Referece Area of 2D Airfoil

walex · September 16, 2009, 03:55

Hi everybody,

can somebody tell me how the reference area is determined in OF 1.5? Until now I used the chordlength * mesh-extrusion in z direction. But I am not sure as my calculated Cd and Cl values are defnitely wrong.

Thanks
Alex

walex · September 16, 2009, 04:48

Hi,

to avoid any misunderstanding: Th question could also be for which area OF does calculate the forces? (2D)

Alex

hansel · September 16, 2009, 16:42

My impression was that openfoam calculates the forces on all faces of the object and vector sums them. Then divides the drag vector and lift vectors by density, U^2 and the reference area that you specified to get Cd and Cl.

I believe chord_length * wing_length is the standard equation for wing reference area.

For objects other than wings, the reference area for drag is usually the area that the wind 'sees', but when it comes to wings, its the same area as for lift.

I don't think it's your reference_area that's wrong, I think it's the forces coming out of the simulation
.

September 16, 2009, 03:55	Referece Area of 2D Airfoil	#1
walex New Member Join Date: Apr 2009 Posts: 17 Rep Power: 17	Hi everybody, can somebody tell me how the reference area is determined in OF 1.5? Until now I used the chordlength * mesh-extrusion in z direction. But I am not sure as my calculated Cd and Cl values are defnitely wrong. Thanks Alex

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September 16, 2009, 04:48		#2
walex New Member Join Date: Apr 2009 Posts: 17 Rep Power: 17	Hi, to avoid any misunderstanding: Th question could also be for which area OF does calculate the forces? (2D) Alex

September 16, 2009, 16:42		#3
hansel Senior Member Steve Hansel Join Date: Jun 2009 Location: Colorado, USA Posts: 112 Rep Power: 16	My impression was that openfoam calculates the forces on all faces of the object and vector sums them. Then divides the drag vector and lift vectors by density, U^2 and the reference area that you specified to get Cd and Cl. I believe chord_length * wing_length is the standard equation for wing reference area. For objects other than wings, the reference area for drag is usually the area that the wind 'sees', but when it comes to wings, its the same area as for lift. I don't think it's your reference_area that's wrong, I think it's the forces coming out of the simulation .