Large Scale Interface Detection Model Reference

This model enables the detection of large interface cells and the calculation of the interfacial distance in those cells. This feature allows the implementation of special treatments and transfer terms between the phases including, for example, interphase heat transfer, mass transfer, and turbulence damping. The detection of a large interface also enables the use of a compressive scheme for volume-fraction in the vicinity of the large interface.

This model is required when the Large Scale Interface Turbulence Damping model uses the Geometric Reconstruction method for specifying the interface distance. That is, all cases except the following:

Both phases have the K-Omega turbulence model activated, and both phases use the Egorov turbulence damping method and the Cell Volume interface distance specification method.
One phase has the K-Omega turbulence model activated, and uses the Egorov turbulence damping method and the Cell Volume interface distance specification method. The other phase is laminar.

The Large Scale Interface Detection model allows you to perform implicit multi-stepping with the Volume Fraction Solver. If the global time-step size is small enough to resolve physics sufficiently well, but too large to fulfill HRIC stability requirements, implicit sub-stepping with an appropriate number of sub-steps is a good approach to reduce the global time-step size. With this option, a fixed user-specified number of implicit sub-steps are used for the solution of the volume fraction transport equation. The implicit multi-step solver is not bound to a strict CFL condition and volume fraction transport does not limit the global time-step size.

表 1. Large Scale Interface Detection Reference
Theory	See Interface Detection.
Provided By	[phase interaction] > Models > Optional Models
Example Node Path	[phase interaction] > Models > Large Scale Interface Detection
Requires	Physics continuum selections: Material: Multiphase Multiphase Model: Eulerian Multiphase (EMP), Mixture Multiphase (MMP) (Automatically activates: Multiphase Interaction, Gradients.) A Phase Interaction model is required. Ror Eulerian Multiphase simulations, the Multiple Flow Regime Topology phase interaction is required. Phase interaction selections: Optional Models: Large Scale Interface Detection.
Optional Models	If you want to apply automated time-step control, select Adaptive Time-Step and set the Adaptive Time-Step solver properties. Use the LSI Smoothed Convective CFL Condition time-step provider when Adaptive Interface Sharpening (ADIS) scheme for Volume Fraction Convection is selected. Adaptive Mesh—Use this model if you want to refine the mesh locally and select user-defined refinement criteria that query the flow solution as the simulation runs to control solution fidelity. Select the Lsi Mesh Refinement criterion to control adaptive mesh refinement with respect to the interface between phases for Eulerian Multiphase (EMP). See Adaptive Mesh Refinement.
Properties	See Large Scale Interface Detection Properties.
Activates	Solvers	Implicit Multi-Stepping. See Volume Fraction Solver Properties.
	Field Functions	See Large Scale Interface Detection Field Functions.

Large Scale Interface Detection Properties

Primary Criterion of Interface Detection

The primary criterion

C_{1}

in Eqn. (2313). The default value is 5. The large interface detection becomes more stringent as the primary criterion

C_{1}

is reduced. For

C_{1} < 1

, no cell will be marked as large interface cell as the interface detection condition Eqn. (2313) is not satisfied. Therefore, to turn off interface detection in a desired zone, you set Primary Criterion of Interface Detection to a value below 1 for that zone.

The following methods are available:

Method

Constant—the specified primary criterion for interface detection is applied to all the cells.
Field Function—allows you to disable interface detection in a prescribed zone. You define a field function to specify the zone where Primary Criterion of Interface Detection is set to a value below 1 for those cells. The example images below show the result of when large interface detection is turned off for cells with $x > 0.5$ by setting $C_{1} < 1$ .

Secondary Criterion of Interface Detection

The secondary criterion $C_{2}$ in Eqn. (2314).

This value is used to reduce the raw interface to a one-cell-thick interface.

Number of Cell Layers for Interface Band

Specifies the thickness of the Large Interface Marker Band which represents the large scale interface. The default value is 2 cells.

Large Scale Interface Detection Field Functions

Large Interface Marker of [phase interaction]: A single-cell-thick layer that represents the Large Scale Interface in the phase interaction.
Large Interface Marker Band of [phase interaction]: A marker band that is created by including the neighbouring cells of the Large Interface Marker. The thickness of this band is governed by the value that is specified in the Number of Cell Layers for Interface Band property.