Rayleigh Pitot Tube; Drag Measurement Using Wake Survey and Direct Weighing Method — Lesson 4

This lesson covers the concept of the Rayleigh Pitot tube and its application in drag measurement on cylindrical bodies and other two-dimensional geometries. The lesson begins with an explanation of the Rayleigh Pitot tube and its mounting in a supersonic wind tunnel. It then delves into the use of mercury manometers in high-speed applications due to their higher density. The lesson further explains the measurement of pressure changes in low-speed and high-speed tunnels. The concept of the Rayleigh Pitot tube formula is introduced, which helps in obtaining the free stream Mach number. The lesson also discusses two methods of drag measurement: the Pitot rake for performing wake survey behind the body and the direct weighing method using a mechanical balance.

Video Highlights

01:35 - Explanation of the use of mercury manometers in supersonic wind tunnels.
06:40 - Introduction to the Rayleigh Pitot tube formula for measuring free stream Mach number.
10:59 - Explanation of how to measure drag on a body using a velocity profile in the wake of the body.
26:46 - Explanation of how to use a mechanical balance for drag measurement.

Key Takeaways

- The Rayleigh Pitot tube is used for drag measurement on cylindrical bodies and other two-dimensional geometries.
- Mercury manometers are preferred for high-speed applications due to their higher density.
- The Rayleigh Pitot tube formula helps in obtaining the free stream Mach number.
- The Pitot rake method involves performing a wake survey behind the body to estimate the drag.
- The direct weighing method uses a mechanical balance for drag estimation on a cylindrical body.