BGK and MD Simulations of H2O Supersonic Condensed Jets

Abstract

Homogeneous water condensation and ice formation in supersonic expansions to vacuum for stagnation pressures from 12 to 1,000 mbar are studied using the particle-based Ellipsoidal-Statistical Bhatnagar-Gross-Krook (ES-BGK) method. We find that when condensation starts to occur, at a stagnation pressure of 96 mbar, the increase in the degree of condensation causes an increase in the rotational temperature due to the latent heat of vaporization. The simulated rotational temperature profiles along the plume expansion agree well with measurements confirming the kinetic homogeneous condensation models and the method of simulation. Comparisons of the simulated gas and cluster number densities, cluster size for different stagnation pressures along the plume centerline were made and it is found that the cluster size increase linearly with respect to stagnation pressure, consistent with classical nucleation theory. Dielectric properties of liquid water and a water cluster of size 324 are investigated, and the static dielectric constant, dipole moment autocorrelation function and relative permittivity are computed by means of MD simulations. Optical properties such as the absorption coefficient and various efficiencies are also obtained from the Mie theory. To study the possible damage or contamination, the water clusters obtained in the BGK condensation, colliding with with silica surface are studied in a ReaxFF/MD simulations. The percentage of O and H atoms attached to the surface is obtained for different collision energies.

Tunable Diode Laser Absorption Spectroscopy of Aerospace Flows

“…Whilst steam ejector flow appears to be simple and uncomplicated, it is, in fact, very complex due to supercooling of the water vapour and subsequent condensation. Condensation increases the rotational temperature due to the latent heat of vaporisation [133]. The released condensation energy increases the translational temperature and then the rotational temperature due to the translational-rotational relaxation [133].…”

“…Condensation increases the rotational temperature due to the latent heat of vaporisation [133]. The released condensation energy increases the translational temperature and then the rotational temperature due to the translational-rotational relaxation [133]. Ejector flow consists of a primary nozzle with convergent and divergent sections and a secondary flow that is induced by the primary flow.…”