MONTE-CARLO MODELING OF NITRIC-OXIDE FORMATION BASED ON QUASI-CLASSICAL TRAJECTORY CALCULATIONS

A new chemistry model is developed for the direct simulation Monte Car lo method (DSMC). This model explicitly includes separate biasing of t he reaction cross section to the translational, rotational, and vibrat ional energies of each collision. The multiple parameter model is cali brated using detailed information on the formation of nitric oxide bas ed on quasi-classical trajectory calculations. The trajectory analysis provides reaction cross sections, and the energy distributions of rea ctants and products. In the DSMC approach, product energies are assign ed by the widely used Borgnakke-Larsen approach. The performance of th e new DSMC model is evaluated in terms of reaction cross sections, ene rgy distributions of reacting molecules, energy distributions of nitri c oxide molecules formed in the reaction, and overall reaction rate co efficient. In all cases, the new chemistry model gives favorable agree ment with the trajectory calculations. The excellent agreement obtaine d for product energy distributions indicates that the simple Borgnakke -Larsen energy partitioning scheme is a valid approach for this reacti on. The new Monte Carlo chemistry model is applied to a hypersonic, lo w-density, reacting flow of air. By comparison with a previous chemist ry model, the new model predicts significantly higher concentrations o f nitric oxide. It is also found that nitric oxide molecules are forme d in highly nonequilibrium states. Both of these findings are supporte d by experimental observations. (C) 1997 American Institute of Physics .