Modeling of CO₂ condensation in the high pressure flows using the statistical BGK approach

In this work, we study freely expanding homogeneous condensation flow of CO₂ out of the nozzle exit in the stagnation pressure range of 1 - 5 bars. To this end, we have developed condensation model in the statistical BGK framework, which in turn is implemented on the baseline DSMC code and can handle multi-species polyatomic gas flows. The statistical BGK method was found to be twice as fast and as accurate as DSMC in the previous work of authors for expanding flow of argon through a nozzle [Kumar, R., Titov, E. V., Levin, D. A., Gimelshein, S. F., and Gimelshein, N. E., Application of Statistical-BGK Approach to Modeling of Nozzle Flows in the Near Continuum Regime, AIAA paper 2009-1318, 2009, submitted to the AIAA Journal]. The method can be expected to be much more efficient in the present work involving multi-species polyatomic gas flow than shown in the previous work for argon gas flow. The motivation for the present work comes from an earlier work of Li et al., [Li, Z., Zhong, J., and Levin, D. A., Modeling of CO2 Homogeneous and Heterogeneous Condensation Plumes, AIAA paper 2009-0265, accepted by the Journal of Physical Chemistry B, 2009], in which the DSMC based condensation model was used to simulate the condensation flow of CO₂. The authors of former work could not simulate high pressure (more than 3 bar stagnation pressure) condensation flows because of the huge computational cost associated with the DSMC method. In the present work, we aim to develop capability to be able to simulate high pressure condensation flows. To this end, we use newly developed BGK based condensation model to simulate high pressure condensation flow of CO₂ and compare our simulation results with the experimental data obtained by Ramos et al. ¹ for different stagnation pressure cases. Numerical results are found to agree well with the experimental data for all the cases studied, validating the accuracy of BGK based condensation model in capturing the physics of condensation.