Fluid Statics

In fluid statics, there is no relative motion between fluid particles, so there are no shear stresses present (a shear results from a velocity gradient). This does not mean that the fluid particles are not moving, but only that they are not moving relative to one another; if they are moving, as in a can of water rotating about its axis, they move as a solid body. The only stress involved in fluid statics is the normal stress, the pressure. It is the pressure acting over an area that gives rise to the forces in problems involving fluid statics. The three types of problems that are presented in this chapter are:

(1) fluids at rest, as in the design of a dam;

(2) fluids undergoing linear acceleration, as in a rocket; and
(3) fluids that are rotating about an axis.