Menu

Discussion Forum

New Discussion
Filter

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.

The synthesis and decomposition of forces do not apply to dynamics in COMSOL?

Posted Aug 24, 2019, 11:22 p.m. EDT Structural & Acoustics, Acoustics & Vibrations Version 5.3a 2 Replies

Chuanyong Wang
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi everyone.

I have built three 2D plane strain models in COMSOL, each model was applied dynamic concentrated forces (1 MHz, last 10 microsecond), which are equivalent, at point A as shown in the figure named 'resultant decomposed force', and the results were the displacement of Rayleigh wave in the far field (at point B) on the free surface.

Except for the forces are different, everything else for the three models are the same, the results should be the same since the forces are equivalent. However, the results are not the same, results of force 2 and 3 are the same, results of force 1 is different.

The results for force 1, 2, 3 can be found in the attached pictures. I have no idea why the results are not the same. Does the synthesis and decomposition of forces not apply to dynamics?

Would you please help me? Thank you a lot.

2 Replies Last Post Aug 26, 2019, 2:32 p.m. EDT
Henrik Sönnerlind COMSOL Employee

Please login with a confirmed email address before reporting spam

Posted: 5 years ago Aug 26, 2019, 10:42 a.m. EDT

Hi,

In principle this should be equivalent. So assuming that you did the decomposition correctly, my first guess would be that the time step or tolerance is too relaxed so that all three solutions are wrong but in different ways.

BTW: Did you use local coordinate systems for the force input, or just a manual tranformation?

Regards,
Henrik

-------------------
Henrik Sönnerlind
COMSOL
Hi, In principle this should be equivalent. So assuming that you did the decomposition correctly, my first guess would be that the time step or tolerance is too relaxed so that all three solutions are wrong but in different ways. BTW: Did you use local coordinate systems for the force input, or just a manual tranformation? Regards, Henrik
Chuanyong Wang
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 5 years ago Aug 26, 2019, 2:32 p.m. EDT

Hi Henrik,

Thank you for your answer, I solved the problem just now, I used a rotated coordinate system to load the inclined force, but the sign of the angle I put in was wrong, I would like the original frame to rotate 30 degrees clockwise, so it should be a negative angle, but I filled in a positive angle. Once I correct this, the results are correct. Thank you again.

Hi Henrik, Thank you for your answer, I solved the problem just now, I used a rotated coordinate system to load the inclined force, but the sign of the angle I put in was wrong, I would like the original frame to rotate 30 degrees clockwise, so it should be a negative angle, but I filled in a positive angle. Once I correct this, the results are correct. Thank you again.

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