Contemplation of Nozzle Blockage in Open Jet Wind-Tunnels in View of Different ‘Q’ Determination Techniques

970136

02/24/1997

Event
SAE International Congress and Exposition
Authors Abstract
Content
This paper deals with the correction of aerodynamic interference effects taking place between the nozzle of an open jet wind tunnel and a test model. In order to deduce correct aerodynamic coefficients these interference effects have to be allowed for in the determination of the correct wind tunnel speed. In open jet wind tunnels basically two different methods are used to determine the tunnel speed. One is the so-called nozzle-method, utilizing the pressure difference down the nozzle to determine the nozzle exit velocity or tunnel speed. The other procedure is the so-called plenum-method, where the pressure difference between the settling chamber and the surrounding plenum chamber of the test section is measured and used. In this paper it is shown that both methods yield a systematic error, since the velocity distribution in the nozzle differs from the velocity distribution in an unbounded stream measured at the same distance from the model. In order to compensate for this effect a correction factor is derived with the aid of a simple potential flow model.
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DOI
https://doi.org/10.4271/970136
Pages
12
Citation
Mercker, E., Wickern, G., and Weidemann, J., "Contemplation of Nozzle Blockage in Open Jet Wind-Tunnels in View of Different ‘Q’ Determination Techniques," SAE Technical Paper 970136, 1997, https://doi.org/10.4271/970136.
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Publisher
Published
Feb 24, 1997
Product Code
970136
Content Type
Technical Paper
Language
English