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total weight calculation for a domain with variable density

Posted 28 déc. 2015, 07:36 UTC−5 Materials, Parameters, Variables, & Functions, Studies & Solvers 2 Replies

Aida Karimi
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I’m trying to model a polymer degradation process with Comsol in which I introduced degradation to my model by defining variable concentration of one of its ionomer blocks.
Then I defined its Density as: “(MW1[g/mol]*cIon1[mol/m^3])+const”.
And for calculating polymer weight loss during degradation process: I defined integration over Density.
cIon1=-R1 (which is degradation reaction)
I made sure that degradation reaction is positive by (R1=max(esp^2,r1))
However as I integrate Density on my domain it decreases and then increases after certain time!!!! Please help!!
2 Replies Last Post 3 janv. 2016, 02:59 UTC−5
Nagi Elabbasi Facebook Reality Labs
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Posted: 9 years ago 28 déc. 2015, 08:32 UTC−5
Dear Aida,

You probably mean “clon1t=-R1”. I suggest plotting clon1 to check that it remains positive, and also using a tighter convergence tolerance in your solver.

Nagi Elabbasi
Veryst Engineering
Dear Aida, You probably mean “clon1t=-R1”. I suggest plotting clon1 to check that it remains positive, and also using a tighter convergence tolerance in your solver. Nagi Elabbasi Veryst Engineering
Aida Karimi
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Posted: 9 years ago 3 janv. 2016, 02:59 UTC−5

Dear Aida,

You probably mean “clon1t=-R1”. I suggest plotting clon1 to check that it remains positive, and also using a tighter convergence tolerance in your solver.

Nagi Elabbasi
Veryst Engineering


Dear Nagi,
Thank you for your reply.I checked cIon1 and as you said it becomes negative so I modified my model:
CIon1=max(eps^2,cIon1)
W=CIon1*MW1+const
cIon1t=-R1
R1=max(eps^2,r1)
However the problem is still there, W increases after a certain time. I probe max value for CIon1 in the domain and the confusing fact is the it increases more than the initial value.
Please help.

Aida
[QUOTE] Dear Aida, You probably mean “clon1t=-R1”. I suggest plotting clon1 to check that it remains positive, and also using a tighter convergence tolerance in your solver. Nagi Elabbasi Veryst Engineering [/QUOTE] Dear Nagi, Thank you for your reply.I checked cIon1 and as you said it becomes negative so I modified my model: CIon1=max(eps^2,cIon1) W=CIon1*MW1+const cIon1t=-R1 R1=max(eps^2,r1) However the problem is still there, W increases after a certain time. I probe max value for CIon1 in the domain and the confusing fact is the it increases more than the initial value. Please help. Aida

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