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Thermophysical modelling

1) Species thermophysical properties

The gas composition is given in the constant/pdProperties dictionary in the form of a list.

// Molecular species
// ~~~~~~~~~~~~~~~~~

typeIdList           (N2 O2);

The species thermophysical properties are given in the pdProperties/moleculesProperties dictionary. For the nitrogen molecule, it is defined as follows

N2
{
    mass                                  46.5e-27;
    diameter                              4.17e-10;
    omega                                     0.74;
    alpha                                     1.36;
    rotationalDegreesOfFreedom                   2;
    vibrationalModes                             1;
    characteristicVibrationalTemperature      3371;
    dissociationTemperature                 113500;
    Zref                                     52560;
    referenceTempForZref                      3371;
    Ze                                           0;
}

The Table below lists the meaning of the different keys present in the #speciesName subdictionary. If a key is omitted, then a default value is used whenever possible.

#speciesName subdictionary
Key Units Meaning
mass kg mass of a single particle
diameter m particle diameter
omega - temperature exponent of viscosity
alpha - soft-sphere scattering parameter (default is 1.0, i.e., hard-sphere gas)
rotationalDegreesOfFreedom - number of rotational degrees of freedom (default is 0)
vibrationalModes - number of vibrational energy modes (default is 0)
characteristicVibrationalTemperature K characteristic vibrational temperature (default is 0)
dissociationTemperature K dissociation temperature (default is 0.0)
Zref - reference vibrational collision number (default is 0.0)
referenceTempForZref K reference temperature in the vibrational collision number calculation (default is 0.0)
Ze - charge of the particle (-1: electron, 0: neutral atom and molecule, +1: charged atom and molecule, default is 0)

 

2) Adding/removing energy modes

2.1 Disabling/enabling the rotational mode of a molecule

In the pdProperties/moleculesProperties/#speciesName dictionary, either edit rotationalDegreesOfFreedom to be 0 or remove this key from the dictionary.

In the following example, the rotational energy mode of the N2 molecule is enabled

    rotationalDegreesOfFreedom                   2;

 

2.2 Disabling/enabling the vibrational mode of a molecule

In the pdProperties/moleculesProperties/#speciesName dictionary, remove the vibrationalModes, characteristicVibrationalTemperature, Zref and referenceTempForZref keys.

In the following example, the vibrational energy mode of the N2 molecule is enabled

    vibrationalModes                             1;
    characteristicVibrationalTemperature      3371;
    Zref                                     52560;
    referenceTempForZref                      3371;