Geometry Parts

A geometry part is a collection of surfaces and curves that you wish to address as one object. Parts surfaces and curves can be defined by CAD data or discrete (surface mesh) data, depending on the type of geometry part. A single object is referred to as a leaf-level part; a collection of geometry parts is referred to as a composite part. A surface can contain one or more sets of faces and a curve can contain one or more sets of edges.

Geometry parts provide an efficient way of organizing geometry data in preparation for meshing. Not all parts present in a simulation are required for a given meshing process. You can assemble a particular geometry combination by selectively assigning parts to regions.

Leaf-level parts can be combined to form composite parts, and composite parts can be exploded to their component parts.

Within a given composite part, the leaf-level parts must have unique names although these names can be reused in other composite parts.

Geometry parts, part surfaces, part curves, and part contacts, all have unique indices that you can use in field functions.

Geometry Part Types

The following parts are classified as leaf-level parts (so-called due to their location as the outermost nodes in any part hierarchy):

3D-CAD Parts—parts that originate from 3D-CAD in Simcenter STAR-CCM+ and contain CAD data. They still retain a connection to the originating 3D-CAD body such that if a design parameter is changed then the 3D-CAD part can be updated to match the design change that was made.
CAD Parts—parts that are imported into Simcenter STAR-CCM+ and contain CAD data. Typically, these parts originate from external CAD packages and contain neutral, native, or XML CAD data. Once imported into the geometry part node, they are considered static topologies although they can be transformed and duplicated if necessary.
Mesh Parts without 3D-CAD Association—parts that are imported into Simcenter STAR-CCM+ and contain surface mesh data (discretized surfaces). The tessellation density of these parts cannot be modified after import, although you can modify the part manually using the surface repair tool.
Mesh Parts with 3D-CAD Association—faceted parts that originate from 3D-CAD in Simcenter STAR-CCM+ and contain light-weight (faceted) data only. Once imported into the geometry part node, they still retain a connection to the model in the 3D-CAD modeler.
Shell Parts—parts that are modeled as shells. A shell part has two part surfaces—a front and a back surface. In cases where you want to flip the front and back designation, you can use the Orientation property of the shell part to specify a point that lies beyond the front side of the shell. For more information, see Creating Shells from Parts.
Shape Parts: Block, Cone, Cyclinder, and Sphere—simple shape mesh parts that are created in Simcenter STAR-CCM+. You can edit the dimensions of a shape part at any time. See Creating Shape Parts.
Operation Parts—parts that are the result of part operations in Simcenter STAR-CCM+. See Mesh Operations.

Part Surfaces and Part Curves

A part surface is a collection of patches which make up the shape of the leaf-level part geometry. In order to be valid for use with the meshing tools, each part must be composed of at least one part surface. Patches on part surfaces are composed of a collection of mesh faces. A patch can only belong to one part surface, although a part surface can contain more than one patch. You can control which part surface a patch belongs to using the split by patch feature. See Splitting by Patch.

A part curve is a collection of feature edges which define the sharp edges and features of the leaf-level part geometry. The choice of whether the part curve contains feature edges is made during the import process and is arbitrary depending on the requirements of the geometry.

Part surfaces are stored under the Parts > [geometry part] > Surfaces node and are represented by the

icon. The star on top of the icon indicates that the entity is the default part surface. To set the entity to default, right-click part surface and select Set Default.

Part curves are stored under the Parts > [geometry part] > Curves node and are represented by the

icon. A shell part has a perimeter curve, which is represented by the

icon, as well as interior curves, which are represented by the

icon. The star on top of the icon indicates that the entity is the default part curve. To set the entity to default, right-click part curve and select Set Default.

Part Curves Option Dialog


Mark Sharp Edges	When activated, edges that occur between two faces that meet at an angle equal to or less than the specified Sharp Edge Angle are marked as part curves.
Sharp Edge Angle	The angle above which all edges are marked as part curves when marking sharp edges. If you set the angle to 50, then any angle above 50 is marked as a part curve and any angle below 50 is not.
Mark Free Edges	When activated, all free edges are marked as part curves.
Mark Non-manifold Edges	When activated, all non-manifold edges are marked as part curves.
Mark Patch Perimeters	Marks all edges that surround a patch (a collection of mesh faces on a part or region) as part curves.
Mark Part Surface Perimeters	Marks all edges that surround a part surface (a collection of patches on a geometry part) as part curves.
Mark Boundary Perimeters	Marks all edges that surround a boundary as part curves.
Automatically Fix Errors	Automatically fixes minor errors related to face quality, face proximity, and self-intersection.
Maintain Existing Edges	Keeps edges that are already defined as part curves.

Composite Parts: A composite part is a collection of geometry parts that are grouped together. In Simcenter STAR-CCM+, composite parts have no assembly constraint details, meaning that you cannot constrain the parts with relation to the other parts in the composite part. When you import an assembly from an external CAD package, the position of the parts in space is honored and the geometry parts are brought in under a single composite part. This position of the imported geometry parts is not associative. If you manually move a geometry part, for example using the translate action, the geometry part moves without updating any of the other parts.; Composite parts can contain complex assembly structures that include sub-assemblies, which themselves can contain further sub-assemblies, and so on. The final level is composed of one or more leaf parts.