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The effect of boundary conditions by the side of the nozzle of a low Reynolds number jet

The effect of boundary conditions by the side of the nozzle of a low Reynolds number jet The near flow field of an axially symmetric water jet at Reynolds numbers from about 1,000 to 10,000 is investigated using laser-induced fluorescence (LIF), laser Doppler anemometry and particle tracking velocimetry. Spanwise and streamwise vortices are detected on the longitudinal plane and on cross-sections. Attention is focused onto the effects of rigid or free boundaries sideways to the nozzle outlet (no-slip or free-slip conditions), and particularly on the start up, growth and interaction of large vortical structures. On average, for the free-slip jet these structures develop more gradually and closer to the nozzle than for the no-slip jet; the local mixedness (derived from LIF measurements) is also higher for the free-slip case. Moreover, the measured velocity field decreases more slowly, with a longer potential core and a higher shear layer (momentum) thickness for the free-slip rather than for the no-slip conditions. The relation between spanwise and streamwise large-scale vortices is clarified by the observation that the ejection of fluid in cross-sections through streamwise vortices is coupled to the pairing of spanwise vortices on the longitudinal section. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Experiments in Fluids Springer Journals

The effect of boundary conditions by the side of the nozzle of a low Reynolds number jet

Experiments in Fluids , Volume 33 (2) – Aug 14, 2002

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References (16)

Publisher
Springer Journals
Copyright
Copyright © 2002 by Springer-Verlag
Subject
Engineering; Engineering Fluid Dynamics; Fluid- and Aerodynamics; Engineering Thermodynamics, Heat and Mass Transfer
ISSN
0723-4864
eISSN
1432-1114
DOI
10.1007/s00348-002-0439-2
Publisher site
See Article on Publisher Site

Abstract

The near flow field of an axially symmetric water jet at Reynolds numbers from about 1,000 to 10,000 is investigated using laser-induced fluorescence (LIF), laser Doppler anemometry and particle tracking velocimetry. Spanwise and streamwise vortices are detected on the longitudinal plane and on cross-sections. Attention is focused onto the effects of rigid or free boundaries sideways to the nozzle outlet (no-slip or free-slip conditions), and particularly on the start up, growth and interaction of large vortical structures. On average, for the free-slip jet these structures develop more gradually and closer to the nozzle than for the no-slip jet; the local mixedness (derived from LIF measurements) is also higher for the free-slip case. Moreover, the measured velocity field decreases more slowly, with a longer potential core and a higher shear layer (momentum) thickness for the free-slip rather than for the no-slip conditions. The relation between spanwise and streamwise large-scale vortices is clarified by the observation that the ejection of fluid in cross-sections through streamwise vortices is coupled to the pairing of spanwise vortices on the longitudinal section.

Journal

Experiments in FluidsSpringer Journals

Published: Aug 14, 2002

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