Modeling Reacting Flow Plasma

You can simulate reactions occurring in plasma such as ionization or excitation by combining the Coupled Plasma Electron model and the Complex Chemistry reacting species transport model. You must define the plasma chemical reactions in a Chemkin format mechanism file that can be imported into Simcenter STAR-CCM+ through the Complex Chemistry model. After importing the mechanism, the appropriate models are populated with the plasma species and reactions.

To model reacting flow plasma:

For the fluid region in which you are modeling plasma, edit the [physics continuum], make sure that Auto-select recommended models is activated, and select the following models:


Group Box	Model
Space	Any
Time	Implicit Unsteady or Steady
Material	Multi-Component Gas—in plasma simulations, the multi-component gas is usually a mixture of electrons, ions, neutral, and meta-stable components.
Reaction Regime	Reacting
Reacting Flow Models	Reacting Species Transport
Reacting Species Models	Complex Chemistry—see Complex Chemistry Model Reference
Turbulence Chemistry Interaction	Laminar Flame Concept
Flow	Segregated Flow
Enabled Models	Gradients (selected automatically)
	Segregated Species (selected automatically)
	Segregated Fluid Enthalpy (selected automatically)
Equation of State	Any Constant Density is required if you intend to specify initial conditions or boundary conditions for species in units of molar concentration.
Viscous Regime	Laminar
Optional Models	Plasma—see Plasma Model Reference.
Enabled Models	Coupled Plasma Electron Model (selected automatically)
Enabled Models	Electromagnetism (selected automatically)
Electric Field	Electrostatic Potential
Enabled Models	Charged Species Effects (selected automatically)
Optional Models	If you want to simulate surface reactions at walls, select Surface Chemistry—see Surface Chemistry Model Reference.

Select the Models > Gradients node and set Limiter Method to MinMod.
Import the plasma reaction mechanism in Chemkin format:
1. Right-click the [physics continuum] > Models > Complex Chemistry node and select Import Chemistry Definition (Chemkin format).
2. In the Import Chemkin Files dialog, navigate to and select the Fluid Chemistry Reaction File and the Fluid Thermodynamic Properties File containing the plasma reaction mechanism, then click OK.
  In the Chemkin file, the following reaction keywords are currently supported for specifying different plasma reaction types:
  - TDEP—temperature-dependent reaction
  - EXCI—excitation reaction
  - BOHM—Bohm velocity correction
  - STICK—reaction with sticking coefficient
  - DUP—allows multiple reaction statements with different rate coefficients
After importing the mechanism, the Multi-Component Gas node is populated with the plasma species (ions and neutral species). The Reacting > Reactions node contains the plasma reactions. For example, for Argon plasma reactions:

If you import a chemical mechanism with a TDEP reaction, the Reacting > Reactions > [reaction] > Properties > Species Temperature Dependence node is created where the TDEP Species is shown.

If you import a chemical mechanism with a EXCI reaction, the Reacting > Reactions > [reaction] > Properties > Electron Excitation Energy Loss node is created where the EXCI Value is shown.
Specify conditions and corresponding values for the following:
If you intend to specify initial conditions and/or boundary conditions in units of molar concentration, set the Multi-Component Gas > Material Properties > Density to Constant.
- Continua > [Continuum] > Initial Conditions
  Specifically,
  - Electron Number Density
    For reacting flow plasmas, an appropriate value is between $1.0 E^{12}$ and $1.0 E^{16}$
  - Electron Temperature
    For most reacting flow plasmas, an appropriate value is between 1000 K and 20000 K.
  See Plasma Model Initial Conditions.
- Regions > [Region] > Physics Conditions
  Specifically,
  - Electron Energy Density Source Option
    Activate this property when you want to define the electron energy density source term, $S_{\in, u s r}$ , which is used to calculate the collective electron energy density source term Eqn. (4193) for the energy density transport equation, Eqn. (4186).
  - Electron Source Option
    Activate this property when you want to define the electron source term, $S_{e, u s r}$ , which is used to determine the overall source term contributions for electron number density Eqn. (4192) in the number density transport equation, Eqn. (4184).
    
    See Plasma Model Region Settings
- [Region] > Boundaries > [Boundary] > Physics Conditions
  Specifically,
  - Electron Number Density Specification
  - Electron Thermal Specification
  See Plasma Model Boundary Settings
Set up any monitors, plots, and scenes that you require.
For example, you can monitor:
- Electron temperature
- Molar concentration of Electron (E^-)
- Electron Inelastic Collision Energy Loss
- Electron Energy Source
Run the simulation.