The development and control of nanoscale properties is a major goal in science and technology; for the development of such technologies it is important that there are experimental techniques which allow the monitoring of development processes in real time and in a range of environments. With this in mind much effort has been invested in the development of surface sensitive optical probes. One such technique, reflection anisotropy spectroscopy (RAS), has been applied successfully to a number of different problems since its development in the mid 1980’s. RAS as a surface specific technique is very sensitive to small changes to surface morphology, electronic structure and molecular orientation. This makes RAS a useful technique to study nanoscale changes occurring at surfaces and it is applied here to three such systems, in an attempt to develop a better understanding of both the systems and the technique. Surface defects arising from thermal processing and etching of the sample are considered and are found to have a significant effect on both the electronic structure and the morphology of the surface. The time and temperature dependences of the RAS signatures allow the monitoring of surface dynamic processes. The deposition of a monolayer of adsorbate molecules onto the surface allows a new interface to be created. Monitoring the evolution of this surface during deposition provides information about both the substrate surface and the adsorba te covered surface; a theoretical framework has been outlined to show how the sources of anisotropy from multiple thin film layers combine to give a RAS signal. Azimuth dependent RAS (ADRAS) is known to provide information on surface symmetry and can be used to determine molecular orientation. There are also a number of other angles which affect the RA spectrum from a sample. A tilted molecule causes a breakdown in surface symmetry; this work shows how such an effect can be observed.

This thesis presents the continued development of micro optical phase detection instrumentation capable of measuring void fraction, interfacial area density, interfacial velocity and bubble sizes and their application to measurements in a high speed boundary layer. The instrumentation consists of micro sized sapphire tipped probes tailored to measure in the two-phase flow of air bubbles in water. Probe tips with geometries intended to maximize field life while minimizing intrusiveness were designed, fabricated and characterized. The characterization revealed that the active region of a probe tip can go beyond the highly sensitive 45 degree tip. Controlling the active length of the tips can be achieved through a combination of taper angles and 45 degree tip size, with larger tips having shorter active lengths. The full scale bubbly flow measurements were performed on a 6 m flat bottom survey boat. The aforementioned quantities were measured on bubbles naturally entrained at the bow of the boat. Probes were positioned at the bow of the boat, near the entrainment region and at the stern where the bubbles exit after having interacted with the high shear turbulent boundary layer. Experiments were conducted in fresh water, at the Coralville Lake, IA, and salt water, at the St. Andrews Bay and Gulf Coast near Panama City, FL. The results indicate that the bubbles interact significantly with the boundary layer. At low speeds, in fresh water, bubble accumulation and coalescence is evident by the presence of large bubbles at the stern. At high speeds, in both fresh and salt water, bubble breakup dominates and very small bubbles are produced near the hull of the boat. It was observed that salt water inhibits coalescence, even at low boat speeds. Void fraction was seen to increase with boat speeds above 10 knots and peaks near the wall. Bubble velocities show slip with the wall at all speeds and exhibit large RMS fluctuations, increasing near the wall.

Les colonnes à bulles sont largement utilisées dans les domaines du génie chimique et biologique, grâce à leur configuration simple, exempte de toute partie mobile. Néanmoins, leur extrapolation aux échelles industrielles engendre des modifications de l’hydrodynamique globale (vitesse du liquide, taille des bulles) qui sont encore difficile à prédire avec les outils numériques disponibles.La thèse a pour objectif d’établir une base de données sur l’évolution radiale et axiale de l’hydrodynamique locale (taux de vide, taille de bulles, vitesse liquide), dans différentes tailles de colonnes allant de 0.15 à 3 m de diamètre, pour des vitesses superficielles gaz comprises entre 3 et 35 cm/s, générant des taux de vide atteignant les 35%. Les mesures de taux de vide local, de vitesse de bulles et de la taille verticale des bulles sont réalisées à l’aide d’une sonde optique 1C. De plus, une nouvelle méthode pour mesurer la taille horizontale des bulles à fort taux de vide et en écoulement fortement multidirectionnel est proposée dans cette thèse. Cette méthode est basée sur la corrélation croisée spatiale de signaux provenant de deux sondes optiques placées parallèlement à la même élévation, et à une distance l’une de l’autre devant nécessairement être plus faibles que les bulles les plus petites présentes dans l’écoulement. Les mesures de taille de bulles sont validées en les comparant à un traitement d’images par endoscopie. Pour des vitesses superficielles de gaz supérieures à 9 cm/s, un bon accord est trouvé entre les trois méthodes (sonde optique 1C, corrélation croisée et endoscopie). La taille des bulles augmente légèrement lorsque la vitesse superficielle gaz augmente, par contre elle n’est pas impactée de manière significative par le diamètre des colonnes. Une plus grande ségrégation radiale est tout de même visible dans les plus grandes colonnes testées.Un modèle 1D radial développé pour un écoulement invariant le long de l’axe de la colonne est utilisé pour tester différents formalismes de forces de trainée, utilisant les données expérimentales de taille moyenne de bulles. Les simulations montrent que pour prédire correctement le flux gazeux expérimental, il est nécessaire d’introduire un « swarm factor » (Simonnet et al, 2008) diminuant le coefficient de trainée à fort taux de vide. De plus, des simulations 3D URANS avec Fluent® sont réalisées avec la loi de trainée validée par le modèle 1D précédemment cité. Un bon accord est observé entre les valeurs expérimentales et simulées des profils radiaux de taux de vide et de vitesse liquide, pour des diamètres de colonne allant de 0.4 m à 3 m, et pour des vitesses superficielle gaz de 3 à 35 cm/s. / Bubble columns reactors are widely used in chemical and biological engineering due to its simple configuration without mobile parts. However, the scale-up prediction of a bubble columns reactors is still a challenging process, due to the lack reliable experimental data and models.The present work aims to construct detailed database of the radial and axial evolution of local hydrodynamics properties (gas hold-up, bubble size and velocity, liquid velocity) acquired in several bubble columns in a scale factor of 20 (from 0.15 to 3 m in diameter), for a superficial gas velocity from 3 to 35 cm/s, yielding gas hold-ups up to 35 %. Measurements of local gas hold-up, bubble velocity and bubble vertical size are performed by a 1C mono-fiber optical probe. Moreover, a novel method to measure mean horizontal diameter of bubbles at high void fraction and in a multi-directional flow is proposed. This method is based in the spatial-cross correlation of signal of two optical probes placed parallel side by side, at a given distance from each other, at the same elevation in the column. The validation of the bubble size measurements are performed through a comparison of the results with an endoscopic imaging method. For superficial gas velocities higher than 9 cm/s, a good agreement is found between the three methods (1C mono-fiber optical probe, cross-correlation and endoscopic imaging). A slight increase is registered with the increase of the superficial gas velocity, however there is no significant variation with the column diameter.A 1-D radial model of a bubbly flow (Ueyama and Miyauchi, 1979) developed for a invariant flow along the column axis, is used to benchmark several classic formalisms of the drag force, using experimental average bubble size. Results show that to correctly predict the experimental gas flowrate, it is necessary to use a Swarm factor (Simonnet et al, 2008) that reduces the drag coefficient for high gas hold-up values. Moreover, Fluent® 3D URANS simulations are performed using the previously validated drag force formalism. A good agreement is found between experimental and simulated radial profiles of gas holdup and liquid velocity for column diameters ranging from 0.4 m up to 3 m in diameter in a range of superficial gas velocities from 3 cm/s to 35 cm/s.