Hello and welcome!
In this video, we will learn how to import CAD geometry into the watertight workflow.
Import geometry is the first step in the Watertight geometry workflow,
and as the name suggests the primary function of this task is to import a CAD geometry into the workflow.
Let’s start Fluent in meshing mode and see the CAD Geometry Import in action.
Click on the ‘Select Workflow Type’ drop down and select 'Watertight Geometry'.
You can see that Fluent Meshing loads all the tasks associated with this workflow.
Select Import Geometry by clicking on it.
In the File Format drop down list, you can see that there are two choices - CAD and Mesh.
We will select the 'CAD' option for now, as we are going to import a CAD file in the .scdoc format.
Next, we need to specify a suitable working unit for the meshing process.
Keep in mind that the generated volume mesh will automatically be scaled to meters when
we switch from Fluent meshing to the solver.
For this example, we will use ‘mm’ as the working unit, since the length scale of
the geometry that we are using, is of the order of 100 mm.
The import geometry task also has a couple of advanced options that allow us
to Separate zones based on a particular criterion and enable Custom Faceting.
Let us keep the default settings for now.
We will come back to it in a moment.
Click on the button with three dots to select the file.
As you can see the default file type is set to Ansys CAD formats.
In case you would like to import other CAD formats then please change this to 'Other CAD Formats'.
In this example, we will use the Ansys CAD formats and select the file ‘Exhaust_Manifold.scdoc’.
Fluent Meshing will now import the geometry.
You can see the progress in the console window.
You will notice a green check mark next to the import Geometry task
indicating the successful completion of the import step
and the workflow would progress to the next step as shown here.
If you would like to make any changes to the geometry or update the geometry that was imported,
then you can select the Import geometry task and click on 'Revert and Edit'.
Keep in mind that this will undo all the subsequent steps that you may have completed,
and you will need to go through them again.
Now, let's look into the advanced options.
We have two additional settings.
The first one is the 'Separate Zone By' setting which allows us to separate the zones either
based on a region or a combination of a region and a separation angle.
This may be required for selecting faces for applying local size controls,
if the Named Selections were not created while preparing the geometry.
Additional details about these options can be found in the User’s guide.
The second one is the ‘Use Custom Faceting’.
Enabling this option, by checking this box,
allows users to set the Tolerance and the Maximum Facet Length.
The Tolerance setting is used for specifying the level of facet refinement during the import
and it is recommended that we use a value that is approximately 1/10th of the intended minimum size.
Using a value of zero results in the coarsest possible faceting.
You can also specify a maximum facet length for the imported model which will help to
avoid very large facets during the import.
We can quickly see the effects of these advanced options by analyzing the resulting imports
for the exhaust manifold geometry with different settings.
On the left side we have the imported geometry corresponding to a tolerance of 0,
which corresponds to the coarsest possible faceting, and a max Facet Length of 50,
whereas on the right side, we use a tolerance of 0.01 for the same max facet length.
You can see refined facets of the imported geometry on the right side.
This difference can be quantified if you look at the number of nodes, edges, and faces
in the console output.
Similarly, we can analyze the effect of the Max Facet Length in these two cases.
On the left side we have the imported geometry corresponding to a max Facet Length of 50,
whereas on the right side, the max facet length is set to 5.
For both the imports, we have set the tolerance to 0, corresponding to the coarsest possible faceting.
You can see refined facets of the imported geometry on the right side.
Once again, this difference can be quantified if you look at the number of nodes, edges,
and faces in the console output.
Before we wrap up, let's talk about the pmdb file format.
PMDB files are automatically created from CAD files during the Import Geometry Task.
They can also be exported from SpaceClaim as shown here.
This file format comes in handy when working on Linux.
Since SpaceClaim is not supported on Linux, Fluent Meshing cannot import .scdoc files on Linux.
You can use the exported pmdb file for importing the geometry while working on Linux.
It must be noted that importing a PMDB file requires significantly less time than importing
the CAD files from which it was created.
Therefore, if the geometry is going to change in the Fluent meshing session,
then selecting the PMDB file is going to be faster.
So, to summarize, in this video we learned how to import a CAD geometry
into the Watertight Workflow and the various settings associated with it.
We also discussed the advanced options available for separating zones and enabling custom faceting.
Lastly, we discussed the importance of the pmdb file format.
This brings us to the end of our video.