It is instructive to review briežy the principles of žuid dynamics in order to understand Pitot tube theory and applications.Consider, for example, a constant-density žuid žowing steadily without friction through the simple device shown in Figure 62.1.If it is assumed that there is no heat being added and no sha£ work being produced by the žuid, a simple expression can be developed to describe this žow:

p

w

v

g z

p

w

v

2 2 2

+ + = + +

(62.1)

where p1, v1, z1 are the pressure, velocity, and elevation at the inlet, respectively p2, v2, z2 are the pressure, velocity, and elevation at the outlet, respectively w = ρg is the speciŸc weight of the žuid ρ is the density g = 9.80665 m s−2

Equation 62.1 is the well-known Bernoulli equation. œe following example will demonstrate the use of Equation 62.1 and lead to a discussion of the theory of Pitot tubes.