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Desenvolvimento de uma metodologia de simulação aplicada ao sistema de arrefecimento veicular.; Simulation metodology development applied to the vehicle cooling system.

Quim, Nelson
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 17/05/2007 PT
Relevância na Pesquisa
26.06%
Este trabalho visa o estudo de uma metodologia de simulação numérica aplicada ao processo de troca térmica do motor de um veículo de passeio. O processo de troca térmica é essencial para evitar o superaquecimento do motor, que provoca o rompimento do filme de óleo lubrificante dos pistões e, conseqüentemente, o seu travamento. Essa metodologia será útil nos estudos preliminares do sistema de arrefecimento de um veículo na fase inicial de projeto por meio de simulações virtuais, o que possibilitará a redução de protótipos, além de proporcionar um ganho em tempo de resposta. A metodologia utiliza um programa comercial de CFD para a simulação do processo de troca térmica no interior do compartimento do motor do veículo. As simulações foram realizadas com base nos testes físicos em túnel de vento que fazem parte do desenvolvimento e projeto de automóveis em condições de operação que representam situações críticas integrantes da vida operacional. Essas condições operacionais de teste, tais como a velocidade do veículo, as cargas térmicas, a potência dos ventiladores e outros parâmetros foram utilizadas como condições de contorno na validação do modelo do veículo. O processo de validação de modelos é composto por: validações de itens isolados do sistema de arrefecimento...

Estudo de diferentes tipos de solo em túnel de vento através de simulação numérica.; Study of different types of floor configuration in a tunnel using numeric simulation.

Buscariolo, Filipe Fabian
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 08/10/2009 PT
Relevância na Pesquisa
56.43%
O trabalho aqui apresentado visa estudar diferentes tipos de piso localizados na seção de testes de um túnel de vento e verificar a influência que ocorre em ensaios de automóveis analisando o escoamento entre o veículo e o solo, assim como avaliar alterações no coeficiente de arrasto, utilizando simulações numéricas computacionais. O coeficiente de arrasto de um veículo é uma propriedade aerodinâmica importante e, quanto menor for esse valor, melhor será seu rendimento, além de melhorar o consumo de combustível, item relevante hoje no projeto de novos automóveis. Partindo de um ensaio experimental de uma pequena caminhonete em túnel de vento com piso fixo, um modelo virtual igual é construído e analisado por CFD, nas mesmas condições de teste do ensaio real. A diferença de resultado entre o coeficiente de arrasto medido em túnel de vento e o cálculo por simulação é de 0,25%, mostrando que o método de simulação possui grande confiabilidade. Posteriormente, outras duas simulações considerando dois outros tipos de solo: plataforma elevada e esteira rolante são analisadas e apresentaram diferenças de decréscimo valor de arrasto de 0,002 e 0,012 respectivamente, em relação a simulação com piso fixo...

Dinamica não linear e controle de uma aeronave em voo longitudinal; Non linear dynamics and control of an aircraft in longitudinal flight

Danilo Carlos Pereira
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 30/07/2007 PT
Relevância na Pesquisa
56.26%
Neste trabalho analisou-se a dinâmica não linear de uma aeronave em vôo longitudinal. Efetuou-se a análise do comportamento bifurcacional da aeronave F-8 “Cruzader”. Na análise bifurcacional foi estudado o comportamento topológico desta aeronave tomando-se dois parâmetros de controle: a deflexão do profundor e a alteração da massa da referida aeronave. Ante a pesquisa desenvolvida, foi proposto um projeto de controle linear ótimo com o objetivo de estabilizar as oscilações do ângulo de ataque, considerando-se regiões criticas do comportamento não linear da aeronave. Adicionalmente, incluiu-se no modelo matemático a variação da velocidade longitudinal da aeronave, visto tratar-se de simulações numéricas em um túnel de vento virtual.; In this work it was analyzed the non linear dynamic of an aircraft taken onto longitudinal flight. It was done analysis of the bifurcacional behavior of the aircraft F-8 “Cruzader”. In the bifurcational analysis was studied the topological behavior of this aircraft taken into account two parameters of control: the deflection of the elevator and the alteration of the mass of the related aircraft. In the face of the developed research, an optimum linear control project was proposed with the objective of stabilizing the oscillations of the angle-of-attack. Additionally...

Turbulent wake study of the NREL phase VI wind turbine in a virtual wind tunnel using Large Eddy Simulation

Choudhry, A.; Mo, J.; Arjomandi, M.; Lee, Y.H.
Fonte: Engineers Australia; CDROM / DVDROM Publicador: Engineers Australia; CDROM / DVDROM
Tipo: Conference paper
Publicado em //2012 EN
Relevância na Pesquisa
66.4%
The objective of the current investigation is to achieve a better understanding of the turbulent wake characteristics behind a wind turbine for the purpose of the improvement of the overall wind farm efficiency and a better prediction of the fatigue loads on tandem wind turbines. Large Eddy Simulation was performed at a low wind speed of 7m/s in a numerical wind tunnel model with dimensions similar to the NASA Ames Wind Tunnel (24.4 m x 36.6 m). An ANSYS CFD Fluent solver based on the dynamic Smagorinsky-Lilly model was employed to simulate the flow surrounding the wind turbine placed inside the numerical wind tunnel. For validation purposes, the aerodynamic characteristics of the blade were compared with the published experimental data of the NREL Phase VI. A good agreement was found between the experimental and the numerical results for the surface pressure distributions along the blade. It was observed that in the near-wake the turbulence intensity was a maximum of 12.12% at a distance of three rotor diameters downstream, after which a gradual decrease in the turbulence intensity was observed due to the wake instability. In the far-wake region, the turbulence intensity showed a tendency to increase, due to the presence of counter-rotating helical vortices determining the dynamics of far-wake. The system of vortices in the near-wake becomes unstable and breaks down due to the wake instability at a distance of approximately five rotor diameters downstream of the wind turbine. The vortex breakdown was used to define the boundary between the near and far-wake regions. The collapsed spiral wake was found to spread in all directions in the far-wake resulting in the formation of the two counter-rotating vortices which caused the gradual increase of turbulent intensity. The results and related discussion of the turbulent wake characteristics are presented in the current article.; Amanullah Choudhry...

Effects of wind speed changes on wake instability of a wind turbine in a virtual wind tunnel using large eddy simulation

Mo, J.; Choudhry, A.; Arjomandi, M.; Kelso, R.; Lee, Y.H.
Fonte: Elsevier Science BV Publicador: Elsevier Science BV
Tipo: Artigo de Revista Científica
Publicado em //2013 EN
Relevância na Pesquisa
66.32%
Jang-Oh Mo, Amanullah Choudhry, Maziar Arjomandi, Richard Kelso, Young-Ho Lee

Numerical Wake Visualization for Airfoils Undergoing Forced and Aeroelastic Motions

Jones, K.D.; Center, K.B.
Fonte: Escola de Pós-Graduação Naval Publicador: Escola de Pós-Graduação Naval
Tipo: Conference Paper
Relevância na Pesquisa
36.2%
AIAA Paper No. 96-0055, 34th AIAA Aerospace Sciences Meeting, Reno, Nevada, Jan. 1996.; A virtual wind tunnel is developed by combining a fast, time-stepping flow solver with an interactive animation interface. Inviscid, incompressible flow solutions are provided by an unsteady, potential-flow code with arbitrary airfoils undergoing forced or aeroelastic motions. Aeroelastic response is predicted by a two-degree-of-freedom spring/mass system modeling the structural dynamics of a flexible wing. A boundary layer code may be used to predict viscous flow effects such as transition and the onset of flow separation. The aeroelastic algorithm is coupled with an interactive graphical animation front end, enabling visualization and measurement of the unsteady wake and surrounding flow field. To further enhance the virtual wind tunnel look and feel, an assortment of tools is provided to mimic smoke/dye-injection, wake-vorticity tagging and flow anemometry. The complete package is used both as a research and an instructional tool, providing insight into the complex, unsteady vortical structures behind moving airfoils. Solutions compare well with experimental data while the animation allows a more thorough investigation of the development and evolution of the wake structures in time.

Upgrade of a LabVIEW based data acquisition system for wind tunnel test of a 1/10 scale OH-6A helicopter fuselage

Lines, Philipp A.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: xiv, 83 p. : ill. (some col.)
Relevância na Pesquisa
66.45%
Approved for public release, distribution is unlimited; For over half a century the NPS Aerolabʼ Low Speed Wind Tunnel located in Halligan Hall of the Naval Postgraduate school has served to provide students and faculty with meaningful aerodynamic data for research and problem analysis. New data acquisition hardware was installed three years ago but never fully verified, and contained no integrated software program to collect data from the strain-gauge balance pedestal. Existing National Instruments based hardware for the NPS low-speed wind tunnel was reconfigured to obtain data from the strain-gauge pedestal. Additionally, a data acquisition software program was written in LabVIEW⠭ to accommodate the hardware. The Virtual Instruments (VI) program collects and plots accurate data from all four strain gauges in real-time, producing non-dimensional force and moment coefficients. A research study on the performance of an OH-6A helicopter fuselage was conducted. NPS Aerolabʼ wind tunnel tests consisted of drag, lift, and pitching moment measurements of the OH-6A along yaw and angle-of-attack sweeps. The results of the NPS wind tunnel data were compared against testing conducted on a full-scale OH-6A helicopter in NASA Ames' 40 ft. x 80ft. wind tunnel...

PROSSEIA-VR: training in the virtual environments

Grave, Luís; Escaleira, Cristina; Marcos, Adérito
Fonte: konziel, Agentur für Marketing und Kommunikation, B. Lukacin, Darmstadt, Germany Publicador: konziel, Agentur für Marketing und Kommunikation, B. Lukacin, Darmstadt, Germany
Tipo: Artigo de Revista Científica
Publicado em /09/2001 ENG
Relevância na Pesquisa
46.05%
The Virtual Reality (VR) field can provide a wide variety of industrial applications. We can find several examples in the automobile industry, where VR is used for tasks like design, wind tunnel simulators, assemble/disassemble, etc. However, all these applications are designed to be used by VR experts,or well trained personnel. This happens because the VR devices and the VR interaction metaphors are not yet well developed to fulfil the needs of an inexperienced user, like robustness, failure recovery, easiness of use. All these aspects have to be resolved before an inexperienced user can effectively use such a system. The article reports about a two years CCG's industrial project aimet at solving, at least partially, this problem, targeting the training on wire twist assembly for the automobile industry.

Lessons Learned from an Experiment in Crowdsourcing Complex Citizen Engineering Tasks with Amazon Mechanical Turk

Staffelbach, Matthew; Sempolinski, Peter; Hachen, David; Kareem, Ahsan; Kijewski-Correa, Tracy; Thain, Douglas; Wei, Daniel; Madey, Greg
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 29/06/2014
Relevância na Pesquisa
35.87%
We investigate the feasibility of obtaining highly trustworthy results using crowdsourcing on complex engineering tasks. Crowdsourcing is increasingly seen as a potentially powerful way of increasing the supply of labor for solving society's problems. While applications in domains such as citizen-science, citizen-journalism or knowledge organization (e.g., Wikipedia) have seen many successful applications, there have been fewer applications focused on solving engineering problems, especially those involving complex tasks. This may be in part because of concerns that low quality input into engineering analysis and design could result in failed structures leading to loss of life. We compared the quality of work of the anonymous workers of Amazon Mechanical Turk (AMT), an online crowdsourcing service, with the quality of work of expert engineers in solving the complex engineering task of evaluating virtual wind tunnel data graphs. On this representative complex engineering task, our results showed that there was little difference between expert engineers and crowdworkers in the quality of their work and explained reasons for these results. Along with showing that crowdworkers are effective at completing new complex tasks our paper supplies a number of important lessons that were learned in the process of collecting this data from AMT...

Visual control of flight speed in Drosophila melanogaster

Fry, Steven N.; Rohrseitz, Nicola; Straw, Andrew D.; Dickinson, Michael H.
Fonte: Company of Biologists Publicador: Company of Biologists
Tipo: Article; PeerReviewed Formato: application/pdf; video/quicktime
Publicado em 15/04/2009
Relevância na Pesquisa
25.87%
Flight control in insects depends on self-induced image motion (optic flow), which the visual system must process to generate appropriate corrective steering maneuvers. Classic experiments in tethered insects applied rigorous system identification techniques for the analysis of turning reactions in the presence of rotating pattern stimuli delivered in open-loop. However, the functional relevance of these measurements for visual free-flight control remains equivocal due to the largely unknown effects of the highly constrained experimental conditions. To perform a systems analysis of the visual flight speed response under free-flight conditions, we implemented a `one-parameter open-loop' paradigm using `TrackFly' in a wind tunnel equipped with real-time tracking and virtual reality display technology. Upwind flying flies were stimulated with sine gratings of varying temporal and spatial frequencies, and the resulting speed responses were measured from the resulting flight speed reactions. To control flight speed, the visual system of the fruit fly extracts linear pattern velocity robustly over a broad range of spatio–temporal frequencies. The speed signal is used for a proportional control of flight speed within locomotor limits. The extraction of pattern velocity over a broad spatio–temporal frequency range may require more sophisticated motion processing mechanisms than those identified in flies so far. In Drosophila...

Characterisation and airborne deployment of a new counterflow virtual impactor inlet

Shingler, T.; Dey, S.; Sorooshian, A.; Brechtel, F. J.; Wang, Z.; Metcalf, A.; Coggon, M.; Mülmenstädt, J.; Russell, L. M.; Jonsson, H. H.; Seinfeld, J. H.
Fonte: Copernicus Publications Publicador: Copernicus Publications
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em 06/06/2012
Relevância na Pesquisa
35.97%
A new counterflow virtual impactor (CVI) inlet is introduced with details of its design, laboratory characterisation tests and deployment on an aircraft during the 2011 Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE). The CVI inlet addresses three key issues in previous designs; in particular, the inlet operates with: (i) negligible organic contamination; (ii) a significant sample flow rate to downstream instruments (∼15 l min^(−1)) that reduces the need for dilution; and (iii) a high level of accessibility to the probe interior for cleaning. Wind tunnel experiments characterised the cut size of sampled droplets and the particle size-dependent transmission efficiency in various parts of the probe. For a range of counter-flow rates and air velocities, the measured cut size was between 8.7–13.1 μm. The mean percentage error between cut size measurements and predictions from aerodynamic drag theory is 1.7%. The CVI was deployed on the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS) Twin Otter for thirty flights during E-PEACE to study aerosol-cloud-radiation interactions off the central coast of California in July and August 2011. Results are reported to assess the performance of the inlet including comparisons of particle number concentration downstream of the CVI and cloud drop number concentration measured by two independent aircraft probes. Measurements downstream of the CVI are also examined from one representative case flight coordinated with shipboard-emitted smoke that was intercepted in cloud by the Twin Otter.