CFD Online Logo CFD Online URL
www.cfd-online.com
[Sponsors]
Home > Forums > Software User Forums > OpenFOAM > OpenFOAM Post-Processing

Wrong forces coming from forces function object in controlDict

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

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   April 13, 2016, 09:07
Exclamation Wrong forces coming from forces function object in controlDict
  #1
New Member
 
Université de Sherbrooke
Join Date: Jul 2015
Posts: 6
Rep Power: 9
Jason_Duguay is on a distinguished road
Hello,

I am simulating turbulent flow through a straight pipe (0.254 m in diameter) with pimpleFoam and a standard k-epsilon model. On the invert of the pipe I have placed a number of protruding "baffles" from geometries within snappyHexMesh. The flow through the pipe is 0.035 m^3/s.

I am interested in calculating the pressure drop over the baffled section with an energy approach and also with a momentum based force balance approach. So far, the energy approach has given the correct pressure drop between the upstream and downstream section ((p1avg*rho-p2avg*rho)/(rho*g), but the forces coming from the forces function are much lower than they should be (by about half) and consequently the momentum approach is not working. Also the force due to shear stress on the wall of the pipe is lower than it should be.

The fact that the energy approach is working gives me confidence in model and also leads me to believe that I am somehow incorrectly using the forces function object.

I have been breaking my head over this for the past few days and figured I have exhausted all the leads I could find in other related threads. It would make my day if somebody could help me out.

Here is my forces function object entry in controlDict, I am fairly confident I have entered everything correctly:

forces
{
type forces;
functionObjectLibs ("libforces.so");
patches (baffles);
rhoName rhoInf;
pName p;
UName U;
CofR (0 0 0);
rhoInf 1000;
name forces;
uitype forces;
outputControl outputTime;
outputInterval 1;
format ascii;
}

Also, the baffles are not a continuous geometry - instead the patch is composed of 15 distinct 0.038x0.038*0.01 separated from each other by 0.15 m along the x-axis (main flow direction). Could this have something to do with the problem I am seeing?

Thank you for your help!
Jason_Duguay is offline   Reply With Quote

Reply

Tags
forces, pressure losses, turbulent flow

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
udf error srihari FLUENT 1 October 31, 2016 14:18
LiencubiclowRemodel nzy102 OpenFOAM Bugs 14 January 10, 2012 08:53
controlDict 'forces' function: multiple output files? lordvon OpenFOAM 0 January 10, 2011 16:22
[blockMesh] BlockMeshmergePatchPairs hjasak OpenFOAM Meshing & Mesh Conversion 11 August 15, 2008 07:36
DecomposePar links against liblamso0 with OpenMPI jens_klostermann OpenFOAM Bugs 11 June 28, 2007 17:51


All times are GMT -4. The time now is 19:28.