ABSTRACT The Alcantara Launch Center (ALC) is the main Brazilian access to space. It is positioned over a complex terrain, and it has some important buildings for assembling, integration and launching activities, such as the Mobile Integration Tower. Being in a region of prevalent trade winds, the flow interaction between the complex terrain and the buildings can affect the safety of operations on the platform, and the dispersion of toxic gases emitted during the launching. The main objective of this work was to study the influence of topography and buildings on the atmospheric flow of ALC using computational fluid dynamics (CFD) techniques. Three geometries were considered: simplified terrain (case 1), smooth complex terrain (case 2), and roughness complex terrain (case 3). The flow conditions over ALC were simulated using the ANSYS Fluent 19.0 CFD commercial code. The numerical simulations used a realizable ?-? to model turbulence effects and the results presented a good agreement with the in-situ field measurements for the most complex geometry (case 3). The topography clearly influences the flow pattern at ALC, with the cliff influence over the wind being the major cause for establishing the flow patterns.

Abstract: The Brazilian deep space mission ASTER, as temporarily named, plans to send a small spacecraft to encounter and investigate the triple asteroid 2001-SN263. The launch is scheduled (initially) to occur in 2015, arriving in 2018. The main motivation of the mission is the development of technology and expertise to leverage the national space sector. Within the scientific goals, the investigation of the still unknown asteroid 2001-SN263. The main project guideline is to aggregate the widest possible Brazilian involvement in the platform, the development and operation of subsystems, integration, payload, as well as in the tracking, navigation, guidance and control of the probe. To meet this guideline, among others, the decision for the development of a laser altimeter in Brazil to fly in the mission was taken. This effort is currently coordinated by a group of researchers from the aerospace engineering personnel of UFABC. This article presents the preliminary development plan for the design of this instrument, which was called ALR (ASTER Laser Rangefinder).

O estudo da dinâmica de meso-escala da confluência de duas correntes de contorno oeste num oceano de duas camadas quase-geostrófico, não viscoso e inercial no plano f foi conduzido neste trabalho. A estrutura vertical simplificada do modelo foi obtida através de calibração dinâmica em relação à estrutura modal da região da Confluência Brasil-Malvinas. Essa estrutura modal foi estimada a partir da climatologia da área compreendida entre 35º-40ºS e 50º-60ºW. Dois modelos de dinâmica de contornos foram então desenvolvidos. Estes apresentaram sistema de correntes de contorno oeste com transporte simétrico e duas frentes de vorticidade, uma por camada. O escoamento na camada superior foi sempre convergente, formando um jato zonal que flui para leste. Já o escoamento na camada inferior foi divergente, com jato zonal de velocidades fluindo dominantemente para oeste. Tal configuração garantiu que o sistema fosse baroclinicamente instável. Os resultados dos experimentos mostraram que a presença da confluência, da fronteira meridional e do modo barotrópico no escoamento básico favoreceram ondas longas. Os três experimentos conduzidos com o modelo não-linear mostraram o desenvolvimento tanto do padrão de retroflexão como a emissão de vórtices e dipolos vorticais pelo lóbulo de retroflexão (crista primária na camada superior) e no cavado primário a partir de uma perturbação inicial imposta junto ao contorno oeste. Os cenários obtidos se assemelham qualitativamente àqueles observados na Confluência Brasil-Malvinas. Verificou-se também que, os resultados do modelo não linear seguem aqueles previstos pelo modelo linear em termos de taxas de crescimento, velocidades de fase e comprimento das ondas mais instáveis. Isto sugeriu que enquanto os processos de instabilidade baroclínica são responsáveis pelo crescimento temporal dos meandros, os efeitos não lineares causaram principalmente isolamento das estruturas vorticais em estruturas dipolares, que eventualmente se separam do eixo da corrente.

The study of the mesoscale dynamics of the confluence of two western boundary currents was conducted in this work via a quasi-geostrophic inviscid f-plane two-layer ocean theoretical approach. The simplified vertical structure was calculated through the employment of a dynamic calibration scheme based on the dynamical mode structure of the Brazil-Malvinas Confluence Region. The Brazil-Malvinas mode structure was computed from climatological hydrography of the area delimited by 35º-40ºS and 50º-60ºW. Two contour dynamics models were constructed: a linear and a nonlinear version. The basic flow configuration consisted of two converging western boundary currents that form a zonal eastward current in the upper layer. The lower layer flow was essentially divergent as a result of a westward zonal jet impinging on the western border. This vertical shear choice assured that the system was baroclinically unstable. The results of the model experiments showed that the presence of the confluence, the western meridional boundary and the barotropic mode in the dynamical structure of the basic flow favored long wave patterns. The three experiments conducted with the nonlinear model exhibited the development of both a reflection pattern and vortical dipoles. The dipoles pinched off from either the retroflection lobe (i.e., the primary crest of the wave train) or the primary trough when the baroclinically unstable current system was perturbed at the boundary vicinities. It was verified that the nonlinear model simulations followed the instability properties predicted by the linear model in terms of meander growth rates, phase speeds and most unstable wavelengths. This suggested that while the baroclinic instability mechanism was responsible for the temporal growth of the meanders, the nonlinear effects caused the dipole isolation and pinch off of the finite amplitude meanders. These dipoles could leave and propagate away from the current axis.

O estudo da instabilidade linear de cisalhamento vertical (ou baroclínica) de perfis de jato de direção meridional (norte-sul) é conduzido através de um modelo hidrodinâmico unidimensional, baseado no princípio de conservação de vorticidade potencial quase-geostrófica. Os perfis verticais de jato utilizados nesse trabalho têm motivação no Sistema Corrente do Brasil - Corrente de Contorno Intermediária que flui ao largo da costa sudeste brasileira. Os perfis estão construídos de forma a satisfazer as condições necessárias para ocorrência de instabilidade baroclínica. O modelo hidrodinâmico é baseado no trabalho de Johns (1988) e tem sua formulação apresentada em detalhamento algébrico. Sua física é explorada através de exemplos e comparação com a parte analítica do modelo, com o intuito de subsidiar o diagnóstico das formas com que a instabilidade ocorre na superfície do oceano e internamente na coluna de água. Adicionalmente, o efeito da inclinação do fundo associada ao talude continental é discutido e exemplificado, através de seus efeitos na propagação das ondas instáveis geradas pelos processos de instabilidade.

The study of linear vertical shear instability of meridional (north-south) jets is conducted via an unidimensional hydrodynamic model, based on quasi-geostrophic potential vorticity conservation. The shape of the vertical jet profiles are motivated by the Brazil Current-Intermediate Western Boundary Current System that flows off the Brazilian Southeast coast and are built with the aim to satisfy necessary conditions for occuring baroclinic instability. The hydrodynamic model is based on Johns (1988) and its formulation is presented without the omission of algebraic details. Its physics is explored through numerically-solved examples and comparison with the analytical part of the model. The purpose is to subsidize the diagnosis of forms in which instability occur: at the ocean surface and in the interior of the water column. Additionally, the effect of the continental slope on the instability properties is investigated and discussed, through its effects on the propagation of unstable waves generated by instability process.