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problem of self-defined parameter and build-in variables

Posted Feb 27, 2013, 9:48 p.m. EST Version 4.3a 6 Replies

Chaney Long
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I am using poroelasticity module. I have a problem about the self-defined parameter and build in variables.

I defined shear modules,G, as a function of axial displacement, w (a build in variable), and w is also influenced by G. i.e, they are interacted with each other. But I find that the self defined function G hasn't been invoked by the module.

In other words, how to self define a function or variable which is correlated to build in variable in comsol. I find it doesn't work if I just type a function in the to-be-defined variable.

anyone can give me some suggestions?
6 Replies Last Post Feb 28, 2013, 12:43 p.m. EST
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 28, 2013, 1:49 a.m. EST
Hi

"w" is normally a wariable used by COMSOl for the displacement along "z" (it's also defined if you are in 2D) so you should not use for anything else it as you will get unwanted interactions with then software.

try using my_w instead

--
Good luck
Ivar
Hi "w" is normally a wariable used by COMSOl for the displacement along "z" (it's also defined if you are in 2D) so you should not use for anything else it as you will get unwanted interactions with then software. try using my_w instead -- Good luck Ivar
Chaney Long
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Posted: 1 decade ago Feb 28, 2013, 9:09 a.m. EST

Hi

"w" is normally a wariable used by COMSOl for the displacement along "z" (it's also defined if you are in 2D) so you should not use for anything else it as you will get unwanted interactions with then software.

try using my_w instead

--
Good luck
Ivar


Thanks, Ivar,

I agree with you that w is the displacement along "z" direction, and my self-defined function G is actually a function of "w", i.e. G will change with respect to w. and also the change of G will lead to the variation of w. they interacted with each other. That is what I want.

But after I defined G as a function of w, G=f(w), I found that this equation has been invoked by the modeling calculation. Could you tell me where is the possible problem?

Thanks again.
[QUOTE] Hi "w" is normally a wariable used by COMSOl for the displacement along "z" (it's also defined if you are in 2D) so you should not use for anything else it as you will get unwanted interactions with then software. try using my_w instead -- Good luck Ivar [/QUOTE] Thanks, Ivar, I agree with you that w is the displacement along "z" direction, and my self-defined function G is actually a function of "w", i.e. G will change with respect to w. and also the change of G will lead to the variation of w. they interacted with each other. That is what I want. But after I defined G as a function of w, G=f(w), I found that this equation has been invoked by the modeling calculation. Could you tell me where is the possible problem? Thanks again.
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Feb 28, 2013, 11:30 a.m. EST
Hi

OK I did'nt catch it fully, but aren't you making a "loop" like that ?

--
Good luck
Ivar
Hi OK I did'nt catch it fully, but aren't you making a "loop" like that ? -- Good luck Ivar
Chaney Long
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Posted: 1 decade ago Feb 28, 2013, 11:58 a.m. EST

Hi

OK I did'nt catch it fully, but aren't you making a "loop" like that ?

--
Good luck
Ivar


Hi Ivar,

Yes, a little bit similar to "loop".

My meaning is: I need to self-define a function, G (which is a function of axial displacement in z direction (w), as an input of shear modulus in the "poroelasticity material" part. w is one of the output in this module and its variation will again influence the change of G. That is, the two variables are interacted with each other. But I found that when I just type the formula G=f(w) into the "model 1 ---->definition------->analytic" , this G function was not invoked in the modeling.
[QUOTE] Hi OK I did'nt catch it fully, but aren't you making a "loop" like that ? -- Good luck Ivar [/QUOTE] Hi Ivar, Yes, a little bit similar to "loop". My meaning is: I need to self-define a function, G (which is a function of axial displacement in z direction (w), as an input of shear modulus in the "poroelasticity material" part. w is one of the output in this module and its variation will again influence the change of G. That is, the two variables are interacted with each other. But I found that when I just type the formula G=f(w) into the "model 1 ---->definition------->analytic" , this G function was not invoked in the modeling.
Edgar Kaiser
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Posted: 1 decade ago Feb 28, 2013, 12:34 p.m. EST
You must put your G(w) function into the material properties, otherwise it is just a function definition.

Cheers
Edgar
You must put your G(w) function into the material properties, otherwise it is just a function definition. Cheers Edgar
Chaney Long
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Posted: 1 decade ago Feb 28, 2013, 12:43 p.m. EST

You must put your G(w) function into the material properties, otherwise it is just a function definition.

Cheers
Edgar


Thank you. Edgar,

I put the G(w) into the material properties, and the computing can work smoothly. but I found the the G(w) didn't be invoked by the computing. When I output the result of shear modulus G, I found that G is a constant, not changing as the function indicated.
thanks
[QUOTE] You must put your G(w) function into the material properties, otherwise it is just a function definition. Cheers Edgar [/QUOTE] Thank you. Edgar, I put the G(w) into the material properties, and the computing can work smoothly. but I found the the G(w) didn't be invoked by the computing. When I output the result of shear modulus G, I found that G is a constant, not changing as the function indicated. thanks

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