Academic literature on the topic 'Coupage au jet'
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Journal articles on the topic "Coupage au jet":
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Kozlov, Viktor V., Maria V. Litvinenko, and Grigory V. Kozlov. "The Round Jet in a Cross-Flow (Review)." Siberian Journal of Physics 5, no. 1 (March 1, 2010): 9–28. http://dx.doi.org/10.54362/1818-7919-2010-5-1-9-28.
Abstract:
Results of experimental and numerical studies on characteristics of the developing round jet with parabolic velocity profile in a crossflow are presented. The basic differences of characteristics (parameters, properties) of development of the round jet with parabolic velocity profile and «shock» velocity profile are showed. As it is outlined, the round jet with parabolic velocity profile in a crossflow is transformed to two stationary counter rotating vortices. In the current work it is shown, that the most unsteady high-frequency eigenmodes correspond wave packets onto the couple of counter rotating vortices. Decrease of frequency leads to development of the eigenmodes closer to wall in track of the jet. The growths of penetration of jet into a crossflow and air inflow by near-field of jet from crossflow are observed. In addition, it was shown, that boundary of the jet and crossflow can stretch and become thin under the influence of crossflow.
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Pérez Ramírez, Lucía, Anthony Boucly, Florent Saudrais, Fabrice Bournel, Jean-Jacques Gallet, Emmanuel Maisonhaute, Aleksandar R. Milosavljević, Christophe Nicolas, and François Rochet. "The Fermi level as an energy reference in liquid jet X-ray photoelectron spectroscopy studies of aqueous solutions." Physical Chemistry Chemical Physics 23, no. 30 (2021): 16224–33. http://dx.doi.org/10.1039/d1cp01511g.
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ALVES, LEONARDO S. de B., ROBERT E. KELLY, and ANN R. KARAGOZIAN. "Local stability analysis of an inviscid transverse jet." Journal of Fluid Mechanics 581 (May 22, 2007): 401–18. http://dx.doi.org/10.1017/s0022112007005873.
Abstract:
A local linear stability analysis is performed for a round inviscid jet with constant density that is injected into a uniform crossflow of the same density. The baseflow is obtained from a modified version of the inviscid transverse jet near-field solution of Coelho & Hunt (J. Fluid Mech.vol. 200, 1989, p. 95) which is valid for small values of the crossflow-to-jet velocity ratio λ. A Fourier expansion in the azimuthal direction is used to couple the disturbances with the three-dimensional crossflow. The spatial growth rates of the modes corresponding to the axisymmetric and first helical modes of the free jet as λ → 0 increase as λ increases. The diagonal dominance of the dispersion relation matrix is used as a quantitative criterion to estimate the range of velocity ratios (0 < λ < λc) within which the transverse jet instability can be considered to have a structure similar to that of the free jet. Further, we show that for λ>0 positive and negative helical modes have different growth rates, suggesting an inherent weak asymmetry in the transverse jet.
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Rui, Zilong, Kuibin Zhou, Ruixing Dong, and Xia Shi. "Experimental Study on Double Jet Flames with Different Nozzle Diameters." Advances in Computer and Engineering Technology Research 1, no. 2 (April 18, 2024): 460. http://dx.doi.org/10.61935/acetr.2.1.2024.p460.
Abstract:
Double jet flames are commonly observed in the energy industry. A facility consisting of a double jet flames apparatus, was designed to experimentally simulate the interaction of double jet fires with different spaces and nozzle diameters. It has been found that the exit momentum, nozzle diameters and nozzle spacing significantly affect the flame behavior. The experimental results show that the flame merging probability (Pm) of double jet fires with different nozzle diameters can be fitted with dimensionless parameters that couple the Froude number(Fr) and the distance between fire sources. Additionally, it has been observed that the difference in height between the two flames can be used as a parameter to determine the correlation between flame height and the distance to the nozzle center.
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Haroon, R. F., and D. Roy. "A simulation study of the soft and hard radiations using jets at the LHC." Journal of Physics: Conference Series 2663, no. 1 (December 1, 2023): 012052. http://dx.doi.org/10.1088/1742-6596/2663/1/012052.
Abstract:
Abstract In this work, different aspects of the high-energy radiation are looked at considering the LHC scenario. An event-shape variable and several jet substructure observables are studied with the Mote Carlo event simulators at the 13 TeV center of mass energy scale to mimic the current LHC environment. The event-shape and the jet substructure observables are chosen such that they are not only sensitive to the different aspects of the high energy radiation measurement but also exhibit promising features to distinguish the possible existence of new physics that considers a dark matter candidate decaying into semi-visible jet. It is verified that the observables exhibit significant sensitivities to disentangle two jets to multi-jet radiations, presence of a final state and initial state radiations, presence of a large amount of missing transverse energy as a strong indication of the possible existence of a dark matter as well as couple of promising features of a semi-visible jet are explored.
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RAMAN, GANESH, and RAY TAGHAVI. "Coupling of twin rectangular supersonic jets." Journal of Fluid Mechanics 354 (January 10, 1998): 123–46. http://dx.doi.org/10.1017/s0022112097007441.
Abstract:
Twin jet plumes on aircraft can couple, producing dynamic pressures significant enough to cause structural fatigue. For closely spaced jets with a moderate aspect ratio (e.g. 5), previous work has established that two coupling modes (antisymmetric and symmetric) are kinematically permissible. However, the dynamics of twin-jet coupling have remained unexplored. In this paper a more fundamental assessment of the steady and unsteady aspects of twin-jet coupling is attempted. While we document and discuss the nozzle spacings and Mach numbers over which phase-locked coupling occurs, our concentration is much more on answering the following questions: (a) What mechanism causes the jets to couple in one mode or the other? (b) Why do the jets switch from one mode to another? (c) Are the two modes mutually exclusive or do they overlap at the transition point? Our results reveal, among many things, the following. (i) For very closely spaced twin jets in the side-by-side configuration phased feedback based on source to nozzle exit distance of adjacent jets does not fully explain the coupling modes. However, the ‘null’ phase regions surrounding the jets where the phase of an acoustic wavefront (arriving from downstream) does not vary appears to correlate well with the existence of the symmetric mode. When the ‘null’ regions of adjacent jets do not overlap antisymmetric coupling occurs and when they do overlap the jets couple symmetrically. We provide a simple correlation using a parameter (α) that can be used as a simple test to determine the mode of coupling. (ii) The switch from the antisymmetric to the symmetric mode of coupling appears to occur because of an abrupt shift in the effective screech source from the third to the fourth shock, which in turn causes the ‘null’ phase region surrounding the jets to grow abruptly and overlap. (iii) The two modes are mutually exclusive. Our results provide considerable insight into the twin-jet coupling problem and offer hope for designing twin-jet configurations that minimize damage to aircraft components.
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Cuahquentzi, Noel M., Luis H. H. Gómez, Pablo R. López, Guillermo Urriolagoitia-Calderón, Juan Alfonso Beltrán-Fernández, G. Urriolagoitia-Sosa, Enrique F. Cuamatzi, Arturo O. Ramírez, and Beatriz R. Ángeles. "Evaluation of the Structural Integrity of the Jet Pumps of a Boiling Water Reactor under Hydrodynamic Loading." Defect and Diffusion Forum 348 (January 2014): 261–70. http://dx.doi.org/10.4028/www.scientific.net/ddf.348.261.
Abstract:
The structural integrity of a jet pump assembly of a boiling water reactor (BWR) under hydrodynamic loading was evaluated. This arrangement, which has a riser joined with a couple of jet pumps by the transition piece, is part of the reactor recirculation system. It is submerged in water under pressure. The main function is to induce forced flow through the core of the reactor. A dynamic structural analysis was carried out with the finite element method. The first ten modes of vibration and their natural frequencies were calculated. The first five natural frequencies are in the range between 25 Hz and 40 Hz. In this analysis, it was considered that the jet pump assembly is supported at the riser brace. The restrainer bracket keeps together the riser with the two jet pumps and there is free movement at the slip joints.
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Guo, Wen Liang, and Zheng Guo. "Nozzle Spraying Model of Combustion Thermal Spray." Advanced Materials Research 655-657 (January 2013): 211–17. http://dx.doi.org/10.4028/www.scientific.net/amr.655-657.211.
Abstract:
The flame used in combustion flame spraying is typical of a high-temperature free jet. The flow fields of free jets are multi-phase flows that couple the mass and heat transfer. The analytical and numerical solutions to turbulent flows are engineering approximations. This work uses Prandtle’s mixing-length theory to describe the flame spreading of free combustion spray jet and uses nozzle spray model to describe the distribution of the powder particles sprayed from powder nozzle to the substrate surface. The nozzle geometry and the parameters determine the distribution of the powder particles. The nozzle spray model has the same physical meaning with the jet spreading angle. Experimental measurements were carried by a high-speed CCD camera.
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Guo, Wen Liang, and Zheng Guo. "Research on Jet Flame Extinguishing Process." Applied Mechanics and Materials 635-637 (September 2014): 80–83. http://dx.doi.org/10.4028/www.scientific.net/amm.635-637.80.
Abstract:
The flame used in combustion flame spraying is typical of a high-temperature free jet. The flow fields of free jets are multi-phase flows that couple the mass and heat transfer. This work develops an analytical method to describe free combustion spray jets. The aim of the research is to develop a fully understanding of the characteristics of free-flame jets. Experimental measurements were carried by a unique high-speed continuous CCD camera.
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Zhang, Xinxin, Jianming Peng, Jingqing Chen, Kun Bo, Kun Yin, and Dongyu Wu. "The effect of actuator parameters on the performance of a liquid-jet hammer associated with its jet behavior." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 231, no. 14 (December 26, 2016): 2610–20. http://dx.doi.org/10.1177/0954406216685350.
Abstract:
Bi-stable fluidic amplifier containing no moving parts was used for switching fluid flow passing through it into an actuator in a liquid-jet hammer. So far, there has been no design basis for developing a liquid-jet hammer with high performance. To provide a guidance, this paper elaborates on the computational fluid dynamics simulation method for investigating the effect of actuator parameters on the performance of a liquid-jet hammer associated with its jet behavior. Given that couple mechanism exists between the flow field in the bi-stable fluidic amplifier and the actuator, dynamic mesh technique and a user-defined function written in C programming language were used to update the mesh in the simulations. Two evaluation criteria—pressure recovery and flux utilization ratio—for a liquid-jet hammer were used in this study. Experimental tests were conducted to verify the simulation results, by which the accuracy and reliability of this computational fluid dynamics simulation method was proved. Besides, comprehensive analysis of the flow behavior in the fluidic amplifier of a liquid-jet hammer was performed by the use of computational fluid dynamics visualization method.
Dissertations / Theses on the topic "Coupage au jet":
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Tazibt, Abou-el-Foutouh. "Étude théorique et expérimentale du processus d'accélération de particules abrasives dans un jet d'eau sous très haute pression : interaction avec le matériau à découper." Lille 1, 1995. http://www.theses.fr/1995LIL10003.
Abstract:
L'utilisation de la technologie du jet d'eau abrasif comme procédé de découpage à froid de matériaux tels que les composites et métaux, trouve des champs d'applications divers (aéronautique, industrie de l'automobile, génie civil). Bien que ce procédé soit utile, son support théorique est loin d'être maîtrisé quant à l'optimisation du grand nombre de paramètres de travail (pression hydraulique, débit d'abrasif, profondeur de coupe). La résolution de ce problème ne peut être effective que si l'on considère les facteurs qui conduisent principalement au phénomène de coupe. En effet, grâce à l'énergie cinétique des particules abrasives, le matériau est découpé par arrachement de matière. Ce qui a conduit à la modélisation du processus d'accélération du jet d'eau abrasif selon la démarche macroscopique de la mécanique des milieux continus appliquée aux écoulements biphasiques solide/liquide. En exploitant l'hypothèse de conservation de la quantité de mouvement du mélange, la résolution de l'équation différentielle, non linéaire et à deux inconnues (vitesses de la particule et de l'eau), du mouvement a donné deux solutions analytiques exactes. Celles-ci représentent la variation de la vitesse des phases en fonction de la distance sur l'axe du jet à l'intérieur du tube de focalisation. La méthode utilisée permet non seulement de tenir compte des actions simultanées des forces interfaciales (traînée, masse virtuelle), mais aussi des conditions réelles de fonctionnement du jet, à savoir l'aspiration de particules qui s'accompagne d'air par effet venturi. La validation expérimentale de la modélisation théorique a été menée avec succès en développant une corrélation expérimentale donnant la vitesse des particules à l'impact indépendamment de la modélisation théorique. Cette corrélation repose sur l'interaction du jet avec le matériau et débouche sur un modèle intègre qui donne la profondeur de coupe et la vitesse d'avance en fonction de la vitesse théorique de modélisation et les paramètres de travail.
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Weiss, Laurent. "Contribution au développement d'un procédé de découpe laser haute-énergie / jet d'eau haute-pression couplés : Application à la découpe d'alliages métalliques." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0112/document.
Abstract:
Depuis une dizaine d'années, la découpe par jet hybride où un jet d'eau fait office de guide d'onde pour le laser est utilisée avec succès dans le domaine de la microélectronique. Afin de développer cette technologie pour l'amener vers d'autres marchés tels que l'automobile, la chaudronnerie ou l'aéronautique, il est nécessaire d'augmenter la puissance des lasers et la pression du jet. A ces hauts niveaux énergétiques, les nouvelles interactions qui apparaissent entre la lumière et le fluide ainsi que les modifications du matériau engendrées par le jet hybride n'ont encore jamais été étudiées d'un point de vue physico-chimique. Nous avons donc d'abord mis au point un système permettant de mesurer les propriétés optiques de l'eau à très haute pression dont une application directe pourrait être un capteur optique de pression des fluides. Ainsi et de façon originale, ce travail a permis de mesurer l'indice de réfraction et la polarisabilité de l'eau jusqu'à 250 MPa en modélisant leurs évolutions à l'aide des équations de Tait, de Sellmeier et de Lorentz-Lorenz. Cette étude a débouché sur la création d'un modèle reliant directement la densité du fluide à la mesure de son indice de réfraction. Suite à ces résultats, nous avons pu, après des simulations d'hydrodynamisme, concevoir une tête permettant le couplage d'un laser haute puissance guidé par jet d'eau haute pression. Nous avons alors testé diverses formes de chambres permettant le couplage d'un jet hybride de nouvelle génération. En parallèle, nous avons étudié l'impact physico-chimique d'un jet hybride découplé où le laser et le jet d'eau sont focalisés, pour la découpe, à la surface d'échantillons en acier 301L et en alliage de titane TA6V. Les résultats ont été obtenus par spectroscopie Raman, Diffraction des Rayons X (DRX), microscopie optique et microscopie électronique à balayage couplé à de l'analyse EDS (Energy Dispersive Spectroscopy) et à de l'analyse d'orientation cristallographique (EBSD). Lors de la découpe, des transformations de phases et une couche oxydée apparaissent à la surface des échantillons. Nous avons montré notamment que ces couches d'oxydes ainsi que les résidus de coupe sont en majeure partie constitués de magnétite (Fe3O4) et de rutile (TiO2)For a decade, the hybrid jet cutting where a water jet acts as waveguide for the laser has been successfully used in the field of microelectronics. To develop this technology and bring it up to other markets such as automotive, boiler or aerospace, it is necessary to increase both the laser energy and the water jet pressure. At these high energy levels, new interactions that occur between light and fluid as well as the material changes caused by the hybrid jet have never been studied from a physicochemical point of view. So, at first, we have devised a system allowing measurements of optical properties of water at high pressure with a possible direct application in optical sensor for fluid pressure. In an original way, this work has allowed us to measure the refractive index and polarizability of water up to 250 MPa and model their evolution using Tait, Sellmeier and Lorentz-Lorenz equations, respectively. A direct result of this study is the creation of a model linking directly the fluid density to the measurement of its refractive index. Following these developments and after hydrodynamics simulations, we have designed a specific head for coupling a high power laser guided by high pressure water jet. Then we have tested various head types allowing the coupling of a new generation hybrid jet. In the same time, we have studied the physicochemical impact of decoupled hybrid jet where the laser and water jet are both focused, for cutting, at the surface of 301L steel and titanium alloy TA6V samples. The analysis have been done by Raman spectroscopy, X-ray diffraction (XRD), optical microscopy and scanning electron microscopy coupled with EDS (Energy Dispersive Spectroscopy) analysis and the crystallographic orientation (EBSD) analysis. During cutting, a phase transformation and an oxidized layer appear on the surface of the samples. We have shown in particular that these oxide layers and cutting residues are mainly composed of magnetite (Fe3O4) and rutile (TiO2)
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Xiao, Shenglei. "The investigation on mechanical behaviours of reinforcements and machining properties during manufacturing composites with complex shapes." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1I056/document.
Abstract:
Les caractéristiques mécaniques et le comportement à la déformabilité des renforts sont des connaissances essentielles pour optimiser les procédés de fabrication des composites notamment de formes complexes. Par ailleurs, les propriétés d'usinage des composites déterminent également grandement la performance en service des pièces composites. Cette thèse est consacrée aux trois aspects des procédés de fabrication et d'usinage afin d'explorer les caractéristiques particulières des propriétés mécaniques et des comportements de déformabilité des tissus tressés, qui sont des renforts textiles prometteurs et excellents pour les composites aux formes complexes. Mais également étudier les procédés d'usinage en utilisant la technique du jet d'eau abrasif afin d'améliorer encore l'efficacité de l'usinage sans sacrifier la qualité. Les caractéristiques mécaniques des renforts tressés, en particulier pour les composantes de cisaillement dans le plan, ont d'abord été étudiées et modélisées à partir d’essais de bias-test. Par ailleurs, les tresses triaxiales ont également fait l'objet d'une étude expérimentale de détermination des caractéristiques mécaniques relativement aux paramètres de tressage, tels que l'angle de tressage et le nombre de fils. Le comportement à la déformabilité des tresses triaxiales lors de l’étape de préformage a été analysé et corrélés avec les défauts associés en fonction des différentes conditions du procédé, telles que les pressions appliquées. De plus, l'évolution du comportement à la déformabilité en fonction de l'angle de tressage a été modélisée géométriquement et vérifiée par des résultats expérimentaux. La découpe améliorée multi-passe du jet d'eau abrasif a été introduite dans le processus d'usinage des composites grâce à l'exploration du mécanisme d'enlèvement de matière associée. Il a été conclu expérimentalement qu'une telle technique pouvait améliorer efficacement la qualité et l'efficacité de l'usinageThe mechanical characteristics and deformability behaviours of reinforcements are essential knowledge to optimize manufacturing process composites with complex shapes. Meanwhile, the machining properties of composites also greatly determine the in-service performance of composite parts. This thesis is not only dedicated on the three aspects in manufacturing and machining processes to explore what characters the special features in the mechanical properties and deformability behaviours of braided fabrics, which are promising and excellent textile reinforcements for composites with complex shapes. But also to study machining processes using the abrasive water jet technique in order to further improve machining efficiency without sacrificing quality. The mechanical characteristics of braided fabrics, especially for in-plane shearing phenomenon, were originally investigated and modelled based on bias-extension test. In addition, triaxial braids were also the subject of an experimental study to determine the mechanical characteristics with regard to braiding parameters, such as braiding angle and number of yarns. The deformability behaviour of triaxial braids during the preforming step was analysed and correlated with the associated defects according to the different process conditions, such as the pressures applied. In addition, the evolution of the deformability behaviour as a function of the braiding angle was geometrically modelled and verified by experimental results. The upgraded multi-pass cutting of abrasive waterjet was firstly introduced into composites machining process based on the exploration of the corresponding material removal mechanism. It was experimentally concluded that such technique could effectively enhance the machining quality and efficiency
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Avrit, Antoine. "Étude du comportement d’ablation d’une structure solide par un jet liquide chaud." Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0281.
Abstract:
Les études de sureté pour les réacteurs à neutrons rapides à caloporteur sodium (RNR-Na) ont donné lieu au développement de nouveaux systèmes de mitigation des accidents graves. Lors d'un scénario d'accident grave, une partie plus ou moins importante du cœur du réacteur entre en fusion, formant du corium. Ce corium doit être évacué du cœur afin d'éviter des problèmes de criticité. Des tubes de déchargement ("DCS-M-TT") ont donc été intégrés au design des RNR-Na, afin de transférer le cœur fondu vers un récupérateur de corium. En sortant des tubes de déchargement, le corium forme un jet et s'étale sur le récupérateur ce qui permet de le refroidir plus efficacement. Le jet de corium en sortie des tubes de déchargement étant extrêmement chaud (~ 2000 - 3000 K) lorsqu'il impacte le récupérateur, il peut provoquer son ablation thermique. Il faut donc dimensionner le récupérateur pour qu'il ne soit pas percé par le jet. Des expériences ont été réalisées dans une précédente thèse pour améliorer la compréhension du phénomène d'ablation par un jet à surface libre, avec l'installation HAnSoLO (Hot AblatioN of a SOlid by a Liquid - Observations). De nouveaux résultats ont également été obtenus pour traiter des phénoménologies plus variées dans cette thèse. Ainsi, on s'est intéressé à l'ablation d'un solide par un jet immergé, problème qui présente une phénoménologie différente de celle du cas étudié précédemment. L'effet de la rugosité du solide impacté a également été traité et il a été mis en évidence que la prise en compte de la rugosité est importante pour le dimensionnement du récupérateur. L'ensemble de ces résultats ont été utilisés pour valider un code CFD. Les simulations numériques ont notamment permis d'obtenir des résultats d'ablation très similaires aux résultats expérimentaux pour le cas du jet immergé. Les simulations et expériences devront être complétées à l'avenir pour permettre de traiter numériquement l'ablation d'un solide par un jet de corium dans les conditions du réacteurSafety studies for fast neutron reactors with sodium led to the development of mitigation systems for severe accidents. During a hypothetical severe accident, at least part of the reactor's core melts, leading to the formation of corium. The corium has to be relocated to prevent any criticality problems. Therefore, transfer tubes were integrated to the design of the core to relocate the corium from the core to a core-catcher. A jet of corium exits the transfer tubes and spreads on the core-catcher, allowing a better cooling of the corium. However, thermal ablation of the core-catcher will occur as the temperature of the corium is very high (~ 2000 - 3000 K). Thus, the core-catcher has to be dimensioned to prevent any breach due to the ablation. Experiments were performed during a previous thesis to improve understanding of the phenomenon of ablation by a free-surface jet, with a bench called HAnSoLO (Hot AblatioN of a SOlid by a Liquid - Observations). New results were obtained in the present work to address additional phenomenologies. For instance, the ablation of a solid by an immersed jet was studied. This is another situation that could occur in the real case. The effect of the roughness of the impacted solid was also addressed, and it was shown that taking roughness into account is important to design the core-catcher. All these results were used to validate a CFD code. In particular, the ablation result obtained through the numerical simulations were very similar to the experimental results for the immersed jet case. The simulations and experiments will be completed in the future to numerically treat the ablation of a metallic solid by a corium jet under reactor conditions
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Assoum, Hassan. "Étude expérimentale des couplages entre la dynamique d’un jet qui heurte une plaque fendue et l’émission sonore générée." Thesis, La Rochelle, 2013. http://www.theses.fr/2013LAROS420/document.
Abstract:
Un jet heurtant une plaque fendue peut générer, dans certaines configurations, des nuisances sonores. En effet, l’interaction de l’écoulement et de l’obstacle au niveau de la fente, sous certaines conditions, donne naissance à une perturbation remontant l’écoulement et pouvant contrôler son détachement à sa naissance. La perturbation produite par cette boucle de rétroaction optimise le transfert d’énergie du champ aérodynamique du jet vers le champ acoustique rayonné. Afin d’appréhender la dynamique tourbillonnaire, d’analyser les couplages entre cette dernière et les émissions sonores générées et de mieux comprendre les phénomènes responsables de ces nuisances, un dispositif expérimental basé sur de la métrologie laser a été réalisé. Ce système permet, d’une part, la génération de l’écoulement et la maitrise de ses paramètres (confinement, vitesse, forme,…) et d’autre part, la réalisation de plans lasers et de mesures par imagerie de particules (PIV). Ainsi le travail présenté dans ce manuscrit concerne les couplages qui existent entre la dynamique de l’écoulement heurtant une plaque fendue et les champs acoustiques générés. Les mesures de champs cinématiques d’un jet plan heurtant une plaque fendue par Vélocimétrie par Images de Particules (PIV) sont réalisées simultanément avec des mesures de champs acoustiques. Après avoir caractérisé les écoulements étudiés, on présente par des graphes spatio-temporels, les corrélations entre les signaux acoustiques et les vitesses de l’écoulement depuis la sortie du jet jusqu’à son arrivée à la plaque fendue. Ces corrélations sont calculées de deux manières : à partir de signaux bruts dans un premier temps, puis, dans un second temps, avec une méthode de pré-blanchiment (terme anglo-saxon : ‘’pre-whitening’’). Cette méthode vise à mettre en exergue l’existence d’une instabilité globale du jet qui existe dans les signaux analysés. Cette instabilité est importante pour la boucle de rétroaction des sons auto-entretenus, mais quasiment masquée devant les phénomènes principaux dominants (tourbillons primaires) dans le calcul des inter-corrélationsSelf-sustaining sounds related to aero-acoustic coupling occurs in impinging jets when a feedback loop is present between the jet exit and a slotted plate: the downstream-convected coherent structures and upstream-propagating pressure waves generated by the impingement of the coherent structures on the plate are phase locked at the nozzle exit. The upstream-propagating waves excite the thin shear layer near the nozzle lip and result in periodic coherent structures. The period is determined by the convection speed of the coherent structures and the distance between the nozzle and the plate. Simultaneous measurements of the velocity fields and the acoustic waves in a plane jet impinging a slotted plate were performed using time-resolved particle image velocimetry (PIV) and a microphone. A better understanding of the flow physics and the aero-acoustic coupling are obtained thanks to spatio-temporal cross-correlations between the transverse velocity and the acoustic signals. Cross-correlations are calculated using two different methods: classical analysis of the original signals and by developing a pre-whitening technique. The latter method is useful for analyzing small random signals superimposed on a high amplitude pure tone
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Meslem, Amina. "Contribution à l'étude du couplage thermique entre un jet et un local climatisé." Lyon, INSA, 1997. http://www.theses.fr/1997ISAL0053.
Abstract:
Les travaux que nous présentons se structurent autour d'une analyse du jet issu d'un système de diffusion d'air et du couplage de celui-ci avec un local. La première partie est consacrée à une revue bibliographique sur les jets et les indices qui permettent de qualifier l'ambiance thermique des locaux climatisés. Le deuxième chapitre est réservé à la description du dispositif expérimental que nous avons développé au CETIAT de Villeurbanne. Le troisième chapitre nous conduit à une analyse détaillée du jet d'air froid issu du système de diffusion d'air et à une identification de ses caractéristiques principales. Les résultats obtenus montrent une bonne cohérence par rapport à des études plus classiques menées sur des jets de paroi tridimensionnels et an isothermes. Enfin, le dernier chapitre est consacré à l'étude de la performance du système de diffusion d'air et du confort thermique dans la zone d'occupation du localThe work we present is based both on the analysis of the jet released from an air diffusion system and the coupling of the jet with a dwelling. The first part is devoted to a bibliographical review about jets and the indices allowing to assess the thermal environment of air conditioned dwellings. The second chapter is the description of the experimental set up which has been developed in the CETIAT on Villeurbanne. The third part leads to an accurate analysis of the cold jet issued from the air diffusion system and to an identification of its main characteristics. The results display a good agreement according to more academic studies conducted on 30 and anisothermal wall jets. Finally, the last chapter sets out the study of both the performance of the air diffusion system and the thermal comfort in the occupancy zone of the dwelling
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Radenac, Emmanuel. "Développement et validation d'une méthode numérique pour le couplage fluide / structure en aérothermique instationnaire." Toulouse, ENSAE, 2006. http://www.theses.fr/2006ESAE0018.
Abstract:
Une méthodologie destinée à la simulation des phénomènes aérothermiques instationnaires est développée, étudiée et validée dans ce travail. Elle consiste à coupler deux solveurs de dynamique des fluides et de thermique du solide. Elle est étudiée selon des critères de conservativité, précision et robustesse. Les paramètres du couplage (conditions limites d’interface fluide / solide et correction conservative) sont définis pour assurer la stabilité et un minimum de développements au sein des codes couplés. Une validation expérimentale est également effectuée sur une configuration proche des conditions moteurs d’avion. L'expérience modélise le refroidissement des carters en phase transitoire. Un jet accélérant en écoulement transversal refroidit une plaque plane épaisse chauffée en face arrière. La comparaison des résultats numériques et expérimentaux est encourageante.
8
Mateu, armengol Jan. "Étude numérique des effets du couplage du rayonnement thermique aux jets turbulents libres de vapeur d'eau." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC052/document.
Abstract:
Le rayonnement thermique joue un rôle important dans un large éventail d'applications de génie thermique comprenant des écoulements turbulents. La motivation principale de cette thèse est le besoin croissant de précision et fiabilité dans les simulations numériques appliqué à ce domaine.Cette thèse s’intéresse tout particulièrement à la compréhension physique de l’impact du rayonnement thermique sur la dynamique des fluides et le transfert thermique, ainsi que de l’influence des fluctuations turbulentes sur le transfert radiatif dans les écoulements à couche de cisaillement.L'objectif de cette thèse est de fournir des données haute-fidélités de jets libres turbulents couplés au rayonnement thermique afin de développer et de valider des modèles turbulents d’écoulements à couche de cisaillement prenant en compte les interactions de couplage. À cette fin, les jets libres turbulents sont décrits par des simulations numériques directes (DNS) couplées à une méthode de Monte-Carlo réciproque pour résoudre l'équation de transfert radiatif. La dépendance spectrale des propriétés radiatives est prise en compte avec la méthode Correlated-k (ck). L'étude numérique est réalisée avec la plus grande fidélité pour être aussi représentative que possible d'un jet réel dans un milieu participatif. La simulation est optimisée en termes de temps de calcul en tirant parti d'une méthode d'accélération appelée Acoustic Speed Reduction et en injectant de la turbulence artificielle pour améliorer les conditions d'entrée.Deux simulations directes de jets chauffés couplés au rayonnement thermique sont réalisées. D'une part, un jet chauffé avec un rayonnement modéré a été simulé et l’analyse de ses données DNS couplées a permis de dériver une nouvelle loi d’échelle pour la décroissance du profil de température. Cette mise à l'échelle rend compte des effets de la densité modifiée due à un rayonnement modéré. De plus, cela permet de distinguer si le rayonnement thermique modifie ou non la nature des mécanismes de transfert thermique dans la région développée du jet. D'autre part, un jet libre fortement chauffé a été calculé afin de quantifier les effets du rayonnement sur les champs de température et de vitesse moyens ainsi que sur les moments de second ordre.Outre les données DNS couplées, un solver RANS pour les écoulements à densité variable couplé au rayonnement thermique a été développé au cours de cette thèse. L'objectif était de quantifier directement la précision des modèles turbulents existants et d'identifier les paramètres clés pour une modélisation plus poussée des interactions de couplageRadiation plays an important role in a broad range of thermal engineering applications comprising turbulent flows. The growing need for accurate and reliable numerical simulations to support the design stages of such applications is the main motivation of this thesis.Of special interest in this work are the free-shear flows and the fundamental understanding of how radiation can modify their fluid dynamics and heat trans- port as well as how their turbulence fluctuations can alter radiative transfer. The goal of this thesis is to provide high-fidelity data of turbulent free jets coupled with thermal radiation in order to develop and validate free-shear turbulent models accounting for coupling interactions. To this end, turbulent free jets are described by direct numerical simulations (DNS) coupled to a reciprocal Monte- Carlo method to solve the radiative transfer equation. The spectral dependency of the radiative properties is accounted for with an accurate Correlated-k (ck) method. The numerical study is carried out with state-of-the-art fidelity to be as representative as possible of an actual jet in a participating medium. The simulation is optimized in terms of processing time taking advantage of an acceleration method called Acoustic Speed Reduction and by injecting artificial turbulence to enhance inlet boundaries.Two direct simulations of heated jets coupled with thermal radiation are carried out. On the one hand, a heated jet with moderate radiation is simulated. The analysis of its high-fidelity coupled DNS data has allow to derive a new scaling law for the decay of the temperature profile. This scaling accounts for the effects of modified density due to moderate radiation. Moreover, it allows for distinguishing whether thermal radiation modifies the nature of heat transfer mechanisms in the jet developed region or not. On the other hand, a strongly heated free jet is computed in order to quantify the effects of radiation on mean temperature and velocity fields as well as on second order moments.Besides the coupled DNS data, a RANS solver for variable-density flows coupled with thermal radiation has been implemented during the course of this thesis. The goal is to directly quantify the accuracy of the existing turbulent models, and to identify key parameters for further modeling of coupling interactions
9
Berthiaux, Henri. "Modélisation du broyage fin dans un broyeur à jets d'air et à lit fluidisé : étude du couple broyeur-sélecteur." Vandoeuvre-les-Nancy, INPL, 1994. http://www.theses.fr/1994INPL154N.
Abstract:
Nous avons conçu des outils méthodologiques permettant de construire une modélisation globale des opérations de broyage et de broyage - classification, en prenant en compte les différents phénomènes mis en jeu: cinétique de broyage, écoulement des particules, classification. L’utilisation des formulations classiques du génie des procédés a permis d'introduire la notion de fraction résiduelle, représentative des performances de ces procédés. Des modèles complets ont été bâtis et validés à la fois dans le cas d'un broyeur à billes agité et dans celui d'un broyeur à jets opposés et à lit fluidisé avec classificateur mécanique intégré. Pour ce dernier appareil, et après avoir mis au point des protocoles expérimentaux visant à identifier les contributions des différents processus, la cinétique de broyage a été caractérisée par une loi d'évolution simple, une expression analytique de la courbe de partage du sélecteur a été obtenue et il a mis en évidence la présence d'un volume actif de broyage inclus dans la zone des jets. Des développements d'ordre purement théorique ont été d'autre apportés: modélisation des réseaux de classificateurs par une chaine de Markov, méthode de recherche des fonctions de broyage et de sélection par optimisation
10
Cammas, Jean-Pierre. "Circulation ageostrophique dans les systemes jet-fronts : une etude prospective du couplage dynamique haute et basse troposphere." Clermont-Ferrand 2, 1988. http://www.theses.fr/1988CLF21134.
Abstract:
Cette etude est une analyse experimentale des causes de forcage des circulations ageostrophiques dans les systemes jet-fronts, c'est-a-dire les systemes dynamiques constitues dans la haute troposphere par un maximum de courant-jet et un front d'altitude. Les circulations ageostrophiques associees a ces systemes sont a l'origine de processus encore mal connus tels que les processus de couplage dynamique entre la haute et la basse troposphere et les processus de foliation de tropopause donnant lieu a des echanges stratosphere-troposphere. L'analyse des termes de forcage des circulations ageostrophiques transverses et longitudinales au flux, induites respectivement par les effets inertiels et ceux de courbure, est obtenue par decomposition des champs ageostrophiques dans le repere naturel du vent total au niveau 300 hpa. Les donnees utilisees sont celles des analyses numeriques du modele du centre europeen de prevision meteorologique a moyen terme, ainsi que du modele peridot de la meteorologie nationale francaise pour 3 journees consecutives de la campagne experimentale fronts 84. L'etude experimentale est completee par des analyses isentropes dans des coupes transverses au courant-jet en utilisant les radiosondages du reseau synoptique, et par une detection des foliations de tropopause en utilisant les donnees satellitaires du canal vapeur d'au de meteosat 2 et de contenu en ozone total de l'atmosphere du spectrometre toms de nimbus 7. L'etude met en evidence plusieurs circulations ageostrophiques transverses indirectes interessant toute l'epaisseur de la troposphere, en accord avec des schemas conceptuels recents deduits d'une analyse des termes de forcage geostrophique de l'equation diagnostique de sawyer-eliassen. Dans les zones de courbure du flux, il est montre que la circulation ageostrophique dominante est la circulation longitudinale forcee par le terme d'advection de courbure. L'analyse conj
Books on the topic "Coupage au jet":
1
Zikmund, Rakowski, International Bureau of Strata Mechanics., and International Society of Water Jet Technology., eds. Geomechanics 93: Strata mechanics, numerical methods, water jet cutting, mechanical rock disintegration : proceedings of the international conference Geomechanics 93, Hradec, Ostrava, Czech Republic, 28-30 September 1993. Rotterdam: Balkema, 1994.
2
Rakowski. GEOMECHANICS 93WATER JET CUTTING. Taylor & Francis, 1994.
3
Fontaine, Jonathan. Jeu de Couple: Ecrire Pour Retrouver Son Couple et Se Redécouvrir ! Independently Published, 2020.
4
Desjardins, Denise. Le jeu de l'amour et de la sagesse. Albin Michel, 2000.
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Reinstein, Mara, and Joey Bartolomeo. Brad & Jen: The Rise and Fall of Hollywood's Golden Couple. Wenner, 2005.
6
edition, Gnaka. Jeu et défis de Couple: Le Livre de Jeu Coquin Sexy, Questions Réponses et Action Ou Vérité. Independently Published, 2022.
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Vesquel, Rosie. Jeu Sexuel Pour Pimenter Votre Vie de Couple: Scénarios Sexy Pour des Soirées Hot en Couple - Pimenter Son Couple et Sa Libido. Independently Published, 2021.
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KARI, Ludovic. Livre de Jeux Pour Couple, Jeux Coquins Pour Couple - Adultes Amoureux, Quizz Adultes, Quizz Couple , Mariage , Cadeau Saint Valentin, Jeu Coquin: Défi Entre Amoureux, Livre d'activité Pour Couple. Independently Published, 2020.
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KARI, Ludovic. Livre de Jeux Pour Couple, Jeux Coquins Pour Couple - Adultes Amoureux, Quizz Adultes, Quizz Couple , Mariage , Cadeau Saint Valentin, Jeu Coquin: Défi Entre Amoureux, Livre d'activité Pour Couple. Independently Published, 2020.
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KARI, Ludovic. Livre de Jeux Pour Couple, Jeux Coquins Pour Couple - Adultes Amoureux, Quizz Adultes, Quizz Couple , Mariage , Cadeau Saint Valentin, Jeu Coquin: Défi Entre Amoureux, Livre d'activité Pour Couple. Independently Published, 2020.
Book chapters on the topic "Coupage au jet":
1
Mirabail, Solange. "Le couple." In La famille que je veux, quand je veux ?, 27. ERES, 2003. http://dx.doi.org/10.3917/eres.neiri.2003.02.0027.
2
Paricard-Pioux, Sophie. "La rupture volontaire du couple." In La famille que je veux, quand je veux ?, 105. ERES, 2003. http://dx.doi.org/10.3917/eres.neiri.2003.02.0105.
3
Parfitt, Tudor. "“The Truth of the Origination of the World and Mankind”." In Hybrid Hate, 1–31. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780190083335.003.0001.
Abstract:
The Judeo-Christian tradition maintains that humankind derives from the first couple in the Garden of Eden. St. Augustine even included the so-called monstrous races in the overall category of humanity. This consensus started to fragment in the sixteenth century with the work of Paracelsus and later Giordano Bruno, when alternative theories were put forward to account for human diversity. Their work was followed by others, including Julius Caesar Vanini, Isaac La Peyrère, John Atkins, Voltaire, François Bernier, Carl Linnaeus, Georges Cuvier, Edward Long, and Lord Kames. For most of them, the black and the Jew were the great obstacles to the unity of mankind.
4
Capriotti-Vittozzi, Giuseppina. "Un gruppo scultoreo da Dendera al Museo del Cairo: due fanciulli divini e i due luminari." In Classica Orientalia. Essays presented to Wiktor Andrzej Daszewski on his 75th Birthday, 115–27. DiG Publisher, 2011. http://dx.doi.org/10.37343/pcma.uw.dig.9788371817212.pp.115-127.
Abstract:
The sculptural group in stone reconsidered in this article is a representation of a couple of youthful figures, standing entwined in the coils of two large serpents, crowned with a solar disk and a lunar crescent. The statue was discovered in Dendera in 1918 and is now in the Egyptian Museum in Cairo (JE 46278). A hypothetical identification proposed by the author would see in the figures the twin children of Cleopatra VII and Mark Anthony, represented here as the two Egyptian astral deities. The author explores the iconographic and stylistic issues involved, arriving at a late Ptolemaic date for the sculpture, fitting for the proposed identification.
5
Allouche, Sylvie. "La série 24 heures chrono a-t-elle le pouvoir de nous rendre meilleurs ?" In 24 heures chrono, naissance du genre sécuritaire ? Librairie Philosophique J. Vrin, 2022. http://dx.doi.org/10.53984/philoseries03606.
Abstract:
24 heures chrono met en scène l’opposition entre les deux grandes théories morales que sont l’utilitarisme et le déontologisme autour de la question de savoir si la fin justifie ou non les moyens. Or certains critiques de 24 heures chrono, choqués en particulier par le traitement de la torture dans la série, lui reprochent de manipuler les spectateurs de façon à tous les transformer en utilitaristes assoiffés de torture, autrement dit à les déteriorer sur le plan moral et à les rendre mauvais. Je montre au contraire que 24 heures chrono rend son spectateur meilleur, ou du moins devrait le rendre meilleur, et m’appuie principalement pour ce faire sur la difficulté pour le déontologiste rigoureux de ne pas se rendre coupable de contradiction performative, notamment celle qui consiste à utiliser des arguments de structure utilitariste pour défendre une position déontologiste.
6
McAlister, Elizabeth A. "“The Jew” in the Haitian Imagination: Pre-Modern Anti-Judaism in the Postmodern Caribbean." In Black Zion, 203–28. Oxford University PressNew York, NY, 1999. http://dx.doi.org/10.1093/oso/9780195112573.003.0011.
Abstract:
Abstract Each year in Haiti the Holy Week of Easter sets the stage for spiritual dramas of remembrance, performed in carnivalesque street theater throughout the country. While Catholics reenact the Passion of Jesus and enter with him into his tribulation and resurrection, some practitioners of the Afro-Haitian religion called Vodou organize enormous musical parades called Raras and take to the streets for the spiritual warfare that becomes possible when the angels and saints remove to the underworld, along with Jesus, on Good Friday. The cast of characters who have a hand in the week’s events include the deities of Vodou-especially Baron Simitye, the Vodou “Lord of the Dead”-the zonbi (recently dead) who are his wards, and also Jesus, the two thieves crucified with him, a couple of Haitian army officers who secretly witnessed the resurrection, Pontius Pilate and the Romans, Judas, and “the Jews:’ The week’s ritual events combine the plots and personae of the Christian narrative with the cosmology of various African religions and rehash them in local ritual dramas whose elements draw from the entire history of the Atlantic world, from the European Middle Ages to the contemporary condition of global capitalism in the Americas.
7
Holman, Peter. "‘Waiters upon the Violin’ The Twenty-four Violins at Court." In Four and Twenty Fiddlers, 305–30. Oxford University PressOxford, 1993. http://dx.doi.org/10.1093/oso/9780198161455.003.0013.
Abstract:
Abstract The traditional round of daily attendance or ‘waiting’ at Court ren,aif1ed the prime duty of royal musicians during the Restoration period. The chroniclers of court life took the presence of music so much for granted that they rarely bothered to mention it, but it is clear that the violinists, at least, were still required to attend Whitehall daily while the court was there. On 7 November 1666 twelve of them petitioned the king for arrears of wages, pointing out that they had ‘been com(m)anded to attend yo(u)r Ma(jes)tie and yo(u)r Royall Consort the Queene in all progresses, besides their dayly attendance heere’. A couple of years later, when wages were between six and seven years in arrears, the musicians complained as a body that they had ‘all this winter given their constant attendance morning and evening on this present mask’. We saw in Chapter 12 that John Banister’s Select Band had to be on hand ‘whensoever there shall be occasion for Musick’, and that Banister was required to attend the king ‘constantly to receive our Comands’.
8
McCulloch, Margery Palmer. "Fête du Citron 1924–1926." In Edwin and Willa Muir, 68–82. Oxford University PressOxford, 2023. http://dx.doi.org/10.1093/oso/9780192858047.003.0006.
Abstract:
Abstract 1924–1926.The Muirs meet old friends in London, and make contact with C. M. Grieve (‘Hugh MacDiarmid’) and his wife Peggy in Montrose. The poets respect each other and Edwin admires MacDiarmid’s achievement, but the families have little in common. Willa starts to translate Gerhard Hauptman and plans an essay on women—Women: An Inquiry (1925). Edwin’s reviews and essays are collected as Transition (1926). They find living in Montrose disappointing, and visit friends in the south when they can. Willa suffers a miscarriage in December 1925, and they depart for St Tropez in France. Edwin plans a novel, published as The Marionette (1927), and Willa plans one based on her memories of Montrose. She has a contract to translate Lion Feuchtwanger’s Jew Süss, which will be a big success. Willa feels their time in the south of France is spoiled by the arrival of John Holms, who dominates her husband’s attention. The couple move to Menton, but John Holms is an important person in Edwin’s life, despite Willa’s reservations. He was a charismatic and gifted talker who impressed almost everyone he met, including the millionairess Peggy Guggenheim, who will take him as a lover. The Muirs’ sojourn in France comes to an end when Willa finds she is pregnant and they return to Britain.
9
Farne, Hugo, Edward Norris-Cervetto, and James Warbrick-Smith. "Rectal bleeding." In Oxford Cases in Medicine and Surgery. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780198716228.003.0027.
Abstract:
As with all acute patients, always start by assessing ABCDE: airways, breathing, circulation, disability, and exposure. In a patient with acute gastrointestinal (GI) haemorrhage (whether upper or lower), assessing their circulation (i.e. haemodynamic status) is a priority. If there are clinical features to suggest haemodynamic instability—such as hypotension, tachycardia, cool peripheries, tachypnoea, or decreased consciousness—then the immediate priority is to resuscitate the patient before proceeding to a thorough history and examination. The differential diagnosis for rectal bleeding is shown in Figure 21.1. There are a couple of points to note about this differential diagnosis. GI haemorrhage may present as overt or occult bleeding. This table, and the indications of prevalence within it, refers to overt rectal bleeding as occult rectal bleeding will not be noticed by the patient. The second point to note is that upper GI sources of haemorrhage may occasionally present with rectal bleeding alone. Although it is more likely that such upper GI sources will also present with haematemesis, you should note that large volumes of blood in the GI tract can act as a cathartic (stimulant of peristalsis) and the resultant rapid transit through the intestine leads to the passage of red blood per rectum. • How much blood has been passed? This question is directly relevant to your initial haemodynamic status survey. Ask the patient to quantify approximately how much blood they have passed—familiar measures such as a teaspoon, eggcup, or wine glass may be easier for the patient than asking them to provide an estimate in millilitres. Note, however, that it is very easy to overestimate volumes of blood loss if, for example, blood has mixed with water in the toilet bowl. You should additionally enquire about symptoms of hypovolaemia—any light-headedness, collapse, chest pain or breathlessness? • What is the duration and frequency of the symptoms? • What did the blood look like? Generally speaking, the fresher the blood, the more distal the bleed. Substantial bleeding from lesions proximal in the GI tract may present with melaena (jet black, tarry stool caused by bacterial oxidation of haem) or may present as frank blood (haematochezia) if transit times are sufficiently rapid.
10
Gratzer, Walter. "A copper or two." In Eurekas and euphorias, 257–58. Oxford University PressNew York, NY, 2002. http://dx.doi.org/10.1093/oso/9780192804037.003.0159.
Abstract:
Abstract Rudolf Schoenheimer was a German biochemist of exceptional accomplishment. As a Jew, he lost his position in Germany before the Second World War and found refuge, along with many others in the same predicament, in the medical school of Columbia University in New York. There the Head of the Biochemistry Department, Hans Thatcher Clarke, assembled a brilliant, polyglot, and captious galère of Europeans. The years immediately after the war saw a succession of remarkable advances in the chemistry of physiological processes, thanks in large part to the advent of radioactive isotopes [149]; it was now possible to render radioactive, and thus label, substances involved in metabolism and follow their chemical transformations in a cell or in an animal. But radioactive isotopes were still in short supply and precious. Schoenheimer wanted to experiment with radioactively labelled urea, the metabolic end-product excreted by animals and man. A leader in the field of isotope purification was Harold Urey, who agreed to make available to Schoenheimer a minute quantity of ammonium nitrate, greatly enriched in the isotope of nitrogen with an atomic weight of 15, which makes up only a vanishingly small proportion of the Earth’s nitrogen, with its atomic weight of 14. Urey had prepared the material from bulk ammonium nitrate, a dangerous, explosive chemical, which he had illicitly driven into New York from a plant in New Jersey through the Holland Tunnel in the rumble-seat of his coupe. The glass ampoule, which he presented to Schoenheimer, contained the bulk of the world’s supply of the purified isotope, N.
Conference papers on the topic "Coupage au jet":
1
Naboulsi, Samir (Sam). "Couple Diffusion-Thermo-Mechanical Model for Life Prediction of a Turbine Engine Blade." In ASME 2018 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/imece2018-88461.
Abstract:
The failure of engines on jet aircrafts during the past few years has prompted the National Transportation Safety Board (NTSB) to issue an “urgent” recommendation to increase inspections of the engines on U.S. aircraft. Such uncontained engine failures are particularly dangerous, because flying engine parts could puncture fuel or hydraulic lines, damage flight surfaces or even penetrate the fuselage and injure passengers. At issue is older engines found on small number of jets, and the safety and economic impact damage and fracture risk can have on aircraft engines. For example, high-pressure turbine blades are commonly removed from commercial aircraft engines that had been commercially flown by airlines. These engines were brought to the maintenance shop for refurbishment or overhaul. The blades were removed and inspected for damage. The damage was cataloged into three modes of failure, which are thermal-mechanical fatigue (TMF), Oxidation/Erosion (O/E), and Other (O). These show the complexity of damage in turbine engines and the different mechanisms associated with cause of damage. Hence, life prediction of turbine engine is crucial part of the management and sustainment plan to aircraft jet engine. Fretting is often the root cause of nucleation of cracks at attachment of structural components at or in the vicinity of the contact surfaces. Previous effort presented a model to predict fretting fatigue in turbine engine, which is one of the primary phenomena that leads to damage or failure of blade-disk attachments. The influence of thermal effect and temperature fluctuation during engine operation on fretting fatigue damage were investigated. Leveraging these existing capabilities, the present effort focuses on modeling another important damage mechanism in turbine engine blades, which is erosion at high temperatures. Thus a reaction-diffusion model is implemented in addition to the thermo-mechanical one. The model provides a mean to investigate erosion initiation and propagation in turbine engine blades.
2
Chiang, Hsiao-Wei D., and Hsin-Lung Li. "Jet Impingement and Forced Convection Cooling Experimental Study in Rotating Turbine Blades." In ASME Turbo Expo 2009: Power for Land, Sea, and Air. ASMEDC, 2009. http://dx.doi.org/10.1115/gt2009-59795.
Abstract:
Both jet impingement and forced convection are attractive cooling mechanisms and have been widely used in cooling of gas turbine blades. Convective heat transfer from impinging jets is known to yield high local and area averaged heat transfer coefficients. Impingement jets are of particular interest in the cooling of gas turbine components where advancement relies on the ability to dissipate extremely large heat loads. The current research is concerned with the measurement and comparison of both jet impingement and forced convection heat transfer in the Reynolds number range of 10,000 to 30,000. The present study is aimed at experimentally testing two different setups with forced convection and jet impingement in rotating turbine blades up to 700 rpm. This research also focused on to observe how Coriolis forces and impingement cooling inside the passage in rotating conditions within a cooling passage. Local heat transfer coefficients are obtained for each test section through thermal-couple technique with slip rings. The cross section of the passage is 10 mm × 10 mm without ribs. The surface heating condition has a uniform heat flux enforced. The forced convection cooling effects were studied using serpentine passages with three corner turns under different rotating speeds and different inlet Reynolds numbers. The impingement cooling study uses a straight passage with a single jet hole under different Reynolds numbers of the impingement flow and the cross flow. In summary, the main purpose is to study the rotation effects on both the jet impingement and the serpentine convection cooling types. Our study shows that rotation effects increase the serpentine cooling and, on the other hand, reduce the jet impingement cooling.
3
Ugrina, Sandra, and Alison Flatau. "Analytical and Experimental Investigation of Different Synthetic Jet Actuator Configurations." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-62485.
Abstract:
The ultimate goal of this project is to actively control the flow over a micro air vehicle using smart materials. MAVs are a new type of aircraft operating at Reynolds numbers of about 50,000 that are one to two orders of magnitude lower than encountered in larger aircraft. The intention is to implement smart structures and couple them with fluids to improve the deteriorated aerodynamics of MAVs and help improve efficiency, stability and maneuverability of such vehicles. The actuators used in this work for artificially controlling the boundary layer are piezoelectrically driven synthetic jets. We theoretically investigated and predicted the behavior of the synthetic jet as we changed the geometry and material property parameters of the actuator. Analytical results were then compared to the results obtained from the experiments. It is crucial to be able to accurately design a strong unimorph to be implemented as an active component of a synthetic jet actuator and design the geometry configuration of the cavity that will best couple with the chosen membrane. A condenser microphone, a constant temperature anemometer (CTA) and a laser vibrometer were used to quantify actuator performance. It was observed that the size of the cavity and the size and shape of the exit nozzle were related and the performance of the actuator increased when the structure was tuned such that the resonant frequency of the diaphragm and that of the cavity were close to matching. A square unimorph made of PZT-5H and bonded to a 0.20- mm brass shim maximized jet velocity for the actuators studied. Optimum direction of change in the volume and the dimensions of the nozzle will strongly depend on the resonant frequency of the membrane in use. In this situation, increasing either the volume of the cavity or the thickness of the nozzle made the two frequencies move away from each other producing reduction in jet velocity. Increasing the area of the nozzle, made the structure behave more as needed and was taken as a key parameter for tuning the base geometry of the device.
4
Reich, Alton J., and Paul J. Dionne. "Complex Fluid-Structure Interaction in Ink Jet Printer Mechanisms." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-2126.
Abstract:
Abstract Recent advances in the ability to couple fluid and structural analyses have made it possible to simulate the behavior of increasingly complex physical systems. This paper focuses on the simulation of the fluid-structure interaction within a typical ink jet printer. The simulations demonstrate several different methods that may be used to eject a droplet of ink from a reservoir. In each case a membrane at the bottom of the ink reservoir is deformed. The movement of the membrane imparts the momentum necessary for droplet ejection to the fluid. The simulations were performed with a commercial CFD code (CFD-ACE+) that uses a modular simulation approach. This approach allows the tight coupling of the different physical phenomena that contribute to the droplet ejection process.
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Le, Jiang, Liu Zhenxia, Lyu Yaguo, and Zhu Pengfei. "Numerical Study on Flow Characteristics of Liquid Jet in Airflows." In ASME Turbo Expo 2019: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/gt2019-91076.
Abstract:
Abstract The interaction between the fuel jet, the oil jet and the airflow is involved in the afterburner (or ramjet combustion chamber) and the lubricating oil system of the aero-engine respectively. The latter mainly studies the penetration depth of the oil jet into the airflow, the oil jet breakup position and so on. In the under-race lubrication system, the oil jet is deflected due to the high-speed rotation of the oil scoop and some droplets, ligaments are separated. The deflection of the oil jet and the splash of droplets may affect the oil capture efficiency of the under-race lubrication system. At the same time, the configuration of the oil jet nozzle will also have a certain impact on the oil capture efficiency. Therefore, it is necessary to carry out research on the flow characteristics of the oil jet in the airflow, and provide reference for the oil jet nozzle configurations of the under-race lubrication system. In this paper, the calculation results show that the Couple Level-Set and Volume of Fluid (CLSVOF) method is better than the Volume of Fluid (VOF) method. The correlations between the coordinate of the oil jet breakup positions and the liquid-air momentum ratio were concluded. The equation of the trajectory curve was derived for the jet column trajectory before breakup. The difference of the oil jet flow characteristics between single jet nozzle and the twin jet nozzle and the tandem jet nozzle configuration is also studied. Finally, the design method under the tandem jet nozzle configuration is given.
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Teymouri, R. M. B., and G. Ahmadi. "Numerical investigation of the jet formation through the oscillation of a bubble between a couple of parallel walls." In AFM 2010. Southampton, UK: WIT Press, 2010. http://dx.doi.org/10.2495/afm100171.
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Arthurs, David, and Samir Ziada. "The Effect of Fluid-Resonant Coupling in High-Speed Impinging Planar Jet Flows." In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97141.
Abstract:
This study investigates the effect of fluid-resonant coupling, i.e. the coupling between unstable modes of an impinging jet with resonant acoustic modes occurring between the nozzle and the impingement surface, on the self-excited oscillations of high-speed impinging planar jet. In order to investigate this phenomenon, a series of experiments have been performed using a high-speed impinging planar jet with varying nozzle thickness (h) and impingement distance (xo), for a single Mach number in the compressible flow regime. The test results reveal that the jet oscillation is controlled by a fluid-dynamic mechanism for small impingement distances, where the unstable mode of the jet is controlled by the impingement ratio. At larger impingement distances, the response is dominated by a fluid-resonant mechanism, in which the various hydrodynamic modes of the jet couple with different resonant acoustic modes occurring between the nozzle and the impingement surface. Within the fluid-resonant regime the system produces acoustic tones that are excited predominantly as a function of the impingement distance, with the nozzle thickness and impingement ratio having only minor effects on the tone frequency. Flow visualization images show that the same unstable mode is excited for multiple nozzle thicknesses at a constant impingement distance, despite the wide variations in associated impingement ratio.
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De Santiago, Oscar, and Luis San Andrés. "Dynamic Response of a Rotor-Integral Squeeze Film Damper to Couple Imbalances." In ASME Turbo Expo 2000: Power for Land, Sea, and Air. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/2000-gt-0388.
Abstract:
Squeeze film dampers (SFDs) are used in high speed rotating machinery to reduce rotor vibration amplitudes and to isolate transmitted loads through the bearing support structures. SFDs are also effective means to ameliorate destructive subsynchronous vibrations excited by hydrodynamic bearings, seals, impellers and other unknown sources. Modern jet engines demand lighter and flexible structures with compact components to obtain the largest power to weight ratios. This current trend makes evident rotordynamic phenomena that must be adequately addressed by dissipation elements such as SFDs. Integral squeeze film dampers (ISFDs) incorporating built in elastic supports are of reduced weight and length, offer accuracy of positioning, and a split segment construction allowing easier assembly, inspection and retrofit. Yet ISFDs require of extensive experimentation to verify their dynamic forced performance and to prove their reliability for applications on high performance turbomachinery. Measurements of the synchronous response of a test rotor supported on ISFDs and due to couple-imbalances are hereby presented. Masses inserted at two axial planes in the rotor and out of phase by 180° excite the second (conical) mode of vibration of the test rotor. Peak rotor responses at the second critical speeds, vertical and horizontal, allow the determination of amplification factors from which system damping coefficients for the rotor conical motions are extracted. The measurements verify the damping capacity of ISFDs to reduce (conical mode) rotor vibrations.
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Frederick, Mark, Joshua Dudash, Jacqueline O’Connor, Kiran Manoharan, Santosh Hemchandra, and Brian Brubaker. "Impact of PVC Dynamics on Shear Layer Response in a Swirling Jet." In ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64691.
Abstract:
Combustion instability, or the coupling between flame heat release rate oscillations and combustor acoustics, is a significant issue in the operation of gas turbine combustors. This coupling is often driven by oscillations in the flow field. Shear layer roll-up, in particular, has been shown to drive longitudinal combustion instability in a number of systems, including both laboratory and industrial combustors. One method for suppressing combustion instability would be to suppress the receptivity of the shear layer to acoustic oscillations, severing the coupling mechanism between the acoustics and the flame. Previous work suggested that the existence of a precessing vortex core (PVC) may suppress the receptivity of the shear layer, and the goal of this study is to first, confirm that this suppression is occurring, and second, understand the mechanism by which the PVC suppresses the shear layer receptivity. In this paper, we couple experiment with linear stability analysis to determine whether a PVC can suppress shear layer receptivity to longitudinal acoustic modes in a non-reacting swirling flow at a range of swirl numbers. The shear layer response to the longitudinal acoustic forcing manifests as an m = 0 mode since the acoustic field is axisymmetric. The PVC has been shown both in experiment and linear stability analysis to have m = 1 and m = −1 modal content. By comparing the relative magnitude of the m = 0 and m = −1,1 modes, we quantify the impact that the PVC has on the shear layer response. The mechanism for shear layer response is determined using companion forced response analysis, where the shear layer disturbance growth rates mirror the experimental results. Differences in shear layer thickness and azimuthal velocity profiles drive the suppression of the shear layer receptivity to acoustic forcing.
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Ku, Jerry C., Li Tong, and Paul S. Greenberg. "Measurements and Modeling of Soot Formation and Radiation in Microgravity Jet Diffusion Flames." In ASME 1996 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1996. http://dx.doi.org/10.1115/imece1996-0188.
Abstract:
Abstract This is a computational and experimental study for soot formation and radiative heat transfer in jet diffusion flames under normal gravity (1-g) and microgravity (0-g) conditions. Instantaneous soot volume fraction maps are measured using a full-field imaging absorption technique developed by the authors. A compact, self-contained drop rig is used for microgravity experiments in the 2.2-second drop tower facility at NASA Lewis Research Center. On modeling, we have coupled flame structure and soot formation models with detailed radiation transfer calculations. Favre-averaged boundary layer equations with a k-e-g turbulence model are used to predict the flow field, and a conserved scalar approach with an assumed β-pdf are used to predict gaseous species mole fraction. Scalar transport equations are used to describe soot volume fraction and number density distributions, with formation and oxidation terms modeled by one-step rate equations and thermophoretic effects included. An energy equation is included to couple flame structure and radiation analyses through iterations, neglecting turbulence-radiation interactions. The YIX solution for a finite cylindrical enclosure is used for radiative heat transfer calculations. The spectral absorption coefficient for soot aggregates is calculated from the Rayleigh solution using complex refractive index data from a Drude-Lorentz model. The exponential-wide-band model is used to calculate the spectral absorption coefficient for H2O and CO2. It is shown that, when compared to results from true spectral integration, the Rosseland mean absorption coefficient can provide reasonably accurate predictions for the type of flames studied. The soot formation model proposed by Moss, Syed, and Stewart seems to produce better fits to experimental data and more physically sound than the simpler model by Khan et al. Predicted soot volume fraction and temperature results agree well with published data for a normal gravity co-flow laminar flames and turbulent jet flames. Predicted soot volume fraction results also agree with our data for 1-g and 0-g laminar jet flames as well as 1-g turbulent jet flames.