Aeronautical Engineering/hot wire anemometry


Hallo Mr Soderman,

I am using hot wire anemometry from Dantec to measure the turbulent velocit profile of a flat plate. I have calibrated the system several times. Every time i start measuring i get a different value either higher or lower than the actual velocity. I have checked the calibration curve. Their is no problem with that. The system gives a different value of output voltage each time at the same flow velocity resulting in a false velocity value.

Do you have any idea why the output voltage varies each time?

Usman - By checking the calibration curve, I assume you mean placing the probe in a known flow field and getting the correct output. If that is the case, then your problem suggests that a) the turbulent flow is fluctuating, b) the probe position in the turbulence is not constant, c) temperature effects are creeping in, d) statistical randomness is responsible, or e) your signal analysis instrument is flawed. The devil is in the details, and you have the details. Sorry.

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Paul Soderman


Aeronautics, Aerodynamics, Fluid Mechanics, Aeroacoustics, Noise Control, Muffler Design, Wind Tunnel Research.... I know nothing about India - do not ask about schools, jobs, application requirements, career choices, etc. for India. Please, no text message verbiage; I prefer full words in full sentences. Thanks.


38 years as research engineer at NASA


B.S. and M.S. Aeronautical Engineering - U. of Washington, Graduate work Standford U.

Awards and Honors
AIAA Associate Fellow (American Institute of Aeronautics and Astronautics)

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