Nonequilibrium numerical model of homogeneous condensation in argon and water vapor expansions

Abstract

A computational approach capable of modeling homogeneous condensation in nonequilibrium environments is presented. The approach is based on the direct simulation Monte Carlo (DSMC) method, extended as appropriate to include the most important processes of cluster nucleation and evolution at the microscopic level. The approach uses a recombination-reaction energy-dependent mechanism of the DSMC method for the characterization of dimer formation, and the RRK model for the cluster evaporation. Three-step testing and validation of the model is conducted by (i) comparison of clusterization rates in an equilibrium heat bath with theoretical predictions for argon and water vapor and adjustment of the model parameters, (ii) comparison of the nonequilibrium argon cluster size distributions with experimental data, and (iii) comparison of the nonequilibrium water cluster size distributions with experimental measurements. Reasonable agreement was observed for all three parts of the validation.

The temperature and size distribution of large water clusters from a non-equilibrium model

“…[23][24][25] Moreover, the availability of this important experimental quantity enabled the validation of gas dynamics approaches to the cluster growth process at a molecular level. 26,27 The kinetic, first-principle approach to the condensation phenomenon based on a microscopic view of the interaction rates has to be coupled to the properties of the rapidly changing flow. The direct simulation Monte Carlo (DSMC) method was used to tackle this problem for relatively low density plumes.…”

2D models of gas flow and ice grain acceleration in Enceladus’ vents using DSMC methods

“…In the rarefied IL-PRM simulations at the vent entrance the growth rate was at most $0.1s lm/s, and a couple of meters above the vent entrance it was estimated that the grains would evaporate. Here the micron sized grains traversed the vents in less than a second, $0.1-0.4 s. Of course the actual growth/ evaporation rates depend on the energetics at the molecular level (e.g., Jansen et al, 2010), and the rarefaction of gas along the trajectory of a grain as it traverses the vent (e.g., Crowe et al, 1965). The Knudsen number as given in Eq.…”

“…The suggested mass ratio in the plume may be very broad 0.01-1 (e.g., Hedman et al, 2009;Ingersoll and Ewald, 2011;Porco et al, 2006). However, grain condensation can occur within the vents, and the nucleation and growth of grains can subsequently affect the flow field (e.g., Li et al, 2009;Jansen et al, 2010). Examinations on the importance of this feedback on the Enceladus subsurface gas distributions are necessary, but such studies are beyond the scope of this work.…”

“…x ref = 1 where the reference values are defined for of T ref = 273 K (e.g., Combi et al, 2005;Jansen et al, 2010). In the simulations that included internal energy exchange we considered the 3 rotational degrees of freedom for H 2 O. Lastly, we adopted a rotational relaxation number of 4 for water vapor from Roesler and Sahm (1965).…”

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

“…17 Recently, Jansen et al 18 have compared the nonequilibrium argon and water cluster size distributions with experiments and obtained good agreement. In Ref.…”