No description available.

With the aim to understand the synergistic roles played by kinematics, aerodynamics, and inertia in flapping wing maneuvers, this thesis first investigates the plunging motion of a simple flat plate as it is a fundamental motion in the kinematics of many flying animals. A wide range of frequency (k) and amplitude (h) is investigated to account for a robust kinematic characterization in the form of plunge velocity (kh). Leading Edge Vortices (LEVs) are found to be responsible for producing thrust while Trailing Edge Vortices (TEVs) produce drag. The vortex dynamics becomes nonlinear for higher kh and three main vortex-vortex interactions (VVI) are identified in the flow-field. To estimate the sole effect of LEVs on thrust coefficient, TEVs are eliminated by introducing a splitter plate. This resulted in reduced non-linearity in VVI and facilitated a parametrization of aerodynamic thrust coefficient with key kinematic features, frequency (k) and amplitude (h) [C_T= A.k^1.4 h-B where A and B are constants]. This is followed by investigating the more direct problem of bio-inspired MAV research – the interplay of kinematics, aerodynamics, and inertia on maneuvering bat flights. At first, an ascending right turn of a H. pratti bat is investigated to elucidate on the kinematic features and aerodynamic mechanisms used to effectuate the maneuver. Deceleration in flight speed, an increase in flapping frequency, shortening of the upstroke, and thrust generation at the end of the upstroke is observed during this maneuver. The turn is initiated by the synergisytic implementation of roll and yaw rotation where the turning moments are generated by drawing the inside wing closer to the body, by introducing phase lags in force generation between the two wings and by redirecting force production to the outer part of the wing outside of the turn. Upon comparison with a similar maneuver by a H. armiger bat, some commonalities as well as differences were observed. This analysis was followed by a comparative study among different maneuvering flights (a straight flight, two ascending right turns, and a U-turn) in order to establish the complete motion dynamics of a maneuver in action. The individual effects of aerodynamics and wing inertia for maneuvering flights of a H. armiger and H. pratti are investigated. It is found that for both, translation and rotation the overall trajectory trend is mostly driven by the aerodynamic forces and moments, whereas inertial effects drive the intricate intra-cycle fluctuations as well as the vertical velocity and altitude gain during ascent. Additionally, inertial moments play a dominant role for effecting yaw rotations where the importance of the Coriolis and centrifugal moments increase with increasing acuteness of the maneuver, with the largest effect of centrifugal moments being evidenced in the U-turn. / Doctor of Philosophy / The study of flapping wing is of paramount interest in the field of small aerial and aquatic vehicle propulsion. The intricate mechanisms acting behind a flapping wing maneuver can be explained by the synergistic roles played by 3 main components; details of the wing motion or the kinematics, how the air reacts to the wing motion or the aerodynamics, and the effort or force required to move the wings or wing inertia. This dissertation systematically reports the contribution of these components to a flapping flight maneuver. At first, the plunging motion of a simple flat plate is investigated as it is a fundamental motion in the flapping flight of many flying animals. A wide range of frequency and amplitude is investigated and their effect is characterized by a single parameter called "plunge velocity". It is found that, the resultant flow field becomes disorderly for higher plunge velocities which can be characterized by three different types of vortex interactions. The observed results facilitated a robust parametrization of aerodynamic thrust production with key kinematic features, frequency and amplitude. After this, the dissertation focuses on the bio-inspiration aspect of flapping flight by investigating the interplay of kinematics, aerodynamics, and inertia of maneuvering bat flights. At first, an ascending right turn of one species (H. pratti) is investigated to elucidate on the kinematic features and aerodynamic mechanisms used to effectuate the maneuver. Some characteristic features observed are – lowering of flight speed, increase in flapping rate, shortening of upstrokes, and generation of a forward force at the end of the upstroke. It is observed, that the bat turns by using synergistic body rotations in multiple directions which are effected by various techniques such as - drawing the wing inside the turn closer to the body, and changing the timing and location of the forces produced between the two wings. Upon comparison with a similar maneuver by a H. armiger bat, some commonalities as well as differences were observed in the maneuver mechanisms. This analysis was followed by a comparative study among different maneuvering flights (a straight flight, two ascending right turns, and a U-turn) to establish the complete motion dynamics of a maneuver. The individual contributions of aerodynamics and wing inertia for maneuvering flights of a H. armiger and H. pratti are investigated. It is found that for both, translation and rotation the overall trajectory is mostly influenced by the aerodynamic forces and moments, whereas inertial effects are responsible for trajectory fluctuations during a flapping cycle as well contributing to altitude gain during ascent for the H. armiger bat.

Calcite c-axes and e-twin plane orientations were measured in both matrix cements and younger fracture fills from late Cambrian to Middle Ordovician age limestone samples taken from the NW and SE limbs of the Massanutten Syncline, located within the North Mountain thrust sheet. Paleostress magnitude estimates using the Rowe and Rutter (1990) twin density technique indicate a differential stress of 240±31 MPa for samples collected from both limbs of the syncline. Three distinct patterns of paleostress orientations (compression directions) have been detected in the samples; each pattern is observed on both the NW and SE limbs of the syncline. The first pattern, exhibited by calcite grains cementing late fractures, is characterized by a maximum of compression axes oriented sub-perpendicular to bedding possibly indicating either thrust sheet loading or stress refraction associated with folding. Samples in which calcite grains from both fracture fills and earlier matrix cements were measured are characterized by a bimodal distribution of compression axes—the first point maximum being oriented sub-perpendicular to bedding, the second maximum placing compression directions at low to moderate angles to bedding. Restoration of bedding to horizontal results in this second set of compression axes plunging to either the SE or NW, sub-parallel to the regional thrust transport direction. The third pattern, originating from early cements, places compression directions plunging to the NE-SW at angles which are sub-parallel to bedding. These compression directions do not seem to correlate with major tectonic movements or thrust sheet loading and may reflect stresses associated with either movement over lateral ramps or oblique thrusting. / Master of Science

A surface piercing propeller (SPP) is a propeller that is partially submerged in water and is considered a possible solution to high-speed vessels (greater than 50 knots) where cavitation plays a vital role due to its ever-increasing detrimental effects. Computational Fluid Dynamics (CFD) has become a more prevalent solution in recent years due to lower costs and the ability to evaluate varying setups. However, Computational Fluid Dynamics has had problems accurately solving the hydrodynamic loads for an SPP as recently as a few years ago. Accurately predicting these loads is of great importance because it will allow future simulations to add more effects such as cavitation, shaft inclination effects, multiple propellers, and fluid-structure interaction. Using FINE/Marine, a CFD software specifically designed for marine applications simulations with the 841-B SPP model and changing the Froude number (Fn) and advance coefficient (J), an in-depth validation process and extending upon previous results found when combining CFD and surface-piercing propellers was performed. Several cases between J = 0.6 to J = 1 and Fn = 2 to Fn = 6 are first performed to validate the models against experiments, then more complex features such as multiple propellers and shaft inclination angles were included to extend upon previous work of CFD for surface-piercing propellers. This analysis of the results suggests that CFD models could genuinely be validated against current experimental setups, and therefore more complex additions could also be made and with stronger accuracy than in previous years. / Master of Science / Using computers one can analyze the torque and thrust values of surface-piercing propellers(propeller that is only partially submerged) using commercially available software. This software takes inputs such as the speed of the water and the design of the propeller to evaluate the torque and thrust. A surface-piercing propeller operates in what is known as regimes. There are three of these and they are defined by a number known as the advance coefficient which is defined as the ratio of the boat's speed to the propeller speed. The higher this number the higher the boat speed is and the lower the number is the lower the boat speed. Testing the torque and thrust values accurately has not yet been performed using computers and would be of great value to companies and the government because it lowers the cost and time to create and test different propeller designs for their ships. In this thesis, these tests were performed and done so within a 5% accuracy in all experimental testing on this propeller model. Multiple propellers at once were tested as well as moving the shaft farther out of the water was tested to see how this would affect the overall performance. The results were promising in both of the situations listed, but more testing could be performed as well as adding more features such as cavitation and interaction with the hull.

The ability of fish to deform their bodies in steady swimming action is gaining from robotic designers. While bound by the same physical laws, fish have evolved to move in ways that often outperform artificial systems in critical measures such as efficiency, agility, and stealth through thousands of years of natural selection. As we expand our presence in the ocean with deep-sea exploration or offshore drilling for petroleum and natural gas, the demand for prolonging underwater operations is growing significantly. Therefore, it is critical for robotic designers to understand the physics of pisciform (fish-like) locomotion and learn how to effectively implement the propulsive mechanisms into their designs to create the next generation of aquatic robots. Aiming to assist this process, this thesis presents an experimental apparatus called Towed Biolocomotion Emulator (TBE), which is capable of imitating the undulating action of different fish species in steady swimming and can be quickly adapted to different configurations with modular modules. Using the TBE device, an experiment is performed to test its hydrodynamic performance and evaluate the effectiveness of the bio-inspired locomotion implemented on such a mechanical system. The analysis of hydrodynamic data collected from the experiment shows that there exists a small range of kinematic parameters where the undulating motion of the device produces the optimal performance. This result confirms the benefits of utilizing pisciform locomotion for small-scale underwater vehicles. In addition, this thesis also proposes a reduced-order flow model using the unsteady vortex lattice method (UVLM) to predict the hydrodynamic performance of such a system. The proposed model is then validated with the experimental data collected earlier. The tool developed can be employed to quickly explore the possible design space early in the conceptual design stage for such a bio-mimetic vehicle. / Master of Science / It is no surprise that through thousands of years of natural evolution, marine species possess incredible ability to navigate through water. As we expand our presence in the sea, more and more tasks require underwater operations such as ocean exploration, oil-rig maintenance, etc. Yet, most of the underwater robotic vehicles still utilize propellers as the primary propulsive mechanism. In many cases, the bio-inspired propulsion system that mimics the swimming action of fish offers many advantages in agility, maneuverability, and stealth. With the rising interest in the field, the works presented in this thesis aim to expand our understanding of how to implement the bio-inspired propulsive mechanism to robotic design. To achieve this, a mechanical device is designed to mimic the swimming action of different fish species. Then, an experiment is performed to subject the device to different fish-like motions and test their effectiveness. In addition, a reduced-ordered model is also introduced as an alternative method to predict the hydrodynamic performance of this propulsive mechanism. The works presented in this thesis help to expand the toolbox available for the engineer to design the next generation of the underwater robotic vehicle.

La convergence oblique entre les plaques Caraïbes et Amérique du Sud à partir de l'Oligocène a conduit à la formation de la cordillère « Serranía del Interior » (SDI) et de son avant pays au sud (bassin de Maturín) et la ceinture plissée de Monagas. D’abord transpressif (direction NW-SE), le déplacement entre les deux plaques devient à compter de ~12 Ma principalement une translation O-E qui s’accommode principalement sur la faille d’El Pilar. Cependant, des indices de compression active ont été identifiés à la terminaison de la faille d'Urica dans la chaine plissée de Monagas. Pour discuter des mécanismes de cette déformation compressive actuelle, nous avons mis en œuvre une interprétation sismique (2D et 3D), une étude géomorphologique et une étude paléomagnétique. Depuis le front sud de la SDI dans la chaîne plissée de Monagas, l'interprétation sismique et l’analyse géomorphologique se sont concentrées sur les chevauchements de San Félix, Tarragona, Punta de Mata, Jusepín et Amarilis. Deux discordances miocènes (Mid-Miocene Unconformity (MMU) de ~10 Ma et Late Miocene Unconformity (LMU) de ~5,3 Ma) ont été cartographiées sur la sismique. En s’appuyant sur la LMU, il a été calculé à l’aplomb de ces accidents un taux de soulèvement plio-pléistocène de ~0,4 mm/a. Invisibles sur la sismique, des déformations ont aussi été observées en surface sur ces accidents (des terrasses fluviatiles basculées, plissées et faillées et des anomalies de drainage). Datées par des méthodes cosmonucléides (10Be et 26Al), l’âge des terrasses alluviales déformées sont compris entre ~90 ka sur le chevauchement de Tarragona et ~15 ka dans la zone de Punta de Mata. Un taux minimal de soulèvement pléistocène terminal à l’aplomb des chevauchements a été calculé entre 0,1 et 0,6 mm/a. Cette gamme de vitesse recouvre celle renvoyée par la LMU et montre que la déformation n'a pas varié significativement pendant les derniers 5,3 Ma. Ces observations montrent que les chevauchements de Tarragona, Pirital El Furrial et d’autres plus jeunes développés dans la formation Carapita restent actifs. Cette déformation superficielle s’estompe rapidement vers l’est près de la ville Maturín. Nous interprétons cette déformation comme liée au jeu récent de la faille d'Urica qui se termine au sud en queue de cheval. La faille d’Urica accommoderait donc une partie du déplacement entre plaques Caraïbe et Amérique du Sud. Une étude paléomagnétique a été réalisée dans les blocs de Caripe et Bergatín au sein de la SDI où 27 localités ont été échantillonnées dans les sédiments du Crétacé au Paléocène. Une observation clé de cette étude a été la mise en évidence d'une composante paléomagnétique stable déviée vers le Nord Est avec des polarités normale et inverse. Les analyses statistiques de ces composantes indiquent une acquisition postérieure au plissement de la SDI (< ~12 Ma). La déclinaison moyenne dans les blocs de Caripe et de Bergatín indique une rotation horaire de R=37º±4 º autour d’un axe vertical. Le taux de rotation post-Miocene moyen avoisine ~3.7º/Ma et reste probablement actif. Nous proposons de rattacher cette rotation horaire à un système de failles type "Riedel" (Urica et San Francisco) en relation avec la faille d’El Pilar. / In Northeastern Venezuela, the tectonic provinces of the Serranía Del Interior thrust belt (high hills), the Monagas Thrust belt (foothills) and the Maturín foreland basin formed as a result of the oblique convergence between the Caribbean and South American plates since the Oligocene. GPS data show that post 12 My wrenching component between the plates is accommodated predominantly by the E-W strike-slip El Pilar Fault. However, evidence of active compression has been identified in the southern limit of the NW-SE dextral Urica Fault, specifically, in the Monagas Fold and Thrust Belt. In order to constrain the neotectonics of this area, this thesis presents a combined approach, which includes geomorphological study, seismic and paleomagnetism. In the Monagas Fold and Thrust Belt, the geomorphological study and the seismic interpretation were focused on five zones. From the foothills to the deformation front, these zones are: San Felix, Tarragona, Punta de Mata, Jusepín and Amarilis. These areas show surface deformations such as topographic uplifts, tilted terraces, folded terraces, faulted terraces, and drainage anomalies. The dating of the river terraces through 10Be and 26Al methods indicates that these terraces formed in the Late Pleistocene. The oldest terrace located in the Tarragona zone has a maximum exposure age of ~90 ky and the youngest located in the Punta de Mata zone of ~15 ky. From this dating, a minimum vertical deformation rate between ~0.6-0.1 mm/y was calculated for this area. Using the seismic interpretation of a 3D block, the surfaces of two unconformities (MMU and LMU) have been mapped. The age obtained for the LMU (~5.3 My), yield a Plio-Pleistocene uplift rate between ~0.3-0.4 mm/y, which is close to the vertical deformation rate calculated from the terraces dated. These similar rates seem to indicate that the deformation rate in the MFTB has not changed significantly for the last 5.3 My. The deformed surfaces observed in the field and in DEM images coincide vertically with the deep structures interpreted in the seismic lines. I propose that the deformation on the surface is linked to the Tarragona, Pirital, Furrial thrusts and the Amarilis Backthrust activity and to the youngest thrusts developed in the Carapita Formation. However, this surface deformation dies out near the city of Maturín, therefore, the neotectonic deformation is inferred to be caused by local tectonics. I propose that this local compressive deformation could have been generated by a horsetail termination in the southern limit of the Urica Fault which reactivated the oldest thrusts (Tarragona and Pirital thrusts) and deformed the post-Middle Miocene units until reaching the surface. In the zones where the El Pilar Fault mainly accommodates the wrenching component, block rotation is likely. For that reason, a paleomagnetic study was conducted in the Caripe and Bergatín blocks of the Serranía Del Interior where 27 sites were sampled in Cretaceous to Paleocene sediments. Statistics analyses of the components yield a negative bedding-tilt test, indicating that this component was acquired post ~12 My after the folding process in the Serranía del interior. The average declination indicates a clockwise block rotation of R = 37º ± 4º and a post-Middle Miocene rotation rate of ~3.7º/My in both the Caripe and Bergatín blocks. This rotation rate is probably still active. I propose to relate the regional clockwise rotation to the development of a synthetic Riedel shear system formed by the El Pilar Fault (master regional fault) and by the Urica and San Francisco synthetic Riedel shears.

L'influence de l'érosion sur la localisation de la déformation dans une chaîne de montagnes est un phénomène souvent envisagé à la suite de modélisations numériques. Or les données géologiques pertinentes en faveur de cette hypothèse sont encore fort peu nombreuses. Aussi, la mise en évidence d'une évolution temporelle et spatiale de la déformation constitue une observable clef pour tester les relations érosion/localisation de la déformation. Nous testons cet effet, sur un objet géologique soumis à des conditions de déplacements aux limites simples et sur un objet géologique soumis à des conditions climatiques et érosives variables latéralement : le flanc sud de l'Himalaya (située au dessus d'un décollement crustal majeur). Elle est soumise à une convergence continue et de valeur constante depuis au moins une dizaine de millions d'années et sa rhéologie est invariante au cours du temps ; elle est en revanche soumise à un gradient climatique d'est en ouest (transversalement par rapport à la direction de convergence), gradient de plus variable au cours du temps. Nous avons mis en oeuvre des techniques de thermochronologie basse température pour consituer une base de données conséquente, que nous avons utilisée dans des modélisations numériques thermo-cinématiques directes et inverses. Nous montrons que 1) au Népal central,le MHT présente une rampe crustale prononcée, et aucun mécanisme de chevauchement en hors-séquence n'est nécessaire pour expliquer les données, 2) la géométrie du MHT varie d'est en ouest, avec une rampe moins prononcée dans l'est de la chaîne, et 3) les variations latérales en terme de mise en place et de cinétique du MFT sont peu importantes.

Η παρούσα μελέτη παρουσιάζει νέα στοιχεία που αφορούν την τεκτονική και στρωματογραφία του φλύσχη της Νότιας Aιτωλοακαρνανίας και έχει ως στόχο να ερμηνεύσει την τεκτονική εξέλιξη της περιοχής και την κινηματική των επωθήσεων. Γεωλογικά δεδομένα που προέκυψαν από την τεκτονική και στρωματογραφική ανάλυση καθώς και από την ανάλυση αεροφωτογραφιών συνδυάστηκαν με σεισμικές τομές. Οι μεγάλης κλίμακας επωθήσεις της Πίνδου και του Γαβρόβου, που σχηματίζουν ένα προελαύνον προς την προχώρα σύστημα επωθήσεων, δρουν συγχρόνως για μεγάλο διάστημα του Ολιγοκαίνου. Η επώθηση Γαβρόβου χαρακτηρίζεται από σημαντική μετατόπιση (>10 χλμ.), μικρούς ρυθμούς βράχυνσης, και από πολύπλοκη ιστορία προέλασης που περιλαμβάνει και επωθήσεις εκτός ακολουθίας. Επωθήσειςν ΒΒΔ-ΒΔ διεύθυνσης ελέγχουν την τοπογραφία της περιοχής και συνείσφερουν σημαντικά στην πάχυνση του φλύσχη. Η υπέρθεση του φλύσχη ενέτεινε την βύθιση της λεκάνης και την υποβύθιση τμημάτων του φλοιού κάτω από την επώθηση. Η έναρξη της κλαστικής ιζηματογένεσης λαμβάνει χώρα στο Πριαμπόνιο, ενώ το τέλος της προσδιορίστηκε στο Ανώτερο Ολιγόκαινο. Στην Ιόνια λεκάνη η κατώτερη ακολουθία ιζημάτων του φλύσχη αντιστοιχεί σε αποθέσεις εξωτερικού ριπιδίου ενώ η ανώτερη σε αποθέσεις εσωτερικού ριπιδίου-κατωφέρειας. Στην λεκάνη Γαβρόβου επικρατούν κυρίως αποθέσεις εσωτερικού-μέσου ριπιδίου. Τα αποτελέσματα που προκύπτουν από την παρούσα διατριβή υποδηλώνουν ότι το κλασσικό μοντέλο του προελαύνοντος προς την προχώρα συστήματος επωθήσεων, που έχει προταθεί για τις Εξωτερικές Ελληνίδες χρειάζεται σημαντικές τροποποιήσεις. / This study demonstrates new structural and stratigraphic data derived from the syn-orogenic clastic deposits in the Etoloakarnania area, in order to define the structural evolution and the movement history of thrust faults in the area. Geological data derived from structural, stratigraphic analysis and interpretation of air photos combine with data from seismic lines. The crustal-scale Pindos and Gavrovo thrusts,which formed a foreland propagating sequence, acted simultaneously for a long period of Oligocene. The Gavrovo thrust is characterized by significant displacement (>10 km), low shortening rates and a complex propagation history, involving out-of-sequence thrusting. NNW to NW-directed thrusts control the topography of the region and cause a significant thickening of the flysch. The superposition of flysch enhanced further subsidence and underthrusting. The clastic sedimentation began in the Priabonian and lasted till the Late Oligocene. In the Ionian basin the lower part of the clastic sequence corresponds to outer fan deposits, while the upper part corresponds to inner fan-slope deposits. In addition, inner to middle fan associations predominate in the Gavrovo basin. The results of this study show that the classic model of a foreland propagating thrust sequence for the External Hellenides needs significant modifications.

In nature, many of the flapping wings and fins in swimming and flying animals have various degrees of flexibility with strong and coupled solid-fluid interactions between the structure and the fluid. In most cases, the wing structure, the flow and their interactions are complex. This thesis experimentally investigates a ‘simple’ fluid-flexible foil interaction problem: flow generated by a pitching foil with chordwise flexibility. To explore the effect of flexibility on the flow, we study the flow generated in quiescent water (the limiting case of infinite Strouhal number) by a sinusoidally pitching rigid symmetrical NACA0015 foil to which is attached a 0.05 mm thick chordwise flexible polythene flap at the trailing edge. The chordwise length of flap is 0.79 c, where c = 38 mm is the chord length of the rigid foil; span of the foil and flap is 100 mm. Detailed particle image velocimetry (PIV) and flow visualization measurements have been made for twelve cases, corresponding to three pitching amplitudes, ±10◦,± 15◦, ±20◦, and four frequencies, 1, 2, 3 and 4 Hz for each amplitude. For most of these cases, a narrow coherent jet aligned along the center-line, containing a reverse B’enard–K´arm´an vortex street, and a corresponding unidirectional thrust are generated. This thrust is similar to the upward force generated during hovering, but motion of our foil is much simpler than the complex wing kinematics found in birds and insects; also the thrust generation mechanism seems to be different. In our case, the thrust is from a coordinated pushing action of the rigid foil and the flexible flap. Control volume analysis reveals the unsteady nature of thrust generation. In this intricately coupled flow generation problem, chordwise flexibility is found to be crucial in producing the coherent jet. In this thesis, we explore in detail the physics of jet flow produced by the foil with a flexible flap, and identify the importance of flexibility in flow generation. Flap motion ensures appropriate spatial and temporal release of vortices, and also imparts them convective motion, to obtain the staggered pattern that produces the jet. To describe the fluid-flap interaction, we conveniently characterize the flap through a non-dimensional stiffness, ‘effective stiffness’ (EI)∗ of the flap, that captures the effects of both the flap properties as well as the external forcing. With the same flap by changing the pitching parameters, we cover a fairly large (EI)∗ range varying over nearly two orders of magnitude. However, we observed that only moderate (EI)∗ (~0.1 - 1) generates sustained narrow, orderly jet. We provide thrust estimates useful for the design of flapping foil thrusters/propulsors. Although this study has only indirect connections with the hovering in nature, it may be useful in understanding the role of flexibility of bird and insect wings during hovering. In contrast, a foil with a rigid trailing edge produces a weak jet whose inclination changes continually with time. This meandering is observed to be random and independent of the initial conditions over a wide range of pitching parameters.

It is well known that the layout of a large wind turbine cluster aects the energyoutput of the wind farm. The individual placement and distances betweenturbines will in uence the wake spreading and the wind velocity decit. Manyanalytical models and simulations have been made trying to calculate this, butstill there is a lack of experimental data to conrm the models. This thesis isdescribing the preparations and the execution of an experiment that has beenconducted using about 250 small rotating turbine models in a wind tunnel. Theturbine models were developed before the experiment and the characteristicswere investigated. The main focus was laid on special eects occurring in largewind turbine clusters, which were named Global Turbine Array Eects.It was shown that the upstream wind was little aected by a large windfarm downstream, even though there existed a small dierence in wind speedbetween the undisturbed free stream and the wind that arrived to the rstturbines in the wind farm. The dierence in wind speed was shown to beunder 1% of the undisturbed free stream. It was also shown that the densityof the wind farm was related to the reduced wind velocity, with a more densefarm the reduction could get up to 2.5% of the undisturbed free stream at theupstream center turbine. Less velocity decit was observed at the upstreamcorner turbines in the wind farm.When using small rotating turbine models some scaling requirements hadto be considered to make the experiment adaptable to reality. It was concludedthat the thrust coecient of the turbine models was the most important parameterwhen analysing the eects. One problem discussed was the low Reynoldsnumber, an eect always present in wind tunnel studies on small wind turbinemodels.A preliminary investigation of a photo measuring technique was also performed,but the technique was not fully developed. The idea was to take oneor a few photos instantaneously and then calculate the individual rotationalspeed of all the turbine models. It was dicult to apply the technique becauseof uctuations in rotational speed during the experiment, therefore thecalculated values could not represent the mean value over a longer time period.