Institute Aeronautica e Espaco

São Paulo, Brazil

Institute Aeronautica e Espaco

São Paulo, Brazil
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Fuentes J.D.,Pennsylvania State University | Chamecki M.,Pennsylvania State University | Dos Santos R.M.N.,University of the State of Amazonas | Von Randow C.,National Institute for Space Research | And 16 more authors.
Bulletin of the American Meteorological Society | Year: 2016

A field campaign reveals that the Amazon rain forest produces enough chemical species to undergo oxidation and generate aerosols, which can activate into cloud condensation nuclei and potentially influence cloud formation. © 2016 American Meteorological Society.

De Paula I.B.,Pontifical Catholic University of Rio de Janeiro | Wurz W.,University of Stuttgart | Mendonca M.T.,Institute Aeronautica e Espaco | Medeiros M.A.F.,University of Sao Paulo
Journal of Fluid Mechanics | Year: 2017

The influence of a single roughness element on the evolution of two-dimensional (2-D) Tollmien-Schlichting (TS) waves is investigated experimentally. Experiments are carried out in a region of zero pressure gradient of an airfoil section. Downstream from the disturbance source, TS waves interact with a cylindrical roughness element with a slowly oscillating height. The oscillation frequency of the roughness was approximately 1500 times lower than the wave frequency and approximately 250 times slower than the characteristic time of flow passing the region of transition development. Therefore, the roughness behaved as a quasi-steady disturbance. The set-up enabled us to perform hot-wire measurements phase locked to the waves and to the roughness movement. Experimental results show a scattering of the 2-D waves into oblique ones and a relatively weak distortion of the mean flow for roughness heights as large as 0.2 times the boundary layer displacement thickness (λ). Transfer functions for TS wave scattering at the roughness are obtained. Results show an unexpected coincidence in shape with acoustic receptivity functions found in Würz et al. (J. Fluid Mech., vol. 478, 2003, pp. 135-163) for the problem of excitation of TS waves by scattering of acoustic waves at surface roughness. In the present work, the ratio between the incoming 2-D wave amplitude to the amplitude of the scattered oblique waves scaled linearly with the roughness height only for very shallow roughness. For roughness elements higher than 0:08λ and below 0:2λ, the wave scattering exhibited a quadratic variation with respect to the roughness height. In addition, this feature did not vary significantly with respect to TS wave frequency. An analysis of the weakly nonlinear interactions triggered by the roughness element is also carried out, assisted by numerical solution of nonlinear parabolized stability equations, performed for a two-dimensional Blasius boundary layer. A comparison between experiments and simulations reveals that the weakly nonlinear interactions observed are not substantially affected by mean flow distortions that could be produced in the wake of the small and medium sized roughness elements (h < 0:2λ). From a practical perspective, results suggest that scattering coefficients might be employed to include the effect of isolated and medium sized roughness elements in transition prediction tools developed for smooth surfaces. © 2017 Cambridge University Press.

Filho J.B.P.F.,Institute Aeronautica e Espaco | Filho J.B.P.F.,Brazilian Technological Institute of Aeronautics | Reis M.L.C.C.,Institute Aeronautica e Espaco | Reis M.L.C.C.,Brazilian Technological Institute of Aeronautics | And 2 more authors.
Journal of Physics: Conference Series | Year: 2016

Measurements of normalized pressure distribution are carried out over a 1:8 scale half-model of the Sonda III sounding rocket. The objective is to analyze the effect of the implementation of transition devices on the flow over the vehicle. Measurements show that the presence of the transition devices affect pressure distributions in different Mach numbers around the inter-stage region of Sonda III depending on its location and independently of the turbulent transition method employed. The study of these effects plays a significant role for future developments, since transition phenomena and the modification of the boundary layer behaviour due to the expansion can alter the load distributions and the turbulent structures of the flow. Furthermore, the experimental verification of such phenomena is crucial for the correct implementation of computational fluid dynamics calculations, as they might be able to capture the correct flow behaviour in these regions. © Published under licence by IOP Publishing Ltd.

Machado L.A.T.,National Institute for Space Research | Silva Dias M.A.F.,University of Sao Paulo | Morales C.,University of Sao Paulo | Fisch G.,Institute Aeronautica e Espaco | And 26 more authors.
Bulletin of the American Meteorological Society | Year: 2014

CHUVA reveals very diverse cloud processes in tropical continental regions and contributes to improving satellite precipitation estimation, nowcasting, cloud-resolving models, and the understanding of cloud electrification. The acronym for CHUVA is Cloud Processes of the Main Precipitation Systems in Brazil: A Contribution to Cloud-Resolving Modeling and to the Global Precipitation Measurement (GPM). The CHUVA field campaigns, in addition to their focus on the microphysical properties of tropical clouds, have an important role in improving existing algorithms for precipitation retrieval for the GPM mission. CHUVA's principal motivation is the description and understanding of the cloud processes of the various precipitation regimes of Brazil. CHUVA consists of six field campaigns, five of which have already taken place. The sixth will be carried out in 2014 in Manaus as part of the GoAmazon initiative. The CHUVA website is the primary access to the CHUVA information and data. For each campaign, a specific web page was developed. These web pages contain a wide variety of information, including the daily weather report, instrument strategy, instrument locations, quick looks of the main events, data reports, cloud pictures, and the Severe Storm Observation System CHUVA.

Antunes A.P.,Instituto Tecnologico Of Aeronautica | Silva R.G.D.,University of Sao Paulo | Azevedo J.L.F.,Institute Aeronautica e Espaco
27th Congress of the International Council of the Aeronautical Sciences 2010, ICAS 2010 | Year: 2010

The paper presents three-dimensional simulations over a trapezoidal wing with a single slotted flap and a slat, which was a model developed in order to provide a database for CFD validation. This semi-span model has been tested both in the NASA Ames 12-Foot Pressurized Tunnel (PWT) and the NASA Langley 14 by 22 Foot Subsonic Wind Tunnel (SWT). The simulations are performed for two flaps deflections, 20 and 25 degrees, and a few angles of attack; the slat deflection is hold constant at 30 degrees. Different mesh methodologies such as hexahedral meshes, and hybrid prismatic-tetrahedral meshes are used to perform the numerical simulations. In order to observe the accuracy of the obtained aerodynamic coefficients, with respect to mesh refinement, a small number of simulations is performed with finner meshes. The baseline grids range from 7.2 million to 12.8 million cells, while the finner grids are around 23 million cells. © 2010 by the International Council of Aeronautical Sciences - ICAS.

Antunes A.P.,Brazilian Technological Institute of Aeronautics | Da Silva R.G.,University of Sao Paulo | Azevedo J.L.F.,Institute Aeronautica e Espaco
28th Congress of the International Council of the Aeronautical Sciences 2012, ICAS 2012 | Year: 2012

The paper presents simulations over a trapezoidal wing with a single slotted flap and a slat. The calculations are performed for the high-lift configuration know as configuration one, which is characterized by slat and flap deflections of 30° and 25°, respectively. The simulations address both the actual configuration tested, with the supporting brackets for the high-lift devices, as well as a simplified configuration without the brackets. Both hybrid tetrahedral-prismatic and hexahedral meshes are considered in the calculations. For the purpose of analyzing the effect of the turbulence model, simulations are performed using the Spalart-Allmaras, Menter SST and cubic k-e{open} turbulence models. The grids for the configuration without brackets range from 12 million to 22.8 million cells, whereas for the configuration with the brackets the grids vary from 24.8 million, for the coarse mesh, to 69.5 million cells, for the fine mesh.

Breviglieri C.,Brazilian Technological Institute of Aeronautics | Azevedo J.L.F.,Institute Aeronautica e Espaco | Basso E.,Institute Aeronautica e Espaco | Souza M.A.F.,Brazilian Technological Institute of Aeronautics
AIAA Journal | Year: 2010

The present work has the objective of demonstrating the capabilities of a spectral finite volume scheme implemented in a cell-centered finite volume context for unstructured meshes. The two-dimensional Euler equations are considered to represent the flows of interest. The spatial discretization scheme is developed to achieve high resolution for flow problems governed by hyperbolic conservation laws. Roe's flux difference splitting method is used as the numerical approximate Riemann solver. Several applications are performed in order to assess the method capability compared to data available in the literature and also compared to an weighted essentially nonoscillatory scheme. There is good agreement with the comparison data, and efficiency improvements over the weighted essentially nonoscillatory method are observed. The features of the present methodology include an implicit timemarching algorithm; second-, third-, and fourth-order spatial resolution; exact high-order domain boundary representation; and a hierarchical moment limiter to treat flow solution discontinuities.

de Souza D.C.,National Institute for Space Research | Oyama M.D.,Institute Aeronautica e Espaco
Theoretical and Applied Climatology | Year: 2011

The climatic impacts of gradual desertification in the semi-arid area of Northeast Brazil (SANEB) were evaluated using the MM5 regional model. Simulations for the rainy season of SANEB (March, April, and May) were performed. Desertification simulations were grouped into three numerical runs: total (all SANEB covered by desert), partial (desert areas placement based on future environmental degradation scenarios for SANEB), and random desertification (desert areas placed randomly within SANEB). Total desertification led to a pronounced and significant precipitation reduction in large parts of SANEB. Climatic impacts of partial desertification were guided by the southward expansion of desert areas. For intermediate desertification extensions, a dipole pattern with precipitation reduction (increase) in the northern (southern) areas of SANEB was found. Random desertification led to climatic impacts spread over the whole SANEB. In both partial and random desertification, a quasi-linear precipitation reduction was found as desertification extension increases. © 2010 Springer-Verlag.

de Oliveira Neto J.A.,Instituto Tecnologico Of Aeronautica | Basso E.,Instituto Tecnologico Of Aeronautica | Azevedo J.L.F.,Institute Aeronautica e Espaco
27th Congress of the International Council of the Aeronautical Sciences 2010, ICAS 2010 | Year: 2010

The purpose of the present paper is to perform a study of high-lift configurations using Computational Fluid Dynamics (CFD) simulations. Such study is an attempt to establish guidelines for the analysis and design of such devices through computational aerodynamics techniques. Structured and unstructured grids are generated for multielement airfoils and the corresponding Reynoldsaveraged Navier-Stokes (RANS) equation flow solutions are obtained around NLR 7301 and NHLP-2D geometries. As usual with RANS simulations for such high Reynolds number flows, theaddition of turbulence models is required in order to capture the correct turbulent transport.In the present study, the use of the Spalart-Allmaras one-equation, Menter SST two-equation and the k¡e realizable models is considered. The present effort only considers 2-D configurations, in an attempt to reduce the computational costs, and use the available grid points to explore more subtle aspects of the flow results. © 2010 by the International Council of Aeronautical Sciences - ICAS.

Libardi J.,University of Campinas | Ravagnani S.P.,University of Campinas | Morais A.M.F.,Institute Aeronautica e Espaco | Cardoso A.R.,Institute Aeronautica e Espaco
Polimeros | Year: 2010

The aim of this work was to determine the dioctyl azelate (DOZ) plasticizer diffusion coefficient (D) for samples containing the interfaces of rubber, liner and solid composite propellant based on hydroxyl-terminated polybutadiene (HTPB). The samples used in the diffusion study were aged up to 31 days after the cure period at 80 °C. A computer program implementing a mathematical model of Fick's second Law of diffusion was developed to calculate the diffusion coefficient based on concentration data obtained from gas chromatographic analyses. The effects of the diffusion phenomenon were also investigated by Shore A hardness and scanning electron microscope (SEM) techniques. These analyses were carried out using samples aged at room temperature and at 80 °C. The hardness results showed an increasing trend for the samples aged at room temperature; however in the tests carried out at 80 °C they showed the opposite trend. The SEM analyses detected meaningful changes in the surface morphology of the propellant for both aging temperatures.

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