Gas Models
This section describes the models available for describing the thermodynamic and transport properties of gases. As of the writing of this section, there are no plans to include real gas models, and so all models will make the perfect gas assumption. This means that all intermolecular forces are neglected, and the gas is governed by the ideal gas law
The two gas models which are planned to be included in PERFORM differ in how thermodynamic properties (e.g. enthalpy, entropy) and transport properties (e.g. dynamic viscosity, diffusion coefficients) are calculated.
Calorically-perfect Gas
The calorically perfect gas model is activated by setting gas_model = "cpg" in the chem_file. The CPG model assumes that the heat capacity at constant pressure for each species is constant, i.e. \(c_{p,l}(T) = c_{p,l}\). These values are given in the chem_file via cp. The species enthalpies are thus given by
where the reference enthalpies at 0 K are given in the chem_file via enth_ref.
Species dynamic viscosities are computed via Sutherland’s law,
where the species reference temperatures are given in the chem_file via temp_ref, and the reference viscosities via mu_ref. The Sutherland temperature is given as \(S = 110.4\) K. If \(T = 0\) K, then \(\mu_l = \mu_{ref,l}\).
The species thermal conductivities (required for calculating the heat flux) are given by
Where the species Prandtl numbers \(\text{Pr}_l\) are given in the chem_file via pr. The binary diffusion coefficients of each species into the mixture is given by
where the species Schmidt number \(\text{Sc}_l\) are given in the chem_file via sc.
Additional details on the CPG gas model, particularly on computing the mixture thermodynamic and transport properties, can be found in the theory documentation.
Thermally-perfect Gas
Coming soon!