# collisionFrequency¶

Computes the collision frequency matrix for multiple fluids species or the collision time matrix if the inverse quantities are stored. The two approaches used for collisions in fully ionized plasma are thermalSpecies which ignores the relative drift of the fluids and ramboAndDenavit which takes into account the relative drift. thermalSpecies is identical to ramboAndDenavit with the velocities set to 0. A description of this collision model is described in

Rambo, P. W., and J. Denavit. “Interpenetration and ion separation in colliding plasmas.” Physics of Plasmas 1 (1994): 4050.

For neutrals collisions, the collision cross section is obtained using hard sphere model. The relative velocity includes thermal and bulk velocities. Collisions in partiallyIonized plasmas use ramboAndDenavit if both the colliding particles are charged and uses neutrals otherwise.

## Parameters¶

type (string)
type should be either thermalSpecies or ramboAndDenavit or neutrals or partiallyIonized. The thermalSpecies is the classical collision frequency assuming zero relative velocity between the fluids in consideration. ramboAndDenavit assumes that there may be a large relative velocity between species. neutrals uses the hard sphere model to compute collision cross section and the relative velocity includes both thermal and bulk velocitis.
speciesMass (vector float)
The mass of each fluid species
speciesDia (vector float)
The diameter of each fluid species
inverse (boolean)
If inverse is false the the collision frequency is computed, if inverse is true then the collision time is computed.

## Parent Updater Data (type = thermalSpecies)¶

in (string vector, required)

Each species has a Z, T and N variable that must be put into the in variable, so for 2 species in would be

in = [Z1, T1, N1, Z2, T2, N2]

1st Variable

1. Z Is the charge state of the species (positive value)

2nd Variable

1. T Is the temperature of the species

3rd Variable

1. N Is the number density of the species
out (string vector, required)
The output is the collision matrix. The size of the matrix will be numSpecies*numSpecies where here numSpecies is the number of components in the speciesMass vector below.

## Parent Updater Data (type = ramboAndDenavit)¶

in (string vector, required)

Each species has a Z, T, N, V variable that must be put into the in variable, so for 2 species in would be

in = [Z1, T1, N1, V1, Z2, T2, N2, V2]

1st Variable

1. Z Is the charge state of the species (positive value)

2nd Variable

1. T Is the temperature of the species

3rd Variable

1. N Is the number density of the species

4th Variable

1. Vx Is the velocity of the fluid in the X direction
2. Vy Is the velocity of the fluid in the Y direction
3. Vz Is the velocity of the fluid in the Z direction
out (string vector, required)
The output is the collision matrix. The size of the matrix will be numSpecies*numSpecies where here numSpecies is the number of components in the speciesMass vector below.

## Parent Updater Data (type = neutrals)¶

in (string vector, required)

Each species has a T, N, V variable that must be put into the in variable, so for 2 species in would be

in = [T1, N1, V1, T2, N2, V2]

1st Variable

1. T Is the temperature of the species

2nd Variable

1. N Is the number density of the species

3rd Variable

1. Vx Is the velocity of the fluid in the X direction
2. Vy Is the velocity of the fluid in the Y direction
3. Vz Is the velocity of the fluid in the Z direction
out (string vector, required)
The output is the collision matrix. The size of the matrix will be numSpecies*numSpecies where here numSpecies is the number of components in the speciesMass vector below.

## Parent Updater Data (type = partiallyIonized)¶

in (string vector, required)

Each species has a Z, T, N, V variable that must be put into the in variable, so for 2 species in would be

in = [Z1, T1, N1, V1, Z2, T2, N2, V2]

1st Variable

1. Z Is the charge state of the species (positive value)

2nd Variable

1. T Is the temperature of the species

3rd Variable

1. N Is the number density of the species

4th Variable

1. Vx Is the velocity of the fluid in the X direction
2. Vy Is the velocity of the fluid in the Y direction
3. Vz Is the velocity of the fluid in the Z direction
out (string vector, required)
The output is the collision matrix. The size of the matrix will be numSpecies*numSpecies where here numSpecies is the number of components in the speciesMass vector below.

## Example¶

<Equation thisGas>
inverse = false
kind = collisionFrequency
type = ramboAndDenavit
speciesMass = [ELECTRON_MASS, ION_MASS, ION_MASS]
</Equation>