Aerodynamic force on an plunging airfoil
 

Hi every one
I am simulating an airfoil with plunge oscillation and the airfoil, when it has natural shedding in an incompressible low Re flow. The flow is unsteady and I wanna calculate Cp and Cl at different times(some selected time steps). I have read the theodorsen theory and the formulation which he proposed for lift and moment. But it's for thin airfoil in INVISCID incompressible flow.
Now I have some questions:
1) when I want to calculate cp in a special time for airfoil with natural shedding, can I use the simple formula for calculating Cp? I mean Cp=(p-p_inf)/q which P_inf is the pressure in the far field boundary!
2) when I am applying force oscillation, for example plunge oscillation, how can I calculate Cp again?
3)Is it possible to calculate lift coefficient from the following formulation:
Cl=Cz*cos(alfa)-Cx*sin(alfa) or not. If it is not possible does anybody know any book or paper that explains how to calculate them?

Thanks for any words!