ICEM CFD 5.1 New Features Workshop 14 Automatic Hex Meshing of a Bent Bar

ICEM CFD 5.1 New Features

Workshop 14

Automatic Hex Meshing of a Bent Bar


Workshop

ANSYS ICEM CFD v5.1

October 1, 2004Inventory #002157

WS14-2© 2004 ANSYS, Inc.

Create a Project

Choose “Open Project“ Icon

Browse to the desired working directory

Enter the project name

Type in the File name as: BentBar.prj

Tips:

The pull down next to the file name can be used to quickly locate recently used projects.

In Windows, The File browser is a standard Windows file browser offering all the functionality of windows explorer.

In Unix or Linux, similar functionality is also available.

The Project file will contains information about project settings, the working folder and file associations.

Once the geometry, mesh, boundary conditions, parameter files etc. are saved with the project file, simply loading the project file will also load these associated files.


Workshop

ANSYS ICEM CFD v5.1



Import Geometry

Open The Geometry:

File -> Geometry -> Open Geometry Or use the “Open Geometry” ICON

Select: Bar.tin using File Browser

Display: Surfaces by left mouse click on icon

Display: Solid & Wire mode by right mouse click on Surfaces in Display Tree

Display: Transparent mode by right mouse click on Surfaces in Display Tree

Display Tree

Bent Bar


Workshop

ANSYS ICEM CFD v5.1



Build Topology

BUILD TOPOLOGY:

– Geometry -> Repair Geometry -> Build Diagnostic Topology

– Default: Tolerance is auto-calculated as 0.06

– Default: New Part Name is set to Inherited

– Accept all defaults and press Apply

– Observe: Because the New Part Name is set to Inherited Curves & Points will be in the Part of the associated surfaces

– Turn Off: Surface display using the display tree or Wire frame Icon

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Note: Yellow lines would indicate (single edges) a hole.

Tips: •set a reasonable tolerance based on model size•By default, tolerance is set to 1/1000th the size of the model bounding box diagonal, rounded

•Use Part by part option if you are working with an assembly


Workshop

ANSYS ICEM CFD v5.1



Subdivide Surface

Adjust Display:

– Turn on Points

– Adjust surface display to Solid Wire

Create ISO-parametric Curves:

– Geometry -> Create Curves -> Surface Parameter

– Select: the long cylindrical Surface

– Set: Isocurve Methods to Point on Edge

– Select these 4 points

– Press Apply

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Selected Surface

For the auto blocking method to work, surfaces should have 4 sides, the long cylinder only has 3 sides and 360 degrees of curvature. It must be broken up.

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Workshop

ANSYS ICEM CFD v5.1



Subdivide Surface

Create ISO-parametric Curves:

– Geometry -> Repair Geometry -> Build Diagnostic Topology

– Accept all Defaults

– Press Apply

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The curves appear along the cylinder surface. We can use the build diagnostic topology to cut this surface with these curves

The curves change color from green (Unattached) to Red (double edges) to show that they have “Cut in.”


Workshop

ANSYS ICEM CFD v5.1



Assign Element Size:

– Use the new Mesh Parameters option to:

• Mesh -> Set Mesh Params by Parts

– Adjust the Size and Height of the BAR part to 1

– press Apply.

– Hexa Sizes to view

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Set Mesh Sizes

RMB on Surfaces

Hexa icons indicate mesh sizes set on each surface


Workshop

ANSYS ICEM CFD v5.1



Auto Blocking:

– From the Blocking Tab, Click on the Create Block icon

– Select 2D as the Initialize Block Type • This will create a 2D blocking structure for each

surface

• These 2D Blocks will all be connected

– The Default Method is All Mapped, unstructured blocks are also available.

– Select all surfaces with the “a” hotkey

– Accept Defaults and Apply

Blocking is createdBlocks are created and a Blocking branch is added to

the model tree.

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Auto Surface Blocking

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Workshop

ANSYS ICEM CFD v5.1



Pre-mesh Param:

– Blocking => Pre-mesh Params

– Accept Defaults and Apply

This will update the blocking parameters with the parameters applied to the surface mesh parameters.

Display Pre-Mesh

Left Click on Pre-Mesh under the blocking branch of the model tree to display the Pre-mesh

Right click on Pre-Mesh to display as Solid

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Update Sizes and Pre-mesh


Workshop

ANSYS ICEM CFD v5.1



Pre-mesh does not contain separate element information and can only exist along with blocking. Pre-mesh can be converted to Unstructured mesh.

Convert to Unstructured Mesh:

– Right Click on Pre-Mesh under the blocking branch of the model tree

– Select Convert to Unstructured Mesh

Nodes and Elements are created. A “Mesh” branch will appear in the model tree.

Hex Dominant Meshing

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Using this Quad Dominant or pure Quad Mesh, you can use the Hex Dominant Mesher

For more complicated or merely Hex Dominant models, this may be the best solution, but for this model, better hex mesh is available from the Blocking tab!


Workshop

ANSYS ICEM CFD v5.1



2D to 3D Fill:

– Blocking => Create Block => 2D to 3D

– Accept Default Part Solid and method Fill

– Apply

This runs the hex dominant mesher on the blocks and results in 3D blocking.

Generate Pre-mesh to view the mesh

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Blocking 2D to 3D fill

2D to 3D Fill Display Pre-mesh


Workshop

ANSYS ICEM CFD v5.1



The Pure Hex Mesh is higher quality than the hex dominant mesh, except at the corners.

Here the Hexa elements are opened out to almost 180 degrees and quality is poor.

However, since we have access to the blocking topology, we can add an OGRID!

Ogrid

O-grid

Topology

No O-grid O-grid


Workshop

ANSYS ICEM CFD v5.1



O-Grid Creation:

– Blocking => Split Block => Ogrid Block

– Use the Block(s) Picker to select all the Blocks• Use the “v“ hotkey to select all the visible blocks

– Use the Face(s) Picker to select appropriate faces • Generally; the flat surfaces that the Ogrid should

pass through.

• Specifically; The 5 faces highlighted below and the corresponding faces on the other end.

– Apply

Update Sizes:

– Blocking => Premesh Params => Update sizes

– Update All To ensure entity parameters are set for the new edges

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Ogrid

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Workshop

ANSYS ICEM CFD v5.1



The O-grid block topology is automatically created.

Mesh is now aligned with the walls and the element quality is greatly improved.

Other changes can also be made to the blocking file

– Edge Mesh Parameters

– Vertex locations

– Etc.

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Final Mesh

The Pre-mesh and Mesh can be further improved with the Pre-Mesh smoother and hexahedral mesh smoother respectively.

Disp. PremeshConv. to Unstructured

Documents

ICEM CFD 5.1 New Features Workshop 14 Automatic Hex Meshing of a Bent Bar