NACA 0012 Simulation in CFX
 

As a part of my course work, I'm required to obtain Cl and Cd of NACA 0012 aerofoil. I'm able to obtain accurate Cl values for all ranges of AOA. However Cd is usually has an error of 33%. I have tried both structured and unstructured grid, and still obtain similar results. Kindly advise me on CFX settings or mesh settings that would improve my Cd values.