This work is a multi-scale effort to confront the rapidly evolving threat of biological weapons attacks through improved bioaerosol surveillance, detection, and response capabilities. The effects of bioaerosol release characteristics, transport in the atmospheric surface layer, and implications for bioaerosol sampler design and real-time detection were studied to develop risk assessment and modeling tools to enhance our ability to respond to biological weapons attacks. A simple convection-diffusion-sedimentation model was formulated and used to simulate atmospheric bioaerosol dispersion. Model predictions suggest particles smaller than 60 micrometers in aerodynamic diameter (AD) are likely to be transported several kilometers from the source. A five fold increase in effective mass collection rate, a significant bioaerosol detection advantage, is projected for samplers designed to collect particles larger than the traditional limit of 10 micrometers AD when such particles are present in the source distribution. A family of dynamically scaled wetted-wall bioaerosol sampling cyclones (WWC) was studied to provide bioaerosol sampling capability under various threat scenarios. The effects of sampling environment, i.e. air conditions, and air flow rate on liquid recovery rate and response time were systematically studied. The discovery of a critical liquid input rate parameter enabled the description of all data with self-similar relationships. Empirical correlations were then integrated into system control algorithms to maintain microfluidic liquid output rates ideally suited for advanced biological detection technologies. Autonomous ambient air sampling with an output rate of 25 microliters per minute was achieved with open-loop control. This liquid output rate corresponds to a concentration rate on the order of 2,000,000, a substantial increase with respect to other commercially available bioaerosol samplers. Modeling of the WWC was performed to investigate the underlying physics of liquid recovery. The set of conservative equations governing multiphase heat and mass transfer within the WWC were formulated and solved numerically. Approximate solutions were derived for the special cases of adiabatic and isothermal conditions. The heat and mass transfer models were then used to supplement empirical correlations. The resulting semi-empirical models offer enhanced control over liquid concentration factor and further enable the WWC to be deployed as an autonomous bioaerosol sampler. / text

In this thesis, the ribbed ducts of the internal cooling passage in turbine blading are investigated to demonstrate the effects of high speed rotation. Rotation coupled with high temperature operating conditions alters the mean flow, turbulence, and heat transfer augmentation due to Coriolis and centrifugal buoyancy forces that arises from density stratification in the domain. Gas turbine engines operate in particle laden environments (sand, volcanic ash), and particulate matter ingested by the engine can make their way into the blade internal cooling passages over thousands of operating hours. These particulates can deposit on the walls of these cooling passages and degrade performance of the turbine blade. Large-Eddy Simulations (LES) with temperature dependent properties is used for turbulent flow and heat transfer in the ribbed cooling passages and Lagrangian tracking is used to calculate the particle trajectories together with a wall deposition model. The conditions used are Re=100,000, Rotation number, Ro = 0.0 and 0.2, and centrifugal Buoyancy parameters of Bo=0, 0.5, and 1.0. First, the independent effects of Coriolis and centrifugal buoyancy forces are investigated, with a focus on the additional augmentation obtained in heat transfer with the addition of centrifugal buoyancy. Coriolis forces are known to augment heat transfer at the trailing wall and attenuate the same at the leading wall. Phenomenological arguments stated that centrifugal buoyancy augments the effects of Coriolis forces in outward flow in the first pass while opposing the effect of Coriolis forces during inward flow in the second pass. In this study, it was found that in the first pass, centrifugal buoyancy had a greater effect in augmenting heat transfer at the trailing wall than in attenuating heat transfer at the leading wall. On the contrary, it aided heat transfer in the second half of the first pass at the leading wall by energizing the flow near the wall. Also, contrary to phenomenological arguments, inclusion of centrifugal buoyancy augmented heat transfer over Coriolis forces alone on both the leading and trailing walls of the second pass. Sand ingestion is then investigated, by injecting 200,000 particles in the size range of 0.5-175μm with 65% of the particles below 10 μm. Three duct wall temperatures are investigated, 950, 1000 and 1050 °C with an inlet temperature of flow and particles at 527 °C . The impingement, deposition levels, and impact characteristics are recorded as the particles move through the domain. It was found that the Coriolis force greatly increases deposition. This was made prevalent in the first pass, as 84% of the deposits in the domain occurred in the first pass for the rotating case, whereas only 27% of deposits occurred in the first pass for the stationary case with the majority of deposits occurring in the bend region. This was due to an increased interaction with the trailing wall in the rotating case whereas particles in the stationary case were allowed to remain in the mean flow and gain momentum, making rebounding from a wall during collision more likely than deposition. In contrast, the variation of wall temperatures caused little to no change in deposition levels. This was concluded to be a result of the high Reynolds number used in the flow. At high Reynolds numbers, the particles have a short residence times in the internal cooling circuit not allowing the flow and particles to heat up to the wall temperature. Overall, 87% of the injected particles deposited in the rotating duct whereas 58% deposited in the stationary duct. / Master of Science

La compréhension du fonctionnement des aquifères karstiques est un enjeu considérable au vu des structures complexes de ces réservoirs. La forte hétérogénéité des écoulements induit une grande vulnérabilité de ces milieux et des comportements variés au cours des crues en lien avec différents processus de recharge. Dans le Massif du Jura, les aquifères karstiques constituent la principale ressource en eau potable et posent la question de leur rôle dans la dégradation de la qualité de l'eau observée depuis plusieurs décennies. Cette thèse propose différentes approches complémentaires pour mieux comprendre les dynamiques de crues dans ces aquifères sous diverses conditions hydrologiques. Plusieurs systèmes karstiques du Massif du Jura, présentant des dimensions variables et dominés par des mécanismes de recharges distincts, sont caractérisés à partir de suivis physico-chimiques et hydrochimiques détaillés.Tout d'abord, les différents systèmes sont comparés à l'échelle du cycle hydrologique et à l'échelle saisonnière afin d'identifier les processus de recharge dominants (infiltrations localisées et/ou diffuses) ainsi que les signatures hydrochimiques caractéristiques (arrivées allochtones, autochtones et/ou anthropiques). Une étude comparative de deux systèmes met en avant la forte variabilité saisonnière de la réponse hydrochimique sur un système marqué par une recharge localisée importante. Les différents systèmes sont ensuite analysés à une échelle de temps plus fine afin de mieux comprendre les dynamiques de crues. Une crue intense d'automne a été ainsi comparée à de plus petites crues précédées par des périodes d'étiages importantes et marquées par des signatures hydrochimiques anthropiques significatives. A partir de ces résultats, la méthode EMMA (End-Member Mixing Analysis) est appliquée afin d'établir les principaux pôles hydrochirniques responsables des contributions caractéristiques des différents systèmes. Ensuite, au vu du transport important de matières en suspension au cours des crues dans ces aquifères, une partie de ce travail vise à mieux comprendre le rôle et l'impact de ces matières sur le transport dissous et colloïdal. Les éléments traces métalliques (ETM) sont utilisés afin de caractériser l'origine et la dynamique des transferts. Ils apparaissent alors comme des outils pertinents pour identifier des phénomènes de dépôts et de remobilisation de particules dans le système. Ces dynamiques s'observent à la fois sur le système de Fourbanne marqué par une infiltration localisée importante et sur le petit système du Dahon, caractérisé par une infiltration diffuse.Finalement, afin de mieux comprendre la variabilité spatio-temporelle des interactions qui ont lieu au cours des crues le long du conduit karstique, une nouvelle approche de modélisation est définit. Elle propose l'utilisation des équations de l'onde diffusante et d'advection-diffusion avec la même résolution mathématique (solution analytique d'Hayarni (1951)) en supposant une distribution uniforme des échanges le long du conduit. A partir d'une modélisation inverse, elle permet alors d'identifier et d'estimer les échanges en termes de flux hydriques et de flux massiques entre deux stations de mesure. Cette méthodologie est appliquée sur le système de Fourbanne le long de deux tronçons caractérisant (1) la zone non-saturée et (2) zone non-saturée et saturée. L'analyse de plusieurs crues permet d'observer des dynamiques d'échanges variées sur les deux tronçons. Elle permet ainsi d'établir un schéma de fonctionnement du système soulignant des interactions importantes dans la zone saturée et également le rôle de la zone non-saturée pour le stockage dans le système karstique.Ce travail de thèse propose donc un ensemble d'outils riches et complémentaires pour mieux comprendre les dynamiques de crues et montre l'importance de coupler l'analyse des processus hydrodynamiques et hydrochimiques afin de mieux déchiffrer le fonctionnement de ces aquifères. / The understanding of karst aquifer functioning is a major issue, given the complex structures of these reservoirs. The high heterogeneity of the flows induces a high vulnerability of these media and implies distinct behaviours during floods because of various infiltration processes. In the Jura Mountains, karst aquifers constitute the main source of water drinking supply and raise the question of their role in the degradation of water quality observed for several decades. This work uses complementary approaches to better understand the dynamics of floods in aquifers under various hydrological conditions. Several karst systems of the Jura Mountains, varying in size and characterized by distinct recharge processes, are investigated by detailed physico-chemical and hydrochemical monitoring.First, the different systems are compared at the hydrological cycle scale and at the seasonal scale to identify the dominant recharge processes (localized and/or diffuse infiltrations) as well as the characteristic hydrochemical signatures (allochtonous, autochthonous and/or anthropogenic). A comparative study of two systems with distinct recharge processes highlights the high seasonal variability of the hydrochemical response. The different systems are then analysed on a finer time scale to shed light on flood dynamics. An intense autumn flood was thus compared to smaller floods preceded by periods of significant low flow and marked by significant anthropogenic hydrochemical signatures. The EMMA (End-Member Mixing Analysis) method is applied to these results in order to establish the main hydrochemical end-members responsible for the characteristic contributions of the different systems.Then, considering the important transport of suspended matter during floods in these aquifers, part of this work aims to better understand the role and impact of these materials on dissolved and colloidal transport. Metal trace elements (ETM) are used to characterize the origin and transfer dynamics. These are relevant tools to identify the processes of storage and remobilization of the particles in the system. These dynamics are observed both on the Fourbanne system with an important localized infiltration, and on the small Dahon system, characterized by diffuse infiltration.Finally, in order to shed light on the spatio-temporal variability of the interactions that occur along the karst network during floods, a new modelling approach is defined. It is based upon the use of the diffusive wave and advection­diffusion equations with the same mathematical resolution (Hayami's analytical solution (1951)) assuming a uniform distribution of the exchanges along the reach. An inverse modelling approach allows to identify and estimate the exchanges in terms of water flows and solute between two measurement stations. This methodology is applied to the Fourbanne system on two sections characterizing (1) the unsaturated zone and (2) unsaturated and saturated zone. The analysis of several floods highlights the different exchange dynamics on the two sections. It thus makes it possible to establish a functioning scheme of the system, bringing to light the important interactions in the saturated zone and also the storage role of the unsaturated zone in the karst system.This work offers a set of rich and complementary tools to better characterize the dynamics of floods and shows the importance of coupling the analysis of the hydrodynamic and hydrochemical processes to better decipher the functioning of these aquifers.