# error problems between experimental and numerical study

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

 June 12, 2010, 11:24 error problems between experimental and numerical study #1 New Member   ok Join Date: Jun 2010 Posts: 2 Rep Power: 0 Hello, i am a spanish man that are doing an aerodynamic study of a motorsport spoiler. I had done a numerical simulation with star ccm+ and now i am taking some information with this spoilers in a wind tunnel. My project tutor/teacher said me that the cfd can be until 20% of error (more or less) between the cfd mesurements and the mesures of wind tunnel. I don't understand because my mesurements in wind tunnel are ok with Drag component but not with Lift component (Downforce). For example: with 0 degrees inclination the cfd study shows 38,33 N of Downforce and 8,84 N of Drag and the wind tunnel measures are 22,5 N of Downforce and 7,1 N of Drag. If I applicate the teacher's theorem, the drag are in the 20% of error. 7,1 + (20% of 8,84 = 1,77) = 8,87 N but if I do the same with the Downforce the result is not valid with this theory. Someone know if is true that's the maximum error between cfd and experimental study are 20% or can be more?? What can I do? Thanks, david.

 June 15, 2010, 05:23 #2 Senior Member   Join Date: Mar 2009 Posts: 203 Rep Power: 11 Mesh problem, maybe wrong solver.

 June 18, 2010, 01:39 #3 Member   Join Date: Jun 2010 Posts: 33 Rep Power: 9 Can you post a picture of your mesh. As well as tell us your physic models? Then we can try and help! Are you positive all the boundaries are set right??

 June 18, 2010, 07:34 #4 New Member     wayusen Join Date: Oct 2009 Location: Pune Posts: 6 Rep Power: 9 Use fine mesh with quality. __________________

June 18, 2010, 12:45
#5
Senior Member

Join Date: Mar 2009
Posts: 203
Rep Power: 11
Quote:
 Originally Posted by CFD_4 Use fine mesh with quality.