Fuel-air mixing enhancement in axisymmetric jets using an array of synthetic jet actuators around the perimeter of the flows (primarily parallel to the flow axis) was investigated using planar laser-induced fluorescence of acetone. The synthetic jets are a promising new mixing control and enhancement technology with a wide range of capabilities. An image correction scheme that improved on current ones was applied to the images acquired to generate quantitative mixing measurements. Both a single jet and coaxial jets were tested, including different velocity ratios for the coaxial jets. The actuators run at a high frequency (~1.2 kHz), and were tested with all of them on and in other geometric patterns. In addition, amplitude modulation was imposed at a lower frequency (10-100 Hz). The actuators generated small-scale structures in the outer (and inner, for the coaxial jets) mixing layers. These structures significantly enhanced the mixing in the near field (x/D less than 1) of the jets, which would be useful for correcting an off-design condition in a combustor. The amplitude modulation generated large-scale structures that became apparent farther downstream (x/D greater than 1). The impulse at the start of the duty cycle was responsible for creating the structures. The large structures contained broad regions of uniformly mixed fluid, and also entrained fluid significantly. In addition, highly asymmetric forcing geometries displayed the power of the actuators to control the spatial distribution of jet fluid. This spatial control is important for the correction of hot spots in the pattern factor. In order to extend quantitative acetone PLIF to two-phase flows, the remaining unknown photophysical properties of acetone were identified. Tests showed that the technique could simultaneously capture acetone vapor and acetone droplets. A model of droplet fluorescence was developed, and applied to images acquired in a dilute spray. The sensitivity of the model to the value of the unknowns was evaluated, including a best and worst case. The results revealed that several liquid acetone photophysical properties must be measured for the further development of the technique, especially the phosphorescence yield. Quantitative two-phase acetone PLIF will provide a powerful new tool for studying spray flows.

Thermal management challenges for microelectronics are a major issue for future integrated circuits, thanks to the continued exponential growth in component density described by Moore¡¯s Law. Current projections from the International Technology Roadmap for Semiconductors predict that local heat fluxes will exceed 1 kW/cm2 within a decade. There is thus an urgent need to develop new compact, high heat flux forced-liquid and evaporative cooling technologies. Thermometry techniques that can measure temperature fields with micron-scale resolution without disturbing the flow of coolant would be valuable in developing and evaluating new thermal management technologies. Specifically, the ability to estimate local convective heat transfer coefficients, which are proportional to the difference between the bulk coolant and wall surface temperatures, would be useful in developing computationally efficient reduced-order models of thermal transport in microscale heat exchangers. The objective of this doctoral thesis is therefore to develop and evaluate non-intrusive optical thermometry techniques to measure wall surface and bulk liquid temperatures with O(1-10 micronmeter) spatial resolution. Intensity-based fluorescence thermometry (FT), where the temperature distribution of an aqueous fluorescent dye solution is estimated from variations in the fluorescent emission intensity, was used to measure temperatures in steady Poiseuille flow at Reynolds numbers less than 10. The flow was driven through 1 mm square channels heated on one side to create temperature gradients exceeding 8 ¡ÆC/mm along both dimensions of the channel cross-section. In the evanescent-wave fluorescence thermometry (EFT) experiments, a solution of fluorescein was illuminated by evanescent waves to estimate the solution temperature within about 300 nm of the wall. In the dual-tracer FT (DFT) studies, a solution of two fluorophores with opposite temperature sensitivities was volumetrically illuminated over most of the `cross-section of the channel to determine solution temperatures in the bulk flow. The accuracy of both types of FT is determined by comparing the temperature data with numerical predictions obtained with commercial computational fluid dynamics software. The results indicate that EFT can measure wall surface temperatures with an average accuracy of about 0.3 ¡ÆC at a spatial resolution of 10 micronmeter, and that DFT can measure bulk water temperature fields with an average accuracy of about 0.3 ¡ÆC at a spatial resolution of 50 micronmeter in the image plane. The results also suggest that the spatial resolution of the DFT data along the optical axis (i.e., normal to the image plane) is at least an order of magnitude greater than the depth of focus of the imaging system.

Ephemeral patches of hydrodynamic and chemical sensory cues at fine scales are fundamentally important to the life success of plankton populations and thus the overall health and vitality of nearshore marine ecosystems. We employed various tools from experimental fluid mechanics to create ecologically-relevant hydrodynamic and chemical conditions in a recirculating flume system for zooplankton behavioral assays. The goal was to quantify and correlate changes in zooplankton behavior with coincident sensory cues. A laminar, planar free jet (the Bickley jet) was used to create finescale, free shear layers with targeted hydrodynamic characteristics as well as finescale, sharp-edged layers of both beneficial and toxic ("red tide") phytoplankton species. Planar particle image velocimetry (PIV) and laser-induced fluorescence (LIF) were used to quantify the flow and concentration fields, respectively. Behavioral assays with a variety of crustacean zooplankton species including Antarctic krill (Euphausia superba), estuarine crab larvae (Panopeus herbstii), and calanoid copepods (Temora longicornis and Acartia tonsa), each unique in its ecology, morphology, and life history, show clear and statistically-significant behavioral responses to relevant hydrodynamic and chemical cues. Estuarine crab larvae optimize short term and long term behavioral needs (foraging and habitat selection) by sensing and exploiting the information contained in multi-directional free shear flows. In the presence of thin layers of toxic algal exudates (Karenia brevis), T. longicornis and A. tonsa exhibit explicit avoidance behaviors through significant increases in swimming speed and overall behavioral variability resulting in a conspicuous hydrodynamic signature in a risk/benefit behavioral response. Finally, Antarctic krill exploit the hydrodynamic cues contained in a free shear layer to modify swimming behaviors and ultimately graze in a thin phytoplankton layer (Tetraselmis spp.). Each species is able to sense and exploit the information contained in coherent hydrodynamic and chemical sensory cues to change swimming kinematics and alter macroscale trajectory characteristics. Quantifying changes in zooplankton behavior in response to ecologically-relevant sensory cues is a crucial step towards modeling (e.g. via biophysically-coupled individual-based ecosystem models) and managing sustainable marine fisheries.

Optical coherence tomography (OCT) is an imaging method that is considered the optical analog to ultrasound, using the technique of optical interferometry to construct two-dimensional depth-resolved images of tissue microstructure. With a resolution on the order of 10 μm and a penetration depth of 1-2 mm in highly scattering tissue, fiber optics-coupled OCT is an ideal modality for the inspection of the mouse colon with its miniaturization capabilities. In the present study, the complementary modalities laser-induced fluorescence (LIF), which offers information on the biochemical makeup of the tissue, and surface magnifying chromoendoscopy, which offers high contrast surface visualization, are combined with OCT in endoscopic imaging systems for the greater specificity and sensitivity in the differentiation between normal and neoplastic tissue, and for the visualization of biomarkers which are indicative of early events in colorectal carcinogenesis. Oblique incidence reflectometry (OIR) also offers advantages, allowing the calculation of bulk tissue optical properties for use as a diagnostic tool. The study was broken up into three specific sections. First, a dual-modality OCTLIF imaging system was designed, capable of focusing light over 325-1300 nm using a reflective distal optics design. A dual-modality fluorescence-based SMC-OCT system was then designed and constructed, capable of resolving the stained mucosal crypt structure of the in vivo mouse colon. The SMC-OCT instrument's OIR capabilities were then modeled, as a modified version of the probe was used measure tissue scattering and absorption coefficients.

The air-water interface is abundant in the environment, thus it is an important proxy for atmospheric processes such as the uptake and transfer of molecules, heterogeneous reactions, photochemistry, and cloud condensation. This thesis aims to elucidate the role of semi-soluble and insoluble organic coatings on atmospheric processes at the air-water interface. Using glancing-angle LIF it was found that monolayer coatings of 1-octanol and of octanoic acid have opposing effects on the ozonation rate of pyrene at the air-water interface. LIF was also coupled with a Profile Analysis Tensiometer (PAT-1) to measure the effect of stearic acid coating compression on the uptake of HCl to a water droplet. Due to preliminary issues with this novel technique, no significant uptake suppression was observed. The oxidation of benzene by OH radical was also explored briefly, as were the photophysics of photosensitizers and the angle dependence of Raman signal from a D2O pendent droplet.

The air-water interface is abundant in the environment, thus it is an important proxy for atmospheric processes such as the uptake and transfer of molecules, heterogeneous reactions, photochemistry, and cloud condensation. This thesis aims to elucidate the role of semi-soluble and insoluble organic coatings on atmospheric processes at the air-water interface. Using glancing-angle LIF it was found that monolayer coatings of 1-octanol and of octanoic acid have opposing effects on the ozonation rate of pyrene at the air-water interface. LIF was also coupled with a Profile Analysis Tensiometer (PAT-1) to measure the effect of stearic acid coating compression on the uptake of HCl to a water droplet. Due to preliminary issues with this novel technique, no significant uptake suppression was observed. The oxidation of benzene by OH radical was also explored briefly, as were the photophysics of photosensitizers and the angle dependence of Raman signal from a D2O pendent droplet.

Submitted by Edileide Reis (leyde-landy@hotmail.com) on 2013-04-23T14:35:12Z No. of bitstreams: 1 Yuji Watanabe.pdf: 3696013 bytes, checksum: 64d732d452c08c675e78db3f991bf851 (MD5) / Made available in DSpace on 2013-04-23T14:35:12Z (GMT). No. of bitstreams: 1 Yuji Watanabe.pdf: 3696013 bytes, checksum: 64d732d452c08c675e78db3f991bf851 (MD5) Previous issue date: 2002 / Este trabalho é constituído de três etapas, a saber: · planejamento e construção de um aparato experimental para medidas de fluorescência total (LIF) e depolarização fluorescente (PLF) em sistema de injeção em fluxo (FI); testes operacionais visando otimizar parâmetros experimentais; avaliação fotoquímica/fotofísica da cinética e dinâmica molecular duma reação química em FI. O aparato experimental automatizado é constituído de um sistema de detecção de fluorescência, um sistema FI e um sistema ótico. Permite a aquisição com alta resolução espacial (20mm) de perfis de distribuição de concentração (LIF) e de orientação molecular vertical e horizontal (PLF) em função do tempo de transporte do fluxo. Os perfis interpolados em mapas bidimensionais fornecem informações sobre a cinética e a dinâmica molecular dos processos de dispersão axial e radial de amostras em fluxo carregador. Foram medidas tensões interfaciais estáticas, pelo método do ângulo de contato, para escolher a constituição química do percurso analítico e minimizar a sua influência na cinética e na dinâmica molecular de dispersão. Foi determinada a influência da aceleração gravitacional e do número de injeções por período de amostragem, dentre outros parâmetros usuais, no processo de dispersão.Observou-se a existência de padrões de dispersão diferenciados para a Rodamina B (RB) a depender da sua orientação espacial. Isto foi atribuído ao grupo benzóico perpendicular ao grupo xantênico e comprovado pela utilização da Rodamina 6G (R6G) sob as mesmas condições. A contribuição da cinética e da dinâmica moleculares de dispersão no rendimento de uma reaçãoquímica em fluxo foi avaliado com adição de Ca(II), um agente supressor da fluorescência da RB. / Salvador

Low-emissions combustor design is crucially important to gas turbine engine manufacturers. Unfortunately, many designs are susceptible to unsteady oscillations that can result in structural fatigue and increased noise. Computational approaches that resolve flow unsteadiness, for example Large Eddy Simulation (LES), are being explored as one avenue to help understand such phenomena. However, in order to quantifY the accuracy of LES predictions, benchmark validation data in suitably chosen test cases are required. Comprehensive experimental data covering both time-averaged and timeresolved features are currently scarce. It was the aim of this thesis, therefore, to provide such data .in a configuration representing the near-field of a typical gas turbine fuel injector. It was decided to focus on the fuel injector since many unsteady events are believed to originate because of the transient interactions between the fuel injector flow and the main combustor flow. A radial fed two-stream fuel injector, based on a preexisting industrial gas-turbine Turbomeca design was used, since this geometry was known to be susceptible to unsteadiness. The fuel injector was investigated under isothermal conditions to place emphasis on the fluid mechanical behaviour of the fuel injector, including detailed capture of any unsteady phenomena present. Light Sheet Imaging (LSI) systems were used as the primary experimental technique to provide high quality spatially and temporally resolved instantaneous velocity and scalar field information in 2D planes (using ParticieImage Velocimetry (PIV) and Planar LaserInduced Fluorescence (PUF) techniques). Several methods were employed to extract information quantifYing the flow unsteadiness and improve visualisation of timedependent large-scale turbulent structures. Proper Orthogonal Decomposition (POD) analysis enabled clear identification of the dominant modes of energy containing structures. The results indicated that periodic high-energy containing vortex structures occurred in the swirl stream shear layer, emerging from the fuel injector. These formed a two-strong two-weak rotating vortex pattern which propagated down the main duct flow path. The formation of these vortices was found to be a function of the swirl number and originated due to an interaction between the forward moving swirl flow and the furthest upstream penetration point ofthe recirculation zone present in the main duct flow. Dependent on the magnitude of the swirl number (influencing the swirl stream cone angle) and the geometry of the fuel injector, the vortex formation point was sometimes found inside the fuel injector itself. If the vortices originated inside the fuel injector they appeared much more coherent in space and time and of higher energy. A second unsteady high energy containing phenomenon was also identified, namely a Precessing Vortex Core (PVC), which was damped out if the fuel injector contained a central jet. The dynamics of the PVC interacted with the dynamics of the swirl stream shear layer vortices to reduce there strength. Transient scalar measurements indicated that there was a clear connection between the unsteady vortex pattern and the rate of mixing, resulting in bursts of high heat release and is therefore identified as one source of combustor oscillations. Future fuel injector designs need to pay close attention to these unsteady features in selecting swirl number and internal geometry parameters.

Ce travail de thèse est consacré au développement de la technique de fluorescence induite par laser (LIF) à deux photons appliquée à la molécule CO pour des mesures en flammes à haute pression. Différents schémas d'excitation laser à deux photons et de fluorescence sont comparés afin de déterminer celui qui est le mieux adapté à la détection de CO en milieux de combustion. Le schéma de transitions électroniques B1 Σ+ - X1 Σ+ (230 nm) / B1 Σ+ - A1 Π(483 nm) est sélectionné. Un code de calcul des spectres LIF à deux photons de CO est développé pour prédire l'évolution du signal sur une large gamme de températures et de pressions. Des mesures dans une cellule à haute température et haute pression, et dans une flamme laminaire CH4/air à 1 bar sont réalisées de 300 à 1750 K, et de 1 à 13 bar. Les résultats indiquent une dépendance polynomiale d'ordre 2 du décalage spectral avec la pression ainsi que l'asymétrie du spectre qui croît avec la pression entre 300 et 860 K. La limite de détectivité de CO par LIF en ponctuel est estimée de 500 ppm en flamme à 1 bar. L'effet de la température sur les profils spectraux est bien reproduit par la simulation. La comparaison des profils mesurés en flamme à 1 bar avec les profils simulés donne une température de 1750 +-50 K, en accord avec celle prédite par le modèle de combustion. L'effet de la pression sur le profil spectral (décalage, élargissement et asymétrie) est correctement simulé en considérant un profil collisionnel de Lindholm de 1 à 5 bar à 300 K, et de 1 à 7 bar à 860 K. L'imagerie de fluorescence induite par laser de CO a été développée en flamme à 1 bar. La limite de détectivité est déterminée de 900 ppm pour nos conditions expérimentales. / This work is dedicated to the development of two-photon laser induced fluorescence (LIF) of COfor application in high-pressure flames. Different two-photon excitation and fluorescence schemes arecompared in order to determine which one is more suitable for the detection of CO in flames. TheB1Σ+ -X1Σ+ (230 nm)/B1Σ+ -A1Π (483 nm) electronic transitions scheme is chosen. A numericalcode of two-photon LIF spectra is developed to predict the evolution of fluorescence signals over awide range of temperatures and pressures. Measurements in a high temperature and high pressure celland in a laminar CH4/air flame at 1 bar are performed from 300 to 1750 K and from 1 to 13 bars.Results indicate a square dependence of the collisional shift upon pressure and a large asymmetry ofthe spectrum at high pressure between 300 and 860 K. The detection limit is estimated to be 500 ppmin flame at 1 bar. Influence of temperature on LIF spectra is well reproduced by the simulations. Comparisonbetween measured and simulated excitation spectra lead to a flame temperature of 1750+-50K, in accordance with combustion modelling. The Lindholm profile is used in order to reproduce thepressure-dependence of the spectrum in the range 1 to 5 bars at 300 K, and 1 to 7 bars at 860 K.Planar laser induced fluorescence imaging of CO is developed in flame at 1 bar. The detection limit is900 ppm in our experimental conditions.

In this work, resonant laser spectroscopy has been utilized in two major projects --resonance fluorescence measurements in solid-state quantum-confined nanostructures and laser-induced fluorescence measurements in gases. The first project focuses on studying resonant light-matter interactions in semiconductor quantum dots "artificial atoms" with potential applications in quantum information science. Of primary interest is the understanding of fundamental processes and how they are affected by the solid-state matrix. Unlike atoms, quantum dots are susceptible to a variety of environmental influences such as phonon scattering and spectral diffusion. These interactions alter the desired properties of the scattered light and hinder uses in certain single photon source applications. One application of current interest is the use of quantum dots in “quantum repeaters” for which two-photon interference is key. Motivated by such an application we have explored the limits imposed by environmental effects on two quantum dots in the same sample, the scattered light from which is being interfered. We find that both one-photon and two-photon interference, although substantial, are affected in a variety of ways, in particular by spectral diffusion. These observations are discussed and compared with a theoretical model. We further investigated correlations in pulsed resonance fluorescence, and found significant unexpected spectral and temporal deviations from those studied under continuous wave excitation. Under these conditions, the scattered light exhibits Rabi oscillations and photon anti-bunching, while maintaining a rich spectrum containing many spectral features. These observations are discussed and compared with a theoretical model. In the second project, the focus is on the investigation of the possibility of detecting N2+ ions in air using laser induced fluorescence, with potential applications in detection of fissile materials at a distance. A photon-counting analysis reveals that the fluorescence decay rate rapidly increases with increasing N2 pressure and thus limits the detection at elevated pressures, in particular at atmospheric pressure. We show that time-gated detection can be used to isolate N2+ fluorescence from delayed N2 emission. Based on the spontaneous Raman signal from N2 simultaneously observed with N2+ fluorescence, we could estimate a limit of detection in air of order 108-1010 cm3.