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1 Fundamental Concepts of Fluid Mechanics for Mine Ventilation
1.3 Fluid Dynamics
1.3.1 Types of Pressure Present in a Moving Fluid
A moving fluid has the following types of pressure:
Static Pressure (P s )
Static pressure is a concept comparable to atmospheric pressure or the pressure of
gas-filled vessels (Fig. 1.4). This type of pressure is the one that a fluid has regardless
of its speed. In addition, it is the same in all directions and can be positive or negative;
that is, it can help the flow or put up resistance.
Fig. 1.4 Static pressure acting inside an air balloon
Dynamic Pressure (P v )
The dynamic pressure is a measure of the kinetic energy per unit volume possessed
by a fluid particle in its path along a pipe (Fig. 1.5). In other words, it is the type of
pressure caused by the inertia of fluid particles striking a surface perpendicular to
their movement. Mathematically, it can be expressed as (Eq. 1.8):
P v =
1
2
ρv
2
(1.8)
Its relationship with kinetic energy derives from the fact that density (ρ) represents
the mass and v represents the velocity of the fluid.
Total Pressure (P T )
The total pressure is the sum of the two previous ones (Fig. 1.5), that is, (Eq. 1.9):