How Can I Resolve Memory Issues in COMSOL for a Complex 3D Model?

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Discussion Overview

The discussion revolves around resolving memory issues encountered in COMSOL while working on a complex 3D model involving volumetric flow through a cylinder with a porous membrane. Participants explore various strategies for managing memory usage and optimizing the mesh for better performance.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant reports running out of memory on a 3D model with approximately 156,933 elements and seeks recommendations for resolution.
  • Another participant suggests two main options: reducing the mesh size or increasing RAM, and mentions the possibility of creating a swap file, albeit with potential time penalties.
  • A different participant recommends using an O-Grid hex mesh to reduce the number of elements while maintaining mesh quality, arguing that the current element count is manageable for most systems.
  • There is a suggestion to search for references on implementing swap files in COMSOL, indicating a need for guidance on this topic.
  • One participant expresses concern about the complexity of the model given the user's inexperience with COMSOL, suggesting alternative methods for creating a better mesh.
  • Another participant asserts that COMSOL lacks effective meshing tools, implying that manual creation or the use of external software may be necessary for achieving the desired mesh configuration.

Areas of Agreement / Disagreement

Participants express differing opinions on the best approach to mesh optimization and memory management. There is no consensus on the most effective solution, and multiple strategies are proposed without agreement on a single method.

Contextual Notes

Participants highlight limitations related to the user's experience level with COMSOL and the complexity of the model, which may affect the feasibility of the suggested solutions. There are also unresolved questions regarding the specifics of implementing memory management techniques within COMSOL.

Who May Find This Useful

This discussion may be useful for users of COMSOL facing similar memory issues, particularly those working with complex 3D models and seeking advice on mesh optimization and memory management strategies.

juvel006
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I'm running out of memory on my model help! 3D not axisymmetric! Pictures of geometry and mesh attached. Any recommendations on how to make this possible? This is volumetric flow through a cylinder with a thin membrane attached that is porous and utilizes brinkman's equations.
 

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PS: ~ 156933 elements in this domain.
 
You have two options, reduce the size of your mesh, or buy more RAM. You could also create a swap file but that will significantly increase the time required to solve the model.
 
I would be willing to try a swap file due to the time I have. I'll start looking at that but are there any references on how to do this in COMSOL? Thanks!
 
First, I'd HIGHLY recommend using an O-Grid hex mesh. There's no need for tets on a simple geometry like that. You're topology is a square(ish) rectangular prism through the center of the cylinder. Then just basically draw radial lines outward from the corners.

This will let you define exactly how you want the mesh. More importantly, you'll reduce the number of elements for the same quality mesh.

Next, as mentioned you can typically allow swap files or other memory management tools. These are sometimes runtime options, or specified in an input file somewhere. Do a search through the Comsol help to find that stuff.

Lastly, 160k elements is not a lot. If your machine can't handle that kind of run, then as Topher mentioned, get some more RAM. RAM is dirt cheap and you'd be surprised the increases in performance you can get.
 
Any idea on how to do that in COMSOL? I'm very new (< 1 week) at using it. Thanks again
 
You've been using Comsol for less than a week and you're solving a solution involving a porous membrane? I'd say you're out of your ability level already.

Either way, for a better mesh like I mentioned there are a couple methods. For the ANSYS analogy (since that's what I know), I would probably just create the model by hand. Then I could sweep the volumes as needed with proper inflation or spacing.

Alternatively we could bring the geometry into a mesher such as ICEM and do the work in there.
 
Comsol doesn't have a good meshing tool. If you want a O-grid hex mesh you will probably have to create it manually or with another software.
 

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