Resolved Transition Model Reference

The Resolved Transition model uses the same mechanism that the Blob Detection model uses to identify isolated blobs within the VOF or MMP field, using a fixed Volume Fraction Threshold Value of 0.05. You do not need to activate the Blob Detection model in the VOF or the MMP phase. For more information, see Blob Detection Model Reference.

To avoid instability for significantly large Lagrangian volume fraction cases, alongside the adaptive mesh refinement, you are advised to use the Lagrangian Two-Way Coupling Volume Sources Smoothing method with the Resolved Transition model, for VOF and MMP simulations.

Note	The Resolved Transition model is not compatible with the second order time discretization in the Implicit Unsteady solver.

Table 1. Resolved Transition Model Reference
Provided By	[phase interaction] > Models > Optional Models
Example Node Path	Continua > Physics 1 > Models > Multiphase Interaction > Phase Interactions > [phase interaction] > Models > Resolved Transition
Requires	A VOF or MMP Multiphase simulation with the Lagrangian Multiphase model activated. The appropriate Eulerian phase and the corresponding Lagrangian phase defined. A VOF-Lagrangian Phase Interaction or MMP-Lagrangian Phase Interaction with the Eulerian phase and the corresponding Lagrangian phase selected.
Properties	Key properties are: Verbose See Resolved Transition Properties.
Activates	Physics Models	None.
	Model Controls (child nodes)	Eulerian-Lagrangian Transition Criteria See Eulerian-Lagrangian Transition Criteria Properties.
	Field Functions	See Eulerian-Lagrangian Transition Criteria Field Functions .

Resolved Transition Properties

Verbose: Enables verbose output, the details that the model displays in the Output window.

Eulerian-Lagrangian Transition Criteria Properties

Specifies the method for defining the Euerian-Lagrangian transition criteria.

Blob Diameter Criterion
Defines the Eulerian-Lagrangian transition of Eulerian blobs based on the diameter of each blob with the following properties:
- Minimum Blob Diameter
  Eulerian blobs with diameters greater than this value will transition to the Lagrangian phase. If this value is set to 0, all the blobs which have smaller diameter than the maximum blob diameter will transition.
- Maximum Blob Diameter
  Eulerian blobs with diameters smaller than this value will transition to the Lagrangian phase.
Blob Shape Criterion
Defines the transition of Eulerian blobs based on blob sphericity and inertia tensor eigenvalue ratio. With this criterion, transition is only allowed for blobs that are shaped close to a sphere with the following properties:
- Minimum Blob Sphericity
  Eulerian blobs with blob sphericity greater than this value will transition to the Lagrangian phase. Blob sphericity is $ϕ_{i}$ in Eqn. (2637).
- Minimum Blob Inertia Tensor Eigenvalue Ratio
  Eulerian blobs with blob inertia tensor eigenvalue ratio greater than this value will transition to the Lagrangian phase.
Minimum Blob Volume Fraction Criterion
Defines the transition of Eulerian blobs based on the volume fraction associated with the blob cells. This criterion computes the maximum volume fraction $α_{\max}^{k} = \max (α_{i})$ , associated with the Eulerian blob k for cells i. This maximum volume fraction is then compared with a threshold value that you specify—the Minimum Blob Volume Fraction. Eulerian-Lagrangian transition is only allowed for blobs with the maximum blob volume fraction greater than this threshold.
- Minimum Blob Volume Fraction
  Specifies the threshold $α_{u s e r}$ , which is used as a limit in the Eulerian to Lagrangian phase transitioning verification, as given by Eqn. (308). Eulerian blobs with $I_{k} = 1$ are candidates for Eulerian-Lagrangian transition at a given time step:
  Figure 1. EQUATION_DISPLAY
  
  $I_{k} = {\begin{matrix} 1 α_{\max}^{k} \geq α_{u s e r} \\ {0 α_{\max}^{k}}_{} < α_{u s e r} \end{matrix}$
  
  (308)
  You are advised to specify a Minimum Blob Volume Fraction value close to 1. The the default is 0.95.
User Defined Criterion
An optional user defined transition criterion specified with a scalar profile that supports either constant value, field function, tables and user code.

Note

Each criterion returns a value of 1 for the blobs which are candidates for Eulerian-Lagrangian transition and 0 for the blobs that do not meet the criterion conditions. Eulerian-Lagrangian transition takes place only for those Eulerian blobs that satisfy all the criteria set under the Eulerian-Lagrangian Transition Criteria.

Eulerian-Lagrangian Transition Criteria Field Functions

The following field function are available with the Eulerian-Lagrangian Transition Criteria node:

IsTransitioning of [criterion] of [phase interaction]: This stores the results of each transition criterion decision, for all the phase interactions.
Integrated IsTransitioning of [phase interaction]: This gives the integrated results for all the defined transition criteria. A value of 1 indicates which Eulerian blobs will be transitioned to Lagrangian parcels, at any given time-step.