Constructing sub-meshes

By purpose, the sub-mesh is an object used to assign to a sub-shape different meshing parameters than those assigned to the main shape.

Structurally, the sub-mesh is a mesh on a certain sub-shape, or a group of sub-shapes, possibly generated using different meshing algorithms and/or hypotheses than those used to generate the mesh on other sub-shapes.

Creation of a sub-mesh allows to control individually meshing of a certain sub-shape, thus to get a locally coarser or finer mesh, to get elements of different types in the same mesh, etc.

A sub-mesh can be meshed individually. To achieve this, select a sub-mesh and either invoke Compute Sub-mesh vai the contextual menu in the Object Browser or invoke Mesh > Compute menu.

How to get a sub-shape for sub-mesh construction

A sub-shape to create a sub-mesh on should be retrieved from the main shape in one of the following ways:

  • In Geometry module, via New Entity > Explode menu.
  • In Geometry module, by creation of a group (New Entity > Group > Create Group menu).
  • In Mesh module, by Subshape by mesh element generated on a sub-shape of interest. This way is accessible if the mesh is already computed.
  • In Mesh module, by clicking Publish Sub-shape button in a dialog showing Meshing Failed.

How hypotheses are selected among sub-meshes

Internally, definition of meshing parameters to apply for discretization of a certain sub-shape, for example an edge of a compound of solids, starts from searching an algorithm, 1D as for the edge. The following sub-shapes are sequentially checked for presence of a sub-mesh where 1D algorithm is assigned:

  • the edge itself
  • groups of edges containing the edge, if any
  • wires sharing the edge
  • faces sharing the edge
  • groups of faces sharing the edge, if any
  • shells sharing the edge
  • solids sharing the edge
  • groups of solids sharing the edge, if any
  • the main shape

(This sequence of sub-shapes defines the priority of sub-meshes. Thus more local, i.e. assigned to sub-shape of lower dimension, algorithms and hypotheses have higher priority during the search of hypotheses to apply.)

As soon as a 1D algorithm is found, the search stops and the same sequence of sub-shapes is checked to find the main and additional 1D hypotheses, which can be taken into account by the found 1D algorithm.

The multi-dimensional algorithms have a higher priority than uni-dimensional ones if they are assigned to sub-meshes of the same priority.

If meshing parameters are defined on sub-meshes of the same priority, for example, different 1D hypotheses are assigned to two faces sharing an edge, the hypothesis assigned to a sub-shape with a lower ID will be used for meshing. You can Changing sub-mesh priority mutual priority of such concurrent sub-meshes.

How to construct a sub-mesh

Note

Construction of a sub-mesh consists of: * Selecting a mesh which will encapsulate the sub-mesh * Selecting a sub-shape for meshing * Applying one or several About Hypotheses and Basic meshing algorithms which will be used for discretization of this sub-shape.

To construct a sub-mesh: From the Mesh menu select Create Sub-mesh or click “Create Sum-mesh” button in the toolbar.

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“Create Sub-mesh” button

The following dialog box will appear:

_images/createmesh-inv2.png

It allows to define the Name, the parent Mesh and the Geometry (e.g. a face if the parent mesh has been built on box) of the sub-mesh. You can define meshing algorithms and hypotheses in the same way as in Constructing meshes dialog.

Later you can change the applied hypotheses or their parameters in Editing Meshes dialog. Mesh entities generated using changed hypotheses are automatically removed.

Subshape by mesh element

If the parent mesh is already computed, then you can define the Geometry by picking mesh elements computed on a sub-shape of interest in the 3D Viewer, i.e. you do not have to extract this sub-shape in Geometry module beforehand. To start element selection, press Selection button to the right of Geometry label. If this button is already down, then click it to release and then click it again. The following pop-up menu allowing to choose a way of geometry definition will appear.

_images/choose_geom_selection_way.png

Direct geometry selection enables selecting the sub-shape in the Objec Browser. Find geometry by mesh element selection activates the following dialog.

_images/find_geom_by_mesh_elem.png

In this dialog, Element Type defines a kind of element to pick in the Viewer. Instead of picking an element in the Viewer, you can type its ID in Element ID field. Geometry name field allows defining a name of the sub-shape, with which the sub-shape will appear in the Object Browser (if not yet there).

Sub-mesh in the Object Browser

In the Object Browser the structure of the new sub-mesh will be displayed as follows:

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It contains:
  • a sub-mesh name (SubMeshFace1)
  • a reference to the geometrical object on the basis of which the sub-mesh has been constructed (Cylindrical Face_1);
  • Applied hypotheses folder containing references to hypotheses assigned to the sub-mesh;
  • Applied algorithms folder containing references to algorithms assigned to the sub-mesh.

See Also a sample TUI Script of a Construction of a sub-mesh operation.