A Pitot tube is a measuring instrument used to measure fluid flow. The Pitot tube is named after its inventor, Henri Pitot, and was modified to its modern form by Henry Darcy. Captain Nemo and Professor Aronnax contemplating measuring instruments in Twenty Thousand Leagues Under the Sea In physics and engineering, measurement is the activity of comparing physical quantities of real-world objects and events. ... A subset of the phases of matter, fluids include liquids, gases, plasmas and, to some extent, plastic solids. ... Henri Pitot (1695 May 3 - 1771 December 27) was a French hydraulic engineer and the inventor of the pitot tube, which measures flow velocity. ... Henry Philibert Gaspard Darcy (June 10, 1803 - January 3, 1858), was a French scientist who made several important contributions to hydraulics. ...

Pitot tube

The basic instrument consists of two coaxial tubes: the interior tube is open to the flow (i.e. perpendicular), while the exterior tube is open at ninety degrees to the flow (i.e. parallel). A manometer can be used to measure the difference between these two pressures and using Bernoulli's equation the flow rate of the fluid can be calculated. Image File history File links Pitot tube diagram, by mendel, based on public domain (US govt) diagram at [1]. File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Pitot tube diagram, by mendel, based on public domain (US govt) diagram at [1]. File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... coaxial cable In geometry, coaxial means that two or more forms share a common axis; it is the three-dimensional analog of concentric. Coaxial cable, for example, has a conducting wire in the center and a second conducting layer running all the way around the exterior circumference, under the insulation. ... A manometer is a pressure measuring instrument. ... In fluid dynamics, Bernoullis equation, derived by Daniel Bernoulli, describes the behavior of a fluid moving along a streamline. ...

The exterior tube, with an opening parallel to the flow, will register the Static Pressure. The interior tube, with an opening perpendicular to the flow, will register the Stagnation Pressure. Stagnation pressure is made up of Static Pressure plus Dynamic Pressure (caused by the force of the fluid flowing into the tube interior). By measuring the pressure DIFFERENCE between the Static Pressure (exterior tube) and the Stagnation pressure (interior tube) allows the velocity of the fluid flow to be determined.

See also

• Airspeed indicator
• Ventilation engineering