Overset Interface Reference

Interface Manager Properties

The following properties appear on the Interfaces node when overset meshing is active:

Contact Selection Priority

Defines a priority list of interfaces if you assign interfaces from contacts under the Geometry node through dynamic queries. For more details refer to Using Query-Based Selection.

Overset Hierarchy

Sets the priority of the overset regions during the hole-cutting process. Between two overset regions, the one with higher priority controls the hole-cutting. For more details and examples refer to 重叠层次结构.

Direct Intersector

Specifies the method that Simcenter STAR-CCM+ uses to initialize direct interfaces (that is, interfaces not with Indirect connecitivity. It could be with Imprinted, Conformal or Metrics-Based connectivity). The available options are:

Geometry-Based (Legacy): default option. Simcenter STAR-CCM+ computes the intersection of interface boundaries using a geometry-based algorithm. This algorithm uses a single parameter based on a fraction of the minimum edge length around each vertex.
Topology-Based: Simcenter STAR-CCM+ computes the intersection of interface boundaries using a topology-based algorithm. This algorithm identifies large-scale topological features based on detecting conformal and non-conformal faces.

Overset Mesh Interface Properties

Verbosity: Specifies how much extra information is provided in the Output window while the simulation is running. The default is to provide no additional information (None). Increasing verbosity is helpful when you are troubleshooting problem cases.
Region-0: Identifies the Overset region (read-only) with higher priority. The priority controls the hole-cutting between Region-0 and Region-1.
Region-1: Identifies the Background region or the Overset region with lower priority (read-only). The priority controls the hole-cutting between Region-0 and Region-1.
Zero Gap: Indicates the zero gap property (read-only) of the overset interface. Checked when the interface is an ZeroGap interface.
Type: Defines the interface type as Overset Mesh Interface.

Interpolation Option Property

Option

Controls the overset mesh interpolation. Simcenter STAR-CCM+ couples the solution in the overset and background regions by interpolating donor cell values to provide data for acceptor cells.

The available options are as follows:

Linear: Linear for 2D and 3D meshes (Default).
Distance weighted: Weighted based on distances to the four nearest neighbors.
Linear Quasi2D: Linear for 3D meshes with only one layer of cells.
Least Square: Least square for 2D and 3D meshes.

Overset Hole Cutting Options Properties

Alternate Hole Cutting

Determines which hole-cutting approach is used.

There are two hole-cutting approaches in Simcenter STAR-CCM+:

Hole-Cutting Approach	Applicable Overset Settings
Layered Approach	This approach executes a flood filling starting from overset boundary. It is activated internally when the region topology is two-leveled - one overset region and one background region. the overset interface is not a ZeroGap interface. the Overset Topology: Piston is absent the Dynamic Overset Option: Active is absent
Global Approach	This approach does more individual checks for each cells and marks more inactive cells from the background region. It is activated when the overset settings differentiate from the ones mentioned above. the Alternate Hole Cutting is activated explicitly at the overset interface.

Hole-Cutting Approach

Applicable Overset Settings

Layered Approach

This approach executes a flood filling starting from overset boundary. It is activated internally when

the region topology is two-leveled - one overset region and one background region.
the overset interface is not a ZeroGap interface.
the Overset Topology: Piston is absent
the Dynamic Overset Option: Active is absent

Global Approach

This approach does more individual checks for each cells and marks more inactive cells from the background region. It is activated when

the overset settings differentiate from the ones mentioned above.
the Alternate Hole Cutting is activated explicitly at the overset interface.

When you create an overset interface, you can first use the default layered approach. This approach is computationally more efficient than the global approach and suitable for most cases. If the overset interface creation gives overset intersector errors, you can activate the Alternate Hole Cutting to use the global approach. The global approach is more robust when you run the simulation on many cores. The global approach is more sensitive to non-standard overset topologies where the overset boundary does not form a closed surface (see Overset Topology).

Close Proximity

Activate this option when there is a narrow gap between the moving body and a boundary, such as a wall. This option allows more active cells in the overset mesh between the moving body and the boundary. This feature helps to prevent mesh intersector failure when the overset region overlaps the physical boundaries of the background region.

When the moving body goes close to a boundary, the overlapping region of the overset mesh can extend over the boundary. Normally any cell in the overset mesh that has a vertex outside the boundary (and therefore outside the background region) is deactivated. However, when this option is activated, those cells remain active as long as the cell centroid is within the background region. The cell is deactivated only when the cell centroid is outside the boundary.

Prism Layer Shrinkage

When activated, shrinks the prism layers when moving objects enclosed by wall boundaries approach each other closely and form a small gap. See also Setting Up Prism Layer Shrinkage.


Interface Type	Shrinkage Option	Corresponding Physics Value Nodes
Overset Mesh Zero Gap Interface Applicable when regions approach very closely or make contact.	Minimum Gap Distance	Minimum Gap Distance Prevents prism layers from shrinking further when this minimum gap distance is reached. When the prism layers stop shrinking while the wall boundaries keep approaching each other, the Overset Assembly process detects that the distance between the two zero gap wall boundaries is less than the default value of three cell layers, and the cells in the gap become inactive. Flow is prevented through the inactive cells and the gap effectively closes. Therefore, you can use this setting to trigger the closing of an overset mesh zero gap interface at a specified gap distance.

Treat Error as Warning

When activated, overset errors that occur during an overset simulation are treated as warnings. Interpreted as a warning, an overset error does not prevent the simulation that is run from continuing. This option is useful for detecting and investigating overset errors without stopping the simulation. These overset warnings are displayed in the output window.

To make the overset warnings more prominently visible, right-click in the white space of the output window and deselect Information.

Overset Mesh Interface Right-Click Actions

Swap Regions: The Swap Region action swaps the priority of the two interfaced regions in the overset hole-cutting process. As an example assume that the associated regions of Overset Mesh 1 are Region-0 (prioritized) and Region-1 (secondary). To swap the regions, you would right-click the Interfaces > Overset Mesh 1 node and select Swap Regions. As controlling the hierarchy for numerous interfaces is difficult, the better approach is to use the overset hierarchy list. See also: Change the current Overset Hierarchy.