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Volume Expansion
Posted 28.01.2011, 08:02 GMT-5 Version 4.0a 4 Replies
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I'm modeling Volume expansion of a disk shaped material.
I have used a ODE with this Expression :
v-vt=0
v=Vol1 , initial
But I got some errors
Failed to evaluate variable Jacobian.
- Variable: vt
- Global scope
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Could itbe that you are in structural and that v and vt are already used by COMSOL ?
Always use "private names, most 1-2 letter names are already used by COMSOL, sometimes you want to redefine them, but often it gives errors, as you need to know exactly what you are doing
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Good luck
Ivar
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I'm not using Structural. I have chosen ODEs and DAEs.
I have attached the Model.
I'd appreciate it if you could take a look.
Attachments:
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you cannot try to solve for an ODE alone as you have not defined any dependent variables What is v ?, and vol1 ?
You need to define some physics via an PDE and possibly add an ODE if required
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Good luck
Ivar
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Ivar is right (of course!).
But you can in fact solve an ODE, as a global space independent problem. You to define the dependent variable, as Ivar points out, and you can do this by setting Name to v in the Global Equations settings, also, change vol1 to 0 or something else that is defined.
If you want to solve a distributed ODE on a 2D domain (where sources may change with position, but you have no gradient driven transport), use rather a General form PDE and only use the f and da terms.
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Niklas