• DSMC
• shield
• Monte Carlo
• simulation
• re-entry
• heat

Aerothermodynamic investigations of hypersonic re-entry vehicles
provides crucial information to other key disciplines as structures
and materials, assisting the development of efficient and lightweight
thermal protection systems (TPS). Under the transitional flow regime,
where chemical and thermal nonequilibrium are predominant, the
most innovative numerical method for such studies has been the di-
rect simulation Monte Carlo (DSMC) numerical technique. In the
50 years since its invention, the acceptance and applicability of the
DSMC method have increased signicantly. Extensive verication
and validation eorts have led to its greater acceptance, whereas
the increase in computer speed has been the main factor behind
its greater applicability. As the performance of a single processor
reaches its limit, massively parallel computing is expected to play
an even stronger role in its future development.
In the present work, the Monte Carlo simulator OpenFOAM and
Sparta have been studied and benchmarked against experimental,
numerical, and theoretical data for inert and chemically reactive
ows.
The results show the validity of the the data found with the
DSMC. The best setting of the fundamental parameters used by
a DSMC simulator are presented for each software and they are
compared with the guidelines deriving from the theory behind the
Monte Carlo method. In particular the number of particle per cell
it is found to be the most relevant parameter to have right and op-
timized results. It is shown how a simulation with a mean value
of one particle per cell give sufficiently good results with very low
computational resources. This achievement wants to be a reason to
think back to the correct investigation method in the transitional
regime were both the direct simulation Monte Carlo (DSMC) and
the computational uid-dynamics (CFD) can work but with dier-
1
ent computational eort.
In parallel it has been presented the results deriving from this
study in terms of vibration/electron/electronic and translation/rotational
temperature, pressure, Mach number, specie number density needed
to start a design of a thermal shield.