Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.
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.
Error using analytic function
Posted 2012年1月5日 GMT-5 01:00 Materials Version 4.2a 5 Replies
Please login with a confirmed email address before reporting spam
I am solving a 3D Helmholtz problem. The model can be defined by a cube and in the middle of it, I introduced a thin body region that has flux of a given sinusoidal function. I am not able to solve it as there is an error saying
Failed to evaluate expression.
- Expression: d((disp*test(mod1.u))*(dvol),{test@1})
disp being the name of the analytic function. The function i am interested in has the form of A*sin(pi*x).
When I repeat the problem by replacing the function with a constant value, the problem solves normally.
I have attached a sample file here for reference.
Hope someone can help me.
Thank you.
Best rgards,
EH
Attachments:
Please login with a confirmed email address before reporting spam
have you tried to define the derivative of your analytical function, manually ? (see the definition of your analytical function)
it looks like COMSOL is not managing to derive your A*sin(pi*x) function
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
Well, the derivative with respect to x will be A*pi*cos(pi*x) and 0 with respect to y and z. I entered these manually and I still get the same kind of error. Do you know what might be the problem here?
Thank you.
Best regards,
EH
Please login with a confirmed email address before reporting spam
I hadn't open your file, but when you refer to "disp" you need to write disp(x) or disp(y) or whatever that is correct, as the "x" in the function argument is a dummy variable name, you could have called it y, z, or t or whatever. when referring to functions the arguments to be use
then it solves ;) and the derivatives are taken correctly by COMSOL
--
Good luck
Ivar
Please login with a confirmed email address before reporting spam
Yup it solves now. I never thought a missing (x) was the issue. Anyway, it is runnign now. Thank you for your help.
Best wishes,
EH
Please login with a confirmed email address before reporting spam