NACA airfoil with LES

Roland R · October 3, 2011, 09:21

Hello,

I would like to investigate an NACA airfoil with LES. My computer capacity is not too large and I have to calculate a lot of cases. Therefore I would like to study 2D cases only. I know that the 2D simulation is not too correct in case of LES but at the moment there is not other possibility. So if I apply the LES then my result is total bad or it will contain fewer information than in case of 3D ?

Thanks
Roland

ghorrocks · October 3, 2011, 17:42

You cannot do LES in 2D. It is an inherently 3D approach. If you do not have the computing resources to proceed then give up until you do. 2D LES will be a waste of your time.

cfd_newbie · October 4, 2011, 01:05

Quote:

Originally Posted by Roland R

Hello,

I would like to investigate an NACA airfoil with LES. My computer capacity is not too large and I have to calculate a lot of cases. Therefore I would like to study 2D cases only. I know that the 2D simulation is not too correct in case of LES but at the moment there is not other possibility. So if I apply the LES then my result is total bad or it will contain fewer information than in case of 3D ?

Thanks
Roland

You may do a kind of pseudo 2D where you will extrude your 2D airfoil to some length, this way you would be able to compare your CFd results with that of 2D experimental data.

See the link where similar topic has been discussed earlier -
http://www.cfd-online.com/Forums/main/89070-des-2d.html

ghorrocks · October 4, 2011, 01:14

You can run a 2D LES but your results will be rubbish. You are constraining the third dimension and the turbulence energy cascade will be completely corrupted. LES is inherently 3D and you cannot do it in 2D and hope for results which are close to reality.

October 3, 2011, 09:21	NACA airfoil with LES	#1
Roland R Senior Member Roland Rakos Join Date: Mar 2009 Posts: 131 Rep Power: 17	Hello, I would like to investigate an NACA airfoil with LES. My computer capacity is not too large and I have to calculate a lot of cases. Therefore I would like to study 2D cases only. I know that the 2D simulation is not too correct in case of LES but at the moment there is not other possibility. So if I apply the LES then my result is total bad or it will contain fewer information than in case of 3D ? Thanks Roland

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October 3, 2011, 17:42		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You cannot do LES in 2D. It is an inherently 3D approach. If you do not have the computing resources to proceed then give up until you do. 2D LES will be a waste of your time.

October 4, 2011, 01:14		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	You can run a 2D LES but your results will be rubbish. You are constraining the third dimension and the turbulence energy cascade will be completely corrupted. LES is inherently 3D and you cannot do it in 2D and hope for results which are close to reality.