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

Getting forces on fixations from a pressure field

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

Reply
 
LinkBack Thread Tools Display Modes
Old   July 24, 2012, 17:27
Default Getting forces on fixations from a pressure field
  #1
Member
 
Charles
Join Date: May 2011
Location: France
Posts: 78
Rep Power: 6
Santos-Dumont is on a distinguished road
Hello Fluent guys,

I'm working on a aircraft project and I have a tricky analysis to do.
The aircraft have a pod mounted under it's fuselage. The pod have the shape on a very long bathtub and it is used to protect some electronic equipments.

The pod is held by something like 40 screws along it's perimeter. The force is indeed not equally distributed on each screws.

I would like to know if it's possible to get the actual stress (due to aerodynamic forces) on each screws ?
Calculating the pressure field is easy but I don't think that Fluent itself is capable of computing the stress on the screws. I was thinking of an export of the pressure field and then a static analysis with the pressure field as an input force. Using the Ansys Workbench may be helpful.

So I would like to have your opinion on that problem. Did some of you guys experiences a similar simulation ?

Thanks
Charles
Santos-Dumont is offline   Reply With Quote

Old   July 25, 2012, 16:19
Default
  #2
Member
 
Charles
Join Date: May 2011
Location: France
Posts: 78
Rep Power: 6
Santos-Dumont is on a distinguished road
This thread needs a little lift
Santos-Dumont is offline   Reply With Quote

Old   July 25, 2012, 20:37
Default
  #3
Member
 
NormalVector's Avatar
 
NormalVector
Join Date: Oct 2010
Posts: 72
Rep Power: 6
NormalVector is on a distinguished road
I don't think you can output mechanical stress, it is a CFD program after all. . You might be able to find a way to export the pressure field and bring it into Abaqus or something.
NormalVector is offline   Reply With Quote

Old   July 26, 2012, 02:02
Default
  #4
Senior Member
 
flotus1's Avatar
 
Alex
Join Date: Jun 2012
Location: Germany
Posts: 1,107
Rep Power: 19
flotus1 will become famous soon enoughflotus1 will become famous soon enough
In the workbench environment, it is actually straightforward to export the pressure on a surface you get from a CFD simulation and use it as a boundary condition for stress calculations in one of the other tools.
I rather see difficulties concerning computational cost solving the stress analysis with 40 screws.
flotus1 is offline   Reply With Quote

Old   July 26, 2012, 02:37
Default
  #5
Member
 
Charles
Join Date: May 2011
Location: France
Posts: 78
Rep Power: 6
Santos-Dumont is on a distinguished road
Hi Alex, thanks for the answer.

I tried to do a simple export and surprizingly, it worked pretty well. On the Static Structural I now have a pressure load given by Fluent. For the screws analysis, I was thinking of adding 40 points on my geometry and then use then to create Fixed Support. Then I shall be able to get the reaction on each support and therefore the stress on each screws by calculating Stress = Force / Surface

I'll try that on a simple model to see if it works
Santos-Dumont is offline   Reply With Quote

Old   July 26, 2012, 02:56
Default
  #6
Senior Member
 
flotus1's Avatar
 
Alex
Join Date: Jun 2012
Location: Germany
Posts: 1,107
Rep Power: 19
flotus1 will become famous soon enoughflotus1 will become famous soon enough
Well your approach (using fixed support instead of screws) will give you results.
But calculating Stress=Force/Area for a screw doesn't work. Since the screw and the material are already under stress before any load is applied (due to the pre-tightening of the screw), the calculation is more complex than that.

You could create a proper model of one screw connection and apply the loads you get from the structural analysis here.
flotus1 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


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pressure BC for combustion chamber Giuki FLUENT 1 July 19, 2011 11:35
custom pressure field at the faces Souviktor FLUENT 0 April 3, 2009 08:09
Problem with rhoSimpleFoam matteo_gautero OpenFOAM Running, Solving & CFD 0 February 28, 2008 07:51
How to get Pressure field from velocity field qunwuhe@hotmail.com Main CFD Forum 4 October 14, 2007 07:38
Hydrostatic pressure in 2-phase flow modeling (long) DS & HB Main CFD Forum 0 January 8, 2000 16:00


All times are GMT -4. The time now is 05:10.