Atmospheric flow at Alcântara Launch Center by numerical simulations

Name: Karine Klippel
Type: MSc dissertation
Publication date: 02/03/2020

Namesort descending Role
Elisa Valentim Goulart Advisor *

Examining board:

Namesort descending Role
Bruno Furieri Internal Examiner *
Cayo Prado Fernandes Francisco External Examiner *
Elisa Valentim Goulart Advisor *
Gilberto Fernando Fisch Co advisor *
Ramon Silva Martins External Examiner *

Summary: The Alcântara Launch Center (CLA) is the main brazilian gateway to space. The launch pad area
(SPL) is positioned 150 meters from the coast, on an irregular cliff, approximately 40 meters
high. The atmospheric flow in the SPL is influenced by the cliff, the roughness change (ocean -
continent) and the buildings like the mobile integration tower (TMI) and the exit tower, which can
affect the safety of operations on the platform and the dispersion of toxic gases emitted during the
launching. Toxic gases, like hydrogen chloride (HCl), are an important impact of the launching
at the CLA. The flow field is one of the main factors that influence atmospheric dispersion,
determining the efficiency of the transport of the contaminants. Therefore, understanding the
flow pattern around the SPL buildings and the changes caused by the topography are important
to establish the conditions in which the CLA is exposed and provide the necessary background
for studies on pollutant dispersion. In this context, the objective of this work was to study the
atmospheric flow in the CLA, through numerical simulations, including the topography and the
meteorological conditions of the region. For this, three different configurations were considered:
simplified terrain (case 1), smooth complex terrain (case 2) and roughness complex terrain (case
3). The incident flow was obtained from re-analysis data, considering a neutral atmospheric
condition. Regarding case 3, the directions of the incident flow were: 70, 45 and 90o
. The
numerical model used was the realizable κ − ε, based on the Reynolds-Averaged Navier-Stokes
(RANS) equations. The solutions to the equations were obtained by ANSYS FLUENT 19.0,
using the finite volume method. The results of the numerical simulations presented a good
agreement with the field measurements for the most complex geometry (case 3). The topography
and incident wind direction influenced the flow pattern in the SPL. The cliff was the major
responsible for changing the flow, especially for case 1, WHERE it has been represented by a step.
The regions with greater turbulence along the domain were accentuated or attenuated according
to the direction of the incident wind. For 70 and 45o directions, the rocket launch site was
mainly affected by the turbulent wake behind the exit tower. While the 90o wind direction, the
wake generated by the TMI interfered the most at the launch site. A numerical simulation of
HCL dispersion was also performed considering a hypothetical case of aborted launch, with an
emission rate of 29.4 kg/s for 5 minutes. The results pointed out dangerous HCl concentrations
for short exposure, mainly close to the source. The plume of the pollutant was carried by the
wind and took about 10 minutes to leave the domain.

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