Mapped Contact Interface

The Mapped Contact Interface is an indirect interface type between fluid/solid and solid/solid boundaries that allows for a non-conformal mesh.

This interface type is a variation of contact interface type applicable to indirect interfaces. The mapped contact interface relies on an indirect association between faces of the interfacing boundaries, for data mappers, rather than the imprinted connection used for direct interfaces.

The Mapped Contact Interface is created on the volume meshes generated by the meshing process. When the interface is created from two boundaries, two new interface boundaries are automatically added. The original boundaries from which the interface is created are not destroyed.

Each face of the original boundary is linked with a group of faces on the opposing boundary using a proximity-based algorithm. Once the associativity of all the faces on the original boundary has been processed, the faces are split into an associated face-set and a disassociated face-set.

The associated face-set is transferred on to the interface boundary, while the unassociated face-set is retained on the original boundary. This is analogous to the creation of a direct interface, except that this process does not result in any new faces.

The main advantage of a Mapped Contact Interface is that it allows for a non-conformal mesh across the interface. This type of mesh is desirable in cases where the interfacing boundaries have different mesh resolutions. For instance, the heat conduction in the solid region requires a coarser mesh compared to resolving the boundary layer in the fluid domain. By precluding the need for imprinting, this approach retains the high quality of the originally created mesh and also reduces the resultant face count. A co-product of this approach is better accuracy in computing the face gradients as well as better quality mesh for visualization. This approach is also better suited for cases where the geometric features are not equally resolved on either side of the interface. While imprinting may leave more non-intersected faces, this technique can find an associated face on the opposing boundary more robustly.

When a boundary of a Mapped Contact Interface is attached to a region for which the overset method is applied, the data across the interface is only exchanged between active cell faces and the boundary faces on the other side of the interface. A boundary cell face is considered active when its associated cell is an active cell. The inactive cells of the overset region do not participate in the interface data exchange.

The Mapped Contact Interface has properties, conditions, values, and a pop-up menu.

Mapped Contact Interface Properties

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

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.
Type: Defines the type of interface. Must be set to Mapped Contact Interface.
Topology: Defines the connection type between the interfaces. Only the Indirect type is possible.
Connectivity: Defines how the boundaries on two sides of the interface are connected. Only Mapped connectivity is possible.

Mapped Contact Interface Conditions

The following physics conditions depend on the physics models that are active in the physics continua.

Energy Coupling Option

Specifies implicit or explicit coupling of the energy equation across the interface. Implicit is the default. The Explicit option results in the mapping of thermal fields across the two interface boundaries. The Explicit method for the Energy Coupling Option is available only when the interface connects a fluid and a solid region. See Explicit Energy Coupling Thermal Boundary Conditions.

For coupling finite volume Fluid to finite volume Solid Energy models, use Implicit when the time scales on fluid and solid sides are similar. If they are very different, use Explicit.
For coupling finite volume Fluid and finite element Solid Energy models, use Explicit.
For coupling a fluid film shell region to a solid region, only the Explicit option is available.
For relative mesh motion between fluid-side and solid-side mesh, use Implicit when that option is available.

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.

Mechanical Interaction

Specifies the type of contact between the two solid regions.

Bonded—The contacting surfaces undergo continuous displacements. If the solid regions are different materials, discontinuities in the strain are preserved across the material interface.
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.

Explicit Energy Coupling Thermal Boundary Conditions

When the Energy Coupling Option is set to Explicit, the following conditions apply on the two interface boundaries:

Fluid interface boundary: Temperature thermal boundary condition
Solid interface boundary: Convection thermal boundary condition

Find each at Regions > [region] > Boundaries > [mapped contact boundary].

Explicit Energy Coupling Thermal Boundary Physics Values

The following boundary physics values are set automatically according to the Time Averaging Option selection for the solid interface boundary (for Ambient Temperature and Heat Transfer Coefficient) or the fluid interface boundary (for Static Temperature). The profile methods map the corresponding values from the interface boundary on the other side of the interface to this interface boundary.

Time Averaging Option

Sets whether time-averaging occurs before mapping across explicit mapped interface boundaries, and if so, what kind of averaging.

When the Energy Coupling Option underneath the Mapped Contact interface is set to Explicit and an unsteady time model is selected for one continuum, the Time Averaging Option then becomes available for the two associated interface boundaries.

Option	Corresponding Value Nodes
Instantaneous No time averaging (default)	None.
Sliding Window Average Time average of mapped fields over the specified number of previous samples.	Sliding Time Averaging Parameters Sliding Sample Window Size The number of samples to be averaged. Sampling Delta Time The minimum time between samples used for calculating the average.
Running Average Time average of mapped fields for samples after the specified sampling delay time.	Running Time Averaging Parameters Sampling delay The minimum time before sample collection starts, for averaging, to avoid initial transients.

注	Explicit Mapped Contact Interface is currently not compatible with mesh motion (rigid body motion, overset, etc.). Due to relative movement between associated interface boundaries, whenever the interface is reset, both instantaneous and time-averaged fields prepared for mapping are cleared.

Ambient Temperature

Automatically set for the solid interface boundary. Does not map the values directly but uses the Heat Transfer Coefficient and either the Mapped Reference Temperature (for no time averaging) or the Mapped Averaged Reference Temperature (for time averaging), computed from mapped values of Boundary Heat Flux and Heat Transfer Coefficient.

Heat Transfer Coefficient

Automatically set for the solid interface boundary. When the Laminar Flow model is selected, uses either the Mapped Local Heat Transfer Coefficient method (for no time averaging) or the Mapped Averaged Local Heat Transfer Coefficient method (for time averaging).

When the Turbulent Flow model is selected, the default is set to either the Mapped Specified Y+ Heat Transfer Coefficient method (for no time averaging) or the Mapped Averaged Specified Y+ Heat Transfer Coefficient method (for time averaging). This can be changed to the Mapped Local Heat Transfer Coefficient method (for no time averaging) or the Mapped Averaged Local Heat Transfer Coefficient method (for time averaging).

Static Temperature

Automatically set for the fluid interface boundary. Uses the Mapped Temperature method.

Mapped Contact Interface Values

Some of the following physics values depend on the physics models that are active in the physics continua.

Mapped Interface Tolerance

Activates the search algorithm and specifies tolerances that the algorithm uses to find the neighbors to the cells.

Proximity Check—When activated, the minimum proximity check occurs.
Minimum Proximity—The relative distance (based on cell size) to the target cell. 1 is equivalent to 100%.
Normal Directions check—When activated, the normal direction check occurs.
Minimum Angle—The angle, in degrees, between the source and target face normals. When the minimum angle is 0, the two normals point in the same direction, when 180, the normals point toward each other.

For contact-based interfaces, you can set these properties independently for each of the contacts that are assigned to an interface. To specify tolerances per contact, or group of contacts, activate the Specify by Part Subgroup property. The procedure for setting per-contact values for mapped interfaces is similar to the procedure for setting per-contact values for direct interfaces. For more information, see Adjusting the Interface Intersection Tolerance.

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 activated, the function is computed using data from the cell next to the boundary identified by the Boundary-0 property of the interface.

Dimensions—specify the resistance in units of $m^{2} \cdot K / W$ or similar. Read Only.
Method—specify the input method type from Constant, Field Function, Table, or User Code.

Heat Flux

Specifies the heat transferred per unit area. It is activated when the Energy Source Option is set to Heat Flux.

Dimensions—specify the heat flux in units of W/m² or similar. Read only.
Method—specify the input method type from Constant, Field Function, Table, or User Code.

Heat Source

Specifies the heat transferred. It is activated when the Energy Source Option is set to Heat Source.

Dimensions—Specify the heat source in units of W or similar. Read only.
Method—Specify the input method type from Constant, Field Function, Table, or User Code.

Interpolation Stencil

Specifies the method that Simcenter STAR-CCM+ uses for connecting the mesh faces on the two sides of the interface:

Compact—This scheme builds a connectivity map by finding the nearest neighbor of a face on the opposite side of the interface. The scheme includes a symmetry specification step which can add extra faces to the stencil (that is, if a face on boundary 0 sees a face on boundary 1, then the face on boundary 1 will also see the face on boundary 0). After the connectivity map is created, face area ratios are used to define the interpolation weights.
Imprint—This scheme builds a connectivity map by finding all the faces on the opposite side of the interfaces that overlap with a face.

Compared to the Compact method, the Imprint method results in better connectivity that leads to more accurate enforcement of physics conditions at the interface. However, the Compact stencil is more tolerant to mesh irregularities, whereas the imprint process can fail in the case of poor quality meshes.

Field Functions

Mapped contact interfaces activate field functions that allow you to assess the quality of intersection at the interface:

Mapped Facet Count: Indicates how many faces of the opposing boundary are identified as connections. Available for all boundaries that participate in a mapped interface. For a mapped interface boundary, you can visualize the total number of connections by selecting the corresponding boundary node under Representations > Volume Mesh > Finite Volume Regions > [Region] > Boundaries > [Boundary].
Mapped Facet Area Match: Indicates the ratio between the sum of overlap areas of the partner faces and the area of the current face. A value close to 1.0 indicates that interface initialization was effective. The value can deviate largely from 1.0 for partially overlapping faces.