Calculation of intermediate hypersonic flow using multi-temperature model

Our previous study revealed that the existing two-temperature model reasonably well reproduced the shock stand-off distance for a sphere in the intermediate hypersonic range, except for the cases where chemical reactions were almost frozen but vibrationally highly excited. In order to explain the cause of distinction, a four-temperature description of the intermediate hypersonic flowfield has been attempted. The model assigns a translational temperature and three different vibrational temperatures, one for each of three molecular species, O₂, N₂, and NO. Calculated shock stand-off distances for several conditions, for which the discrepancy was seen in the two-temperature calculation, are compared with the corresponding experimental data measured with a ballistic range and the calculated results using a two-temperature model. The agreement, however, is only slightly improved by the use of the present four-temperature model. A possible explanation of the modest improvement is indicated.