Ce travail a pour objectif l’étude du tourbillon conique engendré à partir d’une maquette générique représentant un montant de baie de véhicule automobile. Cette structure tourbillonnaire est responsable de fortes fluctuations sur les vitres latérales et génère du bruit dans l’habitacle. Ces véhicules étant soumis à des vents turbulents, la sensibilité de la dynamique de cette structure tourbillonnaire à une turbulence amont a été étudiée, en plaçant une grille à l’entrée de la veine d’essais de la soufflerie.Les propriétés spatiales et temporelles des champs de vitesse et de pression pariétale ont été étudiées en associant simultanément la mesure de la vitesse par Stéréo-PIV haute fréquence à la mesure de pression pariétale fluctuante par capteurs déportés. Nous avons montré qu’un niveau modéré de turbulence amont (intensité : 6%) se traduit par une modification très importante de la dynamique du tourbillon et de la pression pariétale fluctuante associée. Notre conjecture est qu’en l’absence de turbulence externe, la contribution principale au Cp’ est liée à l’empreinte du coeur tourbillonnaire et du décollement secondaire induit. Au contraire, en présence de turbulence amont, la forte augmentation du Cp’ semble associée à une réponse globale de la structure tourbillonnaire.L’étude de la dynamique spatio-temporelle à partir des corrélations pression-vitesse a permis de mettre en évidence le couplage fort existant entre la dynamique de la nappe cisaillée et celle du coeur de la structure tourbillonnaire. Il existe ainsi une modulation de la fréquence de battement de la structure pilotée par la géométrie de la maquette et par les caractéristiques de la turbulence amont (intensité et échelle intégrale). / This work aims to study conical vortices generated from a generic model representing the A-pillar of an automotive vehicle. This vortex structure is responsible of strong fluctuations on the side window and generates noise in the cabin. As these vehicles are subjected to the turbulent wind, the sensitivity of vortex structure dynamics to an upstream turbulence was studied by adding a grid at the test section entrance of the wind tunnel.The spatial and temporal properties of the velocity fields and the wall pressure were studied by simultaneously combining High Speed Stereo-PIV and wall fluctuating pressure measurements with distant sensors. It is shown that a moderate level of upstream turbulence (6% of intensity) results in a very significant change of the vortex dynamics and the associated wall fluctuating pressure. Our assumption is that in the absence of external turbulence, the main Cp’ contributionis linked to the footprint of the vortex core and of the induced secondary separation. On the contrary, in the presence of upstream turbulence, the strong increase of Cp’ seems to be associated with a global response of the vortex structure. The study of the spatio-temporal dynamics withpressure-velocity correlations allowed highlighting the strong coupling between the dynamics ofthe shear layer and of the core of the vortex structure. Thus, there is a modulation of the flapping frequency of the vortex controlled by the geometry of the model and by the characteristics ofthe upstream turbulence (intensity and integral length scale).

Le séchage est une opération unitaire pratiquée depuis des millénaires pour laquelle les connaissances scientifiques sont encore très incomplètes. Il est cependant de plus en plus nécessaire de « bien » sécher afin d’atteindre une combinaison optimale du temps de séchage, de l’énergie consommée et surtout de la qualité du produit final. Ceci est d’autant plus vrai dans le cadre du séchage alimentaire où de nombreux produits sont très sensibles à la température et à la déshydratation. C’est le cas de la levure de boulanger dont la capacité à dégager du CO2, pour faire gonfler la pâte à pain par exemple, diminue très souvent lorsque le séchage est réalisé dans des mauvaises conditions opératoires. L’utilisation de séchoirs particuliers tels que les lits à jet coniques devrait permettre d’améliorer le séchage en terme d’efficacité et de qualité finale. L’objectif principal de cette thèse est de contribuer à mieux comprendre et modéliser le séchage de levures en lit à jet conique en utilisant une approche multi-échelles. <p>Le séchage d’un grain de levure isolé est caractérisé à l’aide d’un nouveau dispositif thermogravimétrique dans lequel il est possible de mesurer l’évolution des dimensions du grain ainsi que sa température de surface. Les résultats obtenus sont alors utilisé pour construire et valider un nouveau modèle du séchage d’un grain de levure basé sur l’existence de trois types d’eau et permettant de prédire l’évolution du contenu en eau et de la température du grain. L’analyse combinée du modèle et des résultats expérimentaux permet de mettre en avant que le rétrécissement des grains de levures au cours du séchage n’a pas d’impact significatif sur la vitesse de séchage et qu’il est essentiel de modéliser correctement la température du grain.<p>L’écoulement de solides dans le lit à jet conique est caractérisé expérimentalement au moyen de la technique de poursuite de particule radioactive (RPT). Un post-traitement des données brutes (évolution temporelle de la position du traceur) est développé pour déduire un certain nombre de paramètres liés à l’écoulement du solide :forme des régions du lit à jet (jet, anneau et fontaine), distributions de l’écoulement des solides entre les régions, distribution de temps de séjour des solides dans le lit, vitesses et débits moyens des solides, et taux de gaz dans le jet et l’anneau. Les résultats expérimentaux ont notamment permis de montrer que la forme du jet ne dépend quasiment pas de la vitesse d’injection de l’air; de même, le rapport du débit volumique de solides d’une région du lit à l’autre avec la vitesse moyenne du solide dans l’anneau donne une valeur constante pour une hauteur de lit stagnant donnée. Des corrélations empiriques sont également développées pour prédire les vitesses et débits moyens de solides ainsi que les temps de séjour moyens des solides dans les différentes régions du lit.<p>L’écoulement du gaz dans le lit à jet conique est caractérisé expérimentalement par la mesure des distributions de temps de séjour (RTD) du gaz dans le lit par l’injection et la détection d’un gaz radioactif dans le lit à jet en opération. L’existence d’un écoulement non négligeable du gaz dans l’anneau du lit est mise en évidence. Les vitesses moyennes du gaz dans le jet et l’anneau ainsi que la portion du débit total qui passe dans le jet sont déduites des courbes de RTD. Il est identifié que le gaz circule au moins deux fois plus vite dans le jet que dans l’anneau, ce qui mène à des échanges de matières entre un solide et le gaz plus intenses dans le jet que dans l’anneau.<p>Des expériences de séchage de levure sont réalisées dans un lit à jet conique afin de caractériser l’effet des conditions opératoires sur le séchage. Un nouveau modèle multi-échelles décrivant le séchage de levure en lit à jet est présenté; celui-ci est basé sur les résultats des caractérisations expérimentales et des modélisations du séchage d’un grain de levure isolé et de l’écoulement solide-gaz dans le lit à jet conique. Le modèle phénoménologique ne possède qu’un seul paramètre et permet de très bien reproduire les résultats des expériences de séchage de levure en lit à jet conique. Il tient notamment compte du fait que dans un lit à jet, la saturation de l’air en vapeur d’eau au passage du lit peut être un phénomène limitant pour la vitesse de séchage, surtout en début de séchage.<p>La caractérisation de l’évolution au cours du séchage de la capacité de la levure à dégager du CO2 dans une pâte à pain a également été réalisée pour un grain de levure isolé et pour le séchage en lit à jet conique. Des conclusions similaires sont présentées dans les deux cas. En effet, la dégradation de la levure est liée à l’enlèvement de l’eau intracellulaire (type D, fin du séchage en-dessous de contenu en eau d’environ 0,5 (d.b.)) et c’est avant tout la vitesse avec laquelle cette eau est enlevée qui contrôle la qualité finale du produit. L’enlèvement de l’eau intercellulaire (type E, début du séchage) n’a pas d’influence significative sur la dégradation de la levure. Dans tous les cas, la dégradation est amplifiée lorsque la température du solide dépasse 40°C.<p>/<p>Drying is a unit operation that is practiced since thousands of years and which for scientific knowledge is still very incomplete. However it is more and more necessary to dry « well » in order to reach an optimal combination between drying duration, consumed energy and also final product quality. This is even truer in the case of food drying involving a lot of products that are very sensitive to temperature and dehydration. Baker’s yeast often encounters a drastic decrease of its gassing power, which makes for instance inflate bread dough, when drying is operated in wrong conditions. Using special driers such as conical spouted beds should allow improving drying in terms of efficiency and final quality. The main objective of this thesis is to contribute to better understand and model Baker’s yeast drying in a conical spouted bed by using a multiscale approach.<p>Drying of a single Baker’s yeast pellet is characterised by using a new thermogravimetric set up where the evolution of the pellet dimensions and surface temperature can be measured during drying. The obtained results are then used to develop and validate a new model of the drying of a Baker’s yeast pellet. The model is based on the existence of three types of water in yeast and it allows predicting the evolution of the pellet’s moisture content and temperature during drying. The combined analysis of the model and the experimental results permits to put forward that pellet’s shrinkage during drying have no significant influence on the drying rate and that it is really essential to correctly model the pellet’s temperature.<p>Solid flow in the conical spouted bed is experimentally characterised by using a radioactive particle tracking technique (RPT). A post-treatment of rough data (time-evolution of the tracer position) is developed in order to predict a series of parameters linked to the solid flow: shape of the bed regions (spout, annulus and fountain), distributions of solid flow in the bed regions, residence time distribution of the solids in the bed, mean solids velocities and flowrates, and voidage in the spout and annulus. Experimental results allowed to show that the shape of the spout is nearly not influenced by inlet air velocity; also, the ratio of volumetric solid flowrate between the different regions of the bed and of the mean solids velocity in the annulus has a constant value for a given static bed height. Empirical correlations are also developed in order to predict the mean solids’ velocities and flowrates, and the mean residence time of the solids in each region of the bed.<p>Gas flow in the conical spouted bed is experimentally characterised by measuring gas residence time distributions (RTD) in the bed through the injection and detection of a radioactive gas tracer into the operated spouted bed. The existence of non-negligible gas flow in the annulus of the bed is highlighted. Mean gas velocities in the spout and annulus, and the part of the total gas flow going to the spout are deducted from the RTD curves. It is identified that gas moves at least twice faster in the spout than in the annulus, which leads to mass exchanges between solid and gas that are more intense in the spout than in the annulus.<p>Baker’s yeast drying experiments are done in a conical spouted bed in order to characterise the effects of operating conditions on drying. A new multiscale model, describing Baker’s yeast drying in conical spouted bed, is presented; it is based on experimental results and on the models of a single pellet drying and of gas-solid flows in the conical spouted bed. This phenomenological model has only one unknown parameter and permits reproducing the experimental results of Baker’s yeast drying in conical spouted bed. It takes into account the fact that, in a spouted bed, vapour saturation of the air during its residence time in the bed can be a limiting phenomena for the drying rate, especially in the beginning of the drying.<p>The characterisation of the evolution of the Baker’s yeast gassing power in a bread dough during the drying has also been done in the case of a single pellet drying and in the case of spouted bed drying. Similar conclusions are presented for both cases. Indeed, yeast degradation is linked to intracellular water removal (type D, end of the drying below a moisture content of around 0,5 (d.b.)) and it is mostly the rate of this water removal that controls the final quality of the product. Intercellular water removal (type E, beginning of the drying) has no significant influence on yeast degradation. In all the cases, degradation is amplified when solid temperature is higher than 40°C.<p> / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

The thesis deals with numerical modeling of planar Sierpinski monopole and modified Sierpinski monopole, outgoing from Sierpinski structure. Next, it focuses on modeling of the conical modified monopole and conical Sierpinski monopole created by transferring of modified structure to conical surface. The properties of these multi-band antennas are verified by simulations in CST Microwave Studio 2009 and compared with the results published in available literature. The conical Sierpinski monopole is then optimized according to specified criteria. The optimized antenna is designed and its properties are experimentally verified.

This master’s thesis describes the theoretical analysis of the Sierpinski triangle structure. On the basis of this structure, a planar version of the Sierpinski monopole is firstly designed. Then, by using a transfer of the planar motive to the conical surface, conical and cascade Sierpinski monopoles are designed. All simulations are calculated by CST Microwave Studio 2011. In the thesis, four types of cascade Sierpinski monopole are proposed. The investigated parameters are reflection coefficient, input impedance, radiation properties, polarization and bandwidth. The attention is primarily focused on the design and experimental verification of the selected conical shape cascade Sierpinski monopole set on the bands GSM 900, GSM 1800 and Wi-fi 2,4 GHz.

Light or photons can excite electrons in a molecule, leading to creation of electronically excited states. Such processes are ubiquitous in nature, such as, vision, photo-protection of DNA/RNA nucleobases, light harvesting, energy and charger transfer etc. This photoexcitation induces nuclear motion on the excited states, leading the excess energy to dissipate either non-radiatively via internal conversion back down to the ground state, isomerization, and dissociation, or radiatively via fluorescence and phosphorescence. In this dissertation, we investigate the non-radiative processes in organic chromophores that ensue in an ultrafast manner, mediated via conical intersections (CoIn). Description of such excited state processes generally require multi-reference treatment because of quasi-degeneracy near CoIns. Hence, most insight about these processes is typically gained by constructing potential energy surface (PES) using multi-reference electronic structure methods along important reaction coordinates. Nonetheless, the aforementioned static treatment fails to provide any dynamical information, such as, excited state lifetime, state populations, branching ratio, quantum yield etc. In this dissertation, we have gone beyond the static treatment by undertaking computationally expensive non-adiabatic excited state molecular dynamics simulations employing trajectory surface hopping (TSH) methodology on PESs created on-the-fly using multi-reference electronic structure methods. This allows us to compare theoretical results to experimental observables, when possible, strengthening the explanations underlying those processes. Our goal is to examine the effect of structure, and of electronic structure methods on the excited state dynamics. We have examined the non-adiabatic excited state dynamics of cis,cis-1,3-cyclooctadiene (cc-COD), a cyclic diene, in an effort to systematically compare and contrast the dynamics of cc-COD to that of other well studied conjugated molecules. Such exploration is very significant, since the majority of the molecules involved in natural photoexcited processes, include an ethylenic double bond or alternating double bonds creating conjugation. Our calculations have revealed ultrafast sub-ps decay for cc-COD, and have illustrated that the internal conversion dynamics is facilitated by CoIns, dominated by twisting of one of the double bonds and pyramidalization of one of the carbons of that double bond, similar to trans-1,3-butadiene and unlike 1,3-cyclohexadiene (CHD). Our high-level electronic structure calculations have also explained the features in the experimental time-resolved photoelectron spectrum of cc-COD. Another molecule of biological importance, uracil, was also investigated using TSH simulations, by systematically increasing dynamical correlation. We have found that the inclusion of dynamical correlation for uracil leads to an almost barrierless PES on S2, leading to a faster decay and no population trap on this state. Uracil also contains a double bond and the simulations have revealed that the ultrafast relaxation is dominated by an ethylenic twist and pyramidalization of a carbon of that bond, increasing importance of such nuclear motion in photoexcited molecular dynamics. A comparison of the molecules studied have illustrated that the rigid molecules, such as uracil, CHD, have a very local CoIn seam space, whereas cc-COD, which is flexible having many low frequency degrees of freedom, has a non-local or extended CoIn seam space. Overall, the work performed in this dissertation, elucidates the significance of structure and conjugation, in the photoinduced coupled electron-nuclear dynamics in organic molecules. / Chemistry

There are a number of global navigation satellite systems (GNSS), in use or planed, which are used for navigation on earth but also for autonomous navigation of satellites in low earth orbit (LEO). It would be desirable to also have autonomous navigation in geosynchronous earth orbit (GEO) to reduce costs and make it possible to get higher accuracy on the position of the satellite. One part of the navigation system is the GNSS antenna which is examined in this master thesis. The specifications of the antenna were first decided and then three antenna alternatives were investigated in greater detail: a monofilar helix antenna, a three element circular array antenna and a twelve element circular array antenna. The result was that they would all work as a GNSS antenna in GEO but none could be judged to be the best under all circumstances. The size requirement for the mission and the used GNSS receiver would primarily decide which fits the mission best. / Det finns ett antal världstäckande navigeringssystem (GNSS), i användning och planerade, som används för navigation på jorden fast också för autonom navigation för satelliter i låg bana runt jorden. Det skulle också vara önskvärt att använda autonom navigation för satelliter i geostationär omloppsbana (GEO) för att reducera kostnaden och få högre positions noggrannhet. En del av navigationssystemet är GNSS antennen vilken är undersökt i detta examensarbete. Specifikationerna för antennen bestämdes först och sedan undersöktes tre olika antennalternativ i detalj: en monofilär helixantenn, en tre elements cirkulär gruppantenn och en tolv elements cirkulär gruppantenn. Resultatet var att alla alternativen skulle fungera som en GNSS antenn i GEO-bana fast inget av alternativen är bäst i alla förhållanden. Storlekskraven för uppdraget och vilken GNSS mottagare som skall användas påverkar vilket av alternativen som passar uppdraget bäst.

Asphalt and concrete reclamation machines are used to cut roadways when a repair is required. The performance of these machines can affect the quality of road repairs, and cost/profitability for both contractors and governments. We believe that several performance characteristics in reclamation machines are governed by the placement and pattern of cutting picks on the cutter head. Previous studies, focused on mining and excavation applications, have shown strong correlation between placement and wear. The following study employs a screening experiment (observational study) to find significant contributors to tool wear, in applications of asphalt milling or reclamation. We have found that picks fail by two primary modes: tip breakage, and body abrasive wear. Results indicate that the circumferential spacing of a bit, relative to neighboring bits, has the strongest effect on tip breakage. We have also shown that bit skew angle has a large positive effect on body abrasive wear.

This thesis discusses the development and application of theoretical and computational methods to study three-body processes. The main focus is on the calculation of three-body resonances and bound states. This broadly includes the study of Efimov states and resonances, three-body shape resonances, three-body Feshbach resonances, three-body pre-dissociated states in systems with a conical intersection, and the calculation of three-body recombination rate coefficients. The method was applied to a number of systems. A chapter of the thesis is dedicated to the related study of deriving correlation diagrams for three-body states before and after a three-body collision. More specifically, the thesis discusses the calculation of the H+H+H three-body recombination rate coefficient using the developed method. Additionally, we discuss a conceptually simple and effective diabatization procedure for the calculation of pre-dissociated vibrational states for a system with a conical intersection. We apply the method to H_3, where the quantum molecular dynamics are notoriously difficult and where non-adiabatic couplings are important, and a correct description of the geometric phase associated with the diabatic representation is crucial for an accurate representation of these couplings. With our approach, we were also able to calculate Efimov-type resonances. The calculations of bound states and resonances were performed by formulating the problem in hyperspherical coordinates, and obtaining three-body eigenstates and eigen-energies by applying the hyperspherical adiabatic separation and the slow variable discretization. We employed the complex absorbing potential to calculate resonance energies and lifetimes, and introduce an uniquely defined diabatization procedure to treat X_3 molecules with a conical intersection. The proposed approach is general enough to be applied to problems in nuclear, atomic, molecular and astrophysics.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第23686号 / 理博第4776号 / 新制||理||1684(附属図書館) / 京都大学大学院理学研究科数学・数理解析専攻 / (主査)教授 並河 良典, 教授 玉川 安騎男, 教授 望月 拓郎 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

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