Science.gov

Sample records for air turbulence detection

  1. Lockheed Electra - animation showing air turbulence detection

    NASA Technical Reports Server (NTRS)

    1999-01-01

    On Mar. 24, 1998, an L-188 Electra aircraft owned by the National Science Foundation, Arlington, Virginia, and operated by the National Center for Atmospheric Research, Boulder, Colorado, flew near Boulder with an Airborne Coherent LiDAR (Light Detection and Ranging) for Advanced In-flight Measurement. This aircraft was on its first flight to test its ability to detect previously invisible forms of clear air turbulence. Coherent Technologies Inc., Lafayette, Colorado, built the LiDAR device for the NASA Dryden Flight Research Center, Edwards, California. NASA Dryden participated in the effort as part of the NASA Aviation Safety Program, for which the lead center was Langley Research Center, Hampton, Virginia. Results of the test indicated that the device did successfully detect the clear air turbulence. Computer animation of the clear air turbulence (CAT) detection system known as the 'Airborne Coherent LiDAR for Advanced In-flight Measurement' was tested aboard the National Science Foundation L-188 Lockheed Electra.

  2. Aspects of clear air turbulence severity forecasting and detection

    NASA Technical Reports Server (NTRS)

    Ehernberger, L. J.

    1982-01-01

    Factors influencing the accuracy of the forecasts of incidences of clear air turbulence (CAT) are discussed, along with techniques for improved verification. Descriptive ranking terms for the intensity of CAT events, ranging from light to extreme, are developed, and meteorological parameters used for predictions are reviewed, including jetstream core location, vertical and horizontal wind shears, stable layers, tropopause height, trough speed, 500-mb vorticity, surface fronts, pressure centers and cyclogenesis, and wind speeds near mountain ridges. Methods of remote detection of CAT, particularly by using radiometry sensitive to the IR water vapor band, are noted to have had some success in detecting actual CAT events and decreasing false alarms. Statistical aspects of CAT encounter severity are discussed, including the establishment of confidence intervals for thresholds of detection of CATs of varying intensities.

  3. Flight Tests of the DELICAT Airborne LIDAR System for Remote Clear Air Turbulence Detection

    NASA Astrophysics Data System (ADS)

    Vrancken, Patrick; Wirth, Martin; Ehret, Gerhard; Witschas, Benjamin; Veerman, Henk; Tump, Robert; Barny, Hervé; Rondeau, Philippe; Dolfi-Bouteyre, Agnès; Lombard, Laurent

    2016-06-01

    An important aeronautics application of lidar is the airborne remote detection of Clear Air Turbulence which cannot be performed with onboard radar. We report on a DLR-developed lidar system for the remote detection of such turbulent areas in the flight path of an aircraft. The lidar, consisting of a high-power UV laser transmitter and a direct detection system, was installed on a Dutch research aircraft. Flight tests executed in 2013 demonstrated the performance of the lidar system to detect local subtle variations in the molecular backscatter coefficient indicating the turbulence some 10 to 15 km ahead.

  4. Development of CO2 laser Doppler instrumentation for detection of clear air turbulence, volume 1

    NASA Technical Reports Server (NTRS)

    Harris, C. E.; Jelalian, A. V.

    1979-01-01

    Modification, construction, test and operation of an advanced airborne carbon dioxide laser Doppler system for detecting clear air turbulence are described. The second generation CAT program and those auxiliary activities required to support and verify such a first-of-a-kind system are detailed: aircraft interface; ground and flight verification tests; data analysis; and laboratory examinations.

  5. Tentative detection of clear-air turbulence using a ground-based Rayleigh lidar.

    PubMed

    Hauchecorne, Alain; Cot, Charles; Dalaudier, Francis; Porteneuve, Jacques; Gaudo, Thierry; Wilson, Richard; Cénac, Claire; Laqui, Christian; Keckhut, Philippe; Perrin, Jean-Marie; Dolfi, Agnès; Cézard, Nicolas; Lombard, Laurent; Besson, Claudine

    2016-05-01

    Atmospheric gravity waves and turbulence generate small-scale fluctuations of wind, pressure, density, and temperature in the atmosphere. These fluctuations represent a real hazard for commercial aircraft and are known by the generic name of clear-air turbulence (CAT). Numerical weather prediction models do not resolve CAT and therefore provide only a probability of occurrence. A ground-based Rayleigh lidar was designed and implemented to remotely detect and characterize the atmospheric variability induced by turbulence in vertical scales between 40 m and a few hundred meters. Field measurements were performed at Observatoire de Haute-Provence (OHP, France) on 8 December 2008 and 23 June 2009. The estimate of the mean squared amplitude of bidimensional fluctuations of lidar signal showed excess compared to the estimated contribution of the instrumental noise. This excess can be attributed to atmospheric turbulence with a 95% confidence level. During the first night, data from collocated stratosphere-troposphere (ST) radar were available. Altitudes of the turbulent layers detected by the lidar were roughly consistent with those of layers with enhanced radar echo. The derived values of turbulence parameters Cn2 or CT2 were in the range of those published in the literature using ST radar data. However, the detection was at the limit of the instrumental noise and additional measurement campaigns are highly desirable to confirm these initial results. This is to our knowledge the first successful attempt to detect CAT in the free troposphere using an incoherent Rayleigh lidar system. The built lidar device may serve as a test bed for the definition of embarked CAT detection lidar systems aboard airliners. PMID:27140350

  6. Tentative detection of clear-air turbulence using a ground-based Rayleigh lidar.

    PubMed

    Hauchecorne, Alain; Cot, Charles; Dalaudier, Francis; Porteneuve, Jacques; Gaudo, Thierry; Wilson, Richard; Cénac, Claire; Laqui, Christian; Keckhut, Philippe; Perrin, Jean-Marie; Dolfi, Agnès; Cézard, Nicolas; Lombard, Laurent; Besson, Claudine

    2016-05-01

    Atmospheric gravity waves and turbulence generate small-scale fluctuations of wind, pressure, density, and temperature in the atmosphere. These fluctuations represent a real hazard for commercial aircraft and are known by the generic name of clear-air turbulence (CAT). Numerical weather prediction models do not resolve CAT and therefore provide only a probability of occurrence. A ground-based Rayleigh lidar was designed and implemented to remotely detect and characterize the atmospheric variability induced by turbulence in vertical scales between 40 m and a few hundred meters. Field measurements were performed at Observatoire de Haute-Provence (OHP, France) on 8 December 2008 and 23 June 2009. The estimate of the mean squared amplitude of bidimensional fluctuations of lidar signal showed excess compared to the estimated contribution of the instrumental noise. This excess can be attributed to atmospheric turbulence with a 95% confidence level. During the first night, data from collocated stratosphere-troposphere (ST) radar were available. Altitudes of the turbulent layers detected by the lidar were roughly consistent with those of layers with enhanced radar echo. The derived values of turbulence parameters Cn2 or CT2 were in the range of those published in the literature using ST radar data. However, the detection was at the limit of the instrumental noise and additional measurement campaigns are highly desirable to confirm these initial results. This is to our knowledge the first successful attempt to detect CAT in the free troposphere using an incoherent Rayleigh lidar system. The built lidar device may serve as a test bed for the definition of embarked CAT detection lidar systems aboard airliners.

  7. Development of CO2 laser Doppler instrumentation for detection of clear air turbulence, volume 2: Appendices

    NASA Technical Reports Server (NTRS)

    Harris, C. E.; Jelalian, A. V.

    1979-01-01

    Analyses of the mounting and mount support systems of the clear air turbulence transmitters verify that satisfactory shock and vibration isolation are attained. The mount support structure conforms to flight crash safety requirements with high margins of safety. Restraint cables reinforce the mounts in the critical loaded forward direction limiting maximum forward system deflection to 1 1/4 inches.

  8. Experimental Validation of a Forward Looking Interferometer for Detection of Clear Air Turbulence due to Mountain Waves

    NASA Technical Reports Server (NTRS)

    Schaffner, Philip R.; Daniels, Taumi S.; West, Leanne L.; Gimmestad, Gary G.; Lane, Sarah E.; Burdette, Edward M.; Smith, William L.; Kireev, Stanislav; Cornman, Larry; Sharman, Robert D.

    2012-01-01

    The Forward-Looking Interferometer (FLI) is an airborne sensor concept for detection and estimation of potential atmospheric hazards to aircraft. The FLI concept is based on high-resolution Infrared Fourier Transform Spectrometry technologies that have been developed for satellite remote sensing. The FLI is being evaluated for its potential to address multiple hazards, during all phases of flight, including clear air turbulence, volcanic ash, wake vortices, low slant range visibility, dry wind shear, and icing. In addition, the FLI is being evaluated for its potential to detect hazardous runway conditions during landing, such as wet or icy asphalt or concrete. The validation of model-based instrument and hazard simulation results is accomplished by comparing predicted performance against empirical data. In the mountain lee wave data collected in the previous FLI project, the data showed a damped, periodic mountain wave structure. The wave data itself will be of use in forecast and nowcast turbulence products such as the Graphical Turbulence Guidance and Graphical Turbulence Guidance Nowcast products. Determining how turbulence hazard estimates can be derived from FLI measurements will require further investigation.

  9. Turbulence Detection and Mitigation Element

    NASA Technical Reports Server (NTRS)

    Bogue, Rod

    2003-01-01

    This paper presents viewgraphs on turbulence detection and mitigation technologies in weather accident prevention. The topics include: 1) Organization; 2) Scope of Turbulence Effort; 3) Background; 4) Turbulence Detection and Mitigation Program Metrics; 5) Approach; 6) Turbulence Team Relationships; 7) WBS Structure; 8) Deliverables; 9) TDAM Changes; 10) FY-01 Results/Accomplishments; 11) Out-year Plans; and 12) Element Status.

  10. Turbulent Methane-Air Combustion

    NASA Technical Reports Server (NTRS)

    Yaboah, Yaw D.; Njokwe, Anny; James, LaShanda

    1996-01-01

    This study is aimed at enhancing the understanding of turbulent premixed methane-air combustion. Such understanding is essential since: (1) many industries are now pursuing lighter hydrocarbon alternative fuels and the use of premixed flames to reduce pollutant emissions, and (2) the characteristic dimensions and flow rates of most industrial combustors are often large for flows to be turbulent. The specific objectives of the study are: (1) to establish the effects of process variables (e.g., flow rate, fuel/air ratio, chlorinated hydro-carbons, and pressure) on the emissions and flow structure (velocity distribution, streamlines, vorticity and flame shape), and (2) to develop a mechanistic model to explain the observed trends. This includes the acquisition of Dantec FlowMap Particle Image Velocimeter. The design and fabrication of the premixed burner has also been completed. The study is now at the stage of testing of equipment and analytical instruments. The presentation will give details on the tasks completed and on the current and future plans. The project is progressing well and all activities are on schedule. The outlook for the success of the project is bright.

  11. A Laboratory Investigation of Turbulence Detection Using a Laser

    NASA Technical Reports Server (NTRS)

    Bourquin, Kent; Shigemoto, Fred H.

    1965-01-01

    Calculations and experiments have been undertaken to determine the property of the backscattered laser-return signal that undergoes the most significant change in a turbulent region as compared with a nonturbulent region. If the turbulent region is composed mainly of air molecules, the detection of a shift in the frequency property appears to be the most promising. Therefore at this time the main effort at the Ames Research Center is focused on the implementation and laboratory evaluation of a clear-air turbulence detector utilizing a laser source and observing the frequency change.

  12. The 1979 clear air turbulence flight test program

    NASA Technical Reports Server (NTRS)

    Weaver, E. A.

    1980-01-01

    A clear air turbulence (CAT) flight test to evaluate and test four different sensors in the detection and measuring of CAT and other meteorological targets that relate to turbulence is discussed. The primary types of CAT investigated were mountain wave CAT, jetstream CAT, CAT in cirrus clouds, and CAT in frontal wind shears, troughs, and ridges. The sensors included the CO2 pulsed Doppler lidar and three radiometers. One of the radiometers, at a frequency of 55.5 GHz, looked at atmospheric temperature structure. Another, at a frequency of 180.1 GHz, looked at atmospheric water vapor and investigated the feasibility of measuring at the microwave frequency the turbulence features seen in the infrared (IR) frequencies. An IR radiometer at 27 to 33 microns was the fourth sensor. This last device and the temperature structure radiometer worked well at all flight levels.

  13. Broadband Phase Spectroscopy over Turbulent Air Paths.

    PubMed

    Giorgetta, Fabrizio R; Rieker, Gregory B; Baumann, Esther; Swann, William C; Sinclair, Laura C; Kofler, Jon; Coddington, Ian; Newbury, Nathan R

    2015-09-01

    Broadband atmospheric phase spectra are acquired with a phase-sensitive dual-frequency-comb spectrometer by implementing adaptive compensation for the strong decoherence from atmospheric turbulence. The compensation is possible due to the pistonlike behavior of turbulence across a single spatial-mode path combined with the intrinsic frequency stability and high sampling speed associated with dual-comb spectroscopy. The atmospheric phase spectrum is measured across 2 km of air at each of the 70,000 comb teeth spanning 233  cm(-1) across hundreds of near-infrared rovibrational resonances of CO(2), CH(4), and H(2)O with submilliradian uncertainty, corresponding to a 10(-13) refractive index sensitivity. Trace gas concentrations extracted directly from the phase spectrum reach 0.7 ppm uncertainty, demonstrated here for CO(2). While conventional broadband spectroscopy only measures intensity absorption, this approach enables measurement of the full complex susceptibility even in practical open path sensing.

  14. Broadband Phase Spectroscopy over Turbulent Air Paths

    NASA Astrophysics Data System (ADS)

    Giorgetta, Fabrizio R.; Rieker, Gregory B.; Baumann, Esther; Swann, William C.; Sinclair, Laura C.; Kofler, Jon; Coddington, Ian; Newbury, Nathan R.

    2015-09-01

    Broadband atmospheric phase spectra are acquired with a phase-sensitive dual-frequency-comb spectrometer by implementing adaptive compensation for the strong decoherence from atmospheric turbulence. The compensation is possible due to the pistonlike behavior of turbulence across a single spatial-mode path combined with the intrinsic frequency stability and high sampling speed associated with dual-comb spectroscopy. The atmospheric phase spectrum is measured across 2 km of air at each of the 70 000 comb teeth spanning 233 cm-1 across hundreds of near-infrared rovibrational resonances of CO2 , CH4 , and H2O with submilliradian uncertainty, corresponding to a 10-13 refractive index sensitivity. Trace gas concentrations extracted directly from the phase spectrum reach 0.7 ppm uncertainty, demonstrated here for CO2 . While conventional broadband spectroscopy only measures intensity absorption, this approach enables measurement of the full complex susceptibility even in practical open path sensing.

  15. Submerged turbulence detection with optical satellites

    NASA Astrophysics Data System (ADS)

    Gibson, Carl H.; Keeler, R. Norris; Bondur, Valery G.; Leung, Pak T.; Prandke, H.; Vithanage, D.

    2013-01-01

    During fall periods in 2002, 2003 and 2004 three major oceanographic expeditions were carried out in Mamala Bay, Hawaii. These were part of the RASP Remote Anthropogenic Sensing Program. Ikonos and Quickbird optical satellite images of sea surface glint revealed !100 m spectral anomalies in km2 averaging patches in regions leading from the Honolulu Sand Island Municipal Outfall diffuser to distances up to 20 km. To determine the mechanisms behind this phenomenon, the RASP expeditions monitored the waters adjacent to the outfall with an array of hydrographic, optical and turbulence microstructure sensors in anomaly and ambient background regions. Drogue tracks and mean turbulence parameters for 2 ! 104 microstructure patches were analyzed to understand complex turbulence, fossil turbulence and zombie turbulence near-vertical internal wave transport processes. The dominant mechanism appears to be generic to stratified natural fluids including planet and star atmospheres and is termed beamed zombie turbulence maser action (BZTMA). Most of the bottom turbulent kinetic energy is converted to ! 100 m fossil turbulence waves. These activate secondary (zombie) turbulence in outfall fossil turbulence patches that transmit heat, mass, chemical species, momentum and information vertically to the sea surface for detection in an efficient maser action. The transport is beamed in intermittent mixing chimneys.

  16. Submerged turbulence detection with optical satellites

    NASA Astrophysics Data System (ADS)

    Gibson, Carl H.; Keeler, R. Norris; Bondur, Valery G.; Leung, Pak T.; Prandke, H.; Vithanage, D.

    2007-09-01

    During fall periods in 2002, 2003 and 2004 three major oceanographic expeditions were carried out in Mamala Bay, Hawaii. These were part of the RASP Remote Anthropogenic Sensing Program. Ikonos and Quickbird optical satellite images of sea surface glint revealed ~100 m spectral anomalies in km2 averaging patches in regions leading from the Honolulu Sand Island Municipal Outfall diffuser to distances up to 20 km. To determine the mechanisms behind this phenomenon, the RASP expeditions monitored the waters adjacent to the outfall with an array of hydrographic, optical and turbulence microstructure sensors in anomaly and ambient background regions. Drogue tracks and mean turbulence parameters for 2 × 10 4 microstructure patches were analyzed to understand complex turbulence, fossil turbulence and zombie turbulence near-vertical internal wave transport processes. The dominant mechanism appears to be generic to stratified natural fluids including planet and star atmospheres and is termed beamed zombie turbulence maser action (BZTMA). Most of the bottom turbulent kinetic energy is converted to ~ 100 m fossil turbulence waves. These activate secondary (zombie) turbulence in outfall fossil turbulence patches that transmit heat, mass, chemical species, momentum and information vertically to the sea surface for detection in an efficient maser action. The transport is beamed in intermittent mixing chimneys.

  17. Observations of clear air turbulence by high power radar.

    PubMed

    Browning, K A; Watkins, C D

    1970-07-18

    Clear air turbulence is a hazard to aviation and is thought to have important effects on atmospheric dynamics. This article describes the structure and evolution of clear air turbulence at high altitudes as revealed by a high power radar and vertical soundings of wind and temperature.

  18. Computed Turbulent Free Shear Flow Of Air

    NASA Technical Reports Server (NTRS)

    Viegas, J. R.; Rubesin, M. W.

    1992-01-01

    Standard k-epsilon model of turbulence yields fairly accurate results. Symposium paper discusses numerical simulation of turbulent free shear flow of nonreacting compressible fluid. Ability to compute such flows essential to advances in design.

  19. Microwave temperature profiler for clear air turbulence prediction

    NASA Technical Reports Server (NTRS)

    Gary, Bruce L. (Inventor)

    1992-01-01

    A method is disclosed for determining Richardson Number, Ri, or its reciprocal, RRi, for clear air prediction using measured potential temperature and determining the vertical gradient of potential temperature, d(theta)/dz. Wind vector from the aircraft instrumentation versus potential temperature, dW/D(theta), is determined and multiplies by d(theta)/dz to obtain dW/dz. Richardson number or its reciprocal is then determined from the relationship Ri = K(d theta)/dz divided by (dW/dz squared) for use in detecting a trend toward a threshold value for the purpose of predicting clear air turbulence. Other equations for this basic relationship are disclosed together with the combination of other atmospheric observables using multiple regression techniques.

  20. Application of infrared radiometers for airborne detection of clear air turbulence and low level wind shear, airborne infrared low level wind shear detection test

    NASA Technical Reports Server (NTRS)

    Kuhn, P. M.

    1985-01-01

    The feasibility of infrared optical techniques for the advance detection and avoidance of low level wind shear (LLWS) or low altitude wind shear hazardous to aircraft operations was investigated. A primary feasibility research effort was conducted with infrared detectors and instrumentation aboard the NASA Ames Research Center Learjet. The main field effort was flown on the NASA-Ames Dryden B57B aircraft. The original approach visualized a forward-looking, infrared transmitting (KRS-5) window through which signals would reach the detector. The present concept of a one inch diameter light pipe with a 45 deg angled mirror enables a much simpler installation virtually anywhere on the aircraft coupled with the possibility of horizontal scanning via rotation of the forward directed mirror. Present infrared detectors and filters would certainly permit ranging and horizontal scanning in a variety of methods. CRT display technology could provide a contoured picture with possible shear intensity levels from the infrared detection system on the weather radar or a small adjunct display. This procedure shoud be further developed and pilot evaluated in a light aircraft such as a Cessna 207 or equivalent.

  1. Using Indirect Turbulence Measurements for Real-Time Parameter Estimation in Turbulent Air

    NASA Technical Reports Server (NTRS)

    Martos, Borja; Morelli, Eugene A.

    2012-01-01

    The use of indirect turbulence measurements for real-time estimation of parameters in a linear longitudinal dynamics model in atmospheric turbulence was studied. It is shown that measuring the atmospheric turbulence makes it possible to treat the turbulence as a measured explanatory variable in the parameter estimation problem. Commercial off-the-shelf sensors were researched and evaluated, then compared to air data booms. Sources of colored noise in the explanatory variables resulting from typical turbulence measurement techniques were identified and studied. A major source of colored noise in the explanatory variables was identified as frequency dependent upwash and time delay. The resulting upwash and time delay corrections were analyzed and compared to previous time shift dynamic modeling research. Simulation data as well as flight test data in atmospheric turbulence were used to verify the time delay behavior. Recommendations are given for follow on flight research and instrumentation.

  2. Fuel economizer employing improved turbulent mixing of fuel and air

    SciTech Connect

    Howes, L.D.

    1980-11-25

    A fuel economizer is described for internal combustion engines which increases turbulence of the fuel and air mixture in the carburetor by decreasing the throat of its venturi to a predetermined minimum necessary to induce fuel flow through its fuel jets and then downstream of the venturi adding further atmospheric air for complete combustion.

  3. Turbulent drag reduction over air- and liquid- impregnated surfaces

    NASA Astrophysics Data System (ADS)

    Rosenberg, Brian J.; Van Buren, Tyler; Fu, Matthew K.; Smits, Alexander J.

    2016-01-01

    Results on turbulent skin friction reduction over air- and liquid-impregnated surfaces are presented for aqueous Taylor-Couette flow. The surfaces are fabricated by mechanically texturing the inner cylinder and chemically modifying the features to make them either non-wetting with respect to water (air-infused, or superhydrophobic case), or wetting with respect to an oil that is immiscible with water (liquid-infused case). The drag reduction, which remains fairly constant over the Reynolds number range tested (100 ≤ Reτ ≤ 140), is approximately 10% for the superhydrophobic surface and 14% for the best liquid-infused surface. Our results suggest that liquid-infused surfaces may enable robust drag reduction in high Reynolds number turbulent flows without the shortcomings associated with conventional superhydrophobic surfaces, namely, failure under conditions of high hydrodynamic pressure and turbulent flow fluctuations.

  4. NASA technical advances in aircraft occupant safety. [clear air turbulence detectors, fire resistant materials, and crashworthiness

    NASA Technical Reports Server (NTRS)

    Enders, J. H.

    1978-01-01

    NASA's aviation safety technology program examines specific safety problems associated with atmospheric hazards, crash-fire survival, control of aircraft on runways, human factors, terminal area operations hazards, and accident factors simulation. While aircraft occupants are ultimately affected by any of these hazards, their well-being is immediately impacted by three specific events: unexpected turbulence encounters, fire and its effects, and crash impact. NASA research in the application of laser technology to the problem of clear air turbulence detection, the development of fire resistant materials for aircraft construction, and to the improvement of seats and restraint systems to reduce crash injuries are reviewed.

  5. Energetics of the Beamed Zombie Turbulence Maser Action Mechanism for Remote Detection of Submerged Oceanic Turbulence

    NASA Astrophysics Data System (ADS)

    Gibson, C. H.; Bondur, V. G.; Keeler, R. N.; Leung, P. T.

    2011-11-01

    Sea surface brightness spectral anomalies from a Honolulu municipal outfall have been detected from space satellites in 200 km2 areas extending 20 km from the wastewater diffuser (Bondur 2005, Keeler et al. 2005, Gibson et al. 2005). Dropsonde and towed body microstructure measurements show outfall enhanced viscous and temperature dissipation rates above the turbulence trapping layer. Fossil turbulence waves and secondary (zombie, zebra) turbulence waves break as they propagate near-vertically and then break again near the surface to produce wind ripple smoothing in narrow frequency band (zebra) patterns from soliton-like sources of secondary turbulence energy acting on fossils advected from the outfall. The 30-250 m solitons reflect a nonlinear cascade from tidal and current kinetic energy to boundary layer turbulence events, to fossil turbulence waves, to internal soliton and tidal waves. Secondary (zombie) turbulence acts on outfall fossil patches to amplify, channel in chimneys, and vertically beam ambient internal wave energy just as energized metastable molecules around stars amplify and beam quantum frequencies in astrophysical masers. Kilowatts of buoyancy power from the treatment plant produces fossil turbulence patches trapped below the thermocline. Beamed zombie turbulence maser action (BZTMA) in mixing chimneys amplifies these kilowatts into the megawatts of surface turbulence dissipation required to affect brightness on wide sea surface areas by maser action vertical beaming of fossil-wave-power extracted from gigawatts dissipated by intermittent bottom turbulence events on topography from the tides and currents.

  6. Simultaneous video stabilization and moving object detection in turbulence.

    PubMed

    Oreifej, Omar; Li, Xin; Shah, Mubarak

    2013-02-01

    Turbulence mitigation refers to the stabilization of videos with nonuniform deformations due to the influence of optical turbulence. Typical approaches for turbulence mitigation follow averaging or dewarping techniques. Although these methods can reduce the turbulence, they distort the independently moving objects, which can often be of great interest. In this paper, we address the novel problem of simultaneous turbulence mitigation and moving object detection. We propose a novel three-term low-rank matrix decomposition approach in which we decompose the turbulence sequence into three components: the background, the turbulence, and the object. We simplify this extremely difficult problem into a minimization of nuclear norm, Frobenius norm, and l1 norm. Our method is based on two observations: First, the turbulence causes dense and Gaussian noise and therefore can be captured by Frobenius norm, while the moving objects are sparse and thus can be captured by l1 norm. Second, since the object's motion is linear and intrinsically different from the Gaussian-like turbulence, a Gaussian-based turbulence model can be employed to enforce an additional constraint on the search space of the minimization. We demonstrate the robustness of our approach on challenging sequences which are significantly distorted with atmospheric turbulence and include extremely tiny moving objects.

  7. Calibration of NASA Turbulent Air Motion Measurement System

    NASA Technical Reports Server (NTRS)

    Barrick, John D. W.; Ritter, John A.; Watson, Catherine E.; Wynkoop, Mark W.; Quinn, John K.; Norfolk, Daniel R.

    1996-01-01

    A turbulent air motion measurement system (TAMMS) was integrated onboard the Lockheed 188 Electra airplane (designated NASA 429) based at the Wallops Flight Facility in support of the NASA role in global tropospheric research. The system provides air motion and turbulence measurements from an airborne platform which is capable of sampling tropospheric and planetary boundary-layer conditions. TAMMS consists of a gust probe with free-rotating vanes mounted on a 3.7-m epoxy-graphite composite nose boom, a high-resolution inertial navigation system (INS), and data acquisition system. A variation of the tower flyby method augmented with radar tracking was implemented for the calibration of static pressure position error and air temperature probe. Additional flight calibration maneuvers were performed remote from the tower in homogeneous atmospheric conditions. System hardware and instrumentation are described and the calibration procedures discussed. Calibration and flight results are presented to illustrate the overall ability of the system to determine the three-component ambient wind fields during straight and level flight conditions.

  8. Progress in Development of an Airborne Turbulence Detection System

    NASA Technical Reports Server (NTRS)

    Hamilton, David W.; Proctor, Fred H.

    2006-01-01

    Aircraft encounters with turbulence are the leading cause of in-flight injuries (Tyrvanas 2003) and have occasionally resulted in passenger and crew fatalities. Most of these injuries are caused by sudden and unexpected encounters with severe turbulence in and around convective activity (Kaplan et al 2005). To alleviate this problem, the Turbulence Prediction and Warning Systems (TPAWS) element of NASA s Aviation Safety program has investigated technologies to detect and warn of hazardous in-flight turbulence. This effort has required the numerical modeling of atmospheric convection: 1) for characterizing convectively induced turbulence (CIT) environments, 2) for defining turbulence hazard metrics, and 3) as a means of providing realistic three-dimensional data sets that can be used to test and evaluate turbulence detection sensors. The data sets are being made available to industry and the FAA for certification of future airborne turbulence-detection systems (ATDS) with warning capability. Early in the TPAWS project, a radar-based ATDS was installed and flight tested on NASA s research aircraft, a B-757. This ATDS utilized new algorithms and hazard metrics that were developed for use with existing airborne predictive windshear radars, thus avoiding the installation of new hardware. This system was designed to detect and warn of hazardous CIT even in regions with weak radar reflectivity (i.e. 5-15 dBz). Results from an initial flight test of the ATDS were discussed in Hamilton and Proctor (2002a; 2002b). In companion papers (Proctor et al 2002a; 2002b), a numerical simulation of the most significant encounter from that flight test was presented. Since the presentation of these papers a second flight test has been conducted providing additional cases for examination. In this paper, we will present results from NASA s flight test and a numerical model simulation of a turbulence environment encountered on 30 April 2002. Progress leading towards FAA certification of

  9. Temperature gradients and clear-air turbulence probabilities

    NASA Technical Reports Server (NTRS)

    Bender, M. A.; Panofsky, H. A.; Peslen, C. A.

    1976-01-01

    In order to forecast clear-air turbulence (CAT) in jet aircraft flights, a study was conducted in which the data from a special-purpose instrument aboard a Boeing 747 jet airliner were compared with satellite-derived radiance gradients, conventional temperature gradients from analyzed maps, and temperature gradients obtained from a total air temperature sensor on the plane. The advantage of making use of satellite-derived data is that they are available worldwide without the need for radiosonde observations, which are scarce in many parts of the world. Major conclusions are that CAT probabilities are significantly higher over mountains than flat terrain, and that satellite radiance gradients appear to discriminate between CAT and no CAT better than conventional temperature gradients over flat lands, whereas the reverse is true over mountains, the differences between the two techniques being not large over mountains.

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

    NASA Technical Reports Server (NTRS)

    Fine, Burton

    1957-01-01

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

  11. Airborne Turbulence Detection and Warning ACLAIM Flight Test Results

    NASA Technical Reports Server (NTRS)

    Hannon, Stephen M.; Bagley, Hal R.; Soreide, Dave C.; Bowdle, David A.; Bogue, Rodney K.; Ehernberger, L. Jack

    1999-01-01

    The Airborne Coherent Lidar for Advanced Inflight Measurements (ACLAIM) is a NASA/Dryden-lead program to develop and demonstrate a 2 micrometers pulsed Doppler lidar for airborne look-ahead turbulence detection and warning. Advanced warning of approaching turbulence can significantly reduce injuries to passengers and crew aboard commercial airliners. The ACLAIM instrument is a key asset to the ongoing Turbulence component of NASA's Aviation Safety Program, aimed at reducing the accident rate aboard commercial airliners by a factor of five over the next ten years and by a factor of ten over the next twenty years. As well, the advanced turbulence warning capability can prevent "unstarts" in the inlet of supersonic aircraft engines by alerting the flight control computer which then adjusts the engine to operate in a less fuel efficient, and more turbulence tolerant, mode. Initial flight tests of the ACLAIM were completed in March and April of 1998. This paper and presentation gives results from these initial flights, with validated demonstration of Doppler lidar wind turbulence detection several kilometers ahead of the aircraft.

  12. The physical and empirical basis for a specific clear-air turbulence risk index

    NASA Technical Reports Server (NTRS)

    Keller, J. L.

    1985-01-01

    An improved operational CAT detection and forecasting technique is developed and detailed. This technique is the specific clear air turbulence risk (SCATR) index. This index shows some promising results. The improvements seen using hand analyzed data, as a result of the more realistic representation of the vertical shear of the horizontal wind, are also realized in the data analysis used in the PROFS/CWP application. The SCATR index should improve as database enhancements such as profiler and VAS satellite data, which increase the resolution in space and time, are brought into even more sophisticated objective analysis schemes.

  13. Structures in magnetohydrodynamic turbulence: detection and scaling.

    PubMed

    Uritsky, V M; Pouquet, A; Rosenberg, D; Mininni, P D; Donovan, E F

    2010-11-01

    We present a systematic analysis of statistical properties of turbulent current and vorticity structures at a given time using cluster analysis. The data stem from numerical simulations of decaying three-dimensional magnetohydrodynamic turbulence in the absence of an imposed uniform magnetic field; the magnetic Prandtl number is taken equal to unity, and we use a periodic box with grids of up to 1536³ points and with Taylor Reynolds numbers up to 1100. The initial conditions are either an X -point configuration embedded in three dimensions, the so-called Orszag-Tang vortex, or an Arn'old-Beltrami-Childress configuration with a fully helical velocity and magnetic field. In each case two snapshots are analyzed, separated by one turn-over time, starting just after the peak of dissipation. We show that the algorithm is able to select a large number of structures (in excess of 8000) for each snapshot and that the statistical properties of these clusters are remarkably similar for the two snapshots as well as for the two flows under study in terms of scaling laws for the cluster characteristics, with the structures in the vorticity and in the current behaving in the same way. We also study the effect of Reynolds number on cluster statistics, and we finally analyze the properties of these clusters in terms of their velocity-magnetic-field correlation. Self-organized criticality features have been identified in the dissipative range of scales. A different scaling arises in the inertial range, which cannot be identified for the moment with a known self-organized criticality class consistent with magnetohydrodynamics. We suggest that this range can be governed by turbulence dynamics as opposed to criticality and propose an interpretation of intermittency in terms of propagation of local instabilities. PMID:21230595

  14. Structures in magnetohydrodynamic turbulence: detection and scaling.

    PubMed

    Uritsky, V M; Pouquet, A; Rosenberg, D; Mininni, P D; Donovan, E F

    2010-11-01

    We present a systematic analysis of statistical properties of turbulent current and vorticity structures at a given time using cluster analysis. The data stem from numerical simulations of decaying three-dimensional magnetohydrodynamic turbulence in the absence of an imposed uniform magnetic field; the magnetic Prandtl number is taken equal to unity, and we use a periodic box with grids of up to 1536³ points and with Taylor Reynolds numbers up to 1100. The initial conditions are either an X -point configuration embedded in three dimensions, the so-called Orszag-Tang vortex, or an Arn'old-Beltrami-Childress configuration with a fully helical velocity and magnetic field. In each case two snapshots are analyzed, separated by one turn-over time, starting just after the peak of dissipation. We show that the algorithm is able to select a large number of structures (in excess of 8000) for each snapshot and that the statistical properties of these clusters are remarkably similar for the two snapshots as well as for the two flows under study in terms of scaling laws for the cluster characteristics, with the structures in the vorticity and in the current behaving in the same way. We also study the effect of Reynolds number on cluster statistics, and we finally analyze the properties of these clusters in terms of their velocity-magnetic-field correlation. Self-organized criticality features have been identified in the dissipative range of scales. A different scaling arises in the inertial range, which cannot be identified for the moment with a known self-organized criticality class consistent with magnetohydrodynamics. We suggest that this range can be governed by turbulence dynamics as opposed to criticality and propose an interpretation of intermittency in terms of propagation of local instabilities.

  15. NASA Turbulence Technologies In-Service Evaluation: Delta Air Lines Report-Out

    NASA Technical Reports Server (NTRS)

    Amaral, Christian; Dickson, Steve; Watts, Bill

    2007-01-01

    Concluding an in-service evaluation of two new turbulence detection technologies developed in the Turbulence Prediction and Warning Systems (TPAWS) element of the NASA Aviation Safety and Security Program's Weather Accident Prevention Project (WxAP), this report documents Delta's experience working with the technologies, feedback gained from pilots and dispatchers concerning current turbulence techniques and procedures, and Delta's recommendations regarding directions for further efforts by the research community. Technologies evaluated included an automatic airborne turbulence encounter reporting technology called the Turbulence Auto PIREP System (TAPS), and a significant enhancement to the ability of modern airborne weather radars to predict and display turbulence of operational significance, called E-Turb radar.

  16. Aeronautical diagnostics for Clear-Air Turbulence forecast at Meteofrance in the context of DELICAT European project

    NASA Astrophysics Data System (ADS)

    Audrey, Crespin; Christine, Lebot; Yves, Bouteloup; Francois, Bouyssel

    2011-12-01

    A study on Clear-Air Turbulence (abbreviated by CAT) forecast in a Numerical Weather Model is presented in this paper. The main objective of this study is to evaluate ARPEGE Meteofrance-NWP model's ability to reproduce CAT, by calculating various CAT indices at the regional scale (over Europe) in this model. The list of indices used here is inspired from that proposed by R. Sharman & Wolff (2006). Calculated indices are then compared with AMDARs (Aircraft Meteorological DAta Relay) turbulence measurements during winter, early in 2010. This work was performed within DELICAT european project (*DEmonstration of LIdar based Clear-Air Turbulence detection), in the Seventh Research Framework program of the European Union [FP7], in Meteofrance national weather agency.

  17. Flow on Magnetizable Particles in Turbulent Air Streams. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Davey, K. R.

    1979-01-01

    The flow of magnetizable particles in a turbulent air stream in the presence of an imposed magnetic field and the phenomenon of drag reduction produced by the introduction of particles in turbulent boundary layer are investigated. The nature of the particle magnetic force is discussed and the inherent difference between electric and magnetic precipitation is considered. The incorporation of turbulent diffusion theory with an imposed magnetic migration process both with and without inertia effects is examined.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  19. Phase-detection measurements in free-surface turbulent shear flows

    NASA Astrophysics Data System (ADS)

    Chanson, Hubert

    2016-04-01

    High-velocity self-aerated flows are described as ‘white waters’ because of the entrained air bubbles. The air entrainment induces a drastic change in the multiphase flow structure of the water column and this leads to significant bubble-turbulence interactions, turbulence modulation and associated mixing processes impacting on the bulk flow properties. In these high-velocity free-surface turbulent flows, the phase-detection needle probe is a most reliable instrumentation. The signal processing of a phase-detection probe is re-visited herein. It is shown that the processing may be performed on the raw probe signal as well as the thresholded data. The latter yields the time-averaged void fraction, the bubble count rate, the particle chord time distributions and the particle clustering properties within the particulate flow regions. The raw probe signal analysis gives further the auto-correlation time scale and the power spectrum density function. Finally dimensional considerations are developed with a focus on the physical modelling of free-surface flows in hydraulic structures. It is argued that the notion of scale effects must be defined in terms of some specific set of air-water flow properties within well-defined testing conditions, while a number of free-surface flow characteristics are more prone to scale effects than others, even in large-size physical facilities.

  20. The physical and empirical basis for a specific clear-air turbulence risk index

    NASA Technical Reports Server (NTRS)

    Keller, J. L.

    1986-01-01

    The fundamental emphasis of this research was to develop a technique which would be a significant improvement over those currently used for flight planning to avoid clear air turbulence (CAT). The technique should, ideally, be both quantitative in determining potential intensity and specific in locating regions of relatively high risk. Furthermore, it should not rely on specialized data but be functional using the currently available rawinsonde observation (raob) system. Encouraging results documented in an earlier investigation were considered compelling enough to warrant a closer look into the possibilities of a Specific Clear Air Turbulence Risk (SCATR) index approach to the clear air turbulence problem. Unlike that research, which considered sustained periods of flight in light to moderate clear air turbulence, this study focuses on several cases of documented severe CAT. Results of these case studies suggest that a SCATR index is not an unrealizable goal and that uses of such an index, event in its current prototype level of development, are also apparent.

  1. Aircraft Measurements Of Refractive And Clear Air Turbulence: Spectra, Budgets, And The Prediction Problem

    NASA Astrophysics Data System (ADS)

    Cote, O.; Dobosy, R.; Roadcap, J.; Crawford, T.; Hacker, J.

    Four turbulence measurement campaigns were performed in the winter sub-tropical jet streams of south coastal Japan and Australia during 1998-2001 with the objective to capture the dynamics of severe refractive and clear air turbulence events. The aircraft used was the GROB 520T EGRETT, which is owned and operated by Airborne Research Australia a unit of Flinders University of South Australia. Severe turbulence events are difficult to forecast and measure but are of critical importance to commercial air safety (NASA -FAA) and the High-Energy Laser (HEL) propagation disturbances. Measurements have shown that weak turbulence/severe turbulence events are associated with anisotropy/isotropy of the turbulent velocity spectra/structure parameters. Strong turbulence events are associated with Froude number that are near unity; weak turbulence with Froude numbers 1. The role that fluctuating velocity-pressure gradient correlation in maintaining strong turbulence, the limited success of Richardson number as a predictor, and limitations of diagnostic prediction schemes based on mesoscale model output will be considered.

  2. Moving object detection and tracking in videos through turbulent medium

    NASA Astrophysics Data System (ADS)

    Halder, Kalyan Kumar; Tahtali, Murat; Anavatti, Sreenatha G.

    2016-06-01

    This paper addresses the problem of identifying and tracking moving objects in a video sequence having a time-varying background. This is a fundamental task in many computer vision applications, though a very challenging one because of turbulence that causes blurring and spatiotemporal movements of the background images. Our proposed approach involves two major steps. First, a moving object detection algorithm that deals with the detection of real motions by separating the turbulence-induced motions using a two-level thresholding technique is used. In the second step, a feature-based generalized regression neural network is applied to track the detected objects throughout the frames in the video sequence. The proposed approach uses the centroid and area features of the moving objects and creates the reference regions instantly by selecting the objects within a circle. Simulation experiments are carried out on several turbulence-degraded video sequences and comparisons with an earlier method confirms that the proposed approach provides a more effective tracking of the targets.

  3. Super Ensemble-based Aviation Turbulence Guidance (SEATG) for Air Traffic Management (ATM)

    NASA Astrophysics Data System (ADS)

    Kim, Jung-Hoon; Chan, William; Sridhar, Banavar; Sharman, Robert

    2014-05-01

    Super Ensemble (ensemble of ten turbulence metrics from time-lagged ensemble members of weather forecast data)-based Aviation Turbulence Guidance (SEATG) is developed using Weather Research and Forecasting (WRF) model and in-situ eddy dissipation rate (EDR) observations equipped on commercial aircraft over the contiguous United States. SEATG is a sequence of five procedures including weather modeling, calculating turbulence metrics, mapping EDR-scale, evaluating metrics, and producing final SEATG forecast. This uses similar methodology to the operational Graphic Turbulence Guidance (GTG) with three major improvements. First, SEATG use a higher resolution (3-km) WRF model to capture cloud-resolving scale phenomena. Second, SEATG computes turbulence metrics for multiple forecasts that are combined at the same valid time resulting in an time-lagged ensemble of multiple turbulence metrics. Third, SEATG provides both deterministic and probabilistic turbulence forecasts to take into account weather uncertainties and user demands. It is found that the SEATG forecasts match well with observed radar reflectivity along a surface front as well as convectively induced turbulence outside the clouds on 7-8 Sep 2012. And, overall performance skill of deterministic SEATG against the observed EDR data during this period is superior to any single turbulence metrics. Finally, probabilistic SEATG is used as an example application of turbulence forecast for air-traffic management. In this study, a simple Wind-Optimal Route (WOR) passing through the potential areas of probabilistic SEATG and Lateral Turbulence Avoidance Route (LTAR) taking into account the SEATG are calculated at z = 35000 ft (z = 12 km) from Los Angeles to John F. Kennedy international airports. As a result, WOR takes total of 239 minutes with 16 minutes of SEATG areas for 40% of moderate turbulence potential, while LTAR takes total of 252 minutes travel time that 5% of fuel would be additionally consumed to entirely

  4. Airborne measurements of surface layer turbulence over the ocean during cold air outbreaks

    NASA Technical Reports Server (NTRS)

    Chou, Shu-Shien; Yeh, Eueng-Nan

    1987-01-01

    The spectral characteristics of surface layer turbulence for the near-shore cloud street regions over the Atlantic Ocean were examined using 50-m level data of airborne measurements of atmospheric turbulence spectra above the western Atlantic Ocean during cold air outbreaks. The present study, performed for the Mesoscale Air-Sea Exchange (MASEX) experiment, extends and completes the preliminary analyses of Chou and Yeh (1987). In the inertial subrange, a near 4/3 ratio was observed between velocity spectra normal to and those along the aircraft heading. A comparison of the turbulent kinetic energy budgets with those of Wyngaard and Cote (1971) and Caughey and Wyngaard (1979) data indicates that the turbulent kinetic energy in the surface layer is dissipated less in the MASEX data than in data obtained by the previous groups.

  5. Modeling exposure close to air pollution sources in naturally ventilated residences: association of turbulent diffusion coefficient with air change rate.

    PubMed

    Cheng, Kai-Chung; Acevedo-Bolton, Viviana; Jiang, Ruo-Ting; Klepeis, Neil E; Ott, Wayne R; Fringer, Oliver B; Hildemann, Lynn M

    2011-05-01

    For modeling exposure close to an indoor air pollution source, an isotropic turbulent diffusion coefficient is used to represent the average spread of emissions. However, its magnitude indoors has been difficult to assess experimentally due to limitations in the number of monitors available. We used 30-37 real-time monitors to simultaneously measure CO at different angles and distances from a continuous indoor point source. For 11 experiments involving two houses, with natural ventilation conditions ranging from <0.2 to >5 air changes per h, an eddy diffusion model was used to estimate the turbulent diffusion coefficients, which ranged from 0.001 to 0.013 m² s⁻¹. The model reproduced observed concentrations with reasonable accuracy over radial distances of 0.25-5.0 m. The air change rate, as measured using a SF₆ tracer gas release, showed a significant positive linear correlation with the air mixing rate, defined as the turbulent diffusion coefficient divided by a squared length scale representing the room size. The ability to estimate the indoor turbulent diffusion coefficient using two readily measurable parameters (air change rate and room dimensions) is useful for accurately modeling exposures in close proximity to an indoor pollution source.

  6. Effect of turbulence characteristics on local flame structure of H2 air premixed flames

    NASA Astrophysics Data System (ADS)

    Nada, Y.; Tanahashi, M.; Miyauchi, T.

    2004-04-01

    Direct numerical simulations (DNS) of turbulent premixed flames are conducted to investigate effects of turbulence characteristics on the local flame structure. A detailed kinetic mechanism including 12 reactive species and 27 elementary reactions is used to represent the H2-air reaction in turbulence. Numerical conditions of DNS can be classified into a wrinkled-flamelets regime, a corrugated-flamelets regime and thin reaction zones near the boundary of Karlovitz number Ka=1.0 of the turbulent-combustion diagram. For all cases, the distribution of heat-release rate shows a three-dimensionally connected sheet-like feature, even though the heat-release rate highly fluctuates along the flamefront. The heat-release rate tends to increase at the flamefronts that are convex towards the burnt side. For the turbulent premixed flames in the corrugated-flamelets regime, the handgrip structure is produced by the intrusion of the coherent fine-scale eddy into the flame and the heat-release rate in this structure increases up to 1.2 times of that of a laminar flame. In the wrinkled-flamelets regime, the spire-like structure of the flamefront is created due to the coherent fine-scale eddies in turbulence. By identifying flame elements in turbulence, their statistical characteristics are also discussed. This article was chosen from Selected Proceedings of the Third International Symposium on Turbulence and Shear Flow Phenomena (Sendai, Japan, 24-27 June 2003) ed N Kasagi et al.

  7. Development of Interfacial Structure in a Confined Air-Water Cap-Turbulent and Churn-Turbulent Flow

    SciTech Connect

    Xiaodong Sun; Seungjin Kim; Ling Cheng; Mamoru Ishii; Beus, Stephen G.

    2002-07-01

    The objective of the present work is to study and model the interfacial structure development of air-water two-phase flow in a confined test section. Experiments of a total of 9 flow conditions in cap-turbulent and churn-turbulent flow regimes are carried out in a vertical air-water upward two-phase flow experimental loop with a test section of 200-mm in width and 10-mm in gap. Miniaturized four-sensor conductivity probes are used to measure local two-phase parameters at three different elevations for each flow condition. The bubbles captured by the probes are categorized into two groups in view of the two-group interfacial area transport equation, i.e., spherical/distorted bubbles as Group 1 and cap/churn-turbulent bubbles as Group 2. The acquired parameters are time-averaged local void fraction, interfacial velocity, bubble number frequency, interfacial area concentration, and bubble Sauter mean diameter for both groups of bubbles. Also, the line-averaged and area-averaged data are presented and discussed. The comparisons of these parameters at different elevations demonstrate the development of interfacial structure along the flow direction due to bubble interactions. (authors)

  8. Development of Interfacial Structure in a Confined Air-Water Cap-Turbulent and Churn-Turbulent Flow

    SciTech Connect

    X. Sun; S. Kim; L. Cheng; M. Ishii; S.G. Beus

    2001-10-31

    The objective of the present work is to study and model the interfacial structure development of air-water two-phase flow in a confined test section. Experiments of a total of 9 flow conditions in a cap-turbulent and churn-turbulent flow regimes are carried out in a vertical air-water upward two-phase flow experimental loop with a test section of 20-cm in width and 1-cm in gap. The miniaturized four-sensor conductivity probes are used to measure local two-phase parameters at three different elevations for each flow condition. The bubbles captured by the probes are categorized into two groups in view of the two-group interfacial area transport equation, i.e., spherical/distorted bubbles as Group 1 and cap/churn-turbulent bubbles as Group 2. The acquired parameters are time-averaged local void fraction, interfacial velocity, bubble number frequency, interfacial area concentration, and bubble Sauter mean diameter for both groups of bubbles. Also, the line-averaged and area-averaged data are presented and discussed. The comparisons of these parameters at different elevations demonstrate the development of interfacial structure along the flow direction due to bubble interactions.

  9. Experimental study of the structure of isotropic turbulence with intermediate range of Reynolds number. [sea-air interaction

    NASA Technical Reports Server (NTRS)

    Ling, S. C.; Saad, A.

    1977-01-01

    The energetic isotropic turbulence generated by a waterfall of low head was found to be developed in part through the unstable two-phase flow of entrained air bubbles. The resulting turbulent field had a turbulent Reynolds number in excess of 20,000 and maintained a self-similar structure throughout the decay period studied. The present study may provide some insight into the structure of turbulence produced by breaking waves over the ocean.

  10. Simulation Analysis of Air Flow and Turbulence Statistics in a Rib Grit Roughened Duct

    PubMed Central

    Vogiatzis, I. I.; Denizopoulou, A. C.; Ntinas, G. K.; Fragos, V. P.

    2014-01-01

    The implementation of variable artificial roughness patterns on a surface is an effective technique to enhance the rate of heat transfer to fluid flow in the ducts of solar air heaters. Different geometries of roughness elements investigated have demonstrated the pivotal role that vortices and associated turbulence have on the heat transfer characteristics of solar air heater ducts by increasing the convective heat transfer coefficient. In this paper we investigate the two-dimensional, turbulent, unsteady flow around rectangular ribs of variable aspect ratios by directly solving the transient Navier-Stokes and continuity equations using the finite elements method. Flow characteristics and several aspects of turbulent flow are presented and discussed including velocity components and statistics of turbulence. The results reveal the impact that different rib lengths have on the computed mean quantities and turbulence statistics of the flow. The computed turbulence parameters show a clear tendency to diminish downstream with increasing rib length. Furthermore, the applied numerical method is capable of capturing small-scale flow structures resulting from the direct solution of Navier-Stokes and continuity equations. PMID:25057511

  11. Simulation analysis of air flow and turbulence statistics in a rib grit roughened duct.

    PubMed

    Vogiatzis, I I; Denizopoulou, A C; Ntinas, G K; Fragos, V P

    2014-01-01

    The implementation of variable artificial roughness patterns on a surface is an effective technique to enhance the rate of heat transfer to fluid flow in the ducts of solar air heaters. Different geometries of roughness elements investigated have demonstrated the pivotal role that vortices and associated turbulence have on the heat transfer characteristics of solar air heater ducts by increasing the convective heat transfer coefficient. In this paper we investigate the two-dimensional, turbulent, unsteady flow around rectangular ribs of variable aspect ratios by directly solving the transient Navier-Stokes and continuity equations using the finite elements method. Flow characteristics and several aspects of turbulent flow are presented and discussed including velocity components and statistics of turbulence. The results reveal the impact that different rib lengths have on the computed mean quantities and turbulence statistics of the flow. The computed turbulence parameters show a clear tendency to diminish downstream with increasing rib length. Furthermore, the applied numerical method is capable of capturing small-scale flow structures resulting from the direct solution of Navier-Stokes and continuity equations.

  12. Ocean Winds and Turbulent Air-Sea Fluxes Inferred From Remote Sensing

    NASA Technical Reports Server (NTRS)

    Bourassa, Mark A.; Gille, Sarah T.; Jackson, Daren L.; Roberts, J. Brent; Wick, Gary A.

    2010-01-01

    Air-sea turbulent fluxes determine the exchange of momentum, heat, freshwater, and gas between the atmosphere and ocean. These exchange processes are critical to a broad range of research questions spanning length scales from meters to thousands of kilometers and time scales from hours to decades. Examples are discussed (section 2). The estimation of surface turbulent fluxes from satellite is challenging and fraught with considerable errors (section 3); however, recent developments in retrievals (section 3) will greatly reduce these errors. Goals for the future observing system are summarized in section 4. Surface fluxes are defined as the rate per unit area at which something (e.g., momentum, energy, moisture, or CO Z ) is transferred across the air/sea interface. Wind- and buoyancy-driven surface fluxes are called surface turbulent fluxes because the mixing and transport are due to turbulence. Examples of nonturbulent processes are radiative fluxes (e.g., solar radiation) and precipitation (Schmitt et al., 2010). Turbulent fluxes are strongly dependent on wind speed; therefore, observations of wind speed are critical for the calculation of all turbulent surface fluxes. Wind stress, the vertical transport of horizontal momentum, also depends on wind direction. Stress is very important for many ocean processes, including upper ocean currents (Dohan and Maximenko, 2010) and deep ocean currents (Lee et al., 2010). On short time scales, this horizontal transport is usually small compared to surface fluxes. For long-term processes, transport can be very important but again is usually small compared to surface fluxes.

  13. Synchronization of clocks through 12 km of strongly turbulent air over a city

    NASA Astrophysics Data System (ADS)

    Sinclair, Laura C.; Swann, William C.; Bergeron, Hugo; Baumann, Esther; Cermak, Michael; Coddington, Ian; Deschênes, Jean-Daniel; Giorgetta, Fabrizio R.; Juarez, Juan C.; Khader, Isaac; Petrillo, Keith G.; Souza, Katherine T.; Dennis, Michael L.; Newbury, Nathan R.

    2016-10-01

    We demonstrate real-time, femtosecond-level clock synchronization across a low-lying, strongly turbulent, 12-km horizontal air path by optical two-way time transfer. For this long horizontal free-space path, the integrated turbulence extends well into the strong turbulence regime corresponding to multiple scattering with a Rytov variance up to 7 and with the number of signal interruptions exceeding 100 per second. Nevertheless, optical two-way time transfer is used to synchronize a remote clock to a master clock with femtosecond-level agreement and with a relative time deviation dropping as low as a few hundred attoseconds. Synchronization is shown for a remote clock based on either an optical or microwave oscillator and using either tip-tilt or adaptive-optics free-space optical terminals. The performance is unaltered from optical two-way time transfer in weak turbulence across short links. These results confirm that the two-way reciprocity of the free-space time-of-flight is maintained both under strong turbulence and with the use of adaptive optics. The demonstrated robustness of optical two-way time transfer against strong turbulence and its compatibility with adaptive optics is encouraging for future femtosecond clock synchronization over very long distance ground-to-air free-space paths.

  14. Detecting deterministic nature of pressure measurements from a turbulent combustor

    NASA Astrophysics Data System (ADS)

    Tony, J.; Gopalakrishnan, E. A.; Sreelekha, E.; Sujith, R. I.

    2015-12-01

    Identifying nonlinear structures in a time series, acquired from real-world systems, is essential to characterize the dynamics of the system under study. A single time series alone might be available in most experimental situations. In addition to this, conventional techniques such as power spectral analysis might not be sufficient to characterize a time series if it is acquired from a complex system such as a thermoacoustic system. In this study, we analyze the unsteady pressure signal acquired from a turbulent combustor with bluff-body and swirler as flame holding devices. The fractal features in the unsteady pressure signal are identified using the singularity spectrum. Further, we employ surrogate methods, with translational error and permutation entropy as discriminating statistics, to test for determinism visible in the observed time series. In addition to this, permutation spectrum test could prove to be a robust technique to characterize the dynamical nature of the pressure time series acquired from experiments. Further, measures such as correlation dimension and correlation entropy are adopted to qualitatively detect noise contamination in the pressure measurements acquired during the state of combustion noise. These ensemble of measures is necessary to identify the features of a time series acquired from a system as complex as a turbulent combustor. Using these measures, we show that the pressure fluctuations during combustion noise has the features of a high-dimensional chaotic data contaminated with white and colored noise.

  15. Detecting deterministic nature of pressure measurements from a turbulent combustor.

    PubMed

    Tony, J; Gopalakrishnan, E A; Sreelekha, E; Sujith, R I

    2015-12-01

    Identifying nonlinear structures in a time series, acquired from real-world systems, is essential to characterize the dynamics of the system under study. A single time series alone might be available in most experimental situations. In addition to this, conventional techniques such as power spectral analysis might not be sufficient to characterize a time series if it is acquired from a complex system such as a thermoacoustic system. In this study, we analyze the unsteady pressure signal acquired from a turbulent combustor with bluff-body and swirler as flame holding devices. The fractal features in the unsteady pressure signal are identified using the singularity spectrum. Further, we employ surrogate methods, with translational error and permutation entropy as discriminating statistics, to test for determinism visible in the observed time series. In addition to this, permutation spectrum test could prove to be a robust technique to characterize the dynamical nature of the pressure time series acquired from experiments. Further, measures such as correlation dimension and correlation entropy are adopted to qualitatively detect noise contamination in the pressure measurements acquired during the state of combustion noise. These ensemble of measures is necessary to identify the features of a time series acquired from a system as complex as a turbulent combustor. Using these measures, we show that the pressure fluctuations during combustion noise has the features of a high-dimensional chaotic data contaminated with white and colored noise. PMID:26764769

  16. Detecting deterministic nature of pressure measurements from a turbulent combustor.

    PubMed

    Tony, J; Gopalakrishnan, E A; Sreelekha, E; Sujith, R I

    2015-12-01

    Identifying nonlinear structures in a time series, acquired from real-world systems, is essential to characterize the dynamics of the system under study. A single time series alone might be available in most experimental situations. In addition to this, conventional techniques such as power spectral analysis might not be sufficient to characterize a time series if it is acquired from a complex system such as a thermoacoustic system. In this study, we analyze the unsteady pressure signal acquired from a turbulent combustor with bluff-body and swirler as flame holding devices. The fractal features in the unsteady pressure signal are identified using the singularity spectrum. Further, we employ surrogate methods, with translational error and permutation entropy as discriminating statistics, to test for determinism visible in the observed time series. In addition to this, permutation spectrum test could prove to be a robust technique to characterize the dynamical nature of the pressure time series acquired from experiments. Further, measures such as correlation dimension and correlation entropy are adopted to qualitatively detect noise contamination in the pressure measurements acquired during the state of combustion noise. These ensemble of measures is necessary to identify the features of a time series acquired from a system as complex as a turbulent combustor. Using these measures, we show that the pressure fluctuations during combustion noise has the features of a high-dimensional chaotic data contaminated with white and colored noise.

  17. Progress in Turbulence Detection via GNSS Occultation Data

    NASA Technical Reports Server (NTRS)

    Cornman, L. B.; Goodrich, R. K.; Axelrad, P.; Barlow, E.

    2012-01-01

    The increased availability of radio occultation (RO) data offers the ability to detect and study turbulence in the Earth's atmosphere. An analysis of how RO data can be used to determine the strength and location of turbulent regions is presented. This includes the derivation of a model for the power spectrum of the log-amplitude and phase fluctuations of the permittivity (or index of refraction) field. The bulk of the paper is then concerned with the estimation of the model parameters. Parameter estimators are introduced and some of their statistical properties are studied. These estimators are then applied to simulated log-amplitude RO signals. This includes the analysis of global statistics derived from a large number of realizations, as well as case studies that illustrate various specific aspects of the problem. Improvements to the basic estimation methods are discussed, and their beneficial properties are illustrated. The estimation techniques are then applied to real occultation data. Only two cases are presented, but they illustrate some of the salient features inherent in real data.

  18. Twisted photon entanglement through turbulent air across Vienna.

    PubMed

    Krenn, Mario; Handsteiner, Johannes; Fink, Matthias; Fickler, Robert; Zeilinger, Anton

    2015-11-17

    Photons with a twisted phase front can carry a discrete, in principle, unbounded amount of orbital angular momentum (OAM). The large state space allows for complex types of entanglement, interesting both for quantum communication and for fundamental tests of quantum theory. However, the distribution of such entangled states over large distances was thought to be infeasible due to influence of atmospheric turbulence, indicating a serious limitation on their usefulness. Here we show that it is possible to distribute quantum entanglement encoded in OAM over a turbulent intracity link of 3 km. We confirm quantum entanglement of the first two higher-order levels (with OAM=± 1ħ and ± 2ħ). They correspond to four additional quantum channels orthogonal to all that have been used in long-distance quantum experiments so far. Therefore, a promising application would be quantum communication with a large alphabet. We also demonstrate that our link allows access to up to 11 quantum channels of OAM. The restrictive factors toward higher numbers are technical limitations that can be circumvented with readily available technologies.

  19. Twisted photon entanglement through turbulent air across Vienna.

    PubMed

    Krenn, Mario; Handsteiner, Johannes; Fink, Matthias; Fickler, Robert; Zeilinger, Anton

    2015-11-17

    Photons with a twisted phase front can carry a discrete, in principle, unbounded amount of orbital angular momentum (OAM). The large state space allows for complex types of entanglement, interesting both for quantum communication and for fundamental tests of quantum theory. However, the distribution of such entangled states over large distances was thought to be infeasible due to influence of atmospheric turbulence, indicating a serious limitation on their usefulness. Here we show that it is possible to distribute quantum entanglement encoded in OAM over a turbulent intracity link of 3 km. We confirm quantum entanglement of the first two higher-order levels (with OAM=± 1ħ and ± 2ħ). They correspond to four additional quantum channels orthogonal to all that have been used in long-distance quantum experiments so far. Therefore, a promising application would be quantum communication with a large alphabet. We also demonstrate that our link allows access to up to 11 quantum channels of OAM. The restrictive factors toward higher numbers are technical limitations that can be circumvented with readily available technologies. PMID:26578763

  20. Twisted photon entanglement through turbulent air across Vienna

    PubMed Central

    Krenn, Mario; Handsteiner, Johannes; Fink, Matthias; Fickler, Robert; Zeilinger, Anton

    2015-01-01

    Photons with a twisted phase front can carry a discrete, in principle, unbounded amount of orbital angular momentum (OAM). The large state space allows for complex types of entanglement, interesting both for quantum communication and for fundamental tests of quantum theory. However, the distribution of such entangled states over large distances was thought to be infeasible due to influence of atmospheric turbulence, indicating a serious limitation on their usefulness. Here we show that it is possible to distribute quantum entanglement encoded in OAM over a turbulent intracity link of 3 km. We confirm quantum entanglement of the first two higher-order levels (with OAM=± 1ℏ and ± 2ℏ). They correspond to four additional quantum channels orthogonal to all that have been used in long-distance quantum experiments so far. Therefore, a promising application would be quantum communication with a large alphabet. We also demonstrate that our link allows access to up to 11 quantum channels of OAM. The restrictive factors toward higher numbers are technical limitations that can be circumvented with readily available technologies. PMID:26578763

  1. Detection of a turbulent gas component associated with a starless core with subthermal turbulence in the Orion A cloud

    NASA Astrophysics Data System (ADS)

    Ohashi, Satoshi; Tatematsu, Ken'ichi; Sanhueza, Patricio; Hirota, Tomoya; Choi, Minho; Mizuno, Norikazu

    2016-07-01

    We report the detection of a wing component in NH3 emission towards the starless core TUKH122 with subthermal turbulence in the Orion A cloud. This NH3 core is suggested to be on the verge of star formation because the turbulence inside the NH3 core is almost completely dissipated, and also because it is surrounded by CCS, which resembles the prestellar core L1544 in Taurus showing infall motions. Observations were carried out with the Nobeyama 45-m telescope at 0.05 km s-1 velocity resolution. We find that the NH3 line profile consists of two components. The quiescent main component has a small linewidth of 0.3 km s-1 dominated by thermal motion, and the red-shifted wing component has a large linewidth of 1.36 km s-1 representing turbulent motion. These components show kinetic temperatures of 11 and <30 K, respectively. Furthermore, there is a clear velocity offset between the NH3 quiescent gas (Local Standard of Rest velocity = 3.7 km s-1) and the turbulent gas (4.4 km s-1). The centroid velocity of the turbulent gas corresponds to that of the surrounding gas traced by the 13CO (J = 1-0) and CS (J = 2-1) lines. Large Velocity Gradient (LVG) model calculations for CS and CO show that the turbulent gas has a temperature of 8-13 K and an H2 density of ˜104 cm-3, suggesting that the temperature of the turbulent component is also ˜10 K. The detections of both NH3 quiescent and wing components may indicate a sharp transition from the turbulent parent cloud to the quiescent dense core.

  2. Single snapshot performance simulations for POST Detection Turbulence Compensation

    NASA Astrophysics Data System (ADS)

    Dayton, Dave; Kelly, Brian; Gonglewski, John

    1990-11-01

    Post Detection Turbulence Compensation has been proposed as a technique to obtain diffraction limited imaging through the atmosphere. The technique consists of two simultaneous measurements, one made at a point conjugate to the pupil plane of an optical system and one at its focal plane. The optical transfer function of the atmosphere is constructed from the pupil plane measurement. This is then deconvolved from the focal plane image. The result is an image with a resolution at or near the diffraction limit of the imaging system. The process is highly nonlinear, and as a result the quality of the restored images is difficult to estimate analytically. In an attempt to understand the characteristics of this process, computer models have been developed to simulate speckle holography image compensation. Results of computer simulations showing reconstructed image quality versus light levels are presented.

  3. Direct numerical simulations of turbulent non-premixed methane-air flames modeled with reduced kinetics

    NASA Technical Reports Server (NTRS)

    Card, J. M.; Chen, J. H.; Day, M.; Mahalingam, S.

    1994-01-01

    Turbulent non-premixed stoichiometric methane-air flames modeled with reduced kinetics have been studied using the direct numerical simulation approach. The simulations include realistic chemical kinetics, and the molecular transport is modeled with constant Lewis numbers for individual species. The effect of turbulence on the internal flame structure and extinction characteristics of methane-air flames is evaluated. Consistent with earlier DNS with simple one-step chemistry, the flame is wrinkled and in some regions extinguished by the turbulence, while the turbulence is weakened in the vicinity of the flame due to a combination of dilatation and an increase in kinematic viscosity. Unlike previous results, reignition is observed in the present simulations. Lewis number effects are important in determining the local stoichiometry of the flame. The results presented in this work are preliminary but demonstrate the feasibility of incorporating reduced kinetics for the oxidation of methane with direct numerical simulations of homogeneous turbulence to evaluate the limitations of various levels of reduction in the kinetics and to address the formation of thermal and prompt NO(x).

  4. Application of the Hilbert-Huang Transform to the Estimation of Air-Sea Turbulent Fluxes

    NASA Astrophysics Data System (ADS)

    Wang, Juanjuan; Song, Jinbao; Huang, Yansong; Fan, Conghui

    2013-06-01

    The Hilbert-Huang transform (HHT) is applied to analyzing the turbulent time series obtained within the atmospheric boundary layer over the ocean. A method based on the HHT is introduced to reduce the influence of non-turbulent motions on the eddy-covariance based flux by removing non-turbulent modes from the time series. The scale dependence of the flux is examined and a gap mode is identified to distinguish between turbulent modes and non-turbulent modes. To examine the effectiveness of this method it is compared with three conventional methods (block average, moving-window average, and multi-resolution decomposition). The data used are from three sonic anemometers installed on a moored buoy at about 6, 4 and 2.7 m height above the sea surface. For each method, along-wind and cross-wind momentum fluxes and sensible heat fluxes at the three heights are calculated. According to the assumption of a constant-flux layer, there should be no significant difference between the fluxes at the three heights. The results show that the fluxes calculated using HHT exhibit a smaller difference and higher correlation than the other methods. These results support the successful application of HHT to the estimation of air-sea turbulent fluxes.

  5. Field observations of turbulent dissipation rate profiles immediately below the air-water interface

    NASA Astrophysics Data System (ADS)

    Wang, Binbin; Liao, Qian

    2016-06-01

    Near surface profiles of turbulence immediately below the air-water interface were measured with a free-floating Particle Image Velocimetry (PIV) system on Lake Michigan. The surface-following configuration allowed the system to measure the statistics of the aqueous-side turbulence in the topmost layer immediately below the water surface (z≈0˜15 cm, z points downward with 0 at the interface). Profiles of turbulent dissipation rate (ɛ) were investigated under a variety of wind and wave conditions. Various methods were applied to estimate the dissipation rate. Results suggest that these methods yield consistent dissipation rate profiles with reasonable scattering. In general, the dissipation rate decreases from the water surface following a power law relation in the top layer, ɛ˜z-0.7, i.e., the slope of the decrease was lower than that predicted by the wall turbulence theory, and the dissipation was considerably higher in the top layer for cases with higher wave ages. The measured dissipation rate profiles collapse when they were normalized with the wave speed, wave height, water-side friction velocity, and the wave age. This scaling suggests that the enhanced turbulence may be attributed to the additional source of turbulent kinetic energy (TKE) at the "skin layer" (likely due to micro-breaking), and its downward transport in the water column.

  6. Neutral air turbulence and temperatures in the vicinity of polar mesosphere summer echoes

    NASA Astrophysics Data System (ADS)

    Lübken, Franz-Josef; Rapp, Markus; Hoffmann, Peter

    2002-08-01

    A total of 8 sounding rocket flights with measurements of neutral air turbulence in the upper mesosphere have been performed in the past 10 years with simultaneous and nearly co-located radar measurements of polar mesosphere summer echoes (PMSE). These measurements took place close to the rocket ranges in northern Norway (Andøya Rocket Range, 69°N) and in northern Sweden (Esrange, 68°N). A detailed comparison demonstrates that there is no apparent correlation between PMSE and neutral air turbulence and that in fact turbulence is absent in the majority of all PMSE events (no turbulence in 7 out of 10 PMSE layers). This suggests that neutral turbulence and other mechanisms affecting the neutral atmosphere at very small spatial scales play a minor role in creating PMSE, contrary to the speculations published in the literature. The main mechanism for creating PMSE remains unidentified. A comparison of PMSE with simultaneous temperature profiles derived from falling sphere and ionization gauge measurements shows that PMSE are practically always present at altitudes where the temperature is low enough for water ice particles to exist. This supports the general understanding that PMSE are closely related to charged water ice particles. On the other hand, the measurements also demonstrate that low enough temperatures are not sufficient for PMSE to exist. Temperature lapse rates were deduced from the high-altitude-resolution ionization gauge measurements. Within the PMSE layers the temperature lapse rate is typically +1-2 K/km with a rather large variability of +/-5-10 K/km. Adiabatic lapse rates have never been found within a PMSE layer, which suggests that turbulence cannot have been active for a substantial period. This again supports the idea that neutral air turbulence plays a minor role in creating PMSE. Probably the only common physical reason for PMSE and turbulence is the background temperature profile, which supports the creation of ice particles (since

  7. Ambient air contamination: Characterization and detection techniques

    NASA Technical Reports Server (NTRS)

    Nulton, C. P.; Silvus, H. S.

    1985-01-01

    Techniques to characterize and detect sources of ambient air contamination are described. Chemical techniques to identify indoor contaminants are outlined, they include gas chromatography, or colorimetric detection. Organics generated from indoor materials at ambient conditions and upon combustion are characterized. Piezoelectric quartz crystals are used as precision frequency determining elements in electronic oscillators.

  8. Experimental study on turbulent structure of humid air flame in a bluff-body burner

    NASA Astrophysics Data System (ADS)

    Ge, Bing; Zang, Shu-Sheng; Guo, Pei-Qing

    2009-06-01

    The main objective of the present experimental study is to analyze the turbulent structure in humid air non-premixed flame, and determine the effect of humidity on the flow field and the flame stability limit in turbulent non-premixed flame. Particle Image Velocimetry (PIV) is used to capture the instantaneous appearance of vortex structures and obtain the quantitative velocity field. The distributions of Reynolds shear stress, mean and root-mean squared fluctuating (rms) velocities are examined to get insight into the effect of fuel-to-air velocity ratio on velocity flow field. The results show that with steam addition, the air-driven vortex in the bluff-body wake is thinner; the biggest peaks of rms velocity and Reynolds shear stress are lower; the distance between the peaks of rms velocity on the sides of centerline reduces. Besides these, the flame stability is affected. Both central fuel penetration limit and partially quenching limit reduce with steam addition.

  9. Current state and prospects of researches on the control of turbulent boundary layer by air blowing

    NASA Astrophysics Data System (ADS)

    Kornilov, V. I.

    2015-07-01

    The paper presents the analytical review of the current state of the investigations and development trends on the problem of turbulent friction and aerodynamic drag reduction in simple model configurations, which is among key ones in modern aeromechanics. Under consideration is the modern fast progressing method of the turbulent flow control by air- and other gases (micro)blowing through a permeable surface, which is utilized in incompressible and compressible turbulent boundary layers. Several computational results to understand the essential flow physics are also included. The problem of simulation of the flow over a perforated wall where some ambiguities, in particular, at the permeable/impermeable boundary being still remained is discussed. Special attention is paid to the analysis of most important experimental and numerical results obtained with the air blowing through a finely-perforated surface, analysis of the physical peculiarities and regularities of the flow with the blowing, probability to describe the properties of such a flow within simple approach frameworks, evaluation of the efficiency of this control method, as well as the trends and opportunities of this method progress in view of state-of-the-art achievements. Although this technology has a penalty for developing the effective turbulent-flow control method, some modifications of the air blowing are an attractive alternative for real applications.

  10. Investigation of Ignition and Combustion Processes of Diesel Engines Operating with Turbulence and Air-storage Chambers

    NASA Technical Reports Server (NTRS)

    Petersen, Hans

    1938-01-01

    The flame photographs obtained with combustion-chamber models of engines operating respectively, with turbulence chamber and air-storage chambers or cells, provide an insight into the air and fuel movements that take place before and during combustion in the combustion chamber. The relation between air velocity, start of injection, and time of combustion was determined for the combustion process employing a turbulence chamber.

  11. Model for estimating the refractive-index structure constant in clear-air intermittent turbulence.

    PubMed

    d'Auria, G; Marzano, F S; Merlo, U

    1993-05-20

    We explain discrepancies in comparing estimations of the refractive-index structure constant C(n)(2) in clear air by means of different techniques by taking into account atmospheric intermittency effects. We formulate a model of C(n)(2) in intermittent turbulence on the basis of the Tatarskii theory, and we calculate the mean value of C(n)(2) through a probabilistic approach. We deduce a factor, which gives a measure of the statistical reduction of turbulence that is due to intermittency, within the model framework. A procedure for estimating the mean value of C(n)(2) from data of a specific radiosonde observation is illustrated.

  12. Microwave detection of air showers with MIDAS

    NASA Astrophysics Data System (ADS)

    Facal San Luis, P.; Alekotte, I.; Alvarez, J.; Berlin, A.; Bertou, X.; Bogdan, M.; Bohacova, M.; Bonifazi, C.; Carvalho, W. R.; de Mello Neto, J. R. T.; Genat, J. F.; Mills, E.; Monasor, M.; Privitera, P.; Reyes, I. C.; Rouille D'Orfeuil, B.; Santos, E. M.; Wayne, S.; Williams, C.; Zas, E.

    2012-01-01

    MIDAS (MIcrowave Detector of Air Showers) is a prototype of a microwave telescope to detect extensive air showers: it images a 20°×10° region of the sky with a 4.5 m parabolic reflector and 53 feeds in the focal plane. It has been commissioned in March 2010 and is currently taking data. We present the design, performance and first results of MIDAS.

  13. Spectra of concentration of air pollution for turbulent convection

    SciTech Connect

    Patel, S.R.

    1996-12-31

    Very recently the study of formation and destruction of photochemical smog is increasing at both small and large scale. Also the transport of chemical species through the Planetary Boundary Layer (PBL) of the atmosphere is a key of the global change problem and will have to be parameterized more reliably than in the past. Further, in the air pollution modeling, the usual practice of neglecting the concentration correlation in the atmospheric photochemical reaction has recently been recognized as a source of serious error. So, it is important to study the various aspects of the concentration fluctuations (of air pollution) with chemical reaction. A model of the spectrum of concentration of air pollution with chemical reaction has been developed using the models of Hill and Hill and Clifford. The results obtained are applicable for arbitrary Schmidt number. Further, for the case of pure mixing (without chemical reaction) and the concentration replaced by temperature, the form of the spectra obtained here reduces to the form obtained by Hill and Clifford. This study also shows that, in the case of pure mixing, the concentration decays in a natural manner, but if the concentration selected is that of the chemical reactant, then the effect is that the dispersion of the concentration is much more rapid.

  14. Turbulence

    NASA Astrophysics Data System (ADS)

    Frisch, Uriel

    1996-01-01

    Written five centuries after the first studies of Leonardo da Vinci and half a century after A.N. Kolmogorov's first attempt to predict the properties of flow, this textbook presents a modern account of turbulence, one of the greatest challenges in physics. "Fully developed turbulence" is ubiquitous in both cosmic and natural environments, in engineering applications and in everyday life. Elementary presentations of dynamical systems ideas, probabilistic methods (including the theory of large deviations) and fractal geometry make this a self-contained textbook. This is the first book on turbulence to use modern ideas from chaos and symmetry breaking. The book will appeal to first-year graduate students in mathematics, physics, astrophysics, geosciences and engineering, as well as professional scientists and engineers.

  15. Analysis of turbulent free jet hydrogen-air diffusion flames with finite chemical reaction rates

    NASA Technical Reports Server (NTRS)

    Sislian, J. P.

    1978-01-01

    The nonequilibrium flow field resulting from the turbulent mixing and combustion of a supersonic axisymmetric hydrogen jet in a supersonic parallel coflowing air stream is analyzed. Effective turbulent transport properties are determined using the (K-epsilon) model. The finite-rate chemistry model considers eight reactions between six chemical species, H, O, H2O, OH, O2, and H2. The governing set of nonlinear partial differential equations is solved by an implicit finite-difference procedure. Radial distributions are obtained at two downstream locations of variables such as turbulent kinetic energy, turbulent dissipation rate, turbulent scale length, and viscosity. The results show that these variables attain peak values at the axis of symmetry. Computed distributions of velocity, temperature, and mass fraction are also given. A direct analytical approach to account for the effect of species concentration fluctuations on the mean production rate of species (the phenomenon of unmixedness) is also presented. However, the use of the method does not seem justified in view of the excessive computer time required to solve the resulting system of equations.

  16. Direct numerical simulation of a turbulent stably stratified air flow above a wavy water surface

    NASA Astrophysics Data System (ADS)

    Druzhinin, O. A.; Troitskaya, Yu. I.; Zilitinkevich, S. S.

    2016-01-01

    The influence of the roughness of the underlaying water surface on turbulence is studied in a stably stratified boundary layer (SSBL). Direct numerical simulation (DNS) is conducted at various Reynolds (Re) and Richardson (Ri) numbers and the wave steepness ka. It is shown that, at constant Re, the stationary turbulent regime is set in at Ri below the threshold value Ri c depending on Re. At Ri > Ri c , in the absence of turbulent fluctuations near the wave water surface, three-dimensional quasiperiodical structures are identified and their threshold of origin depends on the steepness of the surface wave on the water surface. This regime is called a wave pumping regime. The formation of three-dimensional structures is explained by the development of parametric instability of the disturbances induced by the surface water in the air flow. The DNS results are quite consistent with prediction of the theoretical model of the SSBL flow, in which solutions for the disturbances of the fields of velocity and temperature in the wave pumping regime are found to be a solution of a two-dimensional linearized system with the heterogeneous boundary condition, which is caused by the presence of the surface wave. In addition to the turbulent fluctuations, the three-dimensional structures in the wave pumping regime provide for the transfer of impulse and heat, i.e., the increase in the roughness of the water-air boundary caused by the presence of waves intensifies the exchange in the SSBL.

  17. Turbulent Fluxes and Pollutant Mixing during Wintertime Air Pollution Episodes in Complex Terrain.

    PubMed

    Holmes, Heather A; Sriramasamudram, Jai K; Pardyjak, Eric R; Whiteman, C David

    2015-11-17

    Cold air pools (CAPs) are stagnant stable air masses that form in valleys and basins in the winter. Low wintertime insolation limits convective mixing, such that pollutant concentrations can build up within the CAP when pollutant sources are present. In the western United States, wintertime CAPs often persist for days or weeks. Atmospheric models do not adequately capture the strength and evolution of CAPs. This is in part due to the limited availability of data quantifying the local turbulence during the formation, maintenance, and destruction of persistent CAPs. This paper presents observational data to quantify the turbulent mixing during two CAP episodes in Utah's Salt Lake Valley during February of 2004. Particulate matter (PM) concentration data and turbulence measurements for CAP and non-CAP time periods indicate that two distinct types of mixing scenarios occur depending on whether the CAP is dry or cloudy. Where cloudy, CAPs have enhanced vertical mixing due to top-down convection from the cloud layer. A comparison between the heat and momentum fluxes during 5 days of a dry CAP episode in February to those of an equivalent 5 day time period in March with no CAP indicates that the average turbulent kinetic energy during the CAP was suppressed by approximately 80%.

  18. Weather Associated with the Fall-2000 Turbulence Flight Tests

    NASA Technical Reports Server (NTRS)

    Hamilton, David W.; Proctor, Fred H.

    2003-01-01

    This viewgraph presentation provides information on three flight tests in which NASA Langley's ARIES B-757 research aircraft was intentionally piloted into areas with a high risk for severe atmospheric turbulence. During its encounter with turbulence, instruments aboard the aircraft monitored wind, temperature and acceleration, and onboard Doppler radar detected forward turbulence. Data was collected along a spectrum, from smooth air to severe turbulence.

  19. Alternating-Current Equipment for the Measurement of Fluctuations of Air Speed in Turbulent Flow

    NASA Technical Reports Server (NTRS)

    Mock, W C , Jr

    1937-01-01

    Recent electrical and mechanical improvements have been made in the equipment developed at the National Bureau of Standards for measurement of fluctuations of air speed in turbulent flow. Data useful in the design of similar equipment are presented. The design of rectified alternating-current power supplies for such apparatus is treated briefly, and the effect of the power supplies on the performance of the equipment is discussed.

  20. Ionospheric plasma Turbulence detection in the VLF data observed by DEMETER Satellite

    NASA Astrophysics Data System (ADS)

    Sondhiya, Deepak Kumar; Gwal, Ashok Kumar; Kumar, Sushil

    2016-07-01

    The electromagnetic wave data in the Very Low Frequency (VLF) range detected by DEMETER satellite has been analyzed, with special attention to the variation in spectral characteristics and non-linear effects, using the statistical and wavelet based techniques.The enhancement in statistical parameters shows the coherent structure and intermittent phenomenon which is the signature of turbulence. The characteristics features of VLF disturbances have further been studied using the wavelet and bispectral analysis tools which provide useful information on the plasma turbulence.A more interesting result emerges when the low-frequency turbulence emissions produce turbulence in VLF range. Finally, the relevance of the various turbulence mechanisms and their importance in ionospheric turbulence is discussed. Keywords:DEMETER, Earthquake, Phenomena of Intermittence, Coherent Structure.

  1. Flame front surface characteristics in turbulent premixed propane/air combustion

    SciTech Connect

    Guelder, O.L.; Smallwood, G.J.; Wong, R.; Snelling, D.R.; Smith, R.; Deschamps, B.M.; Sautet, J.C.

    2000-03-01

    The characteristics of the flame front surfaces in turbulent premixed propane/air flames were investigated. Flame front images were obtained using laser-induced fluorescence (LIF) of OH and Mie scattering on two Bunsen-type burners of 11.2-mm and 22.4-mm diameters. Nondimensional turbulence intensity, u{prime}/S{sub L}, was varied from 0.9 to 15, and the Reynolds number, based on the integral length scale, varied from 40 to 467. Approximately 100 images were recorded for each experimental condition. Fractal parameters (fractal dimension, inner and outer cutoffs) and corresponding standard deviations were determined by analysis of the flame front images using the caliper technique. The fractal dimensions derived from OH and Mie scattering images are almost identical. However, inner and outer cutoffs from OH images are consistently higher than those obtained from Mie scattering. The self-similar region of the flame front wrinkling is about a decade for all flames studied. In the nondimensional turbulence intensity range from 1 to 15, it was found that the mean fractal dimension is about 2.2 and it does not show any dependence on turbulence intensity. This contradicts the findings of the previous studies that showed that the fractal dimension asymptotically reaches to 2.35--2.37 when the nondimensional turbulence intensity u{prime}/S{sub L} exceeds 3. It is shown that the reason for this discrepancy is the image analysis method used in the previous studies. Examples are given to show the inadequacy of the circle method used in previous studies for extraction of fractal parameters from flame front images. The fractal parameters obtained so far, in this and previous studies, are not capable of correctly predicting the turbulent burning velocity using the available fractal area closure model.

  2. The performance of heterodyne detection system for partially coherent beams in turbulent atmosphere

    NASA Astrophysics Data System (ADS)

    Chengqiang, Li; Tingfeng, Wang; Heyong, Zhang; Jingjiang, Xie; Lisheng, Liu; Shuai, Zhao; Jin, Guo

    2015-12-01

    The performance of heterodyne system is discussed for partially coherent beams in turbulent atmosphere by introducing turbulence spectrum of refractive-index fluctuations. Several analytic formulae for the heterodyne detection system using the partially coherent Gaussian Schell-model beam are presented. Based on Tatarskii spectrum model, some numerical results are given for the variation in the heterodyne efficiency with the misalignment angle, detector diameter, turbulence conditions, and parameters of the overlapping beams. According to the numerical results, we find that the turbulent atmosphere degrades the heterodyne efficiency significantly, and the variation in heterodyne efficiency is even slower against the misalignment angle in turbulence. For the deterministic received signal and the detector, the performance of the heterodyne detection can be adjusted by controlling the local oscillator signal parameters.

  3. Response of flame thickness and propagation speed under intense turbulence in spatially developing lean premixed methane–air jet flames

    DOE PAGES

    Sankaran, Ramanan; Hawkes, Evatt R.; Yoo, Chun Sang; Chen, Jacqueline H.

    2015-06-22

    Direct numerical simulations of three-dimensional spatially-developing turbulent Bunsen flames were performed at three different turbulence intensities. We performed these simulations using a reduced methane–air chemical mechanism which was specifically tailored for the lean premixed conditions simulated here. A planar-jet turbulent Bunsen flame configuration was used in which turbulent preheated methane–air mixture at 0.7 equivalence ratio issued through a central jet and was surrounded by a hot laminar coflow of burned products. The turbulence characteristics at the jet inflow were selected such that combustion occured in the thin reaction zones (TRZ) regime. At the lowest turbulence intensity, the conditions fall onmore » the boundary between the TRZ regime and the corrugated flamelet regime, and progressively moved further into the TRZ regime by increasing the turbulent intensity. The data from the three simulations was analyzed to understand the effect of turbulent stirring on the flame structure and thickness. Furthermore, statistical analysis of the data showed that the thermal preheat layer of the flame was thickened due to the action of turbulence, but the reaction zone was not significantly affected. A global and local analysis of the burning velocity of the flame was performed to compare the different flames. Detailed statistical averages of the flame speed were also obtained to study the spatial dependence of displacement speed and its correlation to strain rate and curvature.« less

  4. Response of flame thickness and propagation speed under intense turbulence in spatially developing lean premixed methane–air jet flames

    SciTech Connect

    Sankaran, Ramanan; Hawkes, Evatt R.; Yoo, Chun Sang; Chen, Jacqueline H.

    2015-06-22

    Direct numerical simulations of three-dimensional spatially-developing turbulent Bunsen flames were performed at three different turbulence intensities. We performed these simulations using a reduced methane–air chemical mechanism which was specifically tailored for the lean premixed conditions simulated here. A planar-jet turbulent Bunsen flame configuration was used in which turbulent preheated methane–air mixture at 0.7 equivalence ratio issued through a central jet and was surrounded by a hot laminar coflow of burned products. The turbulence characteristics at the jet inflow were selected such that combustion occured in the thin reaction zones (TRZ) regime. At the lowest turbulence intensity, the conditions fall on the boundary between the TRZ regime and the corrugated flamelet regime, and progressively moved further into the TRZ regime by increasing the turbulent intensity. The data from the three simulations was analyzed to understand the effect of turbulent stirring on the flame structure and thickness. Furthermore, statistical analysis of the data showed that the thermal preheat layer of the flame was thickened due to the action of turbulence, but the reaction zone was not significantly affected. A global and local analysis of the burning velocity of the flame was performed to compare the different flames. Detailed statistical averages of the flame speed were also obtained to study the spatial dependence of displacement speed and its correlation to strain rate and curvature.

  5. Direct Numerical Simulations of Autoignition in Stratified Dimethyl-ether (DME)/Air Turbulent Mixtures

    SciTech Connect

    Bansal, Gaurav; Mascarenhas, Ajith; Chen, Jacqueline H.

    2014-10-01

    In our paper, two- and three-dimensional direct numerical simulations (DNS) of autoignition phenomena in stratified dimethyl-ether (DME)/air turbulent mixtures are performed. A reduced DME oxidation mechanism, which was obtained using rigorous mathematical reduction and stiffness removal procedure from a detailed DME mechanism with 55 species, is used in the present DNS. The reduced DME mechanism consists of 30 chemical species. This study investigates the fundamental aspects of turbulence-mixing-autoignition interaction occurring in homogeneous charge compression ignition (HCCI) engine environments. A homogeneous isotropic turbulence spectrum is used to initialize the velocity field in the domain. Moreover, the computational configuration corresponds to a constant volume combustion vessel with inert mass source terms added to the governing equations to mimic the pressure rise due to piston motion, as present in practical engines. DME autoignition is found to be a complex three-staged process; each stage corresponds to a distinct chemical kinetic pathway. The distinct role of turbulence and reaction in generating scalar gradients and hence promoting molecular transport processes are investigated. Then, by applying numerical diagnostic techniques, the different heat release modes present in the igniting mixture are identified. In particular, the contribution of homogeneous autoignition, spontaneous ignition front propagation, and premixed deflagration towards the total heat release are quantified.

  6. Direct Numerical Simulations of Autoignition in Stratified Dimethyl-ether (DME)/Air Turbulent Mixtures

    DOE PAGES

    Bansal, Gaurav; Mascarenhas, Ajith; Chen, Jacqueline H.

    2014-10-01

    In our paper, two- and three-dimensional direct numerical simulations (DNS) of autoignition phenomena in stratified dimethyl-ether (DME)/air turbulent mixtures are performed. A reduced DME oxidation mechanism, which was obtained using rigorous mathematical reduction and stiffness removal procedure from a detailed DME mechanism with 55 species, is used in the present DNS. The reduced DME mechanism consists of 30 chemical species. This study investigates the fundamental aspects of turbulence-mixing-autoignition interaction occurring in homogeneous charge compression ignition (HCCI) engine environments. A homogeneous isotropic turbulence spectrum is used to initialize the velocity field in the domain. Moreover, the computational configuration corresponds to amore » constant volume combustion vessel with inert mass source terms added to the governing equations to mimic the pressure rise due to piston motion, as present in practical engines. DME autoignition is found to be a complex three-staged process; each stage corresponds to a distinct chemical kinetic pathway. The distinct role of turbulence and reaction in generating scalar gradients and hence promoting molecular transport processes are investigated. Then, by applying numerical diagnostic techniques, the different heat release modes present in the igniting mixture are identified. In particular, the contribution of homogeneous autoignition, spontaneous ignition front propagation, and premixed deflagration towards the total heat release are quantified.« less

  7. Analysis of turbulent free-jet hydrogen-air diffusion flames with finite chemical reaction rates

    NASA Technical Reports Server (NTRS)

    Sislian, J. P.; Glass, I. I.; Evans, J. S.

    1979-01-01

    A numerical analysis is presented of the nonequilibrium flow field resulting from the turbulent mixing and combustion of an axisymmetric hydrogen jet in a supersonic parallel ambient air stream. The effective turbulent transport properties are determined by means of a two-equation model of turbulence. The finite-rate chemistry model considers eight elementary reactions among six chemical species: H, O, H2O, OH, O2 and H2. The governing set of nonlinear partial differential equations was solved by using an implicit finite-difference procedure. Radial distributions were obtained at two downstream locations for some important variables affecting the flow development, such as the turbulent kinetic energy and its dissipation rate. The results show that these variables attain their peak values on the axis of symmetry. The computed distribution of velocity, temperature, and mass fractions of the chemical species gives a complete description of the flow field. The numerical predictions were compared with two sets of experimental data. Good qualitative agreement was obtained.

  8. Air Monitoring for Hazardous Gas Detection

    NASA Technical Reports Server (NTRS)

    Arkin, C. Richard; Naylor, Guy; Haskell, William; Floyd, David; Curley, Charles; Griffin, Timothy P.; Adams, Frederick; Follistein, Duke

    2003-01-01

    The Hazardous Gas Detection Lab is involved in the design and development of instrumentation that can detect and quantify various hazardous gases. Traditionally these systems are designed for leak detection of the cryogenic gases used for the propulsion of the Shuttle and other vehicles. Mass spectrometers are the basis of these systems, which provide excellent quantitation, sensitivity, selectivity, response and limits of detection. Unfortunately, these systems are large, heavy and expensive. This feature limits the ability to perform gas analysis in certain applications. Smaller and lighter mass spectrometer systems could be used in many more applications primarily due to the portability of the system. Such applications would include air analysis in confined spaces, in-situ environmental analysis and emergency response. In general, system cost is lowered as size is reduced. With a low cost air analysis system, several systems could be utilized for monitoring large areas. These networked systems could be deployed at job-sites for worker safety, throughout a community for pollution warnings, or dispersed in a battlefield for early warning of chemical or biological threats. Presented will be information on the first prototype of this type of system. Included will be field trial data, with this prototype performing air analysis autonomously from an aircraft.

  9. Turbulent heat and mass transfers across a thermally stratified air-water interface

    NASA Technical Reports Server (NTRS)

    Papadimitrakis, Y. A.; Hsu, Y.-H. L.; Wu, J.

    1986-01-01

    Rates of heat and mass transfer across an air-water interface were measured in a wind-wave research facility, under various wind and thermal stability conditions (unless otherwise noted, mass refers to water vapor). Heat fluxes were obtained from both the eddy correlation and the profile method, under unstable, neutral, and stable conditions. Mass fluxes were obtained only under unstable stratification from the profile and global method. Under unstable conditions the turbulent Prandtl and Schmidt numbers remain fairly constant and equal to 0.74, whereas the rate of mass transfer varies linearly with bulk Richardson number. Under stable conditions the turbulent Prandtl number rises steadily to a value of 1.4 for a bulk Richardson number of about 0.016. Results of heat and mass transfer, expressed in the form of bulk aerodynamic coefficients with friction velocity as a parameter, are also compared with field data.

  10. Flamelet modelling of propane--air chemistry in turbulent non-premixed combustion

    SciTech Connect

    Askari-Sardhai, A.; Liew, S.K.; Moss, J.B.

    1985-01-01

    This short paper describes the application of the flamelet modelling approach to the prediction of the species concentration field in a turbulent propane-air flame. The structure of the laminar flamelet, the microscopic element in the model, is computed using a semi-global expression for fuel disappearance in conjunction with an established reaction scheme for the oxidation of CO and H/sub 2/. Detailed predictions for a turbulent jet-flame are compared with available experimental data. The significant measure of non-equilibrium which the flamelet introduces leads to substantial improvements in the prediction of CO, H/sub 2/, and C/sub 3/H/sub 8/ mass fractions in comparison with the simplest alternative model, that of full chemical equilibrium.

  11. Air-sea fluxes and surface layer turbulence around a sea surface temperature front

    NASA Technical Reports Server (NTRS)

    Friehe, C. A.; Shaw, W. J.; Davidson, K. L.; Rogers, D. P.; Large, W. G.; Stage, S. A.; Crescenti, G. H.; Khalsa, S. J. S.; Greenhut, G. K.; Li, F.

    1991-01-01

    The observed effects of sharp changes in sea surface temperature (SST) on the air-sea fluxes, surface roughness, and the turbulence structure in the surface layer and the marine atmospheric boundary layer are discussed. In situ flux and turbulence observations were carried out from three aircraft and two ships within the FASINEX framework. Three other aircraft used remote sensors to measure waves, microwave backscatter, and lidar signatures of cloud tops. Descriptions of the techniques, intercomparison of aircraft and ship flux data, and use of different methods for analyzing the fluxes from the aircraft data are described. Changing synoptic weather on three successive days yielded cases of wind direction both approximately parallel and perpendicular to a surface temperature front. For the wind perpendicular to the front, wind over both cold-to-warm and warm-to-cold surface temperatures occurred. Model results consistent with the observations suggest that an internal boundary layer forms at the SST.

  12. Monte-Carlo computation of turbulent premixed methane/air ignition

    NASA Astrophysics Data System (ADS)

    Carmen, Christina Lieselotte

    The present work describes the results obtained by a time dependent numerical technique that simulates the early flame development of a spark-ignited premixed, lean, gaseous methane/air mixture with the unsteady spherical flame propagating in homogeneous and isotropic turbulence. The algorithm described is based upon a sub-model developed by an international automobile research and manufacturing corporation in order to analyze turbulence conditions within internal combustion engines. Several developments and modifications to the original algorithm have been implemented including a revised chemical reaction scheme and the evaluation and calculation of various turbulent flame properties. Solution of the complete set of Navier-Stokes governing equations for a turbulent reactive flow is avoided by reducing the equations to a single transport equation. The transport equation is derived from the Navier-Stokes equations for a joint probability density function, thus requiring no closure assumptions for the Reynolds stresses. A Monte-Carlo method is also utilized to simulate phenomena represented by the probability density function transport equation by use of the method of fractional steps. Gaussian distributions of fluctuating velocity and fuel concentration are prescribed. Attention is focused on the evaluation of the three primary parameters that influence the initial flame kernel growth-the ignition system characteristics, the mixture composition, and the nature of the flow field. Efforts are concentrated on the effects of moderate to intense turbulence on flames within the distributed reaction zone. Results are presented for lean conditions with the fuel equivalence ratio varying from 0.6 to 0.9. The present computational results, including flame regime analysis and the calculation of various flame speeds, provide excellent agreement with results obtained by other experimental and numerical researchers.

  13. Meteorological and operational aspects of 46 clear air turbulence sampling missions with an instrument B-57B aircraft. Volume 1: Program summary

    NASA Technical Reports Server (NTRS)

    Davis, R. E.; Champine, R. A.; Ehernberger, L. J.

    1979-01-01

    The results of 46 clear air turbulence (CAT) probing missions conducted with an extensively instrumented B-57B aircraft are summarized. Turbulence samples were obtained under diverse conditions including mountain waves, jet streams, upper level fronts and troughs, and low altitude mechanical and thermal turbulence. CAT was encouraged on 20 flights comprising 77 data runs. In all, approximately 4335 km were flown in light turbulence, 1415 km in moderate turbulence, and 255 km in severe turbulence during the program. The flight planning, operations, and turbulence forecasting aspects conducted with the B-57B aircraft are presented.

  14. Spatiotemporal detection of Kelvin waves in quantum turbulence simulations

    NASA Astrophysics Data System (ADS)

    Clark di Leoni, P.; Mininni, P. D.; Brachet, M. E.

    2015-12-01

    We present evidence of Kelvin excitations in space-time resolved spectra of numerical simulations of quantum turbulence. Kelvin waves are transverse and circularly polarized waves that propagate along quantized vortices, for which the restitutive force is the tension of the vortex line, and which play an important role in theories of superfluid turbulence. We use the Gross-Pitaevskii equation to model quantum flows, letting an initial array of well-organized vortices develop into a turbulent bundle of intertwined vortex filaments. By achieving high spatial and temporal resolution we are able to calculate space-time resolved mass density and kinetic energy spectra. Evidence of Kelvin and sound waves is clear in both spectra. Identification of the waves allows us to extract the spatial spectrum of Kelvin waves, clarifying their role in the transfer of energy.

  15. Extreme air-sea surface turbulent fluxes in mid latitudes - estimation, origins and mechanisms

    NASA Astrophysics Data System (ADS)

    Gulev, Sergey; Natalia, Tilinina

    2014-05-01

    Extreme turbulent heat fluxes in the North Atlantic and North Pacific mid latitudes were estimated from the modern era and first generation reanalyses (NCEP-DOE, ERA-Interim, MERRA NCEP-CFSR, JRA-25) for the period from 1979 onwards. We used direct surface turbulent flux output as well as reanalysis state variables from which fluxes have been computed using COARE-3 bulk algorithm. For estimation of extreme flux values we analyzed surface flux probability density distribution which was approximated by Modified Fisher-Tippett distribution. In all reanalyses extreme turbulent heat fluxes amount to 1500-2000 W/m2 (for the 99th percentile) and can exceed 2000 W/m2 for higher percentiles in the western boundary current extension (WBCE) regions. Different reanalyses show significantly different shape of MFT distribution, implying considerable differences in the estimates of extreme fluxes. The highest extreme turbulent latent heat fluxes are diagnosed in NCEP-DOE, ERA-Interim and NCEP-CFSR reanalyses with the smallest being in MERRA. These differences may not necessarily reflect the differences in mean values. Analysis shows that differences in statistical properties of the state variables are the major source of differences in the shape of PDF of fluxes and in the estimates of extreme fluxes while the contribution of computational schemes used in different reanalyses is minor. The strongest differences in the characteristics of probability distributions of surface fluxes and extreme surface flux values between different reanalyses are found in the WBCE extension regions and high latitudes. In the next instance we analyzed the mechanisms responsible for forming surface turbulent fluxes and their potential role in changes of midlatitudinal heat balance. Midlatitudinal cyclones were considered as the major mechanism responsible for extreme turbulent fluxes which are typically occur during the cold air outbreaks in the rear parts of cyclones when atmospheric conditions

  16. Turbulent transport across an interface between dry and humid air in a stratified environment

    NASA Astrophysics Data System (ADS)

    Gallana, Luca; de Santi, Francesca; di Savino, Silvio; Iovieno, Michele; Ricchiardone, Renzo; Tordella, Daniela

    2014-11-01

    The transport of energy and water vapor across a thin layer which separates two decaying isotropic turbulent flows with different kinetic energy and humidity is considered. The interface is placed in a shearless stratified environment in temporal decay. This system reproduces a few aspects of small scale turbulent transport across a dry air/moist air interface in an atmospheric like context. In our incompressible DNS at Reλ = 250 , Boussinesq's approximation is used for momentum and energy transport while the vapor is modeled as a passive scalar (Kumar, Schumacher & Shaw 2014). We investigated different stratification levels with an initial Fr between 0.8 and 8 in presence of a kinetic energy ratio equal to 7. As the buoyancy term becomes of the same order of the inertial ones, a spatial redistribution of kinetic energy, dissipation and vapor concentration is observed. This eventually leads to the onset of a well of kinetic energy in the low energy side of the mixing layer which blocks the entrainment of dry air. Results are discussed and compared with laboratory and numerical experiments. A posteriori estimates of the eventual compression/expansion of fluid particles inside the interfacial mixing layer are given (Nance & Durran 1994).

  17. Optical detection of radon decay in air

    PubMed Central

    Sand, Johan; Ihantola, Sakari; Peräjärvi, Kari; Toivonen, Harri; Toivonen, Juha

    2016-01-01

    An optical radon detection method is presented. Radon decay is directly measured by observing the secondary radiolumines cence light that alpha particles excite in air, and the selectivity of coincident photon detection is further enhanced with online pulse-shape analysis. The sensitivity of a demonstration device was 6.5 cps/Bq/l and the minimum detectable concentration was 12 Bq/m3 with a 1 h integration time. The presented technique paves the way for optical approaches in rapid radon detec tion, and it can be applied beyond radon to the analysis of any alpha-active sample which can be placed in the measurement chamber. PMID:26867800

  18. Optical detection of radon decay in air.

    PubMed

    Sand, Johan; Ihantola, Sakari; Peräjärvi, Kari; Toivonen, Harri; Toivonen, Juha

    2016-02-12

    An optical radon detection method is presented. Radon decay is directly measured by observing the secondary radiolumines cence light that alpha particles excite in air, and the selectivity of coincident photon detection is further enhanced with online pulse-shape analysis. The sensitivity of a demonstration device was 6.5 cps/Bq/l and the minimum detectable concentration was 12 Bq/m(3) with a 1 h integration time. The presented technique paves the way for optical approaches in rapid radon detec tion, and it can be applied beyond radon to the analysis of any alpha-active sample which can be placed in the measurement chamber.

  19. NBC detection in air and water

    NASA Technical Reports Server (NTRS)

    Hartley, Frank T.; Smith, Steven J.; McMurtry, Gary M.

    2003-01-01

    Participating in a Navy STTR project to develop a system capable of the 'real-time' detection and quanitification of nuclear, biological and chemical (NBC) warfare agents, and of related industrial chemicals including NBC agent synthesis by-products in water and in air immediately above the water's surface. This project uses JPL's Soft Ionization Membrane (SIM) technology which totally ionizes molecules without fragmentation (a process that can markedly improve the sensitivity and specificity of molecule compostition identification), and JPL's Rotating Field Mass Spectrometer (RFMS) technology which has large enough dynamic mass range to enable detection of nuclear materials as well as biological and chemical agents. This Navy project integrates these JPL Environmental Monitoring UnitS (REMUS) an autonomous underwater vehicle (AUV). It is anticipated that the REMUS AUV will be capable of 'real-time' detection and quantification of NBC warefare agents.

  20. A turbulence-driven air fumigation facility for studying air pollution effects on vegetation

    SciTech Connect

    Lipfert, F.; Lewin, K.; Hendrey, G.; Nagy, J. ); Alexander, Y. . Applied Mathematics Dept.)

    1990-10-01

    Studying the effects of atmospheric perturbations on plant growth has usually involved compromises between realism and convenience. Isolating the effects of specific parameters, such as air pollution, elevated CO{sub 2} concentration, or water stress, requires a manipulated rather than a completely natural environment. Attempts to develop large free-air controlled exposure systems date back several years, primarily for experimental exposures to elevated levels of air pollutants such as SO{sub 2} or ozone. These early systems suffered from two types of problems: imprecise control of the exposure gas concentrations; substantial spatial variability within the exposed plots. The Free-Air CO{sub 2} Enrichment (FACE) open-air fumigation system, developed at Brookhaven National Laboratory (BNL), has addressed both of these problem areas. This system differs from other free-air exposure systems in that the injection gas is pre-diluted in ambient air to an average 3--4% by volume, and the injection gas mass flow is adjusted each second by the micoprocessor-driven controller. This document discusses the design and performance of this facility. 3 refs., 4 figs., 1 tab.

  1. Air Shower Detection by Bistatic Radar

    NASA Astrophysics Data System (ADS)

    Othman, M. Abou Bakr; Allen, C.; Belz, J.; Besson, D.; Farhang-Boroujeny, B.; Ikeda, D.; Kunwar, S.; Lundquist, J. P.; Kravchenko, I.; Myers, I.; Nakamura, T.; Sagawa, H.; Sokolsky, P.; Takai, H.; Terasawa, T.; Thomson, G. B.

    2011-09-01

    Progress in the field of high-energy cosmic rays is currently limited by the rarity of the most interesting rays striking the Earth. Indeed, the continuation of the field beyond the current generation of observatories may become financially and practically impossible if new ways are not found to achieve remote coverage over large portions of the Earth's surface. We describe the development of an observatory based on such a new technique: the remote sensing via bistatic radar technology of cosmic ray induced extensive air showers. We build on pilot studies performed by MARIACHI which have demonstrated that air shower radar echoes are detectable, the opportunity afforded by the location of the Northern Hemisphere's largest ``conventional'' cosmic ray observatory (The Telescope Array) in radio-quiet western Utah, and the donation of analog television transmission equipment to this effort by a local television station.

  2. Identification of vortex-induced clear-air turbulence using airline flight records

    NASA Technical Reports Server (NTRS)

    Parks, E. K.; Wingrove, R. C.; Bach, R. E.; Mehta, R. S.

    1984-01-01

    The nature and cause of clear-air turbulence is being investigated, in cooperation with the National Transportation Safety Board, using the flight records available from airline encounters with severe turbulence. This paper presents two case studies of severe turbulence which indicate that the airplanes involved encountered vortex arrays which were generated by destabilized wind-shear layers near the tropopause. In order to identify and analyze vortex patterns (i.e., vortex strength, size, and spacings), potential-flow models of vortex arrays were developed that describe reasonably well the wind patterns derived from the airliner flight records. The results of this analysis indicate that in the two cases studied, the vortex cores had diameters in the range of 900 to 1,200 ft with tangential velocities in the range of 70 to 85 ft/sec. This study presents the first identification and analysis of vortex arrays from airline flight data. The results are compared with theoretical predictions and previous observations.

  3. Mode S and ADS-B as a Source of Clear-Air Turbulence Measurements

    NASA Astrophysics Data System (ADS)

    Kopeć, Jacek; Kwiatkowski, Kamil; de Haan, Siebren; Malinowski, Szymon

    2016-04-01

    Clear-Air Turbulence (CAT) beside being the most common cause for commercial aircraft incidents in the cruise phase is a complex physical phenomenon. CAT is an effect of various underlying physical mechanisms such as different kinds of hydrodynamic instabilities or large scale forcing. In order to properly understand and correctly forecast it one needs a significant amount of observation data. Up to date the best available observations are the in-situ EDR (from eddy dissipation rate - a measure of turbulence intensity). Those observations are reported every ~1 min of flight (roughly every 15 km). Yet their availability is limited by the willingness of the airlines to cooperate in adjusting on-board software. However there is a class of data that can be accessed more freely. In this communication we present and discuss a feasibility analysis of the three methods of processing Mode S/ADS-B messages into viable turbulence measurements. The Mode S/ADS-B messages are unrestricted navigational data broadcast by most of the commercial aircraft. The unique characteristic of this data is a very high temporal resolution. This allows to employ processing which results in obtaining turbulence information characterized by spatial resolution comparable with the best available data sources. Moreover due to using Mode-S/ASS-B data, the number of aircraft that are providing observations increases significantly. The methods are either using simple positioning information available in the ADS-B or high-resolution wind information from the Mode S. The paper is largely based on the results of the methods application to the data originating from DELICAT flight campaign that took place in 2013. The flight campaign was conducted using NLR operated Cessna Citation II. The reference Mode-S/ADS-B data partly overlapping with the research flights were supplied by the KNMI. Analysis shows very significant potential of the Mode-S wind based methods. J. M. Kopeć, K. Kwiatkowski, S. de Haan, and

  4. Chemiluminescent detection of organic air pollutants

    SciTech Connect

    Marley, N.A.; Gaffney, J.S.; Chen, Yu-Harn

    1996-04-01

    Chemiluminescent reactions can be used for specific and highly sensitive detection of a number of air pollutants. Among these are chemiluminescent reactions of ozone with NO or organics and reactions of luminol with a variety of oxidants. Reported here are studies exploring (1) the use of the temperature dependence of the chemiluminescent reactions of ozone with organic pollutants as a means of differentiating types of hydrocarbon classes and (2) the use of luminol techniques to monitor atmospheric concentrations of nitrogen dioxide (NO{sub 2}) and organic oxidants, specifically peroxyacyl nitrates (PANs). Coupling gas chromatography to the chemiluminescent detectors allows the measurement of individual species at very low concentrations.

  5. Velocity measurements within a shock and reshock induced air/SF6 turbulent mixing zone

    NASA Astrophysics Data System (ADS)

    Haas, Jean-Francois; Bouzgarrou, Ghazi; Bury, Yannick; Jamme, Stephane; Joly, Laurent; Shock-induced mixing Team

    2012-11-01

    A turbulent mixing zone (TMZ) is created in a shock tube (based in ISAE, DAEP) when a Mach 1.2 shock wave in air accelerates impulsively to 70 m/s an air/SF6 interface. The gases are initially separated by a 1 μm thick plastic microfilm maintained flat and parallel to the shock by two wire grids. The upper grid of square spacing 1.8 mm imposes the nonlinear initial perturbation for the Richtmyer-Meshkov instability (RMI). After interaction with a reshock and a rarefaction, the TMZ remains approximately stagnant but much more turbulent. High speed Schlieren visualizations enable the choice of abscissae for Laser Doppler Velocity (LDV) measurements. For a length of the SF6 section equal to 250 mm, the LDV abscissae are 43, 135 and 150 mm from the initial position of the interface. Because of numerous microfilm fragments in the flow and a limited number of olive oil droplets as seeding particles for the LDV, statistical convergence requires the superposition of a least 50 identical runs at each abscissa. The dependence of TMZ structure and velocity field on length of the SF6 section between 100 and 300 mm will be presented. This experimental investigation is carried out in support of modeling and multidimensional simulation efforts at CEA, DAM, DIF. Financial support from CEA is thanksfully appreciated by ISAE.

  6. 2-D Numerical Simulation of Eruption Clouds : Effects of Turbulent Mixing between Eruption Cloud and Air

    NASA Astrophysics Data System (ADS)

    Suzuki, Y.; KOYAGUCHI, T.; OGAWA, M.; Hachisu, I.

    2001-05-01

    Mixing of eruption cloud and air is one of the most important processes for eruption cloud dynamics. The critical condition of eruption types (eruption column or pyroclastic flow) depends on efficiency of mixing of eruption cloud and the ambient air. However, in most of the previous models (e.g., Sparks,1986; Woods, 1988), the rate of mixing between cloud and air is taken into account by introducing empirical parameters such as entrainment coefficient or turbulent diffusion coefficient. We developed a numerical model of 2-D (axisymmetrical) eruption columns in order to simulate the turbulent mixing between eruption column and air. We calculated the motion of an eruption column from a circular vent on the flat surface of the earth. Supposing that relative velocity of gas and ash particles is sufficiently small, we can treat eruption cloud as a single gas. Equation of state (EOS) for the mixture of the magmatic component (i.e. volcanic gas plus pyroclasts) and air can be expressed by EOS for an ideal gas, because volume fraction of the gas phase is very large. The density change as a function of mixing ratio between air and the magmatic component has a strong non-linear feature, because the density of the mixture drastically decreases as entrained air expands by heating. This non-linear feature can be reproduced by changing the gas constant and the ratio of specific heat in EOS for ideal gases; the molecular weight increases and the ratio of specific heat approaches 1 as the magmatic component increases. It is assumed that the dynamics of eruption column follows the Euler equation, so that no viscous effect except for the numerical viscosity is taken into account. Roe scheme (a general TVD scheme for compressible flow) is used in order to simulate the generation of shock waves inside and around the eruption column. The results show that many vortexes are generated around the boundary between eruption cloud and air, which results in violent mixing. When the size of

  7. TECNAIRE winter field campaign: turbulent characteristics and their influence on air quality conditions

    NASA Astrophysics Data System (ADS)

    Yagüe, Carlos; Román Cascón, Carlos; Maqueda, Gregorio; Sastre, Mariano; Arrillaga, Jon A.; Artíñano, Begoña; Diaz-Ramiro, Elías; Gómez-Moreno, Francisco J.; Borge, Rafael; Narros, Adolfo; Pérez, Javier

    2016-04-01

    An urban field campaign was conducted at an air pollution hot spot in Madrid city (Spain) during winter 2015 (from 16th February to 2nd March). The zone selected for the study is a square (Plaza Fernández Ladreda) located in the southern part of the city. This area is an important intersection of several principal routes, and therefore a significant impact in the air quality of the area is found due to the high traffic density. Meteorological data (wind speed and direction, air temperature, relative humidity, pressure, precipitation and global solar radiation) were daily recorded as well as micrometeorological measurements obtained from two sonic anemometers. To characterize this urban atmospheric boundary layer (uABL), micrometeorological parameters (turbulent kinetic energy -TKE-, friction velocity -u∗- and sensible heat flux -H-) are calculated, considering 5-minute average for variance and covariance evaluations. Furthermore, synoptic atmospheric features were analyzed. As a whole, a predominant influence of high pressure systems was found over the Atlantic Ocean and western Spain, affecting Madrid, but during a couple of days (17th and 21st February) some atmospheric instability played a role. The influence of the synoptic situation and specially the evolution of the micrometeorological conditions along the day on air quality characteristics (Particulate Matter concentrations: PM10, PM2.5 and PM1, and NOx concentrations) are analyzed and shown in detail. This work has been financed by Madrid Regional Research Plan through TECNAIRE (P2013/MAE-2972).

  8. A Methodology for Determining Statistical Performance Compliance for Airborne Doppler Radar with Forward-Looking Turbulence Detection Capability. Second Corrected Copy Issued May 23, 2011

    NASA Technical Reports Server (NTRS)

    Bowles, Roland L.; Buck, Bill K.

    2009-01-01

    The objective of the research developed and presented in this document was to statistically assess turbulence hazard detection performance employing airborne pulse Doppler radar systems. The FAA certification methodology for forward looking airborne turbulence radars will require estimating the probabilities of missed and false hazard indications under operational conditions. Analytical approaches must be used due to the near impossibility of obtaining sufficient statistics experimentally. This report describes an end-to-end analytical technique for estimating these probabilities for Enhanced Turbulence (E-Turb) Radar systems under noise-limited conditions, for a variety of aircraft types, as defined in FAA TSO-C134. This technique provides for one means, but not the only means, by which an applicant can demonstrate compliance to the FAA directed ATDS Working Group performance requirements. Turbulence hazard algorithms were developed that derived predictive estimates of aircraft hazards from basic radar observables. These algorithms were designed to prevent false turbulence indications while accurately predicting areas of elevated turbulence risks to aircraft, passengers, and crew; and were successfully flight tested on a NASA B757-200 and a Delta Air Lines B737-800. Application of this defined methodology for calculating the probability of missed and false hazard indications taking into account the effect of the various algorithms used, is demonstrated for representative transport aircraft and radar performance characteristics.

  9. Numerical study of turbulence-influence mechanism on arc characteristics in an air direct current circuit breaker

    NASA Astrophysics Data System (ADS)

    Wu, Mingliang; Yang, Fei; Rong, Mingzhe; Wu, Yi; Qi, Yang; Cui, Yufei; Liu, Zirui; Guo, Anxiang

    2016-04-01

    This paper focuses on the numerical investigation of arc characteristics in an air direct current circuit breaker (air DCCB). Using magneto-hydrodynamics (MHD) theory, 3D laminar model and turbulence model are constructed and calculated. The standard k-epsilon model is utilized to consider the turbulence effect in the arc chamber of the DCCB. Several important phenomena are found: the arc column in the turbulence-model case is more extensive, moves much more slowly than the counterpart in the laminar-model case, and shows stagnation at the entrance of the chamber, unlike in the laminar-model case. Moreover, the arc voltage in the turbulence-model case is much lower than in the laminar-model case. However, the results in the turbulence-model case show a much better agreement with the results of the breaking experiments under DC condition than in the laminar-model case, which is contradictory to the previous conclusions from the arc researches of both the low-voltage circuit breaker and the sulfur hexafluoride (SF6) nozzle. First, in the previous air-arc research of the low-voltage circuit breaker, it is assumed that the air plasma inside the chamber is in the state of laminar, and the laminar-model application gives quite satisfactory results compared with the experiments, while in this paper, the laminar-model application works badly. Second, the turbulence-model application in the arc research of the SF6-nozzle performs much better and gives higher arc voltage than the laminar-model application does, whereas in this paper, the turbulence-model application predicts lower arc voltage than the laminar-model application does. Based on the analysis of simulation results in detail, the mechanism of the above phenomena is revealed. The transport coefficients are strongly changed by turbulence, which will enhance the arc diffusion and make the arc volume much larger. Consequently, the arc appearance and the distribution of Lorentz force in the turbulence-model case

  10. Turbulence at the Air-Water Interface in Lakes of Different Sizes: Consequences for Gas Transfer Coefficients

    NASA Astrophysics Data System (ADS)

    MacIntyre, S.; Crowe, A. T.; Amaral, J. H.; Arneborg, L.; Bastviken, D.; Forsberg, B. R.; Melack, J. M.; Tota, J.; Tedford, E. W.; Karlsson, J.; Podgrajsek, E.; Andersson, A.; Rutgersson, A.

    2014-12-01

    Similarity scaling predicts that wind induced shear will be the dominant source of turbulence near the air-water interface in lakes with low to moderate wind forcing. Turbulence is expected to be enhanced with wave activity; results are conflicting on the effects of heating and cooling. We measured turbulence with an acoustic Doppler velocimeter (ADV) and / or a temperature-gradient microstructure profiler and obtained correlative time series measurements of meteorology and water column temperature in a 800 m2 arctic pond, a 1 ha boreal lake, and a large tropical reservoir. Turbulence measurements with both instruments corroborated those calculated from similarity scaling in the boreal lake. Within the arctic pond, dissipation rates obtained with the ADV were in agreement with those from similarity scaling when winds exceeded ~1.5 m/s with a greater frequency of measurable dissipation rates when surface waves were present. Dissipation rates in the tropical reservoir reached and often exceeded 10-6 m2 s-3 in the upper meter under light winds and decreased by an order of magnitude with cooling or rainfall. Under cooling, dissipation rates were at least an order of magnitude higher in the uppermost 25 cm bin than in the water column below. Gas transfer coefficients calculated from concurrent measurements of greenhouse gas fluxes with floating chambers and the surface renewal model using the estimates of turbulence were in agreement. These results support the predictions of Monin-Obuhov similarity scaling in that shear dominates turbulence production near the air-water interface under heating and cooling, illustrate spatial variability in turbulence production in small water bodies due to the intermittency of wind interacting with the water's surface, are in agreement with prior oceanic observations that shear and associated turbulence can be intensified in shallow mixing layers under heating with light winds, and illustrate the utility of similarity scaling for

  11. Soot formation in turbulent nonpremixed kerosine-air flames burning at elevated pressure: Experimental measurement

    SciTech Connect

    Young, K.J.; Stewart, C.D.; Moss, J.B.

    1994-12-31

    Detailed scalar property maps have been constructed for turbulent jet flames of prevaporized kerosine, burning in a coflowing air stream and confined within an optically accessed cylindrical chamber, which permits operation at elevated pressure. Time-averaged measurements of spatially resolved soot volume fraction by path-integrated laser absorption and tomographic inversion, temperature by fine wire thermocouple, and mixture fraction by microprobe sampling and mass spectrometric analysis are reported at chamber pressures from 1 to 6.4 bar. While the principal objective of the study has been to develop a database for modelling and computational prediction, the centerline data admit presentation in a standardized form, based on the centerline flame length to the maximum soot concentration, which permits analysis of the pressure dependence from turbulent flames of differing sizes. In this form, the peak soot volume fractions and soot formation rates appear linearly dependent on pressure, exhibiting a peak mass fraction of soot carbon of 7%, substantially independent of pressure. The peak soot loading, at the highest pressure investigated, approaches 120 gm{sup {minus}3} before complete laser extinction renders the flame inaccessible to further measurement. The high carbon loading and enhanced radiative loss lead to reduced mean temperatures throughout the flame by comparison with more widely studied gaseous fuels such as ethylene. Measured temperatures do not exceed 1,438 K anywhere on the centerline of the flame at 1 bar, for example.

  12. Turbulent Transfer Coefficients and Calculation of Air Temperature inside Tall Grass Canopies in Land Atmosphere Schemes for Environmental Modeling.

    NASA Astrophysics Data System (ADS)

    Mihailovic, D. T.; Alapaty, K.; Lalic, B.; Arsenic, I.; Rajkovic, B.; Malinovic, S.

    2004-10-01

    A method for estimating profiles of turbulent transfer coefficients inside a vegetation canopy and their use in calculating the air temperature inside tall grass canopies in land surface schemes for environmental modeling is presented. The proposed method, based on K theory, is assessed using data measured in a maize canopy. The air temperature inside the canopy is determined diagnostically by a method based on detailed consideration of 1) calculations of turbulent fluxes, 2) the shape of the wind and turbulent transfer coefficient profiles, and 3) calculation of the aerodynamic resistances inside tall grass canopies. An expression for calculating the turbulent transfer coefficient inside sparse tall grass canopies is also suggested, including modification of the corresponding equation for the wind profile inside the canopy. The proposed calculations of K-theory parameters are tested using the Land Air Parameterization Scheme (LAPS). Model outputs of air temperature inside the canopy for 8 17 July 2002 are compared with micrometeorological measurements inside a sunflower field at the Rimski Sancevi experimental site (Serbia). To demonstrate how changes in the specification of canopy density affect the simulation of air temperature inside tall grass canopies and, thus, alter the growth of PBL height, numerical experiments are performed with LAPS coupled with a one-dimensional PBL model over a sunflower field. To examine how the turbulent transfer coefficient inside tall grass canopies over a large domain represents the influence of the underlying surface on the air layer above, sensitivity tests are performed using a coupled system consisting of the NCEP Nonhydrostatic Mesoscale Model and LAPS.


  13. Detecting and tracking moving objects in long-distance imaging through turbulent medium.

    PubMed

    Chen, Eli; Haik, Oren; Yitzhaky, Yitzhak

    2014-02-20

    The challenge of detecting and tracking moving objects in imaging throughout the atmosphere stems from the atmospheric turbulence effects that cause time-varying image shifts and blur. These phenomena significantly increase the miss and false detection rates in long-range horizontal imaging. An efficient method was developed, which is based on novel criteria for objects' spatio-temporal properties, to discriminate true from false detections, following an adaptive thresholding procedure for foreground detection and an activity-based false alarm likeliness masking. The method is demonstrated on significantly distorted videos and compared with state of the art methods, and shows better false alarm and miss detection rates. PMID:24663319

  14. Standoff alpha radiation detection via excited state absorption of air

    SciTech Connect

    Yao, Jimmy; Yin, Stuart Shizhuo; Brenizer, Jack; Hui, Rongqing

    2013-06-24

    A standoff alpha radiation detection technique based on the physical mechanism of excited state absorption of air molecules was explored and is presented in this paper. Instead of directly detecting the radiation via measuring the intensity of radiation induced air fluorescence, the radiation is detected via the excited state absorption of alpha radiation excited/ionized air molecules. Both theoretical analyses and experimental verifications were conducted. The experimental results confirmed that the radiation could be detected via excited state absorption of radiation excited/ionized air molecules at a 10 m standoff distance, which was consistent with the theoretical analyses.

  15. Computational fluid dynamics for modeling the turbulent natural convection in a double air-channel solar chimney system

    NASA Astrophysics Data System (ADS)

    Zavala-Guillén, I.; Xamán, J.; Álvarez, G.; Arce, J.; Hernández-Pérez, I.; Gijón-Rivera, M.

    2016-03-01

    This study reports the modeling of the turbulent natural convection in a double air-channel solar chimney (SC-DC) and its comparison with a single air-channel solar chimney (SC-C). Prediction of the mass flow and the thermal behavior of the SC-DC were obtained under three different climates of Mexico during one summer day. The climates correspond to: tropical savannah (Mérida), arid desert (Hermosillo) and temperate with warm summer (Mexico City). A code based on the Finite Volume Method was developed and a k-ω turbulence model has been used to model air turbulence in the solar chimney (SC). The code was validated against experimental data. The results indicate that during the day the SC-DC extracts about 50% more mass flow than the SC-C. When the SC-DC is located in Mérida, Hermosillo and Mexico City, the air-changes extracted along the day were 60, 63 and 52, respectively. The air temperature at the outlet of the chimney increased up to 33%, 38% and 61% with respect to the temperature it has at the inlet for Mérida, Hermosillo and Mexico City, respectively.

  16. Detection of turbulent coherent motions in a forest canopy part II: Time-scales and conditional averages

    NASA Astrophysics Data System (ADS)

    Collineau, Serge; Brunet, Yves

    1993-10-01

    Turbulent exchanges between plant canopies and the atmosphere are known to be strongly affected by intermittent coherent motions, which appear on time traces of turbulent variables as periodic, large-amplitude excursions from the mean. Detecting these features requires objective and powerful signal analysis techniques. We investigate here the possibilities offered by the recently developed wavelet transform, presented in a companion paper. For this purpose, a set of data acquired in a 13.5 m high pine forest in southwestern France was used, which provided time series of wind velocities and air temperature recorded at two levels simultaneously, under moderately unstable conditions. Firstly, a duration scale of the active part of coherent motions was estimated from the wavelet variance. Then, we focused on the detection itself of large-scale features; several wavelet functions were tested, and the results compared with those obtained from more classical conditional sampling methods such as VITA and WAG. A mean time interval Δ=1.8 h/u * ( h being the canopy height and u * the friction velocity) between contiguous coherent motions was obtained. The features extracted from the various traces and ensemble-averaged over 30 min periods appeared very similar throughout the four hours of data studied. They provided a dynamic description of the ejection-sweep process, readily observable at both levels. An alternate Reynolds decomposition of the instantaneous turbulent fields, using the conditionally averaged signals, allowed the relative importance of large- and small-scale contributions to momentum and heat fluxes to be estimated. The results were found to be in good agreement with comparable studies.

  17. Turbulent burning velocities of premixed CH{sub 4}/diluent/air flames in intense isotropic turbulence with consideration of radiation losses

    SciTech Connect

    Shy, S.S.; Yang, S.I.; Lin, W.J.; Su, R.C.

    2005-10-01

    This paper presents turbulent burning velocities, S{sub T}, of several premixed CH{sub 4}/diluent/air flames at the same laminar burning velocity S{sub L}=0.1 m/s for two equivalence ratios f=0.7 and 1.4 near flammability limits with consideration of radiation heat losses from small (N{sub 2} diluted) to large (CO{sub 2} diluted). Experiments are carried out in a cruciform burner, in which the long vertical vessel is used to provide a downward propagating premixed flame and the large horizontal vessel equipped with a pair of counterrotating fans and perforated plates can be used to generate an intense isotropic turbulence in the central region between the two perforated plates. Turbulent flame speeds are measured by four different arrangements of pairs of ion-probe sensors at different positions from the top to the bottom of the central region in the burner. It is found that the effect of gas velocity on S{sub T} measured in the central region can be neglected. Simultaneous measurements using the pressure transducer and ion-probe sensors show that the pressure rise due to turbulent burning has little influence on S{sub T}. These measurements prove the accuracy of the S{sub T} data. At f=0.7, the percentage of [(S{sub T}/S{sub L}){sub CO{sub 2}}-(S{sub T}/S{sub L}){sub N{sub 2}}]/(S{sub T}/S{sub L}){sub N{sub 2}} decreases gradually from -4 to -17% when values of u{sup '}/S{sub L} increase from 4 to 46, while at f=1.4 such decrease is much more abrupt from -19 to -53% when values of u{sup '}/S{sub L} only increase from 4 to 18. The larger the radiation losses, the smaller the values of S{sub T}. This decreasing effect is augmented by increasing u{sup '}/S{sub L} and is particularly pronounced for rich CH{sub 4} flames. When u{sup '}/S{sub L}=18, lean CO{sub 2} and/or N{sub 2}-diluted CH{sub 4} flames have much higher, 3.6 and/or 1.8 times higher, values of S{sub T}/S{sub L} than rich CO{sub 2} and/or N{sub 2}-diluted CH{sub 4} flames, respectively. It is found that

  18. Influence of turbulent flow on the explosion parameters of micro- and nano-aluminum powder-air mixtures.

    PubMed

    Liu, Xueling; Zhang, Qi

    2015-12-15

    The environmental turbulence intensity has a significant influence on the explosion parameters of both micro- and nano-Al at the time of ignition. However, explosion research on turbulence intensity with respect to micro- and nano-Al powders is still insufficient. In this work, micro- and nano-aluminum powders were investigated via scanning electron microscopy (SEM), and their particle size distributions were measured using a laser diffraction analyzer under dispersing air pressures of 0.4, 0.6, and 0.8 MPa in a 20 L cylindrical, strong plexiglass vessel. The particle size distributions in three different mass ratio mixtures of micro- and nano-Al powders (micro-Al:nano-Al[massratio]=95:5, 90:10, and 85:15) were also measured. The results show that the agglomerate size of nano-Al powder is an order of magnitude larger than the nanoparticles' actual size. Furthermore, the turbulence intensity ranges (Urms) of the Al powder-air mixtures were measured using particle image velocimetry (PIV) under dispersing air pressures of 0.4, 0.6, and 0.8 MPa. The effect of turbulence intensity on the explosion characteristics of the micro- and nano-Al powders was investigated using a 20 L cylindrical explosion vessel. The results of micro-Al and nano-Al powder-air mixtures with a stoichiometric concentration of 337.00 g·m(-3) were discussed for the maximum explosion pressure, the maximum rate of pressure increase and the maximum effective burning velocity under the different turbulence intensity. PMID:26276701

  19. Influence of turbulent flow on the explosion parameters of micro- and nano-aluminum powder-air mixtures.

    PubMed

    Liu, Xueling; Zhang, Qi

    2015-12-15

    The environmental turbulence intensity has a significant influence on the explosion parameters of both micro- and nano-Al at the time of ignition. However, explosion research on turbulence intensity with respect to micro- and nano-Al powders is still insufficient. In this work, micro- and nano-aluminum powders were investigated via scanning electron microscopy (SEM), and their particle size distributions were measured using a laser diffraction analyzer under dispersing air pressures of 0.4, 0.6, and 0.8 MPa in a 20 L cylindrical, strong plexiglass vessel. The particle size distributions in three different mass ratio mixtures of micro- and nano-Al powders (micro-Al:nano-Al[massratio]=95:5, 90:10, and 85:15) were also measured. The results show that the agglomerate size of nano-Al powder is an order of magnitude larger than the nanoparticles' actual size. Furthermore, the turbulence intensity ranges (Urms) of the Al powder-air mixtures were measured using particle image velocimetry (PIV) under dispersing air pressures of 0.4, 0.6, and 0.8 MPa. The effect of turbulence intensity on the explosion characteristics of the micro- and nano-Al powders was investigated using a 20 L cylindrical explosion vessel. The results of micro-Al and nano-Al powder-air mixtures with a stoichiometric concentration of 337.00 g·m(-3) were discussed for the maximum explosion pressure, the maximum rate of pressure increase and the maximum effective burning velocity under the different turbulence intensity.

  20. Experimental assessment of spanwise-oscillating dielectric electroactive surfaces for turbulent drag reduction in an air channel flow

    NASA Astrophysics Data System (ADS)

    Gatti, Davide; Güttler, Andreas; Frohnapfel, Bettina; Tropea, Cameron

    2015-05-01

    In the present work, wall oscillations for turbulent skin friction drag reduction are realized in an air turbulent duct flow by means of spanwise-oscillating active surfaces based on dielectric electroactive polymers. The actuator system produces spanwise wall velocity oscillations of 820 mm/s semi-amplitude at its resonance frequency of 65 Hz while consuming an active power of a few 100 mW. The actuators achieved a maximum integral drag reduction of 2.4 %. The maximum net power saving, budget of the power benefit and cost of the control, was measured for the first time with wall oscillations. Though negative, the net power saving is order of magnitudes higher than what has been estimated in previous studies. Two new direct numerical simulations of turbulent channel flow show that the finite size of the actuator only partially explains the lower values of integral drag reduction typically achieved in laboratory experiments compared to numerical simulations.

  1. OAFlux Satellite-Based High-Resolution Analysis of Air-Sea Turbulent Heat, Moisture, and Momentum Fluxes

    NASA Astrophysics Data System (ADS)

    Yu, Lisan

    2016-04-01

    The Objectively Analyzed air-sea Fluxes (OAFlux) project at the Woods Hole Oceanographic Institution has recently developed a new suite of products: the satellite-based high-resolution (HR) air-sea turbulent heat, moisture, and momentum fluxes over the global ocean from 1987 to the present. The OAFlux-HR fluxes are computed from the COARE bulk algorithm using air-sea variables (vector wind, near-surface humidity and temperature, and ocean surface temperature) derived from multiple satellite sensors and multiple missions. The vector wind time series are merged from 14 satellite sensors, including 4 scatterometers and 10 passive microwave radiometers. The near-surface humidity and temperature time series are retrieved from 11 satellite sensors, including 7 microwave imagers and 4 microwave sounders. The endeavor has greatly improved the depiction of the air-sea turbulent exchange on the frontal and meso-scales. The OAFlux-HR turbulent flux products are valuable datasets for a broad range of studies, including the study of the long-term change and variability in the oean-surface forcing functions, quantification of the large-scale budgets of mass, heat, and freshwater, and assessing the role of the ocean in the change and variability of the Earth's climate.

  2. Will Climate Change Increase Transatlantic Aviation Turbulence?

    NASA Astrophysics Data System (ADS)

    Williams, P. D.; Joshi, M. M.

    2013-12-01

    Atmospheric turbulence causes most weather-related aircraft incidents. Commercial aircraft encounter moderate-or-greater turbulence tens of thousands of times each year world-wide, injuring probably hundreds of passengers (occasionally fatally), costing airlines tens of millions of dollars, and causing structural damage to planes. Clear-air turbulence is especially difficult to avoid, because it cannot be seen by pilots or detected by satellites or on-board radar. Clear-air turbulence is linked to atmospheric storm tracks and jet streams, which are projected to be strengthened by anthropogenic climate change. However, the response of clear-air turbulence to climate change has not previously been studied. Here we show using computer simulations that clear-air turbulence changes significantly within the transatlantic flight corridor when the concentration of carbon dioxide in the atmosphere is doubled. At cruise altitudes within 50-75°N and 10-60°W in winter, most clear-air turbulence measures show a 10-40% increase in the median strength of turbulence and a 40-170% increase in the frequency of occurrence of moderate-or-greater turbulence. Our results suggest that climate change will lead to bumpier transatlantic flights by the middle of this century. Journey times may lengthen and fuel consumption and emissions may increase. Aviation is partly responsible for changing the climate, but our findings show for the first time how climate change could affect aviation.

  3. Will climate change increase transatlantic aviation turbulence?

    NASA Astrophysics Data System (ADS)

    Williams, Paul; Joshi, Manoj

    2013-04-01

    Atmospheric turbulence causes most weather-related aircraft incidents. Commercial aircraft encounter moderate-or-greater turbulence tens of thousands of times each year world-wide, injuring probably hundreds of passengers (occasionally fatally), costing airlines tens of millions of dollars, and causing structural damage to planes. Clear-air turbulence is especially difficult to avoid, because it cannot be seen by pilots or detected by satellites or on-board radar. Clear-air turbulence is linked to atmospheric jet streams, which are projected to be strengthened by anthropogenic climate change. However, the response of clear-air turbulence to climate change has not previously been studied. Here we show using computer simulations that clear-air turbulence changes significantly within the transatlantic flight corridor when the concentration of carbon dioxide in the atmosphere is doubled. At cruise altitudes within 50-75°N and 10-60°W in winter, most clear-air turbulence measures show a 10-40% increase in the median strength of turbulence and a 40-170% increase in the frequency of occurrence of moderate-or-greater turbulence. Our results suggest that climate change will lead to bumpier transatlantic flights by the middle of this century. Journey times may lengthen and fuel consumption and emissions may increase. Aviation is partly responsible for changing the climate, but our findings show for the first time how climate change could affect aviation.

  4. From pores to eddies - linking diffusion-based evaporative fluxes from porous surfaces with a turbulent air boundary layer

    NASA Astrophysics Data System (ADS)

    Haghighi, E.; Or, D.

    2012-04-01

    Evaporation affects hydration and energy balance of terrestrial surfaces. Evaporation rates exhibit complex dynamics reflecting interactions between external conditions and internal transport properties of a the drying porous surface Motivated by recent progress in estimating evaporative fluxes from isolated pores across laminar air sublayer, we seek to expand the description and quantify evaporation across a turbulent boundary layer. We adopt concepts from surface renewal (SR) theory focusing on turbulent exchange with individual eddies and linking eddies surface footprint and their local boundary layer over patches of a drying surface. The model resolves diffusive exchange during limited residence time and integrates fluxes over the entire surface to quantify mean evaporative fluxes from drying surfaces into turbulent airflows accounting for subsurface internal transport processes and diffusive exchanges. Input parameters and model evaluation would be based on data from spatially and temporally resolved Infrared (IR) thermography of drying surfaces under prescribe turbulent regimes conducted in a wind-tunnel experiment. The study provides basic ingredients and building blocks essential for upscaling the results to estimation of evaporative fluxes at the field and landscape scales. Keywords: Evaporation; Turbulent Coupling; Surface Renewal; Infrared Imaging.

  5. Summary of Turbulence Data Obtained During United Air Lines Flight Evaluation of an Experimental C Band (5.5 cm) Airborne Weather Radar

    NASA Technical Reports Server (NTRS)

    Coe, E. C.; Fetner, M. W.

    1954-01-01

    Data on atmospheric turbulence in the vicinity of thunderstorms obtained during a flight evaluation of an experimental C band (5.5 cm) airborne radar are summarized. The turbulence data were obtained with an NACA VGH recorder installed in a United Air Lines DC-3 airplane.

  6. Modeling 3D conjugate heat and mass transfer for turbulent air drying of Chilean papaya in a direct contact dryer

    NASA Astrophysics Data System (ADS)

    Lemus-Mondaca, Roberto A.; Vega-Gálvez, Antonio; Zambra, Carlos E.; Moraga, Nelson O.

    2016-03-01

    A 3D model considering heat and mass transfer for food dehydration inside a direct contact dryer is studied. The k- ɛ model is used to describe turbulent air flow. The samples thermophysical properties as density, specific heat, and thermal conductivity are assumed to vary non-linearly with temperature. FVM, SIMPLE algorithm based on a FORTRAN code are used. Results unsteady velocity, temperature, moisture, kinetic energy and dissipation rate for the air flow are presented, whilst temperature and moisture values for the food also are presented. The validation procedure includes a comparison with experimental and numerical temperature and moisture content results obtained from experimental data, reaching a deviation 7-10 %. In addition, this turbulent k- ɛ model provided a better understanding of the transport phenomenon inside the dryer and sample.

  7. Studying Galactic interstellar turbulence through fluctuations in synchrotron emission. First LOFAR Galactic foreground detection

    NASA Astrophysics Data System (ADS)

    Iacobelli, M.; Haverkorn, M.; Orrú, E.; Pizzo, R. F.; Anderson, J.; Beck, R.; Bell, M. R.; Bonafede, A.; Chyzy, K.; Dettmar, R.-J.; Enßlin, T. A.; Heald, G.; Horellou, C.; Horneffer, A.; Jurusik, W.; Junklewitz, H.; Kuniyoshi, M.; Mulcahy, D. D.; Paladino, R.; Reich, W.; Scaife, A.; Sobey, C.; Sotomayor-Beltran, C.; Alexov, A.; Asgekar, A.; Avruch, I. M.; Bell, M. E.; van Bemmel, I.; Bentum, M. J.; Bernardi, G.; Best, P.; Bırzan, L.; Breitling, F.; Broderick, J.; Brouw, W. N.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; Conway, J. E.; de Gasperin, F.; de Geus, E.; Duscha, S.; Eislöffel, J.; Engels, D.; Falcke, H.; Fallows, R. A.; Ferrari, C.; Frieswijk, W.; Garrett, M. A.; Grießmeier, J.; Gunst, A. W.; Hamaker, J. P.; Hassall, T. E.; Hessels, J. W. T.; Hoeft, M.; Hörandel, J.; Jelic, V.; Karastergiou, A.; Kondratiev, V. I.; Koopmans, L. V. E.; Kramer, M.; Kuper, G.; van Leeuwen, J.; Macario, G.; Mann, G.; McKean, J. P.; Munk, H.; Pandey-Pommier, M.; Polatidis, A. G.; Röttgering, H.; Schwarz, D.; Sluman, J.; Smirnov, O.; Stappers, B. W.; Steinmetz, M.; Tagger, M.; Tang, Y.; Tasse, C.; Toribio, C.; Vermeulen, R.; Vocks, C.; Vogt, C.; van Weeren, R. J.; Wise, M. W.; Wucknitz, O.; Yatawatta, S.; Zarka, P.; Zensus, A.

    2013-10-01

    Aims: The characteristic outer scale of turbulence (i.e. the scale at which the dominant source of turbulence injects energy to the interstellar medium) and the ratio of the random to ordered components of the magnetic field are key parameters to characterise magnetic turbulence in the interstellar gas, which affects the propagation of cosmic rays within the Galaxy. We provide new constraints to those two parameters. Methods: We use the LOw Frequency ARray (LOFAR) to image the diffuse continuum emission in the Fan region at (l,b) ~ (137.0°, +7.0°) at 80'' × 70'' resolution in the range [146, 174] MHz. We detect multi-scale fluctuations in the Galactic synchrotron emission and compute their power spectrum. Applying theoretical estimates and derivations from the literature for the first time, we derive the outer scale of turbulence and the ratio of random to ordered magnetic field from the characteristics of these fluctuations. Results: We obtain the deepest image of the Fan region to date and find diffuse continuum emission within the primary beam. The power spectrum displays a power law behaviour for scales between 100 and 8 arcmin with a slope α = -1.84 ± 0.19. We find an upper limit of ~20 pc for the outer scale of the magnetic interstellar turbulence toward the Fan region, which is in agreement with previous estimates in literature. We also find a variation of the ratio of random to ordered field as a function of Galactic coordinates, supporting different turbulent regimes. Conclusions: We present the first LOFAR detection and imaging of the Galactic diffuse synchrotron emission around 160 MHz from the highly polarized Fan region. The power spectrum of the foreground synchrotron fluctuations is approximately a power law with a slope α ≈ -1.84 up to angular multipoles of ≲1300, corresponding to an angular scale of ~8 arcmin. We use power spectra fluctuations from LOFAR as well as earlier GMRT and WSRT observations to constrain the outer scale of

  8. Additional research on instabilities in atmospheric flow systems associated with clear air turbulence

    NASA Technical Reports Server (NTRS)

    Stoeffler, R. C.

    1972-01-01

    Analytical and experimental fluid mechanics studies were conducted to investigate instabilities in atmospheric flow systems associated with clear air turbulence. The experimental portion of the program was conducted using an open water channel which allows investigation of flows having wide ranges of shear and density stratification. The program was primarily directed toward studies of the stability of straight, stratified shear flows with particular emphasis on the effects of velocity profile on stability; on studies of three-dimensional effects on the breakdown region in shear layers; on the the interaction of shear flows with long-wave length internal waves; and on the stability of shear flows consisting of adjacent stable layers. The results of these studies were used to evaluate methods used in analyses of CAT encounters in the atmosphere involving wave-induced shear layer instabilities of the Kelvin-Helmholta type. A computer program was developed for predicting shear-layer instability and CAT induced by mountain waves. This technique predicts specific altitudes and locations where CAT would be expected.

  9. Detachment of tobacco-smoke-material carriers from surfaces by turbulent air flow.

    PubMed

    Ibrahim, A H; Ghosh, S; Dunn, P F

    2009-01-01

    The influence of tobacco-smoke-material (TSM) on the detachment of microparticles from surfaces by turbulent air flow was investigated experimentally. Both clean and dusty glass surfaces were subjected to TSM either before or after the deposition of 64 microm to 76 microm-diameter stainless steel microparticles onto the surfaces. The TSM was generated by mechanically puffing research-grade cigarettes inside a smoking box that contained the surfaces. Microparticle detachment characteristics were studied in a wind tunnel using video microphotography. Measured nicotine concentration was used to determine the amount of TSM deposited on a surface.The 5% and 50% threshold velocities for detachment were used to quantify the effect of TSM on microparticle detachment. These velocities were compared with those obtained using a clean surface with no TSM exposure. The effect of TSM exposure on microparticle detachment depended significantly on whether exposure occurred before or after microparticle deposition. TSM exposure before microparticle deposition had little effect. TSM exposure after deposition delayed detachment to much higher velocities. The presence of dust on the surface with TSM also delayed detachment and increased the variability in the detachment velocities as compared to the case of a clean surface with no TSM exposure.

  10. Boundary layer analysis in turbulent Rayleigh-Bénard convection in air: experiment versus simulation.

    PubMed

    Li, Ling; Shi, Nan; du Puits, Ronald; Resagk, Christian; Schumacher, Jörg; Thess, André

    2012-08-01

    We report measurements and numerical simulations of the three-dimensional velocity and temperature fields in turbulent Rayleigh-Bénard convection in air. Highly resolved velocity and temperature measurements inside and outside the boundary layers have been directly compared with equivalent data obtained in direct numerical simulations (DNSs). This comparison comprises a set of two Rayleigh numbers at Ra=3×10(9) and 3×10(10) and a fixed aspect ratio; this is the ratio between the diameter and the height of the Rayleigh-Bénard cell of Γ=1. We find that the measured velocity data are in excellent agreement with the DNS results while the temperature data slightly differ. In particular, the measured mean temperature profile does not show the linear trend as seen in the DNS data, and the measured gradients at the wall are significantly higher than those obtained from the DNS. Both viscous and thermal boundary layer thickness scale with respect to the Rayleigh number as δ(v)~Ra(-0.24) and δ(θ)~Ra(-0.24), respectively.

  11. Modeling of turbulent supersonic H2-air combustion with an improved joint beta PDF

    NASA Technical Reports Server (NTRS)

    Baurle, R. A.; Hassan, H. A.

    1991-01-01

    Attempts at modeling recent experiments of Cheng et al. indicated that discrepancies between theory and experiment can be a result of the form of assumed probability density function (PDF) and/or the turbulence model employed. Improvements in both the form of the assumed PDF and the turbulence model are presented. The results are again used to compare with measurements. Initial comparisons are encouraging.

  12. Air Monitoring for Hazardous Gas Detection

    NASA Technical Reports Server (NTRS)

    Arkin, C. Richard; Griffin, Timothy P.; Adams, Frederick W.; Naylor, Guy; Haskell, William; Floyd, David; Curley, Charles; Follistein, Duke W.

    2004-01-01

    The Hazardous Gas Detection Lab (HGDL) at Kennedy Space Center is involved in the design and development of instrumentation that can detect and quantify various hazardous gases. Traditionally these systems are designed for leak detection of the cryogenic gases used for the propulsion of the Shuttle and other vehicles. Mass spectrometers are the basis of these systems, which provide excellent quantitation, sensitivity, selectivity, response times and detection limits. A Table lists common gases monitored for aerospace applications. The first five gases, hydrogen, helium, nitrogen, oxygen, and argon are historically the focus of the HGDL.

  13. Relationships between stratospheric clear air turbulence and synoptic meteorological parameters over the western United States between 12-20 km altitude

    NASA Technical Reports Server (NTRS)

    Scoggins, J. R.; Clark, T. L.; Possiel, N. C.

    1975-01-01

    Procedures for forecasting clear air turbulence in the stratosphere over the western United States from rawinsonde data are described and results presented. Approaches taken to relate meteorological parameters to regions of turbulence and nonturbulence encountered by the XB-70 during 46 flights at altitudes between 12-20 km include: empirical probabilities, discriminant function analysis, and mountainwave theory. Results from these techniques were combined into a procedure to forecast regions of clear air turbulence with an accuracy of 70-80 percent. A computer program was developed to provide an objective forecast directly from the rawinsonde sounding data.

  14. Detection of hydrogen chloride gas in air

    NASA Technical Reports Server (NTRS)

    Gregory, G. L.

    1978-01-01

    Launch vehicle effluent (LVE) monitoring is part of NASA's overall tropospheric and stratospheric environmental program. Following nine techniques are evaluated and developed in report: bubbler method, pH measurements, indicator tubes, microcoulometers, modified condensation nuclei counter, dual-isotope absorption, gas-filter correlation, chemiluminescent nitric oxide detection, chemiluminescent luminol-oxidation detection.

  15. The study of droplet-laden turbulent air-flow over waved water surface by direct numerical simulation

    NASA Astrophysics Data System (ADS)

    Druzhinin, Oleg A.; Troitskaya, Yuliya I.; Zilitinkevich, Sergej S.

    2016-04-01

    The detailed knowledge of the interaction of wind with surface water waves is necessary for correct parameterization of turbulent exchange at the air-sea interface in prognostic models. At sufficiently strong winds, sea-spray-generated droplets interfere with the wind-waves interaction. The results of field experiments and laboratory measurements (Andreas et al., JGR 2010) show that mass fraction of air-borne spume water droplets increases with the wind speed and their impact on the carrier air-flow may become significant. Phenomenological models of droplet-laden marine atmospheric boundary layer (Kudryavtsev & Makin, Bound.-Layer Met. 2011) predict that droplets significantly increase the wind velocity and suppress the turbulent air stress. The results of direct numerical simulation (DNS) of a turbulent particle-laden Couette flow over a flat surface show that inertial particles may significantly reduce the carrier flow vertical momentum flux (Richter & Sullivan, GRL 2013). The results also show that in the range of droplet sizes typically found near the air-sea interface, particle inertial effects are significant and dominate any particle-induced stratification effects. However, so far there has been no attempt to perform DNS of a droplet-laden air-flow over waved water surface. In this report, we present results of DNS of droplet-laden, turbulent Couette air-flow over waved water surface. The carrier, turbulent Couette-flow configuration in DNS is similar to that used in previous numerical studies (Sullivan et al., JFM 2000, Shen et al., JFM 2010, Druzhinin et al., JGR 2012). Discrete droplets are considered as non-deformable solid spheres and tracked in a Lagrangian framework, and their impact on the carrier flow is modeled with the use of a point-force approximation. The droplets parameters in DNS are matched to the typical known spume-droplets parameters in laboratory and field experiments. The DNS results show that both gravitational settling of droplets and

  16. Microwave detection of air showers with the MIDAS experiment

    NASA Astrophysics Data System (ADS)

    Privitera, Paolo; Alekotte, I.; Alvarez-Muñiz, J.; Berlin, A.; Bertou, X.; Bogdan, M.; Boháčová, M.; Bonifazi, C.; Carvalho, W. R.; de Mello Neto, J. R. T.; Facal San Luis, P.; Genat, J. F.; Hollon, N.; Mills, E.; Monasor, M.; Reyes, L. C.; Rouille d'Orfeuil, B.; Santos, E. M.; Wayne, S.; Williams, C.; Zas, E.

    2011-03-01

    Microwave emission from Extensive Air Showers could provide a novel technique for ultra-high energy cosmic rays detection over large area and with 100% duty cycle. We describe the design, performance and first results of the MIDAS (MIcrowave Detection of Air Showers) detector, a 4.5 m parabolic dish with 53 feeds in its focal plane, currently installed at the University of Chicago.

  17. Numerical analysis of reaction-diffusion effects on species mixing rates in turbulent premixed methane-air combustion

    SciTech Connect

    Richardson, E.S.; Grout, R.W.; Chen, J.H.; Sankaran, R.

    2010-03-15

    The scalar mixing time scale, a key quantity in many turbulent combustion models, is investigated for reactive scalars in premixed combustion. Direct numerical simulations (DNS) of three-dimensional, turbulent Bunsen flames with reduced methane-air chemistry have been analyzed in the thin reaction zones regime. Previous conclusions from single step chemistry DNS studies are confirmed regarding the role of dilatation and turbulence-chemistry interactions on the progress variable dissipation rate. Compared to the progress variable, the mixing rates of intermediate species is found to be several times greater. The variation of species mixing rates are explained with reference to the structure of one-dimensional premixed laminar flames. According to this analysis, mixing rates are governed by the strong gradients which are imposed by flamelet structures at high Damkoehler numbers. This suggests a modeling approach to estimate the mixing rate of individual species which can be applied, for example, in transported probability density function simulations. Flame-turbulence interactions which modify the flamelet based representation are analyzed. (author)

  18. Measurements of soot, OH, and PAH concentrations in turbulent ethylene/air jet flames

    SciTech Connect

    Lee, Seong-Young; Turns, Stephen R.; Santoro, Robert J.

    2009-12-15

    This paper presents results from an investigation of soot formation in turbulent, non-premixed, C{sub 2}H{sub 4}/air jet flames. Tests were conducted using a H{sub 2}-piloted burner with fuel issuing from a 2.18 mm i.d. tube into quiescent ambient air. A range of test conditions was studied using the initial jet velocity (16.2-94.1 m/s) as a parameter. Fuel-jet Reynolds numbers ranged from 4000 to 23,200. Planar laser-induced incandescence (LII) was employed to determine soot volume fractions, and laser-induced fluorescence (LIF) was used to measure relative hydroxyl radical (OH) concentrations and polycyclic aromatic hydrocarbons (PAHs) concentrations. Extensive information on the structure of the soot and OH fields was obtained from two-dimensional imaging experiments. Quantitative measurements were obtained by employing the LII and LIF techniques independently. Imaging results for soot, OH, and PAH show the existence of three soot formation/oxidation regions: a rapid soot growth region, in which OH and soot particles lie in distinctly different radial locations; a mixing-dominated region controlled by large-scale motion; and a soot-oxidation region in which the OH and soot fields overlap spatially, resulting in the rapid oxidation of soot particles. Detailed quantitative analyzes of soot volume fractions and OH and soot zone thicknesses were performed along with the temperature measurement using the N{sub 2}-CARS system. Measurements of OH and soot zone thicknesses show that the soot zone thickness increases linearly with axial distance in the soot formation region, whereas the OH zone thickness is nearly constant in this region. The OH zone thickness then rapidly increases with downstream distance and approximately doubles in the soot-oxidation region. Probability density functions also were obtained for soot volume fractions and OH concentrations. These probability density functions clearly define the spatial relationships among the OH, PAH concentrations, the

  19. High-Reynolds-number turbulent-boundary-layer wall pressure fluctuations with skin-friction reduction by air injection.

    PubMed

    Winkel, Eric S; Elbing, Brian R; Ceccio, Steven L; Perlin, Marc; Dowling, David R

    2008-05-01

    The hydrodynamic pressure fluctuations that occur on the solid surface beneath a turbulent boundary layer are a common source of flow noise. This paper reports multipoint surface pressure fluctuation measurements in water beneath a high-Reynolds-number turbulent boundary layer with wall injection of air to reduce skin-friction drag. The experiments were conducted in the U.S. Navy's Large Cavitation Channel on a 12.9-m-long, 3.05-m-wide hydrodynamically smooth flat plate at freestream speeds up to 20 ms and downstream-distance-based Reynolds numbers exceeding 200 x 10(6). Air was injected from one of two spanwise slots through flush-mounted porous stainless steel frits (approximately 40 microm mean pore diameter) at volume flow rates from 17.8 to 142.5 l/s per meter span. The two injectors were located 1.32 and 9.78 m from the model's leading edge and spanned the center 87% of the test model. Surface pressure measurements were made with 16 flush-mounted transducers in an "L-shaped" array located 10.7 m from the plate's leading edge. When compared to no-injection conditions, the observed wall-pressure variance was reduced by as much as 87% with air injection. In addition, air injection altered the inferred convection speed of pressure fluctuation sources and the streamwise coherence of pressure fluctuations.

  20. Power spectral measurements of clear-air turbulence to long wavelengths for altitudes up to 14,000 meters

    NASA Technical Reports Server (NTRS)

    Murrow, H. N.; Mccain, W. E.; Rhyne, R. H.

    1982-01-01

    Measurements of three components of clear air atmospheric turbulence were made with an airplane incorporating a special instrumentation system to provide accurate data resolution to wavelengths of approximately 12,500 m (40,000 ft). Flight samplings covered an altitude range from approximately 500 to 14,000 m (1500 to 46,000 ft) in various meteorological conditions. Individual autocorrelation functions and power spectra for the three turbulence components from 43 data runs taken primarily from mountain wave and jet stream encounters are presented. The flight location (Eastern or Western United States), date, time, run length, intensity level (standard deviation), and values of statistical degrees of freedom for each run are provided in tabular form. The data presented should provide adequate information for detailed meteorological correlations. Some time histories which contain predominant low frequency wave motion are also presented.

  1. The effect of clear-air turbulence on a model of the general circulation of the atmosphere

    NASA Technical Reports Server (NTRS)

    Heck, W. J.; Panofsky, H. A.; Bender, M. A.

    1977-01-01

    Mixing coefficients due to clear-air turbulence are estimated from turbulence observations from aircraft, and from large-scale dissipation estimates from the large-scale energy budgets. Maximum coefficients occur near middle-latitude jet streams, and eddy viscosity there is of order of 10 sq m/sec; eddy conductivity is estimated to be about ten times smaller. These coefficients are introduced into the 12-layer general circulation model of the National Center of Atmospheric Research. They produce an apparently significant, though small reduction in maximum speed of the jet, and a reduction in eddy energy. Further, the stratospheric polar-night jet is produced at about the correct location with about the correct intensity.

  2. Air pollution detection using MODIS data

    NASA Astrophysics Data System (ADS)

    Harbula, Jan; Kopacková, Veronika

    2011-11-01

    The quality of the environment has a great impact on public health while air quality is a major factor that is especially relevant for respiratory diseases. PM10 (particulate matter below 10 μ) particles are among the most dangerous pollutants, which enter the lower respiratory tract and cause serious health problems. Obtaining reliable air pollution data is limited to a number of ground measuring stations and their spatial location. We used an alternative approach and created statistical models that employed remotely sensed imageries. To establish empirical relationships, we used multi-temporal (2006-2009) MODIS aerosol optical thickness data (product MOD04, Level 2) and the PM10 ground mass concentrations. The north-western part of the Czech Republic (namely the Karlovarský and the Ustecký regions) was chosen as a test site, as all the different types of cultural landscape (forest-economical, agricultural, mining, and urban) can be found within one MODIS scene. This study was focused on the various aspects as follows (i) analysis of MODIS AOT / stationary PM10 time-series trend between 2006-2009, (ii) establishing a linear relationship between PM10 and AOT values for each station and (iii) evaluation of a spatial relationship of the annual mean AE (Ångstrom Exponent) and PM10 values.

  3. Market Assessment of Forward-Looking Turbulence Sensing Systems

    NASA Technical Reports Server (NTRS)

    Kauffmann, Paul; Sousa-Poza, Andres

    2001-01-01

    In recognition of the importance of turbulence mitigation as a tool to improve aviation safety, NASA's Aviation Safety Program developed a Turbulence Detection and Mitigation Sub-element. The objective of this effort is to develop highly reliable turbulence detection technologies for commercial transport aircraft to sense dangerous turbulence with sufficient time warning so that defensive measures can be implemented and prevent passenger and crew injuries. Current research involves three forward sensing products to improve the cockpit awareness of possible turbulence hazards. X-band radar enhancements will improve the capabilities of current weather radar to detect turbulence associated with convective activity. LIDAR (Light Detection and Ranging) is a laser-based technology that is capable of detecting turbulence in clear air. Finally, a possible Radar-LIDAR hybrid sensor is envisioned to detect the full range of convective and clear air turbulence. To support decisions relating to the development of these three forward-looking turbulence sensor technologies, the objective of this study was defined as examination of cost and implementation metrics. Tasks performed included the identification of cost factors and certification issues, the development and application of an implementation model, and the development of cost budget/targets for installing the turbulence sensor and associated software devices into the commercial transport fleet.

  4. The relationship between ocean surface turbulence and air-sea gas transfer velocity: An in-situ evaluation

    NASA Astrophysics Data System (ADS)

    Esters, L.; Landwehr, S.; Sutherland, G.; Bell, T. G.; Saltzman, E. S.; Christensen, K. H.; Miller, S. D.; Ward, B.

    2016-05-01

    Although the air-sea gas transfer velocity k is usually parameterized with wind speed, the so-called small-eddy model suggests a relationship between k and ocean surface dissipation of turbulent kinetic energy ɛ. Laboratory and field measurements of k and ɛ have shown that this model holds in various ecosystems. Here, field observations are presented supporting the theoretical model in the open ocean. These observations are based on measurements from the Air-Sea Interaction Profiler and eddy covariance CO2 and DMS air-sea flux data collected during the Knorr11 cruise. We show that the model results can be improved when applying a variable Schmidt number exponent compared to a commonly used constant value of 1/2. Scaling ɛ to the viscous sublayer allows us to investigate the model at different depths and to expand its applicability for more extensive data sets.

  5. Controlled simulation of optical turbulence in a temperature gradient air chamber

    NASA Astrophysics Data System (ADS)

    Toselli, Italo; Wang, Fei; Korotkova, Olga

    2016-05-01

    Atmospheric turbulence simulator is built and characterized for in-lab optical wave propagation with controlled strength of the refractive-index fluctuations. The temperature gradients are generated by a sequence of heat guns with controlled individual strengths. The temperature structure functions are measured in two directions transverse to propagation path with the help of a thermocouple array and used for evaluation of the corresponding refractive-index structure functions of optical turbulence.

  6. Air-flow distortion and turbulence statistics near an animal facility

    NASA Astrophysics Data System (ADS)

    Prueger, J. H.; Eichinger, W. E.; Hipps, L. E.; Hatfield, J. L.; Cooper, D. I.

    The emission and dispersion of particulates and gases from concentrated animal feeding operations (CAFO) at local to regional scales is a current issue in science and society. The transport of particulates, odors and toxic chemical species from the source into the local and eventually regional atmosphere is largely determined by turbulence. Any models that attempt to simulate the dispersion of particles must either specify or assume various statistical properties of the turbulence field. Statistical properties of turbulence are well documented for idealized boundary layers above uniform surfaces. However, an animal production facility is a complex surface with structures that act as bluff bodies that distort the turbulence intensity near the buildings. As a result, the initial release and subsequent dispersion of effluents in the region near a facility will be affected by the complex nature of the surface. Previous Lidar studies of plume dispersion over the facility used in this study indicated that plumes move in complex yet organized patterns that would not be explained by the properties of turbulence generally assumed in models. The objective of this study was to characterize the near-surface turbulence statistics in the flow field around an array of animal confinement buildings. Eddy covariance towers were erected in the upwind, within the building array and downwind regions of the flow field. Substantial changes in turbulence intensity statistics and turbulence-kinetic energy (TKE) were observed as the mean wind flow encountered the building structures. Spectra analysis demonstrated unique distribution of the spectral energy in the vertical profile above the buildings.

  7. Background modeling for moving object detection in long-distance imaging through turbulent medium.

    PubMed

    Elkabetz, Adiel; Yitzhaky, Yitzhak

    2014-02-20

    A basic step in automatic moving objects detection is often modeling the background (i.e., the scene excluding the moving objects). The background model describes the temporal intensity distribution expected at different image locations. Long-distance imaging through atmospheric turbulent medium is affected mainly by blur and spatiotemporal movements in the image, which have contradicting effects on the temporal intensity distribution, mainly at edge locations. This paper addresses this modeling problem theoretically, and experimentally, for various long-distance imaging conditions. Results show that a unimodal distribution is usually a more appropriate model. However, if image deblurring is performed, a multimodal modeling might be more appropriate. PMID:24663312

  8. Reprint of: A numerical modelling of gas exchange mechanisms between air and turbulent water with an aquarium chemical reaction

    NASA Astrophysics Data System (ADS)

    Nagaosa, Ryuichi S.

    2014-08-01

    This paper proposes a new numerical modelling to examine environmental chemodynamics of a gaseous material exchanged between the air and turbulent water phases across a gas-liquid interface, followed by an aquarium chemical reaction. This study uses an extended concept of a two-compartment model, and assumes two physicochemical substeps to approximate the gas exchange processes. The first substep is the gas-liquid equilibrium between the air and water phases, A(g)⇌A(aq), with Henry's law constant H. The second is a first-order irreversible chemical reaction in turbulent water, A(aq)+H2O→B(aq)+H+ with a chemical reaction rate κA. A direct numerical simulation (DNS) technique has been employed to obtain details of the gas exchange mechanisms and the chemical reaction in the water compartment, while zero velocity and uniform concentration of A is considered in the air compartment. The study uses the different Schmidt numbers between 1 and 8, and six nondimensional chemical reaction rates between 10(≈0) to 101 at a fixed Reynolds number. It focuses on the effects of the Schmidt number and the chemical reaction rate on fundamental mechanisms of the gas exchange processes across the interface.

  9. A numerical modelling of gas exchange mechanisms between air and turbulent water with an aquarium chemical reaction

    NASA Astrophysics Data System (ADS)

    Nagaosa, Ryuichi S.

    2014-01-01

    This paper proposes a new numerical modelling to examine environmental chemodynamics of a gaseous material exchanged between the air and turbulent water phases across a gas-liquid interface, followed by an aquarium chemical reaction. This study uses an extended concept of a two-compartment model, and assumes two physicochemical substeps to approximate the gas exchange processes. The first substep is the gas-liquid equilibrium between the air and water phases, A(g)⇌A(aq), with Henry's law constant H. The second is a first-order irreversible chemical reaction in turbulent water, A(aq)+H2O→B(aq)+H+ with a chemical reaction rate κA. A direct numerical simulation (DNS) technique has been employed to obtain details of the gas exchange mechanisms and the chemical reaction in the water compartment, while zero velocity and uniform concentration of A is considered in the air compartment. The study uses the different Schmidt numbers between 1 and 8, and six nondimensional chemical reaction rates between 10(≈0) to 101 at a fixed Reynolds number. It focuses on the effects of the Schmidt number and the chemical reaction rate on fundamental mechanisms of the gas exchange processes across the interface.

  10. Clinical considerations concerning detection of venous air embolism.

    PubMed

    Albin, M S; Carroll, R G; Maroon, J C

    1978-01-01

    Venous air embolism during neurosurgical procedures (detected by Doppler Ultrasound and aspiration via a right atrial catheter) was noted in 100 of 400 patients in the sitting position, 5 of 60 patients in the lateral position, 7 of 48 patients in the supine position, and 1 of 10 individuals monitored in the prone position. We confirmed venous air embolism in many of these cases by using serial technetium-macroaggregated albumin lung scans. Gravitational gradients from the venous portal of entrance to the right side of the heart were as small as 5.0 cm, with aspiration of 200 ml of air occurring. Doppler ultrasonic air bubble detection and aspiration through a previously inserted right atrial catheter are critical factors in the diagnosis and treatment of this condition.

  11. Feasibility of radar detection of extensive air showers

    NASA Astrophysics Data System (ADS)

    Stasielak, J.; Engel, R.; Baur, S.; Neunteufel, P.; Šmída, R.; Werner, F.; Wilczyński, H.

    2016-01-01

    Reflection of radio waves off the short-lived plasma produced by the high-energy shower particles in the air is simulated, considering various radar setups and shower geometries. We show that the plasma produced by air showers has to be treated always as underdense. Therefore, we use the Thomson cross-section for scattering of radio waves corrected for molecular quenching and we sum coherently contributions of the reflected radio wave over the volume of the plasma disk to obtain the time evolution of the signal arriving at the receiver antenna. The received power and the spectral power density of the radar echo are analyzed. Based on the obtained results, we discuss possible modes of radar detection of extensive air showers. We conclude that the scattered signal is too weak for the radar method to provide an efficient and inexpensive method of air shower detection.

  12. Turbulent flow field and air entrainment in laboratory plunging breaking waves

    NASA Astrophysics Data System (ADS)

    Na, Byoungjoon; Chang, Kuang-An; Huang, Zhi-Cheng; Lim, Ho-Joon

    2016-05-01

    This paper presents laboratory measurements of turbulent flow fields and void fraction in deep-water plunging breaking waves using imaging and optical fiber techniques. Bubble-size distributions are also determined based on combined measurements of velocity and bubble residence time. The most excited mode of the local intermittency measure of the turbulent flow and its corresponding length scale are obtained using a wavelet-based method and found to correlate with the swirling strength and vorticity. Concentrated vortical structures with high intermittency are observed near the lower boundaries of the aerated rollers where the velocity shear is high; the length scale of the deduced eddies ranges from 0.05 to 0.15 times the wave height. The number of bubbles with a chord length less than 2 mm demonstrates good correlation with the swirling strength. The power-law scaling and the Hinze scale of the bubbles determined from the bubble chord length distribution compare favorably with existing measurements. The turbulent dissipation rate, accounting for void fraction, is estimated using mixture theory. When void fraction is not considered, the turbulent dissipation rate is underestimated by more than 70% in the initial impinging and the first splash-up roller. A significant discrepancy of approximately 67% between the total energy dissipation rate and the turbulence dissipation rate is found. Of this uncounted dissipation, 23% is caused by bubble-induced dissipation.

  13. Spot detection accuracy analysis in turbulent channel for free space optical communication

    NASA Astrophysics Data System (ADS)

    Liu, Yan-Fei; Dai, Yong-Hong; Yu, Sheng-Lin; Xin, Shan; Chen, Jing; Ai, Yong

    2015-10-01

    Increasingly importance has been taken seriously for high frame rate CMOS camera to optical communication acquisition pointing and tacking (APT) system, with its compact structure, easy to developed and adapted to beacon light spot detection in atmospheric channel. As spot position accuracy directly determines the performance of space optical communication, it is very important to design a high precision spot center algorithm. Usually spot location algorithm uses gravity algorithm, shape center capturing algorithm or self-adaption threshold algorithm. In experiments we analyzed the characteristics of the spots which transmitted through atmospheric turbulence and studied light transmission characteristics in turbulent channel. We carried out a beacon light detection experiments in a distance of 3.4km, collected the beacon spots on CMOS camera and signal light power. We calculated spot position with two different algorithm and compared the calculation accuracy between field dispersive spot and ideal Gaussian laser spot. Experiment research show that, gravity center algorithm should be more suitable for beacon beam spot which accuracy can be improved about 1.3 pixels for a Gaussian spot. But the shape center algorithm has higher precision. The reasons were analyzed which made an important preparation for subsequent testing.

  14. A field study of air flow and turbulent features of advection fog

    NASA Technical Reports Server (NTRS)

    Connell, J. D.

    1979-01-01

    The setup and initial operation of a set of specialized meteorological data collection hardware are described. To study the life cycle of advection fogs at a lake test site, turbulence levels in the fog are identified, and correlated with the temperature gradients and mean wind profiles. A meteorological tower was instrumented to allow multiple-level measurements of wind and temperature on a continuous basis. Additional instrumentation was: (1)hydrothermograph, (2)microbarograph, (3)transmissometers, and (4)a boundary layer profiler. Two types of fogs were identified, and important differences in the turbulence scales were noted.

  15. Further Experiments on the Flow and Heat Transfer in a Heated Turbulent Air Jet

    NASA Technical Reports Server (NTRS)

    Corrsin, Stanley; Uberoi, Mahinder S

    1950-01-01

    Measurements have been made of the mean-total-head and mean-temperature fields in a round turbulent jet with various initial temperatures. The results show that the jet spreads more rapidly as its density becomes lower than that of the receiving medium, even when the difference is not sufficiently great to cause dynamic-pressure function. Rough analytical considerations have given the same relative spread. The effective "turbulent Prandtl number" for a section of the fully developed jet was found to be equal to the true (laminar) Prandtl number within the accuracy measurement.

  16. Infrared thermography for detection of laminar-turbulent transition in low-speed wind tunnel testing

    NASA Astrophysics Data System (ADS)

    Joseph, Liselle A.; Borgoltz, Aurelien; Devenport, William

    2016-05-01

    This work presents the details of a system for experimentally identifying laminar-to-turbulent transition using infrared thermography applied to large, metal models in low-speed wind tunnel tests. Key elements of the transition detection system include infrared cameras with sensitivity in the 7.5- to 14.0-µm spectral range and a thin, insulating coat for the model. The fidelity of the system was validated through experiments on two wind-turbine blade airfoil sections tested at Reynolds numbers between Re = 1.5 × 106 and 3 × 106. Results compare well with measurements from surface pressure distributions and stethoscope observations. However, the infrared-based system provides data over a much broader range of conditions and locations on the model. This paper chronicles the design, implementation and validation of the infrared transition detection system, a subject which has not been widely detailed in the literature to date.

  17. Minimum detectable air velocity by thermal flow sensors.

    PubMed

    Issa, Safir; Lang, Walter

    2013-08-19

    Miniaturized thermal flow sensors have opened the doors for a large variety of new applications due to their small size, high sensitivity and low power consumption. Theoretically, very small detection limits of air velocity of some micrometers per second are achievable. However, the superimposed free convection is the main obstacle which prevents reaching these expected limits. Furthermore, experimental investigations are an additional challenge since it is difficult to generate very low flows. In this paper, we introduce a physical method, capable of generating very low flow values in the mixed convection region. Additionally, we present the sensor characteristic curves at the zero flow case and in the mixed convection region. Results show that the estimated minimum detectable air velocity by the presented method is 0.8 mm/s. The equivalent air velocity to the noise level of the sensor at the zero flow case is about 0.13 mm/s.

  18. Minimum Detectable Air Velocity by Thermal Flow Sensors

    PubMed Central

    Issa, Safir; Lang, Walter

    2013-01-01

    Miniaturized thermal flow sensors have opened the doors for a large variety of new applications due to their small size, high sensitivity and low power consumption. Theoretically, very small detection limits of air velocity of some micrometers per second are achievable. However, the superimposed free convection is the main obstacle which prevents reaching these expected limits. Furthermore, experimental investigations are an additional challenge since it is difficult to generate very low flows. In this paper, we introduce a physical method, capable of generating very low flow values in the mixed convection region. Additionally, we present the sensor characteristic curves at the zero flow case and in the mixed convection region. Results show that the estimated minimum detectable air velocity by the presented method is 0.8 mm/s. The equivalent air velocity to the noise level of the sensor at the zero flow case is about 0.13 mm/s. PMID:23966190

  19. Generalized Slope Detection and Ranging turbulence profiling at Las Campanas Observatory

    NASA Astrophysics Data System (ADS)

    Goodwin, Michael; Jenkins, Charles; Lambert, Andrew

    2016-09-01

    We present two models of the optical turbulence profile (model-OTP) for Las Campanas Observatory (LCO) based on measurements conducted during 2007 and 2008 using the Generalized Slope Detection and Ranging (SLODAR) method. The model-OTPs can be used as input into simulations to assess the performance of adaptive optics for the Giant Magellan Telescope. Of particular interest is the strength of the ground-layer turbulence for ground-layer adaptive optics. A total of two 1-week observing data was collected using a purpose-built instrument where observations of a bright double star are imaged by 24 × 24 Shack-Hartmann taken with the LCO 100-inch du Pont telescope. The analysis of the data yielded model-OTP consisting of a handful of statistically prominent thin layers that are statistically separated into the ground layer (below 0.5 km) and the free atmosphere for good (25 per cent), typical (50 per cent) and bad (25 per cent) observing conditions. We demonstrate that using the novel technique of Generalized SLODAR we were able to achieve three times the nominal height resolution of SLODAR and uncover important structural details in the ground layer.

  20. Radio Detection of Air Showers with LOFAR and AERA

    NASA Astrophysics Data System (ADS)

    Hörandel, Jörg R.

    Radio detection of extensive air showers is a new method to measure the properties of high-energy cosmic rays. Recent results are reviewed from the LOFAR radio telescope and the Auger Engineering Radio Array (AERA) at the Pierre Auger Observatory.

  1. Sound propagation in narrow tubes including effects of viscothermal and turbulent damping with application to charge air coolers

    NASA Astrophysics Data System (ADS)

    Knutsson, Magnus; Åbom, Mats

    2009-02-01

    Charge air coolers (CACs) are used on turbocharged internal combustion engines to enhance the overall gas-exchange performance. The cooling of the charged air results in higher density and thus volumetric efficiency. It is also important for petrol engines that the knock margin increases with reduced charge air temperature. A property that is still not very well investigated is the sound transmission through a CAC. The losses, due to viscous and thermal boundary layers as well as turbulence, in the narrow cooling tubes result in frequency dependent attenuation of the transmitted sound that is significant and dependent on the flow conditions. Normally, the cross-sections of the cooling tubes are neither circular nor rectangular, which is why no analytical solution accounting for a superimposed mean flow exists. The cross-dimensions of the connecting tanks, located on each side of the cooling tubes, are large compared to the diameters of the inlet and outlet ducts. Three-dimensional effects will therefore be important at frequencies significantly lower than the cut-on frequencies of the inlet/outlet ducts. In this study the two-dimensional finite element solution scheme for sound propagation in narrow tubes, including the effect of viscous and thermal boundary layers, originally derived by Astley and Cummings [Wave propagation in catalytic converters: Formulation of the problem and finite element scheme, Journal of Sound and Vibration 188 (5) (1995) 635-657] is used to extract two-ports to represent the cooling tubes. The approximate solutions for sound propagation, accounting for viscothermal and turbulent boundary layers derived by Dokumaci [Sound transmission in narrow pipes with superimposed uniform mean flow and acoustic modelling of automobile catalytic converters, Journal of Sound and Vibration 182 (5) (1995) 799-808] and Howe [The damping of sound by wall turbulent shear layers, Journal of the Acoustical Society of America 98 (3) (1995) 1723-1730], are

  2. A wavelet-based approach to detect climate change on the coherent and turbulent component of the atmospheric circulation

    NASA Astrophysics Data System (ADS)

    Faranda, Davide; Defrance, Dimitri

    2016-06-01

    The modifications of atmospheric circulation induced by anthropogenic effects are difficult to capture because wind fields feature a complex spectrum where the signal of large-scale coherent structures (planetary, baroclinic waves and other long-term oscillations) is mixed up with turbulence. Our purpose is to study the effects of climate changes on these two components separately by applying a wavelet analysis to the 700 hPa wind fields obtained in climate simulations for different forcing scenarios. We study the coherent component of the signal via a correlation analysis to detect the persistence of large-scale or long-lasting structures, whereas we use the theory of autoregressive moving-average stochastic processes to measure the spectral complexity of the turbulent component. Under strong anthropogenic forcing, we detect a significant climate change signal. The analysis suggests that coherent structures will play a dominant role in future climate, whereas turbulent spectra will approach a classical Kolmogorov behaviour.

  3. An experimental and numerical study into turbulent condensing steam jets in air

    NASA Astrophysics Data System (ADS)

    Oerlemans, S.; Badie, R.; Van Dongen, M. E. H.

    Temperatures, velocities, and droplet sizes are measured in turbulent condensing steam jets produced by a facial sauna, for varying nozzle diameters and varying initial velocities (Re=3,600-9,200). The release of latent heat due to droplet condensation causes the temperature in the two-phase jet to be significantly higher than in a single-phase jet. At some distance from the nozzle, droplets reach a maximum size and start to evaporate again, which results in a change in sign of latent heat release. The distance of maximum size is determined from droplet size measurements. The experimental results are compared with semi-analytical expressions and with a fully coupled numerical model of the turbulent condensing steam jet. The increase in centreline temperature due to droplet condensation is successfully predicted.

  4. Interpretation of combined wind profiler and aircraft-measured tropospheric winds and clear air turbulence

    NASA Technical Reports Server (NTRS)

    Thomson, D. W.; Syrett, William J.; Fairall, C. W.

    1991-01-01

    In the first experiment, it was found that wind profilers are far better suited for the detailed examination of jet stream structure than are weather balloons. The combination of good vertical resolution with not previously obtained temporal resolution reveals structural details not seen before. Development of probability-derived shear values appears possible. A good correlation between pilot reports of turbulence and wind shear was found. In the second experiment, hourly measurements of wind speed and direction obtained using two wind profiling Doppler radars during two prolonged jet stream occurrences over western Pennsylvania were analyzed. In particular, the time-variant characteristics of derived shear profiles were examined. Profiler data dropouts were studied in an attempt to determine possible reasons for the apparently reduced performance of profiling radar operating beneath a jet stream. Richardson number and wind shear statistics were examined along with pilot reports of turbulence in the vicinity of the profiler.

  5. The detailed flame structure of highly stretched turbulent premixed methane-air flames

    SciTech Connect

    Chen, Y.C.; Peters, N.; Schneemann, G.A.; Wruck, N.; Renz, U.; Mansour, M.S.

    1996-11-01

    The premixed stoichiometric turbulent methane flames are investigated on a piloted Bunsen burner with mean nozzle exit velocities of 65, 50, and 30 m/s. Advanced laser diagnostics of the flow field using two-component and two-point laser Doppler anemometer, as well as of the scalar fields with 2-D Rayleigh thermometry and line Raman/Rayleigh laser-induced predissociation fluorescence techniques, are applied to obtain both the instantaneous and mean flame structure in terms of velocity, temperature, and major species concentrations, as well as turbulent kinetic energy and length scales. The three flames cover the entire range of the distributed-reaction-zones regime from the borderline to the well-stirred reactor regime to the flamelet regime. Measurements were from X/D = 2.5 above the nozzle exit plane to X/D = 12.5 downstream. Thus, a complete database is established for comparison with the numerical predictions. Within the mixing layer between the unburnt gas and the pilot flame, the instantaneous temperatures are much lower than the adiabatic flame temperature due to the short residence time and heat loss to the burner. With increasing residence time the mean flame temperature increases in the axial direction. The radial mixing of the turbulence generated with the shear layers between the nozzle jet stream and surrounding pilot stream is suppressed, such that the turbulence kinetic energy remains nearly constant on the centerline. From the two-dimensional temperature fields instantaneous iso-temperature contours are plotted showing broad regions where burnt and unburnt gas are partially mixed. These regions are interpreted in terms of the quench scale {ell}{sub q} = ({epsilon}{tau}{sub c}{sup 3}){sup 1/2}. The measured values of the flame brush thickness are proportional to the quench scale for the two high-velocity flames, whereas the low-velocity flame exhibits essential flamelet behavior.

  6. Circular polarization shift keying with homodyne coherent detection in gamma-gamma atmospheric turbulence channel

    NASA Astrophysics Data System (ADS)

    Hong, Yan; Yuan, Xueguang; Zhang, Yangan; Zhang, Yue; Wang, Limeng; Ma, Huihui

    2015-08-01

    We propose a communication system of Circular Polarization Shift Keying (CPolSK) with homodyne coherent detection in free-space optical (FSO) communication with Gamma-Gamma atmospheric turbulence channel. The system need no polarization coordinate alignment, thus the complexity is reduced. Meanwhile, we derived the closed bit error rate (BER) expression of the system compared with the coherent on-off keying (OOK) system. Simulation results show that CPolSK with homodyne system is highly insensitive to the phase noise and BER performance is greatly promoted compared to OOK modulation, the signal-to-noise ratio (SNR) of receiving is reduced about 8dB when the system has the same BER performance under same conditions.

  7. Using an ensemble data set of turbulent air-sea fluxes to evaluate the IPSL climate model in tropical regions

    NASA Astrophysics Data System (ADS)

    Gainusa-Bogdan, Alina; Servonnat, Jerome; Braconnot, Pascale

    2014-05-01

    Low-latitude turbulent ocean-atmosphere fluxes play a major role in the ocean and atmosphere dynamics, heat distribution and availability for meridional transport to higher latitudes, as well as for the global freshwater cycle. Their representation in coupled ocean-atmosphere models is thus of chief importance in climate simulations. Despite numerous reports of important observational uncertainties in large-scale turbulent flux products, only few model flux evaluation studies attempt to quantify and directly consider these uncertainties. To address this problem for large-scale, climatological flux evaluation, we assemble a comprehensive database of 14 climatological surface flux products, including in situ-based, satellite, hybrid and reanalysis data sets. We develop an associated analysis protocol and use it together with this database to offer an observational ensemble approach to model flux evaluation. We use this approach to perform an evaluation of the representation of the intertropical turbulent air-sea fluxes in a suite of CMIP5 historical simulations run with different recent versions of the IPSL model. To enhance model understanding, we consider both coupled and forced atmospheric model configurations. For the same purpose, we not only analyze the surface fluxes, but also their associated meteorological state variables and inter-variable relationships. We identify an important, systematic underestimation of the near-surface wind speed and a significant exaggeration of the sea-air temperature contrast in all the IPSL model versions considered. Furthermore, the coupled model simulations develop important sea surface temperature and associated air humidity bias patterns. Counterintuitively, these biases do not systematically transfer to significant biases in the surface fluxes. This is due to a combination of compensation of effects and the large flux observational spread. Our analyses reveal several inconsistencies in inter-variable relationships between

  8. Detection of tau neutrinos by imaging air Cherenkov telescopes

    NASA Astrophysics Data System (ADS)

    Góra, D.; Bernardini, E.

    2016-09-01

    This paper investigates the potential to detect tau neutrinos in the energy range of 1-1000 PeV searching for very inclined showers with imaging Cherenkov telescopes. A neutrino induced tau lepton escaping from the Earth may decay and initiate an air shower which can be detected by a fluorescence or Cherenkov telescope. We present here a study of the detection potential of Earth-skimming neutrinos taking into account neutrino interactions in the Earth crust, local matter distributions at various detector sites, the development of tau-induced showers in air and the detection of Cherenkov photons with IACTs. We analyzed simulated shower images on the camera focal plane and implemented generic reconstruction chains based on Hillas parameters. We find that present IACTs can distinguish air showers induced by tau neutrinos from the background of hadronic showers in the PeV-EeV energy range. We present the neutrino trigger efficiency obtained for a few configurations being considered for the next-generation Cherenkov telescopes, i.e. the Cherenkov Telescope Array. Finally, for a few representative neutrino spectra expected from astrophysical sources, we compare the expected event rates at running IACTs to what is expected for the dedicated IceCube neutrino telescope.

  9. Measurements and comparison of the probability density and covariance functions of laser beam intensity fluctuations in a hot-air turbulence emulator with the maritime atmospheric environment

    NASA Astrophysics Data System (ADS)

    Nelson, C.; Avramov-Zamurovic, S.; Malek-Madani, R.; Korotkova, O.; Sova, R.; Davidson, F.

    2012-10-01

    A hot-air turbulence emulator is employed for generating controlled optical clear air turbulence in the weak fluctuation regime in laboratory conditions. The analysis of the first and second-order statistical moments of the fluctuating intensity of a propagating infra-red (IR) laser beam through the turbulence emulator is made and the results are compared with bi-directional shore-to-ship maritime data collected during two 2009 mid-Atlantic Coast field tests utilizing single-mode adaptive optics terminals at a range of 10.7 km, as well as with a 633 nm Helium Neon laser propagating across land and water at the United States Naval Academy.

  10. Modeling of turbulent supersonic H2-air combustion with a multivariate beta PDF

    NASA Technical Reports Server (NTRS)

    Baurle, R. A.; Hassan, H. A.

    1993-01-01

    Recent calculations of turbulent supersonic reacting shear flows using an assumed multivariate beta PDF (probability density function) resulted in reduced production rates and a delay in the onset of combustion. This result is not consistent with available measurements. The present research explores two possible reasons for this behavior: use of PDF's that do not yield Favre averaged quantities, and the gradient diffusion assumption. A new multivariate beta PDF involving species densities is introduced which makes it possible to compute Favre averaged mass fractions. However, using this PDF did not improve comparisons with experiment. A countergradient diffusion model is then introduced. Preliminary calculations suggest this to be the cause of the discrepancy.

  11. The MIDAS experiment: MIcrowave Detection of Air Showers

    NASA Astrophysics Data System (ADS)

    Facal, Pedro; Bohacova, Martina; Monasor, Maria; Privitera, Paolo; Reyes, Luis C.; Williams, Cristopher

    2010-02-01

    Recent measurements suggest that extensive air showers initiated by high energy cosmic rays (above 1 EeV) emit signals in the microwave band of the EM spectrum caused by the collisions of the free-electrons with the atmospheric neutral molecules in the plasma produced by the passage of the shower. Such emission is isotropic and could allow the detection of air showers with 100% duty cycle and a calorimetric-like energy measurement - a significant improvement over current detection techniques. We have built a MIDAS prototype, which consists of a 4.5 m diameter antenna with a cluster of 55 feed-horns in the 4 GHz range, covering a 10^o x10^o field of view, with self-triggering capability. The details of the prototype and first results will be presented. )

  12. Innovations in air sampling to detect plant pathogens

    PubMed Central

    West, JS; Kimber, RBE

    2015-01-01

    Many innovations in the development and use of air sampling devices have occurred in plant pathology since the first description of the Hirst spore trap. These include improvements in capture efficiency at relatively high air-volume collection rates, methods to enhance the ease of sample processing with downstream diagnostic methods and even full automation of sampling, diagnosis and wireless reporting of results. Other innovations have been to mount air samplers on mobile platforms such as UAVs and ground vehicles to allow sampling at different altitudes and locations in a short space of time to identify potential sources and population structure. Geographical Information Systems and the application to a network of samplers can allow a greater prediction of airborne inoculum and dispersal dynamics. This field of technology is now developing quickly as novel diagnostic methods allow increasingly rapid and accurate quantifications of airborne species and genetic traits. Sampling and interpretation of results, particularly action-thresholds, is improved by understanding components of air dispersal and dilution processes and can add greater precision in the application of crop protection products as part of integrated pest and disease management decisions. The applications of air samplers are likely to increase, with much greater adoption by growers or industry support workers to aid in crop protection decisions. The same devices are likely to improve information available for detection of allergens causing hay fever and asthma or provide valuable metadata for regional plant disease dynamics. PMID:25745191

  13. Fast detection of air contaminants using immunobiological methods

    NASA Astrophysics Data System (ADS)

    Schmitt, Katrin; Bolwien, Carsten; Sulz, Gerd; Koch, Wolfgang; Dunkhorst, Wilhelm; Lödding, Hubert; Schwarz, Katharina; Holländer, Andreas; Klockenbring, Torsten; Barth, Stefan; Seidel, Björn; Hofbauer, Wolfgang; Rennebarth, Torsten; Renzl, Anna

    2009-05-01

    The fast and direct identification of possibly pathogenic microorganisms in air is gaining increasing interest due to their threat for public health, e.g. in clinical environments or in clean rooms of food or pharmaceutical industries. We present a new detection method allowing the direct recognition of relevant germs or bacteria via fluorescence-labeled antibodies within less than one hour. In detail, an air-sampling unit passes particles in the relevant size range to a substrate which contains antibodies with fluorescence labels for the detection of a specific microorganism. After the removal of the excess antibodies the optical detection unit comprising reflected-light and epifluorescence microscopy can identify the microorganisms by fast image processing on a single-particle level. First measurements with the system to identify various test particles as well as interfering influences have been performed, in particular with respect to autofluorescence of dust particles. Specific antibodies for the detection of Aspergillus fumigatus spores have been established. The biological test system consists of protein A-coated polymer particles which are detected by a fluorescence-labeled IgG. Furthermore the influence of interfering particles such as dust or debris is discussed.

  14. Conflict Detection and Resolution for Future Air Transportation Management

    NASA Technical Reports Server (NTRS)

    Krozel, Jimmy; Peters, Mark E.; Hunter, George

    1997-01-01

    With a Free Flight policy, the emphasis for air traffic control is shifting from active control to passive air traffic management with a policy of intervention by exception. Aircraft will be allowed to fly user preferred routes, as long as safety Alert Zones are not violated. If there is a potential conflict, two (or more) aircraft must be able to arrive at a solution for conflict resolution without controller intervention. Thus, decision aid tools are needed in Free Flight to detect and resolve conflicts, and several problems must be solved to develop such tools. In this report, we analyze and solve problems of proximity management, conflict detection, and conflict resolution under a Free Flight policy. For proximity management, we establish a system based on Delaunay Triangulations of aircraft at constant flight levels. Such a system provides a means for analyzing the neighbor relationships between aircraft and the nearby free space around air traffic which can be utilized later in conflict resolution. For conflict detection, we perform both 2-dimensional and 3-dimensional analyses based on the penetration of the Protected Airspace Zone. Both deterministic and non-deterministic analyses are performed. We investigate several types of conflict warnings including tactical warnings prior to penetrating the Protected Airspace Zone, methods based on the reachability overlap of both aircraft, and conflict probability maps to establish strategic Alert Zones around aircraft.

  15. An integrated fiber-optic turbulence sensor and its applications in maritime atmospheric optical turbulence research

    NASA Astrophysics Data System (ADS)

    Xiao, Shu-mei; Mei, Hai-ping; Wang, Qian; Rao, Rui-zhong

    2013-08-01

    An integrated fiber-optic turbulence sensor based on non-balanced fiber-optic Mach-Zehnder interferometer with a small air gap as light path difference has been designed for detecting air refractive index fluctuation. For avoiding sensing signal fading and perturbations from circumstance during signal transmission, the phase generated carrier is used. The turbulence induced air refractive index fluctuations are demodulated by the algorithm of correlation. Background noise of the sensor is below10-17 . By comparing with the refractive index structure constant measured by fine-wire resistance thermometer, results show good agreement in both their magnitude and tendency. For its outstanding property of corrosion protection, the sensor is especially suitable for maritime atmospheric optical turbulence research, which is verified by one month sea beach investigation. Some results of the maritime optical turbulence intensity are reported in the end.

  16. Correlation of turbulent burning velocities of ethanol-air, measured in a fan-stirred bomb up to 1.2 MPa

    SciTech Connect

    Bradley, D.; Lawes, M.; Mansour, M.S.

    2011-01-15

    The turbulent burning velocity is defined by the mass rate of burning and this also requires that the associated flame surface area should be defined. Previous measurements of the radial distribution of the mean reaction progress variable in turbulent explosion flames provide a basis for definitions of such surface areas for turbulent burning velocities. These inter-relationships. in general, are different from those for burner flames. Burning velocities are presented for a spherical flame surface, at which the mass of unburned gas inside it is equal to the mass of burned gas outside it. These can readily be transformed to burning velocities based on other surfaces. The measurements of the turbulent burning velocities presented are the mean from five different explosions, all under the same conditions. These cover a wide range of equivalence ratios, pressures and rms turbulent velocities for ethanol-air mixtures. Two techniques are employed, one based on measurements of high speed schlieren images, the other on pressure transducer measurements. There is good agreement between turbulent burning velocities measured by the two techniques. All the measurement are generalised in plots of burning velocity normalised by the effective unburned gas rms velocity as a function of the Karlovitz stretch factor for different strain rate Markstein numbers. For a given value of this stretch factor a decrease in Markstein number increases the normalised burning velocity. Comparisons are made with the findings of other workers. (author)

  17. X-33 Rev-F Turbulent Aeroheating Results From Test 6817 in NASA Langley 20-Inch Mach 6 Air Tunnel and Comparisons With Computations

    NASA Technical Reports Server (NTRS)

    Hollis, Brian R.; Horvath, Thomas J.; Berry, Scott A.

    2003-01-01

    Measurements and predictions of the X-33 turbulent aeroheating environment have been performed at Mach 6, perfect-gas air conditions. The purpose of this investigation was to compare measured turbulent aeroheating levels on smooth models, models with discrete trips, and models with arrays of bowed panels (which simulate bowed thermal protections system tiles) with each other and with predictions from two Navier-Stokes codes, LAURA and GASP. The wind tunnel testing was conducted at free stream Reynolds numbers based on length of 1.8 x 10(exp 6) to 6.1 x 10(exp 6) on 0.0132 scale X-33 models at a = 40-deg. Turbulent flow was produced by the discrete trips and by the bowed panels at ill but the lowest Reynolds number, but turbulent flow on the smooth model was produced only at the highest Reynolds number. Turbulent aeroheating levels on each of the three model types were measured using global phosphor thermography and were found to agree to within .he estimated uncertainty (plus or minus 15%) of the experiment. Computations were performed at the wind tunnel free stream conditions using both codes. Turbulent aeroheating levels predicted using the LAURA code were generally 5%-10% lower than those from GASP, although both sets of predictions fell within the experimental accuracy of the wind tunnel data.

  18. Investigation of the temperature field in a turbulent air flow in the channels with structured packing

    NASA Astrophysics Data System (ADS)

    Perepelitsa, B. V.

    2007-12-01

    Temperature distribution and intensity of temperature pulsations in the airflow in a complex heat exchanger of “Frenkel packing” type were studied experimentally. Measurements were carried out at the airflow between two corrugated plates with triangular embossing, directed at 90° relative to each other. The temperature in the flow was measured by a special thermocouple probe. The hot junction of the thermocouple did not exceed 10 μm. The effect of contact points and Reynolds number on static characteristics of temperature in a turbulent airflow is analysed. The main attention is paid to temperature distribution in an elementary cell. According to the studies, there is a considerable difference between temperature distributions in the flow at the back and front sides of the channel.

  19. Experimental study for the detection of the laminar/turbulent aerodynamic transition on a wing aircraft, using fiber optic sensors

    NASA Astrophysics Data System (ADS)

    Molin, S.; Dolfi, D.; Doisy, M.; Seraudie, A.; Arnal, D.; Coustols, E.; Mandle, J.

    2010-09-01

    We demonstrate the feasibility of detection of the nature (laminar/turbulent/transitional) of the aerodynamic boundary layer of a profile of a wing aircraft model, using a Distributed FeedBack (DFB) Fiber Laser as optical fiber sensor. Signals to be measured are pressure variations : ΔP~1Pa at few 100Hz in the laminar region and ΔP~10Pa at few kHz in the turbulent region. Intermittent regime occurring in-between these two regions (transition) is characterized by turbulent bursts in laminar flow. Relevant pressure variations have been obtained in a low-speed research-type wind tunnel of ONERA Centre of Toulouse. In order to validate the measurements, a "classical" hot film sensor, the application and use of which have been formerly developed and validated by ONERA, has been placed at the neighborhood of the fiber sensor. The hot film allows measurement of the boundary layer wall shear stress whose characteristics are a well known signature of the boundary layer nature (laminar, intermittent or turbulent) [1]. In the three regimes, signals from the fiber sensor and the hot film sensor are strongly correlated, which allows us to conclude that a DFB fiber laser sensor is a good candidate for detecting the boundary layer nature, and thus for future integration in an aircraft wing. The work presented here has been realized within the framework of "Clean Sky", a Joint Technology Initiative of the European Union.

  20. Using Cellular Communication Networks To Detect Air Pollution.

    PubMed

    David, Noam; Gao, H Oliver

    2016-09-01

    Accurate real time monitoring of atmospheric conditions at ground level is vital for hazard warning, meteorological forecasting, and various environmental applications required for public health and safety. However, conventional monitoring facilities are costly and often insufficient, for example, since they are not representative of the larger space and are not deployed densely enough in the field. There have been numerous scientific works showing the ability of commercial microwave links that comprise the data transmission infrastructure in cellular communication networks to monitor hydrometeors as a potential complementary solution. However, despite the large volume of research carried out in this emerging field during the past decade, no study has shown the ability of the system to provide critical information regarding air quality. Here we reveal the potential for identifying atmospheric conditions prone to air pollution by detecting temperature inversions that trap pollutants at ground level. The technique is based on utilizing standard signal measurements from an existing cellular network during routine operation. PMID:27490182

  1. Using Cellular Communication Networks To Detect Air Pollution.

    PubMed

    David, Noam; Gao, H Oliver

    2016-09-01

    Accurate real time monitoring of atmospheric conditions at ground level is vital for hazard warning, meteorological forecasting, and various environmental applications required for public health and safety. However, conventional monitoring facilities are costly and often insufficient, for example, since they are not representative of the larger space and are not deployed densely enough in the field. There have been numerous scientific works showing the ability of commercial microwave links that comprise the data transmission infrastructure in cellular communication networks to monitor hydrometeors as a potential complementary solution. However, despite the large volume of research carried out in this emerging field during the past decade, no study has shown the ability of the system to provide critical information regarding air quality. Here we reveal the potential for identifying atmospheric conditions prone to air pollution by detecting temperature inversions that trap pollutants at ground level. The technique is based on utilizing standard signal measurements from an existing cellular network during routine operation.

  2. Climate simulations with a new air-sea turbulent flux parameterization in the National Center for Atmospheric Research Community Atmosphere Model (CAM3)

    NASA Astrophysics Data System (ADS)

    Ban, Junmei; Gao, Zhiqiu; Lenschow, Donald H.

    2010-01-01

    This study examines climate simulations with the National Center for Atmospheric Research Community Atmosphere Model version 3 (NCAR CAM3) using a new air-sea turbulent flux parameterization scheme. The current air-sea turbulent flux scheme in CAM3 consists of three basic bulk flux equations that are solved simultaneously by an iterative computational technique. We recently developed a new turbulent flux parameterization scheme where the Obukhov stability length is parameterized directly by using a bulk Richardson number, an aerodynamic roughness length, and a heat roughness length. Its advantages are that it (1) avoids the iterative process and thus increases the computational efficiency, (2) takes account of the difference between z0m and z0h and allows large z0m/z0h, and (3) preserves the accuracy of iteration. An offline test using Tropical Ocean-Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE) data shows that the original scheme overestimates the surface fluxes under very weak winds but the new scheme gives better results. Under identical initial and boundary conditions, the original CAM3 and CAM3 coupled with the new turbulent flux scheme are used to simulate the global distribution of air-sea surface turbulent fluxes, and precipitation. Comparisons of model outputs against the European Remote Sensing Satellites (ERS), the Objectively Analyzed air-sea Fluxes (OAFlux), and Climate Prediction Center (CPC) Merged Analysis of Precipitation (CMAP) show that: (1) the new scheme produces more realistic surface wind stress in the North Pacific and North Atlantic trade wind belts and wintertime extratropical storm track regions; (2) the latent heat flux in the Northern Hemisphere trade wind zones shows modest improvement in the new scheme, and the latent heat flux bias in the western boundary current region of the Gulf Stream is reduced; and (3) the simulated precipitation in the new scheme is closer to observation in the Asian monsoon

  3. Fiber optic sensor technology for air conformal ice detection

    NASA Astrophysics Data System (ADS)

    Ikiades, Aris A.; Armstrong, David J.; Hare, George G.; Konstantaki, Mary; Crossley, Samuel D.

    2004-03-01

    Ice accretion on flying surfaces affects the aerodynamic performance and handling qualities of aircraft, and may require different pilot corrective action, dependent upon the surface that ice is accreting onto. The current methodology for ice detection usually relies on an indirect method, normally based on ambient air temperature, and liquid water content. When a pre-set threshold level is reached, the ice protection system is activated, whether or not ice is accreting on critical surfaces. This method is not cost effective or efficient for an ice protection system. Air Conformal Ice Detection System (ACIDS) obviates these problems by using a 'direct" method of detection and measurement the presence and thickness of ice. This paper outlines some of the preliminary experimental work done on the optical properties of ice grown in an icing tunnel on the leading edge of an aerofoil leading to the development of a Fibre Optic Direct Ice Detector sensor (DID) with emphasis. The result of this studies have shown that with suitable processing it is possible to use fibre optic sensors to determine the thickness of ice and texture of the ice accreted in the vicinity of the sensor. In the latter part of this paper basic fibre optic architecture is discussed and together with some preliminary results for representative icing runs.

  4. Ultrasonic bistatic Doppler sonar in air for personnel motion detection

    NASA Astrophysics Data System (ADS)

    Ekimov, Alexander; Hickey, Craig J.

    2012-06-01

    The National Center for Physical Acoustics (NCPA) at the University of Mississippi is working on the application of ultrasonic Doppler sonars in air for personnel motion detection. Two traditional Doppler sonar configurations, a monostatic and a bistatic, are being studied. In the monostatic configuration, the distance between the transmitter and the receiver is small. The proximity of the source to the receiver places a limitation on the system associated with the overloading of the receivers' input due to acoustic energy leakage from the transmitters' output. The maximum range of detection is therefore limited by the dynamic range of the acquisition system. In a bistatic Doppler ultrasonic sonar, the source and receiver are spaced apart and the acoustic energy along the direct path does not constrain the maximum acoustic power level output of the transmitter. In a monostatic configuration the acoustic signal suffers from beam spreading and natural absorption during propagation from the transmitter to the target and from the target back to the receiver. In a bistatic configuration the acoustic propagation is in one direction only and theoretically the detection distance can be twice the monostatic distance. For comparison the experiments of a human walking in a building hallway using the bistatic and monostaic Doppler sonars in air were conducted. The experimental results for human signatures from these Doppler sonars are presented and discussed.

  5. Accounting for observational uncertainties in the evaluation of low latitude turbulent air-sea fluxes simulated in a suite of IPSL model versions

    NASA Astrophysics Data System (ADS)

    Servonnat, Jerome; Braconnot, Pascale; Gainusa-Bogdan, Alina

    2015-04-01

    Turbulent momentum and heat (sensible and latent) fluxes at the air-sea interface are key components of the whole energetic of the Earth's climate and their good representation in climate models is of prime importance. In this work, we use the methodology developed by Braconnot & Frankignoul (1993) to perform a Hotelling T2 test on spatio-temporal fields (annual cycles). This statistic provides a quantitative measure accounting for an estimate of the observational uncertainty for the evaluation of low-latitude turbulent air-sea fluxes in a suite of IPSL model versions. The spread within the observational ensemble of turbulent flux data products assembled by Gainusa-Bogdan et al (submitted) is used as an estimate of the observational uncertainty for the different turbulent fluxes. The methodology holds on a selection of a small number of dominating variability patterns (EOFs) that are common to both the model and the observations for the comparison. Consequently it focuses on the large-scale variability patterns and avoids the possibly noisy smaller scales. The results show that different versions of the IPSL couple model share common large scale model biases, but also that there the skill on sea surface temperature is not necessarily directly related to the skill in the representation of the different turbulent fluxes. Despite the large error bars on the observations the test clearly distinguish the different merits of the different model version. The analyses of the common EOF patterns and related time series provide guidance on the major differences with the observations. This work is a first attempt to use such statistic on the evaluation of the spatio-temporal variability of the turbulent fluxes, accounting for an observational uncertainty, and represents an efficient tool for systematic evaluation of simulated air-seafluxes, considering both the fluxes and the related atmospheric variables. References Braconnot, P., and C. Frankignoul (1993), Testing Model

  6. Finite-Difference Solution for Laminar or Turbulent Boundary Layer Flow over Axisymmetric Bodies with Ideal Gas, CF4, or Equilibrium Air Chemistry

    NASA Technical Reports Server (NTRS)

    Hamilton, H. Harris, II; Millman, Daniel R.; Greendyke, Robert B.

    1992-01-01

    A computer code was developed that uses an implicit finite-difference technique to solve nonsimilar, axisymmetric boundary layer equations for both laminar and turbulent flow. The code can treat ideal gases, air in chemical equilibrium, and carbon tetrafluoride (CF4), which is a useful gas for hypersonic blunt-body simulations. This is the only known boundary layer code that can treat CF4. Comparisons with experimental data have demonstrated that accurate solutions are obtained. The method should prove useful as an analysis tool for comparing calculations with wind tunnel experiments and for making calculations about flight vehicles where equilibrium air chemistry assumptions are valid.

  7. Detecting excess ionizing radiation by electromagnetic breakdown of air

    SciTech Connect

    Granatstein, Victor L.; Nusinovich, Gregory S.

    2010-09-15

    A scheme is proposed for detecting a concealed source of ionizing radiation by observing the occurrence of breakdown in atmospheric air by an electromagnetic wave whose electric field surpasses the breakdown field in a limited volume. The volume is chosen to be smaller than the reciprocal of the naturally occurring concentration of free electrons. The pulse duration of the electromagnetic wave must exceed the avalanche breakdown time (10-200 ns) and could profitably be as long as the statistical lag time in ambient air (typically, microseconds). Candidate pulsed electromagnetic sources over a wavelength range, 3 mm>{lambda}>10.6 {mu}m, are evaluated. Suitable candidate sources are found to be a 670 GHz gyrotron oscillator with 200 kW, 10 {mu}s output pulses and a Transversely Excited Atmospheric-Pressure (TEA) CO{sub 2} laser with 30 MW, 100 ns output pulses. A system based on 670 GHz gyrotron would have superior sensitivity. A system based on the TEA CO{sub 2} laser could have a longer range >100 m.

  8. Intensification of winter transatlantic aviation turbulence in response to climate change

    NASA Astrophysics Data System (ADS)

    Williams, Paul D.; Joshi, Manoj M.

    2013-07-01

    Atmospheric turbulence causes most weather-related aircraft incidents. Commercial aircraft encounter moderate-or-greater turbulence tens of thousands of times each year worldwide, injuring probably hundreds of passengers (occasionally fatally), costing airlines tens of millions of dollars and causing structural damage to planes. Clear-air turbulence is especially difficult to avoid, because it cannot be seen by pilots or detected by satellites or on-board radar. Clear-air turbulence is linked to atmospheric jet streams, which are projected to be strengthened by anthropogenic climate change. However, the response of clear-air turbulence to projected climate change has not previously been studied. Here we show using climate model simulations that clear-air turbulence changes significantly within the transatlantic flight corridor when the concentration of carbon dioxide in the atmosphere is doubled. At cruise altitudes within 50-75°N and 10-60°W in winter, most clear-air turbulence measures show a 10-40% increase in the median strength of turbulence and a 40-170% increase in the frequency of occurrence of moderate-or-greater turbulence. Our results suggest that climate change will lead to bumpier transatlantic flights by the middle of this century. Journey times may lengthen and fuel consumption and emissions may increase. Aviation is partly responsible for changing the climate, but our findings show for the first time how climate change could affect aviation.

  9. Laboratory investigations of the heat and momentum transfer in the stably stratified air turbulent boundary layer above the wavy surface

    NASA Astrophysics Data System (ADS)

    Sergeev, Daniil; Troitskaya, Yuliya; Vdovin, Maxim

    2015-04-01

    the spray of droplets generation, especially heat transfer. The work was supported by RFBR grants (14-05-91767, 14-08-31740, 15-35-20953) and RSF grant 14-17-00667 and by President grant for young scientists MK-3550.2014.5 References: 1. Emanuel, K. A. Sensitivity of tropical cyclones to surface exchange coefficients and a revised steady-state model incorporating eye dynamics // J. Atmos. Sci., 52(22), 3969-3976,1995. 2. Brian K. Haus, Dahai Jeong, Mark A. Donelan, Jun A. Zhang, and Ivan Savelyev Relative rates of sea-air heat transfer and frictional drag in very high winds // GEOPHYSICAL RESEARCH LETTERS, VOL. 37, L07802, doi:10.1029/2009GL042206, 2010 3. Yu. I. Troitskaya, D.A. Sergeev, A.A. Kandaurov, G.A Baidakov, M.A. Vdovin, V.I. Kazakov Laboratory and theoretical modeling of air-sea momentum transfer under severe wind conditions // JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 117, C00J21, 13 PP., 2012 doi:10.1029/2011JC007778 4. Yu.I.Troitskaya, D.A.Sergeev, A.A.Kandaurov, M.I. Vdovin, A.A. Kandaurov, E.V.Ezhova, S.S.Zilitinkevich Momentum and buoyancy exchange in a turbulent air boundary layer over a wavy water surface. Part 2. Wind wave spectra // Nonlinear. Geoph. Processes, Vol. 20, P. 841-856, 2013.

  10. The effect of different inlet conditions of air in a rectangular channel on convection heat transfer: Turbulence flow

    SciTech Connect

    Kurtbas, Irfan

    2008-10-15

    Theoretical and empirical correlations for duct flow are given for hydrodynamically and thermally developed flow in most of previous studies. However, this is commonly not a realistic inlet configuration for heat exchanger, in which coolant flow generally turns through a serpentine shaped passage before entering heat sinks. Accordingly, an experimental investigation was carried out to determine average heat transfer coefficients in uniformly heated rectangular channel with 45 and 90 turned flow, and with wall mounted a baffle. The channel was heated through bottom side with the baffle. In present work, a detailed study was conducted for three different height of entry channel (named as the ratio of the height of entry channel to the height of test section (anti H{sub c}=h{sub c}/H)) by varying Reynolds number (Re{sub Dh}). Another variable parameter was the ratio of the baffle height to the channel height (anti H{sub b}=h{sub b}/H). Only one baffle was attached on the bottom (heating) surface. The experimental procedure was validated by comparing the data for the straight channel with no baffle. Reynolds number (Re{sub Dh}) was varied from 2800 to 30,000, so the flow was considered as only turbulent regime. All experiments were conduced with air accordingly; Prandtl number (Pr) was approximately fixed at 0.71. The results showed that average Nusselt number for {theta}=45 and {theta}=90 were 9% and 30% higher, respectively, than that of the straight channel without baffle. Likewise, the pressure drop increased up to 4.4 to 5.3 times compare to the straight channel. (author)

  11. Turbulence detection in a stenosed artery bifurcation by numerical simulation of pulsatile blood flow using the low-Reynolds number turbulence model.

    PubMed

    Ghalichi, Farzan; Deng, Xiaoyan

    2003-01-01

    The pulsatile blood flow in a partially blocked artery is significantly altered as the flow regime changes through the cardiac cycle. This paper reports on the application of a low-Reynolds turbulence model for computation of physiological pulsatile flow in a healthy and stenosed carotid artery bifurcation. The human carotid artery was chosen since it has received much attention because atherosclerotic lesions are frequently observed. The Wilcox low-Re k-omega turbulence model was used for the simulation since it has proven to be more accurate in describing transition from laminar to turbulent flow. Using the FIDAP finite element code a validation showed very good agreement between experimental and numerical results for a steady laminar to turbulent flow transition as reported in a previous publication by the same authors. Since no experimental or numerical results were available in the literature for a pulsatile and turbulent flow regime, a comparison between laminar and low-Re turbulent calculations was made to further validate the turbulence model. The results of this study showed a very good agreement for velocity profiles and wall shear stress values for this imposed pulsatile laminar flow regime. To explore further the medical aspect, the calculations showed that even in a healthy or non-stenosed artery, small instabilities could be found at least for a portion of the pulse cycle and in different sections. The 40% and 55% diameter reduction stenoses did not significantly change the turbulence characteristics. Further results showed that the presence of 75% stenoses changed the flow properties from laminar to turbulent flow for a good portion of the cardiac pulse. A full 3D simulation with this low-Re-turbulence model, coupled with Doppler ultrasound, can play a significant role in assessing the degree of stenosis for cardiac patients with mild conditions.

  12. Detection of room air contamination of angiographic CO2 with use of a gas analyzer.

    PubMed

    Culp, William C; Culp, William C

    2002-07-01

    The purpose of this study was to describe a practical method to detect room air contamination in CO2 used for angiography. Samples of CO2 with known room air contamination levels were used in a "bag system" of CO2 delivery and sampled by a gas analyzer commonly used in anesthesia. Nitrogen levels were reliably detected indicating contamination with as little as 2% air. Oxygen levels were reliably detected, indicating contamination with as little as 5% air. Measured CO2 values were unreliable with higher-than-true values at all levels except 100%. All clinically important amounts of N2 and O2 contamination were readily detected by this practical method.

  13. Adaptive Combining of Coherently Detected PPM Signals in the Presence of Atmospheric Turbulence

    NASA Technical Reports Server (NTRS)

    Fernandez, Michela Munoz; Vilnrotter, Victor A.

    2004-01-01

    Adaptive combining of experimentally obtained heterodyned pulse position modulated (PPM) signals with pulse-to-pulse coherence, in the presence of simulated spatial distortions resembling atmospheric turbulence, is demonstrated. The adaptively combined PPM signals are phased up via an LMS algorithm suitably optimized to operate with PPM in the presence of additive shot-noise. A convergence study of the algorithm is presented, and results with both computer simulated and experimentally obtained PPM signals are presented and analyzed.

  14. SWIR sky glow imaging for detection of turbulence in the upper atmosphere

    NASA Astrophysics Data System (ADS)

    Dayton, David; Nolasco, Rudy; Allen, Jeff; Myers, Mike; Gonglewski, John; Fertig, Gregory; Burns, Dennis; Mons, Ishan

    2010-08-01

    It is well known that luminance from photo-chemical reactions of hydroxyl ions in the upper atmosphere (~85 km altitude) produces a significant amount of night time radiation in the short wave infra-red (SWIR) band between 0.9 and 1.7 μm wave length. This has been demonstrated as an effective illumination source for night time imaging applications. It addition it has been shown that observation of the spatial and temporal variations of the illumination can be used to characterize atmospheric tidal wave actions in the sky glow region. These spatiotemporal variations manifest themselves as traveling wave patterns whose period and velocity are related to the wind velocity at 85 km as well as the turbulence induced by atmospheric vertical instabilities. Ground to space observation systems especially those employing adaptive optics are adversely affected by high altitude turbulence and winds. In this paper we propose the use of sky glow observations to predict and characterize image system degradation due to upper atmosphere turbulence.

  15. Aircraft Dynamic Modeling in Turbulence

    NASA Technical Reports Server (NTRS)

    Morelli, Eugene A.; Cunninham, Kevin

    2012-01-01

    A method for accurately identifying aircraft dynamic models in turbulence was developed and demonstrated. The method uses orthogonal optimized multisine excitation inputs and an analytic method for enhancing signal-to-noise ratio for dynamic modeling in turbulence. A turbulence metric was developed to accurately characterize the turbulence level using flight measurements. The modeling technique was demonstrated in simulation, then applied to a subscale twin-engine jet transport aircraft in flight. Comparisons of modeling results obtained in turbulent air to results obtained in smooth air were used to demonstrate the effectiveness of the approach.

  16. In Situ Detection of Strong Langmuir Turbulence Processes in Solar Type III Radio Bursts

    NASA Technical Reports Server (NTRS)

    Golla, Thejappa; Macdowall, Robert J.; Bergamo, M.

    2012-01-01

    The high time resolution observations obtained by the WAVES experiment of the STEREO spacecraft in solar type III radio bursts show that Langmuir waves often occur as intense localized wave packets. These wave packets are characterized by short durations of only a few ms and peak intensities, which well exceed the supersonic modulational instability (MI) thresholds. These timescales and peak intensities satisfy the criterion of the solitons collapsed to spatial scales of a few hundred Debye lengths. The spectra of these wave packets consist of primary spectral peaks corresponding to beam-resonant Langmuir waves, two or more sidebands corresponding to down-shifted and up-shifted daughter Langmuir waves, and low frequency enhancements below a few hundred Hz corresponding to daughter ion sound waves. The frequencies and wave numbers of these spectral components satisfy the resonance conditions of the modulational instability (MI). Moreover, the tricoherences, computed using trispectral analysis techniques show that these spectral components are coupled to each other with a high degree of coherency as expected of the MI type of four wave interactions. The high intensities, short scale lengths, sideband spectral structures and low frequency spectral enhancements and, high levels of tricoherences amongst the spectral components of these wave packets provide unambiguous evidence for the supersonic MI and related strong turbulence processes in type III radio bursts. The implication of these observations include: (1) the MI and related strong turbulence processes often occur in type III source regions, (2) the strong turbulence processes probably play very important roles in beam stabilization as well as conversion of Langmuir waves into escaping radiation at the fundamental and second harmonic of the electron plasma frequency, fpe, and (3) the Langmuir collapse probably follows the route of MI in type III radio bursts.

  17. Carbon Dioxide Detection and Indoor Air Quality Control.

    PubMed

    Bonino, Steve

    2016-04-01

    When building ventilation is reduced, energy is saved because it is not necessary to heat or cool as much outside air. Reduced ventilation can result in higher levels of carbon dioxide, which may cause building occupants to experience symptoms. Heating or cooling for ventilation air can be enhanced by a DCV system, which can save energy while providing a comfortable environment. Carbon dioxide concentrations within a building are often used to indicate whether adequate fresh air is being supplied to the building. These DCV systems use carbon dioxide sensors in each space or in the return air and adjust the ventilation based on carbon dioxide concentration; the higher the concentration, the more people occupy the space relative to the ventilation rate. With a carbon dioxide sensor DCV system, the fresh air ventilation rate varies based on the number ofpeople in the space, saving energy while maintaining a safe and comfortable environment.

  18. Air

    MedlinePlus

    ... do to protect yourself from dirty air . Indoor air pollution and outdoor air pollution Air can be polluted indoors and it can ... this chart to see what things cause indoor air pollution and what things cause outdoor air pollution! Indoor ...

  19. Thermal Detection of Turbulent and Laminar Dissipation in Vortex Front Motion

    NASA Astrophysics Data System (ADS)

    Hosio, J. J.; Eltsov, V. B.; Krusius, M.

    2013-06-01

    We report on direct measurements of the energy dissipated in the spin-up of the superfluid component of 3He-B. A vortex-free sample is prepared in a cylindrical container, where the normal component rotates at constant angular velocity. At a temperature of 0.20 T c, seed vortices are injected into the system using the shear-flow instability at the interface between 3He-B and 3He-A. These vortices interact and create a turbulent burst, which sets a propagating vortex front into motion. In the following process, the free energy stored in the initial vortex-free state is dissipated leading to the emission of thermal excitations, which we observe with a bolometric measurement. We find that the turbulent front contains less than the equilibrium number of vortices and that the superfluid behind the front is partially decoupled from the reference frame of the container. The final equilibrium state is approached in the form of a slow laminar spin-up as demonstrated by the slowly decaying tail of the thermal signal.

  20. Laminar-to-turbulence and relaminarization zones detection by simulation of low Reynolds number turbulent blood flow in large stenosed arteries.

    PubMed

    Tabe, Reza; Ghalichi, Farzan; Hossainpour, Siamak; Ghasemzadeh, Kamran

    2016-08-12

    Laminar, turbulent, transitional, or combine areas of all three types of viscous flow can occur downstream of a stenosis depending upon the Reynolds number and constriction shape parameter. Neither laminar flow solver nor turbulent models for instance the k-ω (k-omega), k-ε (k-epsilon), RANS or LES are opportune for this type of flow. In the present study attention has been focused vigorously on the effect of the constriction in the flow field with a unique way. It means that the laminar solver was employed from entry up to the beginning of the turbulent shear flow. The turbulent model (k-ω SST Transitional Flows) was utilized from starting of turbulence to relaminarization zone while the laminar model was applied again with onset of the relaminarization district. Stenotic flows, with 50 and 75% cross-sectional area, were simulated at Reynolds numbers range from 500 to 2000 employing FLUENT (v6.3.17). The flow was considered to be steady, axisymmetric, and incompressible. Achieving results were reported as axial velocity, disturbance velocity, wall shear stress and the outcomes were compared with previously experimental and CFD computations. The analogy of axial velocity profiles shows that they are in acceptable compliance with the empirical data. As well as disturbance velocity and wall shear stresses anticipated by this new approach, part by part simulation, are reasonably valid with the acceptable experimental studies.

  1. Laminar-to-turbulence and relaminarization zones detection by simulation of low Reynolds number turbulent blood flow in large stenosed arteries.

    PubMed

    Tabe, Reza; Ghalichi, Farzan; Hossainpour, Siamak; Ghasemzadeh, Kamran

    2016-08-12

    Laminar, turbulent, transitional, or combine areas of all three types of viscous flow can occur downstream of a stenosis depending upon the Reynolds number and constriction shape parameter. Neither laminar flow solver nor turbulent models for instance the k-ω (k-omega), k-ε (k-epsilon), RANS or LES are opportune for this type of flow. In the present study attention has been focused vigorously on the effect of the constriction in the flow field with a unique way. It means that the laminar solver was employed from entry up to the beginning of the turbulent shear flow. The turbulent model (k-ω SST Transitional Flows) was utilized from starting of turbulence to relaminarization zone while the laminar model was applied again with onset of the relaminarization district. Stenotic flows, with 50 and 75% cross-sectional area, were simulated at Reynolds numbers range from 500 to 2000 employing FLUENT (v6.3.17). The flow was considered to be steady, axisymmetric, and incompressible. Achieving results were reported as axial velocity, disturbance velocity, wall shear stress and the outcomes were compared with previously experimental and CFD computations. The analogy of axial velocity profiles shows that they are in acceptable compliance with the empirical data. As well as disturbance velocity and wall shear stresses anticipated by this new approach, part by part simulation, are reasonably valid with the acceptable experimental studies. PMID:27567769

  2. Stirring turbulence with turbulence

    NASA Astrophysics Data System (ADS)

    van de Water, Willem; Ergun Cekli, Hakki; Joosten, Rene

    2011-11-01

    We stir wind-tunnel turbulence with an active grid that consists of rods with attached vanes. The time-varying angle of these rods is controlled by random numbers. We study the response of turbulence on the statistical properties of these random numbers. The random numbers are generated by the Gledzer-Ohkitani-Yamada shell model, which is a simple dynamical model of turbulence that produces a velocity field displaying inertial-range scaling behavior. The range of scales can be adjusted by selection of shells. We find that the largest energy input and the smallest anisotropy are reached when the time scale of the random numbers matches that of the large eddies in the wind-tunnel turbulence. A large mismatch of these times creates a flow with interesting statistics, but it is not turbulence.

  3. CH+(1-0) Line Detection in a High-z Hyper-Luminous Galaxy SDP17b: the First Probe of a Massive Turbulent Region

    NASA Astrophysics Data System (ADS)

    Falgarone, E.; Zwaan, M.; Godard, B.; Bussmann, S.; Bergin, E.; Omont, A.; Bournaud, F.; Elbaz, D.; Andreani, P.

    2015-12-01

    We illustrate the power of CH+ spectroscopy at high spectral resolution with the first detection by ALMA of a CH+(J=1-0) line in an hyper-luminous galaxy, SDP17b at z=2.3. Unlike other molecular tracers, the unique chemical and spectroscopic properties of the CH+ cation make it a tracer of the turbulent energy trail, from its scale of injection to that of dissipation at which CH+ forms. In SDP17b, CH+ emission and absorption are detected. The emission line is broad and the absorption is seen against the dust continuum and the emission. The absorption probes a massive turbulent region of low density, while the emission may arise in a large number of irradiated shocks that could be located in the large turbulent region or in the star-forming disk.

  4. Detecting and defining air pollutants: one laboratory's experiences and approaches

    SciTech Connect

    Lindgren, J.L.; Krauss, H.J.; Mgebroff, J.S.

    1980-08-01

    The Texas Air Control Board is the agency responsible for maintaining the quality of the ambient air of Texas. An extensive network of continuous and noncontinuous monitors is used to defect air quality trends in the state. The samples submitted may be gaseous, liquid, or solid. X-ray fluorescence spectroscopy (XRF) is used for various elements. XRF was used specifically for lead emissions, sulfur dioxide emissions and toxic metals. However, atomic absorption is better for beryllium and arsenic. Gas chromatography (GC), high pressure liquid chromatography (HPLC), and gas chromatography/mass spectrometry (GC/MS) are employed in organic analysis as complements to each other. HPLC has been effectively used in the analysis of samples for herbicides. The defection of vinyl chloride monomer (VCM) is accomplished with a photoionization defector (PID) and flame ionization detector (FID) in series. There are many examples of a multi-instrument approach to analysis of samples. Gas chromatography and mass spectroscopy were used for nitrobenzene analysis. The complexity of ambient air sampler often requires a multinstrumental approach if the sample is to be qualitatively and quantitatively analyzed so that the information can be used for corrective action or to identify potential problems of air pollution. 2 figures. (DP)

  5. The study of the properties of turbulent stably stratified air flow over water surface by direct numerical simulation

    NASA Astrophysics Data System (ADS)

    Druzhinin, Oleg; Troitskaya, Yuliya; Zilitinkevich, Sergej

    2014-05-01

    Parameterization of turbulent momentum and heat fluxes in a turbulent, stably stratified boundary layer flow over water surface is important for numerical climate modeling and weather prediction. In this work, the detailed structure and statistical characteristics of a turbulent, stably stratified atmospheric boundary layer flow over water surface is studied by direct numerical simulation (DNS). The most difficult case for modeling is that of flows at high Reynolds numbers and sufficiently steep surface waves, when strongly non-linear effects (e.g. sheltering, boundary layer separation, vortex formation etc.) are encountered. Of special interest is the influence of the wind flow stratification on the properties of boundary-layer turbulence and the turbulent momentum and heat fluxes. In DNS a two-dimensional water wave with different wave age parameters (c/u*, where u* is the friction velocity and c is the wave celerity), wave slope ka varying from 0 to 0.2 and bulk Reynolds number Re (from 15000 to 80000) and different Richardson numbers are considered. The shape of the water wave is prescribed and does not evolve under the action of the wind. The full, 3D Navier-Stokes equations under the Boussinesq approximation are solved in curvilinear coordinates in a frame of reference moving the phase velocity of the wave. The shear driving the flow is created by an upper plane boundary moving horizontally with a bulk velocity in the x-direction. Periodic boundary conditions are considered in the horizontal (x) and lateral (y) directions, and no-slip boundary condition is considered in the vertical z-direction. The grid of 360 x 240 x 360 nodes in the x, y, and z directions is used. The Adams-Bashforth method is employed to advance the integration in time and the equation for the pressure is solved iteratively. Ensemble-averaged velocity and pressure fields are evaluated by averaging over time and the spanwise coordinate. Profiles of the mean velocity and turbulent stresses

  6. Modeling and Simulation of Turbulent Flows through a Solar Air Heater Having Square-Sectioned Transverse Rib Roughness on the Absorber Plate

    PubMed Central

    Yadav, Anil Singh; Bhagoria, J. L.

    2013-01-01

    Solar air heater is a type of heat exchanger which transforms solar radiation into heat energy. The thermal performance of conventional solar air heater has been found to be poor because of the low convective heat transfer coefficient from the absorber plate to the air. Use of artificial roughness on a surface is an effective technique to enhance the rate of heat transfer. A CFD-based investigation of turbulent flow through a solar air heater roughened with square-sectioned transverse rib roughness has been performed. Three different values of rib-pitch (P) and rib-height (e) have been taken such that the relative roughness pitch (P/e = 14.29) remains constant. The relative roughness height, e/D, varies from 0.021 to 0.06, and the Reynolds number, Re, varies from 3800 to 18,000. The results predicted by CFD show that the average heat transfer, average flow friction, and thermohydraulic performance parameter are strongly dependent on the relative roughness height. A maximum value of thermohydraulic performance parameter has been found to be 1.8 for the range of parameters investigated. Comparisons with previously published work have been performed and found to be in excellent agreement. PMID:24222752

  7. Stirring turbulence with turbulence

    NASA Astrophysics Data System (ADS)

    Cekli, Hakki Ergun; Joosten, René; van de Water, Willem

    2015-12-01

    We stir wind-tunnel turbulence with an active grid that consists of rods with attached vanes. The time-varying angle of these rods is controlled by random numbers. We study the response of turbulence on the statistical properties of these random numbers. The random numbers are generated by the Gledzer-Ohkitani-Yamada shell model, which is a simple dynamical model of turbulence that produces a velocity field displaying inertial-range scaling behavior. The range of scales can be adjusted by selection of shells. We find that the largest energy input and the smallest anisotropy are reached when the time scale of the random numbers matches that of the largest eddies of the wind-tunnel turbulence. A large mismatch of these times creates a highly intermittent random flow with interesting but quite anomalous statistics.

  8. Air monitoring and detection of chemical and biological agents

    SciTech Connect

    Leonelli, J.; Althouse, M.L.

    1999-06-01

    This volume contains the proceedings of SPIE`s remote sensing symposium which was held November 2--3, 1998 in Boston, Massachusetts. Topics of discussion include the following: system simulations, atmospheric modeling, and performance prediction studies of chemical warfare remote sensing technologies; ultraviolet laser-induced fluorescence and aerosol detection methods for remote sensing of biological warfare agents; passive detection methods for remote detection of chemical warfare agents; and lidar-based system performance assessments, demonstrations, and new concepts for chemical warfare/biological warfare detection.

  9. Cellular burning in lean premixed turbulent hydrogen-air flames: Coupling experimental and computational analysis at the laboratory scale

    NASA Astrophysics Data System (ADS)

    Day, M. S.; Bell, J. B.; Cheng, R. K.; Tachibana, S.; Beckner, V. E.; Lijewski, M. J.

    2009-07-01

    One strategy for reducing US dependence on petroleum is to develop new combustion technologies for burning the fuel-lean mixtures of hydrogen or hydrogen-rich syngas fuels obtained from the gasification of coal and biomass. Fuel-flexible combustion systems based on lean premixed combustion have the potential for dramatically reducing pollutant emissions in transportation systems, heat and stationary power generation. However, lean premixed flames are highly susceptible to fluid-dynamical combustion instabilities making robust and reliable systems difficult to design. Low swirl burners are emerging as an important technology for meeting design requirements in terms of both reliability and emissions for next generation combustion devices. In this paper, we present simulations of a lean, premixed hydrogen flame stabilized on a laboratory-scale low swirl burner. The simulations use detailed chemistry and transport without incorporating explicit models for turbulence or turbulence/chemistry interaction. Here we discuss the overall structure of the flame and compare with experimental data. We also use the simulation data to elucidate the characteristics of the turbulent flame interaction and how this impacts the analysis of experimental measurements.

  10. Dimensionality estimate of the manifold in chemical composition space for a turbulent premixed H2+air flame

    SciTech Connect

    Tonse, Shaheen R.; Brown, Nancy J.

    2003-02-26

    The dimensionality (D) of manifolds of active chemical composition space has been measured using three different approaches: the Hausdorff geometrical binning method, Principal Component Analysis, and the Grassberger-Procaccia cumulative distribution method. A series of artificial manifolds is also generated using a Monte Carlo approach to discern the advantages and limitations of the three methods. Dimensionality is quantified for different levels of turbulent intensity in a simulation of the interactions of a 2D premixed hydrogen flame with a localized region of turbulence superimposed over the cold region upstream of the flame front. The simulations are conducted using an adaptive mesh refinement code for low Mach number reacting flows. By treating the N{sub s} species and temperature of the local thermo-chemical state as a point in multi-dimensional chemical composition space, a snapshot of a flame region is mapped into chemical composition space to generate the manifold associated with the 2-D flame system. An increase in D was observed with increasing turbulent intensity for all three methods. Although each method provides useful information, the Grassberger-Procaccia method is subject to fewer artifacts than the other two thereby providing the most reliable quantification of D.

  11. Calculation of Turbulent Expansion Processes

    NASA Technical Reports Server (NTRS)

    Tollmien, Walter

    1945-01-01

    On the basis of certain formulas recently established by L. Prandtl for the turbulent interchange of momentum in stationary flows, various cases of "free turbulence" - that is, of flows without boundary walls - are treated in the present report. Prandtl puts the apparent shearing stress introduced by the turbulent momentum interchange. This present report deals first with the mixing of an air stream of uniform velocity with the adjacent still air, than with the expansion or diffusion of an air jet in the surrounding air space.

  12. USING CANINES IN SOURCE DETECTION OF INDOOR AIR POLLUTANTS

    EPA Science Inventory

    Dogs have been used extensively in law enforcement and military applications to detect narcotics and explosives for over thirty years. Dogs are regularly used in arson investigations to detect accelerants since they are much more accurate at discriminating between accelerants an...

  13. New Generation Meteorological Satellite Imager Aviation Decision Support Applications for Detection of Convection, Turbulence, and Volcanic Ash

    NASA Astrophysics Data System (ADS)

    Feltz, Wayne

    2016-04-01

    A suite of aviation related decision support products have been in development to meet GOES-R science requirements since 2008 and are being evaluated to assess meteorological hazards to aircraft in flight derived from the current generation of European Spinning Enhanced Visible and Infrared Imager (SEVIRI) imager data. This presentation will focus on GOES-R Advanced Baseline Imager (ABI) measurement requirements relating to satellite-based aviation convective, turbulence, and volcanic ash/SO2 products that can be applied globally on next generation geostationary imagers including the Japanese Himawari, South Korean COMS (AMI), and European Metop-SG imagers. These new methodologies have relevance on current generation GOES and SEVIRI imagers, and overview will include discussion on how product utility has been improved through satellite GOES-R/JPSS Proving Ground NOAA testbed activities. Satellite-based decision support for aviation context toward improvement of future air transportation route planning and warning for the general public with emphasis on successfully bridging research to operations will also be discussed with anticipated October 2016 launch of GOES-R.

  14. AIRS Detection of Dust: Global Map for July 2003

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The averaged brightness temperature differences between the 961 and 1231 cm-1 AIRS channels for July 2003, reveal long range transport of Sahara Dust across the Atlantic.

    The Atmospheric Infrared Sounder Experiment, with its visible, infrared, and microwave detectors, provides a three-dimensional look at Earth's weather. Working in tandem, the three instruments can make simultaneous observations all the way down to the Earth's surface, even in the presence of heavy clouds. With more than 2,000 channels sensing different regions of the atmosphere, the system creates a global, 3-D map of atmospheric temperature and humidity and provides information on clouds, greenhouse gases, and many other atmospheric phenomena. The AIRS Infrared Sounder Experiment flies onboard NASA's Aqua spacecraft and is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., under contract to NASA. JPL is a division of the California Institute of Technology in Pasadena.

  15. Remote sensing of turbulence in the clear atmosphere with 2-micron lidars

    NASA Technical Reports Server (NTRS)

    Martinson, Robert J.; Flint, John H.

    1994-01-01

    The development of an eye-safe, airborne LIDAR that exploits the decorrelation of the heterodyne signal to detect clear air turbulence is reported. A one watt average power transmitter is capable of detecting clear air turbulence to over 20 km is subvisual cirrus (an environment highly correlated with instabilities of sratified shear layers). In the absence of subvisual cirrus, a 4 km detection range is maintained. A table depicting the warning time in seconds with respect to the aircraft speed and instrument range (in kilometers) is presented.

  16. A simple method for the detection of PM2.5 air pollutions using MODIS data

    NASA Astrophysics Data System (ADS)

    Kato, Yoshinobu

    2016-05-01

    In recent years, PM2.5 air pollution is a social and transboundary environmental issue with the rapid economic growth in many countries. As PM2.5 is small and includes various ingredients, the detection of PM2.5 air pollutions by using satellite data is difficult compared with the detection of dust and sandstorms. In this paper, we examine various images (i.e., single-band images, band-difference images, RGB composite color images) to find a good method for detecting PM2.5 air pollutions by using MODIS data. A good method for the detection of PM2.5 air pollution is {R, G, B = band10, band9, T11}, where T11 is the brightness temperature of band31. In this composite color image, PM2.5 air pollutions are represented by light purple or pink color. This proposed method is simpler than the method by Nagatani et al. (2013), and is useful to grasp the distribution of PM2.5 air pollutions in the wide area (e.g., from China and India to Japan). By comparing AVI image with the image by proposed method, DSS and PM2.5 air pollutions can be classified.

  17. Failure Monitoring and Leakage Detection for Underground Storage of Compressed Air Energy in Lined Rock Caverns

    NASA Astrophysics Data System (ADS)

    Kim, Hyung-Mok; Rutqvist, Jonny; Kim, Hyunwoo; Park, Dohyun; Ryu, Dong-Woo; Park, Eui-Seob

    2016-02-01

    Underground compressed air energy storage (CAES) in lined rock caverns (LRCs) provides a promising solution for storing energy on a large scale. One of the essential issues facing underground CAES implementation is the risk of air leakage from the storage caverns. Compressed air may leak through an initial defect in the inner containment liner, such as imperfect welds and construction joints, or through structurally damaged points of the liner during CAES operation for repeated compression and decompression cycles. Detection of the air leakage and identification of the leakage location around the underground storage cavern are required. In this study, we analyzed the displacement (or strain) monitoring method to detect the mechanical failure of liners that provides major pathways of air leakage using a previously developed numerical technique simulating the coupled thermodynamic and geomechanical behavior of underground CAES in LRCs. We analyzed the use of pressure monitoring to detect air leakage and characterize the leakage location. From the simulation results, we demonstrated that tangential strain monitoring at the inner face of sealing liners could enable one to detect failure. We also demonstrated that the use of the cross-correlation method between pressure history data measured at various sensors could identify the air leak location. These results may help in the overall design of a monitoring and alarm system for the successful implementation and operation of CAES in LRCs.

  18. Linearity of Air-Biased Coherent Detection for Terahertz Time-Domain Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Tianwu; Iwaszczuk, Krzysztof; Wrisberg, Emil Astrup; Denning, Emil Vosmar; Jepsen, Peter Uhd

    2016-06-01

    The performance of air-biased coherent detection (ABCD) in a broadband two-color laser-induced air plasma system for terahertz time-domain spectroscopy (THz-TDS) has been investigated. Fundamental parameters of the ABCD detection, including signal-to-noise ratio (SNR), dynamic range (DR), and linearity of detection have been characterized. Moreover, the performance of a photomultiplier tube (PMT) and an avalanche photodiode (APD) as photodetector in the ABCD have been compared. We have observed nonlinear behavior of PMT detector, which leads to artificial gain factor in TDS spectroscopy. The APD turns out to have superior linearity and three times higher dynamic compared to the PMT.

  19. NO concentration imaging in turbulent nonpremixed flames

    SciTech Connect

    Schefer, R.W.

    1993-12-01

    The importance of NO as a pollutant species is well known. An understanding of the formation characteristics of NO in turbulent hydrocarbon flames is important to both the desired reduction of pollutant emissions and the validation of proposed models for turbulent reacting flows. Of particular interest is the relationship between NO formation and the local flame zone, in which the fuel is oxidized and primary heat release occurs. Planar imaging of NO provides the multipoint statistics needed to relate NO formation to the both the flame zone and the local turbulence characteristics. Planar imaging of NO has been demonstrated in turbulent flames where NO was seeded into the flow at high concentrations (2000 ppm) to determine the gas temperature distribution. The NO concentrations in these experiments were significantly higher than those expected in typical hydrocarbon-air flames, which require a much lower detectability limit for NO measurements. An imaging technique based on laser-induced fluorescence with sufficient sensitivity to study the NO formation mechanism in the stabilization region of turbulent lifted-jet methane flames.

  20. Detection of severe air pollution from multidirectional perspectives

    NASA Astrophysics Data System (ADS)

    Mukai, Sonoyo; Sano, Itaru; Nakata, Makiko; Yasumoto, Masayoshi

    2015-10-01

    This work intends to consider the retrieval algorithms of remote sensing for severe air pollutions. In these cases mixture of aerosols and clouds, namely aerosols in cloudy scenes and/or clouds in heavy aerosol episode, are often occurred. Aerosol retrieval in the hazy atmosphere has been achieved based on radiation simulation method of successive order of scattering (MSOS). JAXA has been developing the new Earth observing system GCOM-C satellite. GCOM-C will be launched in early of 2017 and board the polarization sensor SGLI. The SGLI has multi (19)-channels as MODIS and measures polarized reflected sunlight at wavelengths of 0.679 μm and 0.869 μm as POLDER. The radiance and polarization degree are taken into account here in the severe biomass burning episode over Borneo islands in Indonesia observed by PARASOL / POLDER and Aqua/MODIS. As a result the possibility of JAXA / GCOM-C / SGLI related to remote sensing for a mixture case of aerosols and clouds can be examined.

  1. Radio detection of cosmic ray induced air showers at the Pierre Auger Observatory

    NASA Astrophysics Data System (ADS)

    Fliescher, Stefan; Pierre Auger Collaboration

    2012-01-01

    AERA—the Auger Engineering Radio Array—is currently being set up at the southern site of the Pierre Auger Observatory. AERA will explore the potential of the radio-detection technique to cosmic ray induced air showers with respect to the next generation of large-scale surface detectors. As AERA is co-located with the low-energy enhancements of the Pierre Auger Observatory, the observation of air showers in coincidence with the Auger surface and fluorescence detector will allow to study the radio emission processes in detail and to calibrate the radio signal. Finally, the combined reconstruction of shower parameters with three independent techniques promises new insights into the nature of cosmic rays in the transition region from 1017 to 1019 eV.Besides the detection of coherent radiation in the MHz frequency range, the setups AMBER—Air-shower Microwave Bremsstrahlung Experimental Radiometer—and MIDAS—MIcrowave Detection of Air Showers—prepare to check the possibility to detect air showers due the emission of molecular bremsstrahlung in the GHz range at the Auger site.This article presents the status of the radio-detection setups and discusses their physics potential as well as experimental challenges. Special focus is laid on the first stage of AERA which is the startup to the construction of a 20 km2 radio array.

  2. Detection of Upward Air Showers with the EUSO Experiments

    NASA Technical Reports Server (NTRS)

    Takahashi, Y.; Hillman, L.; Zuccaro, Al; Adams, J.; Cline, D.

    2003-01-01

    Upward-going showers in the atmosphere can be detected by an orbiting satellite with appropriate instrumentation. If the method only uses directional Cherenkov radiation, it is difficult to discriminate the red shower events from the background noises of very short pulse. A spectroscopic polychromatic optical design can intentionally blur the focusing of photons at shorter wavelengths (300 - 330 nm), spreading the image size to 2 x 2 or 3 x 3 pixels. False triggers due to random chance coincidence of noises can be drastically reduced with a spectroscopic polychromatic, refractive telescope.

  3. Evolution of the air/SF6 turbulent mixing zone for different lengths of SF6: shock tube visualizations and 3D simulations

    NASA Astrophysics Data System (ADS)

    Haas, Jean-Francois; Griffond, Jerome; Souffland, Denis; Bouzgarrou, Ghazi; Bury, Yannick; Jamme, Stephane

    2015-11-01

    A turbulent mixing zone (TMZ) is created in a vertical shock tube (based in ISAE DAEP) when a Mach 1.2 shock wave in air accelerates impulsively to 70 m/s an air/SF6 interface. The gases are initially separated by a thin nitrocellulose membrane maintained flat and parallel to the shock by two wire grids. The upper grid (SF6 side) of square mesh spacing hu 1.8 or 12.1 mm is expected to seed perturbation for the Richtmyer-Meshkov instability (RMI) while the lower grid with hl 1 mm is needed to prevent the membrane from bulging prior to the shot. The experiments were carried out for different lengths L of SF6 between the initial interface and the shock tube's end plate: 10, 15, 20, 25 and 30 cm. The time resolved Schlieren image processing based on space and frequency filtering yields similar evolution for the TMZ thickness. Before reshock, the thickness grows initially fast then slows down and reaches different values (10 to 14 mm) according to L. Soon after reshock, the TMZ thickness growths rate is 21 mm/ms independently of L and hu. Numerical Schlieren images generated from 3D numerical simulations (performed at CEA DAM IDF) are analyzed as the experimental ones for L 15 and 25 cm and for hu 1.8 and 12.1 mm. The very weak experimental dependence on hu is not obtained by simulation as expected from dimensional reasoning. This discrepancy remains paradoxical.

  4. Severe turbulence and maneuvering from airline flight records

    NASA Technical Reports Server (NTRS)

    Wingrove, R. C.; Basch, R. E., Jr.

    1992-01-01

    Digital flight records from reported clear-air turbulence incidents are used to determine winds, to determine maneuver G loads, and to analyze control problems. Severe turbulence is found downwind of mountains and thunderstorms associated with vortices in atmospheric waves. It is also found in strong updrafts above thunderstorm buildups that are not detected by onboard weather radar. An important finding is that there are large maneuvering loads in over half of the reported clear-air turbulence incidents. Maneuvering loads are determined through an analysis of the short-term variations in elevator deflection and aircraft pitch angle. For altitude control in mountain waves the results indicate that small pitch angle changes with proper timing are sufficient to counter the vertical winds. For airspeed control in strong mountain waves, however, there is neither the available thrust nor the quickness in engine response necessary to counter the large and rapid variations in horizontal wind.

  5. Detection of the transitional layer between laminar and turbulent flow areas on a wing surface. [using an accelerometer to measure pressure levels during wind tunnel tests

    NASA Technical Reports Server (NTRS)

    Hood, W. R.

    1980-01-01

    A system is disclosed for detecting the laminar to turbulent boundary layer transition on a surface while simultaneously taking pressure measurements. The system uses an accelerometer for producing electrical signals proportional to the noise levels along the surface and a transducer for producing electrical signals proportional to pressure along the surface. The signals generated by the accelerometer and transducer are sent to a data reduction system for interpretation and storage.

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

    PubMed

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

    2014-05-28

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

  7. Radio detection of extensive air showers at the Pierre Auger Observatory

    NASA Astrophysics Data System (ADS)

    Berat, C.

    2013-08-01

    The Pierre Auger Observatory explores the potential of radio-detection techniques to measure extensive air showers (EAS) induced by ultra-high energy cosmic rays. To study in detail the mechanisms responsible for radio emission in the MHz range, the Auger Engineering Radio Array has been installed at the Observatory. Presently consisting of 24 radio-detection stations, this number will grow to 150 units covering an area of almost 20 km2. Novel detection techniques based on the GHz emission from the EAS are currently being studied. AMBER (Air-shower Microwave Bremsstrahlung Experimental Radiometer) and MIDAS (Microwave Detection of Air Showers) are prototypes for a large imaging dish antenna. In EASIER (Extensive Air Shower Identification using Electron Radiometer), the microwave emission is detected by antenna horns located on each surface detector. MIDAS is a self-triggering system while AMBER and EASIER use the trigger from the Auger detectors to record the emission. The status of these radio-detection R&D efforts at the Pierre Auger Observatory will be reported.

  8. Generation and detection of whistler wave induced space plasma turbulence at Gakona, Alaska

    NASA Astrophysics Data System (ADS)

    Rooker, L. A.; Lee, M. C.; Pradipta, R.; Watkins, B. J.

    2013-07-01

    We report on high-frequency wave injection experiments using the beat wave technique to study the generation of very-low-frequency (VLF) whistler waves in the ionosphere above Gakona, Alaska. This work is aimed at investigating whistler wave interactions with ionospheric plasmas and radiation belts. The beat wave technique involves injecting two X-mode waves at a difference frequency in the VLF range using the High-frequency Active Auroral Research Program (HAARP) heating facility. A sequence of beat wave-generated whistler waves at 2, 6.5, 7.5, 8.5, 9.5, 11.5, 15.5, 22.5, 28.5 and 40.5 kHz were detected in our 2011 experiments. We present Modular Ultra-high-frequency Ionospheric Radar (MUIR) (446 MHz) measurements of ion lines as the primary diagnosis of ionospheric plasma effects caused by beat wave-generated whistler waves. A magnetometer and digisonde were used to monitor the background ionospheric plasma conditions throughout the experiments. Our theoretical and data analyses show that VLF whistler waves can effectively interact with ionospheric plasmas via two different four-wave interaction processes leading to energization of electrons and ions. These preliminary results support our Arecibo experiments to study NAU-launched 40.75 kHz whistler wave interactions with space plasmas.

  9. Influence and impact of the parametrization of the turbulent air-sea fluxes on atmospheric moisture and convection in the tropics

    NASA Astrophysics Data System (ADS)

    Torres, Olivier; Braconnot, Pascale; Gainusa-Bogdan, Alina; Hourdin, Frédéric; Marti, Olivier; Pelletier, Charles

    2016-04-01

    The turbulent fluxes across the ocean/atmosphere interface represent one of the principal driving forces of the global atmospheric and oceanic circulation and are also responsible for various phenomena like the water supply to the atmospheric column, which itself is extremely important for atmospheric convection. Although the representation of these fluxes has been the subject of major studies, it still remains a very challenging problem. Our aim is to better understand the role of these fluxes in climate change experiments and in the equator-pole redistribution of heat and water by the oceanic and atmospheric circulation. For this, we are developing a methodology starting from idealized 1D experiments and going all the way up to fully coupled ocean-atmosphere simulations of past and future climates. The poster will propose a synthesis of different simulations we have performed with a 1D version of the LMDz atmosphere model towards a first objective of understanding how different parameterizations of the turbulent fluxes affect the moisture content of the atmosphere and the feedback with the atmospheric boundary layer and convection schemes. Air-sea fluxes are not directly resolved by the models because they are subgrid-scale phenomena and are therefore represented by parametrizations. We investigate the differences between several 1D simulations of the TOGA-COARE campaign (1992-1993, Pacific warm pool region), for which 1D boundary conditions and observations are available to test the results of atmospheric models. Each simulation considers a different version of the LMDz model in terms of bulk formula (four) used to compute the turbulent fluxes. We also consider how the representation of gustiness in these parameterizations affects the results. The use of this LMDz test case (very constrained within an idealized framework) allows us to determine how the response of surface fluxes helps to reinforce or damp the atmospheric water vapor content or cloud feedbacks

  10. Modeling of Air Attenuation Effects on Gamma Detection at Altitude

    SciTech Connect

    R. S. Detwiler

    2002-10-01

    This paper focuses on modeling the detection capabilities of NaI sensor systems at high altitudes for ground sources. The modeling was done with the Monte Carlo N-Transport (MCNP) code developed at Los Alamos National Laboratory. The specific systems modeled were the fixed wing and helicopter aircraft sensor systems, assets of the U. S. Department of Energy's National Nuclear Security Administration Nevada Operations Office (NNSA/NV) Aerial Measuring System (AMS). In previous (2001) modeling, Sodium Iodine (NaI) detector responses were simulated for both point and distributed surface sources as a function of gamma energy and altitude. For point sources, photo-peak efficiencies were calculated for a zero radial distance and an offset equal to the altitude. For distributed sources approximating an infinite plane, gross count efficiencies were calculated and normalized to a uniform surface deposition of 1 {micro}Ci/m{sup 2}. To validate the calculations, benchmark measurements were made for simple source-detector configurations. The 2002 continuation of the modeling presented here includes checking models against available data, and modifications to allow more effective and accurate directional biasing of ground point and distributed sources. Fixed-wing data results will be shown for two point sources as a function of altitude.

  11. The Turbulent Boundary Layer Near the Air-Water Interface on a Surface-Piercing Flat Plate

    NASA Astrophysics Data System (ADS)

    Washuta, Nathan; Masnadi, Naeem; Duncan, James H.

    2015-11-01

    Turbulent fluctuations in the vicinity of the water free surface along a flat, vertically oriented surface-piercing plate are studied experimentally using a laboratory-scale experiment. In this experiment, a meter-wide stainless steel belt travels horizontally in a loop around two rollers with vertically oriented axes, which are separated by 7.5 meters. This belt device is mounted inside a large water tank with the water level set just below the top edge of the belt. The belt, rollers, and supporting frame are contained within a sheet metal box to keep the device dry except for one 6-meter-long straight test section between rollers. The belt is launched from rest with a 3- g acceleration in order to quickly reach steady state velocity. This creates a temporally evolving boundary layer analogous to the spatially evolving boundary layer created along a flat-sided ship moving at the same velocity, with a length equivalent to the length of belt that has passed the measurement region since the belt motion began. Cinematic Stereo PIV measurements are performed in planes parallel to the free surface by imaging the flow from underneath the tank in order to study the modification of the boundary layer flow field due to the effects of the water free surface. The support of the Office of Naval Research under grant N000141110029 is gratefully acknowledged.

  12. Satellite sensing of submerged fossil turbulence and zombie turbulence

    NASA Astrophysics Data System (ADS)

    Gibson, Carl H.

    2004-11-01

    Surface brightness anomalies from a submerged municipal wastewater outfall trapped by buoyancy in an area 0.1 km^2 are surprisingly detected from space satellites in areas > 200 km^2. How is this possible? Microstructure measurements near the outfall diffuser reveal enhanced turbulence and temperature dissipation rates above the 50 m trapping depth. Near-vertical radiation of internal waves by fossil and zombie turbulence microstructure patches produce wind ripple smoothing with 30-50 m internal wave patterns in surface Fourier brightness anomalies near the outfall. Detections at 10-14 km distances are at 100-220 m bottom boundary layer (BBL) fossil turbulence scales. Advected outfall fossils form zombie turbulence patches in internal wave patterns as they extract energy, vorticity, turbulence and ambient vertical internal wavelength information as their density gradients are tilted by the waves. As the zombies fossilize, patterned energy radiates near-vertically to produce the detected Fourier anomalies. Zombie turbulence patches beam extracted energy in a preferred direction with a special frequency, like energized metastable molecules in a chemical maser. Thus, kilowatts to produce the submerged field of advected fossil outfall turbulence patches are amplified by beamed zombie turbulence maser action (BZTMA) into megawatts of turbulence dissipation to affect sea surface brightness on wide surface areas using gigawatts of BBL fossil turbulence wave energy available.

  13. A k-omega multivariate beta PDF for supersonic turbulent combustion

    NASA Technical Reports Server (NTRS)

    Alexopoulos, G. A.; Baurle, R. A.; Hassan, H. A.

    1993-01-01

    In a recent attempt by the authors at predicting measurements in coaxial supersonic turbulent reacting mixing layers involving H2 and air, a number of discrepancies involving the concentrations and their variances were noted. The turbulence model employed was a one-equation model based on the turbulent kinetic energy. This required the specification of a length scale. In an attempt at detecting the cause of the discrepancy, a coupled k-omega joint probability density function (PDF) is employed in conjunction with a Navier-Stokes solver. The results show that improvements resulting from a k-omega model are quite modest.

  14. Detection of Mycoplasma hyopneumoniae by Air Sampling with a Nested PCR Assay

    PubMed Central

    Stärk, Katharina D. C.; Nicolet, Jacques; Frey, Joachim

    1998-01-01

    This article describes the first successful detection of airborne Mycoplasma hyopneumoniae under experimental and field conditions with a new nested PCR assay. Air was sampled with polyethersulfone membranes (pore size, 0.2 μm) mounted in filter holders. Filters were processed by dissolution and direct extraction of DNA for PCR analysis. For the PCR, two nested pairs of oligonucleotide primers were designed by using an M. hyopneumoniae-specific DNA sequence of a repeated gene segment. A nested PCR assay was developed and used to analyze samples collected in eight pig houses where respiratory problems had been common. Air was also sampled from a mycoplasma-free herd. The nested PCR was highly specific and 104 times as sensitive as a one-step PCR. Under field conditions, the sampling system was able to detect airborne M. hyopneumoniae on 80% of farms where acute respiratory disease was present. No airborne M. hyopneumoniae was detected on infected farms without acute cases. The chance of successful detection was increased if air was sampled at several locations within a room and at a lower air humidity. PMID:9464391

  15. A Theory and Model of Conflict Detection in Air Traffic Control: Incorporating Environmental Constraints

    ERIC Educational Resources Information Center

    Loft, Shayne; Bolland, Scott; Humphreys, Michael S.; Neal, Andrew

    2009-01-01

    A performance theory for conflict detection in air traffic control is presented that specifies how controllers adapt decisions to compensate for environmental constraints. This theory is then used as a framework for a model that can fit controller intervention decisions. The performance theory proposes that controllers apply safety margins to…

  16. Prediction of hydrodynamics and chemistry of confined turbulent methane-air flames with attention to formation of oxides of nitrogen

    NASA Technical Reports Server (NTRS)

    Elghobashi, S.; Spalding, D. B.; Srivatsa, S. K.

    1977-01-01

    A formulation of the governing partial differential equations for fluid flow and reacting chemical species in a tubular combustor is presented. A numerical procedure for the solution of the governing differential equations is described, and models for chemical equilibrium and chemical kinetics calculations are presented. The chemical equilibrium model is used to characterize the hydrocarbon reactions. The chemical kinetics model is used to predict the concentrations of the oxides of nitrogen. The combustor consists of a cylindrical duct of varying cross sections with concentric streams of gaseous fuel and air entering the duct at one end. Four sample cases with specified inlet and boundary conditions are considered, and the results are discussed

  17. Detection of virulent Rhodococcus equi in exhaled air samples from naturally infected foals.

    PubMed

    Muscatello, G; Gilkerson, J R; Browning, G F

    2009-03-01

    Virulent Rhodococcus equi causes pyogranulomatous bronchopneumonia in foals. The route of infection of foals has been considered to be inhalation of aerosolized bacteria from soil that is contaminated with equine feces. Thus, disease caused by R. equi has been regarded as an opportunistic infection of environmental origin and not a contagious disease. In this study, we report the exhalation of virulent R. equi from the respiratory tract of naturally infected foals. A handheld air-monitoring system was used to recover virulent R. equi from the exhaled breath of foals, and the concentration of virulent R. equi organisms in exhaled air was compared to the concentration in environmental air samples taken from the holding pens and lane areas on farms. R. equi strains carrying the vapA gene of the virulence plasmid were detected by using colony blotting and DNA hybridization techniques in cultures of exhaled air from 67% (37/55) of foals tested. The concentration of virulent R. equi organisms in exhaled air from foals was significantly higher than that in environmental air (P<0.001). There were no significant differences in the median concentrations of virulent R. equi bacteria exhaled by clinically healthy or diseased foals. The high concentrations of virulent R. equi bacteria in exhaled air suggested that aerosol transmission between foals is possible and may have a significant impact on the prevalence of R. equi pneumonia on farms. The air sampling technique described is potentially useful as a noninvasive method for the detection and quantification of virulent R. equi in the respiratory tract of foals.

  18. Turbulent Navier-Stokes Flow Analysis of an Advanced Semispan Diamond-Wing Model in Tunnel and Free Air at High-Lift Conditions

    NASA Technical Reports Server (NTRS)

    Ghaffari, Farhad; Biedron, Robert T.; Luckring, James M.

    2002-01-01

    Turbulent Navier-Stokes computational results are presented for an advanced diamond wing semispan model at low-speed, high-lift conditions. The numerical results are obtained in support of a wind-tunnel test that was conducted in the National Transonic Facility at the NASA Langley Research Center. The model incorporated a generic fuselage and was mounted on the tunnel sidewall using a constant-width non-metric standoff. The computations were performed at to a nominal approach and landing flow conditions.The computed high-lift flow characteristics for the model in both the tunnel and in free-air environment are presented. The computed wing pressure distributions agreed well with the measured data and they both indicated a small effect due to the tunnel wall interference effects. However, the wall interference effects were found to be relatively more pronounced in the measured and the computed lift, drag and pitching moment. Although the magnitudes of the computed forces and moment were slightly off compared to the measured data, the increments due the wall interference effects were predicted reasonably well. The numerical results are also presented on the combined effects of the tunnel sidewall boundary layer and the standoff geometry on the fuselage forebody pressure distributions and the resulting impact on the configuration longitudinal aerodynamic characteristics.

  19. A comparison of airborne eddy correlation and bulk aerodynamic methods for ocean-air turbulent fluxes during cold-air outbreaks

    NASA Technical Reports Server (NTRS)

    Chou, Shu-Hsien

    1993-01-01

    The viscous interfacial-sublayer model of Liu et al. (1979) is used to derive four bulk schemes (LKB, FG, D, and DB), with the flux-profile relationships of Lie et al., Francey and Garratt (1981), Dyer (1974), and Dyer and Bradley (1982). These schemes, with stability-dependent transfer coefficients, are tested against the eddy-correlation fluxes measured at the 50-m flight level above the western Atlantic Ocean during cold-air outbreaks. The bulk fluxes of momentum (tau), sensible heat (H), and latent heat (E) are found to increase with various von Karman constants. The dependence of transfer coefficients on wind speeds and roughness lengths is discussed. The transfer coefficients for tau and E agree excellently between LKB and FG. The ratio of the coefficent for H of LKB to that of FG, increasing with decreasing stability, is very sensitive to stability at low winds, but approaches the neutral value of 1.25 at high winds.

  20. A dedicated on-line detecting system for auto air dryers

    NASA Astrophysics Data System (ADS)

    Shi, Chao-yu; Luo, Zai

    2013-10-01

    According to the correlative automobile industry standard and the requirements of manufacturer, this dedicated on-line detecting system is designed against the shortage of low degree automatic efficiency and detection precision of auto air dryer in the domestic. Fast automatic detection is achieved by combining the technology of computer control, mechatronics and pneumatics. This system can detect the speciality performance of pressure regulating valve and sealability of auto air dryer, in which online analytical processing of test data is available, at the same time, saving and inquiring data is achieved. Through some experimental analysis, it is indicated that efficient and accurate detection of the performance of auto air dryer is realized, and the test errors are less than 3%. Moreover, we carry out the type A evaluation of uncertainty in test data based on Bayesian theory, and the results show that the test uncertainties of all performance parameters are less than 0.5kPa, which can meet the requirements of operating industrial site absolutely.

  1. Prediction of hydrodynamics and chemistry of confined turbulent methane-air frames in a two concentric tube combustor

    NASA Technical Reports Server (NTRS)

    Markatos, N. C.; Spalding, D. B.; Srivatsa, S. K.

    1978-01-01

    A formulation of the governing partial differential equations for fluid flow and reacting chemical species in a two-concentric-tube combustor is presented. A numerical procedure for the solution of the governing differential equations is described and models for chemical-equilibrium and chemical-kinetics calculations are presented. The chemical-equilibrium model is used to characterize the hydrocarbon reactions. The chemical-kinetics model is used to predict the concentrations of the oxides of nitrogen. The combustor considered consists of two coaxial ducts. Concentric streams of gaseous fuel and air enter the inlet duct at one end; the flow then reverses and flows out through the outer duct. Two sample cases with specified inlet and boundary conditions are considered and the results are discussed.

  2. Biological threat detection in the air and on the surface: how to define the risk.

    PubMed

    Trafny, Elżbieta Anna; Lewandowski, Rafał; Stępińska, Małgorzata; Kaliszewski, Miron

    2014-08-01

    The improvements in the existing methods of rapid detection and biological pathogen surveillance are still needed. The new spectroscopic methods that rely on the unique structural features and intrinsic fluorescence of microorganisms are well fitted for monitoring the spread of airborne biological agents or their reagentless detection in the air, and these methods may bring a new quality to bioaerosols remote detection. This review describes the problem of the confidence in the environmental testing results that may affect clearance standard, sampling techniques, and the estimation of risk of human exposure to the low concentrations of harmful microorganisms during bioterrorist event or naturally occurring outbreaks. Higher recovery efficiency of dangerous biological agents from the air and contaminated surfaces would enable more reliable environmental human risk exposure assessment. PMID:24917429

  3. An air fluorescence imaging system for the detection of radiological contamination

    NASA Astrophysics Data System (ADS)

    Inrig, Elizabeth; Erhardt, Lorne; Koslowsky, Vernon; Andrews, Bob; Ing, Harry; Dick, Michael; Forget, Patrick

    2011-05-01

    On-site detection and measurement of the activity and extent of alpha (α) contamination presents a significant challenge to radiation detection personnel. Due to the short range of these particles, conventional detection techniques involve bringing a probe within a few centimetres of the suspect area. Performing a thorough survey of an area is a time consuming, painstaking, and potentially dangerous task, as personnel may be exposed to harmful radiation. Conventional detectors may have fragile Mylar windows which are highly prone to breakage. The instrumentation under development employs a novel approach: instead of detecting the radiation directly, it detects radiation-induced air fluorescence surrounding the contaminated area. Optical imaging is used to determine the spatial extent of the contamination, providing a much more rapid, accurate and robust tool for in-situ contamination measurements. A mobile, near-field, wide-angle, fast optical system has been designed and constructed to detect and image this radiation-induced air fluorescence. It incorporates large-area position-sensitive photo-multiplier tubes, UV filters, a specially constructed fast electronic shutter, and an aspherical phase mask to significantly increase the instrument's depth-of-field. First tests indicate that a 0.3 μCi α source can be detected in less than 10 seconds at a standoff distance of 1.5 meters.

  4. Biomimetic air sampling for detection of low concentrations of molecules and bioagents : LDRD 52744 final report.

    SciTech Connect

    Hughes, Robert Clark

    2003-12-01

    Present methods of air sampling for low concentrations of chemicals like explosives and bioagents involve noisy and power hungry collectors with mechanical parts for moving large volumes of air. However there are biological systems that are capable of detecting very low concentrations of molecules with no mechanical moving parts. An example is the silkworm moth antenna which is a highly branched structure where each of 100 branches contains about 200 sensory 'hairs' which have dimensions of 2 microns wide by 100 microns long. The hairs contain about 3000 pores which is where the gas phase molecules enter the aqueous (lymph) phase for detection. Simulations of diffusion of molecules indicate that this 'forest' of hairs is 'designed' to maximize the extraction of the vapor phase molecules. Since typical molecules lose about 4 decades in diffusion constant upon entering the liquid phase, it is important to allow air diffusion to bring the molecule as close to the 'sensor' as possible. The moth acts on concentrations as low as 1000 molecules per cubic cm. (one part in 1e16). A 3-D collection system of these dimensions could be fabricated by micromachining techniques available at Sandia. This LDRD addresses the issues involved with extracting molecules from air onto micromachined structures and then delivering those molecules to microsensors for detection.

  5. Air-brush multi-walled carbon nanotube capacitive sensor for dimethyl methylphosphonate detection

    NASA Astrophysics Data System (ADS)

    Jing, Hongjun; Jiang, Yadong; Du, Xiaosong

    2012-10-01

    Multi-walled carbon nanotube (MWNT) films were prepared on interdigital electrodes by air-brush technique, and their sensing properties to dimethyl methylphosphonate (DMMP) were studied. The MWNT films were observed by scanning electron microscope. The capacitive response to different concentrations of DMMP vapor was investigated at room temperature. The results showed that the capacitance and loss tangent of the air-brush MWNT sensor both decreased rapidly in varying concentrations ranging from 2.4 to 12 ppm. The sensitivity of capacitance was higher than that of the loss tangent at all the concentrations of DMMP vapors. The sensor exhibited high sensitivity and fast response for DMMP vapor detection.

  6. Predicting two-dimensional turbulence

    NASA Astrophysics Data System (ADS)

    Cerbus, R. T.; Goldburg, W. I.

    2015-04-01

    Prediction is a fundamental objective of science. It is more difficult for chaotic and complex systems like turbulence. Here we use information theory to quantify spatial prediction using experimental data from a turbulent soap film. At high Reynolds number, Re, where a cascade exists, turbulence becomes easier to predict as the inertial range broadens. The development of a cascade at low Re is also detected.

  7. Detection and quantification of reactive oxygen species (ROS) in indoor air.

    PubMed

    Montesinos, V Nahuel; Sleiman, Mohamad; Cohn, Sebastian; Litter, Marta I; Destaillats, Hugo

    2015-06-01

    Reactive oxygen species (ROS), such as free radicals and peroxides, are environmental trace pollutants potentially associated with asthma and airways inflammation. These compounds are often not detected in indoor air due to sampling and analytical limitations. This study developed and validated an experimental method to sample, identify and quantify ROS in indoor air using fluorescent probes. Tests were carried out simultaneously using three different probes: 2',7'-dichlorofluorescin (DCFH) to detect a broad range of ROS, Amplex ultra Red® (AuR) to detect peroxides, and terephthalic acid (TPA) to detect hydroxyl radicals (HO(•)). For each test, air samples were collected using two impingers in series kept in an ice bath, containing each 10 mL of 50 mM phosphate buffer at pH 7.2. In tests with TPA, that probe was also added to the buffer prior to sampling; in the other two tests, probes and additional reactants were added immediately after sampling. The concentration of fluorescent byproducts was determined fluorometrically. Calibration curves were developed by reacting DCFH and AuR with known amounts of H2O2, and using known amounts of 2-hydroxyterephthalic acid (HTPA) for TPA. Low detection limits (9-13 nM) and quantification limits (18-22 nM) were determined for all three probes, which presented a linear response in the range 10-500 nM for AuR and TPA, and 100-2000 nM for DCFH. High collection efficiency (CE) and recovery efficiency (RE) were observed for DCFH (CE=RE=100%) and AuR (CE=100%; RE=73%) by sampling from a laboratory-developed gas phase H2O2 generator. Interference of co-occurring ozone was evaluated and quantified for the three probes by sampling from the outlet of an ozone generator. The method was demonstrated by sampling air emitted by two portable air cleaners: a strong ozone generator (AC1) and a plasma generator (AC2). High ozone levels emitted by AC1 did not allow for simultaneous determination of ROS levels due to high background levels

  8. The mechanism of two-dimensional pocket formation in lean premixed methane-air flames with implications to turbulent combustion

    SciTech Connect

    Chen, J.H.; Echekki, T.; Kollmann, W.

    1999-01-01

    The mechanism of unburnt pocket formation in an unsteady two-dimensional premixed lean methane-air flame is investigated using direct numerical simulations. Theoretical results for nonlinear diffusion equations combined with analytical examples are used to interpret some of the results. Flame structure and propagation show three distinct stages of pocket formation: (1) flame channel closing involving head-on quenching of flames, (2) cusp recovery, and (3) pocket burnout. The flame channel closing and subsequent pocket burnout are mutual annihilation events that feature curvature, diffusion normal to the flame front, unsteady strain rate effects, and singularities in flame propagation and stretch rate. The results show that during channel closing and pocket burnout thermo-diffusive and chemical interactions result in the acceleration of the flames prior to annihilation; the time scales associated with the final stage of mutual annihilation and the initial stage of cusp recovery are significantly smaller than diffusive and convective time scales. Peak radical concentrations resulting from flame channel closing and pocket burnout exceed peak laminar values by as much as 25%. After the merging of the fuel consumption layers, radical production and flame structure shifts more towards an H{sub 2}/CO/O{sub 2} system at the expense of hydrocarbon reactions. Species thermodiffusive interaction times are shorter than the unstrained one-dimensional counterpart due to unsteady strain and convection. Curvature effects on the flame propagation are prominent during pocket burnout and cusp recovery. The recovery stage shows strong dependence on diffusion of radicals left from the channel closing stage. This diffusion is amplified by the strong curvature of the flame cusp.

  9. Quantitative Assessment of Detection Frequency for the INL Ambient Air Monitoring Network

    SciTech Connect

    A. Jeffrey Sondrup; Arthur S. Rood

    2014-11-01

    A quantitative assessment of the Idaho National Laboratory (INL) air monitoring network was performed using frequency of detection as the performance metric. The INL air monitoring network consists of 37 low-volume air samplers in 31 different locations. Twenty of the samplers are located on INL (onsite) and 17 are located off INL (offsite). Detection frequencies were calculated using both BEA and ESER laboratory minimum detectable activity (MDA) levels. The CALPUFF Lagrangian puff dispersion model, coupled with 1 year of meteorological data, was used to calculate time-integrated concentrations at sampler locations for a 1-hour release of unit activity (1 Ci) for every hour of the year. The unit-activity time-integrated concentration (TICu) values were calculated at all samplers for releases from eight INL facilities. The TICu values were then scaled and integrated for a given release quantity and release duration. All facilities modeled a ground-level release emanating either from the center of the facility or at a point where significant emissions are possible. In addition to ground-level releases, three existing stacks at the Advanced Test Reactor Complex, Idaho Nuclear Technology and Engineering Center, and Material and Fuels Complex were also modeled. Meteorological data from the 35 stations comprising the INL Mesonet network, data from the Idaho Falls Regional airport, upper air data from the Boise airport, and three-dimensional gridded data from the weather research forecasting model were used for modeling. Three representative radionuclides identified as key radionuclides in INL’s annual National Emission Standards for Hazardous Air Pollutants evaluations were considered for the frequency of detection analysis: Cs-137 (beta-gamma emitter), Pu-239 (alpha emitter), and Sr-90 (beta emitter). Source-specific release quantities were calculated for each radionuclide, such that the maximum inhalation dose at any publicly accessible sampler or the National

  10. Containerless Ripple Turbulence

    NASA Technical Reports Server (NTRS)

    Putterman, Seth; Wright, William; Duval, Walter; Panzarella, Charles

    2002-01-01

    interaction. Furthermore, the steady state distribution of energy again follows a Kolmogorov scaling law; in this case the ripple energy is distributed according to 1/k (sup 7/4). Again, in parallel with vortex turbulence ripple turbulence exhibits intermittency. The problem of ripple turbulence presents an experimental opportunity to generate data in a controlled, benchmarked system. In particular the surface of a sphere is an ideal environment to study ripple turbulence. Waves run around the sphere and interact with each other, and the effect of walls is eliminated. In microgravity this state can be realized for over 2 decades of frequency. Wave turbulence is a physically relevant problem in its own right. It has been studied on the surface of liquid hydrogen and its application to Alfven waves in space is a source of debate. Of course, application of wave turbulence perspectives to ocean waves has been a major success. The experiment which we plan to run in microgravity is conceptually straightforward. Ripples are excited on the surface of a spherical drop of fluid and then their amplitude is recorded with appropriate photography. A key challenge is posed by the need to stably position a 10cm diameter sphere of water in microgravity. Two methods are being developed. Orbitec is using controlled puffs of air from at least 6 independent directions to provided the positioning force. This approach has actually succeeded to position and stabilize a 4cm sphere during a KC 135 segment. Guigne International is using the radiation pressure of high frequency sound. These transducers have been organized into a device in the shape of a dodecahedron. This apparatus 'SPACE DRUMS' has already been approved for use for combustion synthesis experiments on the International Space Station. A key opportunity presented by the ripple turbulence data is its use in driving the development of codes to simulate its properties.

  11. Containerless Ripple Turbulence

    NASA Astrophysics Data System (ADS)

    Putterman, Seth; Wright, William; Duval, Walter; Panzarella, Charles

    2002-11-01

    interaction. Furthermore, the steady state distribution of energy again follows a Kolmogorov scaling law; in this case the ripple energy is distributed according to 1/k 7/4. Again, in parallel with vortex turbulence ripple turbulence exhibits intermittency. The problem of ripple turbulence presents an experimental opportunity to generate data in a controlled, benchmarked system. In particular the surface of a sphere is an ideal environment to study ripple turbulence. Waves run around the sphere and interact with each other, and the effect of walls is eliminated. In microgravity this state can be realized for over 2 decades of frequency. Wave turbulence is a physically relevant problem in its own right. It has been studied on the surface of liquid hydrogen and its application to Alfven waves in space is a source of debate. Of course, application of wave turbulence perspectives to ocean waves has been a major success. The experiment which we plan to run in microgravity is conceptually straightforward. Ripples are excited on the surface of a spherical drop of fluid and then their amplitude is recorded with appropriate photography. A key challenge is posed by the need to stably position a 10cm diameter sphere of water in microgravity. Two methods are being developed. Orbitec is using controlled puffs of air from at least 6 independent directions to provided the positioning force. This approach has actually succeeded to position and stabilize a 4cm sphere during a KC 135 segment. Guigne International is using the radiation pressure of high frequency sound. These transducers have been organized into a device in the shape of a dodecahedron. This apparatus 'SPACE DRUMS' has already been approved for use for combustion synthesis experiments on the International Space Station. A key opportunity presented by the ripple turbulence data is its use in driving the development of codes to simulate its properties.

  12. Turbulence in Natural Environments

    NASA Astrophysics Data System (ADS)

    Banerjee, Tirtha

    Problems in the area of land/biosphere-atmosphere interaction, hydrology, climate modeling etc. can be systematically organized as a study of turbulent flow in presence of boundary conditions in an increasing order of complexity. The present work is an attempt to study a few subsets of this general problem of turbulence in natural environments- in the context of neutral and thermally stratified atmospheric surface layer, the presence of a heterogeneous vegetation canopy and the interaction between air flow and a static water body in presence of flexible protruding vegetation. The main issue addressed in the context of turbulence in the atmospheric surface layer is whether it is possible to describe the macro-states of turbulence such as mean velocity and turbulent velocity variance in terms of the micro-states of the turbulent flow, i.e., a distribution of turbulent kinetic energy across a multitude of scales. This has been achieved by a `spectral budget approach' which is extended for thermal stratification scenarios as well, in the process unifying the seemingly different and unrelated theories of turbulence such as Kolmogorov's hypothesis, Heisenberg's eddy viscosity, Monin Obukhov Similarity Theory (MOST) etc. under a common framework. In the case of a more complex scenario such as presence of a vegetation canopy with edges and gaps, the question that is addressed is in what detail the turbulence is needed to be resolved in order to capture the bulk flow features such as recirculation patterns. This issue is addressed by a simple numerical framework and it has been found out that an explicit prescription of turbulence is not necessary in presence of heterogeneities such as edges and gaps where the interplay between advection, pressure gradients and drag forces are sufficient to capture the first order dynamics. This result can be very important for eddy-covariance flux calibration strategies in non-ideal environments and the developed numerical model can be

  13. Radio detection of cosmic ray air showers in the digital era

    NASA Astrophysics Data System (ADS)

    Huege, Tim

    2016-03-01

    In 1965 it was discovered that cosmic ray air showers emit impulsive radio signals at frequencies below 100 MHz. After a period of intense research in the 1960s and 1970s, however, interest in the detection technique faded almost completely. With the availability of powerful digital signal processing techniques, new attempts at measuring cosmic ray air showers via their radio emission were started at the beginning of the new millennium. Starting with modest, small-scale digital prototype setups, the field has evolved, matured and grown very significantly in the past decade. Today's second-generation digital radio detection experiments consist of up to hundreds of radio antennas or cover areas of up to 17 km2. We understand the physics of the radio emission in extensive air showers in detail and have developed analysis strategies to accurately derive from radio signals parameters which are related to the astrophysics of the primary cosmic ray particles, in particular their energy, arrival direction and estimators for their mass. In parallel to these successes, limitations inherent in the physics of the radio signals have also become increasingly clear. In this article, we review the progress of the past decade and the current state of the field, discuss the current paradigm of the radio emission physics and present the experimental evidence supporting it. Finally, we discuss the potential for future applications of the radio detection technique to advance the field of cosmic ray physics.

  14. Detection of Cherenkov light from air showers with Geiger-APDs

    NASA Astrophysics Data System (ADS)

    Otte, A.N. Britvich, I.; Biland, A.; Goebel, F.; Lorenz, E.; Pauss, F.; Renker, D.; Röser, U.; Schweizer, T.

    We have detected Cherenkov light from air showers with Geiger-mode APDs (G-APDs). G-APDs are novel semiconductor photon-detectors which offer several advantages compared to conventional photomultiplier tubes in the field of air shower detection. Folded with the Cherenkov spectrum the response of G-APDs is up to a factor of three higher if compared with classical photomultipliers. Moreover they offer high gain (~105-106) at low operation voltages (<100 V). Under operation they can withstand excessive and prolonged exposure to bright light and are also mechanical robust. Dark count rates of some G-APDs are below the level of light coming from the night sky. Furthermore G-APDs can be mass-produced which allows to considerably reduce the costs of these sensors. According to the present state of the development of G-APD they promise to be a major progress for gamma-ray astronomy. Here we report on the detection of Cherenkov light from air showers with G-APD. We discuss first test results and the advantages and problems of G-APDs in Cherenkov telescopes.

  15. Detection of volatile organic compounds indicative of human presence in the air.

    PubMed

    Kwak, Jae; Geier, Brian A; Fan, Maomian; Gogate, Sanjay A; Rinehardt, Sage A; Watts, Brandy S; Grigsby, Claude C; Ott, Darrin K

    2015-07-01

    Volatile organic compounds were collected and analyzed from a variety of indoor and outdoor air samples to test whether human-derived compounds can be readily detected in the air and if they can be associated with human occupancy or presence. Compounds were captured with thermal desorption tubes and then analyzed by gas chromatography with mass spectrometry. Isoprene, a major volatile organic compound in exhaled breath, was shown to be the best indicator of human presence. Acetone, another major breath-borne compound, was higher in unoccupied or minimally occupied areas than in human-occupied areas, indicating that its majority may be derived from exogenous sources. The association of endogenous skin-derived compounds with human occupancy was not significant. In contrast, numerous compounds that are found in foods and consumer products were detected at elevated levels in the occupied areas. Our results revealed that isoprene and many exogenous volatile organic compounds consumed by humans are emitted at levels sufficient for detection in the air, which may be indicative of human presence.

  16. Detection and Attribution of the surface air temperature during last millennium

    NASA Astrophysics Data System (ADS)

    Peng, Dongdong; Zhou, Tianjun; Man, Wenmin

    2016-04-01

    An optimal detection method was employed to compare the reconstructed and model-simulated changes of surface air temperature during last millennium. Model simulations are from CESM1-CAM5, which include 28-member ensembles in total, i.e., 5-member ensembles volcanic forcing runs, 4-member ensembles solar forcing runs, 3-member ensembles forcing runs for land use, orbital, greenhouse gases, and 10-member ensembles runs from combined 5 individual external forcing. Analyses were conducted from hemispherical to continental scale. Results show that combined effect of all the external forcings can be detected for both Northern and Southern Hemisphere, and for the continent of Europe, Arctic and Antarctic. The influence of volcanic eruption and solar activity can be detected for all the hemispheres and nearly all the continents of North Hemisphere. Land use forcing can be detected for all the continents of Northern Hemisphere, but only detected for one continent of Southern Hemisphere, i.e., South America. The orbital forcing is detected for all the continents of Northern Hemisphere, but not detected for the Northern Hemisphere as whole. Influence of greenhouse gases can rarely be detected from hemispherical to continental scale.

  17. Plasma turbulence

    SciTech Connect

    Horton, W.; Hu, G.

    1998-07-01

    The origin of plasma turbulence from currents and spatial gradients in plasmas is described and shown to lead to the dominant transport mechanism in many plasma regimes. A wide variety of turbulent transport mechanism exists in plasmas. In this survey the authors summarize some of the universally observed plasma transport rates.

  18. Detection of air pollution events over Évora-Portugal during 2009

    NASA Astrophysics Data System (ADS)

    Filipa Domingues, Ana; Bortoli, Daniele; Silva, Ana Maria; Kulkarni, Pavan; Antón, Manuel

    2010-05-01

    All over the world pollutant industries, traffic and other natural and anthropogenic sources are responsible for air pollution affecting health and also the climate. At the moment the monitoring of air quality in urban and country regions become an urgent concern in the atmospheric studies due to the impact of global air pollution on climate and on the environment. One of the evidences of the global character of air pollution is that it not only affects industrialized countries but also reaches less developed countries with pollution gases and particles generated for elsewhere. The development and the employment of instruments and techniques for measure the variation of atmospheric trace gases and perform their monitoring are crucial for the improvement of the air quality and the control of pollutants emissions. One of the instruments able to perform the air quality monitoring is the Spectrometer for Atmospheric TRacers Measurements (SPATRAM) and it is installed at the CGÉs Observatory in Évora (38.5° N, 7.9° W, 300 m asl). This UV-VIS Spectrometer is used to carry out measurements of the zenith scattered radiation (290- 900 nm) to retrieve the vertical content of some atmospheric trace gases such as O3 and NO2 in stratosphere, using Differential Optical Absorption Spectroscopy (DOAS) methodology. Although SPATRAM, in its actual geometric and operational configuration - zenith sky looking and passive mode measurements, is not able to detect small variations of tracers in the troposphere it is possible to identify enhancements in the pollution loads due to air masses movements from polluted sites. In spite of the fact that Evora is a quite unpolluted city the deep analysis of the DOAS output, namely the quantity of gas (in this case NO2) present along the optical path of measurements (SCD - Slant Column Density) allows for the detection of unpredicted variations in the diurnal NO2 cycle. The SPATRAḾs data allows the identification of polluting events which

  19. Analyse linéaire d'une turbulence homogène cisaillée stablement stratifiée

    NASA Astrophysics Data System (ADS)

    El Hattay, Mohamed; Lili, Taieb

    2007-07-01

    The evolution of a stably stratified homogeneous turbulence (SSHT) with mean shear is studied according to two nondimensional parameters: the Richardson number Ri and Prandtl number Pr. A linear analysis in spectral space gives access to the evolution of various physical characteristics of such turbulence (Reynolds stress, kinetic energy, potential energy, turbulent heat fluxes). More precisely, the dependence of transition Richardson number on Prandtl number is given in the interval [0.3;50] and results in a power law decrease. To cite this article: M. El Hattay, T. Lili, C. R. Mecanique 335 (2007).

  20. RAZOR EX Anthrax Air Detection System for detection of Bacillus anthracis spores from aerosol collection samples: collaborative study.

    PubMed

    Hadfield, Ted; Ryan, Valorie; Spaulding, Usha K; Clemens, Kristine M; Ota, Irene M; Brunelle, Sharon L

    2013-01-01

    The RAZOR EX Anthrax Air Detection System was validated in a collaborative study for the detection of Bacillus anthracis in aerosol collection buffer. Phosphate-buffered saline was charged with 1 mg/mL standardized dust to simulate an authentic aerosol collection sample. The dust-charged buffer was spiked with either B. anthracis Ames at 2000 spores/mL or Bacillus cereus at 20 000 spores/mL. Twelve collaborators participated in the study, with four collaborators at each of three sites. Each collaborator tested 12 replicates of B. anthracis in dust-charged buffer and 12 replicates of B. cereus in dust-charged buffer. All samples sets were randomized and blind-coded. All collaborators produced valid data sets (no collaborators displayed systematic errors) and there was only one invalid data point. After unblinding, the analysis revealed a cross-collaborator probability of detection (CPOD) of 1.00 (144 positive results from 144 replicates, 95% confidence interval 0.975-1.00) for the B. anthracis samples and a CPOD of 0.00 (0 positive results from 143 replicates, 95% confidence interval 0.00-0.0262) for the B. cereus samples. These data meet the requirements of AOAC Standard Method Performance Requirement 2010.003, developed by the Stakeholder Panel on Agent Detection Assays. PMID:23767365

  1. Support vector data description for detecting the air-ground interface in ground penetrating radar signals

    NASA Astrophysics Data System (ADS)

    Wood, Joshua; Wilson, Joseph

    2011-06-01

    In using GPR images for landmine detection it is often useful to identify the air-ground interface in the GRP signal for alignment purposes. A common simple technique for doing this is to assume that the highest return in an A-scan is from the reflection due to the ground and to use that as the location of the interface. However there are many situations, such as the presence of nose clutter or shallow sub-surface objects, that can cause the global maximum estimate to be incorrect. A Support Vector Data Description (SVDD) is a one-class classifier related to the SVM which encloses the class in a hyper-sphere as opposed to using a hyper-plane as a decision boundary. We apply SVDD to the problem of detection of the air-ground interface by treating each sample in an A-scan, with some number of leading and trailing samples, as a feature vector. Training is done using a set of feature vectors based on known interfaces and detection is done by creating feature vectors from each of the samples in an A-scan, applying the trained SVDD to them and selecting the one with the least distance from the center of the hyper-sphere. We compare this approach with the global maximum approach, examining both the performance on human truthed data and how each method affects false alarm and true positive rates when used as the alignment method in mine detection algorithms.

  2. Uncertainty for data with non-detects: Air toxic emissions from combustion

    SciTech Connect

    Zhao, Y.C.; Frey, H.C.

    2006-12-15

    Air toxic emission factor datasets often contain one or more points below a single or multiple detection limits and such datasets are referred to as 'censored.' Conventional methods used to deal with censored datasets include removing non-detects, replacing the censored points with zero, half of the detection limit, or the detection limit. However, the estimated means of the censored dataset by conventional methods are usually biased. Maximum likelihood estimation (MLE) and bootstrap simulation have been demonstrated as a statistically robust method to quantify variability and uncertainty of censored datasets and can provide asymptotically unbiased mean estimates. The MLE/bootstrap method is applied to 16 cases of censored air toxic emission factors, including benzene, formaldehyde, benzo(a)pyrene, mercury, arsenic, cadmium, total chromium, chromium VI and lead from coal, fuel oil, and/or wood waste external combustion sources. The proportion of censored values in the emission factor data ranges from 4 to 80%. Key factors that influence the estimated uncertainty in the mean of censored data are sample size and inter-unit variability. The largest range of uncertainty in the mean was obtained for the external coal combustion benzene emission factor, with 95 confidence interval of the mean equal to minus 93 to plus 411%.

  3. The influence of salt aerosol on alpha radiation detection by WIPP continuous air monitors

    SciTech Connect

    Bartlett, W.T.; Walker, B.A.

    1997-08-01

    Waste Isolation Pilot Plant (WIPP) alpha continuous air monitor (CAM) performance was evaluated to determine if CAMs could detect accidental releases of transuranic radioactivity from the underground repository. Anomalous alpha spectra and poor background subtraction were observed and attributed to salt deposits on the CAM sampling filters. Microscopic examination of salt laden sampling filters revealed that aerosol particles were forming dendritic structures on the surface of the sampling filters. Alpha CAM detection efficiency decreased exponentially as salt deposits increased on the sampling filters, suggesting that sampling-filter salt was performing like a fibrous filter rather than a membrane filter. Aerosol particles appeared to penetrate the sampling-filter salt deposits and alpha particle energy was reduced. These findings indicate that alpha CAMs may not be able to detect acute releases of radioactivity, and consequently CAMs are not used as part of the WIPP dynamic confinement system. 12 refs., 12 figs., 1 tab.

  4. Photon and neutron interrogation techniques for chemical explosives detection in air cargo: A critical review

    SciTech Connect

    Runkle, Robert C.; White, Timothy A.; Miller, Erin A.; Caggiano, Joseph A.; Collins, Brian A.

    2009-05-21

    Scanning cargo transported via aircraft ("air cargo") for explosive threats is a problem that, at present, lacks a comprehensive technical solution. While explosives detection in the baggage-scanning domain has a rich history that sheds light on potential solutions for air cargo, baggage scanning differs in several ways and thus one cannot look to the present array of technologies. Some contemporary solutions, like trace analysis, are not readily applied to cargo due to sampling challenges while the larger geometry of air cargo makes others less effective. This review article examines an array of interrogation techniques using photons and neutrons as incident particles. We first present a summary of the signatures and observables explosives provide and review how they have been exploited in baggage scanning. Following this is a description of the challenges posed by the air cargo application space. After considering interrogation sources, methods focused on transmission imaging, sub-surface examination and elemental characterization are described. It is our goal to shed light on the technical promise of each method while largely deferring questions that revolve around footprint, safety and conduct of operations. Our overarching intent is that a comprehensive understanding of potential techniques will foster development of a comprehensive solution.

  5. Application of a laser Doppler vibrometer for air-water to subsurface signature detection

    NASA Astrophysics Data System (ADS)

    Land, Phillip; Roeder, James; Robinson, Dennis; Majumdar, Arun

    2015-05-01

    There is much interest in detecting a target and optical communications from an airborne platform to a platform submerged under water. Accurate detection and communications between underwater and aerial platforms would increase the capabilities of surface, subsurface, and air, manned and unmanned vehicles engaged in oversea and undersea activities. The technique introduced in this paper involves a Laser Doppler Vibrometer (LDV) for acousto-optic sensing for detecting acoustic information propagated towards the water surface from a submerged platform inside a 12 gallon water tank. The LDV probes and penetrates the water surface from an aerial platform to detect air-water surface interface vibrations caused by an amplifier to a speaker generating a signal generated from underneath the water surface (varied water depth from 1" to 8"), ranging between 50Hz to 5kHz. As a comparison tool, a hydrophone was used simultaneously inside the water tank for recording the acoustic signature of the signal generated between 50Hz to 5kHz. For a signal generated by a submerged platform, the LDV can detect the signal. The LDV detects the signal via surface perturbations caused by the impinging acoustic pressure field; proving a technique of transmitting/sending information/messages from a submerged platform acoustically to the surface of the water and optically receiving the information/message using the LDV, via the Doppler Effect, allowing the LDV to become a high sensitivity optical-acoustic device. The technique developed has much potential usage in commercial oceanography applications. The present work is focused on the reception of acoustic information from an object located underwater.

  6. Minimal Prospects for Radio Detection of Extensive Air Showers in the Atmosphere of Jupiter

    NASA Astrophysics Data System (ADS)

    Bray, J. D.; Nelles, A.

    2016-07-01

    One possible approach for detecting ultra-high-energy cosmic rays and neutrinos is to search for radio emission from extensive air showers created when they interact in the atmosphere of Jupiter, effectively utilizing Jupiter as a particle detector. We investigate the potential of this approach. For searches with current or planned radio telescopes we find that the effective area for detection of cosmic rays is substantial (˜3 × 107 km2), but the acceptance angle is so small that the typical geometric aperture (˜103 km2 sr) is less than that of existing terrestrial detectors, and cosmic rays also cannot be detected below an extremely high threshold energy (˜1023 eV). The geometric aperture for neutrinos is slightly larger, and greater sensitivity can be achieved with a radio detector on a Jupiter-orbiting satellite, but in neither case is this sufficient to constitute a practical detection technique. Exploitation of the large surface area of Jupiter for detecting ultra-high-energy particles remains a long-term prospect that will require a different technique, such as orbital fluorescence detection.

  7. Weak beacon detection for air-to-ground optical wireless link establishment.

    PubMed

    Han, Yaoqiang; Dang, Anhong; Tang, Junxiong; Guo, Hong

    2010-02-01

    In an air-to-ground free-space optical communication system, strong background interference seriously affects the beacon detection, which makes it difficult to establish the optical link. In this paper, we propose a correlation beacon detection scheme under strong background interference conditions. As opposed to traditional beacon detection schemes, the beacon is modulated by an m-sequence at the transmitting terminal with a digital differential matched filter (DDMF) array introduced at the receiving end to detect the modulated beacon. This scheme is capable of suppressing both strong interference and noise by correlation reception of the received image sequence. In addition, the DDMF array enables each pixel of the image sensor to have its own DDMF of the same structure to process its received image sequence in parallel, thus it makes fast beacon detection possible. Theoretical analysis and an outdoor experiment have been demonstrated and show that the proposed scheme can realize fast and effective beacon detection under strong background interference conditions. Consequently, the required beacon transmission power can also be reduced dramatically.

  8. Airborne detection and quantification of swine influenza a virus in air samples collected inside, outside and downwind from swine barns.

    PubMed

    Corzo, Cesar A; Culhane, Marie; Dee, Scott; Morrison, Robert B; Torremorell, Montserrat

    2013-01-01

    Airborne transmission of influenza A virus (IAV) in swine is speculated to be an important route of virus dissemination, but data are scarce. This study attempted to detect and quantify airborne IAV by virus isolation and RRT-PCR in air samples collected under field conditions. This was accomplished by collecting air samples from four acutely infected pig farms and locating air samplers inside the barns, at the external exhaust fans and downwind from the farms at distances up to 2.1 km. IAV was detected in air samples collected in 3 out of 4 farms included in the study. Isolation of IAV was possible from air samples collected inside the barn at two of the farms and in one farm from the exhausted air. Between 13% and 100% of samples collected inside the barns tested RRT-PCR positive with an average viral load of 3.20E+05 IAV RNA copies/m³ of air. Percentage of exhaust positive air samples also ranged between 13% and 100% with an average viral load of 1.79E+04 RNA copies/m³ of air. Influenza virus RNA was detected in air samples collected between 1.5 and 2.1 Km away from the farms with viral levels significantly lower at 4.65E+03 RNA copies/m³. H1N1, H1N2 and H3N2 subtypes were detected in the air samples and the hemagglutinin gene sequences identified in the swine samples matched those in aerosols providing evidence that the viruses detected in the aerosols originated from the pigs in the farms under study. Overall our results indicate that pigs can be a source of IAV infectious aerosols and that these aerosols can be exhausted from pig barns and be transported downwind. The results from this study provide evidence of the risk of aerosol transmission in pigs under field conditions.

  9. Airborne Detection and Quantification of Swine Influenza A Virus in Air Samples Collected Inside, Outside and Downwind from Swine Barns

    PubMed Central

    Corzo, Cesar A.; Culhane, Marie; Dee, Scott; Morrison, Robert B.; Torremorell, Montserrat

    2013-01-01

    Airborne transmission of influenza A virus (IAV) in swine is speculated to be an important route of virus dissemination, but data are scarce. This study attempted to detect and quantify airborne IAV by virus isolation and RRT-PCR in air samples collected under field conditions. This was accomplished by collecting air samples from four acutely infected pig farms and locating air samplers inside the barns, at the external exhaust fans and downwind from the farms at distances up to 2.1 km. IAV was detected in air samples collected in 3 out of 4 farms included in the study. Isolation of IAV was possible from air samples collected inside the barn at two of the farms and in one farm from the exhausted air. Between 13% and 100% of samples collected inside the barns tested RRT-PCR positive with an average viral load of 3.20E+05 IAV RNA copies/m3 of air. Percentage of exhaust positive air samples also ranged between 13% and 100% with an average viral load of 1.79E+04 RNA copies/m3 of air. Influenza virus RNA was detected in air samples collected between 1.5 and 2.1 Km away from the farms with viral levels significantly lower at 4.65E+03 RNA copies/m3. H1N1, H1N2 and H3N2 subtypes were detected in the air samples and the hemagglutinin gene sequences identified in the swine samples matched those in aerosols providing evidence that the viruses detected in the aerosols originated from the pigs in the farms under study. Overall our results indicate that pigs can be a source of IAV infectious aerosols and that these aerosols can be exhausted from pig barns and be transported downwind. The results from this study provide evidence of the risk of aerosol transmission in pigs under field conditions. PMID:23951164

  10. A practical fiber optic air-ratio sensor operating by flame color detection

    NASA Astrophysics Data System (ADS)

    Yamaguchi, T.; Grattan, K. T. V.; Uchiyama, H.; Yamada, T.

    1997-01-01

    This article discusses the development of a simple fiber-optic sensor used to detect the air-ratio in a premix type gas boiler, by monitoring and appraising the color of the flame emission, including the effect of radical emissions. Such boilers with a multi-port plate burner show an improved thermal efficiency, with the environmentally friendly effect of a reduction in both NOx and CO in the exhaust gas. The sensor is used to monitor and maintain the air-ratio in order to enable effective feedback control, and a low-cost, durable and small sensor solution is presented. Tests carried out show the potential of the sensor for use outside the laboratory and image processing techniques are used to analyze the spectral features of the emissions seen to confirm the spectral regions of use of the fiber-optic sensor.

  11. Sensitivities of five alpha continuous air monitors for detection of airborne sup 239 Pu

    SciTech Connect

    McIsaac, C.V.; Amaro, C.R.

    1992-07-01

    Results of measurements of the sensitivities of five alpha continuous air monitors (CAMs) for detection of airborne {sup 239}Pu are presented. Four commercially available alpha CAMs (Kurz model 8311, Merlin Gerin Edgar, RADeCO model 452, and Victoreen model 758) and a prototype alpha CAM currently in use at Argonne National Laboratory- West (ANL-W) were tested sampling natural ambient air and laboratory-generated atmospheres laden with either blank dust or dust containing nCi/g concentrations of {sup 239}Pu. Cumulative alpha spectra were stored at 30 or 60 minute intervals during each sampling and were subsequently analyzed using three different commonly used alpha spectrum analysis algorithms. The effect of airborne dust concentration and sample filter porosity on detector resolution and sensitivity for airborne {sup 239}Pu are described.

  12. Sensitivities of five alpha continuous air monitors for detection of airborne {sup 239}Pu

    SciTech Connect

    McIsaac, C.V.; Amaro, C.R.

    1992-07-01

    Results of measurements of the sensitivities of five alpha continuous air monitors (CAMs) for detection of airborne {sup 239}Pu are presented. Four commercially available alpha CAMs (Kurz model 8311, Merlin Gerin Edgar, RADeCO model 452, and Victoreen model 758) and a prototype alpha CAM currently in use at Argonne National Laboratory- West (ANL-W) were tested sampling natural ambient air and laboratory-generated atmospheres laden with either blank dust or dust containing nCi/g concentrations of {sup 239}Pu. Cumulative alpha spectra were stored at 30 or 60 minute intervals during each sampling and were subsequently analyzed using three different commonly used alpha spectrum analysis algorithms. The effect of airborne dust concentration and sample filter porosity on detector resolution and sensitivity for airborne {sup 239}Pu are described.

  13. Environmental sensor technologies and procedures for detecting and identifying indoor air pollution. Final report

    SciTech Connect

    O'Connor, E.T.; Kermath, D.; Kemme, M.R.

    1992-03-01

    Public concern about environmental quality now encompasses the indoor environment-the buildings where people work and live. In recent years researchers have been discovering new links between indoor air quality (IAQ) and the occupants' comfort, health, and productivity. As the operator of many thousands of buildings, and the employer of the millions of people who use those buildings, the U.S. Army has a strong interest in maintaining and promoting good IAQ. This report presents a concise summary of the key IAQ parameters of interest to building managers, the most common indoor air contaminants, the variety of sensor technology currently available for detect and identifying those contaminants, and basic procedures for using that technology.

  14. Hidden disbond detection in spent nuclear fuel storage systems using air-coupled ultrasonics

    NASA Astrophysics Data System (ADS)

    Song, Homin; Popovics, John S.

    2016-04-01

    This paper studies an air-coupled ultrasonic scanning approach for damage assessment in steel-clad concrete structures. An air-coupled ultrasonic sender generates guided plate waves in the steel cladding and a small contact-type receiver measures the corresponding wave responses. A frequency-wavenumber (f-k) domain signal filtering technique is used to isolate the behavior of the fundamental symmetric (S0) mode of the guided plate waves. The behavior of the S0 mode is sensitive to interface bonding conditions. The proposed inspection approach is verified by a series of experiments performed on laboratory-scale specimens. The experimental results demonstrate that hidden disbond between steel cladding and underlying concrete substrate can be successfully detected with the ultrasonic test setup and the f-k domain signal filtering technique.

  15. Detection of satratoxin g and h in indoor air from a water-damaged building.

    PubMed

    Gottschalk, Christoph; Bauer, Johann; Meyer, Karsten

    2008-08-01

    The occurrence of Stachybotrys chartarum in indoor environments has been linked to adverse health effects as well as few cases of pulmonary haemorrhages in humans. Although the highly toxic secondary metabolites of this fungus, like satratoxin G and H, were frequently claimed with outbreaks of such diseases, these toxins have hardly been identified in the air of naturally contaminated indoor environments. Herein, a case of a LC-MS/MS-confirmed occurrence of airborne S. chartarum-toxins in a water-damaged dwelling is reported. Satratoxin G (0.25 ng/m(3)) and satratoxin H (0.43 ng/m(3)) were detected. This provides further evidence that Stachybotrys-toxins can be transferred from mouldy indoor materials into air, which could be a factor in the aetiology of health symptoms related to the sick building syndrome. PMID:18443920

  16. Leaky wave detection at air-solid interfaces by laser interferometry

    PubMed

    Mattei; Adler

    2000-03-01

    A recently developed optical heterodyne interferometer is proved to be sensitive to detect ultrasonic waves leaking out from metals (and from non-metals as well) several centimeters away from the metal surface in air. This measurement is based on the detection of the optical index variation in air due to the leaky wave. Experiments were carried out using both ultrasonic leaky Rayleigh and leaky Lamb waves in the low-megahertz region. Optical measurements of these leaky wave velocities in semi-infinite materials and plates, which are related to elastic constants of the materials, showed a good correlation to the predicted values. Optical measurements of the amplitude of the leaky waves were used to obtain attenuation coefficients, which correlate to the structural integrity of the materials. Surface and near-surface defects were also detected. This optical method can be used for metals with low-reflectivity surfaces. Thus, it can be used for non-polished surfaces and can be extended for non-contact, non-destructive evaluation applications. PMID:10829728

  17. On the Possibility of Radar Detection of Ultra-high Energy Cosmic Ray- and Neutrino-induced Air Showers

    NASA Technical Reports Server (NTRS)

    Gorham, P.

    1999-01-01

    We show that cosmic rays air showers resulting from primaries with energies above 10(sup 19) eV should be straightforward to detect with radar ranging techniques, where the radar echoes are produced by scattering from the column of ionized air produced by the shower.

  18. Wall Turbulence.

    ERIC Educational Resources Information Center

    Hanratty, Thomas J.

    1980-01-01

    This paper gives an account of research on the structure of turbulence close to a solid boundary. Included is a method to study the flow close to the wall of a pipe without interferring with it. (Author/JN)

  19. Wave turbulence

    NASA Astrophysics Data System (ADS)

    Nazarenko, Sergey

    2015-07-01

    Wave turbulence is the statistical mechanics of random waves with a broadband spectrum interacting via non-linearity. To understand its difference from non-random well-tuned coherent waves, one could compare the sound of thunder to a piece of classical music. Wave turbulence is surprisingly common and important in a great variety of physical settings, starting with the most familiar ocean waves to waves at quantum scales or to much longer waves in astrophysics. We will provide a basic overview of the wave turbulence ideas, approaches and main results emphasising the physics of the phenomena and using qualitative descriptions avoiding, whenever possible, involved mathematical derivations. In particular, dimensional analysis will be used for obtaining the key scaling solutions in wave turbulence - Kolmogorov-Zakharov (KZ) spectra.

  20. Direct Detection of C_2H_2 in Air and Human Breath by Cw-Crds

    NASA Astrophysics Data System (ADS)

    Schmidt, Florian M.; Vaittinen, Olavi; Metsälä, Markus; Halonen, Lauri

    2010-06-01

    Continuous wave cavity ring-down spectroscopy (cw-CRDS) is an established cavity-enhanced absorption technique that can provide the necessary sensitivity, selectivity and fast acquisition time for many applications involving the detection of trace species. We present a simple but highly sensitive cw-CRDS spectrometer based on an external cavity diode laser operating in the near-infrared region. This instrument allows us to directly detect acetylene (C_2H_2) mixing ratios in air with a detection limit of 120 parts per trillion by volume (pptv) measuring on a C_2H_2 absorption line at 6565.620 cm-1. Acetylene is a combustion product that is routinely used in environmental monitoring as a marker for anthropogenic emissions. In a recent work, the spectrometer was employed to measure the level of acetylene in indoor and outdoor air in Helsinki. Continuous flow measurements with high time resolution (one minute) revealed strong fluctuations in the acetylene mixing ratio in outdoor air during daytime. Due to its non-invasive nature and fast response time, the analysis of exhaled breath for medical diagnostics is an excellent and straightforward alternative to methods using urine or blood samples. In an ongoing study, the cw-CRDS instrument is used to establish the baseline level of acetylene in the breath of the healthy population. An elevated amount of acetylene in breath could indicate exposure to combustion exhausts or other volatile organic compound (VOC) rich sources. The latest results of this investigation will be presented. F. M. Schmidt, O. Vaittinen, M. Metsälä, P. Kraus and L. Halonen, submitted for publication in Appl. Phys. B.

  1. Current Progresses of Midass: Microbial Detection in Air System for Space

    NASA Astrophysics Data System (ADS)

    Abaibou, Hafid; Lasseur, Christophe; Mabilat, Claude; Storrs-Mabilat, Michele; Guy, Michel; Raffestin, Stephanie; Sole Bosquet, Jaume

    For the long term manned missions, microbial contamination is a major risk for crew members and hardware. This risk has first been documented by Russian scientists then by other organizations as a consequence of the contamination of metabolic consumables (water, air), and also the hardware degradation. Rapid molecular biology techniques offer an attractive alternative to traditional culture-based methods. They allow fast time to results for contamination detection and quick implementation of appropriate corrective action when required. However, to date, there are no such available system due to the technical challenges required to meet the sensitivity and specificity needs of the test and the requirement for full automation, from sampling to results interpretation. In response to this, over the last decade, the European Space Agency (ESA) and bioMérieux initiated a co-development of MIDASS, the world’s first fully automated system for the monitoring of the environmental microbial load in confined spaces, including clean rooms and hospital wards. The system is based on molecular technologies (sample preparation/amplification/detection) and enables rapid and simple determination of the microbiological contamination level in less than 3 hours. It relies on NASBA-amplification for the detection of selected micro-organisms (indicators or pathogens) at determined risk-levels (200 and 1 CFU /m3 air, respectively). Successful progresses were recently made for the space-application workpackage of this project: a lab-on-a-card design for air-testing in a first scope was endorsed by a successful ESA Preliminary Design Review, paving the way to spatialization steps (phases C and D). Data will be presented with regards to system design and biological performances.

  2. Detection of Measles Virus RNA in Air and Surface Specimens in a Hospital Setting.

    PubMed

    Bischoff, Werner E; McNall, Rebecca J; Blevins, Maria W; Turner, JoLyn; Lopareva, Elena N; Rota, Paul A; Stehle, John R

    2016-02-15

    Measles virus (MeV) is known to be highly contagious, with an infectious period lasting from 4 days before to 4 days after rash onset. An unvaccinated, young, female patient with measles confirmed by direct epidemiologic link was hospitalized on day 5 after rash onset. Environmental samples were collected over the 4-day period of hospitalization in a single room. MeV RNA was detectable in air specimens, on surface specimens, and on respirators on days 5-8 after rash onset. This is the first report of environmental surveillance for MeV, and the results suggest that MeV-infected fomites may be present in healthcare settings.

  3. Direct detection of salmonella cells in the air of livestock stables by real-time PCR.

    PubMed

    Fallschissel, Kerstin; Kämpfer, Peter; Jäckel, Udo

    2009-11-01

    A SYBR Green real-time quantitative polymerase chain reaction (qPCR) assay for specific detection and quantification of airborne Salmonella cells in livestock housings is presented. A set of specific primers was tested and validated for specific detection and quantification of Salmonella-specific invA genes of DNA extracted from bioaerosol samples. Application of the method to poultry house bioaerosol samples showed concentrations ranging from 2.2 x 10(1) to 3 x 10(6) Salmonella targets m(-3) of air. Salmonella were also detected by a cultivation-based approach in some samples, but concentrations were two to three magnitudes lower than the concentrations detected by molecular biological results. Specificity of results was demonstrated by cloning analyses of PCR products, which were exclusively assigned to the genus Salmonella. However, by molecular methods, microorganisms are detected independently of their viability status, leading to an overestimation of concentration. Hence, the survival rate of Salmonella cells was measured on filter surfaces during filtration samplings where 82% of the cells died within 20 min of filtration. The results clearly show the specificity and practicability of the established qPCR assay for analysis and quantification of salmonellae in bioaerosols. The results demonstrate airborne Salmonella workplace concentrations in poultry production of up to 3.3% of 4',6-Diamidino-2-phenylindole-counted total cell numbers.

  4. Microwave Detection of Cosmic Ray Air Showers at the Pierre Auger Observatory, an R&D Effort

    NASA Astrophysics Data System (ADS)

    Williams, Christopher; the Pierre Auger Collaboration

    The measurement of microwave emission from air showers initiated by ultra-high energy cosmic rays may open the possibility of developing a novel detection technique. This new technique possesses the advantage of the fluorescence detection technique -the reconstruction of the longitudinal shower profile -combined with a 100% duty cycle, minimal atmospheric attenuation and the use of low cost commercial equipment. Placing prototype detectors at the Auger site provides for coincidence detection of air showers using established methods, ultimately assessing the feasibility of detecting air showers through microwave radiation. Two complementary techniques are currently being pursued at the Pierre Auger Observatory. MIDAS (Microwave Detection of Air Showers), AMBER (Air-shower Microwave Bremsstrahlung Experimental Radiometer), and FDWave are prototypes for large imaging dish antennas. EASIER (Extensive Air Shower Identification using Electron Radiometer), the second technique, utilizes horn antennas located on each Auger Surface Detector station for detection of microwave emission. MIDAS is a self-triggering system while AMBER, FDWave and EASIER use the trigger from the Auger detectors to record the microwave emission. The development status and future plans for these measurements is reported.

  5. On-line air-tightness and insertion loss simultaneous detection method of high air-tightness fiber optic penetration connector

    NASA Astrophysics Data System (ADS)

    Zhang, Jingchuan; Yang, Xiaoning; Wang, Jing; Jiang, Junfeng

    2015-08-01

    The high air-tightness multicore fiber optic penetration connector is a core component for the optical fiber sensing and communication technologies applied in the space environment simulator under the vacuum thermal environment. High air-tightness and insertion loss are the two key indexes of the fiber optic penetration connector. The air-tightness and insertion loss on-line synchronous detection method was proposed. First, established hardware-in-the-loop testing platform by using the vacuum pumping system, the vacuum vessel, the helium mass spectrometer leak detector and optical time-domain reflectmeter, then, described the air tightness and insertion loss on-line detection principle, finally, designed a detection test scheme and air-tightness and insertion loss were tested. Experimental results indicate that the leakage rate is lower than 1.0×10-7Pa•L/S, the minimum of which is1.0×10-10Pa•L/S and the insertion loss at wave length window 1550 nm is +/-0.07db, which is less than +/-0.1db. It can lay the data basis for the design of opto-mechanical combination and later period fine processing.

  6. 2013 R&D 100 Award: DNATrax could revolutionize air quality detection and tracking

    ScienceCinema

    Farquar, George

    2016-07-12

    A team of LLNL scientists and engineers has developed a safe and versatile material, known as DNA Tagged Reagents for Aerosol Experiments (DNATrax), that can be used to reliably and rapidly diagnose airflow patterns and problems in both indoor and outdoor venues. Until DNATrax particles were developed, no rapid or safe way existed to validate air transport models with realistic particles in the range of 1-10 microns. Successful DNATrax testing was conducted at the Pentagon in November 2012 in conjunction with the Pentagon Force Protection Agency. This study enhanced the team's understanding of indoor ventilation environments created by heating, ventilation and air conditioning (HVAC) systems. DNATrax are particles comprised of sugar and synthetic DNA that serve as a bar code for the particle. The potential for creating unique bar-coded particles is virtually unlimited, thus allowing for simultaneous and repeated releases, which dramatically reduces the costs associated with conducting tests for contaminants. Among the applications for the new material are indoor air quality detection, for homes, offices, ships and airplanes; urban particulate tracking, for subway stations, train stations, and convention centers; environmental release tracking; and oil and gas uses, including fracking, to better track fluid flow.

  7. 2013 R&D 100 Award: DNATrax could revolutionize air quality detection and tracking

    SciTech Connect

    Farquar, George

    2014-04-03

    A team of LLNL scientists and engineers has developed a safe and versatile material, known as DNA Tagged Reagents for Aerosol Experiments (DNATrax), that can be used to reliably and rapidly diagnose airflow patterns and problems in both indoor and outdoor venues. Until DNATrax particles were developed, no rapid or safe way existed to validate air transport models with realistic particles in the range of 1-10 microns. Successful DNATrax testing was conducted at the Pentagon in November 2012 in conjunction with the Pentagon Force Protection Agency. This study enhanced the team's understanding of indoor ventilation environments created by heating, ventilation and air conditioning (HVAC) systems. DNATrax are particles comprised of sugar and synthetic DNA that serve as a bar code for the particle. The potential for creating unique bar-coded particles is virtually unlimited, thus allowing for simultaneous and repeated releases, which dramatically reduces the costs associated with conducting tests for contaminants. Among the applications for the new material are indoor air quality detection, for homes, offices, ships and airplanes; urban particulate tracking, for subway stations, train stations, and convention centers; environmental release tracking; and oil and gas uses, including fracking, to better track fluid flow.

  8. The influence of salt aerosol on alpha radiation detection by WIPP continuous air monitors

    SciTech Connect

    Bartlett, W.T.; Walker, B.A.

    1996-01-01

    Alpha continuous air monitors (CAMs) will be used at the Waste Isolation Pilot Plant (WIPP) to measure airborne transuranic radioactivity that might be present in air exhaust or in work-place areas. WIPP CAMs are important to health and safety because they are used to alert workers to airborne radioactivity, to actuate air-effluent filtration systems, and to detect airborne radioactivity so that the radioactivity can be confined in a limited area. In 1993, the Environmental Evaluation Group (EEG) reported that CAM operational performance was affected by salt aerosol, and subsequently, the WIPP CAM design and usage were modified. In this report, operational data and current theories on aerosol collection were reviewed to determine CAM quantitative performance limitations. Since 1993, the overall CAM performance appears to have improved, but anomalous alpha spectra are present when sampling-filter salt deposits are at normal to high levels. This report shows that sampling-filter salt deposits directly affect radon-thoron daughter alpha spectra and overall monitor efficiency. Previously it was assumed that aerosol was mechanically collected on the surface of CAM sampling filters, but this review suggests that electrostatic and other particle collection mechanisms are more important than previously thought. The mechanism of sampling-filter particle collection is critical to measurement of acute releases of radioactivity. 41 refs.

  9. Influence of avenue-trees on air quality at the urban neighborhood scale. Part I: quality assurance studies and turbulent Schmidt number analysis for RANS CFD simulations.

    PubMed

    Gromke, Christof; Blocken, Bert

    2015-01-01

    Flow and dispersion of traffic pollutants in a generic urban neighborhood with avenue-trees were investigated with Computational Fluid Dynamics (CFD). In Part I of this two-part contribution, quality assessment and assurance for CFD simulations in urban and vegetation configurations were addressed,before in Part II flow and dispersion in a generic urban neighborhood with multiple layouts of avenue trees were studied. In a first step, a grid sensitivity study was performed that inferred that a cell count of 20 per building height and 12 per canyon width is sufficient for reasonable grid insensitive solutions. Next, the performance of the realizable k-ε turbulence model in simulating urban flows and of the applied vegetation model in simulating flow and turbulence in trees was validated. Finally, based on simulations of street canyons with and without avenue-trees, an appropriate turbulent Schmidt number or modeling dispersion in the urban neighborhood was determined as Sc(t) =0.5.

  10. An Ultrasonic and Air Pressure Sensing System for Detection of Behavior before Getting out of Bed Aided by Fuzzy Theory

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Hayato; Nakajima, Hiroshi; Taniguchi, Kazuhiko; Kobashi, Syoji; Hata, Yutaka

    This paper proposes a sensing system for a behavior detection system using an ultrasonic oscillosensor and an air pressure sensor. The ultrasonic oscillosensor sensor has a cylindrical tank filled with water. It detects the vibration of the target object from the signal reflected from the water surface. This sensor can detect a biological vibration by setting to the bottom bed frame. The air pressure sensor consists of a polypropylene sheet and an air pressure sensor, and detects the pressure information by setting under the bed's mattress. An increase (decrease) in the load placed on the bed is detected by the increase (decrease) in the pressure of the air held in the tube attached to the sheet. We propose a behavior detection system using both sensors, complementally. The system recognizes three states (nobody in bed, keeping quiet in bed, moving in bed) using both sensors, and we detect the behavior before getting out of bed by recognized these states. Fuzzy logic plays a primary role in the system. As the fundamental experiment, we applied the system to five healthy volunteers, the system successfully recognized three states, and detected the behavior before getting out of bed. As the clinical experiment, we applied the system to four elderly patients with dementia, the system exactly detected the behavior before getting out of the bed with enough time for medical care support.

  11. The EUSTACE break-detection algorithm for a global air temperature dataset

    NASA Astrophysics Data System (ADS)

    Brugnara, Yuri; Auchmann, Renate; Brönnimann, Stefan

    2016-04-01

    EUSTACE (EU Surface Temperature for All Corners of Earth) is an EU-funded project that has started in 2015; its goal is to produce daily estimates of surface air temperature since 1850 across the globe for the first time by combining surface and satellite data using novel statistical techniques. For land surface data (LSAT), we assembled a global dataset of ca. 35000 stations where daily maximum and minimum air temperature observations are available, taking advantage of the most recent data rescue initiatives. Beside quantity, data quality also plays an important role for the success of the project; in particular, the assessment of the homogeneity of the temperature series is crucial in order to obtain a product suitable for the study of climate change. This poster describes a fully automatic state-of-the-art break-detection algorithm that we developed for the global LSAT dataset. We evaluate the performance of the method using artificial benchmarks and present various statistics related to frequency and amplitude of the inhomogeneities detected in the real data. We show in particular that long-term temperature trends calculated from raw data are more often underestimated than overestimated and that this behaviour is mostly related to inhomogeneities affecting maximum temperatures.

  12. Fisk-based criteria to support validation of detection methods for drinking water and air.

    SciTech Connect

    MacDonell, M.; Bhattacharyya, M.; Finster, M.; Williams, M.; Picel, K.; Chang, Y.-S.; Peterson, J.; Adeshina, F.; Sonich-Mullin, C.; Environmental Science Division; EPA

    2009-02-18

    This report was prepared to support the validation of analytical methods for threat contaminants under the U.S. Environmental Protection Agency (EPA) National Homeland Security Research Center (NHSRC) program. It is designed to serve as a resource for certain applications of benchmark and fate information for homeland security threat contaminants. The report identifies risk-based criteria from existing health benchmarks for drinking water and air for potential use as validation targets. The focus is on benchmarks for chronic public exposures. The priority sources are standard EPA concentration limits for drinking water and air, along with oral and inhalation toxicity values. Many contaminants identified as homeland security threats to drinking water or air would convert to other chemicals within minutes to hours of being released. For this reason, a fate analysis has been performed to identify potential transformation products and removal half-lives in air and water so appropriate forms can be targeted for detection over time. The risk-based criteria presented in this report to frame method validation are expected to be lower than actual operational targets based on realistic exposures following a release. Note that many target criteria provided in this report are taken from available benchmarks without assessing the underlying toxicological details. That is, although the relevance of the chemical form and analogues are evaluated, the toxicological interpretations and extrapolations conducted by the authoring organizations are not. It is also important to emphasize that such targets in the current analysis are not health-based advisory levels to guide homeland security responses. This integrated evaluation of chronic public benchmarks and contaminant fate has identified more than 200 risk-based criteria as method validation targets across numerous contaminants and fate products in drinking water and air combined. The gap in directly applicable values is

  13. Spatial Cluster Detection of Air Pollution Exposure Inequities across the United States

    PubMed Central

    Zou, Bin; Peng, Fen; Wan, Neng; Mamady, Keita; Wilson, Gaines J.

    2014-01-01

    Air quality is known to be a key factor in affecting the wellbeing and quality of life of the general populous and there is a large body of knowledge indicating that certain underrepresented groups may be overexposed to air pollution. Therefore, a more precise understanding of air pollution exposure as a driving cause of health disparities between and among ethnic and racial groups is necessary. Utilizing 52,613 urban census tracts across the United States, this study investigates age, racial, educational attainment and income differences in exposure to benzene pollution in 1999 as a case. The study examines spatial clustering patterns of these inequities using logistic regression modeling and spatial autocorrelation methods such as the Global Moran's I index and the Anselin Local Moran's I index. Results show that the age groups of 0 to 14 and those over 60 years old, individuals with less than 12 years of education, racial minorities including Blacks, American Indians, Asians, some other races, and those with low income were exposed to higher levels of benzene pollution in some census tracts. Clustering analyses stratified by age, education, and race revealed a clear case of disparities in spatial distribution of exposure to benzene pollution across the entire United States. For example, people aged less than 4 years from the western south and the Pacific coastal areas exhibit statistically significant clusters. The findings confirmed that there are geographical-location based disproportionate pattern of exposures to benzene air pollution by various socio-demographic factors across the United States and this type of disproportionate exposure pattern can be effectively detected by a spatial autocorrelation based cluster analysis method. It is suggested that there is a clear and present need for programs and services that will reduce inequities and ultimately improve environmental conditions for all underrepresented groups in the United States. PMID:24647354

  14. Spatial cluster detection of air pollution exposure inequities across the United States.

    PubMed

    Zou, Bin; Peng, Fen; Wan, Neng; Mamady, Keita; Wilson, Gaines J

    2014-01-01

    Air quality is known to be a key factor in affecting the wellbeing and quality of life of the general populous and there is a large body of knowledge indicating that certain underrepresented groups may be overexposed to air pollution. Therefore, a more precise understanding of air pollution exposure as a driving cause of health disparities between and among ethnic and racial groups is necessary. Utilizing 52,613 urban census tracts across the United States, this study investigates age, racial, educational attainment and income differences in exposure to benzene pollution in 1999 as a case. The study examines spatial clustering patterns of these inequities using logistic regression modeling and spatial autocorrelation methods such as the Global Moran's I index and the Anselin Local Moran's I index. Results show that the age groups of 0 to 14 and those over 60 years old, individuals with less than 12 years of education, racial minorities including Blacks, American Indians, Asians, some other races, and those with low income were exposed to higher levels of benzene pollution in some census tracts. Clustering analyses stratified by age, education, and race revealed a clear case of disparities in spatial distribution of exposure to benzene pollution across the entire United States. For example, people aged less than 4 years from the western south and the Pacific coastal areas exhibit statistically significant clusters. The findings confirmed that there are geographical-location based disproportionate pattern of exposures to benzene air pollution by various socio-demographic factors across the United States and this type of disproportionate exposure pattern can be effectively detected by a spatial autocorrelation based cluster analysis method. It is suggested that there is a clear and present need for programs and services that will reduce inequities and ultimately improve environmental conditions for all underrepresented groups in the United States.

  15. Development and Testing of an Air Fluorescence Imaging System for the Detection of Radiological Contamination

    SciTech Connect

    Inrig, Elizabeth; Koslowsky, Vern; Andrews, Bob; Dick, Michael; Forget, Patrick; Ing, Harry; Hugron, Roger; Wong, Larry

    2011-12-13

    Detection of radionuclides emitting short-range radiation, such as {alpha} and low-energy {beta} particles, has always presented a challenge, particularly when such radionuclides are dispersed over a wide area. In this situation, conventional detection methods require the area of interest to be surveyed using a fragile probe at very close range--a slow, error-prone, and potentially dangerous process that may take many hours for a single room. The instrument under development uses a novel approach by imaging radiation-induced fluorescence in the air surrounding a contaminated area, rather than detecting the radiation directly. A robust and portable system has been designed and built that will allow contaminated areas to be rapidly detected and delineated. The detector incorporates position-sensitive photo-multiplier tubes, UV filters, a fast electronic shutter and an aspherical phase mask that significantly increases the depth-of-field. Preliminary tests have been conducted using sealed {sup 241}Am sources of varying activities and surface areas. The details of the instrument design will be described and the results of recent testing will be presented.

  16. Released air during vapor and air cavitation

    NASA Astrophysics Data System (ADS)

    Jablonská, Jana; Kozubková, Milada

    2016-06-01

    Cavitation today is a very important problem that is solved by means of experimental and mathematical methods. The article deals with the generation of cavitation in convergent divergent nozzle of rectangular cross section. Measurement of pressure, flow rate, temperature, amount of dissolved air in the liquid and visualization of cavitation area using high-speed camera was performed for different flow rates. The measurement results were generalized by dimensionless analysis, which allows easy detection of cavitation in the nozzle. For numerical simulation the multiphase mathematical model of cavitation consisting of water and vapor was created. During verification the disagreement with the measurements for higher flow rates was proved, therefore the model was extended to multiphase mathematical model (water, vapor and air), due to release of dissolved air. For the mathematical modeling the multiphase turbulence RNG k-ɛ model for low Reynolds number flow with vapor and air cavitation was used. Subsequently the sizes of the cavitation area were verified. In article the inlet pressure and loss coefficient depending on the amount of air added to the mathematical model are evaluated. On the basis of the approach it may be create a methodology to estimate the amount of released air added at the inlet to the modeled area.

  17. Early detection of foot-and-mouth disease virus from infected cattle using a dry filter air sampling system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Foot-and-mouth disease (FMD) is a highly contagious livestock disease of high economic impact. Early detection of FMD virus (FMDV) is fundamental for rapid outbreak control. Air sampling collection has been demonstrated as a useful technique for detection of FMDV RNA in infected animals, related to ...

  18. Holographic turbulence.

    PubMed

    Adams, Allan; Chesler, Paul M; Liu, Hong

    2014-04-18

    We construct turbulent black holes in asymptotically AdS4 spacetime by numerically solving Einstein's equations. Using the AdS/CFT correspondence we find that both the dual holographic fluid and bulk geometry display signatures of an inverse cascade with the bulk geometry being well approximated by the fluid-gravity gradient expansion. We argue that statistically steady-state black holes dual to d dimensional turbulent flows have horizons whose area growth has a fractal-like structure with fractal dimension D=d+4/3.

  19. Turbulence in Compressible Flows

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Lecture notes for the AGARD Fluid Dynamics Panel (FDP) Special Course on 'Turbulence in Compressible Flows' have been assembled in this report. The following topics were covered: Compressible Turbulent Boundary Layers, Compressible Turbulent Free Shear Layers, Turbulent Combustion, DNS/LES and RANS Simulations of Compressible Turbulent Flows, and Case Studies of Applications of Turbulence Models in Aerospace.

  20. Variable density turbulence tunnel facility.

    PubMed

    Bodenschatz, E; Bewley, G P; Nobach, H; Sinhuber, M; Xu, H

    2014-09-01

    The Variable Density Turbulence Tunnel at the Max Planck Institute for Dynamics and Self-Organization in Göttingen, Germany, produces very high turbulence levels at moderate flow velocities, low power consumption, and adjustable kinematic viscosity between 10(-4) m(2)/s and 10(-7) m(2)/s. The Reynolds number can be varied by changing the pressure or flow rate of the gas or by using different non-flammable gases including air. The highest kinematic viscosities, and hence lowest Reynolds numbers, are reached with air or nitrogen at 0.1 bar. To reach the highest Reynolds numbers the tunnel is pressurized to 15 bars with the dense gas sulfur hexafluoride (SF6). Turbulence is generated at the upstream ends of two measurement sections with grids, and the evolution of this turbulence is observed as it moves down the length of the sections. We describe the instrumentation presently in operation, which consists of the tunnel itself, classical grid turbulence generators, and state-of-the-art nano-fabricated hot-wire anemometers provided by Princeton University [M. Vallikivi, M. Hultmark, S. C. C. Bailey, and A. J. Smits, Exp. Fluids 51, 1521 (2011)]. We report measurements of the characteristic scales of the flow and of turbulent spectra up to Taylor Reynolds number R(λ) ≈ 1600, higher than any other grid-turbulence experiment. We also describe instrumentation under development, which includes an active grid and a Lagrangian particle tracking system that moves down the length of the tunnel with the mean flow. In this configuration, the properties of the turbulence are adjustable and its structure is resolvable up to R(λ) ≈ 8000.

  1. Detection and imaging of atmospheric radio flashes from cosmic ray air showers.

    PubMed

    Falcke, H; Apel, W D; Badea, A F; Bähren, L; Bekk, K; Bercuci, A; Bertaina, M; Biermann, P L; Blümer, J; Bozdog, H; Brancus, I M; Buitink, S; Brüggemann, M; Buchholz, P; Butcher, H; Chiavassa, A; Daumiller, K; de Bruyn, A G; de Vos, C M; Di Pierro, F; Doll, P; Engel, R; Gemmeke, H; Ghia, P L; Glasstetter, R; Grupen, C; Haungs, A; Heck, D; Hörandel, J R; Horneffer, A; Huege, T; Kampert, K-H; Kant, G W; Klein, U; Kolotaev, Y; Koopman, Y; Krömer, O; Kuijpers, J; Lafebre, S; Maier, G; Mathes, H J; Mayer, H J; Milke, J; Mitrica, B; Morello, C; Navarra, G; Nehls, S; Nigl, A; Obenland, R; Oehlschläger, J; Ostapchenko, S; Over, S; Pepping, H J; Petcu, M; Petrovic, J; Plewnia, S; Rebel, H; Risse, A; Roth, M; Schieler, H; Schoonderbeek, G; Sima, O; Stümpert, M; Toma, G; Trinchero, G C; Ulrich, H; Valchierotti, S; van Buren, J; van Cappellen, W; Walkowiak, W; Weindl, A; Wijnholds, S; Wochele, J; Zabierowski, J; Zensus, J A; Zimmermann, D

    2005-05-19

    The nature of ultrahigh-energy cosmic rays (UHECRs) at energies >10(20) eV remains a mystery. They are likely to be of extragalactic origin, but should be absorbed within approximately 50 Mpc through interactions with the cosmic microwave background. As there are no sufficiently powerful accelerators within this distance from the Galaxy, explanations for UHECRs range from unusual astrophysical sources to exotic string physics. Also unclear is whether UHECRs consist of protons, heavy nuclei, neutrinos or gamma-rays. To resolve these questions, larger detectors with higher duty cycles and which combine multiple detection techniques are needed. Radio emission from UHECRs, on the other hand, is unaffected by attenuation, has a high duty cycle, gives calorimetric measurements and provides high directional accuracy. Here we report the detection of radio flashes from cosmic-ray air showers using low-cost digital radio receivers. We show that the radiation can be understood in terms of the geosynchrotron effect. Our results show that it should be possible to determine the nature and composition of UHECRs with combined radio and particle detectors, and to detect the ultrahigh-energy neutrinos expected from flavour mixing.

  2. Application of SOS umu-test for the detection of genotoxic volatile chemicals and air pollutants.

    PubMed

    Ong, T M; Stewart, J; Wen, Y F; Whong, W Z

    1987-01-01

    The SOS umu-test has been used for the detection of DNA-damaging agents. In this system the plasmid pSK1002 carrying a fused gene umuC-lacZ was introduced into Salmonella typhimurium TA1535. The SOS function induced by genotoxic agents is detected by a colorimetric measurement of beta-galactosidase activity encoded by the lacZ gene, which is regulated by the Umu operon. This system was used with modifications to study the SOS function inducibility of volatile chemicals (propylene oxide, methyl bromide, and ethylene dibromide) and air pollutants (diesel emission, welding fumes, and cigarette smoke). Tester cells were exposed directly to the test material. The enzyme activity of the treated cells was measured according to the established procedure. Results of the study showed that all chemicals and pollutants tested induced SOS function in a dose-related manner. These results indicate that the SOS umu-test is potentially useful for the in situ detection of genotoxic agents in occupational settings.

  3. Turbulent mixing condensation nucleus counter

    NASA Astrophysics Data System (ADS)

    Mavliev, Rashid

    The construction and operating principles of the Turbulent Mixing Condensation Nucleus Counter (TM CNC) are described. Estimations based on the semiempirical theory of turbulent jets and the classical theory of nucleation and growth show the possibility of detecting particles as small as 2.5 nm without the interference of homogeneous nucleation. This conclusion was confirmed experimentally during the International Workshop on Intercomparison of Condensation Nuclei and Aerosol Particle Counters (Vienna, Austria). Number concentration, measured by the Turbulent Mixing CNC and other participating instruments, is found to be essentially equal.

  4. Estimating Atmospheric Turbulence From Flight Records

    NASA Technical Reports Server (NTRS)

    Wingrove, R. C.; Bach, R. E., Jr.; Schultz, T. A.

    1991-01-01

    Method for estimation of atmospheric turbulence encountered by airplanes utilizes wealth of data captured by multichannel digital flight-data recorders and air-traffic-control radar. Developed as part of continuing effort to understand how airplanes respond to such potentially hazardous phenomena as: clear-air turbulence generated by destabilized wind-shear layers above mountains and thunderstorms, and microbursts (intense downdrafts striking ground), associated with thunderstorms. Reconstructed wind fields used to predict and avoid future hazards.

  5. DOD (USAF) turbulence accidents and incidents

    NASA Technical Reports Server (NTRS)

    Miller, Douglas

    1987-01-01

    A summary of Air Force turbulence related mishaps for the last ten years of Air Force mishaps is presented from a perspective of where it has been, where it is now, and where it is going. In addition to accounts of major mishaps, a summary of what actions were taken to preclude future similar mishaps is presented. Also, a discussion of some of the things being done now and being planned for the future to prevent turbulence related mishaps is presented.

  6. Reconstruction of inclined air showers detected with the Pierre Auger Observatory

    SciTech Connect

    Collaboration: Pierre Auger Collaboration

    2014-08-01

    We describe the method devised to reconstruct inclined cosmic-ray air showers with zenith angles greater than 60° detected with the surface array of the Pierre Auger Observatory. The measured signals at the ground level are fitted to muon density distributions predicted with atmospheric cascade models to obtain the relative shower size as an overall normalization parameter. The method is evaluated using simulated showers to test its performance. The energy of the cosmic rays is calibrated using a sub-sample of events reconstructed with both the fluorescence and surface array techniques. The reconstruction method described here provides the basis of complementary analyses including an independent measurement of the energy spectrum of ultra-high energy cosmic rays using very inclined events collected by the Pierre Auger Observatory.

  7. Reconstruction of inclined air showers detected with the Pierre Auger Observatory

    SciTech Connect

    Aab, Alexander; et al.

    2014-08-08

    We describe the method devised to reconstruct inclined cosmic-ray air showers with zenith angles greater than 60° detected with the surface array of the Pierre Auger Observatory. The measured signals at the ground level are fitted to muon density distributions predicted with atmospheric cascade models to obtain the relative shower size as an overall normalization parameter. The method is evaluated using simulated showers to test its performance. The energy of the cosmic rays is calibrated using a sub-sample of events reconstructed with both the fluorescence and surface array techniques. The reconstruction method described here provides the basis of complementary analyses including an independent measurement of the energy spectrum of ultra-high energy cosmic rays using very inclined events collected by the Pierre Auger Observatory.

  8. Fast-neutron/gamma-ray radiography scanner for the detection of contraband in air cargo containers

    NASA Astrophysics Data System (ADS)

    Eberhardt, J.; Liu, Y.; Rainey, S.; Roach, G.; Sowerby, B.; Stevens, R.; Tickner, J.

    2006-05-01

    There is a worldwide need for efficient inspection of cargo containers at airports, seaports and road border crossings. The main objectives are the detection of contraband such as illicit drugs, explosives and weapons. Due to the large volume of cargo passing through Australia's airports every day, it is critical that any scanning system should be capable of working on unpacked or consolidated cargo, taking at most 1-2 minutes per container. CSIRO has developed a fast-neutron/gamma-ray radiography (FNGR) method for the rapid screening of air freight. By combining radiographs obtained using 14 MeV neutrons and 60Co gamma-rays, high resolution images showing both density and material composition are obtained. A near full-scale prototype scanner has been successfully tested in the laboratory. With the support of the Australian Customs Service, a full-scale scanner has recently been installed and commissioned at Brisbane International Airport.

  9. Heterodyne measurements of laser light scattering by a turbulent phase screen.

    PubMed

    Ridley, Kevin D; Watson, Stephen M; Jakeman, Eric; Harris, Michael

    2002-01-20

    We report experiments in which a fiber-coupled heterodyne laser system operating at a wavelength of 1.5 microm is used to measure the phase fluctuations induced on a laser beam by passage through a thin layer of turbulent air and subsequent propagation through free space. We investigate the statistical properties and power spectra of the phase and its rate of change, in addition to the intensity statistics. We find that the power spectrum of the rate of change of phase has a simple negative exponential form. We discuss our results in the context of the problem of detection of phase variations over an extended turbulent atmospheric path. PMID:11905580

  10. Turbulent combustion

    SciTech Connect

    Talbot, L.; Cheng, R.K.

    1993-12-01

    Turbulent combustion is the dominant process in heat and power generating systems. Its most significant aspect is to enhance the burning rate and volumetric power density. Turbulent mixing, however, also influences the chemical rates and has a direct effect on the formation of pollutants, flame ignition and extinction. Therefore, research and development of modern combustion systems for power generation, waste incineration and material synthesis must rely on a fundamental understanding of the physical effect of turbulence on combustion to develop theoretical models that can be used as design tools. The overall objective of this program is to investigate, primarily experimentally, the interaction and coupling between turbulence and combustion. These processes are complex and are characterized by scalar and velocity fluctuations with time and length scales spanning several orders of magnitude. They are also influenced by the so-called {open_quotes}field{close_quotes} effects associated with the characteristics of the flow and burner geometries. The authors` approach is to gain a fundamental understanding by investigating idealized laboratory flames. Laboratory flames are amenable to detailed interrogation by laser diagnostics and their flow geometries are chosen to simplify numerical modeling and simulations and to facilitate comparison between experiments and theory.

  11. Turbulence modeling

    NASA Technical Reports Server (NTRS)

    Bardina, Jorge E.

    1995-01-01

    The objective of this work is to develop, verify, and incorporate the baseline two-equation turbulence models which account for the effects of compressibility into the three-dimensional Reynolds averaged Navier-Stokes (RANS) code and to provide documented descriptions of the models and their numerical procedures so that they can be implemented into 3-D CFD codes for engineering applications.

  12. A method to determine true air temperature fluctuations in clouds with liquid water fraction and estimate water droplet effect on the calculations of the spectral structure of turbulent heat fluxes in cumulus clouds based on aircraft data

    NASA Astrophysics Data System (ADS)

    Strunin, Alexander M.; Zhivoglotov, Dmitriy N.

    2014-03-01

    Liquid water droplets could distort aircraft temperature measurements in clouds, leading to errors in calculated heat fluxes and incorrect flux distribution pattern. The estimation of cloud droplet effect on the readings of the high-frequency aircraft thermometer employed at the Central Aerological Observatory (CAO) was based on an experimental study of the sensor in a wind tunnel, using an air flow containing liquid water droplets. Simultaneously, calculations of the distribution of speed and temperature in a flow through the sensitive element of the sensor were fulfilled. This permitted estimating the coefficient of water content effect on temperature readings. Another way of estimating cloud droplet effect was based on the analysis of data obtained during aircraft observations of cumulus clouds in a tropical zone (Cuba Island). As a result, a method of correcting air temperature and recovering true air temperature fluctuations inside clouds was developed. This method has provided consistent patterns of heat flux distribution in a cumulus area. Analysis of the results of aircraft observations of cumulus clouds with temperature correction fulfilled has permitted investigation of the spectral structure of the fields of air temperature and heat fluxes to be performed in cumulus zones based on wavelet transformation. It is shown that mesoscale eddies (over 500 m in length) were the main factor of heat exchange between a cloud and the ambient space. The role of turbulence only consisted in mixing inside the cloud.

  13. Using CO2 Lidar for Standoff Detection of a Perfluorocarbon Tracer in Air

    SciTech Connect

    Heiser,J.H.; Smith, S.; Sedlacek, A.

    2008-02-06

    The Tag, Track and Location System Program (TTL) is investigating the use of PFTs as tracers for tagging and tracking items of interest or fallen soldiers. In order for the tagging and tracking to be valuable there must be a location system that can detect the PFTs. This report details the development of an infrared lidar platform for standoff detection of PFTs released into the air from a tagged object or person. Furthering work performed using a table top lidar system in an indoor environment; a mobile mini lidar platform was assembled using an existing Raman lidar platform, a grating tunable CO{sub 2} IR laser, Judson HgCdTe detector and miscellaneous folding optics and electronics. The lidar achieved {approx}200 ppb-m sensitivity in laboratory and indoor testing and was then successfully demonstrated at an outdoor test. The lidar system was able to detect PFTs released into a vehicle from a distance of 100 meters. In its final, fully optimized configuration the lidar was capable of repeatedly detecting PFTs in the air released from tagged vehicles. Responses were immediate and clear. This report details the results of a proof-of-concept demonstration for standoff detection of a perfluorocarbon tracer (PFT) using infrared lidar. The project is part of the Tag, Track and Location System Program and was performed under a contract with Tracer Detection Technology Corp. with funding from the Office of Naval Research. A lidar capable of detecting PFT releases at distance was assembled by modifying an existing Raman lidar platform by incorporating a grating tunable CO{sub 2} IR laser, Judson HgCdTe detector and miscellaneous folding optics and electronics. The lidar achieved {approx}200 ppb-m sensitivity in laboratory and indoor testing and was successfully demonstrated at an outdoor test. The demonstration test (scripted by the sponsor) consisted of three parked cars, two of which were tagged with the PFT. The cars were located 70 (closest) to 100 meters (farthest

  14. Detection Of Multilayer Cavities By Employing RC-DTH Air Hammer System And Cavity Auto Scanning Laser System

    NASA Astrophysics Data System (ADS)

    Luo, Yongjiang; Li, Lijia; Peng, Jianming; Yin, Kun; Li, Peng; Gan, Xin; Zhao, Letao; Su, Wei

    2015-12-01

    The subterranean cavities are seriously threatened to construction and mining safety, and it's important to obtain the exact localization and dimensions of subterranean cavities for the planning of geotechnical and mining activities. Geophysical investigation is an alternative method for cavity detection, but it usually failed for the uncertainly solution of information and data obtained by Geophysical methods. Drilling is considered as the most accurate method for cavity detection. However, the conventional drilling methods can only be used for single cavity detection, and there is no effective solution for multilayer cavities detection have been reported. In this paper, a reverse circulation (RC) down-the-hole (DTH) air hammer system with a special structured drill bit is built and a cavity auto scanning laser system based on laser range finding technique was employed to confirm the localization and dimensions of the cavities. This RC-DTH air hammer system allows drilling through the upper cavities and putting the cavity auto scanning laser system into the cavity area through the central passage of the drill tools to protect the detection system from collapsing of borehole wall. The RC-DTH air hammer system was built, and field tests were conducted in Lanxian County Iron Ore District, which is located in Lv Liang city of Shan Xi province, the northwest of china. Field tests show that employing the RC-DTH air hammer system assisted by the cavity auto scanning laser system is an efficiency method to detect multilayer cavities.

  15. Flame front configuration of turbulent premixed flames

    SciTech Connect

    Furukawa, Junichi; Maruta, Kaoru; Hirano, Toshisuke

    1998-02-01

    The present study is performed to explore dependence of the wrinkle scale of propane-air turbulent premixed flames on the characteristics of turbulence in the nonreacting flow, burner size, and mixture ratio. The wrinkle scales are examined and expressed in the frequency distribution of the radii of flame front curvatures. The average wrinkle scale depends not only on the characteristics of turbulence in the nonreacting flow but also on burner diameter and mixture ratio. The average wrinkle scale of a lean propane-air flame is larger than those of the near stoichiometric and rich flames. The smallest wrinkle scale of turbulent premixed flame is in the range of 0.75--1.0 mm, which is much larger than the Kolmogorov scale of turbulence in the nonreacting flow.

  16. Heart rate turbulence.

    PubMed

    Cygankiewicz, Iwona

    2013-01-01

    Heart rate turbulence (HRT) is a baroreflex-mediated biphasic reaction of heart rate in response to premature ventricular beats. Heart rate turbulence is quantified by: turbulence onset (TO) reflecting the initial acceleration of heart rate following premature beat and turbulence slope (TS) describing subsequent deceleration of heart rate. Abnormal HRT identifies patients with autonomic dysfunction or impaired baroreflex sensitivity due to variety of disorders, but also may reflect changes in autonomic nervous system induced by different therapeutic modalities such as drugs, revascularization, or cardiac resynchronization therapy. More importantly, impaired HRT has been shown to identify patients at high risk of all-cause mortality and sudden death, particularly in postinfarction and congestive heart failure patients. It should be emphasized that abnormal HRT has a well-established role in stratification of postinfarction and heart failure patients with relatively preserved left ventricular ejection fraction. The ongoing clinical trials will document whether HRT can be used to guide implantation of cardioverter-defibrillators in this subset of patients, not covered yet by ICD guidelines. This review focuses on the current state-of-the-art knowledge regarding clinical significance of HRT in detection of autonomic dysfunction and regarding the prognostic significance of this parameter in predicting all-cause mortality and sudden death.

  17. Heart rate turbulence.

    PubMed

    Cygankiewicz, Iwona

    2013-01-01

    Heart rate turbulence (HRT) is a baroreflex-mediated biphasic reaction of heart rate in response to premature ventricular beats. Heart rate turbulence is quantified by: turbulence onset (TO) reflecting the initial acceleration of heart rate following premature beat and turbulence slope (TS) describing subsequent deceleration of heart rate. Abnormal HRT identifies patients with autonomic dysfunction or impaired baroreflex sensitivity due to variety of disorders, but also may reflect changes in autonomic nervous system induced by different therapeutic modalities such as drugs, revascularization, or cardiac resynchronization therapy. More importantly, impaired HRT has been shown to identify patients at high risk of all-cause mortality and sudden death, particularly in postinfarction and congestive heart failure patients. It should be emphasized that abnormal HRT has a well-established role in stratification of postinfarction and heart failure patients with relatively preserved left ventricular ejection fraction. The ongoing clinical trials will document whether HRT can be used to guide implantation of cardioverter-defibrillators in this subset of patients, not covered yet by ICD guidelines. This review focuses on the current state-of-the-art knowledge regarding clinical significance of HRT in detection of autonomic dysfunction and regarding the prognostic significance of this parameter in predicting all-cause mortality and sudden death. PMID:24215748

  18. Experimental determination of thermal turbulence effects on a propagating laser beam

    NASA Astrophysics Data System (ADS)

    Ndlovu, Sphumelele C.; Chetty, Naven

    2015-08-01

    The effect of turbulence on propagating laser beams has been a subject of interest since the evolution of lasers back in 1959. In this work, an inexpensive and reliable technique for producing interferograms using a point diffraction interferometer (PDI) was considered to experimentally study the turbulence effects on a laser beam propagating through air. The formed interferograms from a propagating beamwere observed and digitally processed to study the strength of atmospheric turbulence. This technique was found to be sensitive enough to detect changes in applied temperature with distance between the simulated turbulence and laser path. These preliminary findings indicated that we can use a PDI method to detect and localise atmospheric turbulence parameters. Such parameters are very important for use in the military (defence laser weapons) and this is vital for South Africa (SA) since it has natural resources, is involved in peace keeping and mediation for other countries, and hence must have a strong defence system that will be able to locate, detect and destroy incoming missiles and other threatening atmospheric systems in order to protect its environment and avoid the initiation of countermeasures on its land.

  19. Wave Turbulence

    NASA Astrophysics Data System (ADS)

    Newell, Alan C.; Rumpf, Benno

    2011-01-01

    In this article, we state and review the premises on which a successful asymptotic closure of the moment equations of wave turbulence is based, describe how and why this closure obtains, and examine the nature of solutions of the kinetic equation. We discuss obstacles that limit the theory's validity and suggest how the theory might then be modified. We also compare the experimental evidence with the theory's predictions in a range of applications. Finally, and most importantly, we suggest open challenges and encourage the reader to apply and explore wave turbulence with confidence. The narrative is terse but, we hope, delivered at a speed more akin to the crisp pace of a Hemingway story than the wordjumblingtumbling rate of a Joycean novel.

  20. Turbulence modeling

    NASA Technical Reports Server (NTRS)

    Rubesin, Morris W.

    1987-01-01

    Recent developments at several levels of statistical turbulence modeling applicable to aerodynamics are briefly surveyed. Emphasis is on examples of model improvements for transonic, two-dimensional flows. Experience with the development of these improved models is cited to suggest methods of accelerating the modeling process necessary to keep abreast of the rapid movement of computational fluid dynamics into the computation of complex three-dimensional flows.

  1. First detection of Cherenkov light from cosmic-particle-induced air showers by Geiger-mode avalanche photodiodes

    NASA Astrophysics Data System (ADS)

    Biland, A.; Britvitch, I.; Lorenz, E.; Otte, N.; Pauss, F.; Renker, D.; Ritt, S.; Roeser, U.; Schneebeli, M.

    2007-10-01

    We report on first tests of Geiger-mode APDs (G-APD) to detect Cherenkov light from cosmic particle induced air showers. The motivation for this study stems from the requirement to improve the sensitivity of large imaging atmospheric Cherenkov telescopes (IACT) by replacing the photomultipliers (PMT) by high detection efficiency G-APDs. Three tests have been carried out, confirming sufficiently high light sensitivity of blue-sensitive G-APDs as future replacement of PMTs in IACTs.

  2. Air Embolism Detected During Computed Tomography Fluoroscopically Guided Transthoracic Needle Biopsy

    SciTech Connect

    Hirasawa, Satoshi Hirasawa, Hiromi; Taketomi-Takahashi, Ayako; Morita, Hideo; Tsushima, Yoshito; Amanuma, Makoto; Endo, Keigo

    2008-01-15

    Air embolism is a rare but potentially fatal complication of percutaneous needle biopsy of the lung. We report a case of cerebral air embolism which occurred during computed tomography (CT)-guided needle biopsy. Air entering the aorta is depicted on CT-fluoroscopy images of the procedure.

  3. Development of a combined air sampling and quantitative real-time PCR method for detection of Legionella spp.

    PubMed

    Sirigul, Chomrach; Wongwit, Waranya; Phanprasit, Wantanee; Paveenkittiporn, Wantana; Blacksell, Stuart D; Ramasoota, Pongrama

    2006-05-01

    The objective of this study was to develop and optimize the combined methods of air sampling and real time polymerase chain reaction (real-time PCR) for quantifying aerosol Legionella spp. Primers and TaqMan hydrolysis probe based on 5S rRNA gene specific for Legionella spp were used to amplify a specific DNA product of 84 bp. The impinger air sampler plus T-100 sampling pump was used to collect aerosol Legionella and as low as 10 fg of Legionella DNA per reaction could detected. Preliminary studies demonstrated that the developed method could detect aerosol Legionella spp 1.5-185 organisms /500 l of air within 5 hours, in contrast to culture method, that required a minimum of 7-10 days. PMID:17120970

  4. Impact of surface disinfection and sterile draping of furniture on room air quality in a cardiac procedure room with a ventilation and air-conditioning system (extrusion airflow, cleanroom class 1b (DIN 1946-4)).

    PubMed

    Below, Harald; Ryll, Sylvia; Empen, Klaus; Dornquast, Tina; Felix, Stefan; Rosenau, Heike; Kramer, Sebastian; Kramer, Axel

    2010-09-21

    In a cardiac procedure room, ventilated by a ventilation and air-conditioning system with turbulent mixed airflow, a protection zone in the operating area could be defined through visualization of airflows. Within this protection zone, no turbulence was detectable in the room air.Under the given conditions, disinfection of all surfaces including all furniture and equipment after the last operation and subsequent draping of furniture and all equipment that could not be removed from the room with sterile surgical drapes improved the indoor room air quality from cleanroom class C to cleanroom class B. This also allows procedures with elevated requirements to be performed in room class 1b.

  5. Acceleration of rain initiation by cloud turbulence.

    PubMed

    Falkovich, G; Fouxon, A; Stepanov, M G

    2002-09-12

    Vapour condensation in cloud cores produces small droplets that are close to one another in size. Droplets are believed to grow to raindrop size by coalescence due to collision. Air turbulence is thought to be the main cause for collisions of similar-sized droplets exceeding radii of a few micrometres, and therefore rain prediction requires a quantitative description of droplet collision in turbulence. Turbulent vortices act as small centrifuges that spin heavy droplets out, creating concentration inhomogeneities and jets of droplets, both of which increase the mean collision rate. Here we derive a formula for the collision rate of small heavy particles in a turbulent flow, using a recently developed formalism for tracing random trajectories. We describe an enhancement of inertial effects by turbulence intermittency and an interplay between turbulence and gravity that determines the collision rate. We present a new mechanism, the 'sling effect', for collisions due to jets of droplets that become detached from the air flow. We conclude that air turbulence can substantially accelerate the appearance of large droplets that trigger rain.

  6. Space-based detection of missing sulfur dioxide sources of global air pollution

    NASA Astrophysics Data System (ADS)

    McLinden, Chris A.; Fioletov, Vitali; Shephard, Mark W.; Krotkov, Nick; Li, Can; Martin, Randall V.; Moran, Michael D.; Joiner, Joanna

    2016-07-01

    Sulfur dioxide is designated a criteria air contaminant (or equivalent) by virtually all developed nations. When released into the atmosphere, sulfur dioxide forms sulfuric acid and fine particulate matter, secondary pollutants that have significant adverse effects on human health, the environment and the economy. The conventional, bottom-up emissions inventories used to assess impacts, however, are often incomplete or outdated, particularly for developing nations that lack comprehensive emission reporting requirements and infrastructure. Here we present a satellite-based, global emission inventory for SO2 that is derived through a simultaneous detection, mapping and emission-quantifying procedure, and thereby independent of conventional information sources. We find that of the 500 or so large sources in our inventory, nearly 40 are not captured in leading conventional inventories. These missing sources are scattered throughout the developing world--over a third are clustered around the Persian Gulf--and add up to 7 to 14 Tg of SO2 yr-1, or roughly 6-12% of the global anthropogenic source. Our estimates of national total emissions are generally in line with conventional numbers, but for some regions, and for SO2 emissions from volcanoes, discrepancies can be as large as a factor of three or more. We anticipate that our inventory will help eliminate gaps in bottom-up inventories, independent of geopolitical borders and source types.

  7. Space-Based Detection of Missing Sulfur Dioxide Sources of Global Air Pollution

    NASA Technical Reports Server (NTRS)

    McLinden, Chris A.; Fioletov, Vitali; Shephard, Mark W.; Krotkov, Nick; Li, Can; Martin, Randall V.; Moran, Michael D.; Joiner, Joanna

    2016-01-01

    Sulfur dioxide is designated a criteria air contaminant (or equivalent) by virtually all developed nations. When released into the atmosphere, sulfur dioxide forms sulfuric acid and fine particulate matter, secondary pollutants that have significant adverse effects on human health, the environment and the economy. The conventional, bottom-up emissions inventories used to assess impacts, however, are often incomplete or outdated, particularly for developing nations that lack comprehensive emission reporting requirements and infrastructure. Here we present a satellite-based, global emission inventory for SO2 that is derived through a simultaneous detection, mapping and emission-quantifying procedure, and thereby independent of conventional information sources. We find that of the 500 or so large sources in our inventory, nearly 40 are not captured in leading conventional inventories. These missing sources are scattered throughout the developing world-over a third are clustered around the Persian Gulf-and add up to 7 to 14 Tg of SO2 yr(exp -1), or roughly 6-12% of the global anthropogenic source. Our estimates of national total emissions are generally in line with conventional numbers, but for some regions, and for SO2 emissions from volcanoes, discrepancies can be as large as a factor of three or more. We anticipate that our inventory will help eliminate gaps in bottom-up inventories, independent of geopolitical borders and source types.

  8. Detection of Coxiella burnetii in Ambient Air after a Large Q Fever Outbreak

    PubMed Central

    de Rooij, Myrna M. T.; Borlée, Floor; Smit, Lidwien A. M.; de Bruin, Arnout; Janse, Ingmar; Heederik, Dick J. J.; Wouters, Inge M.

    2016-01-01

    One of the largest Q fever outbreaks ever occurred in the Netherlands from 2007–2010, with 25 fatalities among 4,026 notified cases. Airborne dispersion of Coxiella burnetii was suspected but not studied extensively at the time. We investigated temporal and spatial variation of Coxiella burnetii in ambient air at residential locations in the most affected area in the Netherlands (the South-East), in the year immediately following the outbreak. One-week average ambient particulate matter < 10 μm samples were collected at eight locations from March till September 2011. Presence of Coxiella burnetii DNA was determined by quantitative polymerase chain reaction. Associations with various spatial and temporal characteristics were analyzed by mixed logistic regression. Coxiella burnetii DNA was detected in 56 out of 202 samples (28%). Airborne Coxiella burnetii presence showed a clear seasonal pattern coinciding with goat kidding. The spatial variation was significantly associated with number of goats on the nearest goat farm weighted by the distance to the farm (OR per IQR: 1.89, CI: 1.31–2.76). We conclude that in the year after a large Q fever outbreak, temporal variation of airborne Coxiella burnetii is suggestive to be associated with goat kidding, and spatial variation with distance to and size of goat farms. Aerosol measurements show to have potential for source identification and attribution of an airborne pathogen, which may also be applicable in early stages of an outbreak. PMID:26991094

  9. Detection of Coxiella burnetii in Ambient Air after a Large Q Fever Outbreak.

    PubMed

    de Rooij, Myrna M T; Borlée, Floor; Smit, Lidwien A M; de Bruin, Arnout; Janse, Ingmar; Heederik, Dick J J; Wouters, Inge M

    2016-01-01

    One of the largest Q fever outbreaks ever occurred in the Netherlands from 2007-2010, with 25 fatalities among 4,026 notified cases. Airborne dispersion of Coxiella burnetii was suspected but not studied extensively at the time. We investigated temporal and spatial variation of Coxiella burnetii in ambient air at residential locations in the most affected area in the Netherlands (the South-East), in the year immediately following the outbreak. One-week average ambient particulate matter < 10 μm samples were collected at eight locations from March till September 2011. Presence of Coxiella burnetii DNA was determined by quantitative polymerase chain reaction. Associations with various spatial and temporal characteristics were analyzed by mixed logistic regression. Coxiella burnetii DNA was detected in 56 out of 202 samples (28%). Airborne Coxiella burnetii presence showed a clear seasonal pattern coinciding with goat kidding. The spatial variation was significantly associated with number of goats on the nearest goat farm weighted by the distance to the farm (OR per IQR: 1.89, CI: 1.31-2.76). We conclude that in the year after a large Q fever outbreak, temporal variation of airborne Coxiella burnetii is suggestive to be associated with goat kidding, and spatial variation with distance to and size of goat farms. Aerosol measurements show to have potential for source identification and attribution of an airborne pathogen, which may also be applicable in early stages of an outbreak. PMID:26991094

  10. Detection of Campylobacter Bacteria in Air Samples for Continuous Real-Time Monitoring of Campylobacter Colonization in Broiler Flocks▿

    PubMed Central

    Olsen, Katja N.; Lund, Marianne; Skov, Julia; Christensen, Laurids S.; Hoorfar, Jeffrey

    2009-01-01

    Improved monitoring tools are important for the control of Campylobacter bacteria in broiler production. In this study, we compare the sensitivities of detection of Campylobacter by PCR with feces, dust, and air samples during the lifetimes of broilers in two poultry houses and conclude that the sensitivity of detection of Campylobacter in air is comparable to that in other sample materials. Profiling of airborne particles in six poultry houses revealed that the aerodynamic conditions were dependent on the age of the chickens and very comparable among different poultry houses, with low proportions of particles in the 0.5- to 2-μm-diameter range and high proportions in the 2- to 5-μm-diameter range. Campylobacter could also be detected by PCR in air samples collected at the hanging stage during the slaughter process but not at the other stages tested at the slaughterhouse. The exploitation of airborne dust in poultry houses as a sample material for the detection of Campylobacter and other pathogens provides an intriguing possibility, in conjunction with new detection technologies, for allowing continuous or semicontinuous monitoring of colonization status. PMID:19201953

  11. Detection of Campylobacter bacteria in air samples for continuous real-time monitoring of Campylobacter colonization in broiler flocks.

    PubMed

    Olsen, Katja N; Lund, Marianne; Skov, Julia; Christensen, Laurids S; Hoorfar, Jeffrey

    2009-04-01

    Improved monitoring tools are important for the control of Campylobacter bacteria in broiler production. In this study, we compare the sensitivities of detection of Campylobacter by PCR with feces, dust, and air samples during the lifetimes of broilers in two poultry houses and conclude that the sensitivity of detection of Campylobacter in air is comparable to that in other sample materials. Profiling of airborne particles in six poultry houses revealed that the aerodynamic conditions were dependent on the age of the chickens and very comparable among different poultry houses, with low proportions of particles in the 0.5- to 2-microm-diameter range and high proportions in the 2- to 5-microm-diameter range. Campylobacter could also be detected by PCR in air samples collected at the hanging stage during the slaughter process but not at the other stages tested at the slaughterhouse. The exploitation of airborne dust in poultry houses as a sample material for the detection of Campylobacter and other pathogens provides an intriguing possibility, in conjunction with new detection technologies, for allowing continuous or semicontinuous monitoring of colonization status.

  12. Using geo-targeted social media data to detect outdoor air pollution

    NASA Astrophysics Data System (ADS)

    Jiang, W.; Wang, Y.; Tsou, M. H.; Fu, X.

    2016-06-01

    Outdoor air pollution has become a more and more serious issue over recent years (He, 2014). Urban air quality is measured at air monitoring stations. Building air monitoring stations requires land, incurs costs and entails skilled technicians to maintain a station. Many countries do not have any monitoring stations and even lack any means to monitor air quality. Recent years, the social media could be used to monitor air quality dynamically (Wang, 2015; Mei, 2014). However, no studies have investigated the inter-correlations between real-space and cyberspace by examining variation in micro-blogging behaviors relative to changes in daily air quality. Thus, existing methods of monitoring AQI using micro-blogging data shows a high degree of error between real AQI and air quality as inferred from social media messages. In this paper, we introduce a new geo-targeted social media analytic method to (1) investigate the dynamic relationship between air pollution-related posts on Sina Weibo and daily AQI values; (2) apply Gradient Tree Boosting, a machine learning method, to monitor the dynamics of AQI using filtered social media messages. Our results expose the spatiotemporal relationships between social media messages and real-world environmental changes as well suggesting new ways to monitor air pollution using social media.

  13. Turbulent Jets?

    NASA Astrophysics Data System (ADS)

    Wilde, B. H.; Rosen, P. A.; Foster, J. M.; Perry, T. S.; Steinkamp, M. J.; Robey, H. F.; Khokhlov, A. M.; Gittings, M. L.; Coker, R. F.; Keiter, P. A.; Knauer, J. P.; Drake, R. P.; Remington, B. A.; Bennett, G. R.; Sinars, D. B.; Campbell, R. B.; Mehlhorn, T. A.

    2003-10-01

    Over the last few years we have fielded numerous supersonic jet experiments on the NOVA and OMEGA lasers and Sandia's pulsed-power Z-machine in a collaboration between Los Alamos National Laboratory, the Atomic Weapons Establishment, Lawrence Livermore National Laboratory, and Sandia National Laboratory. These experiments are being conducted to help validate our radiation-hydrodynamic codes, especially the newly developing ASC codes. One of the outstanding questions is whether these types of jets should turn turbulent given their high Reynolds number. Recently we have modified our experiments to have more Kelvin-Helmholtz shear, run much later in time and therefore have a better chance of going turbulent. In order to diagnose these large (several mm) jets at very late times ( 1000 ns) we are developing point-projection imaging on both the OMEGA laser, the Sandia Z-Machine, and ultimately at NIF. Since these jets have similar Euler numbers to jets theorized to be produced in supernovae explosions, we are also collaborating with the astrophysics community to help in the validation of their new codes. This poster will present a review of the laser and pulsed-power experiments and a comparison of the data to simulations by the codes from the various laboratories. We will show results of simulations wherein these jets turn highly 3-dimensional and show characteristics of turbulence. With the new data, we hope to be able to validate the sub-grid-scale turbulent mix models (e. g. BHR) that are being incorporated into our codes.*This work is performed under the auspices of the U. S. Department of Energy by the Los Alamos National Laboratory Laboratory under Contract No. W-7405-ENG-36, Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48, the Laboratory for Laser Energetics under Contract No. DE-FC03-92SF19460, Sandia National Laboratories under Contract No. DE-AC04-94AL85000, the Office of Naval Research, and the NASA Astrophysical Theory Grant.

  14. Effectiveness of Air Drying and Magnification Methods for Detecting Initial Caries on Occlusal Surfaces Using Three Different Diagnostic Aids.

    PubMed

    Goel, Deepti; Sandhu, Meera; Jhingan, Pulkit; Sachdev, Vinod

    2016-01-01

    Objective-The aim of this study was to assess the effect of magnification and air-drying on detection of carious lesion. Study Design-44 human extracted premolars were selected with sound occlusal surfaces without frank cavitation. The Diagnostic techniques used were Unaided visual examination, Magnifying Loupes (4.2×) and Stereomicroscope (10×, before and after air-drying) and then the teeth were sectioned bucco-lingually and both the surfaces were examined under Stereomicroscope (50×) to assess the presence or absence of carious lesion in the pit and fissures. The scores were compared to obtain Cohen's kappa coefficient (Reproducibility) and subjected to the Friedman Test and Paired t test. Sensitivity, specificity and positive predictive value used to assess accuracy. Results-On Statistical analysis, visual examination before and after air drying had highest specificity but lowest sensitivity compared to different diagnostic techniques. Magnifying loupes after air-drying had highest sensitivity and lowest specificity compared to other diagnostic techniques. Conclusion-Air drying combined with magnifying aids are cost-effective, reliable method for detection of early carious lesion. If used in pediatric clinical practice, any undesirable pain and discomfort to the patient due to invasive procedures and helps in employing preventive measures. PMID:27472570

  15. Turbulence and Mountain Wave Conditions Observed with an Airborne 2-Micron Lidar

    NASA Technical Reports Server (NTRS)

    Teets, Edward H., Jr.; Ashburn, Chris; Ehernberger, L. J.; Bogue, Rodney K.

    2006-01-01

    Joint efforts by the National Aeronautics and Space Administration, the Department of Defense, and industry partners are enhancing the capability of airborne wind and turbulence detection. The Airborne Coherent Lidar (light detection and ranging) for Advanced In-Flight Measurements was flown on three series of flights to assess its capability over a range of altitudes, air mass conditions, and gust phenomena. This report describes the observation of mountain waves and turbulence induced by mountain waves over the Tehachapi and Sierra Nevada mountain ranges by lidar on board the NASA Airborne Science DC-8 (McDonnell Douglas Corporation, Long Beach, California) airplane during two flights. The examples in this report compare lidar-predicted mountain waves and wave-induced turbulence to subsequent airplane-measured true airspeed. Airplane acceleration data is presented describing the effects of the wave-induced turbulence on the DC-8 airplane. Highlights of the lidar-predicted airspeed from the two flights show increases of 12 m/s at the mountain wave interface and peak-to-peak airspeed changes of 10 m/s and 15 m/s in a span of 12 s in moderate turbulence.

  16. Complete Genome Sequence of Enterovirus D68 Detected in Classroom Air and on Environmental Surfaces

    PubMed Central

    Bonny, Tania S.; Morris, J. Glenn; Loeb, Julia C.

    2016-01-01

    We amplified and sequenced the complete genome of enterovirus D68 (EV-D68) that had been collected from classroom air using a filter-based air sampling method and by swab sampling of environmental surfaces. Relatively high levels of EV-D68 genome equivalents were found per cubic meter of air by quantitative real-time reverse transcription-PCR (RT-PCR). PMID:27313311

  17. The acoustics of turbulent flow

    NASA Astrophysics Data System (ADS)

    Rimskii-Korsakov, A. V.

    Papers are presented on such topics as the excitation of sound by small perturbations of entropy and vorticity in spatially nonuniform flows of a compressible ideal gas; the aeroacoustic characteristics of acoustically excited jets; the noise intensity and spectrum in a turbulent boundary layer on a flat plate; sound refraction in a turbulent shear flow; and the spectrum of spatial correlations of turbulent pressure pulsations at a wall at high Reynolds numbers. Consideration is also given to a comparative study of the acoustic fields of air and helium jets at subsonic outflow speeds; the effect of external boundary layer flow on jet-noise characteristics; wing-profile noise in turbulent flow; sound emission from an unsteady boundary layer; and the sound-field characteristics of a moving source (with application to aircraft-noise analysis). The effect of a sound field on coherent structures in turbulent flow, aerodynamic forces causing fan vibration and noise, and a silencer for a jet-aircraft powerplant are also examined. For individual items see A84-28803 to A84-28820

  18. A turbulence model for buoyant flows based on vorticity generation.

    SciTech Connect

    Domino, Stefan Paul; Nicolette, Vernon F.; O'Hern, Timothy John; Tieszen, Sheldon R.; Black, Amalia Rebecca

    2005-10-01

    A turbulence model for buoyant flows has been developed in the context of a k-{var_epsilon} turbulence modeling approach. A production term is added to the turbulent kinetic energy equation based on dimensional reasoning using an appropriate time scale for buoyancy-induced turbulence taken from the vorticity conservation equation. The resulting turbulence model is calibrated against far field helium-air spread rate data, and validated with near source, strongly buoyant helium plume data sets. This model is more numerically stable and gives better predictions over a much broader range of mesh densities than the standard k-{var_epsilon} model for these strongly buoyant flows.

  19. Turbulence mitigation methods and their evaluation

    NASA Astrophysics Data System (ADS)

    van Eekeren, Adam W. M.; Dijk, Judith; Schutte, Klamer

    2014-10-01

    In general, long range detection, recognition and identification in visual and infrared imagery are hampered by turbulence caused by atmospheric conditions. The amount of turbulence is often indicated by the refractive-index structure parameter Cn2. The value of this parameter and its variation is determined by the turbulence effects over the optical path. Especially along horizontal optical paths near the surface (land-to-land scenario) large values and fluctuations of Cn2 occur, resulting in an extremely blurred and shaky image sequence. Another important parameter is the isoplanatic angle, θ0, which is the angle where the turbulence is approximately constant. Over long horizontal paths the values of θ0 are typically very small; much smaller than the field-of-view of the camera. Typical image artefacts that are caused by turbulence are blur, tilt and scintillation. These artefacts occur often locally in an image. Therefore turbulence corrections are required in each image patch of the size of the isoplanatic angle. Much research has been devoted to the field of turbulence mitigation. One of the main advantages of turbulence mitigation is that it enables visual recognition over larger distances by reducing the blur and motion in imagery. In many (military) scenarios this is of crucial importance. In this paper we give a brief overview of two software approaches to mitigate the visual artifacts caused by turbulence. These approaches are very diverse in complexity. It is shown that a more complex turbulence mitigation approach is needed to improve the imagery containing medium turbulence. The basic turbulence mitigation method is only capable of mitigating low turbulence.

  20. Broadband spectroscopic lidar for SWIR/MWIR detection of gaseous pollutants in air

    NASA Astrophysics Data System (ADS)

    Lambert-Girard, Simon; Hô, Nicolas; Bourliaguet, Bruno; Lemieux, Dany; Piché, Michel; Babin, François

    2012-11-01

    A broadband SWIR/MWIR spectroscopic lidar for detection of gaseous pollutants in air is presented for doing differential optical absorption spectroscopy (DOAS). One of the distinctive parts of the lidar is the use of a picosecond PPMgO:LN OPG (optical parametric generator) capable of generating broadband (10 to <100 nm FWHM) and tunable (1.5 to 3.9 μm) SWIR/MWIR light. The optical source layout and properties are presented, along with a description of the lidar breadboard. Results from indoor simulated typical operation of the lidar will be discussed, the operation consisting in emitting the broadband coherent light along a line of sight (LOS) and measuring the back-scattering returns from of a topographic feature or aerosols. A second distinctive part is the gated MCT-APD focal plane array used in the output plane of the grating spectrograph of the lidar system. The whole of the returned spectra is measured, within a very short time gate, at every pulse and at a resolution of a few tenths to a few nm. Light is collected by a telescope with variable focus for maximum coupling of the return to the spectrograph. Since all wavelengths are emitted and received simultaneously, the atmosphere is "frozen" during the path integrated measurement and hopefully reduces the baseline drift problem encountered in many broadband scanning approaches. The resulting path integrated gas concentrations are retrieved by fitting the molecular absorption features present in the measured spectra. The use of broadband pulses of light and of DOAS fitting procedures make it also possible to measure more than one gas at a time, including interferents. The OPG approach enables the generation of moderate FWHM continua with high spectral energy density and tunable to absorption features of a great number of molecules. Proposed follow-on work and applications will also be presented.

  1. Temporal and spatial trend detection of maximum air temperature in Iran during 1960-2005

    NASA Astrophysics Data System (ADS)

    Kousari, Mohammad Reza; Ahani, Hossein; Hendi-zadeh, Razieh

    2013-12-01

    Trends of maximum air temperature (T max) were investigated in three time scales including annual, seasonal, and monthly time series in 32 synoptic stations in the whole of Iran during 1960-2005. First, nonparametric Mann-Kendall test after removal of the lag-1 serial correlation component from the T max time series was used for trend detection and spatial distribution of various trends was mapped. Second, Sen's slope estimator was used to determine the median slope of positive or negative T max trends. Third, 10-year moving average low-pass filter was applied to facilitate the trend analysis and the smoothed time series derived from the mentioned filter were clustered in three clusters for each time series and then were plotted to show their spatial distribution patterns in Iran. Results showed that there are considerable significant positive trends of T max in warm months including April, June, July, August and September and warm seasons. These trends can be found in an annual time scale which indicated almost 50% positive trends. However, cold months and seasons did not exhibit a remarkable significant trend. Although it was rather difficult to detect particular spatial distribution of significant trends, some parts in west, north-east and south-east and central regions of the country showed more positive trends. In an annual time scale, Kermanshah located in west regions indicates most change at (+) 0.41 °C per decade. On the one hand, many clusters of normalized and filtered T max time series revealed the increasing trend after 1970 which has dramatically risen after around 1990. It is in accordance with many other findings for temperature time series from different countries and therefore, it can be generated from simultaneous changes in a bigger scale than regional one. On the other hand, the concentration of increasing trends of T max in warm seasons and their accordance to plants growing season in Iran can raise the importance of the role of frequent

  2. Defect detection performance of the UCSD non-contact air-coupled ultrasonic guided wave inspection of rails prototype

    NASA Astrophysics Data System (ADS)

    Mariani, Stefano; Nguyen, Thompson V.; Sternini, Simone; Lanza di Scalea, Francesco; Fateh, Mahmood; Wilson, Robert

    2016-04-01

    The University of California at San Diego (UCSD), under a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, is developing a system for high-speed and non-contact rail defect detection. A prototype using an ultrasonic air-coupled guided wave signal generation and air-coupled signal detection, paired with a real-time statistical analysis algorithm, has been realized. This system requires a specialized filtering approach based on electrical impedance matching due to the inherently poor signal-to-noise ratio of air-coupled ultrasonic measurements in rail steel. Various aspects of the prototype have been designed with the aid of numerical analyses. In particular, simulations of ultrasonic guided wave propagation in rails have been performed using a Local Interaction Simulation Approach (LISA) algorithm. The system's operating parameters were selected based on Receiver Operating Characteristic (ROC) curves, which provide a quantitative manner to evaluate different detection performances based on the trade-off between detection rate and false positive rate. The prototype based on this technology was tested in October 2014 at the Transportation Technology Center (TTC) in Pueblo, Colorado, and again in November 2015 after incorporating changes based on lessons learned. Results from the 2015 field test are discussed in this paper.

  3. Detecting CO2 and CH4 Urban Emissions using Column-Integrated Dry Air mole Fractions, In-Situ Tower Dry Air Mole Fractions, and WRF Modeling

    NASA Astrophysics Data System (ADS)

    Hillyard, P. W.; Lauvaux, T.; Podolske, J. R.; Iraci, L. T.; Miles, N. L.; Richardson, S.; Davis, K.; Roehl, C. M.; Wunch, D.; Wennberg, P. O.; Blavier, J. F.; Allen, N.; Barrow, E.; Deng, A.

    2015-12-01

    Total column measurements of atmospheric gases are important because of their ability to be performed via satellites that provide global coverage. Here we will present measurements of CO2 and CH4 dry air mole fractions obtained using a Fourier Transform Spectrometer (FTS) as part of the Total Carbon Column Observing Nework (TCCON). These measurements were performed in Indianapolis as part of the Indianapolis Flux Experiment (INFLUX). We will extract urban emission signals using high resolution modeling and in-situ tower measurements of CO2 and CH4 mixing ratios. In addition to quantifying the influence of surface emissions on the column measurements, we will also decompose the atmospheric columns into sub-layers to identify the origin of air masses at various altitudes. We will show that the variability in the origins of air masses increases the complexity of the observed signals in the column, which limits our ability to combine surface and column measurements. This work will also highlight the potential application of using total column measurements to detect local urban signals. We conclude that the deployment of multiple column sensors is required in order to measure the upwind (background) and downwind (urban) conditions. Such work provides a test case for using these methods with satellite measurements such as GOSAT and OCO-2 that provide global coverage.

  4. USING CANINES IN SOURCE DETECTION OF INDOOR AIR POLLUTANTS EPA SCIENCE FORUM

    EPA Science Inventory

    Scent detection dogs have been used extensively in law enforcement and military applications to detect narcotics and explosives for over thirty years. Controlled laboratory studies have documented accurate detection by dogs of specific compounds associated with explosives and nar...

  5. Quantitative Evaluation of an Air-monitoring Network Using Atmospheric Transport Modeling and Frequency of Detection Methods.

    PubMed

    Rood, Arthur S; Sondrup, A Jeffrey; Ritter, Paul D

    2016-04-01

    A methodology has been developed to quantify the performance of an air-monitoring network in terms of frequency of detection. Frequency of detection is defined as the fraction of "events" that result in a detection at either a single sampler or network of samplers. An "event" is defined as a release to the atmosphere of a specified amount of activity over a finite duration that begins on a given day and hour of the year. The methodology uses an atmospheric transport model to predict air concentrations of radionuclides at the samplers for a given release time and duration. Another metric of interest determined by the methodology is called the network intensity, which is defined as the fraction of samplers in the network that have a positive detection for a given event. The frequency of detection methodology allows for evaluation of short-term releases that include effects of short-term variability in meteorological conditions. The methodology was tested using the U.S. Department of Energy Idaho National Laboratory Site ambient air-monitoring network consisting of 37 low-volume air samplers in 31 different locations covering a 17,630 km region. Releases from six major facilities distributed over an area of 1,435 km were modeled and included three stack sources and eight ground-level sources. A Lagrangian Puff air dispersion model (CALPUFF) was used to model atmospheric transport. The model was validated using historical Sb releases and measurements. Relevant 1-wk release quantities from each emission source were calculated based on a dose of 1.9×10 mSv at a public receptor (0.01 mSv assuming release persists over a year). Important radionuclides were Am, Cs, Pu, Pu, Sr, and tritium. Results show the detection frequency was over 97.5% for the entire network considering all sources and radionuclides. Network intensity results ranged from 3.75% to 62.7%. Evaluation of individual samplers indicated some samplers were poorly located and added little to the overall

  6. Ultimate detectability of volatile organic compounds: how much further can we reduce their ambient air sample volumes for analysis?

    PubMed

    Kim, Yong-Hyun; Kim, Ki-Hyun

    2012-10-01

    To understand the ultimately lowest detection range of volatile organic compounds (VOCs) in air, application of a high sensitivity analytical system was investigated by coupling thermal desorption (TD) technique with gas chromatography (GC) and time-of-flight (TOF) mass spectrometry (MS). The performance of the TD-GC/TOF MS system was evaluated using liquid standards of 19 target VOCs prepared in the range of 35 pg to 2.79 ng per μL. Studies were carried out using both total ion chromatogram (TIC) and extracted ion chromatogram (EIC) mode. EIC mode was used for calibration to reduce background and to improve signal-to-noise. The detectability of 19 target VOCs, if assessed in terms of method detection limit (MDL, per US EPA definition) and limit of detection (LOD), averaged 5.90 pg and 0.122 pg, respectively, with the mean coefficient of correlation (R(2)) of 0.9975. The minimum quantifiable mass of target analytes, when determined using real air samples by the TD-GC/TOF MS, is highly comparable to the detection limits determined experimentally by standard. In fact, volumes for the actual detection of the major aromatic VOCs like benzene, toluene, and xylene (BTX) in ambient air samples were as low as 1.0 mL in the 0.11-2.25 ppb range. It was thus possible to demonstrate that most target compounds including those in low abundance could be reliably quantified at concentrations down to 0.1 ppb at sample volumes of less than 10 mL. The unique sensitivity of this advanced analytical system can ultimately lead to a shift in field sampling strategy with smaller air sample volumes facilitating faster, simpler air sampling (e.g., use of gas syringes rather than the relative complexity of pumps or bags/canisters), with greatly reduced risk of analyte breakthrough and minimal interference, e.g., from atmospheric humidity. The improved detection limits offered by this system can also enhance accuracy and measurement precision. PMID:22934885

  7. Statistical turbulence theory and turbulence phenomenology

    NASA Technical Reports Server (NTRS)

    Herring, J. R.

    1973-01-01

    The application of deductive turbulence theory for validity determination of turbulence phenomenology at the level of second-order, single-point moments is considered. Particular emphasis is placed on the phenomenological formula relating the dissipation to the turbulence energy and the Rotta-type formula for the return to isotropy. Methods which deal directly with most or all the scales of motion explicitly are reviewed briefly. The statistical theory of turbulence is presented as an expansion about randomness. Two concepts are involved: (1) a modeling of the turbulence as nearly multipoint Gaussian, and (2) a simultaneous introduction of a generalized eddy viscosity operator.

  8. The potential of passive-remote Fourier transform infrared (FTIR) spectroscopy to detect organic emissions under the Clean Air Act

    SciTech Connect

    Demirgian, J.C.; Hammer, C.L. ); Kroutil, R.T. )

    1992-01-01

    The Clean Air Act of 1990 regulates the emission of 198 air toxics. Currently, there is no existing technology by which a regulatory agency can independently determine if a facility is in compliance. We have successfully tested the ability of passive-remote Fourier transform infrared (FTIR) spectroscopy to detect chemical plumes released in the field. Additional laboratory releases demonstrated that FTIR spectroscopy can detect target analytes in mixtures containing components which have overlapping absorbances. The FTIR spectrometer was able to identify and quantify each component released with an average quantitative error of less than 20% using partial least squares (PLS) analysis and 40% using classical least squares analysis (CLS) when calibration files containing pure components and mixtures were used. Calibration files containing only pure analytes resulted in CLS outperforming PLS analyses.

  9. The potential of passive-remote Fourier transform infrared (FTIR) spectroscopy to detect organic emissions under the Clean Air Act

    SciTech Connect

    Demirgian, J.C.; Hammer, C.L.; Kroutil, R.T.

    1992-07-01

    The Clean Air Act of 1990 regulates the emission of 198 air toxics. Currently, there is no existing technology by which a regulatory agency can independently determine if a facility is in compliance. We have successfully tested the ability of passive-remote Fourier transform infrared (FTIR) spectroscopy to detect chemical plumes released in the field. Additional laboratory releases demonstrated that FTIR spectroscopy can detect target analytes in mixtures containing components which have overlapping absorbances. The FTIR spectrometer was able to identify and quantify each component released with an average quantitative error of less than 20% using partial least squares (PLS) analysis and 40% using classical least squares analysis (CLS) when calibration files containing pure components and mixtures were used. Calibration files containing only pure analytes resulted in CLS outperforming PLS analyses.

  10. Radiation Detection Field Test at the Federal Express (FedEx) Air Cargo Facility at Denver International Airport (DIA)

    SciTech Connect

    Weirup, D; Waters, A; Hall, H; Dougan, A; Trombino, D; Mattesich, G; Hull, E; Bahowick, S; Loshak, A; Gruidl, J

    2004-02-11

    Lawrence Livermore National Laboratory (LLNL) recently conducted a field-test of radiation detection and identification equipment at the air cargo facility of Federal Express (FedEx) located at Denver International Airport (DIA) over a period of two weeks. Comprehensive background measurements were performed and were analyzed, and a trial strategy for detection and identification of parcels displaying radioactivity was implemented to aid in future development of a comprehensive protection plan. The purpose of this project was threefold: {sm_bullet} Quantify background radiation environments at an air cargo facility. {sm_bullet} Quantify and identify ''nuisance'' alarms. {sm_bullet} Evaluate the performance of various isotope identifiers deployed in an operational environment (in this case, the operational environment included the biggest blizzard in over 90 years!).

  11. Simulation of the Turbulent air Flow Over a Circular Cavity with a Variable Opening Angle in an U-Shaped Channel

    NASA Astrophysics Data System (ADS)

    Isaev, S. A.; Baranov, P. A.; Usachov, A. E.; Zhukova, Yu. V.; Vysotskaya, A. A.; Malyshkin, D. A.

    2015-07-01

    A numerical investigation of the influence of the opening angle of a circular cavity in an U-shaped channel and the Reynolds number of a fluid fl ow in this channel on the local characteristics and turbulence of this fl ow has been performed based on the solution of the Reynolds equations, closed by the old and new Menter shear-stress transfer models and two variants of this model accounting for the curvature of streamlines, with the use of multiblock computational technologies realized in the VP2/3 package. The results of calculations were compared with each other and with experimental data of I. Castro and R. Savelsberg. This comparison has shown that the best agreement between the numerical predictions and experiments is obtained in the case where calculations are performed within the framework of the Leshtsiner-Rody-Isaev approach with correction for the eddy viscosity of the fluid fl ow. It was established that with increase in the Reynolds number and in the opening angle of the cavity the circulation flow in the near-wall layer of the vortex trapped in the cavity intensifies at a practically constant vorticity in the core of the vortex.

  12. Detection of Lightning-produced NOx by Air Quality Monitoring Stations in Israel

    NASA Astrophysics Data System (ADS)

    Yair, Y.; Shalev, S.; Saaroni, H.; Ziv, B.

    2011-12-01

    Lightning is the largest natural source for the production of nitrogen oxides (LtNOx) in the troposphere. Since NOx are greenhouse gases, it is important to know the global production rate of LtNOx for climate studies (present estimates range from 2 to 8 Tg per year) and to model its vertical distribution (Ott et al., 2010). One of the key factors for such an estimate is the yield of a single lightning flash, namely the number of molecules produced for each Joule of energy deposited along the lightning channel. We used lightning stroke data from the Israel Lightning Location System (ILLS) together with NOx data obtained from the national network of air quality monitoring stations operated by the Israeli Ministry of Environmental Protection. Looking for the fingerprints of LtNOx in the general ambient concentrations, usually most affected by pollution from urban sources, we looked only for CG strokes occurring within a radius of 3 km from the location of an air-quality monitoring station. This lowered the number of relevant cases from 605,413 strokes detected in the 2004/5 through 2009/10 seasons to 1,897 strokes. We applied a threshold of > 60kA reducing the number of events to 35. The results showed that there was no consistent rising trend in the NOx concentrations in the hour following the lightning (the lifetime near the ground is expected to be a few hours; Zhang et al., 2003). However, when considering only those events when the prevailing wind was in the direction from the stroke location toward the sensor (7 cases), a clear increase of few ppb following the stroke was observed in 5 cases [see Fig.]. This increase is well correlated with the wind speed, suggesting an effective transport from the stroke location to the sensor. Weaker winds allow dilution and result in smaller observed increases of LtNOx. Separate analysis of additional 17 cases in which the strokes were located < 500 m from the monitoring station (with any peak current above 7 kA) showed no

  13. Flexible Wing Base Micro Aerial Vehicles: Towards Flight Autonomy: Vision-Based Horizon Detection for Micro Air Vehicles

    NASA Technical Reports Server (NTRS)

    Nechyba, Michael C.; Ettinger, Scott M.; Ifju, Peter G.; Wazak, Martin

    2002-01-01

    Recently substantial progress has been made towards design building and testifying remotely piloted Micro Air Vehicles (MAVs). This progress in overcoming the aerodynamic obstacles to flight at very small scales has, unfortunately, not been matched by similar progress in autonomous MAV flight. Thus, we propose a robust, vision-based horizon detection algorithm as the first step towards autonomous MAVs. In this paper, we first motivate the use of computer vision for the horizon detection task by examining the flight of birds (biological MAVs) and considering other practical factors. We then describe our vision-based horizon detection algorithm, which has been demonstrated at 30 Hz with over 99.9% correct horizon identification, over terrain that includes roads, buildings large and small, meadows, wooded areas, and a lake. We conclude with some sample horizon detection results and preview a companion paper, where the work discussed here forms the core of a complete autonomous flight stability system.

  14. Physics of Stratocumulus Top (POST): turbulence characteristics

    NASA Astrophysics Data System (ADS)

    Jen-La Plante, Imai; Ma, Yongfeng; Nurowska, Katarzyna; Gerber, Hermann; Khelif, Djamal; Karpinska, Katarzyna; Kopec, Marta K.; Kumala, Wojciech; Malinowski, Szymon P.

    2016-08-01

    Turbulence observed during the Physics of Stratocumulus Top (POST) research campaign is analyzed. Using in-flight measurements of dynamic and thermodynamic variables at the interface between the stratocumulus cloud top and free troposphere, the cloud top region is classified into sublayers, and the thicknesses of these sublayers are estimated. The data are used to calculate turbulence characteristics, including the bulk Richardson number, mean-square velocity fluctuations, turbulence kinetic energy (TKE), TKE dissipation rate, and Corrsin, Ozmidov and Kolmogorov scales. A comparison of these properties among different sublayers indicates that the entrainment interfacial layer consists of two significantly different sublayers: the turbulent inversion sublayer (TISL) and the moist, yet hydrostatically stable, cloud top mixing sublayer (CTMSL). Both sublayers are marginally turbulent, i.e., the bulk Richardson number across the layers is critical. This means that turbulence is produced by shear and damped by buoyancy such that the sublayer thicknesses adapt to temperature and wind variations across them. Turbulence in both sublayers is anisotropic, with Corrsin and Ozmidov scales as small as ˜ 0.3 and ˜ 3 m in the TISL and CTMSL, respectively. These values are ˜ 60 and ˜ 15 times smaller than typical layer depths, indicating flattened large eddies and suggesting no direct mixing of cloud top and free-tropospheric air. Also, small scales of turbulence are different in sublayers as indicated by the corresponding values of Kolmogorov scales and buoyant and shear Reynolds numbers.

  15. Bat wing air pressures may deflect prey structures to provide echo cues for detecting prey in clutter.

    PubMed

    Kuc, Roman; Kuc, Victor

    2012-09-01

    Bats have remarkable echolocation capabilities to detect prey in darkness. While it is clear how bats do this for prey that is isolated, moving, or noisy, their ability to find still and quiet prey within clutter has remained a mystery. A video published by the ChiRoPing group shows the gleaning bat Micronycteris microtis capturing a still dragonfly specimen sitting on a leaf surface. While hovering over the dragonfly, the bat's wings exert air forces that cause the dragonfly wings to deflect in synchrony with the bat's wing beats. This paper illustrates that echoes from such deflecting wings vary in both amplitude and time-of-flight, producing robust echo cues that permit prey detection, even when the prey is embedded within clutter. Experiments with a dragonfly specimen mounted on a leaf driven by periodic air puffs produced wing deflections that were sensed with sonar pulses. Results demonstrate that echo variations synchronized with periodic air puffs are easily distinguishable from surrounding clutter, even when clutter produces the first echoes. These results suggest a strategy that bats can employ to detect still and silent prey embedded within cluttered environments.

  16. Integrated optics ring-resonator chemical sensor for detection of air contamination

    NASA Technical Reports Server (NTRS)

    Manfreda, A. M.; Homer, M. L.; Ksendzov, A.

    2004-01-01

    We report a silicon nitride-based ring resonator chemical sensor with sensing polymer coating. Its sensitivity to isopropanol in air is at least 50 ppm - well under the permissible exposure level of 400 ppm.

  17. Intregrated optics ring-resonator chemical sensor for detection of air contamination

    NASA Technical Reports Server (NTRS)

    Ksendzov, Alexander; Homer, Margie L.; Manfreda, Allison M.

    2004-01-01

    We report a silicon nitride-based ring resonator chemical sensor with sensing polymer coating. Its sensitivity to isopropanol in air is at least 50 ppm - well under the permissible exposure level of 400 ppm.

  18. Advanced Turbulence Modeling Concepts

    NASA Technical Reports Server (NTRS)

    Shih, Tsan-Hsing

    2005-01-01

    The ZCET program developed at NASA Glenn Research Center is to study hydrogen/air injection concepts for aircraft gas turbine engines that meet conventional gas turbine performance levels and provide low levels of harmful NOx emissions. A CFD study for ZCET program has been successfully carried out. It uses the most recently enhanced National combustion code (NCC) to perform CFD simulations for two configurations of hydrogen fuel injectors (GRC- and Sandia-injector). The results can be used to assist experimental studies to provide quick mixing, low emission and high performance fuel injector designs. The work started with the configuration of the single-hole injector. The computational models were taken from the experimental designs. For example, the GRC single-hole injector consists of one air tube (0.78 inches long and 0.265 inches in diameter) and two hydrogen tubes (0.3 inches long and 0.0226 inches in diameter opposed at 180 degree). The hydrogen tubes are located 0.3 inches upstream from the exit of the air element (the inlet location for the combustor). To do the simulation, the single-hole injector is connected to a combustor model (8.16 inches long and 0.5 inches in diameter). The inlet conditions for air and hydrogen elements are defined according to actual experimental designs. Two crossing jets of hydrogen/air are simulated in detail in the injector. The cold flow, reacting flow, flame temperature, combustor pressure and possible flashback phenomena are studied. Two grid resolutions of the numerical model have been adopted. The first computational grid contains 0.52 million elements, the second one contains over 1.3 million elements. The CFD results have shown only about 5% difference between the two grid resolutions. Therefore, the CFD result obtained from the model of 1.3-million grid resolution can be considered as a grid independent numerical solution. Turbulence models built in NCC are consolidated and well tested. They can handle both coarse and

  19. Calorimetric detection of the conical terahertz radiation from femtosecond laser filaments in air

    NASA Astrophysics Data System (ADS)

    Houard, Aurélien; Liu, Yi; Mysyrowicz, André; Leriche, Bernadette

    2007-12-01

    The spectral distribution of the conical terahertz emission from a femtosecond laser filament in air is measured with a bolometric detector and a set of filters, confirming that the main part of the emission lies between 0.5 and 3THz. The efficiency of this terahertz emission is compared with that obtained in air via four wave mixing of femtosecond laser pulses at ω and 2ω in the presence of a plasma.

  20. Determination of nitro polynuclear aromatic hydrocarbons in air and diesel particulate matter using liquid chromatography with electrochemical and fluorescence detection

    SciTech Connect

    MacCrehan, W.A.; May, W.E.; Yang, S.D.; Benner, B.A. Jr.

    1988-02-01

    Three different approaches to the liquid chromatographic detection of nitro polynuclear aromatic hydrocarbons in air and diesel particulate extracts are presented, based on differential pulse (LCDPD) and amperometric (LCEC) electrochemical detection and fluorescence detection following online reduction to the amine (LCFI). The particulate extraction/fractionation procedure for each detection approach is discussed. The operational advantages of oxygen removal with a platinum oxygen scrubber (all three types of detection), the use of modulated pulse detection, and wavelength-programmed fluorescence detection are explored. 1-Nitropyrene is determined in Standard Reference Material (SRM) 1650 diesel particulate matter and in several other round robin samples by all three methods. Results are compared to those obtained by other techniques (gas chromatography/mass spectrometry) and by other laboratories (LCFI). Additionally, 2-nitrofluorene, 9-nitroanthracene, 7-nitrobenz(a)anthracene, and 6-nitrobenzo(a)pyrene are determined in SRM 1650 by LCFI. The detection limits for 1-nitropyrene (expressed as picograms) are 5200 (LCDPD), 60 (LCEC), and 10 (LCFI).

  1. Design considerations and performance characteristics of AirSentinel: a new UV-LIF bio-aerosol threat detection trigger

    NASA Astrophysics Data System (ADS)

    DeFreez, Richard; Merrill, Ezra; Albanna, Sam; Davis, Bert; Call, Charles

    2005-10-01

    AirSentinel® is a new low cost, compact ultraviolet-based light induced fluorescence (UV-LIF) bio-aerosol threat detection trigger. Earlier UV-LIF triggers, for example, FLAPS, BARTS, BAWS, Bioni, and BioLert, have used UV laser sources to induce fluorescence of biological aerosols. Two recent developments from the DARPA MTO SUVOS program, BAST and TAC-BIO, use UV LEDs for the same purpose, thereby broadening the term UV-LIF to mean laser or LED induced autofluorescence. All of these earlier triggers interrogate aerosols on a particle-by-particle basis on- the-fly. The major trade-off for these instruments is cost, size, and complexity versus counting efficiency (probability of detection) with the lower size end of the respirable range being most difficult to detect. AirSentinel® employs a different approach to UV-LIF detection: aerosol concentration by collection on a surface, surface interrogation, and surface rejuvenation prior to repeated concentration and interrogation cycles. Aerosol particle concentration via impaction on a surface addresses the issue of small particle counting efficiency since the fluorescence from the sum of the particles is the sum of the fluorescence signals from the collected particles, typically hundreds or thousands in number. Surface interrogation for a LIF signal is accomplished by illumination with a 280 nm and/or a 365 nm LED. As expected, test results show better relative detection performance using 280 nm excitation LEDs for bio-toxin simulants and somewhat better performance at 365 nm for standard Bacillus globigii spore targets. AirSentinel® beta technology is currently in long term testing in a number of public and other government buildings.

  2. CHARACTERIZING MAGNETIZED TURBULENCE IN M51

    SciTech Connect

    Houde, Martin; Fletcher, Andrew; Beck, Rainer; Hildebrand, Roger H.; Vaillancourt, John E.; Stil, Jeroen M.

    2013-03-20

    We use previously published high-resolution synchrotron polarization data to perform an angular dispersion analysis with the aim of characterizing magnetized turbulence in M51. We first analyze three distinct regions (the center of the galaxy, and the northwest and southwest spiral arms) and can clearly discern the turbulent correlation length scale from the width of the magnetized turbulent correlation function for two regions and detect the imprint of anisotropy in the turbulence for all three. Furthermore, analyzing the galaxy as a whole allows us to determine a two-dimensional Gaussian model for the magnetized turbulence in M51. We measure the turbulent correlation scales parallel and perpendicular to the local mean magnetic field to be, respectively, {delta}{sub ||} = 98 {+-} 5 pc and {delta} = 54 {+-} 3 pc, while the turbulent-to-ordered magnetic field strength ratio is found to be B{sub t}/B{sub 0} = 1.01 {+-} 0.04. These results are consistent with those of Fletcher et al., who performed a Faraday rotation dispersion analysis of the same data, and our detection of anisotropy is consistent with current magnetized turbulence theories.

  3. Seasonality in submesoscale turbulence.

    PubMed

    Callies, Jörn; Ferrari, Raffaele; Klymak, Jody M; Gula, Jonathan

    2015-04-21

    Although the strongest ocean surface currents occur at horizontal scales of order 100 km, recent numerical simulations suggest that flows smaller than these mesoscale eddies can achieve important vertical transports in the upper ocean. These submesoscale flows, 1-100 km in horizontal extent, take heat and atmospheric gases down into the interior ocean, accelerating air-sea fluxes, and bring deep nutrients up into the sunlit surface layer, fueling primary production. Here we present observational evidence that submesoscale flows undergo a seasonal cycle in the surface mixed layer: they are much stronger in winter than in summer. Submesoscale flows are energized by baroclinic instabilities that develop around geostrophic eddies in the deep winter mixed layer at a horizontal scale of order 1-10 km. Flows larger than this instability scale are energized by turbulent scale interactions. Enhanced submesoscale activity in the winter mixed layer is expected to achieve efficient exchanges with the permanent thermocline below.

  4. Large Eddy Simulation of Stable Boundary Layer Turbulent Processes in Complex Terrain

    SciTech Connect

    Eric D. Skyllingstad

    2005-01-26

    Research was performed using a turbulence boundary layer model to study the behavior of cold, dense flows in regions of complex terrain. Results show that flows develop a balance between turbulent entrainment of warm ambient air and dense, cold air created by surface cooling. Flow depth and strength is a function of downslope distance, slope angle and angle changes, and the ambient air temperature.

  5. Direct numerical simulation of turbulent mixing in regular and fractal grid turbulence

    NASA Astrophysics Data System (ADS)

    Suzuki, Hiroki; Nagata, Kouji; Sakai, Yasuhiko; Hayase, Toshiyuki

    2010-12-01

    Turbulent mixing in regular and fractal grid turbulence is investigated in this work by using direct numerical simulation (DNS). Two types of turbulence-generating grids are used: a biplane square grid (regular grid) and a square fractal grid. The thickness ratios tr of the fractal grids are set at 5.0 and 8.5. The grid solidity is maintained at σ=0.36 for all the grids. The mesh Reynolds number, ReM=U0Meff/ν, is set at 2500 for all cases, where U0 is the cross-sectionally averaged mean velocity; Meff, the effective mesh size; and ν, the kinematic viscosity. The grids are numerically generated using the immersed boundary method at 4Meff downstream of the entrance to the computational domain. The computational domain size normalized by Meff is 64×8×8 in the streamwise, vertical and spanwise directions for the regular grid and 64×16×16 for the fractal grids. Scalar mixing layers that initially have a step profile develop downstream of the grids. The Prandtl number is set at Pr=0.71 considering the heat transfer in air flow. Instantaneous temperature fields, instantaneous fluctuating temperature fields and fundamental turbulent statistics are presented. The results show that turbulent mixing is more strongly enhanced in fractal grid turbulence than in regular grid turbulence for the same ReM. In fractal grid turbulence, turbulent mixing is more strongly enhanced at tr=8.5 than at tr=5.0.

  6. Lifted turbulent jet flames

    NASA Astrophysics Data System (ADS)

    Hammer, Jay A.

    Experiments were conducted on lifted, turbulent jet diffusion flames. An automated technique using a linear photodiode array was implemented to measure the temporal history of the liftoff height h. The measurements enabled accurate determination of the mean liftoff height [...] under a wide range of flow conditions, including several fuels, nozzle diameters, and exit velocities [...]. The results showed an approximately linear relationship between [...] and [...], with a slight dependence on Reynolds number. A strain-rate model for liftoff, based on far-field scaling of turbulent jets, provides an explanation for the linear dependence of [...] on [...]. Measurements were also made in which the nozzle fluid contained varying amounts of air, where it was found that the slope of the [...] vs. [...] line increases faster than predicted by far-field scaling of turbulent jets. The discrepancy is attributed to near-field effects.The amplitudes of the fluctuations in h were found to be of the order of the local large scale of the jet. There is a slight increase in normalized fluctuation level [...] with [...], and there is some variation of [...] with fuel type. The time scales of the fluctuations of h were found to be considerably longer than the local large-scale time of the turbulence [...]. By using fuels of different chemical times to vary [...], the measured correlation time [...] normalized by [...] was found to collapse with Richardson number [...]. Experiments in which the nozzles were oriented horizontally showed no change in [...], however. Additional experiments were conducted to investigate alternative explanations for the variation of [...] with [...]. These experiments included measuring the flame length L simultaneously with h, and measuring the visible radiation I simultaneously with h. L(t) was found to be nearly uncorrelated with h(t), dismissing the possibility that a feedback mechanism from L to h controls the fluctuations of h. Although I(t) is highly

  7. Turbulence and Mountain Wave Conditions Observed with an Airborne 2-Micron Lidar

    NASA Technical Reports Server (NTRS)

    Teets, Edward H., Jr.; Ehernberger, Jack; Bogue, Rodney; Ashburn, Chris

    2007-01-01

    Joint efforts by the National Aeronautics and Space Administration (NASA), the Department of Defense, and industry partners are enhancing the capability of airborne wind and turbulence detection. The Airborne Coherent Lidar for Advanced In-Flight Measurements (ACLAIM) was flown on three series of flights to assess its capability over a range of altitudes, air mass conditions, and gust phenomena. This paper describes the observation of mountain waves and turbulence induced by mountain waves over the Tehachapi and Sierra Nevada mountain ranges in southern California by lidar onboard the NASA Airborne Science DC-8 airplane. The examples in this paper compare lidar-predicted mountain waves and wave-induced turbulence to subsequent aircraft-measured true airspeed. Airplane acceleration data is presented describing the effects of the wave-induced turbulence on the DC-8 airplane. Highlights of the lidar-predicted airspeed from the two flights show increases of 12 m/s at the mountain wave interface and peak-to-peak airspeed changes of 10 m/s and 15 m/s in a span of 12 s in moderate turbulence.

  8. Turbulence and mountain wave conditions observed with an airborne 2-micron lidar

    NASA Technical Reports Server (NTRS)

    Teets, Edward H., Jr.; Ashburn, Chris; Ehernberger, Jack; Bogue, Rodney

    2006-01-01

    Joint efforts by the National Aeronautics and Space Administration (NASA), the Department of Defense, and industry partners are enhancing the capability of airborne wind and turbulence detection. The Airborne Coherent Lidar for Advanced In-Flight Measurements (ACLAIM) was flown on three series of flights to assess its capability over a range of altitudes, air mass conditions, and gust phenomena. This paper describes the observation of mountain waves and turbulence induced by mountain waves over the Tehachapi and Sierra Nevada mountain ranges (California, USA) by lidar onboard the NASA Airborne Science DC-8 airplane. The examples in this paper compare lidar-predicted mountain waves and wave-induced turbulence to subsequent aircraft-measured true airspeed. Airplane acceleration data is presented describing the effects of the wave-induced turbulence on the DC-8 airplane. Highlights of the lidar-predicted airspeed from the two flights show increases of 12 meters per second (m/s) at the mountain wave interface and peak-to-peak airspeed changes of 10 m/s and 15 m/s in a span of 12 seconds in moderate turbulence.

  9. Highly resolved measurements of atmospheric turbulence with the new 2d-Atmospheric Laser Cantilever Anemometer

    NASA Astrophysics Data System (ADS)

    Jeromin, A.; Schaffarczyk, A. P.; Puczylowski, J.; Peinke, J.; Hölling, M.

    2014-12-01

    For the investigation of atmospheric turbulent flows on small scales a new anemometer was developed, the so-called 2d-Atmospheric Laser Cantilever Anemometer (2d-ALCA). It performs highly resolved measurements with a spatial resolution in millimeter range and temporal resolution in kHz range, thus detecting very small turbulent structures. The anemometer is a redesign of the successfully operating 2d-LCA for laboratory application. The new device was designed to withstand hostile operating environments (rain and saline, humid air). In February 2012, the 2d-ALCA was used for the first time in a test field. The device was mounted in about 53 m above ground level on a lattice tower near the German North Sea coast. Wind speed was measured by the 2d-ALCA at 10 kHz sampling rate and by cup anemometers at 1 Hz. The instantaneous wind speed ranged from 8 m/s to 19 m/s at an average turbulence level of about 7 %. Wind field characteristics were analyzed based on cup anemometer as well as 2d-ALCA. The combination of both devices allowed the study of atmospheric turbulence over several magnitudes in turbulent scales.

  10. Design of an integrated sensor system for the detection of traces of different molecules in the air

    NASA Astrophysics Data System (ADS)

    Strle, D.; Muševič, I.

    2015-04-01

    This article presents the design of a miniature detection system and its associated signal processing electronics, which can detect and selectively recognize vapor traces of different materials in the air - including explosives. It is based on the array of surface-functionalized COMB capacitive sensors and extremely low noise, analog, integrated electronic circuit, hardwired digital signal processing hardware and additional software running on a PC. The instrument is sensitive and selective, consumes a minimum amount of energy, is very small (few mm3) and cheap to produce in large quantities, and is insensitive to mechanical influences. Using an electronic detection system built of low noise analog front-end and hard-wired digital signal processing, it is possible to detect less than 0.3ppt of TNT molecules in the atmosphere (3 TNT molecules in 1013 molecules of the air) at 25°C on a 1 Hz bandwidth using very small volume and approx. 10 mA current from a 5V supply voltage. The sensors are implemented in a modified MEMS process and analog electronics in 0.18 um CMOS technology.

  11. Detection of defect parameters using nonlinear air-coupled emission by ultrasonic guided waves at contact acoustic nonlinearities.

    PubMed

    Delrue, Steven; Van Den Abeele, Koen

    2015-12-01

    Interaction of ultrasonic guided waves with kissing bonds (closed delaminations and incipient surface breaking cracks) gives rise to nonlinear features at the defect location. This causes higher harmonic frequency ultrasonic radiation into the ambient air, often referred to as Nonlinear Air-Coupled Emission (NACE), which may serve as a nonlinear tag to detect the defects. This paper summarizes the results of a numerical implementation and simulation study of NACE. The developed model combines a 3D time domain model for the nonlinear Lamb wave propagation in delaminated samples with a spectral solution for the nonlinear air-coupled emission. A parametric study is conducted to illustrate the potential of detecting defect location, size and shape by studying the NACE acoustic radiation patterns in different orientation planes. The simulation results prove that there is a good determination potential for the defect parameters, especially when the radiated frequency matches one of the resonance frequencies of the delaminated layer, leading to a Local Defect Resonance (LDR). PMID:26208725

  12. Meteorology Associated with Turbulence Encounters During NASA's Fall-2000 Flight Experiments

    NASA Technical Reports Server (NTRS)

    Hamilton, David W.; Proctor, Fred H.

    2002-01-01

    Initial flight experiments have been conducted to investigate convectively induced turbulence and to test technologies for its airborne detection. Turbulence encountered during the experiments is described with sources of data measured from in situ sensors, groundbased and airborne Doppler radars, and aircraft video. Turbulence measurements computed from the in situ system were quantified in terms of RMS normal loads (sigma(sub Delta n)), where 0.20 g is less than or equal to sigma(sub Delta n) is less than or equal to 0.30 g is considered moderate and sigma(sub Delta n) is greater than 0.30 g is severe. During two flights, 18 significant turbulence encounters (sigma(sub Delta) is greater than or equal to 0.20 g) occurred in the vicinity of deep convection; 14 moderate and 4 severe. In all cases, the encounters with turbulence occurred along the periphery of cumulus convection. These events were associated with relatively low values of radar reflectivity, i.e. RRF is less than 35 dBz, with most levels being below 20 dBz. The four cases of severe turbulence occurred in precipitation and were centered at the interface between a cumulus updraft turret and a downwind downdraft. Horizontal gradients of vertical velocity at this interface were found to be strongest on the downwind side of the cumulus turrets. Furthermore, the greatest loads to the aircraft occurred while flying along, not orthogonal to, the ambient environmental wind vector. During the two flights, no significant turbulence was encountered in the clear air (visual meteorological conditions), not even in the immediate vicinity of the deep convection.

  13. The problem of atmospheric turbulence

    NASA Technical Reports Server (NTRS)

    Toomre, J.; HILL; MERRYFIELD; GOUGH

    1984-01-01

    All ground-based observations of the solar five-minute oscillations are affected by turbulence in the Earth's atmosphere that leads to substantial refractive index variations. The turbulent motions serve to mix an air mass that is thermally stratified in the vertical, thereby producing intermittent thermal fluctuations over a wide range of heights in the atmosphere. These thermal structures yield refractive index changes that deflect the light path in a complicated way, producing intricate variations of amplitude and phase in what might have started out as simple plane waves. Since the fluid turbulence is statistical in nature, so too is the optical turbulence which is an integral measure of the refractive index changes along the light travel path. All of this produces what is usually called atmospheric seeing, which consists of image motion, blurring and distortion across the field of view. The effects of atmospheric seeing upon observations of five-minute oscillations carried out from the ground were assessed. This will help to provide a baseline estimate of the scienctific benefits that might accrue if one were able to observe the same oscillations from a space observatory unfettered by seeing effects.

  14. Pulsar timing noise from superfluid turbulence

    NASA Astrophysics Data System (ADS)

    Melatos, Andrew; Link, Bennett

    2014-01-01

    Shear-driven turbulence in the superfluid interior of a neutron star exerts a fluctuating torque on the rigid crust, causing the rotational phase to walk randomly. The phase fluctuation spectrum is calculated analytically for incompressible Kolmogorov turbulence and is found to be red; the half-power point is set by the observed spin-down rate, the crust-superfluid lag and the dynamical response time of the superfluid. Preliminary limits are placed on the latter quantities using selected time- and frequency-domain data. It is found that measurements of the normalization and slope of the power spectrum are reproduced for reasonable choices of the turbulence parameters. The results point preferentially to the neutron star interior containing a turbulent superfluid rather than a turbulent Navier-Stokes fluid. The implications for gravitational wave detection by pulsar timing arrays are discussed briefly.

  15. TURBULENT SHEAR ACCELERATION

    SciTech Connect

    Ohira, Yutaka

    2013-04-10

    We consider particle acceleration by large-scale incompressible turbulence with a length scale larger than the particle mean free path. We derive an ensemble-averaged transport equation of energetic charged particles from an extended transport equation that contains the shear acceleration. The ensemble-averaged transport equation describes particle acceleration by incompressible turbulence (turbulent shear acceleration). We find that for Kolmogorov turbulence, the turbulent shear acceleration becomes important on small scales. Moreover, using Monte Carlo simulations, we confirm that the ensemble-averaged transport equation describes the turbulent shear acceleration.

  16. DETECTION AND IDENTIFICATION OF TOXIC AIR POLLUTANTS USING AIRBORNE LWIR HYPERSPECTRAL IMAGING

    EPA Science Inventory

    Gaseous releases from petrochemical, refinery, and electrical production facilities can contribute to regional air quality problems. Fugitive emissions or leaks can be costly to industry in terms of lost materials and products. Ground-based sampling and monitoring for leaks are t...

  17. Detection of Extensive Cosmic Air Showers by Small Scintillation Detectors with Wavelength-Shifting Fibres

    ERIC Educational Resources Information Center

    Aiola, Salvatore; La Rocca, Paola; Riggi, Francesco; Riggi, Simone

    2012-01-01

    A set of three small scintillation detectors was employed to measure correlated events due to the passage of cosmic muons originating from extensive air showers. The coincidence rate between (any) two detectors was extracted as a function of their relative distance. The difference between the arrival times in three non-aligned detectors was used…

  18. Sensitive indoor air monitoring of monoterpenes using different adsorbents and thermal desorption gas chromatography with mass-selective detection.

    PubMed

    Hollender, Juliane; Sandner, Frank; Möller, Manfred; Dott, Wolfgang

    2002-07-12

    A simple method using active trapping on adsorbents and thermal desorption followed by GC-MS analysis was developed for the indoor air monitoring of monoterpenes. The study was carried out using a dynamically generated atmosphere consisting of 11 monoterpenes: camphene, camphor, delta 3-carene, 1,8-cineol, limonene, linalool, alpha-pinene, beta-pinene, alpha-terpinene, gamma-terpinene, fenchyl alcohol. The influence of the different adsorbents Tenax TA, Tenax GR, Carbosieve SIII, Chromosorb 106 on the yield of six selected monoterpenes at indoor air concentrations was studied. The adsorbent Tenax GR gave relatively the best yields followed by Tenax TA. Detection limits of approximately 1 microgram m3 were determined with Tenax GR for most of the monoterpenes.

  19. The role of non-invasive biomarkers in detecting acute respiratory effects of traffic-related air pollution.

    PubMed

    Scarpa, M C; Kulkarni, N; Maestrelli, P

    2014-09-01

    The role of non-invasive methods in the investigation of acute effects of traffic-related air pollution is not clearly established. We evaluated the usefulness of non-invasive biomarkers in detecting acute air pollution effects according to the age of participants, the disease status, their sensitivity compared with lung function tests and their specificity for a type of pollutant. Search terms lead to 535 titles, among them 128 had potentially relevant abstracts. Sixtynine full papers were reviewed, while 59 articles were excluded as they did not meet the selection criteria. Methods used to assess short-term effects of air pollution included analysis of nasal lavage (NAL) for the upper airways, and induced sputum (IS), exhaled breath condensate (EBC) and exhaled nitric oxide (FeNO) for central and lower airways. There is strong evidence that FeNO evaluation is useful independently from subject age, while IS analysis is suitable almost for adults. Biomarker changes are generally observed upon pollutant exposure irrespective of the disease status of the participants. None of the biomarkers identified are specific for a type of pollutant exposure. Based on experimental exposure studies, there is moderate evidence that IS analysis is more sensitive than lung function tests, whereas this is not the case for biomarkers obtained by NAL or EBC. Cells and some cytokines (IL-6, IL-8 and myeloperoxidase) have been measured both in the upper respiratory tract (NAL) and in the lower airways (IS). Overall, the response to traffic exposure seems different in the two compartments. In conclusion, this survey of current literature displays the complexity of this research field, highlights the significance of short-term studies on traffic pollution and gives important tips when planning studies to detect acute respiratory effects of air pollution in a non-invasive way.

  20. Turbulent reacting flow computations including turbulence-chemistry interactions

    NASA Technical Reports Server (NTRS)

    Narayan, J. R.; Girimaji, S. S.

    1992-01-01

    A two-equation (k-epsilon) turbulence model has been extended to be applicable for compressible reacting flows. A compressibility correction model based on modeling the dilatational terms in the Reynolds stress equations has been used. A turbulence-chemistry interaction model is outlined. In this model, the effects of temperature and species mass concentrations fluctuations on the species mass production rates are decoupled. The effect of temperature fluctuations is modeled via a moment model, and the effect of concentration fluctuations is included using an assumed beta-pdf model. Preliminary results obtained using this model are presented. A two-dimensional reacting mixing layer has been used as a test case. Computations are carried out using the Navier-Stokes solver SPARK using a finite rate chemistry model for hydrogen-air combustion.

  1. Imaging through turbulence using a plenoptic sensor

    NASA Astrophysics Data System (ADS)

    Wu, Chensheng; Ko, Jonathan; Davis, Christopher C.

    2015-09-01

    Atmospheric turbulence can significantly affect imaging through paths near the ground. Atmospheric turbulence is generally treated as a time varying inhomogeneity of the refractive index of the air, which disrupts the propagation of optical signals from the object to the viewer. Under circumstances of deep or strong turbulence, the object is hard to recognize through direct imaging. Conventional imaging methods can't handle those problems efficiently. The required time for lucky imaging can be increased significantly and the image processing approaches require much more complex and iterative de-blurring algorithms. We propose an alternative approach using a plenoptic sensor to resample and analyze the image distortions. The plenoptic sensor uses a shared objective lens and a microlens array to form a mini Keplerian telescope array. Therefore, the image obtained by a conventional method will be separated into an array of images that contain multiple copies of the object's image and less correlated turbulence disturbances. Then a highdimensional lucky imaging algorithm can be performed based on the collected video on the plenoptic sensor. The corresponding algorithm will select the most stable pixels from various image cells and reconstruct the object's image as if there is only weak turbulence effect. Then, by comparing the reconstructed image with the recorded images in each MLA cell, the difference can be regarded as the turbulence effects. As a result, the retrieval of the object's image and extraction of turbulence effect can be performed simultaneously.

  2. X-33 Turbulent Aeroheating Measurements and Predictions

    NASA Technical Reports Server (NTRS)

    Hollis, Brian R.; Berry, Scott A.; Horvath, Thomas J.

    2002-01-01

    Measurements and predictions of the X-33 turbulent aeroheating environment have been performed for Mach 6, perfect-gas air conditions. The purpose of this investigation was to compare turbulent aeroheating predictions from two Navier-Stokes codes, LAURA and GASP, with each other and with experimental data in which turbulent flow was produced through either natural transition or forced transition using roughness elements. The wind tunnel testing was conducted at free stream Reynolds numbers of 0.72 x 10(exp 7)/m to 2.4 x 10(exp 7)/m (2.2 x 10(exp 6)/ft to 7.3 x 10(exp 6)/ft) on 0.254 m (10.0-in.) X-33 models at alpha = 40 deg with smooth surfaces, smooth surfaces with discrete trips, and surfaces with simulated bowed thermal protection system panels. Turbulent flow was produced by the discrete trips and bowed panels for all but the lowest Reynolds number, while turbulent flow on the smooth model was produced only at the highest Reynolds number. Turbulent aeroheating levels on each of the three model types were measured using global phosphor thermography and agreed to within the experimental accuracy (+/= 15%) of the test technique. Computations were performed at the wind tunnel free stream conditions using both codes. Turbulent aeroheating levels predicted using the LAURA code were generally 5%-10% lower than those from GASP, although both sets of predictions fell within the experimental accuracy of the wind tunnel data.

  3. Measurement techniques investigated for detection of hydrogen chloride gas in ambient air

    NASA Technical Reports Server (NTRS)

    Gregory, G. L.

    1976-01-01

    Nine basic techniques are discussed, ranging from concentration (parts per million) to dosage only (parts per million-seconds) measurement techniques. Data for each technique include lower detection limit, response time, instrument status, and in some cases, specificity. Several techniques discussed can detect ambient hydrogen chloride concentrations below 1 part per million with a response time of seconds.

  4. An experimental study of reactive turbulent mixing

    NASA Technical Reports Server (NTRS)

    Cooper, L. P.; Marek, C. J.; Strehlow, R. A.

    1977-01-01

    An experimental study of two coaxial gas streams, which react very rapidly, was performed to investigate the mixing characteristics of turbulent flow fields. The center stream consisted of a CO-N2 mixture and the outer annular stream consisted of air vitiated by H2 combustion. The streams were at equal velocity (50 m/sec) and temperature (1280 K). Turbulence measurements were obtained using hot film anemometry. A sampling probe was used to obtain time averaged gas compositions. Six different turbulence generators were placed in the annular passage to alter the flow field mixing characteristics. The turbulence generators affected the bulk mixing of the streams and the extent of CO conversion to different degrees. The effects can be related to the average eddy size (integral scale) and the bulk mixing. Higher extents of conversion of CO to CO2 were found be increasing the bulk mixing and decreasing the average eddy size.

  5. Development of portable mass spectrometer with electron cyclotron resonance ion source for detection of chemical warfare agents in air.

    PubMed

    Urabe, Tatsuya; Takahashi, Kazuya; Kitagawa, Michiko; Sato, Takafumi; Kondo, Tomohide; Enomoto, Shuichi; Kidera, Masanori; Seto, Yasuo

    2014-01-01

    A portable mass spectrometer with an electron cyclotron resonance ion source (miniECRIS-MS) was developed. It was used for in situ monitoring of trace amounts of chemical warfare agents (CWAs) in atmospheric air. Instrumental construction and parameters were optimized to realize a fast response, high sensitivity, and a small body size. Three types of CWAs, i.e., phosgene, mustard gas, and hydrogen cyanide were examined to check if the mass spectrometer was able to detect characteristic elements and atomic groups. From the results, it was found that CWAs were effectively ionized in the miniECRIS-MS, and their specific signals could be discerned over the background signals of air. In phosgene, the signals of the 35Cl+ and 37Cl+ ions were clearly observed with high dose-response relationships in the parts-per-billion level, which could lead to the quantitative on-site analysis of CWAs. A parts-per-million level of mustard gas, which was far lower than its lethal dosage (LCt50), was successfully detected with a high signal-stability of the plasma ion source. It was also found that the chemical forms of CWAs ionized in the plasma, i.e., monoatomic ions, fragment ions, and molecular ions, could be detected, thereby enabling the effective identification of the target CWAs. Despite the disadvantages associated with miniaturization, the overall performance (sensitivity and response time) of the miniECRIS-MS in detecting CWAs exceeded those of sector-type ECRIS-MS, showing its potential for on-site detection in the future. PMID:24211802

  6. Development of portable mass spectrometer with electron cyclotron resonance ion source for detection of chemical warfare agents in air.

    PubMed

    Urabe, Tatsuya; Takahashi, Kazuya; Kitagawa, Michiko; Sato, Takafumi; Kondo, Tomohide; Enomoto, Shuichi; Kidera, Masanori; Seto, Yasuo

    2014-01-01

    A portable mass spectrometer with an electron cyclotron resonance ion source (miniECRIS-MS) was developed. It was used for in situ monitoring of trace amounts of chemical warfare agents (CWAs) in atmospheric air. Instrumental construction and parameters were optimized to realize a fast response, high sensitivity, and a small body size. Three types of CWAs, i.e., phosgene, mustard gas, and hydrogen cyanide were examined to check if the mass spectrometer was able to detect characteristic elements and atomic groups. From the results, it was found that CWAs were effectively ionized in the miniECRIS-MS, and their specific signals could be discerned over the background signals of air. In phosgene, the signals of the 35Cl+ and 37Cl+ ions were clearly observed with high dose-response relationships in the parts-per-billion level, which could lead to the quantitative on-site analysis of CWAs. A parts-per-million level of mustard gas, which was far lower than its lethal dosage (LCt50), was successfully detected with a high signal-stability of the plasma ion source. It was also found that the chemical forms of CWAs ionized in the plasma, i.e., monoatomic ions, fragment ions, and molecular ions, could be detected, thereby enabling the effective identification of the target CWAs. Despite the disadvantages associated with miniaturization, the overall performance (sensitivity and response time) of the miniECRIS-MS in detecting CWAs exceeded those of sector-type ECRIS-MS, showing its potential for on-site detection in the future.

  7. Out of thin air: Sensory detection of oxygen and carbon dioxide

    PubMed Central

    Scott, Kristin

    2011-01-01

    Oxygen and carbon dioxide levels vary in different environments and locally fluctuate during respiration and photosynthesis. Recent studies in diverse animals have identified sensory neurons that detect these external variations and direct a variety of behaviors. Detection allows animals to stay within a preferred environment as well as identify potential food or dangers. The complexity of sensation is reflected in the fact that neurons compartmentalize detection into increases, decreases, short-range and long-range cues. Animals also adjust their responses to these prevalent signals in context of other cues, allowing for flexible behaviors. In general, the molecular mechanisms for detection suggest that sensory neurons adopted ancient strategies for cellular detection and coupled them to brain activity and behavior. This review highlights the multiple strategies that animals use to extract information about their environment from variations in oxygen and carbon dioxide. PMID:21262460

  8. In-Service Evaluation of the Turbulence Auto-PIREP System and Enhanced Turbulence Radar Technologies

    NASA Technical Reports Server (NTRS)

    Prince, Jason B.; Buck, Bill K.; Robinson, Paul A.; Ryan, Tim

    2007-01-01

    From August 2003 to December 2006, In-Service Evaluations (ISE) of the Turbulence Auto-PIREP System (TAPS) and Enhanced Turbulence (E-Turb) Radar, technologies developed in NASA's Turbulence Prediction and Warning System (TPAWS) element of its Aviation Safety and Security Program (AvSSP), were conducted. NASA and AeroTech Research established an industry team comprising AeroTech, Delta Air Lines, Rockwell Collins, and ARINC to conduct the ISEs. The technologies were installed on Delta aircraft and their effectiveness was evaluated in day-to-day operations. This report documents the establishment and conduct of the ISEs and presents results and feedback from various users.

  9. Detection of an autoreactive T-cell population within the polyclonal repertoire that undergoes distinct autoimmune regulator (Aire)-mediated selection.

    PubMed

    Taniguchi, Ruth T; DeVoss, Jason J; Moon, James J; Sidney, John; Sette, Alessandro; Jenkins, Marc K; Anderson, Mark S

    2012-05-15

    The autoimmune regulator (Aire) plays a critical role in central tolerance by promoting the display of tissue-specific antigens in the thymus. To study the influence of Aire on thymic selection in a physiological setting, we used tetramer reagents to detect autoreactive T cells specific for the Aire-dependent tissue-specific antigen interphotoreceptor retinoid-binding protein (IRBP), in the polyclonal repertoire. Two class II tetramer reagents were designed to identify T cells specific for two different peptide epitopes of IRBP. Analyses of the polyclonal T-cell repertoire showed a high frequency of activated T cells specific for both IRBP tetramers in Aire(-/-) mice, but not in Aire(+/+) mice. Surprisingly, although one tetramer-binding T-cell population was efficiently deleted in the thymus in an Aire-dependent manner, the second tetramer-binding population was not deleted and could be detected in both the Aire(-/-) and Aire(+/+) T-cell repertoires. We found that Aire-dependent thymic deletion of IRBP-specific T cells relies on intercellular transfer of IRBP between thymic stroma and bone marrow-derived antigen-presenting cells. Furthermore, our data suggest that Aire-mediated deletion relies not only on thymic expression of IRBP, but also on proper antigen processing and presentation of IRBP by thymic antigen-presenting cells.

  10. Measurement of temperature and density fluctuations in turbulence using an ultraviolet laser

    NASA Technical Reports Server (NTRS)

    Massey, G. A.

    1984-01-01

    Noninvasive measurement of density and temperature fluctuations in turbulent air flow was examined. The approach used fluorescence of oxygen molecules which are selectively excited by a tunable vacuum ultraviolet laser beam. The strength of the fluorescence signal and its dependence on laser wavelength vary with the density and temperature of the air in the laser beam. Because fluorescence can be detected at 90 degrees from the beam propagation direction, spatial resolution in three dimensions, rather than path-integrated measurements can be achieved. With spatial resolutions of the order of a millimeter and at supersonic air velocities it is necessary to perform each measurement in a time of the order of a microsecond; this is possible by by using laser pulses of ten nanosecond duration. In this method atmospheric O2 is excited by the emission of a tunable ArF excimer laser, and the fluorescence, which spans the 210 to 420 range, is detected by an ultraviolet phototube.

  11. DNS of the effects of thermal stratication and turbulent mixing on H2/air ignition in a constant volume, and comparison with the multi-zone model.

    SciTech Connect

    Sankaran, Ramanan; Chen, Jacqueline H.; Hawkes, Evatt R.; Im, Hong G.

    2005-01-01

    The influence of thermal stratification on auto-ignition at constant volume and high pressure is studied by Direct Numerical Simulation (DNS) with complex H{sub 2}/air chemistry with a view to providing better understanding of combustion processes in homogeneous charge compression ignition engines. In particular the dependence of overall ignition progress on initial mixture conditions is determined. The propagation speed of ignition fronts that emanate from 'hot spots' given by a temperature spectrum is monitored by using the displacement velocity of a scalar that tracks the location of maximum heat release. The evolution of the front velocity is compared for different initial temperature distributions and the role of scalar dissipation of heat and mass is identified. It is observed that both deagrative as well as spontaneous ignition front propagation occur depending upon the local temperature gradient. It is found that the ratio of the instantaneous front speed to the deflagrative speed is a good measure of the local mode of propagation. This is verified by examining the energy and species balances. A parametric study in the amplitudes of the initial temperature fluctuation is performed and shows that this parameter has a significant influence on the observed combustion mode. Higher levels of stratification lead to more front-like structures. Predictions of the multi-zone model are presented and explained using the diagnostics developed.

  12. Distinguishing ichthyogenic turbulence from geophysical turbulence

    NASA Astrophysics Data System (ADS)

    Pujiana, Kandaga; Moum, James N.; Smyth, William D.; Warner, Sally J.

    2015-05-01

    Measurements of currents and turbulence beneath a geostationary ship in the equatorial Indian Ocean during a period of weak surface forcing revealed unexpectedly strong turbulence beneath the surface mixed layer. Coincident with the turbulence was a marked reduction of the current speeds registered by shipboard Doppler current profilers, and an increase in their variability. At a mooring 1 km away, measurements of turbulence and currents showed no such anomalies. Correlation with the shipboard echo sounder measurements indicate that these nighttime anomalies were associated with fish aggregations beneath the ship. The fish created turbulence by swimming against the strong zonal current in order to remain beneath the ship, and their presence affected the Doppler speed measurements. The principal characteristics of the resultant ichthyogenic turbulence are (i) low wave number roll-off of shear spectra in the inertial subrange relative to geophysical turbulence, (ii) Thorpe overturning scales that are small compared with the Ozmidov scale, and (iii) low mixing efficiency. These factors extend previous findings by Gregg and Horne (2009) to a very different biophysical regime and support the general conclusion that the biological contribution to mixing the ocean via turbulence is negligible.

  13. Proportional counter device for detecting electronegative species in an air sample

    DOEpatents

    Allman, S.L.; Chen, F.C.; Chen, C.H.

    1994-03-08

    Apparatus for detecting an electronegative species comprises an analysis chamber, an inlet communicating with the analysis chamber for admitting a sample containing the electronegative species and an ionizable component, a radioactive source within the analysis chamber for emitting radioactive energy for ionizing a component of the sample, a proportional electron detector within the analysis chamber for detecting electrons emitted from the ionized component, and a circuit for measuring the electrons and determining the presence of the electronegative species by detecting a reduction in the number of available electrons due to capture of electrons by the electronegative species. 2 figures.

  14. Proportional counter device for detecting electronegative species in an air sample

    DOEpatents

    Allman, Steve L.; Chen, Fang C.; Chen, Chung-Hsuan

    1994-01-01

    Apparatus for detecting an electronegative species comprises an analysis chamber, an inlet communicating with the analysis chamber for admitting a sample containing the electronegative species and an ionizable component, a radioactive source within the analysis chamber for emitting radioactive energy for ionizing a component of the sample, a proportional electron detector within the analysis chamber for detecting electrons emitted from the ionized component, and a circuit for measuring the electrons and determining the presence of the electronegative species by detecting a reduction in the number of available electrons due to capture of electrons by the electronegative species.

  15. Odor Landscapes in Turbulent Environments

    NASA Astrophysics Data System (ADS)

    Celani, Antonio; Villermaux, Emmanuel; Vergassola, Massimo

    2014-10-01

    The olfactory system of male moths is exquisitely sensitive to pheromones emitted by females and transported in the environment by atmospheric turbulence. Moths respond to minute amounts of pheromones, and their behavior is sensitive to the fine-scale structure of turbulent plumes where pheromone concentration is detectible. The signal of pheromone whiffs is qualitatively known to be intermittent, yet quantitative characterization of its statistical properties is lacking. This challenging fluid dynamics problem is also relevant for entomology, neurobiology, and the technological design of olfactory stimulators aimed at reproducing physiological odor signals in well-controlled laboratory conditions. Here, we develop a Lagrangian approach to the transport of pheromones by turbulent flows and exploit it to predict the statistics of odor detection during olfactory searches. The theory yields explicit probability distributions for the intensity and the duration of pheromone detections, as well as their spacing in time. Predictions are favorably tested by using numerical simulations, laboratory experiments, and field data for the atmospheric surface layer. The resulting signal of odor detections lends itself to implementation with state-of-the-art technologies and quantifies the amount and the type of information that male moths can exploit during olfactory searches.

  16. DETECTION AND IDENTIFICATION OF TOXIC AIR POLLUTANTS USING AIRBORNE LWIR HYPERSPECTRAL IMAGING

    EPA Science Inventory

    Airborne longwave infrared LWIR) hyperspectral imagery was utilized to detect and identify gaseous chemical release plumes at sites in sourthern Texzas. The Airborne Hysperspectral Imager (AHI), developed by the University of Hawaii was flown over a petrochemical facility and a ...

  17. Air pollution - Remote detection of several pollutant gases with a laser heterodyne radiometer

    NASA Technical Reports Server (NTRS)

    Menzies, R. T.; Shumate, M. S.

    1974-01-01

    An infrared heterodyne radiometer with a spectral resolution of 0.04 reciprocal centimeters has been used to remotely detect samples of ozone, sulfur dioxide, ammonia, and ethylene at room temperature, and samples of nitric oxide at 390 K. Each gas was observed in a background of nitrogen or oxygen at atmospheric pressure. Sensitivities to some of these gases are adequate for detection of ambient concentrations as low as a few parts per billion.

  18. Crossing turbulent boundaries: interfacial flux in environmental flows.

    PubMed

    Grant, Stanley B; Marusic, Ivan

    2011-09-01

    Advances in the visualization and prediction of turbulence are shedding new light on mass transfer in the turbulent boundary layer. These discoveries have important implications for many topics in environmental science and engineering, from the transport of earth-warming CO2 across the sea-air interface, to nutrient processing and sediment erosion in rivers, lakes, and the ocean, to pollutant removal in water and wastewater treatment systems. In this article we outline current understanding of turbulent boundary layer flows, with particular focus on coherent turbulence and its impact on mass transport across the sediment-water interface in marine and freshwater systems. PMID:21793569

  19. Turbulent Dispersion of Traffic Emissions

    NASA Astrophysics Data System (ADS)

    Staebler, R. M.; Gordon, M.; Liggio, J.; Makar, P.; Mihele, C.; Brook, J.; Wentzell, J. J.; Gong, S.; Lu, G.; Lee, P.

    2010-12-01

    Emissions from the transportation sector are a significant source of air pollution. Ongoing efforts to reduce the impacts require tools to provide guidance on policies regarding fuels, vehicle types and traffic control. The air quality models currently used to predict the effectiveness of policies typically treat traffic emissions as a source uniformly distributed across the surface of a model grid. In reality, emissions occur along lines above the surface, in an initially highly concentrated form, and are immediately mixed by traffic-enhanced turbulence. Differences between model and reality in terms of both chemistry and dispersion are to be expected. The ALMITEE (Advancing Local-scale Modeling through Inclusion of Transportation Emission Experiments) subproject FEVER (Fast Evolution of Vehicle Emissions from Roadways), conducted on multi-lane highways in the Toronto area in the summer of 2010, included measurements to quantify the evolution and dispersion of traffic emissions. Continuous micro-meteorological data (heat and momentum fluxes, temperature, humidity and incoming solar radiation) were collected 10m from the road, next to a traffic camera used to determine traffic density, composition and speed. Sonic anemometers and an aircraft turbulence probe mounted on a mobile lab provided measurements of turbulent dispersion both directly in traffic on the highway as well as on perpendicular side roads, as a function of distance from the highway. The mobile lab was equipped with instruments to characterize the aerosol size and mass distributions, aerosol composition including black carbon content, NO, NO2, CO2, CO, SO2 and VOCs at high time resolution. Preliminary results on the consequences of turbulent dispersion of traffic emissions levels under a variety of conditions will be disseminated.

  20. Application of Frequency of Detection Methods in Design and Optimization of the INL Site Ambient Air Monitoring Network

    SciTech Connect

    Rood, Arthur S.; Sondrup, A. Jeffrey

    2015-11-01

    This report presents an evaluation of a hypothetical INL Site monitoring network and the existing INL air monitoring network using frequency of detection methods. The hypothetical network was designed to address the requirement in 40 CFR Part 61, Subpart H (2006) that “emissions of radionuclides to ambient air from U.S. DOE facilities shall not exceed those amounts that would cause any member of the public to receive in any year an effective dose equivalent exceeding 10 mrem/year.” To meet the requirement for monitoring only, “radionuclide releases that would result in an effective dose of 10% of the standard shall be readily detectable and distinguishable from background.” Thus, the hypothetical network consists of air samplers placed at residence locations that surround INL and at other locations where onsite livestock grazing takes place. Two exposure scenarios were used in this evaluation: a resident scenario and a shepherd/rancher scenario. The resident was assumed to be continuously present at their residence while the shepherd/rancher was assumed to be present 24-hours at a fixed location on the grazing allotment. Important radionuclides were identified from annual INL radionuclide National Emission Standards for Hazardous Pollutants reports. Important radionuclides were defined as those that potentially contribute 1% or greater to the annual total dose at the radionuclide National Emission Standards for Hazardous Pollutants maximally exposed individual location and include H-3, Am-241, Pu-238, Pu 239, Cs-137, Sr-90, and I-131. For this evaluation, the network performance objective was set at achieving a frequency of detection greater than or equal to 95%. Results indicated that the hypothetical network for the resident scenario met all performance objectives for H-3 and I-131 and most performance objectives for Cs-137 and Sr-90. However, all actinides failed to meet the performance objectives for most sources. The shepherd/rancher scenario showed

  1. Characteristics of turbulent/non-turbulent interfaces in wakes in stably-stratified fluidsO

    NASA Astrophysics Data System (ADS)

    Watanabe, Tomoaki; Riley, James; de Bruyn Kops, Stephen; Diamessis, Peter; Zhou, Qi

    2015-11-01

    The evolution of turbulent patches generated by the wake of a sphere in stably-stratified fluids is studied using direct numerical simulations. The DNS data analysis focuses on the investigation of the characteristics of turbulent/non-turbulence interfaces forming at the wake edge. Unlike the case for non-stratified fluids, because of the non-negligible enstrophy level in internal waves outside the stratified wake, enstrophy cannot be used as a marker for turbulent regions. We show that potential enstrophy is appropriate as a marker for turbulent regions in flows where both turbulence and internal waves exist. Therefore the interface is detected as an isosurface of constant potential enstrophy, and statistics can be calculated conditioned on the distance from the interface. Various quantities are examined from the wake interior to the region outside the wake, and show how the flow properties are adjusted between turbulent and non-turbulent regions near the interface. Based on the conditional analysis, we also report evidence for the strong influence of internal waves on turbulence inside the wake. ONR Grants N00014-13-1-0665 and N00014-12-1-0583; HPCMP Frontier Project FPCFD-FY14-007; JSPS KAKENHI No. 25002531.

  2. Experimental investigation into infrasonic emissions from atmospheric turbulence.

    PubMed

    Shams, Qamar A; Zuckerwar, Allan J; Burkett, Cecil G; Weistroffer, George R; Hugo, Derek R

    2013-03-01

    Clear air turbulence (CAT) is the leading cause of in-flight injuries and in severe cases can result in fatalities. The purpose of this work is to design and develop an infrasonic array network for early warning of clear air turbulence. The infrasonic system consists of an infrasonic three-microphone array, compact windscreens, and data management system. Past experimental efforts to detect acoustic emissions from CAT have been limited. An array of three infrasonic microphones, operating in the field at NASA Langley Research Center, on several occasions received signals interpreted as infrasonic emissions from CAT. Following comparison with current lidar and other past methods, the principle of operation, the experimental methods, and experimental data are presented for case studies and confirmed by pilot reports. The power spectral density of the received signals was found to fit a power law having an exponent of -6 to -7, which is found to be characteristics of infrasonic emissions from CAT, in contrast to findings of the past.

  3. Sulfur Dioxide Plume from Mt. Etna Eruption 2002 as Detected with AIRS Data

    NASA Technical Reports Server (NTRS)

    2007-01-01

    Mt. Etna, a volcano on the island of Sicily, erupted on October 26, 2002. Preliminary analysis of data taken by the Atmospheric Infrared Sounder (AIRS) on NASA's Aqua satellite on October 28 shows the instrument can provide an excellent means to study the evolution and structure of the sulfur dioxide plume emitted from volcanoes. These data also demonstrate that AIRS can be used to obtain the total mass of sulfur dioxide injected into the atmosphere during a volcanic event, information that may help us to better understand these dangerous natural occurrences in the future.

    The image clearly shows the sulfur dioxide plume. This image was created by comparing data taken at two different frequencies, or channels, and creating one image that highlights the differences between these two channels. Both channels are sensitive to water vapor, but one of the channels is also sensitive to sulfur dioxide. By subtracting out the common water vapor signal in both channels, the sulfur dioxide feature remains and shows up as an enhancement in the difference image.

    The Atmospheric Infrared Sounder Experiment, with its visible, infrared, and microwave detectors, provides a three-dimensional look at Earth's weather. Working in tandem, the three instruments can make simultaneous observations all the way down to the Earth's surface, even in the presence of heavy clouds. With more than 2,000 channels sensing different regions of the atmosphere, the system creates a global, 3-D map of atmospheric temperature and humidity and provides information on clouds, greenhouse gases, and many other atmospheric phenomena. The AIRS Infrared Sounder Experiment flies onboard NASA's Aqua spacecraft and is managed by NASA's Jet Propulsion Laboratory, Pasadena, Calif., under contract to NASA. JPL is a division of the California Institute of Technology in Pasadena.

  4. Novel method for detecting the hadronic component of extensive air showers

    SciTech Connect

    Gromushkin, D. M.; Volchenko, V. I.; Petrukhin, A. A.; Stenkin, Yu. V.; Stepanov, V. I.; Shchegolev, O. B.; Yashin, I. I.

    2015-05-15

    A novel method for studying the hadronic component of extensive air showers (EAS) is proposed. The method is based on recording thermal neutrons accompanying EAS with en-detectors that are sensitive to two EAS components: an electromagnetic (e) component and a hadron component in the form of neutrons (n). In contrast to hadron calorimeters used in some arrays, the proposed method makes it possible to record the hadronic component over the whole area of the array. The efficiency of a prototype array that consists of 32 en-detectors was tested for a long time, and some parameters of the neutron EAS component were determined.

  5. Impact of Atmospheric Turbulence on Beam Propagation

    SciTech Connect

    Strasburg, Jana D.; Harper, Warren W.; William E Thompson & Richard L Brunson

    2004-09-08

    A trailer-based sensor system has been developed for remote chemical sensing applications. The detection scheme utilizes quantum cascade lasers operating in the long-wave infrared. It has been determined that atmospheric turbulence is the dominating noise source for this system. For this application, horizontal path lengths vary from several hundred meters to several kilometers resulting in weak to moderate to strong turbulence conditions.

  6. Prioritizing testing of organic compounds detected as gas phase air pollutants: structure-activity study for human contact allergens.

    PubMed Central

    Johnson, R; Macina, O T; Graham, C; Rosenkranz, H S; Cass, G R; Karol, M H

    1997-01-01

    Organic compounds that are used or generated anthropogenically in large quantities in cities can be identified through their presence in the urban atmosphere and in air pollutant source emissions. Compounds identified by this method were screened to evaluate their potential to act as contact allergens. The CASE and MULTICASE computer programs, which are based on the detection of structure-activity relationships (SAR), were used to evaluate this potential. These relationships first are determined by comparing chemical structures to biological activity within a learning set comprised of 458 compounds, each of which had been tested experimentally in human trials for its sensitization potential. Using the information contained in this learning set, CASE and MULTICASE predicted the activity of 238 compounds found in the atmosphere for their ability to act as contact allergens. The analysis finds that 21 of 238 compounds are predicted to be active contact allergens (probability >0.5), with potencies ranging from mild to very strong. The compounds come from chemical classes that include chlorinated aromatics and chlorinated hydrocarbons, N-containing compounds, phenols, alkenes, and an S-containing compound. Using the measured airborne concentrations or emission rates of these compounds as an indication of the extent of their use, together with their predicted potencies, provides an efficient method to prioritize the experimental assessment of contact sensitization of untested organic compounds that can be detected as air pollutants. Images Figure 1. PMID:9300925

  7. Determination of mercaptans at microgram-per-cubic-meter levels in air by gas chromatography with photoionization detection

    SciTech Connect

    Stein, V.B.; Narang, R.S.

    1982-05-01

    A method for the gas chromatographic (GC) determination of ethyl, tert-butyl, propyl, sec-butyl, and n-butyl mercaptans in air using a photoionization detector (PID) was established by using air sampling bags. Up to 5 mL of sample was injected into a Hewlett-Packard Model 588OA GC fitted with a 9 ft glass column packed with 100/120 mesh Chromosorb W AW DMCS and coated with 15% SF-96 and 6% OV-225. The oven was held at 65 /sup 0/C and the nitrogen flow rate was 30 mL/min. The photoionization detector was attached to the GC and held at 200 /sup 0/C. The GC detection limit was determined to be 0.06 ng for n-butyl mercaptan and 0.02 ng for the remaining mercaptans with precisions (n = 8, 1sigma, 4 ng) of +/- 7.3, +/- 8.5, +/- 8.1, and +/- 10% for ethyl, tert-butyl, propyl, sec-butyl, and n-butyl mercaptan, respectively. With a 5-mL injection volume, sensitivity is about 2 ..mu..g/m/sup 3/ which is as sensitive as detection by smell since the oder threshold is about 2-4 ..mu..g/m/sup 3/.

  8. Evaluation of a method to detect Mycobacterium bovis in air samples from infected Eurasian badgers (Meles meles) and their setts.

    PubMed

    Jones, R M; Ashford, R; Cork, J; Palmer, S; Wood, E; Spyvee, P; Parks, S; Bennett, A; Brewer, J; Delahay, R; Chambers, M; Sawyer, J

    2013-05-01

    Environmental air sampling was evaluated as a method to detect the presence of M. bovis in the vicinity of infected badgers and their setts. Airborne particles were collected on gelatine filters using a commercially available air sampling instrument and tested for the presence of M. bovis using bacteriological culture and real-time PCR. The sensitivity of bacteriological culture was broadly similar to that of real-time PCR when testing samples artificially spiked with M. bovis. Sampling was undertaken from directly under the muzzles of badgers which had been experimentally infected with M. bovis (37 samples), within enclosures housing the experimentally infected animals (50 samples), and in the vicinity of setts with resident infected wild badgers (52 samples). The methods employed did not detect M. bovis from either infected badgers or artificial or natural setts known to contain infected animals. However, samples taken at four of the six natural setts were positive for Mycobacterium gordonae.

  9. Laser hybrid micro/nano-structuring of Si surfaces in air and its applications for SERS detection.

    PubMed

    Yang, Jing; Li, Jiabao; Du, Zheren; Gong, Qihuang; Teng, Jinghua; Hong, Minghui

    2014-01-01

    Surface enhanced Raman spectroscopy (SERS) has been widely investigated as an effective technique for low-concentration bio-chemical molecules detection. A rapid two-step approach to fabricate SERS substrates with high controllability in ambient air is developed. Dynamic laser ablation directly creates microgroove on the Si substrate. Meanwhile, nanoparticles are synthesized via the nucleation of laser induced plasma species and the air molecules. It configures the Si surface into four different regions decorated with nanoparticles at different sizes. With Ag film coating, these nanoparticles function as hotspots for SERS. Microsquare arrays are fabricated on the Si surface as large-area SERS substrates by the laser ablation in horizontal and vertical directions. In each microsquare, it exhibits quasi-3D structures with randomly arranged and different shaped nanoparticles aggregated in more than one layer. With Ag film deposition, uniform SERS signals are obtained by detecting the 4-methylbenzenethiol molecules. The SERS signal intensity is determined by the size and shape distributions of the nanoparticles, which depend on the laser processing parameters. With the optimal laser fluence, the SERS signals show a uniform enhancement factor up to 5.5 × 10(6). This provides a high-speed and low-cost method to produce SERS substrates over a large area. PMID:25324167

  10. History of wind shear turbulence models

    NASA Technical Reports Server (NTRS)

    Cusimano, Lou

    1987-01-01

    The Office of Flight Operations, Flight Technical Programs Div., at the FAA Headquarters, interfaces with industry, R&D communities and air carriers during the introduction of new types of equipment into operational services. A brief highlight of the need which FAA operations sees for new wind shear and turbulence data sets from the viewpoint of equipment certification and simulation is presented.

  11. Introduction to quantum turbulence

    PubMed Central

    Barenghi, Carlo F.; Skrbek, Ladislav; Sreenivasan, Katepalli R.

    2014-01-01

    The term quantum turbulence denotes the turbulent motion of quantum fluids, systems such as superfluid helium and atomic Bose–Einstein condensates, which are characterized by quantized vorticity, superfluidity, and, at finite temperatures, two-fluid behavior. This article introduces their basic properties, describes types and regimes of turbulence that have been observed, and highlights similarities and differences between quantum turbulence and classical turbulence in ordinary fluids. Our aim is also to link together the articles of this special issue and to provide a perspective of the future development of a subject that contains aspects of fluid mechanics, atomic physics, condensed matter, and low-temperature physics. PMID:24704870

  12. Modeling Compressed Turbulence

    SciTech Connect

    Israel, Daniel M.

    2012-07-13

    From ICE to ICF, the effect of mean compression or expansion is important for predicting the state of the turbulence. When developing combustion models, we would like to know the mix state of the reacting species. This involves density and concentration fluctuations. To date, research has focused on the effect of compression on the turbulent kinetic energy. The current work provides constraints to help development and calibration for models of species mixing effects in compressed turbulence. The Cambon, et al., re-scaling has been extended to buoyancy driven turbulence, including the fluctuating density, concentration, and temperature equations. The new scalings give us helpful constraints for developing and validating RANS turbulence models.

  13. LOPES — Recent Results and Open Questions on the Radio Detection of Air Showers

    NASA Astrophysics Data System (ADS)

    Schröder, F. G.; Apel, W. D.; Arteaga-Velázquez, J. C.; Bähren, L.; Bekk, K.; Bertaina, M.; Biermann, P. L.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Cantoni, E.; Chiavassa, A.; Daumiller, K.; de Souza, V.; Di Pierro, F.; Doll, P.; Engel, R.; Falcke, H.; Fuchs, B.; Gemmeke, H.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Horneffer, A.; Huber, D.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Krömer, O.; Kuijpers, J.; Link, K.; Łuczak, P.; Ludwig, M.; Mathes, H. J.; Melissas, M.; Morello, C.; Oehlschläger, J.; Palmieri, N.; Pierog, T.; Rautenberg, J.; Rebel, H.; Roth, M.; Rühle, C.; Saftoiu, A.; Schieler, H.; Schmidt, A.; Schoo, S.; Sima, O.; Toma, G.; Trinchero, G. C.; Weindl, A.; Wochele, J.; Zabierowski, J.; Zensus, J. A.

    2015-08-01

    LOPES was a digital antenna array operating for approximately 10 years until spring 2013 at the Karlsruhe Institute of Technology (KIT). Triggered by the co-located KASCADE-Grande air-shower experiment, it measured the radio signal of around 1000 cosmic-ray air showers with energies E ≳ 1017 eV in an effective band of 43 - 74 MHz. Using the interferometric technique of cross-correlation beamforming, LOPES could reconstruct the shower direction with an accuracy < 0.7°, the shower energy with a precision < 20%, and the atmospheric depth of the shower maximum, Xmax, with a precision < 95g/cm2. In particular the reconstruction of the shower maximum suffers from significant measurement uncertainties due to the radio-loud environment of the site. This article summarizes our latest results on the reconstruction of the shower maximum, using two independent methods: the steepness of the hyperbolic radio wavefront and the slope of the lateral distribution of the radio amplitude. Moreover, we show vectorial measurements of the electric field with the tripole antennas of the latest LOPES setup. Finally, we discuss open questions as well as the potential impact of the lessons learned at LOPES for future antenna arrays.

  14. Detection of Bacillus anthracis DNA in complex soil and air samples using next-generation sequencing.

    PubMed

    Be, Nicholas A; Thissen, James B; Gardner, Shea N; McLoughlin, Kevin S; Fofanov, Viacheslav Y; Koshinsky, Heather; Ellingson, Sally R; Brettin, Thomas S; Jackson, Paul J; Jaing, Crystal J

    2013-01-01

    Bacillus anthracis is the potentially lethal etiologic agent of anthrax disease, and is a significant concern in the realm of biodefense. One of the cornerstones of an effective biodefense strategy is the ability to detect infectious agents with a high degree of sensitivity and specificity in the context of a complex sample background. The nature of the B. anthracis genome, however, renders specific detection difficult, due to close homology with B. cereus and B. thuringiensis. We therefore elected to determine the efficacy of next-generation sequencing analysis and microarrays for detection of B. anthracis in an environmental background. We applied next-generation sequencing to titrated genome copy numbers of B. anthracis in the presence of background nucleic acid extracted from aerosol and soil samples. We found next-generation sequencing to be capable of detecting as few as 10 genomic equivalents of B. anthracis DNA per nanogram of background nucleic acid. Detection was accomplished by mapping reads to either a defined subset of reference genomes or to the full GenBank database. Moreover, sequence data obtained from B. anthracis could be reliably distinguished from sequence data mapping to either B. cereus or B. thuringiensis. We also demonstrated the efficacy of a microbial census microarray in detecting B. anthracis in the same samples, representing a cost-effective and high-throughput approach, complementary to next-generation sequencing. Our results, in combination with the capacity of sequencing for providing insights into the genomic characteristics of complex and novel organisms, suggest that these platforms should be considered important components of a biosurveillance strategy.

  15. Leak detection using structure-borne noise

    NASA Technical Reports Server (NTRS)

    Holland, Stephen D. (Inventor); Chimenti, Dale E. (Inventor); Roberts, Ronald A. (Inventor)

    2010-01-01

    A method for detection and location of air leaks in a pressure vessel, such as a spacecraft, includes sensing structure-borne ultrasound waveforms associated with turbulence caused by a leak from a plurality of sensors and cross correlating the waveforms to determine existence and location of the leak. Different configurations of sensors and corresponding methods can be used. An apparatus for performing the methods is also provided.

  16. Particle-Generated Turbulence in Dispersed Homogeneous Flows

    NASA Astrophysics Data System (ADS)

    Chen, J.-H.; Faeth, G. M.; Wu, J.-S.

    1998-11-01

    Homogeneous turbulence generated by uniform fluxes of monodisperse spherical particles moving through a uniform flowing gas was studied, motivated by the importance of this turbulence production mechanism for dense sprays, bubbly flows, rainstorms and the like. Measurements of phase velocities, moments, probability density functions, temporal power spectra, spatial integral scales and particle fluxes were obtained using phase-discriminating laser velocimetry and particle sampling in a counterflowing particle/air wind tunnel. Instantaneous velocity records showed that particle wake disturbances were the same as the properties of laminar-like turbulent wakes that have been observed for particle wakes at intermediate Reynolds numbers in turbulent environments. Relative turbulence intensities are proportional to the square-root of particle kinetic energy dissipation rates, in accord with simple stochastic theory. Other properties, however, exhibit complex behavior due to contributions from both particle wakes and interwake turbulence.

  17. Large Eddy Simulations of Severe Convection Induced Turbulence

    NASA Technical Reports Server (NTRS)

    Ahmad, Nash'at; Proctor, Fred

    2011-01-01

    Convective storms can pose a serious risk to aviation operations since they are often accompanied by turbulence, heavy rain, hail, icing, lightning, strong winds, and poor visibility. They can cause major delays in air traffic due to the re-routing of flights, and by disrupting operations at the airports in the vicinity of the storm system. In this study, the Terminal Area Simulation System is used to simulate five different convective events ranging from a mesoscale convective complex to isolated storms. The occurrence of convection induced turbulence is analyzed from these simulations. The validation of model results with the radar data and other observations is reported and an aircraft-centric turbulence hazard metric calculated for each case is discussed. The turbulence analysis showed that large pockets of significant turbulence hazard can be found in regions of low radar reflectivity. Moderate and severe turbulence was often found in building cumulus turrets and overshooting tops.

  18. Propagation of a Free Flame in a Turbulent Gas Stream

    NASA Technical Reports Server (NTRS)

    Mickelsen, William R; Ernstein, Norman E

    1956-01-01

    Effective flame speeds of free turbulent flames were measured by photographic, ionization-gap, and photomultiplier-tube methods, and were found to have a statistical distribution attributed to the nature of the turbulent field. The effective turbulent flame speeds for the free flame were less than those previously measured for flames stabilized on nozzle burners, Bunsen burners, and bluff bodies. The statistical spread of the effective turbulent flame speeds was markedly wider in the lean and rich fuel-air-ratio regions, which might be attributed to the greater sensitivity of laminar flame speed to flame temperature in those regions. Values calculated from the turbulent free-flame-speed analysis proposed by Tucker apparently form upper limits for the statistical spread of free-flame-speed data. Hot-wire anemometer measurements of the longitudinal velocity fluctuation intensity and longitudinal correlation coefficient were made and were employed in the comparison of data and in the theoretical calculation of turbulent flame speed.

  19. Investigations of the evolution of turbulent gas explosions

    NASA Astrophysics Data System (ADS)

    Foerster, H.; Steen, H.

    1986-10-01

    The explosion in turbulent stochiometric propane-air mixtures was investigated as a contribution to the safety evaluation of explosions. The effect of the turbulence parameters (average fluctuation velocity u' and average vortex ball diameter L) on the damage-effect-determining flame velocity were studied. Tests show that L is determined by the size of the turbulence field and by the geometry at the boundaries. An almost linear increase of vt as a function of u' (at fixed L) is found for the experimentally accessible turbulence intensities. Contrary to simple model expectations, a significant increase of vt as a function of L (at fixed u') is also found. Therefore, u' as well as L have to be considered in the safety evaluation. Tests show that the maximum explosion pressure increase is not only determined by the turbulence state of the mixture, but also by apparatus factors such as container size and geometry as well as the type of turbulence excitation.

  20. Analysis of small scale turbulent structures and the effect of spatial scales on gas transfer

    NASA Astrophysics Data System (ADS)

    Schnieders, Jana; Garbe, Christoph

    2014-05-01

    The exchange of gases through the air-sea interface strongly depends on environmental conditions such as wind stress and waves which in turn generate near surface turbulence. Near surface turbulence is a main driver of surface divergence which has been shown to cause highly variable transfer rates on relatively small spatial scales. Due to the cool skin of the ocean, heat can be used as a tracer to detect areas of surface convergence and thus gather information about size and intensity of a turbulent process. We use infrared imagery to visualize near surface aqueous turbulence and determine the impact of turbulent scales on exchange rates. Through the high temporal and spatial resolution of these types of measurements spatial scales as well as surface dynamics can be captured. The surface heat pattern is formed by distinct structures on two scales - small-scale short lived structures termed fish scales and larger scale cold streaks that are consistent with the footprints of Langmuir Circulations. There are two key characteristics of the observed surface heat patterns: 1. The surface heat patterns show characteristic features of scales. 2. The structure of these patterns change with increasing wind stress and surface conditions. In [2] turbulent cell sizes have been shown to systematically decrease with increasing wind speed until a saturation at u* = 0.7 cm/s is reached. Results suggest a saturation in the tangential stress. Similar behaviour has been observed by [1] for gas transfer measurements at higher wind speeds. In this contribution a new model to estimate the heat flux is applied which is based on the measured turbulent cell size und surface velocities. This approach allows the direct comparison of the net effect on heat flux of eddies of different sizes and a comparison to gas transfer measurements. Linking transport models with thermographic measurements, transfer velocities can be computed. In this contribution, we will quantify the effect of small scale

  1. Development and validation of two LC-MS/MS methods for the detection and quantification of amphetamines, designer amphetamines, benzoylecgonine, benzodiazepines, opiates, and opioids in urine using turbulent flow chromatography.

    PubMed

    Schaefer, Nadine; Peters, Benjamin; Schmidt, Peter; Ewald, Andreas H

    2013-01-01

    In the context of driving ability diagnostics in Germany, administrative cutoffs for various drugs and pharmaceuticals in urine have been established. Two liquid chromatography-tandem mass spectrometry methods for simultaneous detection and quantification of amphetamines, designer amphetamines, benzoylecgonine, benzodiazepines, opiates, and opioids in urine were developed and validated. A 500-μL aliquot of urine was diluted and fortified with an internal standard solution. After enzymatic cleavage, online extraction was performed by an ion-exchange/reversed-phase turbulent flow column. Separation was achieved by using a reversed-phase column and gradient elution. For detection, a Thermo Fisher TSQ Quantum Ultra Accurate Mass tandem mass spectrometer with positive electrospray ionization was used, and the analytes were measured in multiple-reaction monitoring mode detecting two transitions per precursor ion. The total run time for both methods was about 15 min. Validation was performed according to the guidelines of the Society of Toxicological and Forensic Chemistry. The results of matrix effect determination were between 78% and 116%. The limits of detection and quantification for all drugs, except zopiclone, were less than 10 ng/mL and less than 25 ng/mL, respectively. Calibration curves ranged from 25 to 200 ng/mL for amphetamines, designer amphetamines, and benzoylecgonine, from 25 to 250 ng/mL for benzodiazepines, from 12.5 to 100 ng/mL for morphine, codeine, and dihydrocodeine, and from 5 to 50 ng/mL for buprenorphine and norbuprenorphine. Intraday and interday precision values were lower than 15%, and bias values within ± 15% were achieved. Turbulent flow chromatography needs no laborious sample preparation, so the workup is less time-consuming compared with gas chromatography-mass spectrometry methods. The methods are suitable for quantification of multiple analytes at the cutoff concentrations required for driving ability diagnostics in Germany.

  2. Development and validation of two LC-MS/MS methods for the detection and quantification of amphetamines, designer amphetamines, benzoylecgonine, benzodiazepines, opiates, and opioids in urine using turbulent flow chromatography.

    PubMed

    Schaefer, Nadine; Peters, Benjamin; Schmidt, Peter; Ewald, Andreas H

    2013-01-01

    In the context of driving ability diagnostics in Germany, administrative cutoffs for various drugs and pharmaceuticals in urine have been established. Two liquid chromatography-tandem mass spectrometry methods for simultaneous detection and quantification of amphetamines, designer amphetamines, benzoylecgonine, benzodiazepines, opiates, and opioids in urine were developed and validated. A 500-μL aliquot of urine was diluted and fortified with an internal standard solution. After enzymatic cleavage, online extraction was performed by an ion-exchange/reversed-phase turbulent flow column. Separation was achieved by using a reversed-phase column and gradient elution. For detection, a Thermo Fisher TSQ Quantum Ultra Accurate Mass tandem mass spectrometer with positive electrospray ionization was used, and the analytes were measured in multiple-reaction monitoring mode detecting two transitions per precursor ion. The total run time for both methods was about 15 min. Validation was performed according to the guidelines of the Society of Toxicological and Forensic Chemistry. The results of matrix effect determination were between 78% and 116%. The limits of detection and quantification for all drugs, except zopiclone, were less than 10 ng/mL and less than 25 ng/mL, respectively. Calibration curves ranged from 25 to 200 ng/mL for amphetamines, designer amphetamines, and benzoylecgonine, from 25 to 250 ng/mL for benzodiazepines, from 12.5 to 100 ng/mL for morphine, codeine, and dihydrocodeine, and from 5 to 50 ng/mL for buprenorphine and norbuprenorphine. Intraday and interday precision values were lower than 15%, and bias values within ± 15% were achieved. Turbulent flow chromatography needs no laborious sample preparation, so the workup is less time-consuming compared with gas chromatography-mass spectrometry methods. The methods are suitable for quantification of multiple analytes at the cutoff concentrations required for driving ability diagnostics in Germany. PMID

  3. Development of a method to detect and quantify Aspergillus fumigatus conidia by quantitative PCR for environmental air samples.

    PubMed

    McDevitt, James J; Lees, Peter S J; Merz, William G; Schwab, Kellogg J

    2004-10-01

    Exposure to Aspergillus fumigatus is linked with respiratory diseases such as asthma, invasive aspergillosis, hypersensitivity pneumonitis, and allergic bronchopulmonary aspergillosis. Molecular methods using quantitative PCR (qPCR) offer advantages over culture and optical methods for estimating human exposures to microbiological agents such as fungi. We describe an assay that uses lyticase to digest A. fumigatus conidia followed by TaqMan qPCR to quantify released DNA. This method will allow analysis of airborne A. fumigatus samples collected over extended time periods and provide a more representative assessment of chronic exposure. The method was optimized for environmental samples and incorporates: single tube sample preparation to reduce sample loss, maintain simplicity, and avoid contamination; hot start amplification to reduce non-specific primer/probe annealing; and uracil-N-glycosylase to prevent carryover contamination. An A. fumigatus internal standard was developed and used to detect PCR inhibitors potentially found in air samples. The assay detected fewer than 10 A. fumigatus conidia per qPCR reaction and quantified conidia over a 4-log10 range with high linearity (R2 >0.99) and low variability among replicate standards (CV=2.0%) in less than 4 h. The sensitivity and linearity of qPCR for conidia deposited on filters was equivalent to conidia calibration standards. A. fumigatus DNA from 8 isolates was consistently quantified using this method, while non-specific DNA from 14 common environmental fungi, including 6 other Aspergillus species, was not detected. This method provides a means of analyzing long term air samples collected on filters which may enable investigators to correlate airborne environmental A. fumigatus conidia concentrations with adverse health effects.

  4. High-resolution ion pulse ionization chamber with air filling for the 222Rn decays detection

    NASA Astrophysics Data System (ADS)

    Gavrilyuk, Yu. M.; Gangapshev, A. M.; Gezhaev, A. M.; Etezov, R. A.; Kazalov, V. V.; Kuzminov, V. V.; Panasenko, S. I.; Ratkevich, S. S.; Tekueva, D. A.; Yakimenko, S. P.

    2015-11-01

    The construction and characteristics of the cylindrical ion pulse ionization chamber (CIPIC) with a working volume of 3.2 L are described. The chamber is intended to register α-particles from the 222Rn and its daughter's decays in the filled air sample. The detector is less sensitive to electromagnetic pick-ups and mechanical noises. The digital pulse processing method is proposed to improve the energy resolution of the ion pulse ionization chamber. An energy resolution of 1.6% has been achieved for the 5.49 MeV α-line. The dependence of the energy resolution on high voltage and working media pressure has been investigated and the results are presented.

  5. Detection of regional air pollution episodes utilizing satellite data in the visual range

    NASA Technical Reports Server (NTRS)

    Bowley, C. J.; Burke, H. K.; Barnes, J. C.

    1981-01-01

    A comparative analysis of satellite-observed haze patterns and ground-based aerosol measurements is carried out for July 20-23, 1978. During this period, a significant regional air pollution episode existed across the northeastern United States, accompanied by widespread haze, reduced surface visibility, and elevated sulfate levels measured by the Sulfate Regional Experiment (SURE) network. The results show that the satellite-observed haze patterns correlate closely with the area of reported low surface visibility (less than 4 mi) and high sulfate levels. Quantitative information on total aerosol loading derived from the satellite-digitized data, using an atmospheric radiative transfer model, agrees well with the results obtained from the ground-based measurements.

  6. [Molecular detection of Saint Louis encephalitis virus in mosquitoes in Buenos Aires].

    PubMed

    Beltrán, Fernando J; Bechara, Yamila I; Guido, Guillermo G; Cicuttin, Gabriel L; Beaudoin, Juan B; Gury Dohmen, Federico E

    2014-01-01

    During March 2013 a population of eared doves (Zenaida auriculata) was established in the center of City of Buenos Aires. Considering the role of these birds as host competent for Saint Louis encephalitis virus (SLEV), a CDC light trap was put in place to perform entomologic surveillance. During this month 5 pools of mosquitoes (n = 48) were collected and taxonomically determined. Three of them were classified as Culex pipiens (n = 10) and the other two were Culex spp. (n = 38). In this case, the mosquitoes species could not be determined due to that individuals were damaged. One of the Culex spp. pool was found to be positive for Saint Louis encephalitis virus by molecular techniques. This was then sequenced and classified as genotype III.

  7. Legionella detection and subgrouping in water air-conditioning cooling tower systems in Kuwait.

    PubMed

    Al-Matawah, Qadreyah; Al-Zenki, Sameer; Al-Azmi, Ahmad; Al-Waalan, Tahani; Al-Salameen, Fadila; Hejji, Ahmad Ben

    2015-07-01

    The main aim of the study was to test for the presence of Legionnaires' disease-causing microorganisms in air-conditioned buildings in Kuwait using molecular technologies. For this purpose, 547 samples were collected from 38 cooling towers for the analysis of Legionella pneumophila. These samples included those from water (n = 178), air (n = 231), and swabs (n = 138). Out of the 547 samples, 226 (41%) samples were presumptive positive for L. pneumophila, with L. pneumophila viable counts in the positive water samples ranging from 1 to 88 CFU/ml. Of the Legionella culture-positive samples, 204 isolates were examined by latex agglutination. These isolates were predominately identified as L. pneumophila serogroup (sg) 2-14. Using the Dresden panel of monoclonal antibodies, 74 representatives isolates were further serogrouped. Results showed that 51% of the isolates belonged to serogroup 7 followed by 1 (18%) and 3 (18%). Serogroups 4 (4%) and 10 (7%) were isolated at a lower frequency, and two isolates could not be assigned to a serogroup. These results indicate the wide prevalence of L. pneumophila serogroup 7 as the predominant serogroup at the selected sampling sites. Furthermore, the 74 L. pneumophila (sg1 = 13; sg3 = 13; sg4 = 3; sg7 = 38; sg10 = 5; sgX = 2) isolates were genotyped using the seven gene protocol sequence-based typing (SBT) scheme developed by the European Working Group for Legionella Infections (EWGLI). The results show that Legionella isolates were discriminated into nine distinct sequence typing (ST) profiles, five of which were new to the SBT database of EWGLI. Additionally, all of the ST1 serogroup 1 isolates were of the OLDA/Oxford subgroup. These baseline data will form the basis for the development of a Legionella environmental surveillance program and used for future epidemiological investigations.

  8. Legionella detection and subgrouping in water air-conditioning cooling tower systems in Kuwait.

    PubMed

    Al-Matawah, Qadreyah; Al-Zenki, Sameer; Al-Azmi, Ahmad; Al-Waalan, Tahani; Al-Salameen, Fadila; Hejji, Ahmad Ben

    2015-07-01

    The main aim of the study was to test for the presence of Legionnaires' disease-causing microorganisms in air-conditioned buildings in Kuwait using molecular technologies. For this purpose, 547 samples were collected from 38 cooling towers for the analysis of Legionella pneumophila. These samples included those from water (n = 178), air (n = 231), and swabs (n = 138). Out of the 547 samples, 226 (41%) samples were presumptive positive for L. pneumophila, with L. pneumophila viable counts in the positive water samples ranging from 1 to 88 CFU/ml. Of the Legionella culture-positive samples, 204 isolates were examined by latex agglutination. These isolates were predominately identified as L. pneumophila serogroup (sg) 2-14. Using the Dresden panel of monoclonal antibodies, 74 representatives isolates were further serogrouped. Results showed that 51% of the isolates belonged to serogroup 7 followed by 1 (18%) and 3 (18%). Serogroups 4 (4%) and 10 (7%) were isolated at a lower frequency, and two isolates could not be assigned to a serogroup. These results indicate the wide prevalence of L. pneumophila serogroup 7 as the predominant serogroup at the selected sampling sites. Furthermore, the 74 L. pneumophila (sg1 = 13; sg3 = 13; sg4 = 3; sg7 = 38; sg10 = 5; sgX = 2) isolates were genotyped using the seven gene protocol sequence-based typing (SBT) scheme developed by the European Working Group for Legionella Infections (EWGLI). The results show that Legionella isolates were discriminated into nine distinct sequence typing (ST) profiles, five of which were new to the SBT database of EWGLI. Additionally, all of the ST1 serogroup 1 isolates were of the OLDA/Oxford subgroup. These baseline data will form the basis for the development of a Legionella environmental surveillance program and used for future epidemiological investigations. PMID:25701245

  9. A pore scale study on turbulent combustion in porous media

    NASA Astrophysics Data System (ADS)

    Jouybari, N. F.; Maerefat, M.; Nimvari, M. E.

    2016-02-01

    This paper presents pore scale simulation of turbulent combustion of air/methane mixture in porous media to investigate the effects of multidimensionality and turbulence on the flame within the pores of porous media. In order to investigate combustion in the pores of porous medium, a simple but often used porous medium consisting of a staggered arrangement of square cylinders is considered in the present study. Results of turbulent kinetic energy, turbulent viscosity ratio, temperature, flame speed, convective heat transfer and thermal conductivity are presented and compared for laminar and turbulent simulations. It is shown that the turbulent kinetic energy increases from the inlet of burner, because of turbulence created by the solid matrix with a sudden jump or reduction at the flame front due to increase in temperature and velocity. Also, the pore scale simulation revealed that the laminarization of flow occurs after flame front in the combustion zone and turbulence effects are important mainly in the preheat zone. It is shown that turbulence enhances the diffusion processes in the preheat zone, but it is not enough to affect the maximum flame speed, temperature distribution and convective heat transfer in the porous burner. The dimensionless parameters associated with the Borghi-Peters diagram of turbulent combustion have been analyzed for the case of combustion in porous media and it is found that the combustion in the porous burner considered in the present study concerns the range of well stirred reactor very close to the laminar flame region.

  10. Ignition in laminar and turbulent nonpremixed counterflow

    NASA Astrophysics Data System (ADS)

    Blouch, John Dewey

    2002-01-01

    Investigations into nonpremixed ignition were conducted to examine the influence of complex chemistry and flow turbulence as found in practical combustion systems. The counterflow configuration, where a hot air jet ignited a cold (298K) fuel jet, was adopted in experiments and calculations. The study of the ignition of large alkane hydrocarbons focused on the effects of fuel structure by investigating the reference fuels n-heptane and iso-octane. The ignition response of these fuels was similar to smaller fuels with similar molecular structures. This conclusion was reinforced by showing that the ignition temperature became nearly insensitive to fuel molecule size above C4, but continued to depend on whether the structure was linear or branched. The effects of turbulence were studied by adding perforated plates to the burner to generate controlled levels of turbulence. This configuration was examined in detail experimentally and computationally without reaction, and subsequently the effects of turbulence on ignition were studied with hydrogen as the fuel. The results indicated that at low turbulence intensities, ignition is enhanced relative to laminar ignition, but as the turbulence intensity increases the ignition temperature also increases, demonstrating that optimal conditions for ignition exist at low turbulence intensities. At high pressures, where HO2 chemistry is important, all turbulent ignition temperatures were higher than laminar ones, and the increasing temperature trend with turbulence intensity was still observed. At low fuel concentrations, a different ignition mode was observed where the transition from a weakly reacting state to a flame occurred over a range of temperatures where the flame was repeatedly ignited and extinguished. Turbulent ignition was modeled by solving a joint scalar PDF equation using a Monte Carlo technique. The absence of significant heat release prior to ignition enabled the use of a frozen flow solution, solved separately

  11. Global and local statistics in turbulent convection at low Prandtl numbers

    NASA Astrophysics Data System (ADS)

    Scheel, Janet D.; Schumacher, Jörg

    2016-09-01

    Statistical properties of turbulent Rayleigh-Benard convection at low Prandtl numbers (Pr), which are typical for liquid metals such as mercury, gallium or liquid sodium, are investigated in high-resolution three-dimensional spectral element simulations in a closed cylindrical cell with an aspect ratio of one and are compared to previous turbulent convection simulations in air. We compare the scaling of global momentum and heat transfer. The scaling exponents are found to be in agreement with experiments. Mean profiles of the root-mean-square velocity as well as the thermal and kinetic energy dissipation rates have growing amplitudes with decreasing Prandtl number which underlies a more vigorous bulk turbulence in the low-Pr regime. The skin-friction coefficient displays a Reynolds-number dependence that is close to that of an isothermal, intermittently turbulent velocity boundary layer. The thermal boundary layer thicknesses are larger as Pr decreases and conversely the velocity boundary layer thicknesses become smaller. We investigate the scaling exponents and find a slight decrease in exponent magnitude for the thermal boundary layer thickness as Pr decreases, but find the opposite case for the velocity boundary layer thickness scaling. A growing area fraction of turbulent patches close to the heating and cooling plates can be detected by exceeding a locally defined shear Reynolds number threshold. This area fraction is larger for lower Pr at the same Ra. Our analysis of the kurtosis of the locally defined shear Reynolds number demonstrates that the intermittency in the boundary layer is significantly increased for the lower Prandtl number and for sufficiently high Rayleigh number compared to convection in air. This complements our previous findings of enhanced bulk intermittency in low-Prandtl-number convection.

  12. Gamma-ray nuclear resonance absorption (γ-NRA) for explosives detection in air cargo

    NASA Astrophysics Data System (ADS)

    Vartsky, D.; Goldberg, M. B.; Engler, G.; Goldschmidt, A.; Feldman, G.; Bar, D.; Sayag, E.; Katz, D.; Krauss, R. A.

    1999-06-01

    The γ-NRA method has been utilized to detect explosives concealed in aviation containers loaded with a variety of cargo. In γ-NRA, gamma-rays at an energy of 9.17 MeV undergo a resonant nuclear attenuation component proportional to the integrated density of 14N nuclei along the line of sight from source to detector. When inspecting objects in transmission mode, projected images of nitrogen density of their contents can be generated. In an experiment performed earlier this year at the Dynamitron accelerator lab. of Birmingham Univ., U.K., diverse items such as passenger bags, electronic equipment, paper goods and mixed cargo were scanned along with explosives simulants. The results from this run will be presented and anticipated performance ratings of an operational explosives detection system (EDS) discussed.

  13. Detection and identification of toxic air pollutants using airborne LWIR hyperspectral imaging

    NASA Astrophysics Data System (ADS)

    Williams, David J.; Feldman, Barry L.; Williams, Tim J.; Pilant, Drew; Lucey, Paul G.; Worthy, L. D.

    2005-01-01

    Airborne longwave infrared (LWIR) hyperspectral imagery was utilized to detect and identify gaseous chemical release plumes at sites in southern Texas. The Airborne Hyperspectral Imager (AHI), developed by the University of Hawai"i, was flown over a petrochemical facility and a confined animal feeding operation on a modified DC-3 during April, 2004. Data collected by the AHI system was successfully used to detect and identify numerous plumes at both sites. Preliminary results indicate the presence of benzene and ammonia and several other organic compounds. Emissions were identified using regression analysis on atmospherically compensated data. Data validation was conducted using facility emission inventories. This technology has great promise for monitoring and inventorying facility emissions, and may be used as means to assist ground inspection teams to focus on actual fugitive emission points.

  14. Laser beam propagation in atmospheric turbulence

    NASA Technical Reports Server (NTRS)

    Murty, S. S. R.

    1979-01-01

    The optical effects of atmospheric turbulence on the propagation of low power laser beams are reviewed in this paper. The optical effects are produced by the temperature fluctuations which result in fluctuations of the refractive index of air. The commonly-used models of index-of-refraction fluctuations are presented. Laser beams experience fluctuations of beam size, beam position, and intensity distribution within the beam due to refractive turbulence. Some of the observed effects are qualitatively explained by treating the turbulent atmosphere as a collection of moving gaseous lenses of various sizes. Analytical results and experimental verifications of the variance, covariance and probability distribution of intensity fluctuations in weak turbulence are presented. For stronger turbulence, a saturation of the optical scintillations is observed. The saturation of scintillations involves a progressive break-up of the beam into multiple patches; the beam loses some of its lateral coherence. Heterodyne systems operating in a turbulent atmosphere experience a loss of heterodyne signal due to the destruction of coherence.

  15. Effects of submesoscale turbulence on ocean tracers

    NASA Astrophysics Data System (ADS)

    Smith, Katherine M.; Hamlington, Peter E.; Fox-Kemper, Baylor

    2016-01-01

    Ocean tracers such as carbon dioxide, nutrients, plankton, and oil advect, diffuse, and react primarily in the oceanic mixed layer where air-sea gas exchange occurs and light is plentiful for photosynthesis. There can be substantial heterogeneity in the spatial distributions of these tracers due to turbulent stirring, particularly in the submesoscale range where partly geostrophic fronts and eddies and small-scale three-dimensional turbulence are simultaneously active. In this study, a large eddy simulation spanning horizontal scales from 20 km down to 5 m is used to examine the effects of multiscale turbulent mixing on nonreactive passive ocean tracers from interior and sea-surface sources. The simulation includes the effects of both wave-driven Langmuir turbulence and submesoscale eddies, and tracers with different initial and boundary conditions are examined in order to understand the respective impacts of small-scale and submesoscale motions on tracer transport. Tracer properties are characterized using spatial fields and statistics, multiscale fluxes, and spectra, and the results detail how tracer mixing depends on air-sea tracer flux rate, tracer release depth, and flow regime. Although vertical fluxes of buoyancy by submesoscale eddies compete with mixing by Langmuir turbulence, vertical fluxes of tracers are often dominated by Langmuir turbulence, particularly for tracers that are released near the mixed-layer base or that dissolve rapidly through the surface, even in regions with pronounced submesoscale activity. Early in the evolution of some tracers, negative eddy diffusivities occur co-located with regions of negative potential vorticity, suggesting that symmetric instabilities or other submesoscale phenomenon may act to oppose turbulent mixing.

  16. Turbulence generation in homogeneous dilute particle- laden flows

    NASA Astrophysics Data System (ADS)

    Chen, Jeng-Horng

    Homogeneous turbulence generated by the motion of particles in dispersed multiphase flows was studied both theoretically and experimentally, motivated by applications to sprays, particle-laden jets, bubble plumes and rainstorms, among others. The experiments involved uniform fluxes of monodisperse spherical particles falling through a slow upflow of air. Particle fluxes and phase velocities were measured by sampling and phase-discriminating laser Doppler velocimetry (LDV), respectively. Measured particle velocities included mean and fluctuating streamwise and cross-stream velocities and probability density functions (PDF's). Measured continuous-phase velocities included mean and fluctuating streamwise and cross-stream velocities, PDF's and the higher moments of velocity fluctuations such as skewness and kurtosis, energy spectra of velocity fluctuations and integral length scales based on streamwise velocity fluctuations. Continuous-phase velocity measurements included conditional averages for particle wake disturbances and the turbulent inter-wake region surrounding these disturbances as well as overall flow properties. Present and earlier results in the literature provided particle Reynolds numbers of 38-990, particle volume fractions less than 0.01% and turbulence intensities (normalized by mean particle relative velocities) of 0.1-10.0%. Theory included characterization of particle wake disturbances as laminar-like turbulent wakes observed for intermediate particle Reynolds numbers in turbulent environments, characterization of the turbulent inter-wake region by analogy to grid-generated isotropic turbulence, and estimation of overall flow properties by conditional averaging of the properties of the wake disturbances and the turbulent inter-wake region. Present measurements showed that particle wake disturbances during turbulence generation were properly characterized by the properties of laminar-like turbulent wakes. The turbulent inter-wake region was

  17. An experimental study of air-assist atomizer spray flames

    NASA Technical Reports Server (NTRS)

    Mao, Chien-Pei; Wang, Geng; Chigier, Norman

    1988-01-01

    It is noted that air-assisted atomizer spray flames encountered in furnaces, boilers, and gas turbine combustors possess a more complex structure than homogeneous turbulent diffusion flames, due to the swirling motion introduced into the fuel and air flows for the control of flame stability, length, combustion intensity, and efficiency. Detailed comparisons are presented between burning and nonburning condition measurements of these flames obtained by nonintrusive light scattering phase/Doppler detection. Spray structure is found to be drastically changed within the flame reaction zone, with changes in the magnitude and shape of drop number density, liquid flux, mean drop size diameter, and drop mean axial velocity radial distributions.

  18. Real-time monitoring of bioaerosols via cell-lysis by air ion and ATP bioluminescence detection.

    PubMed

    Park, Chul Woo; Park, Ji-Woon; Lee, Sung Hwa; Hwang, Jungho

    2014-02-15

    In this study, we introduce a methodology for disrupting cell membranes with air ions coupled with ATP bioluminescence detection for real-time monitoring of bioaerosol concentrations. A carbon fiber ionizer was used to extract ATP from bacterial cells for generating ATP bioluminescence. Our methodology was tested using Staphylococcus epidermidis and Escherichia coli, which were aerosolized with an atomizer, and then indoor bioaerosols were also used for testing the methodology. Bioaerosol concentrations were estimated without culturing which requires several days for colony formation. Correlation equations were obtained for results acquired using our methodology (Relative Luminescent Unit (RLU)/m(3)) and a culture-based (Colony Forming Unit (CFU)/m(3)) method; CFU/m(3)=1.8 × measured RLU/m(3) for S. epidermidis and E. coli, and CFU/m(3)=1.1 × measured RLU/m(3) for indoor bioaerosols under the experimental conditions. Our methodology is an affordable solution for rapidly monitoring bioaerosols due to rapid detection time (cell-lysis time: 3 min; bioluminescence detection time: <1 min) and easy operation.

  19. Economic crisis detected from space: Air quality observations over Athens/Greece

    NASA Astrophysics Data System (ADS)

    Vrekoussis, M.; Richter, A.; Hilboll, A.; Burrows, J. P.; Gerasopoulos, E.; Lelieveld, J.; Barrie, L.; Zerefos, C.; Mihalopoulos, N.

    2013-01-01

    Using both satellite observations of tropospheric NO2 columns and a number of economic metrics, we investigate the impact of the economic crisis (from 2008 onward) on air quality over Greece, and Athens in particular. The multiannual analysis shows that NO2 columns over Athens have been significantly reduced in the range 30-40%. This decline is further supported by surface measurements of atmospheric NO2 mixing ratios. Additionally, the declining local concentrations of NO, CO, and SO2 are associated with an increase in ozone due to reduced titration by NO. In particular, regression analysis revealed that the reduction of NO2 (0.3 ± 0.2 ppbv y-1) and SO2 (0.2 ± 0.1 ppbv y-1) during the period 2000-2007, significantly accelerated during the economic crisis period (from 2008 onward), reaching 2.3 ± 0.2 ppbv y-1 and 0.7 ± 0.1 ppbv y-1, respectively. The strong correlations between pollutant concentrations and economic indicators show that the economic recession has resulted in proportionally lower levels of pollutants in large parts of Greece.

  20. Air pollution at a hotspot location in Delhi: Detecting trends, seasonal cycles and oscillations

    NASA Astrophysics Data System (ADS)

    Kandlikar, Milind

    This paper uses spectral methods to analyze changes in air quality at a single monitoring site in Delhi since 2000. Power spectral density calculations of daily concentration data for particulate matter (PM10), carbon monoxide (CO), oxides of nitrogen (NO x) and oxides of sulfur (SO x) reveal the presence of trends and periodic oscillations for all the pollutants. Singular Spectrum Analysis (SSA) is used to decompose daily data into statistically significant non-linear trends, seasonal cycles and other oscillations. Periods of sharp reductions were observed for both SO x and CO concentrations in 2001 and 2002, respectively. NO x concentration trends show a sustained rise from 2000 to 2004, followed by small decline thereafter. PM10 concentration trends remain essentially unchanged over the time period. All pollutants also show strong annual and biannual cycles. The observed trends in CO and NO x likely relate changes in Delhi's vehicular traffic emissions. The sharp drop in both the trend and amplitude of the seasonal cycle of CO coincides with the switch to Compressed Natural Gas (CNG) as a fuel for Delhi's public transport fleet. Observed changes in SO x and PM10 concentrations were most likely caused by sources unrelated to vehicular traffic.

  1. Microbiological detection of bacteria in animal products seized in baggage of international air passengers to Brazil.

    PubMed

    de Melo, Cristiano Barros; de Sá, Marcos Eielson Pinheiro; Sabino, Valéria Mourão; de Fatima Boechat-Fernandes, Maria; Santiago, Marco Túlio; Schwingel, Fábio Fraga; Freitas, Cleverson; Magioli, Carlos Alberto; Cabral-Pinto, Sergio; McManus, Concepta; Seixas, Luiza

    2015-01-01

    Airline travel favours the transmission of diseases, given the short time it takes to travel long distances. In this study, animal products without health certificates seized in international air passengers' baggage at Guarulhos (GRU) and Galeão (GIG) airports in Brazil underwent a microbiological evaluation. Analyses (1610) were carried out on 322 seizures to test for the presence of total and thermotolerant coliforms, as well as Staphylococcus aureus counts and the presence of Listeria monocytogenes and Salmonella. Most seizures analysed showed coliform contamination and coliforms were present above acceptable limits in 83.4% (40/48) of the products that had some type of contamination. The second most prevalent microorganism found was L. monocytogenes in 22.9% (11/48) and S. aureus was cultivated in 14.58% (7/48) of seizures. Among the items seized in the present work, Salmonella was found in one seizure of pig sausage. Contamination of animal products with microbiological pathogens of importance to public health and indicators of the bad quality of the food were shown in the present study.

  2. Air motion sensing hairs of arthropods detect high frequencies at near-maximal mechanical efficiency

    PubMed Central

    Bathellier, Brice; Steinmann, Thomas; Barth, Friedrich G.; Casas, Jérôme

    2012-01-01

    Using measurements based on particle image velocimetry in combination with a novel compact theoretical framework to describe hair mechanics, we found that spider and cricket air motion sensing hairs work close to the physical limit of sensitivity and energy transmission in a broad range of relatively high frequencies. In this range, the hairs closely follow the motion of the incoming flow because a minimum of energy is dissipated by forces acting in their basal articulation. This frequency band is located beyond the frequency at which the angular displacement of the hair is maximum which is between about 40 and 600 Hz, depending on hair length (Barth et al. [1] Phil. Trans. R. Soc. Lond. B 340, 445–461 (doi:10.1098/rstb.1993.0084)). Given that the magnitude of natural airborne signals is known to decrease with frequency, our results point towards the possible existence of spectral signatures in the higher frequency range that may be weak but of biological significance. PMID:22171067

  3. Microbiological detection of bacteria in animal products seized in baggage of international air passengers to Brazil.

    PubMed

    de Melo, Cristiano Barros; de Sá, Marcos Eielson Pinheiro; Sabino, Valéria Mourão; de Fatima Boechat-Fernandes, Maria; Santiago, Marco Túlio; Schwingel, Fábio Fraga; Freitas, Cleverson; Magioli, Carlos Alberto; Cabral-Pinto, Sergio; McManus, Concepta; Seixas, Luiza

    2015-01-01

    Airline travel favours the transmission of diseases, given the short time it takes to travel long distances. In this study, animal products without health certificates seized in international air passengers' baggage at Guarulhos (GRU) and Galeão (GIG) airports in Brazil underwent a microbiological evaluation. Analyses (1610) were carried out on 322 seizures to test for the presence of total and thermotolerant coliforms, as well as Staphylococcus aureus counts and the presence of Listeria monocytogenes and Salmonella. Most seizures analysed showed coliform contamination and coliforms were present above acceptable limits in 83.4% (40/48) of the products that had some type of contamination. The second most prevalent microorganism found was L. monocytogenes in 22.9% (11/48) and S. aureus was cultivated in 14.58% (7/48) of seizures. Among the items seized in the present work, Salmonella was found in one seizure of pig sausage. Contamination of animal products with microbiological pathogens of importance to public health and indicators of the bad quality of the food were shown in the present study. PMID:25466683

  4. Antennas for the detection of radio emission pulses from cosmic-ray induced air showers at the Pierre Auger Observatory

    NASA Astrophysics Data System (ADS)

    Abreu, P.; Aglietta, M.; Ahlers, M.; Ahn, E. J.; Albuquerque, I. F. M.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Almela, A.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Alves Batista, R.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Antičić, T.; Aramo, C.; Arganda, E.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Badescu, A. M.; Balzer, M.; Barber, K. B.; Barbosa, A. F.; Bardenet, R.; Barroso, S. L. C.; Baughman, B.; Bäuml, J.; Baus, C.; Beatty, J. J.; Becker, K. H.; Bellétoile, A.; Bellido, J. A.; BenZvi, S.; Berat, C.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, F.; Blanco, M.; Bleve, C.; Blümer, H.; Boháčová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brancus, I.; Brogueira, P.; Brown, W. C.; Bruijn, R.; Buchholz, P.; Bueno, A.; Buroker, L.; Burton, R. E.; Caballero-Mora, K. S.; Caccianiga, B.; Caramete, L.; Caruso, R.; Castellina, A.; Catalano, O.; Cataldi, G.; Cazon, L.; Cester, R.; Chauvin, J.; Cheng, S. H.; Chiavassa, A.; Chinellato, J. A.; Chirinos Diaz, J.; Chudoba, J.; Cilmo, M.; Clay, R. W.; Cocciolo, G.; Collica, L.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cook, H.; Cooper, M. J.; Coppens, J.; Cordier, A.; Coutu, S.; Covault, C. E.; Creusot, A.; Criss, A.; Cronin, J.; Curutiu, A.; Dagoret-Campagne, S.; Dallier, R.; Daniel, B.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; De Donato, C.; de Jong, S. J.; De La Vega, G.; de Mello Junior, W. J. M.; de Mello Neto, J. R. T.; De Mitri, I.; de Souza, V.; de Vries, K. D.; del Peral, L.; del Río, M.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Díaz Castro, M. L.; Diep, P. N.; Diogo, F.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; dos Anjos, J. C.; Dova, M. T.; D'Urso, D.; Dutan, I.; Ebr, J.; Engel, R.; Erdmann, M.; Escobar, C. O.; Espadanal, J.; Etchegoyen, A.; Facal San Luis, P.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Fick, B.; Figueira, J. M.; Filevich, A.; Filipčič, A.; Fliescher, S.; Fracchiolla, C. E.; Fraenkel, E. D.; Fratu, O.; Fröhlich, U.; Fuchs, B.; Gaior, R.; Gamarra, R. F.; Gambetta, S.; García, B.; Garcia Roca, S. T.; Garcia-Gamez, D.; Garcia-Pinto, D.; Gascon Bravo, A.; Gemmeke, H.; Ghia, P. L.; Giller, M.; Gitto, J.; Glass, H.; Gold, M. S.; Golup, G.; Gomez Albarracin, F.; Gómez Berisso, M.; Gómez Vitale, P. F.; Gonçalves, P.; Gonzalez, J. G.; Gookin, B.; Gorgi, A.; Gouffon, P.; Grashorn, E.; Grebe, S.; Griffith, N.; Grigat, M.; Grillo, A. F.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Hansen, P.; Harari, D.; Harrison, T. A.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Herve, A. E.; Hojvat, C.; Hollon, N.; Holmes, V. C.; Homola, P.; Hörandel, J. R.; Horvath, P.; Hrabovský, M.; Huber, D.; Huege, T.; Insolia, A.; Ionita, F.; Italiano, A.; Jansen, S.; Jarne, C.; Jiraskova, S.; Josebachuili, M.; Kadija, K.; Kampert, K. H.; Karhan, P.; Kasper, P.; Katkov, I.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kelley, J. L.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapp, J.; Koang, D.-H.; Kotera, K.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuempel, D.; Kulbartz, J. K.; Kunka, N.; La Rosa, G.; Lachaud, C.; LaHurd, D.; Latronico, L.; Lauer, R.; Lautridou, P.; Le Coz, S.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Lopez Agüera, A.; Louedec, K.; Lozano Bahilo, J.; Lu, L.; Lucero, A.; Ludwig, M.; Lyberis, H.; Maccarone, M. C.; Macolino, C.; Maldera, S.; Maller, J.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, J.; Marin, V.; Maris, I. C.; Marquez Falcon, H. R.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Martraire, D.; Masías Meza, J. J.; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurel, D.; Maurizio, D.; Mazur, P. O.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Mertsch, P.; Meurer, C.; Meyhandan, R.; Mićanović, S.; Micheletti, M. I.; Minaya, I. A.; Miramonti, L.; Molina-Bueno, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morales, B.; Morello, C.; Moreno, E.; Moreno, J. C.; Mostafá, M.; Moura, C. A.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navarro, J. L.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Neuser, J.; Nhung, P. T.; Niechciol, M.; Niemietz, L.; Nierstenhoefer, N.; Nitz, D.; Nosek, D.; Nožka, L.; Oehlschläger, J.; Olinto, A.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Parente, G.; Parizot, E.; Parra, A.; Pastor, S.; Paul, T.; Pech, M.; Pekala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Petrera, S.; Petrolini, A.; Petrov, Y.; Pfendner, C.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.; Platino, M.; Plum, M.; Ponce, V. H.; Pontz, M.; Porcelli, A.; Privitera, P.; Prouza, M.; Quel, E. J.; Querchfeld, S.; Rautenberg, J.; Ravel, O.; Ravignani, D.; Revenu, B.; Ridky, J.; Riggi, S.; Risse, M.; Ristori, P.; Rivera, H.; Rizi, V.; Roberts, J.; Rodrigues de Carvalho, W.; Rodriguez, G.; Rodriguez Cabo, I.; Rodriguez Martino, J.; Rodriguez Rojo, J.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Rossler, T.; Roth, M.; Rouillé-d'Orfeuil, B.; Roulet, E.; Rovero, A. C.; Rühle, C.; Saftoiu, A.; Salamida, F.; Salazar, H.; Salesa Greus, F.; Salina, G.; Sánchez, F.; Santo, C. E.; Santos, E.; Santos, E. M.; Sarazin, F.; Sarkar, B.; Sarkar, S.; Sato, R.; Scharf, N.; Scherini, V.; Schieler, H.; Schiffer, P.; Schmidt, A.; Scholten, O.; Schoorlemmer, H.; Schovancova, J.; Schovánek, P.; Schröder, F.; Schulte, S.; Schuster, D.; Sciutto, S. J.; Scuderi, M.; Segreto, A.; Settimo, M.; Shadkam, A.; Shellard, R. C.; Sidelnik, I.; Sigl, G.; Silva Lopez, H. H.; Sima, O.; Śmiałkowski, A.; Šmída, R.; Snow, G. R.; Sommers, P.; Sorokin, J.; Spinka, H.; Squartini, R.; Srivastava, Y. N.; Stanic, S.; Stapleton, J.; Stasielak, J.; Stephan, M.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Šuša, T.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Szuba, M.; Tapia, A.; Tartare, M.; Taşcău, O.; Tcaciuc, R.; Thao, N. T.; Thomas, D.; Tiffenberg, J.; Timmermans, C.; Tkaczyk, W.; Todero Peixoto, C. J.; Toma, G.; Tomankova, L.; Tomé, B.; Tonachini, A.; Travnicek, P.; Tridapalli, D. B.; Tristram, G.; Trovato, E.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Valdés Galicia, J. F.; Valiño, I.; Valore, L.; van Aar, G.; van den Berg, A. M.; van Vliet, A.; Varela, E.; Vargas Cárdenas, B.; Vázquez, J. R.; Vázquez, R. A.; Veberič, D.; Verzi, V.; Vicha, J.; Videla, M.; Villaseñor, L.; Wahlberg, H.; Wahrlich, P.; Wainberg, O.; Walz, D.; Watson, A. A.; Weber, M.; Weidenhaupt, K.; Weindl, A.; Werner, F.; Westerhoff, S.; Whelan, B. J.; Widom, A.; Wieczorek, G.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Will, M.; Williams, C.; Winchen, T.; Wommer, M.; Wundheiler, B.; Yamamoto, T.; Yapici, T.; Younk, P.; Yuan, G.; Yushkov, A.; Zamorano Garcia, B.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zaw, I.; Zepeda, A.; Zhou, J.; Zhu, Y.; Zimbres Silva, M.; Ziolkowski, M.; Charrier, D.; Denis, L.; Hilgers, G.; Mohrmann, L.; Philipps, B.; Seeger, O.

    2012-10-01

    The Pierre Auger Observatory is exploring the potential of the radio detection technique to study extensive air showers induced by ultra-high energy cosmic rays. The Auger Engineering Radio Array (AERA) addresses both technological and scientific aspects of the radio technique. A first phase of AERA has been operating since September 2010 with detector stations observing radio signals at frequencies between 30 and 80 MHz. In this paper we present comparative studies to identify and optimize the antenna design for the final configuration of AERA consisting of 160 individual radio detector stations. The transient nature of the air shower signal requires a detailed description of the antenna sensor. As the ultra-wideband reception of pulses is not widely discussed in antenna literature, we review the relevant antenna characteristics and enhance theoretical considerations towards the impulse response of antennas including polarization effects and multiple signal reflections. On the basis of the vector effective length we study the transient response characteristics of three candidate antennas in the time domain. Observing the variation of the continuous galactic background intensity we rank the antennas with respect to the noise level added to the galactic signal.

  5. How to reliably detect molecular clusters and nucleation mode particles with Neutral cluster and Air Ion Spectrometer (NAIS)

    NASA Astrophysics Data System (ADS)

    Manninen, Hanna E.; Mirme, Sander; Mirme, Aadu; Petäjä, Tuukka; Kulmala, Markku

    2016-08-01

    To understand the very first steps of atmospheric particle formation and growth processes, information on the size where the atmospheric nucleation and cluster activation occurs, is crucially needed. The current understanding of the concentrations and dynamics of charged and neutral clusters and particles is based on theoretical predictions and experimental observations. This paper gives a standard operation procedure (SOP) for Neutral cluster and Air Ion Spectrometer (NAIS) measurements and data processing. With the NAIS data, we have improved the scientific understanding by (1) direct detection of freshly formed atmospheric clusters and particles, (2) linking experimental observations and theoretical framework to understand the formation and growth mechanisms of aerosol particles, and (3) parameterizing formation and growth mechanisms for atmospheric models. The SOP provides tools to harmonize the world-wide measurements of small clusters and nucleation mode particles and to verify consistent results measured by the NAIS users. The work is based on discussions and interactions between the NAIS users and the NAIS manufacturer.

  6. Trace-gas detection in ambient air with a thermoelectrically cooled, pulsed quantum-cascade distributed feedback laser.

    PubMed

    Kosterev, A A; Tittel, F K; Gmachl, C; Capasso, F; Sivco, D L; Baillargeon, J N; Hutchinson, A L; Cho, A Y

    2000-12-20

    A pulsed quantum-cascade distributed feedback laser operating at near room temperature was used for sensitive high-resolution IR absorption spectroscopy of ambient air at a wavelength of approximately 8 microm. Near-transform-limited laser pulses were obtained owing to short (approximately 5-ns) current pulse excitation and optimized electrical coupling. Fast and slow computer-controlled frequency scanning techniques were implemented and characterized. Fast computer-controlled laser wavelength switching was used to acquire second-derivative absorption spectra. The minimum detectable absorption was found to be 3 x 10(-4) with 10(5) laser pulses (20-kHz repetition rate), and 1.7 x 10(-4) for 5 x 10(5) pulses, based on the standard deviation of the linear regression analysis.

  7. Determination of chlorpyrifos in air, leaves and soil from a greenhouse by gas-chromatography with nitrogen-phosphorus detection, high-performance liquid chromatography and capillary electrophoresis.

    PubMed

    Guardino, X; Obiols, J; Rosell, M G; Farran, A; Serra, C

    1998-10-01

    Chlorpyrifos was determined in air, leaves and soil in a greenhouse in order to establish performance differences between gas-chromatography with nitrogen-phosphorus detection (GC-NPD) and high-performance liquid chromatographic and capillary electrophoretic methods and to assess the farm workers' risk of overexposure due to air exposure and/or skin contact with this compound. Results obtained indicate that the three analytical techniques, with the specific procedures described, can be used, although only GC-NPD provides an operative limit of detection in air. Chlorpyrifos levels in air are dependent on time and greenhouse ventilation, whereas it remains for a long time on leaf surfaces and soil. As a consequence, specific instructions can be established for farm workers in order to avoid skin and respiratory exposure to chlorpyrifos.

  8. One-dimensional turbulence

    SciTech Connect

    Kerstein, A.R.

    1996-12-31

    One-Dimensional Turbulence is a new turbulence modeling strategy involving an unsteady simulation implemented in one spatial dimension. In one dimension, fine scale viscous and molecular-diffusive processes can be resolved affordably in simulations at high turbulence intensity. The mechanistic distinction between advective and molecular processes is thereby preserved, in contrast to turbulence models presently employed. A stochastic process consisting of mapping {open_quote}events{close_quote} applied to a one-dimensional velocity profile represents turbulent advection. The local event rate for given eddy size is proportional to the velocity difference across the eddy. These properties cause an imposed shear to induce an eddy cascade analogous in many respects to the eddy cascade in turbulent flow. Many scaling and fluctuation properties of self-preserving flows, and of passive scalars introduced into these flows, are reproduced.

  9. Turbulence generation by waves

    SciTech Connect

    Kaftori, D.; Nan, X.S.; Banerjee, S.

    1995-12-31

    The interaction between two-dimensional mechanically generated waves, and a turbulent stream was investigated experimentally in a horizontal channel, using a 3-D LDA synchronized with a surface position measuring device and a micro-bubble tracers flow visualization with high speed video. Results show that although the wave induced orbital motion reached all the way to the wall, the characteristics of the turbulence wall structures and the turbulence intensity close to the wall were not altered. Nor was the streaky nature of the wall layer. On the other hand, the mean velocity profile became more uniform and the mean friction velocity was increased. Close to the free surface, the turbulence intensity was substantially increased as well. Even in predominantly laminar flows, the introduction of 2-D waves causes three dimensional turbulence. The turbulence enhancement is found to be proportional to the wave strength.

  10. Economical crisis detected from space: Trends in air quality of Athens in Greece

    NASA Astrophysics Data System (ADS)

    Vrekoussis, Mihalis; Richter, Andreas; Hilboll, Andreas; Burrows, John P.; Zerefos, Christos; Gerasopoulos, Evangelos; Lelieveld, Jos; Barrie, Leonard; Mihalopoulos, Nikos

    2013-04-01

    Data from three satellite spectrometers (SCIAMACHY, GOME2 and OMI) have been analyzed together with a number of economic metrics to investigate the impact of the economic crisis (from 2008 onward) on air quality over Greece, and Athens in particular. Athens is a heavily polluted city due to the extensive number of registered vehicles, the presence of industrial regions close to the city, the complex topography of the area favouring pollutant accumulation, the intense photochemical processes favoured by high temperature and insolation and the reception of transboundary pollution. The multiannual analysis shows a significant 30-40% reduction of primary gaseous pollutants in the form of NO2 tropospheric columnar densities observed over Athens, during the economic recession period, indicating large reductions in pollutant emissions. This decline is further supported by surface measurements of atmospheric NO2 mixing ratios. Additionally, the declining local concentrations of NO, CO, SO2 are associated with an increase in ozone due to reduced titration by NO. In particular, regression analysis revealed that the reduction of NO2 (0.3±0.2 ppbv y-1) and SO2 (0.2±0.1ppbv y-1) during the period 2000-2007, significantly accelerated during the economic crisis period (from 2008 onward), reaching 2.3±0.2 ppbv y-1 and 0.7±0.1 ppbv y-1, respectively. The strong correlations between pollutant concentrations and economic indicators show that economic recession has resulted in proportionally lower levels of pollutants not only in Athens but also in large parts of Greece.

  11. Use of cooperative unmanned air and ground vehicles for detection and disposal of mines

    NASA Astrophysics Data System (ADS)

    Zawodny MacArthur, Erica; MacArthur, Donald; Crane, Carl

    2005-11-01

    The objective of this research is to extend the sensing capabilities of a multi-vehicle ground system by incorporating the environmental perception abilities of unmanned aerial vehicles. The aerial vehicle used in this research is a Miniature Aircraft Gas Xcell RC helicopter. It is outfitted with a sensor payload containing stereo vision cameras, GPS, and a digital compass. Geo- referenced images are gathered using the above sensors that are used in this research to create a map of the operating region. The ground vehicle used in this research is an automated Suzuki Mini-Quad ATV. It has the following onboard sensors: single-vision camera, laser range device, digital compass, GPS, and an encoder. The ground vehicle uses the above sensors and the map provided by the helicopter to traverse the region, locate, and isolate simulated land mines. The base station consists of a laptop that provides a communication link between the aerial and ground vehicle systems. It also provides the operator with system operation information and statistics. All communication between the vehicles and the base station is performed using JAUS (Joint Architecture for Unmanned Systems) messages. The JAUS architecture is employed as a means to organize inter-vehicle and intra-vehicle communication and system component hierarchy. The purpose of JAUS is to provide interoperability between various unmanned systems and subsystems for both military and commercial applications. JAUS seeks to achieve this through the development of functionally cohesive building blocks called components whose interface messages are clearly defined. The JAUS architecture allows for a layered control strategy which has specific message sets for each layer of control. Implementation of the JAUS architecture allows for ease of software development for a multi- vehicle system. This experiment demonstrates how an air-ground vehicle system can be used to cooperatively locate and dispose of simulated mines.

  12. Effect of prior dust collection on detection, counting efficiency, and energy resolution for alpha continuous air monitors

    SciTech Connect

    Newton, G.J.; Hoover, M.D.

    1994-11-01

    For the past several years, we have supported the DOE Waste Isolation Pilot Plant (WIPP) project by evaluating the capabilities and performance of the Eberline Alpha 6 continuous air monitor (CAM). This evalution has focused on the ability of the CAM to correctly report plutonium in the presence of salt dust. Tests involving the simultaneous collection of plutonium and salt have shown that burial by salt can degrade the detection of plutonium, but that this interference is negligible when salt concentrations are below about 0.2 mg/m{sup 3}. Throughout the evalution, it has been assumed that salt burial is a concern for slow, chronic release of plutonium, but that any acute release of plutonium would be collected on the top surface of the filter or salt and would be unattenuated. The spectral quality of alpha radiation detection on membrane filters is observed to improve with filter loading. This is attributed to the probability that accumulations of dust tend to fill in surface irregularities of the collection filter at a a faster rate than they create additional surface irregularities. The validity of these assumptions about the improved detection of plutonium on salt-layer surfaces has recently been questioned. Based on electron micrographic examination of salt-laden filters, it has been speculated that collection of salt dust on a membrane filter results in formation of pores, fissures, and dendritic shapes of salt on the filter surface. If plutonium were collected, particles could penetrate into the pores and fissures, resulting in a degraded or lost signal from the plutonium. Because no experimental evidence existed to answer the concern, the purpose of the current study was to quantify any differences between detection of plutonium on clean or salt-laden filters.

  13. Fault detection and isolation of aircraft air data/inertial system

    NASA Astrophysics Data System (ADS)

    Berdjag, D.; Cieslak, J.; Zolghadri, A.

    2013-12-01

    A method for failure detection and isolation (FDI) for redundant aircraft sensors is presented. The outputs of the concerned sensors are involved in the computation of flight control laws, and the objective is to eliminate any fault before propagation in the control loop when selecting a unique flight parameter among a set (generally, three) of redundant measurements. The particular case of an oscillatory failure is investigated. The proposed method allows an accurate FDI of erroneous sensor and computes a consolidated parameter based on the fusion of data from remaining valid sensors. The benefits of the presented method are to enhance the data fusion process with FDI techniques which improve the performance of the fusion when only few sources (less than three) are initially valid.

  14. Detection of particulate air pollution plumes from major point sources using ERTS-1 imagery

    NASA Technical Reports Server (NTRS)

    Lyons, W. A.; Pease, S. R.

    1973-01-01

    The Earth Resources Technology Satellite (ERTS-1) launched by NASA in July 1972 has been providing thousands of high resolution multispectral images of interest to geographers, cartographers, hydrologists, and agroculturists. It has been found possible to detect the long-range (over 50 km) transport of suspected particulate plumes from the Chicago-Gary steel mill complex over Lake Michigan. The observed plumes are readily related to known steel mills, a cement plant, refineries, and fossil-fuel power plants. This has important ramifications when discussing the interregional transport of atmospheric pollutants. Analysis reveals that the Multispectral Scanner Band 5 (0.6 to 0.7 micrometer) provides the best overall contrast between the smoke and the underlying water surface.

  15. Detecting air pollution stress in southern California vegetation using Landsat Thematic Mapper band data

    SciTech Connect

    Westman, W.E.; Price, C.V.

    1988-09-01

    Landsat Thematic Mapper (TM) and aircraft-borne Thematic Mapper simulator (TMS) data were collected over two areas of natural vegetation in southern California exposed to gradients of pollutant dose, particularly in photochemical oxidants: the coastal sage scrub of the Santa Monica Mountains in the Los Angeles basin, and the yellow pine forests in the southern Sierra Nevada. In both situations, natural variations in canopy closure, with subsequent exposure of understory elements (e.g.,rock or soil, chaparral, grasses, and herbs), were sufficient to cause changes in spectral variation that could obscure differences due to visible foliar injury symptoms observed in the field. TM or TMS data are therefore more likely to be successful in distinguishing pollution injury from background variation when homogeneous communities with closed canopies are subjected to more severe pollution-induced structural and/or compositional change. The present study helps to define the threshold level of vegetative injury detectable by TM data. 26 references.

  16. Detecting air pollution stress in southern California vegetation using Landsat Thematic Mapper band data

    NASA Technical Reports Server (NTRS)

    Westman, Walter E.; Price, Curtis V.

    1988-01-01

    Landsat Thematic Mapper (TM) and aircraft-borne Thematic Mapper simulator (TMS) data were collected over two areas of natural vegetation in southern California exposed to gradients of pollutant dose, particularly in photochemical oxidants: the coastal sage scrub of the Santa Monica Mountains in the Los Angeles basin, and the yellow pine forests in the southern Sierra Nevada. In both situations, natural variations in canopy closure, with subsequent exposure of understory elements (e.g.,rock or soil, chaparral, grasses, and herbs), were sufficient to cause changes in spectral variation that could obscure differences due to visible foliar injury symptoms observed in the field. TM or TMS data are therefore more likely to be successful in distinguishing pollution injury from background variation when homogeneous communities with closed canopies are subjected to more severe pollution-induced structural and/or compositional change. The present study helps to define the threshold level of vegetative injury detectable by TM data.

  17. Turbulent mixing& combustion in TNT explosions

    SciTech Connect

    Kuhl, A L; Ferguson, R E; Oppenheim, A K; Seizew, M R

    2000-12-12

    Effects of turbulent mixing induced by explosion of a 1-g spherical TNT charge in air are investigated. The detonation wave in the charge transforms the solid explosive (C{sub 7}H{sub 5}N{sub 3}O{sub 6}) to gaseous products, rich in C{sub (S)}, and CO. The detonation pressure ({approx}210 kb) causes the products to expand rapidly, driving a blast wave into the surrounding air (Brode, 1959). The interface between the products and air is unstable (Richtmyer, 1960; Meshkov, 1960; Anisimov & Zel'dovich, 1977). As shown in Collage Ia-c, this region rapidly transitions into a turbulent mixing layer (Kuhl, 1996). As the embedded shock, I, implodes, it draws the mixing structures (Taylor cavities) into the origin (Collage Id-e). In this way air becomes distributed throughout the hot detonation products gases. This process is enhanced by shock reflections from confining walls. In either case (confined or unconfined), rapid combustion takes place where the expanded detonation products play the role of fuel. This leads to a dramatic increase in chamber pressure (Fig. 1)-in contrast to a corresponding TNT explosion in nitrogen. The problem was modeled as turbulent combustion in an unmixed system at large Reynolds, Peclet and Damkohler numbers (Kuhl et al, 1997). The numerical solution was obtained by a high-order Godunov scheme (Colella & Glaz, 1985). Adaptive Mesh Refinement (Berger & Colella, 1989) was used to follow the turbulent mixing on the computational grid in as much detail as possible. The results reveal all the dynamic features (Fig. 2) of the exothermic process of combustion controlled by fluid-mechanic transport in a highly turbulent field (Kuhl & Oppenheim, 1997), in contrast to the conventional reaction-diffusion mechanism of Zel'dovich & Frank-Kamenetskii (1938).

  18. Tactical missile turbulence problems

    NASA Technical Reports Server (NTRS)

    Dickson, Richard E.

    1987-01-01

    Of particular interest is atmospheric turbulence in the atmospheric boundary layer, since this affects both the launch and terminal phase of flight, and the total flight for direct fire systems. Brief discussions are presented on rocket artillery boost wind problems, mean wind correction, turbulent boost wind correction, the Dynamically Aimed Free Flight Rocket (DAFFR) wind filter, the DAFFR test, and rocket wake turbulence problems. It is concluded that many of the turbulence problems of rockets and missiles are common to those of aircraft, such as structural loading and control system design. However, these problems have not been solved at this time.

  19. Triggering filamentation using turbulence

    NASA Astrophysics Data System (ADS)

    Eeltink, D.; Berti, N.; Marchiando, N.; Hermelin, S.; Gateau, J.; Brunetti, M.; Wolf, J. P.; Kasparian, J.

    2016-09-01

    We study the triggering of single filaments due to turbulence in the beam path for a laser of power below the filamenting threshold. Turbulence can act as a switch between the beam not filamenting and producing single filaments. This positive effect of turbulence on the filament probability, combined with our observation of off-axis filaments, suggests the underlying mechanism is modulation instability caused by transverse perturbations. We hereby experimentally explore the interaction of modulation instability and turbulence, commonly associated with multiple filaments, in the single-filament regime.

  20. A preliminary test of the application of the Lightning Detection and Ranging System (LDAR) as a thunderstorm warning and location device for the FHA including a correlation with updrafts, turbulence, and radar precipitation echoes

    NASA Technical Reports Server (NTRS)

    Poehler, H. A.

    1978-01-01

    Results of a test of the use of a Lightning Detection and Ranging (LDAR) remote display in the Patrick AFB RAPCON facility are presented. Agreement between LDAR and radar precipitation echoes of the RAPCON radar was observed, as well as agreement between LDAR and pilot's visual observations of lightning flashes. A more precise comparison between LDAR and KSC based radars is achieved by the superposition of LDAR precipitation echoes. Airborne measurements of updrafts and turbulence by an armored T-28 aircraft flying through the thunderclouds are correlated with LDAR along the flight path. Calibration and measurements of the accuracy of the LDAR System are discussed, and the extended range of the system is illustrated.

  1. Inhomogeneous turbulence in magnetic reconnection

    NASA Astrophysics Data System (ADS)

    Yokoi, Nobumitsu

    2016-07-01

    Turbulence is expected to play an essential role in enhancing magnetic reconnection. Turbulence associated with magnetic reconnection is highly inhomogeneous: it is generated by inhomogeneities of the field configuration such as the velocity shear, temperature gradient, density stratification, magnetic shear, etc. This self-generated turbulence affects the reconnection through the turbulent transport. In this reconnection--turbulence interaction, localization of turbulent transport due to dynamic balance between several turbulence effects plays an essential role. For investigating inhomogeneous turbulence in a strongly nonlinear regime, closure or turbulence modeling approaches provide a powerful tool. A turbulence modeling approach for the magnetic reconnection is introduced. In the model, the mean-field equations with turbulence effects incorporated are solved simultaneously with the equations of turbulent statistical quantities that represent spatiotemporal properties of turbulence under the effect of large-scale field inhomogeneities. Numerical simulations of this Reynolds-averaged turbulence model showed that self-generated turbulence enhances magnetic reconnection. It was pointed out that reconnection states may be divided into three category depending on the turbulence level: (i) laminar reconnection; (ii) turbulent reconnection, and (iii) turbulent diffusion. Recent developments in this direction are also briefly introduced, which includes the magnetic Prandtl number dependence, spectral evolution, and guide-field effects. Also relationship of this fully nonlinear turbulence approach with other important approaches such as plasmoid instability reconnection will be discussed.

  2. Using Social Media to Detect Outdoor Air Pollution and Monitor Air Quality Index (AQI): A Geo-Targeted Spatiotemporal Analysis Framework with Sina Weibo (Chinese Twitter)

    PubMed Central

    Tsou, Ming-Hsiang; Fu, Xiaokang

    2015-01-01

    Outdoor air pollution is a serious problem in many developing countries today. This study focuses on monitoring the dynamic changes of air quality effectively in large cities by analyzing the spatiotemporal trends in geo-targeted social media messages with comprehensive big data filtering procedures. We introduce a new social media analytic framework to (1) investigate the relationship between air pollution topics posted in Sina Weibo (Chinese Twitter) and the daily Air Quality Index (AQI) published by China’s Ministry of Environmental Protection; and (2) monitor the dynamics of air quality index by using social media messages. Correlation analysis was used to compare the connections between discussion trends in social media messages and the temporal changes in the AQI during 2012. We categorized relevant messages into three types, retweets, mobile app messages, and original individual messages finding that original individual messages had the highest correlation to the Air Quality Index. Based on this correlation analysis, individual messages were used to monitor the AQI in 2013. Our study indicates that the filtered social media messages are strongly correlated to the AQI and can be used to monitor the air quality dynamics to some extent. PMID:26505756

  3. Using Social Media to Detect Outdoor Air Pollution and Monitor Air Quality Index (AQI): A Geo-Targeted Spatiotemporal Analysis Framework with Sina Weibo (Chinese Twitter).

    PubMed

    Jiang, Wei; Wang, Yandong; Tsou, Ming-Hsiang; Fu, Xiaokang

    2015-01-01

    Outdoor air pollution is a serious problem in many developing countries today. This study focuses on monitoring the dynamic changes of air quality effectively in large cities by analyzing the spatiotemporal trends in geo-targeted social media messages with comprehensive big data filtering procedures. We introduce a new social media analytic framework to (1) investigate the relationship between air pollution topics posted in Sina Weibo (Chinese Twitter) and the daily Air Quality Index (AQI) published by China's Ministry of Environmental Protection; and (2) monitor the dynamics of air quality index by using social media messages. Correlation analysis was used to compare the connections between discussion trends in social media messages and the temporal changes in the AQI during 2012. We categorized relevant messages into three types, retweets, mobile app messages, and original individual messages finding that original individual messages had the highest correlation to the Air Quality Index. Based on this correlation analysis, individual messages were used to monitor the AQI in 2013. Our study indicates that the filtered social media messages are strongly correlated to the AQI and can be used to monitor the air quality dynamics to some extent.

  4. Using Social Media to Detect Outdoor Air Pollution and Monitor Air Quality Index (AQI): A Geo-Targeted Spatiotemporal Analysis Framework with Sina Weibo (Chinese Twitter).

    PubMed

    Jiang, Wei; Wang, Yandong; Tsou, Ming-Hsiang; Fu, Xiaokang

    2015-01-01

    Outdoor air pollution is a serious problem in many developing countries today. This study focuses on monitoring the dynamic changes of air quality effectively in large cities by analyzing the spatiotemporal trends in geo-targeted social media messages with comprehensive big data filtering procedures. We introduce a new social media analytic framework to (1) investigate the relationship between air pollution topics posted in Sina Weibo (Chinese Twitter) and the daily Air Quality Index (AQI) published by China's Ministry of Environmental Protection; and (2) monitor the dynamics of air quality index by using social media messages. Correlation analysis was used to compare the connections between discussion trends in social media messages and the temporal changes in the AQI during 2012. We categorized relevant messages into three types, retweets, mobile app messages, and original individual messages finding that original individual messages had the highest correlation to the Air Quality Index. Based on this correlation analysis, individual messages were used to monitor the AQI in 2013. Our study indicates that the filtered social media messages are strongly correlated to the AQI and can be used to monitor the air quality dynamics to some extent. PMID:26505756

  5. Convectively Induced Turbulence Encountered During NASA's Fall-2000 Flight Experiments

    NASA Technical Reports Server (NTRS)

    Hamilton, David W.; Proctor, Fred H.

    2002-01-01

    Aircraft encounters with atmospheric turbulence are a leading cause of in-flight injuries aboard commercial airliners and cost the airlines millions of dollars each year. Most of these injuries are due to encounters with turbulence in and around convection. In a recent study of 44 turbulence accident reports between 1990 and 1996, 82% of the cases were found to be near or within convective activity (Kaplan et al. 1999). According to NTSB accident reports, pilots' descriptions of these turbulence encounters include 'abrupt', 'in Instrument Meteorological Conditions (IMC)', 'saw nothing on the weather radar', and 'the encounter occurred while deviating around' convective activity. Though the FAA has provided guidelines for aircraft operating in convective environments, turbulence detection capability could decrease the number of injuries by alerting pilots of a potential encounter. The National Aeronautics and Space Administration, through its Aviation Safety Program, is addressing turbulence hazards through research, flight experiments, and data analysis. Primary focus of this program element is the characterization of turbulence and its environment, as well as the development and testing of hazard estimation algorithms for both radar and in situ detection. The ultimate goal is to operationally test sensors that will provide ample warning prior to hazardous turbulence encounters. In order to collect data for support of these activities, NASA-Langley's B-757 research aircraft was directed into regions favorable for convectively induced turbulence (CIT). On these flights, the airborne predictive wind shear (PWS) radar, augmented with algorithms designed for turbulence detection, was operated in real time to test this capability. In this paper, we present the results of two research flights when turbulence was encountered. Described is an overview of the flights, the general radar performance, and details of four encounters with severe turbulence.

  6. In situ detection of lung cancer volatile fingerprints using bronchoscopic air-sampling.

    PubMed

    Santonico, M; Lucantoni, G; Pennazza, G; Capuano, R; Galluccio, G; Roscioni, C; La Delfa, G; Consoli, D; Martinelli, E; Paolesse, R; Di Natale, C; D'Amico, A

    2012-07-01

    Lung cancer diagnosis via breath analysis has to overcome some issues that can be summarized by two crucial points: (1) further developments for more performant breath sampling technologies; (2) discovering more differentiated volatile fingerprints to be ascribed to specific altered biological mechanisms. The present work merges these two aspects in a pilot study, where a breath volume, sampled via endoscopic probe, is analyzed by an array of non-selective gas sensors. Even if the original non-invasive methods of breath analysis has been laid in favour of the endoscopic means, the innovative technique here proposed allows the analysis of the volatile mixtures directly sampled near the tumor mass. This strategy could open the way for a better understanding of the already obtained discrimination among positive and negative cancer cases. The results obtained so far confirm the established discrimination capacity. This allows to discriminate the different subtypes of lung cancer with 75% of correct classification between adenocarcinoma and squamous cell carcinoma. This result suggests that a 'zoom-in' on the cancer settled inside the human body can increase the resolution power of key-volatiles detection, allowing the discrimination among different cancer fingerprints. We report this novel technique as a robust support for a better comprehension of the promising results obtained so far and present in literature; it is not to be intended as a replacement for non-invasive breath sampling procedure with the endoscope.

  7. Detection of the Crab Nebula By UV Imaging of TeV Gamma Ray Air Showers

    NASA Astrophysics Data System (ADS)

    Chantell, M.

    1994-12-01

    With successful detection of TeV gamma ray fluxes from the Crab Nebula and the AGN, MRK421, the Whipple Observatory Gamma Ray Collaboration has demonstrated the sensitivity of the Cherenkov imaging technique in ground-based gamma-ray astronomy. This technique uses an array of 109 blue-sensitive photomultipliers to image the Cherenkov radiation produced when TeV gamma and cosmic rays enter the earth's atmosphere. One major limitation of this technique is the requirement of absolutely dark skies during observations. The presence of the moon rules out the possibility of making observations because of the high sensitivity of the photomultipliers used in the camera. To address this limitation we have developed a camera which utilizes solar-blind photomultpliers with primary sensitivity from 220nm to 280nm allowing observations even in the presence of the full moon. After two years of UV observations of the Crab Nebula we have demonstrated the ability to discriminate gamma rays from the hadronic background with an energy threshold of approximately 1 TeV. The development of this camera makes it possible to increase the duty cycle of the 10 meter telescope allowing observations in bright time. Additionally the insensitivity to background star light allows this camera to observe sources in bright regions of the galactic plane, where high background light levels have limited the usefulness of the visible camera.

  8. Detection of biological particles in ambient air using Bio-Aerosol Mass Spectrometry

    SciTech Connect

    McJimpsey, E L; Steele, P T; Coffee, K R; Fergenson, D P; Riot, V J; Woods, B W; Gard, E E; Frank, M; Tobias, H J; Lebrilla, C

    2006-03-16

    The Bio-Aerosol Mass Spectrometry (BAMS) system is an instrument used for the real time detection and identification of biological aerosols. Particles are drawn from the atmosphere directly into vacuum and tracked as they scatter light from several continuous wave lasers. After tracking, the fluorescence of individual particles is excited by a pulsed 266nm or 355nm laser. Molecules from those particles with appropriate fluorescence properties are subsequently desorbed and ionized using a pulsed 266nm laser. Resulting ions are analyzed in a dual polarity mass spectrometer. During two field deployments at the San Francisco International Airport, millions of ambient particles were analyzed and a small but significant fraction were found to have fluorescent properties similar to Bacillus spores and vegetative cells. Further separation of non-biological background particles from potential biological particles was accomplished using laser desorption/ionization mass spectrometry. This has been shown to enable some level of species differentiation in specific cases, but the creation and observation of higher mass ions is needed to enable a higher level of specificity across more species. A soft ionization technique, matrix-assisted laser desorption/ionization (MALDI) is being investigated for this purpose. MALDI is particularly well suited for mass analysis of biomolecules since it allows for the generation of molecular ions from large mass compounds that would fragment under normal irradiation. Some of the initial results from a modified BAMS system utilizing this technique are described.

  9. Design, Modeling, Fabrication, and Evaluation of the Air Amplifier for Improved Detection of Biomolecules by Electrospray Ionization Mass Spectrometry

    PubMed Central

    Robichaud, Guillaume; Dixon, R. Brent; Potturi, Amarnatha S.; Cassidy, Dan; Edwards, Jack R.; Sohn, Alex; Dow, Thomas A.; Muddiman, David C.

    2010-01-01

    Through a multi-disciplinary approach, the air amplifier is being evolved as a highly engineered device to improve detection limits of biomolecules when using electrospray ionization. Several key aspects have driven the modifications to the device through experimentation and simulations. We have developed a computer simulation that accurately portrays actual conditions and the results from these simulations are corroborated by the experimental data. These computer simulations can be used to predict outcomes from future designs resulting in a design process that is efficient in terms of financial cost and time. We have fabricated a new device with annular gap control over a range of 50 to 70 μm using piezoelectric actuators. This has enabled us to obtain better aerodynamic performance when compared to the previous design (2× more vacuum) and also more reproducible results. This is allowing us to study a broader experimental space than the previous design which is critical in guiding future directions. This work also presents and explains the principles behind a fractional factorial design of experiments methodology for testing a large number of experimental parameters in an orderly and efficient manner to understand and optimize the critical parameters that lead to obtain improved detection limits while minimizing the number of experiments performed. Preliminary results showed that several folds of improvements could be obtained for certain condition of operations (up to 34 folds). PMID:21499524

  10. Direct detection of formaldehyde in air by a novel NAD+- and glutathione-independent formaldehyde dehydrogenase-based biosensor.

    PubMed

    Achmann, S; Hermann, M; Hilbrig, F; Jérôme, V; Hämmerle, M; Freitag, R; Moos, R

    2008-05-15

    An amperometric enzyme-based sensor-system for the direct detection of formaldehyde in air is under investigation. The biosensor is based on a native bacterial NAD(+)- and glutathione-independent formaldehyde dehydrogenase as biorecognition element. The enzyme was isolated from Hyphomicrobium zavarzinii strain ZV 580, grown on methylamine hydrochloride in a fed-batch process. The sensor depends on the enzymatic conversion of the analyte to formic acid. Released electrons are detected in an amperometric measurement at 0.2V vs. Ag/AgCl reference electrode by means of a redox-mediator. To optimize the sensing device, Ca(2+) and pyrroloquinoline quinone (PQQ) were added to the buffer solution as reconstitutional substances. At this stage, the sensor shows linear response in the tested ppm-range with a sensitivity of 0.39 microA/ppm. The signal is highly reproducible with respect to sensitivity and base line signal. Reproducibility of sensitivity is more than 90% within the same bacterial batch and even when enzyme of different bacterial batches is used. PMID:18585147

  11. Flight Tests of the Turbulence Prediction and Warning System (TPAWS)

    NASA Technical Reports Server (NTRS)

    Hamilton, David W.; Proctor, Fred H.; Ahmad, Nashat N.

    2012-01-01

    Flight tests of the National Aeronautics and Space Administration's Turbulence Prediction And Warning System (TPAWS) were conducted in the Fall of 2000 and Spring of 2002. TPAWS is a radar-based airborne turbulence detection system. During twelve flights, NASA's B-757 tallied 53 encounters with convectively induced turbulence. Analysis of data collected during 49 encounters in the Spring of 2002 showed that the TPAWS Airborne Turbulence Detection System (ATDS) successfully detected 80% of the events at least 30 seconds prior to the encounter, achieving FAA recommended performance criteria. Details of the flights, the prevailing weather conditions, and each of the turbulence events are presented in this report. Sensor and environmental characterizations are also provided.

  12. Rapid growth of cloud droplets by turbulence.

    PubMed

    Dallas, V; Vassilicos, J C

    2011-10-01

    Assuming perfect collision efficiency, we demonstrate that turbulence can initiate and sustain the rapid growth of very small water droplets in air even when these droplets are too small to cluster, and even without having to take gravity and small-scale intermittency into account. This is because the range of local Stokes numbers of identical droplets in the turbulent flow field is broad enough even when small-scale intermittency is neglected. This demonstration is given for turbulence which is one order of magnitude less intense than is typical in warm clouds but with a volume fraction which, even though small, is nevertheless large enough for an estimated a priori frequency of collisions to be ten times larger than in warm clouds. However, the time of growth in these conditions turns out to be one order of magnitude smaller than in warm clouds.

  13. [Clostridium difficile diarrhea: frequency of detection in a medical center in Buenos Aires, Argentina].

    PubMed

    Fernandez Canigia, L; Nazar, J; Arce, M; Dadamio, J; Smayevsky, J; Bianchini, H

    2001-01-01

    Clostridium difficile has been recognized as the most important enteric pathogen of nosocomial antibiotic-associated diarrhea (CDAD) in adults from industrialized countries. The importance of C. difficile as a cause of diarrhea in ambulatory patients appears underestimated or under-recognized. Since the 1980's, outbreaks of CDAD have been increasingly reported, but there are few data available in Argentina. We developed a retrospective study to provide some information about CDAD in our country. From July 1998 to November 1999, a total of 245 fecal specimens from hospitalized and some ambulatory patients were tested in order to confirm the diagnosis of CDAD. C. difficile cytotoxin (toxin B) was identified by detecting its cytopathic effect on monolayers of McCoy culture cells. For culture and isolation of C. difficile, stool samples were prepared by ethanol shock prior to plating onto a selective medium which contained blood, cefoxitin and fructose. Of the 245 samples, 14 (5.8%) were identified as positive by the cell cytotoxicity assay. Using the criteria of isolation of cytotoxigenic C. difficile positivity increased to 6.5% (16 samples). Thirteen of the positive results were from hospitalized patients (81.3%) and 3 (18.7%) from outpatients. The mean age of inpatients was 72.9 years (ranging from 47 to 88). All patients had received 2 or more antimicrobial agents (most of them beta-lactams) 2 months before the appearance of diarrhea. There was one patient who had received only chemotherapy. The prevalence of CDAD in this study was less than in others previously reported. This difference may be due to the fact that not all general practitioners include testing for C. difficile when the patient with diarrhea had previously received antibiotics. More educational programs should be directed to all physicians, concerning the role of C. difficile as an important enteric pathogen in patients who have undergone treatment with antimicrobial or chemotherapeutic agents.

  14. A MODEL OF TURBULENT DIFFUSION FLAMES AND NITRIC OXIDE GENERATION

    EPA Science Inventory

    The report describes a new view of mixing and chemical reactions in turbulent fuel jets discharging into air. Review of available fundamental data from jet flames leads to the idea that mixing begins with a large scale, inviscid intertwining of entrained air and fuel throughout t...

  15. Thermography of volcanic areas on Piton de la Fournaise, Reunion Island : Mapping surface properties and possible detection of convective air flow within volcanic debris

    NASA Astrophysics Data System (ADS)

    Antoine, R.; Baratoux, D.; Rabinowicz, M.; Saracco, G.; Bachelery, P.; Staudacher, T.; Fontaine, F.

    2007-12-01

    We report on the detection of air convection in a couple of quasi circular cavities forming the 300 years old volcanically inactive cone of Formica Leo (Piton de la Fournaise, Reunion Island) [1]. Infrared thermal images of the cone have been acquired in 2006 from a hand held camera at regular time interval during a complete diurnal cycle. During night and dawn, the data display hot rims and cold centers. Both the conductivity contrasts of the highly porous soils filling the cavities and their 30° slopes are unable to explain the systematic rim to center temperature drop. Accordingly, this signal could be attributed to an air convection dipping inside the highly porous material at the center of each cavity, then flowing upslope along the base of the soil layer, before exiting it along the rims. Anemometrical and electrical data acquired in 2007 allow for the first time the direct detection of this air flow on the field: dipping gas velocities are measured at the center of the cone and self-potentials anomalies [2] generated by the humid air flow in the porous medium are detected. To quantify this process, we present 2D/3D numerical models of air convection in a sloped volcanic soil with a surface temperature evolving between day and night and taking into account electrical phenomena created by the air flow. At this present stage, this work constitutes a first step to investigate the deep structure of the active caldera of Bory-Dolomieu. The detection of the air flow at the surface could be of paramount importance for the understanding of volcanic hazards of the Reunion volcano. [1] Antoine et. al, submitted to G-Cubed [2] Darnet, PhD, Université Louis Pasteur (2003)

  16. Comparison of Aperture Averaging and Receiver Diversity Techniques for Free Space Optical Links in Presence of Turbulence and Various Weather Conditions

    NASA Astrophysics Data System (ADS)

    Kaur, Prabhmandeep; Jain, Virander Kumar; Kar, Subrat

    2014-12-01

    In this paper, we investigate the performance of a Free Space Optic (FSO) link considering the impairments caused by the presence of various weather conditions such as very clear air, drizzle, haze, fog, etc., and turbulence in the atmosphere. Analytic expression for the outage probability is derived using the gamma-gamma distribution for turbulence and accounting the effect of weather conditions using the Beer-Lambert's law. The effect of receiver diversity schemes using aperture averaging and array receivers on the outage probability is studied and compared. As the aperture diameter is increased, the outage probability decreases irrespective of the turbulence strength (weak, moderate and strong) and weather conditions. Similar effects are observed when the number of direct detection receivers in the array are increased. However, it is seen that as the desired level of performance in terms of the outage probability decreases, array receiver becomes the preferred choice as compared to the receiver with aperture averaging.

  17. MHD turbulent processes

    NASA Technical Reports Server (NTRS)

    Montgomery, David

    1988-01-01

    Three areas of study in MHD turbulence are considered. These are the turbulent relaxation of the toroidal Z pinch, density fluctuations in MHD fluids, and MHD cellular automata. A Boolean computer game that updates a cellular representation in parallel and that has macroscopic averages converging to solutions of the two-dimensional MHD equations is discussed.

  18. Propagation properties of an optical vortex carried by a Bessel-Gaussian beam in anisotropic turbulence.

    PubMed

    Cheng, Mingjian; Guo, Lixin; Li, Jiangting; Huang, Qingqing

    2016-08-01

    Rytov theory was employed to establish the transmission model for the optical vortices carried by Bessel-Gaussian (BG) beams in weak anisotropic turbulence based on the generalized anisotropic von Karman spectrum. The influences of asymmetry anisotropic turbulence eddies and source parameters on the signal orbital angular momentum (OAM) mode detection probability of partially coherent BG beams in anisotropic turbulence were discussed. Anisotropic characteristics of the turbulence could enhance the OAM mode transmission performance. The spatial partially coherence of the beam source would increase turbulent aberration's effect on the optical vortices. BG beams could dampen the influences of the turbulence because of their nondiffraction and self-healing characteristics.

  19. Propagation properties of an optical vortex carried by a Bessel-Gaussian beam in anisotropic turbulence.

    PubMed

    Cheng, Mingjian; Guo, Lixin; Li, Jiangting; Huang, Qingqing

    2016-08-01

    Rytov theory was employed to establish the transmission model for the optical vortices carried by Bessel-Gaussian (BG) beams in weak anisotropic turbulence based on the generalized anisotropic von Karman spectrum. The influences of asymmetry anisotropic turbulence eddies and source parameters on the signal orbital angular momentum (OAM) mode detection probability of partially coherent BG beams in anisotropic turbulence were discussed. Anisotropic characteristics of the turbulence could enhance the OAM mode transmission performance. The spatial partially coherence of the beam source would increase turbulent aberration's effect on the optical vortices. BG beams could dampen the influences of the turbulence because of their nondiffraction and self-healing characteristics. PMID:27505641

  20. Studying Turbulence Using Numerical Simulation Databases, 2. Proceedings of the 1988 Summer Program

    NASA Technical Reports Server (NTRS)

    1988-01-01

    The focus of the program was on the use of direct numerical simulations of turbulent flow for study of turbulence physics and modeling. A special interest was placed on turbulent mixing layers. The required data for these investigations were generated from four newly developed codes for simulation of time and spatially developing incompressible and compressible mixing layers. Also of interest were the structure of wall bounded turbulent and transitional flows, evaluation of diagnostic techniques for detection of organized motions, energy transfer in isotropic turbulence, optical propagation through turbulent media, and detailed analysis of the interaction of vortical structures.

  1. Elasto-inertial turbulence.

    PubMed

    Samanta, Devranjan; Dubief, Yves; Holzner, Markus; Schäfer, Christof; Morozov, Alexander N; Wagner, Christian; Hof, Björn

    2013-06-25

    Turbulence is ubiquitous in nature, yet even for the case of ordinary Newtonian fluids like water, our understanding of this phenomenon is limited. Many liquids of practical importance are more complicated (e.g., blood, polymer melts, paints), however; they exhibit elastic as well as viscous characteristics, and the relation between stress and strain is nonlinear. We demonstrate here for a model system of such complex fluids that at high shear rates, turbulence is not simply modified as previously believed but is suppressed and replaced by a different type of disordered motion, elasto-inertial turbulence. Elasto-inertial turbulence is found to occur at much lower Reynolds numbers than Newtonian turbulence, and the dynamical properties differ significantly. The friction scaling observed coincides with the so-called "maximum drag reduction" asymptote, which is exhibited by a wide range of viscoelastic fluids.

  2. Elasto-inertial turbulence

    PubMed Central

    Samanta, Devranjan; Dubief, Yves; Holzner, Markus; Schäfer, Christof; Morozov, Alexander N.; Wagner, Christian; Hof, Björn

    2013-01-01

    Turbulence is ubiquitous in nature, yet even for the case of ordinary Newtonian fluids like water, our understanding of this phenomenon is limited. Many liquids of practical importance are more complicated (e.g., blood, polymer melts, paints), however; they exhibit elastic as well as viscous characteristics, and the relation between stress and strain is nonlinear. We demonstrate here for a model system of such complex fluids that at high shear rates, turbulence is not simply modified as previously believed but is suppressed and replaced by a different type of disordered motion, elasto-inertial turbulence. Elasto-inertial turbulence is found to occur at much lower Reynolds numbers than Newtonian turbulence, and the dynamical properties differ significantly. The friction scaling observed coincides with the so-called “maximum drag reduction” asymptote, which is exhibited by a wide range of viscoelastic fluids. PMID:23757498

  3. Relationship Between Vortex Meander and Ambient Turbulence

    NASA Technical Reports Server (NTRS)

    Rossow, Vernon J.; Hardy, Gordon H.; Meyn, Larry A.

    2006-01-01

    Efforts are currently underway to increase the capacity of airports by use of closely-spaced parallel runways. If such an objective is to be achieved safely and efficiently during both visual and instrument flight conditions, it will be necessary to develop more precise methods for the prediction of the motion and spread of the hazard posed by the lift-generated vortex-wakes of aircraft, and their uncertainties. The purpose of the present study is to relate the motion induced in vortex filaments by turbulence in the ambient flow field to the measured turbulence in the flow field. The problem came about when observations made in the two largest NASA wind tunnels indicated that extended exposure of vortex wakes to the turbulence in the wind tunnel air stream causes the centers of the vortices to meander about with time at a given downstream station where wake measurements are being made. Although such a behavior was expected, the turbulence level based on the maximum amplitude of meander was much less than the root-mean-squared value measured in the free-stream of the wind tunnel by use of hot-film anemometers. An analysis of the time-dependent motion of segments of vortex filaments as they interact with an eddy, indicates that the inertia of the filaments retards their motion enough in the early part of their travel to account for a large part of the difference in the two determinations of turbulence level. Migration of vortex filaments from one turbulent eddy to another (probably with a different orientation), is believed to account for the remainder of the difference. Methods that may possibly be developed for use in the measurement of the magnitude of the more intense eddies in turbulent flow fields and how they should be adjusted to predict vortex meander are then discussed.

  4. Liquid infused surfaces in turbulent channel flow

    NASA Astrophysics Data System (ADS)

    Fu, Matthew; Stone, Howard; Smits, Alexander; Jacobi, Ian; Samaha, Mohamed; Wexler, Jason; Shang, Jessica; Rosenberg, Brian; Hellström, Leo; Fan, Yuyang; Wang, Karen; Lee, Kevin; Hultmark, Marcus

    2014-11-01

    A turbulent channel flow facility is used to measure the drag reduction capabilities and dynamic behavior of liquid-infused micro-patterned surfaces. Liquid infused surfaces have been proposed as a robust alternative to traditional air-cushion-based superhydrophobic surfaces. The mobile liquid lubricant creates a surface slip with the outer turbulent shear flow as well as an energetic sink to dampen turbulent fluctuations. Micro-manufactured surfaces can be mounted flush in the channel and exposed to turbulent flows. Two configurations are possible, both capable of producing laminar and turbulent flows. The first configuration allows detailed investigation of the infused liquid layer and the other allows well resolved pressure gradient measurements. Both of the configurations have high aspect ratios 15-45:1. Drag reduction for a variety of liquid-infused surface architectures is quantified by measuring pressure drop in the channel. Flow in the oil film is simultaneously visualized using fluorescent dye. Supported under ONR Grants N00014-12-1-0875 and N00014-12-1-0962 (program manager Ki-Han Kim).

  5. Causes of non-Kolmogorov turbulence in the atmosphere.

    PubMed

    Lukin, V P; Nosov, E V; Nosov, V V; Torgaev, A V

    2016-04-20

    In the present work, we briefly describe a model for atmospheric turbulence energy on the basis of experimental data obtained in Siberia. A series of new studies is considered and the results of our long-term experimental observations are summarized. The results of these studies form the basis for an explanation of some effects in interactions between optical waves and atmospheric turbulence. Our numerous experimental results point to the possible generation of so-called coherent turbulence in the atmosphere. When analyzing the problem, we proceeded based on our own experimental data and comprehension that the coherent turbulence is a result of the action of self-organizing nonlinear processes, which run in continuous media, including atmospheric air. The experimental data confirmed the effect of attenuation of light fluctuations in coherent turbulence.

  6. Market Assessment of Forward-Looking Turbulence Sensing Systems

    NASA Technical Reports Server (NTRS)

    Kauffmann, Paul

    2003-01-01

    This viewgraph presentation provides a cost benefit analysis of three next-generation forward-looking turbulence sensing systems: X band turbulence radar system for convective turbulence, LIDAR based turbulence systems to sense clear air turbulence and a combined hybrid system. Parameters for the cost benefit analysis were established using a business model which considered injury rates, cost of injuries, indirect costs, market penetration rate estimates and product success characteristics. Topics covered include: study approach, business case equations, data acquisition, benchmark analysis. Data interpretation from the cost benefit analysis is presented. The researchers conclude that the market potential for these products is based primarily on injury cost reduction and that X band radar systems have the greatest chance for commercial success.

  7. General scale-dependent anisotropic turbulence and its impact on free space optical communication system performance.

    PubMed

    Toselli, Italo; Korotkova, Olga

    2015-06-01

    We generalize a recently introduced model for nonclassic turbulent spatial power spectrum involving anisotropy along two mutually orthogonal axes transverse to the direction of beam propagation by including two scale-dependent weighting factors for these directions. Such a turbulent model may be pertinent to atmospheric fluctuations in the refractive index in stratified regions well above the boundary layer and employed for air-air communication channels. When restricting ourselves to an unpolarized, coherent Gaussian beam and a weak turbulence regime, we examine the effects of such a turbulence type on the OOK FSO link performance by including the results on scintillation flux, probability of fade, SNR, and BERs.

  8. Combining a focused air-puff system with phase-sensitive optical coherence tomography for the detection of soft-tissue tumors based on elasticity measurement

    NASA Astrophysics Data System (ADS)

    Wang, Shang; Li, Jiasong; Vantipalli, Srilatha; Manapuram, Ravi Kiran; Ingram, Davis R.; Twa, Michael D.; Lazar, Alexander J.; Lev, Dina C.; Pollock, Raphael E.; Larin, Kirill V.

    2013-03-01

    We combine a focused air-puff system with phase-sensitive optical coherence tomography (PhS-OCT) to measure the elasticity of soft tissues. Surface waves (SWs) on soft tissues are induced by a low-pressure, short-duration air stream from an air-puff system and measured using a high-sensitivity PhS-OCT imaging system. Young's modulus of soft tissues can be quantified based on the group velocity of SWs. To precisely control the excitation pressure, the air-puff system was characterized with a high-resolution analog pressure transducer. We studied the feasibility of this method for the non-contact detection of soft-tissue tumors. Ex vivo human fat and myxoma were used for these pilot experiments. Results demonstrate that this optical non-contact technique can be used to differentiate soft-tissue tumors from normal tissues based on measurements of their elasticity.

  9. Combustion-turbulence interaction in the turbulent boundary layer over a hot surface

    SciTech Connect

    Ng, T.T.; Cheng, R.K.; Robben, F.; Talbot, L.

    1982-01-01

    The turbulence-combustion interaction in a reacting turbulent boundary layer over a heated flat plate was studied. Ethylene/air mixture with equivalence ratio of 0.35 was used. The free stream velocity was 10.5 m/s and the wall temperature was 1250/sup 0/K. Combustion structures visualization was provided by high-speed schlieren photographs. Fluid density statistics were deduced from Rayleigh scattering intensity measurements. A single-component laser Doppler velocimetry system was used to obtain mean and root-mean-square velocity distributions, the Reynolds stress, the streamwise and the cross-stream turbulent kinetic energy diffusion, and the production of turbulent kinetic energy by Reynolds stress. The combustion process was dominated by large-scale turbulent structures of the boundary layer. Combustion causes expansion of the boundary layer. No overall self-similarity is observed in either the velocity or the density profiles. Velocity fluctuations were increased in part of the boundary layer and the Reynolds stress was reduced. The turbulent kinetic energy diffusion pattern was changed significantly and a modification of the boundary layer assumption will be needed when dealing with this problem analytically. 11 figures, 1 table.

  10. Direct numerical simulation of turbulent mixing in grid-generated turbulence

    NASA Astrophysics Data System (ADS)

    Nagata, Kouji; Suzuki, Hiroki; Sakai, Yasuhiko; Hayase, Toshiyuki; Kubo, Takashi

    2008-12-01

    Turbulent mixing of passive scalar (heat) in grid-generated turbulence (GGT) is simulated by means of direct numerical simulation (DNS). A turbulence-generating grid, on which the velocity components are set to zero, is located downstream of the channel entrance, and it is numerically constructed on the staggered mesh arrangement using the immersed boundary method. The grid types constructed are: (a) square-mesh biplane grid, (b) square-mesh single-plane grid, (c) composite grid consisting of parallel square-bars and (d) fractal grid. Two fluids with different temperatures are provided separately in the upper and lower streams upstream of the turbulence-generating grids, generating the thermal mixing layer behind the grids. For the grid (a), simulations for two different Prandtl numbers of 0.71 and 7.1, corresponding to air and water flows, are conducted to investigate the effect of the Prandtl number. The results show that the typical grid turbulence and shearless mixing layer are generated downstream of the grids. The results of the scalar field show that a typical thermal mixing layer is generated as well, and the effects of the Prandtl numbers on turbulent heat transfer are observed.

  11. Turbulent mixing and transport in a thermally stratified interfacial layer in decaying grid turbulence

    NASA Astrophysics Data System (ADS)

    Jayesh, Yoon, Kyunghwan; Warhaft, Z.

    1991-05-01

    A stably stratified mixing layer, sandwiched in between regions of neutral turbulence, was studied in decaying grid turbulence. The layer, which was shearless, was formed by heating the upper half of the flow by means of elements placed at the entrance to the plenum of a large, open circuit low speed wind tunnel 0.91×0.91 m2 in cross section and 9.14 m in length. The hot air above mixed with the cold below forming the stratified layer in between. As the flow evolved and the turbulence decayed, the buoyancy forces increased relative to the inertial forces (i.e., the Richardson number increased) causing the heat flux to collapse. This resulted in a thinning of the mixing layer with downstream distance (rather than growth which occurs for the passive case). Inside the layer the vertical velocity variance diminished and the vertical heat flux correlation coefficient was reduced to zero. Smoke wire photographs showed a wavylike damped region inside the layer, surrounded by the normal, more energetic turbulence outside. Second-order turbulence quantities scaled in the same way with the local Richardson number both along the layer and across it. The two stably stratified cases studied had centerline Froude numbers of 95 and 65 at 40 mesh lengths from the grid. The results are compared to a passive thermal mixing layer and are contrasted with recent experiments concerning a constant temperature gradient in grid turbulence.

  12. Turbulent mixing and transport in a thermally stratified interfacial layer in decaying grid turbulence

    SciTech Connect

    Jayesh; Yoon, K.; Warhaft, Z. )

    1991-05-01

    A stably stratified mixing layer, sandwiched in between regions of neutral turbulence, was studied in decaying grid turbulence. The layer, which was shearless, was formed by heating the upper half of the flow by means of elements placed at the entrance to the plenum of a large, open circuit low speed wind tunnel 0.91{times}0.91 m{sup 2} in cross section and 9.14 m in length. The hot air above mixed with the cold below forming the stratified layer in between. As the flow evolved and the turbulence decayed, the buoyancy forces increased relative to the inertial forces (i.e., the Richardson number increased) causing the heat flux to collapse. This resulted in a thinning of the mixing layer with downstream distance (rather than growth which occurs for the passive case). Inside the layer the vertical velocity variance diminished and the vertical heat flux correlation coefficient was reduced to zero. Smoke wire photographs showed a wavylike damped region inside the layer, surrounded by the normal, more energetic turbulence outside. Second-order turbulence quantities scaled in the same way with the local Richardson number both along the layer and across it. The two stably stratified cases studied had centerline Froude numbers of 95 and 65 at 40 mesh lengths from the grid. The results are compared to a passive thermal mixing layer and are contrasted with recent experiments concerning a constant temperature gradient in grid turbulence.

  13. Turbulence statistics in turbulent spots in a transitional boundary layer subject to free-stream turbulence

    NASA Astrophysics Data System (ADS)

    Rehill, Brendan; Ed J. Walsh Collaboration; Philipp Schlatter, Luca Brandt Collaboration; Tamer A. Zaki Collaboration; Donald M. McEligot Collaboration

    2011-11-01

    Within the boundary layer transition region turbulent spots emerge and grow to form the fully-turbulent boundary layer. This paper examines the turbulent statistics within turbulent spots in a transitional boundary layer subject to free-stream turbulence intensity of 4 . 7 % . Conditionally sampled DNS results, where the laminar and turbulent contributions to the transition region are separated, are used to obtain the relevant statistics. Conditional sampling of the data provides some improvement over the more classical time-space-averaged data reduction techniques, through providing more insight into the true turbulent statistics within turbulent spots. The statistics are compared to the lowest fully-turbulent DNS available in the literature to identify how the turbulent spots develop and form the fully-turbulent state. Stokes Institute, University of Limerick, Limerick, Ireland

  14. Wall turbulence control

    NASA Technical Reports Server (NTRS)

    Wilkinson, Stephen P.; Lindemann, A. Margrethe; Beeler, George B.; Mcginley, Catherine B.; Goodman, Wesley L.; Balasubramanian, R.

    1986-01-01

    A variety of wall turbulence control devices which were experimentally investigated are discussed; these include devices for burst control, alteration of outer flow structures, large eddy substitution, increased heat transfer efficiency, and reduction of wall pressure fluctuations. Control of pre-burst flow was demonstrated with a single, traveling surface depression which is phase-locked to elements of the burst production process. Another approach to wall turbulence control is to interfere with the outer layer coherent structures. A device in the outer part of a boundary layer was shown to suppress turbulence and reduce drag by opposing both the mean and unsteady vorticity in the boundary layer. Large eddy substitution is a method in which streamline curvature is introduced into the boundary layer in the form of streamwise vortices. Riblets, which were already shown to reduce turbulent drag, were also shown to exhibit superior heat transfer characteristics. Heat transfer efficiency as measured by the Reynolds Analogy Factor was shown to be as much as 36 percent greater than a smooth flat plate in a turbulent boundary layer. Large Eddy Break-Up (LEBU) which are also known to reduce turbulent drag were shown to reduce turbulent wall pressure fluctuation.

  15. Modeling turbulent flame propagation

    SciTech Connect

    Ashurst, W.T.

    1994-08-01

    Laser diagnostics and flow simulation techniques axe now providing information that if available fifty years ago, would have allowed Damkoehler to show how turbulence generates flame area. In the absence of this information, many turbulent flame speed models have been created, most based on Kolmogorov concepts which ignore the turbulence vortical structure, Over the last twenty years, the vorticity structure in mixing layers and jets has been shown to determine the entrainment and mixing behavior and these effects need to be duplicated by combustion models. Turbulence simulations reveal the intense vorticity structure as filaments and simulations of passive flamelet propagation show how this vorticity Creates flame area and defines the shape of the expected chemical reaction surface. Understanding how volume expansion interacts with flow structure should improve experimental methods for determining turbulent flame speed. Since the last decade has given us such powerful new tools to create and see turbulent combustion microscopic behavior, it seems that a solution of turbulent combustion within the next decade would not be surprising in the hindsight of 2004.

  16. UAS Air Traffic Controller Acceptability Study. 2; Evaluating Detect and Avoid Technology and Communication Delays in Simulation

    NASA Technical Reports Server (NTRS)

    Comstock, James R., Jr.; Ghatas, Rania W.; Consiglio, Maria C.; Chamberlain, James P.; Hoffler, Keith D.

    2015-01-01

    This study evaluated the effects of communications delays and winds on air traffic controller ratings of acceptability of horizontal miss distances (HMDs) for encounters between Unmanned Aircraft Systems (UAS) and manned aircraft in a simulation of the Dallas-Ft. Worth (DFW) airspace. Fourteen encounters per hour were staged in the presence of moderate background traffic. Seven recently retired controllers with experience at DFW served as subjects. Guidance provided to the UAS pilots for maintaining a given HMD was provided by information from Detect and Avoid (DAA) self-separation algorithms (Stratway+) displayed on the Multi-Aircraft Control System. This guidance consisted of amber "bands" on the heading scale of the UAS navigation display indicating headings that would result in a loss of well clear between the UAS and nearby traffic. Winds tested were successfully handled by the DAA algorithms and did not affect the controller acceptability ratings of the HMDs. Voice communications delays for the UAS were also tested and included one-way delay times of 0, 400, 1200, and 1800 msec. For longer communications delays, there were changes in strategy and communications flow that were observed and reported by the controllers. The aim of this work is to provide useful information for guiding future rules and regulations applicable to flying UAS in the NAS. Information from this study will also be of value to the Radio Technical Commission for Aeronautics (RTCA) Special Committee 228 - Minimum Performance Standards for UAS.

  17. A turbulence indicator utilizing the diffusion of heat

    NASA Technical Reports Server (NTRS)

    Schubauer, G B

    1936-01-01

    This report describes a method of determining the turbulence in wind tunnels. The effect of turbulence upon the diffusion of heat from a small electrically heated wire in an air stream was investigated. The turbulence of the stream was introduced by a series of geometrically similar screens placed one at a time across the upstream section of the tunnel. With the wire set at various distances from the screens, curves of temperature distribution were obtained by traversing the heated wake at a distance of 2 inches behind the wire with a small thermocouple.

  18. PREFACE: Turbulent Mixing and Beyond Turbulent Mixing and Beyond

    NASA Astrophysics Data System (ADS)

    Abarzhi, Snezhana I.; Gauthier, Serge; Rosner, Robert

    2008-10-01

    (continuous DNS/LES/RANS, Molecular dynamics, Monte-Carlo, predictive modeling) New Experimental Diagnostics (novel methods for flow visualization and control, high-tech) The First International Conference `Turbulent Mixing and Beyond' was organized by the following members of the Organizing Committee: Snezhana I Abarzhi (chairperson, Chicago, USA) Malcolm J Andrews (Los Alamos National Laboratory, USA) Sergei I Anisimov (Landau Institute for Theoretical Physics, Russia) Serge Gauthier (Commissariat à l'Energie Atomique, France) Donald Q Lamb (The University of Chicago, USA) Katsunobu Nishihara (Institute for Laser Engineering, Osaka, Japan) Bruce A Remington (Lawrence Livermore National Laboratory, USA) Robert Rosner (Argonne National Laboratory, USA) Katepalli R Sreenivasan (International Centre for Theoretical Physics, Italy) Alexander L Velikovich (Naval Research Laboratory, USA) The Organizing Committee gratefully acknowledges the financial support of the Conference Sponsors: National Science Foundation (NSF), USA (Divisions and Programs Directors: Drs A G Detwiler, L M Jameson, E L Lomon, P E Phelan, G A Prentice, J A Raper, W Schultz, P R Westmoreland; PI: Dr S I Abarzhi) Air Force Office of Scientific Research (AFOSR), USA (Program Director: Dr J D Schmisseur; PI: Dr S I Abarzhi) European Office of Aerospace Research and Development (EOARD) of the AFOSR, UK (Program Chief: Dr S Surampudi; PI: Dr S I Abarzhi) International Centre for Theoretical Physics (ICTP), Trieste, Italy (Centre's Director: Dr K R Sreenivasan) The University of Chicago and The Argonne National Laboratory (ANL), USA (Laboratory's Director: Dr R Rosner) Commissariat à l'Energie Atomique (CEA), France (Directeur de Recherche: Dr S Gauthier) Department of Energy, Los Alamos National Laboratory (LANL), USA (Program manager: Dr R J Hanrahan; Group Leader: Dr M J Andrew) The DOE ASC Alliance Center for Astrophysical Thermonuclear Flashes, The University of Chicago, USA (Center's Director: Dr D Q Lamb

  19. Molecular optical air data system (MOADS)

    NASA Astrophysics Data System (ADS)

    Tchoryk, Peter, Jr.; Watkins, Christopher B.; Lindemann, Scott K.; Hays, Paul B.; Nardell, Carl A.

    2001-09-01

    The Molecular Optical Air Data System (MOADS) is a compact optical instrument that can directly measure wind speed and direction, density, and temperature of the air surrounding an aircraft. From these measurements, a complete set of air data products can be determined. Single-axis wind tunnel testing of wind speed and density has just been completed for the current prototype. These wind tunnel measurements have shown that the current prototype meets wind speed accuracy predictions and initial results from density testing indicate a high level of correlation with absolute pressure transducer measurements. A preliminary design for the next generation instrument, the Joint Optical Air Data System (JOADS), has been completed and is intended to meet Joint Striker Fighter (JSF) requirements. Work is also underway to evaluate the application of MOADS to Unmanned Air Vehicles (UAVs), Reusable Launch Vehicles (RLVs), helicopters and weapon systems. Extensions of MOADS technology to wind shear, gust alleviation, and clear air turbulence detection for commercial aircraft are also being pursued. The basic instrument operation, preliminary ground testing (wind tunnel) results, comparison of these results to simulations, next generation instrument capabilities, and plans for a flight demonstration are discussed.

  20. Scaling of turbulent flame speed for expanding flames with Markstein diffusion considerations.

    PubMed

    Chaudhuri, Swetaprovo; Wu, Fujia; Law, Chung K

    2013-09-01

    In this paper we clarify the role of Markstein diffusivity, which is the product of the planar laminar flame speed and the Markstein length, on the turbulent flame speed and its scaling, based on experimental measurements on constant-pressure expanding turbulent flames. Turbulent flame propagation data are presented for premixed flames of mixtures of hydrogen, methane, ethylene, n-butane, and dimethyl ether with air, in near-isotropic turbulence in a dual-chamber, fan-stirred vessel. For each individual fuel-air mixture presented in this work and the recently published iso-octane data from Leeds, normalized turbulent flame speed data of individual fuel-air mixtures approximately follow a Re_{T,f}^{0.5} scaling, for which the average radius is the length scale and thermal diffusivity is the transport property of the turbulence Reynolds number. At a given Re_{T,f}^{}, it is experimentally observed that the normalized turbulent flame speed decreases with increasing Markstein number, which could be explained by considering Markstein diffusivity as the leading dissipation mechanism for the large wave number flame surface fluctuations. Consequently, by replacing thermal diffusivity with the Markstein diffusivity in the turbulence Reynolds number definition above, it is found that normalized turbulent flame speeds could be scaled by Re_{T,M}^{0.5} irrespective of the fuel, equivalence ratio, pressure, and turbulence intensity for positive Markstein number flames. PMID:24125342