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How do integral equation be the boundary condition when solve PDE problem?
Posted 16 oct. 2010, 02:36 UTC−4 5 Replies
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The PDE problem I want to solve includes a boundary condition which is a integral equation. How to handle it?
for example:
if the problem is:
du1/dx=2*x^2+u2
du2/dx=x*u1
x(-[0,2]
the boundary conditons are :
u1(0)=1
u2(0)=2
int(u1,0,2)=10
Then the last is the especial condition want to be dealed with.
It is very possible that the results is oscillating. But it is not important. What I want to know is the way to import the integral boundary condition.
My Comsol is V4.0, the mph file with no the integral condition is attached.
Thanks in advance.
youf.
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have you tried to add a global equation u3=int(u1,0,2) and then force it to 10 ?
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Good luck
Ivar
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Thanks for your help!
The error of "Unknown function. - Name: Int" was obtained when I followed your advice. The error occured again when "Int" was instead by "Integral". It seems that there was no built-in "integral function" in "Global equation".
Then how to handle it?
thank you very much!
youf.
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sorry for that int() is my shortcut for integration (Model coupling)
--
Good luck
Ivar
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another thing, when I see a PDE solution that is oscillating in line with the mesh, I know by experience that then the BC are overconstraine and your equation set is not correct, so I believe your example is not a coherent set of equations and BC's, there is something too much in there ;)
--
Good luck
Ivar
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Thanks for your help very much!
I has tried the "integration (Model coupling)" setting, but unfortunately the satisfying result can not be obtained. I think I must tried again and the process is required for a new user of Comsol.
Thank you for testing the example. It has not real significance. What I want to know is setting the integral equation. The boundary conditions is really too many for the equations.
youf.