The end of the tube

摘要

The Pace of technological change ― from passenger jets to helicopters ― has been staggering over the past 100 years, yet there are still a few critical components that have remained unchanged. One is the Pitot tube ― a simple mechanical device at the heart of the speedometer on most modern aircraft ― designed almost 300 years ago by French inventor Henri Pitot, to measure fluid velocity. The basic instrument consists of two coaxial tubes: an interior tube that is open to the flow, and an exterior tube open at 90 degrees to the flow. By measuring the difference between these two pressures the flow rate of the fluid can be calculated.