Global ETD Search

1	Study of the Effects of Geometric Parameters and Yaw Angle on Drag Generation in Clean Rectangular Cavities Shiyani, Dhaval 24 September 2018 (has links) No description available. Engineering CFD OpenFOAM Cavity flow Drag Yaw angle Geometric modifications
2	Counterflowing jets: scaling factors and mean concentration fields Torres Garcia, Luis A. Unknown Date No description available. PLIF Calibration Counterflowing Jet Concentration Scales Yaw-angle Laser Fluorescence Scalar
3	Counterflowing jets: scaling factors and mean concentration fields Torres Garcia, Luis A. 11 1900 (has links) An experimental investigation of the mean scalar concentration field of jets into a uniform counterflow stream using planar laser induced fluorescence is presented. The centerline decay and radial spreading of the mean concentration field of the jet were investigated. Jet to counterflow velocity ratios ranging between 4 to 19 were used for two different jet diameters. Universal forms for the centerline concentration decay, and radial concentration profiles of the jet are presented. Scaling factors of the centerline concentration decay are introduced. The jet growth rate was found to be divided into two regions: the linear growth region and the power law growth region. The effects of inlet yaw angles on the penetration length, axial concentration decay and similarity region of the counterflowing jet are presented. A minimal effect of the tested inlet yaw angles on the concentration field was observed. Empirical expressions to predict the centerline concentration decay are given. PLIF Calibration Counterflowing Jet Concentration Scales Yaw-angle Laser Fluorescence Scalar
4	Assessing Wake Shading Effects in Wind Farms : Impact of turbine spacing and yaw angle Tesfaye, Dawit Kefyalew January 2024 (has links) This study investigates the wake shading effect in wind farms, focusing on turbine spacing, horizontal rotor tilt (yaw angle), wind speed, and power production. With the global population increasing, the demand for energy continues to rise, emphasizing the importance of renewable energy sources like wind power. In wind farms, where multiple turbines operate together, the wake effect resulting from one turbine's influence on wind flow for others significantly impacts their power production. This research is focused around Jädraås Wind Power Park in Sweden, using a scaled model of a section of this park in a controlled environment to conduct a detailed analysis. Utilizing both experimental setups in a wind tunnel and numerical simulations for visualization, the study explores the dynamics of wake interactions among turbines and proposes to mitigate their adverse effects.Through the experiments conducted in the wind tunnel, the results demonstrate significant wakeinduced power losses at downstream turbines. The yaw adjustment mechanism of the upstream turbine is used so as to see how it has affected the power output of downstream turbine. The results also indicate significant reductions in power production as a function of turbine spacing. Specifically, the maximum reduction in power output, influenced by the presence of two upstream turbines, occurred at closer spacings between them: a decrease of 66% at 2.08D (2.08 Rotor Diameters between the downstream and the nearest upstream turbine) and 45% at 4.15D. Conversely, at broader spacings of 7.29D and 8.3D, the reductions were more moderate, a decrease of 28% and 18%, respectively. These findings underscore the critical influence of spatial arrangement on the wake-induced power losses within wind farms.Through an investigation of two purposely positioned upstream and downstream turbines at 4D meter of spacing, the optimal yaw angle for maximum combined power generation has been predicted using sinusoidal fitting, the results indicated that at yaw angle range of ±11° of theupstream turbine rotor, a maximum combined power output has been observed. Hence, a sophisticated optimization mechanism should be employed in an operating wind farm so as tolower wake effects. Wind farm wake shading power deficit wind tunnel yaw angle turbine spacing Energy Systems Energisystem
5	Investigation of fluid-dynamic cavity oscillations and the effects of flow angle in an automotive context using an open-jet wind tunnel. Milbank, Juliette, milbank@turbulenflow.com.au January 2005 (has links) Aeroacoustic whistles are a significant source of customer complaints to automotive manufacturers. Whistles can occur on many such components, but the relative position and configuration of rearview mirrors means they are a more problematic source of tonal noise on vehicles. The low subsonic complex turbulent flow, combined with small cavity scales, determines the possible whistle mechanisms. The one considered to be most problematic, fluid-dynamic cavity resonance, is the topic of this research thesis. The research scope is limited to the automotive environment of external rearview mirrors and the fluid-dynamic resonance mechanism: low subsonic Mach number, M = 0.05 - 0.13; laminar boundary layers; and two-dimensional, acoustically compact cavities. The low unit-cost of rearview mirrors and the desire to have simple identification and prediction schemes, that could be used by production engineers, determined an empirical approach. A search of the existing literature revealed that there were some data on cavities of the above scale in low Mach number flow, but quoted errors in empirical descriptions were large and there was very little research on the effects of flow yaw angle on the chosen resonance mechanism. The research therefore aims to determine whether existing empirical descriptions of fluid-dynamic cavity resonance are suitable for the prediction of the resonance characteristics, with sufficient accuracy to enable unambiguous identification of the presence of the resonance and its mechanism. A second aim is to investigate the effects of a feature of the automotive flow environment, flow yaw angle, on the resonance. Flow yaw angle is determined by those components of the flow in the same plane as the surface in which the cavity is situated. An experimental program was undertaken using a purpose-built aeroacoustic wind tunnel and a simple cavity model. Testing with two types of cavity configurations, as well as flow visualisation, investigated the main features of the resonance in time-averaged yawed flow. Within the scope of this thesis, it is shown that fluid-dynamic cavity resonance characteristics can be accurately identified by a simple empirical model, even in yawed flow. Various descriptors allow identification of the resonance threshold, stage, frequency and relative amplitude in non-yawed flow, while the frequency and stage can also be identified in yawed flow. The relative decrease in resonance amplitude in yawed flow, although identified for these experiments, would depend on the degree of spanwise variation in the boundary layer characteristics for a given cavity configuration. The results also identify significant issues with testing in a free jet tunnel, due to the nature of fluid-dynamic cavity resonance and the fluctuation energy content in free shear layers. Despite this, the thesis aims are achieved, and appropriate design guidelines are produced for automotive designers. cavities fluid-dynamic oscillations self-sustained oscillations shear tones flow yaw angle automotive open-jet wind tunnel free shear layer interaction
6	Analyse expérimentale et numérique du comportement de véhicules terrestres en présence d'un vent latéral instationnaire / Experimental and numerical analysis about ground vehicles behaviour when subjected to an unsteady side wind Volpe, Raffaele 11 March 2013 (has links) L’aérodynamique latérale des véhicules automobiles suscite de nos jours de plus en plus d’intérêt de la part des constructeurs. L’automobiliste est en effet soumis quotidiennement à de forts courants d’air latéraux, que ce soit lors du dépassement d’un autre véhicule, ou alorsen passant dans un couloir de vent du à la topographie du terrain (passage devant un espace entre deux immeubles par exemple). Les efforts aérodynamiques mis en jeu dans ces situations peuvent provoquer des mouvements non désirés du véhicule, pouvant avoir des conséquences dramatiques si le conducteur se laisse surprendre. Des études expérimentales reproduisant les effets d’un dérapage dynamique ont mis en évidence des phénomènes transitoires importants mettant à défaut les modèles stationnaires généralement pratiqués par les constructeurs pour qualifier le comportement de leurs véhicules en présence de dérapage. Les mécanismes responsables de ces phénomènes transitoires sont encore mal connus de la communauté scientifique. Ce travail propose d’approfondir ce sujet au travers de l’étude de l’aérodynamique d’un véhicule terrestre fixe soumis à un vent longitudinal et à une rafale de vent latéral. Le but principal est d’identifier les structures tourbillonnaires au moyen de mesures PIV et de calculs numériques des champs de vitesse autour d’une maquette automobile et de les corréler aux efforts aérodynamiques. Un accord entre l’ISAT, composante de l’Université de Bourgogne, et l’Institut Supérieurde l’Aéronautique et de l’Espace (ISAE) de Toulouse a permis de mener l’étude avec les ressources de cet établissement. Le moyen d’essai principal, créé par l’ISAE, est le banc« rafale latérale », constitué d’une soufflerie principale et d’une soufflerie secondaire, dont la sortie à volet déferlants (« Mexican Wave ») est inspirée de l’approche proposée par Ryan et Dominy (2000). L’analyse expérimentale a été effectuée à l’aide de la PIV résolue en temps et stéréoscopique, et d’une balance dard instationnaire à cinq composantes. Un banc« numérique » identique a été constitué à l’aide du logiciel FLUENT©, pour des calculs 3D. De plus, un modèle 2D annexe, basé sur la méthode « meshless », a été développé pour de futures investigations, en raison de sa robustesse pour des problèmes à fortes discontinuités et sa bonne adaptabilité aux problèmes avec frontières mobiles.Une première phase de ce travail a consisté en la mise au point des bancs expérimental et numérique, avec génération d’un champ de dérapage homogène, de 21° dans la zone de mesure. L’évolution du dérapage en chaque point respecte bien la forme d’un créneau imposé par la rafale. Pour l’analyse des efforts, deux géométries de maquette ont été étudiées, à savoir un corps de Windsor à culot droit générant, pour un écoulement longitudinal, des structures de sillage bidimensionnelles, et son homologue à culot incliné de 25°, générant des tourbillons « cigare ». Des pics d’efforts ont été observés à l’arrivée de la rafale, tout comme la littérature le prédit. Pour ce qui est du coefficient du moment de lacet, les sursauts sont de 29 % et 19 % respectivement pour la maquette à culot droit et celle à culot incliné, par rapport aux valeurs stationnaires. Concernant le coefficient de force de dérive, ils sont de 10 % et 14 %, respectivement. Lors de nos essais, ces efforts se sont établis après 5.5 longueurs de maquette. Afin d’expliquer la différence de comportement entre les deux maquettes en termes d’efforts, l’évolution temporelle des tourbillons nommés, dans ce mémoire, ΓA, ΓB, ΓC et Γ1 à été discutée. Il en est ressorti une forte corrélation entre la circulation du tourbillon ΓA, le plusénergétique, naissant à l’avant du flanc sous le vent de la maquette, et les efforts latéraux, de sorte que ce tourbillon serait le meilleur témoin des phénomènes instationnaires mis en jeu dans l’étude de l’effet du vent latéral. [...] / The automotive manufacturers are nowadays more and more interested in crosswind aerodynamics. Indeed, the driver is subjected every day to strong side air flows, for example when overtaking another vehicle or when passing through a lateral wind wall, generated by terrain topography (as in the case of the passage near the empty space between two buildings).The aerodynamic efforts generated in these situations can lead to undesired lateral deviations,which can be dramatic if the driver is surprised. Different experimental studies, reproducing the effects of a dynamic yaw angle, pointed out the issues of the steady methods, commonly used to qualify the vehicle crosswind behaviour. Little is still known about the physics behind these unsteady phenomena. This is the main topic of this work, by studying the aerodynamics of a fixed vehicle subjected to both a longitudinal flow and a side wind gust. The goal is the identification of the near-vehicle vortex structures, by means of PIV measurements and CFD calculations, and their correlation with the evolution of the efforts. An agreement between the ISAT, a department of the University of Burgundy, and the ISAE of Toulouse, permitted to carry out this research with the resources of the latter laboratory. The work focuses on the use of the “rafale latérale” (side gust) test bench, made up with a main wind tunnel connected with an auxiliary one by means of a shutter system,whose opening is held by a “Mexican Wave” law. This approach is inspired by the work of Dominy and Ryan (2000). The experimental analysis was carried out by means of Time-Resolved and stereoscopic PIV, and by a five components unsteady balance as well. Anidentical test bench was numerically reproduced with the 3D CFD software FLUENT©.Moreover, an additional 2D CFD model, based on the meshless method, has been developed for future studies. This kind of approximation method has been chosen for its robustness innon-continuous problems and because of its adaptability when moving boundaries are needed.The first phase of this work consisted on wind tunnels set-up, both for the real test bench and for the CFD model. The yaw angle field is homogeneous, 21° in the measurement region. The yaw angle evolution, at given point, respects the step wise behaviour, imposed by the gust passage. As far as the efforts are concerned, two versions of the Windsor body car model were studied, that is a squareback geometry, generating, for longitudinal flows, 2D wakestructures, and a fastback geometry (rear window inclined by 25°), producing cone-liketrailing vortices. Force overshoots were seen after the gust arrival, as seen in literature. In particular, the yaw moment coefficient overshoots are 29% and 19% higher than the steady yaw angle tests, for the squareback and the fastback geometries, respectively. If the side forceis concerned, the entities of these overshoots are 10% and 14%, respectively. Our testspointed out that efforts establish after the vehicle has driven 5.5 times its length in thecrosswind. In order to explain the different behaviour of the two geometries, it is discussed about the unsteady evolution of the vortices called, in this report, ΓA, ΓB, ΓC et Γ1. A strong correlation between the side efforts and the circulation of the most energetic vortex, ΓA,having its origin in the front leeward side of the vehicle. The ΓA vortex is so the best index for the study of the crosswind unsteady phenomena. The coupled analysis between vortex structures and efforts confirmed the presence of a higher side force for the squareback geometry. The inverted effect has been observed for the yaw moment Mécanique des fluides Aérodynamique automobile Rafale de vent latéral Vent traversier Aérodynamique instationnaire Angle de dérapage Efforts instationnaires TR-PIV PIV stéréoscopique CFD 3D LES Structures tourbillonnaires Fluid mechanics Vehicle aerodynamics Side wind gust Crosswind Unsteady Yaw angle Unsteady efforts TR-PIV Stereoscopic PIV 3D CFD LES Vortex structures 532 620.1 629.2
7	Experimentální analýza proudu vzduchu z vyústky přístrojové desky osobního vozu s využitím kouřové metody a návrh hodnocení kvality vyústky / Experimental analysis of air stream from a car blower using smoke method and design of the blower quality assessment Krška, Lukáš January 2011 (has links) The aim of this work was the analysis of air current from the right outlet, using the smoke method and the subsequent determination of a method for application. A further task was to establish a method for determining the upper and lower vertical routing, yaw angle (ß) and angle of inclination (?) of the air current. The experiment aims to approximate conditions as close to those experienced in the actual vehicle. After assembling a track with a soot blower (outlet) in the laboratory and defining the coordinates of the vehicle, the air current was subjected to visualization within the range of five positions of the vanes. Visualization was achieved by the use of technology for the smoke method. We used a light plane with a customized system of coordinates, a smoke generator for visualizing the air current being emitted and a camera for recording images. During our research we established the upper and lower cut off at the specific closures of the horizontal vanes of the soot blower. We determined a common analogy between the experimental track used in the experiment and the circumstances in the actual vehicle. We acquired the yaw angles (ß) and the angles of inclination (?) in the light plane and, after conversion, in the system of coordinates of the vehicle for all five settings of the vanes. The assessment of the given soot blower was undertaken according to the values achieved.
8	Vizualizace proudu z větrací vyústky pro přístrojovou desku osobního vozu / Visualization of air jet from ventilation outlet of a passenger car dashboard Bečica, Radek January 2013 (has links) Goal of this master´s thesis is to experimentally analyse air jet from ventilation outlet of a passenger car dashboard using smoke visualization and to describe this air jet. Air flow was set at 30 m3/h according to requirements from Škoda Auto s.r.o. from previous experiments on a similar ventilation outlet. First type of measuring rig which was developed for previous experiments was disassembled and replaced with a new modern measuring rig which is supposed to be used for next visualizations and experiments. Visualization was performed using smoke method and laser light plane. Air jet was photographed for five defined ventilation outlet adjustments and that for a jet to free space and for a jet flowing along a wall. The wall represented a front left door of a car. Results were processed by computer and presented as pictures and tables. Resulting angles were transformed to the main coordinate system of a car. Ventilation outlet functionality with respect to the air distribution in a car was evaluated afterwards.
9	Railway curve squeal: Statistical analysis of train speed impact on squeal noise Asplund, Ruben January 2024 (has links) No description available. ml operation maintenance railway maintenance railway curve machine learning statistics railway train passenger train x60 squeal noise curve squeal squealing noise squeal wheel squeal squealing programming system development computer engineering data visualization data preprocessing industrial computer systems matlab python vibration vibrations vibration signals signals and systems filtering signal processing computer systems communication system infrastructure technology infrastructure track t-test z-test random forest xgboost feature importance speed detection band-pass filter script yaw angle angle of attack decision tree gbdt filter temperature humidity dew point curve radius cloud accelerometers sensors track rail statistical analysis acoustics sound ai artificial intelligence gradient boosting decision trees curve software development drift underhåll järnvägsunderhåll järnvägskurva maskininlärning statistik järnväg tåg x60 skrikljud snäva kurvor kurvradie kurvskrik hjulskrik programmering systemutveckling datateknik data industriella datorsystem matlab python vibration signaler vibrations signaler signaler och system filtrering signalbehandling datorsystem kommunikationssystem infrastrukturteknik infrastruktur spår t-test z-test random forest Södertälje band-pass filter hastighets detektion attackvinkeln anfallsvinkel IMx SKF temperatur fuktighet daggpunkt accelerometer järnvägskurvskrik tåg hastighetens statistisk analys akustik ljud ai kurva kurvor mjukvaruutveckling artificiell intelligens Infrastructure Engineering Infrastrukturteknik Signal Processing Signalbehandling Communication Systems Kommunikationssystem Computer Systems Datorsystem

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