|MadSci Network: Engineering|
Pitot and static tubes are flow measuring devices that measure velocity. They are usually located on a section of the aircraft where the air flow has not yet been affected by the body of the plane (e.g. on the bottom, front of the plane or on the front of the wing, depending on the type of plane).
Pitot tubes are open, L-shaped tubes that have one end open to the drive wind and the other connected to a pressure measuring device (refer to Figure 1 on this webpage: http://www.kele.com/refflow1.htm). Perpendicular to the main tube, is the static tube. This tube measures static pressure (Ps). This is the pressure that is exerted radially in all directions.....like inside a balloon. (ref: http://www.kele.com/refflow1.htm)
The pitot tube measures the total pressure (Pt) in the tube. This pressure is comprised of the velocity pressure (Pv - pressure due to the momentum of the drive wind) and the static pressure. (i.e. Pv+Ps=Pt). If we isolate Pv (i.e. Pv=Pt-Ps), we can then calculate the velocity of the airflow using the following equation:
v = 1096 * (Pv / D)^1/2 where D = density of the fluid (i.e. air)(refer to webpage: http://www.kele.com/refflow1.htm for further info on this calculation)
This was just a brief overview of pitot and static tubes. To write any more would just be too repetitious of the several web pages that I have found. For more info, please refer to the websites I have listed below. I hope I was of some help to you. If you have any further questions, please feel free to email me.
Dictionary of Technical Terms for Aerospace Use
Measuring Air Flow
Try the links in the MadSci Library for more information on Engineering.
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