[TouZ]

I'm doing my thesis on plain flapped NACA 0012 airfoil. I ran some simulations where flap angle was varied from 10-50 degrees. But when I plot the curve of Cd Vs mach number, for 40 and 50 degrees of flap angle maximum Cd occurs at Mach 0.5 instead of Mach 1. And with increasing mach number Cd decreases afterwards . But, for 10, 20 and 30 degrees of flap angle it conforms to the standard curve somewhat. Way is this happening?? If this is the real case, can anyone explain the physical mechanism occurring there??