How can I fix this error in COMSOL Multiphysics 3.5a?

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Alin Dobre

Dear Mehran,

There are a set of reasons that could be the source of this type of error. Judging by the "Undefined_value_found_during_constraint_handling", you should check again all your variables names and make sure that they are called the same every time you mention them (e.g. in the Boundary or Subdomain Settings). Comsol is case sensitive, so you should also be careful with this one too.

"Last time the step is not converged." shows that your are conducting a time dependent study. If possible in your case, did you try to solve the problem using the simpler case of a stationary solver?

Samira Motaghinasab

Alin is right, check everywhere you use variables and make sure that variables name are the same especially in the expressions you have defined.

Mehran Dadfar

Dears I use an example of comsol in monolith reactor simulation, it was a tube that had symmetry boundary condition so its break to a quadrant, now I change my geometry to a quarter square with same boundary conditions but this error occur, I attach the related file.

Miss Samira Motaghinasab I use chemical engineering, pseudo 3d, mass transport, convection and diffusion for simulation of monolith reactor for CO removal in a first order reaction

I have worked with COMSOL (mass transport, diffusion) but now I am away of my PC. I will check it and come back to you.

Shahrulnizahani Mohammad Din

Salam/ Hi

Pls check your variables. Perhaps some of your variables is not defined properly.

Hello everybody, I found my problem solve: because of velocity profile equation was hyperbolic and my my surface area was square in corners the velocity equation returned negative values and you know negative velocity is undefined :)

Thanks a lot for taking time out for me.