MONTE CARLO CALCULATIONS OF DIATOMIC MOLECULE GAS FLOWS INCLUDING ROTATIONAL MODE EXCITATION

摘要

The direct simulation Monte Carlo method is used to solve the Boltzmann equation for flows of an internally excited nonequilibrium gas, namely, of rotationally excited homonuclear diatomic nitrogen In this study, the semi-classical transition probability model of Itikawa is investi¬gated for its ability to simulate flow fields far from equilibrium The behavior of diatomic nitrogen is examined for several different nonequilibrium initial states that are subjected to uniform mean flow without boundary interactionsnA sample of 1000 model molecules was observed as the gas relaxed to a steady state starting from three specified initial states The initial states considered are (1) complete equilibrium, (2) nonequilibrium equipartition (I e , all rotational energy states are assigned the mean energy level that obtains at equilibrium with a Boltzmann distribution at the translational temperature), and (3) nonequipartition (l e , the mean rotational energy is different from the equilibrium mean value with respect to the translational energy states) Since only uniform flow is considered, the effect of elastic collisions is ignored in the Monte Carlo simulationnIn all cases investigated the present model satisfactorily simulated the principal features of the relaxation effects in nonequilibrium flow of diatomic molecules.