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

Pressure centroid

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

Reply
 
LinkBack Thread Tools Display Modes
Old   October 7, 2009, 09:20
Default Pressure centroid
  #1
New Member
 
Join Date: Sep 2009
Posts: 19
Rep Power: 7
emanuele is on a distinguished road
Does anybody knows what's the way to display where the center of a pressure acting on a surface is located??

Many thaks in advance.
Emanuele
emanuele is offline   Reply With Quote

Old   October 9, 2009, 04:59
Default
  #2
Senior Member
 
Join Date: Mar 2009
Posts: 203
Rep Power: 9
Maddin is on a distinguished road
Area of maximum pressure?
Maddin is offline   Reply With Quote

Old   October 9, 2009, 05:56
Default
  #3
New Member
 
Join Date: Sep 2009
Posts: 19
Rep Power: 7
emanuele is on a distinguished road
I mean the center of pressure...or better....i need to know how to find the point on a body where the total sum of the hydrodynamic pressure field acts,causing a force and no moment about that point.
How to find the position of that point relatively to a coordinate system.
emanuele is offline   Reply With Quote

Old   October 9, 2009, 07:58
Default
  #4
New Member
 
Join Date: May 2009
Posts: 7
Rep Power: 8
mrjonezz is on a distinguished road
Correct me if I am wrong, but out of the top of my head I'd say you'd have to calculate the equilibrium of moments around the X and Y-axis from the geometrical center of area of the surface (don't know how to calculate that). So you need a script that adds all the moments around the X/Y axis from all the cells relative to this one point.

With this you'll be able to determine the y and x-coordinate (relative to geometrical center of area) of the point where those moments are zero on the surface and this must be the point where the area averaged pressure force has it's point of contact.

It's been a while since technical mechanics 1 but this must be it ore something like that.

--mrjonezz
mrjonezz is offline   Reply With Quote

Old   October 9, 2009, 08:06
Default
  #5
New Member
 
Join Date: Sep 2009
Posts: 19
Rep Power: 7
emanuele is on a distinguished road
of course it is possible to calculate it by hand...but i would like to do it easyer :-)
emanuele is offline   Reply With Quote

Old   October 9, 2009, 08:12
Default
  #6
New Member
 
Join Date: May 2009
Posts: 7
Rep Power: 8
mrjonezz is on a distinguished road
Well not by hand...just write a script ;-)
I hope I did not insult you with my post! :-) Of course you know!

You just want to know if there is a feature already...Sorry but I am new to CCM+ so not able to help.
mrjonezz is offline   Reply With Quote

Old   October 9, 2009, 08:15
Default
  #7
New Member
 
Join Date: Sep 2009
Posts: 19
Rep Power: 7
emanuele is on a distinguished road
don't worry...you didn't...nexst step is to learn how to manage with scripts :-)
emanuele is offline   Reply With Quote

Old   October 9, 2009, 08:21
Default
  #8
New Member
 
Join Date: May 2009
Posts: 7
Rep Power: 8
mrjonezz is on a distinguished road
Please let me know when you've figure it out...Sounds like a script that could come in handy! :-)
mrjonezz is offline   Reply With Quote

Old   October 9, 2009, 09:15
Default
  #9
New Member
 
Join Date: Sep 2009
Posts: 19
Rep Power: 7
emanuele is on a distinguished road
ok,i ll manage to do it by the mean of matlab!
emanuele is offline   Reply With Quote

Old   April 13, 2010, 20:35
Default
  #10
New Member
 
Join Date: Jan 2010
Posts: 8
Rep Power: 7
Actone-Zero is on a distinguished road
can we do it through the reports : surface integral of x*p/surface integral of p ?
Actone-Zero is offline   Reply With Quote

Old   April 14, 2010, 03:26
Default
  #11
New Member
 
Lin Möllenhoff
Join Date: Apr 2010
Location: Munich
Posts: 7
Rep Power: 7
lin123 is on a distinguished road
Hi,
you could define 3 user Field Functions for that.
(3 for x, y and z components)
shouldn t be so difficult!
greeds,
Lin
lin123 is offline   Reply With Quote

Old   April 14, 2010, 12:36
Default
  #12
New Member
 
Join Date: Jan 2010
Posts: 8
Rep Power: 7
Actone-Zero is on a distinguished road
In fact i wondering if, once you have the field function, the surface integral is correct in STAR.
Actone-Zero is offline   Reply With Quote

Old   April 15, 2010, 00:17
Default
  #13
Senior Member
 
Join Date: Mar 2009
Posts: 203
Rep Power: 9
Maddin is on a distinguished road
In some versions you have some bugs in 2D when using a extrusion which is normal to the boundary.
Maddin is offline   Reply With Quote

Old   April 15, 2010, 11:40
Default
  #14
New Member
 
Join Date: Jan 2010
Posts: 8
Rep Power: 7
Actone-Zero is on a distinguished road
I use 2D domain but I have tested in 3D it gives the same results.
I use 2 field functions, one is $$Position[0]*$Pressure and the other is just $Pressure, then I use the Surface Pressure reports and do the division. The pressure center computed stay around the middle of the airfoil but it should be around the aerodynamic center (1/4 chord).

Anyone have an idea?
Actone-Zero is offline   Reply With Quote

Old   April 23, 2010, 15:22
Default
  #15
Member
 
John
Join Date: Aug 2009
Posts: 93
Rep Power: 8
nomad is on a distinguished road
Can you attach the pressure distribution on the airfoil?
nomad 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
Neumann pressure BC and velocity field Antech Main CFD Forum 0 April 25, 2006 02:15
Gas pressure question Dan Moskal Main CFD Forum 0 October 24, 2002 22:02
what the result is negatif pressure at inlet chong chee nan FLUENT 0 December 29, 2001 06:13
Hydrostatic pressure in 2-phase flow modeling (CFX4.2) HB &DS CFX 0 January 9, 2000 14:19
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 12:50.