Related Resources: fluid flow

Stagnation Pressure Incompressible Fluid

Fluid Flow Engineering and Design
Thermodynamics

Pitot Tube Velocity of Fluid Flow Measurement

Pitot tube stagnation pressure equation for an incompressible fluid

Pitot Stagnation pressure Measurement

Eq. 1
v = [ ( 2 / ρ ) ( P_o - P_s ) / γ ]^0.5

Eq. 2
v = [ 2 g ( P_o - P_s ) / γ ]^0.5

where

v = velocity of the fluid (ft / sec)
P_o = stagnation pressure (lbm / ft²)
P_s = static pressure of the fluid at the elevation where the measurement is taken (lbm / ft²)
g = gravity acceleration of gravity (32.2 ft / sec²)
ρ = density of air (lbm / ft³)
γ = specific weight of fluid (lbm / ft³)

Standard air density = 1.225 kg / m³ = .07492 lbs/ft³

Eq. 3
γ = ρ g

For a compressible fluid. Use the equation for an incompressible fluid if the Mach number ≤ 0.3.

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Source

2013 ASHRAE Handbook - Fundamentals, ASHRAE: 2013.