Setting Morpher Boundary Properties

Specify the morpher properties on the boundaries of your simulation.

You set the morpher boundary properties in addition to the physics boundary conditions (such as velocity inlets, walls and symmetry planes). Moving boundaries must be assigned displacement settings; other boundaries can be set as fixed, constrained, or floating.

Create any field functions or read in any tables that you intend to use for prescribing motion on boundaries (described in the next step).

Note This step is not required when the morphing boundary conditions come from an internal source (such as solid deformation).
Identify the boundaries for which you supply a displacement. Within Regions > [region] > Boundaries, for each moving boundary:
1. Select the [boundary] > Physics Conditions > Morpher Specification node and set Specification to Displacement.
2. Select the Physics Conditions > Morpher Displacement Specification node and set Specification to one of the following options:
  - Total: applies a displacement to boundary vertices as a linear total amount per time-step relative to the initial position of the same vertices at time zero
  - Incremental: applies a linear displacement to boundary vertices as an amount relative to the vertex positions of the previous time-step or iteration
  - Internal: applies a displacement field that is computed internally by other models in Simcenter STAR-CCM+ and is treated as an incremental displacement
  - Grid Velocity: applies a displacement that is calculated from the velocity that you provide for the given time-step. This option only appears if the flow is set to unsteady by choosing the appropriate time model in the physics continuum
  - Co-ordinate Offset: applies a displacement that is calculated from a vector profile with respect to the chosen coordinate system
3. For all options (apart from Internal), Simcenter STAR-CCM+ adds a corresponding value node within Physics Values. Select this node and define the displacement or velocity (see Morpher Boundary Condition Reference).
4. If your application requires that the cell height of the prism layer adjacent to the moving boundary remains constant, then activate Rigid Prism Layer Morphing within [boundary] > Physics Value > Rigid Prism Layer Morphing. This node appears for boundaries with Fixed or Displacement morpher specification. (see Morpher Boundary Condition Reference).

Identify the boundaries where the mesh should be constrained to slide across a plane or surface as it deforms (for example a moving piston in contact with a cylinder wall). For each of these boundaries:

Select the [boundary] > Physics Conditions > Morpher Specification node and set Specification to Constraint .

Select the Physics Conditions > Morpher Constraint Specification node and set constraint to one of the following options:

Boundary Plane: mesh vertices can slide along the boundary, which must be planar

Fixed Boundary Plane: as for the Fixed morpher specification, except that the RBF morpher does not take control points from the boundary. This difference saves computational effort.

Note	Be aware when using Fixed Boundary Plane as it effectively produces an infinite plane that can intersect other parts of the grid unintentionally restricting the morphing at these points. This option is not recommended for the BSpline morpher

Initial Boundary: the boundary vertices slide along the original boundary vertices at time zero. These act as a guide surface, which can be of any arbitrary shape.
Part Surface: the boundary vertices slide along a part surface that used is used as a guide surface, which can have any reasonable position and shape. The part surface can already exist as a feature of the model, or it can be produced for the purposes of providing a guide surface. There is no need to construct a part so as it coincides with the original region geometry.

For all options, apart from Initial Boundary, complete the Constraint setup by choosing from the following options:
- Boundary Plane: Within Morpher Plane Constraint Specification, choose whether to activate Use Triangulated Plane, which allows Rigid Body Motion to be applied to the boundary
- Fixed Boundary Plane: For the RBF morpher, select Physics Values > Morpher Plane Options and set the Damping Factor and Continuity Level as appropriate to you simulation.
  There are no options that need to be set for the BSpline morpher
- Part Surface: Select Physics Values > Part Surface and choose the part surface along which vertices must slide.
  Note You may also apply additional rigid body motions to a Part Surface
Symmetry planes are automatically specified as Constraint and are designated as Boundary Planes.

Identify any boundaries whose vertices should float in response to the mesh deformation. For each floating boundary:
1. Select the [boundary] > Physics Conditions > Morpher Specification node and set Specification to Floating.

All remaining boundaries have their Morpher Specification set to Fixed by default.

If you are using the RBF morpher—for each of the remaining (fixed) boundaries, select the [boundary] > Physics Values > Morpher Thinout Factor node and adjust the Vertex Thinout Factor. If the shape of the boundary changes rapidly, leave the factor at a value close to 1.0. If the boundary shape is smooth, or almost planar, reduce the factor to 0.5 or less.