Chapter 6
Sweep Meshing
ANSYS Meshing
Application Introduction
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Sweep Meshing
Overview
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Training Manual
Sweep Approaches for Hexahedral Meshing
Sweeping Terminology
Challenges with Sweeping
Comparing Workbench Sweep Methods
Sweep Meshing Approach
Sweepable Bodies
Inflation for a Swept Mesh
Sweep Method Mesh Controls
Sweep or Thin Sweep?
Thin Model Sweeps
Workshop 6.1 Swept Mesh for a Multibody Part
Workshop 6.2 Thin Model Sweep
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Sweep Meshing
Sweep Methods for Hexahedral Meshing
Training Manual
There are 3 hex meshing or sweeping approaches in Workbench
ANSYS Meshing:
1. Sweep Method
• Traditional sweep method
• Improved at R12
2. Thin Sweep Method
• New at R11
• Improved at R12
3. Multizone
• New at R12
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Sweep Meshing
Sweeping Terminology
Training Manual
In evaluation of which method to use there are some important terms to
consider/understand.
• When creating a hex mesh, a source face is meshed and then extruded
to the target face
• Other faces are called side face(s)
• The sweeping direction or path is defined by the side face(s)
• The layers of elements between the source and target faces are
created through interpolation schemes and projected to the side face(s).
Side face
Sweep Path
Target face
Source face
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Sweep Meshing
Sweeping Terminology
Training Manual
• To mesh a complete solid/fluid, several sweep operations may be
required
• Geometry decomposition (splitting/etc) is done:
– to control the mesh (get layered mesh in a gap)
– or to create sweepable bodies.
• To mesh the sweepable
bodies conformally the
bodies should be grouped
into a multibody part.
• Here the geometry has
been split into several
bodies each with a single
source and target face
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Sweep Meshing
Challenges with Sweeping
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Training Manual
Sweeping will only work for geometries that are sweepable. The
following are some limitations that pose challenges for sweep mesh
methods:
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Multiple source or target faces
Multiple sides along sweep direction (although multiple sides may
pose quality issues due to additional constraints they impose)
Geometry decomposition into sweepable regions
How geometry is constructed, VTs, etc.
Unclear source/target/side definitions
Handling of Multibody parts:
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Unclear sweep direction through multibody parts
Conformal meshing (both for parts where all/most bodies are swept, and those
where some bodies are being meshed with free methods i.e. tetrahedral)
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Sweep Meshing
Challenges with Sweeping
Training Manual
The Thin Sweep and MultiZone methods were introduced to help resolve
some of the difficulties with the general sweep approach.
Thin Sweep Method:
• Good at handling multiple sources and targets for thin parts
MultiZone Method
• Provides free decomposition approach: attempts to slice up the model
without having to do this manually to the geometry
• Supports multi-source and multi-target approach
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Sweep Meshing
Comparing Workbench Sweep Methods
Training Manual
Thin Sweep Method:
• Sweeps multiple sources to
paired multiple targets
• Good substitute for midsurfacing
shell models to get a pure hex mesh
Sweep Method:
• Sweeps a single
source/face to a
single target/face.
• Does a good job
of handling multiple
side faces along sweep
• Geometry needs to be
decomposed so that
each sweep path is
represented by 1 body.
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MultiZone Method:
• Free decomposition approach
• Multiple sources to multiple targets
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Sweep Meshing
Sweep Meshing Approach
Training Manual
• Sweepable bodies can be meshed efficiently
with hexahedral and wedge elements using
this technique
• Sweep Meshing Approach
– Source and target faces that are topologically
on the opposite sides of the body are either
manually or automatically chosen.
– Source face meshed with quadrilateral and
triangular faces
– Source face mesh copied to the target face.
– Hexahedral or wedge elements generated
connecting the two faces and following the
exterior topology of the body
• Single source/single target for a body
• Can apply single Sweep Method to multiple
bodies in a single part
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Sweep Meshing
Sweepable Bodies
Training Manual
• A body is sweepable if:
– It contains no completely enclosed voids
– There is at least one path from a source
surface to a target surface connected by
edges or closed surfaces
– There are no hard divisions defined such that
there would a different number of divisions on
corresponding edges of a source and target
face
• Can preview via a right-click on Show
Sweepable Bodies
– Will not find axis sweepable bodies, but these
can always be set manually
• Source and target faces do not have to be
flat or parallel
• Cross-sectional shape does not have to be
constant
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Sweep Meshing
Inflation for Swept Meshes
Training Manual
• For a swept mesh, inflation is
applied by selecting the edges
from which inflation is desired on
the source face
• The Src/Trg Selection on the Mesh
method should therefore be set to
either Manual Source or Manual
Source and Target
•Once a source is defined, you will
then be able to define inflation
•Inflation for a swept mesh will use
the Pre inflation algorithm
•Only the First Layer or Total
Thickness options are available
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Sweep Meshing
Sweep Method Mesh Controls
Training Manual
• Free Face Mesh Type
– Quad/Tri (Default)
– All Tri
– All Quad
• Type
– Element Size (Soft Constraint)
– Number of Divisions (Hard Constraint)
• Sweep Bias Type
– Same as edge biasing (from source to
target) but no graphical feedback
• Constrain Boundary (multibody parts)
– Yes prevents the mesher from splitting
the elements at the boundary of a swept
mesh region to aid in meshing.
– No allows splitting since the boundary is
not constrained (Default)
– Yes prevents tetrahedral and pyramid
elements from being introduced into a
hexahedral/wedge mesh.
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Sweep Meshing
Sweeping Around Bends
Training Manual
• When sweeping geometry that contains many twists/bends, the swept
mesher can produce twisted elements, causing the mesher to fail
– Depends on the underlying topology of the geometry
– Geometry created in several steps (e.g. a series of Extrudes and Revolves)
is more likely to cause problems
• One way to avoid this is to create geometry in a single 3D operation
– Use a Sweep operation rather than a series of Extrudes/Revolves
– In some CAD packages extruding/sweeping along a single spline curve
produces better topology than extruding/sweeping along a segmented
curve
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Sweep Meshing
Sweep or Thin Sweep?
Training Manual
Thin Sweep Method:
• Sweeps multiple sources to
paired multiple targets
• Good substitute for midsurfacing
shell models to get a pure hex mesh
Sweep Method:
• Sweeps a single
source/face to a
single target/face.
• Does a good job
of handling multiple
side faces along sweep
• Geometry needs to be
decomposed so that
each sweep path is
represented by 1 body.
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Some models can be
meshed with either
approach
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Sweep Meshing
When to use Sweep vs. Thin Sweep
Training Manual
Use Sweep Method When:
• The side faces are not “thin”*.
• You only have 1 source and 1 target
• The sweep direction changes along the path
Use Thin Sweep Method When:
• The side faces are “thin”*.
• You have multiple sources and targets
• Path is linear
* In general, “thin” means that the side faces are small in relation to the
source faces (aspect ratio of sides/sources is ~ 1/5th)
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Sweep Meshing
Thin Model Sweeps
Training Manual
• Thin models with more than
one source and face can be
swept using the Automatic or
Manual Thin Model
– Model should be thin and
source(s) and target(s)
cannot touch each other.
– The model must have an
obvious “side”
– Multibody parts are
supported, but only one
element through the
thickness is allowed
– No inflation or bias in sweep
direction
– Multiple sources captured,
multiple targets ignored
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Sweep Meshing
Thin Solid Sweep Treatment
Training Manual
Multiple target
Multiple source
Multiple sources captured
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Multiple targets ignored
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Workshop 6.1
Sweep Meshing for
a Multibody Part
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Sweep Meshing
Goals
Training Manual
This workshop demonstrates the use of a sweep method for a multibody part
and shows how edge sizings can be used to specify the mesh gradation
in the sweep direction. It also demonstrates inflation for a swept mesh.
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Sweep Meshing
Importing Geometry
Training Manual
1. Copy the multi.agdb file from
the Tutorial Files folder to your
working directory
2. Start Workbench and doubleclick the Mesh entry in the
Component Systems panel
3. Right-click on Geometry in the
Mesh entry in the Project
Schematic and select Import
Geometry/Browse
4. Browse to the multi.agdb file
you copied and click Open.
Note that the Geometry entry
in the Project Schematic now
has a green check mark.
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Sweep Meshing
Insert Sweep Mesh
Training Manual
5. Double click the Mesh entry in
the Mesh object on the Project
Schematic
6. Close the Meshing Options
Panel at the right without setting
anything.
7. Right-click on Mesh and insert a
Method. Select both bodies and
set the method to Sweep.
8. Set the Src/Trg selection to
Manual Source and select the
two faces shown as the Source
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Sweep Meshing
Edge Sizing
Training Manual
9. Define an Edge Sizing for the 2 edges shown with 20 Hard Divisions. Set the
Bias Type to shrink towards the ends and set the Bias Factor to 4
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Sweep Meshing
Sweep Settings
Training Manual
10. On the Mesh Options, set the Physics Preference to CFD and the Solver
Preference to Fluent. Turn off the Advanced Size Function and set an Element
Size of 0.25 [cm]. Expand the Statistics entry and set the Mesh Metric to
Skewness
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Sweep Meshing
Initial Mesh
Training Manual
11. Generate the Mesh. Note the effect of the Edge Sizing and the Max Skewness
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Sweep Meshing
Inflating the Method
Training Manual
12. Inflate the Sweep Method selecting the 8 edges shown. Set the Inflation Option to
Total Thickness and set 5 layers with a Maximum Thickness of 0.5 [cm].
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Sweep Meshing
Inflated Mesh
Training Manual
13. Generate the Mesh. Observe the nature of the mesh and the Max Skewness.
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Workshop 6.2
Thin Model Sweep
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Sweep Meshing
Goals
Training Manual
This workshop demonstrates the use of the Thin Model Sweep method
for a single body with multiple elements through the thickness.
It also shows how Virtual Topology can be used to convert the model
to a form suitable for a normal sweep which allows bias in the sweep
direction and inflation
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Sweep Meshing
Importing Geometry
Training Manual
1. Copy the thinmodel.agdb file
from the Tutorial Files folder to
your working directory
2. Start Workbench and doubleclick the Mesh entry in the
Component Systems panel
3. Right-click on Geometry in the
Mesh entry in the Project
Schematic and select Import
Geometry/Browse
4. Browse to the thinmodel.agdb
file you copied and click Open.
Note that the Geometry entry
in the Project Schematic now
has a green check mark.
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Sweep Meshing
Insert Sweep Mesh
Training Manual
5. Double click the Mesh entry in
the Mesh object on the Project
Schematic
6. Close the Meshing Options
Panel at the right without setting
anything.
7. Right-click on Mesh and insert a
Method. Select the body and set
the method to Sweep.
8. Set the Src/Trg selection to
Manual Thin and select the three
faces shown as the Source.
9. Set the Sweep Num Divs to 4
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Sweep Meshing
Mesh Sizing and Metric
Training Manual
10. Click on Mesh in the Outline
11. Change the Physics Preference to
CFD and the Solver Preference to
Fluent
12. Expand the Sizing Entry and note
that the Advanced Size Function is
set to On: Curvature
13. Set the Max Face Size to 0.10 [in].
(Note: if the units are set to some
other system, click on Units in the
Menu Bar and change to U.S.
Customary (in, lbm, …)
14. Expand the Statistics entry and set
the Mesh Metric to Skewness
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Sweep Meshing
Mesh and Mesh Quality
Training Manual
15. Generate the Mesh. Note the Mesh count and Skewness metric
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Sweep Meshing
Inserting a Virtual Face
Training Manual
16. If the 3 faces on the source and target faces are combined
into single faces using Virtual Topology, the resulting
model can be swept meshed with a Manual Source which
will allow for inflation and a bias in the sweep direction.
Highlight Model in the Project Outline and then left-click
on the Virtual Topology entry.
17. Set the selection filter to faces and select the 3 faces which
comprise the Sweep source
18. Right click on the Virtual Topology entry which
appeared in the Outline and choose Insert Virtual Cell
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Sweep Meshing
Modifying the Sweep Method
Training Manual
19. Add a second Virtual Face for the 3
faces on the Target
20. On the Sweep Method, you will need to
change Src/Trg option to Manual Source
and enter the Virtual source face you
created
21. Note that you can now set a bias in the
sweep direction. Set the bias to be finer
on the ends with a Sweep Bias of 2.
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Sweep Meshing
Inflating the Sweep
Training Manual
22. Right-click on the Sweep Method in the
Outline and choose Inflate This Method
23. Pick the 8 outer edges of the Source
Virtual Face as the Geomety and set the
Inflation Option to Total Thickness with a
value of 0.10 [in].
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Sweep Meshing
Inflated Mesh
Training Manual
24. Generate the mesh. Note the inflation from the outer edges and the bias in the
sweep direction.
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