hy2Foam is an open-source two-temperature computational fluid dynamics (CFD) solver that has been developed to tackle the highly complex flow physics of the hypersonic planetary atmospheric entry. Implemented within the OpenFOAM framework, the code has the capability to model physical phenomena relative to the high-speed chemically-reacting environment surrounding a spacecraft. The core of the solver initially relied on OpenFOAM solvers rhoCentralFoam and reactingFoam and it has been complemented with many new features, some of which are listed below

  • non-equilibrium Navier-Stokes-Fourier equations: Park’s two-temperature model is implemented and the choice of having a single or multiple vibrational energy pools is left to the user. The energy transfers taking place between the different energy pools are
    • Vibrational-Translational (V—T)
    • Vibrational-Vibrational (V—V)
    • Heavy-particle — electron (H—e)
  • addition of the electronic and electron energy modes
  • finite-rate chemistry
  • chemistry-vibration coupling: Park TTv model, coupled vibration-dissociation-vibration (CVDV) model
  • customizable chemistry databases (Park 1993, Park 1994, Dunn & Kang 1973, quantum-kinetics: Scanlon 2015) including dissociation, electron impact dissociation, electron impact ionization, associative ionization, exchange and charge exchange reactions
  • capability to handle species with several characteristic vibrational temperatures (e.g., CO2) for the Mars atmospheric entry
  • transport models: Blottner and Eucken, power law and Eucken, Sutherland and Eucken, constant
  • species diffusion models: Lewis number, generalised Fick’s law, SCEBD model, inclusion of the effect of the pressure gradient
  • mixing rules: Wilke, Armaly & Sutton
  • turbulence models (no changes made to OF-v1706): laminar, k-omega SST, k-Epsilon, Spalart Allmaras, etc
  • computation of the convective & diffusive wall heat flux
  • computation of the mean free path and breakdown parameter
  • modifications to the Smoluchowski temperature jump and Maxwell velocity slip boundary conditions. Possibility to gradually increase the inlet flow velocity
  • adaptive mesh refinement (DyM) based on the Mach number gradient or normalised gradients of density or pressure
  • all dictionaries can be re-read on-the-fly which is handy on a high-performance computer
  • layer functions for the strongly-coupled hybrid CFD-DSMC code hyperFoam


This work was initiated at the University of Strathclyde and was funded by the Engineering and Physical Sciences Research Council (EPSRC) from February 2014 until early 2017.
Volunteering work from mid-2017 onwards.

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