Skip to content
Survpedia
ESEN
Inventions
Generated with AI2 min read

Pitot Tube

Pitot Tube

Made of

GlassCopperBrass

Brief description

A Pitot tube is a pressure measurement instrument used to measure fluid flow velocity. It operates by converting the kinetic energy of a moving fluid into pressure energy, allowing for precise speed measurement in liquid or gas streams.

Use / Function

  • Primary Use: Measuring flow velocity in fluids (pipes, open channels) and air speed in aviation/wind tunnels.
  • Secondary Uses: Monitoring industrial gas flow rates and hydraulic research.
  • Scale: Domestic lab apparatus to industrial flow systems and aircraft instrumentation.

Operating principle

  1. Stagnation Point: The open tip facing directly into the fluid flow creates a stagnation point where fluid speed drops to zero.
  2. Dynamic Pressure: The stagnation pressure equals the static pressure plus dynamic pressure ($\frac{1}{2} \rho v^2$).
  3. Differential Measurement: Static pressure is measured from side ports perpendicular to flow.
  4. Velocity Calculation: The difference between total stagnation pressure and static pressure indicates fluid velocity using Bernoulli’s principle.

How to create it

  1. Tube Shaping: Form a rigid L-shaped tube out of Glass or Copper tubing.
  2. Impact Opening: Ensure the front opening is clean and pointed parallel into the fluid current.
  3. Static Ports: Drill small side holes perpendicular to the main tube body for static pressure sampling.
  4. Manometer Connection: Attach the open ends of the impact and static tubes to a U-tube liquid manometer containing water or oil.
  5. Calibration: Calibrate pressure height differences ($\Delta h$) against known flow velocities.

Materials needed

  • Tubing: Copper, Brass, or Glass.
  • Indicator Fluid: Water, oil, or mercury for the connected manometer.
  • Connectors: Flexible rubber or plastic hosing.

Variants and improvements

  • Simple Pitot Tube: Single tube measuring total stagnation pressure compared to ambient.
  • Pitot-Static Tube (Prandtl Tube): Integrates static ports directly into an outer concentric tube.
  • Electronic Pressure Transducer: Replaces liquid manometer with electronic differential pressure sensors.

Limits and risks

  • Clogging: Small openings can easily become clogged by particles or ice in the fluid stream.
  • Alignment Sensitivity: Must be aligned accurately with the flow direction; misalignment causes measurement errors.
  • Low Speed Limitations: Less accurate at extremely low fluid velocities where differential pressure is minimal.