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Classic examples of modeling

Posted 13 nov. 2009, 08:17 UTC−5 4 Replies

SaeidS
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The lumped formulation of the variation of concentration of a salt (no reaction) in a CSTR (continuous Stirred Tank Reactor) is a classical example of modeling and could be done analyticallly in many different types of initial conditions.
I wonder if models like this have been redone with COMSOL in past. This could be a nice way of using COMSOL with classical modeling course even from the earliest stage.
4 Replies Last Post 15 janv. 2010, 11:57 UTC−5
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Minghui Tay
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Posted: 1 decade ago 12 janv. 2010, 19:28 UTC−5
Hi Saeid!

Good day!

Currently, I have been working on a laminar CSTR with Comsol 3.5a, using Moving Mesh (ALE) and incompressible Navier Stokes.

I started with 2D simulation, which was successful but inadequate to closely represent a CSTR. A 3D model is necessary.

However, I am facing a problem when solving the 3D model. I have been getting the error "Failed to find consistent initial values". Although I tried to do it step-by-step by solving the incompressible NS first and followed by combing with MM (ALE), I got the same error message when trying to solve NS in transient state. Solving NS in the steady-state is not a problem for both BICGSTAB and UMFPACK solvers.

Do you have any suggestion or solution to my problem?

Thanks!
Hi Saeid! Good day! Currently, I have been working on a laminar CSTR with Comsol 3.5a, using Moving Mesh (ALE) and incompressible Navier Stokes. I started with 2D simulation, which was successful but inadequate to closely represent a CSTR. A 3D model is necessary. However, I am facing a problem when solving the 3D model. I have been getting the error "Failed to find consistent initial values". Although I tried to do it step-by-step by solving the incompressible NS first and followed by combing with MM (ALE), I got the same error message when trying to solve NS in transient state. Solving NS in the steady-state is not a problem for both BICGSTAB and UMFPACK solvers. Do you have any suggestion or solution to my problem? Thanks!
SaeidS
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Posted: 1 decade ago 15 janv. 2010, 08:03 UTC−5
Hi Minghui,

I believe the best would be to contact COMSOL as I do not have that deep knowledge on how best to apply the boundary conditions.

Sorry that I could not be of help.

Regards,
Saeid
Hi Minghui, I believe the best would be to contact COMSOL as I do not have that deep knowledge on how best to apply the boundary conditions. Sorry that I could not be of help. Regards, Saeid
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Posted: 1 decade ago 15 janv. 2010, 11:32 UTC−5

The lumped formulation of the variation of concentration of a salt (no reaction) in a CSTR(...)


Hi Saeid,
with regards to your original question: With lumped I assume you mean perfect mixing and thereby no space gradients. Have a look at the Reaction Engineering Lab ( www.comsol.com/products/reaction/ ). It is packed with such models.

Niklas
[QUOTE] The lumped formulation of the variation of concentration of a salt (no reaction) in a CSTR(...)[/QUOTE] Hi Saeid, with regards to your original question: With [i]lumped[/i] I assume you mean perfect mixing and thereby no space gradients. Have a look at the Reaction Engineering Lab ( http://www.comsol.com/products/reaction/ ). It is packed with such models. Niklas
SaeidS
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Posted: 1 decade ago 15 janv. 2010, 11:57 UTC−5
Hi Niklas,

Thanks for the response.

As I understand I need to have the Reaction Engineering Lab module.

I have the two modules of Chenical Engineering and Heat Transfer. I thought the simple classical models of chemcial engineering such as CSTR without space gradients could be found in the Chemical Engineering Module. However, it seems that is not the case.

Thanks again,
Saeid
Hi Niklas, Thanks for the response. As I understand I need to have the Reaction Engineering Lab module. I have the two modules of Chenical Engineering and Heat Transfer. I thought the simple classical models of chemcial engineering such as CSTR without space gradients could be found in the Chemical Engineering Module. However, it seems that is not the case. Thanks again, Saeid

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