Fluid Statics

Pascal's Law

In the absence of shearing stress, pressure at any point in fluid in independent of direction.

Px = Py = Pz

BASIC EQUATION FOR THE PRESSURE FIELD

AT Rest,

For incompressible Fluid,

Absolute Pressure

Pressure measured with reference to absolute zero. 

• Absolute pressure can not be zero.
• Gauge pressure can be positive or negative.
• At mean sea level atmospheric pressure is 1.01x10^5 Pa or 1 Bar.

Hydrostatic Force on a plane Surface

The force must be perpendicular to the surface since there are no shearing stresses present when fluid is at rest. The pressure will vary linearly with the depth if the fluid is incompressible.

• Magnitude of FR is independent of angle θ.
• FR is perpendicular to the surface.
• Location of resultant force :

Hydrostatic force for Curved surface

• Horizontal Force (FH) : This can be computed by projecting the surface upon a vertical plane and multiplying the projected area by the pressure at its own center of area.
• Vertical Force (Fv) : It is equal to the weight of the liquid block lying above the curved surface upto the free surface.