Obtaining Whole Domain Reports through Idealizations

Idealizations operate on reports in the same manner as transforms operate on displayers in a visualization scene. When you activate the Account for Idealization property on reports that have it, Simcenter STAR-CCM+ applies the properties of the related idealizations to the regions referred to by the report. In this way, the reported value accounts for the whole domain.

For example, if you have an axisymmetric region and you activate Account for Idealization on a report for mass flow through a region boundary, Simcenter STAR-CCM+ automatically multiplies the boundary mass flow value by 2*PI.

When calculating key metrics for a turbomachine, such as mass flow and force, it is desirable to report values for the whole machine, not only the blade passage model. A typical turbomachinery use case involves reporting of:

• Mass flow through the inlet, outlet, and each inter-row interface
• Mass flow through the cooling inlet, purge flow inlet, or leakage outlet
• Mass flow imbalance (outlet mass flow – inlet mass flow)
• Torque
• Axial force

In the current release of Simcenter STAR-CCM+, there are three basic types of idealization:

Periodic

Periodic interface idealizations are created whenever periodic interfaces are detected in a boundary interface. For details about periodic interfaces, see Periodic Interface Topology. For reports using this idealization, only periodic boundaries are supported as inputs.

Creation and deletion of a periodic interface idealization is tied to the Topology property of a boundary interface. Applying the Periodic option creates the associated periodic interface idealization, while selection of any other option results in deletion of the associated periodic interface idealization, if one exists.

Extrusion

Extrusion idealizations provide a non-unit thickness for objects modeled with 2D physics. For 2D axisymmetric, extrusion idealizations apply the 2PI multiplier. Linear, helical, and axisymmetric extrusions are supported.

An extrusion idealization is automatically created when you associate a region to a physics continuum that specifies a 2D or an axisymmetric model. One extrusion idealization is created for each region.

Negative extrusion thickness represents extruding the 2D region in the -Z direction, while positive thickness represents extruding it in the +Z direction.

Valid inputs for the extrusion thickness are constant values and parameter values. Reports and field functions are not valid as inputs.

There are two types of extrusion idealization:

• Axisymmetric extrusion idealization (if the region is assigned to a continuum that has an Axisymmetric model)
• Linear extrusion idealization (if the region is assigned to a continuum that has a Two-Dimensional model)

Symmetric

Symmetry idealizations are created whenever Simcenter STAR-CCM+ detects regions that contain a symmetry boundary.

For reports using this idealization, only symmetry boundaries are supported as inputs, provided the following conditions are met:

• In the region that generates the idealization, the symmetry boundaries fall into no more than three distinct planes.

  However, multiple boundaries can share the same plane. This situation can exist, for example, if you have two different part surfaces cut by the same geometric symmetry plane, and you assign those two part surfaces to different boundaries.

• For a region containing multiple symmetry boundaries, the set of planes defined by these boundaries is orthogonal.

This idealization affects different quantities as follows:

• Scalar quantities are multiplied by the number of repeats, which is $2^n$ , where n is the number of reflection planes.
• For each reflection plane, forces have their in-plane components doubled and their out-of-plane component zeroed. Thus for one reflection plane the force parallel to the reflection plane is doubled and the force perpendicular is zeroed; for two reflection planes the force parallel to the intersection line between the planes is quadrupled, and the force perpendicular to the intersection line is zeroed; and for three reflection planes all three components of force are zeroed.
• For each reflection plane, moments have their in-plane components zeroed and their out-of-plane component doubled. For two or more reflection planes, this results in all components of moment being zeroed.

Compositions of Idealizations

If one of the three idealization types on its own is not enough to reconstruct the whole domain, a composition of idealizations is applied. While Simcenter STAR-CCM+ creates these compositions automatically, you can also construct your own. If necessary, you can re-order compositions that Simcenter STAR-CCM+ creates.

One use-case in which a manual re-ordering of idealizations is required is when there are regions in the simulation that require different idealizations. For example, a simulation might have one region modeled as a 2D 60 degree wedge whereas the other region is modeled as a 2D full circle. Both regions represent a 3D cylindrical domain. To reconstruct the 3D domain, the first region requires a composition of periodic repeat idealization followed by an extrusion idealization. The second region requires only an extrusion idealization. In this case you could flip the default ordering (Periodic Repeat Idealization > Extrusion Idealization to Extrusion Idealization > Periodic Repeat Idealization and apply region 1 to the periodic repeat idealization and region 2 to the extrusion idealization.

To remove a nested idealization node from within its parent node, drag it onto the Idealizations node.

Of the report types that can be used with idealizations, only the following work with idealization composition: Center of Loads, Force, Magnetic Force, Magnetic Torque, Mass Flow, and Moment.

To use idealizations: