ABSTRACT: The flow patterns over a finite square cylinder of aspect ratio of 3 were analyzed experimentally in a subsonic wind tunnel using the time-resolved particle image velocimetry (TR - PIV) techniques. The near wake flow structures and vortex shedding characteristics were investigated using mean flow analysis, spectral analysis and proper orthogonal decomposition (POD). The cylinders were fixed on a elliptical leading edge flat plate, creating a boundary layer which interacted with the cylinder wake. The 2D PIV measurements were conducted at a low horizontal plane, z/h = 0.3, to investigate possible boundary layer interactions. Due to the complexity of the phenomena, the flow was characterized both in terms of average behavior and time-resolved velocity fields. Both symmetrical and anti-symmetrical vortices structures occur in the cylinder wake, which can be identified based on the coefficients of the first four POD modes. The results indicated that the alternating Karman vortex structures are dominant, described by the first two POD modes.

ABSTRACT: This study aimed to analyze the time series behavior of the Southern Oscillation Index through techniques using Fast Fourier Transform, computing the autocorrelation function, and the calculation of the Hurst coefficient. The methodology of Hurst Exponent calculation uses different lags, which are computed in the time series of Southern Oscillation Index. The persistent behavior in the time series can be characterized by calculating the Hurst Exponent, seeking for more behavioral information, as the existence of persistence and/or terms of long-range memory in the series. The results show a persistence of the climate in terms of long-memory Southern Oscillation Index time series, which can help to understand a complex dynamic behavior in climate effects at global-scale level and specifically its influence in northeastern Brazil, in the region of the Alcântara Launch Center. The R package tseriesChaos was used in the analysis of the Southern Oscillation Index time series, estimating the largest Lyapunov exponent, which indicates the existence of chaotic behavior in time series. The resampling technique was used in a permutation test between the surface wind data in the São Luís airport, Maranhão State, and the Southern Oscillation Index. The permutation test results showed that the time series of monthly average wind speed in the São Luís airport is correlated with the variability of Southern Oscillation Index, statistically correlated to the confidence interval at the 5% level. The results showed the possibility of using autoregressive models to represent average variable meteorology in the behavior analysis as well as trends in the climate, more specifically a possible climatic influence of El Niño-Southern Oscillation in wind strength in the Alcântara Launch Center.

ABSTRACT: This paper introduces a new approach to represent the rocket exhaust effluents into an atmospheric dispersion model considering the trajectory and variable burning rates of a Satellite Vehicle Launcher, taking into account the buoyancy of the exhausted gases. It presents a simulation for a Satellite Vehicle Launcher flight at 12:00Z in a typical day of the dry season (Sept 17, 2008) at the Centro de Lançamento de Alcântara using the Weather Research and Forecasting Model coupled with a modified chemistry module to take into account the gases HCl, CO, CO2, and particulate matter emitted from the rocket engine. The results show that the HCl levels are dangerous in the first hour after the launching into the Launch Preparation Area and at the Technical Meteorological Center region; the CO levels are critical for the first 10 min after the launching, representing a high risk for human activities at the proximities of the launching pad.

A estrutura do campo de vento e da turbulência atmosférica gerada no interior de uma cavidade rasa é analisada com o uso de ensaios realizados em túnel de vento e simulação numérica com um modelo bidimensional de grandes turbilhões (LES). As cavidades são maquetes estáticas, que podem representar regiões de pequenas clareiras na Amazônia ou de "canyons" urbanos representando a geometria de cidades modernas. Os resultados sugerem que, apesar das diferenças de escalas, a organização da turbulência nos dois experimentos contém similaridades em algumas regiões. Foi verificada a dependência que a intensidade da turbulência, o perfil do vento e termos do balanço de Energia Cinética Turbulenta têm com a velocidade do fluxo livre, com as dimensões (largura) da cavidade e com a posição relativa dentro da cavidade.

The structure of the wind field and atmospheric turbulence generated inside a shallow cavity is analyzed using wind tunnel tests and a 2-D Large-Eddy Simulation (LES) model. The cavities are static mock-up that can represent small clearings inside forest in Amazonia or urban canyons representing the geometry of modern cities. The results suggest that, despite differences in the scales, the organization of turbulence in the two experiments contains similarities in some regions. It was verified the dependency of the turbulence, wind profile and Turbulent Kinetic Energy dependence against flow above canopy, its size and its relative position inside the gap.