© 2011 ANSYS, Inc. March 16, 20121
14.0 ANSYS Meshing
Duraivelan DakshinamoorthySr. Technical Services Engineer
ANSYS Houston
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ANSYS Service Pack 14.0.1
Service pack R14.0 Pre‐Load (R14.0.1) available on ANSYS Customer Portal, in Software download area)
Bug in 14.0 (“QA WB2012‐01”):
Description of ErrorUnder some circumstances, the database for a Mechanical or Mesh system (e.g., SYS.mechdband SYS.mshdb, respectively) can become permanently damaged upon saving a Workbench Project file. A damaged database will display an unusual file size of 20KB. Attempts to open or edit it will yield errors such as:
"Unable to open file" "Unable set unit system for geometry""Unable to set generate input file. Unable to get environment""Unable to obtain linked environment IDs. Unable to get model"
Suggested User Action For Running in R14.0To prevent the error, disable the options to Pre‐Load the Mechanical and Mesh Editors in Workbench via:
Tools > Options > Mechanical > Pre‐Load the Mechanical EditorTools > Options > Meshing > Pre‐Load the Meshing Editor
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Rapid Meshing of Assemblies:• Reduce time spent in CAD & Meshing
– Improved handling of complicated geometries– Extract flow volume during meshing
General Improvements in Meshing Process:• Improved meshing algorithms:
– Hybrid (hex/tet) meshing– Shell meshing
• Improved process & flexibility• Improved robustness• Improved speed
ANSYS 14.0 Meshing Goals
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ANSYS Meshing Application:Assembly Meshing:• What is it? How will it help?• Technical overviewGeneral Meshing Improvements:• Example Benefits• Technical overview
ANSYS ICEM CFD:Technical overview
ANSYS TGrid:Technical overview
Overview:
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Assembly Meshing
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Assembly MeshingAssembly meshing is a top‐down meshing approach to mesh all parts at 1 time:• Use of virtual bodies (material points) to extract flow regions from dirty geometry• Support for:
– Meshing solids from sheet bodies– Conformal mesh between parts w/out having multibody parts– Support for overlapping bodies
Material point
Assembly
Capping Face
Handling face-edge connectivity
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• Assembly meshing replaces 13.0 CutCell Meshing at the GUI level• Supports both CutCell and Tetrahedral meshes• CutCell meshing maintains characteristics from 13.0
– High fraction of hex and prismatic cells– Supports global size functions, feature capture, tessellation, etc. controls– Operates on parts, multi‐body parts, etc. with new option to define virtual bodies– Patch independent:
• Eliminates the need for pinch control and VT operations
• Creates conformal meshesacross parts in contact
– Eliminates the need for multi‐body part generation in CAD
• Ability to create flow volumes from a “closed” set of bodies (sheet or solid)– Eliminates the need for Boolean/Fill operations in CAD
Assembly Meshing: Characteristics
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• CutCell: still Polyhedra upon Export– No support for CFX solver– No option to export non‐polyhedra meshes (except from TGrid)
• Tetrahedron: only integrated with Fluent– Produces Linear Tets, not suitable for Mechanical solvers– For CFX (unsupported work‐around):
• Set Physics to Fluent • export the mesh in Fluent format• Import mesh into a CFX system
• Ability to create flow volumes from:– A “closed” void bounded by
• solids and capping surface• Fluid surfaces• The above, fully enclosed in a fluid volume
Assembly Meshing: Notes
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1. Define Coordinate system insidethe Fluid Void
2. Insert a Virtual body3. Assign the proper Coordinate
System to the Material Point in the details of the Virtual Body
4. Done
Assembly Meshing: Flow Volume Extraction
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#2
#3
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Assembly Meshing: Keep Solid Mesh
In the Assembly Meshing panel, you can choose to keep or discard the mesh in all solids
Parts can be marked as Fluids/Solids
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Inflation Improvements
Industrial Example:• 68 Million cells, 5 inflation layers• Total Mesh Time:
•R13: 6 hrs 39 mins•R14: 3 hrs 38 mins
Speed and Flexibility of inflation:• Several improvements to both assembly and part meshing– Better quality during stair stepping– Better handling of high aspect ratio inflation– Improved speed of inflation creation ~30‐100%
• Assembly Meshing Flexibility– CutCell: Full support of 2‐stage inflation
• CutCell and inflation in two separate steps– Within the working session
– Tetrahedron: Uses pre‐inflation• Faster, more layers, and better quality
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Also supported for Virtual Bodies• Program controlled inflation acts only on Fluid Bodies
Assembly Meshing: Automatic Inflation
CutCell + Inflation Tetrahedron + Inflation
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• A special cell cutting algorithm has been developed to properly capture sharp 3D angles
• Can be used to improve feature capturing in general• Insert a “Sharp Angle” and pick adjacent faces • Example:
Assembly Meshing: Sharp Angle Tool
Sharp angles in the Flow volume of drill bit
Mesh without Sharp Angle
Mesh with Sharp Angle
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Find leaks using material points:• Any time you are using material points (for internal flow), and it is leaking to the outside, you can automatically see the leak‐path together with the surface mesh
Assembly Meshing Leak Handling:Leakage Path
There is a small gap between the valve plug and the valve seat
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Using Contacts for Assembly meshing:• Workbench has extensive capabilities to detect contact (interfaces) between parts.
• Until now, that contact information has been of little use to FLUENT users, but that has changed at 14.0
• Contacts have several purposes for Assembly Meshing:– Closing of small gaps using contact sizing– Find thin sections– Find Contacts
• Features at contact pairs are preserved• Contacts are also used in Fluid Surface picker helper
Assembly Meshing Leak Handling:Contact (Interface) Regions
For example, in this image the circled edges would be removed without contact defined since the feature angle is below the default
(40 degrees)
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Contact sizing: Three simple steps1. Insert a Face‐Face Contact between
the entities that are leaking– Face/Face or Face/Edge
2. Drag and drop the contacton top of the Mesh Icon
– Creates a Contact sizing
3. Adjust Contact sizing– Should be bigger than the gap
• Limited to gaps up to 1/5 of min‐size
4. Generate Mesh
Assembly Meshing Leak Handling:Closing Leaks up to 1/5 of min size
#1
#2
#3
Pick the face of the valve plug (blue)and the edge of the valve seat (red)
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Why locate thin sections (3D bodies)?• Avoid Leakage• The assembly meshing method produces better quality meshes if thin baffles and fins are well resolved
• By using the Find Thin Sections tool, these can be found in advance and appropriate sizing can be applied
Assembly Meshing: Finding Thin Sections
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Assembly Meshing: Fluid Surfaces
Creating Fluid Surfaces for Flow Volume meshing• Description– Pick all faces that make up the wetted surface of the flow volume
• Applications– Mainly used when only flow volume is needed
• No conjugate heat transfer• Advantage– Faster– Less memory– Reduction of leakages
• Approach– Insert Virtual Body– Insert Fluid Surface (select faces)
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Assembly Meshing: Fluid Surfaces
• To manually select all the faces making up all the flow volume is in many assemblies too time consuming– To help out with this task, we have added a new picker helper: Extend to Connection!
• To use this, you need to have proper connections defined– Connections are created automatically in WB, so to start with: delete all the old connections !
• Create New Connections– Make sure min‐size is properly set !– RMB – Find Contacts
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Assembly Meshing: Fluid Surfaces
• Start by picking all capping faces– Use the Tree to confirm the number of capping faces (Surface Bodies)
– In big models, hide all 3D‐bodies !
• Select faces in the fluid regionaway from contacts– Extend to connections, does not work if the face is already in “contact”
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Assembly Meshing: Fluid Surfaces
• The extend to connection will help, but usually not pick all remaining faces
• In this case, two facesare missing
• In total 136 faces were picked using about 10 manual picks
• Are we sure that all thefaces are picked?– If not, meshing will leak
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Assembly Meshing: Fluid Surfaces
• To see missing faces, hide all bodies and look at the picked faces in the mesh group
• Faces could extend outside the flow volume• Note: Fluid Surfaces will ignore baffles
• Resulting mesh:
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Assembly Meshing: Miscellaneous Features
• Size Function improvements– Separate Min size for Curvature and Proximity
– Less mesh clustering– Support for Body of Influence
• “Mesh Unite” Fluid or Solid bodies using Mesh Groups– Improve quality of the mesh by releasing geometry constraints at interfaces
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General Meshing Improvements
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Key Technology Areas:
• Selective Meshing Worksheet
• Virtual Topologies
• Hex Meshing
• Tet Meshing
• Shell Meshing
• Mesh Connections
• Contacts for Fluent
General Meshing Improvements
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• Controls order of body meshing:– Allows selective body meshing to remain persistent– User can record meshing operations, or add steps manually
Selective Meshing Worksheet
For Example: User wants an all hex mesh on quarter
piston model
Due to complexity in meshing, user may
want to control sequence of meshing
stepsIf recording, steps will
be automatically created.
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Meshing steps relate to Named Selection:– When recording, named selections are created for user
Selective Meshing Worksheet: Recording
For example, if recording meshing steps, and user meshes 1 body:1. Step will be added to Worksheet2. Named selection will automatically be
created3. Step will not be included in output to
solver unless “Send to Solver” is changed to “Yes’
#1
#2
#3
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User can also manually create meshing steps, w/out mesh having to be computed:
1. Create Named Selection with bodies to be meshed in that step– Set “Send to Solver” option to “No”
2. In Worksheet, RMB and select Add and then select the Named Selection you created in Step #1
Selective Meshing Worksheet: Manual
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When meshing, if the order in Worksheet needs to be adjusted, this can be done in 1 of several ways:
1. Add, Delete steps
2. Change Contentsof Named Selection
Selective Meshing Worksheet: Editing
Note: Add will only append to end of Worksheet, so option #2 is often better.
Also, use Active/Inactive options for more flexibility, see following slides
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If meshing a complicated model, use a strategy that allows flexibility. For example:
Selective Meshing Worksheet: Strategy
Depending on meshing strategy I may want to control the mesh in some regions, and then build mesh up from there.In this example, I want to mesh bodies in following order:1. Mesh central region2. Mesh bodies above central region3. Mesh bodies below central region
In this way, I can better control mesh quality and improve the amount of hex mesh
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– Meshing steps can be made active or inactive• In this case, after meshing middle and top piston sections, make top section’s steps inactive before meshing bottom sections. This will improve performance and flexibility.
– If while working, user needs to change order of meshing, steps can be modified by changing contents of named selections• Named selections can contain 1 body or multiple bodies.
• Use additional inactive steps for greater flexibility.
Selective Meshing Worksheet: Use of Inactive steps
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Generate Mesh:– Steps in worksheet are only necessary when user control is required. – Bodies that are not in Worksheet are meshed after Worksheet steps are completed.
– User can step through selective meshing steps by using RMBGenerate Mesh Through This Step
Selective Meshing Worksheet
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Improved automation, flexibility, and usability:– More interactive usage through direct graphics interaction rather than tree objects
– Ability to run “Auto VT” on selected edges, faces or bodies
– Clustering of faces/edges– Create hard vertex– Face splits– Interactive editing
Virtual Topologies
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Virtual Topologies: Interactive editing
Tree view is replaced with graphical selections:
Select objects and RMBOperate, or use icon palette to:– Merge Edges or Faces– Split Edges or Faces– Create Hard Vertex– Shuffle through VTs (order depicts order of creation)– Edit VTs to see VT options– Delete
Virtual Topology Detail View:– Global behavior– Statistics view added
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Virtual Topologies: Interactive editing
Face Clustering:
Auto‐VT on selection:• In similar fashion user can select group of faces, or bodies and generate auto‐VT on this selection.
Delete, Edit, etc. also work on multiple selection sets
Select faces and click Virtual Cell icon
Cluster 1Cluster 2
2 Virtual Faces created. 1 for each cluster.
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Virtual Topologies: VT Hard Vertex
Create VT Hard Vertex:• Pick on face, screen selection point is where vertex will be created:
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Virtual Topologies: Edge splits
Create VT edge splits:• Pick on edge, screen selection point will be used to split the edge
Repeat for other 2
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Virtual Topologies: Face splits
Create VT face splits from vertex pairs:• Select 2 vertices and split face
Repeat for other 2
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Virtual Topologies: Example: Blunt body
Flexibility: Allows user to get mapped or swept mesh for non‐mappable/non‐sweepable bodies
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Virtual Topologies: Interactively edit splits
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Virtual Topologies: Notes
• When legacy models are read into 14.0, the objects are removed from the tree, but user can access the VTs interactively from graphics
• Use Arrow keys to shuffle through VTs in graphics similar to how users shuffled through objects in tree in past
• Suppressed VTs are no longer supported: upon legacy import suppressed VTs not attached to a suppressed object are deleted (w/warning given)
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Virtual Topologies: Example: Intersecting Pipes
Use Virtual Splits for hex meshing
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Virtual Topologies:Example: Automotive component
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Virtual Topology: Quarter Piston
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Robustness Improvements:– MultiZone, Sweep and Thin Sweep– Improved case handling for MultiZone
MultiZone improvements:– Performance improvements– Support for match mesh control– All Prisms option
Hex Meshing
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MultiZone: Robustness improvements
Support for:• Handling of cylindrical side faces
• Imprinting– Through bodies– Through long stretches of connected side faces
– Through side faces– General improvements
• Support for edge splits
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MultiZone: Mesh Matching
Added Support for Mesh Matching:– Cyclic/Periodic Symmetry and/or match mesh control
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MultiZone: Performance Improvements
0:00
2:24
4:48
7:12
9:36
12:00
14:24
12.1 13.0 14.0
Speed Improvements:– Better performance for swept blocks– Improved multibody part handling
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• Robustness and Quality improvements in tri surface meshing, inflation and tet meshing
• Separated Min Size for Curvature and Proximity
• Added new option for Advancing Front Triangle Surface Meshing
Tet Meshing
Program Controlled: Default, mesher determines approach by surface type, face topology and defeatured boundaries.Advancing Front: Mesher uses Adv. Front unless it fails, then it falls back to other approaches.
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Connections for Fluent
• In 14.0, information in the contact folder will be written as mesh interfaces for Fluent
• If you have contacts/connections in an old database, The user is asked to remove the contact information
• A new WB option to NOT generate contacts automatically is available
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Connections for Fluent
• Start Workbench and open ToolsOptions• Go to Either Meshing or Mechanical
• Unselect “Auto Detect Contact on Attach”
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Productivity enhancements through increased robustness, flexibility, and efficiency• Over 200 defects and feature requests resolved
• User interface– Selection and Display Enhancements– Model tree enhancements– Enhanced Subsets
• Mesh Editing– Enhanced Prism editing, refinement, etc.
• Output– Enhanced output to CGNS, ANSYS FLUENT
ANSYS ICEM CFD 14.0 Update
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Driven by Assembly meshing technology exposed in ANSYS Meshing• Assembly Meshing features– Material points
• /mesh/cutcell/set/create‐material‐points– Sharp angle and feature capturing
• /mesh/cutcell/set/set‐thin‐cut‐faces• /mesh/cutcell/set/set‐thin‐cut‐edges
– Leak path, CutCell‐to‐Tet conversion, etc.• Prism speedup (~2x)• Defect fixing– Wrapper, CutCell, surface meshing, tet meshing, topology handling, prisms, etc.
• Updated wrapper templates – Contact support for latest version, tutorials
TGrid 14.0 Update
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Summary:
• 14.0 provides many improvements focusing on robustness, automation, persistence, and flexibility in meshing solutions
• Assembly meshing provides a top down meshing solution that caters to more complex models
• Selective part/body meshing allows for greater flexibility to control the mesh quality
• We continue to advance Extended meshing solutions and technologies
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Questions?