×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!
  • Students Click Here

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Jobs

acoustic modal analysis_ Workbench

acoustic modal analysis_ Workbench

acoustic modal analysis_ Workbench

(OP)
Hello!

I'm trying to do an acoustic modal analysis on a vocal tract mesh using Workbench 19. After importing the mesh from ICEM CFD (as .uns) a created a Named selection of the mouth and set a Boundary condition of 0 Pa accoustic pressure in there. I also created an Acoustic body so that the programme knows what body to use (i also set the speed of sound and mass density accordingly).

The goal is to compute the first 6 modes for the vowel /:a (their frequencies). After the calculation, I get 2.-6. mode calculated correctly, but the first mode is way off (see attached pic)(should be somewhere around 650). Any idea what I might be doing wrong?

Thanks in advance!


RE: acoustic modal analysis_ Workbench

Hi freiwyk,

Can you describe your boundary conditions a little more? How did you get a rigid body mode?

Suggestions:
- In your mode shapes, see if the 0 Pa acoustic pressure was respected. I suspect it is not, thus the presence of 0Hz rigid body mode.
- Since Ansys v18.2, "Modal Acoustics" is native in WB Analysis Systems now without need for ACT. You could give that a shot.
- Have you tried creating a simple room to check your process? (e.g. link)


Kind regards,
Jason

RE: acoustic modal analysis_ Workbench

(OP)
Hello Jason,

The only things I set were Accoustic pressure in the mouth area to 0 Pa (see attached picture) and Acoustic body as my imported geometry (the entire body).

I'm not sure if the acoustic pressure condition was respected, but I guess not, because the pressure is constant throughout the whole tract in the first mode (see attached pic). The computation is being run on ANSYS 17.2., my mistake.

I think I might be missing a condition somewhere, but I can't seem to find it.

I'm new to both ANSYS and acoustics, so I apologize in advance for any misleading information I might have provided :)

Thanks,
freiwyk

RE: acoustic modal analysis_ Workbench

Hi freiwyk,

Looks like the P=0 was not respected. Try V19.0 if you can. Otherwise, use a command snippet.

CODE --> apdl

cmsel, s, yourNamedSelectionMouthSet
D, all, pres, 0
allsel 


Kind regards,
Jason

RE: acoustic modal analysis_ Workbench

(OP)
[SOLVED]

Hello Jason,

You were right, it was not respected. Although I still really can't understand the reason behind it, all I had to do was change the Acoustic pressure from 'Named Selection' to 'Geometry Selection' (but still using the exactly same nodes). After that, everything worked like a charm. Nevertheless, it took me quite some time to find :)

Thank you for your time and effort!


Regards,

Michael

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login


Resources

eBook - 10 Reasons to Choose CATIA on the Cloud
To compete in today’s fast-paced and competitive market, smaller and newer firms need a powerful platform that will enable them to compete with bigger players, without the heavy investments needed in computer hardware, software and personnel. Download Now
White Paper - Smart Manufacturing for Electronics
This white paper describes a transformative approach to electronics manufacturing made possible by the addition of Mentor Graphics to the Siemens family. It describes a completely digitalized strategy that supports both printed circuit board (PCB) and mechanical design and manufacturing, uniting the entire product lifecycle – from idea and production to customers and back. Download Now

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close