Charge Accumulation
Use the Charge Accumulation node to compute the charge accumulation on a particle immersed in a gas background with free ions as a function of time.
Charge Accumulation in the theory section.
Enter a value or expression for the Temperature T (SI unit: K). The default value is 293.15 K. If a physics interface that computes the gas temperature is present, then this can be selected from the list as a model input.
Enter a value or expression for the Pressure p (SI unit: Pa). The default value is 1 atm. If a physics interface that computes the gas pressure is present, then this can be selected from the list as a model input.
The gas temperature and pressure are used to compute the gas number density, which is used to compute the ion mobility from the given ion reduced mobility.
Particle charging model
Select a Particle charging Model: Lawless (the default), Classical diffusion, Classical field, Classical diffusion and Field, or White.
Initial accumulated charge number
Enter a value for the Initial accumulated charge number Za,j (dimensionless). The default is 0.
Particle Properties
This section is only available when one of the following options is selected from the Particle charging model list: Lawless, Classical field, or Classical diffusion and Field.
Select as option from the Particle electric properties list: Dielectric (the default), or Conductive. If Dielectric is selected, enter a value for the Particle relative permittivity εr,p (dimensionless) in the settings for the Particle Properties node.
Ion Properties
Enter a value or expression for the Space charge density ρq (SI unit: C/m3). The default value is 10-5 C/m3. If a physics interface that computes the space charge density is present, then this can be selected from the list.
If the charging model Lawless, Classical diffusion, Classical field, or Classical diffusion and Field is selected from the Particle charging model list, enter a value or expression for the Reduced ion mobility μiN (SI unit: 1/(Vms)). The default value is 3 × 1021 1/(Vms).
Enter a value or expression for the Ion Temperature Ti (SI unit: K). The default value is 293.1 K.
If the charging model White is selected from the Particle charging model list enter a value or expression for the Ion Mass Mi (SI unit: kg/mol). The default is 100 g/mol.
Electric field
This section is only available when one of the following options is selected from the Particle charging model list: Lawless, Classical field, or Classical diffusion and Field.
Select an option from the Specify force using list: Electric potential (the default) or Electric field.
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For Electric potential enter a value or expression for the Electric potential V (SI unit: V). If the electric potential is computed by another physics interface then it can be selected from the list.
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For Electric field enter values or expressions in the table for the Electric field E (SI unit: V/m) based on space dimension. If the electric field is computed by another physics interface then it can be selected from the list.