Adjusting the Interface Intersection Tolerances (Geometry-Based Method)

When the geometry-based intersector is selected, the property Geometric Tolerance limits the distance by which vertices on the adapted boundary can move to match vertices, edges, and faces on the fixed boundary.

The Geometric Tolerance is specified as a fraction (from 0 to 1) of the length of the smallest edge attached to the vertex. The default value is 0.05 (which is 5% of the smallest attached edge length).

For each vertex on the adapted boundary of the interface, this tolerance is used to define the radius of a cylindrical volume within which the vertex moves during intersection. This cylindrical volume is centered on a projection vector that has the vertex as its origin, and whose direction is computed from the normals of adjacent faces. The length of the cylinder is ten times its radius.

To set the intersection tolerance:

  1. To select the geometry-based method for the interface Direct Intersector, select the Interfaces node from the simulation tree and set Direct Intersector to Geometry-Based (Legacy).
  2. Select the Interfaces > [interface] > Physical Values > Intersection node and set Geometric Tolerance.


For contact-mode boundary interfaces, you can set independent tolerances for the contacts that are assigned to the interface. See also: Contact-Mode Boundary Interfaces. With this approach, you create groups of contacts and set the tolerance independently for each group. To create groups of contacts:
  1. Select the relevant Interfaces > [interface] node and activate Allow Per-Contact Values.
  2. Expand the [interface] > Contact Subgroupings > Subgrouping 1 node.
    By default, all contacts are grouped under a single subgroup. To create more subgroups, right-click the Subgrouping 1 node and select New.
To assign contacts to a subgroup:
  1. Select the Subgrouping 1 > [Subgroup] node and set Objects to the relevant contacts.
Specify the tolerance for each subgroup:
  1. Select the [interface] > Physical Values > Intersection node and activate Specify by Part Subgroup.
  2. Select the relevant Intersection > By Contact Subgroup > [Subgroup] node and set the Geometric Tolerance.
If the interface creation results in unmatched faces, you can try changing the interface intersection tolerance:
  1. Before you change Geometric Tolerance, reset the interface.
  2. Increase the Geometric Tolerance.
    The example below shows a case where the interface creation was not 100% successful, as it left unmatched faces (shown in gray) in the interface:

    In this case increasing the tolerance value corrected the fault and allowed all of the faces to be matched: