Rarefied Flow Field Analysis on a Re-entry Vehicle
525
5 Chemical Model
The continuous collision of air molecules with the REV increases the temperature
of the order of thousands of degree Kelvin in its vicinity. This temperature causes
dissociation of gas molecules (O 2 , N 2 and NO). Considering chemical reactions in an
analysis, gives more realistic behaviour of gas molecules. Quantum Kinematic (QK) model by Bird [2] incorporates dissociation and recombination reactions. Reference [2] by Bird does not consider for the charged particles and hence is applicable
for neutral gas molecules only. Reference [3] considers the importance of implementing charged reactions and is given for reactions in charged particles. ‘Modified
Q-K’ model incorporates these both qualities and is implemented in dsmcFOAM
+ which is used for the current study with air as the combination of 11 species
(N 2 , O 2 , NO, N
+
2 , O
+
2 , NO
+
, N, N
+
, O, O
+ and e
− ).
6 Validation
The validation case was evaluated on a 70° spherically blunt cone configuration.
The DSMC results carried out by Moss and their comparison with LENS facility
experimental results are given in Ref. [4] for the same configuration. The current
DSMC analysis was performed using Nitrogen (N 2 ) as a test gas and the results are
given in Figs. 3 and 4. Figure 3 shows the variation of pressure on the wall of the
configuration. It can be seen that pressure is nearly constant on the forebody followed
by the sharp expansion at the corner. The pressure on base of the model and sting
region is very small. Figure 4 shows pressure colour pallet over the entire domain
and thick shockwave can be observed just before the configuration at the normalized
axial location of ~0.45.
Fig. 3 Pressure variation on
wall
525
5 Chemical Model
The continuous collision of air molecules with the REV increases the temperature
of the order of thousands of degree Kelvin in its vicinity. This temperature causes
dissociation of gas molecules (O 2 , N 2 and NO). Considering chemical reactions in an
analysis, gives more realistic behaviour of gas molecules. Quantum Kinematic (QK) model by Bird [2] incorporates dissociation and recombination reactions. Reference [2] by Bird does not consider for the charged particles and hence is applicable
for neutral gas molecules only. Reference [3] considers the importance of implementing charged reactions and is given for reactions in charged particles. ‘Modified
Q-K’ model incorporates these both qualities and is implemented in dsmcFOAM
+ which is used for the current study with air as the combination of 11 species
(N 2 , O 2 , NO, N
+
2 , O
+
2 , NO
+
, N, N
+
, O, O
+ and e
− ).
6 Validation
The validation case was evaluated on a 70° spherically blunt cone configuration.
The DSMC results carried out by Moss and their comparison with LENS facility
experimental results are given in Ref. [4] for the same configuration. The current
DSMC analysis was performed using Nitrogen (N 2 ) as a test gas and the results are
given in Figs. 3 and 4. Figure 3 shows the variation of pressure on the wall of the
configuration. It can be seen that pressure is nearly constant on the forebody followed
by the sharp expansion at the corner. The pressure on base of the model and sting
region is very small. Figure 4 shows pressure colour pallet over the entire domain
and thick shockwave can be observed just before the configuration at the normalized
axial location of ~0.45.
Fig. 3 Pressure variation on
wall