Release 11.0 Documentation for ANSYS Workbench
This method of meshing complements the free mesher that produces tetrahedron elements. If a body's topology is recognized as sweepable, the body can be meshed very efficiently with hexahedral and wedge elements using this technique. The number of nodes and elements for a swept body is usually much smaller than ones meshed with the free mesher. In addition, the time to create these elements is much smaller.
Workbench will automatically check to see if the body fulfills the topological requirements for sweeping. It will then choose two faces that are topologically on the opposite sides of the body. These faces are called the source and target faces. Workbench will mesh the source face with quadrilateral and triangular faces and then copy that mesh onto the target face. It then generates either hexahedral or wedge elements connecting the two faces and following the exterior topology of the body.
A body cannot be swept if any of these conditions exist:
There is more than one set of continuously connected faces in the body.
There is a completely contained internal void in the body.
No two faces in the body are opposite to one another in the body's topology and have edges connecting each of the first face's vertices with the second face's vertices (in other words it cannot find a source and target face).
If a Sizing control is used on a body with hard edge sizing and the source and target faces contain hard divisions which are not the same for each respective edge.
When sweeping it is only neccesary to apply hard divisions to one leg of the sweep path. If the path 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 bodies source or target face then more hard divisions may be needed to constrain the sweeper.
To preview any bodies that can be sweep meshed, click Mesh on the Tree Outline and right-click the mouse. Select Show Sweepable Bodies to display bodies that fulfill the requirements of a sweepable body. However, even if these requirements are met, the shape of the body may at times still result in poorly shaped elements. In these cases, the tetrahedron mesher is used to mesh the body.
Show Sweepable Bodies only displays bodies that can be swept where the source and target are not adjacent on an axis. It cannot automatically determine axis-sweepable bodies. However, more enhanced sweeping capability, including axis-sweeping, is available by using the Sweep option of the Method mesh control.
Other characteristics of sweeping include the following:
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 operation will often succeed even if the shape of the source face is different from the shape of the target face. However, drastically different shapes can cause element shape failures.
Sweeping does not require your model to have a constant cross section. However, the best results are obtained for constant or linearly varying cross sections.
Axis Sweep Representation:
Edge Only Sweep Path:
Edge Plus Closed Surface Sweep Path:
In deciding which area should be designated as the source area for sweeping, the program uses the following rules, in the order as listed below. The sweeper will check all the rules until it finds a rule to use. Once a higher order rule is used, all the lower rules will not be considered. For example, if none of the first five rules apply, it will check against rule 6. In this case, if a face is plane (flat) and the other face is not a plane (not flat), the flat face will be picked as the source and the test will be terminated.
Manually set control - specify both source and target: The source and target for sweeping will be exactly as the user specifies. This is the fastest way of meshing. It will eliminate searching for a possible source and target. For axis-sweeping, this method must be used.
Manually set control - specify source: Once the user specifies a source area, the program will try to find the target suitable to the source. The source will be exactly as specified.
Mapped Face Mesh control: The program finds the face with a Mapped Face Mesh control applied to it.
Number of loops: The face with the largest number of loops will be picked as source face.
Number of lines: The face with the largest number of lines will be picked as source face.
Flat face: A flat face has higher priority for being a source face.
Less sharing: In most cases, a face might be used by one or a maximum of two bodies. If every one is flat (plane), the one used by the least number of bodies (that is, used by just one body) will be picked as source face.
Larger area: The largest area will be picked as the source.
The Single Source Single Target Sweeper must have at least one path between the source face and target face. The side faces of the sweep do not need to be singular but they must all be sub-mappable and have single loops The source face cannot be a closed analytic such as a full cylinder, torus or sphere. However, partial analytics are acceptable as source and target faces
Example (a) showing invalid closed cylindrical face as source face:
(b) valid open cylindrical face as source face:
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(c) Multiply Connected Side Faces:
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Thin Model Sweeper Topology Requirements
The Thin Model Sweeper can be N source to N target faces or N source to 1 target face or 1 source to N targets. In the case of N targets, those faces may be defeatured out of the model There can only be on edge and one face between the source and target faces. Virtual topology can be used to merge multiple edges into 1 edge for this sweeper
Example showing (a) N Source to 1 Target or 1 Target to N Source Topology
(b) N Source to N Target Topology
(c) 1 Source to N Target Mesh
(d) N Source to 1 Target Mesh
(e) N Source to N Target Mesh
Use Virtual Topology to create a single edge between source and target faces.
Mesh controls and the Thin Model Sweeper
Mesh Controls applied on the target faces/edges are ignored. Only mesh controls applied to the source faces/edges are respected.
Example of (a) Mapped Face Control is ignored because it is applied to the target face
(b) Mapped Face Control is respected because it is applied to the source face
