1. Workshop 15 Hybrid meshing of a simple HVAC assembly

2. 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.

3. Display Tree Open Geometry HVAC 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

4. Manage Parts
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
Hexa
Interface
Tetra

5. Hexa Meshing #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
Compute Pre-Mesh

6. Build Topology #1 #2
Now lets switch to the tetra portion. Turn off the Hex_Part assembly and turn on the Tetra_Part assembly. #3
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 #4 #5
Many curves are filtered out
Only essential feature curves remain #6 #7

7. Control Display through RMB
Set Mesh Sizes #1 #3 #2 #4
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 #5
Control Display through RMB
Tetra icons indicate tetra mesh sizes set on each surface

8. Control Display #1
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.
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

9. Mesh Tetrahedral Mesh Tetrahedral:#1 #2
Mesh Tetrahedral:
Mesh -> Mesh Tet -> From geometry
Activate: “Smooth transition”
Activate: “Run as batch process”
Activate: “Only visible geometry”
press Apply. #3 #4 #5 #6 #7

10. Load Hex Mesh with Tetra Mesh#1 #2
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 #3
This Merge simply concatenates the mesh files, the nodes are not connected

11. 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
Quads
Triangles
Overlapping Triangles and quads

12. Inspect interface volume
Display Mesh Volumes in the model tree
Zooming in reveals that the mesh needs to be merged
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

13. Merge Mesh Merge mesh: Edit Mesh => Repair Mesh => Merge Meshes#1 #2 #3 #6 #4
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. #5 #7

14. Delete shells The interface quads still remain#1 #2 #3
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 #4 #5

15. Mesh Prism Add Prism Layers: Mesh => Mesh Prism#1 #3 #2
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! #4 #6 #7 #5 #8

16. Display Hybrid Mesh 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

17. Quads Tris Prisms Tetras Hexas Pyramids Next steps 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
Prisms
Tetras
Hexas
Pyramids