Dissertations / Theses on the topic 'Edge velocity'

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1

Spitz, Nicolas. "Prediction of Trailing Edge Noise from Two-Point Velocity Correlations." Thesis, Virginia Tech, 2005. http://hdl.handle.net/10919/32637.

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This thesis presents the implementation and validation of a new methodology developed by Glegg et al. (2004) for solving the trailing edge noise problem. This method is based on the premises that the noise produced by a surface can be computed by the integral of the cross product between the velocity and vorticity fields, of the boundary layer and shed vorticity (Howe (1978)). To extract the source terms, proper orthogonal decomposition is applied to the velocity cross spectrum to extract modes of the unsteady velocity and vorticity. The new formulation of the trailing edge noise problem by Glegg et al. (2004) is attractive because it applies to the high frequencies of interest but does not require an excessive computational effort. Also, the nature of the formulation permits the identification of the modes producing the noise and their associated velocity fluctuations as well as the regions of the boundary layer responsible for the noise production. The source terms were obtained using the direct numerical simulation of a turbulent channel flow by Moser et al. (1998). Two-point velocity and vorticity statistics of this data set were obtained by averaging 41 instantaneous fields. For comparisons purposes, experimental boundary layer data by Adrian et al. (2000) was chosen. Statistical reduction of 50 velocity fields obtained by particle image velocimetry was performed and analysis of the two-point correlation function showed features similar to the DNS data case. Also, proper orthogonal decomposition revealed identical dominant modes and eddy structures in the flow, therefore justifying considering the channel flow as an external boundary layer for noise calculations. Comparison of noise predictions with experimental data from Brooks et al. (1989) showed realistic results with the largest discrepancies, on the order of 5 dB, occurring at the lowest frequencies. The DNS results are least applicable at these frequencies, since these correspond to the longest streamwise lengthscales, which are the most affected by the periodicity conditions used in the DNS and also are the least representative of the turbulence in an external boundary layer flow. Most of the noise was shown to be produced by low-frequency streamwise velocity modes in the bottom 10% of the boundary layer and locations closest to the wall. Only 6 modes were required to obtain noise levels within 1 dB of the total noise. Finally, the method for predicting spatial velocity correlation from Reynolds stress data in wake flows, originally developed by Devenport et al. (1999, 2001) and Devenport and Glegg (2001), was adapted to boundary-layer type flows. This method, using Reynolds stresses and the prescription of a lengthscale to extrapolate the full two-point correlation, was shown to produce best results for a lengthscale prescribed as proportional to the turbulent macroscale. Noise predictions using modeled two-point statistics showed good agreement with the DNS inferred data in all but frequency magnitude, a probable consequence of the modeling of the correlation function in the streamwise direction. Other quantities associated to noise were seen to be similar to the ones obtained using the DNS.
Master of Science
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2

Eisenman, Adam. "Estimating light edge velocity based on retinal ganglion cell spike trains." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40323.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 136-137).
This thesis is intended to present a specific sub-problem of a larger one we call the 'Inverse Problem'. We wish to estimate the velocity (speed and direction) of an edge of light which is moving on the photoreceptor layer of a rabbit retinal patch. We make these estimates based solely on the electrical response measured from the retinal ganglion cells (RGCs). We present various algorithms for doing so and present sensitivity analysis of such algorithms. We test the performance of the algorithms on data recorded from retina and on data produced by simulation. We find that we are able to extract enough information about the edge velocity from ON and OFF RGCs when the edge of light is wide. However, our best algorithm's performance decays significantly as the edge of light gets narrower. This leads us to develop algorithms that use ON-OFF directionally selective (DS) cells in conjunction with non-directional ON and OFF cells to produce better estimates of the velocity for narrow edges of light. In addition, we develop a model to simulate the response of a DS cell to 1-dimensional light motion.
by Adam Eisenman.
S.M.
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3

Malhotra, Anjum. "Low velocity edge impact on composite laminates : damage tolerance and numerical simulations." Thesis, Queen Mary, University of London, 2014. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8571.

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Composite laminates are increasingly being used in more complex structural applications where edges and cut outs are inevitable. These applications include wing skins of military and civil aircraft, further aerospace applications as well as automotive panels and critical structures. Composite components in such applications are highly susceptible to damage. Composites behave in a different manner to conventional metallic materials, which has introduced several design problems not previously encountered. One such problem has been the susceptibility of the material to accidental low energy impacts which frequently leave no visible mark on the impacted surface but considerable internal damage. Investigation of the residual strength and stiffness of composites after edge impact has become important for the design of aerospace components. Previously, the research work involved central impact of composite laminates but in this research we are investigating edge impact behaviour of composite laminates as parts of composite structures are particularly vulnerable to impacts, including near the edge of an inspection port or other aperture. Furthermore, impacts to such areas may lead to more severe damage near the edge of the laminate rather than the surface. Thus the present work extends these investigations to impact on the edge of composite laminates. The thesis includes both experimental investigations and finite element simulations of impact damage on the plane of the laminate near the edge (near-edge), and on the edge (on-edge) of composite laminates. A comparison with centre impact with on and near-edge impact is done to understand the damage on the edges and away from the edges. A new design has been developed and implemented to perform edge impact experiments. The research investigated the effects of various parameters like thickness, absorbed energies, force-time histories and damage behaviour of composite laminate. The damage size and mechanisms have been explored. Impact simulation was carried out using finite element code Abaqus. Explicit solution technique of the code was used to analyse the edge impact phenomenon. Results of the finite element analysis were compared with experiments. The residual strength of the laminates under compressive and tensile loading has been measured. Tensions after impact (TAI) tests were conducted to evaluate the residual load carrying capacity. The effect of edge impact on the low velocity impact response and the residual tensile strength is discussed via the test results. This thesis also includes computed tomography as the main technique for micro level damage characterisation and investigates the study of damage mechanisms of glass/epoxy laminates subjected to edge impact with varying energy levels and thickness. Computed Tomography aims to provide damage behaviour such as internal damage state, delaminations during different types of edge impact.
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4

Josefsson, Mattias. "3D camera with built-in velocity measurement." Thesis, Linköpings universitet, Datorseende, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-68632.

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In today's industry 3D cameras are often used to inspect products. The camera produces both a 3D model and an intensity image by capturing a series of profiles of the object using laser triangulation. In many of these setups a physical encoder is attached to, for example, the conveyor belt that the product is travelling on. The encoder is used to get an accurate reading of the speed that the product has when it passes through the laser. Without this, the output image from the camera can be distorted due to a variation in velocity. In this master thesis a method for integrating the functionality of this physical encoder into the software of the camera is proposed. The object is scanned together with a pattern, with the help of this pattern the object can be restored to its original proportions.
I dagens industri används ofta 3D-kameror för att inspektera produkter. Kameran producerar en 3D-modell samt en intensitetsbild genom att sätta ihop en serie av profilbilder av objektet som erhålls genom lasertriangulering. I många av dessa uppställningar används en fysisk encoder som återspeglar hastigheten på till exempel transportbandet som produkten ligger på. Utan den här encodern kan bilden som kameran fångar bli förvrängd på grund av hastighetsvariationer. I det här examensarbetet presenteras en metod för att integrera funktionaliteten av encodern in i kamerans mjukvara. För att göra detta krävs att ett mönster placeras längs med objektet som ska bli skannat. Mönstret återfinns i bilden fångad av kameran och med hjälp av detta mönster kan hastigheten bestämmas och objektets korrekta proportioner återställas.
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5

Sierchio, Jennifer Marie. "Comparison of edge turbulence velocity analysis techniques using Gas Puff Imaging data on Alcator C-Mod." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91073.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Physics, 2014.
30
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 117-119).
In the past, two methods for analyzing data from the Gas Puff Imaging diagnostic on Alcator C-Mod have been used. One uses temporal and spatial Fourier analysis to obtain wavenumber-frequency spectra, from which a phase velocity is computed [1, 2]. The other is based on time-delay cross-correlation of successive images used to track the motion of discrete emission structures [3, 4]. Several Gas-Puff-Imaging experiments were conducted to obtain data taken using the GPI Phantom Camera. The analysis of and results from these data are discussed in [3]. The results showed that the tracking time-delay-estimation technique found poloidal velocity magnitudes in the 0.1-1.4 km/sec range. However, independent examination of these data using the Fourier analysis yielded magnitudes up to a factor of 10 larger for the same data, and sometimes even disagreed with the direction of motion found. To understand the reasons for these discrepancies, we designed and generated synthetic data that mimics the real data. The user inputs the velocities, sizes, intensities, and distributions of the synthetic emission structures. We have used the synthetic data to test each code rigorously for strengths, weaknesses, and weighting. We have found that the Fourier analysis perfectly returns the correct poloidal velocity when there is no radial velocity component present. We have found that the tracking TDE analysis weights low frequency, low wavenumber features most heavily since they are typically the most intense, but systematically returns a smaller velocity than expected due to issues associated with averaging. After adjusting for these issues, the tracking TDE code now returns the correct value of the poloidal and radial velocities to within 10% for synthetic data as long as there is only one velocity present in the synthetic simulation. We applied these corrections to the analysis of the real data, and found that the measurements changed little in most cases. We then examined, in detail, the Fourier-analysis-derived "conditional" spectra for each shot, and determined that the likely causes for the discrepancies are due either to multiple velocities with emission structures moving in opposite directions in the same field of view or to non-zero "dispersion" in which lower-frequency/lower-wavenumber features are moving with one phase velocity and higher-frequency/higher-wavenumber features are moving with a different phase velocity. In a couple of cases, there may be a radial component in the actual images that may affect the poloidal velocity measurement for the Fourier analysis. Accounting for these explanations, we believe that we have resolved the discrepancies in many cases, and can explain it in the others.
by Jennifer Marie Sierchio.
S.M.
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6

Glenn, Timothy Scott 1971. "Velocity measurement of laser energy induced Rayleigh surface waves on bulk substrates employing the optical beam deflection (knife-edge detection) method." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/49947.

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7

Whitehouse, David Richard Carleton University Dissertation Engineering Aerospace. "The effect of axial velocity ratio, turbulence intensity, incidence and leading edge geometry on the off-design performance of a turbine blade cascade." Ottawa, 1993.

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8

Abraham, Rohit Mathew. "An Experimental Study of Scuffing Performance of a Helical Gear Pair Subjected to Different Lubrication Methods." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1397228984.

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9

Leybros, Robin. "Etude des vitesses de dérive fluides dans le plasma de bord des tokamaks : modélisation numérique et comparaison simulation/expérience." Thesis, Ecole centrale de Marseille, 2015. http://www.theses.fr/2015ECDM0006/document.

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Le transport des particules et de la chaleur dans la zone de bord des tokamaks joue un rôle déterminant à la fois sur les performances du plasma confiné et sur l’extraction de la puissance et ainsi la durée de vie des composants face au plasma. C’est dans ce contexte que s’inscrit ce travail de thèse, qui porte sur le rôle joué par les écoulements transverses au champ magnétique dans l’équilibre entre dynamique parallèle et dynamique perpendiculaire qui régit la région périphérique d’un tokamak. Ces écoulements peuvent produire des asymétries poloïdales du dépôt de chaleur et de particules sur les composants face au plasma, et plus généralement des asymétries des diverses quantités dans le plasma. Les vitesses de dérive radiale sont d’origine électrique (liées à la présence d’un champ électrique radial résultant de l’équilibre des charges) ou liées aux effets de la géométrie toroïdale induisant une inhomogénéité du champ magnétique (vitesse de gradient-courbure). Pour progresser dans la compréhension de ces phénomènes, la modélisation numérique du transport et de la turbulence en géométrie complexe est indispensable. En complément, des outils de diagnostic synthétique permettant de modéliser les processus de mesure dans les plasmas numériques sont développés pour permettre une comparaison réaliste entre modèles et expériences. La modélisation des vitesses de dérive perpendiculaire a été introduite dans le code SOLEDGE2D décrivant le transport de la densité, quantité de mouvement et énergie d’un plasma de tokamak. Nous avons d’abord étudié l’impact d’un champ électrique prescrit sur les équilibres plasma, pour comprendre les mécanismes à l’origine des asymétries du plasma et étudier l’établissement d’écoulement parallèle et d’asymétrie du dépôt de chaleur sur les composants face au plasma. Nous avons ensuite implémenté un modèle auto-consistant de résolution du potentiel électrique dans les équations fluides de SOLEDGE2D afin de comprendre l’équilibre du champ électrique et d’étudier l’effet de la configuration magnétique du tokamak et de la vitesse de gradient-courbure sur ce dernier. Dans la deuxième partie de cette thèse, un diagnostic synthétique permettant de modéliser les mesures expérimentales de rétro-diffusion Doppler a été développé et testé en vue d’être appliqué aux simulations du code fluide 3D turbulent, TOKAM3X. Ce diagnostic permet de mesurer la vitesse perpendiculaire du plasma à partir du mouvement des fluctuations de densité. Il a été utilisé ici pour comparer les asymétries de vitesse observées expérimentalement aux asymétries mesurées dans les simulations numériques
The transport of heat and particles in the edge of tokamaks plays a key role in both the performance of the confined plasma and the extraction of power and thus the lifetime of the plasma facing components. It’s in this context that this thesis is inscribed, which focuses on the role played by the transverse magnetic field flows in the balance between parallel and perpendicular dynamic that governs the edge region of a tokamak. These flows can produce poloidal asymmetries of heat and particles deposit on plasma facing components and generally asymmetries of various amounts in plasma. The radial drift velocities are due to the presence of a radial electric field resulting from charge balance (electric drift velocity) or related to effects of the toroidal geometry inducing a magnetic field inhomogeneity (curvature drift velocity). To advance the understanding of these phenomena, numerical modeling of transport and turbulence in complex geometries is essential. In addition, synthetic diagnostic tools for modeling the measurement process in numerical plasmas are developed to enable a realistic comparison between models and experiments. Modeling of perpendicular drift velocities was introduced into the SOLEDGE2D code describing the transport of the density, momentum and energy of a tokamak plasma. We first studied the impact of a prescribed electric field on plasma equilibrium to understand the mechanisms behind plasma asymmetries and study the establishment of parallel flows and asymmetry of the heat flux on plasma facing components. Then we implemented a self-consistent model solving the electric potential in SOLEDGE2D fluid equations to understand the equilibrium of the electric field and to study the effect of the magnetic configuration of the tokamak and the curvature drift velocity on it. In the second part of this thesis, a synthetic diagnosis modeling the experimental measurements of Doppler backscattering was developed and tested in order to be applied to simulations of 3D turbulent fluid code TOKAM3X. This diagnosis measures the perpendicular velocity of the plasma from the movement of the density fluctuations. It was used to compare the perpendicular velocity asymmetries observed experimentally to asymmetries measured in numericalsimulations
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10

Lismonde, Baudouin. "Champ de vitesse au bord d'attaque et dans le spot laminaire d'un écoulement sur une plaque plane." Grenoble 1, 1987. http://www.theses.fr/1987GRE10074.

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Calcul numerique des champs de vitesse, de pression et de temperature dans la zone pres du bord d'attaque ou il faut utiliser une approximation d'ordre 3 de la couche limite. Mesure des trois composantes de la vitesse de l'ecoulement perturbe par un microjet instantane traversant la couche limite laminaire
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11

Lindeberg, Tony. "Discrete Scale-Space Theory and the Scale-Space Primal Sketch." Doctoral thesis, KTH, Numerisk analys och datalogi, NADA, 1991. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-58570.

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This thesis, within the subfield of computer science known as computer vision, deals with the use of scale-space analysis in early low-level processing of visual information. The main contributions comprise the following five subjects: The formulation of a scale-space theory for discrete signals. Previously, the scale-space concept has been expressed for continuous signals only. We propose that the canonical way to construct a scale-space for discrete signals is by convolution with a kernel called the discrete analogue of the Gaussian kernel, or equivalently by solving a semi-discretized version of the diffusion equation. Both the one-dimensional and two-dimensional cases are covered. An extensive analysis of discrete smoothing kernels is carried out for one-dimensional signals and the discrete scale-space properties of the most common discretizations to the continuous theory are analysed. A representation, called the scale-space primal sketch, which gives a formal description of the hierarchical relations between structures at different levels of scale. It is aimed at making information in the scale-space representation explicit. We give a theory for its construction and an algorithm for computing it. A theory for extracting significant image structures and determining the scales of these structures from this representation in a solely bottom-up data-driven way. Examples demonstrating how such qualitative information extracted from the scale-space primal sketch can be used for guiding and simplifying other early visual processes. Applications are given to edge detection, histogram analysis and classification based on local features. Among other possible applications one can mention perceptual grouping, texture analysis, stereo matching, model matching and motion. A detailed theoretical analysis of the evolution properties of critical points and blobs in scale-space, comprising drift velocity estimates under scale-space smoothing, a classification of the possible types of generic events at bifurcation situations and estimates of how the number of local extrema in a signal can be expected to decrease as function of the scale parameter. For two-dimensional signals the generic bifurcation events are annihilations and creations of extremum-saddle point pairs. Interpreted in terms of blobs, these transitions correspond to annihilations, merges, splits and creations. Experiments on different types of real imagery demonstrate that the proposed theory gives perceptually intuitive results.

QC 20120119

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12

Cantoni, Lorenzo. "Load Control Aerodynamics in Offshore Wind Turbines." Thesis, KTH, Kraft- och värmeteknologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291417.

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Due to the increase of rotor size in horizontal axis wind turbine (HAWT) during the past 25 years in order to achieve higher power output, all wind turbine components and blades in particular, have to withstand higher structural loads. This upscalingproblem could be solved by applying technologies capable of reducing aerodynamic loads the rotor has to withstand, either with passive or active control solutions. These control devices and techniques can reduce the fatigue load upon the blades up to 40% and therefore less maintenance is needed, resulting in an important money savings for the wind farm manager. This project consists in a study of load control techniques for offshore wind turbines from an aerodynamic and aeroelastic point ofview, with the aim to assess a cost effective, robust and reliable solution which could operate maintenance free in quite hostile environments. The first part of this study involves 2D and 3D aerodynamic and aeroelastic simulations to validate the computational model with experimental data and to analyze the interaction between the fluid and the structure. The second part of this study is an assessment of the unsteady aerodynamic loads produced by a wind gust over the blades and to verify how a trailing edge flap would influence the aerodynamic control parameters for the selected wind turbine blade.
På grund av ökningen av rotorstorleken hos horisontella vindturbiner (HAWT) under de senaste 25 åren, en design som har uppstod för att uppnå högre effekt, måste alla vindkraftkomponenter och blad stå emot högre strukturella belastningar. Detta uppskalningsproblem kan lösas genom att använda metoder som kan minska aerodynamiska belastningar som rotorn måste tåla, antingen med passiva eller aktiva styrlösningar. Dessa kontrollanordningar och tekniker kan minska utmattningsbelastningen på bladen med upp till 40 % och därför behövs mindre underhåll, vilket resulterar i viktiga besparingar för vindkraftsägaren. Detta projekt består av en studie av lastkontrolltekniker för havsbaserade vindkraftverk ur en aerodynamisk och aeroelastisk synvinkel, i syfte att bedöma en kostnadseffektiv, robust och pålitlig lösning som kan fungera underhållsfri i tuffa miljöer. Den första delen av denna studie involverar 2D- och 3D-aerodynamiska och aeroelastiska simuleringar för att validera beräkningsmodellen med experimentella data och för att analysera interaktionen mellan fluiden och strukturen. Den andra delen av denna studie är en bedömning av de ojämna aerodynamiska belastningarna som produceras av ett vindkast över bladen och för att verifiera hur en bakkantklaff skulle påverka de aerodynamiska styrparametrarna för det valda vindturbinbladet.
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Marin, Ospina Yohan Manuel. "Etude de l'influence de la dilution du combustible et de l'oxydant dans le processus de décrochage de flammes-jet non-prémélangées et l'émission de polluants." Thesis, Rouen, INSA, 2016. http://www.theses.fr/2016ISAM0025/document.

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La compréhension des mécanismes pilotes de la stabilisation des flammes-jet non-prémélangées constitue un point clé dans la caractérisation des modes opératoires des brûleurs industriels fonctionnant en régime de combustion diluée. Ce travail porte son attention sur l'étude expérimentale de l'influence de la dilution du combustible ou de l'air, sur le processus de décrochage et l'émission des polluants d'une flamme-jet non-prémélangée accrochée au brûleur. L'investigation est menée via un grand nombre d'expériences par combinaison des conditions suivantes : i) dioxyde de carbone (CO2), azote (N2), argon (Ar) et vapeur d'eau (H2Ov), sont utilisés comme diluants ; ii) deux configurations de dilution : dilution de l'air ou dilution du combustible ; iii) un couple de vitesses d'air et de combustible couvrant le domaine d'hystérésis de la flamme dans sa totalité, du régime de jet laminaire à celui de jet turbulent. Ceci permet de discriminer l'influence des effets intrinsèques à la nature du diluant de celle de l'aérodynamique des réactants (combustible et oxydant), dans la stabilité de la flamme accrochée. En particulier, les différences comportementales de la réponse de la flamme à la dilution de l'air ou à celle du combustible, sont analysées. Ces deux configurations de dilution diffèrent par deux effets de mélange, indépendants de la réaction, qui jouent un rôle important dans le cas de la dilution du combustible, mais sont négligeables dans le cas de celle de l'air : i) un effet dû à la modification de la fraction de mélange stœchiométrique. ii) un impact mécanique induit par l'apport de matière (diluants) responsable d'une augmentation de la vitesse des réactants. L'étude se divise en trois principales étapes. D'abord la réponse globale de la flamme à la dilution est étudiée via ses limites de décrochage quantifiées par les fractions molaires critiques des diluants dans l'oxydant ou dans le combustible, mesurées au décrochage. Le nombre de Peclet du combustible, Pef, est identifié comme le nombre adimensionnel qui ordonne ces limites de décrochage de manière homothétique pour tous les diluants. Grâce au comportement homothétique deux coefficients d'affinité, Kd,ox pour le cas de la dilution de l'air et Kd,f pour celle du combustible, sont introduits. Ils sont définis comme le rapport entre la limite de décrochage obtenue avec un diluant et celle obtenue avec le CO2 , à Pef = cste. Ceux-ci permettent l'établissement de deux polynômes génériques décrivant les limites de décrochage pour tous les diluants testés et dans toute la gamme des conditions aérodynamiques étudiées. En effet, Kd,ox et Kd,f englobent l'ensemble des effets physico-chimiques d'un diluant (dilution pure, thermique, propriétés de transport, chimie) et ceux des impacts mécaniques, affectant la stabilité de la flamme. Ils permettent de trouver les lois d'auto-similitude au décrochage pour un diluant chimiquement faible quelconque, à partir des résultats obtenus dans ce travail. Ensuite, une étude locale et détaillée du processus de décrochage induit par la dilution est réalisée. Celui-ci se base sur l'approche du bout propagatif décrivant la stabilité de la flamme accrochée comme résultant d'un équilibre à sa base entre la vitesse de l'écoulement et la vitesse de propagation. Afin de démontrer le lien entre cette approche et la stabilité de la flamme, une analyse approfondie des caractéristiques de sa base (localisation, intensité du radical CH* et champ de vitesses) est réalisée. Les résultats confirment la pertinence de l'approche du bout propagatif, comme mécanisme descriptif de la stabilisation de la flamme accrochée en présence de dilution. Enfin, une étude caractérisant aussi bien l'influence de la nature des diluants que celle de la configuration de dilution choisie (air ou combustible), sur l'émission des polluants (suies, NOx et CO), est présentée
Understanding the main mechanisms piloting non-premixed jet flame stability is an important point in characterizing the operation modes of industrials burners in which dilution is involved. This work puts special emphasis on the experimental study of the influence of air-side and methane-side dilution in the lifting process of attached non-premixed jet flames. The study is based on numerous experiments combining the following conditions : i) carbon dioxide (CO2), nitrogen (N2), argon (Ar) or water vapor (H20v,) used as diluents d ; ii) two diluted configurations : air-side or methane-side dilution ; iii) two air and fuel velocities covering the entire flame hysteresis domain, from the laminar to the turbulent regime. This allows the influence of the intrinsic diluent nature effects to be discriminated from those of the aerodynamics of the reactants (fuel and oxidant), in attached flame stability. In particular, the behavioral differences of the flame response to air-side or to fuel-side dilution are analyzed. These two configurations differ by two mixing effects which are independent of the combustion reaction, and which are significant when the fuel is diluted, but negligible when air is diluted : i) an effect due to the changes in the stoichiometric mixture fraction ; ii) a mechanical impact induced by the addition of matter (diluents) producing an increase in the bulk velocity of the reactants. The study is composed of three parts. First, the global flame response to dilution is analyzed on the basis of the lifting limits defined as the critical molar fractions of the diluents in the fuel or in the oxidant measured at liftoff. The fuel Peclet number, Pef, appears as the dimensionless number which puts these limits in a homothetic order. This homothetic behavior allows the introduction of two affinity parameters, Kd,ox for air-side dilution and Kd,f for fuel-side dilution. They are defined by the ratio of the flame lifting limits calculated with a diluent d and with CO2, at Pef=const. Kd,ox and Kd, allow two generic polynomial laws to be established describing the flame lifting limits for all the diluents and in the whole range of aerodynamic conditions of this study. Indeed, Kd,ox and Kd,f encompass all the diluent effects affecting flame stability (pure dilution, thermal, transport, chemical), to which mechanical impacts are added. These coefficients make it possible to obtain the self-similarity laws of the lifting limits for any chemically-weak diluent, by using the results obtained in this work. Then, a local and detailed study of the flame lifting process induced by dilution is presented. This is based on the flame-leading-edge approach describing flame stability as a result of the balance between the incoming gas velocity of the reactants and the flame propagation velocity at the flame base. In order to show the link between this approach and flame stability, an extensive analysis of the flame-base characteristics (location, CH* emission intensity and velocity field) is carried out. The results attest to the pertinence of the propagative flame-leading-edge, as the mechanism describing the attached flame stability under dilution. Finally, a study concerning the influence of both the diluent nature and the diluted configuration (air or fuel) on pollutant emissions (soot, NOx and CO) is presented
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Ležovič, Tomáš. "Experimentální analýza proudu vzduchu z ofukovače osobního vozu s využitím žárového anemometru a návrh hodnocení kvality ofukovače." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2011. http://www.nusl.cz/ntk/nusl-229643.

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The master’s thesis deals with air flow in the interior of automobile Škoda Octavia. The attention is focused only at a side ventilating outlet. Author’s effort was to propose the appropriate criteria for evaluation and assessment of ventilating outlet quality and elaborate the methodology of measurement for these criteria. Then follows the application of the methodology and measurement of velocity field of air flow from the outlet by the method of hot wire anemometry. The thesis also contains comparison of the results with the results attained by the smoke visualization.
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15

Kunze, Claudia. "Acoustic and velocity measurements in the flow past an airfoil trailing edge." 2004. http://etd.nd.edu/ETD-db/theses/available/etd-04022004-092958/.

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16

"Effects of edge safety factor on the toroidal flow velocity of the STOR-M plasma." Thesis, 2015. http://hdl.handle.net/10388/ETD-2015-02-1962.

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The effect of changing edge safety factor on the toroidal flow of the STOR-M plasma has been investigated during the application of both resonant magnetic perturbation (RMP) and compact torus injection (CTI). The edge safety factor was varied by varying the plasma current while keeping the toroidal field constant. A Czyner-Turner spectrometer was used to collect the spectral data from which the velocity of specific impurity ions was diagnosed. Time resolved velocity measurements were inferred from the Doppler wavelength shift of the emission lines. Impurity emission lines at different ionization stages are located at different radial locations within the STOR-M plasma. Properties of these impurity ions are assumed to be closely related the hydrogen ion (main working gas) due to the strong interaction among the ion species. Changing the edge safety factor has a similar effect on the toroidal flow of STOR-M plasma during discharges with both RMP and CTI. A velocity shear was discovered for different impurity ions. The toroidal flow is enhanced for edge ions while a reversal of flow is observed for core ions. As the edge safety factor reduces, the emission location for the core ions is located with q=2 surface and RMP has a significant impact on their toroidal flow velocity. It was also observed that CT injection has a significant effect on the toroidal velocity of the core ions compared to that of the edge ions. In addition, high plasma current (low safety factor) induced large change in the toroidal flow velocity of the STOR-M plasma.
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