Sample records for laminar airflow tla

  1. 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 175min, in a simulated bedroom containing bedding from a cat owner. Total airborne particles (?0.5 - ?10?m 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?m 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

  2. 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

  3. Animating TLA Specifications

    Microsoft Academic Search

    Yassine Mokhtari; Stephan Merz

    1999-01-01

    TLA (the Temporal Logic of Actions) is a linear temporal logic for specifying and reasoning about reactive systems. We define a subset of TLA whose formulas are amenable to validation by animation, with the intent to fa- cilitate the communication between domain and solution experts in the design of reactive systems. The Temporal Logic of Actions (TLA) has been proposed

  4. Logique TLA+ Preuve axiomatique

    E-print Network

    Grigoras, .Romulus

    transitions ­ TLA+ logique 5 / 20 #12;Logique TLA+ Preuve axiomatique V´erification de mod`eles Raffinage de programme Raffinage simple Un programme (concret) Pc raffine un programme (abstrait) Pa si Pc Pa : tout ce+ Preuve axiomatique V´erification de mod`eles Raffinage - exemple Somme abstraite module somme1 extends

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

    PubMed

    Mnsson, Emeli; Hellmark, Bengt; Sundqvist, Martin; Sderquist, 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. TLA in Pictures Leslie Lamport

    E-print Network

    Rajamani, Sriram K.

    1 TLA in Pictures Leslie Lamport Abstract-- Predicate-action diagrams, which are similar- agrams, temporal logic. I. Introduction Pictures aid understanding. A simple flowchart is easier to understand than the equivalent programming-language text. However, complex pictures are confusing. A large

  7. 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.

  8. Specifying and verifying PLC systems with TLA

    Microsoft Academic Search

    Hehua Zhang; Stephan Merz; Ming Gu

    2010-01-01

    We report on a method for formally specifying and verifying programmable logic controllers (PLCs) in the specification language TLA+. The specification framework is generic. It separates the description of the environment from that of the controller itself and its structure is consistent with the scan cycle mechanism used by PLCs. Specifications can be parameterized with the number of replicated components.

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

    Microsoft Academic Search

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

    2001-01-01

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

  10. Verifying Safety Properties With the TLA+ Proof System

    E-print Network

    Chaudhuri, Kaustuv; Lamport, Leslie; Merz, Stephan; 10.1007/978-3-642-14203-1_12

    2010-01-01

    TLAPS, the TLA+ proof system, is a platform for the development and mechanical verification of TLA+ proofs written in a declarative style requiring little background beyond elementary mathematics. The language supports hierarchical and non-linear proof construction and verification, and it is independent of any verification tool or strategy. A Proof Manager uses backend verifiers such as theorem provers, proof assistants, SMT solvers, and decision procedures to check TLA+ proofs. This paper documents the first public release of TLAPS, distributed with a BSD-like license. It handles almost all the non-temporal part of TLA+ as well as the temporal reasoning needed to prove standard safety properties, in particular invariance and step simulation, but not liveness properties.

  11. TLA-55 Rotor Used in Beckman Coulter OptimaTM

    E-print Network

    Pawlowski, Wojtek

    Ultracentrifuges Published by the Centrifuge Instrument Systems Development Center of Beckman Coulter, Inc., Palo, and tested for safety and reliability as part of a Beckman Coulter ultracentrifuge/rotor system. Its safety Alto, California 94304 TL-TB-020C November 2002 2002 Beckman Coulter, Inc. #12;2 TLA-55 Rotor SAFETY

  12. F-16XL Supersonic Laminar Flow Test Flight - Duration: 29 seconds.

    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...

  13. 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.

  14. Natural laminar flow and laminar flow control

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  15. TLA: A Traffic Load Adaptive Congestion Control Algorithm for TCP\\/AQM Networks

    Microsoft Academic Search

    Ming Jiang; Qin Chen

    2006-01-01

    TCP combined with active queue management algorithm is the primary solution of the congestion control problem of IP network. Red and blue are the famous AQM algorithms but neither of them performs well when traffic load is heavy and when the traffic load changes. This paper proposes a new traffic load adaptive AQM algorithm named TLA. The objective of TLA

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

    Microsoft Academic Search

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

    1989-01-01

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

  17. Laminar soot processes

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  18. 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

  19. Laminar flow: The Cessna perspective

    NASA Technical Reports Server (NTRS)

    Peterman, Bruce E.

    1987-01-01

    A review of Natural Laminar Flow (NLF) and Laminar-Flow Control activities over the last twenty years at the Cessna Aircraft Company is presented. Expected NLF benefits and remaining challenges are then described.

  20. Supersonic laminar flow control research

    NASA Technical Reports Server (NTRS)

    Lo, Ching F.

    1994-01-01

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

  1. Development of Power-head based Fan Airflow Station

    E-print Network

    Wang, G.; Liu, M.

    2005-01-01

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

  2. Development of Power-head based Fan Airflow Station

    E-print Network

    Wang, G.; Liu, M.

    2005-01-01

    Development of Power-head Based Fan Airflow Station Gang Wang Research associate University of Nebraska, Lincoln Mingsheng Liu Professor University of Nebraska, Lincoln Abstract Fan airflow measurement is critical for heating... in the main ducts. In order to obtain accurate airflow, Liu developed a fan airflow station to obtain the fan airflow using the fan speed and head based on the regressed fan curve [1]. The experiment was conducted to verify the fan station and an excellent...

  3. 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 found that soot surface oxidation rates were relatively independent of fuel type, were not correlated with O2, CO2, H2O and O collision rates but were correlated with the collision rates of OH with a collision efficiency of 0.14, in agreement with the early measurements in premixed flames of Neoh et al. (1980), after allowing for oxidation by O2 via the classical rate expression of Nagle and Strickland-Constable (1962).

  4. Fresh attack on laminar flow

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    Laminar flow control is a technology with great potential for aircraft drag reduction. Stabilization of laminar boundary layers became known as natural laminar flow (NLF) and research led to the development of NLF airfoils. Research was also conducted on stabilization by suction, referred to as laminar flow control (LFC). Experiments demonstrated that extensive laminar flow could be achieved in flight. However, there remained doubts regarding the practicality of producing, with the technology then available, wing surfaces sufficiently smooth and wavefree to meet laminar-flow criteria and maintaining the wing surface quality in normal service. In 1976, the Aircraft Energy Efficiency (ACEE) program was begun by NASA to develop fuel-conservative technology for commercial transports. The progress of the ACEE program is discussed. Attention is given to LFC wing structures, and LFC leading-edge systems.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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...

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

    E-print Network

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

    2002-01-01

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

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

    PubMed

    Kirst, Henning; Garca-Cerdn, Jose Gines; Zurbriggen, Andreas; Melis, Anastasios

    2012-02-01

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

  13. Parameters associated with persistent airflow obstruction in chronic severe asthma

    Microsoft Academic Search

    D. Bumbacea; D. Campbell; L. Nguyen; D. Carr; P. J. Barnes; D. Robinson; K. F. Chung

    2004-01-01

    The significance of severe airflow obstruction in severe asthma is unclear. The current study determined whether severe airflow obstruction is related to inflammatory or structural changes in the airways. Patients with severe asthma from a tertiary referral clinic were divided into two groups according to their postbronchodilator forced expiratory volume in one second (FEV1): severe persistent airflow limitation (FEV1v50% predicted;

  14. Airflow analysis in an air conditioning room

    Microsoft Academic Search

    Ooi Yongson; Irfan Anjum Badruddin; Z. A. Zainal; P. A. Aswatha Narayana

    2007-01-01

    The aim of superior air conditioning system is no longer constrained to advancing the efficiency of cooling machine, but includes the study of airflow with the assistance of the distribution of several significant parameters. A simple numerical study of the turbulent flow over an enclosed air conditioning system was not practicable a few decades ago since the computer facilities were

  15. MEASURING AIRFLOW DISTRIBUTION IN PEANUT DRYING TRAILERS

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  16. Laminar Plasma Dynamos

    E-print Network

    Zhehui Wang; Vladimir I. Pariev; Cris W. Barnes; Daniel C. Barnes

    2002-03-07

    A new kind of dynamo utilizing flowing laboratory plasmas has been identified. Conversion of plasma kinetic energy to magnetic energy is verified numerically by kinematic dynamo simulations for magnetic Reynolds numbers above 210. As opposed to intrinsically-turbulent liquid-sodium dynamos, the proposed plasma dynamos correspond to laminar flow topology. Modest plasma parameters, 1-20 eV temperatures, 10^{19}-10^{20} m^{-3} densities in 0.3-1.0 m scale-lengths driven by velocities on the order of the Alfven Critical Ionization Velocity (CIV), self-consistently satisfy the conditions needed for the magnetic field amplication. Growth rates for the plasma dynamos are obtained numerically with different geometry and magnetic Reynolds numbers. Magnetic-field-free coaxial plasma guns can be used to sustain the plasma flow and the dynamo.

  17. Laminar Plasma Dynamos

    E-print Network

    Wang, Z; Barnes, C W; Barnes, D C; Wang, Zhehui; Pariev, Vladimir I.; Barnes, Cris W.; Barnes, Daniel C.

    2002-01-01

    A new kind of dynamo utilizing flowing laboratory plasmas has been identified. Conversion of plasma kinetic energy to magnetic energy is verified numerically by kinematic dynamo simulations for magnetic Reynolds numbers above 210. As opposed to intrinsically-turbulent liquid-sodium dynamos, the proposed plasma dynamos correspond to laminar flow topology. Modest plasma parameters, 1-20 eV temperatures, 10^{19}-10^{20} m^{-3} densities in 0.3-1.0 m scale-lengths driven by velocities on the order of the Alfven Critical Ionization Velocity (CIV), self-consistently satisfy the conditions needed for the magnetic field amplication. Growth rates for the plasma dynamos are obtained numerically with different geometry and magnetic Reynolds numbers. Magnetic-field-free coaxial plasma guns can be used to sustain the plasma flow and the dynamo.

  18. 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.

  19. 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

  20. Aerodynamics of laminar separation flutter at a transitional Reynolds number

    NASA Astrophysics Data System (ADS)

    Poirel, D.; Yuan, W.

    2010-10-01

    Experimental observations of self-sustained pitch oscillations of a NACA 0012 airfoil at transitional Reynolds numbers were recently reported. The aeroelastic limit cycle oscillations, herein labelled as laminar separation flutter, occur in the range 5.0104?Rec?1.3105. They are well behaved, have a small amplitude and oscillate about ?=0. It has been speculated that laminar separation leading to the formation of a laminar separation bubble, occurring at these Reynolds numbers, plays an essential role in these oscillations. This paper focuses on the Rec=7.7104 case, with the elastic axis located at 18.6% chord. Considering that the experimental rig acts as a dynamic balance, the aerodynamic moment is derived and is empirically modelled as a generalized Duffing-van-der-Pol nonlinearity. As expected, it behaves nonlinearly with pitch displacement and rate. It also indicates a dynamically unstable equilibrium point, i.e. negative aerodynamic damping. In addition, large eddy simulations of the flow around the airfoil undergoing prescribed simple harmonic motion, using the same amplitude and frequency as the aeroelastic oscillations, are performed. The comparison between the experiment and simulations is conclusive. Both approaches show that the work done by the airflow on the airfoil is positive and both have the same magnitude. The large eddy simulation (LES) computations indicate that at ?=0, the pitching motion induces a lag in the separation point on both surfaces of the airfoil resulting in negative pitching moment when pitching down, and positive moment when pitching up, thus feeding the LCO.

  1. 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.

  2. 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 manufacturer can be cut 40% or more, and the associated greenhouse emissions even more. Cleanroom HVAC systems provide huge opportunities for energy savings in the semiconductor industry. In addition to direct cost reductions in cleanroom investment and operation, energy-efficient designs can reduce maintenance costs, increase power reliability, improve time-to-market in cleanroom production, and improve environmental quality. Companies that use energy efficiency to lower costs and increase productivity can gain a competitive advantage and achieve a higher return on investment. In addition, energy-efficient cleanroom systems conserve energy and natural resources, heightening the company's reputation as an environmentally conscious leader in the community and the industry. A significant portion of energy use in cleanroom environmental systems is associated with recirculating air systems. We will review and analyze design factors and operational performance of airflow systems in ISO Class 5 clean rooms. We will also discuss benefits of efficient cleanroom airflow designs in conjunction with effective cleanroom contamination control. We will consider the following common recirculating air system designs: fan-tower (FT) with pressurized-plenum; distributed air handler unit (AHU); and fan-filter unit (FFU).

  3. Variable Speed Drive Volumetric Tracking (VSDVT) for Airflow Control in Variable Air Volume (VAV) Systems

    E-print Network

    Liu, M.

    2002-01-01

    An airflow control method has been developed for variable air volume (VAV) systems. This airflow control method is named VSD volumetric tracking (VSDVT) since both the supply and return airflows are determined using signals of the variable speed...

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

    PubMed Central

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

    2012-01-01

    The truncated light-harvesting antenna size3 (tla3) DNA insertional transformant of Chlamydomonas reinhardtii is a chlorophyll-deficient mutant with a lighter green phenotype, a lower chlorophyll (Chl) per cell content, and higher Chl a/b ratio than corresponding wild-type strains. Functional analyses revealed a higher intensity for the saturation of photosynthesis and greater light-saturated photosynthetic activity in the tla3 mutant than in the wild type and a Chl antenna size of the photosystems that was only about 40% of that in the wild type. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western-blot analyses showed that the tla3 strain was deficient in the Chl a/b light-harvesting complex. Molecular and genetic analyses revealed a single plasmid insertion in chromosome 4 of the tla3 nuclear genome, causing deletion of predicted gene g5047 and plasmid insertion within the fourth intron of downstream-predicted gene g5046. Complementation studies defined that gene g5047 alone was necessary and sufficient to rescue the tla3 mutation. Gene g5047 encodes a C. reinhardtii homolog of the chloroplast-localized SRP43 signal recognition particle, whose occurrence and function in green microalgae has not hitherto been investigated. Biochemical analysis showed that the nucleus-encoded and chloroplast-localized CrCpSRP43 protein specifically operates in the assembly of the peripheral components of the Chl a/b light-harvesting antenna. This work demonstrates that cpsrp43 deletion in green microalgae can be employed to generate tla mutants with a substantially diminished Chl antenna size. The latter exhibit improved solar energy conversion efficiency and photosynthetic productivity under mass culture and bright sunlight conditions. PMID:23043081

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

    PubMed

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

    2012-12-01

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

  6. 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.

  7. 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.

  8. 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.

  9. AIRFLOW VISUALIZATION IN A MODEL GREENHOUSE G. S. Settles

    E-print Network

    Settles, Gary S.

    AIRFLOW VISUALIZATION IN A MODEL GREENHOUSE G. S. Settles Gas Dynamics Laboratory, Mechanical & Nuclear Engineering Dept. Penn State University, University Park, PA 16802 USA Keywords: Greenhouses, flow visualization, heat transfer, schlieren optics Introduction Airflow in greenhouses has been a subject of concern

  10. Review on airflow in unsaturated zones induced by natural forcings

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  11. Laminar flow research applicable to subsonic aircraft

    NASA Technical Reports Server (NTRS)

    Hefner, J. N.; Wagner, R. D.

    1986-01-01

    Since the beginning of the NASA Aircraft Energy Efficiency (ACEE) program in 1976, significant progress has been made in the development of laminar flow technology for general aviation, commuter, and transport aircraft. Exploitation of new materials, fabrication methods, analysis techniques, and design concepts is providing convincing evidence that practical laminar flow control (LFC) systems for these future subsonic aircraft could become a reality. Program studies indicate that extensive laminar flow might be achieved on small transports with natural laminar flow (NLF) wings and larger transports with hybrid laminar flow (i.e., leading-edge suction on an NLF type of wing). This paper presents an overview of these laminar flow technology developments and describes future efforts in a broadened NASA program to explore the potential and to evaluate the practicality of different laminar flow concepts for commercial transports.

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

    NASA Astrophysics Data System (ADS)

    Pekrek, Stanislav

    2013-12-01

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

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

    PubMed

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

    2013-01-18

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

  14. Applied aspects of laminar-flow technology

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

    An account is given of the development status and performance levels achieved with natural laminar flow (NLF), extended wing chord laminar flow control (LFC), and hybrid laminar flow control (HLFC) concepts combining NLF and partial-chord LFC in the leading-edge region. Attention is given to NLF wing structure construction methods capable of achieving the requisite surface-irregularity tolerances, LFC through wing surface suction slots or perforated skins, and the deleterious effects of insects, ice crystals, and noise disturbance inputs on the ability of NLF, LFC, and HLFC wings to maintain effective laminar flow operation.

  15. Determining Pressure Losses For Airflow In Residential Ductwork

    E-print Network

    Weaver, Kevin Douglas

    2012-02-14

    Airflow pressure losses through rigid metallic and non-metallic flexible ducts were studied and recommendations to improve the rating of flexible ducts were made as part of this study. The testing was done in compliance with ASHRAE Standard 120...

  16. Association of Radiographic Emphysema and Airflow Obstruction with Lung Cancer

    Microsoft Academic Search

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

    2008-01-01

    Rationale: To study the relationship between emphysema and\\/or airflow obstruction and lung cancer in a high-risk population. Objective: We studied lung cancer related to radiographic emphy- sema and spirometric airflow obstruction in tobacco-exposed per- sons who were screened for lung cancer using chest computed tomography (CT). Methods: Subjects completed questionnaires, spirometry, and low- dosehelicalchestCT.CTscanswerescoredforemphysemabasedon National Emphysema Treatment Trial criteria. Multiple

  17. 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 niches of large body size, where cursorial locomotion can be advantageous, as well as other niches requiring great aerobic capacities, such as those using flapping flight. Furthermore, hypoxia may have exerted positive selection for a parasagittal posture, the diaphragm, and reduced erythrocyte size, innovations that enabled increased rates of ventilation and more rapid rates of diffusion in the lung. PMID:26136540

  18. 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

  19. Laminar boundary layer over riblets

    NASA Astrophysics Data System (ADS)

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

    1994-09-01

    Laser doppler anemometry (LDA) measurements and numerical calculations have been made for a laminar boundary layer on triangular riblets. Calculated mean velocity distributions along the riblet contour are in good agreement with the measured ones. The results show that no transversal motion exists above and within the riblet valleys (e.g., no secondary motion). It is found that despite the large wetted area increase, the frictional drag is not increased on riblets relative to a smooth wall. This result suggests that the viscous effects are at play in the drag reduction for a turbulent boundary layer, in the sense that they compensate for the increase in wetted area.

  20. 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; Garca-Cerdn, 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

  1. Dynamics of airflow in a short inhalation

    E-print Network

    Bates, Alister; Cetto, Raul; Calmet, Hadrien; Gambaruto, Alberto; Tolley, Neil; Houzeaux, Guillaume; Schroter, Robert

    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 trans- port 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 litre per second 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 20ms, 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...

  2. 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.

  3. Fifteen Lectures on Laminar and Turbulent Combustion

    E-print Network

    Peters, Norbert

    Fifteen Lectures on Laminar and Turbulent Combustion N. Peters RWTH Aachen Ercoftac Summer School in Combustion Systems 1 Lecture 2: Calculation of Adiabatic Flame Temperatures and Chemical Equilibria 20: Laminar Diffusion Flames: Different Flow Geometries 156 Lecture 11: Turbulent Combustion: Introduction

  4. 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

  5. Spiral Laminar Flow: A revolution in understanding?

    E-print Network

    Greenaway, Alan

    Blood Flow Spiral laminar flow #12;Spiral flow in the Aorta (MRI) Computational Fluid Dynamics 0 10 20Spiral Laminar Flow: A revolution in understanding? Reintroduction of natural blood flow - Amputation #12;Understanding Arterial Disease Arterial Blood Flow #12;Understanding Arterial Disease Arterial

  6. Airflow-induced triboelectric nanogenerator as a self-powered sensor for detecting humidity and airflow rate.

    PubMed

    Guo, Hengyu; Chen, Jie; Tian, Li; Leng, Qiang; Xi, Yi; Hu, Chenguo

    2014-10-01

    Humidity sensors are commonly based on the resistance change of metal oxide semiconductors, which show high sensitivity in low humidity but low sensitivity in high humidity. In this work, we design a novel humidity sensor based on the airflow-induced triboelectric nanogenerator (ATNG) that can serve as a self-powered sensor to detect humidity (especially in high humidity) and airflow rate. The output current or voltage change is investigated under different humidity (20-100% relative humidity) at fixed airflow rate and different airflow rates (15-25 L/min) at a fixed humidity. The working principle of the ATNG-based sensor is illustrated. We find that both output current and voltage can serve as a variable for detecting humidity, while only the output current can serve as a variable for determining airflow rate. Our study demonstrates an innovative approach toward detection of humidity and airflow rate with advantages of self-power, multifunction, low cost, simple fabrication, and high sensitivity. PMID:25192417

  7. 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.

  8. 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.

  9. Respiratory airflow patterns in ponies at rest and during exercise.

    PubMed Central

    Art, T; Lekeux, P

    1988-01-01

    The exercise-induced changes in the equine breathing pattern were studied by analyzing tidal breathing flow-volume loops recorded in ten ponies both at rest and during a standardized exercise. Airflow, tidal volume, esophageal pressure and mask pressure were simultaneously recorded before, during and after a treadmill exercise. From the collected data, respiratory frequency and total pulmonary resistance were calculated, tidal breathing flow-volume loops were retraced using a computerized method and loop indices were measured for each period of the experimental protocol. For each pony, results of three consecutive daily measurements were averaged. The exercise loop indices were compared with the corresponding resting values using a one-way analysis of variance. The significantly changed indices were correlated with respiratory frequency and total pulmonary resistance. Several types of respiratory patterns were observed at rest as well as during exercise, although each pony was relatively constant in its own pattern of breathing. Most resting inspiratory and expiratory airflow curves were found to be biphasic. When ponies started running, the airflow developed an increasingly rectangular pattern. During strenuous exercise, both inspiratory and expiratory airflow curves showed a substantial increase of the volume acceleration and tended to a plateau. The loop indices relating the expiratory to the inspiratory airflow were significantly increased compared with their rest values. Correlations of these indices with respiratory frequency and total pulmonary resistance were weak.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:3167715

  10. Natural laminar flow application to transport aircraft

    NASA Technical Reports Server (NTRS)

    Gratzer, Louis B.

    1990-01-01

    A major goal of NASA during the last 15 years has been the development of laminar flow technology for aircraft drag reduction. Of equal importance is achieving a state of readiness that will allow the successful application of this technology by industry to large, long-range aircraft. Recent progress in achieving extensive laminar flow with limited suction on the Boeing 757 has raised the prospects from practical application of the hybrid laminar flow control (HLFC) concept to subsonic aircraft. Also, better understanding of phenomena affecting laminar flow stability and response to disturbances has encouraged consideration of natural laminar flow (NLF), obtained without suction or active mechanical means, for application to transport aircraft larger than previously thought feasible. These ideas have inspired the current NASA/ASEE project with goals as follows: explore the feasibility of extensive NLF for aircraft at high Reynolds number under realistic flight conditions; determine the potential applications of NLF technology and the conditions under which they may be achieved; and identify existing aircraft that could be adapted to carry out flight experiments to validate NLF technology application. To achieve these objectives, understanding of the physical limits to natural laminar flow and possible ways to extend these limits was sought. The primary factors involved are unit Reynolds number, Mach number, wing sweep, thickness, and lift coefficients as well as surface pressure gradients and curvature. Based on previous and ongoing studies using laminar boundary layer stability theory, the interplay of the above factors and the corresponding transition limits were postulated.

  11. Fifty years of laminar flow flight testing

    NASA Technical Reports Server (NTRS)

    Wagner, R. D.; Maddalon, D. V.; Bartlett, D. W.; Collier, F. S., Jr.

    1988-01-01

    Laminar flow flight experiments conducted over the past 50 years are reviewed. The emphasis is on flight testing conducted under the NASA Laminar Flow Control Program, which has been directed towards the most challenging technology application, the high-subsonic-speed transport. The F111/TACT NLF Glove Flight Test, the F-14 Variable-Sweep Transition Flight Experiment, the 757 Wing-Noise Survey and NLF Glove Flight Test, the NASA Jetstar Leading-Edge Flight Test Program, and the recently initiated Hybrid Laminar-Flow-Control Flight Experiment are discussed.

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

    SciTech Connect

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

    1987-12-01

    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.

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

    Microsoft Academic Search

    J. N. Hefner; F. E. Sabo

    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

  14. 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.

  15. 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 origin of birds. PMID:24336209

  16. A computational study of the respiratory airflow characteristics in normal and obstructed human airways

    E-print Network

    A computational study of the respiratory airflow characteristics in normal and obstructed human subjected to filtering demonstrated higher sensitivity than airway resistance for differentiating normal needed to promote respiratory defense mechanisms. In summary, our model enables the study of airflow

  17. Laminar Flow Control Flight Experiment Design

    E-print Network

    Tucker, Aaron 1975-

    2012-11-29

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

  18. A faster 'transition' to laminar flow

    NASA Technical Reports Server (NTRS)

    Bobbitt, P. J.; Waggoner, E. G.; Harvey, W. D.; Dagenhart, J. R.

    1985-01-01

    A discussion is given of the ongoing research related to laminar flow airfoils, nacelles, and wings where the laminar flow is maintained by a favorable pressure gradient, surface suction or a combination of the two. Design methologies for natural laminar flow airfoil sections and wings for both low and high speed applications are outlined. Tests of a 7-foot chord, 23-deg sweep laminar flow-control airfoil at high subsonic Mach numbers are described, along with the associated stability theory used to design the suction system. The state-of-the-art of stability theory is simply stated and a typical calculation illustrated. In addition, recent computer simulations of transition using the time dependent Navier-Stokes equations are briefly described. Advances in wind tunnel capabilities and instrumentation will be reviewed, followed by the presentation of a few results from both wind tunnels and flight. Finally, some suggestions for future work will complete the paper.

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

    E-print Network

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

    2003-01-01

    Development of In-situ Fan Curve Measurement with One Airflow Measurement Guopeng Liu, Ik-Seong Joo, Li Song, Mingsheng Liu, Ph.D., P.E. Energy Systems Laboratory University of Nebraska ABSTRACT Fan airflow is the key parameter for air... is another issue for this method. Therefore, it is very important to find an effective way to measure the airflow accurately. An airflow control named VSD volumetric tracking (VSDVT) has been developed by Liu [13] recently. This method uses fan...

  20. Optimum plane diffusers in laminar flow

    Microsoft Academic Search

    Hayri Cabuk; Vijay Modi

    1992-01-01

    The paper considers an optimum design of an internal flow component such as a diffuser in laminar flow. The problem of determining the profile of a plane diffuser of given upstream width and length that provides the maximum static pressure rise is solved for 2D incompressible laminar flow governed by the steady-state Navier-Stokes equations. A set of 'adjoint' equations is

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

    E-print Network

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

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

    E-print Network

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

  3. Real-Time Airflow Rate Measurements from Mechanically Ventilated Animal Buildings

    Microsoft Academic Search

    Steven J. Hoff; Dwaine S. Bundy; Minda A. Nelson; Brian C. Zelle; Larry D. Jacobson; Albert J. Heber; Jiqin Ni; Yuanhui Zhang; Jacek A. Koziel; David B. Beasley; Robert Joumard; Juhani Laurikko; Tuan Han; Savas Geivanidis; Zissis Samaras; Tamas tei; Philippe Devaux; Jean-Marc Andre; Stephanie Lacour; Erwin Cornelis; Victor Chang; Lynn Hildemann; Cheng-hisn Chang; Joo-Youp Lee; Tim Keener; Y. Yang; Sheng-Wei Wang; Xiaogang Tang; Zhi-Hua Fan; Xiangmei Wu; Paul Lioy; Panos Georgopoulos; Augustine Quek; Rajasekhar Balasubramanian; Yi-Chi Chen; Lu-Yen Chen; Fu-Tien Jeng

    2009-01-01

    This paper describes techniques used to determine airflow rate in multiple emission point applications typical of animal housing. An accurate measurement of building airflow rate is critical to accurate emission rate estimates. Animal housing facilities rely almost exclusively on ventilation to control inside climate at desired conditions. This strategy results in building airflow rates that range from about three fresh-air

  4. Research on Sensitive Mechanism of Airflow Level Posture Sensor

    Microsoft Academic Search

    Linhua Piao; Yaojie Lv

    2006-01-01

    In this paper, the sensitive mechanism of airflow level posture sensor is explained. By using the finite element method, the stream field by two point heat sources, when the two-dimensional enclosure is inclined, has been obtained by a series of procedure, such as model building, meshing, loads applying and equation solving. In the process ANSYS-FLOTRAN CFD program is applied .The

  5. D. C. surface discharge characteristics in mach 2 rarefied airflow

    Microsoft Academic Search

    L. Leger; E. Depussay; V. Lago

    2009-01-01

    The paper describes a study of an electrical discharge in a supersonic rarefied air flow. The discharge is created by applying negative DC potential difference between two electrodes flush mounted on the surface of a quartz flat plate placed in Mach 2 continuous airflow. The electrodes are arranged in spanwise direction. Two discharges are studied. In the first one, the

  6. Calibration of a novel airflow transducer for use in pneumotachography

    Microsoft Academic Search

    E. F. J. Coolen; M. J. West; P. R. S. White

    1999-01-01

    Wave energy research at Coventry University (formerly Coventry Lanchester Polytechnic) led to the development of the Clam wave energy converter. In operation the Clam allows wave motion to produce air displacement and, through the use of a Wells turbine, electricity may be generated. The need to test the Clam at model scale led to the development of an airflow transducer

  7. Air-flow regulation system for a coal gasifier

    DOEpatents

    Fasching, George E. (Morgantown, WV)

    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.

  8. Airflow obstruction and metabolic syndrome: the Guangzhou Biobank Cohort Study.

    PubMed

    Lam, K-B H; Jordan, R E; Jiang, C Q; Thomas, G N; Miller, M R; Zhang, W S; Lam, T H; Cheng, K K; Adab, P

    2010-02-01

    There is some evidence that chronic obstructive pulmonary disease (COPD) and metabolic syndrome may be related, perhaps through systemic inflammation, which is common to both. However, the association between the two conditions has not yet been clearly shown. The present study involved 7,358 adults aged > or =50 yrs from a population-based survey who underwent spirometry, a structured interview and measurement of fasting metabolic marker levels. Airflow obstruction (forced expiratory volume in 1 s/forced vital capacity ratio of less than the lower limit of normal) was present in 6.7%, and the International Diabetes Federation metabolic syndrome criteria were met by 20.0%. The risk of metabolic syndrome was higher in those with airflow obstruction than in those without (odds ratio (OR) 1.47; 95% confidence interval (CI) 1.12-1.92), after controlling for potential confounders. Of the five components of metabolic syndrome, only central obesity was significantly associated with airflow obstruction (OR 1.43; 95% CI 1.09-1.88) after adjusting for body mass index. A similar association was observed in both never and current smokers. In this Chinese sample, airflow obstruction was associated with metabolic syndrome, and, in particular, its central obesity component. This may help explain the increased risk of cardiovascular diseases in COPD, and so could guide future clinical practice. PMID:19574332

  9. Testing limits to airflow perturbation device (APD) measurements

    Microsoft Academic Search

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

    2008-01-01

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

  10. Shade and Airflow Restriction Effects on Creeping Bentgrass Golf Greens

    Microsoft Academic Search

    K. J. Koh; G. E. Bell; D. L. Martin; N. R. Walker

    2003-01-01

    shade color did not differ from control. Turf density declined in both density or the temporal period of shade. In that study, cultivars due to both airflow restriction and shade compared with control. Air restriction reduced density more than shade in SR1020 perpetual artificial shade averaging 42% of the photo- but not in L93. The severity of brown patch (caused

  11. 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.

  12. Aerodynamic Design for Swept-wing Laminar Flow

    E-print Network

    Belisle, Michael Joseph

    2013-11-08

    (SARGE), a natural laminar flow and passive laminar flow control wing glove flight experiment funded by the NASA Environmentally Responsible Aviation initiative. The experiment seeks to raise the technology readiness level of the spanwise...

  13. 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.

  14. Laminar Flame Speeds of Moist Syngas Mixtures

    SciTech Connect

    Das, A. K.; Kumar, K.; Zhang, Z.; Sung, C. J.

    2011-01-01

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

  15. Laminar flame speeds of moist syngas mixtures

    SciTech Connect

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

    2011-02-15

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

  16. Laminar flow - The past, present, and prospects

    NASA Technical Reports Server (NTRS)

    Wagner, R. D.; Bartlett, D. W.; Collier, F. S., Jr.

    1989-01-01

    Flight research conducted on natural laminar flow (NLF) is discussed. Emphasis is on recent flight testing conducted by the National Aeronautics and Space Administration. To place these flight experiences in perspective, important flight tests from the early days of natural laminar flow research are first reviewed to recall the lessons learned at that time. Then, based on more recent flight experiences and analyses with state-of-the-art boundary layer stability theory, speculation is made on the possibility of extensive NLF on swept wing transport aircraft.

  17. Control of airflow about a high energy laser turret

    NASA Astrophysics Data System (ADS)

    Mandigo, A. M.

    1980-12-01

    A high energy laser system inflicts damage on a target by radiating large amounts of thermal energy onto a small area. Airflow about the laser turret, which is located on top of the aircraft fuselage, is unsteady and causes problems in beam control. The problems are jitter, which is vibration of the laser beam, and optical path distortions. The theory of flow around a cylinder and around a sphere was examined, and several airflow control techniques were screened in an effort to suppress the unsteadiness of the flow. A fairing and turret base suction apparatus was selected and experimentally tested in a wind tunnel. During the course of the experiments several parameters were varied as follows: blower flow rate, spacing between turret and fairing nosepiece, and flow rate in five separate ducts. Results of the tests indicate that the fairing and base suction technique eliminates the unsteadiness. Further research and testing are required to develop this technique for actual use on aircraft.

  18. 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.

  19. 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.

  20. Three-dimensional mapping of airflow over dunes

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2013-05-01

    Similar to the way a river, flowing across Earth's surface, influences sediment transport and shaping of the landscape, coastal winds, which flow over dunes, affect how the dune shapes evolve and how sand is transported along the coast. Wind flow over dunes has been extensively studied, but in most cases, that research has been two-dimensional and focused on straight dunes with smooth slopes and no vegetation or other features that might affect how airflow separates at the crest of the dune.

  1. 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.

  2. Working towards the ideal laminar flow structure

    Microsoft Academic Search

    Bryan E. Humphreys

    2001-01-01

    Airlines and aircraft manufacturers are forecasting significant incerases in passenger traffic over the next 20 years (1), (2) but it is becoming increasingly apparent that, given a future scenario of increasing fuel costs and environmental controls, this is unlikely to be sustainable unless aircraft become more efficient and environmentally friendly than those in service today.Hybrid Laminar Flow (HLF) offers a

  3. Progress in natural laminar flow research

    Microsoft Academic Search

    B. J. Holmes

    1984-01-01

    For decades, since the earliest attempts to obtain natural laminar flow (NLF) on airplanes, three classical objections to its practicality have been held in the aeronautical community. These objectives concerned first, the capability to manufacture practical airframe surfaces smooth enough for NLF; second, the apparent inherent instability and sensitivity of NLF; and third, the accumulation of contamination such as insect

  4. Flight research on natural laminar flow

    Microsoft Academic Search

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

    1986-01-01

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

  5. Tide-induced airflow in a two-layered coastal land with atmospheric pressure fluctuations

    Microsoft Academic Search

    Jian Li; Hongbin Zhan; Guanhua Huang; Kehua You

    2011-01-01

    Tide-induced airflow is commonly seen in coastal lands and affects ground stability especially with a less permeable pavement on the ground surface. A tide-induced airflow model in a two-layered unsaturated zone consisting of a highly permeable layer underneath a less permeable layer was established by Li and Jiao [Li HL, JJ Jiao. One-dimensional airflow in unsaturated zone induced by periodic

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

    PubMed Central

    Li, Hancao; Haddad, Wassim M.

    2012-01-01

    We develop optimal respiratory airflow patterns using a nonlinear multicompartment model for a lung mechanics system. Specifically, we use classical calculus of variations minimization techniques to derive an optimal airflow pattern for inspiratory and expiratory breathing cycles. The physiological interpretation of the optimality criteria used involves the minimization of work of breathing and lung volume acceleration for the inspiratory phase, and the minimization of the elastic potential energy and rapid airflow rate changes for the expiratory phase. Finally, we numerically integrate the resulting nonlinear two-point boundary value problems to determine the optimal airflow patterns over the inspiratory and expiratory breathing cycles. PMID:22719793

  7. 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.

  8. Optimal determination of respiratory airflow patterns using a nonlinear multicompartment model for a lung mechanics system.

    PubMed

    Li, Hancao; Haddad, Wassim M

    2012-01-01

    We develop optimal respiratory airflow patterns using a nonlinear multicompartment model for a lung mechanics system. Specifically, we use classical calculus of variations minimization techniques to derive an optimal airflow pattern for inspiratory and expiratory breathing cycles. The physiological interpretation of the optimality criteria used involves the minimization of work of breathing and lung volume acceleration for the inspiratory phase, and the minimization of the elastic potential energy and rapid airflow rate changes for the expiratory phase. Finally, we numerically integrate the resulting nonlinear two-point boundary value problems to determine the optimal airflow patterns over the inspiratory and expiratory breathing cycles. PMID:22719793

  9. Investigation of a Laminar Flow Leading Edge

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Laminar flow instability in nuclear rockets

    SciTech Connect

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

    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.

  16. Correlated Variability in Laminar Cortical Circuits

    PubMed Central

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

    2012-01-01

    SUMMARY Despite the fact that strong trial-to-trial correlated variability in responses has been reported in many cortical areas, recent evidence suggests that neuronal correlations are much lower than previously thought. Here, we used multicontact laminar probes to revisit the issue of correlated variability in primary visual (V1) cortical circuits. We found that correlations between neurons depend strongly on local network contextwhereas neurons in the input (granular) layers showed virtually no correlated variability, neurons in the output layers (supragranular and infragranular) exhibited strong correlations. The laminar dependence of noise correlations is consistent with recurrent models in which neurons in the granular layer receive intracortical inputs from nearby cells, whereas supragranular and infragranular layer neurons receive inputs over larger distances. Contrary to expectation that the output cortical layers encode stimulus information most accurately, we found that the input network offers superior discrimination performance compared to the output networks. PMID:23141070

  17. Distributed apertures in laminar flow laser turrets

    NASA Astrophysics Data System (ADS)

    Tousley, B. B.

    1981-09-01

    Assume a technology that permits undistorted laser beam propagation from the aft section of a streamlined turret. A comparison of power on a distant airborne target is made between a single aperture in a large scale streamlined turret with a turbulent boundary layer and various arrays of apertures in small scale streamlined turrets with laminar flow. The array performance is mainly limited by the size of each aperture. From an array one might expect, at best, about 40 percent as much power on the target as from a single aperture with equal area. Since the turbulent boundary layer on the large single-turret has negligible effect on beam quality, the array would be preferred (if all development efforts were essentially equal) only if a laminar wake is an operational requirement.

  18. CFD analysis of laminar oscillating flows

    SciTech Connect

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

    2001-01-01

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

  19. 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.

  20. Laminar compressible flow in a tube

    Microsoft Academic Search

    Robert K. Prud'Homme; Thomas W. Chapman; J. Ray Bowen

    1986-01-01

    A two-dimensional solution for the velocity and pressure distributions in steady, laminar, isothermal flow of an ideal gas\\u000a in a long tube is obtained as a double perturbation expension in ?, the radius to length ratio, and ?, the relative pressure drop. It is found that simple approximations estimate the exact\\u000a flow rate-pressure drop relationship accurately.

  1. Flight research on natural laminar flow

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  2. Flight research on natural laminar flow

    NASA Astrophysics Data System (ADS)

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

    1986-12-01

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

  3. Laminar nanofluid flow in microheat-sinks

    Microsoft Academic Search

    J. Koo; C. Kleinstreuer

    2005-01-01

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

  4. Laminar Smoke Points of Wax Candles

    Microsoft Academic Search

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

    2009-01-01

    An experimental investigation of laminar smoke points of candle flames is presented. Adjustable wicks with diameters of 1.77.3mm were used to measure smoke points in quiescent air for 14 different waxes. The measured smoke points increased with wick diameter. Smoke points interpolated to a wick diameter of 4.5mm varied from 4180mm and increased from commercial waxes (candelilla, carnauba, beeswax, paraffin)

  5. Laminar streak enhancement using streamwise grooves

    NASA Astrophysics Data System (ADS)

    Martel, Carlos; Martn, Juan ngel

    2011-11-01

    Laminar streak promotion in a flat plate boundary layer results in an increase of the stability of the Tollmien-Schlichting waves with respect to that of the 2D Blasius profile. This stabilization delays the laminar-turbulent transition, increasing the laminar phase of the flow. The stabilization effect is stronger for higher streak amplitudes, and therefore simple ways of generating high amplitude stable streaks are sought to be used as boundary layer flow control methods. In a recent experiment [Tallamelli & Franson,AIAA 2010-4291] high amplitude stable steady streaks have been produced using Miniature Vortex Generators (MGVs), where one array of MGVs is used to excite the streak and a second array is used downstream to enhance their amplitude. In this presentation we numerically explore the possibility of enhancing the streaks using a different passive mechanism: streamwise grooves carved in the plate. We will present some numerical simulations for different values of the spanwise period of the streaks and of the grooves, and we will show the combinations that provide maximum streak amplitude.

  6. Validation of a Coupled Multizone and CFD Program for Building Airflow and Contaminant Transport Simulations

    E-print Network

    Chen, Qingyan "Yan"

    and CFD simulations used less computing time than the CFD simulations for the whole flow domain. Key words: Multizone, CFD, Coupling, Simulations, Experimental validation INTRODUCTION Multizone airflow network models and Computational Fluid Dynamics (CFD) have been widely used in simulations of building airflow distribution

  7. Effect of fluctuation in inlet airflow temperature on CFD simulation of air-blast chilling process

    Microsoft Academic Search

    Zehua Hu; Da-Wen Sun

    2001-01-01

    Setting the boundary condition of airflow temperature is an important factor affecting the predicting accuracy during the simulation of air-blast chilling process. In this study, numerical simulations using computational fluid dynamics (CFDs) were conducted to predict a coupled heat and mass transfer during chilling of a cooked ham. Based on the experimental airflow temperature data, a mathematical formula expressing the

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

    Microsoft Academic Search

    S K Kim; S K Chung

    2004-01-01

    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

  9. 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.

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

    E-print Network

    Chen, Qingyan "Yan"

    and mechanical ventilation, have been widely used and discussed in indoor environment quality studies [1Particle Image Velocimetry measurement of indoor airflow field: A review of the technologies@tju.edu.cn Abstract Quantifying the airflow field in building room or vehicle cabin indoor space is crucial

  11. Computation of airflow effects on heat and mass transfer in a microwave oven

    Microsoft Academic Search

    Pieter Verboven; Ashim K. Datta; Nguyen Trung Anh; Nico Scheerlinck

    2003-01-01

    The magnitude of surface heat and mass transfer coefficients in microwave ovens is important to control food surface temperature and moisture and are a result of the faint airflow present in the oven cavity and of surface radiation. Magnitude and patterns of airflow inside a microwave oven and the resulting surface heat transfer coefficients were studied using a computational fluid

  12. The influence of airflow on fuel spray characteristics from a slit injector

    Microsoft Academic Search

    Seoksu Moon; Choongsik Bae; Jaejoon Choi; Essam Abo-Serie

    2007-01-01

    Optimization of fuel spray, airflow, and their interaction with the cylinder and piston wall is crucial to achieve stable combustion of stratified charge with minimum emissions in direct-injection spark-ignition (DISI) engines. In this study, the interaction between air and fuel spray from slit injector was investigated in a steady airflow system generated by a wind tunnel under atmospheric conditions. Both

  13. Measurements of the viscous tangential stress in the airflow above wind waves

    Microsoft Academic Search

    F. Veron; G. Saxena; S. K. Misra

    2007-01-01

    The stress and drag at the surface of the ocean are crucial parameters for both short term forecasting and the modeling of long-term global climate trends. However, the partition between viscous, turbulent, and wave stresses, and in particular the effects of airflow separation are not well understood. We present direct measurements of the velocity in the airflow above wind-generated waves.

  14. Trans-laminar-reinforced (TLR) composites

    NASA Astrophysics Data System (ADS)

    Dickinson, Larry Charles

    1997-11-01

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

  15. The effects of airflow modulation and multi-stage defrost on the performance of an air source heat pump

    E-print Network

    Payne, William Vance

    1992-01-01

    Refrigerant Distribution at Steady State . . 14 2. 2 Annual Energy Consumption (kWh/year) for Different Defrost Control Systems. . . 31 2. 3 Frosted Coil Comparison. 37 3. 1 Environmental Room Specifications. 45 3. 2 Description of Test Points. 4. 1 Base.... . . Constant Airflow Performance Characteristics . . . 89 . . . 102 5. 2 System Performance Characteristics with Constant Outdoor Coil Airflow . . 5. 3 Low Airflow and Base Case Performance Comparison, 95% RH . 5. 4 High Airflow Performance...

  16. Aerodynamics of laminar separation flutter at a transitional Reynolds number

    Microsoft Academic Search

    D. Poirel; W. Yuan

    2010-01-01

    Experimental observations of self-sustained pitch oscillations of a NACA 0012 airfoil at transitional Reynolds numbers were recently reported. The aeroelastic limit cycle oscillations, herein labelled as laminar separation flutter, occur in the range 5.0104?Rec?1.3105. They are well behaved, have a small amplitude and oscillate about ?=0. It has been speculated that laminar separation leading to the formation of a laminar

  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. 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.

  20. Airflow Simulation in Engine Compartment by CFD Analysis

    Microsoft Academic Search

    Masanori Dohi; Yoshifusa Sudou; Hideya Noguchi; Naoki Kamada

    1998-01-01

    Getting the information on the inlet airflow and volume through the\\u000d\\u000a\\u0009radiator was the important factor for the estimation of engine cooling\\u000d\\u000a\\u0009performance. Now we developed an improved method of calculation by\\u000d\\u000a\\u0009using STAR-CD, with improved fan modeling and a more precisely shaped\\u000d\\u000a\\u0009vehicle model which includes the cab, front grill, radiator and engine,\\u000d\\u000a\\u0009etc.. In this model, we can

  1. Characterizing buildings for airflow models: What should we measure?

    SciTech Connect

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

    2004-06-01

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

  2. 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).

  3. Effect of Airflow Limitation on Acute Exacerbations in Patients with Destroyed Lungs by Tuberculosis

    PubMed Central

    Lee, Jinwoo; Park, Young Sik; Lee, Chang-Hoon; Lee, Sang-Min; Yim, Jae-Joon; Kim, Young Whan; Han, Sung Koo

    2015-01-01

    History of treatment for tuberculosis (TB) is a risk factor for obstructive lung disease. However, it has been unclear whether the clinical characteristics of patients with destroyed lung by TB differ according to the presence or absence of airflow limitation. The objective of the study was to evaluate differences in acute exacerbations and forced expiratory volume in 1 second (FEV1) decline in patients with destroyed lung by TB according to the presence or absence of airflow limitation. We performed a retrospective cohort study and enrolled patients with destroyed lung by TB. The presence of airflow limitation was defined as FEV1/forced vital capacity (FVC) < 0.7. One hundred and fifty-nine patients were enrolled, and 128 (80.5%) had airflow limitation. The proportion of patients who experienced acute exacerbation was higher in patients with airflow limitation compared to those without (89.1 vs. 67.7%, respectively; P = 0.009). The rate of acute exacerbation was higher in patients with airflow limitation (IRR, 1.19; 95% CI, 1.11-1.27). Low body mass index (X vs. X + 1; HR, 0.944; 95% CI, 0.895-0.996) in addition to airflow limitation (HR, 1.634; 95% CI, 1.012-2.638), was an independent risk factor for acute exacerbation. The annual decline of FEV1 was 2 mL in patients with airflow limitation and 36 mL in those without (P < 0.001). In conclusion, the presence of airflow limitation is an independent risk factor for acute exacerbation in patients with the destroyed lung by TB. PMID:26028926

  4. Durability of hybrid laminar flow control (HLFC) surfaces

    Microsoft Academic Search

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

    2003-01-01

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

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

    Microsoft Academic Search

    M. H. Tuttle; D. V. Maddalon

    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.

  6. Flame/Wall interactions : laminar study of unburnt HC formation

    E-print Network

    Paris-Sud XI, Universit de

    Flame/Wall interactions : laminar study of unburnt HC formation M. Chauvy 1,2 , B. Delhom1 , J (HOQ) on a planar wall and in crevices, are considered. It is well known that they contribute is to use laminar flame simulations (LFS) to understand how the unburnt HC are produced near walls

  7. 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

  8. 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 12% of chord length on the upper surface10,000 times rougher than sailplane wings. Sailplanes depend on extreme wing smoothness to increase the area of laminar flow on the wing surface and minimize drag for extended glides. To understand why the swift does not rely on smooth wings, we used a stethoscope to map laminar flow over preserved wings in a low-turbulence wind tunnel. By combining laminar area, lift, and drag measurements, we show that average area of laminar flow on swift wings is 69% (n?=?3; std 13%) of their total area during glides that maximize flight distance and durationsimilar to high-performance sailplanes. Our aerodynamic analysis indicates that swifts attain laminar flow over their rough wings because their wing size is comparable to the distance the air travels (after a roughness-induced perturbation) before it transitions from laminar to turbulent. To interpret the function of swift wing roughness, we simulated its effect on smooth model wings using physical models. This manipulation shows that laminar flow is reduced and drag increased at high speeds. At the speeds at which swifts cruise, however, swift-like roughness prolongs laminar flow and reduces drag. This feature gives small birds with rudimentary wings an edge during the evolution of glide performance. PMID:24964089

  9. 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.

  10. 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.

  11. Study on the premixed laminar flames of iso-octane

    NASA Astrophysics Data System (ADS)

    Yang, Bo; Hong, Yan-ji; Xu, Qing-yao; Liu, Yi; Cheng, Qi-sheng; Ding, Xiao-yu

    2015-04-01

    Propagation characteristics of premixed laminar iso-octane flames at atmosphere and equivalence ratios from 0.8 to 1.4 are studied in a constant combustion bomb using a schlieren technique, the laminar burning velocity at different initial pressure, temperature, equivalence ratio are calculated through CHEMKIN program. The experimental and calculation results show that the laminar burning velocity of iso-octane rise with the decreasing of initial pressure and rise with the rising of initial temperature . Only changing the initial temperature or pressure ,the maximum laminar burning velocity of iso-octane were both obtained at equivalence ratio 1.1. Flame stability become weak ,when increased the equivalence ratio. The problem of the chemistry reaction mechanism to predict the laminar burning velocity were analysed.

  12. A coupled airflow and energy simulation program for indoor thermal environmental studies

    SciTech Connect

    Srebric, J.; Chen, Q.; Glicksman, L.R.

    2000-07-01

    Design of a thermally comfortable indoor environment requires detailed information about distribution of air velocity, air temperature, relative humidity, and mean radiant temperature and about the heating/cooling load in a space. This research has developed a coupled airflow and energy simulation program to calculate simultaneously the distributions of indoor airflow and thermal comfort and heating/cooling load. The coupled program can take the nonuniform distributions of indoor airflow and heating/cooling load into account. The program can also provide thermal and fluid boundary conditions normally needed for room airflow calculation. This paper demonstrates the program's capacity by applying the program to study the thermal environment in a house and an atrium. The coupled flow-and-energy program is recommended for the design of radiative, convective, and hybrid heating and cooling systems.

  13. 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...

  14. Airflow Simulation and Energy Analysis in Ventilated Room with a New Type of Air Conditioning

    E-print Network

    Liu, D.; Tang, G.; Zhao, F.

    2006-01-01

    Airflow simulation in one ventilated room with radiant heating and natural ventilation has been carried out. Three cases are compared: the closed room, the room with full openings, and the room with small openings. The radiator heating room...

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

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

  16. Control of low velocity airflow along a flat plate with a DC electrical discharge

    Microsoft Academic Search

    Luc Lger; Eric Moreau; Grard Touchard

    2001-01-01

    Ability of a DC electrical discharge to control low velocity airflow along a flat plate is analyzed. Specifically, the electrodes are flush mounted on the insulating surface of the plate creating a tangential corona discharge at close vicinity of the wall. In this paper, visualizations of the low velocity airflow (up to 1.4 m\\/s corresponding to Re=16,000) along the flat

  17. Topographic Steering of Alongshore Airflow over a Vegetated Foredune: Greenwich Dunes, Prince Edward Island, Canada

    Microsoft Academic Search

    Ian J. Walker; Patrick A. Hesp; Robin G. D. Davidson-Arnott; Jeff Ollerhead

    2006-01-01

    WALKER, I.J.; HESP, P.A.; DAVIDSON-ARNOTT, R.G.D., and OLLERHEAD, J., 2006. Topographic steering of along- shore airflow over a vegetated foredune: Greenwich Dunes, Prince Edward Island, Canada. Journal of Coastal Re- search, 22(5), 1278-1291. West Palm Beach (Florida), ISSN 0749-0208. High-frequency measurements of airflow from ultrasonic anemometers and time-averaged cup anemometer profiles were taken during an oblique alongshore sand-transporting event (6.7

  18. Airflow Characteristics of Direct-Type Kitchen Hood Systems in High-Rise Apartment Buildings

    E-print Network

    Park, M.

    2011-01-01

    Airflow characteristics of direct-type kitchen hood systems in high-rise apartment buildings 1 10.19. 2011 Myungsig Park* , Joseph Jun Kim Innovations Optima LLC Bonggil Jeon Dept of Architectural Engineering, Purdue University Geontae Lee... if the adoption of direct- type systems alone in place of the shared-type would yield the level of capture efficiency close to the hood design specification. 3 4 5 6 Figure 1: Layout of apartment used to analyze airflow 7 (a)?24?hour...

  19. Numerical study of the air-flow in an oscillating water column wave energy converter

    Microsoft Academic Search

    J. M. Paixo Conde; L. M. C. Gato

    2008-01-01

    The paper presents a numerical study of the air-flow in a typical pneumatic chamber geometry of an oscillating water column (OWC)-type wave energy converter (WEC), equipped with two vertical-axis air turbines, asymmetrically placed on the top of the chamber. Outwards and inwards, steady and periodic, air-flow calculations were performed to investigate the flow distribution at the turbines inlet sections, as

  20. Investigation on airflows in abnormal nasal cavity with adenoid vegetation by particle image velocimetry

    Microsoft Academic Search

    Sung Kyun Kim; Young Rak Son

    2004-01-01

    Knowledge of airflow characteristics in nasal cavity is essential to understand the physiological and pathological aspects\\u000a of nasal breathing. Several studies have utilizedphysical models of the healthy nasal cavity to investigate the relationship\\u000a between nasal anatomy and airflow. Since the final goal of these works is their contribution to the diagnosisand treatment\\u000a of nasal diseases, the next step on this

  1. Effect of a DC corona electrical discharge on the airflow along a flat plate

    Microsoft Academic Search

    Luc Lger; Eric Moreau; Grard G. Touchard

    2002-01-01

    Ability of a DC electrical discharge to control low-velocity airflow along a flat plate is analyzed. Specifically, the electrodes are flush mounted on the insulating surface of the plate creating a tangential corona discharge at close vicinity of the wall. In this paper, visualizations of the low-velocity airflow (up to 1.4 m\\/s corresponding to Re=16 000) along the flat plate

  2. 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.

  3. Progress in natural laminar flow research

    NASA Technical Reports Server (NTRS)

    Holmes, B. J.

    1984-01-01

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

  4. Progress in natural laminar flow research

    NASA Astrophysics Data System (ADS)

    Holmes, B. J.

    1984-07-01

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

  5. 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.

  6. 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.

  7. 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.

  8. Two-dimensional stability of laminar flames

    NASA Technical Reports Server (NTRS)

    Mukunda, H. S.; Drummond, J. Philip

    1992-01-01

    The stability of laminar flames was studied numerically and the dependence of stability on finite rate chemistry with low activation energy and variable thermodynamic and transport properties was addressed. The calculations show that activation energy and details of chemistry play a minor role in altering the linear neutral stability results from asymptotic analysis. Variable specific heat makes a marginal change to the stability; variable transport properties, on the other hand, tend to substantially enhance the stability from a critical wave number of about 0.50 to 0.20. Also, the effects of variable properties tend to nullify the effects of nonunity Lewis number. When the Lewis number of a single species is different from unity, as is true in a hydrogen-air premixed flame, the stability results remain close to that of unity Lewis number.

  9. 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

  10. Inductively coupled plasma torch with laminar flow cooling

    DOEpatents

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

    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.

  11. 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 ?W and the open-circuit output voltage was from 0.5 V to 1.32 V.

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

    NASA Astrophysics Data System (ADS)

    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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Modeling of NOx formation in circular laminar jet flames

    E-print Network

    Siwatch, Vivek

    2007-04-25

    Emissions of oxides of nitrogen (NOx) from combustion devices is a topic of tremendous current importance. The bulk of the review of NOx emissions has been in the field of turbulent jet flames. However laminar jet flames ...

  19. 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.

  20. 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.

  1. Laminar flow integration: Flight tests status and plans

    Microsoft Academic Search

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

    1986-01-01

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

  2. 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.

  3. Prediction of laminar flame properties of propane-air mixtures

    Microsoft Academic Search

    C. K. Westbrook; W. J. Pitz

    1983-01-01

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

  4. Prediction of laminar flame properties of propane-air mixtures

    Microsoft Academic Search

    C. K. Westbrook; W. J. Pitz

    1985-01-01

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

  5. Airflow limitation by the Global Lungs Initiative equations in a cohort of very old adults.

    PubMed

    Turkeshi, Eralda; Vaes, Bert; Andreeva, Elena; Mathe, Catharina; Adriaensen, Wim; Van Pottelbergh, Gijs; Degryse, Jean-Marie

    2015-07-01

    The cut-off for forced expiratory volume in 1?s (FEV1)/forced vital capacity (FVC) defining airflow limitation for chronic obstructive pulmonary disease (COPD) is still contested. We assessed airflow limitation prevalence by the lower limit of normal (LLN) of Global Lungs Initiative (GLI) 2012 reference values and its predictive ability for all-cause mortality and hospitalisation in very old adults (aged ?80?years) compared with the fixed cut-off.In a Belgian population-based prospective cohort of 411 very old adults, airflow limitation prevalence by the 5th percentile of GLI 2012 z-scores (GLI-LLN) and fixed cut-off (0.70) were compared with COPD reported by general practitioners (GPs). Survival and Cox regression multivariable analysis assessed the association of airflow limitation by both cut-offs with 5-year all-cause mortality and first hospitalisation at 3?years.9.2% had airflow limitation by GLI-LLN and 27% by fixed cut-off, without good agreement (kappa coefficient ?0.40) with GP-reported COPD (9%). Only airflow limitation by GLI-LLN was independently associated with mortality (adjusted hazard ratio 2.10, 95% CI 1.30-3.38). FEV1/FVC <0.70 but ?GLI-LLN (17.8%) had no significantly higher risk for mortality or hospitalisation.In a cohort of very old adults, airflow limitation by GLI-LLN has lower prevalence than by fixed cut-off, independently predicts all-cause mortality and does not miss individuals with significantly higher all-cause mortality and hospitalisation. PMID:25882799

  6. Coupled thermal-fluid-structure behavior of airflow over target irradiated by high-power laser

    NASA Astrophysics Data System (ADS)

    Huang, Yihui; Song, Hongwei; Huang, Chenguang

    2013-05-01

    In this paper, a coupled thermal-fluid-structure numerical model is presented to investigate interactive effects of supersonic airflow, high power laser and metallic target. The numerical model is validated by experiments recently carried out by Lawrence Livermore National Laboratory. The numerical simulation also verified some experimental observations, which show that the convective heat transfer effects of airflow and the aerodynamic pressure play important roles to the damage behavior of laser irradiated target. The convective heat transfer of airflow reduces the temperature of laser irradiated area therefore delays the time reaching damage. When a thin-walled metallic panel is heated up to a high temperature below the melting point, it is softened and the strength nearly vanishes, the aerodynamic pressure becomes a dominant factor that controls the damage pattern even when it is in a low magnitude. The effects of airflow velocity and laser power on the damage behavior of irradiated metallic target are investigated with the aid of the coupled thermal-fluid-structure numerical model, where critical irradiation times to reach the yield failure t yield and melting failure t yield are the main concern. Results show that, when the incidence laser power increases from 500 W/cm2 to 5000 W/cm2, significant drop in failure times are found as the incidence laser power increases. When the Mach number of airflow increases from 1.2 to 4.0 at a given incident laser power, a critical airflow velocity is found for the irradiation time to reach the yield strength and melting point, i.e., the maximum irradiation time to reach failure is found at the Mach 1.8~2.0. The competition of aerodynamic heating before the laser is switch on and airflow cooling after the target is heated up accounts for effects.

  7. 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.

  8. 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.

  9. Feasibility study of laminar flow bodies in fully turbulent flow

    SciTech Connect

    Sarkar, T.; Sayer, P.G.; Fraser, S.M. [Univ. of Strathclyde, Glasgow (United Kingdom)

    1994-12-31

    One of the most important design requirements of long range autonomous underwater vehicles (AUVs) is to minimize propulsive power. An important and relatively easy way of achieving this is by careful selection of hull shape. Two main schools of thought in this respect are: if laminar flow can be maintained for a long length of the body, the effective drag can be reduced; it is not possible to maintain laminar flow for a significant length of the body and hull design should be based on turbulent flow conditions. In this paper, a feasibility study of laminar flow designs is undertaken under the assumption that flow will be turbulent over the entire length. For comparison two laminar flow designs X-35 and F-57 are selected and results are compared with those of two typical torpedo shaped bodies, namely AFTERBODY1 and AFTERBODY2 of DTNSRDC. It has been shown that laminar flow bodies have 10--15% higher drag when flow is turbulent over the entire length. Hence there is some hydrodynamic risk involved in adopting such laminar bodies without further consideration.

  10. Detection of organized airflow in the atmospheric boundary layer and the free atmosphere using a 3D-scanning coherent Doppler lidar

    NASA Astrophysics Data System (ADS)

    Fujiyoshi, Y.; Yamashita, K.; Fujiwara, C.

    2009-07-01

    We will overview organized airflows, turbulent and laminar structures in the atmospheric boundary layer and the free atmosphere newly detected by a 3D-scanning coherent Doppler lidar system (3D-CDL). Study of clouds becomes important especially in recent years, since they play an essential role in global climate systems and the earth environment. The aerosol-cloud interaction is not enough to evaluate aerosol indirect effect. Air-motion is the key factor that connects aerosols and clouds especially in the atmospheric boundary layer. Using the 3D-CDL, we detected such various kinds of atmospheric phenomena as plume, streaks, invisible dust-devils, fog, fire-work, local front, downburst, wake of buildings, gravity waves, Kelvin-Helmholtz instability waves, sea-breeze fronts, fine-weather cumulus, low-level stratus, mid-level clouds, mammatus clouds and cirrus clouds etc. Some of these phenomena are firstly observed by the 3D-CDL. We simulated some phenomena by using a Large Eddy Simulation (LES) model and compared the simulated structures with those observed by the 3D-CDL.

  11. 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.

  12. Regulatory mechanisms of cortical laminar development.

    PubMed

    Casanova, Manuel F; Trippe, Juan

    2006-06-01

    The developing forebrain exhibits a high degree of spatiotemporal regulation of proliferation and cell cycle exit in progenitor cells of its proliferative zones. This results in the balanced deployment of progenitors between asymmetric division, yielding postmitotic neurons and cycling progenitors, and terminal symmetric division, resulting in differentiated daughter cells. Radial glia have been demonstrated to be the principal neuronal progenitor of the cortical primordium. Lineage tracing studies employing real-time imaging in vivo have enhanced understanding of neuronal production and migration. Cortical projection neurons have been shown to arise from the radial migration of precursors generated in the dorsal telencephalon, whereas most interneurons derive from the germinal zone of the ventral telencephalon and migrate tangentially into the primordial cortex. Cells from both populations undergo diverse and complex sequences of migratory activity. Neuronal phenotypic potential is informed in progenitors prior to their last cell division. Laminar and regional fate potential of progenitors becomes progressively restricted with successive cell cycles. This process of neuronal fate specification is regulated by the interaction of programs of transcriptional regulation with extrinsic patterning signals according to time and region of the proliferative zone in which the final mitotic cycle occurs. PMID:16359732

  13. Incipient particle motion in laminar shear flows

    NASA Astrophysics Data System (ADS)

    Rodrguez Agudo, Jos Alberto; Wierschem, Andreas

    2013-04-01

    We study experimentally the critical conditions for incipient motion of spherical particles deposited on a regular substrate under laminar flow conditions. The substrates consist of a monolayer of wall-fixed spheres uniformly sized and regularly arranged in triangular and quadratic configurations. To highlight the effects of exposure, the distance between the substrate spheres is varied in the quadratic arrangement. We found that for particle Reynolds numbers of order one and smaller, the critical Shields parameter is independent from the particle density and from the particle Reynolds numbers but it depends significantly on the geometry of the substrate. We show how different geometrical parameters like the particle arrangement and exposure affect the critical Shields parameter. We particularly focus on the effect of neighboring particles on the onset of particle motion. Unlike single rolling particles, we observe switching between rolling and sliding motion as a consequence of friction between the moving neighbors. In our experiments, this two-particle interaction is the basic difference between the incipient motion of a single and multiple particles, resulting in a significant increment of the critical Shields number.

  14. 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 facilities, cannot involve soot emitting flames in order to ensure that test chamber windows used for experimental observations are not blocked by soot deposits, thereby compromising unusually valuable experimental results. Another important motivation to define conditions where soot is present in diffusion flames is that flame chemistry, transport and radiation properties are vastly simplified when soot is absent, making such flames far more tractable for detailed numerical simulations than corresponding soot-containing flames. Motivated by these observations, the objectives of this phase of the investigation were as follows: (1) Observe flame-sheet shapes (the location of the reaction zone near phi=1) of nonluminous (soot free) laminar jet diffusion flames in both still and coflowing air and use these results to develop simplified models of flame-sheet shapes for these conditions; (2) Observe luminous flame boundaries of luminous (soot-containing) laminar jet diffusion flames in both still and coflowing air and use these results to develop simplified models of luminous flame boundaries for these conditions. In order to fix ideas here, maximum luminous flame boundaries at the laminar smoke point conditions were sought, i.e., luminous flame boundaries at the laminar smoke point; (3) Observe effects of coflow on laminar soot- and smoke-point conditions because coflow has been proposed as a means to control soot emissions and minimize the presence of soot in diffusion flames.

  15. Gosselin, J.R. and Chen, Q. 2008. "A computational method for calculating heat transfer and airflow through a dual airflow window," Energy and Buildings, 40(4), 452-458.

    E-print Network

    Chen, Qingyan "Yan"

    indoor air quality in residential buildings. Existing airflow windows use a single airflow path sustainable design concepts that can improve indoor air quality while conserving energy in buildings (http windows are not as complicated as ventilated facades, but could improve indoor air quality, enhance

  16. 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.

  17. Severe airflow obstruction in a patient with ulcerative colitis and toxic epidermal necrolysis: A case report

    PubMed Central

    TAGUCHI, SHIJIMA; FURUTA, JUNICHI; OHARA, GEN; KAGOHASHI, KATSUNORI; SATOH, HIROAKI

    2015-01-01

    Bronchiolitis is a rare condition mainly affecting the intralobular conducting and transitional small airways. The present study describes a case of severe airflow limitation in a patient with ulcerative colitis who developed toxic epidermal necrolysis following mesalazine therapy. Forced expiratory volume in one second was decreased and a flow-volume curve showed airflow limitation, but the single-breath diffusing capacity of the lung for carbon monoxide (DLCO) and DLCO divided by alveolar volume (DLCO/VA) were not decreased. This rare clinical condition should be considered as a differential diagnosis for subjects presenting with sub-acutely developed airflow obstruction if the findings in chest computed tomography scans demonstrate hyperinflation but few low-attenuation areas. Relatively well-preserved DLCO and DLCO/VA provide a clue to establishing the correct diagnosis. PMID:26136919

  18. Measurements of the viscous tangential stress in the airflow above wind waves

    NASA Astrophysics Data System (ADS)

    Veron, F.; Saxena, G.; Misra, S. K.

    2007-10-01

    The stress and drag at the surface of the ocean are crucial parameters for both short term forecasting and the modeling of long-term global climate trends. However, the partition between viscous, turbulent, and wave stresses, and in particular the effects of airflow separation are not well understood. We present direct measurements of the velocity in the airflow above wind-generated waves. We observe intermittent separation of the viscous sublayer past the crest of the wind waves leading to dramatic along-wave variability in the surface viscous tangential stress. These results hold for wind speeds that would normally be considered low to moderate. These viscous stress measurements in the airflow above the wavy surface, and within the separated region are, to the best of the authors' knowledge, the first of this kind.

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

    PubMed

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

    2003-08-13

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

  20. 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.

  1. Acoustics of laminar boundary layers breakdown

    NASA Astrophysics Data System (ADS)

    Wang, Meng

    1994-12-01

    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.

  2. 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

  3. Tide-induced airflow in a two-layered coastal land with atmospheric pressure fluctuations

    NASA Astrophysics Data System (ADS)

    Li, Jian; Zhan, Hongbin; Huang, Guanhua; You, Kehua

    2011-05-01

    Tide-induced airflow is commonly seen in coastal lands and affects ground stability especially with a less permeable pavement on the ground surface. A tide-induced airflow model in a two-layered unsaturated zone consisting of a highly permeable layer underneath a less permeable layer was established by Li and Jiao [Li HL, JJ Jiao. One-dimensional airflow in unsaturated zone induced by periodic water table fluctuation. Water Resour Res 2005;41:W04007. doi:10.1029/2004WR003916] to describe the one-dimensional airflow with constant atmospheric pressure at the ground surface. In this study, we expand the Li and Jiao model by considering the realistic atmospheric pressure fluctuations and the initial condition. A new transient solution to the airflow model is developed for an initial boundary value problem (IBVP). The transient solution can be used not only to calculate the subsurface air pressure at a future time with a known initial condition, but also to evaluate the asymptotic air pressure variations when time becomes long. The amplitude ratio and phase lag of the subsurface air pressure relative to the tide-induced hydraulic head variations inside the unconfined aquifer below the unsaturated zone are investigated. The results reveal that effect on the subsurface pressure due to changes of atmospheric pressure amplitude depends on the configurations of air resistance in the less permeable layer and the air-filled porosity difference in the two layers. The introduction of atmospheric pressure fluctuations into the airflow model leads to insignificant influence on water table level. A field application of the new solution at Hong Kong International Airport in Hong Kong, China is demonstrated. It indicates that the new transient solution can be conveniently used to evaluate the subsurface air pressure with discrete atmospheric pressure data at the ground surface.

  4. Use of swirling airflow to enhance coating performance of bottom spray fluid bed coaters.

    PubMed

    Heng, P W S; Chan, L W; Tang, E S K

    2006-12-11

    As there is strong interest in coating increasingly smaller particles or pellets for use in compacted dosage forms, there is a need for better small particle coating systems. This study explored the use of swirling airflow to enhance the performance of the bottom spray coating system. Firstly, pellet coating in the non-swirling airflow of conventional Wurster coating was compared with that of swirling airflow in precision coating under standardized conditions. Secondly, precision coating was studied in greater details at different airflow rates (60-100m(3)/h) and partition gaps (6-22mm). Precision coating was found to have higher Reynolds numbers (Re) than Wurster coating, indicating higher turbulence. It produced coated pellets of better properties than Wurster coating, having less agglomeration and gross surface defects, more uniform coats, increased flow and tapped density, and slower drug release. Higher surface roughness did not affect the yield. In precision coating, increasing airflow rates decreased the degree of agglomeration but had minimal effect on pellet quality attributes (colour intensity, colour uniformity and surface roughness) and yields. Increasing partition gaps increased the degree of agglomeration proportionally, but this effect was small. However, greater changes in yield, surface roughness, colour intensity and colour uniformity were detected. This study showed that precision coating, while having a higher drying ability, was able to maintain the same yield and produce coated pellets with superior quality compared to Wurster coating. In precision coating, airflow rate had greater influence on the drying of pellets while partition gap had greater influence on pellet quality attributes. PMID:16920294

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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).

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

    Microsoft Academic Search

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

    2009-01-01

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

  11. Laminar diffusion flamelet models in non-premixed turbulent combustion

    Microsoft Academic Search

    N. Peters

    1984-01-01

    The laminar flamelet concept views a turbulent diffusion flame as\\u000d\\u000a\\u0009an ensemble of laminar diffusion flamelets. Work relevant to the\\u000d\\u000a\\u0009flamelet concept is spread over various fields in the literature:\\u000d\\u000a\\u0009laminar flame studies, asymptotic analysis, theory of turbulence\\u000d\\u000a\\u0009and percolation theory. This review tries to gather and integrate\\u000d\\u000a\\u0009this material in order to derive a self-consistent formulation. Under\\u000d\\u000a\\u0009the assumption

  12. Design of a hybrid laminar flow control nacelle

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    Consideration is given to the potential application of hybrid-laminar-flow control to the external surface of a modern, high-bypass-ratio (HBR) turbofan engine nacelle. With the advent of advanced ultra-HBR fans (with bypass ratios of 10-15), the wetted areas of these nacelles approach 10 percent of the total wetted area of future commercial transports. A hybrid-laminar-flow-control pressure distribution is specified and the corresponding nacelle geometry is computed utilizing a predictor/corrector design method. Linear stability calculations are conducted to provide predictions of the extent of the laminar boundary layer. Performance studies on an advanced twin-engine transport configuration are presented to determine potential benefits in terms of reduced fuel consumption.

  13. CFD Investigations of a Transonic Swept-Wing Laminar Flow Control Flight Experiment

    E-print Network

    Neale, Tyler P.

    2011-08-08

    Laminar flow control has been studied for several decades in an effort to achieve higher efficiencies for aircraft. Successful implementation of laminar flow control technology on transport aircraft could significantly ...

  14. Interactions between Soot and CH* in a Laminar Boundary Layer Type Diffusion Flame in Microgravity

    E-print Network

    Fuentes, Andres; Legros, Guillaume; Claverie, Alain; Joulain, Pierre; Vantelon, Jean-Pierre; Torero, Jose L

    A three-dimensional laminar non-buoyant diffusion flame was studied with the objective of improving the understanding of the soot production. The flame originated from a porous ethylene burner discharging into a laminar ...

  15. 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.

  16. Roughness and waviness requirements for laminar flow surfaces

    NASA Astrophysics Data System (ADS)

    Obara, Clifford J.; Holmes, Bruce J.

    1986-12-01

    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.

  17. Laminar and intermittent flow in a tilted heat pipe.

    PubMed

    Rusaouen, E; Riedinger, X; Tisserand, J-C; Seychelles, F; Salort, J; Castaing, B; Chill, F

    2014-01-01

    Heat transfer measurements performed by Riedinger et al. (Phys. Fluids, 25, 015117 (2013)) showed that in an inclined channel, heated from below and cooled from above with adiabatic walls, the flow is laminar or intermittent (local bursts can occur in the laminar flow) when the inclination angle is sufficiently high and the applied power sufficiently low. In this case, gravity plays a crucial role in the characteristics of the flow. In this paper, we present velocity measurements, and their derived tensors, obtained with Particle Image Velocimetry inside the channel. We, also, propose a model derived from a jet interpretation of the flow. Comparison between experiment and model shows a fair agreement. PMID:24464137

  18. 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.

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

    Microsoft Academic Search

    Pieter Verboven; Nico Scheerlinck; Josse De Baerdemaeker

    2000-01-01

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

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

    Microsoft Academic Search

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

    2003-01-01

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

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

    PubMed

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

    2007-02-01

    Microencapsulation of genetically engineered cells has attracted much attention as an alternative nonviral strategy to gene therapy. Though smaller microcapsules (i.e. less than 300 microm) theoretically have various advantages, technical limitations made it difficult to prove this notion. We have developed a novel microfabricated device, namely a micro-airflow-nozzle (MAN), to produce 100 to 300 microm alginate microcapsules with a narrow size distribution. The MAN is composed of a nozzle with a 60 microm internal diameter for an alginate solution channel and airflow channels next to the nozzle. An alginate solution extruded through the nozzle was sheared by the airflow. The resulting alginate droplets fell directly into a CaCl2 solution, and calcium alginate beads were formed. The device enabled us to successfully encapsulate living cells into 150 microm microcapsules, as well as control microcapsule size by simply changing the airflow rate. The encapsulated cells had a higher growth rate and greater secretion activity of marker protein in 150 microm microcapsules compared to larger microcapsules prepared by conventional methods because of their high diffusion efficiency and effective scaffold surface area. The advantages of smaller microcapsules offer new prospects for the advancement of microencapsulation technology. PMID:17106639

  2. Influence of a DC corona discharge on the airflow along an inclined flat plate

    Microsoft Academic Search

    Luc Lger; Eric Moreau; Guillermo Artana; Grard Touchard

    2001-01-01

    Visualizations and measurements by Particle Imaging Velocimetry are conducted in a wind tunnel in order to determine the influence of a DC corona discharge established between a wire and a plate collecting electrode on the properties of an airflow around a flat plate. Results show that the kinetic energy induced by the ionic wind inside the boundary layer allows a

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

    E-print Network

    Li, C.; Li, N.

    2006-01-01

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

  4. Engineering report for the K3 ventilation system volumetric airflow reduction

    SciTech Connect

    Arndt, T.E., Fluor Daniel Hanford

    1997-03-26

    This engineering report will discuss the ventilation tasks necessary for minimizing the current K3 ventilation systems volumetric airflows while continuing to maintain negative pressures in both the canyon area and the related hot cells, assuring radiological confinement and containment of WESF.

  5. 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.

  6. A study of characteristics of disk vibration and rotating airflow in magneto optical disk drives

    Microsoft Academic Search

    Sookyung Kim; Gyuhyeon Han; Heuigi Son

    1998-01-01

    A study on the dynamic characteristics of rotating disks in magneto optical disk drives is presented. The natural frequencies of the rotating disks are investigated experimentally and numerically. The frequency response and critical speeds of the advanced storage magneto optical (ASMO) disk are discussed. The characteristics of airflow around the disk and their effects on the disk vibrations are also

  7. Computation of the airflow in a pilot scale clean room using K- ? turbulence models

    Microsoft Academic Search

    Olivier Rouaud; Michel Havet

    2002-01-01

    This work deals with the assessment of the airflow in a food-processing clean room. The flow pattern inside the working area of a pilot scale clean room was numerically investigated using a computational fluid dynamics code based on a finite volume formulation. Two versions of the k-? turbulence model were tested: the standard and the RNG version. The analysis of

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

    Microsoft Academic Search

    R. F Slocombe

    1997-01-01

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

  9. CFD Simulation of Airflow in a 17Generation Digital Reference Model of the Human Bronchial Tree

    Microsoft Academic Search

    T. Gemci; V. Ponyavina; Y. Chen; H. Chen; R. Collins

    Computational fluid dynamics (CFD) studies of airflow in a digital reference model of the 17-generation airway (bronchial tree) were accomplished using the FLUENT computational code. The computational mesh was based on the anatomical graph data of a digital reference model by Schmidt et al. (2004) derived from High-Resolution Computer Tomography (HRCT) imaging of an in vitro preparation in which specially

  10. The effect of face resistance on airflow characteristics along a twin development heading

    Microsoft Academic Search

    K. G. Wallace; F. N. Kissell; M. J. Mc Pherson

    1984-01-01

    The effect of face resistance on ventilation air leakage through stoppings was measured in a twin development heading. Face resistance was varied by alternately tightening or loosening the face line brattice to change the line brattice leakage. Results indicated that tight brattice lines are necessary to maintain acceptable airflow at the face but result in higher leakage throughout the entire

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

    Microsoft Academic Search

    Kuang-Yuh Huang; Chien-Tai Huang

    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

  12. THE EFFECT OF FLOOR OPEN AREA ON AIRFLOW DISTRIBUTION IN PEANUT DRYING TRAILERS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Peanut curing wagons have typically been constructed using perforated metal floor with 23% open area (O.A.). Recent designs for larger peanut drying trailers have used perforated metal with 40% O.A. However, no data has been collected to determine the effect of the different O.A. on total airflow ...

  13. Numerical Simulation and Experimental Study on Airflow Characteristics in the Plenum of Underfloor Air Supply

    E-print Network

    Li, X.; Li, N.; Fang, F.; Zhao, D.

    2006-01-01

    Energy-efficient and cost-effective space conditioning in offices and other commercial buildings usually use the underfloor space for the supply air static-pressure plenum. The airflow in a plenum of the underfloor air supply was simulated by a...

  14. Airflow induced by pumping tests in unconfined aquifer with a low-permeability cap

    Microsoft Academic Search

    Jiu Jimmy Jiao; Haipeng Guo

    2009-01-01

    Most analytical and numerical models developed to analyze pumping test data focus on saturated flow below the water table. Traditionally the soil above the initial water table prior to pumping has been thought to have little influence on the test results and has usually been ignored. It is hypothesized that, if the unsaturated zone is capped by low-permeability soil, airflow

  15. A CFD modeling system for airflow and heat transfer in ventilated packaging for fresh foods

    Microsoft Academic Search

    Qian Zou; Linus U. Opara; Robert McKibbin

    2006-01-01

    In the previous paper (Part I) of this series, mathematical models of airflow and heat transfer inside ventilated packaging systems were developed and presented based on the porous media approach. In the present paper (Part II), we describe the CFD methods used to solve the mathematical models for both layered and bulk packaging systems, and the structure of a user-friendly

  16. MICROSCALE AIRFLOW MODELLING USING THE IMMERSED BOUNDARY METHOD AND IMPLICIT LES

    Microsoft Academic Search

    Vladimr Fuka; Josef Brechler

    2007-01-01

    This contribution shows some results when the implicit large eddy simulation (ILES) methodology was used and tested in the 2D model of air-flow around an obstacle. The obstacle is a square cylinder of the infinite length. This geometry enables to use the 2D approach that considerably speeds up the computation. Obtained results have been compared with other results of laboratory

  17. Turbine Air-Flow Test Rig CFD Results for Test Matrix

    NASA Technical Reports Server (NTRS)

    Wilson, Josh

    2003-01-01

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

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

    E-print Network

    Hearst, Marti

    Improving Aviation Safety with Information Visualization: Airflow Hazard Display for Helicopter-Chair Professor Ruzena Bajcsy Professor Paul Wright Fall 2004 #12;Abstract Improving Aviation Safety advances in aviation sensor technology offer the potential for aircraft- based sensors that can gather

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

    SciTech Connect

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

    2007-09-15

    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.

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

    Microsoft Academic Search

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

    2000-01-01

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

  1. PHYSICAL MODELING OF AIRFLOW-WALLS INTERACTIONS TO UNDERSTAND THE SLEEP APNEA SYNDROME

    E-print Network

    Boyer, Edmond

    Cedex, France. 1. ABSTRACT Sleep Apnea Syndrome (SAS) is defined as a partial or total closurePHYSICAL MODELING OF AIRFLOW-WALLS INTERACTIONS TO UNDERSTAND THE SLEEP APNEA SYNDROME Y. Payan1 of the patient upper airways during sleep. The term "collapsus" (or collapse) is used to describe this closure

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

    E-print Network

    Payan, Yohan

    , France {pelorson,perrier}@icp.inpg.fr Abstract. Sleep Apnea Syndrome (SAS) is defined as a partialPhysical Modeling of Airflow-Walls Interactions to Understand the Sleep Apnea Syndrome Yohan Payan1 or total closure of the patient upper airways during sleep. The term "collapsus" (or collapse) is used

  3. Validation of GCM control simulations using indices of daily airflow types over the British Isles

    Microsoft Academic Search

    M Hulme; K R Briffal; P D Jones; C A Senior

    1993-01-01

    In this study, the control simulations of two general circulation model (GCM) experiments are assessed in terms of their ability to reproduce realistic real world weather. The models examined are the UK Meteorological Office high-resolution atmospheric model (UKHI) and a coupled ocean\\/atmosphere model of the Max Planck Institut fr Meteorologic, Hamburg (MPI). An objective classification of daily airflow patterns over

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

    Microsoft Academic Search

    Maxime Forte; Luc Leger; Jrme Pons; Eric Moreau; Grard Touchard

    2005-01-01

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

  5. 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...

  6. Strongly coupled interaction between a ridge of fluid and an external airflow

    E-print Network

    of water that forms on the inside surface of a steam-generating boiler pipe (through which both gas to an external airflow include air-knife and spin-coating processes in industry (see, for example, Chou and Wu [5

  7. Direct numerical simulation of `short' laminar separation bubbles with turbulent reattachment

    Microsoft Academic Search

    M. Alam; N. D. Sandham

    2000-01-01

    Direct numerical simulation of the incompressible Navier Stokes equations is used to study flows where laminar boundary-layer separation is followed by turbulent reattachment forming a closed region known as a laminar separation bubble. In the simulations a laminar boundary layer is forced to separate by the action of a suction profile applied as the upper boundary condition. The separated shear

  8. Direct numerical simulation of 'short' laminar separation bubbles with turbulent reattachmenty

    Microsoft Academic Search

    M. A LAM; N. D. S ANDHAM

    2000-01-01

    Direct numerical simulation of the incompressible Navier{Stokes equations is used to study flows where laminar boundary-layer separation is followed by turbulent reattachment forming a closed region known as a laminar separation bubble. In the simulations a laminar boundary layer is forced to separate by the action of a suction prole applied as the upper boundary condition. The separated shear layer

  9. 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 gave clear indications of the best design choices in producing the hazard visual cues.

  10. 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

  11. Numerical studies of heat transfer enhancements in laminar separated flows

    E-print Network

    Chung, Yongmann M.

    heat transfer enhancements in grooved channel and sharp 180 bend flows of especial relevanceNumerical studies of heat transfer enhancements in laminar separated flows Yongmann M. Chung not always be valid over a significant system extent. For the bend flow, heat transfer enhancements due

  12. Current-driven instabilities in a laminar perpendicular shock

    Microsoft Academic Search

    Don S. Lemons; S. Peter Gary

    1978-01-01

    The linear theory of fully electromagnetic plasma instabilities driven by currents flowing across a magnetic field is investigated, with applications to the laminar perpendicular bow shock. The theory utilizes the local approximation, assumes unmagnetized ions and magnetized electrons, and includes the effects of gradients in the magnetic field magnitude and density. Oblique propagation is considered, and wave numbers may be

  13. Simple laminar dynamos: from two rolls to one

    Microsoft Academic Search

    David Moss

    2008-01-01

    The study of laminar flows with simple streamlines in conducting fluids that might support kinematic dynamo action has a long history. Early successful examples include the Gailitis (1970) dynamo, which has two meridional rolls. We show here that a single meridional roll, considered as a limit of a modified Gailitis-like dynamo, can also support kinematic dynamo action in a deep

  14. TURBULENT-LAMINAR PATTERNS IN PLANE COUETTE Dwight Barkley

    E-print Network

    Barkley, Dwight

    a sig- nificant history in fluid dynamics. In the mid 1960's Coles and van Atta [Coles, 1965, van Atta@limsi.fr Abstract Regular patterns of turbulent and laminar fluid motion arise in plane Couette flow near the lowest computational domains are of minimal size in only two directions. The third direction is taken to be large

  15. Supersonic laminar flow development in a square duct

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  16. Model of Transition from Laminar to Turbulent Flow

    Microsoft Academic Search

    Hidesada Kanda

    2001-01-01

    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

  17. Numerical Aerodynamic Optimization Incorporating Laminar-Turbulent Transition Prediction

    E-print Network

    Zingg, David W.

    Numerical Aerodynamic Optimization Incorporating Laminar-Turbulent Transition Prediction J. Driver-dimensional NewtonKrylov aerodynamic shape optimization algorithm is applied to several optimization problems a striking demonstration of the capability of the Newton Krylov aerodynamic optimization algorithm to design

  18. 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.

  19. NONLINEAR ITERATION METHODS FOR HIGH SPEED LAMINAR COMPRESSIBLE

    E-print Network

    Waterloo, University of

    NONLINEAR ITERATION METHODS FOR HIGH SPEED LAMINAR COMPRESSIBLE NAVIERSTOKES EQUATIONS P correction approach (first order Jacobian, second order residual) for solving the steady state compressible in solving the full Newton Jacobian using an ILU(2) (' 100; 000 unknowns) with CGSTAB acceleration. Keywords

  20. 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.

  1. Sensitivity analysis of transfer functions of laminar flames

    Microsoft Academic Search

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

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

  2. 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.

  3. The stability of the flow in a laminar separation bubble

    Microsoft Academic Search

    Tai Ran Niew

    1993-01-01

    This dissertation reports a study into the underlying concepts used to analyze incompressible laminar separation bubbles. The suggestion that absolute instability could play a role in bubble flows was further developed, and was the focal point of this project. From a review of previous work and preliminary experiments on a backward faxing step, it was suggested that for some bubbles

  4. Laminar epidermal hyperplasia and hyperkeratosis in an equine hoof.

    PubMed

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

    2013-09-01

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

  5. Laminar epidermal hyperplasia and hyperkeratosis in an equine hoof

    PubMed Central

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

    2013-01-01

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

  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. 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.

  8. 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.

  9. 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.

  10. Numerical investigation of the tone noise mechanism over laminar airfoils

    Microsoft Academic Search

    G. Desquesnes; M. Terracol; P. Sagaut

    2007-01-01

    This paper presents the first numerical investigation via direct numerical simulation of the tone noise phenomenon occurring in the flow past laminar airfoils. This phenomenon corresponds to the radiation of discrete acoustic tones in some specific flow conditions, and has received much attention since the 1970s, and several experimental studies have been carried out to identify and understand the underlying

  11. Structure of the quasi-perpendicular laminar bow shock

    Microsoft Academic Search

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

    1975-01-01

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

  12. Optimization of ice making in laminar falling films

    Microsoft Academic Search

    Andr Cliche; Marcel Lacroix

    2006-01-01

    A mathematical model for the optimization of ice making in a laminar falling film is presented. The model is first validated, and a series of numerical experiments are conducted to assess the effects of the mass flow rate, the inlet water temperature and the length and temperature of the cold plate on ice accumulation. The results are then correlated in

  13. 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.

  14. LAMINAR BURNING VELOCITY OF GASOLINES WITH ADDITION OF ETHANOL

    E-print Network

    Boyer, Edmond

    1 LAMINAR BURNING VELOCITY OF GASOLINES WITH ADDITION OF ETHANOL P. Dirrenberger1 , P.A. Glaude*1 WITH ADDITION OF ETHANOL P. Dirrenberger1 , P.A. Glaude*1 , R. Bounaceur1 , H. Le Gall1 , A. Pires da Cruz2 , A. The influence of ethanol as an oxygenated additive has been investigated for these two fuels and has been found

  15. 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.

  16. 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.

  17. Bifurcation and stability analysis of laminar isothermal counterflowing jets

    Microsoft Academic Search

    A. G. S ALINGER; J. N. S HADID; T. J. M OUNTZIARIS

    2006-01-01

    We present a numerical study of the structure and stability of laminar isothermal flows formed by two counterflowing jets of an incompressible Newtonian fluid. We demonstrate that symmetric counterflowing jets with identical mass flow rates exhibit multiple steady states and, in certain cases, time-dependent (periodic) steady states. Two geometric configurations were studied based on the inlet jet shapes: planar and

  18. UNCERTAINTIES IN FAN PRESSURIZATION MEASUREMENTS:April 13, 1995 Submitted to ASTM: Airflow Performance Conference 10/93 LBL-32115

    E-print Network

    UNCERTAINTIES IN FAN PRESSURIZATION MEASUREMENTS:April 13, 1995 Submitted to ASTM: Airflow of California Larry Palmiter Ecotope Inc. ASTM Standard E779 is a test method for measuring the air tightness.

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

    E-print Network

    Lloyd, Michael

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

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

    E-print Network

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

    2010-01-01

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

  1. 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 pressures. Soot concentrations were minimized by selecting conditions at low flowrates and low ambient pressures; this allows identification of actual flame sheets associated with blue emissions of CH and CO2. The present modeling effort follows that of Roper and is useful in explaining many of the trends observed.

  2. The effects of airflow modulation and multi-stage defrost on the performance of an air source heat pump

    E-print Network

    Payne, William Vance

    1992-01-01

    One and Case Two. These defrost schemes attempted to replace defrost compressor energy with the energy stored in the indoor coil material and relatively warm refrigerant. A new term called the defrost coefficient of performance (COP) was defined... Termination and Recovery Period. Base Case Reciprocating Compressor Base Case Accumulator Removal. Base Case Performance Summary 57 59 68 72 75 77 80 89 97 AIRFLOW MODULATION RESULTS . . . 101 Constant Outdoor Coil Airflow Low Outdoor Coil...

  3. Theoretical study of the impact of tide-induced airflow on hydraulic head in air-confined coastal aquifers

    Microsoft Academic Search

    Haipeng Guo; Jiu J. Jiao

    2010-01-01

    Tide-induced hydraulic head fluctuation results in significant airflow above the water table if the aquifer is air-confined, for example, if the aquifer is capped by low permeability materials. Hypothetical studies on the interaction between tidal fluctuation and airflow in coastal aquifers are carried out using an airwater two-phase numerical model. The results show that both the amplitude of the hydraulic

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

    SciTech Connect

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

    2010-02-15

    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)

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

    NASA Astrophysics Data System (ADS)

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

    2007-11-01

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

  6. 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.

  7. Deformation analysis of shape memory polymer for morphing wing skin under airflow

    Microsoft Academic Search

    Weilong Yin; Jingcang Liu; Jinsong Leng

    2009-01-01

    The method for analyzing the out-of-plane deformation of a flexible skin under airflow is developed in this paper. The aerodynamic\\u000a analysis is performed using the CFD software, and the structural analysis is performed using finite element method. The chief\\u000a aim of the present study is to investigate the out-of-plane deformation of the shape memory polymer (SMP) skin at different\\u000a temperatures.

  8. Modeling of air inlets in CFD prediction of airflow in ventilated animal houses

    Microsoft Academic Search

    B. Bjerg; K. Svidt; G. Zhang; S. Morsing; J. O. Johnsen

    2002-01-01

    This study investigates different methods to model wall inlets in computational fluid dynamics (CFD) simulations of airflow in livestock rooms. The experiments were carried out in an 8.5 m long, 3 m high and 10.14 m wide test room equipped with a forced ventilation system. Four wall inlets were distributed symmetrically along an end wall 0.5 m beneath the ceiling.

  9. EMI reduction from airflow aperture arrays using dual-perforated screens and loss

    Microsoft Academic Search

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

    2000-01-01

    Airflow perforations in shielding enclosures can act as apertures facilitating the coupling from internal sources to external electromagnetic interference (EMI). This EMI radiation for single- and dual-screen configurations was studied herein experimentally and with finite-difference time domain (FDTD) modeling. A general EMI reduction of more than 20 dB was achieved for dual-perforated screens spaced 1 cm apart when compared to

  10. Airflow Characteristics of Direct-Type Kitchen Hood Systems in High-Rise Apartment Buildings

    E-print Network

    Park, M.

    2011-01-01

    Airflow characteristics of direct-type kitchen hood systems in high-rise apartment buildings 1 10.19. 2011 Myungsig Park* , Joseph Jun Kim Innovations Optima LLC Bonggil Jeon Dept of Architectural Engineering, Purdue University Geontae Lee..., Samsung C&T, South Korea 2 Introduction ? Today?s high-rise apartment buildings exhibit high degree of air-tightness. ? They are also subjected to stack effect and seasonal, unpredictable, wind pressure variations. ? Therefore, it is questionable...

  11. Airflow circulation cell study of an air-conditioning energy-saving mechanism

    Microsoft Academic Search

    N. A. Tuan; K. D. Huang

    2011-01-01

    It is difficult for a traditional air-conditioning system to satisfy the thermal comfort demands of all occupants of a room as well as energy-saving goals. This is because, traditionally, air-conditioning airflow has been distributed without consideration of occupants needs beyond setting temperature and fan speed to meet thermal comfort standards, such as the predicted mean vote index. Therefore, this paper

  12. Numerical study of airflow in the unsaturated zone induced by sea tides

    Microsoft Academic Search

    Hai-Peng Guo; Jiu J. Jiao

    2008-01-01

    The air pressures in coastal unsaturated zones fluctuate in response to tidal fluctuations. Two-phase air-water flow induced by sea tides in a coastal two-layered subsurface system is investigated through numerical simulations. The system consists of upper and lower layers with permeabilities of kU and kL, respectively. A water table exists in the lower layer. The study demonstrates that airflow in

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

    Microsoft Academic Search

    Jrme Pons; Eric Moreau; Grard Touchard

    2005-01-01

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

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

    PubMed Central

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

    2013-01-01

    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

  15. A numerical investigation of three-dimensional turbulent airflow around WFCAM at the UK Infrared Telescope

    NASA Astrophysics Data System (ADS)

    Chylek, Tomas; Chuter, Timothy C.; Shutt, Dean J.; Doyle, Matthew M.

    2004-09-01

    Recent advancements in computational fluid dynamics (CFD) software development (namely incorporation of unstructured meshing, wall functions and advanced turbulence modeling) now make it possible to perform a full three dimensional turbulent airflow analysis without the need for a supercomputer. A commercially available CFD code was used to investigate the effect of the WFCAM (a wide field camera developed by Astronomy Technology Centre at Royal Observatory of Edinburgh) presence in the airflow through the optical path of the United Kingdom Infrared telescope (UKIRT). The necessity of this investigation arises from the fact that WFCAM is placed directly above the primary mirror of the UKIRT telescope. There is very little information available in the literature about the possible adverse effects of this configuration on telescope performance, namely seeing and additional wind loading. The CFD code chosen to carry out the study utilizes a wall function for treatment of the near-wall solution. This approach requires only one node in the boundary layer and results in a significant reduction of required computing capacity. The results presented in the study include the effects of turbulent fluctuations of the airflow, natural and forced convection, and wind loading predictions on the instrument with the telescope at several positions.

  16. 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.

  17. 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

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

    SciTech Connect

    Kriegseis, J.; Tropea, C. [Institute of Fluid Mechanics and Aerodynamics, Technische Universitaet Darmstadt, Flughafenstr. 19, D-64347 Griesheim (Germany); Center of Smart Interfaces, Technische Universitaet Darmstadt, Flughafenstr. 19, D-64347 Griesheim (Germany); Grundmann, S. [Center of Smart Interfaces, Technische Universitaet Darmstadt, Flughafenstr. 19, D-64347 Griesheim (Germany)

    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.

  19. Chronic endotoxin exposure produces airflow obstruction and lung dendritic cell expansion.

    PubMed

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

    2012-08-01

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

  20. Climatological Characteristics of Springtime Lower Tropospheric Airflow Over Central and Eastern North America

    NASA Astrophysics Data System (ADS)

    Winkler, Julie A.; Harman, Jay R.; Waller, Eleanor A.; Brown, James T.

    1996-07-01

    A climatology of springtime lower tropospheric airflow, as represented by 850 hPa observed winds and 1000 hPa geostrophic winds, is presented for central and eastern North America. The climatology is based on twice-daily grid-point values for 1969-1989 from the operational analyses for the Northern Hemisphere prepared by the USA National Weather Service's National Meteorological Centre. Sixteen-point wind roses are used to show the spatial and temporal distributions by direction category of wind frequency, average speed, and wind run. These analyses are supplemented by resultant wind vector and streamline maps for each month. Evident in the climatological distributions is the declining strength of the circulation from March to May, the northward migration and strengthing of the North Atlantic subtropical anticyclone in late spring, and the nocturnal strengthening and veering of southerly airflow over the southern Great Plains. Additionally, areas of cyclonic and/or anticyclonic resultant flow correspond well with earlier identified centres of cyclogenesis and anticyclogenesis. The results presented here may provide a useful climatological baseline for future studies involving lower tropospheric airflow.

  1. LAMINAR TRANSITIONAL AND TURBULENT BOUNDARY LAYERS FOR COMPRESSIBLE AXISYMMETRIC FLOW

    NASA Technical Reports Server (NTRS)

    Albers, J. A.

    1994-01-01

    This is a finite-difference program for calculating the viscous compressible boundary layer flow over either planar or axisymmetric surfaces. The flow may be initially laminar and progress through a transitional zone to a fully turbulent flow, or it may remain laminar, depending on the imposed boundary conditions, laws of viscosity, and numerical solution of the momentum and energy equations. The flow may also be forced into a turbulent flow at a chosen spot by the data input. The input may contain factors of arbitrary Reynolds number, free-stream Mach number, free stream turbulence, wall heating or cooling, longitudinal wall curvature, wall suction or blowing, and wall roughness. The solution may start from an initial Falkner-Skan similarity profile, an approximate equilibrium turbulent profile, or an initial arbitrary input profile. This program has been implemented on the IBM 7094/7044 Direct Couple System. This program is written in FORTRAN IV and was developed in 1974.

  2. 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.

  3. Gyrotactic trapping in laminar and turbulent Kolmogorov flow

    E-print Network

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

    2014-10-07

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

  4. Hypersonic laminar/turbulent transition: computations and experiments

    NASA Astrophysics Data System (ADS)

    Orlik, E.; Kornilov, V.; Ferrier, M.; Fedioun, I.; Davidenko, D.

    2012-01-01

    In order to predict the laminar/turbulent transition on a hypersonic vehicle forebody at Mach numbers 4 and 6, the three-dimensional (3D) modal linear stability analysis is applied, coupled with the eN method. Nevertheless, N factors are unknown for wind tunnel conditions. Experimental investigations have been carried out on a flat plate in the blowdown wind tunnel T-313 of ITAM RAS (Novosibirsk). At M? = 2 to 6, the position of laminar/turbulent transition was measured by both Pitot tube and thermocouples. Then, stability analysis allows computing N factors at transition on the flat plate: they are about 3 4, typical of conventional wind tunnels. These flat plate correlations can then be used to predict the transition on the forebody in the same wind tunnel. Experiments for the forebody are currently in progress and will allow checking the predicted transition location.

  5. Profiles of Laminar Carbon Tetrachloride\\/Methane\\/Air Flames

    Microsoft Academic Search

    J. S. Morse; V. A. Cundy; T. W. Lester

    1989-01-01

    Stable species mole fraction and temperature profiles are presented for a series of five laminar, atmospheric pressure CCI4\\/CH4\\/air flames. The CI\\/H ratio is varied from 0.073 to 0.61, while the equivalence ratio is varied from 0.76 to 1.17. Gas samples are taken with uncooled quartz microprobes and analyzed by gas chromatography. Temperature measurements are taken with 0.02 cm thermocouple beads

  6. Making Large Suction Panels For Laminar-Flow Control

    NASA Technical Reports Server (NTRS)

    Maddalon, Dal V.

    1991-01-01

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

  7. Distributed acoustic receptivity in laminar flow control configurations

    Microsoft Academic Search

    Meelan Choudhari

    1994-01-01

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

  8. Acoustic receptivity of laminar boundary layers over wavy walls

    Microsoft Academic Search

    M. Wiegel; R. W. Wlezien

    1993-01-01

    Acoustic receptivity of laminar boundary layers over surfaces with nonlocalized low-amplitude periodic waviness is experimentally investigated. An array of 2D strips is used to simulate continuous wall waviness. Particular attention to measurement techniques is required to minimize facility-dependent flow and acoustic field anomalies. Balanced arrays of acoustic sources upstream and downstream of the test section are used to generate a

  9. Distributed acoustic receptivity in laminar flow control configurations

    Microsoft Academic Search

    Meelan Choudhari

    1992-01-01

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

  10. Aerodynamic Design for Swept-wing Laminar Flow

    E-print Network

    Belisle, Michael Joseph

    2013-11-08

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

  11. Unstable modes of laminar round fountains on inclined wall

    NASA Astrophysics Data System (ADS)

    Lamorlette, Aymeric; Mehaddi, Rabah; Vauquelin, Olivier

    2011-04-01

    Experiments were carried out on reversed weak laminar inclined fountains to asses that unstable modes of round fountains are disturbed by the inclination. Indeed, compared to fountains developing on horizontal wall, some modes disappeared while others are split in several modes. This paper aims at describing and mapping these new modes regarding to the inclination and the inlet velocity. Explanations about what made the unstable modes evolve are also proposed.

  12. Calibration of laminar flow meters for process gases

    Microsoft Academic Search

    John D. Wright; Thiago Cobu; Robert F. Berg; Michael R. Moldover

    We calibrated three models of commercially-manufactured, laminar flow meters (LFMs) at four pressures (100, 200, 300, and 400 kPa) with five gases (N2, Ar, He, CO2, and SF6) over a 10:1 flow range using NISTs primary flow standards as references. We combined three items: (1) the calibration data acquired with N2, (2) gas-property data from NISTs database REFPROP 9.0, and

  13. Experimental investigation of oxide nanofluids laminar flow convective heat transfer

    Microsoft Academic Search

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

    2006-01-01

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

  14. Segregated regions in continuous laminar stirred tank reactors

    Microsoft Academic Search

    P. E. Arratia; J. P. Lacombe; T. Shinbrot; F. J. Muzzio

    2004-01-01

    Using visualization techniques, including acid\\/base reactions and UV fluorescence, we provide experimental evidence of segregated regions (islands) during mixing of viscous Newtonian fluids under laminar flow conditions in continuous stirred tank reactors (CSTRs). The effect of inlet\\/outlet stream position and Reynolds number on the dynamics of the mixing processes is examined. Numerical experiments in 3-D map were able to capture

  15. Rich methane premixed laminar flames doped by light unsaturated hydrocarbons

    Microsoft Academic Search

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

    2008-01-01

    In line with the studies presented in Parts I (methane flame seeded with allene and propyne) and II (methane flame seeded with 1,3-butadiene) of this paper, the structure of a laminar rich premixed methane flame doped with cyclopentene has been investigated. The gases of this flame contain 15.3% (molar) of methane, 26.7% of oxygen, and 2.4% cyclopentene, corresponding to an

  16. Soot formation in hydrocarbon\\/air laminar jet diffusion flames

    Microsoft Academic Search

    P. B. Sunderland; G. M. Faeth

    1996-01-01

    Soot processes along the axes of round laminar jet diffusion flames were studied, considering ethane, propane, n-butane, ethylene, propylene, and 1,3-butadiene burning in air at pressures of 2599 kPa. Measurements included soot volume fractions, temperatures, soot structure, concentrations of major gas species and gas velocities. As distance increased along the axes of the flames, significant soot formation began when temperatures

  17. Rich premixed laminar methane flames doped by light unsaturated hydrocarbons

    Microsoft Academic Search

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

    2007-01-01

    In line with the study presented in Part I of this paper, the structure of a rich premixed laminar methane flame doped with 1,3-butadiene has been investigated. The flame contains 20.7% (molar) of methane, 31.4% of oxygen, and 3.3% of 1,3-butadiene, corresponding to an equivalence ratio of 1.8, and a C4H6\\/CH4 ratio of 16%. The flame has been stabilized on

  18. Rich methane premixed laminar flames doped with light unsaturated hydrocarbons

    Microsoft Academic Search

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

    2006-01-01

    The structure of three laminar premixed rich flames has been investigated: a pure methane flame and two methane flames doped by allene and propyne, respectively. The gases of the three flames contain 20.9% (molar) of methane and 33.4% of oxygen, corresponding to an equivalence ratio of 1.25 for the pure methane flame. In both doped flames, 2.49% of CH was

  19. Rich methane premixed laminar flames doped with light unsaturated hydrocarbons

    Microsoft Academic Search

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

    2006-01-01

    The structure of three laminar premixed rich flames has been investigated: a pure methane flame and two methane flames doped by allene and propyne, respectively. The gases of the three flames contain 20.9% (molar) of methane and 33.4% of oxygen, corresponding to an equivalence ratio of 1.25 for the pure methane flame. In both doped flames, 2.49% of C3H4 was

  20. Laminar Incompressible Flow Past Parabolic Bodies at Angles of Attack

    Microsoft Academic Search

    Ercan Erturk; Thomas Corke; Osamah Haddad

    2003-01-01

    Numerical solutions of a two-dimensional steady laminar incompressible flow over semi-infinite parabolic bodies at angles of attack are obtained. All solutions are found by using a modified numerical approach to solve the time-dependent Navier-Stokes equations. A check of our solutions to those that exist in the literature at zero angle of attack showed excellent agreement. In addition, at zero angle

  1. Laminar Incompressible Flow Past Parabolic Bodies at Angles of Attack

    Microsoft Academic Search

    Ercan Erturk; Thomas Corke; Osamah Haddad

    2004-01-01

    Numerical solutions of a two-dimensional steady laminar incompressible flow over semi-infinite parabolic bodies at angles of attack are obtained. All solutions are found by using a modified numerical approach to solve the time- dependent Navier-Stokes equations. The governing equations are written for the stream function and vorticity variables and are solved on a nonuniform body-fitted parabolic grid. A check of

  2. Columnar Connectivity and Laminar Processing in Cat Primary Auditory Cortex

    Microsoft Academic Search

    Craig A. Atencio; Christoph E. Schreiner; Benedikt Grothe

    2010-01-01

    BackgroundRadial intra- and interlaminar connections form a basic microcircuit in primary auditory cortex (AI) that extracts acoustic information and distributes it to cortical and subcortical networks. Though the structure of this microcircuit is known, we do not know how the functional connectivity between layers relates to laminar processing.Methodology\\/Principal FindingsWe studied the relationships between functional connectivity and receptive field properties in

  3. Laminar and Connectional Organization of a Multisensory Cortex

    PubMed Central

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

    2012-01-01

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

  4. The effects of gravity on wrinkled laminar flames

    SciTech Connect

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

    1992-09-01

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

  5. The effects of gravity on wrinkled laminar flames

    SciTech Connect

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

    1992-09-01

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

  6. 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.

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

    Microsoft Academic Search

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

    2011-01-01

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

  8. 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

  9. Laminar Boundary Layer Behind a Strong Shock Moving into Air

    NASA Technical Reports Server (NTRS)

    Mirels, Harold

    1961-01-01

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

  10. Unsteady Laminar CFD Simulation of Undulatory Rainbow Trout Swimming Hydrodynamics

    NASA Astrophysics Data System (ADS)

    Flanagan, Patrick; Hotchkiss, Rollin; Stock, David

    2004-11-01

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

  11. 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.

  12. 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.

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

    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.

  14. 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.

  15. Effects of diluents on laminar premixed hydrogen flames in microgravity

    NASA Astrophysics Data System (ADS)

    Qiao, Li

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

  16. Experimental investigation of recirculating cells in laminar coaxial jets.

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

  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. 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.

  19. Laminar flow transition: A large-eddy simulation approach

    NASA Technical Reports Server (NTRS)

    Biringen, S.

    1982-01-01

    A vectorized, semi-implicit code was developed for the solution of the time-dependent, three dimensional equations of motion in plane Poiseuille flow by the large-eddy simulation technique. The code is tested by comparing results with those obtained from the solutions of the Orr-Sommerfeld equation. Comparisons indicate that finite-differences employed along the cross-stream direction act as an implicit filter. This removes the necessity of explicit filtering along this direction (where a nonhomogeneous mesh is used) for the simulation of laminar flow transition into turbulence in which small scale turbulence will be accounted for by a subgrid scale turbulence model.

  20. 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.

  1. 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

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

    E-print Network

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

    2002-01-01

    Conservation M. Liu Ph.D. P. E. M. Abbas P. E. Y. Zhu Ph.D., P. E. D. E. Claridge Ph.D., P. E. Energy Systems Laboratory Sempra Energy Solutions SSR Inc Energy Systems Laboratory University of Nebraska-Lincoln Houston Houston Texas A&M University... for constant air volume terminal boxes during unoccupied hours. Authors have implemented the airflow reset in dual duct variable air volume terminal boxes [Abbas and Liu, 1996], in dual duct constant air volume terminal boxes [Liu and Zhu, 1998...

  3. 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.

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

    E-print Network

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

    2002-01-01

    Conservation M. Liu Ph.D. P. E. M. Abbas P. E. Y. Zhu Ph.D., P. E. D. E. Claridge Ph.D., P. E. Energy Systems Laboratory Sempra Energy Solutions SSR Inc Energy Systems Laboratory University of Nebraska-Lincoln Houston Houston Texas A&M University... for constant air volume terminal boxes during unoccupied hours. Authors have implemented the airflow reset in dual duct variable air volume terminal boxes [Abbas and Liu, 1996], in dual duct constant air volume terminal boxes [Liu and Zhu, 1998...

  5. Microwave discharge initiated by double laser spark in a supersonic airflow

    NASA Astrophysics Data System (ADS)

    Khoronzhuk, R. S.; Karpenko, A. G.; Lashkov, V. A.; Potapeko, D. P.; Mashek, I. Ch.

    2015-06-01

    In this paper, we report the results of an experimental study of microwave (MW) discharge in the supersonic flow initiated by the laser spark and numerical simulation of multiple laser spark shockwave structures in airflow. The MW discharge initiation has been produced by single and double laser sparks. By using different spatial and temporal configuration of laser sparks in supersonic flow, we demonstrate the feasibility of an MW breakdown threshold decrease and control over shape and location of MW plasma. Calculation of laser spark shock wave structures shows good agreement with experimental shadow photographs both in the front shock wave diameter and its internal structure.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    A new hardware-in-the-loop control strategy to enhance the aerodynamic performance of a two-dimensional morphing laminar wing prototype was developed and tested. The testing was performed in a wind tunnel under cruise flight flow conditions: Mach number ranging from 0.2 to 0.3 and angle of attack from - 1 to 0.5. For each set of flow conditions, the shape of the upper surface of the wing was modified using two independent shape memory alloy actuators. The wing shape was morphed in two sequential steps. The initial morphed shape was controlled using open-loop architecture and the results of an anterior aero-structural numerical optimization study. The final morphed shape was closed-loop controlled using either the wind tunnel balance or an infrared camera as hardware-in-the-loop to give an instantaneous lift-to-drag ratio (L/D) or a laminar flow extension (xtr/c) over the upper surface of the prototype. In respect to the aerodynamic performance of the unactuated wing profile, the L/D gain varies from 10.6 to 15% for the closed-loop control strategy compared to 10.0 to 13.7% for the open-loop control strategy. Laminar flow extension gains, ?xtr/c, measured by infrared camera, were situated in the 29-33% range for both control strategies. However, the results obtained showed that the closed-loop controller could be hindered by the noise of the hardware-in-the-loop signal.

  8. Unsteady laminar flow and convective heat transfer in a sharp 180 bend

    E-print Network

    Chung, Yongmann M.

    Unsteady laminar flow and convective heat transfer in a sharp 180 bend Yongmann M. Chung a , Paul Unsteady laminar flow and heat transfer in a sharp 180 bend is studied numerically to investigate a convective heat transfer regime of especial relevance to electronic systems. Due to the high geometrical

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

    E-print Network

    Lajeunesse, Eric

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

  10. Error estimation and anisotropic mesh refinement for 3d laminar aerodynamic flow simulations

    E-print Network

    Hartmann, Ralf

    Error estimation and anisotropic mesh refinement for 3d laminar aerodynamic flow simulations Tobias Leichta,b , Ralf Hartmann,a,b aInstitute of Aerodynamics and Flow Technology, DLR (German Aerospace Center-dimensional laminar aerodynamic flow simulations. The optimal order symmetric interior penalty discontinuous Galerkin

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

    Microsoft Academic Search

    L. Turner III

    1979-01-01

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

  12. AIR-BREATHING LAMINAR FLOW BASED MICROFLUIDIC FUEL CELL Ranga S. Jayashree1

    E-print Network

    Kenis, Paul J. A.

    AIR-BREATHING LAMINAR FLOW BASED MICROFLUIDIC FUEL CELL Ranga S. Jayashree1 , Lajos Gancs2 , Eric R and solvents were purchased from the vendors indicated below. In addition, formic acid was obtained from Acros of the laminar flow-based microfluidic fuel cell. A 5-mm thick graphite plate (anode, fuel cell grade graphite

  13. Distinct large-scale turbulent-laminar states in transitional pipe flow

    E-print Network

    Barkley, Dwight

    Distinct large-scale turbulent-laminar states in transitional pipe flow David Moxey1 and Dwight) When fluid flows through a channel, pipe, or duct, there are two basic forms of motion: smooth laminar numerical computations in pipes of variable lengths up to 125 diameters to investigate the nature of transi

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

    Microsoft Academic Search

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

    1998-01-01

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

  15. TOWARDS A UNIFIED THEORY OF NEOCORTEX: Laminar Cortical Circuits for Vision and Cognition

    E-print Network

    Spence, Harlan Ernest

    TOWARDS A UNIFIED THEORY OF NEOCORTEX: Laminar Cortical Circuits for Vision and Cognition Stephen Grossberg Department of Cognitive and Neural Systems Center for Adaptive Systems, and Center of Excellence laminar neocortical circuits give rise to biological intelligence. These circuits embody two new

  16. A comparison of computational and experimental lift-off heights of coflow laminar diffusion flames

    E-print Network

    Long, Marshall B.

    A comparison of computational and experimental lift-off heights of coflow laminar diffusion flames was performed, which indicates that the lift-off height is sensitive to the laminar flame speed to be modified to accommodate high dilution flames. 2004 The Combustion Institute. Published by Elsevier Inc

  17. A model of laminar micromixing with application to parallel chemical reactions

    Microsoft Academic Search

    J. Ba?ldyga; A. Roze?; F. Mostert

    1998-01-01

    The effect of laminar micromixing on parallel reactions was studied experimentally and interpreted theoretically using a new model of laminar micromixing, developed by applying an integral transformation to material balance equations in the Lagrangian frame of reference. A solution of sodium hydroxide was contacted with a premixture of hydrochloric acid and ethyl chloroacetate solutions in two reactors: a semibatch tank

  18. Effect of eccentricity on laminar mixing in vessel stirred by double turbine impellers

    Microsoft Academic Search

    Szymon Woziwodzki; ?ukasz J?drzejczak

    2011-01-01

    Laminar mixing is often conducted in industrial processes, for example in polymerization reactors or in biotechnological processes. The laminar flow conditions caused problems of inefficient mixing due to some mixing anomalies like occurrence of the isolated mixing regions (IMR), segregation or compartmentalization phenomena. In this paper, flow visualization experiments are used to examine the size, positions and structure of the

  19. The laminar separation sensor - An advanced transition measurement method for use in wind tunnels and flight

    Microsoft Academic Search

    G. S. Manuel; D. L. Carraway; C. C. Croom

    1987-01-01

    Wind tunnel and flight tests have recently been conducted by the NASA Langley Research Center to explore the ability of laminar separation hot-film sensors to identify the presence of laminar separation as the principal mode of instability amplification leading to transition. This paper describes the different sensor configurations evaluated during the course of testing and presents results from the flight

  20. Interaction of aerodynamic noise with laminar boundary layers in supersonic wind tunnels

    Microsoft Academic Search

    M. R. Schopper

    1984-01-01

    The interaction between incoming aerodynamic noise and the supersonic laminar boundary layer is studied. The noise field is modeled as a Mach wave radiation field consisting of discrete waves emanating from coherent turbulent entities moving downstream within the supersonic turbulent boundary layer. The individual disturbances are likened to miniature sonic booms and the laminar boundary layer is staffed by the

  1. Hybrid intelligent parameter estimation based on grey case-based reasoning for laminar cooling

    E-print Network

    Heil, Matthias

    Hybrid intelligent parameter estimation based on grey case-based reasoning for laminar cooling parameter estimation based on grey case-based reasoning for laminar cooling process Guishan Xing algorithm Grey case-based reasoning Parameter estimation a b s t r a c t In this paper, a hybrid intelligent

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  3. 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.

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

    PubMed

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

    2008-01-01

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

  5. 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.

  6. Streamwise Vorticity Generation in Laminar and Turbulent Jets

    NASA Technical Reports Server (NTRS)

    Demuren, Aodeji O.; Wilson, Robert V.

    1999-01-01

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

  7. Low temperature high current ion beams and laminar flows

    NASA Astrophysics Data System (ADS)

    Cavenago, Marco

    2014-07-01

    Self-consistent Vlasov-Poisson equilibria for the extraction of ions with low temperature Ti are discussed, with comparison to the laminar flow case Ti = 0, in two dimensional diodes. Curvilinear coordinates aligned with laminar beam flow lines are extended to the low ion temperature case, with a reduced current density jd, expressed with cathode integrals. This generalizes one-dimensional interpolation between rays along the cathode coordinate to multidimensional integrations, including also the momentum components, so that jd is free from the granularity defect and noise, typical of standard ray tracing approach. A robust numerical solution procedure is developed, which allows studying current saturated extraction and drift tube effects. A discussion of particle initial conditions determines the emission angles and shows that temperature effect at beam edge is partly balanced by the focus electrode inclination. Results for a typical diode are described, with detail about normalized emittance, here taken strictly proportional to the x - px phase space area, for a beam with non uniform velocities. Contribution to the Topical Issue "Theory and Applications of the Vlasov Equation", edited by Francesco Pegoraro, Francesco Califano, Giovanni Manfredi and Philip J. Morrison.

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

    Microsoft Academic Search

    Zhibao Dong; Guangqiang Qian; Wanyin Luo; Hongtao Wang

    2007-01-01

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

  9. 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.

  10. 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.

  11. 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.

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

    Microsoft Academic Search

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

    2002-01-01

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

  13. Steady state CFD modeling of airflow, heat transfer and moisture loss in a commercial potato cold store

    Microsoft Academic Search

    M. K. Chourasia; T. K. Goswami

    2007-01-01

    Storage loss beyond permissible limit is one of the most important problems in Indian potato cold stores, which has been hindering further growth of this industry. The losses in the stored potatoes have a direct relation to the intricate coupled transport phenomena of heat, mass and momentum transfer therein. Therefore, airflow, heat transfer and moisture loss was investigated in a

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

    E-print Network

    Chen, Qingyan "Yan"

    and the following anthrax cases spawned serious concerns about various possible terrorist attacks in built and subways (Stenner et al. 2001). The anthrax attacks through letters in Florida, New York City by using affordable air filters combined with ultraviolet germicidal irradiation. A multizone airflow

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  16. ES174, Stage 2, 2013: Computational Fluid Dynamics Analysis of airflow around a simple car model using Solidworks Flow

    E-print Network

    Davies, Christopher

    ES174, Stage 2, 2013: Computational Fluid Dynamics Analysis of airflow around a simple car model.denissenko@warwick Step-by-step instructions 1. Build a car of a basic shape. It should be recognisable as a car, but not necessarily with all the shape features and not necessarily well streamlined. Choose the realistic car

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

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

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

    Microsoft Academic Search

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

    2006-01-01

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

  19. Simulation of the effect of local obstructions and blockage on airflow and aerosol deposition in central human airways

    Microsoft Academic Search

    rpd Farkas; Imre Balshzy

    2007-01-01

    Investigation of the effect of sidewall and carinal tumours, airway constrictions and airway blockage on the inspiratory airflow and particle deposition in the large central human airways was the primary objective of this study. A computational fluid and particle dynamics model was implemented, validated and applied in order to simulate the air and particle transport and to quantify the aerosol

  20. Precipitation Hydrometeor Type Relative to the Mesoscale Airflow in Mature Oceanic Deep Convection of the Madden-Julian Oscillation

    E-print Network

    Houze Jr., Robert A.

    1 Precipitation Hydrometeor Type Relative to the Mesoscale Airflow in Mature Oceanic Deep occur near melting level in stratiform region Abstract Composite analysis of mature near mature MCSs. In the convective region: moderate rain occurs within the updraft core; the heaviest rain

  1. Methods for controlling airflow in and around a building under cross-ventilation to improve indoor thermal comfort

    Microsoft Academic Search

    Akashi Mochida; Hiroshi Yoshino; Tomoya Takeda; Toshimasa Kakegawa; Satoshi Miyauchi

    2005-01-01

    This paper investigates methods for controlling airflow in and around a building in order to improve indoor thermal comfort by utilizing cross-ventilation. In the first part of the study, field measurements are carried out to evaluate the effects of cross-ventilation on indoor thermal comfort. It was confirmed that a comfortable indoor thermal environment could be attained in a considerable part

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

    Microsoft Academic Search

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

    2004-01-01

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

  3. Temperature measurement using infrared thermography of the dielectric in a dbd plasma actuator dedicated to subsonic airflow control

    Microsoft Academic Search

    Romain Joussot; Dunpin Hong; Vincent Boucinha; Regine Weber-Rozenbaum; Annie Leroy-Chesneau

    2010-01-01

    In order to use the non-thermal plasmas for subsonic airflow control, plasmas created on a dielectric surface have been widely investigated by researchers and engineers in several coutries1. The plasmas in these studies were mainly generated by a corona discharge or a dielectric barrier discharge (DBD). Usually, electrical parameters including active power are measured as well as the induced ionic

  4. Flame Shapes of Luminous NonBuoyant Laminar Coflowing Jet Diffusion Flames

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    Laminar diffusion flames are of interest as model flame systems that are more tractable for analysis and experiments than practical turbulent diffusion flames. Certainly understanding laminar flames must precede understanding more complex turbulent flames while man'y laminar diffusion flame properties are directly relevant to turbulent diffusion flames using laminar flamelet concepts. 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 structure predictions. Motivated by these observations, the shapes of laminar flames were considered during the present investigation. The present study was limited to nonbuoyant flames because most practical flames are not buoyant. Effects of buoyancy were minimized by observing flames having large flow velocities at small pressures. Present methods were based on the study of the shapes of nonbu,3yant round laminar jet diffusion flames of Lin et al. where it was found that a simple analysis due to Spalding yielded good predictions of the flame shapes reported by Urban et al. and Sunderland et al.

  5. 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.

  6. 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.

  7. A surface integral numerical solution for laminar developed duct flow

    NASA Astrophysics Data System (ADS)

    Khader, M. S.

    1981-12-01

    A surface integral numerical solution for laminar developed flow in ducts of arbitrary shape cross sections is presented. The method is general for any two-dimensional duct with simple or multiple connected regions cross section. The solutions provide information for velocity distribution, friction factor, and wall shear stress. As an application of the present method, solutions for flow in circular and rectangular ducts are obtained. These solutions are used to compare the obtained results and the corresponding exact analytical solutions. Moreover, in order to illustrate the general use of the present scheme, a solution for the case of circular duct containing rod clusters is obtained. The method proved to have several interesting features and advantages over other conventional numerical and analytical techniques.

  8. Laminar boundary-layer flow of non-Newtonian fluid

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  9. 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.

  10. Laminar-to-turbulent transitions over an ablating reentry capsule

    NASA Astrophysics Data System (ADS)

    Komurasaki, Kimiya; Candler, Graham V.

    2000-11-01

    The aerodynamic mechanism of early transition phenomena over an ablating reentry capsule has been analytically examined. A two-equation turbulence model ( k- ? model) was coupled with Reynolds averaged Navier-Stokes equations. Low-Reynolds-number effects on the solid wall were taken into account by modifying the Chien's correction. As a result, transition occurred at the lower Reynolds number with higher ablation rate. The predicted transition-point Reynolds number was 310 4 at the surface-mass-injection rate of 100 g/sm 2. The principal mechanism of this early transition is thought as follows; the viscosity damping effects are reduced and re-laminarization is prevented in the downstream of the capsule surface, due to the turbulence on the surface and due to the pushing out of near-surface stream-lines from the surface by successive mass injection.

  11. Influence of coal properties on forward combustion in laminar flow

    SciTech Connect

    Lockwood, W.R.; Corlett, W.R.; Mortazaui, H.R.; Emery, A.F.

    1986-07-01

    Numerical results are presented for forward combustion in coal channels wherein the flow is laminar. The work is motivated by the need to describe deviations from ideal permeative flow characteristics in theoretical models of underground rubble gasification. For simplicity, the geometry is idealized to a straight circular channel of initially uniform diameter. Coal and inlet gas properties, as well as gas flow rate and initial channel diameter, are arbitrary. A baseline case, in which O/sub 2/-steam is injected into a channel in virgin coal, is chosen to match laboratory work reported by other investigators. The results of independent variation of six major parameters are also shown. Finally, representative results are presented for injection of a hot mixture of steam and gasification products into hot char.

  12. 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).

  13. A viscous instability in axially symmetric laminar shear flows

    NASA Astrophysics Data System (ADS)

    Shakura, N.; Postnov, K.

    2015-04-01

    A viscous instability in shearing laminar axisymmetric hydrodynamic flows around a gravitating centre is described. In the linearized hydrodynamic equations written in the Boussinesq approximation with microscopic molecular transport coefficients, the instability arises when the viscous dissipation is taken into account in the energy equation. Using the local WKB approximation, we derive a third-order algebraic dispersion equation with two modes representing the modified Rayleigh modes R+ and R-, and the third X-mode. We show that in thin accretion flows the viscosity destabilizes one of the Rayleigh modes in a wide range of wavenumbers, while the X-mode always remains stable. In Keplerian flows, the instability increment is found to be a few Keplerian rotational periods at wavelengths with kr 10-50. This instability may cause turbulence in astrophysical accretion discs even in the absence of magnetic field.

  14. 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 LayerTrailing Edge noise (TBL-TE), the Laminar Boundary LayerVortex Shedding (LBL-VS) noise and the Separation Stall (S-S) noise. The TBL-TE is mainly related to the noise generated by turbulent eddies which develop into the boundary layer and usually exhibits a broadband spectrum. The LBL-VS is related to laminar instabilities that can occur within the boundary layer which are responsible for a very late transition and generate a typical peaked tonal noise, while the S-S noise mainly results from the development of large vortices after the separation point. In this paper we propose a numerical analysis targeted to the simulation the LBL-VS noise mechanisms on a NACA 0012 aerofoil, tested at a Reynolds number of 1.1 M and Mach number of 0.2. The aerodynamic simulation is performed with a 2D transient RANS approach using the k-? transitional turbulence model, while the acoustic computations are performed with the FfowcsWilliams-Hawkings (FW-H) acoustic analogy and with a Finite Element (FE) approach solving Lighthill's wave equation. Computed noise spectra are compared with experimental data published by NASA showing a good agreement both for peak location as well as for the predicted noise level.

  15. Impinging laminar jets at moderate Reynolds numbers and separation distances

    NASA Astrophysics Data System (ADS)

    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 200?Re?1400 .

  16. 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.

  17. 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.

  18. Technology developments for laminar boundary layer control on subsonic transport aircraft

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  19. 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.

  20. The classical Starling resistor model often does not predict inspiratory airflow patterns in the human upper airway

    PubMed Central

    Edwards, Bradley A.; Sands, Scott A.; Butler, James P.; Eckert, Danny J.; White, David P.; Malhotra, Atul; Wellman, Andrew

    2014-01-01

    The upper airway is often modeled as a classical Starling resistor, featuring a constant inspiratory airflow, or plateau, over a range of downstream pressures. However, airflow tracings from clinical sleep studies often show an initial peak before the plateau. To conform to the Starling model, the initial peak must be of small magnitude or dismissed as a transient. We developed a method to simulate fast or slow inspirations through the human upper airway, to test the hypothesis that this initial peak is a transient. Eight subjects [4 obstructive sleep apnea (OSA), 4 controls] slept in an iron lung and wore a nasal mask connected to a continuous/bilevel positive airway pressure machine. Downstream pressure was measured using an epiglottic catheter. During non-rapid eye movement (NREM) sleep, subjects were hyperventilated to produce a central apnea, then extrathoracic pressure was decreased slowly (?24 s) or abruptly (<0.5 s) to lower downstream pressure and create inspiratory airflow. Pressure-flow curves were constructed for flow-limited breaths, and slow vs. fast reductions in downstream pressure were compared. All subjects exhibited an initial peak and then a decrease in flow with more negative pressures, demonstrating negative effort dependence (NED). The rate of change in downstream pressure did not affect the peak to plateau airflow ratio: %NED 22 13% (slow) vs. 20 5% (fast), P = not significant. We conclude that the initial peak in inspiratory airflow is not a transient but rather a distinct mechanical property of the upper airway. In contrast to the classical Starling resistor model, the upper airway exhibits marked NED in some subjects. PMID:24458746

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

    PubMed Central

    Chen, Jie; Gutmark, Ephraim

    2013-01-01

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

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

    PubMed

    Chen, Jie; Gutmark, Ephraim

    2014-01-01

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

  3. Wireless communication in the airflow verification system of biological safety cabinet

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-de; Hou, De-xin; Qiu, Jian; Ye, Shu-liang

    2013-01-01

    In recent years, biological safety cabinet has been applied widely and urgently to the biochemistry laboratory. An increasing research need has been asked about the processing safety of the workers. In this safety cabinet system, among series of related factors, the main parameter is airflow velocity. At percent, this measuring work is usually done by processional workers, thus leading to the low efficiency and disadvantages. In this paper, a new method was approved to deal with the current problem, where wireless communication controller and detector. According to the experimental data and the comparison between the two methods, the wireless way is more convenient and more efficient than previous one, and the working distance can be about 730 meters. Meanwhile, the communication system has already been used in Guangzhou Institute of Metrology Laboratory.

  4. Computer simulation of climatic conditions for underground automated mines for standard and reduced airflow requirements

    SciTech Connect

    Partyka, J.; Hardcastle, S.; Kocsis, C.

    1999-07-01

    This study demonstrates the importance of ventilation in an automated mine through climatic simulations. These have been performed on workings located at depths of 1,000 m to 3,000 m below surface in an underground mine. Each active working area employs either an electric or a diesel piece of equipment that has a full load power output of 100 kW to 200 kW. The airflows considered in the mining areas were standard full-flow conditions, i.e., 100% (6.5 m{sup 3}/100 kW), and 125%, 75%, and 50% of full-flow. The analyses show, for instance, that a 100 kW electric machine can increase the dry-bulb temperature in the working area at a 1,000 m level, by 11.5 C (full flow) and 23.1 C (50% flow); at a 2,000 m level, by 10.9 C (full flow) and 21.9 C (50% flow), and at a 3,000 m level, by 10.4 C (full flow) and 20.6 C (50% flow). Overall, through climatic prediction, the analyses show the continued importance ventilation in an automated mine. This is because of the heat from the machinery and the operational temperature limits of such machinery. Such elevated temperatures could also affect the operation of on-board guidance, sensors and image systems of remote-operation and automated mining equipment. Therefore it cannot be assumed that reduced airflow requirements would be the natural result of removing humans from an automated mine.

  5. Subglottal pressure, tracheal airflow, and intrinsic laryngeal muscle activity during rat ultrasound vocalization.

    PubMed

    Riede, Tobias

    2011-11-01

    Vocal production requires complex planning and coordination of respiratory, laryngeal, and vocal tract movements, which are incompletely understood in most mammals. Rats produce a variety of whistles in the ultrasonic range that are of communicative relevance and of importance as a model system, but the sources of acoustic variability were mostly unknown. The goal was to identify sources of fundamental frequency variability. Subglottal pressure, tracheal airflow, and electromyographic (EMG) data from two intrinsic laryngeal muscles were measured during 22-kHz and 50-kHz call production in awake, spontaneously behaving adult male rats. During ultrasound vocalization, subglottal pressure ranged between 0.8 and 1.9 kPa. Pressure differences between call types were not significant. The relation between fundamental frequency and subglottal pressure within call types was inconsistent. Experimental manipulations of subglottal pressure had only small effects on fundamental frequency. Tracheal airflow patterns were also inconsistently associated with frequency. Pressure and flow seem to play a small role in regulation of fundamental frequency. Muscle activity, however, is precisely regulated and very sensitive to alterations, presumably because of effects on resonance properties in the vocal tract. EMG activity of cricothyroid and thyroarytenoid muscle was tonic in calls with slow or no fundamental frequency modulations, like 22-kHz and flat 50-kHz calls. Both muscles showed brief high-amplitude, alternating bursts at rates up to 150 Hz during production of frequency-modulated 50-kHz calls. A differentiated and fine regulation of intrinsic laryngeal muscles is critical for normal ultrasound vocalization. Many features of the laryngeal muscle activation pattern during ultrasound vocalization in rats are shared with other mammals. PMID:21832032

  6. Subglottal pressure, tracheal airflow, and intrinsic laryngeal muscle activity during rat ultrasound vocalization

    PubMed Central

    2011-01-01

    Vocal production requires complex planning and coordination of respiratory, laryngeal, and vocal tract movements, which are incompletely understood in most mammals. Rats produce a variety of whistles in the ultrasonic range that are of communicative relevance and of importance as a model system, but the sources of acoustic variability were mostly unknown. The goal was to identify sources of fundamental frequency variability. Subglottal pressure, tracheal airflow, and electromyographic (EMG) data from two intrinsic laryngeal muscles were measured during 22-kHz and 50-kHz call production in awake, spontaneously behaving adult male rats. During ultrasound vocalization, subglottal pressure ranged between 0.8 and 1.9 kPa. Pressure differences between call types were not significant. The relation between fundamental frequency and subglottal pressure within call types was inconsistent. Experimental manipulations of subglottal pressure had only small effects on fundamental frequency. Tracheal airflow patterns were also inconsistently associated with frequency. Pressure and flow seem to play a small role in regulation of fundamental frequency. Muscle activity, however, is precisely regulated and very sensitive to alterations, presumably because of effects on resonance properties in the vocal tract. EMG activity of cricothyroid and thyroarytenoid muscle was tonic in calls with slow or no fundamental frequency modulations, like 22-kHz and flat 50-kHz calls. Both muscles showed brief high-amplitude, alternating bursts at rates up to 150 Hz during production of frequency-modulated 50-kHz calls. A differentiated and fine regulation of intrinsic laryngeal muscles is critical for normal ultrasound vocalization. Many features of the laryngeal muscle activation pattern during ultrasound vocalization in rats are shared with other mammals. PMID:21832032

  7. Observations and implications of natural laminar flow on practical airplane surfaces

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

    The results of natural laminar flow (NLF) experiments conducted by NASA to determine if modern aircraft structures can benefit from NLF as do sailplanes are presented. Seven aircraft, ranging from a Cessna 210 to a Learjet 28/29, with relatively stiff skins were flown in production configurations with no modifications. Measurements were made of the boundary-layer laminar to turbulent transition locations on various aerodynamic surfaces, the effect of a total loss of laminar flow, the effect of the propeller slipstream on the wing boundary-layer transition and the boundary-layer profiles, the wing section profile drag, the effect of flight through clouds, and insect debris contamination effects. Favorable pressure gradients for NLF were concluded to be feasible up to a transition Reynolds number of 11 million. Laminar flows were observed in propeller slipstreams, and insects were found to cause transition 1/4 of the time.

  8. Natural laminar flow flight experiments on a turbine engine nacelle fairing

    NASA Technical Reports Server (NTRS)

    Obara, C. J.; Hastings, E. C.; Schoenster, J. A.; Parrott, T. L.; Holmes, B. J.

    1986-01-01

    Flight experiments are being conducted with the objective to investigate the interactions between acoustic disturbances and laminar flow in the flight environment. In the experiments, the laminar boundary layer on the nacelles will be exposed to discrete and broadband external noises, and the effect of varying noise levels and frequencies on the stability of the laminar flow will be studied. The present paper provides an overview of the complete project and a status report on the results which have been obtained. The flight experiment is conducted with the aid of a modified research aircraft. The phase I flight tests are concerned with a quick and simple determination of natural laminar flow (NLF) behavior on an engine nacelle. Attention is given to instrumentation, the acoustic noise source, flow visualization, and the test results.

  9. A method of rapidly estimating the position of the laminar separation point

    NASA Technical Reports Server (NTRS)

    Von Doenhoff, Albert E

    1938-01-01

    A method is described of rapidly estimating the position of the laminar separation point from the given pressure distribution along a body; the method is applicable to a fairly wide variety of cases. The laminar separation point is found by the von Karman-Millikan method for a series of velocity distributions along a flat plate, which consist of a region of uniform velocity followed by a region of uniform decreased velocity. It is shown that such a velocity distribution can frequently replace the actual velocity distribution along a body insofar as the effects on laminar separation are concerned. An example of the application of the method is given by using it to calculate the position of the laminar separation point on the NACA 0012 airfoil section at zero lift. The agreement between the position of the separation point calculated according to the present method and that found from more elaborate computations is very good.

  10. Soot Volume Fraction Measurements in a Three-Dimensional Laminar Diffusion Flame established in Microgravity

    E-print Network

    Legros, Guillaume; Joulain, Pierre; Jean-Pierre, Vantelon; Fuentes, Andres; Bertheau, Denis; Torero, Jose L

    2005-05-03

    A methodology for the estimation of the soot volume fraction in a three-dimensional laminar diffusion flame is presented. All experiments are conducted in microgravity and have as objective producing quantitative data ...

  11. Design and operation of a laminar-flow electrostatic-quadrupole-focused acceleration column

    SciTech Connect

    Maschke, A.W.

    1983-06-20

    This report deals with the design principles involved in the design of a laminar-flow electrostatic-quadrupole-focused acceleration column. In particular, attention will be paid to making the parameters suitable for incorporation into a DC MEQALAC design.

  12. Sooting Behaviour Dynamics of a Non-Bouyant Laminar Diffusion Flame

    E-print Network

    Fuentes, Andres; Legros, Guillaume; Rouvreau, Sebastien; Joulain, Pierre; Vantelon, Jean-Pierre; Torero, Jose L; Fernandez-Pello, Carlos

    2007-01-01

    Local soot concentrations in non-buoyant laminar diffusion flames have been demonstrated to be the outcome of two competitive processes, soot formation and soot oxidation. It was first believed that soot formation was the ...

  13. Analysis of Low-Speed Stall Aerodynamics of a Swept Wing with Laminar-Flow Glove

    NASA Technical Reports Server (NTRS)

    Bui, Trong

    2013-01-01

    This is the presentation related to the paper of the same name describing Reynolds Averaged Navier Stokes (RANS) computational Fluid Dynamics (CFD) analysis of low speed stall aerodynamics of a swept wing with a laminar flow wing glove.

  14. Measurements of laminar and turbulent flow in a curved duct with thin inlet boundary layers

    NASA Technical Reports Server (NTRS)

    Taylor, A. M. K. P.; Whitelaw, J. H.; Yianneskis, M.

    1981-01-01

    Laser Doppler velocimetry was used to measure the laminar and turbulent flow in a 90 deg square bend of strong curvature. The boundary layers at the inlet to the bend were approximately 25 percent and 15 percent of the hydraulic diameter for the laminar and turbulent flows, respectively. The development of the pressure driven secondary motion is more rapid for laminar flow: the maximum cross stream component measured was 60 percent of the bulk velocity in contrast to 40 percent for turbulent flow. The streamwise isotachs show that, for laminar flow, large velocities are found progressively nearer to the outer radius of the bend and along the sidewalls. For turbulent flow, the isotachs move towards the inner radius until about 60 deg around the bend where strong secondary motion results in a similar redistribution. Turbulence level and shear stress measurements are also presented.

  15. Fuel-dilution effect on differential molecular diffusion in laminar hydrogen diffusion flames

    Microsoft Academic Search

    Yung-cheng Chen; Jyh-Yuan Chen

    1998-01-01

    Laminar flame calculations have been made for a Tsuji counterflow geometry to investigate salient features caused by the differential diffusion effect in nitrogen-diluted hydrogen diffusion flames. A strong dependence of the differential diffusion parameter \\</p

  16. Video- Demonstration of Laminar Flow in a Liquid Onboard the International Space Station (ISS)

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Saturday Morning Science, the science of opportunity series of applied experiments and demonstrations, performed aboard the International Space Station (ISS) by Expedition 6 astronaut Dr. Don Pettit, revealed some remarkable findings. In this video clip, Pettit demonstrates laminar flow in a rotating film of water. The demonstration is done by placing tracer particles in a water film held in place by a round wire loop, then stirring the system rotationally. The resulting flow clearly demonstrates laminar 2D behavior with spiraling streamlines.

  17. Scanning PIV investigation of the laminar separation bubble on a SD7003 airfoil

    Microsoft Academic Search

    Wei Zhang; Rainer Hain; Christian J. Khler

    2008-01-01

    A laminar separation bubble occurs on the suction side of the SD7003 airfoil at an angle of attack ? = 48 and a low Reynolds\\u000a number less than 100,000, which brings about a significant adverse aerodynamic effect. The spatial and temporal structure\\u000a of the laminar separation bubble was studied using the scanning PIV method at ? = 4 and Re=60,000

  18. Laminar hydathodes in Urticaceae : Survey of tribes and anatomical observations on Pilea pumila and Urtica dioica

    Microsoft Academic Search

    N. R. Lersten; J. D. Curtis

    1991-01-01

    Laminar hydathodes are known from only three dicot families. InUrticaceae they are associated with minor vein junctions in all five tribes, as surveyed from cleared leaves of 43 species in 30 genera. Only one species lacked hydathodes. Exclusively adaxial hydathodes were found in 28 genera. In tribeElatostemeae, laminar hydathodes inPilea andPellionia species are abaxial, adaxial, or on both surfaces. Guttation

  19. A preliminary design study on an acoustic muffler for the laminar flow transition research apparatus

    NASA Technical Reports Server (NTRS)

    Abrahamson, A. L.

    1984-01-01

    An acoustic muffler design of a research tool for studying laminar flow and the mechanisms of transition, the Laminar Flow and Transition Research Apparatus (LFTRA) is investigated. Since the presence of acoustic pressure fluctuations is known to affect transition, low background noise levels in the test section of the LFTRA are mandatory. The difficulties and tradeoffs of various muffler design concepts are discussed and the most promising candidates are emphasized.

  20. Optimal product distribution from laminar flow reactors: Newtonian and other power-law fluids

    Microsoft Academic Search

    Keith L. Levien; Octave Levenspiel

    1999-01-01

    In tubular reactors viscous fluids are in laminar flow. For reactions in series this gives a product distribution different from either plug flow or mixed flow. More importantly, laminar flow depresses the maximum amount of intermediate that can be obtained when compared to plug flow. Here we treat the simple case of an elementary two-step mechanism:(1)[A?R?S]Three special cases of the

  1. Tackling a Hot Paradox: Laminar Soot Processes-2 (LSP-2)

    NASA Technical Reports Server (NTRS)

    Faeth, Gerard M.; Urban, David L.; Over, Ann (Technical Monitor)

    2002-01-01

    The last place you want to be in traffic is behind the bus or truck that is belching large clouds of soot onto your freshly washed car. Besides looking and smelling bad, soot is a health hazard. Particles range from big enough to see to microscopic and can accumulate in the lungs, potentially leading to debilitating or fatal lung diseases. Soot is wasted energy, and therein lies an interesting paradox: Soot forms in a flame's hottest regions where you would expect complete combustion and no waste. Soot enhances the emissions of other pollutants (carbon monoxide and polyaromatic hydrocarbons, etc.) from flames and radiates unwanted heat to combustion chambers (a candle's yellowish glow is soot radiating heat), among other effects. The mechanisms of soot formation are among the most important unresolved problems of combustion science because soot affects contemporary life in so many ways. Although we have used fire for centuries, many fundamental aspects of combustion remain elusive, in part because of limits imposed by the effects of gravity on Earth. Hot or warm air rises quickly and draws in fresh cold air behind it, thus giving flames the classical teardrop shape. Reactions occur in a very small zone, too fast for scientists to observe, in detail, what is happening inside the flame. The Laminar Soot Processes (LSP-2) experiments aboard STS-107 will use the microgravity environment of space to eliminate buoyancy effects and thus slow the reactions inside a flame so they can be more readily studied. 'Laminar' means a simple, smooth fuel jet burning in air, somewhat like a butane lighter. This classical flame approximates combustion in diesel engines, aircraft jet propulsion engines, and furnaces and other devices. LSP-2 will expand on surprising results developed from its first two flights in 1997. The data suggest the existence of a universal relationship, the soot paradigm, that, if proven, will be used to model and control combustion systems on Earth. STS-107 experiments also will help set the stage for extended combustion experiments aboard the International Space Station.

  2. Premixed laminar flame propagation in a rotating vessel

    NASA Astrophysics Data System (ADS)

    Parra, Teresa; Gorczakowski, Andrzej; Chomiak, Jerzy; Jarosinski, Jozef

    2008-11-01

    Combustion in a swirling flow is devoted to burn lean mixture in spark ignition engines since it provides fuel economy and exhaust emission reduction. Therefore it is important to know the flame behavior under centrifugal forces. The flame in a rotating gas is modified by an aerodynamic mechanism due to action of centrifugal forces instead the laminar burning velocity due to chemical kinetics. The paper deals with important characteristics of eddy combustion mechanism such as: flame shape and propagation as a function of the rotation rate. Therefore pictures captured by a video camera are treated with the image processing toolbox from Matlab in order to establish the main characteristics of the flame kernel of a mixture propane -- air at different rotation rates ranging from 500 to 4000 rpm. It is observed that the flame propagates along the rotation axis and that the extinguishing of the flame is involved with the heat losses as soon the flame reaches the wall of the chamber. In addition, the flame shape is quite similar to the intrusion head of a light fluid penetrating into a stagnated heavy fluid.

  3. Cooperative phenomena in laminar fluids: Observation of streamlines

    SciTech Connect

    Fink, Martin A.; Kretschmer, M.; Hoefner, H.; Konopka, U.; Morfill, G.E.; Ratynskaia, S. [Max Planck Institute for extraterrestrial Physics, Giessenbachstrasse, 85741 Garching (Germany); Fortov, V.; Petrov, O.; Usachev, A.; Zobnin, A. [Institute for High Energy Density, Russian Academy of Sciences, ul. Izhorskaya 13/19, 125412 Moscow (Russian Federation)

    2005-10-31

    Complex plasmas are an ideal model system to investigate laminar fluids as they allow to study fluids at the kinetic level. At this level we are able to identify streamlines particle by particle. This gives us the ability to research the behaviour of these streamlines as well as the behaviour of each individual particle of the streamline.We carried out our experiments in a modified GEC-RF-Reference cell. We trapped the particles within two glass rings and forced them to form a circular flow by using several stripe electrodes. In this flow the particles behave like an ideal fluid and form streamlines. By putting an obstacle into the flow we reduce the cross-section. To pass through this constricted cross-section some streamlines have to reconnect. After the obstacle the streamlines split up again. An analysis how streamlines split up and reconnect as result of external pressure on the fluid in our system is presented here.Streamlines also occur if two clouds of particles penetrate each other. We call this 'Lane formation'. Results from our PK-4 experiment are presented here also.

  4. Thermal Behavior of Laminar Periodic Channel Flow over Triangular Baffles

    NASA Astrophysics Data System (ADS)

    Nivesrangsan, P.; Sripattanapipat, S.; Eiamsa-ard, S.; Promvonge, P.

    2010-03-01

    Laminar periodic flow and heat transfer in a two dimensional horizontal channel with isothermal walls and with staggered triangular baffles are numerically investigated. The computations are based on the finite volume method, and the SIMPLE algorithm with QUICK scheme is implemented. The fluid flow and heat transfer characteristics are presented for Reynolds numbers based on the hydraulic diameter of the channel ranging from 100 to 600. Effects of different baffle tip angles on heat transfer and pressure loss in the channel are studied and the results of the triangular baffle are also compared with those of the flat baffle. It is observed that apart from the rise of Reynolds number, the reduction of the baffle tip angle leads to an increase in the Nusselt number and friction factor. According to the computational results for triangular baffles, the optimum thermal performance is found at the baffle angle of 5, baffle height to channel height ratio of 0.5 and baffle spacing to channel height ratio of 1.0. In addition, the thermal performances of the 5-10 triangular baffles are found to be higher than that of the flat baffle for all Reynolds numbers used.

  5. Distributed acoustic receptivity in laminar flow control configurations

    NASA Technical Reports Server (NTRS)

    Choudhari, Meelan

    1992-01-01

    A model problem related to distributed receptivity to free-stream acoustic waves in laminar flow control (LFC) configurations is studied, within the Orr-Sommerfield framework, by a suitable extension of the Goldstein-Ruban theory for receptivity due to localized disturbances on the airfoil surface. The results, thus, complement the earlier work on the receptivity produced by local variations in the surface suction and/or surface admittance. In particular, we show that the cumulative effect of the distributed receptivity can be substantially larger than that of a single, isolated suction strip or slot. Furthermore, even if the receptivity is spread out over very large distances, the most effective contributions come from a relatively short region in vicinity of the lower branch of the neutral stability curve. The length scale of this region is intermediate to that of the mean of these two length scales. Finally, it is found that the receptivity is effectively dominated by a narrow band of Fourier components from the wall-suction and admittance distributions, roughly corresponding to a detuning of less than ten percent with respect to the neutral instability wavenumber at the frequency under consideration. The results suggest that the drop-off in receptivity magnitudes away from the resonant wavenumber is nearly independent of the frequency parameter.

  6. Dental imaging using laminar optical tomography and micro CT

    NASA Astrophysics Data System (ADS)

    Long, Feixiao; Ozturk, Mehmet S.; Intes, Xavier; Kotha, Shiva

    2014-02-01

    Dental lesions located in the pulp are quite difficult to identify based on anatomical contrast, and, hence, to diagnose using traditional imaging methods such as dental CT. However, such lesions could lead to functional and/or molecular optical contrast. Herein, we report on the preliminary investigation of using Laminar Optical Tomography (LOT) to image the pulp and root canals in teeth. LOT is a non-contact, high resolution, molecular and functional mesoscopic optical imaging modality. To investigate the potential of LOT for dental imaging, we injected an optical dye into ex vivo teeth samples and imaged them using LOT and micro-CT simultaneously. A rigid image registration between the LOT and micro-CT reconstruction was obtained, validating the potential of LOT to image molecular optical contrast deep in the teeth with accuracy, non-invasively. We demonstrate that LOT can retrieve the 3D bio-distribution of molecular probes at depths up to 2mm with a resolution of several hundred microns in teeth.

  7. Type I Planet Migration in Weakly Magnetized Laminar Disks

    NASA Astrophysics Data System (ADS)

    Guilet, Jrme; Baruteau, Clment; Papaloizou, John C. B.

    2014-04-01

    Planet migration plays a crucial role in shaping planetary systems, and has therefore received a lot of attention in recent years in an effort to compare the statistical properties of observed exoplanets with the predictions of planet formation and migration theories. By modifying the propagation properties of the waves induced by the planet in the disk, the presence of a strong magnetic field can dramatically influence planet migration, in some cases reversing its direction. The more realistic case of a weaker magnetic field is less clear, although turbulent MHD simulations by Baruteau et al. (2011) suggest an effect on the corotation torque. Here, we present a study of the corotation torque in 2D laminar disks containing a toroidal magnetic field. We performed MHD simulations of the interaction between the magnetic field and the horseshoe motion of the gas, and found that this results in an additional corotation torque. This additional torque can be strong enough to reverse migration even for a field which pressure is only one percent of the thermal pressure. We speculate that this could lead to long range outward migration in the outer part of protoplanetary disks and may explain the observations by direct imaging of planets at several tens of AU from their star like the 4 planets system HR 8799.

  8. Laminar flow around corners triggers the formation of biofilm streamers.

    PubMed

    Rusconi, Roberto; Lecuyer, Sigolene; Guglielmini, Laura; Stone, Howard A

    2010-09-01

    Bacterial biofilms have an enormous impact on medicine, industry and ecology. These microbial communities are generally considered to adhere to surfaces or interfaces. Nevertheless, suspended filamentous biofilms, or streamers, are frequently observed in natural ecosystems where they play crucial roles by enhancing transport of nutrients and retention of suspended particles. Recent studies in streamside flumes and laboratory flow cells have hypothesized a link with a turbulent flow environment. However, the coupling between the hydrodynamics and complex biofilm structures remains poorly understood. Here, we report the formation of biofilm streamers suspended in the middle plane of curved microchannels under conditions of laminar flow. Experiments with different mutant strains allow us to identify a link between the accumulation of extracellular matrix and the development of these structures. Numerical simulations of the flow in curved channels highlight the presence of a secondary vortical motion in the proximity of the corners, which suggests an underlying hydrodynamic mechanism responsible for the formation of the streamers. Our findings should be relevant to the design of all liquid-carrying systems where biofilms are potentially present and provide new insights on the origins of microbial streamers in natural and industrial environments. PMID:20356880

  9. Investigation of Hypersonic Laminar Heating Augmentation in the Stagnation Region

    NASA Technical Reports Server (NTRS)

    Marineau, Eric C.; Lewis, Daniel R.; Smith, Michael S.; Lafferty, John F.; White, Molly E.; Amar, Adam J.

    2012-01-01

    Laminar stagnation region heating augmentation is investigated in the AEDC Tunnel 9 at Mach 10 by performing high frequency surface pressure and heat transfer measurements on the Orion CEV capsule at zero degree angle-of-attack for unit Reynolds numbers between 0.5 and 15 million per foot. Heating augmentation increases with Reynolds number, but is also model size dependent as it is absent on a 1.25-inch diameter model at Reynolds numbers where it reaches up to 15% on a 7-inch model. Heat transfer space-time correlations on the 7-inch model show that disturbances convect at the boundary layer edge velocity and that the streamwise integral scale increases with distance. Therefore, vorticity amplification due to stretching and piling-up in the stagnation region appears to be responsible for the stagnation point heating augmentation on the larger model. This assumption is reinforced by the f(exp -11/3) dependence of the surface pressure spectrum compared to the f(exp -1) dependence in the free stream. Vorticity amplification does not occur on the 1.25- inch model because the disturbances are too large. Improved free stream fluctuation measurements will be required to determine if significant vorticity is present upstream or mostly generated behind the bow shock.

  10. Dynamics of laminar circular jet impingement upon convex cylinders

    NASA Astrophysics Data System (ADS)

    New, T. H.; Long, J.

    2015-02-01

    Flow dynamics associated with a laminar circular jet impinging upon a convex cylinder has been investigated by laser-induced fluorescence and digital particle-image velocimetry techniques. Cylinder-to-jet diameter ratios of 1, 2, and 4 were investigated, while the jet-to-cylinder separation distance was kept at four jet diameters throughout. Flow visualization and ?2 criterion results show that once the jet ring-vortices impinge upon the cylindrical surface, they move away from the impingement point by wrapping themselves partially around the surface. As the cylinder diameter increases, wall boundary layer separation, vortex dipole formation, and separation locations are initiated earlier along the cylindrical surface, producing significantly larger wakes. Along the cylinder straight-edges, ring-vortex cores are significantly smaller after impingement. This is due to accentuated vortex-stretching caused by partial wrapping around the cylindrical surface by the ring-vortices, on top of their movement away from the impingement point. Interestingly, vortex dipoles demonstrate a strong tendency to travel upstream and interact with other upstream vortex dipoles, instead of moving downstream gradually seen for flat-surface jet-impingements. Wall shear stress results are also presented to quantify the effects of cylinder diameter-ratio on surface skin friction distribution. Finally, these preceding observations are corroborated and explained in a three-dimensional flow dynamics model presented here.

  11. Frost Growth and Densification in Laminar Flow Over Flat Surfaces

    NASA Technical Reports Server (NTRS)

    Kandula, Max

    2011-01-01

    One-dimensional frost growth and densification in laminar flow over flat surfaces has been theoretically investigated. Improved representations of frost density and effective thermal conductivity applicable to a wide range of frost circumstances have been incorporated. The validity of the proposed model considering heat and mass diffusion in the frost layer is tested by a comparison of the predictions with data from various investigators for frost parameters including frost thickness, frost surface temperature, frost density and heat flux. The test conditions cover a range of wall temperature, air humidity ratio, air velocity, and air temperature, and the effect of these variables on the frost parameters has been exemplified. Satisfactory agreement is achieved between the model predictions and the various test data considered. The prevailing uncertainties concerning the role air velocity and air temperature on frost development have been elucidated. It is concluded that that for flat surfaces increases in air velocity have no appreciable effect on frost thickness but contribute to significant frost densification, while increase in air temperatures results in a slight increase the frost thickness and appreciable frost densification.

  12. On the theory of laminar boundary layers involving separation

    NASA Technical Reports Server (NTRS)

    Von Karman, TH; Millikan, C

    1934-01-01

    This paper presents a mathematical discussion of the laminar boundary layer, which was developed with a view of facilitating the investigation of those boundary layers in particular for which the phenomenon of separation occurs. The treatment starts with a slight modification of the form of the boundary layer equation first published by Von Mises. Two approximate solutions of this equation are found, one of which is exact at the outer edge of the boundary layer while the other is exact at the wall. The final solution is obtained by joining these two solutions at the inflection points of the velocity profiles. The final solution is given in terms of a series of universal functions for a fairly broad class of potential velocity distributions outside of the boundary layer. Detailed calculations of the boundary layer characteristics are worked out for the case in which the potential velocity is a linear function of the distance from the upstream stagnation point. Finally, the complete separation point characteristics are determined for the boundary layer associated with a potential velocity distribution made up of two linear functions of the distance from the stagnation point. It appears that extensions of the detailed calculations to more complex potential flows can be fairly easily carried out by using the explicit formulae given in the paper. (author)

  13. Velocity fluctuations and energy amplification in laminar fluid flows

    NASA Astrophysics Data System (ADS)

    Ortiz de Zarate, Jose M.; Sengers, Jan V.

    2008-11-01

    We present a systematic procedure for evaluating the intrinsic velocity fluctuations and the resulting intrinsic energy amplification that are always present in laminar fluid flows. For this purpose we formulate a stochastic Orr-Sommerfeld equation and a stochastic Squire equation by applying a fluctuation-dissipation theorem for the random part of the dissipative stresses. From the solution of the stochastic Orr- Sommerfeld and Squire equations the intrinsic energy amplification can be deduced. As an illustration of the procedure we present an explicit solution for the case of planar Couette flow. We first solve the fluctuating hydrodynamics equations in the bulk, obtaining an exact representation of the spatial spectrum of the velocity fluctuations valid for large wave numbers. The resulting energy amplification is proportional to Re^3/2. Next, we show how to a good approximation confinement can be incorporated by a simple Galerkin projection technique. The effect of the boundary conditions is to reduce the energy amplification to a logarithmic dependence on Re. We shall also indicate how an exact solution for the case of confined geometries can be obtained by an expansion into a set of hydrodynamic modes, conveniently expressed in terms of Airy functions.

  14. Erosion of a granular bed driven by laminar fluid flow

    E-print Network

    A. E. Lobkovsky; A. V. Orpe; R. Molloy; A. Kudrolli; D. H. Rothman

    2008-05-01

    Motivated by examples of erosive incision of channels in sand, we investigate the motion of individual grains in a granular bed driven by a laminar fluid to give us new insights into the relationship between hydrodynamic stress and surface granular flow. A closed cell of rectangular cross-section is partially filled with glass beads and a constant fluid flux $Q$ flows through the cell. The refractive indices of the fluid and the glass beads are matched and the cell is illuminated with a laser sheet, allowing us to image individual beads. The bed erodes to a rest height $h_r$ which depends on $Q$. The Shields threshold criterion assumes that the non-dimensional ratio $\\theta$ of the viscous stress on the bed to the hydrostatic pressure difference across a grain is sufficient to predict the granular flux. Furthermore, the Shields criterion states that the granular flux is non-zero only for $\\theta >\\theta_c$. We find that the Shields criterion describes the observed relationship $h_r \\propto Q^{1/2}$ when the bed height is offset by approximately half a grain diameter. Introducing this offset in the estimation of $\\theta$ yields a collapse of the measured Einstein number $q^*$ to a power-law function of $\\theta - \\theta_c$ with exponent $1.75 \\pm 0.25$. The dynamics of the bed height relaxation are well described by the power law relationship between the granular flux and the bed stress.

  15. Columnar Connectivity and Laminar Processing in Cat Primary Auditory Cortex

    PubMed Central

    Atencio, Craig A.; Schreiner, Christoph E.

    2010-01-01

    Background Radial intra- and interlaminar connections form a basic microcircuit in primary auditory cortex (AI) that extracts acoustic information and distributes it to cortical and subcortical networks. Though the structure of this microcircuit is known, we do not know how the functional connectivity between layers relates to laminar processing. Methodology/Principal Findings We studied the relationships between functional connectivity and receptive field properties in this columnar microcircuit by simultaneously recording from single neurons in cat AI in response to broadband dynamic moving ripple stimuli. We used spectrotemporal receptive fields (STRFs) to estimate the relationship between receptive field parameters and the functional connectivity between pairs of neurons. Interlaminar connectivity obtained through cross-covariance analysis reflected a consistent pattern of information flow from thalamic input layers to cortical output layers. Connection strength and STRF similarity were greatest for intralaminar neuron pairs and in supragranular layers and weaker for interlaminar projections. Interlaminar connection strength co-varied with several STRF parameters: feature selectivity, phase locking to the stimulus envelope, best temporal modulation frequency, and best spectral modulation frequency. Connectivity properties and receptive field relationships differed for vertical and horizontal connections. Conclusions/Significance Thus, the mode of local processing in supragranular layers differs from that in infragranular layers. Therefore, specific connectivity patterns in the auditory cortex shape the flow of information and constrain how spectrotemporal processing transformations progress in the canonical columnar auditory microcircuit. PMID:20209092

  16. Flamelet mathematical models for non-premixed laminar combustion

    SciTech Connect

    Carbonell, D.; Perez-Segarra, C.D.; Oliva, A. [Centre Tecnologic de Transferencia de Calor (CTTC), Universitat Politecnica de Catalunya (UPC), Colom 11, E-08222 Terrassa, Barcelona (Spain); Coelho, P.J. [Mechanical Engineering Department, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

    2009-02-15

    Detailed numerical calculations based on the solution of the full transport equations have been compared with flamelet calculations in order to analyse the flamelet concept for laminar diffusion flames. The goal of this work is to study the interactive (Lagrangian Flamelet Model and Interactive Steady Flamelet Model), and non-interactive (Steady Flamelet Model and Enthalpy Defect Flamelet Model) flamelet models considering both differential diffusion and non-differential diffusion situations, and adiabatic and non-adiabatic conditions. Moreover, a new procedure has been employed to obtain enthalpy defects in the flamelet library, the application of which has been found to be encouraging. The effect of using in-situ, local or stoichiometric scalar dissipation rate conditions, and also the effect of using local or stoichiometric conditions to evaluate the flamelet-like time has been analysed. To improve slow species predictions using the non-interactive models, their transport equations are solved with the reaction terms calculated from the flamelet library, also considering local or stoichiometric conditions in the so-called Extended Flamelet Models. (author)

  17. Investigation on the Performance of Fire Detection Systems for Tunnel ApplicationsPart 2: Full-Scale Experiments Under Longitudinal Airflow Conditions

    Microsoft Academic Search

    Z. G. Liu; A. H. Kashef; G. D. Lougheed; G. P. Crampton

    2011-01-01

    This paper presents the results of the full-scale experiments conducted in a laboratory tunnel facility under longitudinal\\u000a airflow conditions and in the Carr-Viger Tunnel. The performance of nine fire detection systems representing five types of\\u000a the fire detection technologies for road tunnel applications was investigated using representative tunnel fire scenarios.\\u000a The changes in fire characteristics caused by longitudinal airflow, such

  18. Effects of cartilaginous rings on airflow and particle transport through simplified and realistic models of human upper respiratory tracts

    NASA Astrophysics Data System (ADS)

    Srivastav, Vivek Kumar; Paul, Akshoy Ranjan; Jain, Anuj

    2013-12-01

    In the present study, computational fluid dynamics (CFD) is used to investigate inspiratory and expiratory airflow characteristics in the human upper respiratory tract for the purpose of identifying the probable locations of particle deposition and the wall injury. Computed tomography (CT) scan data was used to reconstruct a three dimensional respiratory tract from trachea to first generation bronchi. To compare, a simplified model of respiratory tract based on Weibel was also used in the study. The steady state results are obtained for an airflow rate of 45 L/min, corresponding to the heavy breathing condition. The velocity distribution, wall shear stress, static pressure and particle deposition are compared for inspiratory flows in simplified and realistic models and expiratory flows in realistic model only. The results show that the location of cartilaginous rings is susceptible to wall injury and local particle deposition.

  19. Plasma-Based Mixing Actuation in Airflow, Quantitated by Probe Breakdown Fluorescence

    NASA Astrophysics Data System (ADS)

    Leonov, Sergey; Firsov, Alexander; Shurupov, Michail; Yarantsev, Dmitry; Ohio State University Team; JIHT RAS Team

    2013-09-01

    Effective mixing of fuel and oxidizer in air-breathing engine at compressible conditions is an essential problem of high-speed combustion due to short residence time of gas mixture in the combustor of limited length. The effect of the mixing actuation by plasma is observed because of the gasdynamic instability arisen after the long filamentary discharge of submicrosecond duration generated along the contact zone of two co-flown gases. The work is focused on detail consideration of the mechanism of gas instability, promoted by plasma, on effect of the discharge specific localization, and on diagnostics development for qualitative and quantitative estimation of the mixing efficiency. The dynamics of relative concentration of gas components is examined quantitatively by means of Probe Discharge Breakdown Fluorescence (PBF). In this method an optical emission spectra of weak filamentary high-voltage nanosecond probe discharge are collected from local zone of interest in airflow. The first measurements of the mixing efficiency in vicinity of wall-injected secondary gas are presented. It is shown that the method of PBF could deliver experimental data on state of the two-component medium with <1 mcs and <5 mm of time and spatial resolution, correspondingly. Effective mixing of fuel and oxidizer in air-breathing engine at compressible conditions is an essential problem of high-speed combustion due to short residence time of gas mixture in the combustor of limited length. The effect of the mixing actuation by plasma is observed because of the gasdynamic instability arisen after the long filamentary discharge of submicrosecond duration generated along the contact zone of two co-flown gases. The work is focused on detail consideration of the mechanism of gas instability, promoted by plasma, on effect of the discharge specific localization, and on diagnostics development for qualitative and quantitative estimation of the mixing efficiency. The dynamics of relative concentration of gas components is examined quantitatively by means of Probe Discharge Breakdown Fluorescence (PBF). In this method an optical emission spectra of weak filamentary high-voltage nanosecond probe discharge are collected from local zone of interest in airflow. The first measurements of the mixing efficiency in vicinity of wall-injected secondary gas are presented. It is shown that the method of PBF could deliver experimental data on state of the two-component medium with <1 mcs and <5 mm of time and spatial resolution, correspondingly. Funded by AFOSR under Dr Chiping Li supervision

  20. Visualization of the airflow around a life-sized, heated, breathing mannequin at ultralow windspeeds.

    PubMed

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

    2008-07-01

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

  1. F-15B in flight showing Supersonic Natural Laminar Flow (SS-NLF) experiment attached vertically to t

    NASA Technical Reports Server (NTRS)

    1999-01-01

    In-flight photo of the F-15B equipped with the Supersonic Natural Laminar Flow (SS-NLF) experiment. During four research flights, laminar flow was achieved over 80 percent of the test wing at speeds approaching Mach 2. This was accomplished as the sole result of the shape of the wing, without the use of suction gloves, such as on the F-16XL. Laminar flow is a condition in which air passes over a wing in smooth layers, rather than being turbulent The greater the area of laminar flow, the lower the amount of friction drag on the wing, thus increasing an aircraft's range and fuel economy. Increasing the area of laminar flow on a wing has been the subject of research by engineers since the late 1940s, but substantial success has proven elusive. The SS-NLF experiment was intended to provide engineers with the data by which to design natural laminar flow wings.

  2. Exploratory investigation of the use of area suction to eliminate air-flow separation in diffusers having large expansion angles

    NASA Technical Reports Server (NTRS)

    Holzhauser, Curt A; Hall, Leo P

    1956-01-01

    Tests were made at a mean inlet Mach number of 0.2 with area suction applied to conical diffusers with expansion angles of 30 degrees and 50 degrees and exit to inlet area ratios of 2. Air-flow separation was eliminated with suction mass flows of 3 and 4 percent of the inlet mass flows for the 30 degrees and 50 degrees diffusers, respectively.

  3. Interactions between Topographic Airflow and Cloud\\/Precipitation Development during the Passage of a Winter Storm in Arizona

    Microsoft Academic Search

    Roelof T. Bruintjes; Terry L. Clark; William D. Hall

    1994-01-01

    A case study showing comparisons between observations and numerical simulations of the passage of a winter storm over complex terrain is presented. The interactions between the mesoscale and cloud environments and the microphysical and dynamical processes are addressed using both observations and numerical simulations.A three-dimensional, time-dependent nested grid model was used to conduct numerical simulations of the three-dimensional airflow and

  4. Effects of system cycling, evaporator airflow, and condenser coil fouling on the performance of residential split-system air conditioners

    E-print Network

    Dooley, Jeffrey Brandon

    2005-02-17

    EFFECTS OF SYSTEM CYCLING, EVAPORATOR AIRFLOW, AND CONDENSER COIL FOULING ON THE PERFORMANCE OF RESIDENTIAL SPLIT-SYSTEM AIR CONDITIONERS A Thesis by JEFFREY BRANDON DOOLEY Submitted to the Office of Graduate Studies... COIL FOULING ON THE PERFORMANCE OF RESIDENTIAL SPLIT-SYSTEM AIR CONDITIONERS A Thesis by JEFFREY BRANDON DOOLEY Submitted to Texas A&M University in partial fulfillment of the requirements for the degree of MASTER...

  5. The influence of synoptic airflow on UK daily precipitation extremes. Part I: Observed spatio-temporal relationships

    Microsoft Academic Search

    Douglas MaraunTimothy; Timothy J. Osborn; Henning W. Rust

    2011-01-01

    We study the influence of synoptic scale atmospheric circulation on extreme daily precipitation across the United Kingdom,\\u000a using observed time series from 689 rain gauges. To this end we employ a statistical model, that uses airflow strength, direction\\u000a and vorticity as predictors for the generalised extreme value distribution of monthly precipitation maxima. The inferred relationships\\u000a are connected with the dominant

  6. Procedure and Application for Determining the Cold Deck and Hot Deck Airflow in a Dual-Duct System

    E-print Network

    Liu, G.; Mingsheng, L.

    2006-01-01

    ICEBO2006, Shenzhen, China HVAC Technologies for Energy Efficiency, Vol. IV-11-1 Procedure and Application for Determining the Cold Deck and Hot Deck Airflow in a Dual-Duct System Guopeng Liu Mingsheng Liu, Ph.D., P.E. University...). Continuous Commissioning (CC) has been one of the most prominent energy conservation processes for over a decade. CC has been developed to help building owners achieve energy savings, improve thermal comfort and reduce maintenance costs (Liu et al. 1999...

  7. Breathing life into dinosaurs: tackling challenges of soft-tissue restoration and nasal airflow in extinct species.

    PubMed

    Bourke, Jason M; Porter, W M Ruger; Ridgely, Ryan C; Lyson, Tyler R; Schachner, Emma R; Bell, Phil R; Witmer, Lawrence M

    2014-11-01

    The nasal region plays a key role in sensory, thermal, and respiratory physiology, but exploring its evolution is hampered by a lack of preservation of soft-tissue structures in extinct vertebrates. As a test case, we investigated members of the "bony-headed" ornithischian dinosaur clade Pachycephalosauridae (particularly Stegoceras validum) because of their small body size (which mitigated allometric concerns) and their tendency to preserve nasal soft tissues within their hypermineralized skulls. Hypermineralization directly preserved portions of the olfactory turbinates along with an internal nasal ridge that we regard as potentially an osteological correlate for respiratory conchae. Fossil specimens were CT-scanned, and nasal cavities were segmented and restored. Soft-tissue reconstruction of the nasal capsule was functionally tested in a virtual environment using computational fluid dynamics by running air through multiple models differing in nasal soft-tissue conformation: a bony-bounded model (i.e., skull without soft tissue) and then models with soft tissues added, such as a paranasal septum, a scrolled concha, a branched concha, and a model combining the paranasal septum with a concha. Deviations in fluid flow in comparison to a phylogenetically constrained sample of extant diapsids were used as indicators of missing soft tissue. Models that restored aspects of airflow found in extant diapsids, such as appreciable airflow in the olfactory chamber, were judged as more likely. The model with a branched concha produced airflow patterns closest to those of extant diapsids. These results from both paleontological observation and airflow modeling indicate that S. validum and other pachycephalosaurids could have had both olfactory and respiratory conchae. Although respiratory conchae have been linked to endothermy, such conclusions require caution in that our re-evaluation of the reptilian nasal apparatus indicates that respiratory conchae may be more widespread than originally thought, and other functions, such as selective brain temperature regulation, could be important. PMID:25312371

  8. Genome-Wide Association Studies Identify CHRNA5/3 and HTR4 in the Development of Airflow Obstruction

    PubMed Central

    Shrine, Nick R. G.; Loehr, Laura R.; Zhao, Jing Hua; Manichaikul, Ani; Lopez, Lorna M.; Smith, Albert Vernon; Heckbert, Susan R.; Smolonska, Joanna; Tang, Wenbo; Loth, Daan W.; Curjuric, Ivan; Hui, Jennie; Latourelle, Jeanne C.; Henry, Amanda P.; Aldrich, Melinda; Bakke, Per; Beaty, Terri H.; Bentley, Amy R.; Borecki, Ingrid B.; Brusselle, Guy G.; Burkart, Kristin M.; Chen, Ting-hsu; Couper, David; Crapo, James D.; Davies, Gail; Dupuis, Jose; Franceschini, Nora; Gulsvik, Amund; Hancock, Dana B.; Harris, Tamara B.; Hofman, Albert; Imboden, Medea; James, Alan L.; Khaw, Kay-Tee; Lahousse, Lies; Launer, Lenore J.; Litonjua, Augusto; Liu, Yongmei; Lohman, Kurt K.; Lomas, David A.; Lumley, Thomas; Marciante, Kristin D.; McArdle, Wendy L.; Meibohm, Bernd; Morrison, Alanna C.; Musk, Arthur W.; Myers, Richard H.; North, Kari E.; Postma, Dirkje S.; Psaty, Bruce M.; Rich, Stephen S.; Rivadeneira, Fernando; Rochat, Thierry; Rotter, Jerome I.; Artigas, Mara Soler; Starr, John M.; Uitterlinden, Andr G.; Wareham, Nicholas J.; Wijmenga, Cisca; Zanen, Pieter; Province, Michael A.; Silverman, Edwin K.; Deary, Ian J.; Palmer, Lyle J.; Cassano, Patricia A.; Gudnason, Vilmundur; Barr, R. Graham; Loos, Ruth J. F.; Strachan, David P.; London, Stephanie J.; Boezen, H. Marike; Probst-Hensch, Nicole; Gharib, Sina A.; Hall, Ian P.; OConnor, George T.; Tobin, Martin D.; Stricker, Bruno H.

    2012-01-01

    Rationale: Genome-wide association studies (GWAS) have identified loci influencing lung function, but fewer genes influencing chronic obstructive pulmonary disease (COPD) are known. Objectives: Perform meta-analyses of GWAS for airflow obstruction, a key pathophysiologic characteristic of COPD assessed by spirometry, in population-based cohorts examining all participants, ever smokers, never smokers, asthma-free participants, and more severe cases. Methods: Fifteen cohorts were studied for discovery (3,368 affected; 29,507 unaffected), and a population-based family study and a meta-analysis of case-control studies were used for replication and regional follow-up (3,837 cases; 4,479 control subjects). Airflow obstruction was defined as FEV1 and its ratio to FVC (FEV1/FVC) both less than their respective lower limits of normal as determined by published reference equations. Measurements and Main Results: The discovery meta-analyses identified one region on chromosome 15q25.1 meeting genome-wide significance in ever smokers that includes AGPHD1, IREB2, and CHRNA5/CHRNA3 genes. The region was also modestly associated among never smokers. Gene expression studies confirmed the presence of CHRNA5/3 in lung, airway smooth muscle, and bronchial epithelial cells. A single-nucleotide polymorphism in HTR4, a gene previously related to FEV1/FVC, achieved genome-wide statistical significance in combined meta-analysis. Top single-nucleotide polymorphisms in ADAM19, RARB, PPAP2B, and ADAMTS19 were nominally replicated in the COPD meta-analysis. Conclusions: These results suggest an important role for the CHRNA5/3 region as a genetic risk factor for airflow obstruction that may be independent of smoking and implicate the HTR4 gene in the etiology of airflow obstruction. PMID:22837378

  9. Nonlinear aero-thermoelastic analysis of homogeneous and functionally graded plates in supersonic airflow using coupled models

    Microsoft Academic Search

    H. M. Navazi; H. Haddadpour

    2011-01-01

    In this paper, the aeroelastic behavior of homogeneous and functionally graded two- and three-dimensional flat plates is studied under supersonic airflow. The effects of coupled modeling of the aerodynamic heating with flight conditions and the thermal degradation of the plate are investigated, too. The von-Karman nonlinear strains, piston theory and a combination of simple rule of mixtures and the MoriTanaka

  10. Magnetic resonance imaging and computational fluid dynamics (CFD) simulations of rabbit nasal airflows for the development of hybrid CFD/PBPK models

    PubMed Central

    Corley, R. A.; Minard, K. R.; Kabilan, S.; Einstein, D. R.; Kuprat, A. P.; Harkema, J. R.; Kimbell, J. S.; Gargas, M. L.; Kinzell, John H.

    2010-01-01

    The percentages of total airflows over the nasal respiratory and olfactory epithelium of female rabbits were calculated from computational fluid dynamics (CFD) simulations of steady-state inhalation. These airflow calculations, along with nasal airway geometry determinations, are critical parameters for hybrid CFD/physiologically based pharmacokinetic models that describe the nasal dosimetry of water-soluble or reactive gases and vapors in rabbits. CFD simulations were based upon three-dimensional computational meshes derived from magnetic resonance images of three adult female New Zealand White (NZW) rabbits. In the anterior portion of the nose, the maxillary turbinates of rabbits are considerably more complex than comparable regions in rats, mice, monkeys, or humans. This leads to a greater surface area to volume ratio in this region and thus the potential for increased extraction of water soluble or reactive gases and vapors in the anterior portion of the nose compared to many other species. Although there was considerable interanimal variability in the fine structures of the nasal turbinates and airflows in the anterior portions of the nose, there was remarkable consistency between rabbits in the percentage of total inspired airflows that reached the ethmoid turbinate region (~50%) that is presumably lined with olfactory epithelium. These latter results (airflows reaching the ethmoid turbinate region) were higher than previous published estimates for the male F344 rat (19%) and human (7%). These differences in regional airflows can have significant implications in interspecies extrapolations of nasal dosimetry. PMID:19519151

  11. Numerical Simulation of Airway Dimension Effects on Airflow Patterns and Odorant Deposition Patterns in the Rat Nasal Cavity

    PubMed Central

    Wei, Zehong; Xu, Zhixiang; Li, Bo; Xu, Fuqiang

    2013-01-01

    The sense of smell is largely dependent on the airflow and odorant transport in the nasal cavity, which in turn depends on the anatomical structure of the nose. In order to evaluate the effect of airway dimension on rat nasal airflow patterns and odorant deposition patterns, we constructed two 3-dimensional, anatomically accurate models of the left nasal cavity of a Sprague-Dawley rat: one was based on high-resolution MRI images with relatively narrow airways and the other was based on artificially-widening airways of the MRI images by referencing the section images with relatively wide airways. Airflow and odorant transport, in the two models, were determined using the method of computational fluid dynamics with finite volume method. The results demonstrated that an increase of 34 m in nasal airway dimension significantly decreased the average velocity in the whole nasal cavity by about 10% and in the olfactory region by about 12% and increased the volumetric flow into the olfactory region by about 3%. Odorant deposition was affected to a larger extent, especially in the olfactory region, where the maximum odorant deposition difference reached one order of magnitude. The results suggest that a more accurate nasal cavity model is necessary in order to more precisely study the olfactory function of the nose when using the rat. PMID:24204875

  12. Preliminary Investigation of Certain Laminar-Flow Airfoils for Application at High Speeds and Reynolds Numbers

    NASA Technical Reports Server (NTRS)

    Jacobs, E.N.; Abbott, Ira H.; von Doenhoff, A.E.

    1939-01-01

    In order to extend the useful range of Reynolds numbers of airfoils designed to take advantage of the extensive laminar boundary layers possible in an air stream of low turbulence, tests were made of the NACA 2412-34 and 1412-34 sections in the NACA low-turbulence tunnel. Although the possible extent of the laminar boundary layer on these airfoils is not so great as for specially designed laminar-flow airfoils, it is greater than that for conventional airfoils, and is sufficiently extensive so that at Reynolds numbers above 11,000,000 the laminar region is expected to be limited by the permissible 'Reynolds number run' and not by laminar separation as is the case with conventional airfoils. Drag measurements by the wake-survey method and pressure-distribution measurements were made at several lift coefficients through a range of Reynolds numbers up to 11,400,000. The drag scale-effect curve for the NACA 1412-34 is extrapolated to a Reynolds number of 30,000,000 on the basis of theoretical calculations of the skin friction. Comparable skin-friction calculations were made for the NACA 23012. The results indicate that, for certain applications at moderate values of the Reynolds number, the NACA 1412-34 and 2412-34 airfoils offer some advantages over such conventional airfoils as the NACA 23012. The possibility of maintaining a more extensive laminar boundary layer on these airfoils should result in a small drag reduction, and the absence of pressure peaks allows higher speeds to be reached before the compressibility burble is encountered. At lower Reynold numbers, below about 10,000,000, these airfoils have higher drags than airfoils designed to operate with very extensive laminar boundary layers.

  13. Recovery of airflow resistivity of poroelastic beams submitted to transient mechanical stress

    NASA Astrophysics Data System (ADS)

    Ogam, Erick

    2013-01-01

    The airflow resistivities of air-saturated poroelastic slender beams submitted to transient mechanical stress are recovered using fluid and solid borne compressional mode phase velocity expressions drawn from a modified Biot theory. A point where the two dilatational modes intersect and their phase velocities equal is first sought. This point also corresponds to the Biot transitional frequency indicating the frequency at which the solid and the pore fluid start disassociating due to the weakening of the viscous forces by the thinning of the viscous boundary layer in the pores. A bilinear time-frequency (TF) distribution is used to represent on the time-frequency plane, the captured transient mechanical stress waves from which the point of intersection/separation of the two modes is located. The projection of the Eigenfrequencies obtained from a simple 3D finite element modeling of the thin poroelastic beam, on a (TF) diagram, facilitates the identification of the modes. The transition frequencies for the poroelastic beams thus retrieved are verified through the use of variable frequency, single cycle sine wave bursts. The anisotropy of the foams are also revealed by analyzing the transient responses of the poroelastic beam specimens cut from the same panel but in two perpendicular directions in orientation to each other.

  14. Correlation between nasal airflow characteristics and clinical relevance of nasal septal deviation to nasal airway obstruction.

    PubMed

    Kim, Sung Kyun; Heo, Go Eun; Seo, Anna; Na, Yang; Chung, Seung-Kyu

    2014-02-01

    Since the imbalance of the nasal cavities due to nasal septal deviation (NSD) is a commonly observed anatomic variation in healthy adults, clinicians must often decide whether or not it is clinically relevant to the symptoms of nasal airway obstruction (NAO). Main reason for this is a lack of data correlating the symptoms of NAO with objective findings. The aim of our study is to find the correlation between fluid dynamic parameters and the anatomy of nasal cavity with NSD by numerical simulation. We generated 6 computational models of nasal cavities with NSD were created from computed tomographic images: 3 symptomatic patients with NAO and 3 asymptomatic patients. Computational fluid dynamics (CFD) was used to simulate steady inspiratory airflows in each nasal cavity model and compare the fluid dynamic properties of each. In the symptomatic cases, the pressure drop from the naris to the end of the septum was larger, and more uneven flow partitioning was observed. Local maximum velocity and wall shear stress were higher in the symptomatic group than in the asymptomatic group. The symptoms of NAO seem to be related more to the nasal resistance from the naris to the end of the septum than to the total nasal resistance from naris to nasopharynx. Factors correlated with NAO by CFD can be used as elements in patient-specific objective diagnostic tools for NAO in the presence of NSD. PMID:24361464

  15. Multiscale Airflow Model and Aerosol Deposition in Healthy and Emphysematous Rat Lungs

    NASA Astrophysics Data System (ADS)

    Oakes, Jessica; Marsden, Alison; Grandmont, Celine; Darquenne, Chantal; Vignon-Clementel, Irene

    2012-11-01

    The fate of aerosol particles in healthy and emphysematic lungs is needed to determine the toxic or therapeutic effects of inhalable particles. In this study we used a multiscale numerical model that couples a 0D resistance and capacitance model to 3D airways generated from MR images. Airflow simulations were performed using an in-house 3D finite element solver (SimVascular, simtk.org). Seven simulations were performed; 1 healthy, 1 uniform emphysema and 5 different cases of heterogeneous emphysema. In the heterogeneous emphysema cases the disease was confined to a single lobe. As a post processing step, 1 micron diameter particles were tracked in the flow field using Lagrangian particle tracking. The simulation results showed that the inhaled flow distribution was equal for the healthy and uniform emphysema cases. However, in the heterogeneous emphysema cases the delivery of inhaled air was larger in the diseased lobe. Additionally, there was an increase in delivery of aerosol particles to the diseased lobe. This suggests that as the therapeutic particles would reach the diseased areas of the lung, while toxic particles would increasingly harm the lung. The 3D-0D model described here is the first of its kind to be used to study healthy and emphysematic lungs. NSF Graduate Fellowship (Oakes), Burroughs Wellcome Fund (Marsden, Oakes) 1R21HL087805-02 from NHLBI at NIH, INRIA Team Grant.

  16. Plasma morphology and induced airflow characterization of a DBD actuator with serrated electrode

    NASA Astrophysics Data System (ADS)

    Joussot, R.; Leroy, A.; Weber, R.; Rabat, H.; Loyer, S.; Hong, D.

    2013-03-01

    Plasma morphology and airflow induced by a dielectric barrier discharge (DBD) actuator, whose exposed electrode geometry is designed with a serrated configuration, are investigated in quiescent air and compared with a DBD actuator consisting of electrodes designed with a standard linear strip configuration. ICCD imaging, electrical measurements and three-component laser Doppler velocimetry were carried out to compare various features of these two actuators. With the serrated configuration, ICCD images of the discharge show that streamers are bent, whereas with the linear configuration they are straight. These curved streamers induce a three-dimensional flow topology, which is confirmed by friction line visualization and velocity measurements. Whereas a two-dimensional wall-jet is induced with the linear configuration, a transverse velocity component is measured with the serrated configuration, implying the creation of spanwise-periodic vorticity. Phase-averaged velocity measurements allow the temporal variation of this transverse velocity to be highlighted. On both sides of a tooth, it has qualitatively the same variation as the longitudinal velocity with respect to the negative or positive half-cycles of the high voltage signal. Moreover, with the same electrical operating parameters, the measured longitudinal velocity was higher, particularly at the tips.

  17. Short-term effect of humid airflow on antimicrobial air filters using Sophora flavescens nanoparticles.

    PubMed

    Hwang, Gi Byoung; Lee, Jung Eun; Nho, Chu Won; Lee, Byung Uk; Lee, Seung Jae; Jung, Jae Hee; Bae, Gwi-Nam

    2012-04-01

    Bioaerosols have received social and scientific attention because they can be hazardous to human health. Recently, antimicrobial treatments using natural products have been used to improve indoor air quality (IAQ) since they are typically less toxic to humans compared to other antimicrobial substances such as silver, carbon nanotubes, and metal oxides. Few studies, however, have examined how environmental conditions such as the relative humidity (RH), surrounding temperature, and retention time of bacteria on filters affect the filtration and antimicrobial characteristics of a filter treated with such natural products. In this study, we investigated changes in the morphology of the natural nanoparticles, pressure drop, filtration efficiency, and the inactivation rate caused by the short-term effect of humid airflow on antimicrobial fiber filters. Nanoparticles of Sophora flavescens were deposited on the filter media surface using an aerosol process. We observed coalescence and morphological changes of the nanoparticles on fiber filters under humid conditions of an RH >50%. The level of coalescence in these nanoparticles increased with increasing RH. Filters exposed to an RH of 25% have a higher pressure drop than those exposed to an RH >50%. In an inactivation test against Staphylococcus epidermidis bacterial aerosol, the inactivation efficiency at an RH of 25% was higher than that at an RH of 57% or 82%. To effectively apply antimicrobial filters using natural products in the environment, one must characterize the filters under various environmental conditions. Thus, this study provides important information on the use of antimicrobial filters made of natural products. PMID:22369866

  18. CHARACTERIZATION OF AIRFLOWS NEAR THE EXIT OF HVAC REGISTERS USING LASER DOPPLER VELOCIMETRY (LDV).

    SciTech Connect

    TUTU,N.K.; KRISHNA,C.R.; ANDREWS,J.W.; BUTCHER,T.A.

    2003-03-13

    A facility to characterize the airflow at the exit of HVAC registers was designed and fabricated. The objective of this work is to obtain velocity and turbulence data at the exit of registers, which can then be used as an input boundary condition in a modern Computational Fluid Dynamics (CFD) code to predict the velocity and temperature distribution in an enclosure, and also the register performance parameters such as throw. During the course of this work, two commonly used registers were tested. Both registers were 8 inch x 4 inch sidewall registers. Laser Doppler Velocimetry was used to measure the axial and vertical components of the velocity vector at various locations across the face of the registers. For the two cases of registers studied here, the results suggest that the velocity field at the very exit of each of these registers scales with the flow rate through the registers. This means that, in the mode of operation in which the supply fan (of an HVAC system) has a ''High'' and ''Low'' setting, similar velocity scaling would result for the type of registers tested here.

  19. The effect of mako sharkskin on laminar flow separation

    NASA Astrophysics Data System (ADS)

    Bradshaw, Michael; Lang, Amy; Motta, Philip; Habegger, Maria; Hueter, Robert

    2013-11-01

    Many animals possess effective performance enhancing mechanisms, such as the denticles found on the skin of the shortfin mako shark (Isurus oxyrinchus). The shortfin mako, one of the fastest sharks on the planet, is covered by small, tooth-like scales that vary in flexibility over the body. Previous biological findings have shown that the scales increase in flexibility from the leading to trailing edge over the pectoral fin as well as on various sections of the body. It is believed that the scale bristling may provide a mechanism for flow separation control that leads to decreased drag and increased maneuverability. This study involved testing a left pectoral fin of a shortfin mako shark as well as a cylinder with a sharkskin specimen applied circumferentially in a water tunnel facility under static, laminar conditions. Digital Particle Image Velocimetry (DPIV) was used to characterize the flow over the surfaces. Various Reynolds numbers were tested for both configurations, as well as several AOAs for the pectoral fin. The flow over the fin and cylinder were compared to a painted fin and a smooth PVC cylinder, respectively. The study found that the shark scales do, in fact, help to control flow separation. However, in order for the scales to bristle and trap the reversing flow, a certain magnitude of reversed flow and shear is required. This phenomenon seems to be most effective at near stall conditions and at higher Reynolds numbers. Many animals possess effective performance enhancing mechanisms, such as the denticles found on the skin of the shortfin mako shark (Isurus oxyrinchus). The shortfin mako, one of the fastest sharks on the planet, is covered by small, tooth-like scales that vary in flexibility over the body. Previous biological findings have shown that the scales increase in flexibility from the leading to trailing edge over the pectoral fin as well as on various sections of the body. It is believed that the scale bristling may provide a mechanism for flow separation control that leads to decreased drag and increased maneuverability. This study involved testing a left pectoral fin of a shortfin mako shark as well as a cylinder with a sharkskin specimen applied circumferentially in a water tunnel facility under static, laminar conditions. Digital Particle Image Velocimetry (DPIV) was used to characterize the flow over the surfaces. Various Reynolds numbers were tested for both configurations, as well as several AOAs for the pectoral fin. The flow over the fin and cylinder were compared to a painted fin and a smooth PVC cylinder, respectively. The study found that the shark scales do, in fact, help to control flow separation. However, in order for the scales to bristle and trap the reversing flow, a certain magnitude of reversed flow and shear is required. This phenomenon seems to be most effective at near stall conditions and at higher Reynolds numbers. Support from REU grant 1062611 is greatfully acknowledged.

  20. An experimental investigation of an acoustically excited laminar premixed flame

    SciTech Connect

    Kartheekeyan, S.; Chakravarthy, S.R. [Department of Aerospace Engineering, Indian Institute of Technology - Madras, Chennai 600036 (India)

    2006-08-15

    A two-dimensional laminar premixed flame is stabilized over a burner in a confined duct and is subjected to external acoustic forcing from the downstream end. The equivalence ratio of the flame is 0.7. The flame is stabilized in the central slot of a three-slotted burner. The strength of the shear layer of the cold reactive mixture through the central slot is controlled by the flow rate of cold nitrogen gas through the side slots. The frequency range of acoustic excitation is 400-1200 Hz, and the amplitude levels are such that the acoustic velocity is less than the mean flow velocity of the reactants. Time-averaged chemiluminescence images of the perturbed flame front display time-mean changes as compared to the unperturbed flame shape at certain excitation frequencies. Prominent changes to the flame front are in the form of stretching or shrinkage, asymmetric development of its shape, increased/preferential lift-off of one or both of the stabilization points of the flame, and nearly random three-dimensional fluctuations over large time scales under some conditions. The oscillations of the shear layer and the response of the confined jet of the hot products to the acoustic forcing, such as asymmetric flow development and jet spreading, are found to be responsible for the observed mean changes in the flame shape. A distinct low-frequency component ({approx}60-90 Hz) relative to the excitation frequency is observed in the fluctuations of the chemiluminescent intensity in the flame under most conditions. It is observed that fluctuations in the flame area predominantly contribute to the origin of the low-frequency component. This is primarily due to the rollup of vortices and the generation of enthalpy waves at the burner lip. Both of these processes are excited at the externally imposed acoustic time scale, but convect/propagate downstream at the flow time scale, which is much larger. (author)

  1. The unsteady structure of two-dimensional steady laminar separation

    NASA Astrophysics Data System (ADS)

    Ripley, Matthew D.; Pauley, Laura L.

    1993-12-01

    The two-dimensional unsteady incompressible Navier-Stokes equations, solved by a fractional time-step method, were used to investigate separation due to the application of an adverse pressure gradient to a low-Reynolds number boundary layer flow. The inviscid pressure distribution of Gaster [AGARD CP 4, 813 (1966)] was applied in the present computations to study the development of a laminar separation bubble. In all cases studied, periodic vortex shedding occurred from the primary separation region. The shed vortices initially lifted from the boundary layer and then returned towards the surface downstream. The shedding frequency nondimensionalized by the momentum thickness was found to be independent of Reynolds number. The value of the nondimensional Strouhal number, however, was found to differ from the results of Pauley et al. [J. Fluid Mech. 220, 397 (1990)], indicating that the shedding frequency varies with the nondimensional pressure distribution, Cp. The computational results were time averaged over several shedding cycles and the results were compared with Gaster. The numerical study accurately reproduced the major characteristics of the separation found in Gaster's study such as the separation point, the pressure plateau within the upstream portion of the separation bubble, and the reattachment point. The similarity between the experimental results and the time-averaged two-dimensional computational results indicates that the low-frequency velocity fluctuations detected by Gaster are primarily due to the motion of large vortex structures. This suggests that large-scale two-dimensional structures control bubble reattachment and small-scale turbulence contributes a secondary role.

  2. Study of a 1D laminar fan near threshold

    NASA Astrophysics Data System (ADS)

    Mtivier, Francois; Gurit, Laure; Devauchelle, Olivier; Lajeunesse, Eric; Barrier, Laurie

    2013-04-01

    Alluvial sediment transport is often modelled using either linear or non linear diffusion equations. These equations are then used to study the evolution through time of alluvial systems and their dependance on various parameters (such as discharge, subsidence or uplift), initial and boundary conditions . Much of these equations though are valid only for the case when the shear stress exerted by the flow is significantly larger then the critical shear stress for motion inception. In nature however flows most often occurs at conditions where the boundary shear stress on the bed is at or near threshold shear stress. It is for instance well known that the shear stress exerted by the flow on gravel beds is only slightly (~20 %) above the critical value necessary to put grains in motion. It is therefore interesting to study alluvial sediment transport at or near incipient motion. In order to do this we here study theoretically the problem of a simple 1D laminar alluvial fan. The fan has a downstream moving boundary whereas the position of the upstream boundary remains fixed. The fan is fed with a constant flux of sediment and water. Boundary conditions are fixed by the sediment transport relationship for the upstream boundary and by assuming that all sediments are trapped within the fan for the downstream boundary. We use conservations equations together with a Charru et al. (2006) transport law to describe the evolution of the fan surface. We then derive the conservation equations of the fan. Using Taylor expansion and rescaling of coordinates we derive an self-similar solution for the fan shape and discuss the influence of the boundary conditions and parameters. This solution is amenable to experimental test and verification.

  3. Design of a laminar-flow-control supercritical airfoil for a swept wing

    NASA Technical Reports Server (NTRS)

    Allison, D. O.; Dagenhart, J. R.

    1978-01-01

    An airfoil was analytically designed and analyzed for a combination of supercritical flow and laminar flow control (LFC) by boundary layer suction. A shockless inverse method was used to design an airfoil and an analysis method was used in lower surface redesign work. The laminar flow pressure distributions were computed without a boundary layer under the assumption that the laminar boundary layer would be kept thin by suction. Inviscid calculations showed that this 13.5 percent thick airfoil has shockless flows for conditions at and below the design normal Mach number of 0.73 and the design section lift coefficient of 0.60, and that the maximum local normal Mach number is 1.12 at the design point. The laminar boundary layer instabilities can be controlled with suction but the undercut leading edge of the airfoil provides a low velocity, constant pressure coefficients region which is conducive to laminar flow without suction. The airfoil was designed to be capable of lift recovery with no suction by the deflection of a small trailing edge flap.

  4. Placement of C2 laminar screws using three-dimensional fluoroscopy-based image guidance

    PubMed Central

    Foy, Andrew B.

    2007-01-01

    The use of C2 laminar screws in posterior cervical fusion is a relatively new technique that provides rigid fixation of the axis with minimal risk to the vertebral artery. The techniques of C2 laminar screw placement described in the literature rely solely on anatomical landmarks to guide screw insertion. The authors report on their experience with placement of C2 laminar screws using three-dimensional (3D) fluoroscopy-based image-guidance in eight patients undergoing posterior cervical fusion. Overall, fifteen C2 laminar screws were placed. There were no complications in any of the patients. Average follow-up was 10months (range 314months). Postoperative computed tomographic (CT) scanning was available for seven patients allowing evaluation of placement of thirteen C2 laminar screws, all of which were in good position with no spinal canal violation. The intraoperative planning function of the image-guided system allowed for 4-mm diameter screws to be placed in all cases. Using modified Odoms criteria, excellent or good relief of preoperative symptoms was noted in all patients at final follow-up. PMID:18034268

  5. Summary of Transition Results From the F-16XL-2 Supersonic Laminar Flow Control Experiment

    NASA Technical Reports Server (NTRS)

    Marshall, Laurie A.

    2000-01-01

    A variable-porosity suction glove has been flown on the F-16XL-2 aircraft to demonstrate the feasibility of this technology for the proposed High-Speed Civil Transport. Boundary-layer transition data on the titanium glove primarily have been obtained at speeds of Mach 2.0 and altitudes of 15,240-16,764 m (50,000-55,000 ft). The objectives of this flight experiment have been to achieve 0.50-0.60 chord laminar flow on a highly swept wing at supersonic speeds and to provide data to validate codes and suction design. The most successful laminar flow results have not been obtained at the glove design point, a speed of Mach 1.9 at an altitude of 15,240 m (50,000 ft); but rather at a speed of Mach 2.0 and an altitude of 16,154 m (53,000 ft). Laminar flow has been obtained to more than 0.46 wing chord at a Reynolds number of 22.7 x 10(exp 6). A turbulence diverter has been used to initially obtain a laminar boundary layer at the attachment line. A lower-surface shock fence was required to block an inlet shock from the wing leading edge. This paper discusses research variables that directly impact the ability to obtain laminar flow and techniques to correct for these variables.

  6. Boundary-Layer Transition Results from the F-16XL-2 Supersonic Laminar Flow Control Experiment

    NASA Technical Reports Server (NTRS)

    Marshall, Laurie A.

    1999-01-01

    A variable-porosity suction glove has been flown on the F-16XL-2 aircraft to demonstrate the feasibility of this technology for the proposed High-Speed Civil Transport (HSCT). Boundary-layer transition data have been obtained on the titanium glove primarily at Mach 2.0 and altitudes of 53,000-55,000 ft. The objectives of this supersonic laminar flow control flight experiment have been to achieve 50- to 60-percent-chord laminar flow on a highly swept wing at supersonic speeds and to provide data to validate codes and suction design. The most successful laminar flow results have not been obtained at the glove design point (Mach 1.9 at an altitude of 50,000 ft). At Mach 2.0 and an altitude of 53,000 ft, which corresponds to a Reynolds number of 22.7 X 10(exp 6), optimum suction levels have allowed long runs of a minimum of 46-percent-chord laminar flow to be achieved. This paper discusses research variables that directly impact the ability to obtain laminar flow and techniques to correct for these variables.

  7. A History of Suction-Type Laminar Flow Control with Emphasis on Flight Research

    NASA Technical Reports Server (NTRS)

    Braslow, Albert L.

    1999-01-01

    Laminar-flow control is an area of aeronautical research that has a long history at NASA's Langley Research Center, Dryden Flight Research Center, their predecessor organizations, and elsewhere. In this monograph, the author, who spent much of his career at Langley working with this research, presents a history of that portion of laminar-flow technology known as active laminar-flow control, which employs suction of a small quantity of air through airplane surfaces. This important technique offers the potential for significant reduction in drag and, thereby, for large increases in range or reductions in fuel usage for aircraft. For transport aircraft, the reductions in fuel consumed as a result of laminar-flow control may equal 30 percent of present consumption. Given such potential, it is obvious that active laminar-flow control with suction is an important technology. In this study, the author covers the early history of the subject and brings the story all the way to the mid-1990s with an emphasis on flight research, much of which has occurred at Dryden. This is an important monograph that not only encapsulates a lot of history in a brief compass but also does so in language that is accessible to non-technical readers. NASA is publishing it in a format that will enable it to reach the wide audience the subject deserves.

  8. Numerical investigation of pressure drop and heat transfer in developing laminar and turbulent nanofluid flows

    NASA Astrophysics Data System (ADS)

    Ziaei-Rad, Masoud

    2013-07-01

    This paper concerns the study of laminar and turbulent force convection heat transfer and pressure drop between horizontal parallel plates with a nanofluid composed of Al2O3 and water. A set of governing equations are solved using a non-staggered SIMPLE procedure for the velocity-pressure coupling. For the convection-diffusion terms a power-law scheme is employed. A modified k-? model with a two-layer technique for the near-wall region has been used to predict the turbulent viscosity. The effects of nanoparticle volume fraction in the base fluid on laminar and turbulent flow variables are presented and discussed. The velocity and temperature profiles, friction factor, pressure coefficient and Nusselt number at different Reynolds numbers in the entrance region for both the laminar and turbulent flow regimes are reported under different thermal boundary conditions. The results show that the effect of the presence of nanoparticles in the base fluid on hydraulic and thermal parameters for the turbulent flow is not very significant, while the rate of heat transfer for the laminar flow with nanoparticles is greater than that of the base liquid. Furthermore, the thermal boundary layer and consequently the Nusselt number more quickly reach their fully developed values by increasing the percentage of nanoparticles in the base fluid for the laminar flow regime, while no changes in the trend are observed for the turbulent flow.

  9. High Reynolds Number Hybrid Laminar Flow Control (HLFC) Flight Experiment. Report 2; Aerodynamic Design

    NASA Technical Reports Server (NTRS)

    1999-01-01

    This document describes the aerodynamic design of an experimental hybrid laminar flow control (HLFC) wing panel intended for use on a Boeing 757 airplane to provide a facility for flight research on high Reynolds number HLFC and to demonstrate practical HLFC operation on a full-scale commercial transport airplane. The design consists of revised wing leading edge contour designed to produce a pressure distribution favorable to laminar flow, definition of suction flow requirements to laminarize the boundary layer, provisions at the inboard end of the test panel to prevent attachment-line boundary layer transition, and a Krueger leading edge flap that serves both as a high lift device and as a shield to prevent insect accretion on the leading edge when the airplane is taking off or landing.

  10. Flight investigation of natural laminar flow on the Bellanca Skyrocket II

    NASA Technical Reports Server (NTRS)

    Holmes, B. J.; Obara, C. J.; Gregorek, G. M.; Hoffman, M. J.; Freuhler, R. J.

    1983-01-01

    Two major concerns have inhibited the use of natural laminar flow (NLF) for viscous drag reduction on production aircraft. These are the concerns of achieveability of NLF on practical airframe surfaces, and maintainability in operating environments. Previous research in this area left a mixture of positive and negative conclusions regarding these concerns. While early (pre-1950) airframe construction methods could not achieve NLF criteria for waviness, several modern construction methods (composites for example) can achieve the required smoothness. This paper presents flight experiment data on the achieveability and maintainability of NLF on a high-performance, single-propeller, composite airplane, the Bellanca Skyrocket II. The significant contribution of laminar flow to the performance of this airplane was measured. Observations of laminar flow in the propeller slipstream are discussed, as are the effects of insect contamination on the wing. These observations have resulted in a new appreciation of the operational feasibility for achieving and maintaining NLF on modern airframe surfaces.

  11. Technology developments for laminar boundary layer control on subsonic transport aircraft

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  12. Natural Laminar-Flow blades for vertical-axis wind turbines

    SciTech Connect

    Klimas, P.C.

    1982-01-01

    Natural Laminar Flow (NLF) airfoils are those which can achieve significant extents of laminar flow (greater than 30% of chord) solely through favorable pressure gradients. A number of candidate airfoil sections were defined and then screened in a performance simulation. The section selected for fabrication and test was one which supported a 47% chord laminar flow. A comparison of lift and drag coefficients is made. A two-blade set was extruded for a 5-m diameter vertical axis wind turbine. A test series was then conducted at a turbine rotational speed of 175 rpm and a corresponding equatorial Reynolds number of 360,000. Field and wind tunnel tests have been and will be conducted. (LEW)

  13. Feasibility and benefits of laminar flow control on supersonic cruise airplanes

    NASA Technical Reports Server (NTRS)

    Powell, A. G.; Agrawal, S.; Lacey, T. R.

    1989-01-01

    An evaluation was made of the applicability and benefits of laminar flow control (LFC) technology to supersonic cruise airplanes. Ancillary objectives were to identify the technical issues critical to supersonic LFC application, and to determine how those issues can be addressed through flight and wind-tunnel testing. Vehicle types studied include a Mach 2.2 supersonic transport configuration, a Mach 4.0 transport, and two Mach 2-class fighter concepts. Laminar flow control methodologies developed for subsonic and transonic wing laminarization were extended and applied. No intractible aerodynamic problems were found in applying LFC to airplanes of the Mach 2 class, even ones of large size. Improvements of 12 to 17 percent in lift-drag ratios were found. Several key technical issues, such as contamination avoidance and excresence criteria were identified. Recommendations are made for their resolution. A need for an inverse supersonic wing design methodology is indicated.

  14. Formation of a laminar electron flow for 300 GHz high-power pulsed gyrotron

    SciTech Connect

    Yamaguchi, Yuusuke; Tatematsu, Yoshinori; Saito, Teruo; Ikeda, Ryosuke; Mudiganti, Jagadish C.; Ogawa, Isamu; Idehara, Toshitaka [Research Center for Development of Far-Infrared Region, University of Fukui, 3-9-1 Bunkyo, Fukui-shi 910-8507 (Japan)

    2012-11-15

    This paper describes the design of a triode magnetron injection gun for use in a 200 kW, 300 GHz gyrotron. As power and frequency increase, the performance of the gyrotron becomes quite sensitive to the quality of the electron beam. Formation of a laminar electron flow is essential for the realization of a high quality beam with a small velocity spread. In this study, a new method is developed for a quantitative evaluation of the laminarity and is applied to optimize the electrode design. The laminarity depends not only on conventional design parameters such as the cathode slant angle but also on the spatial distribution of the electric field along the beam trajectory. In the optimized design, the velocity pitch factors, {alpha}, larger than 1.2 are obtained at 65 kV, 10 A with spreads, {Delta}{alpha}, less than 5%.

  15. Accounting for Laminar Run & Trip Drag in Supersonic Cruise Performance Testing

    NASA Technical Reports Server (NTRS)

    Goodsell, Aga M.; Kennelly, Robert A.

    1999-01-01

    An improved laminar run and trip drag correction methodology for supersonic cruise performance testing was derived. This method required more careful analysis of the flow visualization images which revealed delayed transition particularly on the inboard upper surface, even for the largest trip disks. In addition, a new code was developed to estimate the laminar run correction. Once the data were corrected for laminar run, the correct approach to the analysis of the trip drag became evident. Although the data originally appeared confusing, the corrected data are consistent with previous results. Furthermore, the modified approach, which was described in this presentation, extends prior historical work by taking into account the delayed transition caused by the blunt leading edges.

  16. Parametric study on laminar flow for finite wings at supersonic speeds

    NASA Technical Reports Server (NTRS)

    Garcia, Joseph Avila

    1994-01-01

    Laminar flow control has been identified as a key element in the development of the next generation of High Speed Transports. Extending the amount of laminar flow over an aircraft will increase range, payload, and altitude capabilities as well as lower fuel requirements, skin temperature, and therefore the overall cost. A parametric study to predict the extent of laminar flow for finite wings at supersonic speeds was conducted using a computational fluid dynamics (CFD) code coupled with a boundary layer stability code. The parameters investigated in this study were Reynolds number, angle of attack, and sweep. The results showed that an increase in angle of attack for specific Reynolds numbers can actually delay transition. Therefore, higher lift capability, caused by the increased angle of attack, as well as a reduction in viscous drag, due to the delay in transition, can be expected simultaneously. This results in larger payload and range.

  17. Study of Turbulent Premixed Flame Propagation using a Laminar Flamelet Model

    NASA Technical Reports Server (NTRS)

    Im, H. G.

    1995-01-01

    The laminar flamelet concept in turbulent reacting flows is considered applicable to many practical combustion systems (Linan & Williams 1993). For turbulent premixed combustion, the laminar flamelet regime is valid when turbulent Karlovitz number is less than unity, which is equivalent to stating that the characteristic thickness of the flame is less than that of a Kolmogorov eddy; this is known as the Klimov-Williams criterion (Williams 1985). In such a case, the flame maintains its laminar structure, and the effect of turbulent flow is merely to wrinkle and strain the flame front. The propagating wrinkled premixed flame can then be described as an infinitesimally thin surface dividing the unburnt fresh mixture and the burnt product.

  18. Comprehensive assessment of meteorological conditions and airflow connectivity during HCCT-2010

    NASA Astrophysics Data System (ADS)

    Tilgner, A.; Schne, L.; Bruer, P.; van Pinxteren, D.; Hoffmann, E.; Spindler, G.; Styler, S. A.; Mertes, S.; Birmili, W.; Otto, R.; Merkel, M.; Weinhold, K.; Wiedensohler, A.; Deneke, H.; Schrdner, R.; Wolke, R.; Schneider, J.; Haunold, W.; Engel, A.; Wber, A.; Herrmann, H.

    2014-09-01

    This study presents a comprehensive assessment of the meteorological conditions and atmospheric flow during the Lagrangian-type "Hill Cap Cloud Thuringia 2010" experiment (HCCT-2010), which was performed in September and October 2010 at Mt. Schmcke in the Thuringian Forest, Germany and which used observations at three measurement sites (upwind, in-cloud, and downwind) to study physical and chemical aerosol-cloud interactions. A Lagrangian-type hill cap cloud experiment requires not only suitable cloud conditions but also connected airflow conditions (i.e. representative air masses at the different measurement sites). The primary goal of the present study was to identify time periods during the 6-week duration of the experiment in which these conditions were fulfilled and therefore which are suitable for use in further data examinations. The following topics were studied in detail: (i) the general synoptic weather situations, including the mesoscale flow conditions, (ii) local meteorological conditions and (iii) local flow conditions. The latter were investigated by means of statistical analyses using best-available quasi-inert tracers, SF6 tracer experiments in the experiment area, and regional modelling. This study represents the first application of comprehensive analyses using statistical measures such as the coefficient of divergence (COD) and the cross-correlation in the context of a Lagrangian-type hill cap cloud experiment. This comprehensive examination of local flow connectivity yielded a total of 14 full-cloud events (FCEs), which are defined as periods during which all connected flow and cloud criteria for a suitable Lagrangian-type experiment were fulfilled, and 15 non-cloud events (NCEs), which are defined as periods with connected flow but no cloud at the summit site, and which can be used as reference cases. The overall evaluation of the identified FCEs provides the basis for subsequent investigations of the measured chemical and physical data during HCCT-2010 (see http://www.atmos-chem-phys.net/special_issue287.html). Results obtained from the statistical flow analyses and regional-scale modelling performed in this study indicate the existence of a strong link between the three measurement sites during the FCEs and NCEs, particularly under conditions of constant southwesterly flow, high wind speeds and slightly stable stratification. COD analyses performed using continuous measurements of ozone and particle (49 nm diameter size bin) concentrations at the three sites revealed, particularly for COD values < 0.1, very consistent time series (i.e. close links between air masses at the different sites). The regional-scale model simulations provided support for the findings of the other flow condition analyses. Cross-correlation analyses revealed typical overflow times of ~15-30 min between the upwind and downwind valley sites under connected flow conditions. The results described here, together with those obtained from the SF6 tracer experiments performed during the experiment, clearly demonstrate that (a) under appropriate meteorological conditions a Lagrangian-type approach is valid and (b) the connected flow validation procedure developed in this work is suitable for identifying such conditions. Overall, it is anticipated that the methods and tools developed and applied in the present study will prove useful in the identification of suitable meteorological and connected airflow conditions during future Lagrangian-type hill cap cloud experiments.

  19. Airflow and nanoparticle deposition in rat nose under various breathing and sniffing conditions

    PubMed Central

    Jiang, Jianbo; Zhao, Kai

    2010-01-01

    Accurate prediction of nanoparticle (1~100 nm) deposition in the rat nasal cavity is important for assessing the toxicological impact of inhaled nanoparticles as well as for potential therapeutic applications. A quasi-steady assumption has been widely adopted in the past investigations on this topic, yet the validity of such simplification under various breathing and sniffing conditions has not been carefully examined. In this study, both steady and unsteady computational fluid dynamics (CFD) simulations were conducted in a published rat nasal model under various physiologically realistic breathing and sniffing flow rates. The transient airflow structures, nanoparticle transport and deposition patterns in the whole nasal cavity and the olfactory region were investigated and compared with steady state simulation of equivalent flow rate. The results showed that (1) the quasi-steady flow assumption for cyclic flow was valid for over 70% of the cycle period during all simulated breathing and sniffing conditions in the rat nasal cavity, or the unsteady effect was only significant during the transition between the respiratory phases; (2) yet the quasi-steady assumption for nanoparticle transport was not valid, except in the vicinity of peak respiration. In general, the total deposition efficiency of nanoparticle during cyclic breathing would be lower than that of steady state due to the unsteady effect on particle transport and deposition, and further decreased with the increase of particle size, sniffing frequency, and flow rate. In the contrary, previous study indicated that for micro-scale particles (0.5~4?m), the unsteady effect would increase deposition efficiencies in rat nasal cavity. Combined, these results suggest that the quasi-steady assumption of nasal particle transport during cycling breathing should be used with caution for an accurate assessment of the toxicological and therapeutic impact of particle inhalation. Empirical equations and effective steady state approximation derived in this study are thus valuable to estimate such unsteady effects in future applications. PMID:21076632

  20. Prevalence and correlates of airflow obstruction in ?317 000 never-smokers in China

    PubMed Central

    Smith, Margaret; Li, Liming; Augustyn, Mareli; Kurmi, Om; Chen, Junshi; Collins, Rory; Guo, Yu; Han, Yabin; Qin, Jingxin; Xu, Guanqun; Wang, Jian; Bian, Zheng; Zhou, Gang; Peto, Richard; Chen, Zhengming

    2014-01-01

    In China, the burden of chronic obstructive disease (COPD) is high in never-smokers but little is known about its causes in this group. We analysed data on 287 000 female and 30 000 male never-smokers aged 3079 years from 10 regions in China, who participated in the China Kadoorie Biobank baseline survey (20042008). Prevalence of airflow obstruction (AFO) (pre-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) <0.7 and below the lower limit of normal (LLN)) was estimated, by age and region. Cross-sectional associations of AFO (FEV1/FVC <0.7), adjusted for confounding, were examined. AFO prevalence defined as FEV1/FVC <0.7 was 4.0% in females and 5.1% in males (mean ages 51 and 54 years, respectively). AFO prevalence defined as FEV1/FVC

  1. Prevalence and correlates of airflow obstruction in ?317,000 never-smokers in China.

    PubMed

    Smith, Margaret; Li, Liming; Augustyn, Mareli; Kurmi, Om; Chen, Junshi; Collins, Rory; Guo, Yu; Han, Yabin; Qin, Jingxin; Xu, Guanqun; Wang, Jian; Bian, Zheng; Zhou, Gang; Peto, Richard; Chen, Zhengming

    2014-07-01

    In China, the burden of chronic obstructive disease (COPD) is high in never-smokers but little is known about its causes in this group. We analysed data on 287 000 female and 30 000 male never-smokers aged 30-79 years from 10 regions in China, who participated in the China Kadoorie Biobank baseline survey (2004-2008). Prevalence of airflow obstruction (AFO) (pre-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) <0.7 and below the lower limit of normal (LLN)) was estimated, by age and region. Cross-sectional associations of AFO (FEV1/FVC <0.7), adjusted for confounding, were examined. AFO prevalence defined as FEV1/FVC <0.7 was 4.0% in females and 5.1% in males (mean ages 51 and 54 years, respectively). AFO prevalence defined as FEV1/FVC

  2. Wing bone laminarity is not an adaptation for torsional resistance in bats

    PubMed Central

    Simons, Erin L.R.

    2015-01-01

    Torsional loading is a common feature of skeletal biomechanics during vertebrate flight. The importance of resisting torsional loads is best illustrated by the convergence of wing bone structure (e.g., long with thin walls) across extant bats and birds. Whether or not such a convergence occurs at the microstructural level is less clear. In volant birds, the humeri and ulnae often contain abundant laminar bony tissue in which primary circumferential vascular canals course concentrically about the long axis of the bone. These circumferential canals and the matrix surrounding them presumably function to resist the tissue-level shear stress caused by flight-induced torsion. Here, we assess whether or not laminar bone is a general adaptive feature in extant flying vertebrates using a histological analysis of bat bones. We sampled the humeri from six adult taxa representing a broad phylogenetic and body size range (61,000 g). Transverse thick sections were prepared from the midshaft of each humerus. Bone tissue was classified based on the predominant orientation of primary vascular canals. Our results show that humeri from bats across a wide phylogenetic and body size range do not contain any laminar bone. Instead, humeri are essentially avascular in bats below about 100 g and are poorly vascularized with occasional longitudinal to slightly radial canals in large bats. In contrast, humeri from birds across a comparable size range (401,000 g) are highly vascularized with a wide range in bone laminarity. Phylogenetically-informed scaling analyses reveal that the difference in vascularity between birds and bats is best explained by higher somatic relative growth rates in birds. The presence of wing bone laminarity in birds and its absence in bats suggests that laminar bone is not a necessary biomechanical feature in flying vertebrates and may be apomorphic to birds. PMID:25780775

  3. Soot Formation in Laminar Acetylene/Air Diffusion Flames at Atmospheric Pressure. Appendix J

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    The flame structure and soot-formation (soot nucleation and growth) properties of axisymmetric laminar coflowing jet diffusion flames were studied experimentally. Test conditions involved acetylene-nitrogen jets burning in coflowing air at atmospheric pressure. Measurements were limited to the axes of the flames and included soot concentrations, soot temperatures, soot structure, major gas species concentrations, radical species (H, OH, and O) concentrations, and gas velocities. The results show that as distance increases along the axes of the flames, detectable soot formation begins when significant H concentrations are present, and ends when acetylene concentrations become small. Species potentially associated with soot oxidation--O2, CO2, H2O, O, and OH-are present throughout the soot-formation region so that soot formation and oxidation proceed at the same time. Strong rates of soot growth compared to soot nucleation early in the soot-formation process, combined with increased rates of soot nucleation and oxidation as soot formation proceeds, causes primary soot particle diameters to reach a maximum relatively early in the soot-formation process. Aggregation of primary soot particles proceeds, however, until the final stages of soot oxidation. Present measurements of soot growth (corrected for soot oxidation) in laminar diffusion flames were consistent with earlier measurements of soot growth in laminar premixed flames and exhibited encouraging agreement with existing hydrogen-abstraction/carbon-addition (HACA) soot growth mechanisms in the literature that were developed based on measurements within laminar premixed flames. Measured primary soot particle nucleation rates in the present laminar diffusion flames also were consistent with corresponding rates measured in laminar premixed flames and yielded a crude correlation in terms of acetylene and H concentrations and the temperature.

  4. Soot Formation in Laminar Acetylene/Air Diffusion Flames at Atmospheric Pressure. Appendix H

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

    The flame structure and soot-formation (soot nucleation and growth) properties of axisymmetric laminar coflowing jet diffusion flames were studied experimentally. Test conditions involved acetylene-nitrogen jets burning in coflowing air at atmospheric pressure. Measurements were limited to the axes of the flames and included soot concentrations, soot temperatures, soot structure, major gas species concentrations, radical species (H, OH, and O) concentrations, and gas velocities. The results show that as distance increases along the axes of the flames, detectable soot formation begins when significant H concentrations are present, and ends when acetylene concentrations become small. Species potentially associated with soot oxidation-O2, CO2, H2O, O, and OH-are present throughout the soot-formation region so that soot formation and oxidation proceed at the same time. Strong rates of soot growth compared to soot nucleation early in the soot-formation process, combined with increased rates of soot nucleation and oxidation as soot formation proceeds, causes primary soot particle diameters to reach a maximum relatively early in the soot-formation process. Aggregation of primary soot particles proceeds, however, until the final stages of soot oxidation. Present measurements of soot growth (corrected for soot oxidation) in laminar diffusion flames were consistent with earlier measurements of soot growth in laminar premixed flames and exhibited encouraging agreement with existing hydrogen-abstraction/carbon-addition (HACA) soot growth mechanisms in the literature that were developed based on measurements within laminar premixed flames. Measured primary soot particle nucleation rates in the present laminar diffusion flames also were consistent with corresponding rates measured in laminar premixed flames and yielded a crude correlation in terms of acetylene and H concentrations and the temperature.

  5. Soot Formation in Laminar Acetylene/Air Diffusion Flames at Atmospheric Pressure. Appendix C

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    The flame structure and soot-formation (soot nucleation and growth) properties of axisymmetric laminar coflowing jet diffusion flames were studied experimentally. Test conditions involved acetylene-nitrogen jets burning in coflowing air at atmospheric pressure. Measurements were limited to the axes of the flames and included soot concentrations, soot temperatures, soot structure, major gas species concentrations, radical species (H, OH, and O) concentrations, and gas velocities. The results show that as distance increases along the axes of the flames, detectable soot formation begins when significant H concentrations are present, and ends when acetylene concentrations become small. Species potentially associated with soot oxidation-O2, CO2, H2O, O, and OH-are present throughout the soot-formation region so that soot formation and oxidation proceed at the same time. Strong rates of soot growth compared to soot nucleation early in the soot-formation process, combined with increased rates of soot nucleation and oxidation as soot formation proceeds, causes primary soot particle diameters to reach a maximum relatively early in the soot-formation process. Aggregation of primary soot particles proceeds, however, until the final stages of soot oxidation. Present measurements of soot growth (corrected for soot oxidation) in laminar diffusion flames were consistent with earlier measurements of soot growth in laminar premixed flames and exhibited encouraging agreement with existing hydrogen-abstraction/carbon-addition (HACA) soot growth mechanisms in the literature that were developed based on measurements within laminar premixed flames. Measured primary soot particle nucleation rates in the present laminar diffusion flames also were consistent with corresponding rates measured in laminar premixed flames and yielded a crude correlation in terms of acetylene and H concentrations and the temperature.

  6. Digital data acquisition and preliminary instrumentation study for the F-16 laminar flow control vehicle

    NASA Technical Reports Server (NTRS)

    Ostowari, Cyrus

    1992-01-01

    Preliminary studies have shown that maintenance of laminar flow through active boundary-layer control is viable. Current research activity at NASA Langley and NASA Dryden is utilizing the F-16XL-1 research vehicle fitted with a laminar-flow suction glove that is connected to a vacuum manifold in order to create and control laminar flow at supersonic flight speeds. This experimental program has been designed to establish the feasibility of obtaining laminar flow at supersonic speeds with highly swept wing and to provide data for computational fluid dynamics (CFD) code calibration. Flight experiments conducted as supersonic speeds have indicated that it is possible to achieve laminar flow under controlled suction at flight Mach numbers greater than 1. Currently this glove is fitted with a series of pressure belts and flush mounted hot film sensors for the purpose of determining the pressure distributions and the extent of laminar flow region past the stagnation point. The present mode of data acquisition relies on out-dated on board multi-channel FM analogue tape recorder system. At the end of each flight, the analogue data is digitized through a long laborious process and then analyzed. It is proposed to replace this outdated system with an on board state-of-the-art digital data acquisition system capable of a through put rate of up to 1 MegaHertz. The purpose of this study was three-fold: (1) to develop a simple algorithm for acquiring data via 2 analogue-to-digital convertor boards simultaneously (total of 32 channels); (2) to interface hot-film/wire anemometry instrumentation with a PCAT type computer; and (3) to characterize the frequency response of a flush mounted film sensor. A brief description of each of the above tasks along with recommendations are given.

  7. The stability of the flow in a laminar separation bubble

    NASA Astrophysics Data System (ADS)

    Niew, Tai Ran

    1993-09-01

    This dissertation reports a study into the underlying concepts used to analyze incompressible laminar separation bubbles. The suggestion that absolute instability could play a role in bubble flows was further developed, and was the focal point of this project. From a review of previous work and preliminary experiments on a backward faxing step, it was suggested that for some bubbles the reattachment region of the flow field could be absolutely unstable. A cornerstone of this view is that the completion of transition is not a prerequisite for the start of reattachment; and that a more fundamental mechanism involves significant interaction between the two processes. This concept was first tested by solving the eigenvalue problem of the Orr-Sommerfeld equation for a family of reverse flow profiles. The results indicated that with sufficient reverse flow, wall-bounded separated shear-layers that are similar to experimentally measured profiles can be absolutely unstable. This is consistent with the hypothesis outlined above. The numerical study also showed that for convectively unstable profiles, the predominant parameter that determines the spatial growth rate of instability waves is the distance of the separated shear layer from the wall. Furthermore, viscosity only has a weak effect on the stability characteristics of both absolutely and convectively unstable profiles at generic bubble Reynolds numbers. Experiments were then carried out on the flow behind a backward facing step using artificially excited instability waves, and the key issues in formulating a conceptually robust experimental method to test the above hypothesis was discussed. If the forcing was carried out with a non-acoustic source, it was shown that the use of impulse excitation could provide a rigorous procedure. Two qualitatively different transition mechanisms, 'wave' and 'spot' type, were also observed in these experiments. A new perspective of bubble behavior was then developed that considered the interaction of turbulent breakdown, reattachment and inducing of reverse flow. The concept of the absolutely unstable reattachment region is an integral part of this view, and the analysis was used to account for the different breakdown processes detected. Based on this alternative framework for analyzing bubble flows, a comprehensive list of fresh areas for future research was also suggested.

  8. Aerodynamic design of a midsized vertical-axis wind turbine using natural laminar-flow blade elements

    Microsoft Academic Search

    P. C. Klimas; D. E. Berg

    1983-01-01

    Natural laminar-flow (NLF) airfoils are those which can achieve significant extents of laminar flow (greater than or equal to 30% chord) solely through favorable pressure gradients. Studies have shown that vertical-axis wind turbines (VAWTs) using NLF sections as blade elements have the potential of producing energy at a significantly lower cost (approx. =20%) than turbines of current design. Sandia National

  9. A flight test investigation of certification requirements for laminar-flow general aviation airplanes

    NASA Technical Reports Server (NTRS)

    Manuel, Gregory S.; Doty, Wayne A.

    1990-01-01

    A modified T210R general aviation aircraft incorporating natural laminar flow (NLF) technology has been subjected to flight tests in order to evaluate its stability and control characteristics. Attention is given to this aircraft's ability to meet certification requirements with significant NLF, as well as with the boundary-layer transition fixed near the leading edge. It is established that the large regions of NLF achieved yielded a significant cruise performance enhancement; loss of laminar flow did not result in significant changes in the stability and control characteristics of the aircraft. FAR Part 23 certification requirements were met.

  10. Design and Experimental Results for a Natural-Laminar-Flow Airfoil for General Aviation Applications

    NASA Technical Reports Server (NTRS)

    Somers, D. M.

    1981-01-01

    A natural-laminar-flow airfoil for general aviation applications, the NLF(1)-0416, was designed and analyzed theoretically and verified experimentally in the Langley Low-Turbulence Pressure Tunnel. The basic objective of combining the high maximum lift of the NASA low-speed airfoils with the low cruise drag of the NACA 6-series airfoils was achieved. The safety requirement that the maximum lift coefficient not be significantly affected with transition fixed near the leading edge was also met. Comparisons of the theoretical and experimental results show excellent agreement. Comparisons with other airfoils, both laminar flow and turbulent flow, confirm the achievement of the basic objective.

  11. Integral method for the calculation of three-dimensional, laminar and turbulent boundary layers

    NASA Technical Reports Server (NTRS)

    Stock, H. W.

    1978-01-01

    The method for turbulent flows is a further development of an existing method; profile families with two parameters and a lag entrainment method replace the simple entrainment method and power profiles with one parameter. The method for laminar flows is a new development. Moment of momentum equations were used for the solution of the problem, the profile families were derived from similar solutions of boundary layer equations. Laminar and turbulent flows at the wings were calculated. The influence of wing tapering on the boundary layer development was shown. The turbulent boundary layer for a revolution ellipsoid is calculated for 0 deg and 10 deg incidence angles.

  12. Measurement of fluid velocity development in laminar pipe flow using laser Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Molki, Arman; Khezzar, Lyes; Goharzadeh, Afshin

    2013-09-01

    In this paper we present a non-intrusive experimental approach for obtaining velocity gradient profiles in a transparent smooth pipe under laminar flow conditions (Re = 925) using a laser Doppler velocimeter (LDV). Measurements were taken within the entrance region of the pipe at l = 300 mm and l = 600 mm from the pipe inlet, in addition to measurements of the fully developed flow at l = 1800 mm. The obtained results show how the velocity profile from upstream of the pipe develops into a classical laminar profile downstream, which matches the theoretical profile well. Additionally, a brief summary of historical information about the development of flow measurement techniques, in particular LDV, is provided.

  13. Nonlinear Formulation of the Bulk Surface Stress over Breaking Waves: Feedback Mechanisms from Air-flow Separation

    NASA Astrophysics Data System (ADS)

    Mueller, James A.; Veron, Fabrice

    2009-01-01

    Historically, our understanding of the air-sea surface stress has been derived from engineering studies of turbulent flows over flat solid surfaces, and more recently, over rigid complex geometries. Over the ocean however, the presence of a free, deformable, moving surface gives rise to a more complicated drag formulation. In fact, within the constant-stress turbulent atmospheric boundary layer over the ocean, the total air-sea stress not only includes the traditional turbulent and viscous components but also incorporates surface-wave effects such as wave growth or decay, air-flow separation, and surface separation in the form of sea-spray droplets. Because each individual stress component depends on and alters the sea state, a simple linear addition of all stress components is too simplistic. In this paper we present a model of the air-sea surface stress that incorporates air-flow separation and its effects on the other stress components, such as a reduction of the surface viscous stress in the separated region as suggested by recent measurements. Naturally, the inclusion of these effects leads to a non-linear stress formulation. This model, which uses a variable normalized dissipation rate of breaking waves and normalized length of the separation bubble, reproduces the observed features of the drag coefficient from low to high wind speeds despite extrapolating empirical wave spectra and breaking wave statistics beyond known limits. The model shows the saturation of the drag coefficient at high wind speeds for both field and laboratory fetches, suggesting that air-flow separation over ocean waves and its accompanying effects may play a significant role in the physics of the air-sea stress, at least at high wind speeds.

  14. Laminar Plunging Jets - Interfacial Rupture and Inception of Entrainment

    NASA Astrophysics Data System (ADS)

    Kishore, Aravind

    Interfacial rupture and entrainment are commonly observed, e.g., air bubbles within a container being filled with water from a faucet. The example involves a liquid jet (density, rho, and viscosity, ?) plunging into a receiving pool of liquid. Below a critical liquid-jet velocity, the interface develops a cusp-like shape within the receiving pool. The cusp becomes sharper with increasing liquid-jet velocity, and at a critical velocity ( Vc), the interface between the liquid and the surrounding fluid (density, rho0, and viscosity, ?0) ruptures. Interfacial tension (sigma) can no longer preserve the integrity of the interface between the two immiscible fluids, and the plunging jet drags/entrains surrounding fluid into the receiving pool. Subsequently, the entrained fluid breaks up into bubbles within the receiving pool. The focus of this dissertation is the numerical prediction of the critical entrainment inception velocities for laminar plunging jets using the Volume-Of-Fluid (VOF) method, a Computational Fluid Dynamics (CFD) method to simulate multi-fluid flows. Canonical to bottle-filling operations in the industry is the plunging-jet configuration -- the liquid jet issues from a nozzle and plunges into a container filled with liquid. Simulations of this configuration require capturing flow phenomena over a large range of length scales (4 orders of magnitude). Results show severe under-prediction of critical entrainment velocities when the maximum resolution is insufficient to capture the sharpening, and eventual rupture, of the interfacial cusp. Higher resolutions resulted in computational meshes with prohibitively large number of cells, and a drastic reduction in time-step values. Experimental results in the literature suggest at least a 100-fold increase in the smallest length scale when the entrained fluid is a liquid instead of air. This narrows the range of length scales in the problem. We exploit the experimental correlation between critical capillary number, Cac = ??Vc/sigma and viscosity ratio, ?0/? in postulating an alternate approach involving scaling of the pertinent physics by using liquids as entrained fluids. The scaling approach is tested using a rotating cylinder placed at the interface between two fluids. A mesh-independence study using successively finer meshes predicted critical entrainment velocity values within about 1% of each other. Numerical predictions compared well with experimental data, with less than 1% difference in the case where exact experimental data was available, and a maximum of 6% difference for cases where experimental data was extrapolated to make the comparison. These results lend credibility to our approach. The effect of densities of the two fluids manifests as buoyancy force at the interfacial cusp. Remarkably, contrary to a priori notions, our simulation results showed that as Deltarho increased, the effect of buoyancy decreased relative to other forces at the interfacial cusp. Finally, we proposed an empirical correlation between Cac and ? 0/? which allows extrapolation of critical entrainment conditions between the rotating-cylinder configuration (with liquids being entrained) to the plunging-jet configuration (with air being entrained). The primary contribution of this research is the physics-based scaling approach utilized to overcome the simulation challenges posed by the physics of interface rupture and entrainment.

  15. Soot microstructure in steady and flickering laminar methane\\/air diffusion flames

    Microsoft Academic Search

    Jie Zhang; Constantine M. Megaridis

    1998-01-01

    An experimental investigation is presented to identify the mechanisms responsible for the enhanced sooting behavior of strongly flickering methane\\/air jet diffusion flames when compared to their steady counterparts. The work extends the implementation of thermophoretic sampling in flickering, co-flow, laminar, diffusion flames. Acoustic forcing of the fuel flow rate is used to phase lock the periodic flame flicker close to

  16. Numerical analysis of heat transfer in an air-filled bayonet tube under laminar conditions

    Microsoft Academic Search

    H. Minhas; G. S. H. Lock

    1996-01-01

    The paper provides details of a numerical study of the bayonet tube under steady, laminar conditions when the fluid is air. Attention is focused on the heat transfer characteristics of the tube. The data constitute a systematic investigation of the effect of the principal parameters on the overall heat transfer rate, represented by a Nusselt number. Specifically discussed are the

  17. Laminar analysis of visually evoked activity in the primary visual cortex.

    PubMed

    Xing, Dajun; Yeh, Chun-I; Burns, Samuel; Shapley, Robert M

    2012-08-21

    Studying the laminar pattern of neural activity is crucial for understanding the processing of neural signals in the cerebral cortex. We measured neural population activity [multiunit spike activity (MUA) and local field potential, LFP] in Macaque primary visual cortex (V1) in response to drifting grating stimuli. Sustained visually driven MUA was at an approximately constant level across cortical depth in V1. However, sustained, visually driven, local field potential power, which was concentrated in the ?-band (20-60 Hz), was greatest at the cortical depth corresponding to cortico-cortical output layers 2, 3, and 4B. ?-band power also tends to be more sustained in the output layers. Overall, cortico-cortical output layers accounted for 67% of total ?-band activity in V1, whereas 56% of total spikes evoked by drifting gratings were from layers 2, 3, and 4B. The high-resolution layer specificity of ?-band power, the laminar distribution of MUA and ?-band activity, and their dynamics imply that neural activity in V1 is generated by laminar-specific mechanisms. In particular, visual responses of MUA and ?-band activity in cortico-cortical output layers 2, 3, and 4B seem to be strongly influenced by laminar-specific recurrent circuitry and/or feedback. PMID:22872866

  18. Predictions and observations of the flow field induced by laminar flow control microperforations

    Microsoft Academic Search

    David G. MacManus; John A. Eaton

    1996-01-01

    Hybrid laminar flow control (HLFC) aims to reduce aircraft skin friction drag by controlling the boundary-layer characteristics through a combination of surface suction and surface profile shaping. Suction is applied through an array of microperforations in the surface; and, to enable HLFC design criteria to be established with confidence, a full understanding of how these suction perforations affect the boundary

  19. Optimized design of an active extrados structure for an experimental morphing laminar wing

    Microsoft Academic Search

    Daniel Coutu; Vladimir Brailovski; Patrick Terriault

    2010-01-01

    This paper focuses on the design of an active extrados structure for an experimental morphing laminar wing, which has been tested in a subsonic wind tunnel. Actuators localized inside the wing box apply individually controlled displacements over the flexible structure, made from laminate composite, to modify the airfoil profile in accordance with the database, which is built using XFoil aerodynamic

  20. Copyright 2007 by ASME1 Laminar Flame Speeds and Strain Sensitivities of Mixtures of H2

    E-print Network

    Seitzman, Jerry M.

    to rich. [Keywords: Syngas, laminar flame speed, reactant preheat, CO2 dilution, N2 dilution] INTRODUCTION Technologies such as integrated gasification combined cycle (IGCC) plants enable combustion of coal, biomass emissions. Synthetic gas (syngas) fuels derived from coal are particularly promising in this regard. Syngas