Thermophysical properties are specified in user-selectable packages that describe collections of models, based on either compressibility (\(\psi\), psi) or density (\(\rho\), rho).

The system starts with the specieβ€”the most basic entity that describes information such as the specie name, molecular weight and gas constant. This is extended by additional models that return thermophysical properties as functions of pressure and temperature.

Requirements vary according to the solver application, e.g. for single phase, multiphase, compressibility- or density-based, chemical reactions etc.

Single phase systems

Thermophysical properties for single phase calculations are specified in the file:


The main thermoType dictionary entry defines the set of models used to describe the system, comprising the entries:

    type            <thermophysical-model>;
    mixture         <mixture-model>;

    transport       <transport-model>;
    thermo          <thermodynamics-model>;
    equationOfState <equation-of-state-model>;
    specie          <specie-model>;

    energy          <energy-model>;

Here, the type entry sets the top-level thermophysical model type, e.g.

  • hePsiThermo : compressibility-based (source code)
  • heRhoThermo : density-based (source code)
  • heheuPsiThermo : compressibility-based with extensions for mixture is burnt/unburnt systems (source code)
  • heSolidThermo : solid-based (source code)

The he prefix signifies the energy variable that may be based on either enthalpy (h) or internal energy (e).

The mixture type depends on the solver application; mixtures that can be approximated by a single component are defined using the pureMixture type:

mixture         pureMixture;

All properties are then defined in a mixture sub-dictionary taking the form:


Each of the mixture entries are described in the following sections:

Available options for the energy entry include:

  • absoluteEnthalpy
  • absoluteInternalEnergy
  • sensibleEnthalpy
  • sensibleInternalEnergy

Multi-component mixtures

Both reacting and non-reacting mixtures are supported by some applications. The required inputs typically follow the pattern described above:

Multiphase systems

Each phase is described separately for multiphase systems, using file names with the convention:


Further information

Source code: