center of pressure

kartik

Hello! I am kartik i have a question in regards to center of pressure. the theory seems to say that the center of pressure should lie at the quarter chord length(from the leading edge) which is the aerodynamice center for a symmetric airfoil. I calculated the COP using fluent and i get it as 0.47( from the leading edge) for zero angloe of attack but as i increase or decrease the angle of attack(i.e at -2,-1,-0.5,0.5,2,4,6) the center of pressure is at 0.25 distance from the leading edge. Airfoild that i am using is naca0012 of one feet chord length Can you tell me whats wrong with zero angle of attack.

thanking you regards kartik