Cl, Cd, Reference Values in 2D?

sniperees · October 12, 2011, 12:37

Hi there,

I'm fairly new to fluent so bear with me.

Let me explain my situation:

I am doing a 2D simulation of airfoils (to be more specific NACA 4421 and NACA 23012) and I am confused with what the Cd and Cl are in terms of. Is the Cd and Cl displayed while the simulation is running in units of per meter?

Also, what should my reference area be? My chord length is 2, however, there are alot of opinions that say that the reference area should be the chord length, others that say that it should be the chord length squared.

If you could give any input, that would be great!

Thanks,

sniperees.

k_k · October 20, 2011, 13:04

Hi,

Use the chord length as the ref length.
Cl and Cd are non dimensional and it cannot not said to be per m. 2D flow simulation over an aerofoil is analogous to flow past a wing of infinite span.

Also make sure that you set the reference pressure correctly.

Cheers

m2montazari · October 20, 2011, 18:04

hi,
in 2d simulations dept=1,length=chord,area=chord
and about cl,cd,cm reference pressure is not important but reference velocity and density should be checked.
yours,
mohammad

jafarizade · October 21, 2011, 10:47

in such a problem for a 2d prblem and for cd and cl refreance values for velocity,density,area and viscosity should be checked!

rajaprathap · July 2, 2016, 03:09

iam getting negative values for cd when trying to simulate flow over 2d airfoil.pls explain how to sort out this issue

October 12, 2011, 12:37	Cl, Cd, Reference Values in 2D?	#1
sniperees New Member Mark Join Date: Oct 2011 Posts: 2 Rep Power: 0	Hi there, I'm fairly new to fluent so bear with me. Let me explain my situation: I am doing a 2D simulation of airfoils (to be more specific NACA 4421 and NACA 23012) and I am confused with what the Cd and Cl are in terms of. Is the Cd and Cl displayed while the simulation is running in units of per meter? Also, what should my reference area be? My chord length is 2, however, there are alot of opinions that say that the reference area should be the chord length, others that say that it should be the chord length squared. If you could give any input, that would be great! Thanks, sniperees.

July 2, 2016, 03:09	about cd	#5
rajaprathap New Member RAJA PRATHAP Join Date: Jul 2016 Posts: 2 Rep Power: 0	iam getting negative values for cd when trying to simulate flow over 2d airfoil.pls explain how to sort out this issue

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October 20, 2011, 13:04		#2
k_k Member Kailash Join Date: May 2011 Location: London, UK Posts: 45 Rep Power: 14	Hi, Use the chord length as the ref length. Cl and Cd are non dimensional and it cannot not said to be per m. 2D flow simulation over an aerofoil is analogous to flow past a wing of infinite span. Also make sure that you set the reference pressure correctly. Cheers

October 20, 2011, 18:04		#3
m2montazari Senior Member Mohammad Join Date: Feb 2010 Location: Shiraz, Iran Posts: 108 Rep Power: 16	hi, in 2d simulations dept=1,length=chord,area=chord and about cl,cd,cm reference pressure is not important but reference velocity and density should be checked. yours, mohammad

October 21, 2011, 10:47		#4
jafarizade New Member Ali Jafarizade Join Date: May 2009 Posts: 22 Rep Power: 16	in such a problem for a 2d prblem and for cd and cl refreance values for velocity,density,area and viscosity should be checked!