Meshing: Cap off for Cap on

October 11, 2012

Oftentimes when you are working with devices with internal fluid flow, the imported CAD design represents the vessel material. The inside is plainly void. This may leave you clueless since it is inside where you want to create a volume mesh for the flow equations. How can you solve this meshing problem in COMSOL?

CAD design of pipe for fluid flow analysis
CAD design of a pipe for fluid flow analysis. Only the solid is present and meshable.

  1. If you are looking to mesh the inside of an internal fluid flow device, you will need to use the Cap Faces feature. This adds a lid to inlet/outlets orifices and fills the inside with a mesh automatically. The cap can be a curved surface if needed.
  2. Cap Faces
    Right click geometry and select Cap Faces.

  3. Then select the bounding edges of the new cap.
  4. Edges next to the new cap are selected
    Select the edges that are adjacent to the new cap.

  5. If you have capped both the inlet and outlet orifices, a volume mesh will be created inside the pipe.
  6. Capped and filled geometry
    The capped and filled geometry.


Comments (8)

Leave a Comment
Log In | Registration
October 12, 2012

I didn’t find this option of CAP FACES for COMSOL 4.3a as I Have tried the same for the similar geometry.


James D. Freels
October 12, 2012

I think this is a CAD import module feature. Also, once used, the CAD import module license stays “checked out” each time this model is opened.

Bjorn Sjodin
October 15, 2012

Yes, this is correct. To get this feature, you will need to have the CAD Import Module or one of the LiveLink products for CAD.

Jeff Hiller
January 27, 2017

Update on Bjorn’s message above: Cap Faces is also available in the Design Module.

John Neumann
January 26, 2018

Is there a tutorial on how to use this? I tried adding cap faces to a model I have (a box with holes in it) and even though I see meshing happening on the cap face itself, it doesn’t look like it goes inside, and I don’t think any new domains were created. If I could just get to the point where I have a domain for where the fluid goes I would be happy. -Thanks

Niklas Rom
January 26, 2018

The channel (void) needs to be capped on all its orifices. If one hole is left uncapped, there will be no internal volume mesh. The capped domain also needs to belong same geometric object. Did you try to do a Form Union of all objects before capping?

Mike Paisley
Mike Paisley
November 19, 2019

Is there a tutorial/application/demo of this? I couldn’t find anything applicable. Or is there a tool that will show where the volume isn’t closed? I am using 5.4. Thanks. –m

Niklas Rom
Niklas Rom
November 20, 2019 COMSOL Employee

Hi Mike, there is tutorial in the documentation CAD Import Module > Introduction > Creating a Fluid Domain Around a Solid Structure > Creating a Domain with Cap Faces. The complete documentation can be found here:!/