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d118i June 13, 2010 10:50

error problems between experimental and numerical study

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?



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