Airstream Modeling with Comsol: Problems & Solutions

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Discussion Overview

The discussion revolves around modeling air streams using Comsol, specifically focusing on issues related to convergence errors and mesh refinement in simulations of airflow through a small jet. Participants explore the challenges faced in achieving reliable results and the potential need for different solvers or modeling approaches.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant reports difficulties with convergence in their Comsol model, experiencing errors related to solution reliability and mesh tolerance.
  • Another participant inquires about the specific errors encountered and the modules being used, suggesting that the physics of air streams should yield some results.
  • A participant mentions trying both incompressible and weakly compressible models but expresses doubt about the reliability of the results obtained.
  • One suggestion is made to use the solver manager to solve modules individually, indicating that issues may stem from the model setup.
  • A question is raised about whether a moving mesh is being utilized in the simulation.
  • Another participant shares their own challenges in modeling an air jet at low pressure, indicating a shared experience in the difficulties of the task.

Areas of Agreement / Disagreement

Participants express varying levels of uncertainty regarding the convergence issues and the effectiveness of different modeling approaches. There is no consensus on a definitive solution or agreement on the best practices for modeling air streams in Comsol.

Contextual Notes

Participants mention limitations related to mesh refinement and solver settings, but specific assumptions or dependencies on definitions are not fully explored. The discussion remains open-ended regarding the resolution of the modeling challenges.

Who May Find This Useful

This discussion may be useful for individuals working on fluid dynamics simulations, particularly those using Comsol for modeling airflows or similar applications.

1234frank1234
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I'm making a model in Comsol.
In it air streams from a pressure chamber through a small jet (1 mm).
It seems i am having problems with it because i can't get the tolerance or getting different errors.
I have revined the mesh as much as the computer can handle but i stil don't make it.
Is this a comon problem with simulating a airstream or do i need some different solver or so?
 
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What errors are you getting? Also what modules are you using? Incompressible, weakly compressible, or compressible? I've never modeled air streams before but the physics of it are relatively simple and you should at least get some type of answer.
 
Sorry for the late reply.
I have tried both incompressible and weakly compressible.
After the error occurred i do get a result but i think it is questionable how much i can rely on that.
The errors i get are:

Failed to find a solution:
No convergence, even when using the minimum damping factor.
Returned solution has not converged.

Also it happens that i can run it for ages with iterations above 1000 and i still didn't get a result.
 
Last edited:
It sounds like a solution can not be found for your model. Are you using only the navier-stokes module? If not, try solving the modules one at a time using the solver manager. If your only use the one, then you need to simply/modify your model so a solution can be found. Comsol is pretty good about converging and usually does so rather quickly. If it can't find a solution there s a good chance something is wrong with your model.
 
does this use a moving mesh?
 
Were you able to model your problem? I am also working on a similar project and can't model the air jet when it comes out of the nozzle at low pressure.


1234frank1234 said:
I'm making a model in Comsol.
In it air streams from a pressure chamber through a small jet (1 mm).
It seems i am having problems with it because i can't get the tolerance or getting different errors.
I have revined the mesh as much as the computer can handle but i stil don't make it.
Is this a comon problem with simulating a airstream or do i need some different solver or so?
 

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