BGK and MD simulations of H2O supersonic condensed jets

Zheng Li, Arnaud Borner, Alireza Ostadhossein, Deborah A. Levin, Adri van Duin

Research output: Chapter in Book/Report/Conference proceedingConference contribution

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. The sensitivity of our results to cluster nucleation model and latent heat values based on bulk water, specific cluster size, or bulk ice are examined. In particular, the ES-BGK simulations are found to be too coarse-grained to provide information on the phase or structure of the clusters formed. For this reason, molecular dynamics simulations of water condensation in a one-dimensional free expansion to simulate the conditions in the core of a plume are performed. We find that the internal structure of the clusters formed depends on the stagnation temperature. A larger cluster of average size 21 was tracked down the expansion, and a calculation of its average internal temperature as well as a comparison of its radial distribution functions (RDFs) with values measured for solid amorphous ice clusters lead us to conclude that this cluster is in a solid-like rather than liquid form. In another molecular-dynamics simulation at a much lower stagnation temperature, a larger cluster of size 324 and internal temperature 200 K was extracted from an expansion plume and equilibrated to determine its RDF and self-diffusion coefficient. The value of the latter shows that this cluster is formed in a supercooled liquid state rather than in an amorphous solid state.

Original languageEnglish (US)
Title of host publicationAIAA AVIATION 2014 -11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference
PublisherAmerican Institute of Aeronautics and Astronautics Inc.
ISBN (Print)9781624102813
StatePublished - Jan 1 2014
Externally publishedYes
EventAIAA AVIATION 2014 -11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference 2014 - Atlanta, GA, United States
Duration: Jun 16 2014Jun 20 2014

Publication series

NameAIAA AVIATION 2014 -11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference

Other

OtherAIAA AVIATION 2014 -11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference 2014
CountryUnited States
CityAtlanta, GA
Period6/16/146/20/14

ASJC Scopus subject areas

  • Aerospace Engineering
  • Mechanical Engineering

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    Li, Z., Borner, A., Ostadhossein, A., Levin, D. A., & van Duin, A. (2014). BGK and MD simulations of H2O supersonic condensed jets. In AIAA AVIATION 2014 -11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference (AIAA AVIATION 2014 -11th AIAA/ASME Joint Thermophysics and Heat Transfer Conference). American Institute of Aeronautics and Astronautics Inc..