Check or Smooth Shapes

Use the Check/Smooth function to check the element quality of shape combinations and optionally smooth the shapes to improve the element quality when applied individually or as part of a combination of shapes.

The check and smooth functionalities are intended to make shape optimization more productive. Shape optimization solvers, like Radioss, will stop iterating if the element quality falls below certain limits. The check and smooth functions help to improve the element quality when shapes are applied simultaneously as well as calculate the maximum and minimum bounds at which the shapes can be applied to ensure successful completion of an optimization run.

From the Morph ribbon, click the Shapes tool.

Figure 1.

The Edit Shapes dialog opens.
Select the shapes to check or smooth.
Right-click one of the selected shapes, and select Check/Smooth from the context menu.
The Check/Smooth dialog opens.

Select the options in the Check/Smooth dialog.

Option	Description
smooth shapes action switch	Select whether to check shapes and combinations, smooth shapes, or smooth shapes and combinations. Check shapes and combinations: check all the selected shapes in all possible combinations and generate a report containing the element quality for each combination. Smooth shapes: smooth all selected shapes individually and generate a report containing the element quality for each combination. Smooth shapes and combinations: smooth all selected shapes individually, and then smooth each combination, optimizing them for element quality. A report containing the element quality for each combination is then generated. This option produces the best element quality when shapes are combined, such as during an optimization run.
Report file	Specify the name of the report file to be generated or click the save icon to select the target file.
Edit checks	Customize the element checks used by smooth shapes. In this dialog that opens, each of the six supported element types can be selected from element type pull down menu. Each of the seven element checks can be made active or inactive for each element type. All three element quality limits can be set separately for each element test and each element type. Use the exclude elements selector to exclude any elements from all element quality checks regardless of the type and test. Note: The element quality settings and excluded elements are persistent, meaning that they will be stored in memory and recalled for future smooth shapes operations until manually cleared. These settings are not saved to the model file and are set to default values when a new session of HyperMesh CFD is launched.
Fix features	Select which nodes will be held fixed during smoothing, which means that the node perturbations of shapes at those nodes will not be affected by smoothing. Edges & feature lines: fix all of the nodes on the edges of the mesh along with all of the nodes lying along feature lines on the external faces of solid elements. Feature lines are determined using the specified feature angle. Edges: fix all of the nodes on the edges of the mesh. Edges & faces: fix all of the nodes on the edges of the mesh along with all of the nodes lying on the external faces of solid elements. None: do not fix any nodes.
Fixed nodes	Select nodes to be held fixed during smoothing, which means that the node perturbations of shapes at those nodes will not be affected by smoothing. The specified nodes will be fixed in addition to any nodes fixed by the fixed nodes selector.
Constraints	Fix: fixes all constrained nodes during smoothing. Fixing nodes means that the node perturbations of shapes at those nodes will not be affected by smoothing. Apply: apply all morph constraints during smoothing.

Click Check/Smooth.

The report file, which is written out regardless of the option selected, will be broken up into three sections.

The first section contains the element quality limits of each active test for each element type. Six element types are supported: trias, quads, tetras, pyras, pentas, and hexas. Seven element quality tests are supported: aspect ratio, skew, minimum angle, maximum angle, warpage, tetra collapse, and jacobian. Each test for each element type has three limits: warning, error, and invalid. If the element quality exceeds one of those limits, a warning or error will be reported. If a test is inactive, dashes will be shown in the limit fields.

Element quality limits
Trias
  Test                Warning     Error     Invalid
    Aspect ratio        50.000    500.000  10000.000
    Skew                75.000     85.000     90.000
    Minimum angle       15.000      3.000      0.000
    Maximum angle      165.000    177.000    180.000
    Warpage            -------    -------    -------
    Tetra collapse     -------    -------    -------
    Jacobian           -------    -------    -------

The second section of the report file contains one sub-section for each combination of the selected shapes. Each sub-section will contain a list of the selected shapes and the multiplier applied to each one for the given combination. Each sub-section will also contain the value of the worst element quality for each of the following active tests: aspect ratio, skew, minimum angle, maximum angle, warpage, tetra collapse, and jacobian. The worst result for each test is measured against the element quality limits to determine whether an optimization run will give a warning or an error, and if so it will be noted in the given sub-section along with the offending element ID and the element test limits for that element type.

Here is an example of section number 15 for a report file with sixteen possible shape combinations.

Combination 15
  Shape        2 applied at   1.0000
  Shape        3 applied at   1.0000
  Shape        4 applied at   1.0000
  Shape        5 applied at   0.0000
  ***** warning - poor element quality *****
  Aspect ratio      4.240
  Skew             60.303   Elem id 112   Limits:  60.000   75.000   90.000
  Minimum angle    26.718
  Maximum angle  158.141
  Warpage           0.000
  Tetra collapse    1.000

The third section of the report file contains the minimum and maximum values for each shape that can be allowed to avoid having an error result, or have the optimization run halt due to element quality.

Optimization errors can be avoided using the following limits:
  Shape        2  upper bound   0.9230   lower bound   0.0000
  Shape        3  upper bound   0.8680   lower bound   0.0000
  Shape        4  upper bound   0.9230   lower bound   0.0000
  Shape        5  upper bound   0.8680   lower bound   0.0000

If you set the upper and lower bounds on your DESVARs to these values, the optimization run should not encounter any errors due to element quality regardless of the combination of shapes applied.