A pitot static tube is used for measuring the velocity of a gas flowing in a duct. The velocity is proportional to

Pitot Tube:

• A pitot tube is also known as a pitot probe is a flow measurement device used to measure fluid flow velocity.
• The basic pitot tube consists of a tube pointing directly into the fluid flow.
•  As this tube contains fluid, a pressure can be measured; the moving fluid is brought to rest (stagnates) as there is no outlet to allow flow to continue.
• This pressure is the stagnation pressure of the fluid, also known as the total pressure of the pitot pressure.

Stagnation pressure = Static pressure + Dynamic pressure

• The velocity of the flowing gas in the pitot tube is given by:

\(u = {\sqrt{2(p_t-p_s)\overρ}}\)

where u = Fluid velocity

ρ = Fluid density

p_t = Stagnation pressure

p_s = Static pressure

• From the above equation, the velocity is proportional to the square root of the difference between the total and static pressures.