Becker, Hottel and Williams have determined many characteristics of the nozzle fluid concentration field of the round turbulent free jet: the mean concentration, concentration fluctuations, intermittency factor, spectrum and correlation functions, and integral scales. In the present work a much larger jet nozzle was used, 7.62 cm throat diameter compared to 0.635 cm in the reference, and the Reynolds number was correspondingly greater around 270,000 compared to 54,000. The same light-scatter technique and smoke marker were employed. Measurements were made up to 6 m downstream of the nozzle, at which point the turbulence scale was enormous compared to the observed control volume. The results support Becker, et al's findings and extend the range of the data. In particular, the spectrum of the concentration fluctuations has been measured into the voscous convective subrange where a (-1) power mode dependency on wave number is indicated, as expected for the slow diffusing smoke marker. Other new results include the skewness, kurtosis, and probability density function of the concentration fluctuations. The probability density, as expected, is essentially Gaussian on the jet centreline, but shows marked skewness towards the jet edges. (Depo)
Some characteristics of concentration fluctuations in free turbulent jets
Einige Kennwerte der Konzentrationsschwankungen in freien, turbulenten Strahlen
TURBULENT SHEAR FLOWS. SYMPOSIUM ; 1 ; 15-29
1977
9 Seiten, 9 Bilder, 15 Quellen
Aufsatz (Konferenz)
Englisch
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