Resultant force magnitude and direction in CFX-post

sohailgermany · April 8, 2009, 09:47

Dear friends,
I have a cylindrical surface pressure distribution. I would like to find out the resultant force magnitude and direction due to the pressure on that surface. How to do it in CFX-Post?. What is the difference between the following two approaches:

1. Function: AreaInt (Variable: Pressure) at the selected location in a certain direction
2. Function: Areaavg(Variable: Force) at the selected location

I think, they both should give same answer, but they are not. Perhaps, I am not understanding it right. It would be great help, if someone explain the difference between them.
Thank you.

ghorrocks · April 8, 2009, 21:31

Hi,

The area integral of pressure does not include wall shear. The best way to get the total force on a surface is using the force_x()@Surface command.

Glenn Horrocks

abhishekchitvar · March 19, 2013, 04:52

Hello All,
Greetings!

@Mr. Glenn Horrocks ; How to find the location of the resultant force using the geometry and pressure distribution?

ghorrocks · March 19, 2013, 05:29

You can calculate it from the force_x() and torque commands. I will leave the derivation of the equations up to you - here's a hint.... torque = force x distance.

abhishekchitvar · March 19, 2013, 08:11

Hello Mr.Glenn Horrocks,

Thanks for quick reply and suggestion.

However, It's not solve our purpose. We have annular cavity with some thickness, we find out the pressure distribution over inner and outer surface.
also calculate the forces in YZ plane and length in X-direction. Using this we have calculate resutant force and angle. But we could not have idea to find the location i.e x distance, in X-direction i.e axially.

As your suggested that calculate torque and then using this it would be possible to calculate the distance. However, the CFX gives the torque in y and z direction too. but we don't have constraint to our geometry.

If you have more views on the same, Let me know.

Thanking you!

singer1812 · March 19, 2013, 09:52

Resultant force location is not unique. It is a vector. Fix one of your points (perhaps on your body) and the other points will fall out.

Maneken · October 27, 2018, 10:32

Quote:

Originally Posted by singer1812

Resultant force location is not unique. It is a vector. Fix one of your points (perhaps on your body) and the other points will fall out.

Dear Edmung, How to see the location of this vector of total force in x/y direction, when you use function calculator? I need to determine the torque about the pivot of a plate due to pressure of fluid, for that purpose I thought I need a distances of forces acting on it. Thanks in advance

April 8, 2009, 09:47	Resultant force magnitude and direction in CFX-post	#1
sohailgermany New Member Join Date: Apr 2009 Posts: 1 Rep Power: 0	Dear friends, I have a cylindrical surface pressure distribution. I would like to find out the resultant force magnitude and direction due to the pressure on that surface. How to do it in CFX-Post?. What is the difference between the following two approaches: 1. Function: AreaInt (Variable: Pressure) at the selected location in a certain direction 2. Function: Areaavg(Variable: Force) at the selected location I think, they both should give same answer, but they are not. Perhaps, I am not understanding it right. It would be great help, if someone explain the difference between them. Thank you.

March 19, 2013, 04:52	Regading the same problem as discuss above.	#3
abhishekchitvar New Member Abhishek Join Date: Nov 2011 Posts: 6 Rep Power: 15	Hello All, Greetings! @Mr. Glenn Horrocks ; How to find the location of the resultant force using the geometry and pressure distribution?

March 19, 2013, 08:11		#5
abhishekchitvar New Member Abhishek Join Date: Nov 2011 Posts: 6 Rep Power: 15	Hello Mr.Glenn Horrocks, Thanks for quick reply and suggestion. However, It's not solve our purpose. We have annular cavity with some thickness, we find out the pressure distribution over inner and outer surface. also calculate the forces in YZ plane and length in X-direction. Using this we have calculate resutant force and angle. But we could not have idea to find the location i.e x distance, in X-direction i.e axially. As your suggested that calculate torque and then using this it would be possible to calculate the distance. However, the CFX gives the torque in y and z direction too. but we don't have constraint to our geometry. If you have more views on the same, Let me know. Thanking you! Last edited by abhishekchitvar; April 8, 2013 at 02:05.

April 8, 2009, 21:31		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	Hi, The area integral of pressure does not include wall shear. The best way to get the total force on a surface is using the force_x()@Surface command. Glenn Horrocks

March 19, 2013, 05:29		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,854 Rep Power: 144	You can calculate it from the force_x() and torque commands. I will leave the derivation of the equations up to you - here's a hint.... torque = force x distance.

March 19, 2013, 09:52		#6
singer1812 Senior Member Edmund Singer P.E. Join Date: Aug 2010 Location: Minneapolis, MN Posts: 511 Rep Power: 21	Resultant force location is not unique. It is a vector. Fix one of your points (perhaps on your body) and the other points will fall out.