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.

Pressure acoustic boundary condition problem

Posted Oct 5, 2010, 1:00 p.m. EDT Acoustics & Vibrations 5 Replies

Silvina Cancelos
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Hi,

I'm having a problem with the Pressure-Acoustic module, specifically with the boundary conditions. What I'm modeling is a wave propagation in a pipe filled with water, what I'm using to model this is the pressure-acoustic transient analysis with axial symmetry and with a pulse generation at one end of the pipe as a boundary condition for a short time.

Here's the problem, when I set the sides of the pipe with hard wall condition (dp/dr=0) I get a reasonable pulse propagation but when I set the side of the pipe to soft wall (P=0), the data that I obtain of the pulse don't make any sense.

What I think that it might be the problem is due to a discontinuity between the condition in the side of the pipe with the ends of the pipe.

The pulse equation that I sent is:

P=10*sin(2*pi*t/0.00037)*sin(2*pi*t/0.0000741)*t<=0.00037/2

I attached two plots with the results. If Somebody can help me I would appreciate the help.
5 Replies Last Post Mar 28, 2011, 6:36 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Oct 6, 2010, 1:56 a.m. EDT
HI

with your oscilalting time pulse, are you using the "strict" or "intermediate" time stepping ? as the automatic one will undersample rapidly your "oscillating pulse"

--
Good luck
Ivar
HI with your oscilalting time pulse, are you using the "strict" or "intermediate" time stepping ? as the automatic one will undersample rapidly your "oscillating pulse" -- Good luck Ivar
Silvina Cancelos
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Oct 6, 2010, 12:02 p.m. EDT
I had used both of them and obtain the same result. Maybe it would be more easy to determine the problem if I upload the mph file. Thanks.
I had used both of them and obtain the same result. Maybe it would be more easy to determine the problem if I upload the mph file. Thanks.
fox mail3771
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Mar 26, 2011, 11:33 p.m. EDT

I had used both of them and obtain the same result. Maybe it would be more easy to determine the problem if I upload the mph file. Thanks.


you have input the P0 (it is the ininatial value, and can not changing with time )


have you solved this question?

[QUOTE] I had used both of them and obtain the same result. Maybe it would be more easy to determine the problem if I upload the mph file. Thanks. [/QUOTE] you have input the P0 (it is the ininatial value, and can not changing with time ) have you solved this question?
Daniel Gonzalez
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Mar 27, 2011, 5:06 p.m. EDT

HI

with your oscilalting time pulse, are you using the "strict" or "intermediate" time stepping ? as the automatic one will undersample rapidly your "oscillating pulse"

--
Good luck
Ivar


Where would you change this setting?
[QUOTE] HI with your oscilalting time pulse, are you using the "strict" or "intermediate" time stepping ? as the automatic one will undersample rapidly your "oscillating pulse" -- Good luck Ivar [/QUOTE] Where would you change this setting?
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
Send Private Message Flag post as spam

Please login with a confirmed email address before reporting spam

Posted: 1 decade ago Mar 28, 2011, 6:36 p.m. EDT
Hi

that is in the solver node/window (a few sub tabs/nodes down) v3.5 and v4

--
Good luck
Ivar
Hi that is in the solver node/window (a few sub tabs/nodes down) v3.5 and v4 -- Good luck Ivar

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