Maximum entropy modeling of vibrational-translational energy exchange in O2+O collisions

Abstract

This work proposes a vibrational-translational energy exchange model based on quasiclassical trajectory (QCT) calculations of O2 + O and Maximum Entropy (ME) considerations. QCT calculations show that collisions favor small vibrational transitions. This favoring drops off first exponentially and then linearly as ∆v increases. Such trends are captured by the new ME-QCT-VT model. The model is verified by comparing its stateto-state cross sections and rates to those calculated directly by QCT. The state-to-state rates match within 30% using 11 fitted parameters for the O2 +O system that has approximately 3,000 ro-vibrational states. In addition, the implementation of the model in direct simulation Monte Carlo (DSMC) method is discussed. Adiabatic DSMC calculations show that the model satisfies detailed balance. The vibrational temperatures and distribution functions predicted by DSMC calculations with the ME-QCT-VT model match masterequation calculations with the complete set of state-to-state rates. The proposed model makes it feasible to upscale ab-initio simulation to DSMC and CFD calculations of a full flowfield.