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Help with COMSOL diffusion model
Posted 6 ago 2014, 05:15 GMT-4 4 Replies
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Hi all,
I was wondering if I could get some help with my COMSOL diffusion model. I have attached a copy of my model with this discussion below.
Essentially, this is what I'm trying to model: there is a certain threshold of nonanal that can be detected by the nose. I want to know what concentration of nonanal can be on an arm such that if the nose is a certain distance away, nonanal can not be detected (aka it is under the threshold concentration).
I have made a model on COMSOL and I get the following error:
After running this model with a normal mesh, I still get the following error:
Failed to evaluate variable Jacobian.
- Variable: D
- Geometry: 1
- Domain: 1 2 4 5
Any help with this will be greatly appreciated!! :)
I was wondering if I could get some help with my COMSOL diffusion model. I have attached a copy of my model with this discussion below.
Essentially, this is what I'm trying to model: there is a certain threshold of nonanal that can be detected by the nose. I want to know what concentration of nonanal can be on an arm such that if the nose is a certain distance away, nonanal can not be detected (aka it is under the threshold concentration).
I have made a model on COMSOL and I get the following error:
After running this model with a normal mesh, I still get the following error:
Failed to evaluate variable Jacobian.
- Variable: D
- Geometry: 1
- Domain: 1 2 4 5
Any help with this will be greatly appreciated!! :)
Attachments:
4 Replies Last Post 7 ago 2014, 06:20 GMT-4
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Posted:
1 decade ago
You have not defined the value of D in the parameters list which is actually empty. Go to Global Definitions and define there parameters. The same applies to your initial value 3, where c is not defined; you cannot use "c" as the initial value because that is the name of the variable you are solving! And you do not need convection box activated because it is set to zero.
With these alterations your model works.
br
Lasse
With these alterations your model works.
br
Lasse
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Posted:
1 decade ago
Hi,
Thank you for your response. What can I make initial condition 3 then? Because I don't know what to make it since that is what I'm trying to find..
Thank you for your response. What can I make initial condition 3 then? Because I don't know what to make it since that is what I'm trying to find..
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Posted:
1 decade ago
You have to define an explicit value for the initial concentration. It can be also time-dependent, but it cannot be a free variable.
Your geometry is such that a 3D model is not needed. I made an axisymmetric 1D model for you, attached. I use version 4.4, I wish you can open it.
Also some figures from the model report are attached.
BR
Lasse
Your geometry is such that a 3D model is not needed. I made an axisymmetric 1D model for you, attached. I use version 4.4, I wish you can open it.
Also some figures from the model report are attached.
BR
Lasse
Attachments:
- cylindrical diffusion.mph
- plotgroup_pg1.png
- plotgroup_pg2.png
- plotgroup_pg3.png
- mesh_mesh1.png
- mesh_mesh1_edg1.png
- mesh_mesh1_edg2.png
- physics_chds.png
- physics_chds_axi1.png
- physics_chds_cdm1.png
- physics_chds_cdm2.png
- physics_chds_init1.png
- physics_chds_init2.png
- physics_chds_nflx1.png
- geom_geom1.png
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Posted:
1 decade ago
Awesome! THank you so much!