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Initialisation

1) The pdInitialiseDict dictionary

The pdInitialiseDict dictionary is located in the system/ folder. The initial number density of all species present in the gas mixture (see A.1 Species thermophysical properties), modal temperatures and velocity are given in the following subdictionary

configurations
(
    configuration
    {
        type    pdMeshFill;

        numberDensities
        {
             Ar            1.4e20;
        };

        translationalTemperature     273.0;
        rotationalTemperature        0.0; 
        vibrationalTemperature       0.0;

        velocity        (100 0 0);
    }
);

where the type pdMeshFill indicates that the entire grid is going to be populated with particles. To start with a grid free of parcels, leave the configurations() list empty.

2) Parcel vs. real particles

The number of real particles represented by a single parcel is set in the constant/pdProperties dictionary

nEquivalentParticles            2e7;

There should be a minimum of 20 parcels per cell whenever possible and nEquivalentParticles should be set accordingly.

3) Creating the 0/ folder

In the working directory, type in:

pdInitialise

This command line will create the 0/ folder. Simulators data is stored into the 0/lagrangian/pd/ subfolder and a volume field, pdSigmaTcRMax, is printed. The main executable will always look for these information in the time folder corresponding to the starting time.

3.1 Simulators data

In the 0/lagrangian/pd/ folder, the files listed in the Table below are created. Each of them contains a dataset of size number of parcels.

3.2 Initial volume fields

• pdSigmaTcRMax is a first estimate of the maximum value taken by the product of the collision cross-section by the relative speed. For a gas mixture, it is usually obtained by considering the properties (diameter, omega, alpha) of the most abundant species. As the simulation proceeds, this field is updated as soon as a new local maximum is found. It requires no user intervention.