Airfoil Polar?

tareqkh · July 5, 2016, 03:38

Hey All,

I was wondering if there is any software that could provide the lift and drag for angle of attacks from -180 to 180? As can be seen from the wind tunnel experiments, the data available is only from -20 to 20. Any help would be really appreciate it.

Kind regard,

fluid23 · July 5, 2016, 09:30

NREL provides a free spreadsheet program called Airfoil Prep that applies the Viterna method for calculating post-stall characteristics of airfoils through 360 degrees.

https://nwtc.nrel.gov/AirFoilPrep
http://www.nrel.gov/docs/fy05osti/36900.pdf

tareqkh · July 7, 2016, 01:24

Thank for your kind help.

Regards,

gfoam · July 13, 2016, 14:42

Hi:
If you are working on wind turbine airfoils NREL has some reports having CL, CD and CM data in such a range of AoA. If you aren't working on wind turbine airfoils, NTRS (NASA Technical Report Server) has some reports with that data. For hi Reynolds and Mach numbers you have the report DATCOM with tendencies on the behavior of that curves at high AoA for some thin profiles.
In the case you are working on a new profile, mmm, well you have to construct your own data with CFD or your own wind tunnel

Regards. Gonzalo

tareqkh · July 13, 2016, 15:59

Thank you for your kind reply. I am currently working on wind turbines and trying to use airfoil polar in order to transform some airfoils from AoA -20 to 20 to -180 to 180. I have observed that what ever airfoil I transform from -180 to 180 the drag and lift are zero. Not really sure whether this is correct or not. Have you had the same experience?

Kind regards,

gfoam · July 14, 2016, 18:20

You are welcome. If with "transform" you mean rotate the airfoil around its pitch reference point, well it is expected that the lift force becomes zero or near zero starting from a high AoA, because the airfoil is at a flow condition named stall where the lift drops drastically but the drag rises drastically too. So, it is strange that in your case the drag drops to zero too. I will double check your result if I were you. Regards
Gonzalo

July 5, 2016, 03:38	Airfoil Polar?	#1
tareqkh Senior Member CFD Join Date: Nov 2010 Location: United States Posts: 243 Rep Power: 16	Hey All, I was wondering if there is any software that could provide the lift and drag for angle of attacks from -180 to 180? As can be seen from the wind tunnel experiments, the data available is only from -20 to 20. Any help would be really appreciate it. Kind regard,

July 5, 2016, 09:30		#2
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	NREL provides a free spreadsheet program called Airfoil Prep that applies the Viterna method for calculating post-stall characteristics of airfoils through 360 degrees. https://nwtc.nrel.gov/AirFoilPrep http://www.nrel.gov/docs/fy05osti/36900.pdf tareqkh likes this.

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July 7, 2016, 01:24		#3
tareqkh Senior Member CFD Join Date: Nov 2010 Location: United States Posts: 243 Rep Power: 16	Thank for your kind help. Regards,

July 13, 2016, 14:42		#4
gfoam Senior Member Gonzalo Join Date: Mar 2011 Location: Argentina Posts: 122 Rep Power: 16	Hi: If you are working on wind turbine airfoils NREL has some reports having CL, CD and CM data in such a range of AoA. If you aren't working on wind turbine airfoils, NTRS (NASA Technical Report Server) has some reports with that data. For hi Reynolds and Mach numbers you have the report DATCOM with tendencies on the behavior of that curves at high AoA for some thin profiles. In the case you are working on a new profile, mmm, well you have to construct your own data with CFD or your own wind tunnel Regards. Gonzalo

July 13, 2016, 15:59		#5
tareqkh Senior Member CFD Join Date: Nov 2010 Location: United States Posts: 243 Rep Power: 16	Thank you for your kind reply. I am currently working on wind turbines and trying to use airfoil polar in order to transform some airfoils from AoA -20 to 20 to -180 to 180. I have observed that what ever airfoil I transform from -180 to 180 the drag and lift are zero. Not really sure whether this is correct or not. Have you had the same experience? Kind regards,

July 14, 2016, 18:20		#6
gfoam Senior Member Gonzalo Join Date: Mar 2011 Location: Argentina Posts: 122 Rep Power: 16	You are welcome. If with "transform" you mean rotate the airfoil around its pitch reference point, well it is expected that the lift force becomes zero or near zero starting from a high AoA, because the airfoil is at a flow condition named stall where the lift drops drastically but the drag rises drastically too. So, it is strange that in your case the drag drops to zero too. I will double check your result if I were you. Regards Gonzalo