Air resistance on a rotating cylinder

[Hajk]

Hi, I have an object that's rotating in the air with constant speed. Now a bit simplified it could be looked as an uniform cylinder that's rotating round and round (not like a propeller). How would air resistance affect this rotation and how could you describe this force with a formula?

Thanks

 

[rcgldr]

Friction and viscosity would cause the air to circulate in the vicinty of the cylinder, with the air's velocity decreasing with distance from the suface of the cylinder. The air's resitance to this would create an opposing drag torque on the cylinder.