setting angle of attack nicely 0°

spalartallmaras · May 20, 2020, 10:00

https://drive.google.com/file/d/1mdJ...ew?usp=sharing

hello,

can anybody give me a small tipp to set an angle of attack nicely? I thought I set the angle with 0° (ventilator blade) correctly, but it seems not like that (see the link). I used freeCad.

Gerry Kan · May 20, 2020, 12:54

Hallo SA:

At first glance your blade does not seem to be at alpha = 0.

If this is a NACA airfoil, draw a straight line from the leading to the trailing edge. The slope of this line is indicative of your angle of attack, that is, at alpha=0 it should be parallel with the horizontal datum line (x-axis). Otherwise the polynomial expression of the foil shape should be defined at alpha = 0 already.

If you want your alpha = 0 defined at zero lift (or Cf = 0), you would need to run some tests (javafoil comes to mind; inviscid flow will do). The lift should vary linearly with alpha around zero lift so you only need two or three points to locate the angle.

Hope that helps, Gerry.

May 20, 2020, 10:00	setting angle of attack nicely 0°	#1
spalartallmaras Member niewiemnic Join Date: Jan 2018 Location: Niemcy Posts: 80 Rep Power: 8	https://drive.google.com/file/d/1mdJ...ew?usp=sharing hello, can anybody give me a small tipp to set an angle of attack nicely? I thought I set the angle with 0° (ventilator blade) correctly, but it seems not like that (see the link). I used freeCad.

May 20, 2020, 12:54		#2
Gerry Kan Senior Member Gerry Kan Join Date: May 2016 Posts: 347 Rep Power: 10	Hallo SA: At first glance your blade does not seem to be at alpha = 0. If this is a NACA airfoil, draw a straight line from the leading to the trailing edge. The slope of this line is indicative of your angle of attack, that is, at alpha=0 it should be parallel with the horizontal datum line (x-axis). Otherwise the polynomial expression of the foil shape should be defined at alpha = 0 already. If you want your alpha = 0 defined at zero lift (or Cf = 0), you would need to run some tests (javafoil comes to mind; inviscid flow will do). The lift should vary linearly with alpha around zero lift so you only need two or three points to locate the angle. Hope that helps, Gerry. Last edited by Gerry Kan; May 21, 2020 at 06:33.

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