Uncoupled physics modules fails to converge while they converge individually

Please login with a confirmed email address before reporting spam

I am trying to couple secondary current distribution (electrolyte potential) with laminar flow physics (velocity, pressure). The two physics models are actually uncoupled. When secondary current distribution physics and laminar flow physics are solved independently, the solution converges. But when they are coupled together, the solution fails to converge even though the two physics are uncoupled.



3 Replies Last Post Oct 9, 2024, 5:02 a.m. EDT

Please login with a confirmed email address before reporting spam

Posted: 3 weeks ago Oct 8, 2024, 4:06 a.m. EDT

I am not sure if I have the solution, but please try to use tertiary current distribution instead, that covers also mass transport. I would also round the corners in the geometry.

Convective transport is known to be a tricky problem to solve. As you certainly know, meshing is very decisive.

Good luck!

I am not sure if I have the solution, but please try to use tertiary current distribution instead, that covers also mass transport. I would also round the corners in the geometry. Convective transport is known to be a tricky problem to solve. As you certainly know, meshing is very decisive. Good luck!

Please login with a confirmed email address before reporting spam

Posted: 3 weeks ago Oct 8, 2024, 3:50 p.m. EDT

Thank you, Lasse! Your suggestion was very helpful. Removing the sharp corners helped and the simulation ran for a longer interval before convergence failure. It still puzzles me that the laminar flow physics problem runs fine even with sharp corners but fails when coupled with the secondary current distribution physics even though this contributes no coupling terms to the laminar flow physics.

My larger problem has coupling of secondary current distribution, transport of diluted species, and laminar flow which effectively is the tertiary current distribution with the supporting electrolyte option.

Thank you, Lasse! Your suggestion was very helpful. Removing the sharp corners helped and the simulation ran for a longer interval before convergence failure. It still puzzles me that the laminar flow physics problem runs fine even with sharp corners but fails when coupled with the secondary current distribution physics even though this contributes no coupling terms to the laminar flow physics. My larger problem has coupling of secondary current distribution, transport of diluted species, and laminar flow which effectively is the tertiary current distribution with the supporting electrolyte option.

Please login with a confirmed email address before reporting spam

Posted: 3 weeks ago Oct 9, 2024, 5:02 a.m. EDT

One more hint: add gradually the flow rate from zero to the target value, using auxiliary sweep below Study Extensions. That uses the previous solution as the initial value for the next. It helps quite often.

One more hint: add gradually the flow rate from zero to the target value, using auxiliary sweep below Study Extensions. That uses the previous solution as the initial value for the next. It helps quite often.

Reply

Please read the discussion forum rules before posting.

Please log in to post a reply.

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.