlled laminar airflow device on personal breathing zone aeroallergen exposure.

    PubMed

    Gore, R B; Boyle, R J; Gore, C; Custovic, A; Hanna, H; Svensson, P; Warner, J O

    2015-02-01

    Temperature-controlled laminar airflow improves symptoms in atopic asthmatics, but its effects on personal allergen exposure are unknown. We aimed to evaluate its effects on personal cat allergen and particulate exposures in a simulated bedroom environment. Five healthy volunteers lay under an active and an inactive temperature-controlled laminar airflow device for 175 min, in a simulated bedroom containing bedding from a cat owner. Total airborne particles (≥0.5 - ≥10 μm diameter) were quantified with a laser particle counter. Airborne allergen was sampled with Institute of Occupational Medicine filters. Inhaled exposure was sampled with nasal air samplers. Allergen-containing particles were quantified by immunoassay. Treatment reduced total airborne particles (>0.5 μm diameter) by >99% (P < 0.001) and reduced airborne allergen concentration within the breathing zone (ratio of median counts = 30, P = 0.043). Treatment reduced inhaled allergen (ratio of median counts = 7, P = 0.043). Treatment was not associated with a change in airborne allergen concentration outside of the breathing zone (P = 0.160). Temperature-controlled laminar airflow treatment of individuals in an allergen-rich experimental environment results in significant reductions in breathing zone allergenic and non-allergenic particle exposure, and in inhaled cat allergen exposure. These findings may explain the clinical benefits of temperature-controlled laminar airflow. PMID:24750266

  4. Microbiological Studies on the Performance of a Laminar Airflow Biological Cabinet

    PubMed Central

    Mcdade, Joseph J.; Sabel, Fred L.; Akers, Ronald L.; Walker, Robert J.

    1968-01-01

    Engineering and microbiological tests indicated that a typical, commercial laminar airflow cabinet was not effective in providing either product protection or agent containment. The cabinet was modified and tested through a series of alternate configurations to establish a set of design criteria. A mock-up cabinet was developed from these design criteria. The mock-up unit was evaluated for efficiency in providing both product protection and agent containment. In these evaluations, challenge methods were developed to simulate normal, in-use laboratory operations. Controlled bacterial or viral aerosol challenges were used at higher than normal levels to provide stringent test conditions. Test results indicated that the mock-up unit was considerably better in preventing agent penetration (0.1 to 0.2 particles per 100 ft3 of air) than the commercial cabinet (5 to 6 particles per 100 ft3 of air) during product protection tests. Similarly, agent containment was considerably better in the new cabinet (particle escape of 2 to 3 per 100 ft3 of air at only one of the five test sites) than in the commercial cabinet (particle escape of 2 to 14 per 100 ft3 of air at three of the five test sites). PMID:4874462

  5. Sequence types of Staphylococcus epidermidis associated with prosthetic joint infections are not present in the laminar airflow during prosthetic joint surgery.

    PubMed

    Månsson, Emeli; Hellmark, Bengt; Sundqvist, Martin; Söderquist, Bo

    2015-07-01

    Molecular characterization of Staphylococcus epidermidis isolates from prosthetic joint infections (PJIs) has demonstrated a predominance of healthcare-associated multi-drug resistant sequence types (ST2 and ST215). How, and when, patients acquire these nosocomial STs is not known. The aim was to investigate if sequence types of S. epidermidis associated with PJIs are found in the air during prosthetic joint surgery. Air sampling was undertaken during 17 hip/knee arthroplasties performed in operating theaters equipped with mobile laminar airflow units in a 500-bed hospital in central Sweden. Species identification was performed using MALDI-TOF MS and 16S rRNA gene analysis. Isolates identified as S. epidermidis were further characterized by MLST and antibiotic susceptibility testing. Seven hundred and thirty-five isolates were available for species identification. Micrococcus spp. (n = 303) and coagulase-negative staphylococci (n = 217) constituted the majority of the isolates. Thirty-two isolates of S. epidermidis were found. S. epidermidis isolates demonstrated a high level of allelic diversity with 18 different sequence types, but neither ST2 nor ST215 was found. Commensals with low pathogenic potential dominated among the airborne microorganisms in the operating field during prosthetic joint surgery. Nosocomial sequence types of S. epidermidis associated with PJIs were not found, and other routes of inoculation are therefore of interest in future studies. PMID:25951935

  6. Timeline Analysis Program (TLA-1)

    NASA Technical Reports Server (NTRS)

    Miller, K. H.

    1976-01-01

    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.

  7. Timeline analysis program (TLA-1), appendices

    NASA Technical Reports Server (NTRS)

    Miller, K. H.

    1976-01-01

    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.

  8. F-16XL Supersonic Laminar Flow Test Flight

    NASA Video Gallery

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

  9. Airflow resistance in soybean

    NASA Astrophysics Data System (ADS)

    Kenghe, R. N.; Nimkar, P. M.; Shirkole, S. S.; Shinde, K. J.

    2012-04-01

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

  10. Airflow control system

    DOEpatents

    Motszko, Sean Ronald; McEnaney, Ryan Patrick; Brush, Jeffrey Alan; Zimmermann, Daniel E.

    2007-03-13

    A dual airflow control system for an environment having a first air zone and a second air zone. The system includes a first input device operable to generate a first input signal indicative of a desired airflow to the first zone and a second input device operable to generate a second input signal indicative of a desired airflow to the second zone. First and second flow regulators are configured to regulate airflow to the first and second zones, respectively, such that the first and second regulators selectively provide the airflow to each of the first and second zones based on the first and second input signals. A single actuator is associated with the first and second flow regulators. The actuator is operable to simultaneously actuate the first and second flow regulators based on an input from the first and second input devices to allow the desired airflows to the first and the second zones.

  11. Assessing multizone airflow software

    SciTech Connect

    Lorenzetti, D.M.

    2001-12-01

    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.

  12. Defining Airflow Obstruction

    PubMed Central

    Eschenbacher, William L.

    2016-01-01

    Airflow obstruction has been defined using spirometric test results when the forced expiratory volume in 1 second (FEV1) to forced vital capacity (FVC) ratio is below a fixed cutoff (<70%) or lower limits of normal (LLN) from reference equations that are based on values from a normal population. However, similar to other positive or abnormal diagnostic test results that are used to identify the presence of disease, perhaps airflow obstruction should be defined based on the values of FEV1/FVC for a population of individuals with known disease such as chronic obstructive pulmonary disease (COPD). Unfortunately, we do not know such a distribution of values of FEV1/FVC for patients with COPD since there is no gold standard for this syndrome or condition. Yet, we have used this physiologic definition of airflow obstruction based on a normal population to identify patients with COPD. In addition, we have defined airflow obstruction as either being present or absent. Instead, we should use a different approach to define airflow obstruction based on the probability or likelihood that the airflow obstruction is present which in turn would give us the probability or likelihood of a disease state such as COPD. PMID:27239557

  13. Laminar Flow Aircraft Certification

    NASA Technical Reports Server (NTRS)

    Williams, Louis J. (Compiler)

    1986-01-01

    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.

  14. Suppression of Tla1 gene expression for improved solar conversion efficiency and photosynthetic productivity in plants and algae

    DOEpatents

    Melis, Anastasios; Mitra, Mautusi

    2010-06-29

    The invention provides method and compositions to minimize the chlorophyll antenna size of photosynthesis by decreasing TLA1 gene expression, thereby improving solar conversion efficiencies and photosynthetic productivity in plants, e.g., green microalgae, under bright sunlight conditions.

  15. Airflow models gaining clout

    SciTech Connect

    Post, N.M.

    1994-10-10

    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}

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

    PubMed Central

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

    2012-01-01

    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

  17. Three-Dimensional Numerical Simulation of Airflow in Nasopharynx.

    NASA Astrophysics Data System (ADS)

    Shome, Biswadip; Wang, Lian-Ping; Santare, Michael H.; Szeri, Andras Z.; Prasad, Ajay K.; Roberts, David

    1996-11-01

    A three-dimensional numerical simulation of airflow in nasopharynx (from the soft palate to the epiglottis) was conducted, using anatomically accurate model and finite element method, to study the influence of flow characteristics on obstructive sleep apnea (OSA). The results showed that the pressure drop in the nasopharynx is in the range 200-500 Pa. Ten different nasopharynx geometries resulting from three OSA treatment therapies (CPAP, mandibular repositioning devices, and surgery) were compared. The results confirmed that the airflow in the nasopharynx lies in the transitional flow regime and thus, a subtle change in the morphology caused by these treatment therapies has a large effect on the airflow. The onset of turbulence can cause as much as 40% of increase in pressure drop. For the transitional flow regime, the k-ɛ turbulence model was found to be the most appropriate model, when compared to the mixing length and the k-ω model, as it correctly reproduces the limiting laminar behavior. In addition, the pressure drop increased approximately as the square of the volumetric flow rate. Supported by NIH.

  18. Aircraft Laminar Flow Control

    NASA Technical Reports Server (NTRS)

    Joslin, Ronald D.

    1998-01-01

    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.

  19. MICROPROCESSOR CONTROL OF ROTOGRAVURE AIRFLOWS

    EPA Science Inventory

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

  20. Laminar Soot Processes

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  1. Visual exploration of nasal airflow.

    PubMed

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

    2009-01-01

    Rhinologists are often faced with the challenge of assessing nasal breathing from a functional point of view to derive effective therapeutic interventions. While the complex nasal anatomy can be revealed by visual inspection and medical imaging, only vague information is available regarding the nasal airflow itself: Rhinomanometry delivers rather unspecific integral information on the pressure gradient as well as on total flow and nasal flow resistance. In this article we demonstrate how the understanding of physiological nasal breathing can be improved by simulating and visually analyzing nasal airflow, based on an anatomically correct model of the upper human respiratory tract. In particular we demonstrate how various Information Visualization (InfoVis) techniques, such as a highly scalable implementation of parallel coordinates, time series visualizations, as well as unstructured grid multi-volume rendering, all integrated within a multiple linked views framework, can be utilized to gain a deeper understanding of nasal breathing. Evaluation is accomplished by visual exploration of spatio-temporal airflow characteristics that include not only information on flow features but also on accompanying quantities such as temperature and humidity. To our knowledge, this is the first in-depth visual exploration of the physiological function of the nose over several simulated breathing cycles under consideration of a complete model of the nasal airways, realistic boundary conditions, and all physically relevant time-varying quantities. PMID:19834215

  2. Development of laminar flow control wing surface porous structure

    NASA Technical Reports Server (NTRS)

    Klotzsche, M.; Pearce, W.; Anderson, C.; Thelander, J.; Boronow, W.; Gallimore, F.; Brown, W.; Matsuo, T.; Christensen, J.; Primavera, G.

    1984-01-01

    It was concluded that the chordwise air collection method, which actually combines chordwise and spanwise air collection, is the best of the designs conceived up to this time for full chord laminar flow control (LFC). Its shallower ducting improved structural efficiency of the main wing box resulting in a reduction in wing weight, and it provided continuous support of the chordwise panel joints, better matching of suction and clearing airflow requirements, and simplified duct to suction source minifolding. Laminar flow control on both the upper and lower surfaces was previously reduced to LFC suction on the upper surface only, back to 85 percent chord. The study concludes that, in addition to reduced wing area and other practical advantages, this system would be lighter because of the increase in effective structural wing thickness.

  3. Laminar Multicell Lithium Batteries

    SciTech Connect

    Bruder, A. H.

    1984-01-31

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

  4. Laminar cells and batteries

    SciTech Connect

    Plasse, P.A.

    1983-06-21

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

  5. Mechanical responses of rat vibrissae to airflow.

    PubMed

    Yu, Yan S W; Graff, Matthew M; Hartmann, Mitra J Z

    2016-04-01

    The survival of many animals depends in part on their ability to sense the flow of the surrounding fluid medium. To date, however, little is known about how terrestrial mammals sense airflow direction or speed. The present work analyzes the mechanical response of isolated rat macrovibrissae (whiskers) to airflow to assess their viability as flow sensors. Results show that the whisker bends primarily in the direction of airflow and vibrates around a new average position at frequencies related to its resonant modes. The bending direction is not affected by airflow speed or by geometric properties of the whisker. In contrast, the bending magnitude increases strongly with airflow speed and with the ratio of the whisker's arc length to base diameter. To a much smaller degree, the bending magnitude also varies with the orientation of the whisker's intrinsic curvature relative to the direction of airflow. These results are used to predict the mechanical responses of vibrissae to airflow across the entire array, and to show that the rat could actively adjust the airflow data that the vibrissae acquire by changing the orientation of its whiskers. We suggest that, like the whiskers of pinnipeds, the macrovibrissae of terrestrial mammals are multimodal sensors - able to sense both airflow and touch - and that they may play a particularly important role in anemotaxis. PMID:27030774

  6. Airflow measurement inaccuracies in aerosol imaging

    SciTech Connect

    Sirr, S.A.; Miltz-Miller, S.; Notman, D.N.; Boyle, M.J.; Boudreau, R.J.; Loken, M.K.

    1986-04-01

    Aerosol production using inclined compressed air tanks may be subject to error caused by airflow meter variability and by the degree of inclination of the air-flow meter. Since most of these tanks are used in an inclined position, it is important for clinicians to be aware of these errors.

  7. Airflow measurement inaccuracies in aerosol imaging.

    PubMed

    Sirr, S A; Miltz-Miller, S; Notman, D N; Boyle, M J; Boudreau, R J; Loken, M K

    1986-04-01

    Aerosol production using inclined compressed air tanks may be subject to error caused by airflow meter variability and by the degree of inclination of the air-flow meter. Since most of these tanks are used in an inclined position, it is important for clinicians to be aware of these errors. PMID:3952316

  8. Laminar Soot Processes (LSP)

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    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

  9. Supersonic Laminar Flow Control Research

    NASA Technical Reports Server (NTRS)

    Lo, Ching F.; Wiberg, Clark G.

    1996-01-01

    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.

  10. Submegabase Clusters of Unstable Tandem Repeats Unique to the Tla Region of Mouse T Haplotypes

    PubMed Central

    Uehara, H.; Ebersole, T.; Bennett, D.; Artzt, K.

    1990-01-01

    We describe here the identification and genomic organization of mouse t haplotype-specific elements (TSEs) 7.8 and 5.8 kb in length. The TSEs exist as submegabase-long clusters of tandem repeats localized in the Tla region of the major histocompatibility complex of all t haplotype chromosomes examined. In contrast, no such clusters were detected among 12 inbred strains of Mus musculus and other Mus species; thus, clusters of TSEs represent the first absolutely qualitative difference between t haplotypes and wild-type chromosomes. Pulsed field gel electrophoresis shows that the number of clusters, and the number of repeats in each cluster are extremely variable. Dramatic quantitative differences of TSEs uniquely distinguish every independent t haplotype from any other. The complete nucleotide sequence of one 7.8-kb TSE reveals significant homology to the ETn (a major transcript in the early embryo of the mouse), and some homologies to intracisternal A-particles and the mammary tumor virus env gene. Apart from the diagnostic relevance to t haplotypes, evolutionary and functional significances are discussed with respect to chromosome structure and genetic recombination. PMID:2076812

  11. Laminar Soot Processes

    NASA Technical Reports Server (NTRS)

    2001-01-01

    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.

  12. Laminar Soot Processes

    NASA Technical Reports Server (NTRS)

    2001-01-01

    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.

  13. Laminar Soot Processes

    NASA Technical Reports Server (NTRS)

    2001-01-01

    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.

  14. Flight experiences with laminar flow

    NASA Technical Reports Server (NTRS)

    Holmes, Bruce J.

    1986-01-01

    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.

  15. Airflow resistance of selected biomass materials

    SciTech Connect

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

    1985-01-01

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

  16. Structure of laminar sooting inverse diffusion flames

    SciTech Connect

    Mikofski, Mark A.; Fernandez-Pello, A. Carlos; Williams, Timothy C.; Shaddix, Christopher R.; Blevins, Linda G.

    2007-06-15

    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)

  17. Continuous laminar smoke generator

    NASA Technical Reports Server (NTRS)

    Weinstein, L. M. (Inventor)

    1985-01-01

    A smoke generator capable of emitting a very thin, laminar stream of smoke for use in high detail flow visualization was invented. The generator is capable of emitting a larger but less stable rope of smoke. The invention consists of a pressure supply and fluid supply which supply smoke generating fluid to feed. The feed tube is directly heated by electrical resistance from current supplied by power supply and regulated by a constant temperature controller. A smoke exit hole is drilled in the wall of feed tube. Because feed tube is heated both before and past exit hole, no condensation of smoke generating occurs at the smoke exit hole, enabling the production of a very stable smoke filament. The generator is small in size which avoids wind turbulence in front of the test model.

  18. Airflow resistance of airflow-regulating devices described by independent coefficients.

    PubMed

    Verkerke, G J; Geertsema, A A; Schutte, H K

    2001-07-01

    Rehabilitation after laryngectomy includes more and more the use of airflow-regulating devices such as shunt valves (SVs), tracheostoma valves (TSVs), and heat and moisture exchange (HME) filters. In determining the quality of those devices, airflow resistance is a very important factor. It is currently defined as pressure drop divided by airflow. However, for most applications, this definition does not result in a pressure- and airflow-independent parameter. Therefore, a new set of parameters is defined and applied to pressure-airflow curves of airflow-regulating devices. Pressure drop over TSVs and HME filters appears to have a squared relationship with flow. In SVs, it has a linear relationship. The new set of parameters describes the pressure-airflow relationship properly for all considered devices. In conclusion, theoretical predictions of flow mechanics appear to be valid for SVs, TSVs, and HME filters. Only 2 coefficients are necessary to describe the pressure-flow characteristics of these airflow-regulating devices, independent of pressure drop over and flow through the device. PMID:11465823

  19. Supersonic Laminar Flow Control Research

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

  20. RANS and LES simulations of the airflow through nasal cavities

    NASA Astrophysics Data System (ADS)

    Lamberti, Giacomo

    2015-11-01

    The prediction of detailed flow patterns in nasal cavities using computational fluid dynamics (CFD) can provide essential information on the potential relationship between patient-specific geometrical characteristics and health problems. The long-term goal of the OpenNOSE project is to develop a reliable open-source computational tool based on the OpenFOAM CFD toolbox that can assist surgeons in their daily practice. The objective of this study was to investigate the effect of the turbulence model and boundary conditions on simulations of the airflow in nasal cavities. The geometry, including paranasal sinuses, was reconstructed from a carefully selected CT scan, and RANS and LES simulations were carried out for steady inspiration and expiration. At a flow rate near 20 l/min, the flow is laminar in most of the domain. During the inspiration phase, turbulence develops in nasopharynx and oropharynx regions; during the expiration phase, another vortical region is observed down the nostrils. A comparison between different boundary conditions suggests the use of a total pressure condition, or alternatively a uniform velocity, at the inlet and outlet. In future work the same geometry will be used for setting up a laboratory experiment, intended to cross-validate the numerical results.

  1. Overview of Laminar Flow Control

    NASA Technical Reports Server (NTRS)

    Joslin, Ronald D.

    1998-01-01

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

  2. Measurement of airflow in residential furnaces

    SciTech Connect

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

    2004-01-24

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

  3. An electromagnetic energy scavenger from direct airflow

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

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

  4. Laminar Flow Analysis

    NASA Astrophysics Data System (ADS)

    Rogers, David F.

    1992-10-01

    The major thrust of this book is to present a technique of analysis that aids the formulation, understanding, and solution of problems of viscous flow. The intent is to avoid providing a "canned" program to solve a problem, offering instead a way to recognize the underlying physical, mathematical, and modeling concepts inherent in the solutions. The reader must first choose a mathematical model and derive governing equations based on realistic assumptions, or become aware of the limitations and assumptions associated with existing models. An appropriate solution technique is then selected. The solution technique may be either analytical or numerical. Computer-aided analysis algorithms supplement the classical analyses. The book begins by deriving the Navier-Stokes equation for a viscous compressible variable property fluid. The second chapter considers exact solutions of the incompressible hydrodynamic boundary layer equations solved with and without mass transfer at the wall. Forced convection, free convection, and the compressible laminar boundary layer are discussed in the remaining chapters. The text unifies the various topics by tracing a logical progression from simple to complex governing differential equations and boundary conditions. Numerical, parametric, and directed analysis problems are included at the end of each chapter.

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

    PubMed

    Tumia, N; Ashcroft, G P

    2002-11-01

    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

  6. 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...

  7. Instrument Measures Airflow Friction Without Contact

    NASA Technical Reports Server (NTRS)

    Monson, D. J.

    1983-01-01

    Dual beam laser interferometer determines airflow friction against body by measuring time-varying thickness of wind sheared oil film. Measurements yield skin friction between film and airstream. Errors from prerun oil flow, tunnel starting transients, and initial surface waves therefore eliminated.

  8. Laminar flow control is maturing

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

  9. Hybrid laminar flow control study

    NASA Technical Reports Server (NTRS)

    1982-01-01

    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.

  10. Supersonic laminar-flow control

    NASA Technical Reports Server (NTRS)

    Bushnell, Dennis M.; Malik, Mujeeb R.

    1987-01-01

    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.

  11. Structure of the airflow above surface waves

    NASA Astrophysics Data System (ADS)

    Buckley, Marc; Veron, Fabrice

    2016-04-01

    Weather, climate and upper ocean patterns are controlled by the exchanges of momentum, heat, mass, and energy across the ocean surface. These fluxes are, in turn, influenced by the small-scale physics at the wavy air-sea interface. We present laboratory measurements of the fine-scale airflow structure above waves, achieved in over 15 different wind-wave conditions, with wave ages Cp/u* ranging from 1.4 to 66.7 (where Cp is the peak phase speed of the waves, and u* the air friction velocity). The experiments were performed in the large (42-m long) wind-wave-current tank at University of Delaware's Air-Sea Interaction laboratory (USA). A combined Particle Image Velocimetry and Laser Induced Fluorescence system was specifically developed for this study, and provided two-dimensional airflow velocity measurement as low as 100 um above the air-water interface. Starting at very low wind speeds (U10~2m/s), we directly observe coherent turbulent structures within the buffer and logarithmic layers of the airflow above the air-water interface, whereby low horizontal velocity air is ejected away from the surface, and higher velocity fluid is swept downward. Wave phase coherent quadrant analysis shows that such turbulent momentum flux events are wave-phase dependent. Airflow separation events are directly observed over young wind waves (Cp/u*<3.7) and counted using measured vorticity and surface viscous stress criteria. Detached high spanwise vorticity layers cause intense wave-coherent turbulence downwind of wave crests, as shown by wave-phase averaging of turbulent momentum fluxes. Mean wave-coherent airflow motions and fluxes also show strong phase-locked patterns, including a sheltering effect, upwind of wave crests over old mechanically generated swells (Cp/u*=31.7), and downwind of crests over young wind waves (Cp/u*=3.7). Over slightly older wind waves (Cp/u* = 6.5), the measured wave-induced airflow perturbations are qualitatively consistent with linear critical layer

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

    NASA Technical Reports Server (NTRS)

    1996-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    1996-01-01

    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.

  14. Laminar flow control for transport aircraft applications

    NASA Technical Reports Server (NTRS)

    Wagner, R. D.

    1986-01-01

    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.

  15. Laminar flow: Challenge and potential

    NASA Technical Reports Server (NTRS)

    Kirchner, Mark E.

    1987-01-01

    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.

  16. Laminar-flow flight experiments

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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.

  17. The Laminar Soot Processes (LSP)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    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.

  18. Hybrid mesh for nasal airflow studies.

    PubMed

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

    2013-01-01

    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

  19. Hybrid Mesh for Nasal Airflow Studies

    PubMed Central

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

    2013-01-01

    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

  20. Operational considerations for laminar flow aircraft

    NASA Technical Reports Server (NTRS)

    Maddalon, Dal V.; Wagner, Richard D.

    1986-01-01

    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.

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

    PubMed Central

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

    2012-01-01

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

  2. Airflow, transport and regional deposition of aerosol particles during chronic bronchitis of human central airways.

    PubMed

    Farkhadnia, Fouad; Gorji, Tahereh B; Gorji-Bandpy, Mofid

    2016-03-01

    In the present study, the effects of airway blockage in chronic bronchitis disease on the flow patterns and transport/deposition of micro-particles in a human symmetric triple bifurcation lung airway model, i.e., Weibel's generations G3-G6 was investigated. A computational fluid and particle dynamics model was implemented, validated and applied in order to evaluate the airflow and particle transport/deposition in central airways. Three breathing patterns, i.e., resting, light activity and moderate exercise, were considered. Using Lagrangian approach for particle tracking and random particle injection, an unsteady particle tracking method was performed to simulate the transport and deposition of micron-sized aerosol particles in human central airways. Assuming laminar, quasi-steady, three-dimensional air flow and spherical non-interacting particles in sequentially bifurcating rigid airways, airflow patterns and particle transport/deposition in healthy and chronic bronchitis (CB) affected airways were evaluated and compared. Comparison of deposition efficiency (DE) of aerosols in healthy and occluded airways showed that at the same flow rates DE values are typically larger in occluded airways. While in healthy airways, particles deposit mainly around the carinal ridges and flow dividers-due to direct inertial impaction, in CB affected airways they deposit mainly on the tubular surfaces of blocked airways because of gravitational sedimentation. PMID:26541595

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

    PubMed

    Burgos, M A; Sanmiguel-Rojas, E; Martín-Alcántara, A; Hidalgo-Martínez, M

    2014-03-01

    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 ࣈ 5.7 L/min and ࣈ 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

  4. Natural Laminar Flow Flight Experiment

    NASA Technical Reports Server (NTRS)

    Steers, L. L.

    1981-01-01

    A supercritical airfoil section was designed with favorable pressure gradients on both the upper and lower surfaces. Wind tunnel tests were conducted in the Langley 8 Foot Transonic Pressure Tunnel. The outer wing panels of the F-111 TACT airplane were modified to incorporate partial span test gloves having the natural laminar, flow profile. Instrumentation was installed to provide surface pressure data as well as to determine transition location and boundary layer characteristics. The flight experiment encompassed 19 flights conducted with and without transition fixed at several locations for wing leading edge sweep angles which varied from 10 to 26 at Mach numbers from 0.80 to 0.85 and altitudes of 7620 meters and 9144 meters. Preliminary results indicate that a large portion of the test chord experienced laminar flow.

  5. Considerations for efficient airflow design in cleanrooms

    SciTech Connect

    Xu, Tengfang

    2004-07-29

    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

  6. Theory of laminar viscous jets

    NASA Astrophysics Data System (ADS)

    Martynenko, O. G.; Korovkin, V. N.; Sokovishin, Iu. A.

    Results of recent theoretical studies of laminar jet flows of a viscous incompressible fluid are reviewed. In particular, attention is given to plane, fan-shaped, axisymmetric, and swirling jet flows; jet flows behind bodies; and slipstream jet flows. The discussion also covers dissipation of mechanical energy in jet flows, jet flows with a zero excess momentum, and asymptotic series expansions in the theory of jet flows.

  7. Laminar electrical cells and batteries

    SciTech Connect

    Bruder, A.H.

    1983-08-23

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

  8. Laminar electrical cells and batteries

    SciTech Connect

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

    1982-11-30

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

  9. Airflow limitation is accompanied by diaphragm dysfunction.

    PubMed

    Hellebrandová, L; Chlumský, J; Vostatek, P; Novák, D; Rýznarová, Z; Bunc, V

    2016-07-18

    Chronic airflow limitation, caused by chronic obstructive pulmonary disease (COPD) or by asthma, is believed to change the shape and the position of the diaphragm due to an increase in lung volume. We have made a comparison of magnetic resonance imaging (MRI) of diaphragm in supine position with pulmonary functions, respiratory muscle function and exercise tolerance. We have studied the differences between patients with COPD, patients with asthma, and healthy subjects. Most interestingly we found the lung hyperinflation leads to the changes in diaphragmatic excursions during the breathing cycle, seen in the differences between the maximal expiratory diaphragm position (DPex) in patients with COPD and control group (p=0.0016). The magnitude of the diaphragmatic dysfunction was significantly related to the airflow limitation expressed by the ratio of forced expiratory volume in 1 s to slow vital capacity (FEV(1)/SVC), (%, p=0.0007); to the lung hyperinflation expressed as the ratio of the residual volume to total lung capacity (RV/TLC), (%, p=0.0018) and the extent of tidal volume constrain expressed as maximal tidal volume (V(Tmax)), ([l], p=0.0002); and the ratio of tidal volume to slow vital capacity (V(T)/SVC), (p=0.0038) during submaximal exercise. These results suggest that diaphragmatic movement fails to contribute sufficiently to the change in lung volume in emphysema. Tests of respiratory muscle function were related to the position of the diaphragm in deep expiration, e.g. neuromuscular coupling (P(0.1)/V(T)) (p=0.0232). The results have shown that the lung volumes determine the position of the diaphragm and function of the respiratory muscles. Chronic airflow limitation seems to change the position of the diaphragm, which thereafter influences inspiratory muscle function and exercise tolerance. There is an apparent relationship between the position of the diaphragm and the pulmonary functions and exercise tolerance. PMID:27070746

  10. Incidence of airflow limitation among employees in Norwegian smelters.

    PubMed

    Søyseth, Vidar; Johnsen, Helle Laier; Bugge, Merete Drevvatne; Hetland, Siri Merete; Kongerud, Johny

    2011-09-01

    We have investigated the association between the incidence of airflow limitation and occupational exposure. The employees (n = 3,924) were investigated annually during five years (n = 16,570) using spirometry. Exposure was classified using job category and a job exposure matrix. Airflow limitation was expressed using two indices: (i) as forced expiratory volume in one second/force vital capacity (FEV(1) /FVC) <0.7 and (ii) lower limit of normal (LLN). The incidence of airflow limitation was 21.2/1000 years(-1) and 15.1/1000 years(-1) using the fixed limit (0.7) and the LLN criterion, respectively. We found a dose-response relationship between the incidence of airflow limitation and tobacco consumption and with job-category in non-smokers. The associations between airflow limitation and covariates were independent of how airflow limitation was defined. The incidence of airflow limitation defined as FEV(l) /FVC <0.7 yielded higher incidence rates of airflow limitation than LLN. We found a significant association between the incidence of airflow limitation and occupational exposure in non-smokers. PMID:21360726

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

    PubMed Central

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

    2012-01-01

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

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

    PubMed

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

    2012-10-01

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

  13. Analysis of the laminar flamelet concept for nonpremixed laminar flames

    SciTech Connect

    Claramunt, K.; Consul, R.; Carbonell, D.; Perez-Segarra, C.D.

    2006-06-15

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

  14. On laminar and turbulent friction

    NASA Technical Reports Server (NTRS)

    Von Karman, TH

    1946-01-01

    Report deals, first with the theory of the laminar friction flow, where the basic concepts of Prandtl's boundary layer theory are represented from mathematical and physical points of view, and a method is indicated by means of which even more complicated cases can be treated with simple mathematical means, at least approximately. An attempt is also made to secure a basis for the computation of the turbulent friction by means of formulas through which the empirical laws of the turbulent pipe resistance can be applied to other problems on friction drag. (author)

  15. Lithium batteries with laminar anodes

    SciTech Connect

    Bruder, A.H.

    1986-11-04

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

  16. Chevrons formation in laminar erosion

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

    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.

  17. Burning Laminar Jet Diffusion Flame

    NASA Technical Reports Server (NTRS)

    2003-01-01

    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.

  18. Laminar Jet Diffusion Flame Burning

    NASA Technical Reports Server (NTRS)

    2003-01-01

    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.

  19. 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...

  20. Laminar and Turbulent Flow in Water

    ERIC Educational Resources Information Center

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

    2010-01-01

    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…

  1. Laminar-flow wind tunnel experiments

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    Although most of the laminar flow airfoils recently developed at the NASA Langley Research Center were intended for general aviation applications, low-drag airfoils were designed for transonic speeds and wind tunnel performance tested. The objective was to extend the technology of laminar flow to higher Mach and Reynolds numbers and to swept leading edge wings representative of transport aircraft to achieve lower drag and significantly improved operation costs. This research involves stabilizing the laminar boundary layer through geometric shaping (Natural Laminar Flow, NLF) and active control involving the removal of a portion of the laminar boundary layer (Laminar-Flow Control, LFC), either through discrete slots or perforated surface. Results show that extensive regions of laminar flow with large reductions in skin friction drag can be maintained through the application of passive NLF boundary-layer control technologies to unswept transonic wings. At even greater extent of laminar flow and reduction in the total drag level can be obtained on a swept supercritical airfoil with active boundary layer-control.

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

    NASA Technical Reports Server (NTRS)

    1996-01-01

    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.

  3. Exact averaging of laminar dispersion

    NASA Astrophysics Data System (ADS)

    Ratnakar, Ram R.; Balakotaiah, Vemuri

    2011-02-01

    We use the Liapunov-Schmidt (LS) technique of bifurcation theory to derive a low-dimensional model for laminar dispersion of a nonreactive solute in a tube. The LS formalism leads to an exact averaged model, consisting of the governing equation for the cross-section averaged concentration, along with the initial and inlet conditions, to all orders in the transverse diffusion time. We use the averaged model to analyze the temporal evolution of the spatial moments of the solute and show that they do not have the centroid displacement or variance deficit predicted by the coarse-grained models derived by other methods. We also present a detailed analysis of the first three spatial moments for short and long times as a function of the radial Peclet number and identify three clearly defined time intervals for the evolution of the solute concentration profile. By examining the skewness in some detail, we show that the skewness increases initially, attains a maximum for time scales of the order of transverse diffusion time, and the solute concentration profile never attains the Gaussian shape at any finite time. Finally, we reason that there is a fundamental physical inconsistency in representing laminar (Taylor) dispersion phenomena using truncated averaged models in terms of a single cross-section averaged concentration and its large scale gradient. Our approach evaluates the dispersion flux using a local gradient between the dominant diffusive and convective modes. We present and analyze a truncated regularized hyperbolic model in terms of the cup-mixing concentration for the classical Taylor-Aris dispersion that has a larger domain of validity compared to the traditional parabolic model. By analyzing the temporal moments, we show that the hyperbolic model has no physical inconsistencies that are associated with the parabolic model and can describe the dispersion process to first order accuracy in the transverse diffusion time.

  4. The Evolution of Unidirectional Pulmonary Airflow.

    PubMed

    Farmer, C G

    2015-07-01

    Conventional wisdom holds that the avian respiratory system is unique because air flows in the same direction through most of the gas-exchange tubules during both phases of ventilation. However, recent studies showing that unidirectional airflow also exists in crocodilians and lizards raise questions about the true phylogenetic distribution of unidirectional airflow, the selective drivers of the trait, the date of origin, and the functional consequences of this phenomenon. These discoveries suggest unidirectional flow was present in the common diapsid ancestor and are inconsistent with the traditional paradigm that unidirectional flow is an adaptation for supporting high rates of gas exchange. Instead, these discoveries suggest it may serve functions such as decreasing the work of breathing, decreasing evaporative respiratory water loss, reducing rates of heat loss, and facilitating crypsis. The divergence in the design of the respiratory system between unidirectionally ventilated lungs and tidally ventilated lungs, such as those found in mammals, is very old, with a minimum date for the divergence in the Permian Period. From this foundation, the avian and mammalian lineages evolved very different respiratory systems. I suggest the difference in design is due to the same selective pressure, expanded aerobic capacity, acting under different environmental conditions. High levels of atmospheric oxygen of the Permian Period relaxed selection for a thin blood-gas barrier and may have resulted in the homogeneous, broncho-alveolar design, whereas the reduced oxygen of the Mesozoic selected for a heterogeneous lung with an extremely thin blood-gas barrier. These differences in lung design may explain the puzzling pattern of ecomorphological diversification of Mesozoic mammals: all were small animals that did not occupy niches requiring a great aerobic capacity. The broncho-alveolar lung and the hypoxia of the Mesozoic may have restricted these mammals from exploiting

  5. Experimental evidence of condensation-driven airflow

    NASA Astrophysics Data System (ADS)

    Bunyard, P.; Hodnett, M.; Poveda, G.; Burgos Salcedo, J. D.; Peña, C.

    2015-10-01

    The dominant "convection" model of atmospheric circulation is based on the premise that hot air expands and rises, to be replaced by colder air, thereby creating horizontal surface winds. A recent theory put forward by Makarieva and Gorshkov (2007, 2013) maintains that the primary motive force of atmospheric circulation derives from the intense condensation and sharp pressure reduction that is associated with regions where a high rate of evapotranspiration from natural closed-canopy forests provides the "fuel" for cloud formation. The net result of the "biotic pump" theory is that moist air flows from ocean to land, drawn in by the pressure changes associated with a high rate of condensation. To test the physics underpinning the biotic pump theory, namely that condensation of water vapour, at a sufficiently high rate, results in an uni-directional airflow, a 5 m tall experimental apparatus was designed and built, in which a 20 m3 body of atmospheric air is enclosed inside an annular 14 m long space (a "square donut") around which it can circulate freely, allowing for rotary air flows. One vertical side of the apparatus contains some 17 m of copper refrigeration coils, which cause condensation. The apparatus contains a series of sensors measuring temperature, humidity and barometric pressure every five seconds, and air flow every second. The laws of Newtonian physics are used in calculating the rate of condensation inside the apparatus. The results of more than one hundred experiments show a highly significant correlation, with r2 > 0.9, of airflow and the rate of condensation. The rotary air flows created appear to be consistent both in direction and velocity with the biotic pump hypothesis, the critical factor being the rate change in the partial pressure of water vapour in the enclosed body of atmospheric air. Air density changes, in terms of kinetic energy, are found to be orders of magnitude smaller than the kinetic energy of partial pressure change. The

  6. Numerical simulation of laboratory fume hood airflow performance

    SciTech Connect

    Kirkpatrick, A.T.; Reither, R.

    1998-12-31

    A three-dimensional computational fluid dynamics (CFD) analysis has been used to predict airflow patterns in laboratory fume hoods. The simulation includes bypass fume hood primary operational features including the top and bottom bypasses, front airfoils, and rear-slotted baffles. All results were validated experimentally, and the simulation was found to adequately predict fume hood airflow patterns. The results indicate that fume hood flow patterns are highly dependent on inlet flow boundary conditions so that the computation must include the near field room airflow. Additionally, the study included the effects on the fume hood airflow of sash height changes, an operator positioned outside the fume hood, and equipment within the main fume hood chamber. It was shown that for conditions of a fully open sash height, a person in front of the fume hood, and an object inside the fume hood, the fume hood experiences a loss of containment of the flow.

  7. Airflows generated by an impacting drop.

    PubMed

    Bischofberger, Irmgard; Ray, Bahni; Morris, Jeffrey F; Lee, Taehun; Nagel, Sidney R

    2016-03-28

    A drop impacting a solid surface with sufficient velocity will splash and emit many small droplets. However, lowering the ambient air pressure suppresses splashing completely. This effect, robustly found for different liquid and substrate properties, raises the fundamental question of how air affects a spreading drop. In a combined experimental and numerical study we characterize the flow of air induced by the drop after it hits the substrate, using a modified Schlieren optics technique combined with high-speed video imaging and Lattice-Boltzmann simulations. Our experiments reveal the emergence of air structures on different length scales. On large scales, the airflow induced in the drop's wake leads to vortex structures due to interaction with the substrate. On smaller scales, we visualize a ring structure above the outer edge of the spreading liquid generated by the spreading of the drop. Our simulations reveal the interaction between the wake vorticity and the flows originating from the rapidly escaping air from below the impacting drop. We show that the vorticity is governed by a balance between inertial and viscous forces in the air, and is unrelated to the splashing threshold. PMID:26809314

  8. Dynamics of airflow in a short inhalation

    PubMed Central

    Bates, A. J.; Doorly, D. J.; Cetto, R.; Calmet, H.; Gambaruto, A. M.; Tolley, N. S.; Houzeaux, G.; Schroter, R. C.

    2015-01-01

    During a rapid inhalation, such as a sniff, the flow in the airways accelerates and decays quickly. The consequences for flow development and convective transport of an inhaled gas were investigated in a subject geometry extending from the nose to the bronchi. The progress of flow transition and the advance of an inhaled non-absorbed gas were determined using highly resolved simulations of a sniff 0.5 s long, 1 l s−1 peak flow, 364 ml inhaled volume. In the nose, the distribution of airflow evolved through three phases: (i) an initial transient of about 50 ms, roughly the filling time for a nasal volume, (ii) quasi-equilibrium over the majority of the inhalation, and (iii) a terminating phase. Flow transition commenced in the supraglottic region within 20 ms, resulting in large-amplitude fluctuations persisting throughout the inhalation; in the nose, fluctuations that arose nearer peak flow were of much reduced intensity and diminished in the flow decay phase. Measures of gas concentration showed non-uniform build-up and wash-out of the inhaled gas in the nose. At the carina, the form of the temporal concentration profile reflected both shear dispersion and airway filling defects owing to recirculation regions. PMID:25551147

  9. Conditions for laminar flow in geophysical vortices

    NASA Astrophysics Data System (ADS)

    Fiedler, Brian H.

    1989-01-01

    The sufficient condition for inviscid, helical instability at large wavenumbers is applied to solutions for columnar vortices arising from the vortical flow of an end-wall boundary layer. The end-wall vortex arising from the laminar boundary layer under a potential vortex will be unstable at sufficiently high Reynolds number. Hoewever, if the end-wall boundary layer is turbulent, the end-wall vortex can be stable and laminar even at very high Reynolds number; therefore, stable, laminar tornadoes and waterspouts are suggested as theoretical possibilities.

  10. Measuring rates of outdoor airflow into HVAC systems

    SciTech Connect

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

    2002-10-01

    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.

  11. Development of an ultrasonic airflow measurement device for ducted air.

    PubMed

    Raine, Andrew B; Aslam, Nauman; Underwood, Christopher P; Danaher, Sean

    2015-01-01

    In this study, an in-duct ultrasonic airflow measurement device has been designed, developed and tested. The airflow measurement results for a small range of airflow velocities and temperatures show that the accuracy was better than 3.5% root mean square (RMS) when it was tested within a round or square duct compared to the in-line Venturi tube airflow meter used for reference. This proof of concept device has provided evidence that with further development it could be a low-cost alternative to pressure differential devices such as the orifice plate airflow meter for monitoring energy efficiency performance and reliability of ventilation systems. The design uses a number of techniques and design choices to provide solutions to lower the implementation cost of the device compared to traditional airflow meters. The design choices that were found to work well are the single sided transducer arrangement for a "V" shaped reflective path and the use of square wave transmitter pulses ending with the necessary 180° phase changed pulse train to suppress transducer ringing. The device is also designed so that it does not have to rely on high-speed analogue to digital converters (ADC) and intensive digital signal processing, so could be implemented using voltage comparators and low-cost microcontrollers. PMID:25954952

  12. Development of an Ultrasonic Airflow Measurement Device for Ducted Air

    PubMed Central

    Raine, Andrew B.; Aslam, Nauman; Underwood, Christopher P.; Danaher, Sean

    2015-01-01

    In this study, an in-duct ultrasonic airflow measurement device has been designed, developed and tested. The airflow measurement results for a small range of airflow velocities and temperatures show that the accuracy was better than 3.5% root mean square (RMS) when it was tested within a round or square duct compared to the in-line Venturi tube airflow meter used for reference. This proof of concept device has provided evidence that with further development it could be a low-cost alternative to pressure differential devices such as the orifice plate airflow meter for monitoring energy efficiency performance and reliability of ventilation systems. The design uses a number of techniques and design choices to provide solutions to lower the implementation cost of the device compared to traditional airflow meters. The design choices that were found to work well are the single sided transducer arrangement for a “V” shaped reflective path and the use of square wave transmitter pulses ending with the necessary 180° phase changed pulse train to suppress transducer ringing. The device is also designed so that it does not have to rely on high-speed analogue to digital converters (ADC) and intensive digital signal processing, so could be implemented using voltage comparators and low-cost microcontrollers. PMID:25954952

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  14. Soot Formation in Laminar Premixed Flames

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  15. Process for making laminar batteries

    SciTech Connect

    Plasse, P.A.

    1986-09-30

    This patent describes the process of making laminar cells, which consists of perforating a first elongated web of liquid impervious, electrically nonconducting thermoplastic material with a spaced rectangular array of apertures arranged in rows across the direction of elongation of the web and in columns parallel to the direction of elongation of the web adding patches of electrically conductive material. Each patch comprises a sheet of conductive plastic adhered to a coterminous layer of electrode particles in a binder to a first side of the first web with the conductive plastic side of each patch in contact with the borders of a different one of the apertures to form a spaced rectangular array of the patches on the firs web. A piece of separator material is adhered to the first web over each of the patches on the first side of the first web, placing spaced elongated strips of metal on the first web on a second side of the first web opposite the first side, the metal strips being aligned with and each overlying a different one of the columns.

  16. Airflow analysis in mechanically ventilated obstructed rooms

    NASA Astrophysics Data System (ADS)

    Priest, John Brian

    1999-11-01

    Local and mean air velocities and standard deviations were measured in realistic rooms. Obstructions represented occupants and equipment in the rooms, internal heat loads varied and supply air temperature differed from room averages. Experimental setups differed for the isothermal and nonisothermal tests. Room dimensions for isothermal tests were 2.44 m high by 4.88 x 4.88 m. Ten different obstruction ratios using three different inlet types were analyzed. Obstructions covered 0 to 30% floor area and from 0 to 75% of room height. Air was supplied at ventilation rates ranging between 0.8 and 1.1 m 3/s. Room dimensions for the nonisothermal tests were 2.44 m high by 3.66 x 7.32 m. Obstruction differences between solid versus open partitions for farrowing crates were investigated for three commercially available inlets using two ventilation loads. Ventilation rates were 0.11 to 1.18 m 3/s, simulating cold and warm weather ventilation conditions, respectively. Based on these data and theoretical calculations, a kinetic energy model that predicts average room air velocity and energy level was developed as a practical room air flow design and analysis tool. It was recommended that designers interested in using CFD as a tool should use a three dimensional laminar model for acceptable qualitative flow results. It was concluded that for typical room flowrates and inlet types the room air distribution system is obstruction ratio independent. Local velocities and standard deviations varied with each obstruction setup and inlet combination. However, average air velocities and turbulence intensities were not influenced by obstruction setups or inlet configurations. The decay rate of mean velocity kinetic energy in the bulk flow region was independent of obstructions and inlets. Room average kinetic energy was a function of the supplied kinetic energy within the supply jet plus internal kinetic energy resulting from internal heat load (convective energy).

  17. Minimum airflow reset of single-duct VAV terminal boxes

    NASA Astrophysics Data System (ADS)

    Cho, Young-Hum

    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

  18. Importance of Airflow for Physiologic and Ergogenic Effects of Precooling

    PubMed Central

    Morrison, Shawnda A.; Cheung, Stephen; Cotter, James D.

    2014-01-01

    Context: Cooling the body before exercise (precooling) has been studied as an ergogenic aid for many thermal conditions; however, airflow accompanying exercise is seldom reported. Objective: To determine whether the physiologic and ergogenic benefits of precooling before endurance exercise may be negated with semirealistic airflow in hot conditions. Design: Crossover study. Setting: Climate-controlled chamber in a research laboratory. Patients or Other Participants: Ten fit, healthy cyclists. Intervention(s): After a familiarization trial, participants completed 4 randomized, counterbalanced sessions consisting of no precooling versus precooling and no fan airflow versus airflow (~4.8 m/s) during exercise. Precooling was via chest-deep immersion (~24°C) for 1 hour or until core temperature dropped 0.5°C. Participants then cycled at 95% ventilatory threshold in a hot environment (temperature = 30°C, relative humidity = 50%) until volitional exhaustion, core temperature reached >39.5°C, or heart rate reached >95% of maximum. Main Outcome Measure(s): Thermal strain was assessed via core temperature (esophageal and rectal thermistors) and mean skin temperature (thermistors at 10 sites) and cardiovascular strain via heart rate and ratings of perceived exertion. Results: Endurance time (28 ± 12 minutes without precooling or airflow) increased by 30 ± 23 minutes with airflow (~109%; 95% confidence interval = 12, 45 minutes; P < .001) and by 16 ± 15 minutes with precooling (~61%; 95% confidence interval = 4, 25 minutes; P = .013), but it was not further extended when the strategies were combined (29 ± 21 minutes longer than control). During cycling without precooling or airflow, mean core and skin temperatures were higher than in all other trials. Precooling reduced heart rate by 7–11 beats/min during the first 5 minutes of exercise, but this attenuation ended by 15 minutes. Conclusions: Most laboratory-based precooling studies have (inadvertently) overestimated

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

    PubMed

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

    2006-08-01

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

  20. Effect of Airflows on Repetitive Nanosecond Volume Discharges

    NASA Astrophysics Data System (ADS)

    Tang, Jingfeng; Wei, Liqiu; Huo, Yuxin; Song, Jian; Yu, Daren; Zhang, Chaohai

    2016-03-01

    Atmospheric pressure discharges excited by repetitive nanosecond pulses have attracted significant attention for various applications. In this paper, a plate-plate discharge with airflows is excited by a repetitive nanosecond pulse generator. Under different experiment conditions, the applied voltages, discharge currents, and discharge images are recorded. The plasma images presented here indicate that the volume discharge modes vary with airflow speeds, and a diffuse and homogeneous volume discharge occurs at the speed of more than 35 m/s. The role of airflows provides different effects on the 2-stage pulse discharges. The 1st pulse currents nearly maintain consistency for different airflow speeds. However, the 2nd pulse current has a change trend of first decreasing and then rapidly increasing, and the value difference for 2nd pulse currents is about 20 A under different airflows. In addition, the experimental results are discussed according to the electrical parameters and discharge images. supported by National Natural Science Foundation of China (Nos. 51006027, 51437002, and 51477035)

  1. Resistance to forced airflow through layers of composting organic material.

    PubMed

    Teixeira, Denis Leocádio; de Matos, Antonio Teixeira; Melo, Evandro de Castro

    2015-02-01

    The objective of this study was to adjust equations to estimate the static pressure gradient of airflow through layers of organic residues submitted to two stages of biochemical degradation, and to evaluate the static pressure drop of airflow thought the material layer. Measurements of static pressure drop in the layers of sugarcane bagasse and coffee husks mixed with poultry litter on day 0 and after 30 days of composting were performed using a prototype with specific airflow rates ranging from 0.02 to 0.13 m(3) s(-1) m(-2). Static pressure gradient and specific airflow rate data were properly fit to the Shedd, Hukill & Ives and Ergun models, which may be used to predict the static pressure gradient of air to be blown through the organic residue layers. However, the Shedd model was that which best represented the phenomenon studied. The static pressure drop of airflow increased as a power of the material layer thickness and showed tendency for decreasing with the biochemical degradation time of the organic material. PMID:25536861

  2. Parallel Computation of Airflow in the Human Lung Model

    NASA Astrophysics Data System (ADS)

    Lee, Taehun; Tawhai, Merryn; Hoffman, Eric. A.

    2005-11-01

    Parallel computations of airflow in the human lung based on domain decomposition are performed. The realistic lung model is segmented and reconstructed from CT images as part of an effort to build a normative atlas (NIH HL-04368) documenting airway geometry over 4 decades of age in healthy and disease-state adult humans. Because of the large number of the airway generation and the sheer complexity of the geometry, massively parallel computation of pulmonary airflow is carried out. We present the parallel algorithm implemented in the custom-developed characteristic-Galerkin finite element method, evaluate the speed-up and scalability of the scheme, and estimate the computing resources needed to simulate the airflow in the conducting airways of the human lungs. It is found that the special tree-like geometry enables the inter-processor communications to occur among only three or four processors for optimal parallelization irrespective of the number of processors involved in the computation.

  3. Airflow Hazard Visualization for Helicopter Pilots: Flight Simulation Study Results

    NASA Technical Reports Server (NTRS)

    Aragon, Cecilia R.; Long, Kurtis R.

    2005-01-01

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

  4. Airflow studies in a forced ventilated chamber with low partitions

    SciTech Connect

    Chow, W.K.; Tsui, K.F.

    1995-12-31

    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.

  5. Unidirectional pulmonary airflow patterns in the savannah monitor lizard.

    PubMed

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

    2014-02-20

    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

  6. Laminar Heating Validation of the OVERFLOW Code

    NASA Technical Reports Server (NTRS)

    Lillard, Randolph P.; Dries, Kevin M.

    2005-01-01

    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.

  7. Laminar and turbulent flow in water

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

    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 turbulent and laminar flow, and let, in an accessible way, data be taken to analyse the conditions under which both flows are present. We found research articles about turbulence measurements, using sophisticated equipment, but they do not use the perturbation of the free surface of the flowing liquid to show or measure the turbulence.

  8. Wing Leading Edge Joint Laminar Flow Tests

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

  9. Flow/Soot-Formation Interactions in Nonbuoyant Laminar Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  10. Study of Airflow Out of the Mouth During Speech.

    ERIC Educational Resources Information Center

    Catford, J.C.; And Others

    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…

  11. Air-flow regulation system for a coal gasifier

    DOEpatents

    Fasching, George E.

    1984-01-01

    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.

  12. Smoothed Two-Dimensional Edges for Laminar Flow

    NASA Technical Reports Server (NTRS)

    Holmes, B. J.; Liu, C. H.; Martin, G. L.; Domack, C. S.; Obara, C. J.; Hassan, A.; Gunzburger, M. D.; Nicolaides, R. A.

    1986-01-01

    New concept allows passive method for installing flaps, slats, iceprotection equipment, and other leading-edge devices on natural-laminar-flow (NLF) wings without causing loss of laminar flow. Two-dimensional roughness elements in laminar boundary layers strategically shaped to increase critical (allowable) height of roughness. Facilitates installation of leading-edge devices by practical manufacturing methods.

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

    SciTech Connect

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

    1987-12-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  15. Laminar Entrained Flow Reactor (Fact Sheet)

    SciTech Connect

    Not Available

    2014-02-01

    The Laminar Entrained Flow Reactor (LEFR) is a modular, lab scale, single-user reactor for the study of catalytic fast pyrolysis (CFP). This system can be employed to study a variety of reactor conditions for both in situ and ex situ CFP.

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

    NASA Astrophysics Data System (ADS)

    Huang, Xianmin

    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

  17. Computational Investigation of Dynamic Glottal Aperture Effects on Respiratory Airflow

    NASA Astrophysics Data System (ADS)

    Xi, Jinxiang; Yan, Hong; Dong, Haibo

    2008-11-01

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

  18. Airflow and Particle Transport in the Human Respiratory System

    NASA Astrophysics Data System (ADS)

    Kleinstreuer, C.; Zhang, Z.

    2010-01-01

    Airflows in the nasal cavities and oral airways are rather complex, possibly featuring a transition to turbulent jet-like flow, recirculating flow, Dean's flow, vortical flows, large pressure drops, prevailing secondary flows, and merging streams in the case of exhalation. Such complex flows propagate subsequently into the tracheobronchial airways. The underlying assumptions for particle transport and deposition are that the aerosols are spherical, noninteracting, and monodisperse and deposit upon contact with the airway surface. Such dilute particle suspensions are typically modeled with the Euler-Lagrange approach for micron particles and in the Euler-Euler framework for nanoparticles. Micron particles deposit nonuniformly with very high concentrations at some local sites (e.g., carinal ridges of large bronchial airways). In contrast, nanomaterial almost coats the airway surfaces, which has implications of detrimental health effects in the case of inhaled toxic nanoparticles. Geometric airway features, as well as histories of airflow fields and particle distributions, may significantly affect particle deposition.

  19. Efficient airflow design for cleanrooms improves business bottom lines

    SciTech Connect

    Xu, Tengfang

    2003-01-05

    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.

  20. Numerical calculations of strained premixed laminar flames

    NASA Astrophysics Data System (ADS)

    Darabiha, N.; Candel, S.; Marble, F. E.

    The structure of a strained laminar flame in the vicinity of a stagnation point is examined numerically. The stagnation point is established by the counterflow of fresh mixture and hot products. This situation is described by standard reactive boundary layer equations. The numerical scheme used to solve the similar boundary layer equations put in F-V form (block-implicit) is an adaptation of the schemes proposed by Blottner (1979). The calculations are performed first on an uniform grid and then confirmed with an adaptive grid method due to Smooke (1982). Numerical calculations allow an exact description of the flame structure in physical and also reduced coordinates. Predictions of Libby and Williams (1982) for high and intermediate values of the strain rate based on activation energy asymptotics are confirmed. For low strain rates (ordinary unstrained laminar flame) the mass rate of reaction per unit flame area differs from that obtained by activation energy asymptotics.

  1. Laminar flow instability in nuclear rockets

    SciTech Connect

    Black, D.L. )

    1993-01-20

    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.

  2. Insect contamination protection for laminar flow surfaces

    NASA Technical Reports Server (NTRS)

    Croom, Cynthia C.; Holmes, Bruce J.

    1986-01-01

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

  3. The Structure and Stability of Laminar Flames

    NASA Technical Reports Server (NTRS)

    Buckmaster, John

    1993-01-01

    This review paper on the structure and stability of laminar flames considers such phenomena as heterogeneous mixtures, acoustic instabilities, flame balls and related phenomena, radiation effects, the iodate oxidation of arsenous acid and 'liquid flame fronts', approximate kinetic mechanisms and asymptotic approximations, and tribrachial or triple flames. The topics examined here indicate three themes that may play an important role in laminar flame theory in the coming years: microgravity experiments, kinetic modeling, and turbulence modeling. In the discussion of microgravity experiments it is pointed out that access to drop towers, the Space Shuttle and, in due course, the Space Station Freedom will encourage the development of experiments well designed to isolate the fundamental physics of combustion.

  4. Coupling of wrinkled laminar flames with gravity

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    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.

  5. Natural laminar flow hits smoother air

    NASA Technical Reports Server (NTRS)

    Holmes, B. J.

    1985-01-01

    Natural laminar flow (NLF) may be attained in aircraft with lower cost, weight, and maintenance penalties than active flow laminarization by means of a slot suction system. A high performance general aviation jet aircraft possessing a moderate degree of NLF over wing, fuselage, empennage and engine nacelles will accrue a 24 percent reduction in total aircraft drag in the cruise regime. NASA-Langley has conducted NLF research centered on the use of novel airfoil profiles as well as composite and milled aluminum alloy construction methods which minimize three-dimensional aerodynamic surface roughness and waviness. It is noted that higher flight altitudes intrinsically reduce unit Reynolds numbers, thereby minimizing turbulence for a given cruise speed.

  6. Morphodynamic modeling of erodible laminar channels

    NASA Astrophysics Data System (ADS)

    Devauchelle, Olivier; Josserand, Christophe; Lagrée, Pierre-Yves; Zaleski, Stéphane

    2007-11-01

    A two-dimensional model for the erosion generated by viscous free-surface flows, based on the shallow-water equations and the lubrication approximation, is presented. It has a family of self-similar solutions for straight erodible channels, with an aspect ratio that increases in time. It is also shown, through a simplified stability analysis, that a laminar river can generate various bar instabilities very similar to those observed in natural rivers. This theoretical similarity reflects the meandering and braiding tendencies of laminar rivers indicated by F. Métivier and P. Meunier [J. Hydrol. 27, 22 (2003)]. Finally, we propose a simple scenario for the transition between patterns observed in experimental erodible channels.

  7. Air Trapping and Airflow Obstruction in Newborn Cystic Fibrosis Piglets

    PubMed Central

    Adam, Ryan J.; Michalski, Andrew S.; Bauer, Christian; Abou Alaiwa, Mahmoud H.; Gross, Thomas J.; Awadalla, Maged S.; Bouzek, Drake C.; Gansemer, Nicholas D.; Taft, Peter J.; Hoegger, Mark J.; Diwakar, Amit; Ochs, Matthias; Reinhardt, Joseph M.; Hoffman, Eric A.; Beichel, Reinhard R.; Meyerholz, David K.

    2013-01-01

    Rationale: Air trapping and airflow obstruction are being increasingly identified in infants with cystic fibrosis. These findings are commonly attributed to airway infection, inflammation, and mucus buildup. Objectives: To learn if air trapping and airflow obstruction are present before the onset of airway infection and inflammation in cystic fibrosis. Methods: On the day they are born, piglets with cystic fibrosis lack airway infection and inflammation. Therefore, we used newborn wild-type piglets and piglets with cystic fibrosis to assess air trapping, airway size, and lung volume with inspiratory and expiratory X-ray computed tomography scans. Micro–computed tomography scanning was used to assess more distal airway sizes. Airway resistance was determined with a mechanical ventilator. Mean linear intercept and alveolar surface area were determined using stereologic methods. Measurements and Main Results: On the day they were born, piglets with cystic fibrosis exhibited air trapping more frequently than wild-type piglets (75% vs. 12.5%, respectively). Moreover, newborn piglets with cystic fibrosis had increased airway resistance that was accompanied by luminal size reduction in the trachea, mainstem bronchi, and proximal airways. In contrast, mean linear intercept length, alveolar surface area, and lung volume were similar between both genotypes. Conclusions: The presence of air trapping, airflow obstruction, and airway size reduction in newborn piglets with cystic fibrosis before the onset of airway infection, inflammation, and mucus accumulation indicates that cystic fibrosis impacts airway development. Our findings suggest that early airflow obstruction and air trapping in infants with cystic fibrosis might, in part, be caused by congenital airway abnormalities. PMID:24168209

  8. Airflow pattern complexity and airway obstruction in asthma.

    PubMed

    Veiga, Juliana; Lopes, Agnaldo J; Jansen, José M; Melo, Pedro L

    2011-08-01

    The scientific and clinical value of a measure of complexity is potentially enormous because complexity appears to be lost in the presence of illness. The authors examined the effect of elevated airway obstruction on the complexity of the airflow (Q) pattern of asthmatic patients analyzing the airflow approximate entropy (ApEnQ). This study involved 11 healthy controls, 11 asthmatics with normal spirometric exams, and 40 asthmatics with mild (14), moderate (14), and severe (12) airway obstructions. A significant (P < 0.02) reduction in the ApEnQ was observed in the asthmatic patients. This reduction was significantly correlated with spirometric indexes of airway obstruction [FEV(1) (%): R = 0.31, P = 0.013] and the total respiratory impedance (R = -0.39; P < 0.002). These results are in close agreement with pathophysiological fundamentals and suggest that the airflow pattern becomes less complex in asthmatic patients, which may reduce the adaptability of the respiratory system to perform the exercise that is associated with daily life activities. This analysis was able to identify respiratory changes in patients with mild obstruction with an adequate accuracy (83%). Higher accuracies were obtained in patients with moderate and severe obstructions. The analysis of airflow pattern complexity by the ApEnQ was able to provide new information concerning the changes associated with asthma. In addition, this analysis was also able to contribute to the detection of the adverse effects of asthma. Because these measurements are easy to perform, such a technique may represent an alternative and/or a complement to other conventional exams to help the clinical evaluations of asthmatic patients. PMID:21565988

  9. A model for simulating airflow and pollutant dispersion around buildings

    SciTech Connect

    Chan, S T; Lee, R L

    1999-02-24

    A three-dimensional, numerical mode1 for simulating airflow and pollutant dispersion around buildings is described. The model is based on an innovative finite element approach and fully implicit time integration techniques. Linear and nonlinear eddy viscosity/diffusivity submodels are provided for turbulence parameterization. Mode1 predictions for the flow-field and dispersion patterns around a surface-mounted cube are compared with measured data from laboratory experiments.

  10. Trans-Laminar-Reinforced (TLR) Composites

    NASA Technical Reports Server (NTRS)

    Hinders, Mark; Dickinson, Larry

    1997-01-01

    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.

  11. Laminar Flow in the Ocean Ekman Layer

    NASA Astrophysics Data System (ADS)

    Woods, J. T. H.

    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

  12. Airflow Simulations around OA Intake Louver with Electronic Velocity Sensors

    SciTech Connect

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

    2009-04-01

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

  13. Realistic glottal motion and airflow rate during human breathing.

    PubMed

    Scheinherr, Adam; Bailly, Lucie; Boiron, Olivier; Lagier, Aude; Legou, Thierry; Pichelin, Marine; Caillibotte, Georges; Giovanni, Antoine

    2015-09-01

    The glottal geometry is a key factor in the aerosol delivery efficiency for treatment of lung diseases. However, while glottal vibrations were extensively studied during human phonation, the realistic glottal motion during breathing is poorly understood. Therefore, most current studies assume an idealized steady glottis in the context of respiratory dynamics, and thus neglect the flow unsteadiness related to this motion. This is particularly important to assess the aerosol transport mechanisms in upper airways. This article presents a clinical study conducted on 20 volunteers, to examine the realistic glottal motion during several breathing tasks. Nasofibroscopy was used to investigate the glottal geometrical variations simultaneously with accurate airflow rate measurements. In total, 144 breathing sequences of 30s were recorded. Regarding the whole database, two cases of glottal time-variations were found: "static" or "dynamic" ones. Typically, the peak value of glottal area during slow breathing narrowed from 217 ± 54 mm(2) (mean ± STD) during inspiration, to 178 ± 35 mm(2) during expiration. Considering flow unsteadiness, it is shown that the harmonic approximation of the airflow rate underevaluates the inertial effects as compared to realistic patterns, especially at the onset of the breathing cycle. These measurements provide input data to conduct realistic numerical simulations of laryngeal airflow and particle deposition. PMID:26159687

  14. Field measurement of uncontrolled airflow and depressurization in restaurants

    SciTech Connect

    Cummings, J.B.; Fairey, P.W.; Withers, C.R. Jr.; McKendry, B.B.; Moyer, N.A.

    1996-11-01

    Field investigations were done in seven restaurants (subsample of a study of 63 commercial buildings) to identify uncontrolled airflows and pressure imbalances. Testing included building airtightness tests, identification of building air barrier locations, duct system airtightness, characterization of pressure differentials, building airflow balance, and infiltration/ventilation rates. All restaurants were found to operate at negative pressures that ranged from {minus}0.003 in. w.c. ({minus}0.8 Pa) to {minus}0.173 in. w.c. ({minus}43 Pa) and averaged {minus}0.051 in. w.c. ({minus}12.7 Pa) under normal operation. The variables that affect depressurization are large exhaust fans, missing or undersized make up air, intermittent outdoor air caused by the cycling of air handlers, dirty outdoor air and make up air filters, and building airtightness. These uncontrolled airflows and pressure imbalances impact energy use, ventilation rates, sizing of heating and air-conditioning systems, indoor comfort, relative humidity, moisture damage to building materials, mold and mildew growth, operation of combustion equipment, and indoor air quality.

  15. Energy Harvesting from Human Motion Using Footstep-Induced Airflow

    NASA Astrophysics Data System (ADS)

    Fu, H.; Xu, R.; Seto, K.; Yeatman, E. M.; Kim, S. G.

    2015-12-01

    This paper presents an unobtrusive in-shoe energy harvester converting foot-strike energy into electricity to power wearable or portable devices. An air-pumped turbine system is developed to address the issues of the limited vertical deformation of shoes and the low frequency of human motion that impede harvesting energy from this source. The air pump is employed to convert the vertical foot-strike motion into airflow. The generated airflow passes through the miniaturized wind turbine whose transduction is realized by an electromagnetic generator. Energy is extracted from the generator with a higher frequency than that of footsteps, boosting the output power of the device. The turbine casing is specifically designed to enable the device to operate continuously with airflow in both directions. A prototype was fabricated and then tested under different situations. A 6 mW peak power output was obtained with a 4.9 Ω load. The achievable power from this design was estimated theoretically for understanding and further improvement.

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

    NASA Technical Reports Server (NTRS)

    Smith, S. C.

    1985-01-01

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

  17. Flame Structure and Scalar Properties in Microgravity Laminar Fires

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  19. Laminar natural convection under nonuniform gravity.

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

  20. Large eddy simulations of laminar separation bubble

    NASA Astrophysics Data System (ADS)

    Cadieux, Francois

    The flow over blades and airfoils at moderate angles of attack and Reynolds numbers ranging from ten thousand to a few hundred thousands undergoes separation due to the adverse pressure gradient generated by surface curvature. In many cases, the separated shear layer then transitions to turbulence and reattaches, closing off a recirculation region -- the laminar separation bubble. To avoid body-fitted mesh generation problems and numerical issues, an equivalent problem for flow over a flat plate is formulated by imposing boundary conditions that lead to a pressure distribution and Reynolds number that are similar to those on airfoils. Spalart & Strelet (2000) tested a number of Reynolds-averaged Navier-Stokes (RANS) turbulence models for a laminar separation bubble flow over a flat plate. Although results with the Spalart-Allmaras turbulence model were encouraging, none of the turbulence models tested reliably recovered time-averaged direct numerical simulation (DNS) results. The purpose of this work is to assess whether large eddy simulation (LES) can more accurately and reliably recover DNS results using drastically reduced resolution -- on the order of 1% of DNS resolution which is commonly achievable for LES of turbulent channel flows. LES of a laminar separation bubble flow over a flat plate are performed using a compressible sixth-order finite-difference code and two incompressible pseudo-spectral Navier-Stokes solvers at resolutions corresponding to approximately 3% and 1% of the chosen DNS benchmark by Spalart & Strelet (2000). The finite-difference solver is found to be dissipative due to the use of a stability-enhancing filter. Its numerical dissipation is quantified and found to be comparable to the average eddy viscosity of the dynamic Smagorinsky model, making it difficult to separate the effects of filtering versus those of explicit subgrid-scale modeling. The negligible numerical dissipation of the pseudo-spectral solvers allows an unambiguous

  1. Subsonic natural-laminar-flow airfoils

    NASA Technical Reports Server (NTRS)

    Somers, Dan M.

    1992-01-01

    An account is given of the development history of natural laminar-flow (NLF) airfoil profiles under guidance of an experimentally well-verified theoretical method for the design of airfoils suited to virtually all subcritical applications. This method, the Eppler Airfoil Design and Analysis Program, contains a conformal-mapping method for airfoils having prescribed velocity-distribution characteristics, as well as a panel method for the analysis of potential flow about given airfoils and a boundary-layer method. Several of the NLF airfoils thus obtained are discussed.

  2. Thermal laminarization of a stratified pipe flow

    SciTech Connect

    Oras, J.J.; Kasza, K.E.

    1984-01-01

    The present work constitutes a new program that grew out of a scoping assessment by ANL to determine the propensity for pipe stratification to occur in the reactor outlet nozzles and hot-leg piping of a generic LMFBR during events producing reverse pipe flow. This paper focuses on the role that thermal buoyancy plays relative to being able to laminarize a turbulent stratified shear zone in a horizontal pipe. The preceeding can influence the behavior of a pipe stratified-backflow-recirculation zone (cold plenum water down into the hot pipe flow) which developes as the result of a temperature difference between the pipe flow and the plenum.

  3. Design Considerations for Laminar Flow Control Aircraft

    NASA Technical Reports Server (NTRS)

    Sturgeon, R. F.; Bennett, J. A.

    1976-01-01

    A study was conducted to investigate major design considerations involved in the application of laminar flow control to the wings and empennage of long range subsonic transport aircraft compatible with initial operation in 1985. For commercial transports with a design mission range of 10,186 km (5500 n mil) and a payload of 200 passengers, parametric configuration analyses were conducted to evaluate the effect of aircraft performance, operational, and geometric parameters on fuel efficiency. Study results indicate that major design goals for aircraft optimization include maximization of aspect ratio and wing loading and minimization of wing sweep consistent with wing volume and airport performance requirements.

  4. Velocity profiles in laminar diffusion flames

    NASA Technical Reports Server (NTRS)

    Lyons, Valerie J.; Margle, Janice M.

    1986-01-01

    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.

  5. Evaluation of different airflow sensors at the WIPP facility

    SciTech Connect

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

    1999-07-01

    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.

  6. Integrative pathway genomics of lung function and airflow obstruction.

    PubMed

    Gharib, Sina A; Loth, Daan W; Soler Artigas, María; Birkland, Timothy P; Wilk, Jemma B; Wain, Louise V; Brody, Jennifer A; Obeidat, Ma'en; Hancock, Dana B; Tang, Wenbo; Rawal, Rajesh; Boezen, H Marike; Imboden, Medea; Huffman, Jennifer E; Lahousse, Lies; Alves, Alexessander C; Manichaikul, Ani; Hui, Jennie; Morrison, Alanna C; Ramasamy, Adaikalavan; Smith, Albert Vernon; Gudnason, Vilmundur; Surakka, Ida; Vitart, Veronique; Evans, David M; Strachan, David P; Deary, Ian J; Hofman, Albert; Gläser, Sven; Wilson, James F; North, Kari E; Zhao, Jing Hua; Heckbert, Susan R; Jarvis, Deborah L; Probst-Hensch, Nicole; Schulz, Holger; Barr, R Graham; Jarvelin, Marjo-Riitta; O'Connor, George T; Kähönen, Mika; Cassano, Patricia A; Hysi, Pirro G; Dupuis, Josée; Hayward, Caroline; Psaty, Bruce M; Hall, Ian P; Parks, William C; Tobin, Martin D; London, Stephanie J

    2015-12-01

    Chronic respiratory disorders are important contributors to the global burden of disease. Genome-wide association studies (GWASs) of lung function measures have identified several trait-associated loci, but explain only a modest portion of the phenotypic variability. We postulated that integrating pathway-based methods with GWASs of pulmonary function and airflow obstruction would identify a broader repertoire of genes and processes influencing these traits. We performed two independent GWASs of lung function and applied gene set enrichment analysis to one of the studies and validated the results using the second GWAS. We identified 131 significantly enriched gene sets associated with lung function and clustered them into larger biological modules involved in diverse processes including development, immunity, cell signaling, proliferation and arachidonic acid. We found that enrichment of gene sets was not driven by GWAS-significant variants or loci, but instead by those with less stringent association P-values. Next, we applied pathway enrichment analysis to a meta-analyzed GWAS of airflow obstruction. We identified several biologic modules that functionally overlapped with those associated with pulmonary function. However, differences were also noted, including enrichment of extracellular matrix (ECM) processes specifically in the airflow obstruction study. Network analysis of the ECM module implicated a candidate gene, matrix metalloproteinase 10 (MMP10), as a putative disease target. We used a knockout mouse model to functionally validate MMP10's role in influencing lung's susceptibility to cigarette smoke-induced emphysema. By integrating pathway analysis with population-based genomics, we unraveled biologic processes underlying pulmonary function traits and identified a candidate gene for obstructive lung disease. PMID:26395457

  7. Airflow, gas deposition, and lesion distribution in the nasal passages

    SciTech Connect

    Morgan, K.T.; Monticello, T.M. )

    1990-04-01

    The nasal passages of laboratory animals and man are complex, and lesions induced in the delicate nasal lining by inhaled air pollutants vary considerably in location and nature. The distribution of nasal lesions is generally a consequence of regional deposition of the inhaled material, local tissue susceptibility, or a combination of these factors. Nasal uptake and regional deposition are are influenced by numerous factors including the physical and chemical properties of the inhaled material, such as water solubility and reactivity; airborne concentration and length of exposure; the presence of other air contaminants such as particulate matter; nasal metabolism, and blood and mucus flow. For certain highly water-soluble or reactive gases, nasal airflow patterns play a major role in determining lesion distribution. Studies of nasal airflow in rats and monkeys, using casting and molding techniques combined with a water-dye model, indicate that nasal airflow patterns are responsible for characteristic differences in the distribution of nasal lesions induced by formaldehyde in these species. Local tissue susceptibility is also a complex issue that may be a consequence of many factors, including physiologic and metabolic characteristics of the diverse cell populations that comprise each of the major epithelial types lining the airways. Identification of the principal factors that influence the distribution and nature of nasal lesions is important when attempting the difficult process of determining potential human risks using data derived from laboratory animals. Toxicologic pathologists can contribute to this process by carefully identifying the site and nature of nasal lesions induced by inhaled materials. 61 references.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

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

    SciTech Connect

    DEROSA, D.C.

    1999-08-26

    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.

  10. CFD modeling of pharmaceutical isolators with experimental verification of airflow.

    PubMed

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

    2007-01-01

    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

  11. EFFECT OF AIRFLOW AND HEAT INPUT RATES ON DUCT EFFICIENCY.

    SciTech Connect

    ANDREWS,J.W.

    2003-05-28

    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.

  12. Vapor-Generator Wand Helps To Reveal Airflow Patterns

    NASA Technical Reports Server (NTRS)

    Robelen, David B.

    1993-01-01

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

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

    NASA Technical Reports Server (NTRS)

    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

    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.

  14. A Series of Laminar Jet Flame

    NASA Technical Reports Server (NTRS)

    2003-01-01

    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.

  15. Series of Laminar Soot Processes Experiment

    NASA Technical Reports Server (NTRS)

    2003-01-01

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

  16. Gliding swifts attain laminar flow over rough wings.

    PubMed

    Lentink, David; de Kat, Roeland

    2014-01-01

    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

  17. Gliding Swifts Attain Laminar Flow over Rough Wings

    PubMed Central

    Lentink, David; de Kat, Roeland

    2014-01-01

    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

  18. Mechanism of bronchodilator effect in chronic airflow limitation.

    PubMed Central

    Jaeschke, R; Guyatt, G H; Singer, J; Keller, J; Newhouse, M T

    1991-01-01

    OBJECTIVE: To examine the mechanisms through which two bronchodilators (theophylline and salbutamol) influence dyspnea during daily activities. METHODS: Twenty-four patients with chronic airflow limitation participated in a multiple crossover, randomized, placebo-controlled trial. The effect of theophylline and salbutamol, alone or combined, on pulmonary function and dyspnea during daily activities was examined. Correlations of changes in forced expiratory volume in 1 second (FEV1) and maximum expiratory pressures (MIPs) (independent variables) and changes in dyspnea score during daily activities (dependent variable) were also examined. RESULTS: The two drugs proved to be beneficial the effects in general were additive rather than synergistic. The drugs improved the FEV1; theophylline significantly improved the MIPs. The correlation between the changes in FEV1 and those in dyspnea score, after adjustment for the changes in MIPs, was 0.55 (p less than 0.001). The correlation between the changes in MIPs and those in dyspnea score, after adjustment for the changes in FEV1, was 0.39 (p less than 0.001). CONCLUSIONS: Changes in airway calibre and in respiratory muscle strength play an independent and important role in dyspnea during daily activities in patients with chronic airflow limitation. Changes in airway calibre may be of greater importance. PMID:1984814

  19. Forced-air patient warming blankets disrupt unidirectional airflow.

    PubMed

    Legg, A J; Hamer, A J

    2013-03-01

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

  20. Inspirational airflow patterns in deviated noses: a numerical study.

    PubMed

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

    2013-01-01

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

  1. 42 CFR 84.1149 - Airflow resistance tests; all dust, fume, and mist respirators; minimum requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Airflow resistance tests; all dust, fume, and mist... RESPIRATORY PROTECTIVE DEVICES Dust, Fume, and Mist; Pesticide; Paint Spray; Powered Air-Purifying High Efficiency Respirators and Combination Gas Masks § 84.1149 Airflow resistance tests; all dust, fume, and...

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

    NASA Technical Reports Server (NTRS)

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

    1996-01-01

    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.

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

    SciTech Connect

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

    2011-11-01

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

  4. Systemic leukopenia, evaluation of laminar leukocyte infiltration and laminar lesions in horses with naturally occurring colic syndrome.

    PubMed

    Laskoski, Luciane Maria; Locatelli-Dittrich, Rosangela; Valadão, Carlos Augusto Araújo; Deconto, Ivan; Gonçalves, Kamila Alcala; Montiani-Ferreira, Fabiano; Brum, Juliana Sperotto; de Brito, Harald Fernando Vicente; de Sousa, Renato Silva

    2015-08-01

    The present study was aimed at identifying laminar lesions and leukocyte infiltration in hoof laminar tissue of horses with colic syndrome and its correlation with the total leukocyte count before death. Six healthy horses were used as control group (CG), and eighteen horses with lethal gastrointestinal disease were divided into two groups: leukopenic group (LG) with seven leukopenic horses, and non-leukopenic group (NLG) with 11 horses with total leukocyte count within reference range for the species. Leukocyte infiltration was examined by immunohistochemistry. Laminar lesions were observed in both LG and NLG, with no differences in severity between them. LG showed increase of the leukocyte infiltration in the hoof laminar tissue, when compared to CG and NLG. Horses with severe colic syndrome (LG and NLG) developed intense laminar lesions without clinical signs of laminitis, with increased leukocyte infiltration. However, the LG demonstrated an even higher increase of leukocyte infiltration compared to both CG and NLG. PMID:26267083

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

    NASA Astrophysics Data System (ADS)

    Sakai, Yasuyuki

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

  6. Differently patterned airflows induced by 1-kHz femtosecond laser filaments in a cloud chamber

    NASA Astrophysics Data System (ADS)

    Sun, Haiyi; Liang, Hong; Liu, Yonghong; Ju, Jingjing; Wei, Yingxia; Wang, Cheng; Wang, Tiejun; Liu, Jiansheng; Chin, See Leang; Li, Ruxin; Xu, Zhizhan

    2015-11-01

    Airflow induced by femtosecond laser (800 nm/1 kHz/25 fs) filamentation with different lengths was investigated in a laboratory cloud chamber. Various filament lengths were generated by adjusting laser energy and lens focal length. It was found that airflow patterns are closely related to filament intensity and length. Intense and long filaments are beneficial in updraft generation with large vortices above the filament, while intense and short filaments tend to promote the formation of well-contacted vortices below the filament. Differently patterned airflows induced elliptical snow piles with different masses. We simulated airflow in a cloud chamber numerically taking laser filaments as heat sources. The mechanisms of differently patterned airflow and snow formation induced by filaments were discussed.

  7. Volume Diffuse Dielectric Barrier Discharge Plasma Produced by Nanosecond High Voltage Pulse in Airflow

    NASA Astrophysics Data System (ADS)

    Qi, Haicheng; Gao, Wei; Fan, Zhihui; Liu, Yidi; Ren, Chunsheng

    2016-05-01

    Volume diffuse dielectric barrier discharge (DBD) plasma is produced in subsonic airflow by nanosecond high-voltage pulse power supply with a plate-to-plate discharge cell at 6 mm air gap length. The discharge images, optical emission spectra (OES), the applied voltage and current waveforms of the discharge at the changed airflow rates are obtained. When airflow rate is increased, the transition of the discharge mode and the variations of discharge intensity, breakdown characteristics and the temperature of the discharge plasma are investigated. The results show that the discharge becomes more diffuse, discharge intensity is decreased accompanied by the increased breakdown voltage and time lag, and the temperature of the discharge plasma reduces when airflow of small velocity is introduced into the discharge gap. These phenomena are because that the airflow changes the spatial distribution of the heat and the space charge in the discharge gap. supported by National Natural Science Foundation of China (No. 51437002)

  8. Energy savings from repair of uncontrolled airflow in 18 small commercial buildings

    SciTech Connect

    Withers, C.R. Jr.; Cummings, J.B.; Fairey, P.W.; McKendry, B.B.; Moyer, N.A.

    1996-12-31

    Uncontrolled airflow, including duct leakage, pressure imbalances caused by closed interior doors, and exhaust/intake airflow imbalance, was characterized in 70 commercial buildings. In 18 of these buildings, uncontrolled airflows were repaired and energy savings from these repairs were monitored. In most buildings, the retrofit was duct repair. In other cases, outdoor airflow was reduced and return air transfers were provided. Cooling energy use was reduced by an average 15.1% in these 18 buildings. With an average repair cost of $455 and average cooling energy savings of $195 per year, uncontrolled airflow retrofits proved to be very cost-effective. Various factors indicate that greater energy savings could be achieved in the future.

  9. Possible coseismic laminar and non-laminar flow along subduction megathrusts

    NASA Astrophysics Data System (ADS)

    Ujiie, K.; Noguchi, K.; Saito, T.; Tsutsumi, A.

    2014-12-01

    Coseismic deformation mechanisms during subduction earthquakes remained unclear other than frictional melting recorded in pseudotachylytes. However, the recent mineralogical studies in the shallow plate-boundary thrust in the Nankai subduction zone and the underplating-related duplex-fault zone in the Shimanto accretionary complex exhumed from 4-6 km depth have identified increased heating along the 2 mm-thick, clay-rich fault gouge and the few-centimeters-thick, basalt-derived ultracataclasite, respectively. The microstructures of the fault gouge are characterized by strong preferred orientation of clay particles along the gouge, while those of the ultracataclasite show the random fabric. High-velocity friction experiments were conducted on the disaggregated fault rocks under wet (water-saturated) conditions at different normal stresses, using the rotary shear frictional testing apparatus. The results show the rapid slip weakening with low peak and steady-state shear stress, and a very small slip weakening distance and fracture energy, suggesting the ease of earthquake rupture propagation through the fault materials. The steady-state shear stress is almost independent of normal stress, indicating that the gouge behaved like a fluid during high-velocity shearing. The microstructures after the experiments are marked by the development of foliated zone in the gouge layer, but the random fabric develops in the outermost region of the circular gouge layer. Given the nearly independence of steady-state shear stress on normal stress and the increase in the rotation velocity from the center of the rotation axis during the rotary shear, the change from foliated zone to non-foliated, random fabric in the circular gouge layer could represent the change from laminar to non-laminar (or turbulent) flow associated with the increase in the Reynolds number. The implications for the fault rocks are that the development of foliated and non-foliated zones may represent coseismic

  10. Cortical laminar necrosis following myocardial infarction.

    PubMed

    Lattanzi, Simona; Silvestrini, Mauro; Provinciali, Leandro

    2016-01-01

    The cortical laminar necrosis (CLN) is a permanent injury characterized by the selective delayed necrosis of the cerebral cortex, mainly of the third layer, and usually greater in the depths and sides of the sulci than over the crest of the gyri. The damage involves all cellular components - either neurons, glia cells and blood vessels - and results in a focal cortical band of pan-necrosis detectable in late sub-acute or chronic stages of reduced energy supply to the brain. The CLN has been described in different conditions as hypoxia, hypoglycemia and status epilepticus. At brain CT or MR scans it appears with pathognomonic highly hyperdense or T1-hyperintense lesions following the gyral anatomy of the cerebral cortex. We reported a case of CLN associated to myocardial infarct and discussed the underlying mechanisms. PMID:27375142

  11. A laminar solid core photonic crystal waveguide

    NASA Astrophysics Data System (ADS)

    Willig, R. L.

    2005-11-01

    A one-dimensional model is presented to explain the physics of solid core photonic crystal fibers. The model provides a clear way to demonstrate many of the interesting characteristics of these fibers: variation of cladding index with wavelength, endlessly single-mode operation, short wavelength index limit, long wavelength index limit, and variation of these properties with the air/silica fraction. The effective index is calculated for a laminar cladding consisting of periodic layers of alternating high and low index dielectrics. The waveguide model consists of the same periodic layers surrounding a high-index core through which most of the light propagates. The light is confined by total internal reflection. The model is shown to be an accurate analogue for a more complicated two-dimensional finned dielectric waveguide.

  12. Laminar superlayer at the turbulence boundary.

    PubMed

    Holzner, M; Lüthi, B

    2011-04-01

    In this Letter we present results from particle tracking velocimetry and direct numerical simulation that are congruent with the existence of a laminar superlayer, as proposed in the pioneering work of Corrsin and Kistler (NACA, Technical Report No. 1244, 1955). We find that the local superlayer velocity is dominated by a viscous component and its magnitude is comparable to the characteristic velocity of the smallest scales of motion. This slow viscous process involves a large surface area so that the global rate of turbulence spreading is set by the largest scales of motion. These findings are important for a better understanding of mixing of mass and momentum in a variety of flows where thin layers of shear exist. Examples are boundary layers, clouds, planetary atmospheres, and oceans. PMID:21517388

  13. Flight research on natural laminar flow applications

    NASA Technical Reports Server (NTRS)

    Holmes, Bruce J.; Obara, Clifford J.

    1992-01-01

    Natural laminar flow (NLF) is clearly one of the most potentially attractive drag reduction technologies by virtue of its relative simplicity. NLF is achieved passively, that is, by design of surface shapes to produce favorable pressure gradients. However, it is not without its challenges and limitations. This chapter describes the significant challenges to achieving and maintaining NLF and documents certain of the limitations for practical applications. A brief review of the history and of more recent NLF flight experiments is given, followed by a summary of lessons learned which are pertinent to future applications. The chapter also summarizes important progress in test techniques, particularly in flow visualization and hot-film techniques for boundary-layer measurements in flight.

  14. Base pressure in laminar supersonic flow.

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  15. Laminar flow control SPF/08 feasibility demonstration

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    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.

  16. Toward a laminar-flow-control transport

    NASA Technical Reports Server (NTRS)

    Sturgeon, R. F.

    1978-01-01

    Analyses were conducted to define a practical design for an advanced technology laminar flow control (LRC) transport for initial passenger operation in the early 1990's. Mission requirements, appropriate design criteria, and level of technology for the study aircraft were defined. The characteristics of the selected configuration were established, aircraft and LFC subsystems compatible with the mission requirements were defined, and the aircraft was evaluated in terms of fuel efficiency. A wing design integrating the LFC ducting and metering system into advanced composite wing structure was developed, manufacturing procedures for the surface panel design were established, and environmental and structural testing of surface panel components were conducted. Test results revealed a requirement for relatively minor changes in the manufacturing procedures employed, but have shown the general compatibility of both the selected design and the use of composite materials with the requirements of LFC wing surface panels.

  17. On the combustion of a laminar spray

    NASA Technical Reports Server (NTRS)

    Levy, Yeshayahou; Bulzan, Daniel L.

    1993-01-01

    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.

  18. Thermohydrodynamic analysis for laminar lubricating films

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  19. Laminar flow control perforated wing panel development

    NASA Technical Reports Server (NTRS)

    Fischler, J. E.

    1986-01-01

    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.

  20. Compressible laminar streaks with wall suction

    NASA Astrophysics Data System (ADS)

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

    2013-05-01

    The response of a compressible laminar boundary layer subject to free-stream vortical disturbances and steady mean-flow wall suction is studied. The theoretical frameworks of Leib et al. [J. Fluid Mech. 380, 169-203 (1999), 10.1017/S0022112098003504] and Ricco and Wu [J. Fluid Mech. 587, 97-138 (2007), 10.1017/S0022112007007070], based on the linearized unsteady boundary-region equations, are adopted to study the influence of suction on the kinematic and thermal streaks arising through the interaction between the free-stream vortical perturbations and the boundary layer. In the asymptotic limit of small spanwise wavelength compared with the boundary layer thickness, i.e., when the disturbance flow is conveniently described by the steady compressible boundary region equations, the effect of suction is mild on the velocity fluctuations and negligible on the temperature fluctuations. When the spanwise wavelength is comparable with the boundary layer thickness, small suction values intensify the supersonic streaks, while higher transpiration levels always stabilize the disturbances at all Mach numbers. At larger spanwise wavelengths, very small amplitudes of wall transpiration have a dramatic stabilizing effect on all boundary layer fluctuations, which can take the form of transiently growing thermal streaks, large amplitude streamwise oscillations, or oblique exponentially growing Tollmien-Schlichting waves, depending on the Mach number and the wavelengths. The range of wavenumbers for which the exponential growth occurs becomes narrower and the location of instability is significantly shifted downstream by mild suction, indicating that wall transpiration can be a suitable vehicle for delaying transition when the laminar breakdown is promoted by these unstable disturbances. The typical streamwise wavelength of these disturbances is instead not influenced by suction, and asymptotic triple deck theory predicts the strong changes in growth rate and the very mild

  1. F-111 TACT natural laminar flow glove flight results

    NASA Technical Reports Server (NTRS)

    Montoya, L. C.; Steers, L. L.; Trujillo, B.

    1981-01-01

    Improvements in cruise efficiency on the order of 15 to 40% are obtained by increasing the extent of laminar flow over lifting surfaces. Two methods of achieving laminar flow are being considered, natural laminar flow and laminar flow control. Natural laminar flow (NLF) relies primarily on airfoil shape while laminar flow control involves boundary layer suction or blowing with mechanical devices. The extent of natural laminar flow that could be achieved with consistency in a real flight environment at chord Reynolds numbers in the range of 30 x 10(6) power was evaluated. Nineteen flights were conducted on the F-111 TACT airplane having a NLF airfoil glove section. The section consists of a supercritical airfoil providing favorable pressure gradients over extensive portions of the upper and lower surfaces of the wing. Boundary layer measurements were obtained over a range of wing leading edge sweep angles at Mach numbers from 0.80 to 0.85. Data were obtained for natural transition and for a range of forced transition locations over the test airfoil.

  2. Airflow and optic flow mediate antennal positioning in flying honeybees.

    PubMed

    Roy Khurana, Taruni; Sane, Sanjay P

    2016-01-01

    To maintain their speeds during navigation, insects rely on feedback from their visual and mechanosensory modalities. Although optic flow plays an essential role in speed determination, it is less reliable under conditions of low light or sparse landmarks. Under such conditions, insects rely on feedback from antennal mechanosensors but it is not clear how these inputs combine to elicit flight-related antennal behaviours. We here show that antennal movements of the honeybee, Apis mellifera, are governed by combined visual and antennal mechanosensory inputs. Frontal airflow, as experienced during forward flight, causes antennae to actively move forward as a sigmoidal function of absolute airspeed values. However, corresponding front-to-back optic flow causes antennae to move backward, as a linear function of relative optic flow, opposite the airspeed response. When combined, these inputs maintain antennal position in a state of dynamic equilibrium. PMID:27097104

  3. Effect of airflow on biodrying of gardening wastes in reactors.

    PubMed

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

    2013-05-01

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

  4. Airflow and optic flow mediate antennal positioning in flying honeybees

    PubMed Central

    Roy Khurana, Taruni; Sane, Sanjay P

    2016-01-01

    To maintain their speeds during navigation, insects rely on feedback from their visual and mechanosensory modalities. Although optic flow plays an essential role in speed determination, it is less reliable under conditions of low light or sparse landmarks. Under such conditions, insects rely on feedback from antennal mechanosensors but it is not clear how these inputs combine to elicit flight-related antennal behaviours. We here show that antennal movements of the honeybee, Apis mellifera, are governed by combined visual and antennal mechanosensory inputs. Frontal airflow, as experienced during forward flight, causes antennae to actively move forward as a sigmoidal function of absolute airspeed values. However, corresponding front-to-back optic flow causes antennae to move backward, as a linear function of relative optic flow, opposite the airspeed response. When combined, these inputs maintain antennal position in a state of dynamic equilibrium. DOI: http://dx.doi.org/10.7554/eLife.14449.001 PMID:27097104

  5. Indirect evaporative cooler with condensation of primary airflow

    SciTech Connect

    Vollebregt, H.J.M.; Jong, T. de

    1994-12-31

    In this paper a new application for indirect evaporative cooling is introduced. This cooling principle may be used to cool and dehumidify closed greenhouses. A prototype indirect evaporative cooler with a crossflow configuration was built and its performance was determined in an experimental facility. During tests under Dutch design conditions of the greenhouse and outside air, the plate temperature was less than the dew point of the greenhouse air, so condensation occurred. The rates of sensible and latent heat transferred from the greenhouse air by the prototype cooler were determined. Also, the influence of greenhouse and outside air conditions and airflow rates in the cooler on the enthalpy efficiency was studied. Although the amount of condensation in the prototype indirect evaporative cooler was large, the resulting climate in a closed greenhouse may be more humid than that in a conventional one.

  6. Mushrooms use convectively created airflows to disperse their spores.

    PubMed

    Dressaire, Emilie; Yamada, Lisa; Song, Boya; Roper, Marcus

    2016-03-15

    Thousands of basidiomycete fungal species rely on mushroom spores to spread across landscapes. It has long been thought that spores depend on favorable winds for dispersal--that active control of spore dispersal by the parent fungus is limited to an impulse delivered to the spores to carry them clear of the gill surface. Here we show that evaporative cooling of the air surrounding the pileus creates convective airflows capable of carrying spores at speeds of centimeters per second. Convective cells can transport spores from gaps that may be only 1 cm high and lift spores 10 cm or more into the air. This work reveals how mushrooms tolerate and even benefit from crowding and explains their high water needs. PMID:26929324

  7. Uninstrumented assembly airflow testing in the Annular Flow Distribution facility

    SciTech Connect

    Kielpinski, A.L.

    1992-02-01

    During the Emergency Cooling System phase of a postulated large-break loss of coolant accident (ECS-LOCA), air enters the primary loop and is pumped down the reactor assemblies. One of the experiments performed to support the analysis of this accident was the Annular Flow Distribution (AFD) experiment, conducted in a facility built for this purpose at Babcock and Wilcox Alliance Research Center in Alliance, Ohio. As part of this experiment, a large body of airflow data were acquired in a prototypical mockup of the Mark 22 reactor assembly. This assembly was known as the AFD (or the I-AFD here) reference assembly. The I-AFD assembly was fully prototypical, having been manufactured in SRS`s production fabrication facility. Similar Mark 22 mockup assemblies were tested in several test facilities in the SRS Heat Transfer Laboratory (HTL). Discrepancies were found. The present report documents further work done to address the discrepancy in airflow measurements between the AFD facility and HTL facilities. The primary purpose of this report is to disseminate the data from the U-AFD test, and to compare these test results to the I-AFD data and the U-AT data. A summary table of the test data and the B&W data transmittal letter are included as an attachment to this report. The full data transmittal volume from B&W (including time plots of the various instruments) is included as an appendix to this report. These data are further analyzed by comparing them to two other HTL tests, namely, SPRIHTE 1 and the Single Assembly Test Stand (SATS).

  8. The role of the olfactory recess in olfactory airflow.

    PubMed

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

    2014-05-15

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

  9. Asthma, airflow limitation, and mortality risk in the general population

    PubMed Central

    Huang, Shuang; Vasquez, Monica M; Halonen, Marilyn; Martinez, Fernando D; Guerra, Stefano

    2015-01-01

    Asthma and chronic obstructive pulmonary disease co-exist in a significant proportion of patients. Whether asthma increases mortality risk among subjects with airflow limitation remains controversial. We used data from 2121 adult participants in the population-based TESAOD cohort. At enrollment (1972–73), participants completed questionnaires and lung function tests. Participants were categorized into four groups based on the combination of airflow limitation (AL: FEV1/FVC<70%) and physician-confirmed asthma at baseline. Vital status as of January 2011 was assessed through the National Death Index. Cox proportional hazards models were used to test differences in mortality risk across the four AL/Asthma groups. In multivariate Cox models, the AL+/Asthma+ group had a 114% increased mortality risk over the follow-up as compared with the AL-/Asthma- group (adjHR: 2.14, 1.64–2.79). The corresponding Hazard Ratios were 1.09 (0.89–1.34) and 1.34 (1.14–1.57) for the AL-/Asthma+ and AL+/Asthma- groups, respectively. Among subjects with AL, asthma was associated with increased mortality risk (1.58, 1.17–2.12). However, this increased risk was substantially reduced and no longer significant after further adjustment for baseline FEV1 levels. Similar results were obtained when AL was defined as FEV1/FVC

  10. Numerical simulation of airflow in the human nose.

    PubMed

    Weinhold, Ivo; Mlynski, Gunter

    2004-09-01

    Unobstructed air passageways as well as sufficient contact of the air stream with the mucous membrane are essential for the correct function of the nose. For that, local flow phenomena, which often cannot be captured by standard diagnostic methods, are important. We developed and validated a method for the numerical simulation of the nasal airflow. Two anatomically correct, transparent resin models of human nasal cavities, manufactured by a special casting technology, and the nasal cavities of two patients were reconstructed as Computer Aided Design models based on computed tomography (CT) scans. One of the nasal models and one clinical case represented a normal nasal anatomy, while the others were examples of pathological alterations. The velocity and pressure fields in these reconstructed cavities were calculated for the entire range of physiological nasal inspiration using commercially available computational fluid dynamics software. To validate the results rhinoresistometric data were measured and characteristic streamlines were videotaped for the resin models. The numerical results were in good agreement with the experimental data for the investigated cases. An example of a complex clinical case demonstrates the potential benefit of the developed simulation method for rhinosurgical planning. The results support the assumption that even under the specific conditions of the clinical practice the application of numerical simulation of nasal airflow phenomena may become realistic in the near future. However, important technical issues such as a completely automated reconstruction of the nasal cavity still need to be resolved before such simulations are efficient and cost effective enough to become a standard tool for the rhinologist. PMID:14652769

  11. 42 CFR 84.154 - Airflow resistance test; Type B and Type BE supplied-air respirators; minimum requirements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false Airflow resistance test; Type B and Type BE... APPROVAL OF RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators § 84.154 Airflow resistance test; Type B and Type BE supplied-air respirators; minimum requirements. (a) Airflow resistance shall...

  12. 42 CFR 84.154 - Airflow resistance test; Type B and Type BE supplied-air respirators; minimum requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Airflow resistance test; Type B and Type BE... APPROVAL OF RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators § 84.154 Airflow resistance test; Type B and Type BE supplied-air respirators; minimum requirements. (a) Airflow resistance shall...

  13. 42 CFR 84.153 - Airflow resistance test, Type A and Type AE supplied-air respirators; minimum requirements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false Airflow resistance test, Type A and Type AE... APPROVAL OF RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators § 84.153 Airflow resistance test, Type A and Type AE supplied-air respirators; minimum requirements. (a) Airflow resistance will...

  14. 42 CFR 84.154 - Airflow resistance test; Type B and Type BE supplied-air respirators; minimum requirements.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 42 Public Health 1 2014-10-01 2014-10-01 false Airflow resistance test; Type B and Type BE... APPROVAL OF RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators § 84.154 Airflow resistance test; Type B and Type BE supplied-air respirators; minimum requirements. (a) Airflow resistance shall...

  15. 42 CFR 84.153 - Airflow resistance test, Type A and Type AE supplied-air respirators; minimum requirements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false Airflow resistance test, Type A and Type AE... APPROVAL OF RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators § 84.153 Airflow resistance test, Type A and Type AE supplied-air respirators; minimum requirements. (a) Airflow resistance will...

  16. 42 CFR 84.153 - Airflow resistance test, Type A and Type AE supplied-air respirators; minimum requirements.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Airflow resistance test, Type A and Type AE... APPROVAL OF RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators § 84.153 Airflow resistance test, Type A and Type AE supplied-air respirators; minimum requirements. (a) Airflow resistance will...

  17. 42 CFR 84.154 - Airflow resistance test; Type B and Type BE supplied-air respirators; minimum requirements.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 42 Public Health 1 2013-10-01 2013-10-01 false Airflow resistance test; Type B and Type BE... APPROVAL OF RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators § 84.154 Airflow resistance test; Type B and Type BE supplied-air respirators; minimum requirements. (a) Airflow resistance shall...

  18. 42 CFR 84.153 - Airflow resistance test, Type A and Type AE supplied-air respirators; minimum requirements.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 42 Public Health 1 2012-10-01 2012-10-01 false Airflow resistance test, Type A and Type AE... APPROVAL OF RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators § 84.153 Airflow resistance test, Type A and Type AE supplied-air respirators; minimum requirements. (a) Airflow resistance will...

  19. Laminar Flow Control Leading Edge Systems in Simulated Airline Service

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

  20. Inductively coupled plasma torch with laminar flow cooling

    DOEpatents

    Rayson, Gary D.; Shen, Yang

    1991-04-30

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

  1. The NASA Langley laminar flow control airfoil experiment

    NASA Technical Reports Server (NTRS)

    Harvey, W. D.; Pride, J. D.

    1982-01-01

    A large chord swept supercritical LFC airfoil has been constructed for NASA-Langley's research program to determine the compatibility of supercritical airfoils with suction laminarization and to establish a technology base for future transport designs. Features include a high design Mach number and shock-free flow, as well as the minimization of the laminarization suction through a choice of airfoil geometry and pressure distribution. Two suction surface concepts and a variety of hybrid suction concepts involving combinations of natural and forced laminar flow are to be investigated. The test facility has been modified to insure achievement of required flow quality and transonic interference-free flow over the yawed LFC airfoil.

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

    PubMed

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

    2014-01-01

    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

  3. The Impact of Smoking on Airflow Limitation in Subjects with History of Asthma and Inactive Tuberculosis

    PubMed Central

    Kim, Hyun Jung; Baek, Seunghee; Kim, Hee Jin; Lee, Jae Seung; Oh, Yeon-Mok; Lee, Sang-Do; Lee, Sei Won

    2015-01-01

    Background Although smoking is the most important and modifiable cause of chronic obstructive pulmonary disease (COPD), other risk factors including asthma and tuberculosis (TB) are also associated. It is common for COPD patients to have more than one of these risk factors. The aims of this study were to determine the prevalence of airflow limitation (FEV1/FVC<0.7) according to the risk factors and to investigate their impact and interaction in airflow limitation. Methods From the Korean National Health and Nutrition Examination Survey between 2008 and 2012, we analyzed participants over 40 years of age by spirometry, chest radiograph and questionnaire about asthma and smoking history. Results Of 12,631 participants, 1,548 (12.3%) had airflow limitation. The prevalence of airflow limitation in smokers (≥10 pack-year), asthmatics, and those with inactive TB was 23.9%, 32.1%, and 33.6%. The prevalence increased with the number of risk factors: 86.1% had airflow limitation if they had all three risk factors. Impacts of inactive TB and asthma on airflow limitation were equivalent to 47 and 69 pack-years of smoking, respectively. Airflow limitation resulted from lower levels of smoking in those with inactive TB and asthma. A potential interaction between smoking and inactive tuberculosis in the development of airflow limitation was identified (p = 0.054). Conclusions Asthma and inactive TB lesions increase susceptibility to smoking in the development of airflow limitation. People with these risk factors should be seen as a major target population for anti-smoking campaigns to prevent COPD. PMID:25915938

  4. Ignition in laminar and turbulent nonpremixed counterflow

    NASA Astrophysics Data System (ADS)

    Blouch, John Dewey

    2002-01-01

    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

  5. Assessment of the National Transonic Facility for Laminar Flow Testing

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    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.

  6. Selected experiments in laminar flow: An annotated bibliography

    NASA Technical Reports Server (NTRS)

    Drake, Aaron; Kennelly, Robert A., Jr.

    1992-01-01

    Since the 1930s, there have been attempts to reduce drag on airplanes by delaying laminar to turbulent boundary layer transition. Experiments conducted during the 1940's, while successful in delaying transition, were discouraging because of the careful surface preparation necessary to meet roughness and waviness requirements. The resulting lull in research lasted nearly 30 years. By the late 1970s, airframe construction techniques had advanced sufficiently that the high surface quality required for natural laminar flow (NLF) and laminar flow control (LFC) appeared possible on production aircraft. As a result, NLF and LFC research became widespread. This report is an overview of that research. The experiments summarized herein were selected for their applicability to small transonic aircraft. Both flight and wind tunnel tests are included. The description of each experiment is followed by corresponding references. Part One summarizes NLF experiments; Part Two deals with LFC and hybrid laminar flow control (HLFC) experiments.

  7. Advanced stability theory analyses for laminar flow control

    NASA Technical Reports Server (NTRS)

    Orszag, S. A.

    1980-01-01

    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.

  8. Design of fuselage shapes for natural laminar flow

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    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.

  9. Design of fuselage shapes for natural laminar flow

    NASA Astrophysics Data System (ADS)

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

    1986-03-01

    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.

  10. Studies of premixed laminar and turbulent flames at microgravity

    NASA Technical Reports Server (NTRS)

    Ronney, Paul D.

    1993-01-01

    A two and one-half year experimental and theoretical research program on the properties of laminar and turbulent premixed gas flames at microgravity was conducted. Progress during this program is identified and avenues for future studies are discussed.

  11. Care For Patients With Severe Chronic Airflow Obstruction And Respiratory Failure

    PubMed Central

    Pugsley, S. O.; Robinson, L. A.

    1979-01-01

    The successful care of patients with disorders causing chronic airflow obstruction (CAO) and potential chronic respiratory failure and pulmonary heart disease (cor pulmonale) requires the following: 1. Recognize CAO as the cause of a patient's problem. 2. Describe and measure airflow obstruction and the individual's response to it. 3. Undertake therapeutic trials to maximize airflow. 4. Teach patients monitoring skills and interventions in order to prevent acute respiratory failure and hospital admission. 5. Maintain optimism and interest in the patient's chronic illness, appreciating its impact on the total person and his daily life. PMID:21297794

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

    NASA Technical Reports Server (NTRS)

    Aragon, Cecilia R.

    2004-01-01

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

  13. Natural laminar flow airfoil analysis and trade studies

    NASA Technical Reports Server (NTRS)

    1979-01-01

    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.

  14. Application of natural laminar flow to a supersonic transport concept

    NASA Technical Reports Server (NTRS)

    Fuhrmann, Henri D.

    1993-01-01

    Results are presented of a preliminary investigation into an application of supersonic natural laminar flow (NLF) technology for a high speed civil transport (HSCT) configuration. This study focuses on natural laminar flow without regard to suction devices which are required for laminar flow control (LFC) or hybrid laminar flow control (HLFC). An HSCT design is presented with a 70 deg inboard leading-edge sweep and a 20 deg leading-edge outboard crank to obtain NLF over the outboard crank section. This configuration takes advantage of improved subsonic performance and NLF on the low-sweep portion of the wing while minimizing the wave drag and induced drag penalties associated with low-sweep supersonic cruise aircraft. In order to assess the benefits of increasing natural laminar flow wetted area, the outboard low-sweep wing area is parametrically increased. Using a range of supersonic natural laminar flow transition Reynolds numbers, these aircraft are then optimized and sized for minimum take-off gross weight (TOGW) subject to mission constraints. Results from this study indicate reductions in TOGW for the NLF concepts, due mainly to reductions in wing area and total wing weight. Furthermore, significant reductions in block fuel are calculated throughout the range of transition Reynolds numbers considered. Observations are made on the benefits of unsweeping the wingtips with all turbulent flow.

  15. Particle-Image Velocimetry in Microgravity Laminar Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Sunderland, P. B.; Greenberg, P. S.; Urban, D. L.; Wernet, M. P.; Yanis, W.

    1999-01-01

    This paper discusses planned velocity measurements in microgravity laminar jet diffusion flames. These measurements will be conducted using Particle-Image Velocimetry (PIV) in the NASA Glenn 2.2-second drop tower. The observations are of fundamental interest and may ultimately lead to improved efficiency and decreased emissions from practical combustors. The velocity measurements will support the evaluation of analytical and numerical combustion models. There is strong motivation for the proposed microgravity flame configuration. Laminar jet flames are fundamental to combustion and their study has contributed to myriad advances in combustion science, including the development of theoretical, computational and diagnostic combustion tools. Nonbuoyant laminar jet flames are pertinent to the turbulent flames of more practical interest via the laminar flamelet concept. The influence of gravity on these flames is deleterious: it complicates theoretical and numerical modeling, introduces hydrodynamic instabilities, decreases length scales and spatial resolution, and limits the variability of residence time. Whereas many normal-gravity laminar jet diffusion flames have been thoroughly examined (including measurements of velocities, temperatures, compositions, sooting behavior and emissive and absorptive properties), measurements in microgravity gas-jet flames have been less complete and, notably, have included only cursory velocity measurements. It is envisioned that our velocity measurements will fill an important gap in the understanding of nonbuoyant laminar jet flames.

  16. Laminar Tendon Composites with Enhanced Mechanical Properties

    PubMed Central

    Alberti, Kyle A.; Sun, Jeong-Yun; Illeperuma, Widusha R.; Suo, Zhigang; Xu, Qiaobing

    2015-01-01

    Purpose A strong isotropic material that is both biocompatible and biodegradable is desired for many biomedical applications, including rotator cuff repair, tendon and ligament repair, vascular grafting, among others. Recently, we developed a technique, called “bioskiving” to create novel 2D and 3D constructs from decellularized tendon, using a combination of mechanical sectioning, and layered stacking and rolling. The unidirectionally aligned collagen nanofibers (derived from sections of decellularized tendon) offer good mechanical properties to the constructs compared with those fabricated from reconstituted collagen. Methods In this paper, we studied the effect that several variables have on the mechanical properties of structures fabricated from tendon slices, including crosslinking density and the orientation in which the fibers are stacked. Results We observed that following stacking and crosslinking, the strength of the constructs is significantly improved, with crosslinked sections having an ultimate tens ile strength over 20 times greater than non-crosslinked samples, and a modulus nearly 50 times higher. The mechanism of the mechanical failure mode of the tendon constructs with or without crosslinking was also investigated. Conclusions The strength and fiber organization, combined with the ability to introduce transversely isotropic mechanical properties makes the laminar tendon composites a biocompatiable material that may find future use in a number of biomedical and tissue engineering applications. PMID:25691802

  17. Radiative interactions in laminar duct flows

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  18. A New Approach to Laminar Flowmeters

    PubMed Central

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

    2010-01-01

    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

  19. 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...

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

    PubMed

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

    2012-01-01

    Lung radiotherapy is greatly benefitted when the tumor motion caused by breathing can be modeled. The aim of this paper is to present the importance of using anisotropic and subject-specific tissue elasticity for simulating the airflow inside the lungs. A computational-fluid-dynamics (CFD) based approach is presented to simulate airflow inside a subject-specific deformable lung for modeling lung tumor motion and the motion of the surrounding tissues during radiotherapy. A flow-structure interaction technique is employed that simultaneously models airflow and lung deformation. The lung is modeled as a poroelastic medium with subject-specific anisotropic poroelastic properties on a geometry, which was reconstructed from four-dimensional computed tomography (4DCT) scan datasets of humans with lung cancer. The results include the 3D anisotropic lung deformation for known airflow pattern inside the lungs. The effects of anisotropy are also presented on both the spatiotemporal volumetric lung displacement and the regional lung hysteresis. PMID:23365554

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

    PubMed Central

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

    2012-01-01

    Lung radiotherapy is greatly benefitted when the tumor motion caused by breathing can be modeled. The aim of this paper is to present the importance of using anisotropic and subject-specific tissue elasticity for simulating the airflow inside the lungs. A computational-fluid-dynamics (CFD) based approach is presented to simulate airflow inside a subject-specific deformable lung for modeling lung tumor motion and the motion of the surrounding tissues during radiotherapy. A flow-structure interaction technique is employed that simultaneously models airflow and lung deformation. The lung is modeled as a poroelastic medium with subject-specific anisotropic poroelastic properties on a geometry, which was reconstructed from four-dimensional computed tomography (4DCT) scan datasets of humans with lung cancer. The results include the 3D anisotropic lung deformation for known airflow pattern inside the lungs. The effects of anisotropy are also presented on both the spatiotemporal volumetric lung displacement and the regional lung hysteresis. PMID:23365554

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

  3. Cigarette smoke potentiates asbestos-induced airflow abnormalities

    SciTech Connect

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

    1988-01-01

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

  4. Behavior of submicrometer particles in periodic alveolar airflows.

    PubMed

    Balik, G; Reis, A H; Aydin, M; Miguel, A F

    2008-04-01

    Here, we report a numerical experiment in which submicrometer particle entrainment in a periodic flow that matches those existing in the alveolus in the human lung was simulated for both sedentary and light activity. A spherical cavity with a prescribed velocity profile at the inlet was used to simulate the time-dependent periodical flow of air in the alveolus. Expansion and contraction of the alveolus were simulated by setting a conceptual permeable wall as the outer surface of the model and adjusting the boundary conditions in order to match the continuity of the flow. The simulations were conducted for breathing periods of 5 and 3 s, which match sedentary and light activity conditions, respectively, and the results were extrapolated to the real lung. It was found that, most of the particles mainly followed a straightforward path and reached the opposite side of the alveolar wall in both breathing conditions. The concentration patterns obtained are consistent with the fact that the flow within the alveolus is mainly diffusive and does not greatly depend on the flow velocity. It was found that the particles which are heavier than air move out of phase with the periodic airflow that crosses the alveolus entrance, and that these particles are significantly caught within the alveolus. Particle entrapment increases with breathing rate in accordance with experimental values and indicates that increase in breathing frequency in environments with high concentration of submicrometer particles has the consequence of increasing particle entrapment by several times with respect to normal breathing rate. PMID:18075755

  5. Air-flow separation over unsteady breaking wind waves

    NASA Astrophysics Data System (ADS)

    Saxena, Gaurav

    2005-11-01

    In air-sea interaction processes, when considering wind stress over small-scale breaking waves, there are few direct quantitative experimental investigations into the role of air-flow separation on the interfacial momentum flux. Reul et. al, (1999), found multiple coherent patches of vorticity downwind of the crest that were strongly influenced by the geometric characteristics of the breaker. However, their breakers were generated by dispersive focusing techniques and, therefore, independent of the wind stress. We present experimental results obtained with particle image velocimetry (PIV) where moderate to strong winds directly generate unsteady small-scale breaking waves, a scenario commonly found in the open ocean. Particular attention has been devoted to capturing the spatio-temporal evolution of the air-water interface. Specifically, texture segmentation algorithms typically used for face recognition (Grey Level Co-occurrence Matrix (GLCM) and the Cross-Diagonal Texture Matrix (CDTM)) have been combined to yield robust and accurate estimates of the instantaneous breaker geometry.

  6. Oscillating and star-shaped drops levitated by an airflow.

    PubMed

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

    2013-08-01

    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

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

    SciTech Connect

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

    2006-07-26

    The U.S. Nuclear Regulatory Commission's NUREG-1400 addresses many aspects of air sampling in the work place. Here, we present two detailed examples of the implementation of qualitative air flow studies at different scales using guidelines established by NUREG-1400. In one test, smoke was used to evaluate the airflow patterns within the transfer area of the 105 KE Basin, located on the Hanford Site, Richland, Washington. The purpose of the study was to determine appropriate locations for air monitoring equipment in support of sludge water pumping activities. The study revealed a stagnant layer of the air within the transfer area that made predicting movement of contamination within the transfer area difficult. Without conducting an air flow study, the stagnant layer would not have been identified, and could have resulted in locating samplers at inappropriate locations. In a second test, smoke was used to verify the effectiveness of an air space barrier curtain. The results showed that the curtain adequately separated the two air spaces. The methodology employed in each test provided sound, easy to interpret information that satisfied the requirements of each test.

  8. A miniature airflow energy harvester from piezoelectric materials

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    Laminar diffusion flames are of interest because they provide model flame systems that are far more tractable for analysis and experiments than more practical turbulent diffusion flames. Certainly, understanding flame processes within laminar diffusion flames must precede understanding these processes in more complex turbulent diffusion flames. In addition, many properties of laminar diffusion flames are directly relevant to turbulent diffusion flames using laminar flamelet concepts. Laminar jet diffusion flame shapes (luminous flame boundaries) have been of particular interest since the classical study of Burke and Schumann because they are a simple nonintrusive measurement that is convenient for evaluating flame structure predictions. Thus, consideration of laminar flame shapes is undertaken in the following, emphasizing conditions where effects of gravity are small, due to the importance of such conditions to practical applications. Another class of interesting properties of laminar diffusion flames are their laminar soot and smoke point properties (i.e., the flame length, fuel flow rate, characteristic residence time, etc., at the onset of soot appearance in the flame (the soot point) and the onset of soot emissions from the flame (the smoke point)). These are useful observable soot properties of nonpremixed flames because they provide a convenient means to rate several aspects of flame sooting properties: the relative propensity of various fuels to produce soot in flames; the relative effects of fuel structure, fuel dilution, flame temperature and ambient pressure on the soot appearance and emission properties of flames; the relative levels of continuum radiation from soot in flames; and effects of the intrusion of gravity (or buoyant motion) on emissions of soot from flames. An important motivation to define conditions for soot emissions is that observations of laminar jet diffusion flames in critical environments, e.g., space shuttle and space station

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

  11. Acoustics of laminar boundary layers breakdown

    NASA Technical Reports Server (NTRS)

    Wang, Meng

    1994-01-01

    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.

  12. Endoscopic inter laminar management of lumbar disease

    PubMed Central

    Yadav, Yad Ram; Parihar, Vijay; Kher, Yatin; Bhatele, Pushp Raj

    2016-01-01

    Discectomy for lumbar disc provides faster relief in acute attack than does conservative management. Long-term results of open, microscopy-, and endoscopy-assisted discectomy are same. Early results of endoscopy-assisted surgery are better as compared to that of open surgery in terms of better visualization, smaller incision, reduced hospital stay, better education, lower cost, less pain, early return to work, and rehabilitation. Although microscopic discectomy also has comparable advantages, endoscopic-assisted technique better addresses opposite side pathology. Inter laminar technique (ILT) and trans foraminal technique (TFT) are two main endoscopic approaches for lumbar pathologies. Endoscopy-assisted ILT can be performed in recurrent, migrated, and calcified discs. All lumbar levels including L5-S1 level, intracanalicular, foraminal disc, lumbar canal and lateral recess stenosis, multiple levels, and bilateral lesions can be managed by ILT. Migrated, calcified discs, L5-S1 pathology, lumbar canal, and lateral recess stenosis can be better approached by ILT than by TFT. Most spinal surgeons are familiar with anatomy of ILT. It can be safely performed in foramen stenosis and in uncooperative and anxious patients. There is less risk of exiting nerve root damage, especially in short pedicles and in presence of facet osteophytes as compared to TFT. On the other hand, ILT is more invasive than TFT with more chances of perforations of the dura matter, pseudomeningocele formation, and cerebrospinal fluid fistula in early learning curve. Obtaining microsurgical experience, attending workshops, and suitable patient selection can help shorten the learning curve. Once adequate skill is acquired, this procedure is safe and effective. The surgeon must be prepared to convert to an open procedure, especially in early learning curve. Spinal endoscopy is likely to achieve more roles in future. Endoscopy-assisted ILT is a safer alternative to the microscopic technique. PMID

  13. Airflow resistance of heat and moisture exchange filters with and without a tracheostoma valve.

    PubMed

    Verkerke, Gijsbertus Jacob; Geertsema, Albert Anne; Schutte, Harm K

    2002-04-01

    Rehabilitation of laryngectomees has been furthered by the introduction of heat and moisture exchange (HME) filters, placed over a tracheostoma or on a tracheostoma valve (TSV). The airflow resistance of HME filters is an important factor with regard to the comfort of the patient. The goal of this study was to determine the airflow resistance (defined as the pressure drop over the device divided by the squared airflow through the device) of 4 commercially available HME filters with and without a TSV. The pressure drop over and the airflow through the devices were measured in vitro. Distinct differences among the devices were found. The mean airflow resistance of the HME filters ranged from 135 to 346 Pa x s2/L2, that of TSVs was between 66 and 297 Pa x s2/L2, and that of the combination was between 263 and 454 Pa x s2/L2. The Stom-Vent 2 HME filter and the Adeva Window TSV with an Adeva filter had the lowest airflow resistance of the devices measured in this study. PMID:11991585

  14. Airflow in the Human Nasal Passage and Sinuses of Chronic Rhinosinusitis Subjects

    PubMed Central

    Kumar, Haribalan; Jain, Ravi; Douglas, Richard G.; Tawhai, Merryn H.

    2016-01-01

    Endoscopic surgery is performed on patients with chronic inflammatory disease of the paranasal sinuses to improve sinus ventilation. Little is known about how sinus surgery affects sinonasal airflow. In this study nasal passage geometry was reconstructed from computed tomographic imaging from healthy normal, pre-operative, and post-operative subjects. Transient air flow through the nasal passage during calm breathing was simulated. Subject-specific differences in ventilation of the nasal passage were observed. Velocity magnitude at ostium was different between left and right airway. In FESS, airflow in post-surgical subjects, airflow at the maxillary sinus ostium was upto ten times higher during inspiration. In a Lothrop procedure, airflow at the frontal sinus ostium can be upto four times higher during inspiration. In both post-operative subjects, airflow at ostium was not quasi-steady. The subject-specific effect (of surgery) on sinonasal interaction evaluated through airflow simulations may have important consequences for pre- and post-surgical assessment and surgical planning, and design for improvement of the delivery efficiency of nasal therapeutics. PMID:27249219

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

    PubMed

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

    2013-03-01

    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

  16. The influence of nasal airflow on respiratory and olfactory epithelial distribution in felids.

    PubMed

    Pang, Benison; Yee, Karen K; Lischka, Fritz W; Rawson, Nancy E; Haskins, Mark E; Wysocki, Charles J; Craven, Brent A; Van Valkenburgh, Blaire

    2016-06-15

    The surface area of the maxilloturbinals and fronto-ethmoturbinals is commonly used as an osteological proxy for the respiratory and the olfactory epithelium, respectively. However, this assumption does not fully account for animals with short snouts in which these two turbinal structures significantly overlap, potentially placing fronto-ethmoturbinals in the path of respiratory airflow. In these species, it is possible that anterior fronto-ethmoturbinals are covered with non-sensory (respiratory) epithelium instead of olfactory epithelium. In this study, we analyzed the distribution of olfactory and non-sensory, respiratory epithelia on the turbinals of two domestic cats (Felis catus) and a bobcat (Lynx rufus). We also conducted a computational fluid dynamics simulation of nasal airflow in the bobcat to explore the relationship between epithelial distribution and airflow patterns. The results showed that a substantial amount of respiratory airflow passes over the anterior fronto-ethmoturbinals, and that contrary to what has been observed in caniform carnivorans, much of the anterior ethmoturbinals are covered by non-sensory epithelium. This confirms that in short-snouted felids, portions of the fronto-ethmoturbinals have been recruited for respiration, and that estimates of olfactory epithelial coverage based purely on fronto-ethmoturbinal surface area will be exaggerated. The correlation between the shape of the anterior fronto-ethmoturbinals and the direction of respiratory airflow suggests that in short-snouted species, CT data alone are useful in assessing airflow patterns and epithelium distribution on the turbinals. PMID:27045093

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

    NASA Astrophysics Data System (ADS)

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

    2004-06-01

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

  18. Airflow regulation in variable-speed systems for residential HVAC applications

    SciTech Connect

    Becerra, R.C.; Beifus, B.L.

    1996-11-01

    In the majority of heating, ventilating, and air-conditioning (HVAC) systems, air is the final medium for adding or extracting heat from or to the space to be air conditioned. Air is heated by passing it over a heat transfer device called a coil, which is a heat exchanger with air on the outside and the primary heating/cooling medium (water, steam, electricity, refrigerant, etc.) on the inside. One of the major factors determining heat transfer is the airflow rate, which can be controlled by mechanical means or by controlling the speed of the fan. Centrifugal fans driven by single-speed induction motors traditionally have been used in the JVAC industry but have an airflow characteristic that depends on the static pressure seen by the system. Variable-speed systems are starting to emerge as a strong alternative to traditional systems because of their ability to match the demand of the air-conditioned space, resulting in higher efficiencies and higher comfort. System efficiency can be improved by constraining the range of airflows provided by the fan or blower system in response to system pressure, that is, by controlling the airflow over the heat exchanger. This paper presents a method to regulate airflow independent of the static pressure and without the need for airflow sensors.

  19. Unidirectional pulmonary airflow in vertebrates: a review of structure, function, and evolution.

    PubMed

    Cieri, Robert L; Farmer, C G

    2016-07-01

    Mechanisms explaining unidirectional pulmonary airflow in birds, a condition where lung gases flow in a consistent direction during both inspiration and expiration in some parts of the lung, were suggested as early as the first part of the twentieth century and unidirectional pulmonary airflow has been discovered recently in crocodilians and squamates. Our knowledge of the functional anatomy, fluid dynamics, and significance of this trait is reviewed. The preponderance of the data indicates that unidirectional airflow is maintained by means of convective inertia in inspiratory and expiratory aerodynamic valves in birds. The study of flow patterns in non-avian reptiles is just beginning, but inspiratory aerodynamic valving likely also plays an important role in controlling flow direction in these lungs. Although highly efficient counter and cross-current blood-gas exchange arrangements are possible in lungs with unidirectional airflow, very few experiments have investigated blood-gas exchange mechanisms in the bird lung and blood-gas arrangements in the lungs of non-avian reptiles are completely unknown. The presence of unidirectional airflow in non-volant ectotherms voids the traditional hypothesis that this trait evolved to supply the high aerobic demands of flight and endothermy, and there is a need for new scenarios in our understanding of lung evolution. The potential value of unidirectional pulmonary airflow for allowing economic lung gas mixing, facilitating lung gas washout, and providing for adequate gas exchange during hypoxic conditions is discussed. PMID:27062030

  20. The laminar structure of the common opossum masseter (Didelphis marsupialis).

    PubMed

    Deguchi, T; Takemura, A; Suwa, F

    2001-03-01

    Using three heads of the common opossum (Didelphis marsupialis), which may be considered to have a primitive mammalian form and therefore be appropriate for this study, the laminar structure of the masseter was investigated. We also attempted a comparative anatomical study of the relationships of food habits to the laminar structures of the masseter, zygomatic arch and mandibular ramus. In the common opossum masseter, a total of six layers, the primary and secondary sublayers of the superficial layer, the intermediate layer, and the primary, secondary and third sublayers of the deep layer as a proper masseter, were observed. These layers showed a typical reverse laminar structure, with the layers of tendons and muscles alternating. The maxillomandibularis and zygomaticomandibularis muscles were observed in one layer each, as an improper masseter. The laminar structure of the common opossum masseter was shown to be more similar to that of carnivorous placental animals than that of the herbivorous red kangaroo, a similar marsupial. In regard to the number of layers in the laminar structure of the masseter, the results of both this study and those of our predecessors' showed that differences in food habits affect the deep layer in the proper masseter of marsupials and placental mammals, and that of the maxillomandibularis muscle of placental mammals in the improper masseter. PMID:11392012

  1. Assessment of LAURA for Laminar Supersonic Shallow Cavities

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  2. Soot Formation in Freely-Propagating Laminar Premixed Flames

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  3. Computational Analysis of the G-III Laminar Flow Glove

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  4. Laminarization of Turbulent Boundary Layer on Flexible and Rigid Surfaces

    NASA Technical Reports Server (NTRS)

    Maestrello, Lucio

    2001-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  6. Brief history of laminar flow clean room systems

    SciTech Connect

    Whitfield, W J

    1981-01-01

    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.

  7. Rain-induced subsurface airflow and Lisse effect

    USGS Publications Warehouse

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

    2008-01-01

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

  8. Intratracheal Bleomycin Causes Airway Remodeling and Airflow Obstruction in Mice

    PubMed Central

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

    2014-01-01

    Introduction In addition to parenchymal fibrosis, fibrotic remodeling of the distal airways has been reported in interstitial lung diseases. Mechanisms of airway wall remodeling, which occurs in a variety of chronic lung diseases, are not well defined and current animal models are limited. Methods We quantified airway remodeling in lung sections from subjects with idiopathic pulmonary fibrosis (IPF) and controls. To investigate intratracheal bleomycin as a potential animal model for fibrotic airway remodeling, we evaluated lungs from C57BL/6 mice after bleomycin treatment by histologic scoring for fibrosis and peribronchial inflammation, morphometric evaluation of subepithelial connective tissue volume density, TUNEL assay, and immunohistochemistry for transforming growth factor β1 (TGFβ1), TGFβ2, and the fibroblast marker S100A4. Lung mechanics were determined at 3 weeks post-bleomycin. Results IPF lungs had small airway remodeling with increased bronchial wall thickness compared to controls. Similarly, bleomycin treated mice developed dose-dependent airway wall inflammation and fibrosis and greater airflow resistance after high dose bleomycin. Increased TUNEL+ bronchial epithelial cells and peribronchial inflammation were noted by 1 week, and expression of TGFβ1 and TGFβ2 and accumulation of S100A4+ fibroblasts correlated with airway remodeling in a bleomycin dose-dependent fashion. Conclusions IPF is characterized by small airway remodeling in addition to parenchymal fibrosis, a pattern also seen with intratracheal bleomycin. Bronchial remodeling from intratracheal bleomycin follows a cascade of events including epithelial cell injury, airway inflammation, pro-fibrotic cytokine expression, fibroblast accumulation, and peribronchial fibrosis. Thus, this model can be utilized to investigate mechanisms of airway remodeling. PMID:22394287

  9. Analytical solution of laminar-laminar stratified two-phase flows with curved interfaces

    SciTech Connect

    Brauner, N.; Rovinsky, J.; Maron, D.M.

    1995-09-01

    The present study represents a complete analytical solution for laminar two-phase flows with curved interfaces. The solution of the Navier-Stokes equations for the two-phases in bipolar coordinates provides the `flow monograms` describe the relation between the interface curvature and the insitu flow geometry when given the phases flow rates and viscosity ratios. Energy considerations are employed to construct the `interface monograms`, whereby the characteristic interfacial curvature is determined in terms of the phases insitu holdup, pipe diameter, surface tension, fluids/wall adhesion and gravitation. The two monograms are then combined to construct the system `operational monogram`. The `operational monogram` enables the determination of the interface configuration, the local flow characteristics, such as velocity profiles, wall and interfacial shear stresses distribution as well as the integral characteristics of the two-phase flow: phases insitu holdup and pressure drop.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    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.

  11. Radiotracers application to determine laminar flow at a pipe

    SciTech Connect

    Ramirez-Garcia, F.P.; Cortes-Islas, E. )

    1988-06-01

    To measure gas flow in a gas venting line in an Oil Refinery the method of two points and iodine-131 labelled methyl iodide molecule was used. Forty-four complete sets of data were obtained corresponding to measurements performed in the gas venting line. Conditions of laminar and semi-turbulent flow were found. In the case of laminar flow measurement it was necessary to construct an injection equipment, consisting of a tubing with five slits to simultaneously inject the tracer into the gas stream at different points. For the laminar flow is obtained the transversal distribution of fluid velocities. The mean flow of the gas transported by the line under study was determined, and its standard deviation was calculated.

  12. Lockheed laminar-flow control systems development and applications

    NASA Technical Reports Server (NTRS)

    Lange, Roy H.

    1987-01-01

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

  13. Natural Laminar Flow Design for Wings with Moderate Sweep

    NASA Technical Reports Server (NTRS)

    Campbell, Richard L.; Lynde, Michelle N.

    2016-01-01

    A new method for the aerodynamic design of wings with natural laminar flow is under development at the NASA Langley Research Center. The approach involves the addition of new flow constraints to an existing knowledge-based design module for use with advanced flow solvers. The uniqueness of the new approach lies in the tailoring of target pressure distributions to achieve laminar flow on transonic wings with leading-edge sweeps and Reynolds numbers typical of current transports. The method is demonstrated on the Common Research Model configuration at critical N-factor levels representative of both flight and high-Reynolds number wind tunnel turbulence levels. The design results for the flight conditions matched the target extent of laminar flow very well. The design at wind tunnel conditions raised some design issues that prompted further improvements in the method, but overall has given promising results.

  14. An Experimental Study of Laminarization Induced by Acceleration and Curvature

    NASA Astrophysics Data System (ADS)

    Jackson, R. Brian

    The Generation IV Very High Temperature Reactor (VHTR) design is being actively studied in various countries for application due to its inherent passive safe design, higher thermal efficiencies, and proposed capability of providing high temperature process heat. The pebble bed core is one of two core designs used in gas reactors. In the pebble bed core there are mechanisms present which can cause the flow to laminarize, thus reducing its heat transfer effectiveness. Wind tunnel experiments were conducted using Particle Image Velocimetry (PIV) to investigate boundary layer laminarization due to flow acceleration and convex curvature effects. The flow was subject to acceleration and curvature both separately and together and the flow behavior characterized with velocity flow profiles, mean boundary layer parameters, and turbulence quantities. Laminarization was identified and the influence of acceleration and curvature was characterized.

  15. Laminar and Turbulent Gaseous Diffusion Flames. Appendix C

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  16. IR thermography for dynamic detection of laminar-turbulent transition

    NASA Astrophysics Data System (ADS)

    Simon, Bernhard; Filius, Adrian; Tropea, Cameron; Grundmann, Sven

    2016-05-01

    This work investigates the potential of infrared (IR) thermography for the dynamic detection of laminar-turbulent transition. The experiments are conducted on a flat plate at velocities of 8-14 m/s, and the transition of the laminar boundary layer to turbulence is forced by a disturbance source which is turned on and off with frequencies up to 10 Hz. Three different heating techniques are used to apply the required difference between fluid and structure temperature: a heated aluminum structure is used as an internal structure heating technique, a conductive paint acts as a surface bounded heater, while an IR heater serves as an example for an external heating technique. For comparison of all heating techniques, a normalization is introduced and the frequency response of the measured IR camera signal is analyzed. Finally, the different heating techniques are compared and consequences for the design of experiments on laminar-turbulent transition are discussed.

  17. Method and apparatus for detecting laminar flow separation and reattachment

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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.

  18. Airflow Measurement of the Car HVAC Unit Using Hot-wire Anemometry

    NASA Astrophysics Data System (ADS)

    Fojtlín, Miloš; Planka, Michal; Fišer, Jan; Pokorný, Jan; Jícha, Miroslav

    2016-03-01

    Thermal environment in a vehicular cabin significantly influence drivers' fatigue and passengers' thermal comfort. This environment is traditionally managed by HVAC cabin system that distributes air and modifies its properties. In order to simulate cabin thermal behaviour, amount of the air led through car vents must be determined. The aim of this study was to develop methodology to measure airflow from the vents, and consequently calculate corresponding air distribution coefficients. Three climatic cases were selected to match European winter, summer, and spring / fall conditions. Experiments were conducted on a test vehicle in a climatic chamber. The car HVAC system was set to automatic control mode, and the measurements were executed after the system stabilisation—each case was independently measured three times. To be able to evaluate precision of the method, the airflow was determined at the system inlet (HVAC suction) and outlet (each vent), and the total airflow values were compared. The airflow was calculated by determining a mean value of the air velocity multiplied by an area of inlet / outlet cross-section. Hot-wire anemometry was involved to measure the air velocity. Regarding the summer case, total airflow entering the cabin was around 57 l s-1 with 60 % of the air entering the cabin through dashboard vents; no air was supplied to the feet compartment. The remaining cases had the same total airflow of around 42 l s-1, and the air distribution was focused mainly on feet and windows. The inlet and outlet airflow values show a good match with a maximum mass differential of 8.3 %.

  19. Laminar flow in a recess of a hydrostatic bearing

    NASA Technical Reports Server (NTRS)

    San Andres, Luis A.; Velthuis, Johannes F. M.

    1992-01-01

    The flow in a recess of a hydrostatic journal bearing is studied in detail. The Navier-Stokes equations for the laminar flow of an incompressible liquid are solved numerically in a two-dimensional plane of a typical bearing recess. Pressure- and shear-induced flows, as well as a combination of these two flow conditions, are analyzed. Recess friction, pressure-ram effects at discontinuities in the flow region, and film entrance pressure loss effects are calculated. Entrance pressure loss coefficients over a forward-facing step are presented as functions of the mean flow Reynolds number for pure-pressure and shear-induced laminar flows.

  20. Application of stability theory to laminar flow control

    NASA Technical Reports Server (NTRS)

    Hefner, J. N.; Bushnell, D. M.

    1979-01-01

    The paper summarizes the state-of-the-art for application of stability theory to laminar flow control using suction, wall temperature and/or favorable pressure gradient ('natural laminar flow'). Discussions include current LFC problem areas requiring stability analyses, methods of relating stability theory to transition with results from data and theory comparisons available thus far, and a summary of low disturbance data available for theory calibration on swept wings. Critical issues highlighted are problems peculiar to suction LFC on high performance transonic wings and application of the e-to-the-n-power method to both low and high speed flight data.

  1. Roughness and waviness requirements for laminar flow surfaces

    NASA Technical Reports Server (NTRS)

    Obara, Clifford J.; Holmes, Bruce J.

    1986-01-01

    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.

  2. Method and apparatus for detecting laminar flow separation and reattachment

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  3. Mild Airflow Limitation during N2 Sleep Increases K-complex Frequency and Slows Electroencephalographic Activity

    PubMed Central

    Nguyen, Chinh D.; Wellman, Andrew; Jordan, Amy S.; Eckert, Danny J.

    2016-01-01

    Study Objectives: To determine the effects of mild airflow limitation on K-complex frequency and morphology and electroencephalogram (EEG) spectral power. Methods: Transient reductions in continuous positive airway pressure (CPAP) during stable N2 sleep were performed to induce mild airflow limitation in 20 patients with obstructive sleep apnea (OSA) and 10 healthy controls aged 44 ± 13 y. EEG at C3 and airflow were measured in 1-min windows to quantify K-complex properties and EEG spectral power immediately before and during transient reductions in CPAP. The frequency and morphology (amplitude and latency of P200, N550 and N900 components) of K-complexes and EEG spectral power were compared between conditions. Results: During mild airflow limitation (18% reduction in peak inspiratory airflow from baseline, 0.38 ± 0.11 versus 0.31 ± 0.1 L/sec) insufficient to cause American Academy of Sleep Medicine-defined cortical arousal, K-complex frequency (9.5 ± 4.5 versus 13.7 ± 6.4 per min, P < 0.01), N550 amplitude (25 ± 3 versus 27 ± 3 μV, P < 0.01) and EEG spectral power (delta: 147 ± 48 versus 230 ± 99 μV2, P < 0.01 and theta bands: 31 ± 14 versus 34 ± 13 μV2, P < 0.01) significantly increased whereas beta band power decreased (14 ± 5 versus 11 ± 4 μV2, P < 0.01) compared to the preceding non flow-limited period on CPAP. K-complex frequency, morphology, and timing did not differ between patients and controls. Conclusion: Mild airflow limitation increases K-complex frequency, N550 amplitude, and spectral power of delta and theta bands. In addition to providing mechanistic insight into the role of mild airflow limitation on K-complex characteristics and EEG activity, these findings may have important implications for respiratory conditions in which airflow limitation during sleep is common (e.g., snoring and OSA). Citation: Nguyen CD, Wellman A, Jordan AS, Eckert DJ. Mild airflow limitation during N2 sleep increases k-complex frequency and slows

  4. Computer simulation of airflow through a multi-generation tracheobronchial conducting airway

    SciTech Connect

    Fan, B.; Cheng, Yung-Sung; Yeh, Hsu-Chi

    1995-12-01

    Knowledge of airflow patterns in the human lung is important for an analysis of lung diseases and drug delivery of aerosolized medicine for medical treatment. However, very little systematic information is available on the pattern of airflow in the lung and on how this pattern affects the deposition of toxicants in the lung, and the efficacy of aerosol drug therapy. Most previous studies have only considered the airflow through a single bifurcating airway. However, the flow in a network of more than one bifurcation is more complicated due to the effect of interrelated lung generations. Because of the variation of airway geometry and flow condition from generation to generation, a single bifurcating airway cannot be taken as a representative for the others in different generations. The flow in the network varies significantly with airway generations because of a redistribution of axial momentum by the secondary flow motions. The influence of the redistribution of flow is expected in every generation. Therefore, a systematic information of the airflow through a multi-generation tracheobronchial conducting airway is needed, and it becomes the purpose of this study. This study has provided information on airflow in a lung model which is necessary to the study of the deposition of toxicants and therapeutic aerosols.

  5. Tuberculosis associates with both airflow obstruction and low lung function: BOLD results

    PubMed Central

    Amaral, André F. S.; Coton, Sonia; Kato, Bernet; Tan, Wan C.; Studnicka, Michael; Janson, Christer; Gislason, Thorarinn; Mannino, David; Bateman, Eric D.; Buist, Sonia; Burney, Peter G. J.

    2015-01-01

    Background In small studies and cases series, a history of tuberculosis has been associated with both airflow obstruction, which is characteristic of chronic obstructive pulmonary disease, and restrictive patterns on spirometry. Objective To assess the association between a history of tuberculosis and airflow obstruction and spirometric abnormalities in adults. Methods The study was performed in adults, aged 40 and above, who took part in the multicentre cross-sectional, general population-based, Burden of Obstructive Lung Disease study, had provided acceptable post-bronchodilator spirometry measurements and information on a history of tuberculosis. The associations between a history of tuberculosis and airflow obstruction and spirometric restriction were assessed within each participating centre, and estimates combined using meta-analysis. These estimates were stratified by high and low/middle income countries, according to gross national income. Results A self-reported history of tuberculosis was associated with airflow obstruction (adjusted odds ratio = 2.51, 95% confidence interval 1.83-3.42) and spirometric restriction (adjusted odds ratio = 2.13, 95% confidence interval 1.42-3.19). Conclusion A history of tuberculosis was associated with both airflow obstruction and spirometric restriction, and should be considered as a potentially important cause of obstructive disease and low lung function, particularly where tuberculosis is common. PMID:26113680

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

    PubMed Central

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

    2014-01-01

    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

  7. Investigation on the nasal airflow characteristics of anterior nasal cavity stenosis

    PubMed Central

    Wang, T.; Chen, D.; Wang, P.H.; Chen, J.; Deng, J.

    2016-01-01

    We used a computational fluid dynamics (CFD) model to study the inspiratory airflow profiles of patients with anterior nasal cavity stenosis who underwent curative surgery, by comparing pre- and postoperative airflow characteristics. Twenty patients with severe anterior nasal cavity stenosis, including one case of bilateral stenosis, underwent computed tomography (CT) scans for CFD modelling. The pre- and postoperative airflow characteristics of the nasal cavity were simulated and analyzed. The narrowest area of the nasal cavity in all 20 patients was located within the nasal valve area, and the mean cross-sectional area increased from 0.39 cm2 preoperative to 0.78 cm2 postoperative (P<0.01). Meanwhile, the mean airflow velocity in the nasal valve area decreased from 6.19 m/s to 2.88 m/s (P<0.01). Surgical restoration of the nasal symmetry in the bilateral nasal cavity reduced nasal resistance in the narrow sides from 0.24 Pa.s/mL to 0.11 Pa.s/mL (P<0.01). Numerical simulation of the nasal cavity in patients with anterior nasal cavity stenosis revealed structural changes and the resultant patterns of nasal airflow. Surgery achieved balanced bilateral nasal ventilation and decreased nasal resistance in the narrow region of the nasal cavity. The correction of nasal valve stenosis is not only indispensable for reducing nasal resistance, but also the key to obtain satisfactory curative effect. PMID:27533764

  8. Investigation on the nasal airflow characteristics of anterior nasal cavity stenosis.

    PubMed

    Wang, T; Chen, D; Wang, P H; Chen, J; Deng, J

    2016-01-01

    We used a computational fluid dynamics (CFD) model to study the inspiratory airflow profiles of patients with anterior nasal cavity stenosis who underwent curative surgery, by comparing pre- and postoperative airflow characteristics. Twenty patients with severe anterior nasal cavity stenosis, including one case of bilateral stenosis, underwent computed tomography (CT) scans for CFD modelling. The pre- and postoperative airflow characteristics of the nasal cavity were simulated and analyzed. The narrowest area of the nasal cavity in all 20 patients was located within the nasal valve area, and the mean cross-sectional area increased from 0.39 cm2 preoperative to 0.78 cm2 postoperative (P<0.01). Meanwhile, the mean airflow velocity in the nasal valve area decreased from 6.19 m/s to 2.88 m/s (P<0.01). Surgical restoration of the nasal symmetry in the bilateral nasal cavity reduced nasal resistance in the narrow sides from 0.24 Pa.s/mL to 0.11 Pa.s/mL (P<0.01). Numerical simulation of the nasal cavity in patients with anterior nasal cavity stenosis revealed structural changes and the resultant patterns of nasal airflow. Surgery achieved balanced bilateral nasal ventilation and decreased nasal resistance in the narrow region of the nasal cavity. The correction of nasal valve stenosis is not only indispensable for reducing nasal resistance, but also the key to obtain satisfactory curative effect. PMID:27533764

  9. Incidence of airflow limitation in subjects 65-100 years of age.

    PubMed

    Luoto, Johannes A; Elmståhl, Sölve; Wollmer, Per; Pihlsgård, Mats

    2016-02-01

    The true incidence of chronic obstructive pulmonary disease is largely unknown, because the few longitudinal studies performed have used diagnostic criteria no longer recommended by either the European Respiratory Society or the American Thoracic Society (ATS).We studied the incidence and significance of airflow limitation in a population-based geriatric sample using both an age-dependent predicted lower limit of normal (LLN) value and a fixed-ratio spirometric criterion.Out of 2025 subjects with acceptable spirometry at baseline, 984 subjects aged 65-100 years completed a 6-year follow-up visit. Smoking habits were registered at baseline. Exclusion criteria were non-acceptable spirometry performance according to ATS criteria and inability to communicate. Airflow limitation was defined both according to forced expiratory volume in 1 s (FEV1)/forced vital capacity ratio <0.7 and airflow limitation per 1000 person-years was 28.2 using a fixed ratio and 11.7 with LLN, corresponding to a 1.41-fold higher incidence rate using a fixed ratio. The incidence increased dramatically with age when using a fixed ratio, but less so when using LLN. In addition, a sex effect was observed with the LLN criterion. LLN airflow limitation was associated with increased 5-year mortality. Presence of fixed-ratio airflow limitation in individuals classified by LLN as non-obstructive was not associated with increased mortality. PMID:26677939

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

    NASA Technical Reports Server (NTRS)

    Anders, Scott G.; Fischer, Michael C.

    1999-01-01

    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.

  11. Application of laminar flow control to supersonic transport configurations

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

  12. Flight tests of a supersonic natural laminar flow airfoil

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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 test article was designed with a leading edge sweep of effectively 0° 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 2D 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 that the sensitivity of the flow to the disturbances, which can translate into manufacturing tolerances, was similar to that of subsonic natural laminar flow wings.

  13. The Prospects for Laminar Flow on Hypersonic Airplanes

    NASA Technical Reports Server (NTRS)

    Seiff, Alvin

    1958-01-01

    The factors which affect the extent of laminar flow on airplanes for hypersonic flight are discussed on the basis of the available data. Factors considered include flight Reynolds number, surface roughness, angle of attack, angle of leading-edge sweepback, and aerodynamic interference. Test data are presented for one complete configuration.

  14. Flight Tests of a Supersonic Natural Laminar Flow Airfoil

    NASA Technical Reports Server (NTRS)

    Frederick, Michael A.; Banks, Daniel W.; Garzon, G. A.; Matisheck, J. R.

    2015-01-01

    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 (McDonnell Douglas Corporation, now The Boeing Company, Chicago, Illinois). The test article 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.

  15. Multiple paths to subharmonic laminar breakdown in a boundary layer

    NASA Technical Reports Server (NTRS)

    Zang, Thomas A.; Hussaini, M. Yousuff

    1989-01-01

    Numerical simulations demonstrate that laminar breakdown in a boundary layer induced by the secondary instability of two-dimensional Tollmien-Schlichting waves to three-dimensional subharmonic disturbances need not take the conventional lambda vortex/high-shear layer path.

  16. Laminar Soot Processes Experiment Shedding Light on Flame Radiation

    NASA Technical Reports Server (NTRS)

    Urban, David L.

    1998-01-01

    The Laminar Soot Processes (LSP) experiment investigated soot processes in nonturbulent, round gas jet diffusion flames in still air. The soot processes within these flames are relevant to practical combustion in aircraft propulsion systems, diesel engines, and furnaces. However, for the LSP experiment, the flames were slowed and spread out to allow measurements that are not tractable for practical, Earth-bound flames.

  17. Estimation of Laminar Burning Velocities by Direct Digital Photography

    ERIC Educational Resources Information Center

    Uske, J.; Barat, R.

    2004-01-01

    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.

  18. Application of porous materials for laminar flow control

    NASA Technical Reports Server (NTRS)

    Pearce, W. E.

    1978-01-01

    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.

  19. Electrostatic quadrupole focused particle accelerating assembly with laminar flow beam

    DOEpatents

    Maschke, Alfred W.

    1985-01-01

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

  20. Electrostatic quadrupole focused particle accelerating assembly with laminar flow beam

    DOEpatents

    Maschke, A.W.

    1984-04-16

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

  1. Numerical studies of laminar and turbulent drag reduction, part 2

    NASA Technical Reports Server (NTRS)

    Balasubramanian, R.; Orszag, S. A.

    1983-01-01

    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.

  2. Flame Radiation, Structure, and Scalar Properties in Microgravity Laminar Fires

    NASA Technical Reports Server (NTRS)

    Feikema, Douglas; Lim, Jongmook; Sivathanu, Yudaya

    2007-01-01

    Results from microgravity combustion experiments conducted in the Zero Gravity Research Facility (ZGF) 5.18 second drop facility are reported. The results quantify flame radiation, structure, and scalar properties during the early phase of a microgravity fire. 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 microgravity laminar methane/air, ethylene/nitrogen/air and ethylene/air jet flames. The measured peak mole fractions for water vapor and carbon dioxide are found to be in agreement with state relationship predictions for hydrocarbon/air combustion. The ethylene/air laminar flame conditions are similar to previously reported results including those from 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 report.

  3. Flight Tests of a Supersonic Natural Laminar Flow Airfoil

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

    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.

  4. Computational Optimization of a Natural Laminar Flow Experimental Wing Glove

    NASA Technical Reports Server (NTRS)

    Hartshom, Fletcher

    2012-01-01

    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.

  5. On the growth of turbulent regions in laminar boundary layers

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  6. Combustion Module-1 with Laminar Soot Process (LSP)

    NASA Technical Reports Server (NTRS)

    2004-01-01

    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.

  7. Atomization of water jets and sheets in axial and swirling airflows

    NASA Technical Reports Server (NTRS)

    Ingebo, R. D.

    1977-01-01

    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.

  8. Dynamic Changes in Heart Rate Variability and Nasal Airflow Resistance during Nasal Allergen Provocation Test.

    PubMed

    Seppänen, Tiina M; Alho, Olli-Pekka; Seppänen, Tapio

    2016-01-01

    Allergic rhinitis is a major chronic respiratory disease and an immunoneuronal disorder. We aimed at providing further knowledge on the function of the neural system in nasal allergic reaction. Here, a method to assess simultaneously the nasal airflow resistance and the underlying function of autonomic nervous system (ANS) is presented and used during the nasal provocation of allergic and nonallergic subjects. Continuous nasal airflow resistance and spectral heart rate variability parameters show in detail the timing and intensity differences in subjects' reactions. After the provocation, the nasal airflow resistance of allergic subjects showed a positive trend, whereas LF/HF (Low Frequency/High Frequency) ratio and LF power showed a negative trend. This could imply a gradual sympathetic withdrawal in allergic subjects after the allergen provocation. The groups differed significantly by these physiological descriptors. The proposed method opens entirely new opportunities to research accurately concomitant changes in nasal breathing function and ANS. PMID:27196870

  9. Airflow acceleration performance of asymmetric surface dielectric barrier discharge actuators at different exposed needle electrode heights

    NASA Astrophysics Data System (ADS)

    Yang, Liang; Yan, Hui-Jie; Qi, Xiao-Hua; Hua, Yue; Ren, Chun-Sheng

    2015-12-01

    The use of plasma, created by asymmetric surface dielectric barrier discharge (ASDBD), as aerodynamic actuators to control airflows, has been of widespread concern over the past decades. For the single ASDBD, the actuator performance is dependent on the geometry of actuator and the produced plasma. In this work, a new electrode configuration, i.e., a row of needle, is taken as an exposed electrode for the ASDBD plasma actuator, and the electrode height is adjustable. The effects of different electrode heights on the airflow acceleration behavior are experimentally investigated by measuring surface potential distribution, ionic wind velocity, and mean thrust force production. It is demonstrated that the airflow velocity and thrust force increase with the exposed electrode height and the best actuator performance can be obtained when the exposed electrode is adjusted to an appropriate height. The difference, as analyzed, is mainly due to the distinct plasma spatial distributions at different exposed electrode heights.

  10. Experimental investigation of effects of airflows on plasma-assisted combustion actuator characteristics

    NASA Astrophysics Data System (ADS)

    Liu, Xing-Jian; He, Li-Ming; Yu, Jin-Lu; Zhang, Hua-Lei

    2015-04-01

    The effects of the airflow on plasma-assisted combustion actuator (PACA) characteristics are studied in detail. The plasma is characterized electrically, as well as optically with a spectrometer. Our results show that the airflow has an obvious influence on the PACA characteristics. The breakdown voltage and vibrational temperature decrease, while the discharge power increases compared with the stationary airflow. The memory effect of metastable state species and the transportation characteristics of charged particles in microdischarge channel are the dominant causes for the variations of the breakdown voltage and discharge power, respectively, and the vibrational temperature calculated in this work can describe the electron energy of the dielectric barrier discharge plasma in PACA. These results offer new perspectives for the use of PACA in plasma-assisted combustion. Project supported by the National Natural Science Foundation of China (Grant Nos. 51436008, 50776100, and 51106179).

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

    SciTech Connect

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

    2014-05-15

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

  12. [A nonlinear multi-compartment lung model for optimization of breathing airflow pattern].

    PubMed

    Cai, Yongming; Gu, Lingyan; Chen, Fuhua

    2015-02-01

    It is difficult to select the appropriate ventilation mode in clinical mechanical ventilation. This paper presents a nonlinear multi-compartment lung model to solve the difficulty. The purpose is to optimize respiratory airflow patterns and get the minimum of the work of inspiratory phrase and lung volume acceleration, minimum of the elastic potential energy and rapidity of airflow rate changes of expiratory phrase. Sigmoidal function is used to smooth the respiratory function of nonlinear equations. The equations are established to solve nonlinear boundary conditions BVP, and finally the problem was solved with gradient descent method. Experimental results showed that lung volume and the rate of airflow after optimization had good sensitivity and convergence speed. The results provide a theoretical basis for the development of multivariable controller monitoring critically ill mechanically ventilated patients. PMID:25997262

  13. Analyzing airflow in static ice caves by using the calcFLOW method

    NASA Astrophysics Data System (ADS)

    Meyer, Christiane; Meyer, Ulrich; Pflitsch, Andreas; Maggi, Valter

    2016-04-01

    In this paper we present a method to detect airflow through ice caves and to quantify the corresponding airflow speeds by the use of temperature loggers. The time series of temperature observations at different loggers are cross-correlated. The time shift of best correlation corresponds to the travel time of the air and is used to derive the airflow speed between the loggers. We apply the method to test data observed inside Schellenberger Eishöhle (ice cave). The successful determination of airflow speeds depends on the existence of distinct temperature variations during the time span of interest. Moreover the airflow speed is assumed to be constant during the period used for the correlation analysis. Both requirements limit the applicability of the correlation analysis to determine instantaneous airflow speeds. Nevertheless the method is very helpful to characterize the general patterns of air movement and their slow temporal variations. The correlation analysis assumes a linear dependency between the correlated data. The good correlation we found for our test data confirms this assumption. We therefore in a second step estimate temperature biases and scale factors for the observed temperature variations by a least-squares adjustment. The observed phenomena, a warming and an attenuation of temperature variations, depending on the distance the air traveled inside the cave, are explained by a mixing of the inflowing air with the air inside the cave. Furthermore we test the significance of the determined parameters by a standard F test and study the sensitivity of the procedure to common manipulations of the original observations like smoothing. In the end we will give an outlook on possible applications and further development of this method.

  14. Influence of Airflow on Laboratory Storage of High Moisture Corn Stover

    SciTech Connect

    Lynn M. Wendt; Ian J. Bonner; Amber N. Hoover; Rachel M. Emerson; William A. Smith

    2014-04-01

    Storing high moisture biomass for bioenergy use is a reality in many areas of the country where wet harvest conditions and environmental factors prevent dry storage from being feasible. Aerobic storage of high moisture biomass leads to microbial degradation and self-heating, but oxygen limitation can aid in material preservation. To understand the influence of oxygen presence on high moisture biomass (50 %, wet basis), three airflow rates were tested on corn stover stored in laboratory reactors. Temperature, carbon dioxide production, dry matter loss, chemical composition, fungal abundance, pH, and organic acids were used to monitor the effects of airflow on storage conditions. The results of this work indicate that oxygen availability impacts both the duration of self-heating and the severity of dry matter loss. High airflow systems experienced the greatest initial rates of loss but a shortened microbially active period that limited total dry matter loss (19 %). Intermediate airflow had improved preservation in short-term storage compared to high airflow systems but accumulated the greatest dry matter loss over time (up to 27 %) as a result of an extended microbially active period. Low airflow systems displayed the best performance with the lowest rates of loss and total loss (10 %) in storage at 50 days. Total structural sugar levels of the stored material were preserved, although glucan enrichment and xylan loss were documented in the high and intermediate flow conditions. By understanding the role of oxygen availability on biomass storage performance, the requirements for high moisture storage solutions may begin to be experimentally defined.

  15. How much does nasal cavity morphology matter? Patterns and rates of olfactory airflow in phyllostomid bats

    PubMed Central

    Eiting, Thomas P.; Perot, J. Blair; Dumont, Elizabeth R.

    2015-01-01

    The morphology of the nasal cavity in mammals with a good sense of smell includes features that are thought to improve olfactory airflow, such as a dorsal conduit that delivers odours quickly to the olfactory mucosa, an enlarged olfactory recess at the back of the airway, and a clear separation of the olfactory and respiratory regions of the nose. The link between these features and having a good sense of smell has been established by functional examinations of a handful of distantly related mammalian species. In this paper, we provide the first detailed examination of olfactory airflow in a group of closely related species that nevertheless vary in their sense of smell. We study six species of phyllostomid bats that have different airway morphologies and foraging ecologies, which have been linked to differences in olfactory ability or reliance. We hypothesize that differences in morphology correlate with differences in the patterns and rates of airflow, which in turn are consistent with dietary differences. To compare species, we make qualitative and quantitative comparisons of the patterns and rates of airflow through the olfactory region during both inhalation and exhalation across the six species. Contrary to our expectations, we find no clear differences among species in either the patterns of airflow through the airway or in rates of flow through the olfactory region. By and large, olfactory airflow seems to be conserved across species, suggesting that morphological differences appear to be driven by other mechanical demands on the snout, such as breathing and feeding. Olfactory ability may depend on other aspects of the system, such as the neurobiological processing of odours that work within the existing morphology imposed by other functional demands on the nasal cavity. PMID:25520358

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

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

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

  17. How much does nasal cavity morphology matter? Patterns and rates of olfactory airflow in phyllostomid bats.

    PubMed

    Eiting, Thomas P; Perot, J Blair; Dumont, Elizabeth R

    2015-02-01

    The morphology of the nasal cavity in mammals with a good sense of smell includes features that are thought to improve olfactory airflow, such as a dorsal conduit that delivers odours quickly to the olfactory mucosa, an enlarged olfactory recess at the back of the airway, and a clear separation of the olfactory and respiratory regions of the nose. The link between these features and having a good sense of smell has been established by functional examinations of a handful of distantly related mammalian species. In this paper, we provide the first detailed examination of olfactory airflow in a group of closely related species that nevertheless vary in their sense of smell. We study six species of phyllostomid bats that have different airway morphologies and foraging ecologies, which have been linked to differences in olfactory ability or reliance. We hypothesize that differences in morphology correlate with differences in the patterns and rates of airflow, which in turn are consistent with dietary differences. To compare species, we make qualitative and quantitative comparisons of the patterns and rates of airflow through the olfactory region during both inhalation and exhalation across the six species. Contrary to our expectations, we find no clear differences among species in either the patterns of airflow through the airway or in rates of flow through the olfactory region. By and large, olfactory airflow seems to be conserved across species, suggesting that morphological differences appear to be driven by other mechanical demands on the snout, such as breathing and feeding. Olfactory ability may depend on other aspects of the system, such as the neurobiological processing of odours that work within the existing morphology imposed by other functional demands on the nasal cavity. PMID:25520358

  18. What is normal nasal airflow? A computational study of 22 healthy adults

    PubMed Central

    Zhao, Kai; Jiang, Jianbo

    2014-01-01

    Objective Nasal airflow is essential for functioning of the human nose. Given individual variation in nasal anatomy, there is yet no consensus what constitutes normal nasal airflow patterns. We attempt to obtain such information that is essential to differentiate disease-related variations. Methods Computational fluid dynamics (CFD) simulated nasal airflow in 22 healthy subjects during resting breathing. Streamline patterns, airflow distributions, velocity profiles, pressure, wall stress, turbulence, and vortical flow characteristics under quasi-steady state were analyzed. Patency ratings, acoustically measured minimum cross-sectional area (MCA), and rhinomanometric nasal resistance (NR) were examined for potential correlations with morphological and airflow-related variables. Results Common features across subjects included: >50% total pressure-drop reached near the inferior turbinate head; wall shear stress, NR, turbulence energy, and vorticity were lower in the turbinate than in the nasal valve region. However, location of the major flow path and coronal velocity distributions varied greatly across individuals. Surprisingly, on average, more flow passed through the middle than the inferior meatus and correlated with better patency ratings (r=-0.65, p<0.01). This middle flow percentage combined with peak post-vestibule nasal heat loss and MCA accounted for >70% of the variance in subjective patency ratings and predicted patency categories with 86% success. Nasal index correlated with forming of the anterior dorsal vortex. Expected for resting breathing, the functional impact for local and total turbulence, vorticity, and helicity was limited. As validation, rhinomanometric NR significantly correlated with CFD simulations (r=0.53, p<0.01). Conclusion Significant variations of nasal airflow found among healthy subjects; Key features may have clinically relevant applications. PMID:24664528

  19. Asbestos exposure, cigarette smoking, and airflow limitation in long-term Canadian chrysotile miners and millers

    SciTech Connect

    Begin, R.; Boileau, R.; Peloquin, S.

    1987-01-01

    To investigate further the relationships of asbestos exposure, cigarette smoking, and airflow limitation, we have obtained detailed pulmonary function tests (PFT) in 331 long-term Canadian chrysotile workers, 34 of whom were lifetime nonsmokers. Three disease categories were defined on the bases of standard diagnostic criteria, gallium-67 lung uptake, and the lung pressure-volume curve. Category A was composed of workers without changes suggestive of alveolitis or asbestosis. There were eight nonsmokers (ns), among whom we found a statistically significant 30% reduction in airflow conductance (Gus) at low lung volume, which is consistent with the concept of an asbestos airway lesion. The 85 smokers (sm) of category A had reduction of Gus at both high and low lung volumes. Category B was composed of workers without asbestosis but with evidence of asbestos alveolitis. In the six ns, Gus was significantly reduced to 50% normal at low lung volume. The 59 sm had reduction of Gus at both high and low lung volumes but less severely than sm in category A. Category C was composed of workers with asbestosis. The 20 ns had restrictive pattern of lung function, and Gus was decreased to 39% normal at 50% TLC. The 153 sm in C had airflow reduction comparable to sm in B. We concluded that asbestos exposure, which leads to asbestos airway disease, asbestos peribronchiolar alveolitis, and asbestosis, causes airflow limitation at low lung volume but does not reduce the expiratory flow rates on the flow-volume curve in lifetime nonsmokers. In the smoking asbestos workers with alveolitis or asbestosis, the major component of airflow limitation is a smoking effect. In these smoking workers, rigidity of the lung lessens airflow obstruction associated with smoking at the expense of increased work of breathing.

  20. Analyzing airflow in static ice caves by using the calcFLOW method

    NASA Astrophysics Data System (ADS)

    Meyer, C.; Meyer, U.; Pflitsch, A.; Maggi, V.

    2015-09-01

    In this paper we present a method to detect airflow through ice caves and to quantify the corresponding airflow speeds by the use of temperature loggers. The time series of temperature observations at different loggers are cross-correlated. The time shift of best correlation corresponds to the travel time of the air and is used to derive the airflow speed between the loggers. We apply the method to test data observed inside Schellenberger Eishöhle (ice cave). The successful determination of airflow speeds depends on the existence of distinct temperature variations during the time span of interest. Moreover the airflow speed is assumed to be constant during the period used for the correlation analysis. Both requirements limit the applicability of the correlation analysis to determine instantaneous airflow speeds. Nevertheless the method is very helpful to characterize the general patterns of air movement and their slow temporal variations. The correlation analysis assumes a linear dependency between the correlated data. The good correlation we found for our test data confirms this assumption. We therefore in a second step estimate temperature biases and scale factors for the observed temperature variations by a least squares adjustment. The observed phenomena, a warming and a damping of temperature variations depending on the distance the air traveled inside the cave, are explained by a mixing of the inflowing air with the air inside the cave. Furthermore we test the significance of the determined parameters by a standard F test and study the sensitivity of the procedure to common manipulations of the original observations like smoothing. In the end we will give an outlook on possible applications and further development of this method.

  1. Two-dimensional airflow modeling underpredicts the wind velocity over dunes

    NASA Astrophysics Data System (ADS)

    Michelsen, Britt; Strobl, Severin; Parteli, Eric J. R.; Pöschel, Thorsten

    2015-11-01

    We investigate the average turbulent wind field over a barchan dune by means of Computational Fluid Dynamics. We find that the fractional speed-up ratio of the wind velocity over the three-dimensional barchan shape differs from the one obtained from two-dimensional calculations of the airflow over the longitudinal cut along the dune’s symmetry axis — that is, over the equivalent transverse dune of same size. This finding suggests that the modeling of the airflow over the central slice of barchan dunes is insufficient for the purpose of the quantitative description of barchan dune dynamics as three-dimensional flow effects cannot be neglected.

  2. Two-dimensional airflow modeling underpredicts the wind velocity over dunes

    PubMed Central

    Michelsen, Britt; Strobl, Severin; Parteli, Eric J. R.; Pöschel, Thorsten

    2015-01-01

    We investigate the average turbulent wind field over a barchan dune by means of Computational Fluid Dynamics. We find that the fractional speed-up ratio of the wind velocity over the three-dimensional barchan shape differs from the one obtained from two-dimensional calculations of the airflow over the longitudinal cut along the dune’s symmetry axis — that is, over the equivalent transverse dune of same size. This finding suggests that the modeling of the airflow over the central slice of barchan dunes is insufficient for the purpose of the quantitative description of barchan dune dynamics as three-dimensional flow effects cannot be neglected. PMID:26572966

  3. Research of Structure and Technology for the Micro-Machined Airflow Inclinometer

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Liu, Yu; Zhang, Fuxue

    This paper reported a sensing mechanism of carrier attitude angle with the micro-machined airflow inclinometer, it utilized fluid mechanics and related theories to design the sensitive structure, analyze and certify gas pendulum in a micro-structure hermetic chamber, We used computer aided design and simulation software MEMSPro to design sensing structure layout,and produced in MEMS processing methods. The Micro-machined airflow inclinometer installed on optical dividing head to test. Through the compensation, ± 45° can be realized Nonlinear 1% or less. The sensor has a strong anti-vibration and impact ability, a simple structure and low cost.

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

    NASA Technical Reports Server (NTRS)

    Ingebo, R.

    1983-01-01

    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).

  5. Two-dimensional airflow modeling underpredicts the wind velocity over dunes.

    PubMed

    Michelsen, Britt; Strobl, Severin; Parteli, Eric J R; Pöschel, Thorsten

    2015-01-01

    We investigate the average turbulent wind field over a barchan dune by means of Computational Fluid Dynamics. We find that the fractional speed-up ratio of the wind velocity over the three-dimensional barchan shape differs from the one obtained from two-dimensional calculations of the airflow over the longitudinal cut along the dune's symmetry axis - that is, over the equivalent transverse dune of same size. This finding suggests that the modeling of the airflow over the central slice of barchan dunes is insufficient for the purpose of the quantitative description of barchan dune dynamics as three-dimensional flow effects cannot be neglected. PMID:26572966

  6. A Comparative Study of Airflow and Odorant Deposition in the Mammalian Nasal Cavity

    NASA Astrophysics Data System (ADS)

    Richter, Joseph; Rumple, Christopher; Ranslow, Allison; Quigley, Andrew; Pang, Benison; Neuberger, Thomas; Krane, Michael; van Valkenburgh, Blaire; Craven, Brent

    2013-11-01

    The complex structure of the mammalian nasal cavity provides a tortuous airflow path and a large surface area for respiratory air conditioning, filtering of inspired contaminants, and olfaction. Due to the small and contorted structure of the nasal turbinals, nasal anatomy and function remains poorly understood in most mammals. Here, we utilize high-resolution MRI scans to reconstruct anatomically-accurate models of the mammalian nasal cavity. These data are used to compare the form and function of the mammalian nose. High-fidelity computational fluid dynamics (CFD) simulations of nasal airflow and odorant deposition are presented and used to compare olfactory function across species (primate, rodent, canine, feline, ungulate).

  7. Automating the Solar DRYER—AIRFLOW Control Utilizing Pressure Diffrence Concept

    NASA Astrophysics Data System (ADS)

    Luk, T. B.; Vakhguelt, A.

    2009-08-01

    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.

  8. [Mensurement of airflow resistance in neonatal prongs of nasal CPAP

    PubMed

    Sampietro, V I; Azevedo, M P; Resende, J G

    2000-01-01

    OBJECTIVE: To measure airflow resistance in prongs of nasal CPAP, making use of different gas admission flow (GAF) in the ventilation circuit, in different internal diameters of the nasal prongs, besides verifying whether a GAF responding only to the demand of three times the minute-volume(MV) is enough to the circuit not to be cause of CO(2) retention. METHODOLOGY: Nasal prongs, assembled in the original circuits, were used, having their prongs kept open to the atmosphere. Pressure was read at a pressure monitor, in water centimeters, connected to the appropriate entrance of the circuit. A flowmeter balanced to the pressure was used, gauged at 50 psi, installed to the oxygen net of the Hospital, connected to the assessing set of the CPAP circuit. Initially, making use of the 8 l/min flow and keeping the exhaling set of the circuit closed, it was possible to eliminate the nasal prongs larger than two once the measured resistance was equal to zero. Having nasal parts number zero, 1 and 2 selected for this study, the system was then assembled as for the neonate: the inhaling set to the gas source and the exhaling set sunk into different depths in the water seal (2, 4, 6 and 8 centimeters). At the level of patient analysis, in order to assess the CO(2) retention, a mechanical pulmonary ventilation device was used as gas source and a nasal CPAP circuit was assembled to the device in adequate places. GAF values and FiO(2) were determined in the commands of the mechanical ventilation device. The assessment of gas concentration in the ventilation circuit was made while assisting two newborns. Gas samples were obtained within the ventilation circuit in the system assessing set (samples A), and right after the distal prong to the gas entrance (samples B). To determine MV the Tidal Volume (considered 10ml/kg) was multiplied by the respiratory frequency of the patient; GAF was three times MV. RESULTS: To a maximum GAF of 8 litres/min, only prongs sized zero, 1 and 2 showed

  9. Wing laminar boundary layer in the presence of a propeller slipstream

    NASA Technical Reports Server (NTRS)

    Miley, S. J.; Howard, R. M.; Holmes, B. J.

    1986-01-01

    The effects of a propeller slipstream on the wing laminar boundary layer are being investigated. Hot-wire velocity sensor measurements have been performed in flight and in a wind tunnel. It is shown that the boundary layer cycles between a laminar state and a turbulent state at the propeller blade passage rate. The cyclic length of the turbulent state increases with decreasing laminar stability. Analyses of the time varying velocity profiles show the turbulent state to lie in a transition region between fully laminar and fully turbulent. The observed cyclic boundary layer has characteristics similar to relaminarizing flow and laminar flow with external turbulence.

  10. 42 CFR 84.154 - Airflow resistance test; Type B and Type BE supplied-air respirators; minimum requirements.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 42 Public Health 1 2010-10-01 2010-10-01 false Airflow resistance test; Type B and Type BE..., DEPARTMENT OF HEALTH AND HUMAN SERVICES OCCUPATIONAL SAFETY AND HEALTH RESEARCH AND RELATED ACTIVITIES APPROVAL OF RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators § 84.154 Airflow resistance test;...

  11. 42 CFR 84.155 - Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE...

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 42 Public Health 1 2011-10-01 2011-10-01 false Airflow resistance test; Type C supplied-air respirator, continuous flow class and Type CE supplied-air respirator; minimum requirements. 84.155 Section... Respirators § 84.155 Airflow resistance test; Type C supplied-air respirator, continuous flow class and...

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

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    been some research on the stability of laminar flames, but most studies have focused on turbulent flames. It is also well known that the airflow around the fuel jet can significantly alter the lift off, reattachment and blow out of the jet diffusion flame. Buoyant convection is sufficiently strong in 1-g flames that it can dominate the flow-field, even at the burner rim. In normal-gravity testing, it is very difficult to delineate the effects of the forced airflow from those of the buoyancy-induced flow. Comparison of normal-gravity and microgravity flames provides clear indication of the influence of forced and buoyant flows on the flame stability. The overall goal of the Enclosed Laminar Flames (ELF) investigation (STS-87/USMP-4 Space Shuttle mission, November to December 1997) is to improve our understanding of the effects of buoyant convection on the structure and stability of co-flow diffusion flame, e.g., see http://zeta.lerc.nasa.gov/expr/elf.htm. The ELF hardware meets the experiment hardware limit of the 35-liter interior volume of the glovebox working area, and the 180x220-mm dimensions of the main door. The ELF experiment module is a miniature, fan-driven wind tunnel, equipped with a gas supply system. A 1.5-mm diameter nozzle is located on the duct's flow axis. The cross section of the duct is nominally a 76-mm square with rounded corners. The forced air velocity can be varied from about 0.2 to 0.9 m/s. The fuel flow can be set as high as 3 std. cubic centimeter (cc) per second, which corresponds to a nozzle exit velocity of up to 1.70 m/s. The ELF hardware and experimental procedure are discussed in detail in Brooker et al. The 1-g test results are repeated in several experiments following the STS-87 Mission. The ELF study is also relevant to practical systems because the momentum-dominated behavior of turbulent flames can be achieved in laminar flames in microgravity. The specific objectives of this paper are to evaluate the use reduced model for

  13. Continental Lower-crustal Flow: Channel Flow and Laminar Flow

    NASA Astrophysics Data System (ADS)

    LI, Dewei

    Numerous geological, geophysical and geochemical investigations and finite element modeling indicate that crustal flow layers exist in the continental crust. Both channel flow model and laminar flow model have been created to explain the flow laws and flow mechanisms. As revealed by the channel flow model, a low-viscosity channel in middle to lower crust in orogen or plateau with thick crust and high elevation would flow outward from mountain root in response to lateral pressure gradient resulted from topographic loading or to denudation. However, according to the laminar flow model proposed based on investigation of the Qinghai-Tibet plateau, circulative movement of crustal lithologies with different rheological properties between basin and orogen would occur, under the driving forces resulted from dehydration and melting of subduction plate on active continental margin and from thermal energy related to upwelling and diapiring of intercontinental mantle plume or its gravitational interactions. Similarly, when driven by gravity, the softened or melted substances of the lower crust in a basin would flow laterally toward adjacent mountain root, which would result in a thinned basin crust and a thickened orogenic crust. Partially melted magma within the thickened orogenic lower crust would cause vertical movement of metamorphic rocks of lower to middle crust due to density inversion, and the vertical main stress induced by thermal underplating of lower crust would in turn lead to formation of metamorphic core complexes and low-angle detachment fault systems. Lateral spreading of uplifting mountain due to gravitation potential would result in thrust fault systems on the border between mountain and basin. Meanwhile, detritus produced synchronously by intense erosion of uplifting mountain would be transported and deposited along the marginal deep depression in the foreland basin dragged by lower crust flow. Channel flow is similar to laminar flow in a variety of aspects

  14. Conceptual design for a laminar-flying-wing aircraft

    NASA Astrophysics Data System (ADS)

    Saeed, T. I.

    The laminar-flying-wing aircraft appears to be an attractive long-term prospect for reducing the environmental impact of commercial aviation. In assessing its potential, a relatively straightforward initial step is the conceptual design of a version with restricted sweep angle. Such a design is the topic of this thesis. Subject to constraints, this research aims to; provide insight into the parameters affecting practical laminar-flow-control suction power requirements; identify a viable basic design specification; and, on the basis of this, an assessment of the fuel efficiency through a detailed conceptual design study. It is shown that there is a minimum power requirement independent of the suction system design, associated with the stagnation pressure loss in the boundary layer. This requirement increases with aerofoil section thickness, but depends only weakly on Mach number and (for a thick, lightly-loaded laminar flying wing) lift coefficient. Deviation from the optimal suction distribution, due to a practical chamber-based architecture, is found to have very little effect on the overall suction coefficient. In the spanwise direction, through suitable choice of chamber depth, the pressure drop due to frictional and inertial effects may be rendered negligible. Finally, it is found that the pressure drop from the aerofoil surface to the pump collector ducts determines the power penalty. To identify the viable basic design specification, a high-level exploration of the laminar flying wing design space is performed. The characteristics of the design are assessed as a function of three parameters: thickness-to-chord ratio, wingspan, and unit Reynolds number. A feasible specification, with 20% thickness-to-chord, 80 m span and a unit Reynolds number of 8 x 106 m-1, is identified; it corresponds to a 187 tonne aircraft which cruises at Mach 0.67 and altitude 22,500 ft, with lift coefficient 0.14. On the basis of this specification, a detailed conceptual design is

  15. Shapes of Buoyant and Nonbuoyant Methane Laminar Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

    Sunderland, Peter B.; Yuan, Zeng-Guang; Urban, David L.

    1997-01-01

    Laminar gas jet diffusion flames represent a fundamental combustion configuration. Their study has contributed to numerous advances in combustion, including the development of analytical and computational combustion tools. Laminar jet flames are pertinent also to turbulent flames by use of the laminar flamelet concept. Investigations into the shapes of noncoflowing microgravity laminar jet diffusion flames have primarily been pursued in the NASA Lewis 2.2-second drop tower, by Cochran and coworkers and by Bahadori and coworkers. These studies were generally conducted at atmospheric pressure; they involved soot-containing flames and reported luminosity lengths and widths instead of the flame-sheet dimensions which are of Greater value to theory evaluation and development. The seminal model of laminar diffusion flames is that of Burke and Schumann, who solved the conservation of momentum equation for a jet flame in a coflowing ambient by assuming the velocity of fuel, oxidizer and products to be constant throughout. Roper and coworkers improved upon this model by allowing for axial variations of velocity and found flame shape to be independent of coflow velocity. Roper's suggestion that flame height should be independent of gravity level is not supported by past or present observations. Other models have been presented by Klajn and Oppenheim, Markstein and De Ris, Villermaux and Durox, and Li et al. The common result of all these models (except in the buoyant regime) is that flame height is proportional to fuel mass flowrate, with flame width proving much more difficult to predict. Most existing flame models have been compared with shapes of flames containing soot, which is known to obscure the weak blue emission of flame sheets. The present work involves measurements of laminar gas jet diffusion flame shapes. Flame images have been obtained for buoyant and nonbuoyant methane flames burning in quiescent air at various fuel flow-rates, burner diameters and ambient

  16. Atomization of water jets and sheets in axial and swirling airflows

    NASA Technical Reports Server (NTRS)

    Ingebo, R. D.

    1979-01-01

    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.

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

    PubMed Central

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

    2013-01-01

    Detection for cough in mice has never yielded clearly audible sounds, so there is still a great deal of debates as to whether mice can cough in response to tussive stimuli. Here we introduce an approach for detection of mouse cough based on sound monitoring and airflow signals. 40 Female BALB/c mice were pretreated with normal saline, codeine, capasazepine or desensitized with capsaicin. Single mouse was put in a plethysmograph, exposed to aerosolized 100 µmol/L capsaicin for 3 min, followed by continuous observation for 3 min. Airflow signals of total 6 min were recorded and analyzed to detect coughs. Simultaneously, mouse cough sounds were sensed by a mini-microphone, monitored manually by an operator. When manual and automatic detection coincided, the cough was positively identified. Sound and sound waveforms were also recorded and filtered for further analysis. Body movements were observed by operator. Manual versus automated counts were compared. Seven types of airflow signals were identified by integrating manual and automated monitoring. Observation of mouse movements and analysis of sound waveforms alone did not produce meaningful data. Mouse cough numbers decreased significantly after all above drugs treatment. The Bland-Altman and consistency analysis between automatic and manual counts was 0.968 and 0.956. The study suggests that the mouse is able to present with cough, which could be detected by sound monitoring and respiratory airflow waveform changes. PMID:23555643

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

    EPA Science Inventory

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

  19. Citric acid cough threshold and airway responsiveness in asthmatic patients and smokers with chronic airflow obstruction.

    PubMed Central

    Auffarth, B; de Monchy, J G; van der Mark, T W; Postma, D S; Koëter, G H

    1991-01-01

    The relation between citric acid cough threshold and airway hyperresponsiveness was investigated in 11 non-smoking patients with allergic asthma (mean FEV1 94% predicted) and 25 non-atopic smokers with chronic airflow obstruction (mean FEV1 65% predicted). Cough threshold was determined on two occasions by administering doubling concentrations of citric acid. Seven of the 11 asthmatic subjects and 14 of 25 smokers with chronic airflow obstruction had a positive cough threshold on both test days. Cough threshold measurements were reproducible in both groups (standard deviation of duplicate measurements 1.2 doubling concentrations in asthma, 1.1 doubling concentrations in chronic airflow obstruction). Citric acid provocation did not cause bronchial obstruction in most patients, though four patients had a fall in FEV1 of more than 20% for a short time on one occasion only. No significant difference in cough threshold was found between the two patient groups despite differences in baseline FEV1 values. There was no significant correlation between cough threshold and the provocative concentration of histamine causing a 20% fall in FEV1 (PC20) histamine in either group. Thus sensory nerves can be activated with a tussive agent in patients with asthma and chronic airflow obstruction without causing bronchial smooth muscle contraction. PMID:1948792

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

    ERIC Educational Resources Information Center

    Consumer Dynamics Inc., Rockville, MD.

    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…

  1. Test-Retest Reliability of Respiratory Resistance Measured with the Airflow Perturbation Device

    ERIC Educational Resources Information Center

    Gallena, Sally K.; Solomon, Nancy Pearl; Johnson, Arthur T.; Vossoughi, Jafar; Tian, Wei

    2014-01-01

    Purpose: In this study, the authors aimed to determine reliability of the airflow perturbation device (APD) to measure respiratory resistance within and across sessions during resting tidal (RTB) and postexercise breathing in healthy athletes, and during RTB across trials within a session in athletes with paradoxical vocal fold motion (PVFM)…

  2. Experimental investigation of transient thermal behavior of an airship under different solar radiation and airflow conditions

    NASA Astrophysics Data System (ADS)

    Li, De-Fu; Xia, Xin-Lin; Sun, Chuang

    2014-03-01

    Knowledge of the thermal behavior of airships is crucial to the development of airship technology. An experiment apparatus is constructed to investigate the thermal response characteristics of airships, and the transient temperature distributions of both hull and inner gas are obtained under the irradiation of a solar simulator and various airflow conditions. In the course of the research, the transient temperature change of the experimental airship is measured for four airflow speeds of 0 m/s (natural convection), 3.26 m/s, 5.5 m/s and 7.0 m/s, and two incident solar radiation values of 842.4 W/m2 and 972.0 W/m2. The results show that solar irradiation has significant influence on the airship hull and inner gas temperatures even if the airship stays in a ground airflow environment where the heat transfer is dominated by radiation and convection. The airflow around the airship is conducive to reduce the hull temperature and temperature nonuniformity. Transient thermal response of airships rapidly varies with time under solar radiation conditions and the hull temperature remains approximately constant in ˜5-10 min. Finally, a transient thermal model of airship is developed and the model is validated through comparison with the experimental data.

  3. Computational fluid dynamics (CFD) investigation of impacts of an obstruction on airflow in underground mines

    PubMed Central

    Zhou, L.; Goodman, G.; Martikainen, A.

    2015-01-01

    Continuous airflow monitoring can improve the safety of the underground work force by ensuring the uninterrupted and controlled distribution of mine ventilation to all working areas. Air velocity measurements vary significantly and can change rapidly depending on the exact measurement location and, in particular, due to the presence of obstructions in the air stream. Air velocity must be measured at locations away from obstructions to avoid the vortices and eddies that can produce inaccurate readings. Further, an uninterrupted measurement path cannot always be guaranteed when using continuous airflow monitors due to the presence of nearby equipment, personnel, roof falls and rib rolls. Effective use of these devices requires selection of a minimum distance from an obstacle, such that an air velocity measurement can be made but not affected by the presence of that obstacle. This paper investigates the impacts of an obstruction on the behavior of downstream airflow using a numerical CFD model calibrated with experimental test results from underground testing. Factors including entry size, obstruction size and the inlet or incident velocity are examined for their effects on the distributions of airflow around an obstruction. A relationship is developed between the minimum measurement distance and the hydraulic diameters of the entry and the obstruction. A final analysis considers the impacts of continuous monitor location on the accuracy of velocity measurements and on the application of minimum measurement distance guidelines. PMID:26388684

  4. Airflow produced by dielectric barrier discharge between asymmetric parallel rod electrodes

    SciTech Connect

    Hayashi, Kazuo; Tanaka, Motofumi; Yasui, Hiroyuki; Hashimoto, Kiyoshi

    2007-09-15

    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.

  5. Study on airflow characteristics in the semi-closed irregular narrow flow channel

    NASA Astrophysics Data System (ADS)

    Jin, Yuzhen; Hu, Xiaodong; Zhu, Linhang; Hu, Xudong; Jin, Yingzi

    2016-04-01

    The air-jet loom is widely used in the textile industry. The interaction mechanism of airflow and yarn is not clear in such a narrow flow channel, the gas consumption is relatively large, the yarn motion is unstable and the weft insertion is often interrupted during the operation. In order to study the characteristics of the semi-closed flow field in profiled dents, the momentum conservation equation is modified and the model parameters and boundary conditions are set. Compared with the different r, the ratio of profiled dent's thickness and gap, the results show that the smaller the r is, the smaller the velocity fluctuations of the airflow is. When the angle of profiled dents α is close to zero, the diffusion of the airflow will be less. The experiment is also conducted to verify the result of the simulation with a high-speed camera and pressure sensor in profiled dents. The airflow characteristics in the semi-closed irregular narrow flow channel in the paper would provide the theoretical basis for optimizing the weft insertion process of the air-jet loom.

  6. Cooling tower irrigator layout with allowances for non-uniformity of the airflow velocity field

    NASA Astrophysics Data System (ADS)

    Pushnov, A. S.; Ryabushenko, A. S.

    2016-07-01

    This article covers the results of analysis of aerodynamic processes in the cooling tower irrigator and provides the approaches to optimal layout of preformed packing blocks (of the irrigator) developed based on these results. The analysis of the airflow velocity field in the cooling towers shows that the irrigation space can be broken down into the following zones: the peripheral zone of the cooling tower near the airblast windows, the zone near the cooling tower center, and the intermediate zone. Furthermore, the highest level of nonuniformity of the airflow velocity field in cooling towers is in the zone adjoining the tower's airblast windows. The proposed concept of the cooling tower irrigator's layout is made with allowances for the airflow velocity field characteristics in the cross-section of the irrigation space of the cooling tower. Based on this concept, we suggest that higher irrigator blocks should be placed in the zone of increased airflow consumption, which provides the possibility to enhance the hydraulic resistance and, respectively, decrease the gas flow velocity as well as to boost the efficiency of chilling the circulating water in the cooling tower. For this purpose, additional irrigator blocks can be of the same design as the main irrigator. As an option, it is possible to use blocks of the geometry and design other than the main irrigator block in the cooling tower.

  7. Laminar/turbulent oscillating flow in circular pipes

    NASA Astrophysics Data System (ADS)

    Ahn, Kyung H.; Ibrahim, Mounir B.

    1992-12-01

    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.

  8. Laminar flow test installation in the Boeing Research Wind Tunnel

    NASA Technical Reports Server (NTRS)

    George-Falvy, Dezso

    1990-01-01

    This paper describes the initial wind tunnels tests in the 5- by 8-ft Boeing Research Wind Tunnel of a near full-scale (20-foot chord) swept wing section having laminar flow control (LFC) by slot suction over its first 30 percent chord. The model and associated test apparatus were developed for use as a testbed for LFC-related experimentation in support of preliminary design studies done under contract with the National Aeronautics and Space Administration. This paper contains the description of the model and associated test apparatus as well as the results of the initial test series in which the proper functioning of the test installation was demonstrated and new data were obtained on the sensitivity of suction-controlled laminar flow to surface protuberances in the presence of crossflow due to sweep.

  9. Momentum and heat transport scalings in laminar vertical convection.

    PubMed

    Shishkina, Olga

    2016-05-01

    We derive the dependence of the Reynolds number Re and the Nusselt number Nu on the Rayleigh number Ra and the Prandtl number Pr in laminar vertical convection (VC), where a fluid is confined between two differently heated isothermal vertical walls. The boundary layer equations in laminar VC yield two limiting scaling regimes: Nu∼Pr^{1/4}Ra^{1/4}, Re∼Pr^{-1/2}Ra^{1/2} for Pr≪1 and Nu∼Pr^{0}Ra^{1/4}, Re∼Pr^{-1}Ra^{1/2} for Pr≫1. These theoretical results are in excellent agreement with direct numerical simulations for Ra from 10^{5} to 10^{10} and Pr from 10^{-2} to 30. The transition between the regimes takes place for Pr around 10^{-1}. PMID:27300823

  10. Momentum and heat transport scalings in laminar vertical convection

    NASA Astrophysics Data System (ADS)

    Shishkina, Olga

    2016-05-01

    We derive the dependence of the Reynolds number Re and the Nusselt number Nu on the Rayleigh number Ra and the Prandtl number Pr in laminar vertical convection (VC), where a fluid is confined between two differently heated isothermal vertical walls. The boundary layer equations in laminar VC yield two limiting scaling regimes: Nu˜Pr1/4Ra1/4 , Re˜Pr-1/2Ra1/2 for Pr≪1 and Nu˜Pr0Ra1/4 , Re˜Pr-1Ra1/2 for Pr≫1 . These theoretical results are in excellent agreement with direct numerical simulations for Ra from 105 to 1010 and Pr from 10-2 to 30. The transition between the regimes takes place for Pr around 10-1.

  11. Preliminary aerodynamic design considerations for advanced laminar flow aircraft configurations

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

    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.

  12. Natural laminar flow and airplane stability and control

    NASA Technical Reports Server (NTRS)

    Vandam, Cornelis P.

    1986-01-01

    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.

  13. Strongly coupled interaction between a ridge of fluid and an inviscid airflow

    NASA Astrophysics Data System (ADS)

    Paterson, C.; Wilson, S. K.; Duffy, B. R.

    2015-07-01

    The behaviour of a steady thin sessile or pendent ridge of fluid on an inclined planar substrate which is strongly coupled to the external pressure gradient arising from an inviscid airflow parallel to the substrate far from the ridge is described. When the substrate is nearly horizontal, a very wide ridge can be supported against gravity by capillary and/or external pressure forces; otherwise, only a narrower (but still wide) ridge can be supported. Classical thin-aerofoil theory is adapted to obtain the governing singular integro-differential equation for the profile of the ridge in each case. Attention is focused mainly on the case of a very wide sessile ridge. The effect of strengthening the airflow is to push a pinned ridge down near to its edges and to pull it up near to its middle. At a critical airflow strength, the upslope contact angle reaches the receding contact angle at which the upslope contact line de-pins, and continuing to increase the airflow strength beyond this critical value results in the de-pinned ridge becoming narrower, thicker, and closer to being symmetric in the limit of a strong airflow. The effect of tilting the substrate is to skew a pinned ridge in the downslope direction. Depending on the values of the advancing and receding contact angles, the ridge may first de-pin at either the upslope or the downslope contact line but, in general, eventually both contact lines de-pin. The special cases in which only one of the contact lines de-pins are also considered. It is also shown that the behaviour of a very wide pendent ridge is qualitatively similar to that of a very wide sessile ridge, while the important qualitative difference between the behaviour of a very wide ridge and a narrower ridge is that, in general, for the latter one or both of the contact lines may never de-pin.

  14. Usability Evaluation of a Flight-Deck Airflow Hazard Visualization System

    NASA Technical Reports Server (NTRS)

    Aragon, Cecilia R.

    2004-01-01

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

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

    PubMed

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

    2013-01-01

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

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

    PubMed Central

    Hutchinson, John R.; Farmer, CG

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Aragon, Cecilia Rodriguez

    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

  18. Pulmonary Artery Abnormalities in Ex-smokers with and without Airflow Obstruction.

    PubMed

    Lindenmaier, Tamas J; Kirby, Miranda; Paulin, Gregory; Mielniczuk, Lisa; Cunningham, Ian A; Mura, Marco; Licskai, Christopher; Parraga, Grace

    2016-04-01

    Pulmonary vascular disease is a common complication of chronic obstructive pulmonary disease (COPD), and an important risk factor for COPD exacerbations and death. We explored the relationship between pulmonary artery volumes measured using thoracic computed tomography (CT) and lung structure-function measured using spirometry, CT and magnetic resonance imaging (MRI) in 124 ex-smokers with (n = 68) and without (n = 56) airflow obstruction, and a control group of 35 never-smokers. We observed significantly greater main (p = .01), right (p = .001) and total (p = .003) pulmonary artery volumes in ex-smokers with airflow obstruction as compared to ex-smokers without airflow obstruction. There were also significantly greater pulmonary artery volumes in both ex-smoker subgroups, compared to the never-smoker subgroup (p = .008). For all participants, there were significant correlations for pulmonary artery volumes with the ratio of the forced expiratory volume in 1 s to forced vital capacity (FEV1/FVC), the diffusing capacity of the lung for carbon monoxide (DLCO%pred), airway count, MRI ventilation defect percent and MRI apparent diffusion coefficients. In ex-smokers, ventilation defect percent was significantly correlated with right (r = 0.27, p = .02) and total (r = 0.25, p = .03) pulmonary artery volumes. Multivariate zero-inflated Poisson regression analysis showed that FEV1%pred (p = .004), DLCO%pred (p = .03), the six minute walk distance (p = .04) and total pulmonary artery volume (p = .03) were significant predictors of acute exacerbations of COPD, while the number of previous exacerbations was not. In conclusion, pulmonary artery enlargement measured using thoracic CT was observed even in ex-smokers without airflow obstruction and was predictive of COPD exacerbations in ex-smokers with airflow obstruction. PMID:26606693

  19. An elementary model for autoignition of laminar jets

    PubMed Central

    Gordon, Peter V.; Gotti, Daniel J.; Hegde, Uday G.; Hicks, Michael C.; Kulis, Michael J.; Sivashinsky, Gregory I.

    2015-01-01

    In this paper, we formulate and analyse an elementary model for autoignition of cylindrical laminar jets of fuel injected into an oxidizing ambient at rest. This study is motivated by renewed interest in analysis of hydrothermal flames for which such configuration is common. As a result of our analysis, we obtain a sharp characterization of the autoignition position in terms of the principal physical and geometrical parameters of the problem. PMID:26345080

  20. Ground vibration test of the laminar flow control JStar airplane

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

    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.

  1. The excitation of unstable perturbations in a laminar friction layer

    NASA Technical Reports Server (NTRS)

    Pretsch, Joachim

    1952-01-01

    With the aid of the method of small oscillations which was used successfully in the investigation of the stability of laminar velocity distributions in the presence of two-dimensional perturbations, the excitation of the unstable perturbations for the Hartree velocity distributions occurring in plane boundary-layer flow for decreasing and increasing pressure is calculated as a supplement to a former report. The results of this investigation are to make a contribution toward calculation of the transition point on cylindrical bodies.

  2. Flame Shapes of Nonbuoyant Laminar Jet Diffusion Flames. Appendix K

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  3. Flame Shapes of Nonbuoyant Laminar Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  4. Laminar shocks in high power laser plasma interactions

    SciTech Connect

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

    2014-02-15

    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.

  5. Structure and Soot Formation Properties of Laminar Flames

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  6. Laminar Flow Supersonic Wind Tunnel primary air injector

    NASA Technical Reports Server (NTRS)

    Smith, Brooke Edward

    1993-01-01

    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.

  7. Co-laminar flow cells for electrochemical energy conversion

    NASA Astrophysics Data System (ADS)

    Goulet, Marc-Antoni; Kjeang, Erik

    2014-08-01

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

  8. Type I planet migration in nearly laminar disks

    SciTech Connect

    Li, Hui; Li, Shengtai; Lubow, S H; Lin, D

    2008-01-01

    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.

  9. Natural laminar flow experiments on modern airplane surfaces

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

  10. Detection of Cortical Laminar Architecture Using Manganese-Enhanced MRI

    PubMed Central

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

    2008-01-01

    Changes in Manganese-Enhanced MRI (MEMRI) contrast across the rodent somatosensory cortex were compared to the cortical laminae as identified by tissue histology and administration of an anatomical tracer to cortex and thalamus. Across the cortical thickness, MEMRI signal intensity was low in layer I, increased in layer II, decreased in layer III until mid-layer IV, and increased again, peaking in layer V, before decreasing through layer VI. The reeler mouse mutant was used to confirm that the cortical alternation in MEMRI contrast was related to laminar architecture. Unlike in wild-type mice, the reeler cortex showed no appreciable changes in MEMRI signal, consistent[ACS1] with absence of cortical laminae in histological slides. The tract-tracing ability of MEMRI was used to further confirm assignments and demonstrate laminar specificity. Twelve to sixteen hours after stereotaxic injections of MnCl2 to the ventroposterior thalamic nuclei, an overall increase in signal intensity was detected in primary somatosensory cortex compared to other brain regions. Maximum intensity projection images revealed a distinctly bright stripe located 600 − 700 μm below the pial surface, in layer IV. The data show that both systemic and tract-tracing forms of MEMRI are useful for studying laminar architecture in the brain. PMID:17936913

  11. The Effects of Gravity on Wrinkled Laminar Flames

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    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.

  12. A Joint Numerical-Experimental Study on Impact Induced Intra-laminar and Inter-laminar Damage in Laminated Composites

    NASA Astrophysics Data System (ADS)

    Riccio, A.; Caputo, F.; Di Felice, G.; Saputo, S.; Toscano, C.; Lopresto, V.

    2015-07-01

    The investigation of the mechanical response of fibre-reinforced composite laminates under impact loads can be very difficult due to the occurrence of simultaneous failure phenomena. Indeed, as a consequence of low velocity impacts, intra-laminar damages, like fibre and matrix cracking, and inter-laminar damages, such as delaminations, can take place simultaneously. These damage mechanisms can lead to significant reductions in strength and stability of the composite structure. In this paper a joint numerical-experimental study is proposed which, by means of non-destructive testing techniques (Ultra-sound and thermography) and non-linear explicit FEM analyses, aims to completely characterise the impact induced damage in composite laminates under low velocity impacts. Indeed the proposed numerical tool has been used to improve the understanding of the experimental data obtained by Non-Destructive Techniques. Applications on samples tested according to the AECMA (European Association of Aerospace Manufacturers) prEn6038 standard at three different impact energies are presented. The interaction between numerical and experimental investigation allowed to obtain an exhaustive insight on the different phases of the impact event considering the inter-laminar damage formation and evolution.

  13. A Joint Numerical-Experimental Study on Impact Induced Intra-laminar and Inter-laminar Damage in Laminated Composites

    NASA Astrophysics Data System (ADS)

    Riccio, A.; Caputo, F.; Di Felice, G.; Saputo, S.; Toscano, C.; Lopresto, V.

    2016-06-01

    The investigation of the mechanical response of fibre-reinforced composite laminates under impact loads can be very difficult due to the occurrence of simultaneous failure phenomena. Indeed, as a consequence of low velocity impacts, intra-laminar damages, like fibre and matrix cracking, and inter-laminar damages, such as delaminations, can take place simultaneously. These damage mechanisms can lead to significant reductions in strength and stability of the composite structure. In this paper a joint numerical-experimental study is proposed which, by means of non-destructive testing techniques (Ultra-sound and thermography) and non-linear explicit FEM analyses, aims to completely characterise the impact induced damage in composite laminates under low velocity impacts. Indeed the proposed numerical tool has been used to improve the understanding of the experimental data obtained by Non-Destructive Techniques. Applications on samples tested according to the AECMA (European Association of Aerospace Manufacturers) prEn6038 standard at three different impact energies are presented. The interaction between numerical and experimental investigation allowed to obtain an exhaustive insight on the different phases of the impact event considering the inter-laminar damage formation and evolution.

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  15. Aerodynamic study of a small wind turbine with emphasis on laminar and transition flows

    NASA Astrophysics Data System (ADS)

    Niculescu, M. L.; Cojocaru, M. G.; Crunteanu, D. E.

    2016-06-01

    The wind energy is huge but unfortunately, wind turbines capture only a little part of this enormous green energy. Furthermore, it is impossible to put multi megawatt wind turbines in the cities because they generate a lot of noise and discomfort. Instead, it is possible to install small Darrieus and horizontal-axis wind turbines with low tip speed ratios in order to mitigate the noise as much as possible. Unfortunately, the flow around this wind turbine is quite complex because the run at low Reynolds numbers. Therefore, this flow is usually a mixture of laminar, transition and laminar regimes with bubble laminar separation that is very difficult to simulate from the numerical point of view. Usually, transition and laminar regimes with bubble laminar separation are ignored. For this reason, this paper deals with laminar and transition flows in order to provide some brightness in this field.

  16. Laminarization model for turbulent eddy transport in highly accelerated nozzle turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Schmidt, J. F.; Boldman, D. R.; Todd, C.

    1972-01-01

    A laminarization model which consists of a completely laminar sublayer region near the wall and a turbulent wake region is developed for the turbulent eddy transport in accelerated turbulent boundary layers. This laminarization model is used in a differential boundary layer calculation which was applied to nozzle flows. The resulting theoretical velocity profiles are in good agreement with the experimental nozzle data in the convergent region.

  17. Experimental and numerical analyses of laminar boundary-layer flow stability over an aircraft fuselage forebody

    NASA Technical Reports Server (NTRS)

    Vijgen, Paul M. H. W.; Holmes, Bruce J.

    1987-01-01

    Fuelled by a need to reduce viscous drag of airframes, significant advances have been made in the last decade to design lifting surface geometries with considerable amounts of laminar flow. In contrast to the present understanding of practical limits for natural laminar flow over lifting surfaces, limited experimental results are available examining applicability of natural laminar flow over axisymmetric and nonaxisymmetric fuselage shapes at relevantly high length Reynolds numbers. The drag benefits attainable by realizing laminar flow over nonlifting aircraft components such as fuselages and nacelles are shown. A flight experiment to investigate transition location and transition mode over the forward fuselage of a light twin engine propeller driven airplane is examined.

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

    NASA Astrophysics Data System (ADS)

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

    2005-04-01

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

  19. Computational fluid dynamics modeling of airflow inside lungs using heterogenous anisotropic lung tissue elastic properties.

    PubMed

    Ilegbusi, Olusegun; Li, Ziang; Min, Yugang; Meeks, Sanford; Kupelian, Patrick; Santhanam, Anand P

    2012-01-01

    The aim of this paper is to model the airflow inside lungs during breathing and its fluid-structure interaction with the lung tissues and the lung tumor using subject-specific elastic properties. The fluid-structure interaction technique simultaneously simulates flow within the airway and anisotropic deformation of the lung lobes. The three-dimensional (3D) lung geometry is reconstructed from the end-expiration 3D CT scan datasets of humans with lung cancer. The lung is modeled as a poro-elastic medium with anisotropic elastic property (non-linear Young's modulus) obtained from inverse lung elastography of 4D CT scans for the same patients. The predicted results include the 3D anisotropic lung deformation along with the airflow pattern inside the lungs. The effect is also presented of anisotropic elasticity on both the spatio-temporal volumetric lung displacement and the regional lung hysteresis. PMID:22356987

  20. Airflow energy harvesters of metal-based PZT thin films by self-excited vibration

    NASA Astrophysics Data System (ADS)

    Suwa, E.; Tsujiura, Y.; Kurokawa, F.; Hida, H.; Kanno, I.

    2014-11-01

    We developed self-excited vibration energy harvesters of Pb(Zr,Ti)O3 (PZT) thin films using airflow. To enhance the self-excited vibration, we used 30-μm-thick stainless steel (SS304) foils as base cantilevers on which PZT thin films were deposited by rf-magnetron sputtering. To compensate for the initial bending of PZT/SS304 unimorph cantilever due to the thermal stress, we deposited counter PZT thin films on the back of the SS304 cantilever. We evaluated power-generation performance and vibration mode of the energy harvester in the airflow. When the angle of attack (AOA) was 20° to 30°, large vibration was generated at wind speeds over 8 m/s. By FFT analysis, we confirmed that stable self-excited vibration was generated. At the AOA of 30°, the output power reached 19 μW at wind speeds of 12 m/s.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    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.

  2. Influence of airflow rate and substrate nature on heterogeneous struvite precipitation.

    PubMed

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

    2009-01-01

    In wastewater treatment plants a hard scale consisting of struvite crystals can be formed, in pipes and recirculation pumps, during anaerobic digestion of wastewater. This study was conducted to evaluate the effect of airflow rate and substrate nature on nucleation type, induction period and supersaturation coefficient during struvite precipitation. A crystallization reactor similar to that designed for calcium carbonate precipitation was used. The pH of synthetic wastewater solution was increased by air bubbling. Experimental results indicated that the airflow increased heterogeneous precipitation of struvite. The susceptibility to scale formation was more important on polyamide and polyvinyl chloride than on stainless steel. In all cases, X-ray diffraction and infrared spectroscopy showed that the precipitated solid phase was solely struvite. No difference in crystal morphology was observed. However, at similar experimental conditions, the particle size of struvite was higher for stainless-steel material than that for plastic materials. PMID:19213469

  3. Study of airflow during respiratory cycle in semi-realistic model of human tracheobronchial tree

    NASA Astrophysics Data System (ADS)

    Elcner, Jakub; Zaremba, M.; Maly, M.; Jedelsky, J.; Lizal, F.; Jicha, M.

    2016-06-01

    This article deals with study of airflow under breathing process, which is characteristic by unsteady behavior. Simulations provided by computational fluid dynamics (CFD) was compared with experiments performed on similar geometry of human upper airways. This geometry was represented by mouth cavity of realistic shape connected to an idealized tracheobronchial tree up to fourth generation of branching. Commercial CFD software Star-CCM+ was used to calculate airflow inside investigated geometry and method of Reynolds averaging of Navier-Stokes equations was used for subscribing the turbulent behavior through model geometry. Conditions corresponding to resting state were considered. Comparisons with experiments were provided on several points through trachea and bronchial tree and results with respect to inspiratory and respiratory part of breathing cycle was discussed.

  4. Methane emissions and airflow patterns along longwall faces and through bleeder ventilation systems

    PubMed Central

    Schatzel, Steven J.; Dougherty, Heather N.

    2015-01-01

    The National Institute for Occupational Safety and Health (NIOSH) conducted an investigation of longwall face and bleeder ventilation systems using tracer gas experiments and computer network ventilation. The condition of gateroad entries, along with the caved material’s permeability and porosity changes as the longwall face advances, determine the resistance of the airflow pathways within the longwall’s worked-out area of the bleeder system. A series of field evaluations were conducted on a four-panel longwall district. Tracer gas was released at the mouth of the longwall section or on the longwall face and sampled at various locations in the gateroads inby the shield line. Measurements of arrival times and concentrations defined airflow/gas movements for the active/completed panels and the bleeder system, providing real field data to delineate these pathways. Results showed a sustained ability of the bleeder system to ventilate the longwall tailgate corner as the panels retreated. PMID:26925166

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

    SciTech Connect

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

    2012-06-15

    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.

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

    NASA Astrophysics Data System (ADS)

    Gendelis, S.; Jakovičs, A.

    2010-01-01

    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.

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

    SciTech Connect

    Cheng, Yong-sheng; Deng, Kangyao; Li, Tao

    2010-02-15

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

  8. 3D airflow dynamics over transverse ridges Mpekweni, South Africa: implications for dune field migration behaviour

    NASA Astrophysics Data System (ADS)

    Jackson, Derek; Cooper, Andrew; Green, Andrew; Beyers, Meiring; Wiles, Errol; Benallack, Keegan

    2016-04-01

    Un-vegetated dune fields provide excellent opportunities to examine airflow dynamics over various types and scales of dune landforms. The three dimensional surface over which lower boundary layers travel, help adjust surface airflow and consequently the aeolian response of the dunes themselves. The use of computational fluid dynamic (CFD) modelling in recent studies now enables investigation of the 3D behaviour of airflow over complex terrain, providing new insights into heterogeneous surface flow and aeolian response of dune surfaces on a large (dunefield) scale. Using a largely un-vegetated coastal dune field site at Mpekweni, Eastern Cape, South Africa, a detailed (0.1m gridded) terrestrial laser scanning survey was conducted to create a high resolution topographical surface. Using local wind flow measurements and local met station records as input, CFD modelling was performed for a number of scenarios involving variable direction and magnitude to examine surface flow patterns across multiple dune forms. Near surface acceleration, expansion and separation of airflow inducing convergence and divergence (steering) of flow velocity streamlines are investigated. Flow acceleration over dune crests/brink lines is a key parameter in driving dune migration and slip face dynamics. Dune aspect ratio (height to length) is also important in determining the degree of crestal flow acceleration, with an increase in flow associated with increasing aspect ratios. Variations in dune height appear to be the most important parameter in driving general flow acceleration. The results from the study provide new insights into dune migration behaviour at this site as well as surface flow behaviour across multiple dune configurations and length scales within un-vegetated dune fields.

  9. Payload bay atmospheric vent airflow testing at the Vibration and Acoustic Test Facility

    NASA Technical Reports Server (NTRS)

    Johnston, James D., Jr.

    1988-01-01

    Several concerns related to venting the Space Shuttle Orbiter payload bay during launch led to laboratory experiments with a flight-type vent box installed in the wall of a subsonic wind tunnel. This report describes the test setups and procedures used to acquire data for characterization of airflow through the vent box and acoustic tones radiated from the vent-box cavity. A flexible boundary-layer spoiler which reduced the vent-tone amplitude is described.

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

    PubMed

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

    2009-09-01

    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

  11. Risk factors for persistent airflow limitation: Analysis of 306 patients with asthma

    PubMed Central

    Wang, Lingcheng; Gao, Shuncui; Zhu, Wei; Su, Jun

    2014-01-01

    Objectives : To determine the risk factors associated with persistent airflow limitation in patients with asthma. Method s: This study was designed and carried out in the department of respiratory medicine, fourth People’s Hospital of Jinan City, Shandong province, China between Jan 2012 and Dec 2012. Three hundred and six asthma patients participating in the study were divided into persistent airflow limitation group (PAFL) and no persistent airflow limitation group (NPAFL). The patients participated in pulmonary function tests and sputum induction examination. The clinical data including age, gender, onset age, disease course, smoking history, family history, regular corticosteroid inhalation, hospitalization history and presence of atopy were collected. Results : In 306 patients, 128 (40.5%) were included in PAFL group and 178(59.5%) in NPAFL group. Multivariate analysis demonstrated smoking (≥10 pack-years; OR, 7.1; 95% CI, 1.8 to 31.2), longer asthma duration (≥ 20years) (OR, 6.3; 95% CI, 1.7 to 28.5), absence of regular corticosteroid inhalation (OR, 3.5; 95% CI, 1.1 to 14.5) and neutrophil in induced sputum≥65% (OR, 1.8; 95% CI, 1.0 to 2.8) were independent risk factors for PAFL. Conclusions : Smoking, longer asthma duration and increased neutrophil in induced sputum are risk factors for PAFL, while regular corticosteroid inhalation is protective factor. Smoking cessation and regular corticosteroid inhalation may play an important role in preventing the occurrence of persistent airflow limitation group (PAFL). PMID:25674145

  12. Air infiltration and interzonal airflow measurements in research houses: Final report

    SciTech Connect

    Nagda, N.L.

    1988-08-01

    Four different but complementary methods--the tracer gas dilution method, single tracer constant concentration, passive perfluorocarbon tracers (constant release), and constant release of multiple halocarbon tracers with real-time analysis--were used to obtain detailed information on air infiltration and interzonal airflow rates in two bilevel research houses. The study included measurements of seasonal variations and differences between the houses, one of which was retrofitted in a previous EPRI study to reduce the air leakage area. Measurements showed that there had been little change in whole house infiltration rates during the 4 years since the retrofit. Differences between the houses with respect to whole house air infiltration rates were primarily the result of differences in downstairs air infiltration rates between the two houses. Zone-specific measurements indicated that downstairs infiltration rates were three to nine times higher than upstairs; infiltration rates were 30 to 60 percent lower in the downstairs of the retrofitted house than in the other house. The impact of the retrofit was also reflected by lower rates of airflow from the garage into the downstairs and from the upstairs to the attic. Airflows between the upstairs and downstairs of the houses exhibited seasonal variation due to stack effect action and operation of the central heating and cooling systems. Short-term interzonal airflow rates were as much as an order of magnitude higher than week-long average rates. Results of measurements with the different methods are also compared and discussed as they relate to advantages, limitations, and applicability of the methods in utility-sponsored measurement programs. 30 refs., 22 figs., 16 tabs.

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

    PubMed

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

    2013-05-01

    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

  14. Quality improvement of melt extruded laminar systems using mixture design.

    PubMed

    Hasa, D; Perissutti, B; Campisi, B; Grassi, M; Grabnar, I; Golob, S; Mian, M; Voinovich, D

    2015-07-30

    This study investigates the application of melt extrusion for the development of an oral retard formulation with a precise drug release over time. Since adjusting the formulation appears to be of the utmost importance in achieving the desired drug release patterns, different formulations of laminar extrudates were prepared according to the principles of Experimental Design, using a design for mixtures to assess the influence of formulation composition on the in vitro drug release from the extrudates after 1h and after 8h. The effect of each component on the two response variables was also studied. Ternary mixtures of theophylline (model drug), monohydrate lactose and microcrystalline wax (as thermoplastic binder) were extruded in a lab scale vertical ram extruder in absence of solvents at a temperature below the melting point of the binder (so that the crystalline state of the drug could be maintained), through a rectangular die to obtain suitable laminar systems. Thanks to the desirability approach and a reliability study for ensuring the quality of the formulation, a very restricted optimal zone was defined within the experimental domain. Among the mixture components, the variation of microcrystalline wax content played the most significant role in overall influence on the in vitro drug release. The formulation theophylline:lactose:wax, 57:14:29 (by weight), selected based on the desirability zone, was subsequently used for in vivo studies. The plasma profile, obtained after oral administration of the laminar extruded system in hard gelatine capsules, revealed the typical trend of an oral retard formulation. The application of the mixture experimental design associated to a desirability function permitted to optimize the extruded system and to determine the composition space that ensures final product quality. PMID:25912827

  15. The coupling of conical wrinkled laminar flames with gravity

    SciTech Connect

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

    1995-10-01

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

  16. Laminar circuit organization and response modulation in mouse visual cortex

    PubMed Central

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

    2012-01-01

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

  17. Laminar flow control leading edge systems in simulated airline service

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

    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.

  18. Laminar free convection from a sphere with blowing and suction

    SciTech Connect

    Huang, Mingjer; Chen, Gahokuang )

    1987-05-01

    The effect of mass transfer on free convection from a vertical plate has been studied by Eichhorn (1960), Sparrow and Cess (1961), Merkin (1972), and Parikh (1974). Recently, Merkin (1975) gave an asymptotic series solution for two-dimensional bodies. Minkowycz and Sparrow (1979) studied a vertical cylinder in a natural convective flow. According to their conclusions, the heat transfer rate increases with suction and decreases with blowing. The present note is concerned with the study of the influence of Prandtl number and surface mass transfer on a steady, laminar, free convective flow over a sphere with nonuniform surface temperature or heat flux.

  19. Air Flow in a Separating Laminar Boundary Layer

    NASA Technical Reports Server (NTRS)

    Schubauer, G B

    1936-01-01

    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.

  20. Transient radiative energy transfer in incompressible laminar flows

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  1. A numerical study of laminar flames propagating in stratified mixtures

    NASA Astrophysics Data System (ADS)

    Zhang, Jiacheng

    Numerical simulations are carried out to study the structure and speed of laminar flames propagating in compositionally and thermally stratified fuel-air mixtures. The study is motivated by the need to understand the physics of flame propagation in stratified-charge engines and model it. The specific question of interest in this work is: how does the structure and speed of the flame in the stratified mixture differ from that of the flame in a corresponding homogeneous mixture at the same equivalence ratio, temperature, and pressure? The studies are carried out in hydrogen-air, methane-air, and n-heptane-air mixtures. A 30-species 184-step skeletal mechanism is employed for methane oxidation, a 9-species 21-step mechanism for hydrogen oxidation, and a 37-species 56-step skeletal mechanism for n-heptane oxidation. Flame speed and structure are compared with corresponding values for homogeneous mixtures. For compositionally stratified mixtures, as shown in prior experimental work, the numerical results suggest that when the flame propagates from a richer mixture to a leaner mixture, the flame speed is faster than the corresponding speed in the homogeneous mixture. This is caused by enhanced diffusion of heat and species from the richer mixture to the leaner mixture. In fact, the effects become more pronounced in leaner mixtures. Not surprisingly, the stratification gradient influences the results with shallower gradients showing less effect. The controlling role that diffusion plays is further assessed and confirmed by studying the effect of a unity Lewis number assumption in the hydrogen/air mixtures. Furthermore, the effect of stratification becomes less important when using methane or n-heptane as fuel. The laminar flame speed in a thermally stratified mixture is similar to the laminar flame speed in homogeneous mixture at corresponding unburned temperature. Theoretical analysis is performed and the ratio of extra thermal diffusion rate to flame heat release rate

  2. Aircraft energy efficiency laminar flow control wing design study

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    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.

  3. Hypothyroid cardiomyopathy complicated by a left ventricular laminar thrombus.

    PubMed

    Van Treeck, Benjamin J; Masoud, Amgad G

    2014-01-01

    Clinical hypothyroidism is the most common hormone deficiency in the United States and is found in 0.3% of the U.S. population. It is associated with characteristic symptoms that can be readily identified by a careful history and physical examination. Hypothyroidism affects many bodily systems; in particular the cardiovascular system is impacted via multiple mechanisms.3 Occasionally hypothyroidism leads to transient left ventricular systolic dysfunction, termed hypothyroid cardiomyopathy. A rare sequela of this condition is a left ventricular thrombus, which has been described in two case reports thus far. Here we report a third case of reversible hypothyroid cardiomyopathy complicated by a left ventricular laminar thrombus. PMID:25438369

  4. Spontaneous pediculolysis with associated contralateral laminar fracture. A case report.

    PubMed

    Dhamija, Bhoresh; Kombogiorgas, Dimitris; Harland, Spencer P

    2011-12-01

    The authors report the case of a 38 year-old female with a rare combination of spontaneous pediculolysis with an associated contralateral laminar fracture of the lumbar spine. Multimodal radiological examinations of the whole lumbar spine are recommended in the case of a symptomatic patient with low back pain who is not responding to basic physiotherapy and pain management modalities. This will provide the unsuspecting clinician a method to diagnose this rare cause of low back pain and avoid unnecessary surgical intervention. PMID:22308635

  5. Linearized analysis for compressible laminar boundary layers by ECVL technique

    NASA Astrophysics Data System (ADS)

    Soong, Chyi-Yeou

    1987-04-01

    The effective convective velocity linearization (ECVL) technique of Soong (1984) is applied to simplify the equations for steady two-dimensional compressible laminar boundary-layer flow of a perfect gas with constant Prandtl number and specific heat. The derivation of the linearized momentum equation is explained, and numerical results for zero-pressure-gradient and pressure-gradient flows are presented graphically and compared with experimental measurements and analytical results obtained with other approaches. The accuracy and simplicity of the ECVL method are demonstrated, and its practical applicability is indicated.

  6. Predicting Transition from Laminar to Turbulent Flow over a Surface

    NASA Technical Reports Server (NTRS)

    Rajnarayan, Dev (Inventor); Sturdza, Peter (Inventor)

    2016-01-01

    A prediction of whether a point on a computer-generated surface is adjacent to laminar or turbulent flow is made using a transition prediction technique. A plurality of instability modes are obtained, each defined by one or more mode parameters. A vector of regressor weights is obtained for the known instability growth rates in a training dataset. For an instability mode in the plurality of instability modes, a covariance vector is determined. A predicted local instability growth rate at the point is determined using the covariance vector and the vector of regressor weights. Based on the predicted local instability growth rate, an n-factor envelope at the point is determined.

  7. Laminar flow heat transfer downstream from U-bends

    NASA Astrophysics Data System (ADS)

    Abdelmessih, Amanie Nassif

    1987-05-01

    The laminar flow heat transfer downstream from the unheated, vertical bends in horizontal U-tubes with electrically heated straight tube sections was investigated. For each test section, local axial and peripheral wall temperatures were measured and the local peripheral heat transfer coefficients at the various locations were calculated. The investigation permitted a better understanding of the interaction of the primary, secondary and tertiary flow patterns, i.e., the combination of forced and natural convection with the centrifugal effects. Also, a correlation was developed, which predicts the heat transfer coefficient downstream from an unheated U-bend, and which can be extended to straight tubes.

  8. Manufacturing tolerances for natural laminar flow airframe surfaces

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  9. Acoustic effects on profile drag of a laminar flow airfoil

    NASA Astrophysics Data System (ADS)

    Shearin, John G.; Jones, Michael G.; Baals, Robert A.

    1987-09-01

    A two-dimensional laminar flow airfoil (NLF-0414) was subjected to high-intensity sound (pure tones and white noise) over a frequency range of 2 to 5 kHz, while immersed in a flow of 240 ft/sec (Rn of 3 million) in a quiet flow facility. Using a wake-rake, wake dynamic pressures were determined and the deficit in momentum was used to calculate a two dimensional drag coefficient. Significant increases in drag were observed when the airfoil was subjected to the high intensity sound at critical sound frequencies. However, the increased drag was not accompanied by movement of the transition location.

  10. Analytical Study of Gravity Effects on Laminar Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2009-10-01

    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.

  12. Comparison of Airflows in Weibel-based and CT-based Human Lung Geometries

    NASA Astrophysics Data System (ADS)

    Lin, Ching-Long; Hoffman, Eric A.

    2004-11-01

    The need for patient specific lung geometry for study of pulmonary air flow and drug delivery has been emphasized recently due to the complexity of individual airway tree geometry. The objective of this paper is to assess the notion of patient specific geometry by comparing airflows in an idealized Weibel-based lung model and two realistic human lung geometries. The Weibel-based model is composed of cylinders of differing diameters for various branching and has been used extensively for modeling airflow in lungs. Here a 4-generation Weibel model is considered. The realistic lung geometries are segmented and reconstructured from computerized tomography (CT) images as part of an effort to build a normative atlas (NIH HL-04368) documenting airway geometry over 4 decades of age in healthy and disease-state adult humans. The custom developed Taylor-Galerkin finite element code, which solves the incompressible Navier-Stokes equations, is applied to simulate airflows in these lung geometries. The velocity wave form recorded from a mechanical ventilator is adopted as the inlet pulsatile boundary condition. At the outlets, both the pressure and outflow boundary conditions are applied and compared. The counter-rotating vortices are observed in the Weibel model during both the inspiratory and expiratory cycles, being consistent with previous studies. The flow structures in the CT-based models are much more complicated and counter-rotating vortices are only evident in some regions.

  13. Influence of room geometry and ventilation rate on airflow and aerosol dispersion: implications for worker protection.

    PubMed

    Whicker, Jeffrey J; Wasiolek, Piotr T; Tavani, Rebecca A

    2002-01-01

    Knowledge of dispersion rates and patterns of radioactive aerosols and gases through workrooms is critical for understanding human exposure and for developing strategies for worker protection. The dispersion within rooms can be influenced by complex interactions between numerous variables, but especially ventilation design and room furnishings. For this study, dependence of airflow and aerosol dispersion on workroom geometry (furnishings) and ventilation rate were studied in an experimental room that was designed to approximate a plutonium laboratory. Three different configurations of simulated gloveboxes and two ventilation rates (approximately 6 and 12 air exchanges per hour) were studied. A sonic anemometer was used to measure airflow parameters including all three components of air velocity vectors and turbulence intensity distributions at multiple locations and heights. Aerosol dispersion rates and patterns were measured by releasing aerosols multiple times from six different locations. Aerosol particle concentrations resolved in time and space were measured using 16 multiplexed laser particle counters. Comparisons were made of air velocities, turbulence, and aerosol transport across different ventilation rates and room configurations. A strong influence of ventilation rate on aerosol dispersion rates and air velocity was found, and changes in room geometry had significant effects on aerosol dispersion rates and patterns. These results are important with regards to constant evaluation of placement of air sampling equipment, benchmarking numerical models of room airflow, and design of ventilation and room layouts with consideration of worker safety. PMID:11768799

  14. Parametric study of the cyclic behaviour of a hygroscopic matrix in a desiccant airflow system

    NASA Astrophysics Data System (ADS)

    Ruivo, C. R.; Costa, J. J.; Figueiredo, A. R.

    2011-09-01

    The study of the transport phenomena in desiccant airflow systems has been addressed in numerous research works, some of them concerning combined processes of cooling, dehumidification and energy recovery. In this paper a detailed numerical model is used to simulate the behaviour of a parallel-plate channel, cyclically exposed to two airflows with different inlet conditions, the plate being composed by a substrate and a desiccant porous layer. The modelled channel is considered to be representative of a real channel of a hygroscopic matrix that is operating at steady state regime, like it occurs in desiccant or enthalpy rotors. The numerical results are treated in order to represent the global behaviour of the hygroscopic rotor under steady state conditions. Results of a parametric study are presented as maps of isovalues of the heat and mass transfer rates and of the outlet states of both airflows, considering channels of distinct wall thickness, of different thickness of the desiccant and the subtract layers, together with wide ranges of the rotation speed and of the wheel partition. The mapped results presented provide an overview of the operation characteristics of hygroscopic rotors, allowing a quick determination of the optimum range of values for relevant parameters, such as the rotation speed and the wheel partition. The model is thus an interesting tool for design and manufacture purposes of enthalpy and desiccant wheels.

  15. Association of incidental emphysema with annual lung function decline and future development of airflow limitation

    PubMed Central

    Koo, Hyeon-Kyoung; Jin, Kwang Nam; Kim, Deog Kyeom; Chung, Hee Soon; Lee, Chang-Hoon

    2016-01-01

    Objectives Emphysema is one of the prognostic factors for rapid lung function decline in patients with COPD, but the impact of incidentally detected emphysema on population without spirometric abnormalities has not been evaluated. This study aimed to determine whether emphysema detected upon computed tomography (CT) screening would accelerate the rate of lung function decline and influence the possibility of future development of airflow limitation in a population without spirometric abnormalities. Materials and methods Subjects who participated in a routine screening for health checkup and follow-up pulmonary function tests for at least 3 years between 2004 and 2010 were retrospectively enrolled. The percentage of low-attenuation area below −950 Hounsfield units (%LAA−950) was calculated automatically. A calculated value of %LAA−950 that exceeded 10% was defined as emphysema. Adjusted annual lung function decline was analyzed using random-slope, random-intercept mixed linear regression models. Results A total of 628 healthy subjects within the normal range of spriometric values were included. Multivariable analysis showed that the emphysema group exhibited a faster decline in forced vital capacity (−33.9 versus −18.8 mL/year; P=0.02). Emphysema was not associated with the development of airflow limitation during follow-up. Conclusion Incidental emphysema quantified using CT scan was significantly associated with a more rapid decline in forced vital capacity in the population with normative spirometric values. However, an association between emphysema and future development of airflow limitation was not observed. PMID:26893550

  16. SMA actuators for vibration control and experimental determination of model parameters dependent on ambient airflow velocity

    NASA Astrophysics Data System (ADS)

    Suzuki, Y.

    2016-05-01

    This article demonstrates the practical applicability of a method of modelling shape memory alloys (SMAs) as actuators. For this study, a pair of SMA wires was installed in an antagonistic manner to form an actuator, and a linear differential equation that describes the behaviour of the actuator’s generated force relative to its input voltage was derived for the limited range below the austenite onset temperature. In this range, hysteresis need not be considered, and the proposed SMA actuator can therefore be practically applied in linear control systems, which is significant because large deformations accompanied by hysteresis do not necessarily occur in most vibration control cases. When specific values of the parameters used in the differential equation were identified experimentally, it became clear that one of the parameters was dependent on ambient airflow velocity. The values of this dependent parameter were obtained using an additional SMA wire as a sensor. In these experiments, while the airflow distribution around the SMA wires was varied by changing the rotational speed of the fans in the wind tunnels, an input voltage was conveyed to the SMA actuator circuit, and the generated force was measured. In this way, the parameter dependent on airflow velocity was estimated in real time, and it was validated that the calculated force was consistent with the measured one.

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

    SciTech Connect

    Feustel, H.E.

    1998-08-01

    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.

  18. Elasto-Aerodynamics-Driven Triboelectric Nanogenerator for Scavenging Air-Flow Energy.

    PubMed

    Wang, Shuhua; Mu, Xiaojing; Wang, Xue; Gu, Alex Yuandong; Wang, Zhong Lin; Yang, Ya

    2015-10-27

    Efficient scavenging the kinetic energy from air-flow represents a promising approach for obtaining clean, sustainable electricity. Here, we report an elasto-aerodynamics-driven triboelectric nanogenerator (TENG) based on contact electrification. The reported TENG consists of a Kapton film with two Cu electrodes at each side, fixed on two ends in an acrylic fluid channel. The relationship between the TENG output power density and its fluid channel dimensions is systematically studied. TENG with a fluid channel size of 125 × 10 × 1.6 mm(3) delivers the maximum output power density of about 9 kW/m(3) under a loading resistance of 2.3 MΩ. Aero-elastic flutter effect explains the air-flow induced vibration of Kapton film well. The output power scales nearly linearly with parallel wiring of multiple TENGs. Connecting 10 TENGs in parallel gives an output power of 25 mW, which allows direct powering of a globe light. The TENG is also utilized to scavenge human breath induced air-flow energy to sustainably power a human body temperature sensor. PMID:26343789

  19. Large-eddy simulation of airflow and heat transfer in a general ward of hospital

    NASA Astrophysics Data System (ADS)

    Hasan, Md. Farhad; Himika, Taasnim Ahmed; Molla, Md. Mamun

    2016-07-01

    In this paper, a very popular alternative computational technique, the Lattice Boltzmann Method (LBM) has been used for Large-Eddy Simulation (LES) of airflow and heat transfer in general ward of hospital. Different Reynolds numbers have been used to study the airflow pattern. In LES, Smagorinsky turbulence model has been considered and a discussion has been conducted in brief. A code validation has been performed comparing the present results with benchmark results for lid-driven cavity problem and the results are found to agree very well. LBM is demonstrated through simulation in forced convection inside hospital ward with six beds with a partition in the middle, which acted like a wall. Changes in average rate of heat transfer in terms of average Nusselt numbers have also been recorded in tabular format and necessary comparison has been showed. It was found that partition narrowed the path for airflow and once the air overcame this barrier, it got free space and turbulence appeared. For higher turbulence, the average rate of heat transfer increased and patients near the turbulence zone released maximum heat and felt more comfortable.

  20. Lung matrix metalloproteinase-9 correlates with cigarette smoking and obstruction of airflow.

    PubMed Central

    Kang, Min Jong; Oh, Yeon-Mok; Lee, Jae Cheol; Kim, Dong Gyu; Park, Myung Jae; Lee, Myung Goo; Hyun, In Gyu; Han, Sung Koo; Shim, Young-Soo; Jung, Ki-Suck

    2003-01-01

    Cigarette smoking is the most important risk factor for obstruction of airflow in chronic obstructive pulmonary disease (COPD). Matrix metalloproteinases (MMPs) or an imbalance between MMPs and their inhibitors, the tissue inhibitors of MMP (TIMPs), is considered to play a role in the pathogenesis of COPD. We investigated whether the MMPs expression or the imbalance between MMPs and TIMP-1 is associated with the amount of cigarette smoking and the FEV1 value, in the lung parenchyma of 26 subjects (6 non-smokers and 20 cigarette smokers). First, we performed zymographic analysis to identify the profile of the MMPs, which revealed gelatinolytic bands mainly equivalent to MMP-9 in the smokers. We then measured, using enzyme immunoassay, the concentrations of MMP-9 and its inhibitor, TIMP-1. Correlation analysis revealed that both the MMP-9 concentrations and the molar ratios of MMP-9 to TIMP-1 (MMP-9/TIMP-1) were correlated with the amount of cigarette smoking. Furthermore, MMP-9 concentrations were inversely correlated with FEV1. In conclusion, this study shows that MMP-9 expression in human lung parenchyma is associated with cigarette smoking and also with the obstruction of airflow, suggesting that MMP-9 may play a role in the pathogenesis of the cigarette smoke-induced obstruction of airflow known as the characteristic of COPD. PMID:14676438

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

    PubMed

    Ciprandi, Giorgio; Cirillo, I

    2010-01-01

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

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

    SciTech Connect

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

    2012-07-15

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

  3. Human-Mediated Dispersal of Seeds by the Airflow of Vehicles

    PubMed Central

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

    2013-01-01

    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

  4. Hybridized electromagnetic-triboelectric nanogenerator for scavenging air-flow energy to sustainably power temperature sensors.

    PubMed

    Wang, Xue; Wang, Shuhua; Yang, Ya; Wang, Zhong Lin

    2015-04-28

    We report a hybridized nanogenerator with dimensions of 6.7 cm × 4.5 cm × 2 cm and a weight of 42.3 g that consists of two triboelectric nanogenerators (TENGs) and two electromagnetic generators (EMGs) for scavenging air-flow energy. Under an air-flow speed of about 18 m/s, the hybridized nanogenerator can deliver largest output powers of 3.5 mW for one TENG (in correspondence of power per unit mass/volume: 8.8 mW/g and 14.6 kW/m(3)) at a loading resistance of 3 MΩ and 1.8 mW for one EMG (in correspondence of power per unit mass/volume: 0.3 mW/g and 0.4 kW/m(3)) at a loading resistance of 2 kΩ, respectively. The hybridized nanogenerator can be utilized to charge a capacitor of 3300 μF to sustainably power four temperature sensors for realizing self-powered temperature sensor networks. Moreover, a wireless temperature sensor driven by a hybridized nanogenerator charged Li-ion battery can work well to send the temperature data to a receiver/computer at a distance of 1.5 m. This work takes a significant step toward air-flow energy harvesting and its potential applications in self-powered wireless sensor networks. PMID:25844537

  5. Human-mediated dispersal of seeds by the airflow of vehicles.

    PubMed

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

    2013-01-01

    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

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

    NASA Astrophysics Data System (ADS)

    Huang, Kuang-Yuh; Huang, Chien-Tai

    2011-01-01

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

  7. Approximate entropy as a measure of the airflow pattern complexity in asthma.

    PubMed

    Veiga, Juliana; Faria, Renan C P; Esteves, Guilherme P; Lopes, Agnaldo J; Jansen, Jose M; Melo, Pedro L

    2010-01-01

    The scientific and clinical value of a measure of complexity is potentially enormous because complexity appears to be lost in the presence of illness. The changes introduced by asthma in respiratory mechanics and control of breathing may result in modifications in the airflow pattern. These changes may be interesting clinically, since they can reduce the ability of the patient to perform daily life activities. In this paper, we examine the effect of elevated airway obstruction on the complexity of the airflow pattern of asthmatic patients using the approximate entropy method (ApEnQ). This study involved 5 healthy and asthmatics with normal spirometric exam (5), mild (5), moderate (6) and severe (5) airway obstruction. A significant (p〈0.002) reduction in ApEnQ was observed in asthmatic patients. This reduction was significantly correlated with spirometric indices of airway obstruction (R=0.60; p〈0.001). These results are in close agreement with pathophysiological fundamentals, and suggest that in asthmatic patients the airflow pattern becomes less complex, which may reduce the adaptability of the respiratory system to perform exercise associated with daily life activities. Furthermore, our findings also suggest that ApEnQ may help the clinical evaluation of asthmatic patients. PMID:21096161

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

    PubMed Central

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

    2009-01-01

    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

  9. Investigation of nanosecond pulsed dielectric barrier discharge using plate-to-plate electrode with asymmetric dielectric arrangement in airflow

    NASA Astrophysics Data System (ADS)

    Qi, Haicheng; Fan, Zhihui; Liu, Yidi; Ren, Chunsheng

    2016-05-01

    Atmospheric pressure dielectric barrier discharge plasma is produced in airflow by applying nanosecond high voltage pulses with peak voltage about 35 kV and rising time about 40 ns on a plate-to-plate electrode arrangement. The effects of airflow rate (0-50 m/s) on the discharge characteristics are investigated under different barrier conditions (the bare anode case and the bare cathode case). For both cases, the breakdown voltage and the time lag increase distinctly and the discharge intensity decreases sharply when the airflow rate increases from 0 to 30 m/s, and then keep almost constant until the airflow rate is further increased to 50 m/s. For the bare anode case (the cathode is covered by dielectric plate), the discharge mode transforms gradually from filamentary to diffuse discharge with the increasing airflow rate. While for the bare cathode case, some micro-discharge channels are still excited, though the discharge becomes more diffuse when the airflow rate is higher than 30 m/s. By acquiring the time-resolved images of the discharge, it is proved that it is the primary discharge which becomes diffuse when airflow is introduced and the following two discharges of the same voltage pulse occur principally at the positions where the primary discharge is more intense. And in both cases, the plasma temperatures are reduced, but the degree is different. All the phenomena can be explained mainly by the variation of the space charge distribution when the airflow is introduced into the discharge gap. And it is indicated that the bare anode case has an advantage in obtaining diffuse discharge.

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

  11. Secondary Airflow Structure around Clustered Shrubs and Its Significance for Vegetated Dune Evolution

    NASA Astrophysics Data System (ADS)

    Luo, Wanyin; Dong, Zhibao; Qian, Guangqiang; Lu, Junfeng

    2016-04-01

    Shrubs have an important significance in aeolian processes due to their disturbance of the local airflow. In the formation of vegetated dunes, there is an iterative interaction between shrub geometry, the structure of the secondary airflow, and the interaction between neighboring shrubs. Understanding the dynamics of vegetated dunes thus requires an insight into the airflow fields around shrubs. Based on aerodynamic and aeolian sand physics theory, this project measured the complex secondary flow field and aeolian sand deposition pattern around single and cluster shrubs with varied densities (i.e., 0.05, 0.08, 0.15, 0.20) and gap ratios (the ratio of the gap spacing between the shrub models to the center-to-center distance for the shrub models, ranged from 1.1 to 1.8 with side-by-side arrangement and 1.2 to 4.3 with tandem arrangement) using the particle image velocimetry system through wind tunnle simulation. The relationship between the secondary airflow structure and the shrub's porosity and arrangement was analyzed quantitatively. Research results revealed that porosity (density) is the key parameter to affect the flow patterns around single shrub. Compared to solid obstacles, bleed flow through the shrubs has great influence on the secondary airflow patterns around itself. Under cluster modes, the distance between two adjacent shrubs has great influence on flow field structures around them. The flow patterns around two side-by-side arranged shrubs can be classified into three kinds of modes, that is: single-bluff-body, biased flow pattern and parallel vortex streets. The flow patterns around two tandem arranged shrubs can be classified into three regimes, that is: the extended body regime, reattachment regime and co-shedding regime. The "shadow zone" with low velocity in the lee of shrubs is the optimal position for sand deposition, but its form, size and orientation would varied with the shrub porosity and gap ratio between them. With the increase of the gap

  12. A computationally efficient modelling of laminar separation bubbles

    NASA Astrophysics Data System (ADS)

    Dini, Paolo; Maughmer, Mark D.

    1989-10-01

    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.

  13. A computationally efficient modelling of laminar separation bubbles

    NASA Technical Reports Server (NTRS)

    Dini, Paolo; Maughmer, Mark D.

    1989-01-01

    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.

  14. Experimental investigation of flow instabilities in a laminar separation bubble

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

  15. On Laminar and Turbulent Free Convection in Thin Spherical Shells

    NASA Astrophysics Data System (ADS)

    Feldman, Yuri; Colonius, Tim

    2012-11-01

    Laminar and turbulent free convection flow inside thin spherical shells with isothermal cold and hot boundaries and internal/external radius ratios in the range of 0.85 <=ri /ro <= 0.95 is numerically investigated. The accuracy of the results has been verified by grid independence analysis and DNS-LES comparisons of the flow characteristics for the typical cases. The functional Nu-Ra dependency is extensively investigated for the range of 103 <= Ra <= 1010 including laminar, transitional and fully turbulent flow regimes. For thin shells, we observe considerable deviations from the existing engineering correlations. The deviations tend to increase for transitional and fully turbulent flows. A new correlation for Nu-Ra dependency is proposed and favorably verified by independently obtained experimental end numerical results. The influence of non-uniform temperature distribution along the shell boundaries on the overall heat flux rate is also discussed. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  16. Model of Transition from Laminar to Turbulent Flow

    NASA Astrophysics Data System (ADS)

    Kanda, Hidesada

    2001-11-01

    For circular pipe flows, a model of transition from laminar to turbulent flow has already been proposed and the minimum critical Reynolds number of approximately 2040 was obtained (Kanda, 1999). In order to prove the validity of the model, another verification is required. Thus, for plane Poiseuille flow, results of previous investigations were studied, focusing on experimental data on the critical Reynolds number Rc, the entrance length, and the transition length. Consequently, concerning the natural transition, it was confirmed from the experimental data that (i) the transition occurs in the entrance region, (ii) Rc increases as the contraction ratio in the inlet section increases, and (iii) the minimum Rc is obtained when the contraction ratio is the smallest or one, and there is no-bellshaped entrance or straight parallel plates. Its value exists in the neighborhood of 1300, based on the channel height and the average velocity. Although, for Hagen-Poiseuille flow, the minimum Rc is approximately 2000, based on the pipe diameter and the average velocity, there seems to be no significant difference in the transition from laminar to turbulent flow between Hagen-Poiseuille flow and plane Poiseuille flow (Kanda, 2001). Rc is determined by the shape of the inlet. Kanda, H., 1999, Proc. of ASME Fluids Engineering Division - 1999, FED-Vol. 250, pp. 197-204. Kanda, H., 2001, Proc. of ASME Fluids Engineering Division - 2001.

  17. Laminar flow control leading edge glove flight test article development

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  18. Characteristics of laminar MHD fluid hammer in pipe

    NASA Astrophysics Data System (ADS)

    Huang, Z. Y.; Liu, Y. J.

    2016-01-01

    As gradually wide applications of MHD fluid, transportation as well as control with pumps and valves is unavoidable, which induces MHD fluid hammer. The paper attempts to combine MHD effect and fluid hammer effect and to investigate the characteristics of laminar MHD fluid hammer. A non-dimensional fluid hammer model, based on Navier-Stocks equations, coupling with Lorentz force is numerically solved in a reservoir-pipe-valve system with uniform external magnetic field. The MHD effect is represented by the interaction number which associates with the conductivity of the MHD fluid as well as the external magnetic field and can be interpreted as the ratio of Lorentz force to Joukowsky force. The transient numerical results of pressure head, average velocity, wall shear stress, velocity profiles and shear stress profiles are provided. The additional MHD effect hinders fluid motion, weakens wave front and homogenizes velocity profiles, contributing to obvious attenuation of oscillation, strengthened line packing and weakened Richardson annular effect. Studying the characteristics of MHD laminar fluid hammer theoretically supplements the gap of knowledge of rapid-transient MHD flow and technically provides beneficial information for MHD pipeline system designers to better devise MHD systems.

  19. Laminar flow of two miscible fluids in a simple network

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    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.

  20. Heat Transfer Effects on Laminar Velocity Profiles in Pipe Flow

    NASA Astrophysics Data System (ADS)

    Powell, Robert; Jenkins, Thomas

    1998-11-01

    Heat Transfer Effects on Laminar Velocity Profiles in Pipe Flow. Robert L. Powell, Thomas P. Jenkins Department of Chemical Engineering & Materials Science University of California, Davis, CA 95616 Using laser Doppler velocimetry, we have measured the axial velocity profiles for steady, pressure driven, laminar flow of water in a circular tube. The flow was established in a one inch diameter seamless glass tube. The entry length prior to the measuring section was over one hundred diameters. Reynolds numbers in the range 500-2000 were used. Under conditions where the temperature difference between the fluid and the surroundings differed by as little as 0.2C, we found significant asymmetries in the velocity profiles. This asymmetry was most pronounced in the vertical plane. Varying the temperature difference moved the velocity maximum either above or below the centerline depending upon whether the fluid was warmer or cooler than the room. These results compare well to existing calculations. Using the available theory and our experiments it is possible to identify parameter ranges where non-ideal conditions(not parabolic velocity profiles) will be found. Supported by the EMSP Program of DOE.

  1. Locally induced laminar convection in liquid nitrogen and silicone oils.

    PubMed

    Dubois, C; Duchesne, A; Vanderheyden, B; Vanderbemden, P; Caps, H

    2016-08-01

    We present an experimental study of a laminar convective phenomenon induced by a centimetric heater totally immersed in a liquid pool (Rayleigh number ranging from 10(4) to 10(7)). This local heating is observed to induce a laminar convection that differs from the classical Rayleigh-Bénard cells created by heating the whole bottom of the fluid: the convection pattern is no more periodic. In order to obtain a complete map of the velocity field, we use Particle Image Velocimetry technique. The vertical velocity between the counter-rotating convective cells is used as the relevant physical parameter to describe the phenomenon. The potential cooling applications of this problem lead us to choose liquid nitrogen as an experimental fluid. We thus compare the results obtained for various temperature gradients in liquid nitrogen with experiments performed at room temperature with silicone oils of various viscosities. The theoretical law for the maximal vertical velocity from classical Rayleigh-Bénard experiments is adapted to the specific geometry investigated by using a new definition for the characteristic wavelength. This length is studied and appears to be dependent on the liquid properties. We finally obtain a remarkable agreement between theory and experimental data. PMID:27562830

  2. Transitional regime and laminar-turbulent coexistence in the asymptotic suction boundary layer

    NASA Astrophysics Data System (ADS)

    Khapko, Taras; Schlatter, Philipp; Duguet, Yohann; Henningson, Dan

    2015-11-01

    We study numerically the asymptotic suction boundary layer (ASBL) in the transitional regime on the verge of laminarization. Starting from a turbulent state the Reynolds number Re is decreased in small steps until the laminar state is established. This study protocol allows not only to investigate the regime at the onset of turbulence, but also to identify the critical Reynolds number Reg ~ 270 , below which turbulence is not sustained. In other planar shear flows the transitional regime at the onset takes the form of stable laminar-turbulent bands, however in ASBL no regime of sustained laminar-turbulent coexistence has been identified. The flow stays fully turbulent even at the lowest Re before laminarization. During the laminarization process streamwise turbulent and laminar avenues are created with no oblique interfaces between the two. This behavior is connected with the existence of a large-scale vertical transport, the feature that distinguishes ASBL from the other wall-bounded shear flows. After an artificial forcing is added canceling all spanwise and wall-normal fluctuations above y+ = 100 , transient oblique bands are observed similar to the ones in other subcritical shear flows, while the flow later laminarizes or becomes fully turbulent again.

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

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

    PubMed

    Heitbrink, William A; Santalla-Elias, Javier

    2009-06-01

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

  5. Oxidative stress in hoof laminar tissue of horses with lethal gastrointestinal diseases.

    PubMed

    Laskoski, Luciane Maria; Dittrich, Rosangela Locatelli; Valadão, Carlos Augusto Araújo; Brum, Juliana Sperotto; Brandão, Yara; Brito, Harald Fernando Vicente; de Sousa, Renato Silva

    2016-03-01

    Tissue damage caused by oxidative stress is involved in the pathogenesis of several diseases in animals and man, and is believed to play a role in the development of laminitis in horses. The aim of this study was to investigate the oxidative stress associated with laminar lesions in horses with lethal gastrointestinal disorders. Laminar tissue samples of the hoof of 30 horses were used. Tissue samples were divided as follows: six healthy horses (control group-CG), and 24 horses that died after complications of gastrointestinal diseases (group suffering from gastrointestinal disorders-GDG). Superoxide dismutase (SOD2) and nitrotyrosine immunostaining and the severity of laminar lesions were evaluated. Presence of laminar lesions and immunostaining for nitrotyrosine and SOD2 were only evident in horses from the GDG group. Thus, oxidative stress may play a role in the pathogenesis of laminar lesions secondary to gastrointestinal disorders. PMID:26964719

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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.

  7. Suppression of Soot Formation and Shapes of Laminar Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    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.

  8. Interactions of bluff-body obstacles with turbulent airflows affecting evaporative fluxes from porous surfaces

    NASA Astrophysics Data System (ADS)

    Haghighi, Erfan; Or, Dani

    2015-11-01

    Bluff-body obstacles interacting with turbulent airflows are common in many natural and engineering applications (from desert pavement and shrubs over natural surfaces to cylindrical elements in compact heat exchangers). Even with obstacles of simple geometry, their interactions within turbulent airflows result in a complex and unsteady flow field that affects surface drag partitioning and transport of scalars from adjacent evaporating surfaces. Observations of spatio-temporal thermal patterns on evaporating porous surfaces adjacent to bluff-body obstacles depict well-defined and persistent zonation of evaporation rates that were used to construct a simple mechanistic model for surface-turbulence interactions. Results from evaporative drying of sand surfaces with isolated cylindrical elements (bluff bodies) subjected to constant turbulent airflows were in good agreement with model predictions for localized exchange rates. Experimental and theoretical results show persistent enhancement of evaporative fluxes from bluff-rough surfaces relative to smooth flat surfaces under similar conditions. The enhancement is attributed to formation of vortices that induce a thinner boundary layer over part of the interacting surface footprint. For a practical range of air velocities (0.5-4.0 m/s), low-aspect ratio cylindrical bluff elements placed on evaporating sand surfaces enhanced evaporative mass losses (relative to a flat surface) by up to 300% for high density of elements and high wind velocity, similar to observations reported in the literature. Concepts from drag partitioning were used to generalize the model and upscale predictions to evaporation from surfaces with multiple obstacles for potential applications to natural bluff-rough surfaces.

  9. Porous silver nanosheets: a novel sensing material for nanoscale and microscale airflow sensors

    NASA Astrophysics Data System (ADS)

    Marzbanrad, Ehsan; Zhao, Boxin; Zhou, Norman Y.

    2015-11-01

    Fabrication of nanoscale and microscale machines and devices is one of the goals of nanotechnology. For this purpose, different materials, methods, and devices should be developed. Among them, various types of miniaturized sensors are required to build the nanoscale and microscale systems. In this research, we introduce a new nanoscale sensing material, silver nanosheets, for applications such as nanoscale and microscale gas flow sensors. The silver nanosheets were synthesized through the reduction of silver ions by ascorbic acid in the presence of poly(methacrylic acid) as a capping agent, followed by the growth of silver in the shape of hexagonal and triangular nanoplates, and self-assembly and nanojoining of these structural blocks. At the end of this process, the synthesized nanosheets were floated on the solution. Then, their electrical and thermal stability was demonstrated at 120 °C, and their atmospheric corrosion resistance was clarified at the same temperature range by thermogravimetric analysis. We employed the silver nanosheets in fabricating airflow sensors by scooping out the nanosheets by means of a sensor substrate, drying them at room temperature, and then annealing them at 300 °C for one hour. The fabricated sensors were tested for their ability to measure airflow in the range of 1 to 5 ml min-1, which resulted in a linear response to the airflow with a response and recovery time around 2 s. Moreover, continuous dynamic testing demonstrated that the response of the sensors was stable and hence the sensors can be used for a long time without detectable drift in their response.

  10. Robust Unidirectional Airflow through Avian Lungs: New Insights from a Piecewise Linear Mathematical Model.

    PubMed

    Harvey, Emily P; Ben-Tal, Alona

    2016-02-01

    Avian lungs are remarkably different from mammalian lungs in that air flows unidirectionally through rigid tubes in which gas exchange occurs. Experimental observations have been able to determine the pattern of gas flow in the respiratory system, but understanding how the flow pattern is generated and determining the factors contributing to the observed dynamics remains elusive. It has been hypothesized that the unidirectional flow is due to aerodynamic valving during inspiration and expiration, resulting from the anatomical structure and the fluid dynamics involved, however, theoretical studies to back up this hypothesis are lacking. We have constructed a novel mathematical model of the airflow in the avian respiratory system that can produce unidirectional flow which is robust to changes in model parameters, breathing frequency and breathing amplitude. The model consists of two piecewise linear ordinary differential equations with lumped parameters and discontinuous, flow-dependent resistances that mimic the experimental observations. Using dynamical systems techniques and numerical analysis, we show that unidirectional flow can be produced by either effective inspiratory or effective expiratory valving, but that both inspiratory and expiratory valving are required to produce the high efficiencies of flows observed in avian lungs. We further show that the efficacy of the inspiratory and expiratory valving depends on airsac compliances and airflow resistances that may not be located in the immediate area of the valving. Our model provides additional novel insights; for example, we show that physiologically realistic resistance values lead to efficiencies that are close to maximum, and that when the relative lumped compliances of the caudal and cranial airsacs vary, it affects the timing of the airflow across the gas exchange area. These and other insights obtained by our study significantly enhance our understanding of the operation of the avian respiratory

  11. Numerical analysis of air-flow and temperature field in a passenger car compartment

    NASA Astrophysics Data System (ADS)

    Kamar, Haslinda Mohamed; Kamsah, Nazri; Mohammad Nor, Ahmad Miski

    2012-06-01

    This paper presents a numerical study on the temperature field inside a passenger's compartment of a Proton Wira saloon car using computational fluid dynamics (CFD) method. The main goal is to investigate the effects of different glazing types applied onto the front and rear windscreens of the car on the distribution of air-temperature inside the passenger compartment in the steady-state conditions. The air-flow condition in the passenger's compartment is also investigated. Fluent CFD software was used to develop a three-dimensional symmetrical model of the passenger's compartment. Simplified representations of the driver and one rear passenger were incorporated into the CFD model of the passenger's compartment. Two types of glazing were considered namely clear insulated laminated tint (CIL) with a shading coefficient of 0.78 and green insulated laminate tint (GIL) with a shading coefficient of 0.5. Results of the CFD analysis were compared with those obtained when the windscreens are made up of clear glass having a shading coefficient of 0.86. Results of the CFD analysis show that for a given glazing material, the temperature of the air around the driver is slightly lower than the air around the rear passenger. Also, the use of GIL glazing material on both the front and rear windscreens significantly reduces the air temperature inside the passenger's compartment of the car. This contributes to a better thermal comfort condition to the occupants. Swirling air flow condition occurs in the passenger compartment. The air-flow intensity and velocity are higher along the side wall of the passenger's compartment compared to that along the middle section of the compartment. It was also found that the use of glazing materials on both the front and rear windscreen has no significant effects on the air-flow condition inside the passenger's compartment of the car.

  12. Voluntary Cough Airflow Differentiates Safe Versus Unsafe Swallowing in Amyotrophic Lateral Sclerosis.

    PubMed

    Plowman, Emily K; Watts, Stephanie A; Robison, Raele; Tabor, Lauren; Dion, Charles; Gaziano, Joy; Vu, Tuan; Gooch, Clifton

    2016-06-01

    Dysphagia and aspiration are prevalent in amyotrophic lateral sclerosis (ALS) and contribute to malnutrition, aspiration pneumonia, and death. Early detection of at risk individuals is critical to ensure maintenance of safe oral intake and optimal pulmonary function. We therefore aimed to determine the discriminant ability of voluntary cough airflow measures in detecting penetration/aspiration status in ALS patients. Seventy individuals with ALS (El-Escorial criteria) completed voluntary cough spirometry testing and underwent a standardized videofluoroscopic swallowing evaluation (VFSE). A rater blinded to aspiration status derived six objective measures of voluntary cough airflow and evaluated airway safety using the penetration-aspiration scale (PAS). A between groups ANOVA (safe vs. unsafe swallowers) was conducted and sensitivity, specificity, area under the curve (AUC) and likelihood ratios were calculated. VFSE analysis revealed 24 penetrator/aspirators (PAS ≥3) and 46 non-penetrator/aspirators (PAS ≤2). Cough volume acceleration (CVA), peak expiratory flow rise time (PEFRT), and peak expiratory flow rate (PEFR) were significantly different between airway safety groups (p < 0.05) and demonstrated significant discriminant ability to detect the presence of penetration/aspiration with AUC values of: 0.85, 0.81, and 0.78, respectively. CVA <45.28 L/s/s, PEFR <3.97 L/s, and PEFRT >76 ms had sensitivities of 91.3, 82.6, and 73.9 %, respectively, and specificities of 82.2, 73.9, and 78.3 % for identifying ALS penetrator/aspirators. Voluntary cough airflow measures identified ALS patients at risk for penetration/aspiration and may be a valuable screening tool with high clinical utility. PMID:26803772

  13. Respiratory kinematic and airflow differences between reflex and voluntary cough in healthy young adults

    PubMed Central

    Brandimore, Alexandra E.; Troche, Michelle S.; Huber, Jessica E.; Hegland, Karen W.

    2015-01-01

    Background: Cough is a defensive behavior that can be initiated in response to a stimulus in the airway (reflexively), or on command (voluntarily). There is evidence to suggest that physiological differences exist between reflex and voluntary cough; however, the output (mechanistic and airflow) differences between the cough types are not fully understood. Therefore, the aims of this study were to determine the lung volume, respiratory kinematic, and airflow differences between reflex and voluntary cough in healthy young adults. Methods: Twenty-five participants (14 female; 18–29 years) were recruited for this study. Participants were evaluated using respiratory inductance plethysmography calibrated with spirometry. Experimental procedures included: (1) respiratory calibration, (2) three voluntary sequential cough trials, and (3) three reflex cough trials induced with 200 μM capsaicin. Results: Lung volume initiation (LVI; p = 0.003) and lung volume excursion (LVE; p < 0.001) were significantly greater for voluntary cough compared to reflex cough. The rib cage and abdomen significantly influenced LVI for voluntary cough (p < 0.001); however, only the rib cage significantly impacted LVI for reflex cough (p < 0.001). LVI significantly influenced peak expiratory flow rate (PEFR) for voluntary cough (p = 0.029), but not reflex cough (p = 0.610). Discussion: Production of a reflex cough results in significant mechanistic and airflow differences compared to voluntary cough. These findings suggest that detection of a tussigenic stimulus modifies motor aspects of the reflex cough behavior. Further understanding of the differences between reflex and voluntary cough in older adults and in persons with dystussia (cough dysfunction) will be essential to facilitate the development of successful cough treatment paradigms. PMID:26500560

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

    SciTech Connect

    Romero, M.I.; Brenner, R.J.

    1998-12-31

    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.

  15. Robust Unidirectional Airflow through Avian Lungs: New Insights from a Piecewise Linear Mathematical Model

    PubMed Central

    Harvey, Emily P.; Ben-Tal, Alona

    2016-01-01

    Avian lungs are remarkably different from mammalian lungs in that air flows unidirectionally through rigid tubes in which gas exchange occurs. Experimental observations have been able to determine the pattern of gas flow in the respiratory system, but understanding how the flow pattern is generated and determining the factors contributing to the observed dynamics remains elusive. It has been hypothesized that the unidirectional flow is due to aerodynamic valving during inspiration and expiration, resulting from the anatomical structure and the fluid dynamics involved, however, theoretical studies to back up this hypothesis are lacking. We have constructed a novel mathematical model of the airflow in the avian respiratory system that can produce unidirectional flow which is robust to changes in model parameters, breathing frequency and breathing amplitude. The model consists of two piecewise linear ordinary differential equations with lumped parameters and discontinuous, flow-dependent resistances that mimic the experimental observations. Using dynamical systems techniques and numerical analysis, we show that unidirectional flow can be produced by either effective inspiratory or effective expiratory valving, but that both inspiratory and expiratory valving are required to produce the high efficiencies of flows observed in avian lungs. We further show that the efficacy of the inspiratory and expiratory valving depends on airsac compliances and airflow resistances that may not be located in the immediate area of the valving. Our model provides additional novel insights; for example, we show that physiologically realistic resistance values lead to efficiencies that are close to maximum, and that when the relative lumped compliances of the caudal and cranial airsacs vary, it affects the timing of the airflow across the gas exchange area. These and other insights obtained by our study significantly enhance our understanding of the operation of the avian respiratory

  16. Porous silver nanosheets: a novel sensing material for nanoscale and microscale airflow sensors.

    PubMed

    Marzbanrad, Ehsan; Zhao, Boxin; Zhou, Norman Y

    2015-11-01

    Fabrication of nanoscale and microscale machines and devices is one of the goals of nanotechnology. For this purpose, different materials, methods, and devices should be developed. Among them, various types of miniaturized sensors are required to build the nanoscale and microscale systems. In this research, we introduce a new nanoscale sensing material, silver nanosheets, for applications such as nanoscale and microscale gas flow sensors. The silver nanosheets were synthesized through the reduction of silver ions by ascorbic acid in the presence of poly(methacrylic acid) as a capping agent, followed by the growth of silver in the shape of hexagonal and triangular nanoplates, and self-assembly and nanojoining of these structural blocks. At the end of this process, the synthesized nanosheets were floated on the solution. Then, their electrical and thermal stability was demonstrated at 120 °C, and their atmospheric corrosion resistance was clarified at the same temperature range by thermogravimetric analysis. We employed the silver nanosheets in fabricating airflow sensors by scooping out the nanosheets by means of a sensor substrate, drying them at room temperature, and then annealing them at 300 °C for one hour. The fabricated sensors were tested for their ability to measure airflow in the range of 1 to 5 ml min(-1), which resulted in a linear response to the airflow with a response and recovery time around 2 s. Moreover, continuous dynamic testing demonstrated that the response of the sensors was stable and hence the sensors can be used for a long time without detectable drift in their response. PMID:26451714

  17. A computationally efficient modelling of laminar separation bubbles

    NASA Technical Reports Server (NTRS)

    Maughmer, Mark D.

    1988-01-01

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

  18. A computationally efficient modelling of laminar separation bubbles

    NASA Astrophysics Data System (ADS)

    Dini, Paolo; Maughmer, Mark D.

    1989-02-01

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

  19. A computationally efficient modelling of laminar separation bubbles

    NASA Astrophysics Data System (ADS)

    Maughmer, Mark D.

    1988-02-01

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

  20. A computationally efficient modelling of laminar separation bubbles

    NASA Technical Reports Server (NTRS)

    Dini, Paolo; Maughmer, Mark D.

    1989-01-01

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

  1. Metal-metal laminar composites for high-temperature applications.

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    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 vol % of each phase made from 0.0025 cm, 0.0125 cm, or 0.050 cm laminae, were tested in tension and stress rupture at temperatures of 871 and 1093 C and in impact at 23 and 524 C. A tension and a short-time stress-rupture test was conducted on specimens of 77 vol % W-Re-Hf-C/23 vol % Inconel Alloy 600 at 1093 C.

  2. Metal-metal laminar composites for high temperature applications

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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).

  3. Control of laminar separation over airfoils by acoustic excitation

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.; Mckinzie, D. J.

    1988-01-01

    The effect of acoustic excitation in reducing laminar separation over two-dimensional airfoils at low angles of attack is investigated experimentally. Airfoils of two different cross sections, each with two different chord lengths, are studied in the chord Reynolds number range of 25,000 is less than R sub c is less than 100,000. While keeping the amplitude of the excitation induced velocity perturbation a constant, it is found that the most effective frequency scales as U (sup 3/2)(sub infinity). The parameter St/R (sup 1/2)(sub c), corresponding to the most effective f sub p for all the cases studied, falls in the range of 0.02 to 0.03, St being the Strouhal number based on the chord.

  4. Stability theory applications to laminar-flow control

    NASA Technical Reports Server (NTRS)

    Malik, Mujeeb R.

    1987-01-01

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

  5. Oscillating laminar electrokinetic flow in infinitely extended rectangular microchannels.

    PubMed

    Yang, J; Bhattacharyya, A; Masliyah, J H; Kwok, D Y

    2003-05-01

    This paper has addressed analytically the problem of laminar flow in microchannels with rectangular cross-section subjected to a time-dependent sinusoidal pressure gradient and a sinusoidal electric field. The analytical solution has been determined based on the Debye-Hückel approximation of a low surface potential at the channel wall. We have demonstrated that Onsager's principle of reciprocity is valid for this problem. Parametric studies of streaming potential have shown the dependence of the electroviscous effect not only on the Debye length, but also on the oscillation frequency and the microchannel width. Parametric studies of electroosmosis demonstrate that the flow rate decreases due to an increase in frequency. The obtained solutions for both the streaming potential and electroosmotic flows become those for flow between two parallel plates in the limit of a large aspect ratio. PMID:12725820

  6. Enhanced photocatalysis in a pilot laminar falling film slurry reactor

    SciTech Connect

    Puma, G.L.; Yue, P.L.

    1999-09-01

    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.

  7. On the Oscillation of Combustion of a Laminar Spray

    NASA Technical Reports Server (NTRS)

    Levy, Yeshayahou; Bulzan, Daniel L.

    1995-01-01

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

  8. Numerical Solutions of Supersonic and Hypersonic Laminar Compression Corner Flows

    NASA Technical Reports Server (NTRS)

    Hung, C. M.; MacCormack, R. W.

    1976-01-01

    An efficient time-splitting, second-order accurate, numerical scheme is used to solve the complete Navier-Stokes equations for supersonic and hypersonic laminar flow over a two-dimensional compression corner. A fine, exponentially stretched mesh spacing is used in the region near the wall for resolving the viscous layer. Good agreement is obtained between the present computed results and experimental measurement for a Mach number of 14.1 and a Reynolds number of 1.04 x 10(exp 5) with wedge angles of 15 deg, 18 deg, and 24 deg. The details of the pressure variation across the boundary layer are given, and a correlation between the leading edge shock and the peaks in surface pressure and heat transfer is observed.

  9. Predicting Transition from Laminar to Turbulent Flow over a Surface

    NASA Technical Reports Server (NTRS)

    Rajnarayan, Dev (Inventor); Sturdza, Peter (Inventor)

    2013-01-01

    A prediction of whether a point on a computer-generated surface is adjacent to laminar or turbulent flow is made using a transition prediction technique. A plurality of boundary-layer properties at the point are obtained from a steady-state solution of a fluid flow in a region adjacent to the point. A plurality of instability modes are obtained, each defined by one or more mode parameters. A vector of regressor weights is obtained for the known instability growth rates in a training dataset. For each instability mode in the plurality of instability modes, a covariance vector is determined, which is the covariance of a predicted local growth rate with the known instability growth rates. Each covariance vector is used with the vector of regressor weights to determine a predicted local growth rate at the point. Based on the predicted local growth rates, an n-factor envelope at the point is determined.

  10. A theoretical study of a laminar diffusion flame

    NASA Technical Reports Server (NTRS)

    Frair, K. L.

    1978-01-01

    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.

  11. The numerical calculation of laminar boundary-layer separation

    NASA Technical Reports Server (NTRS)

    Klineberg, J. M.; Steger, J. L.

    1974-01-01

    Iterative finite-difference techniques are developed for integrating the boundary-layer equations, without approximation, through a region of reversed flow. The numerical procedures are used to calculate incompressible laminar separated flows and to investigate the conditions for regular behavior at the point of separation. Regular flows are shown to be characterized by an integrable saddle-type singularity that makes it difficult to obtain numerical solutions which pass continuously into the separated region. The singularity is removed and continuous solutions ensured by specifying the wall shear distribution and computing the pressure gradient as part of the solution. Calculated results are presented for several separated flows and the accuracy of the method is verified. A computer program listing and complete solution case are included.

  12. GASP cloud encounter statistics - Implications for laminar flow control flight

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    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.

  13. Laminar batteries and methods of making the same

    SciTech Connect

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

    1987-05-12

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

  14. Laminar batteries and methods of making the same

    SciTech Connect

    Plasse, P. A.

    1985-09-03

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

  15. Laminar batteries and methods of making the same

    SciTech Connect

    Plasse, P.A.

    1986-09-02

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

  16. High-flaps for natural laminar flow airfoils

    NASA Technical Reports Server (NTRS)

    Morgan, Harry L.

    1986-01-01

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

  17. Numerical simulation of laminar hypersonic flows about an ellipsoid

    NASA Astrophysics Data System (ADS)

    Riedelbauch, S.; Mueller, B.

    The laminar hypersonic flow about a double ellipsoid, which idealizes the nose and cockpit of a spacecraft, were numerically simulated. The calculation method solves the three dimensional thin layer Navier-Stokes equations in a conservative formulation on a surface oriented calculation grid using an implicit/explicit finite difference technique. The conservative formulation allows the correct calculation of embedded compression shocks, while the head wave was treated with a shock-fitting procedure. The calculated flow fields about the ellipsoid show shock-shock and shock-boundary layer interactions in connection with separated flow. Wall flow lines and heat transfer agree qualitatively very well with film-of-oil and thermographic pictures.

  18. Heat Transfer to Longitudinal Laminar Flow Between Cylinders

    NASA Technical Reports Server (NTRS)

    Sparrow, Ephraim M.; Loeffler, Albert L. Jr.; Hubbard, H. A.

    1960-01-01

    Consideration is given to the fully developed heat transfer characteristics for longitudinal laminar flow between cylinders arranged in an equilateral triangular array. The analysis is carried out for the condition of uniform heat transfer per unit length. Solutions are obtained for the temperature distribution, and from these, Nusselt numbers are derived for a wide range of spacing-to-diameter ratios. It is found that as the spacing ratio increases, so also does the wall-to-bulk temperature difference for a fixed heat transfer per unit length. Corresponding to a uniform surface temperature around the circumference of a cylinder, the circumferential variation of the local heat flux is computed. For spacing ratios of 1.5 - 2.0 and greater, uniform peripheral wall temperature and uniform peripheral heat flux are simultaneously achieved. A simplified analysis which neglects circumferential variations is also carried out, and the results are compared with those from the more exact formulation.

  19. The simulation of coherent structures in a laminar boundary layer

    NASA Technical Reports Server (NTRS)

    Breuer, Kenny; Landahl, Marten T.; Spalart, Philippe R.

    1987-01-01

    Coherent structures in turbulent shear flows were studied extensively by several techniques, including the VITA technique which selects rapidly accelerating or decelerating regions in the flow. The evolution of a localized disturbance in a laminar boundary layer shows strong similarity to the evolution of coherent structures in a turbulent-wall bounded flow. Starting from a liftup-sweep motion, a strong shear layer develops which shares many of the features seen in conditionally-sampled turbulent velocity fields. The structure of the shear layer, Reynolds stress distribution, and wall pressure footprint are qualitatively the same, indicating that the dynamics responsible for the structure's evolution are simple mechanisms dependent only on the presence of a high mean shear and a wall and independent of the effects of local random fluctuations and outer flow effects. As the disturbance progressed, the development of streak-like-high- and low-speed regions associated with the three-dimensionality.

  20. Heat transport in laminar flow of erythrocyte suspensions.

    PubMed

    Ahuja, A S

    1975-07-01

    Measurements of thermal conductivity were made in laminar flow of dog and turkey erythrocyte suspensions in a stainless stell tube of about 1 mm ID. These measurements were independent of the shear rate, showing that the red cell motion relative to plasma in flowing blood had no effect on the heat transfer. Measurements of thermal conductivity were further made in suspensions of polystyrene spheres of 100 mum and were found to be dependent upon the shear rate. The Graetz solution corresponding to uniform wall temperature was used for determining the value of thermal conductivity in an apparatus calibrated with tap water. The overall accuracy of the results is within 10%. A model based on the particle rotation with the entrained fluid is proposed. It is pointed out that the diffusion of platelets, red cells, and possibly plasma proteins (such as fibrinogen) will be augmented if they happen to be in the hydrodynamic field of rotating erythrocytes. PMID:1150598

  1. Computational wing design studies relating to natural laminar flow

    NASA Technical Reports Server (NTRS)

    Waggoner, Edgar G.

    1986-01-01

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

  2. Postfragmentation density function for bacterial aggregates in laminar flow

    NASA Astrophysics Data System (ADS)

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

    2011-04-01

    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.

  3. Turbulence and Laminar Structures: Can They Co-Exist?

    NASA Technical Reports Server (NTRS)

    Canuto, V. M.

    2000-01-01

    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).

  4. Periodic and Chaotic Modes in Premixed Laminar Flames

    NASA Astrophysics Data System (ADS)

    El-Hamdi, Mohamed Abbes

    1991-06-01

    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.

  5. Laminar separation control effects of shortfin mako shark skin

    NASA Astrophysics Data System (ADS)

    Bradshaw, Michael Thomas

    Shark skin is investigated as a means of laminar flow separation control due to its preferential flow direction as well as the potential for scales to erect and obstruct low-momentum backflow resulting from an adverse pressure gradient acting on the boundary layer. In this study, the effect of the scales on flow reversal is observed in laminar flow conditions. This is achieved by comparing the flow over a pectoral fin from a shortfin mako shark to that over the same fin that is painted to neutralize the effect of the scales on the flow. The effect of the scales on flow reversal is also observed by comparing the flow over a smooth PVC cylinder to that over the same cylinder with samples of mako shark skin affixed to the entire circumference of the cylinder. These samples were taken from the flank region of the shark because the scales at this location have been shown to have the greatest angle of erection compared to the scales on the rest of the shark's body. Scales at this location have an average crown length of 220 microm with a maximum bristling angle of proximately 50 degrees. Because these scales have the highest bristling angle, they have the best potential for separation control. All data was taken using time-resolved Digital Particle Image Velocimetry. The flow over the pectoral fin was analyzed at multiple angles of attack. It was found that the shark skin had the effect of decreasing the size of the separated region over both the pectoral fin and the cylinder as well as decreasing the magnitudes of the reversing flow found in these regions. For all Reynolds numbers tested, drag reduction over 28% was found when applying the sharkskin to the cylinder.

  6. Numerical Prediction of Laminar Instability Noise for NACA 0012 Aerofoil

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

  7. Impinging laminar jets at moderate Reynolds numbers and separation distances.

    PubMed

    Bergthorson, Jeffrey M; Sone, Kazuo; Mattner, Trent W; Dimotakis, Paul E; Goodwin, David G; Meiron, Dan I

    2005-12-01

    An experimental and numerical study of impinging, incompressible, axisymmetric, laminar jets is described, where the jet axis of symmetry is aligned normal to the wall. Particle streak velocimetry (PSV) is used to measure axial velocities along the centerline of the flow field. The jet-nozzle pressure drop is measured simultaneously and determines the Bernoulli velocity. The flow field is simulated numerically by an axisymmetric Navier-Stokes spectral-element code, an axisymmetric potential-flow model, and an axisymmetric one-dimensional stream-function approximation. The axisymmetric viscous and potential-flow simulations include the nozzle in the solution domain, allowing nozzle-wall proximity effects to be investigated. Scaling the centerline axial velocity by the Bernoulli velocity collapses the experimental velocity profiles onto a single curve that is independent of the nozzle-to-plate separation distance. Axisymmetric direct numerical simulations yield good agreement with experiment and confirm the velocity profile scaling. Potential-flow simulations reproduce the collapse of the data; however, viscous effects result in disagreement with experiment. Axisymmetric one-dimensional stream-function simulations can predict the flow in the stagnation region if the boundary conditions are correctly specified. The scaled axial velocity profiles are well characterized by an error function with one Reynolds-number-dependent parameter. Rescaling the wall-normal distance by the boundary-layer displacement-thickness-corrected diameter yields a collapse of the data onto a single curve that is independent of the Reynolds number. These scalings allow the specification of an analytical expression for the velocity profile of an impinging laminar jet over the Reynolds number range investigated of . PMID:16486059

  8. Flight Tests of a Supersonic Natural Laminar Flow Airfoil

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

    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

  9. Note: Background Oriented Schlieren as a diagnostics for airflow control by plasma actuators.

    PubMed

    Biganzoli, I; Capone, C; Barni, R; Riccardi, C

    2015-02-01

    Background Oriented Schlieren (BOS) is an optical technique sensitive to the first spatial derivative of the refractive index inside a light-transmitting medium. Compared to other Schlieren-like techniques, BOS is more versatile and allows to capture bi-dimensional gradients rather than just one spatial component. We propose to adopt BOS for studying the capabilities of surface dielectric barrier discharges to work like plasma actuators in flow control applications. The characteristics of the BOS we implemented at this purpose are discussed, together with few results concerning the ionic wind produced by the discharge in absence of an external airflow. PMID:25725896

  10. Relation of pulmonary vessel size to transfer factor in subjects with airflow obstruction

    SciTech Connect

    Musk, A.W.

    1983-11-01

    In a group of 61 consecutive patients undergoing assessment of airflow obstruction, a significant linear relation was demonstrated between measurements of the diameter of the midzonal pulmonary vessels on the plain chest radiographs and transfer factor (diffusing capacity for carbon monoxide) (r = 0.46, p < 0.001). Since reduction in transfer factor has been shown to relate to structural emphysema, reduction in midzone vessel caliber implies the same. However, in the individual patient neither the transfer factor nor structural emphysema can be reliably predicted from midzone vessel diameters alone.

  11. Respiratory phase resetting and airflow changes induced by swallowing in humans.

    PubMed Central

    Paydarfar, D; Gilbert, R J; Poppel, C S; Nassab, P F

    1995-01-01

    1. Relationships between the timing of respiration and deglutition were studied in thirty awake healthy subjects at rest. Deglutition was monitored by submental electromyography, pharyngeal manometry and videofluoroscopy. Respiration was recorded by measurement of oronasal airflow and chest wall movement. Three types of deglutition were studied: injected bolus swallows, spontaneous swallows, and visually cued swallows of boluses previously placed in the mouth. 2. The effect of each swallow on respiratory rhythm was characterized by measurement of cophase, defined as the interval between the onset of deglutitive submental EMG activity to the onset of subsequent rescheduled inspirations. Cophase was determined for swallows initiated at different phases of the respiratory cycle. In all subjects deglutition caused phase resetting of respiratory rhythm. Cophase was largest for swallows initiated near the the inspiratory-expiratory (E-I) transition and smallest for swallows initiated near the expiratory-inspiratory (E-I) transition. The pattern of respiratory resetting by deglutition was topologically classified as type 0. This pattern was shown for swallows induced by bolus injection or visual cue, and for spontaneous swallows. 3. The incidence of spontaneous deglutition was influenced by the position of the swallow in the respiratory cycle. Few spontaneous swallows were initiated near the E-I transition whereas most occurred from late inspiration to mid-expiration. 4. Deglutition caused an abrupt decrease in airflow leading to an interval of apnoea, followed by a period of expiration. The duration of deglutition apnoea for spontaneous swallows was shorter than that for 5 ml bolus swallows, and was unaffected by the respiratory phase of swallow initiation. The period of expiration after swallowing was longest for swallows initiated at the I-E transition, and shortest for E-I swallows. 5. The intervals between bolus injection and the onset of deglutition apnoea, and the

  12. Pulmonary function impairment in patients with combined pulmonary fibrosis and emphysema with and without airflow obstruction

    PubMed Central

    Kitaguchi, Yoshiaki; Fujimoto, Keisaku; Hanaoka, Masayuki; Honda, Takayuki; Hotta, Junichi; Hirayama, Jiro

    2014-01-01

    Background The syndrome of combined pulmonary fibrosis and emphysema (CPFE) is a recently described entity associating upper-lobe emphysema and lower-lobe fibrosis. We sought to evaluate differences in pulmonary function between CPFE patients with and without airflow obstruction. Subjects and methods Thirty-one CPFE patients were divided into two groups according to the presence or absence of irreversible airflow obstruction based on spirometry (forced expiratory volume in 1 second/forced vital capacity <70% following inhalation of a β2-agonist) as follows: CPFE patients with airflow obstruction (CPFE OB+ group, n=11), and CPFE patients without airflow obstruction (CPFE OB− group, n=20). Pulmonary function, including respiratory impedance evaluated using impulse oscillometry and dynamic hyperinflation following metronome-paced incremental hyperventilation, was retrospectively analyzed in comparison with that observed in 49 chronic obstructive pulmonary disease (COPD) patients (n=49). Results In imaging findings, low-attenuation-area scores on chest high-resolution computed tomography, representing the degree of emphysema, were significantly lower in the CPFE OB− group than in the CPFE OB+ and COPD groups. In contrast, the severity of pulmonary fibrosis was greater in the CPFE OB− group than in the CPFE OB+ group. In pulmonary function, lung hyperinflation was not apparent in the CPFE OB− group. Impairment of diffusion capacity was severe in both the CPFE OB− and CPFE OB+ groups. Impulse oscillometry showed that respiratory resistance was not apparent in the CPFE OB− group compared with the COPD group, and that easy collapsibility of small airways during expiration of tidal breath was not apparent in the CPFE OB+ group compared with the COPD group. Dynamic hyperinflation following metronome-paced incremental hyperventilation was significantly greater in the COPD group than in the CPFE OB− group, and also tended to be greater in the CPFE OB+ group than

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

    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.

  15. Fine-scale flight strategies of gulls in urban airflows indicate risk and reward in city living.

    PubMed

    Shepard, Emily L C; Williamson, Cara; Windsor, Shane P

    2016-09-26

    Birds modulate their flight paths in relation to regional and global airflows in order to reduce their travel costs. Birds should also respond to fine-scale airflows, although the incidence and value of this remains largely unknown. We resolved the three-dimensional trajectories of gulls flying along a built-up coastline, and used computational fluid dynamic models to examine how gulls reacted to airflows around buildings. Birds systematically altered their flight trajectories with wind conditions to exploit updraughts over features as small as a row of low-rise buildings. This provides the first evidence that human activities can change patterns of space-use in flying birds by altering the profitability of the airscape. At finer scales still, gulls varied their position to select a narrow range of updraught values, rather than exploiting the strongest updraughts available, and their precise positions were consistent with a strategy to increase their velocity control in gusty conditions. Ultimately, strategies such as these could help unmanned aerial vehicles negotiate complex airflows. Overall, airflows around fine-scale features have profound implications for flight control and energy use, and consideration of this could lead to a paradigm-shift in the way ecologists view the urban environment.This article is part of the themed issue 'Moving in a moving medium: new perspectives on flight'. PMID:27528784

  16. Hybrid laminar flow control tests in the Boeing Research Wind Tunnel

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

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

  18. Aircraft energy efficiency laminar flow control glove flight conceptual design study

    NASA Technical Reports Server (NTRS)

    Wright, A. S.

    1979-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    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.

  20. An investigation of transitional Phenomena from Laminar to Turbulent Natural Convection using Compressible Direct Numerical Simulation

    NASA Astrophysics Data System (ADS)

    Li, Chunggang; Tsubokura, Makoto; Complex Phenomena Unified Simulation Research Team

    2014-11-01

    The complete transition from laminar to turbulent natural convection in a long channel is investigated using compressible direct numerical simulation (DNS). Numerical methods of Roe scheme with precontioning and dual time stepping are used for addressing the flow field which is low speed but the density is variable. During the transient development, there are four stages which are laminar, unstable process, relaminarization and turbulence can be obviously identified. After reaching the quasi steady state, the laminar, transition and turbulence simultaneously coexist in the same flow field. Additionally, the comparisons of the statistics with the experimental data are also well consistent.

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

    NASA Technical Reports Server (NTRS)

    Carmichael, B. H.

    1979-01-01

    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.

  2. Calculation of laminar and turbulent boundary layers for two-dimensional time-dependent flows

    NASA Technical Reports Server (NTRS)

    Cebeci, T.

    1977-01-01

    A general method for computing laminar and turbulent boundary layers for two-dimensional time-dependent flows is presented. The method uses an eddy-viscosity formulation to model the Reynolds shear-stress term and a very efficient numerical method to solve the governing equations. The model was applied to steady two-dimensional and three-dimensional flows and was shown to give good results. A discussion of the numerical method and the results obtained by the present method for both laminar and turbulent flows are discussed. Based on these results, the method is efficient and suitable for solving time-dependent laminar and turbulent boundary layers.

  3. A Study of Laminar Separation Bubble in the Concave Region of an Airfoil Using Laser Velocimetry

    NASA Technical Reports Server (NTRS)

    Mangalam, Sivaramakrishnan; Meyers, James F.; Dagenhart, John R.; Harvey, William D.

    1985-01-01

    Laser velocimetry (LV) was used to study the nature of laminar separation bubbles in the concave region of a 1.83-meter airfoil model which was tested in the NASA Langley Low Turbulence Pressure Tunnel. Three component, coincident data from LV measurements including histograms of particle velocity, mean velocity profiles, turbulence intensity, and Reynolds stresses within the shear layer were used to determine the locations of laminar separation, transition, and turbulent reattachment. Boundary-layer parameters determined from velocity profiles were used to compare the results with existing empirical relations for describing the laminar separation bubble.

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

    NASA Astrophysics Data System (ADS)

    Haghighi, Erfan; Or, Dani

    2014-05-01

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

  5. A Numerical Model of Viscoelastic Layer Entrainment by Airflow in Cough

    NASA Astrophysics Data System (ADS)

    Mitran, Sorin M.

    2008-07-01

    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.

  6. Preparation of CNTs rope by electrostatic and airflow field carding with high speed rotor spinning

    NASA Astrophysics Data System (ADS)

    Dai, J. F.; Liu, J. F.; Zou, J. T.; Dai, Y. L.

    2015-12-01

    The large-scale preparation of disorderly CNTs with a length larger than 3 mm using CVD method were aligned in polymer monomer airflow fields in a quartz tube with an internal diameter of 200 μm and a length of 1.5 m. The airflow aligned CNTs at the output end of the pipe connects to a copper nozzle with an electrostatic field of applied voltage 5x105 V/m and space length of 0.03 m, which were further realigned using via electrostatic spinning. End to end spray into the high speed rotor twisted single-stranded carbon nanotubes threads via rotor spinning technology. The essential component of this technique was the use of carbon nanotubes at a high rotory speed (200000 r/min) combined with the double twisting of filaments that were twisted together to increase the radial friction of the entire section. SEM micrography showed that carbon nanotube thread has a uniform diameter of approximately 200 μm. Its tensile strength was tested up to 2.7 Gpa, with a length of several meters.

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

    NASA Astrophysics Data System (ADS)

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

    2007-10-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    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.

  9. Collective odor source estimation and search in time-variant airflow environments using mobile robots.

    PubMed

    Meng, Qing-Hao; Yang, Wei-Xing; Wang, Yang; Zeng, Ming

    2011-01-01

    This paper addresses the collective odor source localization (OSL) problem in a time-varying airflow environment using mobile robots. A novel OSL methodology which combines odor-source probability estimation and multiple robots' search is proposed. The estimation phase consists of two steps: firstly, the separate probability-distribution map of odor source is estimated via Bayesian rules and fuzzy inference based on a single robot's detection events; secondly, the separate maps estimated by different robots at different times are fused into a combined map by way of distance based superposition. The multi-robot search behaviors are coordinated via a particle swarm optimization algorithm, where the estimated odor-source probability distribution is used to express the fitness functions. In the process of OSL, the estimation phase provides the prior knowledge for the searching while the searching verifies the estimation results, and both phases are implemented iteratively. The results of simulations for large-scale advection-diffusion plume environments and experiments using real robots in an indoor airflow environment validate the feasibility and robustness of the proposed OSL method. PMID:22346650

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

    SciTech Connect

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

    2010-08-15

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

  11. Calibration for Thrust and Airflow Measurements in the CE-22 Advanced Nozzle Test Facility

    NASA Technical Reports Server (NTRS)

    Werner, Roger A.; Wolter, John D.

    2010-01-01

    CE-22 facility procedures and measurements for thrust and airflow calibration obtained with choked-flow ASME nozzles are presented. Six calibration nozzles are used at an inlet total pressure from 20 to 48 psia. Throat areas are from 9.9986 to 39.986 sq. in.. Throat Reynolds number varies from 1.8 to 7.9 million. Nozzle gross thrust coefficient (CFG) uncertainty is 0.25 to 0.75 percent, with smaller uncertainly generally for larger nozzles and higher inlet total pressure. Nozzle discharge coefficient (CDN) uncertainty is 0.15 percent or less for all the data. ASME nozzle calibrations need to be done before and after research model testing to achieve these uncertainties. In addition, facility capability in terms of nozzle pressure ratio (NPR) and nozzle airflow are determined. Nozzle pressure ratio of 50 or more is obtainable at 40 psia for throat areas between 20 and 30 sq. in.. Also presented are results for two of the ASME nozzles vectored at 10deg, a dead-weight check of the vertical (perpendicular to the jet axis) force measurement, a calibration of load cell forces for the effects of facility tank deflection with tank pressure, and the calibration of the metric-break labyrinth seal.

  12. An experimental relationship between airflow and carbon dioxide concentrations at a rural site.

    PubMed

    Pérez, Isidro A; Sánchez, M Luisa; García, M Ángeles; Pardo, Nuria

    2015-11-15

    The influence of airflow on CO2 concentrations is considered. Two years of measurements recorded with a Picarro G1301 analyser during the night at a rural site were used. Three concentration groups were formed and were related to wind speed. Yearly, directional, and hourly evolution indicated that the isolated contribution of factors affecting CO2 concentrations proves hard to evaluate. Two approaches to airflow based on average wind and a rotating residual were considered. Around two thirds of observations corresponded to anticyclonic rotations. Firstly, circular hodographs of rotating residuals indicated that wavelengths were in the mesoscale range. The greatest concentrations were linked to the lowest wind speeds and no prevailing directions were revealed by the roundness calculation in a spatial analysis using hexagonal cells. Secondly, composite hodographs for anticyclonic turnings were calculated, the greatest concentrations being associated to hodographs with a pronounced curvature. Moreover, these were successfully parameterised using two models. A harmonic function was first used, which satisfactorily fitted hodographs linked to low and intermediate concentrations. The second model initially described the wind direction of residuals with the error function since its change was slow in early and late night-time. Residuals were later parameterised with a second order logarithmic spiral. This procedure successfully fitted the most curved hodographs of low and high concentrations. PMID:26179780

  13. Detailed predictions of particle aspiration affected by respiratory inhalation and airflow

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    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.

  14. Vibration energy harvesting from an array of flexible stalks exposed to airflow: a theoretical study

    NASA Astrophysics Data System (ADS)

    Gardonio, P.; Zilletti, M.

    2016-03-01

    This paper investigates the vibration energy harvesting of a system formed by an array of identical artificial flexible stalks connected by equal axial springs. The stalks are excited in bending by the propagating eddies produced by a mixing layer airflow at the top end of the canopy. The energy harvesting is localised in one pivotal stalk, which is equipped with a harvester. The paper first contrasts the spectra of the energy harvested by this system and by a classical system, formed by an equal array of mechanically uncoupled beams, which are all equipped with harvesters. Since the proposed system forms a periodic structure, this analysis considers variations of the stiffness of the harvesting stalk and of the connecting springs, which may lead to natural frequencies veering and mode localisation effects. Finally, the paper presents a parametric study that highlights how the bending stiffness of the harvesting stalk, the axial stiffness of the connecting springs and the energy absorption coefficient of the harvester influence the energy extraction. The study shows that, particularly in presence of strongly correlated drag force excitations produced on the stalks by the airflow, the energy harvested with the proposed system with a single harvester is comparable to that of a more complex and more expensive system formed by a whole array of harvesters.

  15. Comparison of Respiratory Resistance Measurements Made with an Airflow Perturbation Device with Those from Impulse Oscillometry

    PubMed Central

    Pan, J.; Saltos, A.; Smith, D.; Johnson, A.; Vossoughi, J.

    2013-01-01

    The airflow perturbation device (APD) has been developed as a portable, easy to use, and a rapid response instrument for measuring respiratory resistance in humans. However, the APD has limited data validating it against the established techniques. This study used a mechanical system to simulate the normal range of human breathing to validate the APD with the clinically accepted impulse oscillometry (IOS) technique. The validation system consisted of a sinusoidal flow generator with ten standardized resistance configurations that were shown to represent a total range of resistances from 0.12 to 0.95 kPa·L−1·s (1.2–9.7 cm H2O·L−1·s). Impulse oscillometry measurements and APD measurements of the mechanical system were recorded and compared at a constant airflow of 0.15 L·s−1. Both the IOS and APD measurments were accurate in assessing nominal resistance. In addition, a strong linear relationship was observed between APD measurements and IOS measurements (R2 = 0.999). A second series of measurements was made on ten human volunteers with external resistors added in their respiratory flow paths. Once calibrated with the mechanical system, the APD gave respiratory resistance measurements within 5% of IOS measurements. Because of their comparability to IOS measurements, APD measurements are shown to be valid representations of respiratory resistance. PMID:27006908

  16. Collective Odor Source Estimation and Search in Time-Variant Airflow Environments Using Mobile Robots

    PubMed Central

    Meng, Qing-Hao; Yang, Wei-Xing; Wang, Yang; Zeng, Ming

    2011-01-01

    This paper addresses the collective odor source localization (OSL) problem in a time-varying airflow environment using mobile robots. A novel OSL methodology which combines odor-source probability estimation and multiple robots’ search is proposed. The estimation phase consists of two steps: firstly, the separate probability-distribution map of odor source is estimated via Bayesian rules and fuzzy inference based on a single robot’s detection events; secondly, the separate maps estimated by different robots at different times are fused into a combined map by way of distance based superposition. The multi-robot search behaviors are coordinated via a particle swarm optimization algorithm, where the estimated odor-source probability distribution is used to express the fitness functions. In the process of OSL, the estimation phase provides the prior knowledge for the searching while the searching verifies the estimation results, and both phases are implemented iteratively. The results of simulations for large-scale advection–diffusion plume environments and experiments using real robots in an indoor airflow environment validate the feasibility and robustness of the proposed OSL method. PMID:22346650

  17. Flight Test Results from the Rake Airflow Gage Experiment on the F-15B Airplane

    NASA Technical Reports Server (NTRS)

    Frederick, Michael A.; Ratnayake, Nalin A.

    2011-01-01

    The Rake Airflow Gage Experiment involves a flow-field survey rake that was flown on the Propulsion Flight Test Fixture at the NASA Dryden Flight Research Center using the Dryden F-15B research test bed airplane. The objective of this flight test was to ascertain the flow-field angularity, local Mach number profile, total pressure distortion, and dynamic pressure at the aerodynamic interface plane of the Channeled Centerbody Inlet Experiment. This new mixed-compression, supersonic inlet is planned for flight test in the near term. Knowledge of the flow-field characteristics at this location underneath the airplane is essential to flight test planning and computational modeling of the new inlet, an< it is also applicable for future propulsion systems research that may use the Propulsion Flight Test Fixture. This report describes the flight test preparation and execution, and the local flow-field properties calculated from pressure measurements of the rake. Data from the two Rake Airflow Gage Experiment research flights demonstrate that the F-15B airplane, flying at a free-stream Mach number of 1.65 and a pressure altitude of 40,000 ft, would achieve the desired local Mach number for the future inlet flight test. Interface plane distortion levels of 2 percent and a local angle of attack of -2 deg were observed at this condition. Alternative flight conditions for future testing and an exploration of certain anomalous data also are provided.

  18. Flight Test Results from the Rake Airflow Gage Experiment on the F-15B Airplane

    NASA Technical Reports Server (NTRS)

    Frederick, Michael A.; Ratnayake, Nalin A.

    2010-01-01

    The Rake Airflow Gage Experiment involves a flow-field survey rake that was flown on the Propulsion Flight Test Fixture at the NASA Dryden Flight Research Center using the Dryden F-15B research test bed airplane. The objective of this flight test was to ascertain the flow-field angularity, local Mach number profile, total pressure distortion, and dynamic pressure at the aerodynamic interface plane of the Channeled Centerbody Inlet Experiment. This new mixed-compression, supersonic inlet is planned for flight test in the near term. Knowledge of the flow-field characteristics at this location underneath the airplane is essential to flight test planning and computational modeling of the new inlet, and it is also applicable for future propulsion systems research that may use the Propulsion Flight Test Fixture. This report describes the flight test preparation and execution, and the local flowfield properties calculated from pressure measurements of the rake. Data from the two Rake Airflow Gage Experiment research flights demonstrate that the F-15B airplane, flying at a free-stream Mach number of 1.65 and a pressure altitude of 40,000 ft, would achieve the desired local Mach number for the future inlet flight test. Interface plane distortion levels of 2 percent and a local angle of attack of 2 were observed at this condition. Alternative flight conditions for future testing and an exploration of certain anomalous data also are provided.

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

    NASA Technical Reports Server (NTRS)

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

    1973-01-01

    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.

  20. Scanning LDV for vibration measurement of filiform hairs in crickets in response to induced airflow

    NASA Astrophysics Data System (ADS)

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

    2006-06-01

    Cercal hairs represent in cricket a wind sensitive escape system, able to detect the airflow generated from predating species. These sensors have been studied as a biomimetic concept to allow the development of MEMS for biomedical use. In particular, the behaviour of the hairs, including airflow response, resonant frequency and damping, has been investigated up to a frequency of 20 kHz. The microscopic nature of the hairs, the complex vibrations of excited hairs and the high damping of the system suggested that the use of Laser Doppler vibrometry could possibly improve the test performance. Two types of tests were performed: in the first case the hairs were indirectly excited using the signal obtained from a vibrating aluminium plate, whilst in the second case the hairs were directly excited using a white noise chirp. The results from the first experiment indicated that the hairs move in-phase with the exciting signal up to frequencies in the order of 10 kHz, responding to the vibration modes of the plate with a signal attenuation of 12 to 20 dB. The chirp experiment revealed the presence of rotational resonant modes at 6850 and 11300 Hz. No clear effect of hair length was perceivable on the vibration response of the filiform sensors. The obtained results proved promising to support the mechanical and vibration characterisation of the hairs and suggest that scanning Laser vibrometry can be used extensively on highly dampened biological materials.