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 The information provided may be out of date.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.
Normal derivative on boundary in PDE Coefficient Form Mode
Posted 05.11.2011, 14:14 GMT-4 Version 3.5a 0 Replies
Please login with a confirmed email address before reporting spam
I am solving a 2-dimensional time depending PDE using the Coefficient Form of the PDE mode. The only dependent variable is u. For post-processing I want to calculate an integral along one boundary for every time step. The integral contains the derivative normal to this boundary. The bounday is along the x axis, so the normal derivative is along y.
What I tried: I have defined a boundary integration variable on the specific boundary. The expression is 0.5*cos(x)*ncu, where ncu shlould be the normal derivative to the boundary.
The user guide says: ncui: Normal components of the c*grad(ui) vector (Coefficient Form only). Only available when solving using coefficient form as solution form.
However, evaluating the exrpession after solving the PDE results in an error:
Error 6142
Cannot evaluate all expressions on any domain
Failed to evaluate variable
Variable: ncu....
I tried then different names for the normal derivative, ncu1, ncu_c, but I am getting the same error.
Any idea what I am doing wrong? Any hint is much appreciated.
Jorg
Hello Jorg Strutwolf
Your Discussion has gone 30 days without a reply. If you still need help with COMSOL and have an on-subscription license, please visit our Support Center for help.
If you do not hold an on-subscription license, you may find an answer in another Discussion or in the Knowledge Base.