Pressure centroid

emanuele · October 7, 2009, 09:20

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

Maddin · October 9, 2009, 04:59

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!

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.

Maddin · April 15, 2010, 00:17

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?

nomad · April 23, 2010, 15:22

Can you attach the pressure distribution on the airfoil?

October 7, 2009, 09:20	Pressure centroid	#1
emanuele New Member Join Date: Sep 2009 Posts: 19 Rep Power: 16	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

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October 9, 2009, 04:59		#2
Maddin Senior Member Join Date: Mar 2009 Posts: 260 Rep Power: 18	Area of maximum pressure?

October 9, 2009, 05:56		#3
emanuele New Member Join Date: Sep 2009 Posts: 19 Rep Power: 16	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.

October 9, 2009, 07:58		#4
mrjonezz New Member Join Date: May 2009 Posts: 7 Rep Power: 16	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

October 9, 2009, 08:06		#5
emanuele New Member Join Date: Sep 2009 Posts: 19 Rep Power: 16	of course it is possible to calculate it by hand...but i would like to do it easyer :-)

October 9, 2009, 08:12		#6
mrjonezz New Member Join Date: May 2009 Posts: 7 Rep Power: 16	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.

October 9, 2009, 08:15		#7
emanuele New Member Join Date: Sep 2009 Posts: 19 Rep Power: 16	don't worry...you didn't...nexst step is to learn how to manage with scripts :-)

October 9, 2009, 08:21		#8
mrjonezz New Member Join Date: May 2009 Posts: 7 Rep Power: 16	Please let me know when you've figure it out...Sounds like a script that could come in handy! :-)

October 9, 2009, 09:15		#9
emanuele New Member Join Date: Sep 2009 Posts: 19 Rep Power: 16	ok,i ll manage to do it by the mean of matlab!

April 13, 2010, 20:35		#10
Actone-Zero New Member Join Date: Jan 2010 Posts: 8 Rep Power: 16	can we do it through the reports : surface integral of x*p/surface integral of p ?

April 14, 2010, 03:26		#11
lin123 New Member Lin Möllenhoff Join Date: Apr 2010 Location: Munich Posts: 7 Rep Power: 16	Hi, you could define 3 user Field Functions for that. (3 for x, y and z components) shouldn t be so difficult! greeds, Lin

April 14, 2010, 12:36		#12
Actone-Zero New Member Join Date: Jan 2010 Posts: 8 Rep Power: 16	In fact i wondering if, once you have the field function, the surface integral is correct in STAR.

April 15, 2010, 00:17		#13
Maddin Senior Member Join Date: Mar 2009 Posts: 260 Rep Power: 18	In some versions you have some bugs in 2D when using a extrusion which is normal to the boundary.

April 15, 2010, 11:40		#14
Actone-Zero New Member Join Date: Jan 2010 Posts: 8 Rep Power: 16	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?

April 23, 2010, 15:22		#15
nomad Member John Join Date: Aug 2009 Posts: 92 Rep Power: 16	Can you attach the pressure distribution on the airfoil?