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Calculating PDEs in polar coordinates
Posted Jan 11, 2010, 11:11 a.m. EST 2 Replies
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To my knowledge, basically, COMSOL Multiphysics can handle governing equations written in several limited coordinates such as cartesian or axisymmetric cylindrical given by COMSOL, at least without any tricks.
However, I have to solve PDEs in polar coordinates. So, I'm wondering if the following scheme is hopeful or desperate.
Firstly, I choose cartesian coordinates and then regard x and y as r and phi, respectively. I'll never put any object in x < 0. Secondly, I have to modify PDE expression so that PDE is physically suitable form to the coordinates system. I think this can be done in PDE System Option. I should avoid all operator such as divergence and gradient because they are probably written assuming cartesian x and y. After I rewrote all the expressions (subdomain, boundary and point), I'll implement simulation.
This post may be ambiguous question and sorry about that. I have to admit that I'm not familiar with FEM business.
I really appreciate if you can kindly tell me any outlook or comment. Thank you.
However, I have to solve PDEs in polar coordinates. So, I'm wondering if the following scheme is hopeful or desperate.
Firstly, I choose cartesian coordinates and then regard x and y as r and phi, respectively. I'll never put any object in x < 0. Secondly, I have to modify PDE expression so that PDE is physically suitable form to the coordinates system. I think this can be done in PDE System Option. I should avoid all operator such as divergence and gradient because they are probably written assuming cartesian x and y. After I rewrote all the expressions (subdomain, boundary and point), I'll implement simulation.
This post may be ambiguous question and sorry about that. I have to admit that I'm not familiar with FEM business.
I really appreciate if you can kindly tell me any outlook or comment. Thank you.
2 Replies Last Post Jan 12, 2010, 2:40 a.m. EST
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Posted:
1 decade ago
Hi
nothing is desparate, but it is true that Comsol is first of all prepared for cartesian, up to you to rewrite it in spherical, polar or cylindrical.
Have you checked the "Support Knowlege Base" search polar on the website ? or go directly to
www.comsol.com/support/knowledgebase/939/
Depending on what you want to do you would need to rewrite several of the equations to handle the coordinate change, but this is nothing else than "traditional" mathematics.
Be aware that FEM is a method that requires still some time to understand specially its limitations and strengths, and what one can do today with COMSOL was rather "impossible" only a few years ago, at least from an engineering point of view, but still its not "just" to click a couple of buttons.
In anycase, have fun doing physics
Good luck
Ivar
nothing is desparate, but it is true that Comsol is first of all prepared for cartesian, up to you to rewrite it in spherical, polar or cylindrical.
Have you checked the "Support Knowlege Base" search polar on the website ? or go directly to
www.comsol.com/support/knowledgebase/939/
Depending on what you want to do you would need to rewrite several of the equations to handle the coordinate change, but this is nothing else than "traditional" mathematics.
Be aware that FEM is a method that requires still some time to understand specially its limitations and strengths, and what one can do today with COMSOL was rather "impossible" only a few years ago, at least from an engineering point of view, but still its not "just" to click a couple of buttons.
In anycase, have fun doing physics
Good luck
Ivar
Please login with a confirmed email address before reporting spam
Posted:
1 decade ago
Thanks a lot.
I've already checked "Support Knowlege Base 939", but I thought this tip still assume x-y coordinate and is not about governing equations but other expressions which users define.
I'll begin on this challenge by modifying governing PDEs and then benchmark my system against simple physical problem. Thanks again.
I've already checked "Support Knowlege Base 939", but I thought this tip still assume x-y coordinate and is not about governing equations but other expressions which users define.
I'll begin on this challenge by modifying governing PDEs and then benchmark my system against simple physical problem. Thanks again.