Biogas is a renewable gaseous fuel with low calorific value and a low burning velocity. This burning characteristic makes stabilizing biogas flame difficult especially in high flow velocity applications, and hence presenting a real challenge for power generation systems. This thesis presents an experimental investigation of the effect of burner geometry (i.e., fuel nozzle geometry and swirl strength of the co-airflow) on the stability limits of a turbulent non-premixed biogas surrogate flame. Three different co-airflow swirl strengths (S = 0, 0.31, 0.79) were implemented using swirl generators with vane angle of 0º, 25º and 50º, respectively. Six different fuel nozzle geometries were used in order to study the effect of fuel jet centerline velocity on the stability limits of a low swirling (i.e., 25º) non-premixed biogas flame. Moreover, the biogas surrogate fuel composition was kept constant (60% CH4 and 40% CO2 by volume) using a mixture of pure methane and carbon dioxide gases. The results of the effect of co-airflow swirl strength on the stability limits of biogas flame revealed that the swirl plays an important role on both the flame mode and its stability limits for both attached and lifted flames. The experimental results revealed that at low swirl strength the attached flame lifts off and stabilizes at a distance above the burner, while at high swirl strength the flame remains attached but shortens and burns blue. Overall, the high swirl attached flame was found to stabilize over a wider range of flow conditions in comparison to the attached and lifted flame produced by low swirl. Importantly, the central fuel jet characteristics (induced by varying the fuel nozzle geometry) were found to drastically influence the upper and lower blowout limits of the low swirl biogas lifted flame, while multi-hole fuel nozzle geometry was found to significantly enhance the stability ranges. 2D PIV data was used to explain the stability limits and the experimental flame results were used to propose semi-empirical correlations capable of describing the turbulent biogas blowout stability limits. / October 2016

Submitted by Marcos Anselmo (marcos.anselmo@unipampa.edu.br) on 2018-09-28T14:54:49Z No. of bitstreams: 1 BIBIANA RIBAS.pdf: 831752 bytes, checksum: 996820e0c99836629d4fd8d1881772d4 (MD5) / Approved for entry into archive by Marcos Anselmo (marcos.anselmo@unipampa.edu.br) on 2018-09-28T14:55:06Z (GMT) No. of bitstreams: 1 BIBIANA RIBAS.pdf: 831752 bytes, checksum: 996820e0c99836629d4fd8d1881772d4 (MD5) / Made available in DSpace on 2018-09-28T14:55:06Z (GMT). No. of bitstreams: 1 BIBIANA RIBAS.pdf: 831752 bytes, checksum: 996820e0c99836629d4fd8d1881772d4 (MD5) Previous issue date: 2017-12-08 / Devido à grande necessidade em aumentar o material genético nos bovinos, as técnicas OPU/PIV vêm sendo aplicadas em larga escala com a finalidade de se obter um maior número de produtos nascidos por ano de fêmeas selecionadas. No entanto, alguns animais apresentam um baixo número de folículos disponíveis para a OPU, enquanto outros apresentam uma baixa taxa de conversão de oócitos em embriões. Neste contexto trabalhos que busquem maximizar os resultados de OPU/PIV são essenciais. Uma das alternativas é manipular farmacologicamente o desenvolvimento folicular para obter oócitos mais competentes para a fecundação in vitro e desenvolvimento embrionário. Por isso, o objetivo deste estudo foi avaliar o efeito de diferentes doses de gonadotrofina coriônica equina (eCG) em um protocolo prévio à OPU, sobre o desenvolvimento folicular, número e qualidade dos oócitos recuperados assim como potencial de fecundação e desenvolvimento embrionário in vitro. Dezesseis vacas doadoras Braford foram submetidas a 4 sessões de OPU com intervalo de 15 dias entre cada aspiração (n=16 por tratamento; cross over), para avaliar o efeito da dose de eCG as doadoras foram dividas de acordo com os respectivos tratamentos (Controle = zero, eCG200 = 200UI de eCG, eCG400 = 400UI de eCG e eCG800 = 800UI de eCG). No início do protocolo de sincronização (D0), as doadoras receberam 2 mg de benzoato de estradiol IM, 12,5 mg de dinoprost trometamina IM e um dispositivo de liberação lenta de P4 intravaginal. No dia 3, as doadoras receberam uma dose de eCG de acordo com cada tratamento e no dia 6, o dispositivo de P4 foi removido e as doadoras submetidas a OPU. Antes da OPU, os vii folículos ovarianos foram visualizados, mensurados e classificados de acordo com o diâmetro em pequenos (<6mm), médios (6-10mm) e grandes (>10mm). Após a OPU, os oócitos viáveis de cada vaca foram levados a MIV e FIV em grupos de acordo com os tratamentos. A MIV foi realizada durante 24h à 39°C em TCM 199 modificado. Para a fecundação in vitro, os espermatozoides de um touro Bos taurus de fertilidade comprovada foram selecionados por gradientes de Percoll e co-incubados com os oócitos por 18h. Após a FIV, 50% dos prováveis zigotos foram avaliados quanto à taxa de fecundação por epifluorescência. O restante dos oócitos foram transferidos para gotas de SOFaaci e cultivados in vitro para avaliação da taxa de clivagem, momento da primeira clivagem e número de células às 48 horas em um sistema de monitoramento embrionário. As análises estatísticas foram realizadas com ANOVA e as médias comparadas pelo teste de Tukey (P<0,05). Não houve diferença no número de folículos, quantidade e qualidade morfológica dos oócitos obtidos entre os tratamentos (P <0,05). A taxa de recuperação de oócitos foi semelhante entre os grupos tratados com eCG, porém, inferior ao grupo Controle (p<0,0001). No entanto, o grupo eCG800 apresentou maior número de folículos médios e grandes (>6mm e >10mm; P <0,00001). Adicionalmente o grupo eCG800 apresentou maior taxa de fecundação normal (54,3±8,5) e menor taxa de polispermia (5.7±4.0) que os demais grupos (P < 0,05). Os grupos eCG800 e Controle tiveram maior taxa de clivagem que os demais tratamentos, 68,6±7,9 e 75,6±6,8, respectivamente. Não houve diferença no momento da primeira clivagem e no número médio de células às 48 h entre os tratamentos. Com base nestes dados, pode-se concluir que a dose de 800UI de eCG aumentou a proporção de folículos >6mm, proporcionando a maior taxa de fecundação normal e uma redução na taxa de polispermia em relação ao Controle e as demais doses de eCG, sem prejuízos a cinética de desenvolvimento embrionário até 48 horas. / Due to the great need to increase the genetic material in cattle, the OPU / PIV techniques have been applied in a large scale in order to obtain a larger number of products born per year of selected females. However, some animals have a low number of follicles available for OPU, while others have a low rate of oocyte conversion in embryos. In this context, works that seek to maximize OPU / PIV results are essential. One of the alternatives is to pharmacologically manipulate follicular development to obtain more competent oocytes for in vitro fertilization and embryonic development. Therefore, the objective of this study was to evaluate the effect of different doses of equine Chorionic Gonadotrophin (eCG) on a protocol prior to OPU, on the follicular development, number and quality of oocytes recovered as well as potential for fertilization and in vitro embryo development. Sixteen Braford donor cows were submitted to 4 OPU sessions with a 15 day interval between each aspiration (n = 16 per treatment, cross over), to evaluate the effect of the eCG dose the donors were divided according to the respective treatments (Control = zero, eCG200 = 200UI of eCG, eCG400 = 400UI of eCG, and eCG800 = 800UI of eCG). At the beginning of the synchronization protocol (D0), the donors received 2 mg of estradiol IM benzoate, 12.5 mg of dinoprost tromethamine IM and a slow intravaginal P4 release device. On day 3, the donors were given a dose of eCG according to each treatment and on day 6, the P4 device was removed and the donors were subjected to OPU. Before OPU, ovarian follicles were visualized, measured and classified according to the diameter in small (< 6 mm), medium (6-10 mm) and large (> 10 mm). After OPU, viable ix oocytes from each cow were taken to IVM and IVF in groups according to treatments. IVM was performed for 24 hours at 39°C in modified TCM 199. For in vitro fertilization, the sperm of a Bos taurus bull of proven fertility were selected by Percoll gradients and co-incubated with the oocytes for 18 h. After IVF, 50% of probable zygotes were evaluated for fertilization rate by epifluorescence. The remaining oocytes were transferred to drops of SOFaaci and cultured in vitro for evaluation of the cleavage rate, time of the first cleavage and cell number at 48 hours in an embryonic monitoring system. Statistical analyzes were performed using ANOVA and the means were compared by the Tukey test (P < 0.05). There was no difference in the number of follicles, quantity and morphological quality of the oocytes obtained between the treatments (P < 0.05). The oocyte recovery rate was similar between the eCG treated groups, but lower than the Control (p < 0.001). However, the eCG800 had a greater number of medium and large follicles (> 6 mm and > 10 mm, P <0.00001). In addition, the eCG800 had a higher normal fertilization rate (54.3 ± 8.5) and a lower rate of polyspermy (5.7 ± 4.0) than the other groups (P < 0.05). The eCG800 and Control had a higher cleavage rate than the other treatments (68.6 ± 7.9 and 75.6 ± 6.8), respectively. There was no difference at the time of the first cleavage and in the average number of cells at 48 h between treatments. Based on these data, it can be concluded that the dose of 800UI of eCG increased the proportion of follicles > 6mm, providing the highest rate of normal fertilization and a reduction in the rate of polyspermia in relation to Control and the other doses of eCG, without impairing the kinetics of embryonic development until at 48 hours.

This thesis is a study of the swimming locomotion of the polychaete worm, Nereis diversicolor. Previous research has shown that there are two distinct jet-like flow regions in the wake of a swimming polychaete worm (Hesselberg 2006). In the first section of this thesis, this flow pattern is studied in greater detail using a high resolution particle image velocimetry (PIV) technique. A small region close to the wave crest of the undulating worm is recorded and the fluid velocity vector fields are plotted. The close-up PIV results show how the jet-like fluid pattern is formed due to the action both of a single sweeping parapodium and to the interaction between adjacent parapodia, proving for the first time that Gray’s (1939) explanation of the propulsion mechanics is in fact correct. The second part of this thesis is focused on the pumping action of the polychaete worm, a behaviour adopted by the worms to create a flow of nutrients through their burrows. Particle image velocimetry (PIV) experiments were performed on tethered polychaete worms, Nereis diversicolor. The tethered worms moved in a gait which was different from that of freely swimming ones. They used a much smaller body wave amplitude, pumping liquid with very high efficiency by cooperative movement of their body and parapodia. In the third part of the thesis, a mechanical model was designed and built. The model consisted of a series of paddle units. Each paddle was driven by a servo motor. Breugem (2008) did a CFD simulation of the paddle model. Similar fluid patterns were generated by the physical model. Reversed flow was found at low Reynolds number (Re) and higher Re situations. The flow direction could be controlled by simply adjusting the beating frequency of paddles. The mechanical model is not sufficient to mimic the pumping locomotion of the worms due to absence of an undulatory movement. The pumping efficiency is low compared to pumping worms.

L’effet Biefeld-Brown, du nom de ses découvreurs dans les années 1920, désigne la force électrohydrodynamique (EHD) s’appliquant sur deux électrodes sous haute tension dans l’air. Si l’origine de cette force a pu faire l’objet de certaines spéculations, il est aujourd'hui admis qu’elle repose sur l’accélération par un fort champ électrique d’un volume d’air partiellement ionisé. Cet effet aussi appelé vent ionique intéresse diverses applications : contrôle actif d’écoulement, augmentation du transfert de chaleur par convection forcée, séchage de denrées alimentaires ou encore la propulsion. Cette thèse, présente une étude expérimentale, théorique et numérique du vent ionique dans une configuration modèle à deux électrodes parallèles. Le faible rendement du vent ionique l’a écarté des applications à la propulsion mais des expériences récentes menées en 2013 montrent qu’il permet d’atteindre un rapport poussée/puissance étonnement élevé. Nous montrons dans une première partie, à partir de mesures et de considérations aérodynamique générales que la poussée générée pourrait suffire à contrebalancer la force de traînée pour certains aéronefs ultra-légers. Ces mesures ont permis de quantifier la force EHD et sa dépendance avec la géométrie des électrodes. En outre, la meilleure configuration à deux collecteurs peut produire une poussée presque deux fois plus importante qu’une configuration avec un seul collecteur, à tension fixée. Ces premiers résultats ont été affinés dans un second temps par les mesures PIV qui ont permis la reconstruction de l’écoulement et du champ de force entre les électrodes. Les vitesses mesurées dépassent rarement 3 m/s, et la force volumique est de l’ordre de 10 N/m 3. L’origine physique de la configuration optimale à deux collecteurs a été éclaircie par la mise en évidence des structures de sillages et de leurs effets instationnaires. Par ailleurs, une analyse théorique générale de la force propulsive nous a permis de confirmer sa dépendance explicite avec le rapport courant sur mobilité ionique. Le courant étant directement lié à la physique de la décharge couronne, la seconde partie de la thèse s’est concentrée sur son analyse théorique et numérique. Une analyse asymptotique a ainsi permis de trouver une expression analytique du champ électrique critique et de la caractéristique courant-tension permettant de connaître l’influence de la densité du gaz et de sa composition sur le courant produit dans des électrodes concentriques. Cette approche asymptotique a été associée à une formulation de décomposition de domaine dans le cadre d’une discrétisation par éléments finis pour analyser des configurations plus générales. Une résolution itérative du système d’équations stationnaires non-linéaire couplées par méthode de Newton est proposée, testée et validée. Cette méthode peut être étendue à des géométries plus complexes, permettant ainsi d’obtenir une condition d’injection des charges prenant en compte la physique complexe de la décharge.

The probability of a fire occurring in space vehicles and facilities is amplified by the amounts of electrical equipment used. Additionally, the lack of egress for space personnel and irreplaceable resources used aboard space vehicles and facilities require a rapid response of a suppression system and quick extinguishment. Current experimental means that exist to gather data in space vehicles and facilities are limited by both size of the experiment and cost. Thus, more economical solutions must be considered. The aim of this research was to develop a reliable and inexpensive methodology for the prediction of flame extinction and suppression in any three-dimensional environment. This project was split into two parts. Part one included the identification and validation of a computational model for the prediction of gas dispersion. Part two involved the development of an analytical parameter for predicting flame extinction. For model validation, an experimental apparatus was constructed. The experimental apparatus was one-eighth of the volume of electronics racks found aboard typical space facilities. The experimental apparatus allowed for the addition of parallel plates to increase the complexity of the geometry. Data acquisition consisted of gas concentration measurements through planar laser induced fluorescence (PLIF) of nitrogen dioxide and velocity field measurements through particle image velocimetry (PIV). A theoretical framework for a generalized Damköhler number for the prediction of local flame extinction was also developed. Based on complexities in this parameter, the computational code FLUENT was determined to be the ideal means for predicting this quantity. The concentration and velocity field measurements provided validation data for the modelling analysis. Comparison of the modelling analysis with experimental data demonstrated that the FLUENT code adequately predicted the transport of gas to a remote location. The 5 FLUENT code was also used to predict gas transport at microgravity conditions. The model demonstrated that buoyancy decreases the time to achieve higher gas concentrations between the parallel plates. As an example of the use of this methodology for a combustion scenario, the model was used to predict flame extinction in a blow-off case (i.e., rapid increase in strain rate) and localized flame extinction (i.e., flame shrinking) in a low-strain dilution case with carbon dioxide over time. The model predictions demonstrated the potential of this methodology with a Damköhler number for the prediction of extinction in three-dimensional environments.

Particle Image Velocimetry (PIV) based pressure field calculation is becoming increasingly popular in experimental fluid dynamics due to its non-intrusive nature. Errors propagated from PIV results to pressure field calculations are unavoidable, and in most cases, non-negligible. However, the specific dynamics of this error propagation process have not been unveiled. This dissertation examines both why and how errors in the experimental data are propagated to the pressure field by direct analysis of the pressure Poisson equation. Error in the pressure calculations are bounded with the error level of the experimental data. The error bounds quantitatively explain why and how many factors (i.e., geometry and length scale of the flow domain, type of boundary conditions) determine the resulting error propagation. The reason that the type of flow and profile of the error matter to the error propagation is also qualitatively illustrated. Numerical and experimental validations are conducted to verify these results. The results and framework introduced in this research can be used to guide the optimization of the experimental design, and potentially estimate the error in the reconstructed pressure field before performing PIV experiments.

According to the American Heart Association about 795,000 people suffer a stroke each year. Of those strokes almost 140,000 are fatal; this makes Stroke the third leading cause of death in the United States behind coronary heart disease and cancer. Hemorrhagic strokes are caused when an artery in the brain ruptures, such as a ruptured aneurysm. One possible treatment for cerebral aneurysm is a porous tubular structure, similar to a stent, called a flow diverter. A flow diverter can be placed across the neck of a cerebral aneurysm to induce the cessation of flow and initiate the formation of an intra-aneurysmal thrombosis. This excludes the aneurysm from the parent artery and returns the flow of blood to normal. The process of flow diversion alone has been shown to take months to fully exclude the aneurysm. It is possible however with an adjuvant therapy called photothrombosis to accelerate this process so that the aneurysm is excluded within minutes. Previous flow diverting devices have been analyzed to determine optimal characteristics, such as braiding angle and wire diameter. From this information a new optimized device was designed and is now in the process of being tested. In order to evaluate the effect of the device, a model must be created. One such model is the rabbit elastase induced aneurysm, which was characterized so that elastomer models could be created for in vitro studies. Particle Image Velocimetry (PIV) is a method of analysis that utilizes very small glass spheres (between 8 mu m and 12 mu m in diameter) to determine the velocity vectors of fluid flow in an in vitro model. These velocities can be used to calculate hydrodynamic circulation and kinetic energy inside an elastomer model of the elastase induced aneurysm. By comparing these values inside the aneurysm with values for previously developed diverters and a control without a diverter, it can be shown that despite changes in the braiding angle and individual wire thickness that the behavior of the devices is not significantly different (P > 0.05). Flow diversion is also being used in concert with photothrombosis. A flow diverter is used to exclude the neck remnant from the parent vessel and to provide a scaffold for the remodeling of the neck. This combination of techniques allows for very fast and near complete occlusion of the aneurysm thereby excluding the aneurysm from the parent vessel and eliminating the risk of a rupture.

This study presents laboratory observations of flow characteristics for regular waves passing a rectangular barge in a two dimensional wave tank. The rectangular barge was fixed and free to roll (one degree of freedom) in a beam sea. Particle image velocimetry (PIV) was employed to measure the velocity field in the vicinity of the structure. The mean velocity and turbulence properties were obtained by phase-averaging the velocity profiles from repeated test runs. The quantitative flow characteristics were represented to elucidate the coupled interactions between the regular wave and the barge in roll motion or fixed condition. Additionally, the turbulence properties including the turbulence length scale and the turbulent kinetic energy budget were investigated to characterize the flow pattern due to the wave interaction. Because all the data including wave elevations, roll motion, and dynamic pressure were synchronized with velocity profiles, the results between the roll motion and the fixed condition were compared. The viscous effects due to the flow separation depend on the relative relation between the wave water particle motion and the roll motion of the barge. The viscous damping mechanism that reduces the roll motion at the roll natural period wave is illustrated. It shows that the vortex flow was mainly induced by the roll motion. For wave periods longer than the roll natural period, the flow was separated in different directions accompanying the roll natural period wave. The longer waves may help the roll motion with the vortex flow predominantly separated by the wave water particle motion rather than the barge motion. This may be called the viscous exciting effect. Moreover, the variations of dynamic pressures near the corners were measured and analyzed along with the viscous effect for both the roll motion and the fixed barge cases.

Cette étude porte sur l'utilisation conjointe (appelée ” couplage ”) de modèle de turbulence à grandes échelles LES (Large Eddy Simulation) et du modèle multiphasique VOF (Volume of Fluid). Cette utilisation conjointe est nécessaire dans de nombreuses applications industrielles comme celles de l'automobile où l'on recherche par exemple à évaluer les prestations diphasiques de l'auvent liées au phénomène d'entraînement et d'ingestion d'une nappe d'eau par le HVAC (système d'air conditionné). Cependant, l'utilisation conjointe de ces méthodes nécessite un traitement particulier de la turbulence proche de la surface liquide afin de reproduire convenablement la quantité de mouvement transmise depuis la phase gazeuse, motrice, jusque dans la phase liquide. Basée sur une approche numérique et expérimentale, notre étude est articulée autour de trois axes. Tout d'abord, le développement de techniques de mesures spécifiques pour l'étude expérimentale de notre problématique: le LeDaR pour mesurer les déformées d'une interface et la PIV d'interface afin d'accéder aux champs de vitesse et de turbulence dans chacune des deux phases. Le second axe est la constitution d'une base de données expérimentales sur une configuration de type jet impactant sur une surface liquide représentative des phénomènes rencontrés dans l'auvent. Enfin, le troisième axe de travail est l'évaluation des modèles existants dans le code Ansys Fluent et à partir de cette analyse le développement et la validation de modèles de couplage LES-VOF. L'évaluation des modèles développés a permis de valider une stratégie de calcul adaptée aux simulations de l'entraînement d'une surface d'eau par un écoulement d'air turbulent.

Experiments were conducted in a free-surface, re-circulating water channel to determine the dependence of spanwise flow uniformity in the near wake of a circular cylinder on the end conditions using Particle Image Velocimetry. The Reynolds number was 10,000. The end conditions consisted of plates with different leading edge geometries and configurations. A cylinder bounded by two endplates with sharp leading edge geometry generated the most uniform near wake. The horseshoe vortex dynamics in the cylinder/ wall and cylinder/endplate junctions were also studied. Upstream flow separation significantly altered the behavior of the horse shoe vortices. Periodic horse shoe vortex oscillation was found for experiments with the upstream flow attached; this periodic oscillation was disrupted with the presence of upstream flow separation. The endplate leading edge distance was also investigated. The oscillation frequency of the horse shoe vortex system was found to decrease with increasing leading edge distance.