Rozprawy doktorskie na temat „Jet-induced”

The effect of hydrogen bonding interactions on the drop generation of both acid and hydroxyl-containing polymer solutions is reported showing that polymer chain relaxation can be influenced through the use of appropriate polymer co-solvent interactions for polymers having weight average molecular weight (Mw) < 100 kDa. Reported for the first time is evidence of flow-induced polymer degradation during inkjet printing for both poly(methylmethacrylate) and polystyrene in good solvent. Polymers having Mw either less than 100 kDa or greater than approximately 1,000 kDa show no evidence of molecular weight degradation. The lower boundary condition is a consequence of low Deborah number imposed by the printhead geometry and the upper boundary condition due to viscoelastic damping. For intermediate molecular weights the effect is greatest at high elongational strain rate and low solution concentration with higher polydispersity polymers being most sensitive to molecular weight degradation. For low polydispersity samples, PDi £ 1.3 chain breakage is essentially centro-symmetric induced either by overstretching when the strain rate increases well beyond a critical value, that is the stretching rate is high enough to exceed the rate of relaxation or by turbulence. For higher polydispersity samples, PDi chain breakage is consistent with almost random scission along the chain inferring that the forces required to break the chain are additionally transmitted either by valence bonds, i.e. network chains and junctions or discrete entanglements rather than solely by hydrodynamic interaction. Preliminary results are presented on the degradation of molecular structure in water of two galactomannan’s in water after inkjet printing. Galactommann’s are known to form complex H-bonded structures in water and the results are consistent with breaking of the H-bonding structure at low reduced concentration with evidence of main chain breakage at higher reduced concentration, c/c* = 0.25.

This work has studied the particle composition of jets by determining the ratios p±/π± and K±/π± in Au + Au and d + Au collisions at √sNN = 200 GeV measured by the STAR experiment at RHIC. Jets were found by measuring the angular azimuthal correlation between particles at high transverse momentum. Jets were then identified by their back-to-back correlation. A technique was developed to identify charged particles using their specific ionisation measured in the STAR Time Projection Chamber (TPC). This thesis contains one of the first implementations of using direct photons to tag jets in heavy ion collisions. An attempt was made to extract a trigger sample rich in direct photons from neutral triggers. The hadron ratios were calculated from the jet yields as a function of transverse momentum in each collision system. Although the away side yield is suppressed in central Au + Au, there is no evidence that the relative particle yields are changed. The hadron ratios for the three systems were found to be consistent with simulated p + p events generated using the Pythia Monte Carlo event generator. This reinforces the conclusion that the fragmentation process is unchanged by interactions with the medium.

The enhancement of heat transfer by active and passive methods has been the subject of many academic and industrial research studies. Internal flows play a major role in many applications and different methods have been utilized to augment the heat transfer to internal flows. Secondary flows consume part of the kinetic energy of the flow and disturb the boundary layer. Inducing secondary flows is known as mechanism for heat transfer enhancement. Secondary flows may be generated by corona discharge and ion-driven flows. When a high electric potential is applied to a conductor, a high electric field will be generated. The high electric field may exceed the partial break-down of the neutral molecules of surrounding gas (air) and generate a low-temperature plasma in the vicinity of the conductor. The generated plasma acts as a source of ions that accelerate under the influence of the electric field and escape beyond the plasma region and move toward the grounded electrode. The accelerating ions collide with neutral particles of the surrounding gas and impose a dragging effect which is interpreted as a body-force to the air particles. The shape and configuration of the emitting and receiving electrodes has a significant impact on the distribution of the electric body-force and the resulting electrically-induced flow field. It turned out that the certain configurations of longitudinal electrodes may cause a jet-like secondary flow field on the cross section of the flow passage in internal flows. The impingement effect of the corona jet on the walls of the channel disturbs the boundary layer, enhances the convective heat transfer, and generates targeted cooling along the centerline of the jet. The results of the current study show that the concentric configuration of a suspended wire-electrode in a circular tube leads to a hydrostatic condition and do not develop any electrically-induced secondary flow; however, the eccentric wire-electrode configuration generates a corona jet along the eccentricity direction. The generated corona jet exhibits interesting specifications similar to conventional inertia-driven air jets which are among common techniques for cooling and heat transfer enhancement. On the other hand, wall-mounted flat electrode pairs along the parallel walls of a rectangular mini-channel develop a similar jet-like flow pattern. The impingement of the corona jet to the receiving wall causes excessive heat transfer enhancement and cooling effect. The flat electrode pairs were also utilized to study the effect of corona discharge on the heat transfer specifications of the internal flow between parallel plates in fully-developed condition. It turned out that the electrically-induced secondary flow along with a pressure-driven main flow generates a swirling effect which can enhance the heat transfer significantly in fully-developed condition.

Dans le cadre de cette thèse, une technique de diagnostic optique a été développée pour mesurer simultanément l’évaporation différentielle, la distribution de température, et la concentration massique de fuel dans un jet multi-composant. Cette technique a été examinée dans les conditions d’un moteurs essence. La technique de mesure est basée sur l’utilisation des deux traceurs excités par une seule longueur d’onde.Pour pouvoir examiner l’évaporation différentielle d’un carburant multi-composant, deux traceurs ont été sélectionnés : le p-difluorobenzène et le 1-methylnaphtalène. Ces traceurs reproduisent deux types de volatilité : faible et moyenne à élevée. Les traceurs choisis fluorescent dans deux régions spectrales distinctes ce qui rend l’application de cette technique possible. Une étude photophysique a été menée pour caractériser les deux traceurs, indépendamment puis en mélange, pour différentes conditions de pression, température, et composition du bain gazeux. L’étude photophysique est essentielle pour pouvoir mesurer quantitativement l’évaporation différentielle. Les résultats photophysiques montrent que le spectre du 1-methylnaphthalène est sensible à la température. Cette caractéristique permet de mesurer la distribution en température dans le jet.Les essais ont été réalisés dans une cellule haute pression / haute température, ca-pable de simuler les conditions d’un moteur thermique. Des sprays générés par un injecteur ECN Spray G et un piézo-électrique d’une ouverture annulaire ont été étudiés. Des mesures initiales ont été menées avec chaque traceur pour pouvoir fixer la proportion de mélange des traceurs. La précision de la méthode de mesure a été calculée suivant une configuration de filtres identiques. Ensuite, les champs de tempé-rature calculés par la LIF et ceux déterminés depuis les champs de concentration massique, ont été comparés. Les résultats démontrent que la température est homo-gène ce qui signifie que les mesures d’évaporation différentielle n’ont pas influencé par la distribution de température dans le jet.Les images obtenues en détectant les signaux depuis le mélange de traceurs ont permis de localiser l’évaporation différentielle. Une variation en distribution spatiale des composants est observée 550–600 K. Cet effet disparaît en augmentant la température, ce qui explique que l’évaporation est plus rapide à haute température. La localisation de l’évaporation différentielle varie avec le type d’injecteur. La géométrie du nez ainsi que la structure du jet a donc un impact sur la formation du mélange
A non-intrusive quantitative laser-induced fluorescence (LIF) technique capable of simultaneously measuring preferential evaporation, temperature distribution, and fuel-mass concentration across a multi-component vaporized spray has been developed and investigated under engine-relevant conditions. The measurement technique is based on two-tracer LIF with single wavelength excitation.To assess preferential evaporation, a tracer pair with suitable co-evaporation and spectral properties was selected based on vapor-liquid equilibrium calculations repre-sentative for gasoline fuels. Evaporation studies have shown that one tracer (p-difluoro-benzene) co-evaporates with the high-to-medium-volatility end of the multi-component fuel while the other (1-methylnaphthalene) co-evaporates with the low-volatility end. For quantitative measurements the photophysical properties of both tracers (each tracer separately and the combined tracers) were determined under a wide range of pressure, temperature, and bath-gas composition conditions. 1-methylnaphthalene LIF shows a strong red-shift with temperature which enables measurements of the temperature distribution across the spray.Spray evaporation and vapor mixing experiments were performed in a high-pressure high-temperature vessel capable of simulating in-cylinder conditions. An ECN Spray-G and a piezo-electric outward opening injector were used in this study. Initial measure-ments were carried out with each tracer added separately to the fuel to assess signal cross-talk and to determine the best tracer concentrations. Once the proportions were determined, accuracy and precision of the method were determined from the LIF-signal ratio of spray images within identical spectral bands. Temperature fields, obtained by two-color 1-methylnaphthalene LIF and derived from fuel concentration maps based on the assumption of adiabatic evaporation, were examined for inhomogeneities in the area of interest since fluctuations potentially influence the two-color method. It was shown that the temperature is homogeneous in the measurement volume.To localize preferential evaporation, two-color two-tracer LIF images were evaluated. Taking into account the measurement accuracy and precision, variations in the spatial distribution of the fuel volatility classes were observed for 550–600 K. At higher tem-peratures, the effect is less pronounced, which is consistent with the fact that evapora-tion is faster. The localization of preferential evaporation varied with each injector used indicating the impact of injector nozzle geometry and jet structure on mixture formation
Eine berührungsfreies quantitatives Verfahren auf Basis von laserinduzierter Fluoreszenz (LIF) wurde entwickelt, um simultan präferenzielle Verdampfung, Temperaturverteilung und Kraftstoffkonzentration im verdampften Bereich eines Mehrkomponenten-Kraftstoffsprays unter motorrelevanten Bedingungen zu messen. Verfahren beruht auf Zwei-tracer-LIF mit Anregungmit einem Laser.Es wurde ein Tracer-Paar mit geeigneten Verdampfungs- und spektralen Eigenschaften auf Basis von Dampf-Flüssigkeits-Gleichgewichtsrechnungen für Otto-Kraftstoffe ausgewählt. Verdampfungsmessungen haben gezeigt, dass ein Tracer (p-Difluorbenzol) gleichzeitig mit dem mittel- und höherflüchtigen Siedeklassen verdampft, während der andere (1-Methylnaphthalin) den schwerflüchtigen Komponentenfolgt. Für quantitative Messungen wurden die photophysikalischen Eigenschaften beider Tracer (einzeln und als Kombination) in einem weiten Bereich von Druck, Temperatur und Gaszusammensetzung bestimmt. 1-Methylnaphthalin-LIF zeigt eine starke Rotverschiebung mit der Temperatur, die Messungen der Temperaturverteilung ermöglicht. Es wurde ein Tracer-Paar mit geeigneten Verdampfungs- und spektralen Eigenschaften auf Basis von Dampf-Flüssigkeits-Gleichgewichtsrechnungen für Otto-Kraftstoffe ausgewählt. Verdampfungsmessungen haben gezeigt, dass ein Tracer (p-Difluorbenzol) gleichzeitig mit dem mittel- und höherflüchtigen Siedeklassen verdampft, während der andere (1-Methylnaphthalin) den schwerflüchtigen Komponentenfolgt. Für quantitative Messungen wurden die photophysikalischen Eigenschaften beider Tracer (einzeln und als Kombination) in einem weiten Bereich von Druck, Temperatur und Gaszusammensetzung bestimmt. 1-Methylnaphthalin-LIF zeigt eine starke Rotverschiebungmit der Temperatur, die Messungen der Temperaturverteilung ermöglicht

Thesis (M.S. in Aeronautical Engineering) Naval Postgraduate School, September 1995.
Thesis advisor(s): S.K. Hebbar, Max F. Platzer. "September 1995." Includes bibliographical references. Also available online.

Transient molecules are of great importance due to their critical role as intermediates in the semiconductor industry, in upper atmosphere reactions, and in astrochemistry. In the present work, reactive intermediates were produced in the laboratory by applying an electric discharge through a suitable precursor gas mixture and studied by means of their laser-induced fluorescence and emission spectra. The band systems of and have been studied in detail. The energy levels of both isotopologues were fitted with a Renner-Teller model, and the isotope relations have been used to test the validity of the derived parameters. The A2Πu - X 2Πg electronic transition of jet-cooled has been detected and shown to originate from the Ω=3/2 spin-orbit component of v=0 of the ground state. For the first time, the 0-0 band has been identified and vibrational assignments have been made. Our ab initio studies show that the extensive observed perturbations are due to spin-orbit interaction between A2Πu(3/2) and B2Δu(3/2) states. The experimental data were fitted to an effective Hamiltonian and yielded the spin-orbit coupling term =240 cm-1. LIF and emission spectra of the transition of N2O+ have been recorded. Both spin-orbit components of the band were studied at high resolution and rotationally analyzed, providing precise molecular constants. Emission spectra provided extensive data on the ground state vibrational levels which were fitted to a Renner-Teller model including spin-orbit and Fermi resonance terms. The previously unknown electronic spectrum of the H2PO radical has been identified. Ab initio predictions were used to aid in the analysis of the data. The band system is assigned as the electronic transition. The excited state molecular structure was determined by rotational analysis of high resolution LIF spectra. The band systems of the HBCl and DBCl free radicals have been studied in detail. This electron promotion involves a linear-bent transition between the two Renner-Teller components of what would be a 2Π electronic state at linearity. Ab initio potential energy surface calculations were used to help in assigning the LIF spectra which involve transitions from the ground state zero-point level to high vibrational levels of the excited state.

Air jet vortex generators were originally investigated by R.A. Wallis. Results showed that their effectiveness in delaying shock induced boundary layer separation was not as good as conventional vane type generators. Recent low speed wind tunnel tests carried out at City University indicated that the strength of the vortex could be increased considerably by using rectangular jet exits rather than round ones as used by Wallis. On this basis an investigation into air jet vortex generators was undertaken to find out whether similar improvements in vortex strength may be gained at transonic speeds and hence achieve a more effective method of controlling shock induced boundary layer separation. It was felt that in order to design air jet vortex generators it would be necessary to understand the mechanism by which an air jet forms a vortex, and to evaluate the effects of various jet parameters on vortex size, strength and position. The parameters investigated in this thesis were: (i) exit shape (ii) exit size (iii) jet direction (iv) jet inclination and (v) blowing pressure. The tests were conducted using a combination of high speed wind tunnel tests and flow visualisation in a water tunnel. The wind tunnel tests used the half aerofoil or 'bump technique' as used by Wallis. Bumps with thickness to chord ratios of 8%, 10% and 14% were tested. Increasing the thickness of the bumps resulted in higher local Mach numbers ahead of the shock and hence an increase in the severity of the shock induced separation. Vane vortex generators designed using the criteria laid down by H.H. Pearcey were used to establish a datum of control effectiveness. As a result of this investigation a method by which an air jet forms a vortex has been proposed together with a hypothesis on the influence of the various jet parameters. The results have shown that air jet vortex generators can be designed to be more effective than conventional vane type generators. Based on the work reported in this thesis a set of design guidelines has been proposed together with suggestions for further work.

A small-scale ground-effect test rig was designed and fabricated to study the ground-plane flow field generated by a STOVL aircraft in hover. The objective of the research was to support NASA Ames Research Center's planning for the upcoming large-scale powered model hover tests for the ARPA sponsored ASTOVL program. Specifically, small-scale oil-flow visualization studies were conducted to make a relative assessment of the aerodynamic interference of two proposed support-strut configurations on the ground-plane stagnation line. A simplified flat-plane model representative of a generic jet-powered STOVL aircraft with both the lift fan and the main engine simulated by air jets, with nozzle pressure ratios closely matching those of the large scale tests, was utilized. The flow visualization data clearly identified an aft shift in the stagnation line location for both strut configurations. Although the data indicated a slight reduction in the aft shift for the wider strut configuration, considering the experimental uncertainties involved it was concluded that either of the strut configurations caused only a minor aerodynamic interference.

The mixing performance of multiple transverse jets has been evaluated experimentally. Measurement techniques included laser Doppler velocimetry and planar laser induced fluorescence. Basic findings are consistent with results presented in literature for single jet mixing behavior. Mixing performance has been compared to literature for the single jet case and the Holdeman parameter has been re-evaluated for effectiveness at low jet numbers. A single jet in a confined crossflow was found to have a local minimum at B(d⁄D) = 0.721. Results for two jets indicate monotonically decreasing unmixedness for the range of conditions tested, with no local optimum apparent. Data for three jets indicate a local optimum at B(d⁄D) = 0.87and relatively flat range of mixing performance in the range of 0.75 < B(d⁄D) < 1.5. Six jets indicate a minimum unmixedness near B(d⁄D) = 0.5, but exhibited poorer mixing performance than all other configurations at the highest values of B(d⁄D)tested. The most optimum configuration tested was six jets at B(d⁄D) = 0.5, resulting in an unmixedness of 0.0192. This value was 76% lower than the next lowest configuration (three jets) at the same B(d⁄D).Total momentum was found to collapse the data well, as configurations more closely matched a historical correlation for second moment of a single confined jet more closely.

Les jets de plasma froid à la pression atmosphérique connaissent un réel engouement dans de nombreux domaines du biomédical depuis la dernière décennie. Dans les différentes applications de ces jets, le plasma généré est amené à interagir avec de nombreux types de surfaces. Les jets de plasma ont une influence sur les surfaces traitées, mais il est maintenant connu que les surfaces traitées influencent également le plasma en fonction de leurs caractéristiques. Le travail mené dans cette thèse a donc pour but de caractériser un jet de plasma froid d'hélium à la pression atmosphérique en contact avec trois types de surfaces (diélectrique, métallique et eau ultrapure) au moyen de différents diagnostics électriques et optiques afin de comprendre l'influence de la nature des surfaces sur les propriétés physiques du plasma et les espèces chimiques générées. La première partie de cette thèse s'intéresse à l'étude de l'influence des surfaces sur le jet de plasma. Différents paramètres sont étudiés, tels que la nature de la surface exposée, le débit de gaz, la distance entre la sortie du dispositif et la surface exposée ou encore la composition du gaz plasmagène. Pour ce faire, nous avons utilisé dans un premier temps l'imagerie Schlieren afin de suivre le flux d'hélium en sortie du dispositif en présence ou non de la décharge. La spectroscopie d'émission a été utilisée pour déterminer les espèces émissives générées par le plasma. L'imagerie rapide nous a permis de suivre la génération et la propagation de la décharge et la distribution de certaines espèces excitées dans le jet avec l'aide de filtres interférentiels passe-bandes. Une cible diélectrique entraîne un étalement de l'onde d'ionisation sur sa surface et une cible conductrice entraîne la formation d'un canal de conduction. L'évolution de la densité d'espèces excitées (OH*, N2*, He* et O*) augmente avec la permittivité relative de la surface traitée. Le rôle joué par les espèces actives générées par les jets de plasma est fondamental dans la cinétique et la chimie des mécanismes liés aux procédés plasma. La seconde étape de la thèse porte donc sur l'évaluation spatiale et temporelle des densités du radical hydroxyle OH, une espèce jouant un rôle majeur dans de nombreux mécanismes. La cartographie spatiale et l'évolution temporelle des densités absolues et relatives de OH ont été obtenues au moyen de diagnostics lasers LIF et PLIF. La densité de OH générée augmente avec la permittivité relative de la surface traitée. On constate que les radicaux OH restent présents dans le canal d'hélium entre deux décharges consécutives (plusieurs dizaines de microsecondes). Enfin, nous nous sommes intéressés à la production d'espèces réactives à longue durée de vie dans l'eau ultrapure traitée par plasma. L'influence de différents paramètres sur la concentration d'espèces dans l'eau traitée a été étudiée dans le but d'optimiser la production de ces espèces. Dans nos conditions expérimentales, la mise à la masse de l'eau ultrapure lors du traitement permet l'augmentation de la concentration de H2O2. Par ailleurs, la mise à la masse induit une diminution la concentration de NO2-
Cold atmospheric pressure plasma jets are a subject of great interest in many biomedical fields for the past decade. In the various applications of these jets, the plasma generated can interact with many types of surfaces. Plasma jets influence the treated surfaces, but it is now well known that the treated surface also influences the plasma according to their characteristics. The work carried out in this thesis therefore aims to characterize a cold helium atmospheric pressure plasma jet in contact with three surfaces (dielectric, metallic and ultrapure water) by means of different electrical and optical diagnostics in order to understand the influence of the nature of the surfaces on the physical properties of the plasma and the chemical species generated. The first part of this thesis is focused on the study of the influence of surfaces on the plasma jet. Different parameters are studied, such as the nature of treated surfaces, the gas flow, the distance between the outlet of the device and the surface or the composition of the injected gas. For this purpose, helium flow at the outlet of the device is followed by Schlieren imagery with and without the discharge. Emission spectroscopy is used to determine the emissive species generated by the plasma. ICCD imagery is employed to follow the generation and the propagation of the discharge and the distribution of several excited species in the jet by using band-pass interference filters. A dielectric target causes the ionization wave to spread over its surface and a conductive target leads to the formation of a conduction channel. The evolution of excited species densities (OH*, N2*, He* and O*) increases with the relative permittivity of the treated surface. As well known, active species generated by plasma jets play a fundamental role in the kinetics and the chemistry of the mechanisms linked to plasma processes. The second part of the present work therefore relates to the spatial and temporal evaluation of the densities of the hydroxyl radical OH which plays a major role in many cellular mechanisms. The spatial mapping and the temporal evolution of the absolute and relative densities of OH are obtained by LIF and PLIF laser diagnostics. The density of OH generated increases with the electrical conductivity of the treated surface. It can be noted that the OH molecules remain present in the helium channel between two consecutive discharges (several tens of microseconds). Finally, we focus on the production of chemical species in ultrapure water treated with plasma. The influence of different parameters on the concentration of species in the treated water has been studied to optimize the production of chemical species. In experimental conditions, grounding the ultrapure water during treatment increases the concentration of H2O2. Furthermore, the grounding induces a decrease in the NO2- concentration

La fluorescence induite par laser multibande est une technique non intrusive permettant d’accéder à la température de la phase liquide dans des milieux complexes. L’application de cette technique dans des liquides monophasiques où le chemin optique est variable (produit de la concentration moléculaire du traceur et de la distance dans le milieu liquide entre le volume de mesure et l’optique de détection) a été considérée. Le rapport des intensités de fluorescence collectées sur deux bandes spectrales permet de s’affranchir de la concentration en traceur fluorescent, de l’intensité laser incidente et du volume de mesure. Une troisième bande spectrale de détection permet de prendre en compte le terme de ré-absorption de la fluorescence dans le cas de chemins optiques non-négligeables et variables. Puis l’application de la technique à la mesure de la température de la phase liquide d’un spray est présentée. Un traitement spécifique du signal a été développé afin de tenir compte de la nature aléatoire du signal de fluorescence liée à la présence de gouttes dans le volume de mesure. De plus, ce traitement a été adapté afin de rendre possible le couplage des données de fluorescence avec des mesures granulométriques effectuées par la technique phase Doppler dans la perspective finale d’obtenir des températures de goutte par classe de taille. Cependant plusieurs phénomènes perturbateurs ont été mis en évidence : - une dépendance inattendue et non linéaire à la taille de goutte du rapport des intensités de fluorescence collectées sur deux bandes spectrales. - une forte diffusion de la lumière laser incidente par le nuage de gouttelettes induit une fluorescence bien au delà de la zone d’excitation laser. Cette fluorescence parasite est néanmoins détectée dans la profondeur de champ du dispositif optique et se conjugue avec l’effet non-linéaire de la taille des gouttes. Une stratégie de correction de ces différents phénomènes est proposée et une expérience de validation est réalisée sur un spray chauffé injecté dans une cellule saturée en vapeur
Multiband laser-induced fluorescence is a non-intrusive technique able to provide a measurement of the liquid phase of complex media. The application of this technique in single phase liquids, with a variable optical path (product of the fluorescent tracer molecular concentration by the distance between the probe volume and the collection optics in the liquid) was considered. The ratio of the fluorescence intensities collected on two spectral bands allows removing the influence of the fluorescence tracer concentration, incident laser intensity and probe volume. A third spectral band of detection is used to take into account the re-absorption of the fluorescence in the case of non negligible and variable optical paths. Then, the application of this technique to the measurement of the temperature of the liquid phase of a spray is presented. A specific data processing was developed in order to take into account the random presence of droplets in the probe volume. Moreover, the processing was adapted to achieve combined fluorescence and droplet size measurements using the phase Doppler technique. The overall foreseen goal is to measure temperature per droplet size class. However, several disturbing phenomena were highlighted: - an unexpected non-linear dependence on the droplet size of the ratio of the fluorescence intensities collected on two spectral bands, - a strong incident laser light scattering by the droplets cloud, which induces a fluorescence beyond the excitation zone. This fluorescence is also collected in the depth of field of the optical device and combines with the non-linear size dependence. A correction strategy of these phenomena was implemented and a validation experiment on a heated spray injected in a vapour-saturated cell was performed

Philosophiae Doctor - PhD
Emerging micropollutants such as bisphenol-A and 2-nitrophenol present a great threat in drinking water due to their adverse effects. Most conventional technologies in water and wastewater treatment are not designed to eliminate these xenobiotics; instead pollutants are merely transferred from one phase to another. Advanced oxidation technologies (AOTs) however, have been identified as suitable routes for the degradation of these potential damaging substances based on free radical mechanisms and use of less expensive chemicals. Moreover, due to the structural complexity of wastewater and the existence of pollutants as mixtures, no single advanced oxidation technology can convincingly remove all forms of contaminants and then most often than not, a combination of treatment processes is required for an effective purification process. Besides, the problem of adequate degradation of emerging contaminants in the environment, when AOT(s) are used individually, they present inherent problems. For instance, powder TiO₂ photocatalysts obstruct light penetration, thus prevent effective interaction of UV light with the target pollutants, and particulates present problems of post-filtration and recovery of catalyst particles after treatment. Additionally, TiO₂ has a high band gap energy, high electron-hole recombination rate, and is prone to aggregation of the suspended particles. Similarly, the dielectric barrier discharge (DBD) system produces ultra violet light and hydrogen peroxide within the plasma zone which is not fully maximised for the mineralization of persistent organic pollutants. Rapid oxidation and aggregation of nano zero valent iron particles in photo-Fentons process reduce the particles mobility and affect its performance. In the same vein, the jet loop reactor (JLR) system is characterised by low impingement yield, which is responsible for low mineralization rate. In light of this background, this research investigated the degradation of bisphenol-A and 2- nitrophenol in aqueous solution using the following combined advanced oxidation methods: DBD/supported TiO₂ or Ag doped TiO₂ photocatalysts, DBD/photo-Fenton induced process and JLR/UV/H₂O₂. The target was to assess the performance of each single system and then identify the best combined AOTs capable of significantly mineralizing the target compounds. Firstly, two materials were developed namely supported TiO₂ and stabilized nano zero valent Fe. The TiO₂ photocatalyst supported on a stainless steel mesh was synthesised using sol-gel solution of 8 % PAN/DMF/TiCl₄. The influence of calcination temperature and holding time on the formation of nanocrystals was investigated. Afterwards, various amounts of metallic silver were deposited on the (optimum) supported TiO₂ photocatalyst using thermal evaporation. The catalysts were characterized by several analytical methods; HRSEM, HRTEM, EDS, SAED, FTIR, TGA-DSC, UV-vis/diffuse reflectance spectroscopy, XRD, BET, and XPS. The photocatalytic activity of the prepared catalysts was determined using methylene blue as a model pollutant under ultra-violet light irradiation. Secondly, the TiO2 photocatalyst and 2.4 % Ag doped TiO₂ nanocomposites obtained as optimums (in section 1) were combined with the DBD to decompose BPA or 2-NP in aqueous solution. Moreover, the photo-Fenton process was applied for degradation of the model pollutants, and different dosages of stabilized nZVI (in the range of 0.02 -1.00 g) were added to the DBD system to induce the photo-Fenton process and improve BPA or 2-NP degradation efficiency. Finally, a jet loop reactor (JLR) presenting advanced mixing by the “impinging effect” was explored to decompose BPA or 2-NP in aqueous solution as a function of inlet applied pressure, solution pH, and initial concentration of BPA or 2-NP. Subsequently, different concentrations of hydrogen peroxide (H₂O₂) were added to the JLR to enhance the mineralization process. Furthermore, a combination of JLR with in-line UV light and H₂O₂ were further utilised to decompose BPA or 2-NP in aqueous solution. The residual concentration of the model compounds and intermediates were analysed using high performance liquid chromatography (HPLC) and liquid chromatography mass spectrometry (LCMS). The concentration of the ozone, hydrogen peroxide and hydroxyl radicals generated by the DBD in the presence or absence of a catalyst was monitored using Ultraviolet-visible spectroscopy and Photoluminescence spectroscopy. The results revealed that the optimal thermal conditions to obtain well supported uniformly grown, highly active crystalline TiO₂ catalysts with high specific surface area was 350 ºC at a 3 h holding time in N2 atmosphere with a flow rate of 20 mL/min. Pyrolysis temperature and holding time played an important role on the crystalline nature and photocatalytic activity of the catalyst. Moreover, 2.4 % Ag doped TiO₂ nanocomposites exhibited higher photocatalytic activity for methylene blue degradation than the undoped supported TiO₂ nanocrystals. The results indicated that combining DBD with 2.4 % Ag doped TiO₂ nanocomposites achieved 89 % and 81 % removal efficiency for BPA or 2-NP compared to 67.22 % or 56.8 % obtain when using the DBD system alone. The 2.4 % Ag doped TiO₂ nanocomposites demonstrated excellent activity and offered photochemical stability after four repeated applications.In the case of the photo-Fenton induced process, nano zero valent iron particles (nZVI) stabilized with polyethylene glycol were synthesised using a modified borohydride reduction method. The HRSEM, BET, XRD, and XPS analysis confirmed the formation of filamentous, high surface area iron nanoparticles in the zero valent state. Unlike combined DBD/Ag doped TiO2 nanocomposites, 100 % or complete removal of BPA or 2-NP in aqueous solution was achieved with DBD/nZVI system within 30 minutes compared to 67.9 % (BPA) or 56.8 % (2-NP) with DBD alone after 80 minutes. The removal efficiency was attributable to the production of an increased concentration of OH radicals as well as existence of a synergetic effect in the combined DBD/nZVI system. Five new transformation products namely: 4-nitrophenol (C₆H₅NO₃), 4-nitrosophenolate (C₆H₄NO₂), 4-(prop-1-en-2-yl) cyclohexa-3,5-diene-1,2-dione, (C₉H₈O₂), 4-(2- hydroxylpropan-2-yl)cyclohexane-3,5-diene-1,2-dione (C₉H₁₀O₃), and 1,2-dimethyl-4-(2- nitropropan-2-yl)benzene (C₉H₁₀NO₄) were identified during the degradation of BPA. While, three aromatic intermediate compounds such as 2-nitro-1,3,5-benzenetriolate (C₆H₂NO₅), 2- nitro-1,4-benzoquinone (C₆H₃NO₄), and 2,5-dihydroxyl-1,4-benzoquinone (C₆H₄O₄) respectively were identified during the degradation of 2-NP for the first time in the DBD with JT14 or JT17 using LC-MS. These intermediate compounds have never been reported in the literature, thereby expanding the number of BPA or 2-NP intermediates in the data base in the DBD/JT14 or DBD/nZVI system. BPA degradation proceeded via ozonation, hydroxylation, dimerization, and decarboxylation and nitration step, while 2-NP proceeded via hydroxylation, nitration and denitration respectively. Furthermore, maximum removal efficiency of BPA or 2-NP in aqueous solution using JLR alone under the optimum solution pH (3), inlet pressure (4 bar), flow rate (0.0007 m3/s) was 14.0 % and 13.2 % respectively after 80 minutes. A removal efficiency of 34.9 % was recorded for BPA while 33.2 % was achieved for 2-NP using combined JLR/UV under the same conditions as JLR alone. For the combined JLR/H₂O₂ under optimum conditions of inlet pressure (4 bar), solution pH (3) and peroxide dosage (0.34 g/L), a 51.3 % and 50.1 % removal efficiency was achieved for BPA and 2-NP respectively under same conditions relative to JLR alone. Combination of JLR/UV/H₂O₂ achieved 77.7 % (BPA) or 76.6 % (2- NP) removal efficiency under the same conditions. The combined JLR/UV/H₂O₂ process was found to be most effective combination under the optimized operating parameters due to existence of a synergetic index value of 6.42 or 6.84. This implies that JLR should be coupled with UV and H₂O₂ to achieve greater mineralization efficiency instead of using the system individually. The obtained experimental data of these combined treatment processes fitted the pseudo-first order kinetic models. The combination of the JLR/UV/H₂O₂ was found to be energy efficient and could effectively degrade BPA or 2-NP in aqueous solution to a greater extent than the JLR, JLR/UV or JLR/H₂O₂ system. However, the total organic carbon (TOC) reduction value by all combined DBD and JLR system recorded was not completely achieved due to the formation of recalcitrant intermediate compounds under the applied conditions. In conclusion, this study is reporting for the first time a combination of supported 2.4 % Ag doped TiO₂ nanocomposites with dielectric barrier discharge system for BPA/2-NP degradation in aqueous solution; a combination jet loop reactor based on impingement with in-line UV lamp and H2O2 for successfully decomposing BPA or 2-NP in aqueous solution; as well as a combination of dielectric barrier discharge system and stabilised nano zero valent iron particles, which induced a photo-Fenton process for highly effective removal of BPA or 2-NP in aqueous solution. This study conclusively supports the hypothesis that combined advanced oxidation technologies offer a sustainable and highly efficient means of achieving partial or complete removal of BPA or 2-NP in aqueous solutions. Considering all the combinations of AOTs investigated in this study, the novel DBD/photo-Fenton-induced process under optimised operating parameters was found to be the most efficient in the elimination of BPA or 2-NP in aqueous solutions. The combination of DBD with photo- Fenton like process offers a promising advanced waste water purification technology in the immediate future. Based on these findings, it is recommended that DBD should be redesigned to prevent loss of ozone and JLR system reconfigured to increase impingement and cavitational yield in order to have an effective combination treatment strategy for waste water purification especially in large scale waste water management.
National Research Foundation (NRF) and Water Research Commission, South Africa

Cette thèse en cotutelle entre la France et le Canada étudie l’accélération d’ions dans l’interaction laser-plasma. La première partie, réalisée au CENBG et sur l’installation PICO2000 du laboratoire LULI à l'École Polytechnique de Palaiseau, présente des études expérimentales, complétées par des simulations numériques de type Particle-In-Cell, portant sur l’accélération d’ions dans l'interaction d'un laser infrarouge de haute puissance avec une cible gazeuse de haute densité. La seconde, réalisée avec le laser ALLS de l’institut EMT INRS, concerne le développement d'une application des faisceaux génerés par laser pour l’analyse élémentaire d’échantillons. Dans le manuscrit, les caractéristiques des deux lasers, des différents diagnostics de particules et d’X utilisés (paraboles de Thomson, films radiochromiques, CCD...) ainsi que les configurations expérimentales sont décrites.Les jets de gaz denses supersoniques utilisés comme cibles d'interaction laser au LULI, sont présentés en détail; depuis leur conception grâce à des simulations de dynamique des fluides, jusqu’à la caractérisation de leurs profils de densité par interférométrie Mach Zehnder. D'autres méthodes optiques comme la strioscopie ont été mises en œuvre pour contrôler la dynamique du jet de gaz et définir l’instant optimal pour effectuer le tir laser. Les spectres obtenus dans differentes conditions d’interaction sont présentés. Ils montrent, dans la direction du laser, des énergies maximales allant jusqu’à 6 MeV pour les protons et 16 MeV pour les ions hélium. Des simulations numériques effectuées avec le code PICLS sont utilisées pour discuter les différentes structures observées dans les spectres et les mécanismes d’interaction sous jacents.Des faisceaux de protons et d’X générés par le laser ALLS dans l’interaction avec des cibles solides d’aluminium, de cuivre et d’or ont été utilisés pour effectuer des analyses de matériaux par les méthodes Particle-induced X-ray emission (PIXE) et X-ray fluorescence (XRF). L’importance relative des deux techniques, XRF et PIXE, est étudiée en fonction de la nature de la cible d’interaction. Les deux diagnostics peuvent être implémentés simultanément ou individuellement, en changeant simplement la cible d'interaction. La double contribution des deux processus améliore l’identification des constituants des matériaux et permet une analyse volumétrique jusqu'à des dizaines de microns et sur de grandes surfaces (~cm2) jusqu'à un seuil de détection de quelques ppms
In this joint thesis, performed between the French Institute CENBG (Bordeaux) and the Canadian Institute INRS (Varennes), laser driven ion acceleration and an application of the beams are studied. The first part, carried out at CENBG and on the PICO2000 laser facility of the LULI laboratory, studies both experimentally and using numerical particle-in-cell (PIC) simulations, the interaction of a high power infrared laser with a high density gas target. The second part, performed at ALLS laser facility of the EMT-INRS institute, investigates the utilization of laser generated beams for elementary analysis of various materials and artifacts. In this work, firstly the characteristics of the two lasers, the experimental configurations, and the different employed particle diagnostics (Thomson parabolas, radiochromic films, etc.) employed are introduced.In the first part, a detailed study of the supersonic high density gas jets which have been used as targets at LULI is presented, from their conceptual design using fluid dynamics simulations, up to the characterization of their density profiles using Mach-Zehnder interferometry. Other optical methods such as strioscopy have been implemented to control the dynamics of the gas jet and thus define the optimal instant to perform the laser shot. The spectra obtained in different interaction conditions are presented, showing maximum energies of up to 6 MeV for protons and 16 MeV for Helium ions in the laser direction. Numerical simulations carried out with the PIC code PICLS are presented and used to discuss the different structures seen in the spectra and the underlying acceleration mechanisms.The second part presents an experiment using laser based sources generated by the ALLS laser to perform a material analysis by the Particle-induced X-ray emission (PIXE) and X-ray fluorescence (XRF) techniques. Proton and X-ray beams produced by the interaction of the laser with Aluminum, Copper and Gold targets were used to make these analyzes. The relative importance of XRF or PIXE is studied depending on the nature of the particle production target. Several spectra obtained for different materials are presented and discussed. The dual contribution of both processes is analyzed and indicates that a combination improves the retrieval of constituents in materials and allows for volumetric analysis up to tens of microns on cm^2 large areas, up to a detection threshold of ppms

Orientador: Hung Kiang Chang
Resumo: O presente estudo explora a avaliação da distribuição de Light Non-Aqueous Phase Liquid (LNAPL) trapeado na zona saturada empregando a técnica de fluorescência induzida por laser (Laser-Induced Fluorescence – LIF). A área de estudo está localizada no município de Paulínia e tem sido investigada para contaminação por Querosene de Aviação (QAV) desde 2002. O equipamento Ultra-Violet Optical Screening Tool (UVOST®) foi utilizado por possuir a capacidade de detectar moléculas de Hidrocarbonetos Policíclicos Aromáticos (PAH) presentes no LNAPL. Foram realizados um teste piloto de bancada e 21 ensaios de perfilagem LIF em campo, incluindo monitoramento de nível d’água (NA) e nível de óleo (NO) sobrenadante em poços existentes. A perfilagem LIF foi empregada para definir com precisão a extensão lateral do LNAPL, bem como sua tipologia. Além disso, a integração de resultados de fluorescência, oscilação sazonal do NA, espessura de QAV e concentração de naftaleno conduziu para um entendimento mais claro da migração lateral e vertical do LNAPL em subsuperfície. Elevadas intensidades de fluorescência relacionadas ao QAV foram detectadas abaixo do NA na situação de descida do LNAPL em períodos de NA baixo, revelando migrações verticais pretéritas, e correspondem à presença de fase livre nesses períodos, previamente registradas em poços de monitoramento. Análises estatísticas dos quatro canais distintos (comprimentos de onda de 350 nm, 400 nm, 450 nm e 500 nm) mostraram forte correlação en... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The present study explores the distribution evaluation of Light Non-Aqueous Phase Liquid (LNAPL) trapped in the saturated zone using Laser-Induced Fluorescence (LIF) technique. The study site is located in the Paulínia municipality and has been investigated for jet fuel contamination since 2002. Ultra-Violet Optical Screening Tool (UVOST®) was used for its capability in detecting Polycyclic Aromatic Hydrocarbon (PAH) molecules present in LNAPL. One pilot test and 21 LIF profiling tests were carried out in the field, including water table (WT) and floating oil level (OL) monitoring in existing wells. LIF profiling was employed to accurately define the lateral extension of weathered LNAPL, as well as its typology. In addiction, the integration of fluorescence results, seasonal fluctuation of WT, jet fuel thickness and naphthalene concentration led to a clear understanding of lateral and vertical migration of the LNAPL in the subsurface. High fluorescence intensities related to the jet fuel were detected below the WT in the situation of falling LNAPL in low WT season, revealing past vertical migration, and these correspond to the presence of free phase in periods of low WT, previously registered in monitoring wells. Statistical analysis of the four distinct channels (wavelength of 350 nm, 400 nm, 450 nm and 500 nm) showed correlation between the referred wavelengths in the presence of the contaminant, allowing differentiating with better refinement the horizons with the presence... (Complete abstract click electronic access below)
Doutor

This work presents searches for dark matter particles in the mono-jet and mono-photon final states using the data collected by the ATLAS experiment during 2015 and 2016. The thesis starts with an introduction to the basic concepts of the Standard Model, followed by a discussion of the dark matter problem and the WIMP hypothesis. The focus then shifts to the description of the experimental facilities to collect the data and reconstruct the collision events. Particular focus is put on the reconstruction and performance of the missing transverse momentum. After characterizing a few theoretical models predicting dark matter particles in the mono-photon and mono-jet final states, the searches in these two signatures are thoroughly discussed, with particular focus on the background estimation techniques. While no significant deviations from the Standard Model predictions are found, the results obtained by these searches further restrict the phase-space where the dark matter particles can lie.

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.

Les molécules aromatiques protonées jouent un rôle important dans les réactions de substitution électrophile aromatique, et dans différents processus biologiques. Ces molécules sont présentes aussi dans d’autres milieux tels que les flammes de combustion, les plasmas de divers hydrocarbures, les ionosphères planétaires (Titan) et le milieu interstellaire. Les molécules protonées sont très stables car elles ont des couches électroniques complètes mais elles sont en général très sensibles à leur environnement local car elles sont chargées : une étude en phase gazeuse est nécessaire pour déterminer leurs propriétés intrinsèques. Jusqu’à présent, très peu de chose était connu sur les molécules protonées isolées en phase gazeuse, seulement quelques résultats étaient disponibles. Ce manque de données venait de la difficulté de générer des molécules protonées en phase gazeuse et surtout de les produire à basse température (la protonation est une réaction exothermique). Récemment, des progrès ont permis d’étudier les molécules protonées en phase gazeuse à très basse température, en particulier par le développement des sources ioniques couplées avec des techniques d'expansion de jet supersonique. Grâce à cette technique on a enregistré le spectre photo fragmentation de l’état fondamental vers le premier état excité (S1←S0) de différentes molécules aromatiques protonées en phase gazeuse. Les molécules que nous avons étudiées peuvent être regroupées en quatre familles : Les molécules polycycliques aromatiques protonées linéaires (benzène, naphtalène, anthracène, tétracène, pentacène). Les molécules polycycliques aromatiques protonées non linéaires (fluorène, phénanthrène, pyrène). Les molécules protonées contenant un hétéro atome (benzaldéhyde, salicylaldéhyde, 1-naphthol et 2-naphthol, indole, aniline). Les agrégats protonés (dimère de benzène, naphtalène (H2O)n, n=1,2,3. naphtalène (NH3)n, n=1,2,3, benzaldéhyde (Ar , N2)). Dans les spectres enregistrés presque toutes les transitions électroniques S1←S0 sont décalées vers le rouge (basse énergie) par rapport à celui des molécules parentes neutres. Ce décalage est dû au caractère transfert de charge du premier état excité. Certains spectres sont résolus vibrationnellement, alors que pour d'autres molécules le spectre ne présente pas de progression vibrationnelle à cause d’un dynamique très rapide de l’état excité menant par des intersections coniques à l’état fondamental. Les spectres d’absorption des molécules protonées sont plus riches en vibrations par comparaison avec les molécules neutre. Cela reflète le changement relativement important de géométrie de l’état excité dû à son caractère transfert de charge. Les résultats expérimentaux ont été complétés par des calculs ab-initio qui ont permis de localiser la transition électronique, déterminer la structure géométrique et électronique, les modes de vibration et, pour certaines de ces molécules, la dynamique de l’état excité. Les calculs sont en général en très bon accord avec les expériences
Protonated aromatic molecules play an important role in electrophilic aromatic substitution reactions, fundamental reactions in organic chemistry and in various biological processes. The interstellar medium is another environment which is likely to contain the protonated aromatic molecules, that’s because these molecules are stable chemically since they are close shell electronic structure. These molecules were also identified in others environments such as combustion flames, plasmas of various hydrocarbons and the upper atmosphere of Titan. Protonated molecules are usually very sensitive to their local environment; a gas phase study is required to determine their intrinsic properties. Until now, very little is known about the isolated protonated molecules, only a few results are available in the literature. This lack of data is due to the difficulties of the production and the cooling of these molecules in gas phase. The technical progress we have done has enabled the study of protonated molecules in the gas phase at very low temperatures, using an ion sources, supersonic jet and the laser induced photofragmentation techniques. Using this technique, we have recorded many electronic spectra (S1←S0) of different protonated molecules. We can regroup the studied molecules into four: Linear protonated polycyclic aromatic molecules (benzene, naphthalene, anthracene, tetracene, pentacene). Nonlinear protonated polycyclic aromatic molecules (fluorene, phenanthrene, pyrene). Protonated molecules containing an hetero atom (benzaldehyde, salicylaldehyde, 1-naphthol and 2-naphthol, indole, aniline). Protonated cluster (dimer of benzene, naphthalene (H2O)n, n = 1,2,3. Naphthalene (NH3)n, n = 1,2,3, benzaldehyde (Ar, N2)). Most of those spectra are red-shifted compare to the spectrums of neutral parent molecules. This red-shift is due to charge transfer character of the first excited state. Some spectra are vibrationally resolved, while for other molecules the spectrum do not shows any vibrational progression. This behaviour is explained by the dynamic of the excited state, this dynamic being usually is very fast, sometimes leading to the ground state through a conical intersection. The spectra of protonated molecules are very active vibrationally in comparison with neutral molecules, many vibrational modes forbidden for neutral molecule becomes active for the protonated one (Franck-Condon factor is not zero). This is reflecting the charge transfer character of the excited state. The experimental results were complemented by ab-initio calculations, which have allowed determining the electronic transition, the geometric and electronic structure of the molecule, the vibrational modes, and for some of these molecules the dynamics of excited state. Calculations are generally in very good agreement with experiments

Le mélange de scalaire actif, qui implique une rétroaction du champ scalaire sur les champs de vitesses, a attiré beaucoup moins d’attention dans la littérature que le mélange du scalaire passif où le champ scalaire se laisse transporter cinématiquement par le champ de vitesse. Dans cette thèse, nous nous intéressons à quelques questions ouvertes au sujet du mélange de scalaire actif. En particulier, on observe une accélération de la transition vers la turbulence pour : un jet léger, et un jet plus visqueux, par rapport au fluide hôte. Nous abordons deux types d’écoulements : I. Jet rond à masse volumique variable : Nous avons conçu et réalisé une expérience permettant la mesure simultanée des champs de vitesses et scalaire dans le champ très proche d’un jet rond à masse volumique variable. Nous utilisons la Vélocimétrie par Images de Particules Stéréoscopique, couplée à la Fluorescence Induite par Laser Planaire. La première question consiste à connaître l’influence des variations de masse volumique sur les toutes premières structures qui apparaissent après l’injection. La seconde question concerne le transfert d’énergie dans l’écoulement. Nous utilisons une approche statistique en deux-points, et analysons les transferts d’énergie et de variance du scalaire dans l’espace des échelles. Enfin, le mélange est quantifié par une approche de statistiques conditionnées à la périphérie du jet, au voisinage de l’Interface Turbulent/Non-Turbulent. Cette méthode révèle des informations qui sont inaccessibles par des moyennes dans un repère de coordonnées cylindriques classique. II. Jet plan temporel à viscosité et diffusivité massique variables : Nous utilisons des données de Simulations Numériques Directes, produites par le Dr. M. Gauding au sein de notre groupe. Le but de ces simulations est d’étudier l’influence de la variation de viscosité et de la diffusivité de masse sur les taux de dissipation de l’énergie cinétique et du scalaire. Pour traiter cette question, nous utilisons une approche de statistiques conditionnées à l’Interface Turbulent/Non-Turbulent. Dans cette région de l’écoulement, nous évaluons le bilan en un point de l’amplitude du vecteur gradient du scalaire, ainsi que le bilan en deux points de la fonction de structure d’ordre deux du scalaire. Nous montrons que les inhomogénéités initiales du scalaire actif ont un effet intense et persistant sur le mélange dans le voisinage de l’Interface Turbulent/Non-Turbulent, et ceci même tard, dans le régime auto-similaire du jet
Active scalar mixing, which modifies the velocity field through variations of either density or viscosity, received much less attention than passive scalars. This thesis aims at unravelling some open questions pertaining to active scalar mixing. Whilst some results point to the facts that mixing occurs faster for i) light jets than for heavy jets, and ii) more viscous fluid released in a less viscous environment. This simple example reveals the necessity of a systematic study of the problem. We focus on two aspects of these very vast questions. I. Variable density round jet. We designed an experimental set-up, which allows measuring both velocity and scalar fields, using simultaneous Stereo Particle Image Velocimetry and Planar Laser Induced Fluorescence. The first question concerns mixing immediately after injection. Therefore, the very near field of the jet was particularly sought. One-point statistics were used to evaluate the large-scale effect of momentum and density variations on the initiation of turbulence. Also, two-point turbulent statistics for velocity and scalar have been appraised. Through this approach, the effects on transition were assessed through scales of turbulent motion. Mixing was also evaluated at the edge of the flow, in the vicinity of the Turbulent/Non-Turbulent Interface. We found additional specificity to variable density mixing, that is inaccessible by averaging on a cylindrical frame of reference. II. Temporally evolving turbulent jet flow with variable viscosity and mass diffusivity. The data consists in Direct Numerical Simulation performed in our group by Dr. M. Gauding. The purpose of these simulations is to study the kinetic energy and scalar dissipation rates in flows with variable momentum and mass diffusivities. We focused on conditional averaging in the vicinity of Turbulent/Non-Turbulent Interface. This data is confronted to one-and-two point transport equations for the momentum and scalar. It is shown that initial gradients of both viscosity and mass diffusivity have an intense and persistent impact on both kinetic energy and scalar dissipation rates, in the vicinity of the Turbulent/Non-Turbulent Interface, albeit a rapidly trend of the jet core towards self-preservation

The existence of small surface discontinuities on a flow surface generate significant pressure fluctuations which can manifest as radiated far field sound and affect the fluctuating near wall pressure field exerted on the flow surface. A significant amount of research has been performed on various step and gap flows; however few have dealt with step heights that are small relative to the incoming boundary layer. Fewer still have been concerned with measuring the effect on the fluctuating wall pressure field or the radiated far field sound from these small surface discontinuities. This study presents the work aimed at scaling the radiated sound from small forward and backward steps, detailing the surface pressure field as a result of these steps, and detailing the far field sound radiated from gap configurations of similar dimension. These measurements were performed in the Virginia Tech Anechoic Wall Jet facility for step heights that ranged from approximately 10% to 100% of the incoming boundary layer height. The results show the influence of step height and boundary layer velocity on the far field sound from forward and backward steps. Very little directivity is seen for either source and the larger step heights considered in this study are shown to not be acoustically compact. A new mixed scaling normalization is proposed for the far field spectra from both types of step, which is shown to reliably collapse the data. Backward steps are shown to be much weaker producers of far field sound than a similarly sized forward step. The implications of this behavior are discussed with respect to the far field sound measured from various gap flows. The fluctuating wall pressure field was measured upstream and downstream of both step configurations. The data shows a slow recovery of the wall pressure field with lasting disturbances up to 100 step heights downstream of the step feature.
Master of Science

Ce projet de recherche avait pour objectif de répondre à un enjeu industriel: Développer un procédé " propre " de métallisation des polymères sans satinage à l'acide chromique (CrVI). Au cours de ce travail, un procédé alternatif s'appuyant sur une technologie innovante de revêtement de surface (la technologie Graftfast®) a été développé. Ce procédé utilisable dans l'eau et à température ambiante permet de greffer chimiquement des polymères vinyliques sur une large gamme de surfaces de natures différentes. Par cette méthode, une couche d'acide polyacrylique (PAA) a été greffée de manière covalente sur différents substrats polymériques (ABS, ABS-PC, PA, PET, PVC, PVDF. . . ). Les propriétés chélatantes des groupes introduits dans ces films minces de polymères ont été mises à contribution pour l'immobilisation de sels métalliques. Une fois réduites au sein de cette interphase, les particules métalliques ont permis la croissance de la couche métallique par immersion dans un bain Electroless en jouant le rôle de catalyseur. Les couches métalliques résultantes ont montré des propriétés électriques et mécaniques identiques à celles obtenues par les procédés industriels actuels. Combiné à des procédés lithographiques bas coûts et innovants, des motifs métalliques localisés sur substrats flexibles et transparents (PET and PVDF) ont été réalisés à l'échelle micrométrique. Afin de répondre encore plus fortement aux contraintes environnementales et économiques actuelles, le procédé de fonctionnalisation de surface par immersion (Graftfast®) a été remplacé par un procédé par impression jet d'encre photo-assisté. Des motifs métalliques sur substrats flexibles du type papier glacé (PVC) ou transparents (PET) avec une résolution micrométrique ont aussi été réalisés. Ces structures présentent également d'excellentes propriétés électriques et mécaniques et laisse envisager une utilisation de ce procédé pour des applications dans le domaine de la microélectronique
The main goal of this research project was to answer to an industrial issue: To develop a "green" process for the electroless plating of polymers without chromic acid (CrVI) etching. During this work, an alternative process based on an innovative surface coating technology (Graftfast® technology) has been developed. This technique which is working in aqueous solution and at room temperature allows to chemically graft vinylic polymers on various types of substrates. Based on this method, a poly(acrylic acid) (PAA) layer has been covalently grafted onto various polymer substrates (ABS, ABS-PC, PA, PET, PVC, PVDF. . . ). Ion exchange properties introduced in these polymer thin films were used to entrap metal salts. Once reduced into this interphase, copper particles act as catalysts of the metal layer growth by immersion into an electroless plating bath. The resulting metal layer owns mechanical and electrical properties competitive with the current industrial processes. Combined with cost-effective and innovative lithographic processes, metal patterns were obtained onto flexible and transparent substrates (PET, PVDF) at the micrometer scale. In order to answer more appropriately to the current environmental and economic constraints, this "wet" Graftfast® surface functionalization process has been replaced by an inkjet-printed and photo-assisted process. This new process also enables to produce metal patterns onto flexible substrates such as glossy papers (PVC) or transparent sheets (PET) with a micrometric resolution. These devices similarly own excellent electrical and mechanical properties and allow considering its use for applications in the microelectronic field

La physique de la couche limite atmosphérique en domaine océanique est principalement régie par les processus couplés liés au vent, à l’état de mer local, et à des effets de flottabilité. Leur compréhension reste néanmoins parcellaire et leurs descriptions théoriques et stochastiques sont pour le moins lacunaires, lorsqu’elles ne sont tout simplement pas mises à mal par les rares observations. Dans un contexte d’exploitation croissante de la ressource éolienne offshore, la mise en place de méthodes numériques visant à une description plus fine des propriétés turbulentes de cette couche limite sera une étape déterminante dans la réduction des coûts et l’optimisation des structures pour des rendements de récupération d’énergie améliorés. Ainsi, un outil numérique a été mis en place afin d’étudier le couplage entre un écoulement atmosphérique et l’état de mer. Un code Large-Eddy Simulation massivement parallèle pour la simulation des écoulements atmosphériques incompressibles développé par P. Sullivan au National Center for Atmospheric Research est couplé à un code spectral d’états de mer non-linéaires développé au Laboratoire de recherche en Hydrodynamique, Energétique et Environnement Atmosphérique. De nombreuses configurations de vents et d’états de mer sont modélisées. On montre que les lois semi empiriques souvent utilisées pour représenter la distribution verticale de la vitesse moyenne du vent sont une bonne approximation dans les situations où un petit état de mer est soumis à un fort vent. Néanmoins, dans le cas de houles très rapides se propageant dans des zones de faible vent, la création d’un jet de vent par la houle invalide ces lois semi-empiriques
Modelling the dynamic coupling of ocean-atmosphere systems requires a fundamental and quantitative understanding of the mechanisms governing the windwave interactions: despite numerous studies, our current understanding remains quite incomplete and, in certain conditions, sparse field observations contradict the usual theoretical and stochastic models. Within the context of a growing exploitation of the offshore wind energy and the development of met ocean models, a fine description of this resource is a key issue. Field experiments and numerical modelling have revealed that atmospheric stability and wave effects, including the dynamic sea surface roughness, are two major factors affecting the wind field over oceans. A numerical tool has been implemented in order to study the coupling between an atmospheric flow and the seastate. A massively parallel large-eddy simulation developed by P. Sullivan at the National Center for Atmospheric Research is then coupled to a High-Order Spectral wave model developed at the Hydrodynamics,Energetics & Atmospheric Environment Laboratory in Ecole Centrale de Nantes. Numerous configurations of wind and sea states are investigated. It appears that, under strongly forced wind conditions above a small sea state, the semi-empirical laws referred to as standards in the international guidelines are a good approximation for the vertical profile of the mean wind speed. However, for light winds overlying fast-moving swell, the presence of a wave induced wind jet is observed, invalidating the use of such logarithmic laws

This thesis is concerned with the development and application of laser induced thermal grating spectroscopy (LITGS) as a tool for thermometry in reacting and non-reacting flows. LITGS signals, which require resonant excitation of an absorbing species in the measurement region to produce a thermal grating, are acquired for systematic measurements of temperature in high pressure flames using OH and NO as target absorbing species in the burned gas. The signal obtained in LITGS measurements appears in the form of a time-based signal with a characteristic frequency proportional to the value or the sound speed of the local medium. With knowledge of the gas composition, the temperature can be derived from the speed of sound measurement. LITGS thermometry using resonant excitation of OH in the burned gas region of in oxygen enriched CH4/O2/N2 and CH4/air laminar flames was performed at elevated pressure (0.5 MPa) for a range of conditions. Measurements were acquired in oxygen enriched flames to provide an environment in which to demonstrate LITGS thermometry under high temperature conditions (up to 2900 K). The primary parameters that influence the quality of LITGS signal were also investigated. The signal contrast, which acts as a marker for the strength of the frequency oscillations, is shown to increase with an increase in the burnt gas density at the measurement point. LITGS employing resonant excitation of NO is also demonstrated for quantitative measurements of temperature in three environments – a static pressure cell at ambient temperature, a non-reacting heated jet at ambient pressure and a laminar premixed CH4/NH3/air flame operating at 0.5 MPa. Flame temperature measurements were acquired at various locations in the burned gas close to a water-cooled stagnation plate, demonstrating the capability of NO-LITGS thermometry for measuring the spatial distribution of temperature in combustion environments. In addition, the parameters that in influence the local temperature rise due to LITGS were also investigated in continuous vapour flows of acetone/air and toluene/air mixtures at atmospheric conditions. Acetone and toluene are commonly targeted species in previous LITGS measurements due to their favourable absorption characteristics. Results indicate that LITGS has the potential to produce accurate and precise measurements of temperature in non-reacting flows, but that the product of the pump intensity at the probe volume and the absorber concentration must remain relatively low to avoid significant localised heating of the measurement region.

This thesis concerns heating and current drive in tokamak plasmas using the fast magnetosonic wave in the ion cyclotron range of frequencies. Fast wave heating is a versatile heating method for thermonuclear fusion plasmas and can provide both ion and electron heating and non-inductive current drive. Predicting and interpreting realistic heating scenarios is however difficult due to the coupled evolution of the cyclotron resonant ion velocity distributions and the wave field. The SELFO code, which solves the coupled wave equation and Fokker-Planck equation for cyclotron resonant ion species in a self-consistent manner, has been upgraded to allow the study of more advanced fast wave heating and current drive scenarios in present day experiments and in preparation for the ITER tokamak. Theoretical and experimental studies related to fast wave heating and current drive with emphasis on fast ion effects are presented. Analysis of minority ion cyclotron current drive in ITER indicates that the use of a hydrogen minority rather than the proposed helium-3 minority results in substantially more efficient current drive. The parasitic losses of power to fusion born alpha particles and beam injected ions are concluded to be acceptably low. Experiments performed at the JET tokamak on polychromatic ion cyclotron resonance heating and on fast wave electron current drive are presented and analysed. Polychromatic heating is demonstrated to increase the bulk plasma ion to electron heating ratio, in line with theoretical expectations, but the fast wave electron current drive is found to be severely degraded by parasitic power losses outside of the plasma. A theoretical analysis of parasitic power losses at radio frequency antennas indicates that the losses can be significantly increased in scenarios with low wave damping and with narrow antenna spectra, such as in electron current drive scenarios.
QC 20100506

Les industries automobile et aéronautique sont confrontées dans le futur proche à une raréfaction des carburants fossiles, ainsi qu'au problème de pollution de l'environnement émis par les systèmes propulsifs. Pour s'affranchir de ces problèmes, l'utilisation de carburants alternatifs censés apporter rendement et préservation de l'environnement, s'est considérablement développée ces derniers temps. Cependant, leurs impacts sur la pollution, consommation et rendement de combustion ne sont toujours pas clairement établis. En particulier, il est nécessaire de quantifier leurs effets sur les phénomènes physiques clés à la base des processus que sont l'évaporation du carburant liquide et le mélange carburant vapeur/air. L'analyse expérimentale de ces processus physiques nécessite alors l'emploi de diagnostics lasers non-intrusifs et quantitatifs, permettant de mesurer des grandeurs physiques comme les distributions spatiales instantanées de température et de concentration du carburant en phase vapeur. Parmi les techniques optiques les plus attrayantes, l'imagerie de fluorescence induite par laser (PLIF) offre de nombreux avantages. L'objectif de la thèse a été, dans un premier temps, de caractériser les propriétés spectroscopiques de quatre carburants multi-composants, le kérosène (Jet A1), le Biomass-to-Liquid (BtL), le Diesel et l'Ester Méthylique Huile Végétale (EMHV) qui, mis à part le premier, possèdent des propriétés spectroscopiques encore peu connues. L'exploitation de leurs propriétés de fluorescence a ensuite permis d'évaluer leurs capacités à fournir des signaux autorisant la mesure de la température et de la concentration du carburant en phase vapeur. Dans un second temps, un étude exhaustive des propriétés de fluorescence de plusieurs cétones (3-pentanone, benzophénone) et aromatiques (fluoranthène, acénaphtène, naphtalène, 1,2,4-triméthylbenzène...) en fonction de la température et du quenching de l'oxygène moléculaire, a été réalisée à pression atmosphérique pour identifier les traceurs fluorescents potentiellement adaptés au dosage optique des quatre carburants. Les données photophysiques collectées ont ensuite été utilisées pour parfaire l'établissement des couples carburants/traceurs fluorescents ainsi que les stratégies de mesures de température et de concentration de carburant associées. L'exploitation des données acquises lors de différentes campagnes de mesures a ainsi mis en évidence la possibilité de détecter simultanément la fluorescence de plusieurs molécules aromatiques (mono-, di- et/ou tri-aromatique) naturellement présentes ou ajoutées artificiellement dans les carburants. Le cas du Diesel a nécessité le développement d'un carburant modèle pour permettre une étude de son évaporation. L'application de cette nouvelle approche PLIF a été validée sur un injecteur hélicoptère LPP de nouvelle génération fonctionnant avec trois carburants spécifiques que sont le Jet A1, le BtL et un mélange Jet A1/BtL

The study of shock-waves in supersonic plasma jets is essential to understanding the complex dynamics involved in many physical systems. Specifically, ion-species separation caused by a shock wave propagating through a plasma is an important but not yet well understood phenomenon. In inertial confinement fusion implosions, a shock wave precedes the rapid compression of a fuel pellet to ignition conditions that theory and computational studies suggest may be separating the fuel and reducing the neutron yield. In astrophysics, the shock wave produced when a supernovae explodes has been shown to have an effect on nucleosynthesis as a result of shock heating. In both these cases the time and length scales make them difficult to study experimentally, but experiments on more reasonable scales can shed light on these phenomena. This body of work provides the basis for doing just that. The work begins by describing the development of a small, linear, plasma-armature railgun designed to accelerate plasma jets in vacuum to high-Mach-number. This is followed by discussion of an experimental campaign to establish a plasma parameter space for the jets, in order to predict how effectively the accelerator can be used to study centimeter-scale shock structures in jet collisions. The final section presents an experimental campaign in which jet collisions are induced, and the resultant structures that appear during the collision are diagnosed to assess how conducive the experiment is to the future study of shock-wave induced species separation in laboratory plasmas. This work is a foundation for future experimental studies of ion-separation mechanisms in a multi-ion-species plasma. This research was supported in part by the National Science Foundation under grant number PHY-1903442.
Doctor of Philosophy
Plasma, the so-called fourth state of matter, is an ionized gas that often behaves like a fluid but can also become magnetized and carry an electric current. This combination leads to a lot of interesting yet often un-intuitive physics, the study of which is very important for understanding a wide array of topics. One subset of this field is the study of shock-wave induced species separation. Just like the shock-wave a jet aircraft produces when it moves through the air at a speed greater than the speed of sound, a plasma shock is characterized by a large change in parameters like density, temperature, and pressure across a very small region. A shock-wave propagating through a plasma can cause different ion species present to separate out, a phenomenon that is driven by the gradients that are present across a shock front. Understanding how these mechanisms work is important to a number of applications, including fusion energy research and astrophysical events. The first section of this work discusses the design and development of a plasma-armature railgun, a device that can produce and accelerate jets of plasma to high-Mach-number within a vacuum chamber. The next and most substantive section of the work presents results from experimental campaigns to characterize the accelerated plasma jets and then to induce plasma-jet collisions with the hope of producing shock-waves that exist on time and spatial scales that can be readily measured in a laboratory setting. This work is a foundation for future experimental attempts to measure separation induced by a shock-wave in order to better understand these complex phenomena.

The discovery reach for the ADD-type Large Extra Dimension (LED) scenario in the CMS Experiment at the LHC is presented by looking at the Monojet + Missing Energy signature, which arises as a result of a single graviton emission accompanied by a quark or gluon. Using Monte Carlo generated events, two LHC run scenarios were considered and compared namely a center-of-mass energy of 14 TeV and integrated luminosity of 100 pb&
#8722
1, and a center-of-mass energy of 10 TeV and integrated luminosity of 200 pb&
#8722
1. Details from extensive trigger studies are presented and offline selection techniques that optimize the signal excess over backgrounds are highlighted. As a result of this study, it is shown that the existing Tevatron limits on the ADD model can be improved through the implementation of this analysis in CMS Experiment with a factor of 3 using the the early LHC data.

L'influence des facteurs de l'environnement sur la floraison et le développement inflorescential de 3 cvs de b. Napus var. Oleifera ont été étudiés dans les conditions contrôlées du phytotron. Le besoin de vernalisation n'est pas absolu pour les trois cultivars. Les températures basses favorisent toujours la floraison en permettant une initiation florale plus précoce et un nombre final de feuilles de l'axe principal plus faible. La précocité de l'initiation florale et le nombre final de feuilles sont liés.

The aim of this thesis is to test the ability of some correlative models to recover both dynamic and thermal characteristics of a fire induced ceiling-jet flow. The flow occurs when the fire plume impinges the ceiling and develops in the radial direction of the fire axis. These correlative models were also compared with a two-zone model (CFAST) and with an advanced calculation method (Computational Fluid Dynamics) for the calculation of the temperature and velocity near the ceiling. These calculations were developed inside an open car park, using different fire events (localized fires). Both temperature and velocity predictions are decisive for sprinklers positioning, fire alarms positions, detectors positions and activation times and back-layering predictions. Simple graphs were depicted for the time of the fire event and another ones were depicted for the maximum value expected during the fire event. Some correlative models agree well with the results obtained with CFAST. The CFD results over predicted the dynamics of the fire events.
O objetivo desta tese é testar a capacidade de alguns modelos correlativos para descrever as características dinâmicas e térmicas de um fluxo de jato de teto induzido por um incêndio. O fluxo ocorre quando a chama de incêndio atinge o teto e se desenvolve na direção radial em relação ao eixo do fogo. Estes modelos correlativos também foram comparados com um modelo de duas zonas (CFAST) e com um método de cálculo avançado (Computational Fluid Dynamics) para o cálculo da temperatura e da velocidade perto do teto. Estes resultados foram determinados dentro de um parque de estacionamento aberto, usando diferentes eventos de incêndio (incêndios localizados). As previsões de temperatura e velocidade são decisivas para o posicionamento dos sprinklers, posições de alarmes de incêndio, posições de detetores e tempos de ativação e previsões de camadas com refluxos. São apresentados gráficos para representação destas quantidades durante o tempo do evento de incêndio e outros gráficos são apresentados para o valor máximo esperado durante o evento de incêndio. Alguns modelos correlativos concordam bem com os resultados obtidos com o CFAST. Os resultados do CFD sobre avaliam a dinâmica dos eventos de incêndio.

碩士
國立臺灣海洋大學
系統工程暨造船學系
94
ABSTRACT The jet flow induced by soap bubble collapse is investigated in our study. Smoke of particle size about 2 is adopted as the seeding to fill the soap bubble. A spike drived by a synchronized signal of the PIV system is used to pierce the soap bubble. Different stages of the transient, soap bubble collapse flow are visualized and measured using the Particle Image Velocimetry method. It is found that, douring the bubble collapsed, a series of Kelvin-Helmholtz vortices are formed around the bubble sphere and a convergent jet is formed in the center of the bubble. Detail velocity distributions of the bubble collapse flow are obtained from the particle image analysis.

碩士
國立清華大學
動力機械學系
81
The main purpose of the present thesis is to investigate the flow structure of an annular jet and its induced flow along the center line in two concentric circular flow channels. In order to deal with the irregular-shaped solid boundaries, a curvilinear coordinate system associated with a Poisson type grid generation technique are employed to construct the grid system needed in the computation. All of the partial differential equation are of elliptic type and are discretized based on the weighting function scheme. The resulting matrix equations are solved by using the SIS (Strongly Implicit Solver) solver. The velocity and the pressure field are directly obtained by following the NAPPLE algorithm on a non- staggered grid system. The effects of Reynolds numbers and pipe lengths on the flow structure are emphasized. According to the numerical results, At higher Reynolds number or shorter pipe lengths, due to the significant pressure loss at the sudden expansion, the pressure level of the main recirculation region is lower than that of the outer environment. Hence the fluid is drawn into the central pipe by the annular jet. On the other hand, at lower Reynolds number or longer pipe lengths, the fluid in the central pipe tends to be blowed out by the relatively high pressure near the main recirculation region. The step formed by the wall thickness of the central pipe is found not to have any advantage to the suction effect.

Filling operations, i.e., dosing a fixed amount of liquid in a bottle, are relevant in many industrial fields. A key aspect is a precise control of the breakup of the stream exiting a nozzle, avoiding events like dripping (falling down of drops) and stringing (formation of filament and threads). Breakup phenomena have been widely studied under constant flow rate conditions and different regimes of filament thinning have been identified. In this work, we analyze the effects of liquid properties and time-varying operating conditions on the breakup dynamics of a Newtonian liquid through Volume-of-Fluid numerical simulations and experiments. This thesis is divided in two main parts. In the first part, we study the dynamics of different classes of Newtonian liquids subjected to flow rates that linearly decrease in time. We find that the operating conditions only partially alter the thinning dynamics and, once a critical dimension of the filament has been reached, the dynamics is fairly described by scaling laws derived for steady-state operating conditions. In the second part, we address the filament breakup problem of a real dosing system. Experiments show the presence of air entrapped in the liquid phase during the process that significantly alters the breakup dynamics. The effect of entrapped air is accounted for in numerical simulations by defining and implementing a new model that adequately describes the compressibility effects induced by the coexistence of the two phases. The dissolved air delays the onset of the thinning phase and determines a slowdown of thinning dynamics. A good quantitative agreement between experiments and simulations in terms of time evolution of the filament radius at a fixed distance from the nozzle is found.

碩士
國立成功大學
航空太空工程學系
86
An underexpanded jet incident to a cavity tube can induce pressure oscillation inside the cavity tube and temperature increase due to heat flux accumulation at the bottom of the tube. The problem is experimentally investigated based on three parameters of nozzle pressure ratio, the cavity tube length and the distance between the nozzle exit and the cavity tube inlet. Two major flow modes which are named as regurgitant mode and screeching mode have been studied. Their flow patterns have been observed by a color schlieren method. For regurgitant mode, the measured major frequency of the pressure oscillation inside the cavity tube is very close to the theoretical fundamental frequency of the flow system. Its amplitude is larger than that for the screeching mode. It has been observed that, owing to the accumulation of the entropy at the cavity tube end during the pressure oscillation process in the regurgitant mode, there exists an endwall-temperaturerising, as well as a large heat-flux transfer occurring, when the jet cavity interacting flow field is in regurgitant. The results show that the oscillating pressure amplitude and frequency are important factorfor the temperature rising.