User-Defined Breakup Model Reference

The User-Defined Breakup model lets you generate child parcels at secondary breakup events based on a breakup regime map you define. The breakup process is random, but properties like particle diameter are determined the same way for every droplet. The droplets do not have parent-child relationships after breakup events. This method is similar to the Stochastic Secondary Droplet (SSD) Breakup model.

Under the User-Defined Breakup node, you can define as many Breakup Outcome nodes as necessary, one for each breakup regime, then describe the regimes under the Breakup Regime Map nodes. See Breakout Regime Map.


Theory	See User-Define Breakup Model.
Provided By	Lagrangian Multiphase > Lagrangian Phases > [phase] > Models > Secondary Breakup
Example Node Path	Lagrangian Multiphase > Lagrangian Phases > [phase] > Models > User-Defined Breakup
Requires	Material: one of Gas, Liquid, Multiphase, Multi-Component Gas, Multi-Component Liquid (For Multiphase, Multi-Component Gas or Multi-Component Liquid, further models are required to expose the Flow models.) Flow: Coupled or Segregated Under the Lagrangian Multiphase model: Particle Type: Material Particles Material: Liquid or Multicomponent Liquid Particle Shape: Spherical Particles
Activates	Model Controls (child nodes)	Breakup Outcomes, Breakup Regime Map
	Field Functions	Breakup Growth Time, Breakup Outcome Index, Droplet Dynamic Viscosity, Droplet Ohnesorge Number, Droplet Surface Tension. See Field Functions.

Breakup Outcomes

The Breakup Outcomes node allows you to define how the child parcels are generated at a breakup event. The User-Defined Breakup node has a child node, Breakup Outcomes. This node has one child node as default, the No Breakup 1 node. This node represents the breakup outcome for the parcels which don’t have any breakup events. The No Breakup 1 node has no properties except the read-only index number. To create additional outcome nodes, right-click Breakup Outcomes and select New > Breakup Outcome. Create enough outcome nodes to define a Breakup Regime Map for every outcome you want to specify. Each Breakup Outcome node is associated with a unique read-only index that is used by the Breakup Regime Map to assign the outcome to each parcel.

Under each Breakup Outcome <n> node is a Child Parcel Generation Methods node.

The properties of the Child Parcel Generation Methods node depend on the generation method selected.

Child Parcel Generation Methods

Method	Corresponding Method Node
Log-Normal Distribution Droplet diameters after breakup follows a log-normal distribution. See Eqn. (3119).	Log-Normal Distribution Properties: Maximum Number of Child Parcels $N_{c}^{u}$ in Eqn. (3121). The default value is 10. Child Droplet Velocity Correction The velocity magnitude $v_{t}$ in Eqn. (3124). The default value is 0. Breakup Times Scale The time from a droplet's injection or formation to its breakup. Each breakup outcome has a breakup time scale. The User-Defined Breakup model sets the Breakup Growth Time field function for each parcel, representing the age of the parcel to the current time. At the next breakup event, the value of Breakup Growth Time must be greater than the value of Breakup Times Scale in addition to satisfying the breakup criteria. At each breakup event, Breakup Growth Time is set to 0 for the parcel. Theoretically Breakup Times Scale represents the time scale at which the breakup instability is growing. If you specify Breakup Times Scale as 0, parcels have breakup events in the same sub-step at which they satisfy the breakup criteria. The default is 0.0. Minimum Child Droplet Diameter The minimum value for $D_{c}$ in Eqn. (3123). The value of $D_{c}$ for a given parcel is selected randomly according to the distribution function of the specified method. The maximum value is the diameter of the parent parcel $D_{0}$ . The default value for $D_{c}$ is 1.0E-7 m. Target Count The number of child droplets generated, $n_{c}$ in Eqn. (3123). The default for is 1000.0. Mean Value $m$ in Eqn. (3119) and Eqn. (3120). Applies only to Log-Normal Distribution and Root-Normal Distribution. Standard Deviation $σ$ in Eqn. (3119) and Eqn. (3120). Applies only to Log-Normal Distribution and Root-Normal Distribution.
Root-Normal Distribution Droplet diameters after breakup follow a root-normal distribution. See Eqn. (3120).	Root-Normal Distribution Uses the same properties as the Log-Normal Distribution node.
Table CDF Droplet diameter ratios $D / D_{0}$ and corresponding Cumulative Distribution Function (CDF) are specified in a table.	Table CDF Properties: Maximum Number of Child Parcels As for Log-Normal Distribution and Root-Normal Distribution. Child Droplet Velocity Correction As for Log-Normal Distribution and Root-Normal Distribution. Breakup Times Scale As for Log-Normal Distribution and Root-Normal Distribution. Minimum Child Droplet Diameter As for Log-Normal Distribution and Root-Normal Distribution. Target Count As for Log-Normal Distribution and Root-Normal Distribution. Table The table listing the diameter data for child droplets. Select from the drop-down menu. The table must be a histogram and include a bin specifying diameter ratio $D / D_{0}$ where $D_{0}$ is the starting diameter of the droplet, and another specifying CDF $F (D)$ . The table needs to have the following features: The CDF column must be named CDF. The diameter ratio column can be named arbitrarily. Its function is identified in the Table: Diameter Ratio property. The diameter ratio increases monotonically and the range is in the range 0 to 1. CDF data increases monotonically and the range is in the range 0 to 1. The child droplet diameter is interpolated by spline from the table data. Table: Diameter Ratio Specifies the values of $D / D_{0}$ . Values must be in the range 0.0 to 1.0. Table: CDF Specifies the values of the cumulative distribution function corresponding to the Diameter Ratio column. Values must be in the range 0.0 to 1.0.

Method

Corresponding Method Node

Log-Normal Distribution: Droplet diameters after breakup follows a log-normal distribution. See Eqn. (3119).

Log-Normal Distribution

Properties:

Maximum Number of Child Parcels: $N_{c}^{u}$ in Eqn. (3121). The default value is 10.
Child Droplet Velocity Correction: The velocity magnitude $v_{t}$ in Eqn. (3124). The default value is 0.
Breakup Times Scale: The time from a droplet's injection or formation to its breakup. Each breakup outcome has a breakup time scale. The User-Defined Breakup model sets the Breakup Growth Time field function for each parcel, representing the age of the parcel to the current time. At the next breakup event, the value of Breakup Growth Time must be greater than the value of Breakup Times Scale in addition to satisfying the breakup criteria. At each breakup event, Breakup Growth Time is set to 0 for the parcel. Theoretically Breakup Times Scale represents the time scale at which the breakup instability is growing. If you specify Breakup Times Scale as 0, parcels have breakup events in the same sub-step at which they satisfy the breakup criteria. The default is 0.0.
Minimum Child Droplet Diameter: The minimum value for $D_{c}$ in Eqn. (3123). The value of $D_{c}$ for a given parcel is selected randomly according to the distribution function of the specified method. The maximum value is the diameter of the parent parcel $D_{0}$ . The default value for $D_{c}$ is 1.0E-7 m.
Target Count: The number of child droplets generated, $n_{c}$ in Eqn. (3123). The default for is 1000.0.
Mean Value: $m$ in Eqn. (3119) and Eqn. (3120). Applies only to Log-Normal Distribution and Root-Normal Distribution.
Standard Deviation: $σ$ in Eqn. (3119) and Eqn. (3120). Applies only to Log-Normal Distribution and Root-Normal Distribution.

Root-Normal Distribution: Droplet diameters after breakup follow a root-normal distribution. See Eqn. (3120).

Root-Normal Distribution

Uses the same properties as the Log-Normal Distribution node.

Table CDF: Droplet diameter ratios $D / D_{0}$ and corresponding Cumulative Distribution Function (CDF) are specified in a table.

Table CDF

Properties:

Maximum Number of Child Parcels