I'm asking this because I tested a NACA 2412 wing with an adjustable flap in a subsonic wind tunnel and I'm getting the lowest Cl values for the highest flap deflection angle.. which to my knowledge is theoretically wrong.
The inlet velocity is 15m/s. What is worrying me is that for a flap angle of 0 degrees, my cl value is a maximum. For 22.5 degrees, it gets less, and then for 45 degrees, it is the least. So the relationship is basically the inverse.
Note: the wing flap deflection is just to change the deflection angle of the flap; the wing area remains constant.
I'm guessing this could be due to increased turbulent flow after a certain flap deflection angle. That angle is what I am trying to determine.