Effects of excitation around jet preferred mode Strouhal number in high-speed jets

Effects of excitation around jet preferred mode Strouhal number in high-speed jets It has been widely reported in the literature that the jet preferred mode Strouhal number varies over a large range of 0.2–0.6, depending upon the facility where the measurement is made as well as the measurement techniques and the location in the jet plume where the measurement is taken. This study investigates this wide variation and potential explanations for it. Active flow control is used to show that the jet is receptive to excitation over a large range of Strouhal numbers and azimuthal modes. The wide variation in the preferred mode Strouhal number is shown to be tightly linked to the evolution, spacing, and scale of the coherent flow structures, which dominate the jet shear layer’s development. The low-end of the range is determined by the minimum Strouhal number at which structures begin to interact with one another in the jet plume. Below this range, structures have no significant effect on the plume’s statistical properties. For Strouhal numbers at the high-end of the range, the development of coherent flow structures shifts upstream toward the nozzle exit and the structures disintegrate earlier in the jet plume. The earlier development and disintegration prevent these structures from strongly impacting the entire flowfield. The results imply that upstream perturbations in the flow present in various facilities could be responsible for the variations in the measured jet preferred mode Strouhal number. Experimental results from schlieren imaging and near- and far-field microphone measurements are used to investigate the preferred mode Strouhal number across this range. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

Effects of excitation around jet preferred mode Strouhal number in high-speed jets

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Publisher
Springer Berlin Heidelberg
Copyright
Copyright © 2017 by Springer-Verlag Berlin Heidelberg
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
D.O.I.
10.1007/s00348-017-2329-7
Publisher site
See Article on Publisher Site

Abstract

It has been widely reported in the literature that the jet preferred mode Strouhal number varies over a large range of 0.2–0.6, depending upon the facility where the measurement is made as well as the measurement techniques and the location in the jet plume where the measurement is taken. This study investigates this wide variation and potential explanations for it. Active flow control is used to show that the jet is receptive to excitation over a large range of Strouhal numbers and azimuthal modes. The wide variation in the preferred mode Strouhal number is shown to be tightly linked to the evolution, spacing, and scale of the coherent flow structures, which dominate the jet shear layer’s development. The low-end of the range is determined by the minimum Strouhal number at which structures begin to interact with one another in the jet plume. Below this range, structures have no significant effect on the plume’s statistical properties. For Strouhal numbers at the high-end of the range, the development of coherent flow structures shifts upstream toward the nozzle exit and the structures disintegrate earlier in the jet plume. The earlier development and disintegration prevent these structures from strongly impacting the entire flowfield. The results imply that upstream perturbations in the flow present in various facilities could be responsible for the variations in the measured jet preferred mode Strouhal number. Experimental results from schlieren imaging and near- and far-field microphone measurements are used to investigate the preferred mode Strouhal number across this range.

Journal

Experiments in FluidsSpringer Journals

Published: Mar 27, 2017

References

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