airfoil y+ value

johnstewart00 · April 2, 2009, 09:49

Hi,
I am having trouble validating a mesh for an airfoil created in gambit.

Fluid is air

I am having trouble getting the wall shear stress.Is it correct that i complete analysis in fluent and then use the value i get from fluent, in wall fluxes, as tau(wall shear stress)

The height of the first cell is 0.00038. not sure of the units
Any help would be very much appreciated because I am at a stand still with my project at the moment

Thanks,
John

harishg · April 3, 2009, 00:52

Yes. You run your code for sometime and depending on if the simulation is RANS/LES wait for steady state or IC effects to vanish and then check the value of yplus. For an airfoil, if you look in the literature, you might find many references on the value of y used to get yplus < 1 for any Re.

Alagesanj · April 4, 2009, 07:35

Hi John,

Your requirement is only tau or something else. Can you give further details.

Usually the first cell height will be in m or mm, i.e. depends on the unit selected in gambit.

From the following link you can find the first cell height

http://geolab.larc.nasa.gov/APPS/YPlus/

Cheers, Alagesan

April 2, 2009, 09:49	airfoil y+ value	#1
johnstewart00 New Member John Stewart Join Date: Apr 2009 Posts: 3 Rep Power: 17	Hi, I am having trouble validating a mesh for an airfoil created in gambit. Fluid is air I am having trouble getting the wall shear stress.Is it correct that i complete analysis in fluent and then use the value i get from fluent, in wall fluxes, as tau(wall shear stress) The height of the first cell is 0.00038. not sure of the units Any help would be very much appreciated because I am at a stand still with my project at the moment Thanks, John Last edited by johnstewart00; April 2, 2009 at 13:54.

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April 3, 2009, 00:52		#2
harishg Senior Member N/A Join Date: Mar 2009 Posts: 189 Rep Power: 17	Yes. You run your code for sometime and depending on if the simulation is RANS/LES wait for steady state or IC effects to vanish and then check the value of yplus. For an airfoil, if you look in the literature, you might find many references on the value of y used to get yplus < 1 for any Re.

April 4, 2009, 07:35		#3
Alagesanj New Member Janarthanan Alagesan Join Date: Mar 2009 Location: Asia Posts: 9 Rep Power: 17	Hi John, Your requirement is only tau or something else. Can you give further details. Usually the first cell height will be in m or mm, i.e. depends on the unit selected in gambit. From the following link you can find the first cell height http://geolab.larc.nasa.gov/APPS/YPlus/ Cheers, Alagesan