@InProceedings{PaolicchiSant:2013:CoEfAe,
author = "Paolicchi, Lu{\'{\i}}s Thiago Lucci Corr{\^e}a and Santos,
Wilson Fernando Nogueira dos",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Instituto
Nacional de Pesquisas Espaciais (INPE)}",
title = "Compressibility effects on the aerodynamic surface quantities of
hypersonic gap flows",
booktitle = "Abstracts...",
year = "2013",
organization = "European Conference For Aeronautics And Space Sciences (eucass
2013), 5.",
note = "Setores de Atividade: Outras atividades profissionais,
cient{\'{\i}}ficas e t{\'e}cnicas.",
keywords = "DMSC, hypersonic flow, rarefied flow, gap.",
abstract = "The thermal protection systems of vehicles like the space shuttle
orbiter or crew rescue vehicle X-38 require gaps between the used
protection elements to account for thermal expansion. For the
optimized design of gaps and protection elements, it is necessary
to predict the flow conditions and thermal loads as accurate as
possible. The flow in the gap is complex because of staggered gap
configuration, radiation cooling, transient flow, etc. In the case
of reentry vehicles, the boundary layer transition prediction is a
requirement to define the thermal protection system. This
protection is usually designed as an assembly of tiles. The gaps
between the tiles may modify the boundary layer state and
eventually promote transition, inducing higher temperature levels
than expected. For the particular case of gaps, some experimental
studies have been conducted in order to understand the physical
aspects of a hypersonic flow past to this type of surface
discontinuities. In general, the major interest in these studies
has gone into considering laminar or turbulent flow in the
continuum flow regime. Nevertheless, there is little understanding
of the physical aspects of a hypersonic flow over gaps related to
the severe aerothermodynamic environment associated to a reentry
vehicle. In this fashion, Paolicchi and Santos [1] have studied
gaps situated in a rarefied hypersonic flow by employing the
Direct Simulation Monte Carlo (DSMC) method. The work was
motivated by the interest in investigating the length-to-depth
(L/H) ratio effects on the flowfield structure. The primary
emphasis was to examine the behavior of the primary properties,
such as velocity, density, pressure and temperature, due to
changes on the gap L/H ratio. The analysis showed that the gap
flow behavior in the transition flow regime differs from that
found in the continuum flow regime, for the conditions
investigated. It was found only one vortex for the L/H ratio of 1,
1/2, 1/3 and 1/4, as shown in the figure below. Conversely, in the
continuum flow regime, the number of vortices inside the gap is
approximately given by the amount H/L. Having established a
physical picture of the flowfield structure in a gap, the current
study expands on the results presented in the previous analysis
[1] by investigating the effects of the compressibility as well as
the L/H ratio on the aerodynamic surface quantities. In this
manner, the purpose of the present account is to investigate
numerically the sensitivity of the heat transfer, pressure and
skin friction coefficients due to changes on the gap L/H ratio and
on the freestream Mach number in the transition flow regime. In
the present account, L/H ratio will change from 1 to 1/4, with L
of 3 mm. The freestream Mach number will be 5, 15 and 25. The
focus of the present study is the low-density region in the upper
atmosphere. At high altitudes, and therefore, low density, the
molecular collision rate is low and the energy exchange occurs
under non-equilibrium conditions. In such a circumstance, the
degree of molecular non-equilibrium is such that the Navier-Stokes
equations are inappropriate. Therefore, the DSMC method will be
employed to calculate the hypersonic two-dimensional flow on the
gaps.",
conference-location = "Munich",
conference-year = "1-5 July, 2013",
label = "lattes: 4859685163568596 2 PaolicchiSant:2013:CoEfAe",
language = "en",
targetfile = "a179-1.pdf",
urlaccessdate = "21 maio 2024"
}