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The shock layer flow over a blunt body entering a
planetary atmosphere at a hypersonic speed will
dissociate and partially ionize. A reliable
prediction of the flow-field for such application
requires a chemical-kinetic model. For Mars
atmosphere, the five species Park'94 is considered
[1]. The dissociation of CO2 is producing C, CO, CO2,
O and O2.
The shock layer flow over a blunt body entering a
planetary atmosphere at a hypersonic speed will
dissociate and partially ionize. A reliable
prediction of the flow-field for such application
requires a chemical-kinetic model. For Mars
atmosphere, the five species Park'94 is considered
[1]. The dissociation of CO2 is producing C, CO, CO2,
O and O2.
The Park'94 kinetic model contains 18 equations
described in Table 1. The forward and reverse
reaction rates for Arrhenius reactions are the
following :
Kf (T) = Af Tbf exp (
-Ef /T) [m3 / (kmol . s)]
Kr (T) = Ar Tbr exp (
-Er /T) [m6 / (kmol2
. s)]
Table 1 shows the constants that were used to determine
the reaction rates.
Table 1. Reactions and constants for reaction
rates
This model was applied for the Mars Sample Return
Orbiter (TC3 test case [2]) using CFD-FASTRAN. The
results are validated by comparison with the
reference results obtained with MISTRAL code [4].
Figure 1 compares CFD-FASTRAN™ results (top) and
Mistral results reported in [4] (bottom) for Mach
number distribution. The results are nearly identical
[3]. The shear layer angle and the size and shape of
the wake are the same. The wake closure point is
indicated by the yellow point (red for Mistral).
Figure 2 plots the mass fractions of species along
the stagnation line.
References
[1] Park, C., Howe, J., Jaffe, R., Candler, G.,
"Review of Chemical-Kinetic Problems of Future NASA
Missions, II: Mars Entries," Journal of
Thermophysics and Heat Transfer, Vol. 8, No. 1,
pp. 9-23, 1994.
[2] Charbonnier, J-M., and Omaly, P., TC3-2: Update
of the axially symmetric test case for high
temperature gas radiation prediction in Mars
atmosphere entry, Workshop 2004-Radiation of High
Temperature Gas, CNES Report Ref. DCT/TV/PR
NT-2004-564, 2004.
[3] Vinteler, D., Megahed M. and Bloch E., TC3-2:
Numerical prediction for mars atmosphere entry
vehicle using a density based solver, Workshop
2006-Radiation of High Temperature Gas, ESA
[4] Dieudonné, W., Spel, M. and Charbonnier,
J-M., "Modeling Sensitivity Analysis for TC3 on the
Orbiter Aero-thermal Properties", Proceedings of
the 1st International Workshop on Radiation of High
Temperature Gases in Atmospheric Entry, Part 2,
ESA SP-533, October 2003.
Regards,
Daniel Vinteler
CFD Support Manager - France
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