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 The information provided may be out of date.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.
Derivatives in COMSOL
Posted 1 gen 2012, 21:17 GMT-5 Version 4.0 1 Reply
Please login with a confirmed email address before reporting spam
Hi! Is there any way to define in COMSOL 4.0 a derivative with respect to a variable which isn't an environment variable (like x,y,z, or time?)
Basically, I defined radius r = sqrt(x^2+y^2+z^2), and I want to define a radial derivative, but I believe COMSOL 4.0 doesn't allow me to use coordinates other than cartesian. How can I get around this problem?
Also, is it correct that I can denote the time derivative of variable "U" by "Ut"? My model gives me an error, I don't know why, and I want to know if this "Ut" notation is what is causing the error, or if it is something else.
Basically, I defined radius r = sqrt(x^2+y^2+z^2), and I want to define a radial derivative, but I believe COMSOL 4.0 doesn't allow me to use coordinates other than cartesian. How can I get around this problem?
Also, is it correct that I can denote the time derivative of variable "U" by "Ut"? My model gives me an error, I don't know why, and I want to know if this "Ut" notation is what is causing the error, or if it is something else.
1 Reply Last Post 2 gen 2012, 04:14 GMT-5
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Hi
check the doc or the help (better upgrade to a newer version) you have spatial and time derivatives, mostly predefined for your dependent variables up to 2nd order if you use "2nd order shape function" with your solver (the default)
else you must create your derivatives via an specific ODE, chekc the KB on the main site
--
Good luck
Ivar
check the doc or the help (better upgrade to a newer version) you have spatial and time derivatives, mostly predefined for your dependent variables up to 2nd order if you use "2nd order shape function" with your solver (the default)
else you must create your derivatives via an specific ODE, chekc the KB on the main site
--
Good luck
Ivar