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

fan vs experimental data

Register Blogs Community New Posts Updated Threads Search

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
Old   June 1, 2010, 08:03
Default fan vs experimental data
  #1
ijk
Member
 
Join Date: Apr 2010
Posts: 33
Rep Power: 16
ijk is on a distinguished road
Hi all,

I am trying to generate a fan curve from experimental data using CFX. I have found that it does not converge steady state so I run it transient.

The fan is an axial fan but I am running in the stalled mixed flow region. I have found that my course mesh using wall functions (yplus100 on blade) is about 15% low in mass flow for a given loading. The steady state is way off.

I have yplus 30 and 1 cases running but they take forever. Perhaps a PHD using CFD was a bad idea.

Are these normal results for CFX? I have some friends who have done similar work with Star CD and they have got transient results within 5%.

I am not 100% that the experimental results are correct as the airflow was measured using anemometers and not a proper venturi setup.

Any advice anyone could give would be much appreciated.

Thanks
ijk is offline   Reply With Quote

Old   June 1, 2010, 19:46
Default
  #2
Super Moderator
 
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 17,844
Rep Power: 144
ghorrocks is just really niceghorrocks is just really niceghorrocks is just really niceghorrocks is just really nice
Getting accurate results in the stalled region is difficult, so you have a difficult project. That means you can expect long run times.

It also means you may not be able to use a turbulence model to get good results, you may be forced to use DES/SAS to get improvement - but that will just increase your run time more.

There are no simple answers in CFD, especially with difficult work like stall modelling.

I would be very surprised that the difference between your results and Star-CD is purely the solver. I would suggest either the user knew what he was doing better or was lucky.
ghorrocks is offline   Reply With Quote

Old   June 7, 2010, 05:42
Default
  #3
ijk
Member
 
Join Date: Apr 2010
Posts: 33
Rep Power: 16
ijk is on a distinguished road
Thanks Glenn
ijk is offline   Reply With Quote

Reply


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
Tecplot. add experimental data into a mesh Alejandro FLUENT 0 December 10, 2008 08:08
How to update polyPatchbs localPoints liu OpenFOAM Running, Solving & CFD 6 December 30, 2005 18:27
Looking for the experimental data COLOPOLO Main CFD Forum 2 January 29, 2004 00:38
Simulated data vs. experimental data moiami FLUENT 0 December 19, 2002 02:03
Experimental data for fence at low Reynolds number Kim Bindesboll Andersen Main CFD Forum 1 September 26, 2002 14:54


All times are GMT -4. The time now is 05:32.