Total pressure, often referred to as stagnation pressure, is measured using a specialized instrument called a Pitot tube.
Understanding the Pitot Tube
The Pitot tube is designed to measure both total and static pressure in a fluid flow. It consists of:
- One opening facing directly into the flow, which measures total pressure.
- One or more openings perpendicular to the flow, which measure static pressure.
How it Works
- Total Pressure Measurement: The opening facing the flow allows the fluid to come to a complete stop (stagnate). This is where the kinetic energy of the fluid is converted into pressure, which is the total or stagnation pressure.
- Static Pressure Measurement: The perpendicular openings measure the pressure of the fluid as it flows past, which is known as the static pressure.
- Differential Calculation: Total pressure can be used to calculate velocity if static pressure is known.
Pitot Tube Applications
Pitot tubes are widely used in various fields:
- Aviation: To measure airspeed of aircraft.
- Automotive: To measure air flow in wind tunnels.
- Fluid Dynamics: To study flow profiles and pressure fields.
- Meteorology: To measure wind speeds.
Summary Table
| Measurement | Pitot Tube Opening | Principle |
|---|---|---|
| Total Pressure | Facing into the flow | Fluid comes to rest; kinetic energy converts to pressure |
| Static Pressure | Perpendicular to flow | Pressure of fluid as it flows past |
In Conclusion
The Pitot tube is a primary device to measure total pressure by facing it into the direction of the fluid flow where it will come to a complete stop and measure the stagnation or total pressure.
