# Tapered Wing Providing low Coefficient of Lift

Hi I am currently analyzing different wing designs using ANSYS Fluent. One of my designs has a straight leading edge but a swept trailing edge thus it is tapered with wing root chord at 50mm and wing tip chord at length 200mm. Wing span is 250mm. (See Picture) The airfoil shape used is the S1223 which has a CL max around 2.3. Therefore using the Lift formula which (i know is approximate), I calculate the wing can produce 58.5N of lift at 36.452m/s.

However using ANSYS Fluent I find the wing can only produce a maximum of 39N of lift which is a CL of 1.5.

I am fairly certain the simulations I'm running are accurate but need advice on what could be causing this difference. Assuming the results I've obtained are correct. What is the reason for the large difference in coefficient of lift ? Let me know if I need to provide any additional information! Any help greatly appreciated! EDIT : Forgot to add that the simulation used assumes the wind tunnel boundary is at wing tip and wing root. Thus the wing span takes up the full wind tunnel.

• the image seems to show the wing inverted -- are you measuring lift in the correct direction for the camber? Apr 10, 2020 at 15:45
• Not sure what you mean by "wind tunnel boundary". You should set the plane corresponding to wing root to be symmetry boundary condition. There should be no boundary on the tip except the normal wall boundary for near field. The far field should be velocity inlet and the trefftz plane should be pressure outlet.
– JZYL
Apr 10, 2020 at 15:55
• I'm actually measuring the downforce that the wing produces so yes I am measuring in the correct direction @ZeissIkon Thanks for your response. Apr 10, 2020 at 16:30
• @JZYL I had set the boundaries to be at the tip and root for the time being, just to determine coefficient of lift neglecting any wing tip vortices. Both were set to be symmetry boundary condition. I have just corrected this according to your advice however there is no change in the lift value I am getting. However there is a small increase in drag. Thanks for your response Apr 10, 2020 at 16:36
• what is your question? Apr 10, 2020 at 19:42