icem cfd 5.1 new features workshop 15 hybrid meshing of a simple hvac assembly

ICEM CFD 5.1 New Features

Workshop 15

Hybrid meshing of a simple HVAC assembly


Workshop

ANSYS ICEM CFD v5.1

October 1, 2004Inventory #002157

WS15-2© 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: HVAC_Hybrid.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 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



Open Geometry

Open The Geometry:

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

Select: Hybrid_HVAC.tin using File Browser

Display: activate Surfaces by left mouse click on icon

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

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

Display Tree

HVAC


Workshop

ANSYS ICEM CFD v5.1



Managing the Model tree will be very important for this tutorial. For your convenience, the two primary halves of the model, the Hex_Part and the Tetra_Part, have been placed in separate assemblies.

The surface between the Hexa and Tetra volumes has been placed in the Interface part

To turn a part or assembly on or off, click on the glasses ICON.

We will start by turning the Tetra assembly OFF

Manage Parts

Hexa

Interface

Tetra


Workshop

ANSYS ICEM CFD v5.1



Turn off the Tetra Assembly so only the Hexa Assembly and interface Surface are active. Its time to Hex Mesh this half of the assembly.

Hex meshing is not the focus of this tutorial, so we can skip the details of this step and load the blocking file I have provided

Load Blocking:

– File => Blocking => Open Blocking Or use the Open Blocking utility icon

– Open: HVACPipeBlocking.blk

Generate Mesh:

– Expand the Blocking branch of the model tree

– Activate the Pre-mesh and Recompute

– RMB on Pre-mesh and select Convert to Unstruct Mesh

– Save the project

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Hexa Meshing

Compute Pre-Mesh


Workshop

ANSYS ICEM CFD v5.1



Many curves are filtered out

Only essential feature curves remain

Build Topology

BUILD TOPOLOGY:

– Geometry -> Repair Geometry -> Build Diagnostic Topology

– Default: Tolerance is auto-calculated as 0.1

– Filter by angle: Turn on Filter points and Filter curves

– Default: New Part Name is set to Inherited

– Turn on: Only active parts

• This will prevent build topology from filtering out the curves on the Hex_Part

– Accept other defaults and press Apply

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Now lets switch to the tetra portion. Turn off the Hex_Part assembly and turn on the Tetra_Part assembly.


Workshop

ANSYS ICEM CFD v5.1



Assign Element Size:

– Mesh -> Set Surface Mesh Params

– Select all the surfaces with the “a” hotkey.

– Set: Maximum element size to 4.

– Defaults: other settings should remain 0.

– press Apply.

Display Element Sizes:

– RMB on surfaces

– Select Tetra Sizes from the pull-down

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Set Mesh Sizes

Control Display through

RMB

Tetra icons indicate tetra mesh sizes set on each surface


Workshop

ANSYS ICEM CFD v5.1



Display:

– Expand the Geometry Branch and activate all the sub branches.

– Make sure the Fluid and Interface part, as well as the Tetra_Part assembly are active.

– Make sure the Hex_Part assembly is inactive

Save Project:

– We will not be able to tetra mesh in batch mode without first saving the project

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Control Display

This next part is very important. We are going to mesh only the visible tetra_part of this HVAC assembly. We need to make sure that all the correct components are visible.


Workshop

ANSYS ICEM CFD v5.1



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Mesh Tetrahedral

Mesh Tetrahedral:

– Mesh -> Mesh Tet -> From geometry

– Activate: “Smooth transition”

– Activate: “Run as batch process”

– Activate: “Only visible geometry”

– press Apply.

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Workshop

ANSYS ICEM CFD v5.1



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Load Hex Mesh with Tetra Mesh

Load Hex Mesh:

– File -> Mesh -> Open Mesh or use Open Mesh icon

– A mesh is already loaded, how do you wish to proceed

• Merge

– Display all the shells and both part assemblies

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This Merge simply concatenates the mesh files, the nodes are not connected


Workshop

ANSYS ICEM CFD v5.1



Inspect Interface shells

View the interface area:

– Expand the mesh branch and the shells branch

– Activate the shells branch

– Turn off all the parts except interface

– Turn off the geometry

– Alternately display and blank the triangles and quads to see that both layers are at the interface and are non conformal

Triangles

Overlapping Triangles and quads

Quads


Workshop

ANSYS ICEM CFD v5.1



Inspect interface volume

Display Mesh Cut Plane:

– RMB on Mesh, select Cut Plane

– The Define Cut Planes window appears

– Change Method to Middle-X

– Adjust Fraction value to 0.65

– Display Mesh Volumes in the model tree

– Zooming in reveals that the mesh needs to be merged


Workshop

ANSYS ICEM CFD v5.1



Merge mesh:

– Edit Mesh => Repair Mesh => Merge Meshes

– Method: Merge volume meshes

– Merge surface mesh parts and select the INTERFACE Part.

– Accept and Apply

Observe:

Using the cut plane, observe that the mesh is now node for node conformal across the interface.

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Merge Mesh

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Workshop

ANSYS ICEM CFD v5.1



The interface quads still remain

Delete the Interface shell mesh:

– Edit Mesh => Delete Elements

– Use the Select mesh elements tool bar to select items by part

– select the INTERFACE part.

– Accept

The interface surface mesh is removed opening up the part for flow.

Save the Project

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Delete shells


Workshop

ANSYS ICEM CFD v5.1



Add Prism Layers:

– Mesh => Mesh Prism

– Name the New volume part “Prism”

• Normally, leave this blank and the prisms will inherit their volume part from the original volume

– Select parts to mesh

• From the popup, select all the parts except the inlet, outlets and interface

• Leave the other fields blank

• Accept

– Set: Initial height to 0.6

– Default: Height ratio of 1.2

– Set: Number of layers to 2

– Compute Params to calculate total height

– Accept the other defaults

– Apply

– Load the Prism Mesh!

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Mesh Prism

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Workshop

ANSYS ICEM CFD v5.1



Display:

– Using the Mesh Cut Plane and transparent surfaces, view the mesh

• The Prism portion is currently an orange color, while the tetra and Hexa are blue and dark blue respectively. On the outer surface, the shells (tri or quad) take on the color of their respective surfaces

• The Volume element types now list Prisms

– More/thicker layers are possible, but limited by the height of the first volumetric hexa

• Prism layers can also be split and redistributed from the Edit Mesh menu

Display Hybrid Mesh


Workshop

ANSYS ICEM CFD v5.1



Observe:

– In the interface region, the prisms are uninterrupted

Next Steps:

– The elements may all need to be in one volume, use the model tree to add all three volume regions into one volume part.

– Smoothing/Diagnostics/Repair

– Use the Output tab to select a solver

– Apply Parameters and boundary conditions if desired

– Export to solver

Next steps

Hexas

TetrasPrisms

Quads Tris

Pyramids

icem cfd 5.1 new features workshop 15 hybrid meshing of a simple hvac assembly

Documents

file geometry

project file

blocking file

file browser display

open geometry icon

open project icon

file associations

geometry repair geometry