Menu

Discussion Forum

New Discussion
Filtern

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 The information provided may be out of date.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.

Plane wave scattering by a rigid sphere

Posted 24.10.2011, 12:56 GMT-4 Acoustics & Vibrations Version 4.2, Version 4.2a 2 Replies

Tiago Lobo
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi,

I'm trying to model a plane wave scattering by a rigid sphere. The problem is: the wave is travelling in the wrong direction. I set the e_r vector to (0,0,1), so result equation for the traveling wave should be: exp(-i*k*z). Them, the wave should be traveling from +z to -z. The result gives me a wave traveling from -z to +z.

thanks.
2 Replies Last Post 29.11.2011, 10:06 GMT-5
COMSOL Moderator

Hello Tiago Lobo

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.

Geoffrey Moss
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 29.11.2011, 09:29 GMT-5
I have seen similar strange behavior. I believe it has to do with the way they formulate the pressure fields (total vs scattered) and propagate the wave. A Kludgy workaround is to change your vector to (0,0,-1). Unless the 'source' of your wave is not at (0,0,0), then your phasing will be unaffected, and the wave will travel in the correct direction.
I have seen similar strange behavior. I believe it has to do with the way they formulate the pressure fields (total vs scattered) and propagate the wave. A Kludgy workaround is to change your vector to (0,0,-1). Unless the 'source' of your wave is not at (0,0,0), then your phasing will be unaffected, and the wave will travel in the correct direction.
Tiago Lobo
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago 29.11.2011, 10:06 GMT-5
Reading the documentation I found the reason for this strange behavior. Oddly, they define the time dependence as exp(i*w*t), instead of the usual exp(-i*w*t), which explains the difference.
To compare results using these 2 definitions you just have to take the conjugate of one of the answers. Put the wave to travel in the - direction will make the imaginary part be out of phase.
Reading the documentation I found the reason for this strange behavior. Oddly, they define the time dependence as exp(i*w*t), instead of the usual exp(-i*w*t), which explains the difference. To compare results using these 2 definitions you just have to take the conjugate of one of the answers. Put the wave to travel in the - direction will make the imaginary part be out of phase.

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