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Experiments on a jet in a crossflow in the low-velocity-ratio regime

Published online by Cambridge University Press:  29 January 2019

L. Klotz*
Affiliation:
Institute of Science and Technology, Am Campus 1, 3400 Klosterneuburg, Austria Institute of Aeronautics and Applied Mechanics, Warsaw University of Technology, Nowowiejska 24, 00-665 Warsaw, Poland
K. Gumowski
Affiliation:
Institute of Aeronautics and Applied Mechanics, Warsaw University of Technology, Nowowiejska 24, 00-665 Warsaw, Poland
J. E. Wesfreid
Affiliation:
Physique et Mécanique des Milieux Hétérogènes, ESPCI Paris, PSL University, CNRS, Sorbonne Université, Université Paris Diderot, Sorbonne Paris Cité, 75005 Paris, France
*
Email address for correspondence: lukasz.klotz@ist.ac.at

Abstract

The hairpin instability of a jet in a crossflow (JICF) for a low jet-to-crossflow velocity ratio is investigated experimentally for a velocity ratio range of $R\in (0.14,0.75)$ and crossflow Reynolds numbers $Re_{D}\in (260,640)$. From spectral analysis we characterize the Strouhal number and amplitude of the hairpin instability as a function of $R$ and $Re_{D}$. We demonstrate that the dynamics of the hairpins is well described by the Landau model, and, hence, that the instability occurs through Hopf bifurcation, similarly to other hydrodynamical oscillators such as wake behind different bluff bodies. Using the Landau model, we determine the precise threshold values of hairpin shedding. We also study the spatial dependence of this hydrodynamical instability, which shows a global behaviour.

Information

Type
JFM Papers
Copyright
© 2019 Cambridge University Press 

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