Interaction Length Scale Model Reference

The interaction length scale is used to define non-dimensional parameters such as the Reynolds number for a phase interaction, and also to compute an interaction area density. The interaction length scale for a continuous-dispersed interaction is chosen to be the mean particle size. For a multiple flow regime interaction you specify the interaction length scale for the first dispersed regime and the second dispersed regime.

表 1. Interaction Length Scale Model Reference
Theory	See Interaction Length Scale.
Provided By	[phase interaction] > Models > Optional Models
Example Node Path	[phase interaction] > Models > Interaction Length Scale
Requires	Physics continuum selections: Material: Multiphase Multiphase Model: Eulerian Multiphase (EMP) (Automatically activates: Multiphase Interaction, Gradients.) Two Eulerian phases are required. A Continuous-Dispersed Topology or Multiple Flow Regime Topology phase interaction is required. Phase interaction selections: Optional Models: Interaction Length Scale (selected automatically)
Properties	Key properties are: Method. See Interaction Length Scale Properties.
Activates	Model Controls	For a Continuous-Dispersed phase interaction only: Interaction Length Scale See Interaction Length Scale Properties. For a Multiple Flow Regime phase interaction only: First Dispersed Regime Interaction Length Scale Second Dispersed Regime Interaction Length Scale See First/Second Dispersed Regime Length Scale Properties.
	Field Functions	See Field Functions.

Interaction Length Scale Properties

Method

Specifies the method for defining the interaction length scale.

Constant
A constant value that represents the mean particle size for the phase interaction.
Field Function
A field function that represents the mean particle size for the phase interaction. For example, in a flow with a constant number density of particles, particle size could be specified to be proportional to the phase volume fraction.
Particle Diameter
Uses the particle diameter of the particle phase, which is set as the dispersed phase. This method is available when the Granular Pressure model is selected in the physics continuum. You can specify the particle diameter in the Material Properties node in the particle phase definition.
See Granular Pressure Model Reference.
Sauter Mean Diameter
Uses the Sauter Mean Diameter of the dispersed phase. This method is made available when the S-gamma model is activated for the dispersed phase.
Kurul Podowski
Specifies bubble size as a function of local subcooling. The Kurul Podowski interaction length scale is an empirical relation that is used in boiling flows. It is available only when the boiling mass transfer rate has been selected with interphase mass transfer.
The Kurul Podowski Interaction Length Scale node has the following properties:
- Minimum Diameter
  The minimum bubble diameter, $D_{m i n}$ in Eqn. (1922).
- Maximum Diameter
  The maximum bubble diameter, $D_{m a x}$ in Eqn. (1922).
- Minimum Diameter Subcooling
  The liquid subcooling temperature corresponding to minimum bubble diameter, $Δ T_{D, m i n}$ in Eqn. (1922).
- Maximum Diameter Subcooling
  The liquid subcooling temperature corresponding to maximum bubble diameter, $Δ T_{D, m a x}$ in Eqn. (1922).
Adaptive Multi Size Group Diameter
The usual and default method for Adaptive Multi Size Group (AMUSIG) simulations.
When this option is selected in a Multi-Speed simulation, each size group automatically uses its own group diameter for the drag force and for other interaction models.
In a Single-Speed simulation, the Sauter or surface-mean diameter is automatically used instead.
See Adaptive Multiple Size-Group Model Reference.

First/Second Dispersed Regime Length Scale Properties

Method

Specifies the method for defining the interaction length scale.

Constant
A constant value that represents the mean particle size for the phase interaction.
Field Function
A field function that represents the mean particle size for the phase interaction. For example, in a flow with a constant number density of particles, particle size could be specified to be proportional to the phase volume fraction.
Sauter Mean Diameter
Uses the Sauter Mean Diameter of the dispersed phase. This method is made available when the S-gamma model is activated for the phase.

Field Functions

The following field function is available for a Continuous-Dispersed phase interaction:

Interaction Length Scale of [phase interaction]: The effective mean diameter of the dispersed phase particles.

The following field functions are available for a Multiple Flow Regime phase interaction:

First Dispersed Regime Interaction Length Scale of [phase interaction]: The interaction length scale $l_{fr}$ is the typical bubble diameter.
Second Dispersed Regime Interaction Length Scale of [phase interaction]: The interaction length scale $l_{sr}$ is the typical droplet diameter.