mesh sweeping

8/10/2019 Mesh Sweeping

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Meshing User's Guide

Contains proprietary and confidential information of ANSYS, Inc.

and its subsidiaries and affiliates

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When sweeping it is only necessary to apply hard divisions to one leg of the sweep p

has multiple edges, you should apply your controls to that path.

If the sweep path is shared by another body and that path lies on the body's sourcethen more hard divisions may be needed to constrain the sweeper.

When using Virtual Topology with sweeping, avoid creating virtual cells that result insurface. Fully closed surfaces cause difficulties for the swept mesher and may result When selecting adjacent faces for inclusion in a virtual cell, it is best to use Virtual Tosome (but not all) of the faces. A good approach is to use Virtual Topology for the s

omit any larger faces from the virtual cell.

To preview any bodies that can be swept meshed, click Mesh on the Tree Outline anmouse. Select Show> Sweepable Bodies from the context menu to display bodiesrequirements of a sweepable body. However, even if these requirements are met, thbody may at times still result in poorly shaped elements. In these cases, the tetrahedused to mesh the body.

The Show Sweepable Bodies feature only displays bodies that can be swept wherand target are not adjacent on an axis. It cannot automatically determine axis-sweepHowever, more enhanced sweeping capability, including axis-sweeping, is available bSweepoption of the Methodmesh control.

For help in diagnosing problems when using the Sweep method, refer to the descripEdge Color Optiontoolbar in the Mechanical help. This toolbar provides access to fintended to improve your ability to distinguish edge and mesh connectivity.

Other Characteristics of General Sweeping

Other characteristics of sweeping include the following:


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The general sweeper ignores the Num Cells Across Gapsetting, which is udefine the proximity size function.

Hard entitiesare not supported for the general sweeper.If the sweep method is applied to a body and a Mapped Face Meshing confor either the body's source or target face, the sweep mesher will fail if a macannot be obtainedfor the face.The source and target faces do not have to be flat or parallel.If the topology of the source and target face is the same, the sweeping opersucceed even if the shape of the source face is different from the shape of thHowever, drastically different shapes can cause element shape failures.Sweeping does not require your model to have a constant cross section. How

results are obtained for constant or linearly varying cross sections.

Figure: Axis Sweep Representation

Figure: Edge Only Sweep Path


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Figure: Edge Plus Closed Surface Sweep Path

Rules Followed By the General Sweeper

In deciding which area should be designated as the source area for general sweepinguses the following rules, in the order as listed below. The sweeper will check all the ra rule to use. Once a higher order rule is used, all the lower rules will not be consideif none of the first five rules apply, it will check against rule 6. In this case, if a face iand the other face is not a plane (not flat), the flat face will be picked as the sourcebe terminated.

1. Manually set control - specify both source and target:The source andsweeping will be exactly as the user specifies. This is the fastest way of mesheliminate searching for a possible source and target. For axis-sweeping, thisbe used. If a face is a source of another body and is not picked as a source o


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body, the aforementioned face will be used as a source.2. Manually set control - specify source:Once the user specifies a source a

program will try to find the target suitable to the source. The source will be especified.

3. Mapped Face Mesh control:The program finds the face with a Mappedcontrol applied to it.

4. Number of loops:The face with the largest number of loops will be picked5. Number of lines:The face with the largest number of lines will be picked a6. Flat face:A flat face has higher priority for being a source face.7. Less sharing:In most cases, a face might be used by one or a maximum o

every one is flat (plane), the one used by the least number of bodies (that isone body) will be picked as source face.

8. Larger area:The largest area will be picked as the source.

Topological Requirements of the General Swe

The general sweeper must have at least one path between the source face and targe

faces of the sweep do not need to be singular but they must all be submappable andloops. The source face cannot be a closed analytic such as a full cylinder, torus or sppartial analytics are acceptable as source and target faces.

Note:

Creo Parametric creates unique topological models that no other CAD screates. In all other CAD systems, non-periodic faces can have only 1 etopological loop. On the other hand, models in Creo Parametric can havnon-periodic faces with multiple exterior loops. This type of topology dopose a problem for the free meshers in the Meshing application. Howev

does pose a problem for the general sweeper. As noted above, side facsweep must have single loops. They cannot have multiple exterior loopif they do, a single path from the source to the target cannot be deterImporting the model into the DesignModeler application breaks the facemultiple exterior loops into multiple faces with single loops because the


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DesignModeler kernel does not support the Creo Parametric topology. Ethe model from Creo Parametric to IGES or STEP format will also resolvissue.

Figure: Example (a) Showing Invalid Closed Cylindrical Face as Source Fac

Figure: Example (b) Valid Open Cylindrical Face as Source Face


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Figure: Example (c) Multiple Connected Side Faces


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Using General Sweep to Mesh a Narrow Chan

The series of images below illustrates the use of general sweep, along with mappedand hard edge sizingcontrols, to mesh a narrow channel body. Figure: Axial Sweepthe source, target, and side areas of the axial sweep model used in this example.

Figure: Axial Sweep Model


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Because the source and target areas to be meshed are a narrow channel and you wameshed with map mesh, it may present difficulties to the mesher. In Figure: Axial SwMapped Face Meshing Control, a mapped face meshing control is defined on the souvertices (two on each side area) have been selected for the Specified Sides contro

Figure: Axial Sweep Model: Mapped Face Meshing Control


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In cases similar to this example, the key to obtaining a successful mesh is the definitedge sizing control to make the two paired parallel edges. As shown in Figure: Axial

Hard Edge Sizing Control, set the Typeto Number of Divisionsand enter a value Number of Divisionsfield (in this case, 50). The Hard option ensures the numberthe same on the pair of edges.

Figure: Axial Sweep Model: Hard Edge Sizing Control


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