Switching criteria for hybrid rarefied gas flow solvers

Duncan A. Lockerby*, Jason M. Reese, Henning Struchtrup

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Switching criteria for hybrid hydrodynamic/molecular gas flow solvers are developed, and are demonstrated to be more appropriate than conventional criteria for identifying thermodynamic non-equilibrium. For switching from a molecular/kinetic solver to a hydrodynamic (continuum-fluid) solver, the criterion is based on the difference between the hydrodynamic near-equilibrium fluxes (i.e. the Navier Stokes stress and Fourier heat. ux) and the actual values of stress and heat flux as computed from the molecular solver. For switching from hydrodynamics to molecular/kinetic, a similar criterion is used but the values of stress and heat. ux are approximated through higher order constitutive relations; in this case, we use the R13 equations. The efficacy of our proposed switching criteria is tested within an illustrative hybrid kinetic/Navier Stokes solver. For the test cases investigated, the results from the hybrid procedure compare very well with the full kinetic solution, and are obtained at a fraction of the computational cost.

Original languageEnglish
Pages (from-to)1581-1598
Number of pages18
JournalProceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences
Issue number2105
Publication statusPublished - 8 May 2009

Keywords / Materials (for Non-textual outputs)

  • local Knudsen number
  • switching criteria
  • breakdown parameter
  • hybrid code
  • rarefied gas flows


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