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Sampling

1) The fieldPropertiesDict dictionary

This dictionary located in the system folder is responsible for computing macroscopic quantities from microscopic particle information and for sampling species and mixture properties to obtain a statistical average. It is composed a list called pdFields() inside which a field dictionary can be repeated as many times as desired. The single field model available is pdVolFields to average volume and boundary fields in the entire domain. Other models are deprecated at present (WIP).

pdFields
(
    field
    {
        fieldModel          	pdVolFields;

        [...]
    }

    field
    {
        fieldModel          	pdVolFields;
        
        [...]
    }
     
);

The pdFields() list should be left empty when there is no need to reconstruct macroscopic fields.

For the O+ species, the macroscopic fields printed by default are:

• pdRhoN_O+: instantaneous number of parcels
• pdRhoNMean_O+: sampled number of parcels
• rhoN_O+: number density
• rhoM_O+: density
• U_O+: velocity vector
• Ma_O+: mach number
• p_O+: pressure (or partial pressure for a mixture)
• translationalT_O+: translational temperature
• rotationalT_O+: rotational temperature
• vibrational_O+: vibrational temperature
• overallT_O+: overall temperature
• fD_O+: force density
• wallShearStress_O+: wall shear stress
• wallHeatFlux_O+: wall heat flux

The field pdSigmaTcRMax has already been introduced in D.2.2 Initial volume fields.

2) Steady-state simulations

In the example below, macroscopic quantities are computed for the O+ and O species (see the pdVolFieldsProperties/typeIds() list) and are given the suffix _O+ and _O (pdVolFieldsProperties/fieldName) in the results folders. The same operation is repeated for the mixture (O+ O), providing that these species are the ones defined in A.1 Species thermophysical properties. The suffix is set to be _mixture.

pdFields
(
    field
    {
        fieldModel          	pdVolFields;

        timeProperties
        {
            timeOption               write;
            resetAtOutput               on;
        }

        pdVolFieldsProperties
        {
            fieldName           O+;
            typeIds             (O+);
        }
    }
    
    field
    {
        fieldModel          	pdVolFields;

        timeProperties
        {
            timeOption               write;
            resetAtOutput               on;
        }

        pdVolFieldsProperties
        {
            fieldName           O;
            typeIds             (O);
        }
    }

    field
    {
        fieldModel          	pdVolFields;

        timeProperties
        {
            timeOption               write;
            resetAtOutput               on;
        }

        pdVolFieldsProperties
        {
            fieldName           mixture;
            typeIds             (O+ O);
        }
    }
     
);

is the key parameter controlling sampling: it is a switch that indicates whether or not cumulative fields recording microscopic information are reset at the end of each iteration. If it is on, the instantaneous solution is printed.

3) Transient simulations

  resetAtOutput must be on for all field dictionaries at all times.