ABSTRACT: One of the most important features of an aerospace vehicle design is its shape, especially the forebody part, since it defines the main characteristics of the vehicle aerodynamic. In this context, the present work has the purpose of investigating the transonic aerodynamic regime in typical vehicle models, with different frontal geometry configurations, using the experimental techniques pressure sensitive paint (PSP) and Schlieren. The aim is to get more insights about the flow patterns over the selected models, regarding the transonic regime, in terms of qualitative density field evaluation, and the identification of important aerodynamic parameters, such as shock wave positioning and pressure gradients over the model, as well as the influence of the forebody configuration in the flow pattern. The test campaign was carried out in the Pilot Transonic Wind Tunnel of the Institute of Aeronautics and Space (IAE; in Portuguese, Instituto de Aeronáutica e Espaço), varying Mach numbers from subsonic to low supersonic. Five forebody configurations mounted in a cylindrical body having the standard cone-cylinder shape as baseline was considered. A description of the phenomena occurring around and on the models surface for all five models is presented, through analyses of the Schlieren images and PSP results.

ABSTRACT This paper presents a wind tunnel study of the flow patterns in the main Brazilian Space Port, the Alcântara Launch Center (ALC), located in the Northwest region, over an irregular coastal cliff of 40 m height. In the ALC region, constant winds of strong incidence are very common, which can change the characteristics of the atmospheric boundary layer and affect safety conditions during launching operations. This study was conducted using a scaled model of the Launching Pad Area (LPA) in ALC complex with the purpose of getting insights about the wind flow patterns, as zones of strong vorticity, in that region when the wind incidence angle and coastal cliff characteristics change. The experiments were carried out in an aerodynamic wind tunnel, and for this reason it was necessary to use some techniques described in the literature to simulate an atmospheric boundary layer in a short test section wind tunnel. Hot-wire anemometer measurements were carried out for turbulence level evaluation with empty wind tunnel test section, and a two-dimensional Particle Image Velocimetry (PIV) was used for flow field velocity measurements in different configurations of wind incidence angle (α), Reynolds number and coastal cliff slope angle (β).

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: It is performed and presented an experimental and numerical investigation over the flow patterns around the fore-body section of a microsatellite launch vehicle in development at Instituto de Aeronáutica e Espaço. The experimental investigation with a VLM-1 model in 1:50 scale is carried out at the Brazilian Pilot Transonic Wind Tunnel, located in the Aerodynamics Division of the mentioned Institute, using the classical schlieren flow visualization technique. Schlieren images are obtained for nominal Mach number varying from 0.9 to 1.01. Numerical simulation using Stanford's SU2 code is conducted together with the experimental investigation in order to improve the understanding of the complex physical phenomena associated with the experimental results of this particular regime. The combination of the 2 techniques allowed the assessment of some important aspects on the flow field around the vehicle in the conditions considered in this study, such as shock wave/boundary-layer interaction. The numerical simulation is also very important, allowing the quantification of some important parameters and confirming the shock wave formation patterns observed in the simulation when compared with the schlieren images. A good agreement regarding the position of the shock wave, when compared with the schlieren images, with a maximum error of about 6%, is observed over the VLM model.

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.

Abstract: Centro de Lançamento de Alcântara is the main Brazilian launching center. In spite of presenting several desirable aspects, due to its proximity to the Equator, it has a peculiar topography because of the existence of a coastal cliff, which modifies the characteristics of the atmospheric boundary layer. This may affect rocket-launching operations, especially when associated with safety procedures. This work is a continuation of previous experimental studies about the airflow pattern at this launching center. An improved way of simulating the atmospheric boundary layer in a short-test section wind tunnel using passive methods is presented here. It is also presented a preliminary analysis of the airflow pattern in Centro de Lançamento de Alcântara, at specific positions as the edge of cliff and around the mobile integration tower, from wind tunnel measurements using particle image velocimetry. Three values of Reynolds number, based on the coastal cliff height, l, ranging from 6.8×105 to 2.0×106, were considered.

Abstract: Alcântara Space Center (ASC) is the Brazilian gate to the space where rockets of different sizes are launched. At ASC there is a relative topographical variation, coastal cliff, which modifies the atmospheric boundary layer characteristics and can cause interference for operations of rockets. In the present work, a simplified model (mock-up) was studied in a wind tunnel. A scale factor of 1:1000 was used and the atmospheric flow was measured using the hot wire anemometer (HWA) and particle image velocimetry (PIV) techniques. Using of HWA it was possible to calculate values of average wind speed and fluctuations in a set of points of the section of tests that representing the region of the ASC. Through these measures, other meteorological parameters that represent the atmospheric flow, such as the friction velocity (u*), the roughness length (z0) from the logarithmic profile and the alpha exponent (a) of the power law were calculated. With the use of the PIV´s technique, the streamlines and the vorticity fields were obtained and it was noticed that the vorticity generated downwind of the coastal cliff has a strong turbulence (vorticities around 2000 s-1). A rectangular building (simulating the mobile integration tower) was inserted at the mock-up and the downwind turbulence was similar to the one generated by the coastal cliff.

Abstract: The Pilot Transonic Wind Tunnel of Institute of Aeronautics and Space (PTT Pilot Transonic Wind Tunnel) is an important result of a tremendous effort to install a high speed wind tunnel complex (TTS acronyms for Transonic and Supersonic Tunnels, in Portuguese) at the IAE, to support Brazilian aerospace research. Its history is described below, startingfrom the moment the TTS project was first conceived, highlighting each successive phase, mentioning the main difficulties encountered, and the solutions chosen, up until the final installation of the Pilotfacility. A brief description of the tunnel's shakedown and calibration phases is also given, together with the present campaigns and proposed activities for the near future.

Abstract: The Alcântara Space Center (ASC) region has a peculiar topography due to the existence of a Coastal cliff, which modifies the atmospheric boundary layer characteristic in a way that can affect rocket launching operations. Wind tunnel measurements can be an important tool for the understanding of turbulence and wind flow pattern characteristics in the ASC neighborhood, along with computational fluid dynamics and observational data. The purpose of this paper is to describe wind tunnel experiments that have been carried out by researchers from the Brazilian Institutions IAE, ITA and INPE. The technologies of Hot-Wire Anemometer and Particle Image Velocimetry (PIV) have been used in these measurements, in order to obtain information about wind flow patterns as velocity fields and vorticity. The wind tunnel measurements are described and the results obtained arepresented.