Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here.
How do integral equation be the boundary condition when solve PDE problem?
Posted 2010/10/16 2:36 GMT-4 5 Replies
Please login with a confirmed email address before reporting spam
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.
Attachments:
Please login with a confirmed email address before reporting spam
have you tried to add a global equation u3=int(u1,0,2) and then force it to 10 ?
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
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.
Please login with a confirmed email address before reporting spam
sorry for that int() is my shortcut for integration (Model coupling)
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
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
Please login with a confirmed email address before reporting spam
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.