Problem with surface pressure integrals
 

Hello: I work with sails, and i use it as parachute. I think in this case all the force over the surface must be from viscous terms ( no too much ciculation arround the sail appear), but when i make a force report the viscous force is very smaller than the pressure force. Does anyone knows why?

Other problem is that the pressure force on the sail and the sail shadow are of the same direction, and i think they must pe opossite.

When this problem appear i put a wall in a down stream inviscid flow, and the Dalambert paradox doesnt appear, There was force!. There are too many things i dont understand. Can anyone help me please?

Thanks