Coefficient of pressure plotting for NACA 0012
 

Hi,
I am simulating the flow over NACA 0012 aerofoil for different angle of attack. Reynolds no is 4e04 and free stream velocity is 1m/s. I am using structured grid with boundary condition @ inlet is velocity inlet. The problem is coefficient of pressure is going more than 1 on lower surface which is not possible. also there is mere change in upper surface cp, but change is visible in lower surface, which is wrong too. Can anyone tell me what could be the reason?