Unrealistic CL values...

Echidna · December 17, 2011, 09:21

Hello everybody.
I am currently making a CFD analysis of a racecar dual-element wing but i keep receiving unrealistic cl values. The value i get is of the order of 3.8 which is too good to be true for a dual-element wing!
The wing has a span of 1.5m and a chord of 320mm. I have set "air at 25deg" as the fluid, 1bar operating pressure, and 50m/s inlet air velocity.
I suspect that something is wrong with the mesh.. I have inflated the wing, setting the first layer thickness at 0.5mm and surface sizing at the wing surfaces at 5mm. I know that my mesh is a bit coarse but my computer power cannot withstand any more loads i am afraid..

Do you think that the meshing could give such a difference in CL and downforce values? Thanks all!

ghorrocks · December 18, 2011, 05:14

Yes, it certainly could. A bad mesh will make your results little better than random numbers.

There is a FAQ on simulation accuracy:
http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F

December 17, 2011, 09:21	Unrealistic CL values...	#1
Echidna Member Join Date: Jun 2010 Posts: 77 Rep Power: 15	Hello everybody. I am currently making a CFD analysis of a racecar dual-element wing but i keep receiving unrealistic cl values. The value i get is of the order of 3.8 which is too good to be true for a dual-element wing! The wing has a span of 1.5m and a chord of 320mm. I have set "air at 25deg" as the fluid, 1bar operating pressure, and 50m/s inlet air velocity. I suspect that something is wrong with the mesh.. I have inflated the wing, setting the first layer thickness at 0.5mm and surface sizing at the wing surfaces at 5mm. I know that my mesh is a bit coarse but my computer power cannot withstand any more loads i am afraid.. Do you think that the meshing could give such a difference in CL and downforce values? Thanks all!

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December 18, 2011, 05:14		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Yes, it certainly could. A bad mesh will make your results little better than random numbers. There is a FAQ on simulation accuracy: http://www.cfd-online.com/Wiki/Ansys..._inaccurate.3F