Boltzmann Model
In the Boltzmann Model node, values for specific discharge parameters are set. The number of parameters needed depends on the property settings for the physics interface.
Boltzmann Settings
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Enter a Gas temperature Tg (SI unit: K). The default is 300 K. The gas temperature influences the amount of energy loss that an electron suffers during an elastic collision. The higher the gas temperature, the lower the energy loss for an electron during an elastic collision.
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Enter an Absolute pressure PA (SI unit: Pa). The default is 1 atm. The absolute pressure is only available when Temporal behavior is set to Time dependent EEDF. The Absolute pressure is used to compute the gas number density.
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If the Electron-electron collisions property is active in the physics interface Electron Energy Distribution Function settings section, enter an estimate for the Electron density ne (SI unit: 1/m3).
There is a weak dependence on the electron density in Equation 3-1 which accounts for the screening of the Coulomb potential by space charge effects (Ref. 1).
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If the Electron-electron collisions property is active in the physics interface Electron Energy Distribution Function settings section, enter an Ionization degree β (dimensionless). The ionization degree can have a significant effect on the shape of the electron energy distribution function. When the ionization degree is very low, the tail of the distribution function tends to decrease very rapidly. As the ionization degree increases, the distribution function tends to become more Maxwellian, resulting in a greater proportion of electrons with higher energies. This can have a profound effect on the rate coefficients for ionization and excitation collisions because of their high energy threshold.
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Enter a Reduced electric field E/N (SI unit: V/m2). The default is 10 Td. The reduced electric field is used as an input to the Boltzmann equation and is responsible to heat the electrons. The Reduced electric field is only available when Temporal behavior is set to Time dependent EEDF. The pressure is used to compute the gas number density.
Mole Fraction Settings
Specify the mole fraction of each of the target species in the set of collision cross sections.
Since the sum of all the mole fractions must be equal to one, select one of the species from the Mole constrained species list. The mole fraction of the selected species is based on the mole fractions of all the other species.
Mole fraction. There are N text fields available for setting the mole fractions of each species, where N is the total number of target species. Enter the Mole fraction expected to be observed in the discharge for each target species. The mole fraction of electronically excited species can have a strong effect on the shape of the electron energy distribution function.
results
It can be a little bit tricky or time consuming to generate plots of certain output data if there are many species present in the model. Therefore, the Results section allows for many common quantities of interest to be plotted by default. Note that if a solution is first computed, then certain values in the Results section are changed, the plots are not automatically updated. The solver configuration should be deleted, and the study recomputed.