Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.

Laminar two phase flow, moving mesh

Please login with a confirmed email address before reporting spam

Hi,
I am going to model a vapor bubble that is growing in the liquid inside a 2D channel. liquid has an inlet velocity that drag the bubble downstream and also bubble is growing due to the mass flux of evaporation that is going to bubble. I am using the "laminar two phase flow moving mesh". I noticed a warning "inverted mesh element " and then it diverges before even the first time step. can anyone help me to fix this?
Thank you in advance.

2 Replies Last Post Apr 14, 2017, 9:51 p.m. EDT

Please login with a confirmed email address before reporting spam

Posted: 7 years ago Apr 11, 2017, 12:02 a.m. EDT
Meisam,
The best thing is to contact the COMSOL support. However, try the following before you contact them:

- Start your simulation without evaporation/condensation and see if it works.
- Try to use the slowest liquid inlet velocity and ramp it up to your desired velocity.
- Use smaller relative and absolute errors.
- Start your simulation with coarser meshes.
- Use the fully coupled solver with PARDISO method (just according to my experience with this physics). Increase the number of allowed iterations, and update the Jacobean on every iteration. Change the damping factor in newton iteration or set it to automatic Newton rather than constant 1.
- Start your simulation with a very small time range (0,1e-3,1e-2). Then increase the time span (1e-2,0.1,1)

If none of the above get your simulation running, then contact COMSOL support.
Amin,
Meisam, The best thing is to contact the COMSOL support. However, try the following before you contact them: - Start your simulation without evaporation/condensation and see if it works. - Try to use the slowest liquid inlet velocity and ramp it up to your desired velocity. - Use smaller relative and absolute errors. - Start your simulation with coarser meshes. - Use the fully coupled solver with PARDISO method (just according to my experience with this physics). Increase the number of allowed iterations, and update the Jacobean on every iteration. Change the damping factor in newton iteration or set it to automatic Newton rather than constant 1. - Start your simulation with a very small time range (0,1e-3,1e-2). Then increase the time span (1e-2,0.1,1) If none of the above get your simulation running, then contact COMSOL support. Amin,

Please login with a confirmed email address before reporting spam

Posted: 7 years ago Apr 14, 2017, 9:51 p.m. EDT
Thank you for your response Amin,
I tested PARDISO but it is not gonna work well. I think it works well for Level Set not ALE.
I am solving the problem decoupling the energy equation and leaving out the evaporation but i could not get converged.
Thank you again.
Thank you for your response Amin, I tested PARDISO but it is not gonna work well. I think it works well for Level Set not ALE. I am solving the problem decoupling the energy equation and leaving out the evaporation but i could not get converged. Thank you again.

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.