Analysis of vibration-dissociation-recombination processes behind strong shock waves of nitrogen

Computations are presented for the relaxation zone behind strong, one-dimensional shock waves of nitrogen. The numerical results are compared with existing experimental data. It is indicated that the derivation of chemical rate coefficients must account for the degree of vibrational nonequilibrium in the flow. A nonequilibrium chemistry model is employed together with equilibrium rate data to compute successfully the flow in several different nitrogen shock waves. The analysis is performed with the direct simulation Monte Carlo method (DSMC). The DSMC code is vectorized for efficient use on a supercomputer. The code simulates translational, rotational, and vibrational energy exchange, and dissociative and recombinative chemical reactions. A new model is proposed for the treatment of three-body recombinative collisions in the DSMC technique, which usually simulates binary collision events. The new formulation represents improvement over previous models in that it can be employed with a wide range of chemical rate data, does not introduce into the flow field troublesome pairs of atoms that may recombine upon further collision (pseudoparticles), and is compatible with the vectorized code.