Menu

Discussion Forum

New Discussion
查找

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.

mass matrix is zero

Posted 2010年5月6日 GMT-4 14:08 1 Reply

Susant Patra
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi,

While solving 1D Helmholtz equation with eigenvalue solver, I am receiving "mass matrix is zero" error. How can I correct it? In my equation setup coefficients "c" and "a" are non-zero and rest are zero.

Thanks for your help.

Regards,
Susant
1 Reply Last Post 2012年6月19日 GMT-4 17:53
COMSOL Moderator

Hello Susant Patra

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.

Kevin McIlhany
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 2012年6月19日 GMT-4 17:53
The short answer is not to use the "Helmholtz Eqn" option when setting up a model. It makes too many assumptions about how you want to reach a solution and it imposes the need to define a mass matrix despite the fact that an eigenvalue problem may or may not have a mass matrix.

The easy fix it to start the model in "PDE Coefficient" mode and simply set the parameters up to be the same as the Helmholtz Eqn. This will work and it won't complain about a "mass matrix".

Good Luck.

-Kevin
The short answer is not to use the "Helmholtz Eqn" option when setting up a model. It makes too many assumptions about how you want to reach a solution and it imposes the need to define a mass matrix despite the fact that an eigenvalue problem may or may not have a mass matrix. The easy fix it to start the model in "PDE Coefficient" mode and simply set the parameters up to be the same as the Helmholtz Eqn. This will work and it won't complain about a "mass matrix". Good Luck. -Kevin

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.

Suggested Content