Computing Center of Pressure

FFD · October 5, 2015, 10:53

Hello,
I want to compute the center of pressure. My thoughts were to find a point were all moments are 0. But i don't know how to find it.

The steve portal have an article about how to find the cop. But I don't really understand the idea behind that method and it doesn't really work. The cop is wrong for sure. I tried it on a simple airfoil and the line_point (described in the Steve Portal) didn't even hit the airfoil. But the CoP should be on the airfoil.

Have you any suggestions?

Regards

-FFD

me3840 · October 5, 2015, 20:21

There are many unique solutions to the CoP in 3D of a body. You must guess where the point is first, and then iterate the position of that point until all moments are zero.

FFD · October 6, 2015, 03:29

I had the same idea. But how I can do itin Star-CCM? I am not really experienced in CFD. I had this idea:
I made a Force and a moment report for every axis.
But these vectors are for the full part. How can I check the force and the moment at a specific point? And How I can iterate the position? My idea would be to run the simulation and create a macro that change the values and check if the moment are 0 at that point. But that would be extremly inefficient.
But if I know how to check the moment at a specific point. Somebody do have any suggestions?

-FFD

me3840 · October 6, 2015, 19:28

The moment/force reports takes as input a coordinate system and direction, so you just pick a point and run the report.

You will have to write a macro to iterate through the positions, yes. It probably won't be as inefficient as you think.

me3840 · October 6, 2015, 19:29

This thread may help:
http://www.cfd-online.com/Forums/ope...aero-body.html

October 5, 2015, 10:53	Computing Center of Pressure	#1
FFD Member Join Date: Aug 2015 Posts: 30 Rep Power: 10	Hello, I want to compute the center of pressure. My thoughts were to find a point were all moments are 0. But i don't know how to find it. The steve portal have an article about how to find the cop. But I don't really understand the idea behind that method and it doesn't really work. The cop is wrong for sure. I tried it on a simple airfoil and the line_point (described in the Steve Portal) didn't even hit the airfoil. But the CoP should be on the airfoil. Have you any suggestions? Regards -FFD

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October 5, 2015, 20:21		#2
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 23	There are many unique solutions to the CoP in 3D of a body. You must guess where the point is first, and then iterate the position of that point until all moments are zero.

October 6, 2015, 03:29		#3
FFD Member Join Date: Aug 2015 Posts: 30 Rep Power: 10	I had the same idea. But how I can do itin Star-CCM? I am not really experienced in CFD. I had this idea: I made a Force and a moment report for every axis. But these vectors are for the full part. How can I check the force and the moment at a specific point? And How I can iterate the position? My idea would be to run the simulation and create a macro that change the values and check if the moment are 0 at that point. But that would be extremly inefficient. But if I know how to check the moment at a specific point. Somebody do have any suggestions? -FFD

October 6, 2015, 19:28		#4
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 23	The moment/force reports takes as input a coordinate system and direction, so you just pick a point and run the report. You will have to write a macro to iterate through the positions, yes. It probably won't be as inefficient as you think.

October 6, 2015, 19:29		#5
me3840 Senior Member Join Date: Nov 2010 Location: USA Posts: 1,232 Rep Power: 23	This thread may help: http://www.cfd-online.com/Forums/ope...aero-body.html