Title: Flow and diffusion characteristics inside the urban area Author: Hana Chaloupecká Department: Department of meteorology and enviroment protection Supervisor: prof. RNDr. Zbyněk Jaňour, DrSc., IT AS CR, v. v. i. Supervisor's e - mail: janour@it.cas.cz Abstract: Uniqueness of different towns, consists of various shapes of buildings. The main topic of this work is to compare concentration diffusion within groups of buildings of various types. We pursued houses made of single blocks of two different lengths - they were placed parallel or in courtyards. For research of pollution diffusion within the housing estates a method of physical modelling has been used. For this purpose we summarized a theory of atmospheric boundary layer and physical modelling at first. Then we pursued experiments. Measuring took place in a model in scale 1 : 300 inside an aerodynamic wind tunnel of the Institute of Thermomechanics AS in Nový Knín. We checked out the requirements placed on similarity of the real boundary layer and boundary layer modelled in the tunnel. By the measuring of concentration in urban areas we weren't watching a plume from the pollution source but we were studying an inversion task. We measured concentrations in two fixed points from different point sources inside the defined areas. A sensitivity of...

This master thesis treats the modelling of a common-rail direct fuel injection system where pressure generation is decoupled from the injection process. It has been shown that the fuel pressure plays a vital role for the general performance of the engine, affecting both emissions and efficiency, and it is carefully regulated to achieve optimal performance at different operating points. In an attempt to facilitate the development of the responsible control algorithms, a simulation framework has been requested. A model describing the complete work cycle of the high-pressure fuel system is developed and implemented in a Simulink environment. It is to a large extent based on the underlying physics and constructed in a modular manner, which allows for different engine configurations to be simulated. The modelled pressure signal is compared to experimental data at different operating points with promising results in capturing the transient behaviour from a low-level perspective. Additionally, it manages to replicate some of the pressure oscillations which has been observed in the real system and it shows good response to changes in the input signals. However, there are some areas which are subject to improvement since capturing the static pressure levels over longer drive cycles has proved to be a difficult task. Overall, the developed model serves as a starting point for future development and validation of control algorithms.

Une nouvelle architecture d’Imagerie Flash Laser, appelée imagerie flash laser mosaïque (IFLM) consistant àvisualiser une scène par acquisition rapide de petites zones ou imagettes a été développée à l’ONERA. Par rapport àl’imagerie Flash laser traditionnelle qui acquiert en une seule fois toute la scène, cette technique permet d’augmenterle niveau de l’éclairement sur chaque imagette mais nécessite de couvrir l’ensemble de la scène d’étude avec unehaute cadence d’échantillonnage spatiale. Cette thèse a pour but d’évaluer les performances de ce nouveau conceptpuis de les comparer à l’imagerie flash laser classique. Dans une première étape, un simulateur complet d’IFLM (Modèle de formation d’image incluant les algorithmes de reconstruction de la scène) a été développé afin de synthétiser tous les phénomènes intervenant dans la formation des images acquises par la caméra puis de réaliser les traitements de restauration nécessaires afin de s’affranchir des artefacts introduits par cette technique. La simulation des images en entrée instrument prend en compte la formedu faisceau de la source, le type de balayage, le canal de propagation (transmission atmosphérique et turbulence) etenfin des bruits instrumentaux. Afin de reconstituer une image complète de la scène à partir des imagettes, trois méthodesde restauration ont été comparées montrant l’apport de notre méthode d’optimisation avec contrainte RL1L2.Dans une seconde étape, ce simulateur bout-en-bout a été utilisé afin de sélectionner le balayage optimal dufaisceau laser pour obtenir la meilleure qualité d’image. Nous avons montré qu’un balayage en quinconce était préférableà un balayage en ligne. Dans une troisième étape, les performances en termes de rapport signal-à-bruit et de contraste ont été évaluées et comparées à des images acquises par imagerie flash laser classique. Les résultats obtenus sur des images synthétiquesont montré que les performances entre ces deux techniques étaient comparables. Enfin, une analyse est menée sur l’étude des performances d’un tel système en tenant compte des technologies disponibles. Compte tenu des caractéristiques actuelles des sources laser et détecteurs, l’imagerie flash laser mosaïque montre son intérêt lorsqu’il faut couvrir un large champ de la scène présentant de faibles évolutions temporelles. / Flash active imaging can be used for surveillance or target identification at long range and Iow visibility conditions. Its principle is based on the illumination of a scene With a pulsed laser which is then backscattered to the sensor. The signal to noise ratio and contrast of the object over the background are increased in comparison With passive imaging. Even though, range and field of view (FOV) are limited for a given laser power. The new active imaging system presented here aims at vercoming this limitation. It acquires the entire scene With a high-speed scanning laser illumination focused on a limited region, whereas at each scan the full frame active image is acquired. The whole image is then reconstructed by mosaicking Il these successive images. A evaluation of the performance of this system is conducted by using a direct physical model of his so-called « mosaic active imaging ». This End to End model, realistic in terms of turbulence effects (scintillation, beam andering.. gives us a sequence of images a synthetic scenes. After describing this model, the reconstruction method will be described. It is based on a total-variation minimization scheme. Finally, the performances of this new concept are ompared to those of a conventional flash active camera by using usual metrics (Johnston's criteria, SNR, ...). For va rious mean laser powers, we quantify the gains expected in terms of range and field of view of this new concept.

Future heavy duty vehicles will be designed and manufactured with improved Advanced Driver Assistance Systems, ADAS. When developing ADAS, an accurate model of the vehicle dynamics greatly simplifies the development process. One element integral to the vehicle lateral dynamics and development of ADAS is the steering system. This thesis aims to develop an accurate model of a heavy duty vehicle steering system suitable for simulations. The input to the system is an input torque at the steering wheel and the output is the wheel angle. Physical models of the system components are developed using bond graphs and known relations. Some components are modelled with non-linear inefficiencies and friction of different complexity. Unknown parameters and functions are identified from measurement data using system identification tools such as, for example, linear regression and non-linear grid search. The different subsystems are identified separately to the extent deemed possible. Different model designs are considered, validated, and compared. The advantages and disadvantages of different model choices are discussed. Finally, a non-linear state space model is selected for its high accuracy and efficiency. As this final model can be used to simulate a heavy duty vehicle steering system on a desktop computer faster than real time, it fulfills its purpose.

[Truncated abstract] The fracture of brittle materials in uniaxial compression is a complex process with the development of cracks generated from initial defects. The fracture mechanism and pattern of crack growth can be altered considerably by the presence of a free surface. In proximity of a free surface, initially stable cracks that require an increase in the load to maintain the crack growth can become unstable such that the crack growth maintains itself without requiring further increase in the load. This leads to a sudden relief of accumulated energy and, in some cases, to catastrophic failures. In the cases of rock and rock mass fracturing, this mechanism manifests itself as skin rockbursts and borehole breakouts or as various non-catastrophic forms of failure, e.g. spalling. Hence, the study of crack-boundary interaction is important in further understanding of such failures especially for the purpose of applications to resource engineering. Two major factors control the effect of the free boundary: the distance from the crack and the boundary shape. Both these factors as well as the effect of the initial defect and the material structure are investigated in this thesis. Three types of boundary shapes - rectilinear, convex and concave - are considered. Two types of initial defects - a circular pore and inclined shear cracks are investigated in homogeneous casting resin, microheterogeneous cement mixes and specially fabricated granulate material. The preexisting defects are artificially introduced in the physical model by the method of inclusion and are found to successfully replicate the feature of pre-existing defects in terms of load-deformation response to the applied external load. It is observed that the possibility of crack growth and the onset of unstable crack growth are affected by the type of initial defect, inclination of the initial crack, the boundary shape and the location of the initial defect with respect to the boundary. The initial defects are located at either the centre or edge of the sample. The stresses required for the wing crack initiation and the onset of unstable crack growth is highest for the initial cracks inclined at 35° to the compression axis, lowest at 45° and subsequently increases towards 60° for all the boundary shapes and crack locations. In the case of convex boundary, the stress of wing crack initiation and the stress of unstable crack growth are lower than for the case of rectilinear and concave boundary for all the crack inclinations and crack locations. The crack growth from a pre-existing crack in a sample with concave boundary is stable, requiring stress increase for each increment of crack growth. The stress of unstable crack growth for the crack situated at the edge of the boundary is lower than the crack located at the centre of the sample for all the crack inclinations and boundary shapes.

Un "problème inverse", dans son sens général, consiste en une «inversion» de la relation de cause à effet. Il ne s'agit pas de produire un phénomène «cause» à partir d'un phénomène «effet», mais plutôt de s'essayer à définir un phénomène «cause» dont un effet observé serait la conséquence.Dans le contexte du formalisme de modélisation physique et de simulation CORDIS-ANIMA, et plus particulièrement dans le cadre de l'interface de création sonore et de composition musicale qui le met en œuvre, GENESIS, créés par le laboratoire ACROE-ICA, on identifie une problématique d'une telle nature : étant donné un phénomène sonore, quel modèle physique construire qui permettrait de l'obtenir ? Cette interrogation est fondamentale dans le cadre du processus de création engagé par l'utilisation de tels outils. En effet, pouvoir décrire et concevoir le procédé qui permet d'engendrer un phénomène ou un événement sonore (musical) préalablement définis est une nécessité inhérente à l'acte de création musicale. Réciproquement, disposer des éléments d'analyse et de décomposition de la chaîne de production du phénomène sonore permet d'envisager, par représentation, traitement direct, composition des éléments de cette décomposition, la production de phénomènes très riches, nouveaux, expressifs et présentant une cohérence intime avec les sons naturels sur lesquels l'expérience perceptive et cognitive est construite.Dans l'objectif d'aborder cette problématique, nous avons dû formuler et étudier deux des aspects fondamentaux qui la sous-tendent. Le premier concerne la description même du résultat final, le phénomène sonore. Celle-ci pouvant être de plusieurs natures et souvent difficile en termes objectifs et quantitatifs, notre approche a tout d'abord consisté à réduire le problème aux notions de contenu spectral, ou encore de « structure modale » définis par une approche phénoménologique de type signal. Le second concerne la nature fonctionnelle et paramétrique des modèles construits au sein du paradigme CORDIS-ANIMA. Étant, par essence, une métaphore du contexte instrumental, tout modèle doit alors être conçu comme la mise en interaction d'un couple « instrument/instrumentiste ». De ces spécifications nous avons alors pu définir UN problème inverse, dont la résolution a demandé la mise au point d'outils d'interprétation de données phénoménologiques en données paramétriques. Ce travail de thèse a finalement abouti à la mise en œuvre de ces nouveaux outils au sein même du logiciel de création GENESIS, ainsi que dans l'environnement didactique qui l'accompagne. Les modèles qui en résultent, répondent à des critères de cohérence, de clarté et ont pour première vocation d'être réintégrés au processus de création. Ils ne constituent pas une finalité en eux-mêmes, mais un appui proposé à l'utilisateur pour compléter sa démarche.En conclusion de ce travail, nous détaillons les directions pouvant être suivies à des fins d'extension ou éventuellement de reformulation de cette problématique. / An “Inverse Problem”, usually consists in an inversion of the cause-to-effect relation. It's not about producing a “cause” phenomenon from a given “effect” phenomenon, but rather defining a “cause” phenomenon of which an observed effect would be the consequence. In the context of the CORDIS-ANIMA physical modeling and simulation formalism, and in particular within the GENESIS interface for sound synthesis and musical creation, both built by the ACROE-ICA laboratory, it is possible to identify such a problem: Considering a sound, which physical model could be built to produce it? This interrogation is fundamental if we consider the creative process engaged by the users of such tools. Indeed, being able to describe and to conceive the process which engenders a previously defined phenomenon or sonic (musical) event is an inherent need for the activity of musical creation. Reciprocally, disposing of elements for analyzing and decomposing the sound phenomenon's production chain allows to consider, by means of representation, direct processing, and re-composition, the production of very rich and expressive phenomena that present an intimate coherency with the natural sounds upon which the perceptive and cognitive experience are built.To approach this problem, we formulated and studied two underlying fundamental aspects. The first one covers the very description of the final result, the sound phenomenon. This description can be of different kinds and is often complex regarding objective and quantitative matters, therefore, our approach has consisted first in a reduction of the general problem by considering spectral content, or “modal structure”, defined by a phenomenological signal based approach. The second aspect concerns the functional and parametrical nature of models built with the CORDIS-ANIMA paradigm. Since all models are inherently a metaphor of an instrumental situation, each one must then be conceived as an interactive combination of an “instrument/instrumentist” couple. From these specifications we have defined ONE inverse problem, whose resolution required developing tools to interpret phenomenological data to parametrical data. Finally, this work has led to the implementation of these new tools in within the GENESIS software, as well as in its didactic environment. The resulting models fulfill coherence and clarity criteria and are intended to reintegrate the creative process. They do not constitute an end in themselves, rather a support proposed to the user in order to complete his process.As a conclusion to this work, we detail further directions that could be pursued in order to extend or possibly reformulate the inverse problem.

L’essai de chargement d’une pointe pénétrométrique (Cone Loading Test, essai CLT) est un nouvel essai de reconnaissance des sols in situ, qui constitue une amélioration majeure de l’essai de pénétration statique avec une pointe piézocône (CPTu). L’essai de chargement de pointe consiste à interrompre la pénétration classique (EN ISO 22476-1) à une cote souhaitée et à réaliser un chargement par paliers successifs de la pointe jusqu’à la rupture du sol.La courbe de chargement, reliant la pression appliquée sur la pointe au tassement de celle-ci,est riche en renseignements sur la déformabilité des sols. L’essai permet donc une caractérisation améliorée des sols en fournissant des paramètres de déformabilité aussi bien que les paramètres de résistance obtenus lors d’un essai de pénétration statique classique.La validation de la méthode d’essai et de son protocole expérimental, a été effectuée selon trois voies complémentaires : expérimentale, numérique et physique. Au niveau expérimental, plusieurs campagnes d’essais ont été réalisées en choisissant des sites intéressants pour le projet et contenants une importante base de données (essais in situ,au laboratoire, essais de pieux, essais sismiques…) comme le site des argiles des Flandres de Merville, un site sableux à Utrecht aux Pays-Bas, et un site sableux à Limelette en Belgique.Les résultats des différentes campagnes ont montré qu’il est possible d’avoir des courbes de chargement exploitables pour le calcul d’un module de déformation, utilisable et comparable en tout point aux modules obtenus par d’autres types d’essais. L’essai est adapté à un panel de sol très varié. Il est plus représentatif de l’état initial dans le sol que d’autres types d’essais.Par ailleurs les conditions aux limites sont bien maîtrisées.Au niveau numérique, une large étude paramétrique a été menée avec le logiciel Plaxis, pour tester l’influence de la géométrie de la pointe, du type de chargement, du modèle de comportement, des paramètres du sol, ainsi que des conditions initiales et au limite du problème. Des essais CLT ont été également réalisés sur des modèles réduits en centrifugeuse, pour tester l’influence de quelques paramètres comme la vitesse de chargement, la géométrie de l’embout de la pointe, la densité du massif ainsi que le niveau de g. Ces essais ont été associés à des essais de chargement de pieu instrumenté et des essais de fondations superficielles et profondes afin de pouvoir relier les paramètres mécaniques de l’essai CLT au comportement des ouvrages. En considérant que la pointe du pénétromètre est un modèle réduit de pieu, une retombée directe de l’essai CLT est sa capacité d’être un outil de dimensionnement de fondations. A cet effet, une méthode directe utilisant la résistance de pointe et le frottement latéral limite de l’essai CLT a été proposée pour calculer la capacité portante et prédire le tassement d’un pieu.Cette méthode consiste en une nouvelle approche transformant les courbes de chargement et celles de mobilisation de frottement d’un essai CLT point par point en courbe charge-déplacement d’un pieu (courbes t-z). / The Cone Loading Test (CLT) is a new in situ test, which constitutes a major improvement to the piezocone penetration test (CPTu). The cone loading test consists in stopping the penetration (EN ISO 22476-1) at a desired depth, and carrying out a loading of the cone by successive load steps until the ground failure.The obtained loading curve, which relates the pressure applied on the cone in each step, to the cone settlement, is rich in information regarding soil deformability. Therefore, the test allows improved soil characterization by providing deformability parameters as well as the strength parameters obtained during a CPT test.The validation of the cone loading test method was conducted by three complementary approaches: experimental, numerical and physical.Several test campaigns were conducted on different sites such as the Merville site (Flanders clay), and two sandy sites in Utrecht (The Netherlands), and Limelette (Belgium). The results of these campaigns have shown that loading curves can be obtained for a modulus calculation, which is comparable to the other investigation tests moduli. The test is suitable for varied soil types. It is more representative of the initial soil state than other test types. Furthermore the boundary conditions are well controlled.In the numerical approach performed with Plaxis finite element modelling software, an important parametric study was done, in order to test the influence of cone geometry, loading type, behaviour model, soil parameters, initial conditions and boundary problem. CLT tests were also performed on reduced scale models in a geotechnical centrifuge. The objective was to test the influence of some parameters such as the loading rate, the cone geometry, the soil density and the level of g. These tests were associated with instrumented pile loading tests as well as shallow and deep foundation tests in order to link the mechanical parameters of the CLT test to the structures’ behaviour. By considering that the cone penetrometer is a reduced pile model, a very practical and interesting outcome is the potential of the cone loading test to be a foundations dimensioning tool. For this purpose, a direct method using the cone resistance and limit side friction of the CLT was proposed to calculate the bearing capacity, and predict the pile settlement. Thismethod is a new approach transforming the loading curves and those of friction mobilization of a CLT, point by point to a load-settlement curve of a pile (t-z curves).

This licentiate thesis describes development of modellingtools, experimental physical modelling and numerical modellingto simulate real combustion processes for advanced industrialutility boiler before and after retrofit. The work presents extended study about formation,destruction and control of pollutants, especially NOx, whichoccur during combustion process. The main aim of this work is to improve mixing process incombustion chamber. To do this, the optimization of placementand direction of additional air and fuel nozzles, the physicalmodelling technique is used. By using that method, it ispossible to obtain qualitative information about processes,which occur in the real boiler. The numerical simulationsverify the results from physical modelling, because duringmathematical modelling quantitative informations about flow andmixing patterns, temperature field, species concentration areobtained. Two 3D cases, before and after retrofit, of pulverized fuelfired boiler at 125 MW output thermal power are simulated. Theunstructured mesh technique is also used to discretize theboiler. The number of grid was 427 656 before retrofit and 513362 after retrofit. The comparisons of results of numericalsimulation before and after retrofit are presented. The resultsfrom physical modelling and numerical simulation are alsoshown. Results present that nozzles of additional air and fuel givea considerably better mixing process, uniform temperature fieldand CO2 mass fraction. The whole combustion chamber worksalmost as a "well stirred reactor", while upper part of boilerworks as a "plug flow reactor". Differences between from measured of temperatures andpredicted temperatures are not too big, the maximum differenceis about 100 K. It seems, that calculated temperatures showgood agreement with measurement data. The results illuminate the potential of physical andnumerical modelling methods as promising tools to deal with thecomplicated combustion processes, even for practicalapplication in the industry. <b>Keywords:</b>air staging, fuel staging, boiler, furnace,computational fluid dynamics, numerical simulation, pollutants,physical modeling, pulverized fuel combustion. / NR 20140805

L’objectif de cette thèse est d’améliorer la compréhension de l’acoustique du piano dans le contexte de la synthèse sonore par modèles physiques. Le manuscrit est décomposé en trois parties principales, dont les deux premières ont pour but la compréhension de l'origine de la double polarisation de la corde de piano, tandis que la dernière se focalise sur l’identification de sources d’un piano complet.Dans la première partie, la non linéarité géométrique, intervenant lorsque les amplitudesde vibration sont grandes, est étudiée afin de comprendre si le couplage non linéaire peut transmettre de l'énergie à une polarisation non initialement excitée et mener ainsi au phénomène de double polarisation. Un développement en échelles multiples est mené sur un modèle de corde de Kirchhoff-Carrier avec les deux extrémités fixes, restreint au mode fondamental de chacune des polarisations. Les deux oscillateurs ont alors des fréquences très proches, on parle de résonance 1:1. La condition d’existence et le critère de stabilitépour l’apparition de double polarisation sont obtenus et validés numériquement sur la base des équations de Kirchhoff-Carrier, ainsi qu’avec un modèle de corde enrichi.Des expériences sont menées sur un dispositif monocorde où les angles de polarisation naturelle de la corde, le désaccord entre les deux polarisations et le comportement non linéaire son observés et identifiés.La seconde partie se concentre sur le couplage entre la corde et le chevalet. Les degrés de liberté de la corde sont couplés au chevalet dont les mouvements (translation/rotation) sont représentés par un ensemble d'oscillateurs. Les fréquences propres des différents systèmes couplés sont analysés. Des schémas numériques sont proposés et mis en {oe}uvre pour une résolution directe. Ces schémas résolvent les équations de corde par une méthode d’éléments finis d’ordre élevé et les équations du chevalet analytiquement. Les conditions de couplage entre corde et chevalet sont assurées par des multiplicateurs de Lagrange. Expérimentalement, la corde est tendue sur le chevalet dans une configuration de type zig-zag et excitée verticalement ou horizontalement. Dans les deux cas, les phénomènes de double polarisation et de double décroissance sont observés et des résultats qualitativement similaires sont obtenus avec les modèles numériques.La dernière partie s'attache à décrire quantitativement les différentes sources vibro-acoustiques d'un piano complet. Une étude est menée en utilisant une analyse des chemins de transfert (transfer path analysis en anglais) sur un piano Bösendorfer 280VC-9. Les contributions de la table d’harmonie, des parties interne et externe de la ceinture, du cadre en fonte et du couvercle sont étudiées dans le domaine fréquentiel. L’analyse montre que la table d’harmonie est le principal contributeur mais que le cadre en fonte et le couvercle jouent également un rôle significatif, en particulier à hautes fréquences. / The objective of this thesis is to improve the understanding of the acoustics of the piano in the context of physically-based sound synthesis. The manuscript is decomposed in three parts, the first two being devoted to the undertsanding of the origin of the double polarisation in piano string, while the third one is dedicated to the identification of sound sources of a complete piano.In the first part, the geometric (large-amplitude) nonlinearity is studied in order to understand if the nonlinear coupling can transfer energy to an initially non excited polarisation, thus leading to the double polarisation phenomenon. A multiple-scaleanalysis is conducted on a Kirchhoff-Carrier string model with fixed boundary conditions at both ends. Each polarisation is restrained to its fundamental mode, leading to two oscillors having nearly equal eigenfrequencies, and thus presenting a 1:1 internal resonance. The existence condition and stability criteria for double polarisation to occur are obtained and validated numerically based on the complete Kirchhoff-Carrier equations, as well as a more enriched third-order string model. Experiments are carried out on a monochord setup where the natural polarisation angles of the string, detuning between the two polarisations and its nonlinear behaviour are observed and identified.The second part is devoted to the string/bridge coupling. The degrees of freedom of the string are coupled to the bridge whose translational and rotational motions are respresented by a set of oscillators. The eigenfrequencies of various coupled systems are analysed. Numerical schemes are proposed and implemented where the string is solved via high-order finite-element method while the lumped bridge is solved analytically and coupled to the string by Lagrange multipliers. Experimentally, the string is strung over a bridge in a zig-zag configuration and excited vertically and horizontally. In both cases, double polarisation and double decay are observed and similar results are also obtained qualitatively in numerical models.The last part is devoted to a quantitative description of the vibroacoustic sources of a Bösendorfer 280VC-9 piano via operational transfer path analysis. The contribution of the soundboard, inner and outer rim, iron frame and lid are investigated in the frequency domain. It is found out that the soundboard is the primary contributor but the iron frame and the lid also play a significant role, especially at high frequencies.

Hydraulically induced scour of the streambed at the base of bridge piers is the leading cause of bridge failures. Despite the significant scientific efforts towards the solution of this challenging engineering problem, there are still no reliable tools for the prediction and mitigation of bridge scour. This shortcoming is attributed to the lack of understanding of the physics behind this phenomenon. The experimental studies that attempted the physical investigation of bridge scour in the past have faced two main limitations: i) The characterization of the dynamic interaction between the flow and the evolving bed that is known to drive scour, was not possible due to the limitations in the available instrumentation and the significant experimental difficulties; ii) Most of the existing literature studies are based on the findings of laboratory experiments whose scale is orders of magnitudes smaller compared to bridges in the field, while the scale effects on the scour depth have never been quantified. The objective of this research was to enhance the existing understanding of the phenomenon by tackling the aforementioned experimental challenges. To accomplish this, the first part of this work involved the development of a new underwater photogrammetric technique for the monitoring of evolving sediment beds. This technique is able to obtain very high resolution measurements of evolving beds, thus allowing the characterization of their dynamic properties (i.e. evolving topography and scour rates) and overcoming existing experimental limitations. Secondly, the underwater photogrammetric technique was applied on a bridge scour experiment, of simple geometry, and the dynamic morphological characteristics of the phenomenon were measured. The detailed measurements along with reasonable comparisons with descriptions of the flow, from past studies, were used to provide insight on the interaction between the flow and the bed and describe quantitatively the mechanisms of scour. Finally, the scale effects on scour were studied via the performance of two experiments under near-prototype conditions. In these experiments the effects of the Reynolds number on the flow and the scour were quantified and implications concerning existing small-scale studies were discussed. / Ph. D.