### 5.8.3. Breakup Models

Breakup kernels are often expressed as a function of the breakup fraction:

| (5–161)

CFX-Solver supports two breakup models.

#### 5.8.3.1. Luo and Svendsen Model

Luo and Svendsen [61] developed a theoretical model for the breakup of drops and bubbles in turbulent suspensions. The model is based on the theory of isotropic turbulence and probability. The breakup kernel is modeled as:

| (5–162)

where:

| (5–163)

is the dimensionless size of eddies in the inertial subrange of isotropic turbulence. The lower limit of the integration is given by:

| (5–164)

where

| (5–165)

and is the minimum eddy ratio and can have a value between 11.4 and 31.4 (defaults to 11.4).

In addition, is a calibration coefficient, , is the continuous-phase eddy dissipation rate, is the continuous-phase kinematic viscosity, and is the surface tension coefficient.

#### 5.8.3.2. User-Defined Models

A custom model for the breakup kernel may also be provided. The model may be a CEL expression or User Routine and may be a function of the diameter and/or mass represented by groups and as well as any fluid variable.

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