CFD Geometry Tools select edge to Build Surface

[kevinwatts]

I am new to Autodesk Simulator CFD 2021 and am trying a simplified setup to get the workflow and steps working first. I have looked a tutorials and examples. I do not know why or how to compete this step.

Refer Tutorial to:

https://help.autodesk.com/view/SCDSE/2021/ENU/?guid=GUID-4B1E7F88-090A-4FAA-BA8A-314D3205F50F

and

https://www.youtube.com/watch?v=7Rv94-Lei9c

Objective:

To define the end point for a gas inlet supply tube by closing the inner surface loop to create a planar surface. In order to conduct a flow analysis.

Given:

OS Windows 10

CAD file created in Fusion 360. Fusion not picking up CFD to export directly. So Exported complete Component assembly as STEP file.

File opened/imported in to Autodesk Simulation CFD 2021

Removed 2 small objects.

“Diagnostics complete” in the Message Window.

Problem:

Using the Geometry Tools – Void Fill (tab) with Edges and Auto-close options selected, I cannot select the inner tube edge to Build Surface.

In my first attempt, the edge was selectable. However, when I clicked Build Surface, the process failed. Now inner edge seems broken. When hovering over the edge it appears as two separate edges “half circles.” Neither seem to be selectable. I have tried starting over again but still cannot select the compete edge.

[Simulator CFD - closed tube edge 2.png]

I tried again to start all over again and ran through the process with Geometry Tools to remove faces and merge edges. Then I got this result:

[Simulator CFD - closed tube edge 7.png]

Temporary Workaround (currently trying)

1. Back in the CAD file I have extruded the inner hole of the tube short of the end by 0.10” so that it appears closed. I am assuming that I can select the inner face and define it with a Boundary Condition for the gas inlet, type, volume, and direction.
2. In the CAD file, I may need to create a separate blank-off Component?

[kevinwatts]

In Simulation CFD 2021 I adjusted the Small Object - Edge tolerance to 0.02413 this may or may not have been important?

In Fusion simplified using one component that includes a tube.

Simulation workspace à clicked on Simplified Solid, clicked on Finish Simplification.

The materials of the component were removed.

Selected Tools (tab) à CFD 2021

Model imported in to Simulation CFD 2021. This time the Geomety Tools window did not popup. Opened Geomety Tools window no Edge or Small Objects to remove. Therefore, I assume that Fusion had cleaned up the model before exporting.

Selected the component in the Unassigned root of the Design Study Bar. Click Edit, and set up material.

Then I switched to Geomety Tools à Void Fill (tab), selected the inner circle of the tube and with Auto-close selected was able to Build Surface.

Output Bar says: “Diagnostic sweep compete. Surface successfully created.”  

Closed Geomety Tools window and the blank is added to the end of the hollow supply tube as desired.

See attached: Simulator CFD - tube blank created.png

[kevinwatts]

When including both the simplified chamber and a simple cylinder as a room. The error is repeated.

Surface successfully created.
Performing full diagnostic sweep...
Check model surface diagnostics. Meshing failure may result with default autosize settings.
Diagnostic sweep complete.

This is my third day with this roadblock. Does anyone have a suggestion?

[kevinwatts]

NEED HELP I AM STILL HAVING PROBLEMS!!

Problem:

Using the Geometry Tools – Void Fill (tab) with Edges and Auto-close options selected, I cannot select the inner tube edge to Build Surface.

I am must run a simulation of a gas being discharged through a device placed within a room.  For an initial test run with CFD, I am trying to create within the ID of a supply hole a “build surface” feature, to be used as a point of supply for the gas.

Going from Fusion à Simulation CFD

I can bring a simplified “device” (even just a short 0.25” hollow tube) component in to Simulation CFD and add a ‘build surface.’ No problems.

[Attached: CO2 Chamber-4 with build surface.png]

[Attached: Tube Test 2-1.png]

I can bring a 20’ x 8’ high hollow room round or square (1.0” walls) component in to Simulation CFD. CFD automatically creates the internal fluid environment, that I can configure as air. No problems.

However, when room and device components are brought in together, I get problems creating the “build surface” feature. First attempt seems to work but the feature disappears after closing the Geometry Tools window.

Last Output Bar – Error Message

Check model surface diagnostics. Meshing failure may result with default autosize settings.

The small object removal tool may prove useful for this model.

Sometimes, no error but no built surface.

What if I just build an internal surface in tube CAD component. Can I select the face and using Boundary Conditions configure it as the supply source for the gas inlet?

I am new to CFD. Please provide detailed suggestions or workaround. Please & Thank you.

[marwan_azzam]

Hello,

Any chance you can share your CAD model with us?

Marwan

[kevinwatts]

Thank you, Marwan for offering to help. I did send a link and password for the test model and CFD file through a private message after your post.

It appears that I have may have found the cause and solution by sheer determination. I want to continue testing today and confirm. There may be better approaches that I am not aware of at this point. I will post to forum as soon as I feel solid about defining the Boundary Conditions for the planner surface and fast Solve without further complications.

Kevin

[kevinwatts · Accepted solution]

Successfully created, gas inlet planner surface!

The following reference seems indicated why I was not previously able to create the planner surface.

Autodesk CFD 2021 - Void Fill

https://help.autodesk.com/view/SCDSE/2021/ENU/?guid=GUID-4B1E7F88-090A-4FAA-BA8A-314D3205F50F

The Void Fill tool provides a facility to create capping surfaces that bound a water-tight internal void. The surfaces and volume that are created are actual geometry that can have boundary conditions, materials, etc., and are meshed as part of the simulation model.

Note: The void fill volume must not overlap any other volumes (although it may completely surround other parts).

I tried to create a blank-off inside the tube. When setting Boundary Conditions for the face the following Warning: Setting cannot be applied to Surface 4: Non-planer surface

Solution

1. Simplified geometry. Reduced the size of the test room for initial testing.
2. Simplified geometry. Used a solid cylinder for the 3D CAD Room component without shelling. Previously shelled to created a wall effect, it worked but that complicated testing at this point.
3. Extended gas inlet geometry outside of the Room component that is used to create an environment filled with air.
4. Defined Material Properties
5. Created the void fill-surface planar surface at inlet of tube below room. Using Geometry Tools – Void Fill (tab) with Edges and Auto-close options selected, select the inner ID of the tube edge to Build Surface which creates a gas inlet planner surface that is not considered part of the model mesh but can be defined using Boundary

I hope this helps others new to CFD.

Kevin

1. Conditions.