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Kuřímský, Lukáš. "Zařízení pro automatizovaná testování řídicích jednotek plynových kotlů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442519.
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This diploma thesis deals with the design and implementation of a computer-controlled device for testing gas boiler control units, especially in the development phase. The reason for creating a test facility is the inadequacy of older test systems and the automation of existing testing. The test device in development consists of individual different cards. Each of the cards inserted into the motherboard performs its function in the system. Each of the cards has a special functionality which simulates the real conditions of the developed product. The basis of most cards is a microcontroller with a Cortex-M core, which communicates with the connected computer using the MODBUS protocol on the RS-485 communication interface. All cards on the bus are connected in parallel and behaves as a SLAVE, while the computer behaves as a MASTER and requests data or sends commands to the cards. The cards represent status switches (switching sensors), resistance and analog temperature sensors, PWM inputs and outputs (for simulation of feedback pumps or flow meters with pulse output). The cards also include a flame simulator, which reliably simulates the electrical properties of the flame and at the same time acts as a fan simulator. The input of the control unit is taken care of by the input card, which is intended for digital detection of the voltage presence in the range of 5 to 230 V DC and AC. Simultaneously, a card for connecting the power supply at zero voltage and disconnecting at zero current is created to supply the tested device with alternating voltage. A schematic diagram was designed or simulated for each card, then the function was verified and on this basis the whole card was created, including the microcontroller firmware. The most suitable solution and function of each card is carefully described and evaluated. All the requirements of the assignment within the work were met and the whole test equipment was manufactured and verified in four versions. In the future, the device is ready for the implementation of an automatic flame simulator and other improvements of individual module cards.
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Myre, David D. "Model fan passage flow simulation." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23962.
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Le, Roux Frederick Nicolaas. "The CFD simulation of an axial flow fan." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4344.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: The purpose of this project is to investigate the method and accuracy of simulating axial ow fans with three-dimensional axisymmetric CFD models. Two models are evaluated and compared with experimental fan data. Veri cation data is obtained from a prototype fan tested in a facility conforming to the BS 848 standards. The ow eld over the blade surfaces is investigated further with a visualization experiment comprising of a stroboscope and wool tufts. Good correlation is found at medium to high ow rates and recommendations are made for simulation at lower ow rates as well as test guidelines at the fan test facility. The results and knowledge gained will be used to amend currently used actuator disc theory for axial ow fan simulation.
AFRIKAANSE OPSOMMING: Die doel van hierdie projek is om die metode en akkuraatheid om aksiaalvloeiwaaiers met drie-dimensionele BVM modelle te simuleer, te ondersoek. Twee modelle word geëvalueer en met eksperimentele waaiertoetse vergelyk. Veri- kasie data is verkry vanaf 'n prototipe waaier wat in 'n fasiliteit getoets is en wat aan die BS 848 standaarde voldoen. Die vloeiveld oor die lemoppervlaktes word ondersoek met 'n visualisering eksperiment wat uit 'n stroboskoop en wolletjies bestaan. Goeie korrelasie word gevind vir medium tot hoë massavloeie en aanbevelings word gemaak vir die simulasie by laer massavloeie met riglyne vir toetswerk in die toets-fasiliteit. Die resultate en kennis opgedoen sal gebruik word in die verbetering van huidige aksieskyfteorie vir numeriese aksiaalvloeiwaaier simulasies.
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Tapp, Eric A. "Development of a cascade simulation of fan-passage flow." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA277234.
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Subramanya, Shreyasu. "Modelling and Simulation of Fan Performance using CFD Group." Thesis, Linköpings universitet, Mekanisk värmeteori och strömningslära, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-171106.
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Performance of vacuum cleaners are affected by factors such static pressure, airflow rate and efficiency. In this thesis work, attempt has been made to design a fan to meet the requirements of suction static pressure and air flow rate and in the process understand the fan design parameters that affect these performance parameters. Parametric study has been conducted for the same, by choosing six fan design parameters. Additionally, ways to increase the fan efficiency has been investigated during the parametric study. Computational Fluid Dynamics is used to visualize the flow inside the fan casing and further to simulate fan performance at an operational point. Steady state RANS and moving reference frames was used to model the turbulence in the fluid flow and rotation of the fan, respectively. Performance curve showing the relation between static suction pressure and mass flow rate is plotted for the base model is in proximity to the required performance. Parametric study was conducted on the six fan design parameters: Fan diameter, number of impeller blades, blade outlet angle, radius of the curve connecting inlet to outlet section of the fan, diffuser exit length and splitter blade length. The range for each parameter analysis was restricted so that static pressure values are around the required performance. Greater performance variation was found with design parameters: fan diameter, blade outlet angle, radius of the curve connecting inlet to outlet section of the fan and diffuser exit length. This variation at low mass flow rate can be majorly attributed to the randomness in the flow captured by entropy contours. At high mass flow rate, blockage in the flow visualized by pressure contours reasoned for the performance variation. Greater performance variation was not when design parameters such as number of blades and splitter blade length were varied. Larger variation of these parameters is required to see better variation.
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Abuelyaman, Eltayeb Salih. "Sequential circuits fault simulation using fan out stem based techniques." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184466.
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This dissertation describes a new simulation technique for an automatic test generation system, SCIRTSS version 4.0 (Sequential Circuit Test Sequence System). This test generation system is driven by the hardware compiler AHPL, a Hardware Programming Language, and an intelligent heuristic-based search for test vector generation. Using a fault-injection gate-level simulator and the generated test vector, all the faulty states of the circuit are simulated in parallel and the simulator is thus able to find all detected faults by a particular input sequence. The major objective of this research was to develop a faster replacement for the existing simulation process. The philosophy of divide and conquer is used in the development of the new simulation technique. Sequential networks are divided into combinational sub-networks, and, if necessary, the combinational sub-networks are further reduced into fan-out free regions. Thus, the problem is reduced to a relatively simple combinational one. In addition to the classical faults, the new simulator attempts to detect CMOS stuck-open faults. Several circuits were tested under SCIRTSS 4.0 using both the existing and the new simulation techniques. The results are listed in this paper to verify superiority of the new simulation technique.
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Seaton, M. Scot. "Performance measurements, flow visualization, and numerical simulation of a crossflow fan." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Mar%5FSeaton.pdf.
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Thesis (M.S. in Aeronautical Engineering)--Naval Postgraduate School, March 2003.Thesis advisor(s): Garth V. Hobson, Raymond P. Shreeve. Includes bibliographical references (p. 69-70). Also available online.
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Kummer, Joseph. "Simulation of the cross-flow fan and application to a propulsive airfoil concept." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2006. http://proquest.umi.com/login?COPT=REJTPTU0NWQmSU5UPTAmVkVSPTI=&clientId=3739.
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Collins, Christopher C. "Preliminary investigation of the shock-boundary layer interaction in a simulated fan passage." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/28460.
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Golden, William L. "Static pressure measurements of the shock-boundary layer interaction in a simulated fan passage." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/23778.
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Zhao, Hui Wen, and zhwtkd@hotmail com. "Development of a dynamic model of a ducted fan VTOL UAV." RMIT University. Aerospace, Mechanical & Manufacturing Engineering, 2010. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20100210.142423.
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The technology of UAV (Unmanned Aerial Vehicle) has developed since its conception many years ago. UAVs have several features such as, computerised and autonomous control without the need for an on-board pilot. Therefore, there is no risk of loss of life and they are easier to maintain than manned aircraft. In addition, UAVs have an extended range/endurance capability, sometimes for several days. This makes UAVs attractive for missions that are typically
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Juanola-Parramon, R. "A far-infrared spectro-spatial space interferometer : instrument simulator and testbed implementation." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1427371/.
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FIRI (Far Infrared Interferometer) is a concept for a spatial and spectral space interferometer with an operating wavelength range 25-300 μm and sub-arcsecond angular resolution, and is based on the combination of two well-known techniques, Stellar Interferometry and Fourier Transform Spectroscopy, to achieve high spectral and spatial resolution in the Far Infrared (Chapter 2). The resulting technique is called Double Fourier Spatio-Spectral Interferometry (Mariotti and Ridgway 1988). With increased spatial and spectral resolution a number of interesting science cases such as the formation and evolution of AGN and the characterization of gas, ice and dust in disks undergoing planetary formation, among others, can be investigated. In this thesis I present two approaches to study the feasibility of a FIRI system a) An experimental approach via the Cardiff University-UCL FIRI Testbed (Chapter 3), a laboratory prototype spectral-spatial interferometer to demonstrate the feasibility of the Double-Fourier technique at the Far-infrared regime, including the Wide-Filed Imaging Interferometry Testbed at the Optical and Near-infrared regime. b) The Far-Infrared Interferometer Instrument Simulator (FIInS) to assess the performance of a space-based system (Chapter 4). The main goal of this software is to simulate both the input and the output of such a system. With FIInS, once a set of modeled scientific data is available, one can compare an input sky map with the synthesized one after data reduction and processing algorithms have been applied. To validate FIInS data from the Cardiff University-UCL FIRI testbed has been used (Chapter 5). FIInS is intended to be a tool for the astronomical community to explore the limits of a space interferometer. For this reason it is also applied to simulated scientific data (Chapter 6), more specifically to simulated circumstellar disks to test the simulator in a more realistic scenario.
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Férand, Mélissa. "Far-field combustion noise modeling of turbofan engine." Thesis, Toulouse, INPT, 2018. http://www.theses.fr/2018INPT0007.
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Depuis l'introduction du moteur à réaction pour la propulsion des avions dans les années 1950, l'acoustique est devenue d'un grand intérêt pour l'industrie du moteur. Alors que les turboréacteurs initiaux étaient dominés par le bruit de jet, l'introduction du moteur à turbofan dans les années 1960 a permis d'atténuer le bruit de jet, mais a introduit le bruit de soufflante. Dans les années 1970, grâce à de nouvelles conceptions avancées pour la réduction du bruit, une réduction majeure du bruit des avions s'en est suivie et la contribution du bruit de combustion a été remise en question. En effet, une réglementation plus restrictive du bruit pourrait exiger que le bruit de fan et de jet soient réduits au point où une réduction du bruit de combustion devienne également nécessaire. En outre, la conception des chambres de combustion est pilotée uniquement par la restriction des polluants chimiques produits par la combustion, l'efficacité et la consommation. L'impact de ces nouveaux concepts sur le bruit de combustion n'est actuellement pas une contrainte prise en compte lors de la conception. Avant d'envisager de réduire le bruit de combustion, il faut d'abord en comprendre les différents mécanismes. Cependant, proposer une méthode de prédiction pour le bruit de combustion n'est pas une tâche facile en raison des multiples interactions physiques impliquées lors des processus de combustion. De nombreuses expériences existent pour évaluer le bruit de combustion causé par les flammes ou des chambres de combustion simplifiées. Cependant, seuls quelques-uns considèrent le chemin de propagation complet du bruit de combustion provenant d'un moteur, car il est difficile d'isoler cette source acoustique du bruit des autres modules du moteur. Les méthodes empiriques basées sur des extrapolations et des simplifications sont souvent utilisées pour prédire le bruit de combustion des moteurs aéronautiques. De nombreuses analogies acoustiques ont également été dérivées à partir de Lighthill. Les travaux de cette thèse proposent d'étudier le bruit de combustion provenant d'un moteur d'avion à l'aide d'une chaine de calcul traitant différents modules de la génération du bruit de combustion à sa propagation en champ lointain. Ils mettent en évidence l'importance du bruit de combustion pour différents points de fonctionnement. Les mécanismes générateurs du bruit seront identifiés dans la chambre de combustion. Le rôle de la turbine en tant qu'atténuateur le bruit et générateur de bruit indirect sera évalué ainsi que la propagation en champ lointain en considérant des milieux inhomogènes. Enfin, uns stratégie alternative sera également proposée afin de considérer l'interaction entre le bruit de combustion et le bruit de jet. Pour se faire des LES de jet forcé par le bruit de combustion seront réalisées. Une nouvelle approche sera proposée à partir de ces résultats qui semblent montrer que le bruit de combustion a un impact sur la turbulence du jetSince the introduction of jet engine for aircraft propulsion in the 1950's, acoustics has become of great interest to the engine industry. While the initial turbojets were jet noise dominated, the introduction of turbofan engine in the 1960's gave relief in jet noise, but introduced fan noise. In the 1970's, with advanced noise reduction design features which provided a major reduction in aircraft noise, combustion noise became an interrogation. Indeed, more restrictive noise regulations could require that noise from the fan and jet be reduced to the point where combustion noise reduction may be required. Moreover, burner designs is controlled solely by the restriction of chemical pollutants produced by combustion, efficiency and consumption. The impact of these new concepts on combustion noise is not a strong constraint for design. Before considering to reduce combustion noise, it is necessary to first understand the different mechanisms. However, proposing a prediction method for combustion noise is not an easy task due to the multiple physical interactions involved during the combustion processes. Many experiments exist to evaluate the combustion noise from flames or combustion test rig. However, only a few include the complete propagation path of combustion noise within an engine device as it is difficult to isolate this acoustic source from the noise of the other engine modules. Empirical methods based on extrapolations and simplifications are often used for the prediction of combustion noise within modern aero-engines. Numerous acoustic analogies have also been derived from Lighthill. The work of this thesis proposes to study the combustion noise coming from an aircraft engine using a computational chain treating different modules from the generation of combustion noise to its propagation in far field. The importance of combustion noise for different operating points is highlighted. The noise-generating mechanisms will be identified in the combustion chamber. The role of the turbine as a noise attenuator and indirect noise generator will be evaluated as well as the far-field propagation considering inhomogeneous fields. Finally, an alternative strategy will also be proposed in order to consider the interaction between combustion noise and jet noise. To do so, LES of jet flow forced with combustion noise will be performed. A new approach will be proposed based on these results which seem to show that the combustion noise has an impact on the turbulence of the jet
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Mullins, Steven. "Computational environment for the development of an FAA compliant level 6 flight training device." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10766.
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Thesis (M.S.)--West Virginia University, 2009.Title from document title page. Document formatted into pages; contains xii, 113 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 76-77).
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Ullo, Silvia Liberata. "Evaluation of scheduling strategies in a semiconductor wafer fab using simulation." Thesis, Massachusetts Institute of Technology, 1992. https://hdl.handle.net/1721.1/128456.
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Thesis (M.S.)--Massachusetts Institute of Technology, Sloan School of Management, 1992.Includes bibliographical references (leaves 105-107).
by Silvia Liberata Ullo.
Thesis (M.S.)--Massachusetts Institute of Technology, Sloan School of Management, 1992.
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Béraud, Nicolas. "Fabrication assistée par ordinateur pour le procédé EBM." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAI052/document.
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Le procédé de fabrication par fusion de poudre à l'aide d'un faisceau d'électrons est appelé procédé Electron Beam Melting (EBM). Il permet la fabrication de pièces métalliques à partir de poudres. Grâce au niveau de qualité (géométrique et mécanique) des pièces produites, le procédé peut être utilisé afin de produire des pièces fonctionnelles et non plus uniquement des prototypes. Ce procédé, ainsi que les autres procédés additifs métalliques, permettent d'envisager le passage de l'impression 3D à la fabrication additive métallique.L'utilisation de la fabrication additive dans un contexte industriel impose le respect de critères en termes de qualité, coût et délai des pièces produites. L'ensemble des étapes numériques de mise en production d'une pièce constitue la chaîne numérique. Cette dernière a un impact fort sur l'ensemble de ces trois critères. Ainsi, cette thèse apporte une réponse à la question suivante :Comment la fabrication assistée par ordinateur peut-elle améliorer le triptyque qualité, coût, délai du procédé de fabrication EBM?Le problème est abordé par la question sous-jacente suivante :Quelles caractéristiques doit posséder un environnement de fabrication assistée par ordinateur adapté au procédé EBM ?Pour répondre à cette question, la chaîne numérique actuelle est analysée . Les principales limites identifiées sont :- l'utilisation de fichiers au format STL- l’impossibilité d’optimiser le procédé à différentes échelles- l’impossibilité de simuler le procédé EBMAfin de résoudre l'ensemble des problèmes énoncés, un environnement de FAO est proposé. Celui-ci permet de centraliser l'ensemble des opérations de mise en production au sein d'un environnement unique. Il autorise le travail avec l'ensemble des formats de fichiers reconnus comme les formats natifs des logiciels de CAO ou le format STEP. Des développements informatiques permettent de concrétiser l’environnement proposé.L'implémentation de l'environnement de FAO a mis en évidence le rôle fondamental de la simulation au sein de celui-ci. Il a donc fallu répondre à la question :Comment obtenir une simulation du procédé EBM permettant sa mise au point hors ligne en temps raisonnable ?Bien que la simulation du procédé EBM est largement traitée dans la littérature scientifique, les études proposées reposent sur la méthode des éléments finis et le temps de calcul nécessaire n'est pas compatible avec une utilisation au sein d'un environnement de FAO. Un type de simulation alternatif a donc été créé : une simulation par abaques. Elle est constituée d’une simulation par la méthode des éléments finis qui permet d'obtenir des cartes de températures pour des cas de chauffes et de refroidissements standards. Ces cartes de températures sont ensuite transformées en abaques. La simulation par abaques est vue comme la succession d'une multitude de cas standards. Ainsi l'algorithme de simulation par abaques cherche l'abaque le plus proche de la situation simulée, afin d’estimer les températures au pas de temps suivant.Cette méthode de simulation a permis une réduction des temps de calcul tout en gardant une précision suffisante pour pouvoir être utilisée pour optimiser les paramètres de fabrication.Grâce à une telle simulation, un outil d'optimisation des stratégies de fusion a pu être créé. Il permet d’améliorer la qualité des pièces produites en calculant des stratégies de fusion respectant certains critères thermiques.Les apports majeurs de ces travaux de thèses sont :- l'établissement d'un cahier des charges pour une chaîne numérique performante en EBM- le développement d'un environnement de FAO adapté au procédé EBM- la mise au point d'une simulation rapide du procédé EBM basée sur des abaques- la création d'un outil d'optimisation des stratégies de fusionThe Electron Beam Melting (EBM) process allows to build metallic parts from powder. Thanks to the geometric and mechanical quality of the parts produced, the EBM process can be used to manufacture functional parts and not only prototypes. This process, with other additive metallic processes, make it possible to consider a transition from 3D printing to metallic additive manufacturing.The use of additive manufacturing in an industrial environment requires compliance with quality, cost and time criteria for the parts produced. The production of manufactured parts involves a series of numerical stages which is called the numerical chain. The numerical chain has a significant impact on the three criteria mentioned above. Thus, this thesis provides an answer to the following question:How Computer Aided Manufacturing can improve the quality, cost and time of the EBM manufacturing process?This problem is addressed through the following underlying question:What are the required characteristics for a Computer Aided Manufacturing system adapted to the EBM process?In order to answer this question, the current numerical chain is analyzed. Three main limitations are found:- the use of STL files format- the process cannot be optimized at different scales- the process cannot be simulatedTo solve these issues, a CAM environment is proposed. It allows the centralization of all numerical operations in a single environment. All supported formats can be used within this environment, such as native CAD file formats or STEP format. Software developments are done to prove the feasibility of such an environment.The CAM environment implementation reveals the crucial role of simulation in this system. It is therefore necessary to answer this second question:How to obtain an EBM process simulation allowing the development of parameters, virtually?Although EBM simulation is a recurrent subject in scientific literature, existing studies are based on the finite elements method but the calculation time needed is too important to be used in an CAM environment. Thus, an alternative type of simulation is created in this thesis: a simulation based on abacus. It is composed of a finite elements model, that allows heat maps generation for standards cases of heating and cooling. These heat maps are then transformed in abacus. The simulation algorithm based on abacus search the nearest abacus from the simulated situation in order to estimate the temperatures at the next time step.This simulation method was used to reduce the calculation time while keeping a sufficient precision to optimize process parameters.With the simulation based on abacus, a tool for the optimization of melting strategies is developed. This tool allows quality improvement for the produced parts through the calculation of melting strategies according to thermic criteria.To summarize, the main contributions of this work are:- the definition of requirements specifications of a powerful numerical chain for the EBM process- the development of a CAM environment adapted to the EBM process- the proposal of a fast simulation for the EBM process, based on abacus- the development of a tool for the optimization of melting strategies
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Magne, Stéphan. "Numerical investigation of tonal noise control of low-speed fans with flow obstruction." Thèse, Université de Sherbrooke, 2015. http://hdl.handle.net/11143/8160.
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Résumé : La réduction du bruit tonal des ventilateurs basse vitesse est un défi très important pour l’industrie. Lorsqu’il émerge du bruit large bande, ce rayonnement est la source de gênes auprès de la population, que ce soit pour de petits ventilateurs d’ordinateurs ou de gros ventilateur miniers. Afin de contrôler le bruit tonal, de nombreuses techniques ont été développées au fil de ces dernières décennies. Une méthode alliant simplicité et efficacité se démarque néanmoins : le contrôle par obstruction de l’écoulement. Malgré les études menées jusqu’alors, les mécanismes aéroacoustiques de réduction du bruit associés à cette méthode restent mal compris. Pour répondre à cette problématique, ce projet de Doctorat s’intéresse à l’étude de l’intéraction entre l’obstruction et le ventilateur au moyen de simulations aéro-acoustiques. De plus, une méthodologie numérique de design de l’obstruction est proposée afin de réduire les coûts associés aux multiples test expérimentaux.Abstract : Tonal noise radiated by low-speed fans is a prime challenge for many industries. When this component emerges from the broadband noise, the acoustic radiation is particularly harsh for the human ear, whether it comes from a small computer cooling fan or from a large mine ventilation fan. Several methods have been developed over the last decades to control tonal noise. Nevertheless, one simple and efficient technique stands out: the adaptive passive control with flow obstruction. Despite all the research conducted on this method, the aeroacoustic mechanisms responsible for the noise reduction are not fully understood. Therefore, the present thesis aims at investing the obstruction-fan interaction using aeroacoustic simulations. Moreover, a numerical design methodology is proposed to reduce the cost induced by extensive experimental tests.
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Thollet, William. "Modélisations simplifiées de turbomachines pour l'analyse par la simulation des installations motrices complexes d'avions." Thesis, Toulouse, ISAE, 2017. http://www.theses.fr/2017ESAE0010/document.
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Cette thèse étudie des méthodes de conception aérodynamique pour les avions de ligne de demain. A l'heure actuelle, les avions de ligne sont en général conçus de manière à ce que les moteurs, conçus séparément du reste de l'aéronef, n'interagissent que très peu avec la cellule de l'avion (la voilure, le fuselage,...). Pour diminuer la consommation de carburant, de nouveaux concepts comme l'ingestion de couche limite émergent, dans lesquels l'avion est conçu pour tirer profit des interactions aérodynamiques qui peuvent s'établir entre le moteur et la cellule de l'avion sur certaines configurations. Il devient alors nécessaire de simuler ces interactions pour s'assurer que le bénéfice pour l'avion en termes de consommation de carburant est réel. La méthode développée dans cette thèse a pour objectif de rendre possible la simulation de ces interactions, à un coût de calcul qui reste acceptable. La soufflante, qui est l'élément du moteur le plus à même d'interagir avec l'avion, est modélisée à l'aide d'un champ de force qui reproduit son aspiration de l'écoulement d'air. Cette approche permet de reproduire les interactions aérodynamiques entre l'avion et ses moteurs à un coût 50 fois inférieur à celui d'une simulation complète du moteur et de l'avion, ce qui permettra en pratique d'optimiser les lignes aérodynamiques des futurs avionsThis work explores new méthodologies for the aerodynamic conception of future commercial aircraft. In general, commercial aircraft are designed to limit aerodynamic interactions between the engines and the airframe. New aircraft concepts such as boundary layer ingestion are now studied, in which the aircraft is designed to take advantage of these interactions. It is then necessary to be able to simulate these interactions to ensure that real benefits in terms of aircraft fuel burn are possible. The methodology that is developed in the présent thesis aims at enabling the simulation of these aerodynamic interactions at affordable computational cost. The fan, which is the part of the engine the most likely to internet with the airframe, is modeled using a force field that reproduces the suction of the air inside the engine. This approach allows to reproduce fan- airframe interactions at a fraction of the cost of a complété simulation of the aircraft and the engines, and enable the practical optimization of the aerodynamic performance of future aircraft
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Chan, Chun Fai [Verfasser]. "Quantum simulation of strongly-correlated two-dimensional fermions in optical lattices / Chun Fai Chan." Bonn : Universitäts- und Landesbibliothek Bonn, 2020. http://d-nb.info/1218301503/34.
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Abdulhamid, Hakim. "Étude de la tolérance aux dommages d'impact sur structure composite en zone de reprise de plis." Thesis, Toulouse, ISAE, 2015. http://www.theses.fr/2015ESAE0005/document.
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La tenue résiduelle à l'impact basse vitesse est un critère dimensionnant des structures composites minces pour l'aéronautique. La majorité des travaux réalisés jusqu'ici porte sur l'analyse du comportement en zone courante. Ce travail élargit le domaine d'étude aux zones de variation d'épaisseur. L'objectif est d'étudier la tolérance aux dommages d'impact d'un stratifié comportant une zone de reprise de plis (ZRP) dans le cadre d'un dialogue essai/ calcul, en menant en parallèle une campagne d'essais expérimentaux et l'adaptation d'un modèle numérique de l'endommagement des composites.Le volet expérimental étudie successivement l'impact, la compression et la fatigue à R=-l après impact (CAI et FAI) d'éprouvettes comportant une ZRP. L'analyse des essais d'impact a permis d'identifier la résistance à l'impact et le mécanisme d'endommagement des éprouvettes. Ensuite, un outillage d'essai adapté à la géométrie des éprouvettes a été conçu pour les essais de CAI et de FAI. Les essais de compression montrent une tenue résiduelle statique après impact similaire à celle des éprouvettes sans perte de plis. Les essais de fatigue menés à 60 070 de la tenue résiduelle statique montrent une propagation des délaminages d'impact (en dessous du BVID) qui mène à la rupture des éprouvettes pour un nombre de cycles relativement faible. Alors que la tolérance aux dommages d'impact des ZRP sous chargement statique est comparable à celle des zones courantes lisses, on constate une forte vulnérabilité de ces zones sous chargement de fatigue.Le volet numérique a permis de tester l'approche DPM (Discrete Ply Model), développé lors de travaux précédents, sur une configuration particulière. Un maillage spécifique a été réalisé pour tenir compte des discontinuités de la ZRP. Au niveau de la loi matériau, une formulation unifiée de la rupture de fibres en traction/compression a été implémentée. Les résultats de la simulation d'impact sont en bonne corrélation avec les données expérimentales. Le modèle est capable de prédire la réponse globale de l'éprouvette ainsi que l'étendu des dommages internes. La modélisation de la CAI a permis de confirmer les mécanismes de rupture identifiés lors des essais. Ces résultats numériques sont remarquables puisqu' aucune modélisation locale particulière n'a été faite pour les arrêts de plis. L'approche DPM s'est révélée suffisamment robuste et bien adaptée à la modélisation de l'endommagement des stratifiés unidirectionnelsThe residual strength after low velocity impact is a sizing criterion of thin composite structures in aeronautics. The majority of work on the subject is focused on the analysis of plain laminates. This study expands the field of interest to tapered area. The objective is to study the impact damage tolerance of a laminate with ply drop-off using an experiment/ modelling dialogue: on one hand carrying experimental test campaign and on other hand adapting numerical modelling of composite damage. The experimental part successively examines the impact, compression and fatigue R=-l after impact (CAI and FAI) of specimens with ply drop-off. Analysis of the impact results has enabled the identification of impact resistance and damage mechanism. Then, a testing tool for CAI and FAI was specially designed to suit the geometry of the specimens. Compression tests show a static residual strength after impact similar to plain laminates. Fatigue tests carried at 60% of CAI strength show a propagation of impact delamination (below B VID). Failure of specimens occurs after a relatively small number of cycles. While the impact damage tolerance of tapered laminates is comparable to plain laminates under static loading, high vulnerability is observed under fatigue loading. The numerical part allowed to test the Discrete Ply Model (DPM), developed in previous works, on a particular configuration. A specific meshing was realized to account for the discontinuities in the ply drop-off area. Regarding the material law, a unified formulation of the fiber breakage in tension/ compression is implemented. Impact simulation results correlated well with the experimental data. The model is able to predict the overall response of the specimen and internal damage. The modeling of the CAI enabled to confirm the failure mechanisms identified during tests. These numerical results are remarkable since no particular local modeling has been realized for the ply drop-off area. DPM approach has proven robust enough and well suited to damage modeling of unidirectional laminates
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Chen, Fang [Verfasser], Hans [Akademischer Betreuer] Hagen, and Bernd [Akademischer Betreuer] Hamann. "The simulation and visualization of multi-phase fluid / Fang Chen. Betreuer: Hans Hagen ; Bernd Hamann." Kaiserslautern : Technische Universität Kaiserslautern, 2013. http://d-nb.info/1033062456/34.
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Kawade, Peeyush S. "Roof and Wall Vents Study under Simulated Hurricane Winds." FIU Digital Commons, 2009. http://digitalcommons.fiu.edu/etd/255.
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Ventilation might seem like a minor consideration, but when properly installed, it can extend the life of the attic and roof structure of residential buildings saving huge dollar amounts in repair costs. The objectives of this study were to measure the wind effect on different kind of vents as the problem is vents are subjected to high wind loads during hurricane events and often fail causing water penetration and damage of interior contents. Wind-induced failure of rooftop vents during a hurricane may result in large openings in the roof that will allow water to penetrate into the building, a puncturing of the roof membrane, again allowing water infiltration, and detached rooftop vents can pose considerable threats as windborne debris. The study found that water infiltration through a vent system is dependent upon the differential pressure as well as the vent mechanism. For vents experiencing higher differential pressures, vent covers can be used during storms to reduce water infiltration. Active controls can also be designed to close the vents automatically as differential pressure increases based on the wind speed and wind angle of attack.
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Fan, Li [Verfasser], Heinz [Akademischer Betreuer] Konietzky, Heinz [Gutachter] Konietzky, Frank [Gutachter] Schilling, and Tao [Gutachter] Xu. "Discrete Element based numerical simulation of crack formation in brittle material by swelling cement / Li Fan ; Gutachter: Heinz Konietzky, Frank Schilling, Tao Xu ; Betreuer: Heinz Konietzky." Freiberg : Technische Universität Bergakademie Freiberg, 2019. http://d-nb.info/1221139509/34.
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Thorp, Kelly R., Douglas J. Hunsaker, Kevin F. Bronson, Pedro Andrade-Sanchez, and Edward M. Barnes. "Cotton Irrigation Scheduling Using a Crop Growth Model and FAO-56 Methods: Field and Simulation Studies." AMER SOC AGRICULTURAL & BIOLOGICAL ENGINEERS, 2017. http://hdl.handle.net/10150/626603.
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Crop growth simulation models can address a variety of agricultural problems, but their use to directly assist in-season irrigation management decisions is less common. Confidence in model reliability can be increased if models are shown to provide improved in-season management recommendations, which are explicitly tested in the field. The objective of this study was to compare the CSM-CROPGRO-Cotton model (with recently updated ET routines) to a well-tested FAO-56 irrigation scheduling spreadsheet by (1) using both tools to schedule cotton irrigation during 2014 and 2015 in central Arizona and (2) conducting a post-hoc simulation study to further compare outputs from these tools. Two replications of each irrigation scheduling treatment and a water-stressed treatment were established on a 2.6 ha field. Irrigation schedules were developed on a weekly basis and administered via an overhead lateral-move sprinkler irrigation system. Neutron moisture meters were used weekly to estimate soil moisture status and crop water use, and destructive plant samples were routinely collected to estimate cotton leaf area index (LAI) and canopy weight. Cotton yield was estimated using two mechanical cotton pickers with differing capabilities: (1) a two-row picker that facilitated manual collection of yield samples from 32 m(2) areas and (2) a four-row picker equipped with a sensor-based cotton yield monitoring system. In addition to statistical testing of field data via mixed models, the data were used for post-hoc reparameterization and fine-tuning of the irrigation scheduling tools. Post-hoc simulations were conducted to compare measured and simulated evapotranspiration, crop coefficients, root zone soil moisture depletion, cotton growth metrics, and yield for each irrigation treatment. While total seasonal irrigation amounts were similar among the two scheduling tools, the crop model recommended more water during anthesis and less during the early season, which led to higher cotton fiber yield in both seasons (p < 0.05). The tools calculated cumulative evapotranspiration similarly, with root mean squared errors (RMSEs) less than 13%; however, FAO-56 crop coefficient (K-c) plots demonstrated subtle differences in daily evapotranspiration calculations. Root zone soil moisture depletion was better calculated by CSM-CROPGRO-Cotton, perhaps due to its more complex soil profile simulation; however, RMSEs for depletion always exceeded 20% for both tools and reached 149% for the FAO-56 spreadsheet in 2014. CSM-CROPGRO-Cotton simulated cotton LAI, canopy weight, canopy height, and yield with RMSEs less than 21%, while the FAO-56 spreadsheet had no capability for such outputs. Through field verification and thorough post-hoc data analysis, the results demonstrated that the CSM-CROPGRO-Cotton model with updated FAO-56 ET routines could match or exceed the accuracy and capability of an FAO-56 spreadsheet tool for cotton water use calculations and irrigation scheduling.
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Roberg, Kristoffer. "Simulation of scheduling algorithms for femtocells in an LTE environment." Thesis, Linköping University, Communication Systems, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-59651.
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The new mobile standard Long Term Evolution delivers high data rates, small delay and a more efficiently utilized RF spectrum. A solution to maintain this performance in user dense areas or areas with bad reception is the deployment of so-called femtocells. Femtocells are small base stations that are deployed indoors and share the RF spectrum with the whole mobile network. The idea is that femtocells will increase mobile operators network coverage and capacity while it at the same time increase users data throughput. There are several challenges with femtocells, both technical and economical ones. The most debated issues is how femtocells should schedule users while operating in an environment where other femtocells and base stations are interfering. In this work we developed a simulation tool to simulate the scheduling interaction between femtocells and base stationsin order to show the performance of radio resource schedulers. This rapport also aims to evaluate an approach to a femtocell scheduler to solve this issue in a satisfying way. The report gives a description of the structure of the implemented simulation tool together with some reflections on how future designs of similar or more complex simulation environments could be done.
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Fang, Zhufeng [Verfasser]. "3D hydrological simulation of a forested headwater catchment: Spatio-temporal validation and scale dependent parameterization / Zhufeng Fang." Bonn : Universitäts- und Landesbibliothek Bonn, 2016. http://d-nb.info/1119888891/34.
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Turner, Emma Catherine. "Evaluating spectral radiances simulated by the HadGEM2 global climate model using longwave satellite measurements." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10047.
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A 'model-to-radiance' comparison of simulated brightness temperatures and radiances from the Hadley Centre Global Environmental Model 2 (HadGEM2-A) with longwave measurements from the High Resolution Infrared Radiation Sounder/4 (HIRS/4) and the Infrared Atmospheric Sounding Interfermeter (IASI) onboard the MetOp-A satellite is presented for all-sky and clear-sky global means. The fast Radiative Transfer model for TOVS 10 (RTTOV-10) is applied to HadGEM2 output to simulate observational-equivalent data. The results are compared with corresponding broadband analyses. A method is developed to extend hyperspectral IASI radiances to cover the whole outgoing terrestrial spectrum, in order to identify any compensating biases, and explore wavebands in the unobserved Far Infrared (FIR) region. For the all-sky HIRS analysis, the model overestimates brightness temperatures in the atmospheric window region with the greatest biases over areas associated with deep convective cloud. In contrast to many global climate models, much smaller clear-sky biases are found indicating that model clouds are the dominating source of error. Simulated values in upper atmospheric CO2 channels approximate observations better as a result of compensating cold biases at the poles and warm biases at lower latitudes, due to a poor representation of the Brewer Dobson circulation in the 38 level 'low-top' configuration of the model. Simulated all and clear-sky outgoing longwave radiation evaluated against the Clouds and the Earth's Radiant Energy System (CERES) and HIRS OLR products reveal good agreement, in part due to cancellation of positive and negative biases. Through physical arguments relating to the spectral energy balance within a cloud, it is suggested that broadband agreement could be the result of a balance between positive window biases and unseen negative biases originating from the water vapour rotational band in the FIR (not sampled by HIRS). Simple sensitivity tests show that dramatically altering existing cloud properties has little effect on the prominent window biases, however raising clouds a maximum of 5 atmospheric levels minimises the error in cloud contaminated channels, due to the introduction of spatially compensating errors. Sensitivities to the way ice clouds are parameterised in RTTOV-10 display a range of up to 2.5 K in window channels but absolute biases still exceed 3 K for all choices. Because of the lack of satellite based FIR observations due to a technological gap in the spectral region, an algorithm is created to 'fill in' the available data. Correlations between selected IASI channels and simulated unobserved wavelengths in the far infrared are used to estimate radiances between 25.25 - 644.75 cm-1 at 0.5 cm-1 intervals. The same method is used in the 2760 - 3000 cm-1 region. The spectrum is validated by comparing the Integrated Nadir Longwave Radiance (INLR) product (spanning the whole 25.25 - 3000 cm-1 range) with the corresponding broadband measurements from the Clouds and the Earth's Radiant Energy System (CERES) instrument on the Terra and Aqua satellites at simultaneous nadir overpasses, revealing mean differences of 0.3 Wm-2sr-1 (0.5% relative difference) lower for IASI relative to CERES and significantly lower biases in nighttime only scenes. Averaged global data over a single month produces mean differences of about 1 Wm-2sr-1 in both the all and the clear-sky (1.2% relative difference). The new high resolution spectrum is presented for global mean clear and total skies where the far infrared is shown to contribute 44% and 47% to the total OLR respectively, which is consistent with previous estimates. In terms of spectral cloud radiative forcing, the FIR contributes 19% and in some subtropical instances appears to be negative, results that would go un-observed with a traditional broadband analysis. The equivalent complete IASI OLR model product is simulated from GCM data using RTTOV-10. The same process of applying predictors to the satellite measurements is applied to the model simulated radiances, with appropriate modifications, to produce a directly comparable model product. Annual mean all-sky radiances are still greatly overestimated at all wavenumbers with a total radiance bias of 4.52 Wm-2 across the whole range. Compensating negative biases outside of the HIRS coverage that were hypothesised are absent, with the far infrared contributing to the overall bias rather than cancelling it. Equivalent clear-sky biases are much lower overall at 0.39 Wm-2, in part due to spectral and spatial cancellation of errors. A flux-to-flux comparison is enabled by estimating the spatial distribution of anisotropic factors, using collated HIRS OLR fluxes and IASI OLR radiances, which yields global mean model fluxes in excess of 12 Wm-2 higher than observations in the all-sky. The difference between this and the fluxes calculated using the climate model's broadband radiation code (Edward-Slingo) are around 10 Wm-2 which is outside the range of uncertainty in the method used to estimate the flux. However, it is discussed that tuning of the climate model's broadband code to known flux values is a required practice to ensure global energy budgets balance but can produce inaccurate parameterised variables. An equivalent analysis adjusting the ice cloud parametrisation to reflect the radiances that have the biggest differences to the original configuration selected showed a bias reduction of 4.5 Wm-2, which is still not enough to completely explain its size, suggesting the existence of residual cloud problems. Finally, it is suggested that the way forward in separating and constraining cloud errors, in both radiative transfer codes, is a rigorous process of testing them with observation cloud properties and reanalysis data as inputs.
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Correia, Pedro Miguel Fernandes. "Simulation of far wake effects generated by offshore wind farms using the WRF model: the Horns Rev test case." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17560.
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Mestrado em Meteorologia e Oceanografia FísicaAvanços tecnológicos e científicos contínuos contribuíram para a melhoria da relação custo/benefício na exploração de energia eólica offshore. Esses avanços levaram ao aumento do número e tamanho de novos parques eólicos offshore. O crescente número de parques em algumas zonas leva a que surjam áreas com uma alta concentração de parques eólicos, algumas delas dentro da raio de influência de outros parques situados na sua vizinhança. Devido à proximidade entre parques, estes podem funcionar como um obstáculo para o fluxo normal do vento e afectar a velocidade do vento noutros parques situados a jusante. Efeitos de esteira distante provocados pelo efeito combinado de efeitos de esteiras de turbinas e de clusters ou parques individuais podem originar deficits de velocidade significativos numa grande área ao redor de uma zona de interesse. O estudo das interacções entre parques eólicos e as resultantes perdas por efeito de esteira em parques eólicos vizinhos é um aspecto importante que deve ser tido em conta quando se decide o "layout" e localização de novos parques offshore. Devido às condições favoráveis para a exploração de energia eólica offshore no Mar de Norte, a concentração de parques eólicos nessa região é alta e continua a aumentar tornando-a uma zona indicada para este tipo de estudo. Quando se considera uma área destas dimensões, o tamanho do domínio e a resolução horizontal podem tornar-se num obstáculo difícil de ultrapassar. Devido a que os modelos actuais usados para o estudo de efeito de esteira necessitam de um poder computacional bastante elevado, é bastante difícil simular áreas com centenas de quilómetros de comprimento que englobam vários parques eólicos offshore com diferentes áreas, características e tipo de turbinas eólicas. A recente implementação de parameterizações de parques eólicos no código fonte de modelos de mesoscala pode constituir uma ferramenta indispensável para ultrapassar estes obstáculos. Usando o modelo de mesoscala Weather Research and Forecasting (WRF), que inclui uma parameterização de parque eólico, simularam-se os parques eólicos offshore de Horns Rev 1 e Horns Rev 2. Este trabalho tenta quantificar o deficit de velocidade no parque de Horns Rev 1 devido à construção do parque de Horns Rev 2 na vizinhança do mesmo. Uma validação dos resultados é efectuada usando dados medidos de várias torres situadas na zona do parque de Horns Rev 1, e uma análise do potencial desta metodologia é efectuada.
Continuous technological and scientific advances have contributed to the improvement of the relation cost-benefi in the exploitation of offshore wind farms. Those advances have propelled the construction of new and larger offshore wind farms and have contributed to a high concentration of wind farms in several areas, some of them built within the radius of influence of other neighbour wind farms. Because of their proximity, some of them might impact the wind conditions on other downstream plants. Pronounced far wakes effects generated by the combination of individual wind turbines and single or clusters of wind farms can provoke significant wind speed deficits within a large radius around a given location. The study of these wind farm interactions and the resulting wake losses on neighbouring wind farms is an important aspect that should be taken into account when deciding the layout and location of new offshore plants. Due to its favourable conditions to wind energy exploitation, the concentration of offshore wind farms in the North Sea region is high and it is still increasing making it a suitable location for this study. When onsidering such a large area, the domain size and resolution of the numerical models might be an obstacle difficult to overcome. Since current wake models require high computational power, it is very di fficult to simulate areas with hundreds of kilometres and several wind farms with different sizes, characteristics and different types of turbines. The recent implementations of wind farm parameterizations in the source code of mesoscale models could provide the required tool to over come those constraints. Using the state of the art Weather Resear ch and Forecasting (WRF) mesoscale model, that in cludes a wind farm parameterization scheme, the Horns Rev 1 and Horns Rev 2 wind farms are simulated. This work tries to ascertain the wind speed deficits in the Horns Rev 1 wind farm due to the constru ction of the Horns Rev 2 plant in its proximity. An evaluation of the results is performed against real measurements from the site and the capabilities of the methodology are disc ussed.
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Follestad, Turid. "Stochastic Modelling and Simulation Based Inference of Fish Population Dynamics and Spatial Variation in Disease Risk." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-41.
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We present a non-Gaussian and non-linear state-space model for the population dynamics of cod along the Norwegian Skagerak coast, embedded in the framework of a Bayesian hierarchical model. The model takes into account both process error, representing natural variability in the dynamics of a population, and observational error, reflecting the sampling process relating the observed data to true abundances. The data set on which our study is based, consists of samples of two juvenile age-groups of cod taken by beach seine hauls at a set of sample stations within several fjords along the coast. The age-structure population dynamics model, constituting the prior of the Bayesian model, is specified in terms of the recruitment process and the processes of survival for these two juvenile age-groups and the mature population, for which we have no data. The population dynamics is specified on abundances at the fjord level, and an explicit down-scaling from the fjord level to the level of the monitored stations is included in the likelihood, modelling the sampling process relating the observed counts to the underlying fjord abundances.
We take a sampling based approach to parameter estimation using Markov chain Monte Carlo methods. The properties of the model in terms of mixing and convergence of the MCMC algorithm and explored empirically on the basis of a simulated data set, and we show how the mixing properties can be improved by re-parameterisation. Estimation of the model parameters, and not the abundances, is the primary aim of the study, and we also propose an alternative approach to the estimation of the model parameters based on the marginal posterior distribution integrating over the abundances.
Based on the estimated model we illustrate how we can simulate the release of juvenile cod, imitating an experiment conducted in the early 20th century to resolve a controversy between a fisherman and a scientist who could not agree on the effect of releasing cod larvae on the mature abundance of cod. This controversy initiated the monitoring programme generating the data used in our study.
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Sadoudi, Yannis. "Simulation numérique de l'interaction soufflante/nacelle en présence de vent de travers." Thesis, Toulouse, ISAE, 2016. http://www.theses.fr/2016ESAE0005/document.
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La conception des nacelles doit répondre à des contraintes géométriques d’encombrement mais aussi à des spécifications motoristes qui précisent les niveaux de performance exigés. Au sol, l’une des principales contraintes imposées par le motoriste concerne le niveau de distorsion de pression totale dans le plan fan quand la nacelle est soumise à un vent de travers. Dans le cas le plus limitant, c’est-à-dire lorsque la direction du vent est perpendiculaire à l’axe de la nacelle, il se produit un décollement au niveau de l’entrée d’air côté vent. L’hétérogénéité de l’écoulement crée des efforts instationnaires sur les aubes du fan. Ces efforts peuvent amener à un régime de pompage endommageant ainsi le moteur. De plus, la tendance actuelle est de réaliser des nacelles courtes, réduisant la distance qu’à l’écoulement pour s’homogénéiser avant d’impacter le fan, conduisant à un couplage entre le décollement et le fan. Le but de cette étude est de simuler numériquement l’écoulement intervenant dans une nacelle courte soumise à un vent de travers et d’étudier l’impact de la présence du fan. Tout d’abord, la définition de la distorsion est basée sur les grandeurs totales. Ainsi, la compréhension du comportement des grandeurs totales au voisinage d’une paroi et l’influence des paramètres numériques sur leur évolution est nécessaire. Une approche analytique et numérique sur plaque plane a permis d’évaluer le comportement des grandeurs totales à la frontière externe de la couche limite et l’influence des paramètres numériques RANS sur leur évolution. Cette étude a permis de choisir les paramètres numériques utilisés pour la simulation de la nacelle. Pour faire ressortir l’influence du fan sur la distorsion, deux types de simulations ont été menés : une simulation de nacelle isolée et une simulation de l’ensemble complet nacelle/fan respectivement comparées à un essai en soufflerie sur une maquette de nacelle isolée et à un essai de moteur complet à échelle 1 :1 réalisé en « soufflerie » à veine ouverte. La description correcte de la distorsion nécessite de prendre en compte les phénomènes de transition. Une méthode innovante de prise en compte de la transition par équations de transport est utilisée. Comme le coût de calcul de l’ensemble complet est prohibitif, la question du découplage du calcul en injectant une distorsion, issue d’une simulation de nacelle isolée, dans un calcul de fan isolé est discutée. La distorsion par vent de travers intervient lorsque l’avion est au sol. Par conséquent, l’impact de la présence du sol est étudié dans le cas de la nacelle isolée. Enfin, le critère de distorsion utilisé présente plusieurs défauts importants et peut être remis en cause. Une nouvelle méthode de mesure et de calcul estétudiéeInlet design must fulfill geometrical constraints and engine requirements. One of these requirementsis the homogeneity of the flow impacting the fan which is quantified by the distortionlevels of stagnation pressure. When the airplane is on the ground and ready to take-off, crosswindconditions are critical for the distorsion level. The most critical case is when the wind directionis normal to the engine axis. Subsonic and supersonic separations occur near the inlet lip. Theso-created heterogeneity produces an unsteady stress on the fan blades which can lead to surge.Furthermore, short inlets are designed nowadays reducing the distance available for the flow tohomogenize before the fan leading to a coupling between the fan and the separated flow region.The aim of this study is to numerically predict the flow in a short inlet under crosswind conditionsand to investigate the fan influence on the distortion. First of all, the distortion definition isbased on stagnation quantities. Therefore, the stagnation quantities behavior and the numericalparameters influence must be investigated. The behavior of the stagnation quantities near theboundary layer edge is studied with analytical and numerical approaches. The numerical parameterschosen for the inlet simulation come from the so-obtained results obtained. In order tohighlight the fan influence on the distortion, two kinds of simulations were proceeded and comparedto experimental results : an isolated inlet simulation and a inlet/fan simulation. To correctlypredict the distortion, transition has to be be taken into account. Therefore an innovative solutionusing transport equations is used. As the computation cost for the inlet/fan computation isprohibitive, the decoupling which consists in injecting on a isolated fan the distortion obtainedduring a isolated inlet computation, is discussed. In fact, crosswind conditions occur when theairplane is on the ground, thus, the ground influence over the inlet distortion is studied for anisolated inlet. Finally, the distortion criterion used in this study has evidenced some strong defectsand can be questioned. Another approach of measurement with another criterion definitionis investigated
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Thiart, G. D. "A numerical procedure for predicting the effects of distorted inflow conditions on the performance of axial flow fans." Thesis, Stellenbosch : University of Stellenbosch, 1991. http://hdl.handle.net/10019.1/5747.
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Thesis (PhD (Mechanical Engineering))--University of Stellenbosch, 1990.Leaves printed on single pages, preliminary pages i- viii and numbered pages 1-1-R5. Includes bibliography, list of tables and figures and list of appendices. Digitized at 330 dpi black and white PDF format (OCR),using KODAK i 1220 PLUS scanner.
ENGLISH ABSTRACT: A numerical procedure for predicting the effect of inlet flow distortions on the performance of axial flow fans is proposed. The study is aimed specifically at fans of low solidity and low hub-to-tip ratios, which have attained some importance with the advent of large directly air-cooled power stations in certain arid regions of the world. The numerical model is an extension to cylindrical polar coordinates of the SIMPLEN algorithm that has been developed by the author previously. The algorithm is implemented in a computer code, FLOVAX, which solves the incompressible Navier-Stokes equations, augmented by the k-Ɛ model of turbulence, on a computational domain that is aligned with the cylindrical polar coordinate system. Several relatively simple flow problems are solved to verify the code: laminar stagnation flow, laminar flow near a rotating disk, turbulent flow near a propeller, turbulent flow through an abrupt axisymmetric expansion, and turbulent swirling flow in an annulus. Good agreement is obtained between the numerical solutions and the corresponding analytical, empirical or published experimental and numerical results. Some experimental results are also presented: measurements of shaft power, volume flow rate and static pressure rise were taken in a setup comprising an axial flow fan mounted in the wall of a wind tunnel. The wind tunnel was used to provide flow across the fan intake, thus establishing distorted inflow conditions. Detailed measurements of the velocity and static pressure distributions in the duct downstream of the fan rotor were also performed. It is clear from the results that flow across the intake of the test fan has a detrimental effect on its performance in that an increased amount of power is necessary to deliver the same flow rate as with no crossflow. In the numerical predictions, blade element theory is used to model the thrust and torque exerted by the fan blades on the air. The numerical results generally confirm the results of the experiment, although the increase in power is underestimated: an increase of only approximately half of the measured increase is predicted. Several recommendations for improvement of the numerical procedure are made.
AFRIKAANSE OPSOMMING: 'n Numeriese prosedure vir die voorspelling van die invloed van versteurings in inlaatvloei op die werking van aksiaalwaaiers word daargestel. Die studie is spesifiek gemik op waaiers van lae soliditeit en lae lempunt-tot-naafverhoudings. Waaiers van hierdie tipe het belangrikheid verwerf sedert die onlangse totstandkoming van groot lugverkoelde kragstasies in sekere droe werelddele. Die numeriese model is 'n uitbreiding na silindriese poolkoordinate van die SIMPLEN-algoritme wat voorheen deur die skrywer ontwikkel is. Die algoritme word geimplementeer in 'n rekenaarkode, FLOVAX, wat die onsamedukbare Navier-Stokes-vergelykings, aangevul deur die k-Ɛ-turbulensiemodel, oplos op 'n berekeningsgebied wat saamval met die silindriese poolkoordinaatstelsel. Verskeie relatief eenvoudige vloeiprobleme word opgelos ter verifikasie van die kode: laminere stagnasievloei, laminere vloei op 'n roterende skyf, turbulente vloei deur 'n propeller, turbulente vloei deur 'n aksiaalsimmetriese vernouing, en turbulente roterende vloei in 'n annulus. Goeie ooreenstemming tussen die numeriese oplossings en die ooreenstemmende analitiese, empiriese of gepubliseerde eksperimentele en numeriese resultate is verkry. Eksperimentele resultate word ook aangebied: metings van asdrywing, volumevloei en statiese drukstyging is geneem in 'n opstelling wat bestaan het uit 'n aksiaalwaaier wat in die wand van 'n windtonnel gemonteer is. Die windtonnel is gebruik om versteurde-invloei-toestande te genereer in die vorm van dwarsvloei oor die waaier-inlaat. Snelheids- en statiese drukverdelings in die kanaal stroom-af van die waaierrotor is ook gemeet. Dit blyk duidelik uit die resultate dat die dwarsvloei oor die inlaat van die toetswaaier 'n nadelige uitwerking het op die werking daarvan in die opsig dat meer drywing nodig is om dieselfde vloeitempo te handhaaf as wat die geval is sonder dwarsvloei. Vir die numeriese voorspellings word van lem-element-teorie gebruik gemaak om die stukrag en draaimoment wat deur die waaier op die lug uitgeoefen word, te modelleer. Die numeriese resultate bevestig oor die algemeen die eksperimentele resultate, alhoewel die drywingstoename onderskat word met sowat die helfte van die gemete toename. Verskeie aanbevelings ter verbetering van die numeriese prosedure word gemaak.
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Derigent, William. "Méthodologie de passage d'un modèle CAO vers un modèle FAO pour des pièces aéronautiques:Prototype logiciel dans le cadre du projet USIQUICK." Phd thesis, Université Henri Poincaré - Nancy I, 2005. http://tel.archives-ouvertes.fr/tel-00105732.
Full textAbstract:
L'automatisation de la chaîne CFAO nécessite la « transformation » du modèle CAO (Conception Assistée par Ordinateur), issu de la conception, en un modèle FAO (Fabrication Assistée par Ordinateur), adapté aux tâches de préparation à la fabrication (détermination des posages, génération des gammes et calcul des trajectoires outils). Notre travail, réalisé dans le cadre du projet RNTL USIQUICK, a pour objectif de proposer une méthodologie de transformation permettant d'aboutir à un modèle FAO dédié à l'usinage 5axes de pièces aéronautiques. En regard de cette problématique, la première partie de ce mémoire présente un état de l'art des différentes méthodes de transformation de modèles par reconnaissance d'entités et met en évidence l'inadéquation de celles-ci aux pièces aéronautiques. Nous proposons alors d'élaborer pour les tâches de préparation à la fabrication un modèle FAO s'appuyant directement sur le modèle CAO B-Rep, auquel sont ajoutées des informations relatives aux possibilités d'usinages des différentes faces le constituant. Chaque face enrichie du modèle est alors considérée comme une entité d'usinage dite « élémentaire ».
Pour aboutir à ce modèle FAO, nous proposons une méthodologie de transformation composée d'une vue statique (modèle de données) et d'une vue dynamique (processus de transformation). La deuxième partie du mémoire présente la vue statique. Elle s'appuie sur le modèle des données nécessaires au processus de transformation obtenu à l'aide de la méthodologie VIM (Viewpoint Integration Modelling). La vue dynamique, présentée dans la troisième partie, est constituée de deux étapes de traitements : la première dite étape « d'enrichissement » complète le modèle CAO par des attributs géométriques et technologiques, la seconde dite étape « d'analyse d'usinabilité » traite ce modèle enrichi afin d'adjoindre aux faces des informations d'usinage. Elle aboutit finalement au modèle FAO composé d'entités élémentaires.
Pour finir, nous validons, dans la dernière partie, les spécifications proposées par le développement et la mise en œuvre d'un démonstrateur sous CATIAV5®. Nous présentons les résultats obtenus sur quelques pièces aéronautiques.
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Swart, Christopher. "Optimising the operation of underground mine refrigeration plants and ventilation fans for minimum electricity cost / Christopher Swart." Thesis, North-West University, 2003. http://hdl.handle.net/10394/339.
Full textAbstract:
This study describes the development and use of a mathematical model that will enable mine operators to
minimise the costs of electricity consumed by the ventilation and refrigeration systems used for
environmental control in deep mines.
This model was calibrated and tested by using actual data from a gold mine near Welkom in South
Africa. In a first simulation, the mine's current practice of controlling conditions to a wet bulb
temperature (Twb) of 25S°C, was optimised. The model demonstrated that this environmental condition
could be sustained at lower electricity consumption. In so doing, the mine realised a saving of 30 000
kWh per day. The energy saving and load management led to a cost saving of R 1.5 million per year.
However, a better indicator of environmental conditions is the Air Cooling Power index, (ACP).
Research has shown that for hard physical work in hot conditions workers need an ACP of 300 w/m2. It
was found that the case study mine actually supplied their workplace with a cooling capacity of 422
w/m2. The new model optimised the refrigeration and ventilation systems in such a manner that the
workers were supplied with exactly 300 w/m2, no more and no less. It was found that by doing this, an
electricity saving of 57 600 kWh per day could be realised when compared with the current mine
practices. The energy saving and load management led to a potential cost saving of R 2.55 million per
year. (Certain capital costs, such as for variable speed drives may have to be incurred to realise these
savings.)
The new model could be further extended to take advantage of the new Real Time Price offerings from
Eskom It will be able to identify an operating point for the refrigeration and ventilation systems to
supply 300 w/m2 for the workers, in real time, at the lowest electricity cost.Thesis (Ph.D. (Mechanical Engineering))--North-West University, Potchefstroom Campus, 2004.
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An-Pan, Lee, and 李安平. "The Simulation Analysis of Fan Bearing." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/14705242683950411466.
Full textAbstract:
碩士華梵大學
機電工程研究所
96
Since the long time， the noise and vibration always speaking of the equipment of fan is a very major problem. Therefore how improves is an important work is at. This research uses specification of the SWB-220-LMDX-QD 876-1942 RPM take the MRT of TAIPEI MAIM station which GREENHECK Corporation produces as the simulation object. At first， we draw up the 3D full-scale mockup by commercial CAD software –Solid Works. We transfer the files to dynamic simulation analysis software – ADAMS. To simulate the fan start， it correlates with spare part the relative motion. We approximately divided into four parts in the simulation part. The first part for aims at fan several items of important spare parts to carry on the characteristic measurements. The second part for aims at situation of the fan actual operation to carry on the simulation analysis， in view of vibrates the influential several items of parts in the simulation process with the fan the characteristic parameter to carry on the adjustment like rotor， the dumping coefficient to carry on the dynamic simulation. The third part the fan rotor for separately identical plane and not the identical plane hypothesize eccentric amount carry the imbalance amount simulation analysis. The fourth part carries on the natural frequency to the fan rotor the analysis. Penetrates this research to be able to utilize the CAD software and the function of ADAMS dynamic simulation， can promote the ability of research and development design.
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Chang, Yuh-Ching, and 張裕慶. "Numerical Simulation of Axial-Flow Fan." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/46259914629144287197.
Full textAbstract:
碩士國立台灣工業技術學院
機械工程技術研究所
85
The purpose of this study is to investigate the two- dimensional flowfield of the axial fan blade by utilizing the theories and numerical methods for turbomachine. With the aid of Vortex-Lattice method, the blade surface is divided into several panels and each element is described by varying singularity strength to calculate the velocity and pressure distributions. The gasdynamic properties of blade are thus computed. In addition, the influence for various blade geometric parameters and inflow conditions are studied. The outcomes show that a large stagger angle results in an increase of blade surface pressure and a decrease of fan''s overall efficiency. Both the positive and negative incidence angles would induce the separation occurred on blade surface. Regards the number of blade, the lower surface appears backwash easily for a fan with less number of blade; however, too many blades may obstruct the flow. Moreover, the rounded leading edge and thin thickness are suggested to gain a better stability and performance of the fan. Besides, the maximum thickness of blade should locate in the vicinity of blade center.
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Wen, Wang Yih, and 王藝文. "Numerical Simulation of a Novel Complex Fan." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/15912662745863062164.
Full textAbstract:
碩士國立臺灣科技大學
機械工程系
93
In this study, the purpose is to devise a novel complex fan, which can meet the requirement of internal space and cooling desire of notebook computer. Overall volume of innovated complex fan is 60×60×15 mm3, and it is consisted of the design features of centrifugal and cross-flow fans. High airflow rate of cross flow fan and the high static pressure of centrifugal fan are the advantages on performance of complex fan. First of all, the centrifugal rotor is designed with the NACA4410 airfoil, and it is fitted in the spiral housing. The prototype is made by CNC machine and tested to serve as reference for further modification. All the performance and noise experiments are executed in AMCA 210-99 chamber and semi-anechoic chamber, respectively. Thereafter, a parametric study on fan geometry is performed to realize the influences caused by those variations. From experimental result, the complex fan yield a better output than the sample does. In numerical analysis, the simulation is divided into three portions. First portion, the optimum complex fan in the experimental program is simulated via the CFD software (STAR-CD). Then, for understanding the flow patterns, the open holes of top and bottom plates are sealed in order to simulate the traditional cross flow fan. Finally, the flow field of complex fan is simulated with various hub size of motor. All recommendations of improvement are raised to enhance the performance characteristics of complex fan via comparing the experiment and simulation result. In summary, while the noise level is kept roughly at the same level, compared to the reference available in the current market, an impressive 4.92 CFM airflow with 6.82 mm-Aq static-pressure gain are delivered by the complex fan with an optimum geometrical parameters operating at 3000rpm.
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Jiang, Bosyuan, and 江帛宣. "Numerical Simulation and Analysis of Compound Fan." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/77661826342902032596.
Full textAbstract:
碩士聖約翰科技大學
自動化及機電整合研究所
100
In this study compound fan (axial fan and centrifugal fan) applied to the thermal module design improvements and testing explore. Change the centrifugal blade length, research and analysis of its air pressure, air volume. Use the simulation software SolidsWorks Flow Simulatiom, analog compound fan change to a different blade length air pressure and air volume, by wind tunnel testing and simulation results are compared with the measured thermal module and fan, do thermal analysis to verify whether the cooling effect is also under the same conditions as the best able to analyze the best product design parameters, and effectively increase their service life and maintain the effectiveness of electronic products. This article wind tunnel measurements and simulations compound fan speed setting 3500 rpm, to change centrifugal fan blade length were 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, a total of five groups parameters to the analysis, then with cooling module set the heating power of 40 W, 50 W, 60 W, do thermal analysis to compare, the results show that when the fan blade length of 10 mm, the air volume of 53.4 CFM, the lowest thermal resistance with the best heat dissipation effect.
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Hu, Wen-Yu, and 胡文彧. "Numerical Simulation and Experimental Investigation of Fan." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/75734000767966850569.
Full textAbstract:
碩士國立交通大學
機械工程研究所
86
This study is to investigate a flow field of common used computer fan. A finite volume method is employed to solve the flow field in the fan. During the computing process, the k-ε turbulent model is used to solve the governing equation of the flow field. In experiment investigation, a dark room and camera is used to film the flow field. However, by using an accurately triggered flashlight, the flow field down below the fan can be clearly recorded. According to the above investigation, the flow is almost stay still in the center below the fan. And there are several vortexes around the center below the fan, which keep the heat generated by the chip from the outgoing flow. After analysing the above phenomenon, to break the geometric symmetry is the most efficient mean to improve the fan efficiency.
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Tseng, Ming-Hsi, and 曾明溪. "Numerical Simulation and Experimental Investigation of Fan." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/73917834657671751632.
Full textAbstract:
碩士國立交通大學
機械工程系
87
This study is to simulate a flow field of common used computer fan. A finite volume method is employed to solve the flow field in the fan. During the computing process, the standard turbulent model is used to solve the governing equation of the flow field. In experimental investigation, film the smoke structure by smoke-wire method, measure the velocity by hot-wire technic at outlet of the tube, and record the pressure at wall of the tube. It is shown that the numerical accuracy is above 70%. According to the numerical investigation, the detail structure of flow field and the raising process of pressure can be understood. After analysing the flow field, change the design of centre shaft can increase the pressure, flow velocity and flux.
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Chun-Kai, Liao, and 廖俊凱. "Vibration Simulation and Analyses of the Centrifugal Fan." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/23415979087568750063.
Full textAbstract:
碩士華梵大學
機電工程學系博碩專班
98
The aim of this paper is to examine the vibration of the centrifugal fan in the notebook computer by using the method of simulations. In this paper, three different kinds of centrifugal fans with angles of 90, 60, and 45 degrees are presented. The fan is enclosed by the top cover and the bottom cover which are hinged by spring elements. The geometric conditions of fans and covers are design and built by using the Solid Works software and the model can be transferred to the ADAMS software. Material properties of parts and constrained conditions between a fan and covers are defined and set in ADAMS. In the analysis of simulation, the angular velocities of the fan are assumed to be from 900 RPM to 6000 RPM. Effects of the angular velocity, spring, and damping coefficients on the vibration of the cover are examined and compared with three different angles of fans.
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LYU, PO-HUNG, and 呂博弘. "Numerical Simulation of Deposion Fan of Debris Flow." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/4ny92k.
Full textAbstract:
碩士逢甲大學
水利工程與資源保育學系
105
In this study, the CCHE2D numerical model was used to simulate the accumulation of debris flow, input triangular discharge hydrograph and Equilibrium sediment calculated by Schoklitsch(1943) formula and Sediment transport volume calculated by Takahashi(1991) formula, refer to the characteristics of debris flow, the debris flow simulation is carried out with the concept of river sediment transport overload, finally, the paper discusses the different time interval and different slope parameters. According to the study and analysis of the test, hereby list the following result: 1. In this study, we discuss the different time interval, mainly because the difference of input data will show different numerical interpolation results. When the time interval is smaller, the number of input data is more The results will be more accurate changes. 2. The main difference between the amount of sediment input and sediment is that the sediment capacity of the model itself is the same under the same conditions. Therefore, the sediment volume and the loss of the sediment at different time intervals Sand body, there is a certain proportion between the two. 3. The maximum area of the accumulation area is 80,850m2 with slope of 6 degrees and the minimum slope of 12 degrees is 78,350 m2. The overall trend of the accumulation area decreases with the increase of the slope, and the accumulation length increases with the slope.
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Wu, Chih-Ming, and 吳志明. "Simulation and design of a piezoelectric actuated fan." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/05464649686150199649.
Full textAbstract:
碩士健行科技大學
機械工程系碩士班
103
The study was the design of the new piezoelectric actuators fan which was combined with the three-phase symmetrical piezoelectric actuator and fan blades from the structural simulation and analysis of the three-phase eccentric thin disc piezoelectric actuator in the existing paper. With the simulation of the three-phase eccentric thin disc piezoelectric actuator vibration mode analyzed by ANSYS dynamic simulation software, there was the three phase continuous driving wave, the wave position in the different cycle was changed continuously and obviously formed a rotational motion force around the driving point screw. The driving fan verified to have rotation ability to become new piezoelectric actuators fan. According to there was no symmetry of the three-phase eccentric thin disc piezoelectric actuator in existing paper, the study designed the three-phase symmetrical piezoelectric actuator combined with the fan from the adjustment and correction of the three-phase eccentric thin disc piezoelectric actuator. The design of the new piezoelectric actuators fan mechanism was the use of SolidWorks graphics software to draw the model of mechanism. The mechanism included the three-phase symmetrical piezoelectric actuator, fixed base of the piezoelectric actuator, fan blades and transmission. The fixed base was designed because the piezoelectric actuator could not install directly in the original axial flow electromagnetic fan. The rotational speed of the new piezoelectric actuators fan could reach up to 2100 rpm in the driving condition of the frequency of 75 kHz and voltage amplitude of 25 V.
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Shao, Songdong. "Simulation of fan formation using a debris mass model." 2002. http://hdl.handle.net/10454/470.
Full textAbstract:
Based on the particle-in-cell computing method, a debris mass model has been established to simulate debris flow fan formation over large downstream
areas. Under the assumption that the debris medium is an assembly of many small, identical debris particle masses, the overall flowbehavior is obtained
by averaging the flow parameters of neighboring debris masses at fixed grid points. The equation of motion for each debris mass is based on the depthaveraged
Navier-Stokes equation in two horizontal dimensions. The friction slope of debris flow is modeled by combining the effects of both the liquid
phase (slurry composed ofwater and fine particles) modeled as a Bingham fluid and solid phase (coarse particles) in the debris mixture. The rheological
parameters are evaluated according to the density and particle size distribution of the debris material. Convergence of the method is demonstrated by
repeatedly doubling the number of debris masses employed in the computation until insignificant change is observed. The debris mass model is
demonstrated through a prototype application to a documented 1991 debris flowdeposited in the lower reach of the Shawan Ravine inYunnan Province,
China. The final alluvial fan was formed by eight consecutive debris flow events, each lasting about 2000 seconds with a discharge rate of 250 m3/s.
The simulation results are in good agreement with field observations. The general features of debris fan development and configuration are well
predicted.
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Chen, Chen Shiu, and 陳振秀. "Simulation and analysis of the structure strength of fan frame." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/46721074558116279367.
Full textAbstract:
碩士國立高雄應用科技大學
機械與精密工程研究所
99
ABSTRACT The aim of this thesis is to verify the design of the structure of the axial-flow fan by simulating and analyzing its structure strength, and then to obtain the final optimal structure design. When we design a fan, we need to consider the volume, stress, frequency, efficiency and noise problem. The problem of vibration and noise occurs when the fan rotates at high speed. To solve this problem, we make an analysis on the structure of fan to see how it can avoid the impact from the vibration at high speed rotation. The fan we choose to test is with 60 x 15 cm frame, and it is with plastic material PBT+ 30% GF. The size and the material are very important, which is the key point to improve the fan structure. We use ANSYS software to study the relationship of structure, material and mesh. Fan cooling is a main method for radiation, but its vibration at high speed rotation often makes some bad influence on whole machine system. For example: when the structure has little damage, even small vibration will cause resonance and destroy the whole structure. In most cases, the style and structure of a fan is fixed after primary design. Its natural frequency won’t changes unless it is redesigned. So, we can only either expect to change the original design to avoid resonant frequency or make vibration smaller, or change the rotation speed to obtain a more stable fan structure.
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Lin, Tai-Yu, and 林泰余. "The Flowfield and Aeroacoustic Simulation of a F.C. Centrifugal Fan." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/10651320408607455963.
Full textAbstract:
碩士遠東技術學院
機械研究所
94
This study is to investigate the influences on the performance and noise due to installing a resonator into the cut-off or digging a hole and forming a groove on the housing for a F.C. centrifugal fan by applying numerical methods. First of all, a low noise F.C. centrifugal fan using for a base fan in this study and resonators with different types is constructed according to the foregone literatures. Next, install these resonators into the cut-off of the centrifugal fan respectively to get a series of fan models with different type resonator. Then, a series of numerical simulations of turbulence flow and aeroacoustic associated with these fan models and base fan carried out individually. Furthermore, the analysis and comparison of performance and noise among base fan and these fan models performed, also the influences on the aerodynamic performance and noise owing to the resonator installation and the change of resonator’s types was investigated. On the other hand, the design parameters of the groove and hole on the housing of fan were determined respectively according to the results of flowfield visualization for the base fan. Then, a hole was dug on the front plate of the housing, and a sunken groove was formed on the bottom plate of outflow channel of the housing individually. In addition, the flowfield and aeroacoustic of the fans with hole or groove simulated. Consequently, the influences on the aerodynamic performance and aeroacoustic owing to the hole and groove on the housing investigated respectively by comparing these simulation results with the base fan’s one. The numerical results indicate that the fan after installing resonator, in comparison with the base fan, can reduced the pressure and velocity gradient of both cut-off vicinage and inside the housing, as well as reduced the range and strength of both transverse vortex and longitudinal recirculation flow at outflow section. Furthermore, the resonator can reduced the aeroacoustic noise a little but decreased the flow rate. Besides, the influences on the performance and noise owing to the change of resonator’s types were puny. On the other hand, the fan after digging a hole on the front plate of its housing can increased the volume flow rate by 39 % as well as reduced noise output at outflow section by 18 %. Furthermore, the integral velocity between hole’s downstream and outlet were increased to lead the fluid separation moving down and delaying after digging a hole on housing. It also caused the effective outlet area increased, as well as increased the volume flow rate. Besides, the aeroacoustic source distributed mainly between hole’s downstream and outlet for the fan after digging a hole. It was different distinctly form the base fan, which distributed near the cut-off and impeller. Finally, the influences on the performance and noise owing to the groove were puny.
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LO, WEI-CHEN, and 羅韋晨. "Warpage Simulation Analysis for Fan-out Panel Level Packaging Process." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/8g32d7.
Full textAbstract:
碩士國防大學理工學院
機械工程碩士班
107
Fan-out panel-level packaging (FOPLP) technology is known as next-generation fan-out technology because of its high throughput and thin package. However, warpage may occur in the FOPLP process, which causes subsequent yield and reliability problems. Therefore, this thesis adopts finite element software to simulate the warpage generated by FOPLP in each stage process and discusses the influence of FOPLP packaging materials and structural parameters. The aim of this thesis is to determine the appropriate FOPLP geometry design and material parameters for improving the process warpage. For this purpose, the study used ANSYS 17.2 element birth and death techniques to simulate all FOPLP processes for obtaining the warpage values of each process stage. The Taguchi method is applied by using L12 and L8 orthogonal array experiments with an optimal parameter combination to identify important factors. The results of single factor analysis indicate that the warpage can be reduced by decreasing the Young’s modulus of the carrier, Polyimide (PI) Young’s modulus and the PI coefficient of thermal expansion (CTE), and increasing the carrier CTE, Young’s modulus of the epoxy molding compound (EMC), CTE of EMC, die occupancy ratio, and EMC thickness. Furthermore placing small Si blocks around the die can reduce the warpage value by 17% during carrier debonding. According to the experimental optimization results, the optimum factor can reduce the warpage value by 90% for carrier debonding and 98% for molding. Determining the best factor can effectively reduce the warpage in the process. Moreover, Taguchi analysis indicates that the Young’s modulus of EMC and EMC thickness are the most influential parameters for warpage during the carrier debonding process. The carrier CTE and Young’s modulus of the carrier have the most obvious influence on warpage during the EMC molding process.
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Deng, Shang-Shiuan, and 鄧上軒. "Warpage Simulation of Fan-Out Wafer Level Chip Scale Package." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/37274369936517085920.
Full textAbstract:
碩士國立成功大學
機械工程學系碩博士班
97
Wafer level packaging is an important development trend for IC package design. The fan-out wafer level package discussed here has the flip chip form which uses thin-film redistribute then uses solder bump to connect the package to the printed wiring board directly. Liquid compound was used for the encapsulation process. Comparing with wire-bond BGA, the fan-out wafer level package has better electric properties, lower power consumption, and smaller package size. Warpage problem plays an important role in IC encapsulation processes. Previous researchers had focused on warpage analyses with temperature changes between constituent materials and neglected the cure shrinkage effects. However, more and more studies indicate that prediction of warpage according to CTE (Coefficient of Thermal Expansion) was not able to accurately predict the amount of warpage in IC packaging. This paper used mold filling simulation and predicted the amount of warpage considering both thermal and cure induced shrinkage. The liquid compound properties were obtained by various techniques: cure kinetics by differential scanning calorimeter (DSC), cure induced shrinkage by P-V-T-C testing machine. These experimental data were used to formulate the P-V-T-C equation. The P-V-T-C equation was successfully implemented and verified that warpage was governed by both thermal shrinkage and cure shrinkage. The amount of warpage after molding could be accurately predicted with this methodology. The simulation results showed that cure shrinkage of liquid compound was the dominant factor for package warpage after encapsulation. Even after post mold cure, the amount of warpage was still significant.
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江明峰. "Numerical simulation of airflow fields for the cross flow fan." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/34469728645450528783.
Full text
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Tsai, Ching-Yen, and 蔡清研. "MODFLOW groundwater simulation on Chou-Shui Alluvial Fan using integral model." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/47963306504655484413.
Full textAbstract:
碩士國立中正大學
地震研究所暨應用地球物理研究所
95
This study is to make a new conceptual model, called ‘Solid model’ and run the numerical modeling on Chou-Shui Alluvial Fan with MODFLOW-2000 using the new data from the Central Geologic Survey MOEA（1999）. The initial model in this study does not take recharging, pumping, drains, evapotranspiration and so on into consideration. So the results of the initial model just show the characteristics of the rocks in each layer. For example, the hydraulic conductivity in the gravel layer is higher than that in the clay layer, and its gradient of head is lower. Compared with the true situation, it’s shown that the initial model needs corrections. Two corrections are in this study. One is to build some ideal wells with each fixed flow rate in the middle and western areas of Chou-Shui Alluvial Fan. The other is to set up three recharge areas with each fixed recharge rate in the eastern areas of Chou-Shui Alluvial Fan. The corrections are completed comparing to the real head lines in space and to the other models, the layer-by-layer models, from prior studies. The initial results and its corrections verify that it is proper to model some situations of groundwater in Chou-Shui Alluvial Fan using the model in this study. Estimation and evaluation of the flowing groundwater is the other advantage of this solid model.
50
Chun-Tsai, Shih, and 蔡士鈞. "Numerical Simulation of Inter Flow Field Inside a Backward-Inclined Centrifugal Fan." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/32858917800564959138.
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碩士中原大學
機械工程研究所
97
This study employs the numerical approach to simulate the internal flow field of single inlet backward centrifugal fan to correlate the curvature changing of impeller blade. The three-dimensional steady state incompressible flow field inside single inlet backward centrifugal fan is calculated by solving the continuity equation, momentum equation. Additionally compares with the existing experimental result, this model have the same tendency.