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A hybrid rotational CARS scheme with femtosecond pump/Stokes preparation and a high-energy probe, generated by second-harmonic bandwidth compression (SHBC), is described. The instrument is demonstrated for collision- and background-free, kHz-rate temperature/oxygen probing in the product gases of C2H4/air flat flames for both lean and rich conditions.

In this paper, the results of an experimental study of the time-resolved structure of a thermal boundary layer in a pulsating channel flow are presented. The developing laminar regime is investigated. Two techniques were used for time-resolved temperature measurements: a nonintrusive, pure-rotational CARS method and cold-wire anemometry. Results are presented for differing degrees of flow reversal, and the data show that the primary impact of reversed flow is an increase in the instantaneous thermal boundary-layer thickness and a period of decreased instantaneous Nusselt number. For the developing laminar parameter space spanned by the experiments, time-averaged heat-transfer enhancements as high as a factor of two relative to steady flow are observed for nonreversing and partially reversed pulsating flows. It is concluded that reversal is not necessarily a requirement for enhancement.

This paper describes the use of dual-broadband, pure-rotational coherent anti-Strokes Raman spectroscopy (CARS) as a non-intrusive temperature diagnostic for convective-heat-transfer flows. The characteristics of the dual-broadband, pure-rotational CARS technique are discussed, and the technique is compared to other temperature measurement methods. Dual-broadband, pure-rotational CARS was used to measure mean temperature profiles in a low-Reynolds-number, turbulent boundary layer. The results are presented in wall units and compared to the thermal law of the wall for zero-pressure-gradient boundary layers. Temperature data were acquired as close as 50 μm (±25 μm) to the wall, with a spatial resolution of 50 μm normal to the heat transfer surface, and a 2 σ precision limit of ±4 K. The spatial resolution of this experimental method provides detailed information in complex thermal boundary layers and allows for an estimation of the convective heat flux to within an estimated uncertainty of −5% to +25%. Single-laser-shot temperature data were acquired in a gas cell, and the potential for measurement of rms temperature fluctuations is discussed in terms of the resulting probability density functions.

Young athletes are commonly afflicted by sports-related injuries. While evaluating these patients, it is important to consider non-sports-related pathologies so as not to overlook underlying orthopedic conditions that can also present in young athletes. Common orthopedic conditions to consider in young athletes include slipped capital femoral epiphysis (SCFE), Legg–Calve–Perthes disease (LCPD), benign and malignant bone and soft tissue tumors, and juvenile idiopathic arthritis (JIA). These conditions are often preexisting and may be discovered during evaluation of a minor sports-related injury or trauma. Unlike typical sports-related injuries, these conditions often produce symptoms independent of activity. In addition to maintaining a high index of suspicion, a careful history, physical examination, and appropriate imaging studies are necessary to diagnose these conditions. Once the young athlete is diagnosed, proper referral for additional treatment may be required and further participation in sports should be carefully determined.

We present the results of a two year early career LDRD project, which has focused on the development of ultrafast diagnostics to measure temperature, pressure and chemical change during the shock initiation of energetic materials. We compare two single-shot versions of femtosecond rotational CARS to measure nitrogen temperature: chirped-probe-pulse and ps/fs hybrid CARS thermometry. The applicability of measurements to the combustion of energetic materials will be discussed. We have also demonstrated laser shock and particle velocity measurements in thin film explosives using stretched femtosecond laser pulses. We will discuss preliminary results from Al and PETN thin films. Agreement between our results and previous work will be discussed.

A hybrid fs/ps pure-rotational CARS scheme is characterized in furnace-heated air at temperatures from 290 to 800 K. Impulsive femtosecond excitation is used to prepare a rotational Raman coherence that is probed with a ps-duration beam generated from an initially broadband fs pulse that is bandwidth limited using air-spaced Fabry-Perot etalons. CARS spectra are generated using 1.5- and 7.0-ps duration probe beams with corresponding coarse and narrow spectral widths. The spectra are fitted using a simple phenomenological model for both shot-averaged and single-shot measurements of temperature and oxygen mole fraction. Our single-shot temperature measurements exhibit high levels of precision and accuracy when the spectrally coarse 1.5-ps probe beam is used, demonstrating that high spectral resolution is not required for thermometry. An initial assessment of concentration measurements in air is also provided, with best results obtained using the higher resolution 7.0-ps probe. This systematic assessment of the hybrid CARS technique demonstrates its utility for practical application in low-temperature gas-phase systems.

We demonstrate an approach for picosecond probe-beam generation that enables hybrid femtosecond/picosecond pure-rotational coherent anti-Stokes Raman scattering (CARS) measurements in flames. Sum-frequency generation of bandwidth-compressed picosecond radiation from femtosecond pumps with phase-conjugate chirps provides probe pulses with energies in excess of 1 mJ that are temporally locked to the femtosecond pump/Stokes preparation. This method overcomes previous limitations on hybrid femtosecond/picosecond rotational CARS techniques, which have relied upon less efficient bandwidth-reduction processes that have generally resulted in prohibitively low probe energy for flame measurements. We provide the details of the second-harmonic approach and demonstrate the technique in near-adiabatic hydrogen/air flames.

A hybrid fs/ps pure-rotational CARS scheme is characterized for thermometry in furnace-heated air at temperatures from 290 to 800 K. Impulsive femtosecond excitation is used to prepare a rotational Raman coherence that is probed with a ps-duration beam generated from an initially broadband fs pulse that is bandwidth limited using air-spaced Fabry-Perot etalons. CARS spectra are generated using 1.5- and 7-ps duration probe beams with corresponding coarse and narrow spectral widths. The spectra are fitted using a simple phenomenological model for both shot-averaged and single-shot measurements of temperature and oxygen mole fraction. Our single-shot measurements exhibit high levels of precision when the spectrally coarse 1.5-ps probe beam is used. This systematic assessment of the hybrid CARS technique demonstrates its utility for practical application in moderatetemperature gas-phase systems.

Local mass transfer data for high-profile fins in the second row of in-line and staggered, circular-finned tubes are presented for Reynolds numbers from 5000 to 28,000 based on hydraulic diameter and velocity at the minimum flow area. The data, obtained using an optical adaptation of the naphthalene sublimation technique, show that local variations in heat transfer do not cause significant fin efficiency deviations from the analytical solution of Gardner (contrary to earlier reports). Average heat transfer and pressure drop data indicate that the thermal performance of the in-line arrangement is comparable to the staggered configuration.

The effect of gull-wing baffling on the performance of a single-row, annularly finned tube heat exchanger is quantified for Reynolds numbers from 5,000 to 13,000. A novel adaptation of the naphthalene sublimation technique provides optically measured sublimation depths that are used to determine local mass-transfer coefficients with a spatial resolution superior to previously reported data. Local and average heat-transfer data for baffled and unbaffled finned tubes are inferred through the analogy between heat and mass transfer. Local data are used to explain the flow and heat-transfer interactions and their impact on overall heat-transfer performance. Pressure drop data are presented for a complete measure of heat-transfer and pumping power performance, and a performance evaluation criterion is used to compare the heat exchangers. The data indicate that the unbaffled geometry provides nearly the same heat transfer as the baffled arrangement, but the unbaffled geometry incurs only 20 to 25% of the baffled...

We apply ultrafast pure-rotational coherent anti-Stokes Raman scattering (CARS) for temperature and relative oxygen concentration measurements in the plume emanating from a burning, aluminized ammonium-perchlorate propellant strand. Combustion of these metal-based propellants is a particularly hostile environment for laser-based diagnostics, with intense background luminosity and scattering from hot metal particles as large as several hundred micrometers in diameter. CARS spectra that were previously obtained using nanosecond pulsed lasers in an aluminum-particle-seeded flame are examined and are determined to be severely impacted by nonresonant background, presumably as a result of the plasma formed by particulate-enhanced laser-induced breakdown. Introduction of femtosecond/picosecond (fs/ps) laser pulses improves CARS detection by providing time-gated elimination of strong nonresonant background interference. Single-laser-shot fs/ps CARS spectra were acquired from the burning propellant plume, with picosecond probe-pulse delays of 0 and 16 ps from the femtosecond pump and Stokes pulses. At zero delay, nonresonant background overwhelms the Raman-resonant spectroscopic features. Time-delayed probing results in the acquisition of background-free spectra that were successfully fit for temperature and relative oxygen content. Temperature probability densities and temperature/oxygen correlations were constructed from ensembles of several thousand single-laser-shot measurements with the CARS measurement volume positioned within 3 mm or less of the burning propellant surface. The results show that ultrafast CARS is a potentially enabling technology for probing harsh, particle-laden flame environments.

We discuss recent experiments and modeling for the chirped-probe-pulse generation of single-laser-shot femtosecond pure-rotational CARS/CSRS spectra from room-temperature gases. A pure-rotational Raman coherence is impulsively generated using near-transformlimited femtosecond pump/Stokes excitation, and the coherence is probed by stretching a nominally 100-fs near-transform-limited probe beam to approximately 1.7 ps via the refractive-index dispersion in a 30-cm long flint-glass rod. The linearly chirped probe spectrum and phase beat against the time-dependent Raman polarization to generate complex spectra. Chirped-probe-pulse rotational CARS/CSRS offers an interesting alternative to hybrid fs/ps rotational CARS, in which a band-limited pulse of limited energy is used, because all of the available probe pulse energy can be retained in a chirped-probepulse experiment. Our early chirped-probe spectra are presented and the details of our initial model calculations are provided. The temperature sensitivity of the chirped-probe results is illustrated using calculated spectra.

Linkages between poverty and soil fertility decline in sub-Saharan Africa indicate the need for effective strategies to restore soils, while improving smallholder incomes. Combining organic and inorganic nutrient resources offers a promising means to address this issue, via improvements to nutrient cycling and key soil properties. Yet few studies have examined this practice from an economic perspective and none have explored its potential in intensively managed, market vegetable crops. We address this issue through a demonstrative, on-farm research trial examining the agronomic and economic benefits of mixing manure and inorganic fertilizer for smallholder cabbage production in rural Uganda. Cabbage was grown on eight replicate farms in close association with a farmer field school on vegetable production. Inorganic fertilizer, urea and NPK, and cattle manure were applied alone and in combination, based on equivalent monetary inputs, yielding six treatments: (1) 100 % fertilizer, (2) 75 % fertilizer and 25 % manure, (3) 50 % fertilizer and 50 % manure, (4) 25 % fertilizer and 75 % manure, (5) 100 % manure, and (6) a control without nutrient inputs. Initial soil fertility was evaluated prior to planting and cabbage biomass, nutrient content, and market value were assessed at harvest. Our findings demonstrate that combining manure and inorganic fertilizers produced up to 26 % higher biomass and 40 % higher market value on average than fertilizer or manure alone treatments. Incomes could be increased by 114.68 USD per growing season based on the current area of land that farmers dedicate to cabbage production, compared to using manure or inorganic fertilizer alone. Furthermore, the input ratio of manure to fertilizer appears to be flexible and thus easily adjusted to price fluctuations. This research provides a clear means for smallholder farmers to better allocate soil fertility investments and enhance incomes from market vegetable production. This research also highlights the importance of involving farmers in agricultural research for efficient evaluation of new technologies, building local capacity and yielding rapid impacts.

Understanding the particle-particle and shock-particle interactions that occur in dense gas-solid flows is limited by a lack of knowledge of the underlying phenomena. Gas-solid flows are characterized by the particle volume fraction. ϕ p of the flow [1]. For particle volume fractions less than about 0.1%, flow is considered dilute and the effects of particle collisions are negligible [2]. For packed particles, where the .p is greater than about 50%, the flow regime is said to be granular. The dilute and granular regimes have been well studied, but conversely, a substantial knowledge gap exists for dense gas-solid flows, which have intermediate particle volume fractions of about 0.1 to 50%. This regime exists at microsecond time scales during blast-induced dispersal of material when the shocked particles are closely spaced.

We present what we believe to be the first application of the laser-induced incandescence (LII) technique to large-scale fire testing. The construction of an LII instrument for fire measurements is presented in detail. Soot volume fraction imaging from 2 m diameter pool fires burning blended toluene/methanol liquid fuels is demonstrated along with a detailed report of measurement uncertainty in the challenging pool fire environment. Our LII instrument relies upon remotely located laser, optical, and detection systems and the insertion of water-cooled, fiber-bundle-coupled collection optics into the fire plume. Calibration of the instrument was performed using an ethylene/air laminar diffusion flame produced by a Santoro-type burner, which allowed for the extraction of absolute soot volume fractions from the LII images. Single-laser-shot two-dimensional images of the soot layer structure are presented with very high volumetric spatial resolution of the order of 10(-5) cm3. Probability density functions of the soot volume fraction fluctuations are constructed from the large LII image ensembles. The results illustrate a highly intermittent soot fluctuation field with potentially large macroscale soot structures and clipped soot probability densities.

We discuss recent experiments for the characterization of our femtosecond pure rotational CARS facility for observation of Raman transients in N{sub 2} and atmospheric air. The construction of a simplified femtosecond four-wave mixing system with only a single laser source is presented. Pure-rotational Raman transients reveal well-ordered time-domain recurrence peaks associated with the near-uniform spacing of rotational Raman peaks in the spectral domain. Long-time, 100-ps duration observations of the transient Raman polarization are presented, and the observed transients are compared to simulated results. Fourier transformation of the transients reveals two distinct sets of beat frequencies. Simulation results for temperatures from 300-700 K are used to illustrate the temperature sensitivity of the time-domain transients and their Fourier-transform counterparts. And strategies for diagnostics are briefly discussed. These results are being utilized to develop gas-phase measurement strategies for temperature and species concentration.

We discuss two recent diagnostic-development efforts in our laboratory: femtosecond pure-rotational Coherent anti-Stokes Raman scattering (CARS) for thermometry and species detection in nitrogen and air, and nanosecond vibrational CARS measurements of electric fields in air. Transient pure-rotational fs-CARS data show the evolution of the rotational Raman polarization in nitrogen and air over the first 20 ps after impulsive pump/Stokes excitation. The Raman-resonant signal strength at long time delays is large, and we additionally observe large time separation between the fs-CARS signatures of nitrogen and oxygen, so that the pure-rotational approach to fs-CARS has promise for simultaneous species and temperature measurements with suppressed nonresonant background. Nanosecond vibrational CARS of nitrogen for electric-field measurements is also demonstrated. In the presence of an electric field, a dipole is induced in the otherwise nonpolar nitrogen molecule, which can be probed with the introduction of strong collinear pump and Stokes fields, resulting in CARS signal radiation in the infrared. The electric-field diagnostic is demonstrated in air, where the strength of the coherent infrared emission and sensitivity our field measurements is quantified, and the scaling of the infrared signal with field strength is verified.

Pump-probe transient thermoreflectance (TTR) techniques are powerful tools for measuring the thermophysical properties of thin films, such as thermal conductivity, Λ, or thermal boundary conductance, G. This paper examines the assumption of one-dimensional heating on, Λ and G, determination in nanostructures using a pump-probe transient thermoreflectance technique. The traditionally used one-dimensional and axially symmetric cylindrical conduction models for thermal transport are reviewed. To test the assumptions of the thermal models, experimental data from Al films on bulk substrates (Si and glass) are taken with the TTR technique. This analysis is extended to thin film multilayer structures. The results show that at 11 MHz modulation frequency, thermal transport is indeed one dimensional. Error among the various models arises due to pulse accumulation and not accounting for residual heating.

Laser-induced incandescence measurements have recently been obtained from 10% and 30% toluene in methanol blended fuel pool fires of 2-m diameter. Calibration of the instrument was performed using an ethylene/air laminar diffusion flame produced by a Santoro-type burner which allowed the extraction of absolute soot-volume-fractions from these images. Performance of the optical probe was characterized using the laminar diffusion flame and corrections were implemented for signal dependence upon detector gain, flat field, and location within the probe laser sheet when processing the images. Probability density functions of the soot-volume fraction were constructed for the blended fuels used in this study and the mean values were determined to be 0.0077 and 0.028 ppm for the 10% and 30% blended fuels, respectively. Signal trapping was estimated for the two types of blended fuel and it was determined to be negligible for the 10% toluene/methanol blend and require {approx}10% correction for the 30% toluene/methanol blend.

A joint temperature/soot laser-based optical diagnostic was developed for the determination of the joint temperature/soot probability density function (PDF) for hydrocarbon-fueled meter-scale turbulent pool fires. This Laboratory Directed Research and Development (LDRD) effort was in support of the Advanced Simulation and Computing (ASC) program which seeks to produce computational models for the simulation of fire environments for risk assessment and analysis. The development of this laser-based optical diagnostic is motivated by the need for highly-resolved spatio-temporal information for which traditional diagnostic probes, such as thermocouples, are ill-suited. The in-flame gas temperature is determined from the shape of the nitrogen Coherent Anti-Stokes Raman Scattering (CARS) signature and the soot volume fraction is extracted from the intensity of the Laser-Induced Incandescence (LII) image of the CARS probed region. The current state of the diagnostic will be discussed including the uncertainty and physical limits of the measurements as well as the future applications of this probe.

The development of a combined dual-pump coherent anti-Stokes Raman scattering (CARS) and laser-induced incandescence (LII) instrument for the spatially resolved measurement of subgrid-scale temperature/soot data in liquid-fueled pool fires is discussed. Temperature pdfs obtained from the N2 Qbranch CARS signal at the center of a 2-m-diameter toluene/methanol pool fire are summarized. A more detailed discussion of the recent development of a water-jacketed, fiber-optically coupled LII probe for in-fire soot-volume-fraction imaging is presented. Tomographically resolved laser-light-extinction characterization of the soot field in a fuel-rich premixed ethylene-air flame used for calibration of the LII technique is reported, and the performance of the LII-imaging system in the calibration flame is discussed. Twodimensional LII images, which are representative of the spatially resolved, instantaneous soot-volumefraction distributions in a 2-m-diameter toluene/methanol pool fire are provided, and a histogram of the LII signal that is representative of the pdf of the soot-volume-fraction fluctuations at the center of the fire are extracted from these in-fire imaging results. These data demonstrate the potential of the CARS and LII instruments to determine temperature and soot volume fraction in a sooting fire with high temporal and spatial resolution.

Pump-probe transient thermoreflectance (TTR) techniques are powerful tools for measuring thermophysical properties of thin films, such as thermal conductivity, Λ, or thermal boundary conductance, G. This paper examines the assumption of one-dimensional heating on Λ and G determination in nanostructures using a pump-probe transient thermoreflectance technique. The traditionally used one dimensional and radial (3D) models are reviewed. To test the assumptions of the thermal models, experimental data from Al films on bulk substrates (Si and glass) are taken with the TTR technique. This analysis is extended to thin film multilayer structures. Results show that at 11 MHz modulation frequency, thermal transport is indeed one dimensional. Error among the various models arises due to pulse accumulation and not accounting for residual heating.Copyright © 2009 by ASME

Micro-Raman thermometry has been demonstrated to be a feasible technique for obtaining surface temperatures with micron-scale spatial resolution for microelectronic and microelectromechanical systems (MEMSs). However, the intensity of the Raman signal emerging from the probed device is very low and imposes a requirement of prolonged data collection times in order to obtain reliable temperature information. This characteristic currently limits Raman thermometry to steady-state conditions and thereby prevents temperature measurements of transient and fast time-scale events. In this paper, we discuss the extension of the micro-Raman thermometry diagnostic technique to obtain transient temperature measurements on microelectromechanical devices with 100 μs temporal resolution. Through the use of a phase-locked technique we are able to obtain temperature measurements on electrically powered MEMS actuators powered with a periodic signal. Furthermore, we demonstrate a way of obtaining reliable temperature measurements on micron-scale devices that undergo mechanical movement during the device operation.

Introduction:Considerable morbidity, mortality, and costs are associated with household emergency situations involving natural hazards and fires. Many households are poorly prepared for such emergency situations, and little is known about the psychosocial aspects of household emergency preparedness.Problem:The aim of this study is to promote a better understanding of homeowners' experiences and perceptions regarding household emergency situations and related preparedness practices.Methods:A brief survey was administered and three focus group sessions were conducted with homeowners (n = 16) from two metro Atlanta homeowners'associations.The survey inquired about basic demographic information, personal experience with a natural hazard or fire, and awareness of preparedness recommendations. The focus group discussions centered on household emergency preparedness perceptions and practices.Results:Participants defined household emergency preparedness as being able to survive with basic supplies (e.g., water, flashlights) for 48 hours or longer. While most participants had sufficient knowledge of how to prepare for household emergency situations, many did not feel fully prepared or had not completed some common preparedness measures. Concern about protecting family members and personal experience with emergency situations were identified as strong motivations for preparing the household for future emergencies.Conclusions:The focus group findings indicate that most participants have prepared for household emergency situations by discussing the dangers with family members, stockpiling resources, and taking a CPR or first-aid class. However, to the extent that behavior is influenced, there is a gap between maintaining preparedness levels and internalizing preparedness recommendations. Prevention efforts in Georgia should focus on closing that gap.

Particle-Image Velocimetry is used to study the cyclic modulation of the wall shear stress and turbulence properties of an oscillating channel flow. The PIV instrument employed here utilizes a dynamically adjusted delay between the laser pulses to accommodate the wide variations in velocity encountered in the oscillating flow. Both high- and low-magnification digital PIV recordings are obtained to reveal the near-wall boundary layer structure and wall shear stress, as well as the full-field turbulence throughout the channel. We present wall-shear-stress and global turbulence data for Stokes-thickness Reynolds numbers of Reδ = 1220, 2033, and 2875. The results reveal a fully developed turbulent state, relaminarization, and an explosive transition back to turbulence. The flow is examined in detail for the case at Reδ = 1220, where instantaneous PIV realizations at low magnification reveal the structure of the flow during relaminarization and transition back to turbulence. High-magnification PIV results are used to reveal the phase modulation of the mean velocity profiles in the viscous sublayer and logarithmic layers through the half cycle and quantitative profiles of in-plane Reynolds stresses and turbulence production are presented. To our knowledge, this is the first PIV investigation of this canonical unsteady turbulent channel flow and these results represent a needed contribution to the limited turbulence data which exists for unsteady wall flows.

Presented here are broadband, dual-pump CARS measurements which were performed in a 2-meter diameter methanol pool fire. Single-shot temperature and relative mole fractions were obtained simultaneously. The temperatures were compared to traditional thermocouple measurements in the pool fire. It was found that the CARS mean temperatures agree to within 4% of the thermocouple measurements, while the RMS temperatures were an order of magnitude less for the thermocouple. The accuracy and precision of the single-shot temperature measurements were characterized by comparison to a laboratory standard. It was determined that between 500-1400 K the CARS instrument was accurate to better than 4% and the measurements were reproducible to within 6%.

Analysis of the Raman Stokes peak position and its shift has been frequently used to estimate either temperature or stress in microelectronics and microelectromechanical system devices. However, if both fields are evolving simultaneously, the Stokes shift represents a convolution of these effects, making it difficult to measure either quantity accurately. By using the relative independence of the Stokes linewidth to applied stress, it is possible to deconvolve the signal into an estimation of both temperature and stress. Using this property, a method is presented whereby the temperature and stress were simultaneously measured in doped polysilicon microheaters. A data collection and analysis method was developed to reduce the uncertainty in the measured stresses resulting in an accuracy of +/-40 MPa for an average applied stress of -325 MPa and temperature of 520 degrees C. Measurement results were compared to three-dimensional finite-element analysis of the microheaters and were shown to be in excellent agreement. This analysis shows that Raman spectroscopy has the potential to measure both evolving temperature and stress fields in devices using a single optical measurement.

We report an application of coherent anti-Stokes Raman scattering (CARS) to full-scale fire testing. A CARS instrument has been constructed at the newly commissioned FLAME (Fire Laboratory for Accreditation of Models and Experiments) facility at Sandia, where the CARS system has been used for thermometry in 2-m-diameter, turbulent pool fires. The details of a CARS instrument for probing the challenging pool-fire environment are presented, along with the construction of the unique new FLAME facility itself, which has been designed to accommodate optical and laser-based diagnostics to full-scale fire experimentation. Single-shot CARS spectra and best-fit temperatures from turbulent pool fires are presented, and an estimate of the pdf of the temperature fluctuations from the pool-fire environment is obtained.

An experimental study was performed to determine the fraction of the heat flux that is due to radiation (sometimes referred to as radiation partitioning of the total heat flux measurement) to a calorimeter engulfed in a large methanol pool fire to improve understanding and develop high-quality data for the validation of fire models. Diagnostics employed include Coherent Anti-Stokes Raman Spectroscopy (CARS), Particle Image Velocimetry (PIV), total and radiative thermometry, and thermocouples. Data are presented not only for the physics measurements but also for all initial and boundary conditions required as necessary inputs to computational models. The large physical scale, the experimental design (enhanced convection relative to radiation heat transfer), the use of independent measurement techniques, and the attention to data quality, provide a unique dataset that emphasizes the convective component to support numerical fire model validation for convective and radiative heat transfer in fires.

We investigate the utility of dual-pump coherent anti-Stokes Raman scattering (CARS) for investigations of fuel-rich flames with soot volume loadings up to 2.2 ppm. Our initial characterization of a gas-phase propellant simulating burner is presented. The burner investigated consists of alternating fuel and oxidizer tubes with the option for injection of aluminum particles into the flame. We focus on a C2H2-N2-O2 flame, in which no aluminum particles are yet added. For the required flow rates, this burner provides an array of heavily sooting and highly luminous diffusion flames whose temperature is measured by dual-pump CARS. The nature of the observed soot-induced interference in the CARS spectra for several different pump 2 frequencies is documented and CARS temperatures obtained from data in a spectrally “quiet” region, with the CARS signal beam near 483 nm, are presented. Soot volume fractions are imaged by absorption-calibrated laser-induced incandescence (LII) to quantify the soot loadings at which our dual-pump CARS facility provides reliable measurements.

A joint experimental and computational study was performed to evaluate the capability of the Sandia Fire Code VULCAN to predict thermocouple response temperature. Thermocouple temperatures recorded by an Inconel-sheathed thermocouple inserted into a near-adiabatic flat flame were predicted by companion VULCAN simulations. The predicted thermocouple temperatures were within 6% of the measured values, with the error primarily attributable to uncertainty in Inconel 600 emissivity and axial conduction losses along the length of the thermocouple assembly. Hence, it is recommended that future thermocouple models (for Inconel-sheathed designs) include a correction for axial conduction. Given the remarkable agreement between experiment and simulation, it is recommended that the analysis be repeated for thermocouples in flames with pollutants such as soot.

Joint fuel Raman and filtered Rayleigh-scattering (FRS) imaging is demonstrated in a laminar methane-air diffusion flame. These experiments are, to our knowledge, the first reported extension of the FRS technique to nonpremixed combustion. This joint imaging approach allows for correction of the FRS images for the large variations in Rayleigh cross section that occur in diffusion flames and for a secondary measurement of fuel mole fraction. The temperature-dependent filtered Rayleigh cross sections are computed with a six-moment kinetic model for calculation of major-species Rayleigh-Brillouin line shapes and a flamelet-based model for physically judicious estimates of gas-phase chemical composition. Shot-averaged temperatures, fuel mole fractions, and fuel number densities from steady and vortex-strained diffusion flames stabilized on a Wolfhard-Parker slot burner are presented, and a detailed uncertainty analysis reveals that the FRS-measured temperatures are accurate to within +/- 4.5 to 6% of the local absolute temperature.

Experimentally measured temperature profiles along the micron-scale beam of a working thermal actuator are reported for the first time. Using a surface Raman scattering technique, temperature measurements are obtained in a noncontact fashion with submicron spatial resolution and to within an uncertainty of better than ±10 K. The experimental data are used to validate computational predictions of the actuator thermal performance with reasonable agreement between the data and predicted temperatures.Copyright © 2005 by ASME

Fires pose the dominant risk to the safety and security of nuclear weapons, nuclear transport containers, and DOE and DoD facilities. The thermal hazard from these fires primarily results from radiant emission from high-temperature flame soot. Therefore, it is necessary to understand the local transport and chemical phenomena that determine the distributions of soot concentration, optical properties, and temperature in order to develop and validate constitutive models for large-scale, high-fidelity fire simulations. This report summarizes the findings of a Laboratory Directed Research and Development (LDRD) project devoted to obtaining the critical experimental information needed to develop such constitutive models. A combination of laser diagnostics and extractive measurement techniques have been employed in both steady and pulsed laminar diffusion flames of methane, ethylene, and JP-8 surrogate burning in air. For methane and ethylene, both slot and coannular flame geometries were investigated, as well as normal and inverse diffusion flame geometries. For the JP-8 surrogate, coannular normal diffusion flames were investigated. Soot concentrations, polycyclic aromatic hydrocarbon (PAH) laser-induced fluorescence (LIF) signals, hydroxyl radical (OH) LIF, acetylene and water vapor concentrations, soot zone temperatures, and the velocity field were all successfully measured in both steady and unsteady versions of these various flames. Inmore » addition, measurements were made of the soot microstructure, soot dimensionless extinction coefficient (&), and the local radiant heat flux. Taken together, these measurements comprise a unique, extensive database for future development and validation of models of soot formation, transport, and radiation.« less

Simulation-based life-cycle-engineering and the ASCI program have resulted in models of unprecedented size and fidelity. The validation of these models requires high-resolution, multi-parameter diagnostics. Within the thermal-fluids disciplines, the need for detailed, high-fidelity measurements exceeds the limits of current engineering sciences capabilities and severely tests the state of the art. The focus of this LDRD is the development and application of filtered Rayleigh scattering (FRS) for high-resolution, nonintrusive measurement of gas-phase velocity and temperature. With FRS, the flow is laser-illuminated and Rayleigh scattering from naturally occurring sources is detected through a molecular filter. The filtered transmission may be interpreted to yield point or planar measurements of three-component velocities and/or thermodynamic state. Different experimental configurations may be employed to obtain compromises between spatial resolution, time resolution, and the quantity of simultaneously measured flow variables. In this report, we present the results of a three-year LDRD-funded effort to develop FRS combustion thermometry and Aerosciences velocity measurement systems. The working principles and details of our FRS opto-electronic system are presented in detail. For combustion thermometry we present 2-D, spatially correlated FRS results from nonsooting premixed and diffusion flames and from a sooting premixed flame. The FRS-measured temperatures are accurate to within {+-}50 Kmore » (3%) in a premixed CH4-air flame and within {+-}100 K for a vortex-strained diluted CH4-air diffusion flame where the FRS technique is severely tested by large variation in scattering cross section. In the diffusion flame work, FRS has been combined with Raman imaging of the CH4 fuel molecule to correct for the local light scattering properties of the combustion gases. To our knowledge, this is the first extension of FRS to nonpremixed combustion and the first use of joint FRS-Raman imaging. FRS has been applied to a sooting C2H4-air flame and combined with LII to assess the upper sooting limit where FRS may be utilized. The results from this sooting flame show FRS temperatures has potential for quantitative temperature imaging for soot volume fractions of order 0.1 ppm. FRS velocity measurements have been performed in a Mach 3.7 overexpanded nitrogen jet. The FRS results are in good agreement with expected velocities as predicted by inviscid analysis of the jet flowfield. We have constructed a second FRS opto-electronic system for measurements at Sandia's hypersonic wind tunnel. The details of this second FRS system are provided here. This facility is currently being used for velocity characterization of these production hypersonic facilities.« less

Filtered Rayleigh Scattering (FRS) is demonstrated in a premixed, sooting ethylene-air flame. In sooting flames, traditional laser-based temperature-imaging techniques such linear (unfiltered) Rayleigh scatting (LRS) and planar laser-induced fluorescence (PLIF) are rendered intractable due to intense elastic scattering interferences from in-flame soot. FRS partially overcomes this limitation by utilizing a molecular iodine filter in conjunction with an injection-seeded Nd:YAG laser, where the seeded laser output is tuned to line center of a strong iodine absorption transition. A significant portion of the Doppler-broadened molecular Rayleigh signal is then passed while intense soot scattering at the laser line is strongly absorbed. In this paper, we demonstrate the feasibility of FRS for sooting flame thermometry using a premixed, ethylene-air flat flame. We present filtered and unfiltered laser light-scattering images, FRS temperature data, and laser-induced incandescence (LII) measurements of soot volume fraction for fuel-air equivalence ratios of φ = 2.19 and 2.24. FRS-measured product temperatures for these flames are nominally 1500 K. The FRS temperature and image data are discussed in the context of the soot LII results and a preliminary estimate of the upper sooting limit for our FRS system of order 0.1 ppm volume fraction is obtained.

A Doppler global velocimetry (DGV) system has been designed, assembled, and tested for use in a Mach 3.7 overexpanded jet prior to future implementation in a hypersonic wind tunnel. Measurements were made using an iodine cell pressure-broadened with nitrogen buffer gas to selectively absorb light from a frequency-doubled Nd:YAG laser scattering from condensed ethanol particles in the jet flow. Details of the present implementation of the measurement technique and data reduction are presented herein. Calibrations of a pressure-broadened iodine cell have shown that the induced absorption line shift can create velocity biases unless a second iodine cell is scanned simultaneously to provide an independent frequency reference. Exploratory velocity data in the jet have been acquired that are experimentally repeatable and consistent with physical expectations, which lends confidence towards the performance of the assembled system.

This paper describes the application of a filtered-Rayleigh-scattering (FRS) instrument for nonintrusive temperature imaging in a vortex-driven diffusion flame. The FRS technique provides quantitative, spatially correlated temperature data without the flow intrusion or time lag associated with physical probes. Use of a molecular iodine filter relaxes the requirement for clean, particulate-free flowfields and offers the potential for imaging near walls, test section windows and in sooty flames, all of which are preculded in conventional Rayleigh imaging, where background interference from these sources typically overwhelms the weak molecular scattering signal. For combustion applications, FRS allows for full-field temperature imaging without chemical seeding of the flowfield, which makes FRS an attractive alternative to other laser-based imaging methods such as planar laser-induced fluorescencs (PLIF). In this work, the details of our FRS imaging system are presented and temperature measurements from an acoustically forced diffusion flame are provided. The local Rayleigh crosssection is corrected using Raman imaging measurements of the methane fuel molecule, which are then correlated to other major species using a laminar flamelet approach. To our knowledge, this is the first report of joint Raman/FRS imaging for nonpremixed combustion. Measurements are presented from flames driven at 7.5 Hz, where a single vortex stretches the flame, and at 90 Hz, where two consecutive vortices interact to cause a repeatable strain-induced flame-quenching event.

The relative activities of five measles virus (MV) polymerase (L) proteins were compared in an intracellular, plasmid-based replication assay. When coexpressed with N and P proteins from an attenuated strain, L proteins from two attenuated viruses directed the production of up to eight times more reporter protein from an MV minigenome than the three wild-type L proteins. Northern blot analysis demonstrated that the differences in reporter protein production correlated with mRNA transcription levels. Increased activity of polymerases from attenuated viruses equally affected mRNA transcription and minigenome replication. The higher level of transcription may be a consequence of increased template availability or may be an independent effect of the elevated activity of the attenuated polymerases. Coexpression of wild-type L proteins with homologous N and P proteins did not affect the activity of the wild-type polymerases, indicating that the differential activity was a function of the L proteins alone. Use of a minigenome that incorporated two nucleotide changes found in the genomic leader of the three wild-type viruses did not raise the activity of the wild-type L proteins. These data demonstrate that increased polymerase activity differentiates attenuated from wild-type viruses and suggest that functions involved in RNA synthesis contribute to the attenuated phenotype of MV vaccine strains.

This paper reports non-intrusive temperature and velocity imaging measurements in gas-phase flows using acetone planar laser-induced fluorescence (PLIF) thermometry and particle image velocimetry (PIV). The details of the combined PLIF/PIV instrument and the demonstration flow facilities are provided and results are presented from a turbulent Rayleigh-Benard convection flow (PLIF only) and from an unsteady laminar impinging jet flow (combined PLIF/PIV). The data show that PLIF temperature imaging at laboratory scales is most effective for characteristic temperature differences on the order of 100 K of more. Simultaneous gas-phase temperature-velocity images are presented which show that PLIF-PIV holds promise for detailed laboratory scale measurements for gas-phase convective heat-transfer applications at high temperature differences.Copyright © 2002 by ASME