CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > ANSYS > FLUENT

How to calculate pressure forces using custom field functions?

Register Blogs Members List Search Today's Posts Mark Forums Read

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 22, 2009, 07:57
Default How to calculate pressure forces using custom field functions?
  #1
New Member
 
Toni Pujol
Join Date: Jun 2009
Posts: 6
Rep Power: 17
tsagaro is on a distinguished road
Dear all,

I am trying to obtain forces and torques on the blades of an axial fan using a transient simulation. I can obtain them by using the Report => Forces panel. However, I would like to obtain them as a function of time. Therefore, I want to create a Custom Field Function and then make a Monitor => Surface of that Custom Field Function.

In order to be confident with what I am doing, I am currently checking if the Custom Field Function I have written gives the same answer as the Report => Forces panel... and I am making one (or several) mistake(s) I am unable to detect.

For the x component of the pressure force on the surface, I define a Custom Field Function as: p * x-surface- area and Sum over the surface on the Report => Surface Integrals. The result is very different from that I obtain using the Report => Force panel (it also disagrees with y and z components).

Any help?

Thanks,

Toni
tsagaro is offline   Reply With Quote

Old   February 9, 2011, 05:10
Default
  #2
Member
 
J.-H. Wang
Join Date: Oct 2010
Posts: 72
Rep Power: 15
f0208secretx is on a distinguished road
Hi, Toni.

I ran to the same problem with you. I'm wondering if we misunderstand the definition of "X Face Area" in the droplist of "Mesh" or something else, and neither do I know how Fluent calculate the integrals/sum in the surface monitor operation. This makes me really uncomfortable... If you already find the answer, could you share it some time? It would be helpful, thanks.

JH
f0208secretx is offline   Reply With Quote

Old   February 10, 2011, 01:29
Default
  #3
Member
 
J.-H. Wang
Join Date: Oct 2010
Posts: 72
Rep Power: 15
f0208secretx is on a distinguished road
Since that no one reponse to this question, I would answer it myself.

First, I need to admit that "X Face Area" is a strange quantity and it seems no one know what it represents. Even the official manual is written in so abstruse language that I doubt that they cannot figure it out either... I have did some experiments on the quantity yet I still coulnd't get it. After spending hours, I quit on this thing.

I temporarily use the monitor panel to obtain the force coefficient and it sucks because of the restrictions, anyway if there are people who have better advices I would be much appreciated.

JH
f0208secretx is offline   Reply With Quote

Old   April 13, 2011, 03:25
Default
  #4
New Member
 
qingkai
Join Date: Apr 2011
Posts: 11
Rep Power: 15
sailor is on a distinguished road
Hi, JH. Have you solved this problem now?
I have a similar question similar with you, and want to get some advices from you.
You know, in Force Report, we can get the force on Wall only. However, I need the force on Wall and another kind of boundary. So I used p*x-surface-area as you ever used before, but the result seems not reasonable.
Do you have any idea about my problem?


Quote:
Originally Posted by f0208secretx View Post
Since that no one reponse to this question, I would answer it myself.

First, I need to admit that "X Face Area" is a strange quantity and it seems no one know what it represents. Even the official manual is written in so abstruse language that I doubt that they cannot figure it out either... I have did some experiments on the quantity yet I still coulnd't get it. After spending hours, I quit on this thing.

I temporarily use the monitor panel to obtain the force coefficient and it sucks because of the restrictions, anyway if there are people who have better advices I would be much appreciated.

JH
sailor is offline   Reply With Quote

Old   April 13, 2011, 03:34
Default
  #5
Member
 
J.-H. Wang
Join Date: Oct 2010
Posts: 72
Rep Power: 15
f0208secretx is on a distinguished road
Actually we are taking different issues: I was stucked on the transient force report, while you are confused about outputting properties of the non-wall boundaries.

What kind of boundaries are you handling here? Try to identify them in the pre-process procedure as an independent wall. That might help.

JH
f0208secretx is offline   Reply With Quote

Old   April 13, 2011, 03:36
Default
  #6
Member
 
J.-H. Wang
Join Date: Oct 2010
Posts: 72
Rep Power: 15
f0208secretx is on a distinguished road
One more thing, the x-surface-area and the x-face-area is tricky as it seems, you shall examine the mechanisms underlying carefully before utilization. Teach me when you figure it out. :-D
f0208secretx is offline   Reply With Quote

Old   April 13, 2011, 04:03
Default
  #7
New Member
 
qingkai
Join Date: Apr 2011
Posts: 11
Rep Power: 15
sailor is on a distinguished road
Yeah, I set then as Velocity Inlet because I want to simulate the plasma on the surface. But when it is set as Velocity Inlet, cannot be set as Wall at the same time. I will try to figure out.

Quote:
Originally Posted by f0208secretx View Post
Actually we are taking different issues: I was stucked on the transient force report, while you are confused about outputting properties of the non-wall boundaries.

What kind of boundaries are you handling here? Try to identify them in the pre-process procedure as an independent wall. That might help.

JH
sailor is offline   Reply With Quote

Old   June 23, 2017, 15:45
Default How to calculate an equation based on simulated results in post-processing
  #8
Senior Member
 
Astio Lamar
Join Date: May 2012
Location: Pipe
Posts: 186
Rep Power: 14
asal is on a distinguished road
Hello!

I need to get some values in different places in my domain and do a simple math to calculate.

let's assume I have defined Point-A and point-B within the computational domain.

then I want to do this:

1-((Velocity@point-A)/(Velocity@point-B))

How can I implement such equation?
I tried "Custom Field Function" but there I cannot get velocity or whatever quantity over point or boundaries.

Thanks.
asal is offline   Reply With Quote

Reply

Tags
custom field function, pressure forc

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Moving mesh Niklas Wikstrom (Wikstrom) OpenFOAM Running, Solving & CFD 122 June 15, 2014 06:20
Variable Operating Pressure (field) Arturo FLUENT 0 April 30, 2008 15:22
Execute Command with Custom Field Functions Prasad Dudhgaonkar FLUENT 0 March 8, 2007 15:27
2d foil pressure forces problem mayor FLUENT 4 December 1, 2003 03:57
Using SIMPLE david Main CFD Forum 5 July 21, 1999 02:38


All times are GMT -4. The time now is 07:26.