Farfield point vortex (PV) boundary condition correction

koalabryant · September 16, 2015, 10:05

Hi¡¡

I am testing some 2D airfoils in fluent.

I have NASA naca 0012 validation case as reference, and they propose a mesh 500 times chord length, but I've also read some other articles and journals, and the general rule seem to be 20-30 times chord.

They talk about "farfield point vortex (PV) boundary condition correction" if you want to reduce the distance of the farfield boundary, but I don't find any option in fluent which has to do with this.

I thought 20-30 times chord is far enough for an airfoil, but now I'm not very sure, and there are two graphics in nasa validation case which show 17% error with 30 times chord. . (http://turbmodels.larc.nasa.gov/naca..._ffeffect.html)

Could anyone help me?? Thanks¡¡

shereez234 · September 16, 2015, 22:37

Okay I just could not believe it when u said 17% error. And I went to the link and it says 0.17% error.

and FYI 15-30 chord lengths should be enough.

September 16, 2015, 10:05	Farfield point vortex (PV) boundary condition correction	#1
koalabryant New Member Join Date: Jul 2015 Posts: 14 Rep Power: 10	Hi¡¡ I am testing some 2D airfoils in fluent. I have NASA naca 0012 validation case as reference, and they propose a mesh 500 times chord length, but I've also read some other articles and journals, and the general rule seem to be 20-30 times chord. They talk about "farfield point vortex (PV) boundary condition correction" if you want to reduce the distance of the farfield boundary, but I don't find any option in fluent which has to do with this. I thought 20-30 times chord is far enough for an airfoil, but now I'm not very sure, and there are two graphics in nasa validation case which show 17% error with 30 times chord. . (http://turbmodels.larc.nasa.gov/naca..._ffeffect.html) Could anyone help me?? Thanks¡¡

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September 16, 2015, 22:37		#2
shereez234 Senior Member M Sereez Join Date: Jan 2014 Location: England Posts: 352 Blog Entries: 1 Rep Power: 13	Okay I just could not believe it when u said 17% error. And I went to the link and it says 0.17% error. and FYI 15-30 chord lengths should be enough.