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-   -   Pressure centroid (http://www.cfd-online.com/Forums/star-ccm/68964-pressure-centroid.html)

 emanuele October 7, 2009 09:20

Pressure centroid

Does anybody knows what's the way to display where the center of a pressure acting on a surface is located??

Emanuele

Area of maximum pressure?

 emanuele October 9, 2009 05:56

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.

 mrjonezz October 9, 2009 07:58

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

 emanuele October 9, 2009 08:06

of course it is possible to calculate it by hand...but i would like to do it easyer :-)

 mrjonezz October 9, 2009 08:12

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.

 emanuele October 9, 2009 08:15

don't worry...you didn't...nexst step is to learn how to manage with scripts :-)

 mrjonezz October 9, 2009 08:21

Please let me know when you've figure it out...Sounds like a script that could come in handy! :-)

 emanuele October 9, 2009 09:15

ok,i ll manage to do it by the mean of matlab!

 Actone-Zero April 13, 2010 20:35

can we do it through the reports : surface integral of x*p/surface integral of p ?

 lin123 April 14, 2010 03:26

Hi,
you could define 3 user Field Functions for that.;)
(3 for x, y and z components)
shouldn t be so difficult! :rolleyes:
greeds,
Lin

 Actone-Zero April 14, 2010 12:36

In fact i wondering if, once you have the field function, the surface integral is correct in STAR.

In some versions you have some bugs in 2D when using a extrusion which is normal to the boundary.

 Actone-Zero April 15, 2010 11:40

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?