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 The information provided may be out of date.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.

Weak Form Modeling and Multiphysics Coupling in RF Module

Please login with a confirmed email address before reporting spam

Hello All,

I have some problems when using user-defined weak form PDEs and multiphysics coupling for 3D nano particles scattering in the RF module. Please find the attachment for the detailed information. Any comments would be highly appreciated. Thanks in advance.

Cordially,
Tony


11 Replies Last Post Apr 22, 2013, 5:44 p.m. EDT

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 15, 2013, 5:45 p.m. EDT
Hi,

As for your first question, I think the whole matrix equation system solved at last comes from both weak forms of Maxwell's equation and boundary conditions. As you may have noted the original weak form of Maxwell's equation corresponds to the one with negative sign, so if the one without negative sign is used, it's not consistent with the weak form of boundary conditions. I'm not sure, but this could be the reason.

The second one, you said the problem doesn't appear for 2D case, but I don't know how you introduce the coupling for 2D case. I suppose 3D case is the same.

Best
--
Pu, ZHANG ??
Departamento de Física Teórica de la Materia Condensada,
Universidad Autónoma de Madrid,
Madrid, Spain.
Hi, As for your first question, I think the whole matrix equation system solved at last comes from both weak forms of Maxwell's equation and boundary conditions. As you may have noted the original weak form of Maxwell's equation corresponds to the one with negative sign, so if the one without negative sign is used, it's not consistent with the weak form of boundary conditions. I'm not sure, but this could be the reason. The second one, you said the problem doesn't appear for 2D case, but I don't know how you introduce the coupling for 2D case. I suppose 3D case is the same. Best -- Pu, ZHANG ?? Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, Madrid, Spain.

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 15, 2013, 5:55 p.m. EDT
Thanks Pu. You may be right, I will check the boundary constraints. For the 2D coupling case, you just need to consider the in-plane E, and as you mentioned, it has the same formulation expect that some terms reduce to zero.

Cordially,
Tony
Thanks Pu. You may be right, I will check the boundary constraints. For the 2D coupling case, you just need to consider the in-plane E, and as you mentioned, it has the same formulation expect that some terms reduce to zero. Cordially, Tony

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 15, 2013, 5:59 p.m. EDT
I think the second question is about the coupling between the two equations. How do you do that for 2D case? I'm sorry I don't get it.

--
Pu, ZHANG ??
Departamento de Física Teórica de la Materia Condensada,
Universidad Autónoma de Madrid,
Madrid, Spain.
I think the second question is about the coupling between the two equations. How do you do that for 2D case? I'm sorry I don't get it. -- Pu, ZHANG ?? Departamento de Física Teórica de la Materia Condensada, Universidad Autónoma de Madrid, Madrid, Spain.

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 15, 2013, 6:23 p.m. EDT
Hello Pu, for the coupling between two nano wires (2D case), you can use the following weak form for J,
beta^2*Jh1x+Jh2y)*test(Jh1x)-(omega0^2-1i*omega0*gamma)*Jh1*test(Jh1)-1i*omega0*epsilon0_const*omegap^2*emw.Ex*test(Jh1)
beta^2*Jh1x+Jh2y)*test(Jh2y)-(omega0^2-1i*omega0*gamma)*Jh2*test(Jh2)-1i*omega0*epsilon0_const*omegap^2*emw.Ey*test(Jh2)
and the boundary condition reduces to
nx*Jh1+ny*Jh2=0

And, for the Electric field, the user-defined weak form reduces to
-emw.curlEz*test(curlEz)+epsinf*emw.k0)^2*emw.Ex*test(emw.relEx)+emw.Ey*test(emw.relEy))-emw.iomega*mu0_const*(Jh1*test(emw.relEx)+Jh2*test(emw.relEy))

It works good for me.

Cordially,
Tony



Hello Pu, for the coupling between two nano wires (2D case), you can use the following weak form for J, beta^2*Jh1x+Jh2y)*test(Jh1x)-(omega0^2-1i*omega0*gamma)*Jh1*test(Jh1)-1i*omega0*epsilon0_const*omegap^2*emw.Ex*test(Jh1) beta^2*Jh1x+Jh2y)*test(Jh2y)-(omega0^2-1i*omega0*gamma)*Jh2*test(Jh2)-1i*omega0*epsilon0_const*omegap^2*emw.Ey*test(Jh2) and the boundary condition reduces to nx*Jh1+ny*Jh2=0 And, for the Electric field, the user-defined weak form reduces to -emw.curlEz*test(curlEz)+epsinf*emw.k0)^2*emw.Ex*test(emw.relEx)+emw.Ey*test(emw.relEy))-emw.iomega*mu0_const*(Jh1*test(emw.relEx)+Jh2*test(emw.relEy)) It works good for me. Cordially, Tony

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 16, 2013, 3:05 a.m. EDT
Then the 3D should be the same way, just introduce Jh into the weak form of Maxwell's equation.
Then the 3D should be the same way, just introduce Jh into the weak form of Maxwell's equation.

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 16, 2013, 9:34 a.m. EDT
Yes, it should work. I'll double-check the configurations, there must be something wrong. Thanks anyway.
Yes, it should work. I'll double-check the configurations, there must be something wrong. Thanks anyway.

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 16, 2013, 9:35 a.m. EDT
Good luck!
Good luck!

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 16, 2013, 1:08 p.m. EDT
Oh, I just noticed that I was reading your recent paper a few days back which was just accepted by The Journal of Physical Chemistry. What a small world! And I appropriate that you guys cited our paper. Thanks. ^o^
Oh, I just noticed that I was reading your recent paper a few days back which was just accepted by The Journal of Physical Chemistry. What a small world! And I appropriate that you guys cited our paper. Thanks. ^o^

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 16, 2013, 1:12 p.m. EDT
Yes... That's why I'm somewhat familiar with this particular problem. Your paper is closely related to our work. Good to meet you here. Hope everything goes well!
Yes... That's why I'm somewhat familiar with this particular problem. Your paper is closely related to our work. Good to meet you here. Hope everything goes well!

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 16, 2013, 1:21 p.m. EDT
Haha, you guys gave us a very interesting paper. Nice to meet you as well. Enjoy your day.
Haha, you guys gave us a very interesting paper. Nice to meet you as well. Enjoy your day.

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Apr 22, 2013, 5:44 p.m. EDT
I checked the configurations and the coupled equations are good. It seem to me that the problem is the solver. The default iterative solver do not work since the two PDEs are highly coupled compared to the 2D one. If we use direct solvers, e.g., PARDISO, which requires much larger memory, we can get the desired results. Anyway, I believe there could be some iterative solvers suitable for this problem.

Cordially,
Tony
I checked the configurations and the coupled equations are good. It seem to me that the problem is the solver. The default iterative solver do not work since the two PDEs are highly coupled compared to the 2D one. If we use direct solvers, e.g., PARDISO, which requires much larger memory, we can get the desired results. Anyway, I believe there could be some iterative solvers suitable for this problem. Cordially, Tony

Note that while COMSOL employees may participate in the discussion forum, COMSOL® software users who are on-subscription should submit their questions via the Support Center for a more comprehensive response from the Technical Support team.