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Thermophysical modelling

1) Species thermophysical properties

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

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

typeIdList           (N2 O2 NO N O);

The species thermophysical properties are given in the dsmcProperties/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;
    nVibrationalModes                            1;
    vibrationalDegeneracyList                  (1);
    characteristicVibrationalTemperature    (3371);
    dissociationTemperature                 113500;
    Zref                                   (52560);
    referenceTempForZref                    (3371);
    ionisationTemperature                 180798.3;
    charge                                       0;
    nElectronicLevels                           15;
    electronicDegeneracyList
    (
        1 3 6 6 3 1 2 2 5 1 6 6 10 6 6
    );
    electronicEnergyList
    (
        0  9.972e-19 1.1843e-18 1.1881e-18 1.3165e-18 1.3538e-18
          1.3763e-18 1.4483e-18 1.5415e-18 1.6925e-18 1.7242e-18
          1.7707e-18 1.8474e-18 1.9388e-18 2.0778e-18
    );
}

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)
nVibrationalModes - number of vibrational energy modes (default is 0)
vibrationalDegeneracyList - degeneracy of each vibrational energy mode (default is 1, list of size nVibrationalModes)
characteristicVibrationalTemperature K characteristic vibrational temperature (list of size nVibrationalModes)
dissociationTemperature K dissociation temperature (default is 0.0)
Zref - reference vibrational collision number (list of size nVibrationalModes)
referenceTempForZref K reference temperature in the vibrational collision number calculation (list of size nVibrationalModes)
ionisationTemperature K ionisation temperature (default is 1.0e10)
charge - charge of the particle (-1: electron, 0: neutral atom and molecule, +1: charged atom and molecule, default is 0)
nElectronicLevels - number of electronic energy levels (default is 0)
electronicDegeneracyList - degeneracy of each electronic energy level (default is 1, list of size nElectronicLevels)
electronicEnergyList J electronic energy of each electronic energy level (list of size nElectronicLevels)

NB: An example for 5-species air is given in the chemically-reacting heat bath tutorial, on this page.

 

>> Electronic energy unavailable until further notice <<

 

2) Adding/removing energy modes

2.1 Disabling/enabling the rotational mode of a molecule

In the dsmcProperties/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 dsmcProperties/moleculesProperties/#speciesName dictionary, remove the nVibrationalModes, vibrationalDegeneracyList and characteristicVibrationalTemperature keys.

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

    nVibrationalModes                            1;
    vibrationalDegeneracyList                  (1);
    characteristicVibrationalTemperature    (3371);

 

2.3 Disabling/enabling the electronic mode of a particle

In the dsmcProperties/moleculesProperties/#speciesName dictionary, remove the nElectronicLevels, electronicDegeneracyList and electronicEnergyList keys.

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

    nElectronicLevels                           15;
    electronicDegeneracyList
    (
        1 3 6 6 3 1 2 2 5 1 6 6 10 6 6
    );
    electronicEnergyList
    (
        0  9.972e-19 1.1843e-18 1.1881e-18 1.3165e-18 1.3538e-18
          1.3763e-18 1.4483e-18 1.5415e-18 1.6925e-18 1.7242e-18
          1.7707e-18 1.8474e-18 1.9388e-18 2.0778e-18
    );