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These guidelines are based on the working folder located here.

Transport modelling

1) Species shear viscosity and thermal conductivity

1.1 Inviscid simulation

This is done in two steps:

• in the thermophysicalProperties/thermoType dictionary, edit the transport entry to constant;
• in the thermoDEM/#speciesName/transport/constant dictionary, for all species present in the gas mixture, edit the value of the entry mu to be 0.

1.2 Viscous simulation with constant shear viscosity and thermal conductivity

Repeat the two steps presented in §1.1 but edit mu to the desired value (units: kg/m/s). The constant thermal conductivities are set using the kappa (trans-rotational energy mode) and kappave (vibro-electronic energy mode) entries (units: kg/m/s³/K).

1.3 Other transport models

The names of all other available transport models to be loaded using the transport keyword in the thermophysicalProperties/thermoType dictionary are

The coefficients of these models can be found in the thermoDEM/#speciesName dictionary. The first three models are using coefficients located in the transport subdictionary, while the powerLawEucken model requires the species diameter, diameter, and the species temperature exponent of viscosity, omega, located in the specie subdictionary.

1.4 Print species shear viscosity and thermal conductivity

In the transportProperties/transportModels dictionary, edit the state of these two switches to on

    writeViscositySpecies          on;  
    writeThermalConducSpecies      on; 

2) Mixing rules

The available mixing rules are given in the following Table

and the dedicated entry, mixingRule, is located in the transportProperties/transportModels dictionary. The mixture shear viscosity and thermal conductivity can be printed by switching on the following booleans

    writeViscosityMixture          on;  
    writeThermalConducMixture      on; 

NB: There are no reasons to use the molar mixing rule other than for single-species flows or zero-dimensional heat baths.

3) Mass diffusion

3.1 Disable multi-species diffusion

In the transportProperties/transportModels dictionary, edit the following entries to

    multiSpeciesTransport         noSpeciesDiffusion;  
    binaryDiffusionModel          noBinaryDiffusionModel;

3.2 Lewis number model

In the transportProperties/transportModels dictionary, edit the following entries to

    multiSpeciesTransport         LewisNumber;  
    binaryDiffusionModel          noBinaryDiffusionModel;

The Lewis number value can be found in the diffusionModelParameters subdictionary

    diffusionModelParameters
    {
        LewisNumber                    1.4;
        
        [...]
    }

3.3 Fick’s law and binary diffusion models

In the transportProperties/transportModels dictionary, edit the following entry to

    multiSpeciesTransport         Fick; 

Binary diffusion coefficients can be calculated according to any of the models presented in the Table below

The constantBinaryDiffusionModelCoefficients and collisionDataModel entries can be found in the diffusionModelParameters subdictionary. collisionDataModel accepted values are "Gupta1989D", "Gupta1989O", "Gupta1990D", "Gupta1990O", and "Wright2005O".

Example for a binary Nitrogen-Oxygen mixture:

multiSpeciesTransport        Fick;
binaryDiffusionModel         collisionData;  
  
diffusionModelParameters   
{  
     collisionDataModel          "Gupta1989D";   
}  
  
collisionData
{
    tabulatedInteractions
    { 
        // NASA-TM-101528 (Gupta, Yos, Thompson: Feb. 1989)
        // Document ID: 19890011822
        // A review of reaction rates and thermodynamic and transport 
        // properties for the 11-species air model for chemical and thermal
        // nonequilibrium calculations to 30000 K
        Gupta1989D
        {
            // Table VI
            Dbar
            {
                N2_N2 (0.0 0.0112 1.16182 -11.3091);  
                N2_O2 (0.0 0.0465 0.9271 -8.1137);         
            } 
        }
    }  
}  

3.4 SCEBD model

In the transportProperties/transportModels dictionary, edit the following entry to

    multiSpeciesTransport         SCEBD; 

Please refer to §3.3 for the list of available binary diffusion coefficient models.

3.5 Additional features (to Fick and SCEBD models)

Results using the non-corrected forms of Fick’s law and the SCEBD model can be obtained by switching on the useNonCorrectedForm boolean located in the diffusionModelParameters subdictionary (for comparison with the corrected form only). It is turned off by default, which means that the sum of the diffusive fluxes is zero.

NB: The useNonCorrectedForm entry can be deleted from the diffusionModelParameters subdictionary if you wish (safer).

In the same subdictionary, the addPressureGradientTerm switch allows to account for the effects of pressure gradients.