Hi, everyone!
I'm trying to add a Weak Contribution in 0D model in Comsol 6.1, but after clicking to Study I got an error: Undefined variable.
It looks to be a simple task since earlier in the 1D and 2D models I added such a function (Weak Contribution) without any problems.
About the model, I take the built-in model "boltzmann_argon", then I add a simple analytical function an1: if(x>0.5,sqrt(x-0.5),0). After that, I add a Weak Contribution with an expression an1(be.xeedf)*test(F0). After running the solver, I get the error: Undefined variable. I also tried to start the model without test(F0) in Weak Contribution but also got the same error. The question is, how do I add a Weak Contribution to the 0D model correctly? In other Comsol versions also tried, but I got the same error. I looked for answers in the COMSOL documentation, but nothing is written about it there
Dear Yubin He, thank you for your reply.
"test()" is a built-in operator (like as "sum()" or "no jack()" etc.), underlying the weak form of PDE. Do we need to redefine it?
We tried F0, be.F0, comp1.be.F0, which are already defined. It is unclear what to do?
Sincerely, Rabadanov Kurban
F0 is defined in the "boltzmann_argon" model from application's library, in which I tried to add Weak Contribution.
I also tried to redefine F0 in "Definitions - Variables" (Name - reF0, Expression - be.F0), but I also got the Error: Undefined variable F0
Dear Yubin He,
In this model the equation is solved for F0 (i.e. be.F0), be.F0 is a function of the energy be.xeedf, i.e. be.F0(be.xeedf). Yes, we can assume that F0 is a built-in function. The problem is not in the name of this function, but in how to correctly implement the Weak Contribution in the 0D model.
I don't have the Plasma module, but just to stay on the variable name; removing an1(be.xeedf) and leaving test(F0) leads to a 'Unknown variable' message, whereas test(be.F0) on its own seems to be fine. You say you have tried this, so it seems that the combination of an1 and test gives you the problem, perhaps?
Undefined Variable - Knowledge Base
📷
COMSOL
https://www.comsol.com › support › knowledgebase
This error indicates that a variable used in some setting is undefined. It might be a spelling error, or a name of a variable that has not been defined.
Missing: od | Show results with: od
Dear, René Christensen
I tried to do it separately, but also got the same error.
It is like considering the equation of the heat transfer, and we want to add a heat source. In the heat transfer equation, the temperature T is a function of the position x, and if we want to add the additional heat source "HS" in this equation, we do it this way: HS*test(T). In the same way, I'm trying to add the additional source in my model (in my model the F0 is a function of the energy (xe_be in Comsol)). I tried to add just test(F0) I also got an error. René Christensen
Do you have comsol support? They could probably help you out with this...
René Christensen
Unfortunately, my subscription ended last year. And also I didn't find an answer in the Сomsol knowledge base either
- Badges
- Science topic
- Similar topics
- Biological Science
- Biota
- Eukaryota
- Fungi