Contact Interface

A contact interface joins two solid regions, which can be from the same continuum or from different continua, or joins a solid region and a fluid region.

The contact interface type is used to permit conjugate heat transfer between the regions. A contact interface can also be used to specify a surface charge at the interface between a gas and a dielectric (non-conducting) material.

It has properties, conditions, values, and a pop-up menu.

Modeling

For conjugate heat transfer, a thermal contact resistance $R$ can be specified. The relation between the heat flux across the contact interface, $\dot{q} ″$ , and the temperature difference, $Δ T$ , is given by:
图 1. EQUATION_DISPLAY

$\dot{q} ″ = \frac{Δ T}{R}$

(79)

Contact Interface Properties

You can use the properties that are listed below to adjust the specifications of a Contact Interface node.

Geometry

Specifies the geometry source option:

Boundaries: The interface is a boundary-mode interface, which is created by selecting two boundaries.
Contacts: The interface is a contact-mode interface. which is defined directly from part contacts.

Boundary-0

Indicates the "fixed" side of the interface (Read Only).

Boundary-1

Indicates the "adapted" side of the interface (Read Only).

Vertices from boundary-1 are projected onto boundary-0. The orientation can be swapped through the right-click action Reverse Orientation.

Contacts

Displays the part surface contacts. When the Geometry property is Contacts, it shows the part surface contacts. Geometry property is Boundaries, it shows no value.

Type

Defines the type of interface. Must be set to Contact Interface

Topology

Defines the connection type between the interfaces:

In-place—uses the in-place topology.
Periodic—uses the periodic topology.
Repeating—uses the repeating topology.

Connectivity

Defines how the boundaries on the two sides of the interface are connected. Either Conformal or Imprinted is available.

Conformal—for interfaces within regions that are discretized using the finite element method. At a direct interface, finite element models require a conformal match between the mesh faces on the boundaries that are connected through the interface.
This connectivity type tries to enforce an exact one-to-one match between the faces on the opposing boundaries.
Imprinted—for interfaces within regions that are discretized using the finite volume method. The imprinted connectivity type leads to intersected faces.

Allow Per-Contact Values

Allows you to define the interface tolerance individually for each contact. Activates the child property Specify by Part Subgroup.

注	This property is only valid for contact-mode boundary interfaces. See also: Contact-Mode Boundary Interfaces.

Close Adjacent Cells

Creates a watertight intersection by fixing the cell connectivity between the interface faces and side faces along common edges.

With this option, the topology-based intersector adds extra edges to eliminate the gap between the sides, which reduces spurious oscillations in physical quantities.

This property is only available when the Direct Intersector of the Interface Manager node is set to Topology-Based and the Connectivity of the interface is Imprinted.

注	Close Adjacent Cells is not compatible with DFBI Motion.

Reset on Relative Motion

When activated, the interface is reset when there is any relative motion between the two sides.
When deactivated, the interface is reset when the relative motion between the two sides exceeds a relative tolerance based upon minimum edge length.

注	This property is only available when the Connectivity of the interface is Imprinted.

Contact Interface Conditions

Energy Source Option

Provides energy source options for the interface.

None: Do not specify an energy source.
Heat Flux: Specifies a user-defined heat flux in W/m².
Heat Source: Specifies a user-defined heat source in W.

Surface Electric Charge Option

Provides surface electric charge options for the interface.

This option becomes available when the Electromagnetism and Electrostatic Potential models are activated in the physics continuum.

None: Do not specify a surface electric charge.
Surface Charge Density: Specifies a user-defined surface electric charge in s-A/m².

External Load

Specifies the method that is used to define the load. Only available for fluid-solid contact interfaces when the Solid Stress model is activated.

Force: Adds a Force node to the Physics Values node, which must be entered as a vector profile.
Pressure: Adds a Solid Stress Pressure node to the Physics Values node, which must be entered as a scalar profile.
Traction: Adds a Traction node to the Physics Values node, which must be entered as a vector profile.

Mechanical Interaction

Specifies the type of contact between the two solid regions.

Small Sliding Frictionless: The contacting surfaces are free to slide over each other, however movement is prohibited normal to the interface. The shear stress at the contact interface is equal to zero, and the normal forces are equal and opposite. No additional node is added to the tree.
Bonded: The contacting surfaces undergo continuous displacements. If the solid regions are different materials, discontinuities in the strains are preserved across the material interface. No additional nodes are added to the tree.

Thermal Specification

Specifies the thermal conditions at the interface.

Conjugate Heat Transfer: This option adds a Contact Resistance node to the Physics Values node. The temperature at the interface is determined from the heat transferred through the interface.
Specified Temperature: This option adds a Static Temperature node to the Physics Values node. The temperature at the interface is the same for both parent boundaries, as indicated by the selected profile.

Contact Interface Values

Intersection

Specify by Part Subgroup: Specifies sub-grouping for contact-mode boundary interfaces to set up independent intersection properties. See also Contact-Mode Boundary Interfaces and 调整交界面相交容差（基于几何的方法）.

The remaining properties depend on the setting for the Direct Intersector property. This property is set on the Interfaces node (see Interfaces Properties):

Geometry-Based (Legacy)

This Direct Intersector option activates:

Geometric Tolerance: Specifies the maximum projection distance of adapted vertices onto the fixed side in terms of a fraction of minimum local edge length around each vertex. For more details, refer to 调整交界面相交容差（基于几何的方法）.

Topology-Based with Connectivity Imprinted

Match Outer Boundary: when activated, indicates that the interface boundaries are expected to fully overlap on large-scale topological features. Activate this option only when you expect a complete match of the two boundaries of an interface.
By default, this property is deactivated.
Projection Tolerance: maximum orthogonal projection distance in terms of a fraction of local element diameter. Places a limit on how the vertices of the adapted side get projected onto the fixed side. In cases where the two interface boundaries are separated by greater distances, you can increase the Projection Tolerance value to get fewer remainder faces.
By default, the tolerance is set to 0.2.
Angle Threshold: maximum angle (deg) by which the intersector identifies large-scale features that are mapped from the adapted side onto the fixed side. To preserve sharper features, specify a smaller Angle Threshold value. If the boundary meshes have spurious defects, you can specify a larger value.
By default, the value is set to 45 deg.

Topology-Based with Connectivity Conformal

Conformal Tolerance: detects conformal faces in terms of a fraction of local element diameter. If too many conformal faces are matched then you can lower the value. If too few, it can be increased.
By default, the value is set to 0.01
Nonconformal Tolerance: detects non-conformal faces in terms of a fraction of local element diameter. If too many non-conformal faces are matched then you can lower the value. If too few, it can be increased.
By default, the value is set to 0.01

Contact Resistance

The value of the resistance to conduction through the interface. It is entered as a scalar profile. If a field function defines the value and the Ignore Boundary Values property on the field function is ticked, the function is computed using data from the cell next to the boundary. Contact resistance is specified in units of

m^{2} \cdot K / W

(the default) or equivalents. See Eqn. (1684).

Heat Flux

Specify the heat transferred per unit area. Activated when the Energy Source Option is set to Heat Flux. Heat flux is specified in units of W/m² (the default) or equivalents.

Heat Source

Specify the total rate of heat transfer through the interface. Activated when the Energy Source Option is set to Heat Source. Heat source is specified in units of W (the default) or equivalents.

Static Temperature

Specify the temperature at the interface. Activated when the Thermal Specification option is set to Specified Temperature.

Surface Charge Density

Specify the surface charge density profile. Activated when the Surface Electric Charge Option is set to Surface Charge Density. The surface electric charge is specified in units of s-A/m² (the default) or equivalents.