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Difference in results of a model with 3.5a and 4.2a versions

GaneshM Battery Modelling

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Hai,

I have tried to model my problem using PDE module in both COMSOL 3.5a and 4.2a versions. It have 4 dependent variables. I got reasonable results using 3.5a and verified them analytically. When I tried to do the same model using 4.2a , I am getting different results. I have difficulty in finding the reasons for this behavior. Although results are following the same behavior qualitatively, their quantitative values were different. Analytical verification tells me that results were not correct.

I used Identity pairs(IP) and periodic boundary conditions(PBC) in my model.

I suspect that problems with 4.2a as follows.

a). PBC doesn't override the default zero flux condition, it only contributes with it.

For this, I applied a 'continuity' using IP at both boundaries, so that it overrides the default zero flux and contributes with PBC. Results has not changed.

b) Bondary conditions using IP:
In 3.5a, boundary conditions using pairs shows like n.(gamma1- gamma2)= *. If this * equals to 0, it means continuity at given IP. If * equals some value, it means some jump in flux is there at that boundary. (For eg. withdrawing current at electrode).

But in 4.2a its showing n.(gamma)= * instead n.(gamma1- gamma2)= *, I have no other option then to give the same value for * as in 3.5a. It could be the one reason for other results.

Moreover, I have tried linear extrusion coupling parameter alternative to PBC, still I am getting the same results.

I believe that all my inputs are correct and verified many times.

The reason I came to conclude that the problem is with new version is I tried the 3.5a model file with 4.2 and i have some other results than 3.5a, but I remodeled everything new in 4.2a, I am getting the same results as upgraded results, not the results obtained in 3.5a.

It would be great help for me if someone throws light on my issues.

Thank you
Ganesh


3 Replies Last Post 2014年4月1日 GMT-4 13:46
COMSOL Moderator

Hello GaneshM

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Posted: 1 decade ago 2012年2月29日 GMT-5 11:01
I am also interested in this. How to specify a continuity condition like V3.5 in these new versions?

Have you found this now?
I am also interested in this. How to specify a continuity condition like V3.5 in these new versions? Have you found this now?

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 2012年2月29日 GMT-5 13:08
Hi

in V4 you need to define your Definitions Identity pairs (if in Assembly mode or leave COMSOL do it in the geometry FINISH node) then under each physics (or partial physics for multiple physics nodes) you must add a Pair Continuity node

--
Good luck
Ivar
Hi in V4 you need to define your Definitions Identity pairs (if in Assembly mode or leave COMSOL do it in the geometry FINISH node) then under each physics (or partial physics for multiple physics nodes) you must add a Pair Continuity node -- Good luck Ivar

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Posted: 1 decade ago 2014年4月1日 GMT-4 13:46

Hi

in V4 you need to define your Definitions Identity pairs (if in Assembly mode or leave COMSOL do it in the geometry FINISH node) then under each physics (or partial physics for multiple physics nodes) you must add a Pair Continuity node

--
Good luck
Ivar


Hello, Ivar, I'm facing the similar problem to assign a discontinuous flux interior boundary condition.
in 4.3 version, after defining the identity pair and add a Continuity node on the interface, the flux condition shows -n.(k (grad T))_dst= n.(k (grad T))_src, how to impose a flux jump on the interface which is nonzero? Thanks.
[QUOTE] Hi in V4 you need to define your Definitions Identity pairs (if in Assembly mode or leave COMSOL do it in the geometry FINISH node) then under each physics (or partial physics for multiple physics nodes) you must add a Pair Continuity node -- Good luck Ivar [/QUOTE] Hello, Ivar, I'm facing the similar problem to assign a discontinuous flux interior boundary condition. in 4.3 version, after defining the identity pair and add a Continuity node on the interface, the flux condition shows -n.(k (grad T))_dst= n.(k (grad T))_src, how to impose a flux jump on the interface which is nonzero? Thanks.

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