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Can you please tell why my 3D wing in XFLR5 keeps increasing it's lift even after 50 degree AOA, while it's 2D profile stalls after about 10 degrees ?

More details on simulation setup:

  • Airspeed is 15 m/s (Re is about 20000-25000)

  • Wing chord length is 3 cm

  • Wing span is 12 cm

  • Wing is straight

  • Airfoil is symmetric (NACA-0009)

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  • $\begingroup$ Can you export some graphic data about this ? $\endgroup$
    – jkztd
    Jun 21, 2018 at 9:30
  • $\begingroup$ Thanks for your comment. What graph would you like to see ? For the 2D profile I see typical Cl drop after 8-10 degrees. With the 3D wing I refer to Cl parameter at the lower-right side of the 3D view screen. $\endgroup$
    – East_Engineer
    Jun 21, 2018 at 17:52

2 Answers 2

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  1. XFLR5 is not made for this kind of calculation. Do not trust the results.
  2. Stall is not the end of lift. See below for 2D wind tunnel data collected by S. Hörner in his book Fluid Dynamic Lift. 3D results would look similar, but with a less steep gradient around 0° and lower peaks.

180° polar for several airfoils

180° polar for several airfoils

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This is most probably due to the method you used to calculate CL_alpha. There are 3 or 4 possible ways XLFR5 support, for ex. LLT and VLM methods use potential flow based calculation without any viscous effect. If you use viscous mode which is what responsible for stall, you will see that the wing will stall ~10 or lower value depending on your wing layout.

HTH

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