0

I read that the criteria considered when designing a wind turbine airfoil are slightly different to the ones when designing an airfoil for an aircraft. I was wondering, for a low Reynolds number aircraft, is it okay if an airfoil designed for wind turbines were used, and wondered if there were going to be side effects from doing so.

rocket0314
  • 1
  • Wind turbine airfoils do actually work at relative low Reynold numbers. But also other requirements are important in their choice, like being aerodynamically insensitive to dirt, unsteady characteristics, stall characteristics, thick enough to be structurally strong, ... Do you have a particular design or aircraft in mind? – sophit Oct 27 '22 at 07:44
  • A 200 foot wind turbine blade actually will have a much higher Reynolds number near the tips, and a more wing-like relative wind. Since turbine blade (and propeller) speed varies depending on distance from the center, you might notice differences in the airfoil cross section. Why not study aircraft airfoils. – Robert DiGiovanni Oct 27 '22 at 11:31
  • @sophit, I am trying to design a glider with as little drag as possible. I am looking into other airfoils from Drela and Eppler, but wanted to know if it was okay to consider wind turbine airfoils. – rocket0314 Oct 27 '22 at 12:29
  • 1
    Understand, nice project. Well, as said wind turbine airfoils (or, more generally, rotating wing airfoils) must obey other type of requirements than fixed wing airfoils. Furthermore most wind turbines have variable pitch blades and therefore their blades operate always around their best AoA... I wouldn't suggest you to have a look at these airfoils. Anyway NASA LS airfoils are the ones normally used for wind turbine application, especially because their aerodynamic characteristics are stable in respect to dirt on the leading edge. Hope it helps. – sophit Oct 27 '22 at 13:28
  • @sophit Thank you for the input! – rocket0314 Oct 27 '22 at 14:17
  • A little searching found the naca 4415 at the end of a turbine blade. The 4412 might be worth a look too. – Robert DiGiovanni Oct 27 '22 at 21:26
  • Anyway there's a lot of material here about glider airfoils. Maybe you can post a new specific question if you have some doubt: there's a lot of glider enthusiasts around here :-) – sophit Oct 28 '22 at 08:11

1 Answers1

1

Do not take the origin of an airfoil as a criterium for its selection. Judge it purely on its merits for the intended purpose. If a wind turbine airfoil gives you better L/D than any other, use it.

For gliders you need to cover several design points with somewhat conflicting criteria and select the best compromise.

  • Thermalling: The airfoil should allow for a small sink speed at low flight speed. Low structural mass and a high lift coefficient are the most desirable traits here.
  • Gliding: Here the absolute drag counts above all else. If your maximum lift coefficient allows for a smaller wing (you should size the wing for a desired minimum speed), a slightly higher drag coefficient at low lift coefficients can still result in a better overall optimum.
  • Also pick a planform with moderate taper and select different airfoils for root and tip. Tip airfoils must stall gradually and allow some margin for the aileron.

It is important what you design the glider for: A foot-launched, foldable design might need a very different airfoil from one optimized for ridge lift or even aerobatics.

Peter Kämpf
  • 231,832
  • 17
  • 588
  • 929