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.
PH buffer equilibrium reaction from 2D axissymmetric to 3D
Posted 2017年3月1日 GMT-5 11:45 Chemical Reaction Engineering 0 Replies
Please login with a confirmed email address before reporting spam
I want to simulate the pH change around an electrode in an electrolyte with a pH buffer.
I try to model this with the transport of diluted species module with four species: H,OH,A and AH. To simplify, my electrode is just a boundary with an inflow of OH- ions and two equilibrium reactions happening inside the electrolyte:
H+ + OH- -> H20 with equi const 1/Kw Kw=10^-14 water dissociation constant
HA -> H+ + A- with equi const Ka buffer dissociation constant
Starting condition is such that the equilibrium is fulfilled.
Here is my problem:
In 2D axissymmetric everything works fine and the simulation actually correspond to measurement values.
Now I want to look at an asymmetric electrode configuration and model the thing in 3D. So I build the exact same situation as before, same boundary conditions and everything as 2D axissymmetric but in 3D and I get the error message:
Failed to find consistent initial values.
Matrix has zero on diagonal.
Last time step is not converged.
Any help would be greatly appreciated. I have tried so far:
- Making the mesh as small as 70 GB ram can handle
- Tried different solvers: Fully Coupled, Segregated
Hello Michael Matter
Your Discussion has gone 30 days without a reply. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help.
If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base.