Principle of Pitot Tube
Based on Bernoulli's theorem. Measures the difference between the stagnation pressure and static pressure to determine fluid velocity.
Formula
Where:
v = flow velocity
ΔP = difference between stagnation pressure and static pressure
ρ = fluid density
Construction
Pitot Tube: L-shaped tube with an opening facing the flow.
Static Ports: Small holes on the side of the tube to measure static pressure.
Manometer: Measures the pressure difference between the stagnation and static pressures.
Working
The fluid enters the tube, stagnating and creating a high-pressure region.
Static pressure is measured from the ports on the side.
The difference between the stagnation and static pressures is used to calculate the fluid velocity.
Uses
Measuring the velocity of air in HVAC systems.
Used in aircraft to measure airspeed.
Applied in wind tunnel testing and river flow measurements.
Advantages
Simple and inexpensive.
Can measure high-speed flows.
Minimal disturbance to the flow.
Disadvantages
Accuracy can be affected by misalignment with the flow direction.
Limited to point measurement (not for varying velocity profiles).
Requires careful calibration and maintenance.