calculate drag from the circular cylinder

hi guys can any one tell me how to calculate the drag. I have one idea any one suggest me is that right or not.
after i have calculated the flow density. i use the hydrostatic equation to calculte the pressure and integrate in around the cylinder and calculate the life force and drag force?

check out this answer to the same question:,475,482

Hi Waseem SarwarDogar (AOA),
I am also working on the same problem. I develop a code for flows around a circular cylinder but the vorticity contours shows me that there is some instability. I have a code written in c++. If you would like and if you have code for circular cylinder, so may be we can disscus together, may be my code help you a lot and your one help me to find the instabilities reason in my one.
Good luck and bye for now.