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Uncoupled physics modules fails to converge while they converge individually

Posted Oct 7, 2024, 8:38 p.m. EDT Electrochemistry, Physics Interfaces Version 6.0 3 Replies

Subhasis Sarkar
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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.

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3 Replies Last Post Oct 9, 2024, 5:02 a.m. EDT
Lasse Murtomäki
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Posted: 6 months 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!
Subhasis Sarkar
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Posted: 6 months 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.
Lasse Murtomäki
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Posted: 6 months 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.

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