CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > FLUENT

Modeling blast wave FSI, avoiding reflectivity and divergence

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Display Modes
Old   August 13, 2015, 15:56
Default Modeling blast wave FSI, avoiding reflectivity and divergence
  #1
Member
 
Kegan Leckness
Join Date: Mar 2015
Posts: 38
Rep Power: 3
KeganLeckness is on a distinguished road
Hi,

I'm in need of some advice in a two-way FSI simulation using Fluent/Mechanical. I'm modeling blast wave propagation through the ear and am having difficulty applying the pressure in such a way I get the waveforms I need.

See Fig_1. My model consists of three domains. Domain A and C are fluid (air) domains separated by a membrane, domain B. I'm interested in the pressures at the entrance of domain A and on either side of domain B.

The difficulty is here:
The triangular pressure waveform representing the oncoming blast wave can be seen in Fig_2. Assigning this pressure as a UDF on the entrance of domain A does not work - a reflecting wall is put up by Fluent to resist flow coming out of the 'pressure-inlet' and the pressure wavefront continually bounces back and forth between the entrance of domain A and the membrane, B. Implimenting the option to turn off the reflecting, artificial wall changes the waveform too much to be applicable to my case - it destroys the impulse nature of my triangular waveform.

I then tried adding an external flow field to the entrance of domain A, as seen in Fig_3, with a small pressure-inlet. All other boundaries of the external flow field were set to 0 Pa pressure-outlets. Doing this limited the reflectivity issue significantly.

Now, if I apply a 70 kPa pressure to the inlet of the external flow field, only 20 kPa is passed into domain A. Applying greater pressures (>100 kPa) to the external flow field yields AMG temperature Divergence.

Adding the additional domain got rid of my problem of reflectivity, but has limited the pressure levels I can reach inside domain A.

I'm more of a CFX guy (switched for dynamic remeshing) and need asssitance in working around this.

Any advice would be appreciated.
Thank you,
Kegan Leckness
Fig_1.PNG

Fig_2.PNG

Fig_3.jpg


Note: the imaged model is conceptual; mesh quality of the real model is a non-issue.
KeganLeckness is offline   Reply With Quote

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -4. The time now is 15:20.