Answer:
For calculating the total force on a surface must integrate the fluid shear stress over the whole surface.
Explanation:
By definition, the total force from the fluid in the cartesian system of coordinates is defined as:
[tex]F=\int\ {\tau (x,y)} \, dx dy [/tex]
The shear stress can be calculated by applying the Navier-Stokes equations and also can be expressed in other coordinates systems like cylindrical or spherical coordinates system.
