Modeling of CO₂ homogeneous and heterogeneous condensation plumes

A pure CO₂ homogeneous condensation flow is simulated with a new direct simulation Monte Carlo (DSMC)-based condensation model, and comparisons of the measured [Ramos, A.; Fernández, J. M.; Tejeda, G.; Montero, S. Phys. ReV. A 2005, 72, 3204] and simulated CO₂ cluster size and number density distributions were found to agree well for low stagnation pressures. The same carbon dioxide homogeneous condensation model was then applied to the study of an expanding heterogeneous condensation flow of a 5% CO₂ and 95% mixture [Williams, W. D.; Lewis, J. W. L. DTIC Paper No. AEDC-TR-80-16, 1980]. To simulate this case, a new kinetic-based model of N ₂ molecules condensing on CO₂ nuclei was developed using molecular dynamics techniques and was implemented in the DSMC simulation of the expanding mixture. Pure nitrogen flow for the same expansion conditions was observed to not produce any clusters. It was found that incorporation of the heterogeneous condensation process of N₂ molecules condensing on CO₂ nuclei causes the average N₂ cluster size to increase from 10 (the homogeneous condensation result) to about 2000. The simulated Rayleigh scattering intensity results were found to agree well with the experimental data.