Need help with the COP (center of pressure)

damiguez · May 16, 2022, 09:44

Hello everyone.

I am writing because I have been looking for some information about how to calculete the COP of a 3D object in a certain flow but I haven´t found what I was looking for.

I need to calculete the COP coordinates of a 3D object and I don´t know how.

I can know the COP coordinates of a section of the object by using: Results>Reports>Forces>Center of pressure, but I want the generall position of the COP (not the COP of a section).

If there is anbody who can help me with this, I would be very thankful.

Thanks for reading.

LuckyTran · May 16, 2022, 10:39

I am a little confused why it is not enough to just select all regions and get the COP of the entire bodies involved.

Regardless, the CoP can be generalized to systems of bodies the same way that it is a system of forces for any individual body. If you have a collection of CoP reports for individual body sections, you can just recursively apply the averaging method to find the CoP of the entire group.

damiguez · May 16, 2022, 11:04

I know that I can calculate the COP of a system if I have the COP of the bodies which compose the system.

The problem is that I don´t know how to get the COP of a body. If I ask fluent for the CoP I need to say to fluen a plane where I want to calculate the CoP, so I understand that this CoP is the CoP of the section of the body in this plane, not the COP of the full body.

I attach an image to show how ansys fluent ask me to entry a plane.

Thanks for the reply.

https://drive.google.com/file/d/1Jfj...ew?usp=sharing

LuckyTran · May 16, 2022, 12:52

Fluid mechanical forces exerted on bodies are in the form of pressures over surfaces. They're not microwaves that penetrate into bodies. What kind of CoP of a body are you trying to calculate that isn't the one being presented?

Or are you missing the part where you can select more than 1 surface? Try clicking...

damiguez · May 16, 2022, 16:09

I am sorry, I am not an expert in English and maybe I am not explaining it as well as I should.

To make it esier... I need to get the CoP of a 3D body. How should I do it?

LuckyTran · May 17, 2022, 03:19

Is there something that prevents you from selecting (in this example) solid:1 and walls? Shift + click? Click and drag?

And if that does not work then you can get the CoP individually for each zone (solid:1 and walls) and then add them, which you say you already know how to do. Whatever composes the exposed surfaces of your "entire body," select them.

damiguez · May 17, 2022, 03:37

I can select more than 1 body, but this is not the objective. The problem is that I have to select a plane where I want to calculate the CoP and Ansys give me the CoP of this section (CoP of the 2D geometry), not the CoP of the 3D body.

Please, look at the image.

https://drive.google.com/file/d/1Jfj...ew?usp=sharing

May 16, 2022, 09:44	Need help with the COP (center of pressure)	#1
damiguez New Member David Join Date: May 2022 Posts: 4 Rep Power: 4	Hello everyone. I am writing because I have been looking for some information about how to calculete the COP of a 3D object in a certain flow but I haven´t found what I was looking for. I need to calculete the COP coordinates of a 3D object and I don´t know how. I can know the COP coordinates of a section of the object by using: Results>Reports>Forces>Center of pressure, but I want the generall position of the COP (not the COP of a section). If there is anbody who can help me with this, I would be very thankful. Thanks for reading.

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May 16, 2022, 10:39		#2
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,763 Rep Power: 66	I am a little confused why it is not enough to just select all regions and get the COP of the entire bodies involved. Regardless, the CoP can be generalized to systems of bodies the same way that it is a system of forces for any individual body. If you have a collection of CoP reports for individual body sections, you can just recursively apply the averaging method to find the CoP of the entire group.

May 16, 2022, 11:04		#3
damiguez New Member David Join Date: May 2022 Posts: 4 Rep Power: 4	I know that I can calculate the COP of a system if I have the COP of the bodies which compose the system. The problem is that I don´t know how to get the COP of a body. If I ask fluent for the CoP I need to say to fluen a plane where I want to calculate the CoP, so I understand that this CoP is the CoP of the section of the body in this plane, not the COP of the full body. I attach an image to show how ansys fluent ask me to entry a plane. Thanks for the reply. https://drive.google.com/file/d/1Jfj...ew?usp=sharing

May 16, 2022, 12:52		#4
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,763 Rep Power: 66	Fluid mechanical forces exerted on bodies are in the form of pressures over surfaces. They're not microwaves that penetrate into bodies. What kind of CoP of a body are you trying to calculate that isn't the one being presented? Or are you missing the part where you can select more than 1 surface? Try clicking...

May 16, 2022, 16:09		#5
damiguez New Member David Join Date: May 2022 Posts: 4 Rep Power: 4	I am sorry, I am not an expert in English and maybe I am not explaining it as well as I should. To make it esier... I need to get the CoP of a 3D body. How should I do it?

May 17, 2022, 03:19		#6
LuckyTran Senior Member Lucky Join Date: Apr 2011 Location: Orlando, FL USA Posts: 5,763 Rep Power: 66	Is there something that prevents you from selecting (in this example) solid:1 and walls? Shift + click? Click and drag? And if that does not work then you can get the CoP individually for each zone (solid:1 and walls) and then add them, which you say you already know how to do. Whatever composes the exposed surfaces of your "entire body," select them.

May 17, 2022, 03:37		#7
damiguez New Member David Join Date: May 2022 Posts: 4 Rep Power: 4	I can select more than 1 body, but this is not the objective. The problem is that I have to select a plane where I want to calculate the CoP and Ansys give me the CoP of this section (CoP of the 2D geometry), not the CoP of the 3D body. Please, look at the image. https://drive.google.com/file/d/1Jfj...ew?usp=sharing